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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:27:49 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:27:49 +0000 |
| commit | ace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch) | |
| tree | b2d64bc10158fdd5497876388cd68142ca374ed3 /Documentation/admin-guide | |
| parent | Initial commit. (diff) | |
| download | linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip | |
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'Documentation/admin-guide')
374 files changed, 89246 insertions, 0 deletions
diff --git a/Documentation/admin-guide/LSM/LoadPin.rst b/Documentation/admin-guide/LSM/LoadPin.rst new file mode 100644 index 000000000..dd3ca68b5 --- /dev/null +++ b/Documentation/admin-guide/LSM/LoadPin.rst @@ -0,0 +1,31 @@ +======= +LoadPin +======= + +LoadPin is a Linux Security Module that ensures all kernel-loaded files +(modules, firmware, etc) all originate from the same filesystem, with +the expectation that such a filesystem is backed by a read-only device +such as dm-verity or CDROM. This allows systems that have a verified +and/or unchangeable filesystem to enforce module and firmware loading +restrictions without needing to sign the files individually. + +The LSM is selectable at build-time with ``CONFIG_SECURITY_LOADPIN``, and +can be controlled at boot-time with the kernel command line option +"``loadpin.enforce``". By default, it is enabled, but can be disabled at +boot ("``loadpin.enforce=0``"). + +LoadPin starts pinning when it sees the first file loaded. If the +block device backing the filesystem is not read-only, a sysctl is +created to toggle pinning: ``/proc/sys/kernel/loadpin/enabled``. (Having +a mutable filesystem means pinning is mutable too, but having the +sysctl allows for easy testing on systems with a mutable filesystem.) + +It's also possible to exclude specific file types from LoadPin using kernel +command line option "``loadpin.exclude``". By default, all files are +included, but they can be excluded using kernel command line option such +as "``loadpin.exclude=kernel-module,kexec-image``". This allows to use +different mechanisms such as ``CONFIG_MODULE_SIG`` and +``CONFIG_KEXEC_VERIFY_SIG`` to verify kernel module and kernel image while +still use LoadPin to protect the integrity of other files kernel loads. The +full list of valid file types can be found in ``kernel_read_file_str`` +defined in ``include/linux/kernel_read_file.h``. diff --git a/Documentation/admin-guide/LSM/SELinux.rst b/Documentation/admin-guide/LSM/SELinux.rst new file mode 100644 index 000000000..520a1c2c6 --- /dev/null +++ b/Documentation/admin-guide/LSM/SELinux.rst @@ -0,0 +1,33 @@ +======= +SELinux +======= + +If you want to use SELinux, chances are you will want +to use the distro-provided policies, or install the +latest reference policy release from + + https://github.com/SELinuxProject/refpolicy + +However, if you want to install a dummy policy for +testing, you can do using ``mdp`` provided under +scripts/selinux. Note that this requires the selinux +userspace to be installed - in particular you will +need checkpolicy to compile a kernel, and setfiles and +fixfiles to label the filesystem. + + 1. Compile the kernel with selinux enabled. + 2. Type ``make`` to compile ``mdp``. + 3. Make sure that you are not running with + SELinux enabled and a real policy. If + you are, reboot with selinux disabled + before continuing. + 4. Run install_policy.sh:: + + cd scripts/selinux + sh install_policy.sh + +Step 4 will create a new dummy policy valid for your +kernel, with a single selinux user, role, and type. +It will compile the policy, will set your ``SELINUXTYPE`` to +``dummy`` in ``/etc/selinux/config``, install the compiled policy +as ``dummy``, and relabel your filesystem. diff --git a/Documentation/admin-guide/LSM/SafeSetID.rst b/Documentation/admin-guide/LSM/SafeSetID.rst new file mode 100644 index 000000000..0ec34863c --- /dev/null +++ b/Documentation/admin-guide/LSM/SafeSetID.rst @@ -0,0 +1,118 @@ +========= +SafeSetID +========= +SafeSetID is an LSM module that gates the setid family of syscalls to restrict +UID/GID transitions from a given UID/GID to only those approved by a +system-wide allowlist. These restrictions also prohibit the given UIDs/GIDs +from obtaining auxiliary privileges associated with CAP_SET{U/G}ID, such as +allowing a user to set up user namespace UID/GID mappings. + + +Background +========== +In absence of file capabilities, processes spawned on a Linux system that need +to switch to a different user must be spawned with CAP_SETUID privileges. +CAP_SETUID is granted to programs running as root or those running as a non-root +user that have been explicitly given the CAP_SETUID runtime capability. It is +often preferable to use Linux runtime capabilities rather than file +capabilities, since using file capabilities to run a program with elevated +privileges opens up possible security holes since any user with access to the +file can exec() that program to gain the elevated privileges. + +While it is possible to implement a tree of processes by giving full +CAP_SET{U/G}ID capabilities, this is often at odds with the goals of running a +tree of processes under non-root user(s) in the first place. Specifically, +since CAP_SETUID allows changing to any user on the system, including the root +user, it is an overpowered capability for what is needed in this scenario, +especially since programs often only call setuid() to drop privileges to a +lesser-privileged user -- not elevate privileges. Unfortunately, there is no +generally feasible way in Linux to restrict the potential UIDs that a user can +switch to through setuid() beyond allowing a switch to any user on the system. +This SafeSetID LSM seeks to provide a solution for restricting setid +capabilities in such a way. + +The main use case for this LSM is to allow a non-root program to transition to +other untrusted uids without full blown CAP_SETUID capabilities. The non-root +program would still need CAP_SETUID to do any kind of transition, but the +additional restrictions imposed by this LSM would mean it is a "safer" version +of CAP_SETUID since the non-root program cannot take advantage of CAP_SETUID to +do any unapproved actions (e.g. setuid to uid 0 or create/enter new user +namespace). The higher level goal is to allow for uid-based sandboxing of system +services without having to give out CAP_SETUID all over the place just so that +non-root programs can drop to even-lesser-privileged uids. This is especially +relevant when one non-root daemon on the system should be allowed to spawn other +processes as different uids, but its undesirable to give the daemon a +basically-root-equivalent CAP_SETUID. + + +Other Approaches Considered +=========================== + +Solve this problem in userspace +------------------------------- +For candidate applications that would like to have restricted setid capabilities +as implemented in this LSM, an alternative option would be to simply take away +setid capabilities from the application completely and refactor the process +spawning semantics in the application (e.g. by using a privileged helper program +to do process spawning and UID/GID transitions). Unfortunately, there are a +number of semantics around process spawning that would be affected by this, such +as fork() calls where the program doesn't immediately call exec() after the +fork(), parent processes specifying custom environment variables or command line +args for spawned child processes, or inheritance of file handles across a +fork()/exec(). Because of this, as solution that uses a privileged helper in +userspace would likely be less appealing to incorporate into existing projects +that rely on certain process-spawning semantics in Linux. + +Use user namespaces +------------------- +Another possible approach would be to run a given process tree in its own user +namespace and give programs in the tree setid capabilities. In this way, +programs in the tree could change to any desired UID/GID in the context of their +own user namespace, and only approved UIDs/GIDs could be mapped back to the +initial system user namespace, affectively preventing privilege escalation. +Unfortunately, it is not generally feasible to use user namespaces in isolation, +without pairing them with other namespace types, which is not always an option. +Linux checks for capabilities based off of the user namespace that "owns" some +entity. For example, Linux has the notion that network namespaces are owned by +the user namespace in which they were created. A consequence of this is that +capability checks for access to a given network namespace are done by checking +whether a task has the given capability in the context of the user namespace +that owns the network namespace -- not necessarily the user namespace under +which the given task runs. Therefore spawning a process in a new user namespace +effectively prevents it from accessing the network namespace owned by the +initial namespace. This is a deal-breaker for any application that expects to +retain the CAP_NET_ADMIN capability for the purpose of adjusting network +configurations. Using user namespaces in isolation causes problems regarding +other system interactions, including use of pid namespaces and device creation. + +Use an existing LSM +------------------- +None of the other in-tree LSMs have the capability to gate setid transitions, or +even employ the security_task_fix_setuid hook at all. SELinux says of that hook: +"Since setuid only affects the current process, and since the SELinux controls +are not based on the Linux identity attributes, SELinux does not need to control +this operation." + + +Directions for use +================== +This LSM hooks the setid syscalls to make sure transitions are allowed if an +applicable restriction policy is in place. Policies are configured through +securityfs by writing to the safesetid/uid_allowlist_policy and +safesetid/gid_allowlist_policy files at the location where securityfs is +mounted. The format for adding a policy is '<UID>:<UID>' or '<GID>:<GID>', +using literal numbers, and ending with a newline character such as '123:456\n'. +Writing an empty string "" will flush the policy. Again, configuring a policy +for a UID/GID will prevent that UID/GID from obtaining auxiliary setid +privileges, such as allowing a user to set up user namespace UID/GID mappings. + +Note on GID policies and setgroups() +==================================== +In v5.9 we are adding support for limiting CAP_SETGID privileges as was done +previously for CAP_SETUID. However, for compatibility with common sandboxing +related code conventions in userspace, we currently allow arbitrary +setgroups() calls for processes with CAP_SETGID restrictions. Until we add +support in a future release for restricting setgroups() calls, these GID +policies add no meaningful security. setgroups() restrictions will be enforced +once we have the policy checking code in place, which will rely on GID policy +configuration code added in v5.9. diff --git a/Documentation/admin-guide/LSM/Smack.rst b/Documentation/admin-guide/LSM/Smack.rst new file mode 100644 index 000000000..6d44f4fdb --- /dev/null +++ b/Documentation/admin-guide/LSM/Smack.rst @@ -0,0 +1,861 @@ +===== +Smack +===== + + + "Good for you, you've decided to clean the elevator!" + - The Elevator, from Dark Star + +Smack is the Simplified Mandatory Access Control Kernel. +Smack is a kernel based implementation of mandatory access +control that includes simplicity in its primary design goals. + +Smack is not the only Mandatory Access Control scheme +available for Linux. Those new to Mandatory Access Control +are encouraged to compare Smack with the other mechanisms +available to determine which is best suited to the problem +at hand. + +Smack consists of three major components: + + - The kernel + - Basic utilities, which are helpful but not required + - Configuration data + +The kernel component of Smack is implemented as a Linux +Security Modules (LSM) module. It requires netlabel and +works best with file systems that support extended attributes, +although xattr support is not strictly required. +It is safe to run a Smack kernel under a "vanilla" distribution. + +Smack kernels use the CIPSO IP option. Some network +configurations are intolerant of IP options and can impede +access to systems that use them as Smack does. + +Smack is used in the Tizen operating system. Please +go to http://wiki.tizen.org for information about how +Smack is used in Tizen. + +The current git repository for Smack user space is: + + git://github.com/smack-team/smack.git + +This should make and install on most modern distributions. +There are five commands included in smackutil: + +chsmack: + display or set Smack extended attribute values + +smackctl: + load the Smack access rules + +smackaccess: + report if a process with one label has access + to an object with another + +These two commands are obsolete with the introduction of +the smackfs/load2 and smackfs/cipso2 interfaces. + +smackload: + properly formats data for writing to smackfs/load + +smackcipso: + properly formats data for writing to smackfs/cipso + +In keeping with the intent of Smack, configuration data is +minimal and not strictly required. The most important +configuration step is mounting the smackfs pseudo filesystem. +If smackutil is installed the startup script will take care +of this, but it can be manually as well. + +Add this line to ``/etc/fstab``:: + + smackfs /sys/fs/smackfs smackfs defaults 0 0 + +The ``/sys/fs/smackfs`` directory is created by the kernel. + +Smack uses extended attributes (xattrs) to store labels on filesystem +objects. The attributes are stored in the extended attribute security +name space. A process must have ``CAP_MAC_ADMIN`` to change any of these +attributes. + +The extended attributes that Smack uses are: + +SMACK64 + Used to make access control decisions. In almost all cases + the label given to a new filesystem object will be the label + of the process that created it. + +SMACK64EXEC + The Smack label of a process that execs a program file with + this attribute set will run with this attribute's value. + +SMACK64MMAP + Don't allow the file to be mmapped by a process whose Smack + label does not allow all of the access permitted to a process + with the label contained in this attribute. This is a very + specific use case for shared libraries. + +SMACK64TRANSMUTE + Can only have the value "TRUE". If this attribute is present + on a directory when an object is created in the directory and + the Smack rule (more below) that permitted the write access + to the directory includes the transmute ("t") mode the object + gets the label of the directory instead of the label of the + creating process. If the object being created is a directory + the SMACK64TRANSMUTE attribute is set as well. + +SMACK64IPIN + This attribute is only available on file descriptors for sockets. + Use the Smack label in this attribute for access control + decisions on packets being delivered to this socket. + +SMACK64IPOUT + This attribute is only available on file descriptors for sockets. + Use the Smack label in this attribute for access control + decisions on packets coming from this socket. + +There are multiple ways to set a Smack label on a file:: + + # attr -S -s SMACK64 -V "value" path + # chsmack -a value path + +A process can see the Smack label it is running with by +reading ``/proc/self/attr/current``. A process with ``CAP_MAC_ADMIN`` +can set the process Smack by writing there. + +Most Smack configuration is accomplished by writing to files +in the smackfs filesystem. This pseudo-filesystem is mounted +on ``/sys/fs/smackfs``. + +access + Provided for backward compatibility. The access2 interface + is preferred and should be used instead. + This interface reports whether a subject with the specified + Smack label has a particular access to an object with a + specified Smack label. Write a fixed format access rule to + this file. The next read will indicate whether the access + would be permitted. The text will be either "1" indicating + access, or "0" indicating denial. + +access2 + This interface reports whether a subject with the specified + Smack label has a particular access to an object with a + specified Smack label. Write a long format access rule to + this file. The next read will indicate whether the access + would be permitted. The text will be either "1" indicating + access, or "0" indicating denial. + +ambient + This contains the Smack label applied to unlabeled network + packets. + +change-rule + This interface allows modification of existing access control rules. + The format accepted on write is:: + + "%s %s %s %s" + + where the first string is the subject label, the second the + object label, the third the access to allow and the fourth the + access to deny. The access strings may contain only the characters + "rwxat-". If a rule for a given subject and object exists it will be + modified by enabling the permissions in the third string and disabling + those in the fourth string. If there is no such rule it will be + created using the access specified in the third and the fourth strings. + +cipso + Provided for backward compatibility. The cipso2 interface + is preferred and should be used instead. + This interface allows a specific CIPSO header to be assigned + to a Smack label. The format accepted on write is:: + + "%24s%4d%4d"["%4d"]... + + The first string is a fixed Smack label. The first number is + the level to use. The second number is the number of categories. + The following numbers are the categories:: + + "level-3-cats-5-19 3 2 5 19" + +cipso2 + This interface allows a specific CIPSO header to be assigned + to a Smack label. The format accepted on write is:: + + "%s%4d%4d"["%4d"]... + + The first string is a long Smack label. The first number is + the level to use. The second number is the number of categories. + The following numbers are the categories:: + + "level-3-cats-5-19 3 2 5 19" + +direct + This contains the CIPSO level used for Smack direct label + representation in network packets. + +doi + This contains the CIPSO domain of interpretation used in + network packets. + +ipv6host + This interface allows specific IPv6 internet addresses to be + treated as single label hosts. Packets are sent to single + label hosts only from processes that have Smack write access + to the host label. All packets received from single label hosts + are given the specified label. The format accepted on write is:: + + "%h:%h:%h:%h:%h:%h:%h:%h label" or + "%h:%h:%h:%h:%h:%h:%h:%h/%d label". + + The "::" address shortcut is not supported. + If label is "-DELETE" a matched entry will be deleted. + +load + Provided for backward compatibility. The load2 interface + is preferred and should be used instead. + This interface allows access control rules in addition to + the system defined rules to be specified. The format accepted + on write is:: + + "%24s%24s%5s" + + where the first string is the subject label, the second the + object label, and the third the requested access. The access + string may contain only the characters "rwxat-", and specifies + which sort of access is allowed. The "-" is a placeholder for + permissions that are not allowed. The string "r-x--" would + specify read and execute access. Labels are limited to 23 + characters in length. + +load2 + This interface allows access control rules in addition to + the system defined rules to be specified. The format accepted + on write is:: + + "%s %s %s" + + where the first string is the subject label, the second the + object label, and the third the requested access. The access + string may contain only the characters "rwxat-", and specifies + which sort of access is allowed. The "-" is a placeholder for + permissions that are not allowed. The string "r-x--" would + specify read and execute access. + +load-self + Provided for backward compatibility. The load-self2 interface + is preferred and should be used instead. + This interface allows process specific access rules to be + defined. These rules are only consulted if access would + otherwise be permitted, and are intended to provide additional + restrictions on the process. The format is the same as for + the load interface. + +load-self2 + This interface allows process specific access rules to be + defined. These rules are only consulted if access would + otherwise be permitted, and are intended to provide additional + restrictions on the process. The format is the same as for + the load2 interface. + +logging + This contains the Smack logging state. + +mapped + This contains the CIPSO level used for Smack mapped label + representation in network packets. + +netlabel + This interface allows specific internet addresses to be + treated as single label hosts. Packets are sent to single + label hosts without CIPSO headers, but only from processes + that have Smack write access to the host label. All packets + received from single label hosts are given the specified + label. The format accepted on write is:: + + "%d.%d.%d.%d label" or "%d.%d.%d.%d/%d label". + + If the label specified is "-CIPSO" the address is treated + as a host that supports CIPSO headers. + +onlycap + This contains labels processes must have for CAP_MAC_ADMIN + and ``CAP_MAC_OVERRIDE`` to be effective. If this file is empty + these capabilities are effective at for processes with any + label. The values are set by writing the desired labels, separated + by spaces, to the file or cleared by writing "-" to the file. + +ptrace + This is used to define the current ptrace policy + + 0 - default: + this is the policy that relies on Smack access rules. + For the ``PTRACE_READ`` a subject needs to have a read access on + object. For the ``PTRACE_ATTACH`` a read-write access is required. + + 1 - exact: + this is the policy that limits ``PTRACE_ATTACH``. Attach is + only allowed when subject's and object's labels are equal. + ``PTRACE_READ`` is not affected. Can be overridden with ``CAP_SYS_PTRACE``. + + 2 - draconian: + this policy behaves like the 'exact' above with an + exception that it can't be overridden with ``CAP_SYS_PTRACE``. + +revoke-subject + Writing a Smack label here sets the access to '-' for all access + rules with that subject label. + +unconfined + If the kernel is configured with ``CONFIG_SECURITY_SMACK_BRINGUP`` + a process with ``CAP_MAC_ADMIN`` can write a label into this interface. + Thereafter, accesses that involve that label will be logged and + the access permitted if it wouldn't be otherwise. Note that this + is dangerous and can ruin the proper labeling of your system. + It should never be used in production. + +relabel-self + This interface contains a list of labels to which the process can + transition to, by writing to ``/proc/self/attr/current``. + Normally a process can change its own label to any legal value, but only + if it has ``CAP_MAC_ADMIN``. This interface allows a process without + ``CAP_MAC_ADMIN`` to relabel itself to one of labels from predefined list. + A process without ``CAP_MAC_ADMIN`` can change its label only once. When it + does, this list will be cleared. + The values are set by writing the desired labels, separated + by spaces, to the file or cleared by writing "-" to the file. + +If you are using the smackload utility +you can add access rules in ``/etc/smack/accesses``. They take the form:: + + subjectlabel objectlabel access + +access is a combination of the letters rwxatb which specify the +kind of access permitted a subject with subjectlabel on an +object with objectlabel. If there is no rule no access is allowed. + +Look for additional programs on http://schaufler-ca.com + +The Simplified Mandatory Access Control Kernel (Whitepaper) +=========================================================== + +Casey Schaufler +casey@schaufler-ca.com + +Mandatory Access Control +------------------------ + +Computer systems employ a variety of schemes to constrain how information is +shared among the people and services using the machine. Some of these schemes +allow the program or user to decide what other programs or users are allowed +access to pieces of data. These schemes are called discretionary access +control mechanisms because the access control is specified at the discretion +of the user. Other schemes do not leave the decision regarding what a user or +program can access up to users or programs. These schemes are called mandatory +access control mechanisms because you don't have a choice regarding the users +or programs that have access to pieces of data. + +Bell & LaPadula +--------------- + +From the middle of the 1980's until the turn of the century Mandatory Access +Control (MAC) was very closely associated with the Bell & LaPadula security +model, a mathematical description of the United States Department of Defense +policy for marking paper documents. MAC in this form enjoyed a following +within the Capital Beltway and Scandinavian supercomputer centers but was +often sited as failing to address general needs. + +Domain Type Enforcement +----------------------- + +Around the turn of the century Domain Type Enforcement (DTE) became popular. +This scheme organizes users, programs, and data into domains that are +protected from each other. This scheme has been widely deployed as a component +of popular Linux distributions. The administrative overhead required to +maintain this scheme and the detailed understanding of the whole system +necessary to provide a secure domain mapping leads to the scheme being +disabled or used in limited ways in the majority of cases. + +Smack +----- + +Smack is a Mandatory Access Control mechanism designed to provide useful MAC +while avoiding the pitfalls of its predecessors. The limitations of Bell & +LaPadula are addressed by providing a scheme whereby access can be controlled +according to the requirements of the system and its purpose rather than those +imposed by an arcane government policy. The complexity of Domain Type +Enforcement and avoided by defining access controls in terms of the access +modes already in use. + +Smack Terminology +----------------- + +The jargon used to talk about Smack will be familiar to those who have dealt +with other MAC systems and shouldn't be too difficult for the uninitiated to +pick up. There are four terms that are used in a specific way and that are +especially important: + + Subject: + A subject is an active entity on the computer system. + On Smack a subject is a task, which is in turn the basic unit + of execution. + + Object: + An object is a passive entity on the computer system. + On Smack files of all types, IPC, and tasks can be objects. + + Access: + Any attempt by a subject to put information into or get + information from an object is an access. + + Label: + Data that identifies the Mandatory Access Control + characteristics of a subject or an object. + +These definitions are consistent with the traditional use in the security +community. There are also some terms from Linux that are likely to crop up: + + Capability: + A task that possesses a capability has permission to + violate an aspect of the system security policy, as identified by + the specific capability. A task that possesses one or more + capabilities is a privileged task, whereas a task with no + capabilities is an unprivileged task. + + Privilege: + A task that is allowed to violate the system security + policy is said to have privilege. As of this writing a task can + have privilege either by possessing capabilities or by having an + effective user of root. + +Smack Basics +------------ + +Smack is an extension to a Linux system. It enforces additional restrictions +on what subjects can access which objects, based on the labels attached to +each of the subject and the object. + +Labels +~~~~~~ + +Smack labels are ASCII character strings. They can be up to 255 characters +long, but keeping them to twenty-three characters is recommended. +Single character labels using special characters, that being anything +other than a letter or digit, are reserved for use by the Smack development +team. Smack labels are unstructured, case sensitive, and the only operation +ever performed on them is comparison for equality. Smack labels cannot +contain unprintable characters, the "/" (slash), the "\" (backslash), the "'" +(quote) and '"' (double-quote) characters. +Smack labels cannot begin with a '-'. This is reserved for special options. + +There are some predefined labels:: + + _ Pronounced "floor", a single underscore character. + ^ Pronounced "hat", a single circumflex character. + * Pronounced "star", a single asterisk character. + ? Pronounced "huh", a single question mark character. + @ Pronounced "web", a single at sign character. + +Every task on a Smack system is assigned a label. The Smack label +of a process will usually be assigned by the system initialization +mechanism. + +Access Rules +~~~~~~~~~~~~ + +Smack uses the traditional access modes of Linux. These modes are read, +execute, write, and occasionally append. There are a few cases where the +access mode may not be obvious. These include: + + Signals: + A signal is a write operation from the subject task to + the object task. + + Internet Domain IPC: + Transmission of a packet is considered a + write operation from the source task to the destination task. + +Smack restricts access based on the label attached to a subject and the label +attached to the object it is trying to access. The rules enforced are, in +order: + + 1. Any access requested by a task labeled "*" is denied. + 2. A read or execute access requested by a task labeled "^" + is permitted. + 3. A read or execute access requested on an object labeled "_" + is permitted. + 4. Any access requested on an object labeled "*" is permitted. + 5. Any access requested by a task on an object with the same + label is permitted. + 6. Any access requested that is explicitly defined in the loaded + rule set is permitted. + 7. Any other access is denied. + +Smack Access Rules +~~~~~~~~~~~~~~~~~~ + +With the isolation provided by Smack access separation is simple. There are +many interesting cases where limited access by subjects to objects with +different labels is desired. One example is the familiar spy model of +sensitivity, where a scientist working on a highly classified project would be +able to read documents of lower classifications and anything she writes will +be "born" highly classified. To accommodate such schemes Smack includes a +mechanism for specifying rules allowing access between labels. + +Access Rule Format +~~~~~~~~~~~~~~~~~~ + +The format of an access rule is:: + + subject-label object-label access + +Where subject-label is the Smack label of the task, object-label is the Smack +label of the thing being accessed, and access is a string specifying the sort +of access allowed. The access specification is searched for letters that +describe access modes: + + a: indicates that append access should be granted. + r: indicates that read access should be granted. + w: indicates that write access should be granted. + x: indicates that execute access should be granted. + t: indicates that the rule requests transmutation. + b: indicates that the rule should be reported for bring-up. + +Uppercase values for the specification letters are allowed as well. +Access mode specifications can be in any order. Examples of acceptable rules +are:: + + TopSecret Secret rx + Secret Unclass R + Manager Game x + User HR w + Snap Crackle rwxatb + New Old rRrRr + Closed Off - + +Examples of unacceptable rules are:: + + Top Secret Secret rx + Ace Ace r + Odd spells waxbeans + +Spaces are not allowed in labels. Since a subject always has access to files +with the same label specifying a rule for that case is pointless. Only +valid letters (rwxatbRWXATB) and the dash ('-') character are allowed in +access specifications. The dash is a placeholder, so "a-r" is the same +as "ar". A lone dash is used to specify that no access should be allowed. + +Applying Access Rules +~~~~~~~~~~~~~~~~~~~~~ + +The developers of Linux rarely define new sorts of things, usually importing +schemes and concepts from other systems. Most often, the other systems are +variants of Unix. Unix has many endearing properties, but consistency of +access control models is not one of them. Smack strives to treat accesses as +uniformly as is sensible while keeping with the spirit of the underlying +mechanism. + +File system objects including files, directories, named pipes, symbolic links, +and devices require access permissions that closely match those used by mode +bit access. To open a file for reading read access is required on the file. To +search a directory requires execute access. Creating a file with write access +requires both read and write access on the containing directory. Deleting a +file requires read and write access to the file and to the containing +directory. It is possible that a user may be able to see that a file exists +but not any of its attributes by the circumstance of having read access to the +containing directory but not to the differently labeled file. This is an +artifact of the file name being data in the directory, not a part of the file. + +If a directory is marked as transmuting (SMACK64TRANSMUTE=TRUE) and the +access rule that allows a process to create an object in that directory +includes 't' access the label assigned to the new object will be that +of the directory, not the creating process. This makes it much easier +for two processes with different labels to share data without granting +access to all of their files. + +IPC objects, message queues, semaphore sets, and memory segments exist in flat +namespaces and access requests are only required to match the object in +question. + +Process objects reflect tasks on the system and the Smack label used to access +them is the same Smack label that the task would use for its own access +attempts. Sending a signal via the kill() system call is a write operation +from the signaler to the recipient. Debugging a process requires both reading +and writing. Creating a new task is an internal operation that results in two +tasks with identical Smack labels and requires no access checks. + +Sockets are data structures attached to processes and sending a packet from +one process to another requires that the sender have write access to the +receiver. The receiver is not required to have read access to the sender. + +Setting Access Rules +~~~~~~~~~~~~~~~~~~~~ + +The configuration file /etc/smack/accesses contains the rules to be set at +system startup. The contents are written to the special file +/sys/fs/smackfs/load2. Rules can be added at any time and take effect +immediately. For any pair of subject and object labels there can be only +one rule, with the most recently specified overriding any earlier +specification. + +Task Attribute +~~~~~~~~~~~~~~ + +The Smack label of a process can be read from /proc/<pid>/attr/current. A +process can read its own Smack label from /proc/self/attr/current. A +privileged process can change its own Smack label by writing to +/proc/self/attr/current but not the label of another process. + +File Attribute +~~~~~~~~~~~~~~ + +The Smack label of a filesystem object is stored as an extended attribute +named SMACK64 on the file. This attribute is in the security namespace. It can +only be changed by a process with privilege. + +Privilege +~~~~~~~~~ + +A process with CAP_MAC_OVERRIDE or CAP_MAC_ADMIN is privileged. +CAP_MAC_OVERRIDE allows the process access to objects it would +be denied otherwise. CAP_MAC_ADMIN allows a process to change +Smack data, including rules and attributes. + +Smack Networking +~~~~~~~~~~~~~~~~ + +As mentioned before, Smack enforces access control on network protocol +transmissions. Every packet sent by a Smack process is tagged with its Smack +label. This is done by adding a CIPSO tag to the header of the IP packet. Each +packet received is expected to have a CIPSO tag that identifies the label and +if it lacks such a tag the network ambient label is assumed. Before the packet +is delivered a check is made to determine that a subject with the label on the +packet has write access to the receiving process and if that is not the case +the packet is dropped. + +CIPSO Configuration +~~~~~~~~~~~~~~~~~~~ + +It is normally unnecessary to specify the CIPSO configuration. The default +values used by the system handle all internal cases. Smack will compose CIPSO +label values to match the Smack labels being used without administrative +intervention. Unlabeled packets that come into the system will be given the +ambient label. + +Smack requires configuration in the case where packets from a system that is +not Smack that speaks CIPSO may be encountered. Usually this will be a Trusted +Solaris system, but there are other, less widely deployed systems out there. +CIPSO provides 3 important values, a Domain Of Interpretation (DOI), a level, +and a category set with each packet. The DOI is intended to identify a group +of systems that use compatible labeling schemes, and the DOI specified on the +Smack system must match that of the remote system or packets will be +discarded. The DOI is 3 by default. The value can be read from +/sys/fs/smackfs/doi and can be changed by writing to /sys/fs/smackfs/doi. + +The label and category set are mapped to a Smack label as defined in +/etc/smack/cipso. + +A Smack/CIPSO mapping has the form:: + + smack level [category [category]*] + +Smack does not expect the level or category sets to be related in any +particular way and does not assume or assign accesses based on them. Some +examples of mappings:: + + TopSecret 7 + TS:A,B 7 1 2 + SecBDE 5 2 4 6 + RAFTERS 7 12 26 + +The ":" and "," characters are permitted in a Smack label but have no special +meaning. + +The mapping of Smack labels to CIPSO values is defined by writing to +/sys/fs/smackfs/cipso2. + +In addition to explicit mappings Smack supports direct CIPSO mappings. One +CIPSO level is used to indicate that the category set passed in the packet is +in fact an encoding of the Smack label. The level used is 250 by default. The +value can be read from /sys/fs/smackfs/direct and changed by writing to +/sys/fs/smackfs/direct. + +Socket Attributes +~~~~~~~~~~~~~~~~~ + +There are two attributes that are associated with sockets. These attributes +can only be set by privileged tasks, but any task can read them for their own +sockets. + + SMACK64IPIN: + The Smack label of the task object. A privileged + program that will enforce policy may set this to the star label. + + SMACK64IPOUT: + The Smack label transmitted with outgoing packets. + A privileged program may set this to match the label of another + task with which it hopes to communicate. + +Smack Netlabel Exceptions +~~~~~~~~~~~~~~~~~~~~~~~~~ + +You will often find that your labeled application has to talk to the outside, +unlabeled world. To do this there's a special file /sys/fs/smackfs/netlabel +where you can add some exceptions in the form of:: + + @IP1 LABEL1 or + @IP2/MASK LABEL2 + +It means that your application will have unlabeled access to @IP1 if it has +write access on LABEL1, and access to the subnet @IP2/MASK if it has write +access on LABEL2. + +Entries in the /sys/fs/smackfs/netlabel file are matched by longest mask +first, like in classless IPv4 routing. + +A special label '@' and an option '-CIPSO' can be used there:: + + @ means Internet, any application with any label has access to it + -CIPSO means standard CIPSO networking + +If you don't know what CIPSO is and don't plan to use it, you can just do:: + + echo 127.0.0.1 -CIPSO > /sys/fs/smackfs/netlabel + echo 0.0.0.0/0 @ > /sys/fs/smackfs/netlabel + +If you use CIPSO on your 192.168.0.0/16 local network and need also unlabeled +Internet access, you can have:: + + echo 127.0.0.1 -CIPSO > /sys/fs/smackfs/netlabel + echo 192.168.0.0/16 -CIPSO > /sys/fs/smackfs/netlabel + echo 0.0.0.0/0 @ > /sys/fs/smackfs/netlabel + +Writing Applications for Smack +------------------------------ + +There are three sorts of applications that will run on a Smack system. How an +application interacts with Smack will determine what it will have to do to +work properly under Smack. + +Smack Ignorant Applications +--------------------------- + +By far the majority of applications have no reason whatever to care about the +unique properties of Smack. Since invoking a program has no impact on the +Smack label associated with the process the only concern likely to arise is +whether the process has execute access to the program. + +Smack Relevant Applications +--------------------------- + +Some programs can be improved by teaching them about Smack, but do not make +any security decisions themselves. The utility ls(1) is one example of such a +program. + +Smack Enforcing Applications +---------------------------- + +These are special programs that not only know about Smack, but participate in +the enforcement of system policy. In most cases these are the programs that +set up user sessions. There are also network services that provide information +to processes running with various labels. + +File System Interfaces +---------------------- + +Smack maintains labels on file system objects using extended attributes. The +Smack label of a file, directory, or other file system object can be obtained +using getxattr(2):: + + len = getxattr("/", "security.SMACK64", value, sizeof (value)); + +will put the Smack label of the root directory into value. A privileged +process can set the Smack label of a file system object with setxattr(2):: + + len = strlen("Rubble"); + rc = setxattr("/foo", "security.SMACK64", "Rubble", len, 0); + +will set the Smack label of /foo to "Rubble" if the program has appropriate +privilege. + +Socket Interfaces +----------------- + +The socket attributes can be read using fgetxattr(2). + +A privileged process can set the Smack label of outgoing packets with +fsetxattr(2):: + + len = strlen("Rubble"); + rc = fsetxattr(fd, "security.SMACK64IPOUT", "Rubble", len, 0); + +will set the Smack label "Rubble" on packets going out from the socket if the +program has appropriate privilege:: + + rc = fsetxattr(fd, "security.SMACK64IPIN, "*", strlen("*"), 0); + +will set the Smack label "*" as the object label against which incoming +packets will be checked if the program has appropriate privilege. + +Administration +-------------- + +Smack supports some mount options: + + smackfsdef=label: + specifies the label to give files that lack + the Smack label extended attribute. + + smackfsroot=label: + specifies the label to assign the root of the + file system if it lacks the Smack extended attribute. + + smackfshat=label: + specifies a label that must have read access to + all labels set on the filesystem. Not yet enforced. + + smackfsfloor=label: + specifies a label to which all labels set on the + filesystem must have read access. Not yet enforced. + + smackfstransmute=label: + behaves exactly like smackfsroot except that it also + sets the transmute flag on the root of the mount + +These mount options apply to all file system types. + +Smack auditing +-------------- + +If you want Smack auditing of security events, you need to set CONFIG_AUDIT +in your kernel configuration. +By default, all denied events will be audited. You can change this behavior by +writing a single character to the /sys/fs/smackfs/logging file:: + + 0 : no logging + 1 : log denied (default) + 2 : log accepted + 3 : log denied & accepted + +Events are logged as 'key=value' pairs, for each event you at least will get +the subject, the object, the rights requested, the action, the kernel function +that triggered the event, plus other pairs depending on the type of event +audited. + +Bringup Mode +------------ + +Bringup mode provides logging features that can make application +configuration and system bringup easier. Configure the kernel with +CONFIG_SECURITY_SMACK_BRINGUP to enable these features. When bringup +mode is enabled accesses that succeed due to rules marked with the "b" +access mode will logged. When a new label is introduced for processes +rules can be added aggressively, marked with the "b". The logging allows +tracking of which rules actual get used for that label. + +Another feature of bringup mode is the "unconfined" option. Writing +a label to /sys/fs/smackfs/unconfined makes subjects with that label +able to access any object, and objects with that label accessible to +all subjects. Any access that is granted because a label is unconfined +is logged. This feature is dangerous, as files and directories may +be created in places they couldn't if the policy were being enforced. diff --git a/Documentation/admin-guide/LSM/Yama.rst b/Documentation/admin-guide/LSM/Yama.rst new file mode 100644 index 000000000..d9cd937eb --- /dev/null +++ b/Documentation/admin-guide/LSM/Yama.rst @@ -0,0 +1,75 @@ +==== +Yama +==== + +Yama is a Linux Security Module that collects system-wide DAC security +protections that are not handled by the core kernel itself. This is +selectable at build-time with ``CONFIG_SECURITY_YAMA``, and can be controlled +at run-time through sysctls in ``/proc/sys/kernel/yama``: + +ptrace_scope +============ + +As Linux grows in popularity, it will become a larger target for +malware. One particularly troubling weakness of the Linux process +interfaces is that a single user is able to examine the memory and +running state of any of their processes. For example, if one application +(e.g. Pidgin) was compromised, it would be possible for an attacker to +attach to other running processes (e.g. Firefox, SSH sessions, GPG agent, +etc) to extract additional credentials and continue to expand the scope +of their attack without resorting to user-assisted phishing. + +This is not a theoretical problem. `SSH session hijacking +<https://www.blackhat.com/presentations/bh-usa-05/bh-us-05-boileau.pdf>`_ +and `arbitrary code injection +<https://c-skills.blogspot.com/2007/05/injectso.html>`_ attacks already +exist and remain possible if ptrace is allowed to operate as before. +Since ptrace is not commonly used by non-developers and non-admins, system +builders should be allowed the option to disable this debugging system. + +For a solution, some applications use ``prctl(PR_SET_DUMPABLE, ...)`` to +specifically disallow such ptrace attachment (e.g. ssh-agent), but many +do not. A more general solution is to only allow ptrace directly from a +parent to a child process (i.e. direct "gdb EXE" and "strace EXE" still +work), or with ``CAP_SYS_PTRACE`` (i.e. "gdb --pid=PID", and "strace -p PID" +still work as root). + +In mode 1, software that has defined application-specific relationships +between a debugging process and its inferior (crash handlers, etc), +``prctl(PR_SET_PTRACER, pid, ...)`` can be used. An inferior can declare which +other process (and its descendants) are allowed to call ``PTRACE_ATTACH`` +against it. Only one such declared debugging process can exists for +each inferior at a time. For example, this is used by KDE, Chromium, and +Firefox's crash handlers, and by Wine for allowing only Wine processes +to ptrace each other. If a process wishes to entirely disable these ptrace +restrictions, it can call ``prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, ...)`` +so that any otherwise allowed process (even those in external pid namespaces) +may attach. + +The sysctl settings (writable only with ``CAP_SYS_PTRACE``) are: + +0 - classic ptrace permissions: + a process can ``PTRACE_ATTACH`` to any other + process running under the same uid, as long as it is dumpable (i.e. + did not transition uids, start privileged, or have called + ``prctl(PR_SET_DUMPABLE...)`` already). Similarly, ``PTRACE_TRACEME`` is + unchanged. + +1 - restricted ptrace: + a process must have a predefined relationship + with the inferior it wants to call ``PTRACE_ATTACH`` on. By default, + this relationship is that of only its descendants when the above + classic criteria is also met. To change the relationship, an + inferior can call ``prctl(PR_SET_PTRACER, debugger, ...)`` to declare + an allowed debugger PID to call ``PTRACE_ATTACH`` on the inferior. + Using ``PTRACE_TRACEME`` is unchanged. + +2 - admin-only attach: + only processes with ``CAP_SYS_PTRACE`` may use ptrace, either with + ``PTRACE_ATTACH`` or through children calling ``PTRACE_TRACEME``. + +3 - no attach: + no processes may use ptrace with ``PTRACE_ATTACH`` nor via + ``PTRACE_TRACEME``. Once set, this sysctl value cannot be changed. + +The original children-only logic was based on the restrictions in grsecurity. diff --git a/Documentation/admin-guide/LSM/apparmor.rst b/Documentation/admin-guide/LSM/apparmor.rst new file mode 100644 index 000000000..6cf81bbd7 --- /dev/null +++ b/Documentation/admin-guide/LSM/apparmor.rst @@ -0,0 +1,51 @@ +======== +AppArmor +======== + +What is AppArmor? +================= + +AppArmor is MAC style security extension for the Linux kernel. It implements +a task centered policy, with task "profiles" being created and loaded +from user space. Tasks on the system that do not have a profile defined for +them run in an unconfined state which is equivalent to standard Linux DAC +permissions. + +How to enable/disable +===================== + +set ``CONFIG_SECURITY_APPARMOR=y`` + +If AppArmor should be selected as the default security module then set:: + + CONFIG_DEFAULT_SECURITY="apparmor" + CONFIG_SECURITY_APPARMOR_BOOTPARAM_VALUE=1 + +Build the kernel + +If AppArmor is not the default security module it can be enabled by passing +``security=apparmor`` on the kernel's command line. + +If AppArmor is the default security module it can be disabled by passing +``apparmor=0, security=XXXX`` (where ``XXXX`` is valid security module), on the +kernel's command line. + +For AppArmor to enforce any restrictions beyond standard Linux DAC permissions +policy must be loaded into the kernel from user space (see the Documentation +and tools links). + +Documentation +============= + +Documentation can be found on the wiki, linked below. + +Links +===== + +Mailing List - apparmor@lists.ubuntu.com + +Wiki - http://wiki.apparmor.net + +User space tools - https://gitlab.com/apparmor + +Kernel module - git://git.kernel.org/pub/scm/linux/kernel/git/jj/linux-apparmor diff --git a/Documentation/admin-guide/LSM/index.rst b/Documentation/admin-guide/LSM/index.rst new file mode 100644 index 000000000..a6ba95fba --- /dev/null +++ b/Documentation/admin-guide/LSM/index.rst @@ -0,0 +1,49 @@ +=========================== +Linux Security Module Usage +=========================== + +The Linux Security Module (LSM) framework provides a mechanism for +various security checks to be hooked by new kernel extensions. The name +"module" is a bit of a misnomer since these extensions are not actually +loadable kernel modules. Instead, they are selectable at build-time via +CONFIG_DEFAULT_SECURITY and can be overridden at boot-time via the +``"security=..."`` kernel command line argument, in the case where multiple +LSMs were built into a given kernel. + +The primary users of the LSM interface are Mandatory Access Control +(MAC) extensions which provide a comprehensive security policy. Examples +include SELinux, Smack, Tomoyo, and AppArmor. In addition to the larger +MAC extensions, other extensions can be built using the LSM to provide +specific changes to system operation when these tweaks are not available +in the core functionality of Linux itself. + +The Linux capabilities modules will always be included. This may be +followed by any number of "minor" modules and at most one "major" module. +For more details on capabilities, see ``capabilities(7)`` in the Linux +man-pages project. + +A list of the active security modules can be found by reading +``/sys/kernel/security/lsm``. This is a comma separated list, and +will always include the capability module. The list reflects the +order in which checks are made. The capability module will always +be first, followed by any "minor" modules (e.g. Yama) and then +the one "major" module (e.g. SELinux) if there is one configured. + +Process attributes associated with "major" security modules should +be accessed and maintained using the special files in ``/proc/.../attr``. +A security module may maintain a module specific subdirectory there, +named after the module. ``/proc/.../attr/smack`` is provided by the Smack +security module and contains all its special files. The files directly +in ``/proc/.../attr`` remain as legacy interfaces for modules that provide +subdirectories. + +.. toctree:: + :maxdepth: 1 + + apparmor + LoadPin + SELinux + Smack + tomoyo + Yama + SafeSetID diff --git a/Documentation/admin-guide/LSM/tomoyo.rst b/Documentation/admin-guide/LSM/tomoyo.rst new file mode 100644 index 000000000..4bc9c2b4d --- /dev/null +++ b/Documentation/admin-guide/LSM/tomoyo.rst @@ -0,0 +1,65 @@ +====== +TOMOYO +====== + +What is TOMOYO? +=============== + +TOMOYO is a name-based MAC extension (LSM module) for the Linux kernel. + +LiveCD-based tutorials are available at + +http://tomoyo.sourceforge.jp/1.8/ubuntu12.04-live.html +http://tomoyo.sourceforge.jp/1.8/centos6-live.html + +Though these tutorials use non-LSM version of TOMOYO, they are useful for you +to know what TOMOYO is. + +How to enable TOMOYO? +===================== + +Build the kernel with ``CONFIG_SECURITY_TOMOYO=y`` and pass ``security=tomoyo`` on +kernel's command line. + +Please see http://tomoyo.osdn.jp/2.5/ for details. + +Where is documentation? +======================= + +User <-> Kernel interface documentation is available at +https://tomoyo.osdn.jp/2.5/policy-specification/index.html . + +Materials we prepared for seminars and symposiums are available at +https://osdn.jp/projects/tomoyo/docs/?category_id=532&language_id=1 . +Below lists are chosen from three aspects. + +What is TOMOYO? + TOMOYO Linux Overview + https://osdn.jp/projects/tomoyo/docs/lca2009-takeda.pdf + TOMOYO Linux: pragmatic and manageable security for Linux + https://osdn.jp/projects/tomoyo/docs/freedomhectaipei-tomoyo.pdf + TOMOYO Linux: A Practical Method to Understand and Protect Your Own Linux Box + https://osdn.jp/projects/tomoyo/docs/PacSec2007-en-no-demo.pdf + +What can TOMOYO do? + Deep inside TOMOYO Linux + https://osdn.jp/projects/tomoyo/docs/lca2009-kumaneko.pdf + The role of "pathname based access control" in security. + https://osdn.jp/projects/tomoyo/docs/lfj2008-bof.pdf + +History of TOMOYO? + Realities of Mainlining + https://osdn.jp/projects/tomoyo/docs/lfj2008.pdf + +What is future plan? +==================== + +We believe that inode based security and name based security are complementary +and both should be used together. But unfortunately, so far, we cannot enable +multiple LSM modules at the same time. We feel sorry that you have to give up +SELinux/SMACK/AppArmor etc. when you want to use TOMOYO. + +We hope that LSM becomes stackable in future. Meanwhile, you can use non-LSM +version of TOMOYO, available at http://tomoyo.osdn.jp/1.8/ . +LSM version of TOMOYO is a subset of non-LSM version of TOMOYO. We are planning +to port non-LSM version's functionalities to LSM versions. diff --git a/Documentation/admin-guide/README.rst b/Documentation/admin-guide/README.rst new file mode 100644 index 000000000..9a969c015 --- /dev/null +++ b/Documentation/admin-guide/README.rst @@ -0,0 +1,339 @@ +.. _readme: + +Linux kernel release 6.x <http://kernel.org/> +============================================= + +These are the release notes for Linux version 6. Read them carefully, +as they tell you what this is all about, explain how to install the +kernel, and what to do if something goes wrong. + +What is Linux? +-------------- + + Linux is a clone of the operating system Unix, written from scratch by + Linus Torvalds with assistance from a loosely-knit team of hackers across + the Net. It aims towards POSIX and Single UNIX Specification compliance. + + It has all the features you would expect in a modern fully-fledged Unix, + including true multitasking, virtual memory, shared libraries, demand + loading, shared copy-on-write executables, proper memory management, + and multistack networking including IPv4 and IPv6. + + It is distributed under the GNU General Public License v2 - see the + accompanying COPYING file for more details. + +On what hardware does it run? +----------------------------- + + Although originally developed first for 32-bit x86-based PCs (386 or higher), + today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and + UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell, + IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64 Xtensa, and + ARC architectures. + + Linux is easily portable to most general-purpose 32- or 64-bit architectures + as long as they have a paged memory management unit (PMMU) and a port of the + GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has + also been ported to a number of architectures without a PMMU, although + functionality is then obviously somewhat limited. + Linux has also been ported to itself. You can now run the kernel as a + userspace application - this is called UserMode Linux (UML). + +Documentation +------------- + + - There is a lot of documentation available both in electronic form on + the Internet and in books, both Linux-specific and pertaining to + general UNIX questions. I'd recommend looking into the documentation + subdirectories on any Linux FTP site for the LDP (Linux Documentation + Project) books. This README is not meant to be documentation on the + system: there are much better sources available. + + - There are various README files in the Documentation/ subdirectory: + these typically contain kernel-specific installation notes for some + drivers for example. Please read the + :ref:`Documentation/process/changes.rst <changes>` file, as it + contains information about the problems, which may result by upgrading + your kernel. + +Installing the kernel source +---------------------------- + + - If you install the full sources, put the kernel tarball in a + directory where you have permissions (e.g. your home directory) and + unpack it:: + + xz -cd linux-6.x.tar.xz | tar xvf - + + Replace "X" with the version number of the latest kernel. + + Do NOT use the /usr/src/linux area! This area has a (usually + incomplete) set of kernel headers that are used by the library header + files. They should match the library, and not get messed up by + whatever the kernel-du-jour happens to be. + + - You can also upgrade between 6.x releases by patching. Patches are + distributed in the xz format. To install by patching, get all the + newer patch files, enter the top level directory of the kernel source + (linux-6.x) and execute:: + + xz -cd ../patch-6.x.xz | patch -p1 + + Replace "x" for all versions bigger than the version "x" of your current + source tree, **in_order**, and you should be ok. You may want to remove + the backup files (some-file-name~ or some-file-name.orig), and make sure + that there are no failed patches (some-file-name# or some-file-name.rej). + If there are, either you or I have made a mistake. + + Unlike patches for the 6.x kernels, patches for the 6.x.y kernels + (also known as the -stable kernels) are not incremental but instead apply + directly to the base 6.x kernel. For example, if your base kernel is 6.0 + and you want to apply the 6.0.3 patch, you must not first apply the 6.0.1 + and 6.0.2 patches. Similarly, if you are running kernel version 6.0.2 and + want to jump to 6.0.3, you must first reverse the 6.0.2 patch (that is, + patch -R) **before** applying the 6.0.3 patch. You can read more on this in + :ref:`Documentation/process/applying-patches.rst <applying_patches>`. + + Alternatively, the script patch-kernel can be used to automate this + process. It determines the current kernel version and applies any + patches found:: + + linux/scripts/patch-kernel linux + + The first argument in the command above is the location of the + kernel source. Patches are applied from the current directory, but + an alternative directory can be specified as the second argument. + + - Make sure you have no stale .o files and dependencies lying around:: + + cd linux + make mrproper + + You should now have the sources correctly installed. + +Software requirements +--------------------- + + Compiling and running the 6.x kernels requires up-to-date + versions of various software packages. Consult + :ref:`Documentation/process/changes.rst <changes>` for the minimum version numbers + required and how to get updates for these packages. Beware that using + excessively old versions of these packages can cause indirect + errors that are very difficult to track down, so don't assume that + you can just update packages when obvious problems arise during + build or operation. + +Build directory for the kernel +------------------------------ + + When compiling the kernel, all output files will per default be + stored together with the kernel source code. + Using the option ``make O=output/dir`` allows you to specify an alternate + place for the output files (including .config). + Example:: + + kernel source code: /usr/src/linux-6.x + build directory: /home/name/build/kernel + + To configure and build the kernel, use:: + + cd /usr/src/linux-6.x + make O=/home/name/build/kernel menuconfig + make O=/home/name/build/kernel + sudo make O=/home/name/build/kernel modules_install install + + Please note: If the ``O=output/dir`` option is used, then it must be + used for all invocations of make. + +Configuring the kernel +---------------------- + + Do not skip this step even if you are only upgrading one minor + version. New configuration options are added in each release, and + odd problems will turn up if the configuration files are not set up + as expected. If you want to carry your existing configuration to a + new version with minimal work, use ``make oldconfig``, which will + only ask you for the answers to new questions. + + - Alternative configuration commands are:: + + "make config" Plain text interface. + + "make menuconfig" Text based color menus, radiolists & dialogs. + + "make nconfig" Enhanced text based color menus. + + "make xconfig" Qt based configuration tool. + + "make gconfig" GTK+ based configuration tool. + + "make oldconfig" Default all questions based on the contents of + your existing ./.config file and asking about + new config symbols. + + "make olddefconfig" + Like above, but sets new symbols to their default + values without prompting. + + "make defconfig" Create a ./.config file by using the default + symbol values from either arch/$ARCH/defconfig + or arch/$ARCH/configs/${PLATFORM}_defconfig, + depending on the architecture. + + "make ${PLATFORM}_defconfig" + Create a ./.config file by using the default + symbol values from + arch/$ARCH/configs/${PLATFORM}_defconfig. + Use "make help" to get a list of all available + platforms of your architecture. + + "make allyesconfig" + Create a ./.config file by setting symbol + values to 'y' as much as possible. + + "make allmodconfig" + Create a ./.config file by setting symbol + values to 'm' as much as possible. + + "make allnoconfig" Create a ./.config file by setting symbol + values to 'n' as much as possible. + + "make randconfig" Create a ./.config file by setting symbol + values to random values. + + "make localmodconfig" Create a config based on current config and + loaded modules (lsmod). Disables any module + option that is not needed for the loaded modules. + + To create a localmodconfig for another machine, + store the lsmod of that machine into a file + and pass it in as a LSMOD parameter. + + Also, you can preserve modules in certain folders + or kconfig files by specifying their paths in + parameter LMC_KEEP. + + target$ lsmod > /tmp/mylsmod + target$ scp /tmp/mylsmod host:/tmp + + host$ make LSMOD=/tmp/mylsmod \ + LMC_KEEP="drivers/usb:drivers/gpu:fs" \ + localmodconfig + + The above also works when cross compiling. + + "make localyesconfig" Similar to localmodconfig, except it will convert + all module options to built in (=y) options. You can + also preserve modules by LMC_KEEP. + + "make kvm_guest.config" Enable additional options for kvm guest kernel + support. + + "make xen.config" Enable additional options for xen dom0 guest kernel + support. + + "make tinyconfig" Configure the tiniest possible kernel. + + You can find more information on using the Linux kernel config tools + in Documentation/kbuild/kconfig.rst. + + - NOTES on ``make config``: + + - Having unnecessary drivers will make the kernel bigger, and can + under some circumstances lead to problems: probing for a + nonexistent controller card may confuse your other controllers. + + - A kernel with math-emulation compiled in will still use the + coprocessor if one is present: the math emulation will just + never get used in that case. The kernel will be slightly larger, + but will work on different machines regardless of whether they + have a math coprocessor or not. + + - The "kernel hacking" configuration details usually result in a + bigger or slower kernel (or both), and can even make the kernel + less stable by configuring some routines to actively try to + break bad code to find kernel problems (kmalloc()). Thus you + should probably answer 'n' to the questions for "development", + "experimental", or "debugging" features. + +Compiling the kernel +-------------------- + + - Make sure you have at least gcc 5.1 available. + For more information, refer to :ref:`Documentation/process/changes.rst <changes>`. + + - Do a ``make`` to create a compressed kernel image. It is also + possible to do ``make install`` if you have lilo installed to suit the + kernel makefiles, but you may want to check your particular lilo setup first. + + To do the actual install, you have to be root, but none of the normal + build should require that. Don't take the name of root in vain. + + - If you configured any of the parts of the kernel as ``modules``, you + will also have to do ``make modules_install``. + + - Verbose kernel compile/build output: + + Normally, the kernel build system runs in a fairly quiet mode (but not + totally silent). However, sometimes you or other kernel developers need + to see compile, link, or other commands exactly as they are executed. + For this, use "verbose" build mode. This is done by passing + ``V=1`` to the ``make`` command, e.g.:: + + make V=1 all + + To have the build system also tell the reason for the rebuild of each + target, use ``V=2``. The default is ``V=0``. + + - Keep a backup kernel handy in case something goes wrong. This is + especially true for the development releases, since each new release + contains new code which has not been debugged. Make sure you keep a + backup of the modules corresponding to that kernel, as well. If you + are installing a new kernel with the same version number as your + working kernel, make a backup of your modules directory before you + do a ``make modules_install``. + + Alternatively, before compiling, use the kernel config option + "LOCALVERSION" to append a unique suffix to the regular kernel version. + LOCALVERSION can be set in the "General Setup" menu. + + - In order to boot your new kernel, you'll need to copy the kernel + image (e.g. .../linux/arch/x86/boot/bzImage after compilation) + to the place where your regular bootable kernel is found. + + - Booting a kernel directly from a floppy without the assistance of a + bootloader such as LILO, is no longer supported. + + If you boot Linux from the hard drive, chances are you use LILO, which + uses the kernel image as specified in the file /etc/lilo.conf. The + kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or + /boot/bzImage. To use the new kernel, save a copy of the old image + and copy the new image over the old one. Then, you MUST RERUN LILO + to update the loading map! If you don't, you won't be able to boot + the new kernel image. + + Reinstalling LILO is usually a matter of running /sbin/lilo. + You may wish to edit /etc/lilo.conf to specify an entry for your + old kernel image (say, /vmlinux.old) in case the new one does not + work. See the LILO docs for more information. + + After reinstalling LILO, you should be all set. Shutdown the system, + reboot, and enjoy! + + If you ever need to change the default root device, video mode, + etc. in the kernel image, use your bootloader's boot options + where appropriate. No need to recompile the kernel to change + these parameters. + + - Reboot with the new kernel and enjoy. + +If something goes wrong +----------------------- + +If you have problems that seem to be due to kernel bugs, please follow the +instructions at 'Documentation/admin-guide/reporting-issues.rst'. + +Hints on understanding kernel bug reports are in +'Documentation/admin-guide/bug-hunting.rst'. More on debugging the kernel +with gdb is in 'Documentation/dev-tools/gdb-kernel-debugging.rst' and +'Documentation/dev-tools/kgdb.rst'. diff --git a/Documentation/admin-guide/abi-obsolete.rst b/Documentation/admin-guide/abi-obsolete.rst new file mode 100644 index 000000000..594e697aa --- /dev/null +++ b/Documentation/admin-guide/abi-obsolete.rst @@ -0,0 +1,11 @@ +ABI obsolete symbols +==================== + +Documents interfaces that are still remaining in the kernel, but are +marked to be removed at some later point in time. + +The description of the interface will document the reason why it is +obsolete and when it can be expected to be removed. + +.. kernel-abi:: ABI/obsolete + :rst: diff --git a/Documentation/admin-guide/abi-removed.rst b/Documentation/admin-guide/abi-removed.rst new file mode 100644 index 000000000..f9e000c81 --- /dev/null +++ b/Documentation/admin-guide/abi-removed.rst @@ -0,0 +1,5 @@ +ABI removed symbols +=================== + +.. kernel-abi:: ABI/removed + :rst: diff --git a/Documentation/admin-guide/abi-stable.rst b/Documentation/admin-guide/abi-stable.rst new file mode 100644 index 000000000..fc3361d84 --- /dev/null +++ b/Documentation/admin-guide/abi-stable.rst @@ -0,0 +1,14 @@ +ABI stable symbols +================== + +Documents the interfaces that the developer has defined to be stable. + +Userspace programs are free to use these interfaces with no +restrictions, and backward compatibility for them will be guaranteed +for at least 2 years. + +Most interfaces (like syscalls) are expected to never change and always +be available. + +.. kernel-abi:: ABI/stable + :rst: diff --git a/Documentation/admin-guide/abi-testing.rst b/Documentation/admin-guide/abi-testing.rst new file mode 100644 index 000000000..19767926b --- /dev/null +++ b/Documentation/admin-guide/abi-testing.rst @@ -0,0 +1,20 @@ +ABI testing symbols +=================== + +Documents interfaces that are felt to be stable, +as the main development of this interface has been completed. + +The interface can be changed to add new features, but the +current interface will not break by doing this, unless grave +errors or security problems are found in them. + +Userspace programs can start to rely on these interfaces, but they must +be aware of changes that can occur before these interfaces move to +be marked stable. + +Programs that use these interfaces are strongly encouraged to add their +name to the description of these interfaces, so that the kernel +developers can easily notify them if any changes occur. + +.. kernel-abi:: ABI/testing + :rst: diff --git a/Documentation/admin-guide/abi.rst b/Documentation/admin-guide/abi.rst new file mode 100644 index 000000000..bcab3ef25 --- /dev/null +++ b/Documentation/admin-guide/abi.rst @@ -0,0 +1,11 @@ +===================== +Linux ABI description +===================== + +.. toctree:: + :maxdepth: 2 + + abi-stable + abi-testing + abi-obsolete + abi-removed diff --git a/Documentation/admin-guide/acpi/cppc_sysfs.rst b/Documentation/admin-guide/acpi/cppc_sysfs.rst new file mode 100644 index 000000000..e53d76365 --- /dev/null +++ b/Documentation/admin-guide/acpi/cppc_sysfs.rst @@ -0,0 +1,78 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================================================== +Collaborative Processor Performance Control (CPPC) +================================================== + +.. _cppc_sysfs: + +CPPC +==== + +CPPC defined in the ACPI spec describes a mechanism for the OS to manage the +performance of a logical processor on a contiguous and abstract performance +scale. CPPC exposes a set of registers to describe abstract performance scale, +to request performance levels and to measure per-cpu delivered performance. + +For more details on CPPC please refer to the ACPI specification at: + +http://uefi.org/specifications + +Some of the CPPC registers are exposed via sysfs under:: + + /sys/devices/system/cpu/cpuX/acpi_cppc/ + +for each cpu X:: + + $ ls -lR /sys/devices/system/cpu/cpu0/acpi_cppc/ + /sys/devices/system/cpu/cpu0/acpi_cppc/: + total 0 + -r--r--r-- 1 root root 65536 Mar 5 19:38 feedback_ctrs + -r--r--r-- 1 root root 65536 Mar 5 19:38 highest_perf + -r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_freq + -r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_nonlinear_perf + -r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_perf + -r--r--r-- 1 root root 65536 Mar 5 19:38 nominal_freq + -r--r--r-- 1 root root 65536 Mar 5 19:38 nominal_perf + -r--r--r-- 1 root root 65536 Mar 5 19:38 reference_perf + -r--r--r-- 1 root root 65536 Mar 5 19:38 wraparound_time + +* highest_perf : Highest performance of this processor (abstract scale). +* nominal_perf : Highest sustained performance of this processor + (abstract scale). +* lowest_nonlinear_perf : Lowest performance of this processor with nonlinear + power savings (abstract scale). +* lowest_perf : Lowest performance of this processor (abstract scale). + +* lowest_freq : CPU frequency corresponding to lowest_perf (in MHz). +* nominal_freq : CPU frequency corresponding to nominal_perf (in MHz). + The above frequencies should only be used to report processor performance in + frequency instead of abstract scale. These values should not be used for any + functional decisions. + +* feedback_ctrs : Includes both Reference and delivered performance counter. + Reference counter ticks up proportional to processor's reference performance. + Delivered counter ticks up proportional to processor's delivered performance. +* wraparound_time: Minimum time for the feedback counters to wraparound + (seconds). +* reference_perf : Performance level at which reference performance counter + accumulates (abstract scale). + + +Computing Average Delivered Performance +======================================= + +Below describes the steps to compute the average performance delivered by +taking two different snapshots of feedback counters at time T1 and T2. + + T1: Read feedback_ctrs as fbc_t1 + Wait or run some workload + + T2: Read feedback_ctrs as fbc_t2 + +:: + + delivered_counter_delta = fbc_t2[del] - fbc_t1[del] + reference_counter_delta = fbc_t2[ref] - fbc_t1[ref] + + delivered_perf = (refernce_perf x delivered_counter_delta) / reference_counter_delta diff --git a/Documentation/admin-guide/acpi/fan_performance_states.rst b/Documentation/admin-guide/acpi/fan_performance_states.rst new file mode 100644 index 000000000..b9e4b4d14 --- /dev/null +++ b/Documentation/admin-guide/acpi/fan_performance_states.rst @@ -0,0 +1,90 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=========================== +ACPI Fan Performance States +=========================== + +When the optional _FPS object is present under an ACPI device representing a +fan (for example, PNP0C0B or INT3404), the ACPI fan driver creates additional +"state*" attributes in the sysfs directory of the ACPI device in question. +These attributes list properties of fan performance states. + +For more information on _FPS refer to the ACPI specification at: + +http://uefi.org/specifications + +For instance, the contents of the INT3404 ACPI device sysfs directory +may look as follows:: + + $ ls -l /sys/bus/acpi/devices/INT3404:00/ + total 0 + ... + -r--r--r-- 1 root root 4096 Dec 13 20:38 state0 + -r--r--r-- 1 root root 4096 Dec 13 20:38 state1 + -r--r--r-- 1 root root 4096 Dec 13 20:38 state10 + -r--r--r-- 1 root root 4096 Dec 13 20:38 state11 + -r--r--r-- 1 root root 4096 Dec 13 20:38 state2 + -r--r--r-- 1 root root 4096 Dec 13 20:38 state3 + -r--r--r-- 1 root root 4096 Dec 13 20:38 state4 + -r--r--r-- 1 root root 4096 Dec 13 20:38 state5 + -r--r--r-- 1 root root 4096 Dec 13 20:38 state6 + -r--r--r-- 1 root root 4096 Dec 13 20:38 state7 + -r--r--r-- 1 root root 4096 Dec 13 20:38 state8 + -r--r--r-- 1 root root 4096 Dec 13 20:38 state9 + -r--r--r-- 1 root root 4096 Dec 13 01:00 status + ... + +where each of the "state*" files represents one performance state of the fan +and contains a colon-separated list of 5 integer numbers (fields) with the +following interpretation:: + + control_percent:trip_point_index:speed_rpm:noise_level_mdb:power_mw + +* ``control_percent``: The percent value to be used to set the fan speed to a + specific level using the _FSL object (0-100). + +* ``trip_point_index``: The active cooling trip point number that corresponds + to this performance state (0-9). + +* ``speed_rpm``: Speed of the fan in rotations per minute. + +* ``noise_level_mdb``: Audible noise emitted by the fan in this state in + millidecibels. + +* ``power_mw``: Power draw of the fan in this state in milliwatts. + +For example:: + + $cat /sys/bus/acpi/devices/INT3404:00/state1 + 25:0:3200:12500:1250 + +When a given field is not populated or its value provided by the platform +firmware is invalid, the "not-defined" string is shown instead of the value. + +ACPI Fan Fine Grain Control +============================= + +When _FIF object specifies support for fine grain control, then fan speed +can be set from 0 to 100% with the recommended minimum "step size" via +_FSL object. User can adjust fan speed using thermal sysfs cooling device. + +Here use can look at fan performance states for a reference speed (speed_rpm) +and set it by changing cooling device cur_state. If the fine grain control +is supported then user can also adjust to some other speeds which are +not defined in the performance states. + +The support of fine grain control is presented via sysfs attribute +"fine_grain_control". If fine grain control is present, this attribute +will show "1" otherwise "0". + +This sysfs attribute is presented in the same directory as performance states. + +ACPI Fan Performance Feedback +============================= + +The optional _FST object provides status information for the fan device. +This includes field to provide current fan speed in revolutions per minute +at which the fan is rotating. + +This speed is presented in the sysfs using the attribute "fan_speed_rpm", +in the same directory as performance states. diff --git a/Documentation/admin-guide/acpi/index.rst b/Documentation/admin-guide/acpi/index.rst new file mode 100644 index 000000000..b078fdb8f --- /dev/null +++ b/Documentation/admin-guide/acpi/index.rst @@ -0,0 +1,14 @@ +============ +ACPI Support +============ + +Here we document in detail how to interact with various mechanisms in +the Linux ACPI support. + +.. toctree:: + :maxdepth: 1 + + initrd_table_override + ssdt-overlays + cppc_sysfs + fan_performance_states diff --git a/Documentation/admin-guide/acpi/initrd_table_override.rst b/Documentation/admin-guide/acpi/initrd_table_override.rst new file mode 100644 index 000000000..bb24fa6b5 --- /dev/null +++ b/Documentation/admin-guide/acpi/initrd_table_override.rst @@ -0,0 +1,115 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================================ +Upgrading ACPI tables via initrd +================================ + +What is this about +================== + +If the ACPI_TABLE_UPGRADE compile option is true, it is possible to +upgrade the ACPI execution environment that is defined by the ACPI tables +via upgrading the ACPI tables provided by the BIOS with an instrumented, +modified, more recent version one, or installing brand new ACPI tables. + +When building initrd with kernel in a single image, option +ACPI_TABLE_OVERRIDE_VIA_BUILTIN_INITRD should also be true for this +feature to work. + +For a full list of ACPI tables that can be upgraded/installed, take a look +at the char `*table_sigs[MAX_ACPI_SIGNATURE];` definition in +drivers/acpi/tables.c. + +All ACPI tables iasl (Intel's ACPI compiler and disassembler) knows should +be overridable, except: + + - ACPI_SIG_RSDP (has a signature of 6 bytes) + - ACPI_SIG_FACS (does not have an ordinary ACPI table header) + +Both could get implemented as well. + + +What is this for +================ + +Complain to your platform/BIOS vendor if you find a bug which is so severe +that a workaround is not accepted in the Linux kernel. And this facility +allows you to upgrade the buggy tables before your platform/BIOS vendor +releases an upgraded BIOS binary. + +This facility can be used by platform/BIOS vendors to provide a Linux +compatible environment without modifying the underlying platform firmware. + +This facility also provides a powerful feature to easily debug and test +ACPI BIOS table compatibility with the Linux kernel by modifying old +platform provided ACPI tables or inserting new ACPI tables. + +It can and should be enabled in any kernel because there is no functional +change with not instrumented initrds. + + +How does it work +================ +:: + + # Extract the machine's ACPI tables: + cd /tmp + acpidump >acpidump + acpixtract -a acpidump + # Disassemble, modify and recompile them: + iasl -d *.dat + # For example add this statement into a _PRT (PCI Routing Table) function + # of the DSDT: + Store("HELLO WORLD", debug) + # And increase the OEM Revision. For example, before modification: + DefinitionBlock ("DSDT.aml", "DSDT", 2, "INTEL ", "TEMPLATE", 0x00000000) + # After modification: + DefinitionBlock ("DSDT.aml", "DSDT", 2, "INTEL ", "TEMPLATE", 0x00000001) + iasl -sa dsdt.dsl + # Add the raw ACPI tables to an uncompressed cpio archive. + # They must be put into a /kernel/firmware/acpi directory inside the cpio + # archive. Note that if the table put here matches a platform table + # (similar Table Signature, and similar OEMID, and similar OEM Table ID) + # with a more recent OEM Revision, the platform table will be upgraded by + # this table. If the table put here doesn't match a platform table + # (dissimilar Table Signature, or dissimilar OEMID, or dissimilar OEM Table + # ID), this table will be appended. + mkdir -p kernel/firmware/acpi + cp dsdt.aml kernel/firmware/acpi + # A maximum of "NR_ACPI_INITRD_TABLES (64)" tables are currently allowed + # (see osl.c): + iasl -sa facp.dsl + iasl -sa ssdt1.dsl + cp facp.aml kernel/firmware/acpi + cp ssdt1.aml kernel/firmware/acpi + # The uncompressed cpio archive must be the first. Other, typically + # compressed cpio archives, must be concatenated on top of the uncompressed + # one. Following command creates the uncompressed cpio archive and + # concatenates the original initrd on top: + find kernel | cpio -H newc --create > /boot/instrumented_initrd + cat /boot/initrd >>/boot/instrumented_initrd + # reboot with increased acpi debug level, e.g. boot params: + acpi.debug_level=0x2 acpi.debug_layer=0xFFFFFFFF + # and check your syslog: + [ 1.268089] ACPI: PCI Interrupt Routing Table [\_SB_.PCI0._PRT] + [ 1.272091] [ACPI Debug] String [0x0B] "HELLO WORLD" + +iasl is able to disassemble and recompile quite a lot different, +also static ACPI tables. + + +Where to retrieve userspace tools +================================= + +iasl and acpixtract are part of Intel's ACPICA project: +https://acpica.org/ + +and should be packaged by distributions (for example in the acpica package +on SUSE). + +acpidump can be found in Len Browns pmtools: +ftp://kernel.org/pub/linux/kernel/people/lenb/acpi/utils/pmtools/acpidump + +This tool is also part of the acpica package on SUSE. +Alternatively, used ACPI tables can be retrieved via sysfs in latest kernels: +/sys/firmware/acpi/tables diff --git a/Documentation/admin-guide/acpi/ssdt-overlays.rst b/Documentation/admin-guide/acpi/ssdt-overlays.rst new file mode 100644 index 000000000..5ea9f4a3b --- /dev/null +++ b/Documentation/admin-guide/acpi/ssdt-overlays.rst @@ -0,0 +1,181 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============= +SSDT Overlays +============= + +In order to support ACPI open-ended hardware configurations (e.g. development +boards) we need a way to augment the ACPI configuration provided by the firmware +image. A common example is connecting sensors on I2C / SPI buses on development +boards. + +Although this can be accomplished by creating a kernel platform driver or +recompiling the firmware image with updated ACPI tables, neither is practical: +the former proliferates board specific kernel code while the latter requires +access to firmware tools which are often not publicly available. + +Because ACPI supports external references in AML code a more practical +way to augment firmware ACPI configuration is by dynamically loading +user defined SSDT tables that contain the board specific information. + +For example, to enumerate a Bosch BMA222E accelerometer on the I2C bus of the +Minnowboard MAX development board exposed via the LSE connector [1], the +following ASL code can be used:: + + DefinitionBlock ("minnowmax.aml", "SSDT", 1, "Vendor", "Accel", 0x00000003) + { + External (\_SB.I2C6, DeviceObj) + + Scope (\_SB.I2C6) + { + Device (STAC) + { + Name (_HID, "BMA222E") + Name (RBUF, ResourceTemplate () + { + I2cSerialBus (0x0018, ControllerInitiated, 0x00061A80, + AddressingMode7Bit, "\\_SB.I2C6", 0x00, + ResourceConsumer, ,) + GpioInt (Edge, ActiveHigh, Exclusive, PullDown, 0x0000, + "\\_SB.GPO2", 0x00, ResourceConsumer, , ) + { // Pin list + 0 + } + }) + + Method (_CRS, 0, Serialized) + { + Return (RBUF) + } + } + } + } + +which can then be compiled to AML binary format:: + + $ iasl minnowmax.asl + + Intel ACPI Component Architecture + ASL Optimizing Compiler version 20140214-64 [Mar 29 2014] + Copyright (c) 2000 - 2014 Intel Corporation + + ASL Input: minnomax.asl - 30 lines, 614 bytes, 7 keywords + AML Output: minnowmax.aml - 165 bytes, 6 named objects, 1 executable opcodes + +[1] https://www.elinux.org/Minnowboard:MinnowMax#Low_Speed_Expansion_.28Top.29 + +The resulting AML code can then be loaded by the kernel using one of the methods +below. + +Loading ACPI SSDTs from initrd +============================== + +This option allows loading of user defined SSDTs from initrd and it is useful +when the system does not support EFI or when there is not enough EFI storage. + +It works in a similar way with initrd based ACPI tables override/upgrade: SSDT +AML code must be placed in the first, uncompressed, initrd under the +"kernel/firmware/acpi" path. Multiple files can be used and this will translate +in loading multiple tables. Only SSDT and OEM tables are allowed. See +initrd_table_override.txt for more details. + +Here is an example:: + + # Add the raw ACPI tables to an uncompressed cpio archive. + # They must be put into a /kernel/firmware/acpi directory inside the + # cpio archive. + # The uncompressed cpio archive must be the first. + # Other, typically compressed cpio archives, must be + # concatenated on top of the uncompressed one. + mkdir -p kernel/firmware/acpi + cp ssdt.aml kernel/firmware/acpi + + # Create the uncompressed cpio archive and concatenate the original initrd + # on top: + find kernel | cpio -H newc --create > /boot/instrumented_initrd + cat /boot/initrd >>/boot/instrumented_initrd + +Loading ACPI SSDTs from EFI variables +===================================== + +This is the preferred method, when EFI is supported on the platform, because it +allows a persistent, OS independent way of storing the user defined SSDTs. There +is also work underway to implement EFI support for loading user defined SSDTs +and using this method will make it easier to convert to the EFI loading +mechanism when that will arrive. To enable it, the +CONFIG_EFI_CUSTOM_SSDT_OVERLAYS should be chosen to y. + +In order to load SSDTs from an EFI variable the ``"efivar_ssdt=..."`` kernel +command line parameter can be used (the name has a limitation of 16 characters). +The argument for the option is the variable name to use. If there are multiple +variables with the same name but with different vendor GUIDs, all of them will +be loaded. + +In order to store the AML code in an EFI variable the efivarfs filesystem can be +used. It is enabled and mounted by default in /sys/firmware/efi/efivars in all +recent distribution. + +Creating a new file in /sys/firmware/efi/efivars will automatically create a new +EFI variable. Updating a file in /sys/firmware/efi/efivars will update the EFI +variable. Please note that the file name needs to be specially formatted as +"Name-GUID" and that the first 4 bytes in the file (little-endian format) +represent the attributes of the EFI variable (see EFI_VARIABLE_MASK in +include/linux/efi.h). Writing to the file must also be done with one write +operation. + +For example, you can use the following bash script to create/update an EFI +variable with the content from a given file:: + + #!/bin/sh -e + + while [ -n "$1" ]; do + case "$1" in + "-f") filename="$2"; shift;; + "-g") guid="$2"; shift;; + *) name="$1";; + esac + shift + done + + usage() + { + echo "Syntax: ${0##*/} -f filename [ -g guid ] name" + exit 1 + } + + [ -n "$name" -a -f "$filename" ] || usage + + EFIVARFS="/sys/firmware/efi/efivars" + + [ -d "$EFIVARFS" ] || exit 2 + + if stat -tf $EFIVARFS | grep -q -v de5e81e4; then + mount -t efivarfs none $EFIVARFS + fi + + # try to pick up an existing GUID + [ -n "$guid" ] || guid=$(find "$EFIVARFS" -name "$name-*" | head -n1 | cut -f2- -d-) + + # use a randomly generated GUID + [ -n "$guid" ] || guid="$(cat /proc/sys/kernel/random/uuid)" + + # efivarfs expects all of the data in one write + tmp=$(mktemp) + /bin/echo -ne "\007\000\000\000" | cat - $filename > $tmp + dd if=$tmp of="$EFIVARFS/$name-$guid" bs=$(stat -c %s $tmp) + rm $tmp + +Loading ACPI SSDTs from configfs +================================ + +This option allows loading of user defined SSDTs from user space via the configfs +interface. The CONFIG_ACPI_CONFIGFS option must be select and configfs must be +mounted. In the following examples, we assume that configfs has been mounted in +/sys/kernel/config. + +New tables can be loading by creating new directories in /sys/kernel/config/acpi/table +and writing the SSDT AML code in the aml attribute:: + + cd /sys/kernel/config/acpi/table + mkdir my_ssdt + cat ~/ssdt.aml > my_ssdt/aml diff --git a/Documentation/admin-guide/aoe/aoe.rst b/Documentation/admin-guide/aoe/aoe.rst new file mode 100644 index 000000000..a05e75136 --- /dev/null +++ b/Documentation/admin-guide/aoe/aoe.rst @@ -0,0 +1,150 @@ +Introduction +============ + +ATA over Ethernet is a network protocol that provides simple access to +block storage on the LAN. + + http://support.coraid.com/documents/AoEr11.txt + +The EtherDrive (R) HOWTO for 2.6 and 3.x kernels is found at ... + + http://support.coraid.com/support/linux/EtherDrive-2.6-HOWTO.html + +It has many tips and hints! Please see, especially, recommended +tunings for virtual memory: + + http://support.coraid.com/support/linux/EtherDrive-2.6-HOWTO-5.html#ss5.19 + +The aoetools are userland programs that are designed to work with this +driver. The aoetools are on sourceforge. + + http://aoetools.sourceforge.net/ + +The scripts in this Documentation/admin-guide/aoe directory are intended to +document the use of the driver and are not necessary if you install +the aoetools. + + +Creating Device Nodes +===================== + + Users of udev should find the block device nodes created + automatically, but to create all the necessary device nodes, use the + udev configuration rules provided in udev.txt (in this directory). + + There is a udev-install.sh script that shows how to install these + rules on your system. + + There is also an autoload script that shows how to edit + /etc/modprobe.d/aoe.conf to ensure that the aoe module is loaded when + necessary. Preloading the aoe module is preferable to autoloading, + however, because AoE discovery takes a few seconds. It can be + confusing when an AoE device is not present the first time the a + command is run but appears a second later. + +Using Device Nodes +================== + + "cat /dev/etherd/err" blocks, waiting for error diagnostic output, + like any retransmitted packets. + + "echo eth2 eth4 > /dev/etherd/interfaces" tells the aoe driver to + limit ATA over Ethernet traffic to eth2 and eth4. AoE traffic from + untrusted networks should be ignored as a matter of security. See + also the aoe_iflist driver option described below. + + "echo > /dev/etherd/discover" tells the driver to find out what AoE + devices are available. + + In the future these character devices may disappear and be replaced + by sysfs counterparts. Using the commands in aoetools insulates + users from these implementation details. + + The block devices are named like this:: + + e{shelf}.{slot} + e{shelf}.{slot}p{part} + + ... so that "e0.2" is the third blade from the left (slot 2) in the + first shelf (shelf address zero). That's the whole disk. The first + partition on that disk would be "e0.2p1". + +Using sysfs +=========== + + Each aoe block device in /sys/block has the extra attributes of + state, mac, and netif. The state attribute is "up" when the device + is ready for I/O and "down" if detected but unusable. The + "down,closewait" state shows that the device is still open and + cannot come up again until it has been closed. + + The mac attribute is the ethernet address of the remote AoE device. + The netif attribute is the network interface on the localhost + through which we are communicating with the remote AoE device. + + There is a script in this directory that formats this information in + a convenient way. Users with aoetools should use the aoe-stat + command:: + + root@makki root# sh Documentation/admin-guide/aoe/status.sh + e10.0 eth3 up + e10.1 eth3 up + e10.2 eth3 up + e10.3 eth3 up + e10.4 eth3 up + e10.5 eth3 up + e10.6 eth3 up + e10.7 eth3 up + e10.8 eth3 up + e10.9 eth3 up + e4.0 eth1 up + e4.1 eth1 up + e4.2 eth1 up + e4.3 eth1 up + e4.4 eth1 up + e4.5 eth1 up + e4.6 eth1 up + e4.7 eth1 up + e4.8 eth1 up + e4.9 eth1 up + + Use /sys/module/aoe/parameters/aoe_iflist (or better, the driver + option discussed below) instead of /dev/etherd/interfaces to limit + AoE traffic to the network interfaces in the given + whitespace-separated list. Unlike the old character device, the + sysfs entry can be read from as well as written to. + + It's helpful to trigger discovery after setting the list of allowed + interfaces. The aoetools package provides an aoe-discover script + for this purpose. You can also directly use the + /dev/etherd/discover special file described above. + +Driver Options +============== + + There is a boot option for the built-in aoe driver and a + corresponding module parameter, aoe_iflist. Without this option, + all network interfaces may be used for ATA over Ethernet. Here is a + usage example for the module parameter:: + + modprobe aoe_iflist="eth1 eth3" + + The aoe_deadsecs module parameter determines the maximum number of + seconds that the driver will wait for an AoE device to provide a + response to an AoE command. After aoe_deadsecs seconds have + elapsed, the AoE device will be marked as "down". A value of zero + is supported for testing purposes and makes the aoe driver keep + trying AoE commands forever. + + The aoe_maxout module parameter has a default of 128. This is the + maximum number of unresponded packets that will be sent to an AoE + target at one time. + + The aoe_dyndevs module parameter defaults to 1, meaning that the + driver will assign a block device minor number to a discovered AoE + target based on the order of its discovery. With dynamic minor + device numbers in use, a greater range of AoE shelf and slot + addresses can be supported. Users with udev will never have to + think about minor numbers. Using aoe_dyndevs=0 allows device nodes + to be pre-created using a static minor-number scheme with the + aoe-mkshelf script in the aoetools. diff --git a/Documentation/admin-guide/aoe/autoload.sh b/Documentation/admin-guide/aoe/autoload.sh new file mode 100644 index 000000000..815dff469 --- /dev/null +++ b/Documentation/admin-guide/aoe/autoload.sh @@ -0,0 +1,17 @@ +#!/bin/sh +# set aoe to autoload by installing the +# aliases in /etc/modprobe.d/ + +f=/etc/modprobe.d/aoe.conf + +if test ! -r $f || test ! -w $f; then + echo "cannot configure $f for module autoloading" 1>&2 + exit 1 +fi + +grep major-152 $f >/dev/null +if [ $? = 1 ]; then + echo alias block-major-152 aoe >> $f + echo alias char-major-152 aoe >> $f +fi + diff --git a/Documentation/admin-guide/aoe/examples.rst b/Documentation/admin-guide/aoe/examples.rst new file mode 100644 index 000000000..91f3198e5 --- /dev/null +++ b/Documentation/admin-guide/aoe/examples.rst @@ -0,0 +1,23 @@ +Example of udev rules +--------------------- + + .. include:: udev.txt + :literal: + +Example of udev install rules script +------------------------------------ + + .. literalinclude:: udev-install.sh + :language: shell + +Example script to get status +---------------------------- + + .. literalinclude:: status.sh + :language: shell + +Example of AoE autoload script +------------------------------ + + .. literalinclude:: autoload.sh + :language: shell diff --git a/Documentation/admin-guide/aoe/index.rst b/Documentation/admin-guide/aoe/index.rst new file mode 100644 index 000000000..d71c5df15 --- /dev/null +++ b/Documentation/admin-guide/aoe/index.rst @@ -0,0 +1,17 @@ +======================= +ATA over Ethernet (AoE) +======================= + +.. toctree:: + :maxdepth: 1 + + aoe + todo + examples + +.. only:: subproject and html + + Indices + ======= + + * :ref:`genindex` diff --git a/Documentation/admin-guide/aoe/status.sh b/Documentation/admin-guide/aoe/status.sh new file mode 100644 index 000000000..eeec7baae --- /dev/null +++ b/Documentation/admin-guide/aoe/status.sh @@ -0,0 +1,30 @@ +#! /bin/sh +# collate and present sysfs information about AoE storage +# +# A more complete version of this script is aoe-stat, in the +# aoetools. + +set -e +format="%8s\t%8s\t%8s\n" +me=`basename $0` +sysd=${sysfs_dir:-/sys} + +# printf "$format" device mac netif state + +# Suse 9.1 Pro doesn't put /sys in /etc/mtab +#test -z "`mount | grep sysfs`" && { +test ! -d "$sysd/block" && { + echo "$me Error: sysfs is not mounted" 1>&2 + exit 1 +} + +for d in `ls -d $sysd/block/etherd* 2>/dev/null | grep -v p` end; do + # maybe ls comes up empty, so we use "end" + test $d = end && continue + + dev=`echo "$d" | sed 's/.*!//'` + printf "$format" \ + "$dev" \ + "`cat \"$d/netif\"`" \ + "`cat \"$d/state\"`" +done | sort diff --git a/Documentation/admin-guide/aoe/todo.rst b/Documentation/admin-guide/aoe/todo.rst new file mode 100644 index 000000000..dea8db5a3 --- /dev/null +++ b/Documentation/admin-guide/aoe/todo.rst @@ -0,0 +1,17 @@ +TODO +==== + +There is a potential for deadlock when allocating a struct sk_buff for +data that needs to be written out to aoe storage. If the data is +being written from a dirty page in order to free that page, and if +there are no other pages available, then deadlock may occur when a +free page is needed for the sk_buff allocation. This situation has +not been observed, but it would be nice to eliminate any potential for +deadlock under memory pressure. + +Because ATA over Ethernet is not fragmented by the kernel's IP code, +the destructor member of the struct sk_buff is available to the aoe +driver. By using a mempool for allocating all but the first few +sk_buffs, and by registering a destructor, we should be able to +efficiently allocate sk_buffs without introducing any potential for +deadlock. diff --git a/Documentation/admin-guide/aoe/udev-install.sh b/Documentation/admin-guide/aoe/udev-install.sh new file mode 100644 index 000000000..15e86f58c --- /dev/null +++ b/Documentation/admin-guide/aoe/udev-install.sh @@ -0,0 +1,33 @@ +# install the aoe-specific udev rules from udev.txt into +# the system's udev configuration +# + +me="`basename $0`" + +# find udev.conf, often /etc/udev/udev.conf +# (or environment can specify where to find udev.conf) +# +if test -z "$conf"; then + if test -r /etc/udev/udev.conf; then + conf=/etc/udev/udev.conf + else + conf="`find /etc -type f -name udev.conf 2> /dev/null`" + if test -z "$conf" || test ! -r "$conf"; then + echo "$me Error: no udev.conf found" 1>&2 + exit 1 + fi + fi +fi + +# find the directory where udev rules are stored, often +# /etc/udev/rules.d +# +rules_d="`sed -n '/^udev_rules=/{ s!udev_rules=!!; s!\"!!g; p; }' $conf`" +if test -z "$rules_d" ; then + rules_d=/etc/udev/rules.d +fi +if test ! -d "$rules_d"; then + echo "$me Error: cannot find udev rules directory" 1>&2 + exit 1 +fi +sh -xc "cp `dirname $0`/udev.txt $rules_d/60-aoe.rules" diff --git a/Documentation/admin-guide/aoe/udev.txt b/Documentation/admin-guide/aoe/udev.txt new file mode 100644 index 000000000..5fb756466 --- /dev/null +++ b/Documentation/admin-guide/aoe/udev.txt @@ -0,0 +1,26 @@ +# These rules tell udev what device nodes to create for aoe support. +# They may be installed along the following lines. Check the section +# 8 udev manpage to see whether your udev supports SUBSYSTEM, and +# whether it uses one or two equal signs for SUBSYSTEM and KERNEL. +# +# ecashin@makki ~$ su +# Password: +# bash# find /etc -type f -name udev.conf +# /etc/udev/udev.conf +# bash# grep udev_rules= /etc/udev/udev.conf +# udev_rules="/etc/udev/rules.d/" +# bash# ls /etc/udev/rules.d/ +# 10-wacom.rules 50-udev.rules +# bash# cp /path/to/linux/Documentation/admin-guide/aoe/udev.txt \ +# /etc/udev/rules.d/60-aoe.rules +# + +# aoe char devices +SUBSYSTEM=="aoe", KERNEL=="discover", NAME="etherd/%k", GROUP="disk", MODE="0220" +SUBSYSTEM=="aoe", KERNEL=="err", NAME="etherd/%k", GROUP="disk", MODE="0440" +SUBSYSTEM=="aoe", KERNEL=="interfaces", NAME="etherd/%k", GROUP="disk", MODE="0220" +SUBSYSTEM=="aoe", KERNEL=="revalidate", NAME="etherd/%k", GROUP="disk", MODE="0220" +SUBSYSTEM=="aoe", KERNEL=="flush", NAME="etherd/%k", GROUP="disk", MODE="0220" + +# aoe block devices +KERNEL=="etherd*", GROUP="disk" diff --git a/Documentation/admin-guide/auxdisplay/cfag12864b.rst b/Documentation/admin-guide/auxdisplay/cfag12864b.rst new file mode 100644 index 000000000..da385d851 --- /dev/null +++ b/Documentation/admin-guide/auxdisplay/cfag12864b.rst @@ -0,0 +1,98 @@ +=================================== +cfag12864b LCD Driver Documentation +=================================== + +:License: GPLv2 +:Author & Maintainer: Miguel Ojeda <ojeda@kernel.org> +:Date: 2006-10-27 + + + +.. INDEX + + 1. DRIVER INFORMATION + 2. DEVICE INFORMATION + 3. WIRING + 4. USERSPACE PROGRAMMING + +1. Driver Information +--------------------- + +This driver supports a cfag12864b LCD. + + +2. Device Information +--------------------- + +:Manufacturer: Crystalfontz +:Device Name: Crystalfontz 12864b LCD Series +:Device Code: cfag12864b +:Webpage: http://www.crystalfontz.com +:Device Webpage: http://www.crystalfontz.com/products/12864b/ +:Type: LCD (Liquid Crystal Display) +:Width: 128 +:Height: 64 +:Colors: 2 (B/N) +:Controller: ks0108 +:Controllers: 2 +:Pages: 8 each controller +:Addresses: 64 each page +:Data size: 1 byte each address +:Memory size: 2 * 8 * 64 * 1 = 1024 bytes = 1 Kbyte + + +3. Wiring +--------- + +The cfag12864b LCD Series don't have official wiring. + +The common wiring is done to the parallel port as shown:: + + Parallel Port cfag12864b + + Name Pin# Pin# Name + + Strobe ( 1)------------------------------(17) Enable + Data 0 ( 2)------------------------------( 4) Data 0 + Data 1 ( 3)------------------------------( 5) Data 1 + Data 2 ( 4)------------------------------( 6) Data 2 + Data 3 ( 5)------------------------------( 7) Data 3 + Data 4 ( 6)------------------------------( 8) Data 4 + Data 5 ( 7)------------------------------( 9) Data 5 + Data 6 ( 8)------------------------------(10) Data 6 + Data 7 ( 9)------------------------------(11) Data 7 + (10) [+5v]---( 1) Vdd + (11) [GND]---( 2) Ground + (12) [+5v]---(14) Reset + (13) [GND]---(15) Read / Write + Line (14)------------------------------(13) Controller Select 1 + (15) + Init (16)------------------------------(12) Controller Select 2 + Select (17)------------------------------(16) Data / Instruction + Ground (18)---[GND] [+5v]---(19) LED + + Ground (19)---[GND] + Ground (20)---[GND] E A Values: + Ground (21)---[GND] [GND]---[P1]---(18) Vee - R = Resistor = 22 ohm + Ground (22)---[GND] | - P1 = Preset = 10 Kohm + Ground (23)---[GND] ---- S ------( 3) V0 - P2 = Preset = 1 Kohm + Ground (24)---[GND] | | + Ground (25)---[GND] [GND]---[P2]---[R]---(20) LED - + + +4. Userspace Programming +------------------------ + +The cfag12864bfb describes a framebuffer device (/dev/fbX). + +It has a size of 1024 bytes = 1 Kbyte. +Each bit represents one pixel. If the bit is high, the pixel will +turn on. If the pixel is low, the pixel will turn off. + +You can use the framebuffer as a file: fopen, fwrite, fclose... +Although the LCD won't get updated until the next refresh time arrives. + +Also, you can mmap the framebuffer: open & mmap, munmap & close... +which is the best option for most uses. + +Check samples/auxdisplay/cfag12864b-example.c +for a real working userspace complete program with usage examples. diff --git a/Documentation/admin-guide/auxdisplay/index.rst b/Documentation/admin-guide/auxdisplay/index.rst new file mode 100644 index 000000000..e466f0595 --- /dev/null +++ b/Documentation/admin-guide/auxdisplay/index.rst @@ -0,0 +1,16 @@ +========================= +Auxiliary Display Support +========================= + +.. toctree:: + :maxdepth: 1 + + ks0108.rst + cfag12864b.rst + +.. only:: subproject and html + + Indices + ======= + + * :ref:`genindex` diff --git a/Documentation/admin-guide/auxdisplay/ks0108.rst b/Documentation/admin-guide/auxdisplay/ks0108.rst new file mode 100644 index 000000000..a7d3fe509 --- /dev/null +++ b/Documentation/admin-guide/auxdisplay/ks0108.rst @@ -0,0 +1,50 @@ +========================================== +ks0108 LCD Controller Driver Documentation +========================================== + +:License: GPLv2 +:Author & Maintainer: Miguel Ojeda <ojeda@kernel.org> +:Date: 2006-10-27 + + + +.. INDEX + + 1. DRIVER INFORMATION + 2. DEVICE INFORMATION + 3. WIRING + + +1. Driver Information +--------------------- + +This driver supports the ks0108 LCD controller. + + +2. Device Information +--------------------- + +:Manufacturer: Samsung +:Device Name: KS0108 LCD Controller +:Device Code: ks0108 +:Webpage: - +:Device Webpage: - +:Type: LCD Controller (Liquid Crystal Display Controller) +:Width: 64 +:Height: 64 +:Colors: 2 (B/N) +:Pages: 8 +:Addresses: 64 each page +:Data size: 1 byte each address +:Memory size: 8 * 64 * 1 = 512 bytes + + +3. Wiring +--------- + +The driver supports data parallel port wiring. + +If you aren't building LCD related hardware, you should check +your LCD specific wiring information in the same folder. + +For example, check Documentation/admin-guide/auxdisplay/cfag12864b.rst diff --git a/Documentation/admin-guide/bcache.rst b/Documentation/admin-guide/bcache.rst new file mode 100644 index 000000000..6fdb495ac --- /dev/null +++ b/Documentation/admin-guide/bcache.rst @@ -0,0 +1,653 @@ +============================ +A block layer cache (bcache) +============================ + +Say you've got a big slow raid 6, and an ssd or three. Wouldn't it be +nice if you could use them as cache... Hence bcache. + +The bcache wiki can be found at: + https://bcache.evilpiepirate.org + +This is the git repository of bcache-tools: + https://git.kernel.org/pub/scm/linux/kernel/git/colyli/bcache-tools.git/ + +The latest bcache kernel code can be found from mainline Linux kernel: + https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/ + +It's designed around the performance characteristics of SSDs - it only allocates +in erase block sized buckets, and it uses a hybrid btree/log to track cached +extents (which can be anywhere from a single sector to the bucket size). It's +designed to avoid random writes at all costs; it fills up an erase block +sequentially, then issues a discard before reusing it. + +Both writethrough and writeback caching are supported. Writeback defaults to +off, but can be switched on and off arbitrarily at runtime. Bcache goes to +great lengths to protect your data - it reliably handles unclean shutdown. (It +doesn't even have a notion of a clean shutdown; bcache simply doesn't return +writes as completed until they're on stable storage). + +Writeback caching can use most of the cache for buffering writes - writing +dirty data to the backing device is always done sequentially, scanning from the +start to the end of the index. + +Since random IO is what SSDs excel at, there generally won't be much benefit +to caching large sequential IO. Bcache detects sequential IO and skips it; +it also keeps a rolling average of the IO sizes per task, and as long as the +average is above the cutoff it will skip all IO from that task - instead of +caching the first 512k after every seek. Backups and large file copies should +thus entirely bypass the cache. + +In the event of a data IO error on the flash it will try to recover by reading +from disk or invalidating cache entries. For unrecoverable errors (meta data +or dirty data), caching is automatically disabled; if dirty data was present +in the cache it first disables writeback caching and waits for all dirty data +to be flushed. + +Getting started: +You'll need bcache util from the bcache-tools repository. Both the cache device +and backing device must be formatted before use:: + + bcache make -B /dev/sdb + bcache make -C /dev/sdc + +`bcache make` has the ability to format multiple devices at the same time - if +you format your backing devices and cache device at the same time, you won't +have to manually attach:: + + bcache make -B /dev/sda /dev/sdb -C /dev/sdc + +If your bcache-tools is not updated to latest version and does not have the +unified `bcache` utility, you may use the legacy `make-bcache` utility to format +bcache device with same -B and -C parameters. + +bcache-tools now ships udev rules, and bcache devices are known to the kernel +immediately. Without udev, you can manually register devices like this:: + + echo /dev/sdb > /sys/fs/bcache/register + echo /dev/sdc > /sys/fs/bcache/register + +Registering the backing device makes the bcache device show up in /dev; you can +now format it and use it as normal. But the first time using a new bcache +device, it'll be running in passthrough mode until you attach it to a cache. +If you are thinking about using bcache later, it is recommended to setup all your +slow devices as bcache backing devices without a cache, and you can choose to add +a caching device later. +See 'ATTACHING' section below. + +The devices show up as:: + + /dev/bcache<N> + +As well as (with udev):: + + /dev/bcache/by-uuid/<uuid> + /dev/bcache/by-label/<label> + +To get started:: + + mkfs.ext4 /dev/bcache0 + mount /dev/bcache0 /mnt + +You can control bcache devices through sysfs at /sys/block/bcache<N>/bcache . +You can also control them through /sys/fs//bcache/<cset-uuid>/ . + +Cache devices are managed as sets; multiple caches per set isn't supported yet +but will allow for mirroring of metadata and dirty data in the future. Your new +cache set shows up as /sys/fs/bcache/<UUID> + +Attaching +--------- + +After your cache device and backing device are registered, the backing device +must be attached to your cache set to enable caching. Attaching a backing +device to a cache set is done thusly, with the UUID of the cache set in +/sys/fs/bcache:: + + echo <CSET-UUID> > /sys/block/bcache0/bcache/attach + +This only has to be done once. The next time you reboot, just reregister all +your bcache devices. If a backing device has data in a cache somewhere, the +/dev/bcache<N> device won't be created until the cache shows up - particularly +important if you have writeback caching turned on. + +If you're booting up and your cache device is gone and never coming back, you +can force run the backing device:: + + echo 1 > /sys/block/sdb/bcache/running + +(You need to use /sys/block/sdb (or whatever your backing device is called), not +/sys/block/bcache0, because bcache0 doesn't exist yet. If you're using a +partition, the bcache directory would be at /sys/block/sdb/sdb2/bcache) + +The backing device will still use that cache set if it shows up in the future, +but all the cached data will be invalidated. If there was dirty data in the +cache, don't expect the filesystem to be recoverable - you will have massive +filesystem corruption, though ext4's fsck does work miracles. + +Error Handling +-------------- + +Bcache tries to transparently handle IO errors to/from the cache device without +affecting normal operation; if it sees too many errors (the threshold is +configurable, and defaults to 0) it shuts down the cache device and switches all +the backing devices to passthrough mode. + + - For reads from the cache, if they error we just retry the read from the + backing device. + + - For writethrough writes, if the write to the cache errors we just switch to + invalidating the data at that lba in the cache (i.e. the same thing we do for + a write that bypasses the cache) + + - For writeback writes, we currently pass that error back up to the + filesystem/userspace. This could be improved - we could retry it as a write + that skips the cache so we don't have to error the write. + + - When we detach, we first try to flush any dirty data (if we were running in + writeback mode). It currently doesn't do anything intelligent if it fails to + read some of the dirty data, though. + + +Howto/cookbook +-------------- + +A) Starting a bcache with a missing caching device + +If registering the backing device doesn't help, it's already there, you just need +to force it to run without the cache:: + + host:~# echo /dev/sdb1 > /sys/fs/bcache/register + [ 119.844831] bcache: register_bcache() error opening /dev/sdb1: device already registered + +Next, you try to register your caching device if it's present. However +if it's absent, or registration fails for some reason, you can still +start your bcache without its cache, like so:: + + host:/sys/block/sdb/sdb1/bcache# echo 1 > running + +Note that this may cause data loss if you were running in writeback mode. + + +B) Bcache does not find its cache:: + + host:/sys/block/md5/bcache# echo 0226553a-37cf-41d5-b3ce-8b1e944543a8 > attach + [ 1933.455082] bcache: bch_cached_dev_attach() Couldn't find uuid for md5 in set + [ 1933.478179] bcache: __cached_dev_store() Can't attach 0226553a-37cf-41d5-b3ce-8b1e944543a8 + [ 1933.478179] : cache set not found + +In this case, the caching device was simply not registered at boot +or disappeared and came back, and needs to be (re-)registered:: + + host:/sys/block/md5/bcache# echo /dev/sdh2 > /sys/fs/bcache/register + + +C) Corrupt bcache crashes the kernel at device registration time: + +This should never happen. If it does happen, then you have found a bug! +Please report it to the bcache development list: linux-bcache@vger.kernel.org + +Be sure to provide as much information that you can including kernel dmesg +output if available so that we may assist. + + +D) Recovering data without bcache: + +If bcache is not available in the kernel, a filesystem on the backing +device is still available at an 8KiB offset. So either via a loopdev +of the backing device created with --offset 8K, or any value defined by +--data-offset when you originally formatted bcache with `bcache make`. + +For example:: + + losetup -o 8192 /dev/loop0 /dev/your_bcache_backing_dev + +This should present your unmodified backing device data in /dev/loop0 + +If your cache is in writethrough mode, then you can safely discard the +cache device without losing data. + + +E) Wiping a cache device + +:: + + host:~# wipefs -a /dev/sdh2 + 16 bytes were erased at offset 0x1018 (bcache) + they were: c6 85 73 f6 4e 1a 45 ca 82 65 f5 7f 48 ba 6d 81 + +After you boot back with bcache enabled, you recreate the cache and attach it:: + + host:~# bcache make -C /dev/sdh2 + UUID: 7be7e175-8f4c-4f99-94b2-9c904d227045 + Set UUID: 5bc072a8-ab17-446d-9744-e247949913c1 + version: 0 + nbuckets: 106874 + block_size: 1 + bucket_size: 1024 + nr_in_set: 1 + nr_this_dev: 0 + first_bucket: 1 + [ 650.511912] bcache: run_cache_set() invalidating existing data + [ 650.549228] bcache: register_cache() registered cache device sdh2 + +start backing device with missing cache:: + + host:/sys/block/md5/bcache# echo 1 > running + +attach new cache:: + + host:/sys/block/md5/bcache# echo 5bc072a8-ab17-446d-9744-e247949913c1 > attach + [ 865.276616] bcache: bch_cached_dev_attach() Caching md5 as bcache0 on set 5bc072a8-ab17-446d-9744-e247949913c1 + + +F) Remove or replace a caching device:: + + host:/sys/block/sda/sda7/bcache# echo 1 > detach + [ 695.872542] bcache: cached_dev_detach_finish() Caching disabled for sda7 + + host:~# wipefs -a /dev/nvme0n1p4 + wipefs: error: /dev/nvme0n1p4: probing initialization failed: Device or resource busy + Ooops, it's disabled, but not unregistered, so it's still protected + +We need to go and unregister it:: + + host:/sys/fs/bcache/b7ba27a1-2398-4649-8ae3-0959f57ba128# ls -l cache0 + lrwxrwxrwx 1 root root 0 Feb 25 18:33 cache0 -> ../../../devices/pci0000:00/0000:00:1d.0/0000:70:00.0/nvme/nvme0/nvme0n1/nvme0n1p4/bcache/ + host:/sys/fs/bcache/b7ba27a1-2398-4649-8ae3-0959f57ba128# echo 1 > stop + kernel: [ 917.041908] bcache: cache_set_free() Cache set b7ba27a1-2398-4649-8ae3-0959f57ba128 unregistered + +Now we can wipe it:: + + host:~# wipefs -a /dev/nvme0n1p4 + /dev/nvme0n1p4: 16 bytes were erased at offset 0x00001018 (bcache): c6 85 73 f6 4e 1a 45 ca 82 65 f5 7f 48 ba 6d 81 + + +G) dm-crypt and bcache + +First setup bcache unencrypted and then install dmcrypt on top of +/dev/bcache<N> This will work faster than if you dmcrypt both the backing +and caching devices and then install bcache on top. [benchmarks?] + + +H) Stop/free a registered bcache to wipe and/or recreate it + +Suppose that you need to free up all bcache references so that you can +fdisk run and re-register a changed partition table, which won't work +if there are any active backing or caching devices left on it: + +1) Is it present in /dev/bcache* ? (there are times where it won't be) + + If so, it's easy:: + + host:/sys/block/bcache0/bcache# echo 1 > stop + +2) But if your backing device is gone, this won't work:: + + host:/sys/block/bcache0# cd bcache + bash: cd: bcache: No such file or directory + + In this case, you may have to unregister the dmcrypt block device that + references this bcache to free it up:: + + host:~# dmsetup remove oldds1 + bcache: bcache_device_free() bcache0 stopped + bcache: cache_set_free() Cache set 5bc072a8-ab17-446d-9744-e247949913c1 unregistered + + This causes the backing bcache to be removed from /sys/fs/bcache and + then it can be reused. This would be true of any block device stacking + where bcache is a lower device. + +3) In other cases, you can also look in /sys/fs/bcache/:: + + host:/sys/fs/bcache# ls -l */{cache?,bdev?} + lrwxrwxrwx 1 root root 0 Mar 5 09:39 0226553a-37cf-41d5-b3ce-8b1e944543a8/bdev1 -> ../../../devices/virtual/block/dm-1/bcache/ + lrwxrwxrwx 1 root root 0 Mar 5 09:39 0226553a-37cf-41d5-b3ce-8b1e944543a8/cache0 -> ../../../devices/virtual/block/dm-4/bcache/ + lrwxrwxrwx 1 root root 0 Mar 5 09:39 5bc072a8-ab17-446d-9744-e247949913c1/cache0 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/ata10/host9/target9:0:0/9:0:0:0/block/sdl/sdl2/bcache/ + + The device names will show which UUID is relevant, cd in that directory + and stop the cache:: + + host:/sys/fs/bcache/5bc072a8-ab17-446d-9744-e247949913c1# echo 1 > stop + + This will free up bcache references and let you reuse the partition for + other purposes. + + + +Troubleshooting performance +--------------------------- + +Bcache has a bunch of config options and tunables. The defaults are intended to +be reasonable for typical desktop and server workloads, but they're not what you +want for getting the best possible numbers when benchmarking. + + - Backing device alignment + + The default metadata size in bcache is 8k. If your backing device is + RAID based, then be sure to align this by a multiple of your stride + width using `bcache make --data-offset`. If you intend to expand your + disk array in the future, then multiply a series of primes by your + raid stripe size to get the disk multiples that you would like. + + For example: If you have a 64k stripe size, then the following offset + would provide alignment for many common RAID5 data spindle counts:: + + 64k * 2*2*2*3*3*5*7 bytes = 161280k + + That space is wasted, but for only 157.5MB you can grow your RAID 5 + volume to the following data-spindle counts without re-aligning:: + + 3,4,5,6,7,8,9,10,12,14,15,18,20,21 ... + + - Bad write performance + + If write performance is not what you expected, you probably wanted to be + running in writeback mode, which isn't the default (not due to a lack of + maturity, but simply because in writeback mode you'll lose data if something + happens to your SSD):: + + # echo writeback > /sys/block/bcache0/bcache/cache_mode + + - Bad performance, or traffic not going to the SSD that you'd expect + + By default, bcache doesn't cache everything. It tries to skip sequential IO - + because you really want to be caching the random IO, and if you copy a 10 + gigabyte file you probably don't want that pushing 10 gigabytes of randomly + accessed data out of your cache. + + But if you want to benchmark reads from cache, and you start out with fio + writing an 8 gigabyte test file - so you want to disable that:: + + # echo 0 > /sys/block/bcache0/bcache/sequential_cutoff + + To set it back to the default (4 mb), do:: + + # echo 4M > /sys/block/bcache0/bcache/sequential_cutoff + + - Traffic's still going to the spindle/still getting cache misses + + In the real world, SSDs don't always keep up with disks - particularly with + slower SSDs, many disks being cached by one SSD, or mostly sequential IO. So + you want to avoid being bottlenecked by the SSD and having it slow everything + down. + + To avoid that bcache tracks latency to the cache device, and gradually + throttles traffic if the latency exceeds a threshold (it does this by + cranking down the sequential bypass). + + You can disable this if you need to by setting the thresholds to 0:: + + # echo 0 > /sys/fs/bcache/<cache set>/congested_read_threshold_us + # echo 0 > /sys/fs/bcache/<cache set>/congested_write_threshold_us + + The default is 2000 us (2 milliseconds) for reads, and 20000 for writes. + + - Still getting cache misses, of the same data + + One last issue that sometimes trips people up is actually an old bug, due to + the way cache coherency is handled for cache misses. If a btree node is full, + a cache miss won't be able to insert a key for the new data and the data + won't be written to the cache. + + In practice this isn't an issue because as soon as a write comes along it'll + cause the btree node to be split, and you need almost no write traffic for + this to not show up enough to be noticeable (especially since bcache's btree + nodes are huge and index large regions of the device). But when you're + benchmarking, if you're trying to warm the cache by reading a bunch of data + and there's no other traffic - that can be a problem. + + Solution: warm the cache by doing writes, or use the testing branch (there's + a fix for the issue there). + + +Sysfs - backing device +---------------------- + +Available at /sys/block/<bdev>/bcache, /sys/block/bcache*/bcache and +(if attached) /sys/fs/bcache/<cset-uuid>/bdev* + +attach + Echo the UUID of a cache set to this file to enable caching. + +cache_mode + Can be one of either writethrough, writeback, writearound or none. + +clear_stats + Writing to this file resets the running total stats (not the day/hour/5 minute + decaying versions). + +detach + Write to this file to detach from a cache set. If there is dirty data in the + cache, it will be flushed first. + +dirty_data + Amount of dirty data for this backing device in the cache. Continuously + updated unlike the cache set's version, but may be slightly off. + +label + Name of underlying device. + +readahead + Size of readahead that should be performed. Defaults to 0. If set to e.g. + 1M, it will round cache miss reads up to that size, but without overlapping + existing cache entries. + +running + 1 if bcache is running (i.e. whether the /dev/bcache device exists, whether + it's in passthrough mode or caching). + +sequential_cutoff + A sequential IO will bypass the cache once it passes this threshold; the + most recent 128 IOs are tracked so sequential IO can be detected even when + it isn't all done at once. + +sequential_merge + If non zero, bcache keeps a list of the last 128 requests submitted to compare + against all new requests to determine which new requests are sequential + continuations of previous requests for the purpose of determining sequential + cutoff. This is necessary if the sequential cutoff value is greater than the + maximum acceptable sequential size for any single request. + +state + The backing device can be in one of four different states: + + no cache: Has never been attached to a cache set. + + clean: Part of a cache set, and there is no cached dirty data. + + dirty: Part of a cache set, and there is cached dirty data. + + inconsistent: The backing device was forcibly run by the user when there was + dirty data cached but the cache set was unavailable; whatever data was on the + backing device has likely been corrupted. + +stop + Write to this file to shut down the bcache device and close the backing + device. + +writeback_delay + When dirty data is written to the cache and it previously did not contain + any, waits some number of seconds before initiating writeback. Defaults to + 30. + +writeback_percent + If nonzero, bcache tries to keep around this percentage of the cache dirty by + throttling background writeback and using a PD controller to smoothly adjust + the rate. + +writeback_rate + Rate in sectors per second - if writeback_percent is nonzero, background + writeback is throttled to this rate. Continuously adjusted by bcache but may + also be set by the user. + +writeback_running + If off, writeback of dirty data will not take place at all. Dirty data will + still be added to the cache until it is mostly full; only meant for + benchmarking. Defaults to on. + +Sysfs - backing device stats +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +There are directories with these numbers for a running total, as well as +versions that decay over the past day, hour and 5 minutes; they're also +aggregated in the cache set directory as well. + +bypassed + Amount of IO (both reads and writes) that has bypassed the cache + +cache_hits, cache_misses, cache_hit_ratio + Hits and misses are counted per individual IO as bcache sees them; a + partial hit is counted as a miss. + +cache_bypass_hits, cache_bypass_misses + Hits and misses for IO that is intended to skip the cache are still counted, + but broken out here. + +cache_miss_collisions + Counts instances where data was going to be inserted into the cache from a + cache miss, but raced with a write and data was already present (usually 0 + since the synchronization for cache misses was rewritten) + +Sysfs - cache set +~~~~~~~~~~~~~~~~~ + +Available at /sys/fs/bcache/<cset-uuid> + +average_key_size + Average data per key in the btree. + +bdev<0..n> + Symlink to each of the attached backing devices. + +block_size + Block size of the cache devices. + +btree_cache_size + Amount of memory currently used by the btree cache + +bucket_size + Size of buckets + +cache<0..n> + Symlink to each of the cache devices comprising this cache set. + +cache_available_percent + Percentage of cache device which doesn't contain dirty data, and could + potentially be used for writeback. This doesn't mean this space isn't used + for clean cached data; the unused statistic (in priority_stats) is typically + much lower. + +clear_stats + Clears the statistics associated with this cache + +dirty_data + Amount of dirty data is in the cache (updated when garbage collection runs). + +flash_vol_create + Echoing a size to this file (in human readable units, k/M/G) creates a thinly + provisioned volume backed by the cache set. + +io_error_halflife, io_error_limit + These determines how many errors we accept before disabling the cache. + Each error is decayed by the half life (in # ios). If the decaying count + reaches io_error_limit dirty data is written out and the cache is disabled. + +journal_delay_ms + Journal writes will delay for up to this many milliseconds, unless a cache + flush happens sooner. Defaults to 100. + +root_usage_percent + Percentage of the root btree node in use. If this gets too high the node + will split, increasing the tree depth. + +stop + Write to this file to shut down the cache set - waits until all attached + backing devices have been shut down. + +tree_depth + Depth of the btree (A single node btree has depth 0). + +unregister + Detaches all backing devices and closes the cache devices; if dirty data is + present it will disable writeback caching and wait for it to be flushed. + +Sysfs - cache set internal +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +This directory also exposes timings for a number of internal operations, with +separate files for average duration, average frequency, last occurrence and max +duration: garbage collection, btree read, btree node sorts and btree splits. + +active_journal_entries + Number of journal entries that are newer than the index. + +btree_nodes + Total nodes in the btree. + +btree_used_percent + Average fraction of btree in use. + +bset_tree_stats + Statistics about the auxiliary search trees + +btree_cache_max_chain + Longest chain in the btree node cache's hash table + +cache_read_races + Counts instances where while data was being read from the cache, the bucket + was reused and invalidated - i.e. where the pointer was stale after the read + completed. When this occurs the data is reread from the backing device. + +trigger_gc + Writing to this file forces garbage collection to run. + +Sysfs - Cache device +~~~~~~~~~~~~~~~~~~~~ + +Available at /sys/block/<cdev>/bcache + +block_size + Minimum granularity of writes - should match hardware sector size. + +btree_written + Sum of all btree writes, in (kilo/mega/giga) bytes + +bucket_size + Size of buckets + +cache_replacement_policy + One of either lru, fifo or random. + +discard + Boolean; if on a discard/TRIM will be issued to each bucket before it is + reused. Defaults to off, since SATA TRIM is an unqueued command (and thus + slow). + +freelist_percent + Size of the freelist as a percentage of nbuckets. Can be written to to + increase the number of buckets kept on the freelist, which lets you + artificially reduce the size of the cache at runtime. Mostly for testing + purposes (i.e. testing how different size caches affect your hit rate), but + since buckets are discarded when they move on to the freelist will also make + the SSD's garbage collection easier by effectively giving it more reserved + space. + +io_errors + Number of errors that have occurred, decayed by io_error_halflife. + +metadata_written + Sum of all non data writes (btree writes and all other metadata). + +nbuckets + Total buckets in this cache + +priority_stats + Statistics about how recently data in the cache has been accessed. + This can reveal your working set size. Unused is the percentage of + the cache that doesn't contain any data. Metadata is bcache's + metadata overhead. Average is the average priority of cache buckets. + Next is a list of quantiles with the priority threshold of each. + +written + Sum of all data that has been written to the cache; comparison with + btree_written gives the amount of write inflation in bcache. diff --git a/Documentation/admin-guide/binderfs.rst b/Documentation/admin-guide/binderfs.rst new file mode 100644 index 000000000..41a4db00d --- /dev/null +++ b/Documentation/admin-guide/binderfs.rst @@ -0,0 +1,87 @@ +.. SPDX-License-Identifier: GPL-2.0 + +The Android binderfs Filesystem +=============================== + +Android binderfs is a filesystem for the Android binder IPC mechanism. It +allows to dynamically add and remove binder devices at runtime. Binder devices +located in a new binderfs instance are independent of binder devices located in +other binderfs instances. Mounting a new binderfs instance makes it possible +to get a set of private binder devices. + +Mounting binderfs +----------------- + +Android binderfs can be mounted with:: + + mkdir /dev/binderfs + mount -t binder binder /dev/binderfs + +at which point a new instance of binderfs will show up at ``/dev/binderfs``. +In a fresh instance of binderfs no binder devices will be present. There will +only be a ``binder-control`` device which serves as the request handler for +binderfs. Mounting another binderfs instance at a different location will +create a new and separate instance from all other binderfs mounts. This is +identical to the behavior of e.g. ``devpts`` and ``tmpfs``. The Android +binderfs filesystem can be mounted in user namespaces. + +Options +------- +max + binderfs instances can be mounted with a limit on the number of binder + devices that can be allocated. The ``max=<count>`` mount option serves as + a per-instance limit. If ``max=<count>`` is set then only ``<count>`` number + of binder devices can be allocated in this binderfs instance. + +stats + Using ``stats=global`` enables global binder statistics. + ``stats=global`` is only available for a binderfs instance mounted in the + initial user namespace. An attempt to use the option to mount a binderfs + instance in another user namespace will return a permission error. + +Allocating binder Devices +------------------------- + +.. _ioctl: http://man7.org/linux/man-pages/man2/ioctl.2.html + +To allocate a new binder device in a binderfs instance a request needs to be +sent through the ``binder-control`` device node. A request is sent in the form +of an `ioctl() <ioctl_>`_. + +What a program needs to do is to open the ``binder-control`` device node and +send a ``BINDER_CTL_ADD`` request to the kernel. Users of binderfs need to +tell the kernel which name the new binder device should get. By default a name +can only contain up to ``BINDERFS_MAX_NAME`` chars including the terminating +zero byte. + +Once the request is made via an `ioctl() <ioctl_>`_ passing a ``struct +binder_device`` with the name to the kernel it will allocate a new binder +device and return the major and minor number of the new device in the struct +(This is necessary because binderfs allocates a major device number +dynamically.). After the `ioctl() <ioctl_>`_ returns there will be a new +binder device located under /dev/binderfs with the chosen name. + +Deleting binder Devices +----------------------- + +.. _unlink: http://man7.org/linux/man-pages/man2/unlink.2.html +.. _rm: http://man7.org/linux/man-pages/man1/rm.1.html + +Binderfs binder devices can be deleted via `unlink() <unlink_>`_. This means +that the `rm() <rm_>`_ tool can be used to delete them. Note that the +``binder-control`` device cannot be deleted since this would make the binderfs +instance unusable. The ``binder-control`` device will be deleted when the +binderfs instance is unmounted and all references to it have been dropped. + +Binder features +--------------- + +Assuming an instance of binderfs has been mounted at ``/dev/binderfs``, the +features supported by the binder driver can be located under +``/dev/binderfs/features/``. The presence of individual files can be tested +to determine whether a particular feature is supported by the driver. + +Example:: + + cat /dev/binderfs/features/oneway_spam_detection + 1 diff --git a/Documentation/admin-guide/binfmt-misc.rst b/Documentation/admin-guide/binfmt-misc.rst new file mode 100644 index 000000000..59cd902e3 --- /dev/null +++ b/Documentation/admin-guide/binfmt-misc.rst @@ -0,0 +1,151 @@ +Kernel Support for miscellaneous Binary Formats (binfmt_misc) +============================================================= + +This Kernel feature allows you to invoke almost (for restrictions see below) +every program by simply typing its name in the shell. +This includes for example compiled Java(TM), Python or Emacs programs. + +To achieve this you must tell binfmt_misc which interpreter has to be invoked +with which binary. Binfmt_misc recognises the binary-type by matching some bytes +at the beginning of the file with a magic byte sequence (masking out specified +bits) you have supplied. Binfmt_misc can also recognise a filename extension +aka ``.com`` or ``.exe``. + +First you must mount binfmt_misc:: + + mount binfmt_misc -t binfmt_misc /proc/sys/fs/binfmt_misc + +To actually register a new binary type, you have to set up a string looking like +``:name:type:offset:magic:mask:interpreter:flags`` (where you can choose the +``:`` upon your needs) and echo it to ``/proc/sys/fs/binfmt_misc/register``. + +Here is what the fields mean: + +- ``name`` + is an identifier string. A new /proc file will be created with this + name below ``/proc/sys/fs/binfmt_misc``; cannot contain slashes ``/`` for + obvious reasons. +- ``type`` + is the type of recognition. Give ``M`` for magic and ``E`` for extension. +- ``offset`` + is the offset of the magic/mask in the file, counted in bytes. This + defaults to 0 if you omit it (i.e. you write ``:name:type::magic...``). + Ignored when using filename extension matching. +- ``magic`` + is the byte sequence binfmt_misc is matching for. The magic string + may contain hex-encoded characters like ``\x0a`` or ``\xA4``. Note that you + must escape any NUL bytes; parsing halts at the first one. In a shell + environment you might have to write ``\\x0a`` to prevent the shell from + eating your ``\``. + If you chose filename extension matching, this is the extension to be + recognised (without the ``.``, the ``\x0a`` specials are not allowed). + Extension matching is case sensitive, and slashes ``/`` are not allowed! +- ``mask`` + is an (optional, defaults to all 0xff) mask. You can mask out some + bits from matching by supplying a string like magic and as long as magic. + The mask is anded with the byte sequence of the file. Note that you must + escape any NUL bytes; parsing halts at the first one. Ignored when using + filename extension matching. +- ``interpreter`` + is the program that should be invoked with the binary as first + argument (specify the full path) +- ``flags`` + is an optional field that controls several aspects of the invocation + of the interpreter. It is a string of capital letters, each controls a + certain aspect. The following flags are supported: + + ``P`` - preserve-argv[0] + Legacy behavior of binfmt_misc is to overwrite + the original argv[0] with the full path to the binary. When this + flag is included, binfmt_misc will add an argument to the argument + vector for this purpose, thus preserving the original ``argv[0]``. + e.g. If your interp is set to ``/bin/foo`` and you run ``blah`` + (which is in ``/usr/local/bin``), then the kernel will execute + ``/bin/foo`` with ``argv[]`` set to ``["/bin/foo", "/usr/local/bin/blah", "blah"]``. The interp has to be aware of this so it can + execute ``/usr/local/bin/blah`` + with ``argv[]`` set to ``["blah"]``. + ``O`` - open-binary + Legacy behavior of binfmt_misc is to pass the full path + of the binary to the interpreter as an argument. When this flag is + included, binfmt_misc will open the file for reading and pass its + descriptor as an argument, instead of the full path, thus allowing + the interpreter to execute non-readable binaries. This feature + should be used with care - the interpreter has to be trusted not to + emit the contents of the non-readable binary. + ``C`` - credentials + Currently, the behavior of binfmt_misc is to calculate + the credentials and security token of the new process according to + the interpreter. When this flag is included, these attributes are + calculated according to the binary. It also implies the ``O`` flag. + This feature should be used with care as the interpreter + will run with root permissions when a setuid binary owned by root + is run with binfmt_misc. + ``F`` - fix binary + The usual behaviour of binfmt_misc is to spawn the + binary lazily when the misc format file is invoked. However, + this doesn't work very well in the face of mount namespaces and + changeroots, so the ``F`` mode opens the binary as soon as the + emulation is installed and uses the opened image to spawn the + emulator, meaning it is always available once installed, + regardless of how the environment changes. + + +There are some restrictions: + + - the whole register string may not exceed 1920 characters + - the magic must reside in the first 128 bytes of the file, i.e. + offset+size(magic) has to be less than 128 + - the interpreter string may not exceed 127 characters + +To use binfmt_misc you have to mount it first. You can mount it with +``mount -t binfmt_misc none /proc/sys/fs/binfmt_misc`` command, or you can add +a line ``none /proc/sys/fs/binfmt_misc binfmt_misc defaults 0 0`` to your +``/etc/fstab`` so it auto mounts on boot. + +You may want to add the binary formats in one of your ``/etc/rc`` scripts during +boot-up. Read the manual of your init program to figure out how to do this +right. + +Think about the order of adding entries! Later added entries are matched first! + + +A few examples (assumed you are in ``/proc/sys/fs/binfmt_misc``): + +- enable support for em86 (like binfmt_em86, for Alpha AXP only):: + + echo ':i386:M::\x7fELF\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x03:\xff\xff\xff\xff\xff\xfe\xfe\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfb\xff\xff:/bin/em86:' > register + echo ':i486:M::\x7fELF\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x06:\xff\xff\xff\xff\xff\xfe\xfe\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfb\xff\xff:/bin/em86:' > register + +- enable support for packed DOS applications (pre-configured dosemu hdimages):: + + echo ':DEXE:M::\x0eDEX::/usr/bin/dosexec:' > register + +- enable support for Windows executables using wine:: + + echo ':DOSWin:M::MZ::/usr/local/bin/wine:' > register + +For java support see Documentation/admin-guide/java.rst + + +You can enable/disable binfmt_misc or one binary type by echoing 0 (to disable) +or 1 (to enable) to ``/proc/sys/fs/binfmt_misc/status`` or +``/proc/.../the_name``. +Catting the file tells you the current status of ``binfmt_misc/the_entry``. + +You can remove one entry or all entries by echoing -1 to ``/proc/.../the_name`` +or ``/proc/sys/fs/binfmt_misc/status``. + + +Hints +----- + +If you want to pass special arguments to your interpreter, you can +write a wrapper script for it. +See :doc:`Documentation/admin-guide/java.rst <./java>` for an example. + +Your interpreter should NOT look in the PATH for the filename; the kernel +passes it the full filename (or the file descriptor) to use. Using ``$PATH`` can +cause unexpected behaviour and can be a security hazard. + + +Richard Günther <rguenth@tat.physik.uni-tuebingen.de> diff --git a/Documentation/admin-guide/blockdev/drbd/DRBD-8.3-data-packets.svg b/Documentation/admin-guide/blockdev/drbd/DRBD-8.3-data-packets.svg new file mode 100644 index 000000000..f87cfa0dc --- /dev/null +++ b/Documentation/admin-guide/blockdev/drbd/DRBD-8.3-data-packets.svg @@ -0,0 +1,588 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!-- Created with Inkscape (http://www.inkscape.org/) --> +<svg + xmlns:svg="http://www.w3.org/2000/svg" + xmlns="http://www.w3.org/2000/svg" + version="1.0" + width="210mm" + height="297mm" + viewBox="0 0 21000 29700" + id="svg2" + style="fill-rule:evenodd"> + <defs + id="defs4" /> + <g + id="Default" + style="visibility:visible"> + <desc + id="desc180">Master slide</desc> + </g> + <path + d="M 11999,8601 L 11899,8301 L 12099,8301 L 11999,8601 z" + id="path193" + 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17338 17410 17588 17677 17855 18033 18105 18282 18388" + y="20331" + id="tspan1029">rs_complete_io()</tspan> + </text> +</svg> diff --git a/Documentation/admin-guide/blockdev/drbd/conn-states-8.dot b/Documentation/admin-guide/blockdev/drbd/conn-states-8.dot new file mode 100644 index 000000000..025e8cf5e --- /dev/null +++ b/Documentation/admin-guide/blockdev/drbd/conn-states-8.dot @@ -0,0 +1,18 @@ +digraph conn_states { + StandAllone -> WFConnection [ label = "ioctl_set_net()" ] + WFConnection -> Unconnected [ label = "unable to bind()" ] + WFConnection -> WFReportParams [ label = "in connect() after accept" ] + WFReportParams -> StandAllone [ label = "checks in receive_param()" ] + WFReportParams -> Connected [ label = "in receive_param()" ] + WFReportParams -> WFBitMapS [ label = "sync_handshake()" ] + WFReportParams -> WFBitMapT [ label = "sync_handshake()" ] + WFBitMapS -> SyncSource [ label = "receive_bitmap()" ] + WFBitMapT -> SyncTarget [ label = "receive_bitmap()" ] + SyncSource -> Connected + SyncTarget -> Connected + SyncSource -> PausedSyncS + SyncTarget -> PausedSyncT + PausedSyncS -> SyncSource + PausedSyncT -> SyncTarget + Connected -> WFConnection [ label = "* on network error" ] +} diff --git a/Documentation/admin-guide/blockdev/drbd/data-structure-v9.rst b/Documentation/admin-guide/blockdev/drbd/data-structure-v9.rst new file mode 100644 index 000000000..66036b901 --- /dev/null +++ b/Documentation/admin-guide/blockdev/drbd/data-structure-v9.rst @@ -0,0 +1,42 @@ +================================ +kernel data structure for DRBD-9 +================================ + +This describes the in kernel data structure for DRBD-9. Starting with +Linux v3.14 we are reorganizing DRBD to use this data structure. + +Basic Data Structure +==================== + +A node has a number of DRBD resources. Each such resource has a number of +devices (aka volumes) and connections to other nodes ("peer nodes"). Each DRBD +device is represented by a block device locally. + +The DRBD objects are interconnected to form a matrix as depicted below; a +drbd_peer_device object sits at each intersection between a drbd_device and a +drbd_connection:: + + /--------------+---------------+.....+---------------\ + | resource | device | | device | + +--------------+---------------+.....+---------------+ + | connection | peer_device | | peer_device | + +--------------+---------------+.....+---------------+ + : : : : : + : : : : : + +--------------+---------------+.....+---------------+ + | connection | peer_device | | peer_device | + \--------------+---------------+.....+---------------/ + +In this table, horizontally, devices can be accessed from resources by their +volume number. Likewise, peer_devices can be accessed from connections by +their volume number. Objects in the vertical direction are connected by double +linked lists. There are back pointers from peer_devices to their connections a +devices, and from connections and devices to their resource. + +All resources are in the drbd_resources double-linked list. In addition, all +devices can be accessed by their minor device number via the drbd_devices idr. + +The drbd_resource, drbd_connection, and drbd_device objects are reference +counted. The peer_device objects only serve to establish the links between +devices and connections; their lifetime is determined by the lifetime of the +device and connection which they reference. diff --git a/Documentation/admin-guide/blockdev/drbd/disk-states-8.dot b/Documentation/admin-guide/blockdev/drbd/disk-states-8.dot new file mode 100644 index 000000000..d06cfb46f --- /dev/null +++ b/Documentation/admin-guide/blockdev/drbd/disk-states-8.dot @@ -0,0 +1,16 @@ +digraph disk_states { + Diskless -> Inconsistent [ label = "ioctl_set_disk()" ] + Diskless -> Consistent [ label = "ioctl_set_disk()" ] + Diskless -> Outdated [ label = "ioctl_set_disk()" ] + Consistent -> Outdated [ label = "receive_param()" ] + Consistent -> UpToDate [ label = "receive_param()" ] + Consistent -> Inconsistent [ label = "start resync" ] + Outdated -> Inconsistent [ label = "start resync" ] + UpToDate -> Inconsistent [ label = "ioctl_replicate" ] + Inconsistent -> UpToDate [ label = "resync completed" ] + Consistent -> Failed [ label = "io completion error" ] + Outdated -> Failed [ label = "io completion error" ] + UpToDate -> Failed [ label = "io completion error" ] + Inconsistent -> Failed [ label = "io completion error" ] + Failed -> Diskless [ label = "sending notify to peer" ] +} diff --git a/Documentation/admin-guide/blockdev/drbd/drbd-connection-state-overview.dot b/Documentation/admin-guide/blockdev/drbd/drbd-connection-state-overview.dot new file mode 100644 index 000000000..6d9cf0a7b --- /dev/null +++ b/Documentation/admin-guide/blockdev/drbd/drbd-connection-state-overview.dot @@ -0,0 +1,85 @@ +// vim: set sw=2 sts=2 : +digraph { + rankdir=BT + bgcolor=white + + node [shape=plaintext] + node [fontcolor=black] + + StandAlone [ style=filled,fillcolor=gray,label=StandAlone ] + + node [fontcolor=lightgray] + + Unconnected [ label=Unconnected ] + + CommTrouble [ shape=record, + label="{communication loss|{Timeout|BrokenPipe|NetworkFailure}}" ] + + node [fontcolor=gray] + + subgraph cluster_try_connect { + label="try to connect, handshake" + rank=max + WFConnection [ label=WFConnection ] + WFReportParams [ label=WFReportParams ] + } + + TearDown [ label=TearDown ] + + Connected [ label=Connected,style=filled,fillcolor=green,fontcolor=black ] + + node [fontcolor=lightblue] + + StartingSyncS [ label=StartingSyncS ] + StartingSyncT [ label=StartingSyncT ] + + subgraph cluster_bitmap_exchange { + node [fontcolor=red] + fontcolor=red + label="new application (WRITE?) requests blocked\lwhile bitmap is exchanged" + + WFBitMapT [ label=WFBitMapT ] + WFSyncUUID [ label=WFSyncUUID ] + WFBitMapS [ label=WFBitMapS ] + } + + node [fontcolor=blue] + + cluster_resync [ shape=record,label="{<any>resynchronisation process running\l'concurrent' application requests allowed|{{<T>PausedSyncT\nSyncTarget}|{<S>PausedSyncS\nSyncSource}}}" ] + + node [shape=box,fontcolor=black] + + // drbdadm [label="drbdadm connect"] + // handshake [label="drbd_connect()\ndrbd_do_handshake\ndrbd_sync_handshake() etc."] + // comm_error [label="communication trouble"] + + // + // edges + // -------------------------------------- + + StandAlone -> Unconnected [ label="drbdadm connect" ] + Unconnected -> StandAlone [ label="drbdadm disconnect\lor serious communication trouble" ] + Unconnected -> WFConnection [ label="receiver thread is started" ] + WFConnection -> WFReportParams [ headlabel="accept()\land/or \lconnect()\l" ] + + WFReportParams -> StandAlone [ label="during handshake\lpeers do not agree\labout something essential" ] + WFReportParams -> Connected [ label="data identical\lno sync needed",color=green,fontcolor=green ] + + WFReportParams -> WFBitMapS + WFReportParams -> WFBitMapT + WFBitMapT -> WFSyncUUID [minlen=0.1,constraint=false] + + WFBitMapS -> cluster_resync:S + WFSyncUUID -> cluster_resync:T + + edge [color=green] + cluster_resync:any -> Connected [ label="resnyc done",fontcolor=green ] + + edge [color=red] + WFReportParams -> CommTrouble + Connected -> CommTrouble + cluster_resync:any -> CommTrouble + edge [color=black] + CommTrouble -> Unconnected [label="receiver thread is stopped" ] + +} diff --git a/Documentation/admin-guide/blockdev/drbd/figures.rst b/Documentation/admin-guide/blockdev/drbd/figures.rst new file mode 100644 index 000000000..9f73253ea --- /dev/null +++ b/Documentation/admin-guide/blockdev/drbd/figures.rst @@ -0,0 +1,30 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. The here included files are intended to help understand the implementation + +Data flows that Relate some functions, and write packets +======================================================== + +.. kernel-figure:: DRBD-8.3-data-packets.svg + :alt: DRBD-8.3-data-packets.svg + :align: center + +.. kernel-figure:: DRBD-data-packets.svg + :alt: DRBD-data-packets.svg + :align: center + + +Sub graphs of DRBD's state transitions +====================================== + +.. kernel-figure:: conn-states-8.dot + :alt: conn-states-8.dot + :align: center + +.. kernel-figure:: disk-states-8.dot + :alt: disk-states-8.dot + :align: center + +.. kernel-figure:: peer-states-8.dot + :alt: peer-states-8.dot + :align: center diff --git a/Documentation/admin-guide/blockdev/drbd/index.rst b/Documentation/admin-guide/blockdev/drbd/index.rst new file mode 100644 index 000000000..561fd1e35 --- /dev/null +++ b/Documentation/admin-guide/blockdev/drbd/index.rst @@ -0,0 +1,19 @@ +========================================== +Distributed Replicated Block Device - DRBD +========================================== + +Description +=========== + + DRBD is a shared-nothing, synchronously replicated block device. It + is designed to serve as a building block for high availability + clusters and in this context, is a "drop-in" replacement for shared + storage. Simplistically, you could see it as a network RAID 1. + + Please visit https://www.drbd.org to find out more. + +.. toctree:: + :maxdepth: 1 + + data-structure-v9 + figures diff --git a/Documentation/admin-guide/blockdev/drbd/peer-states-8.dot b/Documentation/admin-guide/blockdev/drbd/peer-states-8.dot new file mode 100644 index 000000000..6dc395495 --- /dev/null +++ b/Documentation/admin-guide/blockdev/drbd/peer-states-8.dot @@ -0,0 +1,8 @@ +digraph peer_states { + Secondary -> Primary [ label = "recv state packet" ] + Primary -> Secondary [ label = "recv state packet" ] + Primary -> Unknown [ label = "connection lost" ] + Secondary -> Unknown [ label = "connection lost" ] + Unknown -> Primary [ label = "connected" ] + Unknown -> Secondary [ label = "connected" ] +} diff --git a/Documentation/admin-guide/blockdev/floppy.rst b/Documentation/admin-guide/blockdev/floppy.rst new file mode 100644 index 000000000..0328438eb --- /dev/null +++ b/Documentation/admin-guide/blockdev/floppy.rst @@ -0,0 +1,255 @@ +============= +Floppy Driver +============= + +FAQ list: +========= + +A FAQ list may be found in the fdutils package (see below), and also +at <https://fdutils.linux.lu/faq.html>. + + +LILO configuration options (Thinkpad users, read this) +====================================================== + +The floppy driver is configured using the 'floppy=' option in +lilo. This option can be typed at the boot prompt, or entered in the +lilo configuration file. + +Example: If your kernel is called linux-2.6.9, type the following line +at the lilo boot prompt (if you have a thinkpad):: + + linux-2.6.9 floppy=thinkpad + +You may also enter the following line in /etc/lilo.conf, in the description +of linux-2.6.9:: + + append = "floppy=thinkpad" + +Several floppy related options may be given, example:: + + linux-2.6.9 floppy=daring floppy=two_fdc + append = "floppy=daring floppy=two_fdc" + +If you give options both in the lilo config file and on the boot +prompt, the option strings of both places are concatenated, the boot +prompt options coming last. That's why there are also options to +restore the default behavior. + + +Module configuration options +============================ + +If you use the floppy driver as a module, use the following syntax:: + + modprobe floppy floppy="<options>" + +Example:: + + modprobe floppy floppy="omnibook messages" + +If you need certain options enabled every time you load the floppy driver, +you can put:: + + options floppy floppy="omnibook messages" + +in a configuration file in /etc/modprobe.d/. + + +The floppy driver related options are: + + floppy=asus_pci + Sets the bit mask to allow only units 0 and 1. (default) + + floppy=daring + Tells the floppy driver that you have a well behaved floppy controller. + This allows more efficient and smoother operation, but may fail on + certain controllers. This may speed up certain operations. + + floppy=0,daring + Tells the floppy driver that your floppy controller should be used + with caution. + + floppy=one_fdc + Tells the floppy driver that you have only one floppy controller. + (default) + + floppy=two_fdc / floppy=<address>,two_fdc + Tells the floppy driver that you have two floppy controllers. + The second floppy controller is assumed to be at <address>. + This option is not needed if the second controller is at address + 0x370, and if you use the 'cmos' option. + + floppy=thinkpad + Tells the floppy driver that you have a Thinkpad. Thinkpads use an + inverted convention for the disk change line. + + floppy=0,thinkpad + Tells the floppy driver that you don't have a Thinkpad. + + floppy=omnibook / floppy=nodma + Tells the floppy driver not to use Dma for data transfers. + This is needed on HP Omnibooks, which don't have a workable + DMA channel for the floppy driver. This option is also useful + if you frequently get "Unable to allocate DMA memory" messages. + Indeed, dma memory needs to be continuous in physical memory, + and is thus harder to find, whereas non-dma buffers may be + allocated in virtual memory. However, I advise against this if + you have an FDC without a FIFO (8272A or 82072). 82072A and + later are OK. You also need at least a 486 to use nodma. + If you use nodma mode, I suggest you also set the FIFO + threshold to 10 or lower, in order to limit the number of data + transfer interrupts. + + If you have a FIFO-able FDC, the floppy driver automatically + falls back on non DMA mode if no DMA-able memory can be found. + If you want to avoid this, explicitly ask for 'yesdma'. + + floppy=yesdma + Tells the floppy driver that a workable DMA channel is available. + (default) + + floppy=nofifo + Disables the FIFO entirely. This is needed if you get "Bus + master arbitration error" messages from your Ethernet card (or + from other devices) while accessing the floppy. + + floppy=usefifo + Enables the FIFO. (default) + + floppy=<threshold>,fifo_depth + Sets the FIFO threshold. This is mostly relevant in DMA + mode. If this is higher, the floppy driver tolerates more + interrupt latency, but it triggers more interrupts (i.e. it + imposes more load on the rest of the system). If this is + lower, the interrupt latency should be lower too (faster + processor). The benefit of a lower threshold is less + interrupts. + + To tune the fifo threshold, switch on over/underrun messages + using 'floppycontrol --messages'. Then access a floppy + disk. If you get a huge amount of "Over/Underrun - retrying" + messages, then the fifo threshold is too low. Try with a + higher value, until you only get an occasional Over/Underrun. + It is a good idea to compile the floppy driver as a module + when doing this tuning. Indeed, it allows to try different + fifo values without rebooting the machine for each test. Note + that you need to do 'floppycontrol --messages' every time you + re-insert the module. + + Usually, tuning the fifo threshold should not be needed, as + the default (0xa) is reasonable. + + floppy=<drive>,<type>,cmos + Sets the CMOS type of <drive> to <type>. This is mandatory if + you have more than two floppy drives (only two can be + described in the physical CMOS), or if your BIOS uses + non-standard CMOS types. The CMOS types are: + + == ================================== + 0 Use the value of the physical CMOS + 1 5 1/4 DD + 2 5 1/4 HD + 3 3 1/2 DD + 4 3 1/2 HD + 5 3 1/2 ED + 6 3 1/2 ED + 16 unknown or not installed + == ================================== + + (Note: there are two valid types for ED drives. This is because 5 was + initially chosen to represent floppy *tapes*, and 6 for ED drives. + AMI ignored this, and used 5 for ED drives. That's why the floppy + driver handles both.) + + floppy=unexpected_interrupts + Print a warning message when an unexpected interrupt is received. + (default) + + floppy=no_unexpected_interrupts / floppy=L40SX + Don't print a message when an unexpected interrupt is received. This + is needed on IBM L40SX laptops in certain video modes. (There seems + to be an interaction between video and floppy. The unexpected + interrupts affect only performance, and can be safely ignored.) + + floppy=broken_dcl + Don't use the disk change line, but assume that the disk was + changed whenever the device node is reopened. Needed on some + boxes where the disk change line is broken or unsupported. + This should be regarded as a stopgap measure, indeed it makes + floppy operation less efficient due to unneeded cache + flushings, and slightly more unreliable. Please verify your + cable, connection and jumper settings if you have any DCL + problems. However, some older drives, and also some laptops + are known not to have a DCL. + + floppy=debug + Print debugging messages. + + floppy=messages + Print informational messages for some operations (disk change + notifications, warnings about over and underruns, and about + autodetection). + + floppy=silent_dcl_clear + Uses a less noisy way to clear the disk change line (which + doesn't involve seeks). Implied by 'daring' option. + + floppy=<nr>,irq + Sets the floppy IRQ to <nr> instead of 6. + + floppy=<nr>,dma + Sets the floppy DMA channel to <nr> instead of 2. + + floppy=slow + Use PS/2 stepping rate:: + + PS/2 floppies have much slower step rates than regular floppies. + It's been recommended that take about 1/4 of the default speed + in some more extreme cases. + + +Supporting utilities and additional documentation: +================================================== + +Additional parameters of the floppy driver can be configured at +runtime. Utilities which do this can be found in the fdutils package. +This package also contains a new version of mtools which allows to +access high capacity disks (up to 1992K on a high density 3 1/2 disk!). +It also contains additional documentation about the floppy driver. + +The latest version can be found at fdutils homepage: + + https://fdutils.linux.lu + +The fdutils releases can be found at: + + https://fdutils.linux.lu/download.html + + http://www.tux.org/pub/knaff/fdutils/ + + ftp://metalab.unc.edu/pub/Linux/utils/disk-management/ + +Reporting problems about the floppy driver +========================================== + +If you have a question or a bug report about the floppy driver, mail +me at Alain.Knaff@poboxes.com . If you post to Usenet, preferably use +comp.os.linux.hardware. As the volume in these groups is rather high, +be sure to include the word "floppy" (or "FLOPPY") in the subject +line. If the reported problem happens when mounting floppy disks, be +sure to mention also the type of the filesystem in the subject line. + +Be sure to read the FAQ before mailing/posting any bug reports! + +Alain + +Changelog +========= + +10-30-2004 : + Cleanup, updating, add reference to module configuration. + James Nelson <james4765@gmail.com> + +6-3-2000 : + Original Document diff --git a/Documentation/admin-guide/blockdev/index.rst b/Documentation/admin-guide/blockdev/index.rst new file mode 100644 index 000000000..957ccf617 --- /dev/null +++ b/Documentation/admin-guide/blockdev/index.rst @@ -0,0 +1,16 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============= +Block Devices +============= + +.. toctree:: + :maxdepth: 1 + + floppy + nbd + paride + ramdisk + zram + + drbd/index diff --git a/Documentation/admin-guide/blockdev/nbd.rst b/Documentation/admin-guide/blockdev/nbd.rst new file mode 100644 index 000000000..faf2ac4b1 --- /dev/null +++ b/Documentation/admin-guide/blockdev/nbd.rst @@ -0,0 +1,31 @@ +================================== +Network Block Device (TCP version) +================================== + +1) Overview +----------- + +What is it: With this compiled in the kernel (or as a module), Linux +can use a remote server as one of its block devices. So every time +the client computer wants to read, e.g., /dev/nb0, it sends a +request over TCP to the server, which will reply with the data read. +This can be used for stations with low disk space (or even diskless) +to borrow disk space from another computer. +Unlike NFS, it is possible to put any filesystem on it, etc. + +For more information, or to download the nbd-client and nbd-server +tools, go to https://github.com/NetworkBlockDevice/nbd. + +The nbd kernel module need only be installed on the client +system, as the nbd-server is completely in userspace. In fact, +the nbd-server has been successfully ported to other operating +systems, including Windows. + +A) NBD parameters +----------------- + +max_part + Number of partitions per device (default: 0). + +nbds_max + Number of block devices that should be initialized (default: 16). diff --git a/Documentation/admin-guide/blockdev/paride.rst b/Documentation/admin-guide/blockdev/paride.rst new file mode 100644 index 000000000..e85ad37cc --- /dev/null +++ b/Documentation/admin-guide/blockdev/paride.rst @@ -0,0 +1,207 @@ +=================================== +Linux and parallel port IDE devices +=================================== + +PARIDE v1.03 (c) 1997-8 Grant Guenther <grant@torque.net> +PATA_PARPORT (c) 2023 Ondrej Zary + +1. Introduction +=============== + +Owing to the simplicity and near universality of the parallel port interface +to personal computers, many external devices such as portable hard-disk, +CD-ROM, LS-120 and tape drives use the parallel port to connect to their +host computer. While some devices (notably scanners) use ad-hoc methods +to pass commands and data through the parallel port interface, most +external devices are actually identical to an internal model, but with +a parallel-port adapter chip added in. Some of the original parallel port +adapters were little more than mechanisms for multiplexing a SCSI bus. +(The Iomega PPA-3 adapter used in the ZIP drives is an example of this +approach). Most current designs, however, take a different approach. +The adapter chip reproduces a small ISA or IDE bus in the external device +and the communication protocol provides operations for reading and writing +device registers, as well as data block transfer functions. Sometimes, +the device being addressed via the parallel cable is a standard SCSI +controller like an NCR 5380. The "ditto" family of external tape +drives use the ISA replicator to interface a floppy disk controller, +which is then connected to a floppy-tape mechanism. The vast majority +of external parallel port devices, however, are now based on standard +IDE type devices, which require no intermediate controller. If one +were to open up a parallel port CD-ROM drive, for instance, one would +find a standard ATAPI CD-ROM drive, a power supply, and a single adapter +that interconnected a standard PC parallel port cable and a standard +IDE cable. It is usually possible to exchange the CD-ROM device with +any other device using the IDE interface. + +The document describes the support in Linux for parallel port IDE +devices. It does not cover parallel port SCSI devices, "ditto" tape +drives or scanners. Many different devices are supported by the +parallel port IDE subsystem, including: + + - MicroSolutions backpack CD-ROM + - MicroSolutions backpack PD/CD + - MicroSolutions backpack hard-drives + - MicroSolutions backpack 8000t tape drive + - SyQuest EZ-135, EZ-230 & SparQ drives + - Avatar Shark + - Imation Superdisk LS-120 + - Maxell Superdisk LS-120 + - FreeCom Power CD + - Hewlett-Packard 5GB and 8GB tape drives + - Hewlett-Packard 7100 and 7200 CD-RW drives + +as well as most of the clone and no-name products on the market. + +To support such a wide range of devices, pata_parport is actually structured +in two parts. There is a base pata_parport module which provides an interface +to kernel libata subsystem, registry and some common methods for accessing +the parallel ports. + +The second component is a set of low-level protocol drivers for each of the +parallel port IDE adapter chips. Thanks to the interest and encouragement of +Linux users from many parts of the world, support is available for almost all +known adapter protocols: + + ==== ====================================== ==== + aten ATEN EH-100 (HK) + bpck Microsolutions backpack (US) + comm DataStor (old-type) "commuter" adapter (TW) + dstr DataStor EP-2000 (TW) + epat Shuttle EPAT (UK) + epia Shuttle EPIA (UK) + fit2 FIT TD-2000 (US) + fit3 FIT TD-3000 (US) + friq Freecom IQ cable (DE) + frpw Freecom Power (DE) + kbic KingByte KBIC-951A and KBIC-971A (TW) + ktti KT Technology PHd adapter (SG) + on20 OnSpec 90c20 (US) + on26 OnSpec 90c26 (US) + ==== ====================================== ==== + + +2. Using pata_parport subsystem +=============================== + +While configuring the Linux kernel, you may choose either to build +the pata_parport drivers into your kernel, or to build them as modules. + +In either case, you will need to select "Parallel port IDE device support" +and at least one of the parallel port communication protocols. +If you do not know what kind of parallel port adapter is used in your drive, +you could begin by checking the file names and any text files on your DOS +installation floppy. Alternatively, you can look at the markings on +the adapter chip itself. That's usually sufficient to identify the +correct device. + +You can actually select all the protocol modules, and allow the pata_parport +subsystem to try them all for you. + +For the "brand-name" products listed above, here are the protocol +and high-level drivers that you would use: + + ================ ============ ======== + Manufacturer Model Protocol + ================ ============ ======== + MicroSolutions CD-ROM bpck + MicroSolutions PD drive bpck + MicroSolutions hard-drive bpck + MicroSolutions 8000t tape bpck + SyQuest EZ, SparQ epat + Imation Superdisk epat + Maxell Superdisk friq + Avatar Shark epat + FreeCom CD-ROM frpw + Hewlett-Packard 5GB Tape epat + Hewlett-Packard 7200e (CD) epat + Hewlett-Packard 7200e (CD-R) epat + ================ ============ ======== + +All parports and all protocol drivers are probed automatically unless probe=0 +parameter is used. So just "modprobe epat" is enough for a Imation SuperDisk +drive to work. + +Manual device creation:: + + # echo "port protocol mode unit delay" >/sys/bus/pata_parport/new_device + +where: + + ======== ================================================ + port parport name (or "auto" for all parports) + protocol protocol name (or "auto" for all protocols) + mode mode number (protocol-specific) or -1 for probe + unit unit number (for backpack only, see below) + delay I/O delay (see troubleshooting section below) + ======== ================================================ + +If you happen to be using a MicroSolutions backpack device, you will +also need to know the unit ID number for each drive. This is usually +the last two digits of the drive's serial number (but read MicroSolutions' +documentation about this). + +If you omit the parameters from the end, defaults will be used, e.g.: + +Probe all parports with all protocols:: + + # echo auto >/sys/bus/pata_parport/new_device + +Probe parport0 using protocol epat and mode 4 (EPP-16):: + + # echo "parport0 epat 4" >/sys/bus/pata_parport/new_device + +Probe parport0 using all protocols:: + + # echo "parport0 auto" >/sys/bus/pata_parport/new_device + +Probe all parports using protoocol epat:: + + # echo "auto epat" >/sys/bus/pata_parport/new_device + +Deleting devices:: + + # echo pata_parport.0 >/sys/bus/pata_parport/delete_device + + +3. Troubleshooting +================== + +3.1 Use EPP mode if you can +---------------------------- + +The most common problems that people report with the pata_parport drivers +concern the parallel port CMOS settings. At this time, none of the +protocol modules support ECP mode, or any ECP combination modes. +If you are able to do so, please set your parallel port into EPP mode +using your CMOS setup procedure. + +3.2 Check the port delay +------------------------- + +Some parallel ports cannot reliably transfer data at full speed. To +offset the errors, the protocol modules introduce a "port +delay" between each access to the i/o ports. Each protocol sets +a default value for this delay. In most cases, the user can override +the default and set it to 0 - resulting in somewhat higher transfer +rates. In some rare cases (especially with older 486 systems) the +default delays are not long enough. if you experience corrupt data +transfers, or unexpected failures, you may wish to increase the +port delay. + +3.3 Some drives need a printer reset +------------------------------------- + +There appear to be a number of "noname" external drives on the market +that do not always power up correctly. We have noticed this with some +drives based on OnSpec and older Freecom adapters. In these rare cases, +the adapter can often be reinitialised by issuing a "printer reset" on +the parallel port. As the reset operation is potentially disruptive in +multiple device environments, the pata_parport drivers will not do it +automatically. You can however, force a printer reset by doing:: + + insmod lp reset=1 + rmmod lp + +If you have one of these marginal cases, you should probably build +your pata_parport drivers as modules, and arrange to do the printer reset +before loading the pata_parport drivers. diff --git a/Documentation/admin-guide/blockdev/ramdisk.rst b/Documentation/admin-guide/blockdev/ramdisk.rst new file mode 100644 index 000000000..9ce6101e8 --- /dev/null +++ b/Documentation/admin-guide/blockdev/ramdisk.rst @@ -0,0 +1,153 @@ +========================================== +Using the RAM disk block device with Linux +========================================== + +.. Contents: + + 1) Overview + 2) Kernel Command Line Parameters + 3) Using "rdev" + 4) An Example of Creating a Compressed RAM Disk + + +1) Overview +----------- + +The RAM disk driver is a way to use main system memory as a block device. It +is required for initrd, an initial filesystem used if you need to load modules +in order to access the root filesystem (see Documentation/admin-guide/initrd.rst). It can +also be used for a temporary filesystem for crypto work, since the contents +are erased on reboot. + +The RAM disk dynamically grows as more space is required. It does this by using +RAM from the buffer cache. The driver marks the buffers it is using as dirty +so that the VM subsystem does not try to reclaim them later. + +The RAM disk supports up to 16 RAM disks by default, and can be reconfigured +to support an unlimited number of RAM disks (at your own risk). Just change +the configuration symbol BLK_DEV_RAM_COUNT in the Block drivers config menu +and (re)build the kernel. + +To use RAM disk support with your system, run './MAKEDEV ram' from the /dev +directory. RAM disks are all major number 1, and start with minor number 0 +for /dev/ram0, etc. If used, modern kernels use /dev/ram0 for an initrd. + +The new RAM disk also has the ability to load compressed RAM disk images, +allowing one to squeeze more programs onto an average installation or +rescue floppy disk. + + +2) Parameters +--------------------------------- + +2a) Kernel Command Line Parameters + + ramdisk_size=N + Size of the ramdisk. + +This parameter tells the RAM disk driver to set up RAM disks of N k size. The +default is 4096 (4 MB). + +2b) Module parameters + + rd_nr + /dev/ramX devices created. + + max_part + Maximum partition number. + + rd_size + See ramdisk_size. + +3) Using "rdev" +--------------- + +"rdev" is an obsolete, deprecated, antiquated utility that could be used +to set the boot device in a Linux kernel image. + +Instead of using rdev, just place the boot device information on the +kernel command line and pass it to the kernel from the bootloader. + +You can also pass arguments to the kernel by setting FDARGS in +arch/x86/boot/Makefile and specify in initrd image by setting FDINITRD in +arch/x86/boot/Makefile. + +Some of the kernel command line boot options that may apply here are:: + + ramdisk_start=N + ramdisk_size=M + +If you make a boot disk that has LILO, then for the above, you would use:: + + append = "ramdisk_start=N ramdisk_size=M" + +4) An Example of Creating a Compressed RAM Disk +----------------------------------------------- + +To create a RAM disk image, you will need a spare block device to +construct it on. This can be the RAM disk device itself, or an +unused disk partition (such as an unmounted swap partition). For this +example, we will use the RAM disk device, "/dev/ram0". + +Note: This technique should not be done on a machine with less than 8 MB +of RAM. If using a spare disk partition instead of /dev/ram0, then this +restriction does not apply. + +a) Decide on the RAM disk size that you want. Say 2 MB for this example. + Create it by writing to the RAM disk device. (This step is not currently + required, but may be in the future.) It is wise to zero out the + area (esp. for disks) so that maximal compression is achieved for + the unused blocks of the image that you are about to create:: + + dd if=/dev/zero of=/dev/ram0 bs=1k count=2048 + +b) Make a filesystem on it. Say ext2fs for this example:: + + mke2fs -vm0 /dev/ram0 2048 + +c) Mount it, copy the files you want to it (eg: /etc/* /dev/* ...) + and unmount it again. + +d) Compress the contents of the RAM disk. The level of compression + will be approximately 50% of the space used by the files. Unused + space on the RAM disk will compress to almost nothing:: + + dd if=/dev/ram0 bs=1k count=2048 | gzip -v9 > /tmp/ram_image.gz + +e) Put the kernel onto the floppy:: + + dd if=zImage of=/dev/fd0 bs=1k + +f) Put the RAM disk image onto the floppy, after the kernel. Use an offset + that is slightly larger than the kernel, so that you can put another + (possibly larger) kernel onto the same floppy later without overlapping + the RAM disk image. An offset of 400 kB for kernels about 350 kB in + size would be reasonable. Make sure offset+size of ram_image.gz is + not larger than the total space on your floppy (usually 1440 kB):: + + dd if=/tmp/ram_image.gz of=/dev/fd0 bs=1k seek=400 + +g) Make sure that you have already specified the boot information in + FDARGS and FDINITRD or that you use a bootloader to pass kernel + command line boot options to the kernel. + +That is it. You now have your boot/root compressed RAM disk floppy. Some +users may wish to combine steps (d) and (f) by using a pipe. + + + Paul Gortmaker 12/95 + +Changelog: +---------- + +SEPT-2020 : + + Removed usage of "rdev" + +10-22-04 : + Updated to reflect changes in command line options, remove + obsolete references, general cleanup. + James Nelson (james4765@gmail.com) + +12-95 : + Original Document diff --git a/Documentation/admin-guide/blockdev/zram.rst b/Documentation/admin-guide/blockdev/zram.rst new file mode 100644 index 000000000..e4551579c --- /dev/null +++ b/Documentation/admin-guide/blockdev/zram.rst @@ -0,0 +1,532 @@ +======================================== +zram: Compressed RAM-based block devices +======================================== + +Introduction +============ + +The zram module creates RAM-based block devices named /dev/zram<id> +(<id> = 0, 1, ...). Pages written to these disks are compressed and stored +in memory itself. These disks allow very fast I/O and compression provides +good amounts of memory savings. Some of the use cases include /tmp storage, +use as swap disks, various caches under /var and maybe many more. :) + +Statistics for individual zram devices are exported through sysfs nodes at +/sys/block/zram<id>/ + +Usage +===== + +There are several ways to configure and manage zram device(-s): + +a) using zram and zram_control sysfs attributes +b) using zramctl utility, provided by util-linux (util-linux@vger.kernel.org). + +In this document we will describe only 'manual' zram configuration steps, +IOW, zram and zram_control sysfs attributes. + +In order to get a better idea about zramctl please consult util-linux +documentation, zramctl man-page or `zramctl --help`. Please be informed +that zram maintainers do not develop/maintain util-linux or zramctl, should +you have any questions please contact util-linux@vger.kernel.org + +Following shows a typical sequence of steps for using zram. + +WARNING +======= + +For the sake of simplicity we skip error checking parts in most of the +examples below. However, it is your sole responsibility to handle errors. + +zram sysfs attributes always return negative values in case of errors. +The list of possible return codes: + +======== ============================================================= +-EBUSY an attempt to modify an attribute that cannot be changed once + the device has been initialised. Please reset device first. +-ENOMEM zram was not able to allocate enough memory to fulfil your + needs. +-EINVAL invalid input has been provided. +======== ============================================================= + +If you use 'echo', the returned value is set by the 'echo' utility, +and, in general case, something like:: + + echo 3 > /sys/block/zram0/max_comp_streams + if [ $? -ne 0 ]; then + handle_error + fi + +should suffice. + +1) Load Module +============== + +:: + + modprobe zram num_devices=4 + +This creates 4 devices: /dev/zram{0,1,2,3} + +num_devices parameter is optional and tells zram how many devices should be +pre-created. Default: 1. + +2) Set max number of compression streams +======================================== + +Regardless of the value passed to this attribute, ZRAM will always +allocate multiple compression streams - one per online CPU - thus +allowing several concurrent compression operations. The number of +allocated compression streams goes down when some of the CPUs +become offline. There is no single-compression-stream mode anymore, +unless you are running a UP system or have only 1 CPU online. + +To find out how many streams are currently available:: + + cat /sys/block/zram0/max_comp_streams + +3) Select compression algorithm +=============================== + +Using comp_algorithm device attribute one can see available and +currently selected (shown in square brackets) compression algorithms, +or change the selected compression algorithm (once the device is initialised +there is no way to change compression algorithm). + +Examples:: + + #show supported compression algorithms + cat /sys/block/zram0/comp_algorithm + lzo [lz4] + + #select lzo compression algorithm + echo lzo > /sys/block/zram0/comp_algorithm + +For the time being, the `comp_algorithm` content does not necessarily +show every compression algorithm supported by the kernel. We keep this +list primarily to simplify device configuration and one can configure +a new device with a compression algorithm that is not listed in +`comp_algorithm`. The thing is that, internally, ZRAM uses Crypto API +and, if some of the algorithms were built as modules, it's impossible +to list all of them using, for instance, /proc/crypto or any other +method. This, however, has an advantage of permitting the usage of +custom crypto compression modules (implementing S/W or H/W compression). + +4) Set Disksize +=============== + +Set disk size by writing the value to sysfs node 'disksize'. +The value can be either in bytes or you can use mem suffixes. +Examples:: + + # Initialize /dev/zram0 with 50MB disksize + echo $((50*1024*1024)) > /sys/block/zram0/disksize + + # Using mem suffixes + echo 256K > /sys/block/zram0/disksize + echo 512M > /sys/block/zram0/disksize + echo 1G > /sys/block/zram0/disksize + +Note: +There is little point creating a zram of greater than twice the size of memory +since we expect a 2:1 compression ratio. Note that zram uses about 0.1% of the +size of the disk when not in use so a huge zram is wasteful. + +5) Set memory limit: Optional +============================= + +Set memory limit by writing the value to sysfs node 'mem_limit'. +The value can be either in bytes or you can use mem suffixes. +In addition, you could change the value in runtime. +Examples:: + + # limit /dev/zram0 with 50MB memory + echo $((50*1024*1024)) > /sys/block/zram0/mem_limit + + # Using mem suffixes + echo 256K > /sys/block/zram0/mem_limit + echo 512M > /sys/block/zram0/mem_limit + echo 1G > /sys/block/zram0/mem_limit + + # To disable memory limit + echo 0 > /sys/block/zram0/mem_limit + +6) Activate +=========== + +:: + + mkswap /dev/zram0 + swapon /dev/zram0 + + mkfs.ext4 /dev/zram1 + mount /dev/zram1 /tmp + +7) Add/remove zram devices +========================== + +zram provides a control interface, which enables dynamic (on-demand) device +addition and removal. + +In order to add a new /dev/zramX device, perform a read operation on the hot_add +attribute. This will return either the new device's device id (meaning that you +can use /dev/zram<id>) or an error code. + +Example:: + + cat /sys/class/zram-control/hot_add + 1 + +To remove the existing /dev/zramX device (where X is a device id) +execute:: + + echo X > /sys/class/zram-control/hot_remove + +8) Stats +======== + +Per-device statistics are exported as various nodes under /sys/block/zram<id>/ + +A brief description of exported device attributes follows. For more details +please read Documentation/ABI/testing/sysfs-block-zram. + +====================== ====== =============================================== +Name access description +====================== ====== =============================================== +disksize RW show and set the device's disk size +initstate RO shows the initialization state of the device +reset WO trigger device reset +mem_used_max WO reset the `mem_used_max` counter (see later) +mem_limit WO specifies the maximum amount of memory ZRAM can + use to store the compressed data +writeback_limit WO specifies the maximum amount of write IO zram + can write out to backing device as 4KB unit +writeback_limit_enable RW show and set writeback_limit feature +max_comp_streams RW the number of possible concurrent compress + operations +comp_algorithm RW show and change the compression algorithm +compact WO trigger memory compaction +debug_stat RO this file is used for zram debugging purposes +backing_dev RW set up backend storage for zram to write out +idle WO mark allocated slot as idle +====================== ====== =============================================== + + +User space is advised to use the following files to read the device statistics. + +File /sys/block/zram<id>/stat + +Represents block layer statistics. Read Documentation/block/stat.rst for +details. + +File /sys/block/zram<id>/io_stat + +The stat file represents device's I/O statistics not accounted by block +layer and, thus, not available in zram<id>/stat file. It consists of a +single line of text and contains the following stats separated by +whitespace: + + ============= ============================================================= + failed_reads The number of failed reads + failed_writes The number of failed writes + invalid_io The number of non-page-size-aligned I/O requests + notify_free Depending on device usage scenario it may account + + a) the number of pages freed because of swap slot free + notifications + b) the number of pages freed because of + REQ_OP_DISCARD requests sent by bio. The former ones are + sent to a swap block device when a swap slot is freed, + which implies that this disk is being used as a swap disk. + + The latter ones are sent by filesystem mounted with + discard option, whenever some data blocks are getting + discarded. + ============= ============================================================= + +File /sys/block/zram<id>/mm_stat + +The mm_stat file represents the device's mm statistics. It consists of a single +line of text and contains the following stats separated by whitespace: + + ================ ============================================================= + orig_data_size uncompressed size of data stored in this disk. + Unit: bytes + compr_data_size compressed size of data stored in this disk + mem_used_total the amount of memory allocated for this disk. This + includes allocator fragmentation and metadata overhead, + allocated for this disk. So, allocator space efficiency + can be calculated using compr_data_size and this statistic. + Unit: bytes + mem_limit the maximum amount of memory ZRAM can use to store + the compressed data + mem_used_max the maximum amount of memory zram has consumed to + store the data + same_pages the number of same element filled pages written to this disk. + No memory is allocated for such pages. + pages_compacted the number of pages freed during compaction + huge_pages the number of incompressible pages + huge_pages_since the number of incompressible pages since zram set up + ================ ============================================================= + +File /sys/block/zram<id>/bd_stat + +The bd_stat file represents a device's backing device statistics. It consists of +a single line of text and contains the following stats separated by whitespace: + + ============== ============================================================= + bd_count size of data written in backing device. + Unit: 4K bytes + bd_reads the number of reads from backing device + Unit: 4K bytes + bd_writes the number of writes to backing device + Unit: 4K bytes + ============== ============================================================= + +9) Deactivate +============= + +:: + + swapoff /dev/zram0 + umount /dev/zram1 + +10) Reset +========= + + Write any positive value to 'reset' sysfs node:: + + echo 1 > /sys/block/zram0/reset + echo 1 > /sys/block/zram1/reset + + This frees all the memory allocated for the given device and + resets the disksize to zero. You must set the disksize again + before reusing the device. + +Optional Feature +================ + +writeback +--------- + +With CONFIG_ZRAM_WRITEBACK, zram can write idle/incompressible page +to backing storage rather than keeping it in memory. +To use the feature, admin should set up backing device via:: + + echo /dev/sda5 > /sys/block/zramX/backing_dev + +before disksize setting. It supports only partitions at this moment. +If admin wants to use incompressible page writeback, they could do it via:: + + echo huge > /sys/block/zramX/writeback + +To use idle page writeback, first, user need to declare zram pages +as idle:: + + echo all > /sys/block/zramX/idle + +From now on, any pages on zram are idle pages. The idle mark +will be removed until someone requests access of the block. +IOW, unless there is access request, those pages are still idle pages. +Additionally, when CONFIG_ZRAM_MEMORY_TRACKING is enabled pages can be +marked as idle based on how long (in seconds) it's been since they were +last accessed:: + + echo 86400 > /sys/block/zramX/idle + +In this example all pages which haven't been accessed in more than 86400 +seconds (one day) will be marked idle. + +Admin can request writeback of those idle pages at right timing via:: + + echo idle > /sys/block/zramX/writeback + +With the command, zram will writeback idle pages from memory to the storage. + +Additionally, if a user choose to writeback only huge and idle pages +this can be accomplished with:: + + echo huge_idle > /sys/block/zramX/writeback + +If a user chooses to writeback only incompressible pages (pages that none of +algorithms can compress) this can be accomplished with:: + + echo incompressible > /sys/block/zramX/writeback + +If an admin wants to write a specific page in zram device to the backing device, +they could write a page index into the interface:: + + echo "page_index=1251" > /sys/block/zramX/writeback + +If there are lots of write IO with flash device, potentially, it has +flash wearout problem so that admin needs to design write limitation +to guarantee storage health for entire product life. + +To overcome the concern, zram supports "writeback_limit" feature. +The "writeback_limit_enable"'s default value is 0 so that it doesn't limit +any writeback. IOW, if admin wants to apply writeback budget, they should +enable writeback_limit_enable via:: + + $ echo 1 > /sys/block/zramX/writeback_limit_enable + +Once writeback_limit_enable is set, zram doesn't allow any writeback +until admin sets the budget via /sys/block/zramX/writeback_limit. + +(If admin doesn't enable writeback_limit_enable, writeback_limit's value +assigned via /sys/block/zramX/writeback_limit is meaningless.) + +If admin wants to limit writeback as per-day 400M, they could do it +like below:: + + $ MB_SHIFT=20 + $ 4K_SHIFT=12 + $ echo $((400<<MB_SHIFT>>4K_SHIFT)) > \ + /sys/block/zram0/writeback_limit. + $ echo 1 > /sys/block/zram0/writeback_limit_enable + +If admins want to allow further write again once the budget is exhausted, +they could do it like below:: + + $ echo $((400<<MB_SHIFT>>4K_SHIFT)) > \ + /sys/block/zram0/writeback_limit + +If an admin wants to see the remaining writeback budget since last set:: + + $ cat /sys/block/zramX/writeback_limit + +If an admin wants to disable writeback limit, they could do:: + + $ echo 0 > /sys/block/zramX/writeback_limit_enable + +The writeback_limit count will reset whenever you reset zram (e.g., +system reboot, echo 1 > /sys/block/zramX/reset) so keeping how many of +writeback happened until you reset the zram to allocate extra writeback +budget in next setting is user's job. + +If admin wants to measure writeback count in a certain period, they could +know it via /sys/block/zram0/bd_stat's 3rd column. + +recompression +------------- + +With CONFIG_ZRAM_MULTI_COMP, zram can recompress pages using alternative +(secondary) compression algorithms. The basic idea is that alternative +compression algorithm can provide better compression ratio at a price of +(potentially) slower compression/decompression speeds. Alternative compression +algorithm can, for example, be more successful compressing huge pages (those +that default algorithm failed to compress). Another application is idle pages +recompression - pages that are cold and sit in the memory can be recompressed +using more effective algorithm and, hence, reduce zsmalloc memory usage. + +With CONFIG_ZRAM_MULTI_COMP, zram supports up to 4 compression algorithms: +one primary and up to 3 secondary ones. Primary zram compressor is explained +in "3) Select compression algorithm", secondary algorithms are configured +using recomp_algorithm device attribute. + +Example::: + + #show supported recompression algorithms + cat /sys/block/zramX/recomp_algorithm + #1: lzo lzo-rle lz4 lz4hc [zstd] + #2: lzo lzo-rle lz4 [lz4hc] zstd + +Alternative compression algorithms are sorted by priority. In the example +above, zstd is used as the first alternative algorithm, which has priority +of 1, while lz4hc is configured as a compression algorithm with priority 2. +Alternative compression algorithm's priority is provided during algorithms +configuration::: + + #select zstd recompression algorithm, priority 1 + echo "algo=zstd priority=1" > /sys/block/zramX/recomp_algorithm + + #select deflate recompression algorithm, priority 2 + echo "algo=deflate priority=2" > /sys/block/zramX/recomp_algorithm + +Another device attribute that CONFIG_ZRAM_MULTI_COMP enables is recompress, +which controls recompression. + +Examples::: + + #IDLE pages recompression is activated by `idle` mode + echo "type=idle" > /sys/block/zramX/recompress + + #HUGE pages recompression is activated by `huge` mode + echo "type=huge" > /sys/block/zram0/recompress + + #HUGE_IDLE pages recompression is activated by `huge_idle` mode + echo "type=huge_idle" > /sys/block/zramX/recompress + +The number of idle pages can be significant, so user-space can pass a size +threshold (in bytes) to the recompress knob: zram will recompress only pages +of equal or greater size::: + + #recompress all pages larger than 3000 bytes + echo "threshold=3000" > /sys/block/zramX/recompress + + #recompress idle pages larger than 2000 bytes + echo "type=idle threshold=2000" > /sys/block/zramX/recompress + +Recompression of idle pages requires memory tracking. + +During re-compression for every page, that matches re-compression criteria, +ZRAM iterates the list of registered alternative compression algorithms in +order of their priorities. ZRAM stops either when re-compression was +successful (re-compressed object is smaller in size than the original one) +and matches re-compression criteria (e.g. size threshold) or when there are +no secondary algorithms left to try. If none of the secondary algorithms can +successfully re-compressed the page such a page is marked as incompressible, +so ZRAM will not attempt to re-compress it in the future. + +This re-compression behaviour, when it iterates through the list of +registered compression algorithms, increases our chances of finding the +algorithm that successfully compresses a particular page. Sometimes, however, +it is convenient (and sometimes even necessary) to limit recompression to +only one particular algorithm so that it will not try any other algorithms. +This can be achieved by providing a algo=NAME parameter::: + + #use zstd algorithm only (if registered) + echo "type=huge algo=zstd" > /sys/block/zramX/recompress + +memory tracking +=============== + +With CONFIG_ZRAM_MEMORY_TRACKING, user can know information of the +zram block. It could be useful to catch cold or incompressible +pages of the process with*pagemap. + +If you enable the feature, you could see block state via +/sys/kernel/debug/zram/zram0/block_state". The output is as follows:: + + 300 75.033841 .wh... + 301 63.806904 s..... + 302 63.806919 ..hi.. + 303 62.801919 ....r. + 304 146.781902 ..hi.n + +First column + zram's block index. +Second column + access time since the system was booted +Third column + state of the block: + + s: + same page + w: + written page to backing store + h: + huge page + i: + idle page + r: + recompressed page (secondary compression algorithm) + n: + none (including secondary) of algorithms could compress it + +First line of above example says 300th block is accessed at 75.033841sec +and the block's state is huge so it is written back to the backing +storage. It's a debugging feature so anyone shouldn't rely on it to work +properly. + +Nitin Gupta +ngupta@vflare.org diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst new file mode 100644 index 000000000..91339efdc --- /dev/null +++ b/Documentation/admin-guide/bootconfig.rst @@ -0,0 +1,327 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _bootconfig: + +================== +Boot Configuration +================== + +:Author: Masami Hiramatsu <mhiramat@kernel.org> + +Overview +======== + +The boot configuration expands the current kernel command line to support +additional key-value data when booting the kernel in an efficient way. +This allows administrators to pass a structured-Key config file. + +Config File Syntax +================== + +The boot config syntax is a simple structured key-value. Each key consists +of dot-connected-words, and key and value are connected by ``=``. The value +has to be terminated by semi-colon (``;``) or newline (``\n``). +For array value, array entries are separated by comma (``,``). :: + + KEY[.WORD[...]] = VALUE[, VALUE2[...]][;] + +Unlike the kernel command line syntax, spaces are OK around the comma and ``=``. + +Each key word must contain only alphabets, numbers, dash (``-``) or underscore +(``_``). And each value only contains printable characters or spaces except +for delimiters such as semi-colon (``;``), new-line (``\n``), comma (``,``), +hash (``#``) and closing brace (``}``). + +If you want to use those delimiters in a value, you can use either double- +quotes (``"VALUE"``) or single-quotes (``'VALUE'``) to quote it. Note that +you can not escape these quotes. + +There can be a key which doesn't have value or has an empty value. Those keys +are used for checking if the key exists or not (like a boolean). + +Key-Value Syntax +---------------- + +The boot config file syntax allows user to merge partially same word keys +by brace. For example:: + + foo.bar.baz = value1 + foo.bar.qux.quux = value2 + +These can be written also in:: + + foo.bar { + baz = value1 + qux.quux = value2 + } + +Or more shorter, written as following:: + + foo.bar { baz = value1; qux.quux = value2 } + +In both styles, same key words are automatically merged when parsing it +at boot time. So you can append similar trees or key-values. + +Same-key Values +--------------- + +It is prohibited that two or more values or arrays share a same-key. +For example,:: + + foo = bar, baz + foo = qux # !ERROR! we can not re-define same key + +If you want to update the value, you must use the override operator +``:=`` explicitly. For example:: + + foo = bar, baz + foo := qux + +then, the ``qux`` is assigned to ``foo`` key. This is useful for +overriding the default value by adding (partial) custom bootconfigs +without parsing the default bootconfig. + +If you want to append the value to existing key as an array member, +you can use ``+=`` operator. For example:: + + foo = bar, baz + foo += qux + +In this case, the key ``foo`` has ``bar``, ``baz`` and ``qux``. + +Moreover, sub-keys and a value can coexist under a parent key. +For example, following config is allowed.:: + + foo = value1 + foo.bar = value2 + foo := value3 # This will update foo's value. + +Note, since there is no syntax to put a raw value directly under a +structured key, you have to define it outside of the brace. For example:: + + foo { + bar = value1 + bar { + baz = value2 + qux = value3 + } + } + +Also, the order of the value node under a key is fixed. If there +are a value and subkeys, the value is always the first child node +of the key. Thus if user specifies subkeys first, e.g.:: + + foo.bar = value1 + foo = value2 + +In the program (and /proc/bootconfig), it will be shown as below:: + + foo = value2 + foo.bar = value1 + +Comments +-------- + +The config syntax accepts shell-script style comments. The comments starting +with hash ("#") until newline ("\n") will be ignored. + +:: + + # comment line + foo = value # value is set to foo. + bar = 1, # 1st element + 2, # 2nd element + 3 # 3rd element + +This is parsed as below:: + + foo = value + bar = 1, 2, 3 + +Note that you can not put a comment between value and delimiter(``,`` or +``;``). This means following config has a syntax error :: + + key = 1 # comment + ,2 + + +/proc/bootconfig +================ + +/proc/bootconfig is a user-space interface of the boot config. +Unlike /proc/cmdline, this file shows the key-value style list. +Each key-value pair is shown in each line with following style:: + + KEY[.WORDS...] = "[VALUE]"[,"VALUE2"...] + + +Boot Kernel With a Boot Config +============================== + +There are two options to boot the kernel with bootconfig: attaching the +bootconfig to the initrd image or embedding it in the kernel itself. + +Attaching a Boot Config to Initrd +--------------------------------- + +Since the boot configuration file is loaded with initrd by default, +it will be added to the end of the initrd (initramfs) image file with +padding, size, checksum and 12-byte magic word as below. + +[initrd][bootconfig][padding][size(le32)][checksum(le32)][#BOOTCONFIG\n] + +The size and checksum fields are unsigned 32bit little endian value. + +When the boot configuration is added to the initrd image, the total +file size is aligned to 4 bytes. To fill the gap, null characters +(``\0``) will be added. Thus the ``size`` is the length of the bootconfig +file + padding bytes. + +The Linux kernel decodes the last part of the initrd image in memory to +get the boot configuration data. +Because of this "piggyback" method, there is no need to change or +update the boot loader and the kernel image itself as long as the boot +loader passes the correct initrd file size. If by any chance, the boot +loader passes a longer size, the kernel fails to find the bootconfig data. + +To do this operation, Linux kernel provides ``bootconfig`` command under +tools/bootconfig, which allows admin to apply or delete the config file +to/from initrd image. You can build it by the following command:: + + # make -C tools/bootconfig + +To add your boot config file to initrd image, run bootconfig as below +(Old data is removed automatically if exists):: + + # tools/bootconfig/bootconfig -a your-config /boot/initrd.img-X.Y.Z + +To remove the config from the image, you can use -d option as below:: + + # tools/bootconfig/bootconfig -d /boot/initrd.img-X.Y.Z + +Then add "bootconfig" on the normal kernel command line to tell the +kernel to look for the bootconfig at the end of the initrd file. +Alternatively, build your kernel with the ``CONFIG_BOOT_CONFIG_FORCE`` +Kconfig option selected. + +Embedding a Boot Config into Kernel +----------------------------------- + +If you can not use initrd, you can also embed the bootconfig file in the +kernel by Kconfig options. In this case, you need to recompile the kernel +with the following configs:: + + CONFIG_BOOT_CONFIG_EMBED=y + CONFIG_BOOT_CONFIG_EMBED_FILE="/PATH/TO/BOOTCONFIG/FILE" + +``CONFIG_BOOT_CONFIG_EMBED_FILE`` requires an absolute path or a relative +path to the bootconfig file from source tree or object tree. +The kernel will embed it as the default bootconfig. + +Just as when attaching the bootconfig to the initrd, you need ``bootconfig`` +option on the kernel command line to enable the embedded bootconfig, or, +alternatively, build your kernel with the ``CONFIG_BOOT_CONFIG_FORCE`` +Kconfig option selected. + +Note that even if you set this option, you can override the embedded +bootconfig by another bootconfig which attached to the initrd. + +Kernel parameters via Boot Config +================================= + +In addition to the kernel command line, the boot config can be used for +passing the kernel parameters. All the key-value pairs under ``kernel`` +key will be passed to kernel cmdline directly. Moreover, the key-value +pairs under ``init`` will be passed to init process via the cmdline. +The parameters are concatenated with user-given kernel cmdline string +as the following order, so that the command line parameter can override +bootconfig parameters (this depends on how the subsystem handles parameters +but in general, earlier parameter will be overwritten by later one.):: + + [bootconfig params][cmdline params] -- [bootconfig init params][cmdline init params] + +Here is an example of the bootconfig file for kernel/init parameters.:: + + kernel { + root = 01234567-89ab-cdef-0123-456789abcd + } + init { + splash + } + +This will be copied into the kernel cmdline string as the following:: + + root="01234567-89ab-cdef-0123-456789abcd" -- splash + +If user gives some other command line like,:: + + ro bootconfig -- quiet + +The final kernel cmdline will be the following:: + + root="01234567-89ab-cdef-0123-456789abcd" ro bootconfig -- splash quiet + + +Config File Limitation +====================== + +Currently the maximum config size size is 32KB and the total key-words (not +key-value entries) must be under 1024 nodes. +Note: this is not the number of entries but nodes, an entry must consume +more than 2 nodes (a key-word and a value). So theoretically, it will be +up to 512 key-value pairs. If keys contains 3 words in average, it can +contain 256 key-value pairs. In most cases, the number of config items +will be under 100 entries and smaller than 8KB, so it would be enough. +If the node number exceeds 1024, parser returns an error even if the file +size is smaller than 32KB. (Note that this maximum size is not including +the padding null characters.) +Anyway, since bootconfig command verifies it when appending a boot config +to initrd image, user can notice it before boot. + + +Bootconfig APIs +=============== + +User can query or loop on key-value pairs, also it is possible to find +a root (prefix) key node and find key-values under that node. + +If you have a key string, you can query the value directly with the key +using xbc_find_value(). If you want to know what keys exist in the boot +config, you can use xbc_for_each_key_value() to iterate key-value pairs. +Note that you need to use xbc_array_for_each_value() for accessing +each array's value, e.g.:: + + vnode = NULL; + xbc_find_value("key.word", &vnode); + if (vnode && xbc_node_is_array(vnode)) + xbc_array_for_each_value(vnode, value) { + printk("%s ", value); + } + +If you want to focus on keys which have a prefix string, you can use +xbc_find_node() to find a node by the prefix string, and iterate +keys under the prefix node with xbc_node_for_each_key_value(). + +But the most typical usage is to get the named value under prefix +or get the named array under prefix as below:: + + root = xbc_find_node("key.prefix"); + value = xbc_node_find_value(root, "option", &vnode); + ... + xbc_node_for_each_array_value(root, "array-option", value, anode) { + ... + } + +This accesses a value of "key.prefix.option" and an array of +"key.prefix.array-option". + +Locking is not needed, since after initialization, the config becomes +read-only. All data and keys must be copied if you need to modify it. + + +Functions and structures +======================== + +.. kernel-doc:: include/linux/bootconfig.h +.. kernel-doc:: lib/bootconfig.c + diff --git a/Documentation/admin-guide/braille-console.rst b/Documentation/admin-guide/braille-console.rst new file mode 100644 index 000000000..18e79337d --- /dev/null +++ b/Documentation/admin-guide/braille-console.rst @@ -0,0 +1,38 @@ +Linux Braille Console +===================== + +To get early boot messages on a braille device (before userspace screen +readers can start), you first need to compile the support for the usual serial +console (see :ref:`Documentation/admin-guide/serial-console.rst <serial_console>`), and +for braille device +(in :menuselection:`Device Drivers --> Accessibility support --> Console on braille device`). + +Then you need to specify a ``console=brl``, option on the kernel command line, the +format is:: + + console=brl,serial_options... + +where ``serial_options...`` are the same as described in +:ref:`Documentation/admin-guide/serial-console.rst <serial_console>`. + +So for instance you can use ``console=brl,ttyS0`` if the braille device is connected to the first serial port, and ``console=brl,ttyS0,115200`` to +override the baud rate to 115200, etc. + +By default, the braille device will just show the last kernel message (console +mode). To review previous messages, press the Insert key to switch to the VT +review mode. In review mode, the arrow keys permit to browse in the VT content, +:kbd:`PAGE-UP`/:kbd:`PAGE-DOWN` keys go at the top/bottom of the screen, and +the :kbd:`HOME` key goes back +to the cursor, hence providing very basic screen reviewing facility. + +Sound feedback can be obtained by adding the ``braille_console.sound=1`` kernel +parameter. + +For simplicity, only one braille console can be enabled, other uses of +``console=brl,...`` will be discarded. Also note that it does not interfere with +the console selection mechanism described in +:ref:`Documentation/admin-guide/serial-console.rst <serial_console>`. + +For now, only the VisioBraille device is supported. + +Samuel Thibault <samuel.thibault@ens-lyon.org> diff --git a/Documentation/admin-guide/btmrvl.rst b/Documentation/admin-guide/btmrvl.rst new file mode 100644 index 000000000..ec57740ea --- /dev/null +++ b/Documentation/admin-guide/btmrvl.rst @@ -0,0 +1,124 @@ +============= +btmrvl driver +============= + +All commands are used via debugfs interface. + +Set/get driver configurations +============================= + +Path: /debug/btmrvl/config/ + +gpiogap=[n], hscfgcmd + These commands are used to configure the host sleep parameters:: + bit 8:0 -- Gap + bit 16:8 -- GPIO + + where GPIO is the pin number of GPIO used to wake up the host. + It could be any valid GPIO pin# (e.g. 0-7) or 0xff (SDIO interface + wakeup will be used instead). + + where Gap is the gap in milli seconds between wakeup signal and + wakeup event, or 0xff for special host sleep setting. + + Usage:: + + # Use SDIO interface to wake up the host and set GAP to 0x80: + echo 0xff80 > /debug/btmrvl/config/gpiogap + echo 1 > /debug/btmrvl/config/hscfgcmd + + # Use GPIO pin #3 to wake up the host and set GAP to 0xff: + echo 0x03ff > /debug/btmrvl/config/gpiogap + echo 1 > /debug/btmrvl/config/hscfgcmd + +psmode=[n], pscmd + These commands are used to enable/disable auto sleep mode + + where the option is:: + + 1 -- Enable auto sleep mode + 0 -- Disable auto sleep mode + + Usage:: + + # Enable auto sleep mode + echo 1 > /debug/btmrvl/config/psmode + echo 1 > /debug/btmrvl/config/pscmd + + # Disable auto sleep mode + echo 0 > /debug/btmrvl/config/psmode + echo 1 > /debug/btmrvl/config/pscmd + + +hsmode=[n], hscmd + These commands are used to enable host sleep or wake up firmware + + where the option is:: + + 1 -- Enable host sleep + 0 -- Wake up firmware + + Usage:: + + # Enable host sleep + echo 1 > /debug/btmrvl/config/hsmode + echo 1 > /debug/btmrvl/config/hscmd + + # Wake up firmware + echo 0 > /debug/btmrvl/config/hsmode + echo 1 > /debug/btmrvl/config/hscmd + + +Get driver status +================= + +Path: /debug/btmrvl/status/ + +Usage:: + + cat /debug/btmrvl/status/<args> + +where the args are: + +curpsmode + This command displays current auto sleep status. + +psstate + This command display the power save state. + +hsstate + This command display the host sleep state. + +txdnldrdy + This command displays the value of Tx download ready flag. + +Issuing a raw hci command +========================= + +Use hcitool to issue raw hci command, refer to hcitool manual + +Usage:: + + Hcitool cmd <ogf> <ocf> [Parameters] + +Interface Control Command:: + + hcitool cmd 0x3f 0x5b 0xf5 0x01 0x00 --Enable All interface + hcitool cmd 0x3f 0x5b 0xf5 0x01 0x01 --Enable Wlan interface + hcitool cmd 0x3f 0x5b 0xf5 0x01 0x02 --Enable BT interface + hcitool cmd 0x3f 0x5b 0xf5 0x00 0x00 --Disable All interface + hcitool cmd 0x3f 0x5b 0xf5 0x00 0x01 --Disable Wlan interface + hcitool cmd 0x3f 0x5b 0xf5 0x00 0x02 --Disable BT interface + +SD8688 firmware +=============== + +Images: + +- /lib/firmware/sd8688_helper.bin +- /lib/firmware/sd8688.bin + + +The images can be downloaded from: + +git.infradead.org/users/dwmw2/linux-firmware.git/libertas/ diff --git a/Documentation/admin-guide/bug-bisect.rst b/Documentation/admin-guide/bug-bisect.rst new file mode 100644 index 000000000..325c5d0ed --- /dev/null +++ b/Documentation/admin-guide/bug-bisect.rst @@ -0,0 +1,76 @@ +Bisecting a bug ++++++++++++++++ + +Last updated: 28 October 2016 + +Introduction +============ + +Always try the latest kernel from kernel.org and build from source. If you are +not confident in doing that please report the bug to your distribution vendor +instead of to a kernel developer. + +Finding bugs is not always easy. Have a go though. If you can't find it don't +give up. Report as much as you have found to the relevant maintainer. See +MAINTAINERS for who that is for the subsystem you have worked on. + +Before you submit a bug report read +'Documentation/admin-guide/reporting-issues.rst'. + +Devices not appearing +===================== + +Often this is caused by udev/systemd. Check that first before blaming it +on the kernel. + +Finding patch that caused a bug +=============================== + +Using the provided tools with ``git`` makes finding bugs easy provided the bug +is reproducible. + +Steps to do it: + +- build the Kernel from its git source +- start bisect with [#f1]_:: + + $ git bisect start + +- mark the broken changeset with:: + + $ git bisect bad [commit] + +- mark a changeset where the code is known to work with:: + + $ git bisect good [commit] + +- rebuild the Kernel and test +- interact with git bisect by using either:: + + $ git bisect good + + or:: + + $ git bisect bad + + depending if the bug happened on the changeset you're testing +- After some interactions, git bisect will give you the changeset that + likely caused the bug. + +- For example, if you know that the current version is bad, and version + 4.8 is good, you could do:: + + $ git bisect start + $ git bisect bad # Current version is bad + $ git bisect good v4.8 + + +.. [#f1] You can, optionally, provide both good and bad arguments at git + start with ``git bisect start [BAD] [GOOD]`` + +For further references, please read: + +- The man page for ``git-bisect`` +- `Fighting regressions with git bisect <https://www.kernel.org/pub/software/scm/git/docs/git-bisect-lk2009.html>`_ +- `Fully automated bisecting with "git bisect run" <https://lwn.net/Articles/317154>`_ +- `Using Git bisect to figure out when brokenness was introduced <http://webchick.net/node/99>`_ diff --git a/Documentation/admin-guide/bug-hunting.rst b/Documentation/admin-guide/bug-hunting.rst new file mode 100644 index 000000000..95299b08c --- /dev/null +++ b/Documentation/admin-guide/bug-hunting.rst @@ -0,0 +1,378 @@ +Bug hunting +=========== + +Kernel bug reports often come with a stack dump like the one below:: + + ------------[ cut here ]------------ + WARNING: CPU: 1 PID: 28102 at kernel/module.c:1108 module_put+0x57/0x70 + Modules linked in: dvb_usb_gp8psk(-) dvb_usb dvb_core nvidia_drm(PO) nvidia_modeset(PO) snd_hda_codec_hdmi snd_hda_intel snd_hda_codec snd_hwdep snd_hda_core snd_pcm snd_timer snd soundcore nvidia(PO) [last unloaded: rc_core] + CPU: 1 PID: 28102 Comm: rmmod Tainted: P WC O 4.8.4-build.1 #1 + Hardware name: MSI MS-7309/MS-7309, BIOS V1.12 02/23/2009 + 00000000 c12ba080 00000000 00000000 c103ed6a c1616014 00000001 00006dc6 + c1615862 00000454 c109e8a7 c109e8a7 00000009 ffffffff 00000000 f13f6a10 + f5f5a600 c103ee33 00000009 00000000 00000000 c109e8a7 f80ca4d0 c109f617 + Call Trace: + [<c12ba080>] ? dump_stack+0x44/0x64 + [<c103ed6a>] ? __warn+0xfa/0x120 + [<c109e8a7>] ? module_put+0x57/0x70 + [<c109e8a7>] ? module_put+0x57/0x70 + [<c103ee33>] ? warn_slowpath_null+0x23/0x30 + [<c109e8a7>] ? module_put+0x57/0x70 + [<f80ca4d0>] ? gp8psk_fe_set_frontend+0x460/0x460 [dvb_usb_gp8psk] + [<c109f617>] ? symbol_put_addr+0x27/0x50 + [<f80bc9ca>] ? dvb_usb_adapter_frontend_exit+0x3a/0x70 [dvb_usb] + [<f80bb3bf>] ? dvb_usb_exit+0x2f/0xd0 [dvb_usb] + [<c13d03bc>] ? usb_disable_endpoint+0x7c/0xb0 + [<f80bb48a>] ? dvb_usb_device_exit+0x2a/0x50 [dvb_usb] + [<c13d2882>] ? usb_unbind_interface+0x62/0x250 + [<c136b514>] ? __pm_runtime_idle+0x44/0x70 + [<c13620d8>] ? __device_release_driver+0x78/0x120 + [<c1362907>] ? driver_detach+0x87/0x90 + [<c1361c48>] ? bus_remove_driver+0x38/0x90 + [<c13d1c18>] ? usb_deregister+0x58/0xb0 + [<c109fbb0>] ? SyS_delete_module+0x130/0x1f0 + [<c1055654>] ? task_work_run+0x64/0x80 + [<c1000fa5>] ? exit_to_usermode_loop+0x85/0x90 + [<c10013f0>] ? do_fast_syscall_32+0x80/0x130 + [<c1549f43>] ? sysenter_past_esp+0x40/0x6a + ---[ end trace 6ebc60ef3981792f ]--- + +Such stack traces provide enough information to identify the line inside the +Kernel's source code where the bug happened. Depending on the severity of +the issue, it may also contain the word **Oops**, as on this one:: + + BUG: unable to handle kernel NULL pointer dereference at (null) + IP: [<c06969d4>] iret_exc+0x7d0/0xa59 + *pdpt = 000000002258a001 *pde = 0000000000000000 + Oops: 0002 [#1] PREEMPT SMP + ... + +Despite being an **Oops** or some other sort of stack trace, the offended +line is usually required to identify and handle the bug. Along this chapter, +we'll refer to "Oops" for all kinds of stack traces that need to be analyzed. + +If the kernel is compiled with ``CONFIG_DEBUG_INFO``, you can enhance the +quality of the stack trace by using file:`scripts/decode_stacktrace.sh`. + +Modules linked in +----------------- + +Modules that are tainted or are being loaded or unloaded are marked with +"(...)", where the taint flags are described in +file:`Documentation/admin-guide/tainted-kernels.rst`, "being loaded" is +annotated with "+", and "being unloaded" is annotated with "-". + + +Where is the Oops message is located? +------------------------------------- + +Normally the Oops text is read from the kernel buffers by klogd and +handed to ``syslogd`` which writes it to a syslog file, typically +``/var/log/messages`` (depends on ``/etc/syslog.conf``). On systems with +systemd, it may also be stored by the ``journald`` daemon, and accessed +by running ``journalctl`` command. + +Sometimes ``klogd`` dies, in which case you can run ``dmesg > file`` to +read the data from the kernel buffers and save it. Or you can +``cat /proc/kmsg > file``, however you have to break in to stop the transfer, +since ``kmsg`` is a "never ending file". + +If the machine has crashed so badly that you cannot enter commands or +the disk is not available then you have three options: + +(1) Hand copy the text from the screen and type it in after the machine + has restarted. Messy but it is the only option if you have not + planned for a crash. Alternatively, you can take a picture of + the screen with a digital camera - not nice, but better than + nothing. If the messages scroll off the top of the console, you + may find that booting with a higher resolution (e.g., ``vga=791``) + will allow you to read more of the text. (Caveat: This needs ``vesafb``, + so won't help for 'early' oopses.) + +(2) Boot with a serial console (see + :ref:`Documentation/admin-guide/serial-console.rst <serial_console>`), + run a null modem to a second machine and capture the output there + using your favourite communication program. Minicom works well. + +(3) Use Kdump (see Documentation/admin-guide/kdump/kdump.rst), + extract the kernel ring buffer from old memory with using dmesg + gdbmacro in Documentation/admin-guide/kdump/gdbmacros.txt. + +Finding the bug's location +-------------------------- + +Reporting a bug works best if you point the location of the bug at the +Kernel source file. There are two methods for doing that. Usually, using +``gdb`` is easier, but the Kernel should be pre-compiled with debug info. + +gdb +^^^ + +The GNU debugger (``gdb``) is the best way to figure out the exact file and line +number of the OOPS from the ``vmlinux`` file. + +The usage of gdb works best on a kernel compiled with ``CONFIG_DEBUG_INFO``. +This can be set by running:: + + $ ./scripts/config -d COMPILE_TEST -e DEBUG_KERNEL -e DEBUG_INFO + +On a kernel compiled with ``CONFIG_DEBUG_INFO``, you can simply copy the +EIP value from the OOPS:: + + EIP: 0060:[<c021e50e>] Not tainted VLI + +And use GDB to translate that to human-readable form:: + + $ gdb vmlinux + (gdb) l *0xc021e50e + +If you don't have ``CONFIG_DEBUG_INFO`` enabled, you use the function +offset from the OOPS:: + + EIP is at vt_ioctl+0xda8/0x1482 + +And recompile the kernel with ``CONFIG_DEBUG_INFO`` enabled:: + + $ ./scripts/config -d COMPILE_TEST -e DEBUG_KERNEL -e DEBUG_INFO + $ make vmlinux + $ gdb vmlinux + (gdb) l *vt_ioctl+0xda8 + 0x1888 is in vt_ioctl (drivers/tty/vt/vt_ioctl.c:293). + 288 { + 289 struct vc_data *vc = NULL; + 290 int ret = 0; + 291 + 292 console_lock(); + 293 if (VT_BUSY(vc_num)) + 294 ret = -EBUSY; + 295 else if (vc_num) + 296 vc = vc_deallocate(vc_num); + 297 console_unlock(); + +or, if you want to be more verbose:: + + (gdb) p vt_ioctl + $1 = {int (struct tty_struct *, unsigned int, unsigned long)} 0xae0 <vt_ioctl> + (gdb) l *0xae0+0xda8 + +You could, instead, use the object file:: + + $ make drivers/tty/ + $ gdb drivers/tty/vt/vt_ioctl.o + (gdb) l *vt_ioctl+0xda8 + +If you have a call trace, such as:: + + Call Trace: + [<ffffffff8802c8e9>] :jbd:log_wait_commit+0xa3/0xf5 + [<ffffffff810482d9>] autoremove_wake_function+0x0/0x2e + [<ffffffff8802770b>] :jbd:journal_stop+0x1be/0x1ee + ... + +this shows the problem likely is in the :jbd: module. You can load that module +in gdb and list the relevant code:: + + $ gdb fs/jbd/jbd.ko + (gdb) l *log_wait_commit+0xa3 + +.. note:: + + You can also do the same for any function call at the stack trace, + like this one:: + + [<f80bc9ca>] ? dvb_usb_adapter_frontend_exit+0x3a/0x70 [dvb_usb] + + The position where the above call happened can be seen with:: + + $ gdb drivers/media/usb/dvb-usb/dvb-usb.o + (gdb) l *dvb_usb_adapter_frontend_exit+0x3a + +objdump +^^^^^^^ + +To debug a kernel, use objdump and look for the hex offset from the crash +output to find the valid line of code/assembler. Without debug symbols, you +will see the assembler code for the routine shown, but if your kernel has +debug symbols the C code will also be available. (Debug symbols can be enabled +in the kernel hacking menu of the menu configuration.) For example:: + + $ objdump -r -S -l --disassemble net/dccp/ipv4.o + +.. note:: + + You need to be at the top level of the kernel tree for this to pick up + your C files. + +If you don't have access to the source code you can still debug some crash +dumps using the following method (example crash dump output as shown by +Dave Miller):: + + EIP is at +0x14/0x4c0 + ... + Code: 44 24 04 e8 6f 05 00 00 e9 e8 fe ff ff 8d 76 00 8d bc 27 00 00 + 00 00 55 57 56 53 81 ec bc 00 00 00 8b ac 24 d0 00 00 00 8b 5d 08 + <8b> 83 3c 01 00 00 89 44 24 14 8b 45 28 85 c0 89 44 24 18 0f 85 + + Put the bytes into a "foo.s" file like this: + + .text + .globl foo + foo: + .byte .... /* bytes from Code: part of OOPS dump */ + + Compile it with "gcc -c -o foo.o foo.s" then look at the output of + "objdump --disassemble foo.o". + + Output: + + ip_queue_xmit: + push %ebp + push %edi + push %esi + push %ebx + sub $0xbc, %esp + mov 0xd0(%esp), %ebp ! %ebp = arg0 (skb) + mov 0x8(%ebp), %ebx ! %ebx = skb->sk + mov 0x13c(%ebx), %eax ! %eax = inet_sk(sk)->opt + +file:`scripts/decodecode` can be used to automate most of this, depending +on what CPU architecture is being debugged. + +Reporting the bug +----------------- + +Once you find where the bug happened, by inspecting its location, +you could either try to fix it yourself or report it upstream. + +In order to report it upstream, you should identify the mailing list +used for the development of the affected code. This can be done by using +the ``get_maintainer.pl`` script. + +For example, if you find a bug at the gspca's sonixj.c file, you can get +its maintainers with:: + + $ ./scripts/get_maintainer.pl -f drivers/media/usb/gspca/sonixj.c + Hans Verkuil <hverkuil@xs4all.nl> (odd fixer:GSPCA USB WEBCAM DRIVER,commit_signer:1/1=100%) + Mauro Carvalho Chehab <mchehab@kernel.org> (maintainer:MEDIA INPUT INFRASTRUCTURE (V4L/DVB),commit_signer:1/1=100%) + Tejun Heo <tj@kernel.org> (commit_signer:1/1=100%) + Bhaktipriya Shridhar <bhaktipriya96@gmail.com> (commit_signer:1/1=100%,authored:1/1=100%,added_lines:4/4=100%,removed_lines:9/9=100%) + linux-media@vger.kernel.org (open list:GSPCA USB WEBCAM DRIVER) + linux-kernel@vger.kernel.org (open list) + +Please notice that it will point to: + +- The last developers that touched the source code (if this is done inside + a git tree). On the above example, Tejun and Bhaktipriya (in this + specific case, none really involved on the development of this file); +- The driver maintainer (Hans Verkuil); +- The subsystem maintainer (Mauro Carvalho Chehab); +- The driver and/or subsystem mailing list (linux-media@vger.kernel.org); +- the Linux Kernel mailing list (linux-kernel@vger.kernel.org). + +Usually, the fastest way to have your bug fixed is to report it to mailing +list used for the development of the code (linux-media ML) copying the +driver maintainer (Hans). + +If you are totally stumped as to whom to send the report, and +``get_maintainer.pl`` didn't provide you anything useful, send it to +linux-kernel@vger.kernel.org. + +Thanks for your help in making Linux as stable as humanly possible. + +Fixing the bug +-------------- + +If you know programming, you could help us by not only reporting the bug, +but also providing us with a solution. After all, open source is about +sharing what you do and don't you want to be recognised for your genius? + +If you decide to take this way, once you have worked out a fix please submit +it upstream. + +Please do read +:ref:`Documentation/process/submitting-patches.rst <submittingpatches>` though +to help your code get accepted. + + +--------------------------------------------------------------------------- + +Notes on Oops tracing with ``klogd`` +------------------------------------ + +In order to help Linus and the other kernel developers there has been +substantial support incorporated into ``klogd`` for processing protection +faults. In order to have full support for address resolution at least +version 1.3-pl3 of the ``sysklogd`` package should be used. + +When a protection fault occurs the ``klogd`` daemon automatically +translates important addresses in the kernel log messages to their +symbolic equivalents. This translated kernel message is then +forwarded through whatever reporting mechanism ``klogd`` is using. The +protection fault message can be simply cut out of the message files +and forwarded to the kernel developers. + +Two types of address resolution are performed by ``klogd``. The first is +static translation and the second is dynamic translation. +Static translation uses the System.map file. +In order to do static translation the ``klogd`` daemon +must be able to find a system map file at daemon initialization time. +See the klogd man page for information on how ``klogd`` searches for map +files. + +Dynamic address translation is important when kernel loadable modules +are being used. Since memory for kernel modules is allocated from the +kernel's dynamic memory pools there are no fixed locations for either +the start of the module or for functions and symbols in the module. + +The kernel supports system calls which allow a program to determine +which modules are loaded and their location in memory. Using these +system calls the klogd daemon builds a symbol table which can be used +to debug a protection fault which occurs in a loadable kernel module. + +At the very minimum klogd will provide the name of the module which +generated the protection fault. There may be additional symbolic +information available if the developer of the loadable module chose to +export symbol information from the module. + +Since the kernel module environment can be dynamic there must be a +mechanism for notifying the ``klogd`` daemon when a change in module +environment occurs. There are command line options available which +allow klogd to signal the currently executing daemon that symbol +information should be refreshed. See the ``klogd`` manual page for more +information. + +A patch is included with the sysklogd distribution which modifies the +``modules-2.0.0`` package to automatically signal klogd whenever a module +is loaded or unloaded. Applying this patch provides essentially +seamless support for debugging protection faults which occur with +kernel loadable modules. + +The following is an example of a protection fault in a loadable module +processed by ``klogd``:: + + Aug 29 09:51:01 blizard kernel: Unable to handle kernel paging request at virtual address f15e97cc + Aug 29 09:51:01 blizard kernel: current->tss.cr3 = 0062d000, %cr3 = 0062d000 + Aug 29 09:51:01 blizard kernel: *pde = 00000000 + Aug 29 09:51:01 blizard kernel: Oops: 0002 + Aug 29 09:51:01 blizard kernel: CPU: 0 + Aug 29 09:51:01 blizard kernel: EIP: 0010:[oops:_oops+16/3868] + Aug 29 09:51:01 blizard kernel: EFLAGS: 00010212 + Aug 29 09:51:01 blizard kernel: eax: 315e97cc ebx: 003a6f80 ecx: 001be77b edx: 00237c0c + Aug 29 09:51:01 blizard kernel: esi: 00000000 edi: bffffdb3 ebp: 00589f90 esp: 00589f8c + Aug 29 09:51:01 blizard kernel: ds: 0018 es: 0018 fs: 002b gs: 002b ss: 0018 + Aug 29 09:51:01 blizard kernel: Process oops_test (pid: 3374, process nr: 21, stackpage=00589000) + Aug 29 09:51:01 blizard kernel: Stack: 315e97cc 00589f98 0100b0b4 bffffed4 0012e38e 00240c64 003a6f80 00000001 + Aug 29 09:51:01 blizard kernel: 00000000 00237810 bfffff00 0010a7fa 00000003 00000001 00000000 bfffff00 + Aug 29 09:51:01 blizard kernel: bffffdb3 bffffed4 ffffffda 0000002b 0007002b 0000002b 0000002b 00000036 + Aug 29 09:51:01 blizard kernel: Call Trace: [oops:_oops_ioctl+48/80] [_sys_ioctl+254/272] [_system_call+82/128] + Aug 29 09:51:01 blizard kernel: Code: c7 00 05 00 00 00 eb 08 90 90 90 90 90 90 90 90 89 ec 5d c3 + +--------------------------------------------------------------------------- + +:: + + Dr. G.W. Wettstein Oncology Research Div. Computing Facility + Roger Maris Cancer Center INTERNET: greg@wind.rmcc.com + 820 4th St. N. + Fargo, ND 58122 + Phone: 701-234-7556 diff --git a/Documentation/admin-guide/cgroup-v1/blkio-controller.rst b/Documentation/admin-guide/cgroup-v1/blkio-controller.rst new file mode 100644 index 000000000..dabb80cdd --- /dev/null +++ b/Documentation/admin-guide/cgroup-v1/blkio-controller.rst @@ -0,0 +1,301 @@ +=================== +Block IO Controller +=================== + +Overview +======== +cgroup subsys "blkio" implements the block io controller. There seems to be +a need of various kinds of IO control policies (like proportional BW, max BW) +both at leaf nodes as well as at intermediate nodes in a storage hierarchy. +Plan is to use the same cgroup based management interface for blkio controller +and based on user options switch IO policies in the background. + +One IO control policy is throttling policy which can be used to +specify upper IO rate limits on devices. This policy is implemented in +generic block layer and can be used on leaf nodes as well as higher +level logical devices like device mapper. + +HOWTO +===== + +Throttling/Upper Limit policy +----------------------------- +Enable Block IO controller:: + + CONFIG_BLK_CGROUP=y + +Enable throttling in block layer:: + + CONFIG_BLK_DEV_THROTTLING=y + +Mount blkio controller (see cgroups.txt, Why are cgroups needed?):: + + mount -t cgroup -o blkio none /sys/fs/cgroup/blkio + +Specify a bandwidth rate on particular device for root group. The format +for policy is "<major>:<minor> <bytes_per_second>":: + + echo "8:16 1048576" > /sys/fs/cgroup/blkio/blkio.throttle.read_bps_device + +This will put a limit of 1MB/second on reads happening for root group +on device having major/minor number 8:16. + +Run dd to read a file and see if rate is throttled to 1MB/s or not:: + + # dd iflag=direct if=/mnt/common/zerofile of=/dev/null bs=4K count=1024 + 1024+0 records in + 1024+0 records out + 4194304 bytes (4.2 MB) copied, 4.0001 s, 1.0 MB/s + +Limits for writes can be put using blkio.throttle.write_bps_device file. + +Hierarchical Cgroups +==================== + +Throttling implements hierarchy support; however, +throttling's hierarchy support is enabled iff "sane_behavior" is +enabled from cgroup side, which currently is a development option and +not publicly available. + +If somebody created a hierarchy like as follows:: + + root + / \ + test1 test2 + | + test3 + +Throttling with "sane_behavior" will handle the +hierarchy correctly. For throttling, all limits apply +to the whole subtree while all statistics are local to the IOs +directly generated by tasks in that cgroup. + +Throttling without "sane_behavior" enabled from cgroup side will +practically treat all groups at same level as if it looks like the +following:: + + pivot + / / \ \ + root test1 test2 test3 + +Various user visible config options +=================================== + + CONFIG_BLK_CGROUP + Block IO controller. + + CONFIG_BFQ_CGROUP_DEBUG + Debug help. Right now some additional stats file show up in cgroup + if this option is enabled. + + CONFIG_BLK_DEV_THROTTLING + Enable block device throttling support in block layer. + +Details of cgroup files +======================= + +Proportional weight policy files +-------------------------------- + + blkio.bfq.weight + Specifies per cgroup weight. This is default weight of the group + on all the devices until and unless overridden by per device rule + (see `blkio.bfq.weight_device` below). + + Currently allowed range of weights is from 1 to 1000. For more details, + see Documentation/block/bfq-iosched.rst. + + blkio.bfq.weight_device + Specifies per cgroup per device weights, overriding the default group + weight. For more details, see Documentation/block/bfq-iosched.rst. + + Following is the format:: + + # echo dev_maj:dev_minor weight > blkio.bfq.weight_device + + Configure weight=300 on /dev/sdb (8:16) in this cgroup:: + + # echo 8:16 300 > blkio.bfq.weight_device + # cat blkio.bfq.weight_device + dev weight + 8:16 300 + + Configure weight=500 on /dev/sda (8:0) in this cgroup:: + + # echo 8:0 500 > blkio.bfq.weight_device + # cat blkio.bfq.weight_device + dev weight + 8:0 500 + 8:16 300 + + Remove specific weight for /dev/sda in this cgroup:: + + # echo 8:0 0 > blkio.bfq.weight_device + # cat blkio.bfq.weight_device + dev weight + 8:16 300 + + blkio.time + Disk time allocated to cgroup per device in milliseconds. First + two fields specify the major and minor number of the device and + third field specifies the disk time allocated to group in + milliseconds. + + blkio.sectors + Number of sectors transferred to/from disk by the group. First + two fields specify the major and minor number of the device and + third field specifies the number of sectors transferred by the + group to/from the device. + + blkio.io_service_bytes + Number of bytes transferred to/from the disk by the group. These + are further divided by the type of operation - read or write, sync + or async. First two fields specify the major and minor number of the + device, third field specifies the operation type and the fourth field + specifies the number of bytes. + + blkio.io_serviced + Number of IOs (bio) issued to the disk by the group. These + are further divided by the type of operation - read or write, sync + or async. First two fields specify the major and minor number of the + device, third field specifies the operation type and the fourth field + specifies the number of IOs. + + blkio.io_service_time + Total amount of time between request dispatch and request completion + for the IOs done by this cgroup. This is in nanoseconds to make it + meaningful for flash devices too. For devices with queue depth of 1, + this time represents the actual service time. When queue_depth > 1, + that is no longer true as requests may be served out of order. This + may cause the service time for a given IO to include the service time + of multiple IOs when served out of order which may result in total + io_service_time > actual time elapsed. This time is further divided by + the type of operation - read or write, sync or async. First two fields + specify the major and minor number of the device, third field + specifies the operation type and the fourth field specifies the + io_service_time in ns. + + blkio.io_wait_time + Total amount of time the IOs for this cgroup spent waiting in the + scheduler queues for service. This can be greater than the total time + elapsed since it is cumulative io_wait_time for all IOs. It is not a + measure of total time the cgroup spent waiting but rather a measure of + the wait_time for its individual IOs. For devices with queue_depth > 1 + this metric does not include the time spent waiting for service once + the IO is dispatched to the device but till it actually gets serviced + (there might be a time lag here due to re-ordering of requests by the + device). This is in nanoseconds to make it meaningful for flash + devices too. This time is further divided by the type of operation - + read or write, sync or async. First two fields specify the major and + minor number of the device, third field specifies the operation type + and the fourth field specifies the io_wait_time in ns. + + blkio.io_merged + Total number of bios/requests merged into requests belonging to this + cgroup. This is further divided by the type of operation - read or + write, sync or async. + + blkio.io_queued + Total number of requests queued up at any given instant for this + cgroup. This is further divided by the type of operation - read or + write, sync or async. + + blkio.avg_queue_size + Debugging aid only enabled if CONFIG_BFQ_CGROUP_DEBUG=y. + The average queue size for this cgroup over the entire time of this + cgroup's existence. Queue size samples are taken each time one of the + queues of this cgroup gets a timeslice. + + blkio.group_wait_time + Debugging aid only enabled if CONFIG_BFQ_CGROUP_DEBUG=y. + This is the amount of time the cgroup had to wait since it became busy + (i.e., went from 0 to 1 request queued) to get a timeslice for one of + its queues. This is different from the io_wait_time which is the + cumulative total of the amount of time spent by each IO in that cgroup + waiting in the scheduler queue. This is in nanoseconds. If this is + read when the cgroup is in a waiting (for timeslice) state, the stat + will only report the group_wait_time accumulated till the last time it + got a timeslice and will not include the current delta. + + blkio.empty_time + Debugging aid only enabled if CONFIG_BFQ_CGROUP_DEBUG=y. + This is the amount of time a cgroup spends without any pending + requests when not being served, i.e., it does not include any time + spent idling for one of the queues of the cgroup. This is in + nanoseconds. If this is read when the cgroup is in an empty state, + the stat will only report the empty_time accumulated till the last + time it had a pending request and will not include the current delta. + + blkio.idle_time + Debugging aid only enabled if CONFIG_BFQ_CGROUP_DEBUG=y. + This is the amount of time spent by the IO scheduler idling for a + given cgroup in anticipation of a better request than the existing ones + from other queues/cgroups. This is in nanoseconds. If this is read + when the cgroup is in an idling state, the stat will only report the + idle_time accumulated till the last idle period and will not include + the current delta. + + blkio.dequeue + Debugging aid only enabled if CONFIG_BFQ_CGROUP_DEBUG=y. This + gives the statistics about how many a times a group was dequeued + from service tree of the device. First two fields specify the major + and minor number of the device and third field specifies the number + of times a group was dequeued from a particular device. + + blkio.*_recursive + Recursive version of various stats. These files show the + same information as their non-recursive counterparts but + include stats from all the descendant cgroups. + +Throttling/Upper limit policy files +----------------------------------- + blkio.throttle.read_bps_device + Specifies upper limit on READ rate from the device. IO rate is + specified in bytes per second. Rules are per device. Following is + the format:: + + echo "<major>:<minor> <rate_bytes_per_second>" > /cgrp/blkio.throttle.read_bps_device + + blkio.throttle.write_bps_device + Specifies upper limit on WRITE rate to the device. IO rate is + specified in bytes per second. Rules are per device. Following is + the format:: + + echo "<major>:<minor> <rate_bytes_per_second>" > /cgrp/blkio.throttle.write_bps_device + + blkio.throttle.read_iops_device + Specifies upper limit on READ rate from the device. IO rate is + specified in IO per second. Rules are per device. Following is + the format:: + + echo "<major>:<minor> <rate_io_per_second>" > /cgrp/blkio.throttle.read_iops_device + + blkio.throttle.write_iops_device + Specifies upper limit on WRITE rate to the device. IO rate is + specified in io per second. Rules are per device. Following is + the format:: + + echo "<major>:<minor> <rate_io_per_second>" > /cgrp/blkio.throttle.write_iops_device + + Note: If both BW and IOPS rules are specified for a device, then IO is + subjected to both the constraints. + + blkio.throttle.io_serviced + Number of IOs (bio) issued to the disk by the group. These + are further divided by the type of operation - read or write, sync + or async. First two fields specify the major and minor number of the + device, third field specifies the operation type and the fourth field + specifies the number of IOs. + + blkio.throttle.io_service_bytes + Number of bytes transferred to/from the disk by the group. These + are further divided by the type of operation - read or write, sync + or async. First two fields specify the major and minor number of the + device, third field specifies the operation type and the fourth field + specifies the number of bytes. + +Common files among various policies +----------------------------------- + blkio.reset_stats + Writing an int to this file will result in resetting all the stats + for that cgroup. diff --git a/Documentation/admin-guide/cgroup-v1/cgroups.rst b/Documentation/admin-guide/cgroup-v1/cgroups.rst new file mode 100644 index 000000000..9343148ee --- /dev/null +++ b/Documentation/admin-guide/cgroup-v1/cgroups.rst @@ -0,0 +1,697 @@ +============== +Control Groups +============== + +Written by Paul Menage <menage@google.com> based on +Documentation/admin-guide/cgroup-v1/cpusets.rst + +Original copyright statements from cpusets.txt: + +Portions Copyright (C) 2004 BULL SA. + +Portions Copyright (c) 2004-2006 Silicon Graphics, Inc. + +Modified by Paul Jackson <pj@sgi.com> + +Modified by Christoph Lameter <cl@linux.com> + +.. CONTENTS: + + 1. Control Groups + 1.1 What are cgroups ? + 1.2 Why are cgroups needed ? + 1.3 How are cgroups implemented ? + 1.4 What does notify_on_release do ? + 1.5 What does clone_children do ? + 1.6 How do I use cgroups ? + 2. Usage Examples and Syntax + 2.1 Basic Usage + 2.2 Attaching processes + 2.3 Mounting hierarchies by name + 3. Kernel API + 3.1 Overview + 3.2 Synchronization + 3.3 Subsystem API + 4. Extended attributes usage + 5. Questions + +1. Control Groups +================= + +1.1 What are cgroups ? +---------------------- + +Control Groups provide a mechanism for aggregating/partitioning sets of +tasks, and all their future children, into hierarchical groups with +specialized behaviour. + +Definitions: + +A *cgroup* associates a set of tasks with a set of parameters for one +or more subsystems. + +A *subsystem* is a module that makes use of the task grouping +facilities provided by cgroups to treat groups of tasks in +particular ways. A subsystem is typically a "resource controller" that +schedules a resource or applies per-cgroup limits, but it may be +anything that wants to act on a group of processes, e.g. a +virtualization subsystem. + +A *hierarchy* is a set of cgroups arranged in a tree, such that +every task in the system is in exactly one of the cgroups in the +hierarchy, and a set of subsystems; each subsystem has system-specific +state attached to each cgroup in the hierarchy. Each hierarchy has +an instance of the cgroup virtual filesystem associated with it. + +At any one time there may be multiple active hierarchies of task +cgroups. Each hierarchy is a partition of all tasks in the system. + +User-level code may create and destroy cgroups by name in an +instance of the cgroup virtual file system, specify and query to +which cgroup a task is assigned, and list the task PIDs assigned to +a cgroup. Those creations and assignments only affect the hierarchy +associated with that instance of the cgroup file system. + +On their own, the only use for cgroups is for simple job +tracking. The intention is that other subsystems hook into the generic +cgroup support to provide new attributes for cgroups, such as +accounting/limiting the resources which processes in a cgroup can +access. For example, cpusets (see Documentation/admin-guide/cgroup-v1/cpusets.rst) allow +you to associate a set of CPUs and a set of memory nodes with the +tasks in each cgroup. + +.. _cgroups-why-needed: + +1.2 Why are cgroups needed ? +---------------------------- + +There are multiple efforts to provide process aggregations in the +Linux kernel, mainly for resource-tracking purposes. Such efforts +include cpusets, CKRM/ResGroups, UserBeanCounters, and virtual server +namespaces. These all require the basic notion of a +grouping/partitioning of processes, with newly forked processes ending +up in the same group (cgroup) as their parent process. + +The kernel cgroup patch provides the minimum essential kernel +mechanisms required to efficiently implement such groups. It has +minimal impact on the system fast paths, and provides hooks for +specific subsystems such as cpusets to provide additional behaviour as +desired. + +Multiple hierarchy support is provided to allow for situations where +the division of tasks into cgroups is distinctly different for +different subsystems - having parallel hierarchies allows each +hierarchy to be a natural division of tasks, without having to handle +complex combinations of tasks that would be present if several +unrelated subsystems needed to be forced into the same tree of +cgroups. + +At one extreme, each resource controller or subsystem could be in a +separate hierarchy; at the other extreme, all subsystems +would be attached to the same hierarchy. + +As an example of a scenario (originally proposed by vatsa@in.ibm.com) +that can benefit from multiple hierarchies, consider a large +university server with various users - students, professors, system +tasks etc. The resource planning for this server could be along the +following lines:: + + CPU : "Top cpuset" + / \ + CPUSet1 CPUSet2 + | | + (Professors) (Students) + + In addition (system tasks) are attached to topcpuset (so + that they can run anywhere) with a limit of 20% + + Memory : Professors (50%), Students (30%), system (20%) + + Disk : Professors (50%), Students (30%), system (20%) + + Network : WWW browsing (20%), Network File System (60%), others (20%) + / \ + Professors (15%) students (5%) + +Browsers like Firefox/Lynx go into the WWW network class, while (k)nfsd goes +into the NFS network class. + +At the same time Firefox/Lynx will share an appropriate CPU/Memory class +depending on who launched it (prof/student). + +With the ability to classify tasks differently for different resources +(by putting those resource subsystems in different hierarchies), +the admin can easily set up a script which receives exec notifications +and depending on who is launching the browser he can:: + + # echo browser_pid > /sys/fs/cgroup/<restype>/<userclass>/tasks + +With only a single hierarchy, he now would potentially have to create +a separate cgroup for every browser launched and associate it with +appropriate network and other resource class. This may lead to +proliferation of such cgroups. + +Also let's say that the administrator would like to give enhanced network +access temporarily to a student's browser (since it is night and the user +wants to do online gaming :)) OR give one of the student's simulation +apps enhanced CPU power. + +With ability to write PIDs directly to resource classes, it's just a +matter of:: + + # echo pid > /sys/fs/cgroup/network/<new_class>/tasks + (after some time) + # echo pid > /sys/fs/cgroup/network/<orig_class>/tasks + +Without this ability, the administrator would have to split the cgroup into +multiple separate ones and then associate the new cgroups with the +new resource classes. + + + +1.3 How are cgroups implemented ? +--------------------------------- + +Control Groups extends the kernel as follows: + + - Each task in the system has a reference-counted pointer to a + css_set. + + - A css_set contains a set of reference-counted pointers to + cgroup_subsys_state objects, one for each cgroup subsystem + registered in the system. There is no direct link from a task to + the cgroup of which it's a member in each hierarchy, but this + can be determined by following pointers through the + cgroup_subsys_state objects. This is because accessing the + subsystem state is something that's expected to happen frequently + and in performance-critical code, whereas operations that require a + task's actual cgroup assignments (in particular, moving between + cgroups) are less common. A linked list runs through the cg_list + field of each task_struct using the css_set, anchored at + css_set->tasks. + + - A cgroup hierarchy filesystem can be mounted for browsing and + manipulation from user space. + + - You can list all the tasks (by PID) attached to any cgroup. + +The implementation of cgroups requires a few, simple hooks +into the rest of the kernel, none in performance-critical paths: + + - in init/main.c, to initialize the root cgroups and initial + css_set at system boot. + + - in fork and exit, to attach and detach a task from its css_set. + +In addition, a new file system of type "cgroup" may be mounted, to +enable browsing and modifying the cgroups presently known to the +kernel. When mounting a cgroup hierarchy, you may specify a +comma-separated list of subsystems to mount as the filesystem mount +options. By default, mounting the cgroup filesystem attempts to +mount a hierarchy containing all registered subsystems. + +If an active hierarchy with exactly the same set of subsystems already +exists, it will be reused for the new mount. If no existing hierarchy +matches, and any of the requested subsystems are in use in an existing +hierarchy, the mount will fail with -EBUSY. Otherwise, a new hierarchy +is activated, associated with the requested subsystems. + +It's not currently possible to bind a new subsystem to an active +cgroup hierarchy, or to unbind a subsystem from an active cgroup +hierarchy. This may be possible in future, but is fraught with nasty +error-recovery issues. + +When a cgroup filesystem is unmounted, if there are any +child cgroups created below the top-level cgroup, that hierarchy +will remain active even though unmounted; if there are no +child cgroups then the hierarchy will be deactivated. + +No new system calls are added for cgroups - all support for +querying and modifying cgroups is via this cgroup file system. + +Each task under /proc has an added file named 'cgroup' displaying, +for each active hierarchy, the subsystem names and the cgroup name +as the path relative to the root of the cgroup file system. + +Each cgroup is represented by a directory in the cgroup file system +containing the following files describing that cgroup: + + - tasks: list of tasks (by PID) attached to that cgroup. This list + is not guaranteed to be sorted. Writing a thread ID into this file + moves the thread into this cgroup. + - cgroup.procs: list of thread group IDs in the cgroup. This list is + not guaranteed to be sorted or free of duplicate TGIDs, and userspace + should sort/uniquify the list if this property is required. + Writing a thread group ID into this file moves all threads in that + group into this cgroup. + - notify_on_release flag: run the release agent on exit? + - release_agent: the path to use for release notifications (this file + exists in the top cgroup only) + +Other subsystems such as cpusets may add additional files in each +cgroup dir. + +New cgroups are created using the mkdir system call or shell +command. The properties of a cgroup, such as its flags, are +modified by writing to the appropriate file in that cgroups +directory, as listed above. + +The named hierarchical structure of nested cgroups allows partitioning +a large system into nested, dynamically changeable, "soft-partitions". + +The attachment of each task, automatically inherited at fork by any +children of that task, to a cgroup allows organizing the work load +on a system into related sets of tasks. A task may be re-attached to +any other cgroup, if allowed by the permissions on the necessary +cgroup file system directories. + +When a task is moved from one cgroup to another, it gets a new +css_set pointer - if there's an already existing css_set with the +desired collection of cgroups then that group is reused, otherwise a new +css_set is allocated. The appropriate existing css_set is located by +looking into a hash table. + +To allow access from a cgroup to the css_sets (and hence tasks) +that comprise it, a set of cg_cgroup_link objects form a lattice; +each cg_cgroup_link is linked into a list of cg_cgroup_links for +a single cgroup on its cgrp_link_list field, and a list of +cg_cgroup_links for a single css_set on its cg_link_list. + +Thus the set of tasks in a cgroup can be listed by iterating over +each css_set that references the cgroup, and sub-iterating over +each css_set's task set. + +The use of a Linux virtual file system (vfs) to represent the +cgroup hierarchy provides for a familiar permission and name space +for cgroups, with a minimum of additional kernel code. + +1.4 What does notify_on_release do ? +------------------------------------ + +If the notify_on_release flag is enabled (1) in a cgroup, then +whenever the last task in the cgroup leaves (exits or attaches to +some other cgroup) and the last child cgroup of that cgroup +is removed, then the kernel runs the command specified by the contents +of the "release_agent" file in that hierarchy's root directory, +supplying the pathname (relative to the mount point of the cgroup +file system) of the abandoned cgroup. This enables automatic +removal of abandoned cgroups. The default value of +notify_on_release in the root cgroup at system boot is disabled +(0). The default value of other cgroups at creation is the current +value of their parents' notify_on_release settings. The default value of +a cgroup hierarchy's release_agent path is empty. + +1.5 What does clone_children do ? +--------------------------------- + +This flag only affects the cpuset controller. If the clone_children +flag is enabled (1) in a cgroup, a new cpuset cgroup will copy its +configuration from the parent during initialization. + +1.6 How do I use cgroups ? +-------------------------- + +To start a new job that is to be contained within a cgroup, using +the "cpuset" cgroup subsystem, the steps are something like:: + + 1) mount -t tmpfs cgroup_root /sys/fs/cgroup + 2) mkdir /sys/fs/cgroup/cpuset + 3) mount -t cgroup -ocpuset cpuset /sys/fs/cgroup/cpuset + 4) Create the new cgroup by doing mkdir's and write's (or echo's) in + the /sys/fs/cgroup/cpuset virtual file system. + 5) Start a task that will be the "founding father" of the new job. + 6) Attach that task to the new cgroup by writing its PID to the + /sys/fs/cgroup/cpuset tasks file for that cgroup. + 7) fork, exec or clone the job tasks from this founding father task. + +For example, the following sequence of commands will setup a cgroup +named "Charlie", containing just CPUs 2 and 3, and Memory Node 1, +and then start a subshell 'sh' in that cgroup:: + + mount -t tmpfs cgroup_root /sys/fs/cgroup + mkdir /sys/fs/cgroup/cpuset + mount -t cgroup cpuset -ocpuset /sys/fs/cgroup/cpuset + cd /sys/fs/cgroup/cpuset + mkdir Charlie + cd Charlie + /bin/echo 2-3 > cpuset.cpus + /bin/echo 1 > cpuset.mems + /bin/echo $$ > tasks + sh + # The subshell 'sh' is now running in cgroup Charlie + # The next line should display '/Charlie' + cat /proc/self/cgroup + +2. Usage Examples and Syntax +============================ + +2.1 Basic Usage +--------------- + +Creating, modifying, using cgroups can be done through the cgroup +virtual filesystem. + +To mount a cgroup hierarchy with all available subsystems, type:: + + # mount -t cgroup xxx /sys/fs/cgroup + +The "xxx" is not interpreted by the cgroup code, but will appear in +/proc/mounts so may be any useful identifying string that you like. + +Note: Some subsystems do not work without some user input first. For instance, +if cpusets are enabled the user will have to populate the cpus and mems files +for each new cgroup created before that group can be used. + +As explained in section `1.2 Why are cgroups needed?` you should create +different hierarchies of cgroups for each single resource or group of +resources you want to control. Therefore, you should mount a tmpfs on +/sys/fs/cgroup and create directories for each cgroup resource or resource +group:: + + # mount -t tmpfs cgroup_root /sys/fs/cgroup + # mkdir /sys/fs/cgroup/rg1 + +To mount a cgroup hierarchy with just the cpuset and memory +subsystems, type:: + + # mount -t cgroup -o cpuset,memory hier1 /sys/fs/cgroup/rg1 + +While remounting cgroups is currently supported, it is not recommend +to use it. Remounting allows changing bound subsystems and +release_agent. Rebinding is hardly useful as it only works when the +hierarchy is empty and release_agent itself should be replaced with +conventional fsnotify. The support for remounting will be removed in +the future. + +To Specify a hierarchy's release_agent:: + + # mount -t cgroup -o cpuset,release_agent="/sbin/cpuset_release_agent" \ + xxx /sys/fs/cgroup/rg1 + +Note that specifying 'release_agent' more than once will return failure. + +Note that changing the set of subsystems is currently only supported +when the hierarchy consists of a single (root) cgroup. Supporting +the ability to arbitrarily bind/unbind subsystems from an existing +cgroup hierarchy is intended to be implemented in the future. + +Then under /sys/fs/cgroup/rg1 you can find a tree that corresponds to the +tree of the cgroups in the system. For instance, /sys/fs/cgroup/rg1 +is the cgroup that holds the whole system. + +If you want to change the value of release_agent:: + + # echo "/sbin/new_release_agent" > /sys/fs/cgroup/rg1/release_agent + +It can also be changed via remount. + +If you want to create a new cgroup under /sys/fs/cgroup/rg1:: + + # cd /sys/fs/cgroup/rg1 + # mkdir my_cgroup + +Now you want to do something with this cgroup: + + # cd my_cgroup + +In this directory you can find several files:: + + # ls + cgroup.procs notify_on_release tasks + (plus whatever files added by the attached subsystems) + +Now attach your shell to this cgroup:: + + # /bin/echo $$ > tasks + +You can also create cgroups inside your cgroup by using mkdir in this +directory:: + + # mkdir my_sub_cs + +To remove a cgroup, just use rmdir:: + + # rmdir my_sub_cs + +This will fail if the cgroup is in use (has cgroups inside, or +has processes attached, or is held alive by other subsystem-specific +reference). + +2.2 Attaching processes +----------------------- + +:: + + # /bin/echo PID > tasks + +Note that it is PID, not PIDs. You can only attach ONE task at a time. +If you have several tasks to attach, you have to do it one after another:: + + # /bin/echo PID1 > tasks + # /bin/echo PID2 > tasks + ... + # /bin/echo PIDn > tasks + +You can attach the current shell task by echoing 0:: + + # echo 0 > tasks + +You can use the cgroup.procs file instead of the tasks file to move all +threads in a threadgroup at once. Echoing the PID of any task in a +threadgroup to cgroup.procs causes all tasks in that threadgroup to be +attached to the cgroup. Writing 0 to cgroup.procs moves all tasks +in the writing task's threadgroup. + +Note: Since every task is always a member of exactly one cgroup in each +mounted hierarchy, to remove a task from its current cgroup you must +move it into a new cgroup (possibly the root cgroup) by writing to the +new cgroup's tasks file. + +Note: Due to some restrictions enforced by some cgroup subsystems, moving +a process to another cgroup can fail. + +2.3 Mounting hierarchies by name +-------------------------------- + +Passing the name=<x> option when mounting a cgroups hierarchy +associates the given name with the hierarchy. This can be used when +mounting a pre-existing hierarchy, in order to refer to it by name +rather than by its set of active subsystems. Each hierarchy is either +nameless, or has a unique name. + +The name should match [\w.-]+ + +When passing a name=<x> option for a new hierarchy, you need to +specify subsystems manually; the legacy behaviour of mounting all +subsystems when none are explicitly specified is not supported when +you give a subsystem a name. + +The name of the subsystem appears as part of the hierarchy description +in /proc/mounts and /proc/<pid>/cgroups. + + +3. Kernel API +============= + +3.1 Overview +------------ + +Each kernel subsystem that wants to hook into the generic cgroup +system needs to create a cgroup_subsys object. This contains +various methods, which are callbacks from the cgroup system, along +with a subsystem ID which will be assigned by the cgroup system. + +Other fields in the cgroup_subsys object include: + +- subsys_id: a unique array index for the subsystem, indicating which + entry in cgroup->subsys[] this subsystem should be managing. + +- name: should be initialized to a unique subsystem name. Should be + no longer than MAX_CGROUP_TYPE_NAMELEN. + +- early_init: indicate if the subsystem needs early initialization + at system boot. + +Each cgroup object created by the system has an array of pointers, +indexed by subsystem ID; this pointer is entirely managed by the +subsystem; the generic cgroup code will never touch this pointer. + +3.2 Synchronization +------------------- + +There is a global mutex, cgroup_mutex, used by the cgroup +system. This should be taken by anything that wants to modify a +cgroup. It may also be taken to prevent cgroups from being +modified, but more specific locks may be more appropriate in that +situation. + +See kernel/cgroup.c for more details. + +Subsystems can take/release the cgroup_mutex via the functions +cgroup_lock()/cgroup_unlock(). + +Accessing a task's cgroup pointer may be done in the following ways: +- while holding cgroup_mutex +- while holding the task's alloc_lock (via task_lock()) +- inside an rcu_read_lock() section via rcu_dereference() + +3.3 Subsystem API +----------------- + +Each subsystem should: + +- add an entry in linux/cgroup_subsys.h +- define a cgroup_subsys object called <name>_cgrp_subsys + +Each subsystem may export the following methods. The only mandatory +methods are css_alloc/free. Any others that are null are presumed to +be successful no-ops. + +``struct cgroup_subsys_state *css_alloc(struct cgroup *cgrp)`` +(cgroup_mutex held by caller) + +Called to allocate a subsystem state object for a cgroup. The +subsystem should allocate its subsystem state object for the passed +cgroup, returning a pointer to the new object on success or a +ERR_PTR() value. On success, the subsystem pointer should point to +a structure of type cgroup_subsys_state (typically embedded in a +larger subsystem-specific object), which will be initialized by the +cgroup system. Note that this will be called at initialization to +create the root subsystem state for this subsystem; this case can be +identified by the passed cgroup object having a NULL parent (since +it's the root of the hierarchy) and may be an appropriate place for +initialization code. + +``int css_online(struct cgroup *cgrp)`` +(cgroup_mutex held by caller) + +Called after @cgrp successfully completed all allocations and made +visible to cgroup_for_each_child/descendant_*() iterators. The +subsystem may choose to fail creation by returning -errno. This +callback can be used to implement reliable state sharing and +propagation along the hierarchy. See the comment on +cgroup_for_each_descendant_pre() for details. + +``void css_offline(struct cgroup *cgrp);`` +(cgroup_mutex held by caller) + +This is the counterpart of css_online() and called iff css_online() +has succeeded on @cgrp. This signifies the beginning of the end of +@cgrp. @cgrp is being removed and the subsystem should start dropping +all references it's holding on @cgrp. When all references are dropped, +cgroup removal will proceed to the next step - css_free(). After this +callback, @cgrp should be considered dead to the subsystem. + +``void css_free(struct cgroup *cgrp)`` +(cgroup_mutex held by caller) + +The cgroup system is about to free @cgrp; the subsystem should free +its subsystem state object. By the time this method is called, @cgrp +is completely unused; @cgrp->parent is still valid. (Note - can also +be called for a newly-created cgroup if an error occurs after this +subsystem's create() method has been called for the new cgroup). + +``int can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)`` +(cgroup_mutex held by caller) + +Called prior to moving one or more tasks into a cgroup; if the +subsystem returns an error, this will abort the attach operation. +@tset contains the tasks to be attached and is guaranteed to have at +least one task in it. + +If there are multiple tasks in the taskset, then: + - it's guaranteed that all are from the same thread group + - @tset contains all tasks from the thread group whether or not + they're switching cgroups + - the first task is the leader + +Each @tset entry also contains the task's old cgroup and tasks which +aren't switching cgroup can be skipped easily using the +cgroup_taskset_for_each() iterator. Note that this isn't called on a +fork. If this method returns 0 (success) then this should remain valid +while the caller holds cgroup_mutex and it is ensured that either +attach() or cancel_attach() will be called in future. + +``void css_reset(struct cgroup_subsys_state *css)`` +(cgroup_mutex held by caller) + +An optional operation which should restore @css's configuration to the +initial state. This is currently only used on the unified hierarchy +when a subsystem is disabled on a cgroup through +"cgroup.subtree_control" but should remain enabled because other +subsystems depend on it. cgroup core makes such a css invisible by +removing the associated interface files and invokes this callback so +that the hidden subsystem can return to the initial neutral state. +This prevents unexpected resource control from a hidden css and +ensures that the configuration is in the initial state when it is made +visible again later. + +``void cancel_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)`` +(cgroup_mutex held by caller) + +Called when a task attach operation has failed after can_attach() has succeeded. +A subsystem whose can_attach() has some side-effects should provide this +function, so that the subsystem can implement a rollback. If not, not necessary. +This will be called only about subsystems whose can_attach() operation have +succeeded. The parameters are identical to can_attach(). + +``void attach(struct cgroup *cgrp, struct cgroup_taskset *tset)`` +(cgroup_mutex held by caller) + +Called after the task has been attached to the cgroup, to allow any +post-attachment activity that requires memory allocations or blocking. +The parameters are identical to can_attach(). + +``void fork(struct task_struct *task)`` + +Called when a task is forked into a cgroup. + +``void exit(struct task_struct *task)`` + +Called during task exit. + +``void free(struct task_struct *task)`` + +Called when the task_struct is freed. + +``void bind(struct cgroup *root)`` +(cgroup_mutex held by caller) + +Called when a cgroup subsystem is rebound to a different hierarchy +and root cgroup. Currently this will only involve movement between +the default hierarchy (which never has sub-cgroups) and a hierarchy +that is being created/destroyed (and hence has no sub-cgroups). + +4. Extended attribute usage +=========================== + +cgroup filesystem supports certain types of extended attributes in its +directories and files. The current supported types are: + + - Trusted (XATTR_TRUSTED) + - Security (XATTR_SECURITY) + +Both require CAP_SYS_ADMIN capability to set. + +Like in tmpfs, the extended attributes in cgroup filesystem are stored +using kernel memory and it's advised to keep the usage at minimum. This +is the reason why user defined extended attributes are not supported, since +any user can do it and there's no limit in the value size. + +The current known users for this feature are SELinux to limit cgroup usage +in containers and systemd for assorted meta data like main PID in a cgroup +(systemd creates a cgroup per service). + +5. Questions +============ + +:: + + Q: what's up with this '/bin/echo' ? + A: bash's builtin 'echo' command does not check calls to write() against + errors. If you use it in the cgroup file system, you won't be + able to tell whether a command succeeded or failed. + + Q: When I attach processes, only the first of the line gets really attached ! + A: We can only return one error code per call to write(). So you should also + put only ONE PID. diff --git a/Documentation/admin-guide/cgroup-v1/cpuacct.rst b/Documentation/admin-guide/cgroup-v1/cpuacct.rst new file mode 100644 index 000000000..d30ed81d2 --- /dev/null +++ b/Documentation/admin-guide/cgroup-v1/cpuacct.rst @@ -0,0 +1,50 @@ +========================= +CPU Accounting Controller +========================= + +The CPU accounting controller is used to group tasks using cgroups and +account the CPU usage of these groups of tasks. + +The CPU accounting controller supports multi-hierarchy groups. An accounting +group accumulates the CPU usage of all of its child groups and the tasks +directly present in its group. + +Accounting groups can be created by first mounting the cgroup filesystem:: + + # mount -t cgroup -ocpuacct none /sys/fs/cgroup + +With the above step, the initial or the parent accounting group becomes +visible at /sys/fs/cgroup. At bootup, this group includes all the tasks in +the system. /sys/fs/cgroup/tasks lists the tasks in this cgroup. +/sys/fs/cgroup/cpuacct.usage gives the CPU time (in nanoseconds) obtained +by this group which is essentially the CPU time obtained by all the tasks +in the system. + +New accounting groups can be created under the parent group /sys/fs/cgroup:: + + # cd /sys/fs/cgroup + # mkdir g1 + # echo $$ > g1/tasks + +The above steps create a new group g1 and move the current shell +process (bash) into it. CPU time consumed by this bash and its children +can be obtained from g1/cpuacct.usage and the same is accumulated in +/sys/fs/cgroup/cpuacct.usage also. + +cpuacct.stat file lists a few statistics which further divide the +CPU time obtained by the cgroup into user and system times. Currently +the following statistics are supported: + +user: Time spent by tasks of the cgroup in user mode. +system: Time spent by tasks of the cgroup in kernel mode. + +user and system are in USER_HZ unit. + +cpuacct controller uses percpu_counter interface to collect user and +system times. This has two side effects: + +- It is theoretically possible to see wrong values for user and system times. + This is because percpu_counter_read() on 32bit systems isn't safe + against concurrent writes. +- It is possible to see slightly outdated values for user and system times + due to the batch processing nature of percpu_counter. diff --git a/Documentation/admin-guide/cgroup-v1/cpusets.rst b/Documentation/admin-guide/cgroup-v1/cpusets.rst new file mode 100644 index 000000000..ae646d621 --- /dev/null +++ b/Documentation/admin-guide/cgroup-v1/cpusets.rst @@ -0,0 +1,879 @@ +.. _cpusets: + +======= +CPUSETS +======= + +Copyright (C) 2004 BULL SA. + +Written by Simon.Derr@bull.net + +- Portions Copyright (c) 2004-2006 Silicon Graphics, Inc. +- Modified by Paul Jackson <pj@sgi.com> +- Modified by Christoph Lameter <cl@linux.com> +- Modified by Paul Menage <menage@google.com> +- Modified by Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> + +.. CONTENTS: + + 1. Cpusets + 1.1 What are cpusets ? + 1.2 Why are cpusets needed ? + 1.3 How are cpusets implemented ? + 1.4 What are exclusive cpusets ? + 1.5 What is memory_pressure ? + 1.6 What is memory spread ? + 1.7 What is sched_load_balance ? + 1.8 What is sched_relax_domain_level ? + 1.9 How do I use cpusets ? + 2. Usage Examples and Syntax + 2.1 Basic Usage + 2.2 Adding/removing cpus + 2.3 Setting flags + 2.4 Attaching processes + 3. Questions + 4. Contact + +1. Cpusets +========== + +1.1 What are cpusets ? +---------------------- + +Cpusets provide a mechanism for assigning a set of CPUs and Memory +Nodes to a set of tasks. In this document "Memory Node" refers to +an on-line node that contains memory. + +Cpusets constrain the CPU and Memory placement of tasks to only +the resources within a task's current cpuset. They form a nested +hierarchy visible in a virtual file system. These are the essential +hooks, beyond what is already present, required to manage dynamic +job placement on large systems. + +Cpusets use the generic cgroup subsystem described in +Documentation/admin-guide/cgroup-v1/cgroups.rst. + +Requests by a task, using the sched_setaffinity(2) system call to +include CPUs in its CPU affinity mask, and using the mbind(2) and +set_mempolicy(2) system calls to include Memory Nodes in its memory +policy, are both filtered through that task's cpuset, filtering out any +CPUs or Memory Nodes not in that cpuset. The scheduler will not +schedule a task on a CPU that is not allowed in its cpus_allowed +vector, and the kernel page allocator will not allocate a page on a +node that is not allowed in the requesting task's mems_allowed vector. + +User level code may create and destroy cpusets by name in the cgroup +virtual file system, manage the attributes and permissions of these +cpusets and which CPUs and Memory Nodes are assigned to each cpuset, +specify and query to which cpuset a task is assigned, and list the +task pids assigned to a cpuset. + + +1.2 Why are cpusets needed ? +---------------------------- + +The management of large computer systems, with many processors (CPUs), +complex memory cache hierarchies and multiple Memory Nodes having +non-uniform access times (NUMA) presents additional challenges for +the efficient scheduling and memory placement of processes. + +Frequently more modest sized systems can be operated with adequate +efficiency just by letting the operating system automatically share +the available CPU and Memory resources amongst the requesting tasks. + +But larger systems, which benefit more from careful processor and +memory placement to reduce memory access times and contention, +and which typically represent a larger investment for the customer, +can benefit from explicitly placing jobs on properly sized subsets of +the system. + +This can be especially valuable on: + + * Web Servers running multiple instances of the same web application, + * Servers running different applications (for instance, a web server + and a database), or + * NUMA systems running large HPC applications with demanding + performance characteristics. + +These subsets, or "soft partitions" must be able to be dynamically +adjusted, as the job mix changes, without impacting other concurrently +executing jobs. The location of the running jobs pages may also be moved +when the memory locations are changed. + +The kernel cpuset patch provides the minimum essential kernel +mechanisms required to efficiently implement such subsets. It +leverages existing CPU and Memory Placement facilities in the Linux +kernel to avoid any additional impact on the critical scheduler or +memory allocator code. + + +1.3 How are cpusets implemented ? +--------------------------------- + +Cpusets provide a Linux kernel mechanism to constrain which CPUs and +Memory Nodes are used by a process or set of processes. + +The Linux kernel already has a pair of mechanisms to specify on which +CPUs a task may be scheduled (sched_setaffinity) and on which Memory +Nodes it may obtain memory (mbind, set_mempolicy). + +Cpusets extends these two mechanisms as follows: + + - Cpusets are sets of allowed CPUs and Memory Nodes, known to the + kernel. + - Each task in the system is attached to a cpuset, via a pointer + in the task structure to a reference counted cgroup structure. + - Calls to sched_setaffinity are filtered to just those CPUs + allowed in that task's cpuset. + - Calls to mbind and set_mempolicy are filtered to just + those Memory Nodes allowed in that task's cpuset. + - The root cpuset contains all the systems CPUs and Memory + Nodes. + - For any cpuset, one can define child cpusets containing a subset + of the parents CPU and Memory Node resources. + - The hierarchy of cpusets can be mounted at /dev/cpuset, for + browsing and manipulation from user space. + - A cpuset may be marked exclusive, which ensures that no other + cpuset (except direct ancestors and descendants) may contain + any overlapping CPUs or Memory Nodes. + - You can list all the tasks (by pid) attached to any cpuset. + +The implementation of cpusets requires a few, simple hooks +into the rest of the kernel, none in performance critical paths: + + - in init/main.c, to initialize the root cpuset at system boot. + - in fork and exit, to attach and detach a task from its cpuset. + - in sched_setaffinity, to mask the requested CPUs by what's + allowed in that task's cpuset. + - in sched.c migrate_live_tasks(), to keep migrating tasks within + the CPUs allowed by their cpuset, if possible. + - in the mbind and set_mempolicy system calls, to mask the requested + Memory Nodes by what's allowed in that task's cpuset. + - in page_alloc.c, to restrict memory to allowed nodes. + - in vmscan.c, to restrict page recovery to the current cpuset. + +You should mount the "cgroup" filesystem type in order to enable +browsing and modifying the cpusets presently known to the kernel. No +new system calls are added for cpusets - all support for querying and +modifying cpusets is via this cpuset file system. + +The /proc/<pid>/status file for each task has four added lines, +displaying the task's cpus_allowed (on which CPUs it may be scheduled) +and mems_allowed (on which Memory Nodes it may obtain memory), +in the two formats seen in the following example:: + + Cpus_allowed: ffffffff,ffffffff,ffffffff,ffffffff + Cpus_allowed_list: 0-127 + Mems_allowed: ffffffff,ffffffff + Mems_allowed_list: 0-63 + +Each cpuset is represented by a directory in the cgroup file system +containing (on top of the standard cgroup files) the following +files describing that cpuset: + + - cpuset.cpus: list of CPUs in that cpuset + - cpuset.mems: list of Memory Nodes in that cpuset + - cpuset.memory_migrate flag: if set, move pages to cpusets nodes + - cpuset.cpu_exclusive flag: is cpu placement exclusive? + - cpuset.mem_exclusive flag: is memory placement exclusive? + - cpuset.mem_hardwall flag: is memory allocation hardwalled + - cpuset.memory_pressure: measure of how much paging pressure in cpuset + - cpuset.memory_spread_page flag: if set, spread page cache evenly on allowed nodes + - cpuset.memory_spread_slab flag: if set, spread slab cache evenly on allowed nodes + - cpuset.sched_load_balance flag: if set, load balance within CPUs on that cpuset + - cpuset.sched_relax_domain_level: the searching range when migrating tasks + +In addition, only the root cpuset has the following file: + + - cpuset.memory_pressure_enabled flag: compute memory_pressure? + +New cpusets are created using the mkdir system call or shell +command. The properties of a cpuset, such as its flags, allowed +CPUs and Memory Nodes, and attached tasks, are modified by writing +to the appropriate file in that cpusets directory, as listed above. + +The named hierarchical structure of nested cpusets allows partitioning +a large system into nested, dynamically changeable, "soft-partitions". + +The attachment of each task, automatically inherited at fork by any +children of that task, to a cpuset allows organizing the work load +on a system into related sets of tasks such that each set is constrained +to using the CPUs and Memory Nodes of a particular cpuset. A task +may be re-attached to any other cpuset, if allowed by the permissions +on the necessary cpuset file system directories. + +Such management of a system "in the large" integrates smoothly with +the detailed placement done on individual tasks and memory regions +using the sched_setaffinity, mbind and set_mempolicy system calls. + +The following rules apply to each cpuset: + + - Its CPUs and Memory Nodes must be a subset of its parents. + - It can't be marked exclusive unless its parent is. + - If its cpu or memory is exclusive, they may not overlap any sibling. + +These rules, and the natural hierarchy of cpusets, enable efficient +enforcement of the exclusive guarantee, without having to scan all +cpusets every time any of them change to ensure nothing overlaps a +exclusive cpuset. Also, the use of a Linux virtual file system (vfs) +to represent the cpuset hierarchy provides for a familiar permission +and name space for cpusets, with a minimum of additional kernel code. + +The cpus and mems files in the root (top_cpuset) cpuset are +read-only. The cpus file automatically tracks the value of +cpu_online_mask using a CPU hotplug notifier, and the mems file +automatically tracks the value of node_states[N_MEMORY]--i.e., +nodes with memory--using the cpuset_track_online_nodes() hook. + +The cpuset.effective_cpus and cpuset.effective_mems files are +normally read-only copies of cpuset.cpus and cpuset.mems files +respectively. If the cpuset cgroup filesystem is mounted with the +special "cpuset_v2_mode" option, the behavior of these files will become +similar to the corresponding files in cpuset v2. In other words, hotplug +events will not change cpuset.cpus and cpuset.mems. Those events will +only affect cpuset.effective_cpus and cpuset.effective_mems which show +the actual cpus and memory nodes that are currently used by this cpuset. +See Documentation/admin-guide/cgroup-v2.rst for more information about +cpuset v2 behavior. + + +1.4 What are exclusive cpusets ? +-------------------------------- + +If a cpuset is cpu or mem exclusive, no other cpuset, other than +a direct ancestor or descendant, may share any of the same CPUs or +Memory Nodes. + +A cpuset that is cpuset.mem_exclusive *or* cpuset.mem_hardwall is "hardwalled", +i.e. it restricts kernel allocations for page, buffer and other data +commonly shared by the kernel across multiple users. All cpusets, +whether hardwalled or not, restrict allocations of memory for user +space. This enables configuring a system so that several independent +jobs can share common kernel data, such as file system pages, while +isolating each job's user allocation in its own cpuset. To do this, +construct a large mem_exclusive cpuset to hold all the jobs, and +construct child, non-mem_exclusive cpusets for each individual job. +Only a small amount of typical kernel memory, such as requests from +interrupt handlers, is allowed to be taken outside even a +mem_exclusive cpuset. + + +1.5 What is memory_pressure ? +----------------------------- +The memory_pressure of a cpuset provides a simple per-cpuset metric +of the rate that the tasks in a cpuset are attempting to free up in +use memory on the nodes of the cpuset to satisfy additional memory +requests. + +This enables batch managers monitoring jobs running in dedicated +cpusets to efficiently detect what level of memory pressure that job +is causing. + +This is useful both on tightly managed systems running a wide mix of +submitted jobs, which may choose to terminate or re-prioritize jobs that +are trying to use more memory than allowed on the nodes assigned to them, +and with tightly coupled, long running, massively parallel scientific +computing jobs that will dramatically fail to meet required performance +goals if they start to use more memory than allowed to them. + +This mechanism provides a very economical way for the batch manager +to monitor a cpuset for signs of memory pressure. It's up to the +batch manager or other user code to decide what to do about it and +take action. + +==> + Unless this feature is enabled by writing "1" to the special file + /dev/cpuset/memory_pressure_enabled, the hook in the rebalance + code of __alloc_pages() for this metric reduces to simply noticing + that the cpuset_memory_pressure_enabled flag is zero. So only + systems that enable this feature will compute the metric. + +Why a per-cpuset, running average: + + Because this meter is per-cpuset, rather than per-task or mm, + the system load imposed by a batch scheduler monitoring this + metric is sharply reduced on large systems, because a scan of + the tasklist can be avoided on each set of queries. + + Because this meter is a running average, instead of an accumulating + counter, a batch scheduler can detect memory pressure with a + single read, instead of having to read and accumulate results + for a period of time. + + Because this meter is per-cpuset rather than per-task or mm, + the batch scheduler can obtain the key information, memory + pressure in a cpuset, with a single read, rather than having to + query and accumulate results over all the (dynamically changing) + set of tasks in the cpuset. + +A per-cpuset simple digital filter (requires a spinlock and 3 words +of data per-cpuset) is kept, and updated by any task attached to that +cpuset, if it enters the synchronous (direct) page reclaim code. + +A per-cpuset file provides an integer number representing the recent +(half-life of 10 seconds) rate of direct page reclaims caused by +the tasks in the cpuset, in units of reclaims attempted per second, +times 1000. + + +1.6 What is memory spread ? +--------------------------- +There are two boolean flag files per cpuset that control where the +kernel allocates pages for the file system buffers and related in +kernel data structures. They are called 'cpuset.memory_spread_page' and +'cpuset.memory_spread_slab'. + +If the per-cpuset boolean flag file 'cpuset.memory_spread_page' is set, then +the kernel will spread the file system buffers (page cache) evenly +over all the nodes that the faulting task is allowed to use, instead +of preferring to put those pages on the node where the task is running. + +If the per-cpuset boolean flag file 'cpuset.memory_spread_slab' is set, +then the kernel will spread some file system related slab caches, +such as for inodes and dentries evenly over all the nodes that the +faulting task is allowed to use, instead of preferring to put those +pages on the node where the task is running. + +The setting of these flags does not affect anonymous data segment or +stack segment pages of a task. + +By default, both kinds of memory spreading are off, and memory +pages are allocated on the node local to where the task is running, +except perhaps as modified by the task's NUMA mempolicy or cpuset +configuration, so long as sufficient free memory pages are available. + +When new cpusets are created, they inherit the memory spread settings +of their parent. + +Setting memory spreading causes allocations for the affected page +or slab caches to ignore the task's NUMA mempolicy and be spread +instead. Tasks using mbind() or set_mempolicy() calls to set NUMA +mempolicies will not notice any change in these calls as a result of +their containing task's memory spread settings. If memory spreading +is turned off, then the currently specified NUMA mempolicy once again +applies to memory page allocations. + +Both 'cpuset.memory_spread_page' and 'cpuset.memory_spread_slab' are boolean flag +files. By default they contain "0", meaning that the feature is off +for that cpuset. If a "1" is written to that file, then that turns +the named feature on. + +The implementation is simple. + +Setting the flag 'cpuset.memory_spread_page' turns on a per-process flag +PFA_SPREAD_PAGE for each task that is in that cpuset or subsequently +joins that cpuset. The page allocation calls for the page cache +is modified to perform an inline check for this PFA_SPREAD_PAGE task +flag, and if set, a call to a new routine cpuset_mem_spread_node() +returns the node to prefer for the allocation. + +Similarly, setting 'cpuset.memory_spread_slab' turns on the flag +PFA_SPREAD_SLAB, and appropriately marked slab caches will allocate +pages from the node returned by cpuset_mem_spread_node(). + +The cpuset_mem_spread_node() routine is also simple. It uses the +value of a per-task rotor cpuset_mem_spread_rotor to select the next +node in the current task's mems_allowed to prefer for the allocation. + +This memory placement policy is also known (in other contexts) as +round-robin or interleave. + +This policy can provide substantial improvements for jobs that need +to place thread local data on the corresponding node, but that need +to access large file system data sets that need to be spread across +the several nodes in the jobs cpuset in order to fit. Without this +policy, especially for jobs that might have one thread reading in the +data set, the memory allocation across the nodes in the jobs cpuset +can become very uneven. + +1.7 What is sched_load_balance ? +-------------------------------- + +The kernel scheduler (kernel/sched/core.c) automatically load balances +tasks. If one CPU is underutilized, kernel code running on that +CPU will look for tasks on other more overloaded CPUs and move those +tasks to itself, within the constraints of such placement mechanisms +as cpusets and sched_setaffinity. + +The algorithmic cost of load balancing and its impact on key shared +kernel data structures such as the task list increases more than +linearly with the number of CPUs being balanced. So the scheduler +has support to partition the systems CPUs into a number of sched +domains such that it only load balances within each sched domain. +Each sched domain covers some subset of the CPUs in the system; +no two sched domains overlap; some CPUs might not be in any sched +domain and hence won't be load balanced. + +Put simply, it costs less to balance between two smaller sched domains +than one big one, but doing so means that overloads in one of the +two domains won't be load balanced to the other one. + +By default, there is one sched domain covering all CPUs, including those +marked isolated using the kernel boot time "isolcpus=" argument. However, +the isolated CPUs will not participate in load balancing, and will not +have tasks running on them unless explicitly assigned. + +This default load balancing across all CPUs is not well suited for +the following two situations: + + 1) On large systems, load balancing across many CPUs is expensive. + If the system is managed using cpusets to place independent jobs + on separate sets of CPUs, full load balancing is unnecessary. + 2) Systems supporting realtime on some CPUs need to minimize + system overhead on those CPUs, including avoiding task load + balancing if that is not needed. + +When the per-cpuset flag "cpuset.sched_load_balance" is enabled (the default +setting), it requests that all the CPUs in that cpusets allowed 'cpuset.cpus' +be contained in a single sched domain, ensuring that load balancing +can move a task (not otherwised pinned, as by sched_setaffinity) +from any CPU in that cpuset to any other. + +When the per-cpuset flag "cpuset.sched_load_balance" is disabled, then the +scheduler will avoid load balancing across the CPUs in that cpuset, +--except-- in so far as is necessary because some overlapping cpuset +has "sched_load_balance" enabled. + +So, for example, if the top cpuset has the flag "cpuset.sched_load_balance" +enabled, then the scheduler will have one sched domain covering all +CPUs, and the setting of the "cpuset.sched_load_balance" flag in any other +cpusets won't matter, as we're already fully load balancing. + +Therefore in the above two situations, the top cpuset flag +"cpuset.sched_load_balance" should be disabled, and only some of the smaller, +child cpusets have this flag enabled. + +When doing this, you don't usually want to leave any unpinned tasks in +the top cpuset that might use non-trivial amounts of CPU, as such tasks +may be artificially constrained to some subset of CPUs, depending on +the particulars of this flag setting in descendant cpusets. Even if +such a task could use spare CPU cycles in some other CPUs, the kernel +scheduler might not consider the possibility of load balancing that +task to that underused CPU. + +Of course, tasks pinned to a particular CPU can be left in a cpuset +that disables "cpuset.sched_load_balance" as those tasks aren't going anywhere +else anyway. + +There is an impedance mismatch here, between cpusets and sched domains. +Cpusets are hierarchical and nest. Sched domains are flat; they don't +overlap and each CPU is in at most one sched domain. + +It is necessary for sched domains to be flat because load balancing +across partially overlapping sets of CPUs would risk unstable dynamics +that would be beyond our understanding. So if each of two partially +overlapping cpusets enables the flag 'cpuset.sched_load_balance', then we +form a single sched domain that is a superset of both. We won't move +a task to a CPU outside its cpuset, but the scheduler load balancing +code might waste some compute cycles considering that possibility. + +This mismatch is why there is not a simple one-to-one relation +between which cpusets have the flag "cpuset.sched_load_balance" enabled, +and the sched domain configuration. If a cpuset enables the flag, it +will get balancing across all its CPUs, but if it disables the flag, +it will only be assured of no load balancing if no other overlapping +cpuset enables the flag. + +If two cpusets have partially overlapping 'cpuset.cpus' allowed, and only +one of them has this flag enabled, then the other may find its +tasks only partially load balanced, just on the overlapping CPUs. +This is just the general case of the top_cpuset example given a few +paragraphs above. In the general case, as in the top cpuset case, +don't leave tasks that might use non-trivial amounts of CPU in +such partially load balanced cpusets, as they may be artificially +constrained to some subset of the CPUs allowed to them, for lack of +load balancing to the other CPUs. + +CPUs in "cpuset.isolcpus" were excluded from load balancing by the +isolcpus= kernel boot option, and will never be load balanced regardless +of the value of "cpuset.sched_load_balance" in any cpuset. + +1.7.1 sched_load_balance implementation details. +------------------------------------------------ + +The per-cpuset flag 'cpuset.sched_load_balance' defaults to enabled (contrary +to most cpuset flags.) When enabled for a cpuset, the kernel will +ensure that it can load balance across all the CPUs in that cpuset +(makes sure that all the CPUs in the cpus_allowed of that cpuset are +in the same sched domain.) + +If two overlapping cpusets both have 'cpuset.sched_load_balance' enabled, +then they will be (must be) both in the same sched domain. + +If, as is the default, the top cpuset has 'cpuset.sched_load_balance' enabled, +then by the above that means there is a single sched domain covering +the whole system, regardless of any other cpuset settings. + +The kernel commits to user space that it will avoid load balancing +where it can. It will pick as fine a granularity partition of sched +domains as it can while still providing load balancing for any set +of CPUs allowed to a cpuset having 'cpuset.sched_load_balance' enabled. + +The internal kernel cpuset to scheduler interface passes from the +cpuset code to the scheduler code a partition of the load balanced +CPUs in the system. This partition is a set of subsets (represented +as an array of struct cpumask) of CPUs, pairwise disjoint, that cover +all the CPUs that must be load balanced. + +The cpuset code builds a new such partition and passes it to the +scheduler sched domain setup code, to have the sched domains rebuilt +as necessary, whenever: + + - the 'cpuset.sched_load_balance' flag of a cpuset with non-empty CPUs changes, + - or CPUs come or go from a cpuset with this flag enabled, + - or 'cpuset.sched_relax_domain_level' value of a cpuset with non-empty CPUs + and with this flag enabled changes, + - or a cpuset with non-empty CPUs and with this flag enabled is removed, + - or a cpu is offlined/onlined. + +This partition exactly defines what sched domains the scheduler should +setup - one sched domain for each element (struct cpumask) in the +partition. + +The scheduler remembers the currently active sched domain partitions. +When the scheduler routine partition_sched_domains() is invoked from +the cpuset code to update these sched domains, it compares the new +partition requested with the current, and updates its sched domains, +removing the old and adding the new, for each change. + + +1.8 What is sched_relax_domain_level ? +-------------------------------------- + +In sched domain, the scheduler migrates tasks in 2 ways; periodic load +balance on tick, and at time of some schedule events. + +When a task is woken up, scheduler try to move the task on idle CPU. +For example, if a task A running on CPU X activates another task B +on the same CPU X, and if CPU Y is X's sibling and performing idle, +then scheduler migrate task B to CPU Y so that task B can start on +CPU Y without waiting task A on CPU X. + +And if a CPU run out of tasks in its runqueue, the CPU try to pull +extra tasks from other busy CPUs to help them before it is going to +be idle. + +Of course it takes some searching cost to find movable tasks and/or +idle CPUs, the scheduler might not search all CPUs in the domain +every time. In fact, in some architectures, the searching ranges on +events are limited in the same socket or node where the CPU locates, +while the load balance on tick searches all. + +For example, assume CPU Z is relatively far from CPU X. Even if CPU Z +is idle while CPU X and the siblings are busy, scheduler can't migrate +woken task B from X to Z since it is out of its searching range. +As the result, task B on CPU X need to wait task A or wait load balance +on the next tick. For some applications in special situation, waiting +1 tick may be too long. + +The 'cpuset.sched_relax_domain_level' file allows you to request changing +this searching range as you like. This file takes int value which +indicates size of searching range in levels ideally as follows, +otherwise initial value -1 that indicates the cpuset has no request. + +====== =========================================================== + -1 no request. use system default or follow request of others. + 0 no search. + 1 search siblings (hyperthreads in a core). + 2 search cores in a package. + 3 search cpus in a node [= system wide on non-NUMA system] + 4 search nodes in a chunk of node [on NUMA system] + 5 search system wide [on NUMA system] +====== =========================================================== + +The system default is architecture dependent. The system default +can be changed using the relax_domain_level= boot parameter. + +This file is per-cpuset and affect the sched domain where the cpuset +belongs to. Therefore if the flag 'cpuset.sched_load_balance' of a cpuset +is disabled, then 'cpuset.sched_relax_domain_level' have no effect since +there is no sched domain belonging the cpuset. + +If multiple cpusets are overlapping and hence they form a single sched +domain, the largest value among those is used. Be careful, if one +requests 0 and others are -1 then 0 is used. + +Note that modifying this file will have both good and bad effects, +and whether it is acceptable or not depends on your situation. +Don't modify this file if you are not sure. + +If your situation is: + + - The migration costs between each cpu can be assumed considerably + small(for you) due to your special application's behavior or + special hardware support for CPU cache etc. + - The searching cost doesn't have impact(for you) or you can make + the searching cost enough small by managing cpuset to compact etc. + - The latency is required even it sacrifices cache hit rate etc. + then increasing 'sched_relax_domain_level' would benefit you. + + +1.9 How do I use cpusets ? +-------------------------- + +In order to minimize the impact of cpusets on critical kernel +code, such as the scheduler, and due to the fact that the kernel +does not support one task updating the memory placement of another +task directly, the impact on a task of changing its cpuset CPU +or Memory Node placement, or of changing to which cpuset a task +is attached, is subtle. + +If a cpuset has its Memory Nodes modified, then for each task attached +to that cpuset, the next time that the kernel attempts to allocate +a page of memory for that task, the kernel will notice the change +in the task's cpuset, and update its per-task memory placement to +remain within the new cpusets memory placement. If the task was using +mempolicy MPOL_BIND, and the nodes to which it was bound overlap with +its new cpuset, then the task will continue to use whatever subset +of MPOL_BIND nodes are still allowed in the new cpuset. If the task +was using MPOL_BIND and now none of its MPOL_BIND nodes are allowed +in the new cpuset, then the task will be essentially treated as if it +was MPOL_BIND bound to the new cpuset (even though its NUMA placement, +as queried by get_mempolicy(), doesn't change). If a task is moved +from one cpuset to another, then the kernel will adjust the task's +memory placement, as above, the next time that the kernel attempts +to allocate a page of memory for that task. + +If a cpuset has its 'cpuset.cpus' modified, then each task in that cpuset +will have its allowed CPU placement changed immediately. Similarly, +if a task's pid is written to another cpuset's 'tasks' file, then its +allowed CPU placement is changed immediately. If such a task had been +bound to some subset of its cpuset using the sched_setaffinity() call, +the task will be allowed to run on any CPU allowed in its new cpuset, +negating the effect of the prior sched_setaffinity() call. + +In summary, the memory placement of a task whose cpuset is changed is +updated by the kernel, on the next allocation of a page for that task, +and the processor placement is updated immediately. + +Normally, once a page is allocated (given a physical page +of main memory) then that page stays on whatever node it +was allocated, so long as it remains allocated, even if the +cpusets memory placement policy 'cpuset.mems' subsequently changes. +If the cpuset flag file 'cpuset.memory_migrate' is set true, then when +tasks are attached to that cpuset, any pages that task had +allocated to it on nodes in its previous cpuset are migrated +to the task's new cpuset. The relative placement of the page within +the cpuset is preserved during these migration operations if possible. +For example if the page was on the second valid node of the prior cpuset +then the page will be placed on the second valid node of the new cpuset. + +Also if 'cpuset.memory_migrate' is set true, then if that cpuset's +'cpuset.mems' file is modified, pages allocated to tasks in that +cpuset, that were on nodes in the previous setting of 'cpuset.mems', +will be moved to nodes in the new setting of 'mems.' +Pages that were not in the task's prior cpuset, or in the cpuset's +prior 'cpuset.mems' setting, will not be moved. + +There is an exception to the above. If hotplug functionality is used +to remove all the CPUs that are currently assigned to a cpuset, +then all the tasks in that cpuset will be moved to the nearest ancestor +with non-empty cpus. But the moving of some (or all) tasks might fail if +cpuset is bound with another cgroup subsystem which has some restrictions +on task attaching. In this failing case, those tasks will stay +in the original cpuset, and the kernel will automatically update +their cpus_allowed to allow all online CPUs. When memory hotplug +functionality for removing Memory Nodes is available, a similar exception +is expected to apply there as well. In general, the kernel prefers to +violate cpuset placement, over starving a task that has had all +its allowed CPUs or Memory Nodes taken offline. + +There is a second exception to the above. GFP_ATOMIC requests are +kernel internal allocations that must be satisfied, immediately. +The kernel may drop some request, in rare cases even panic, if a +GFP_ATOMIC alloc fails. If the request cannot be satisfied within +the current task's cpuset, then we relax the cpuset, and look for +memory anywhere we can find it. It's better to violate the cpuset +than stress the kernel. + +To start a new job that is to be contained within a cpuset, the steps are: + + 1) mkdir /sys/fs/cgroup/cpuset + 2) mount -t cgroup -ocpuset cpuset /sys/fs/cgroup/cpuset + 3) Create the new cpuset by doing mkdir's and write's (or echo's) in + the /sys/fs/cgroup/cpuset virtual file system. + 4) Start a task that will be the "founding father" of the new job. + 5) Attach that task to the new cpuset by writing its pid to the + /sys/fs/cgroup/cpuset tasks file for that cpuset. + 6) fork, exec or clone the job tasks from this founding father task. + +For example, the following sequence of commands will setup a cpuset +named "Charlie", containing just CPUs 2 and 3, and Memory Node 1, +and then start a subshell 'sh' in that cpuset:: + + mount -t cgroup -ocpuset cpuset /sys/fs/cgroup/cpuset + cd /sys/fs/cgroup/cpuset + mkdir Charlie + cd Charlie + /bin/echo 2-3 > cpuset.cpus + /bin/echo 1 > cpuset.mems + /bin/echo $$ > tasks + sh + # The subshell 'sh' is now running in cpuset Charlie + # The next line should display '/Charlie' + cat /proc/self/cpuset + +There are ways to query or modify cpusets: + + - via the cpuset file system directly, using the various cd, mkdir, echo, + cat, rmdir commands from the shell, or their equivalent from C. + - via the C library libcpuset. + - via the C library libcgroup. + (https://github.com/libcgroup/libcgroup/) + - via the python application cset. + (http://code.google.com/p/cpuset/) + +The sched_setaffinity calls can also be done at the shell prompt using +SGI's runon or Robert Love's taskset. The mbind and set_mempolicy +calls can be done at the shell prompt using the numactl command +(part of Andi Kleen's numa package). + +2. Usage Examples and Syntax +============================ + +2.1 Basic Usage +--------------- + +Creating, modifying, using the cpusets can be done through the cpuset +virtual filesystem. + +To mount it, type: +# mount -t cgroup -o cpuset cpuset /sys/fs/cgroup/cpuset + +Then under /sys/fs/cgroup/cpuset you can find a tree that corresponds to the +tree of the cpusets in the system. For instance, /sys/fs/cgroup/cpuset +is the cpuset that holds the whole system. + +If you want to create a new cpuset under /sys/fs/cgroup/cpuset:: + + # cd /sys/fs/cgroup/cpuset + # mkdir my_cpuset + +Now you want to do something with this cpuset:: + + # cd my_cpuset + +In this directory you can find several files:: + + # ls + cgroup.clone_children cpuset.memory_pressure + cgroup.event_control cpuset.memory_spread_page + cgroup.procs cpuset.memory_spread_slab + cpuset.cpu_exclusive cpuset.mems + cpuset.cpus cpuset.sched_load_balance + cpuset.mem_exclusive cpuset.sched_relax_domain_level + cpuset.mem_hardwall notify_on_release + cpuset.memory_migrate tasks + +Reading them will give you information about the state of this cpuset: +the CPUs and Memory Nodes it can use, the processes that are using +it, its properties. By writing to these files you can manipulate +the cpuset. + +Set some flags:: + + # /bin/echo 1 > cpuset.cpu_exclusive + +Add some cpus:: + + # /bin/echo 0-7 > cpuset.cpus + +Add some mems:: + + # /bin/echo 0-7 > cpuset.mems + +Now attach your shell to this cpuset:: + + # /bin/echo $$ > tasks + +You can also create cpusets inside your cpuset by using mkdir in this +directory:: + + # mkdir my_sub_cs + +To remove a cpuset, just use rmdir:: + + # rmdir my_sub_cs + +This will fail if the cpuset is in use (has cpusets inside, or has +processes attached). + +Note that for legacy reasons, the "cpuset" filesystem exists as a +wrapper around the cgroup filesystem. + +The command:: + + mount -t cpuset X /sys/fs/cgroup/cpuset + +is equivalent to:: + + mount -t cgroup -ocpuset,noprefix X /sys/fs/cgroup/cpuset + echo "/sbin/cpuset_release_agent" > /sys/fs/cgroup/cpuset/release_agent + +2.2 Adding/removing cpus +------------------------ + +This is the syntax to use when writing in the cpus or mems files +in cpuset directories:: + + # /bin/echo 1-4 > cpuset.cpus -> set cpus list to cpus 1,2,3,4 + # /bin/echo 1,2,3,4 > cpuset.cpus -> set cpus list to cpus 1,2,3,4 + +To add a CPU to a cpuset, write the new list of CPUs including the +CPU to be added. To add 6 to the above cpuset:: + + # /bin/echo 1-4,6 > cpuset.cpus -> set cpus list to cpus 1,2,3,4,6 + +Similarly to remove a CPU from a cpuset, write the new list of CPUs +without the CPU to be removed. + +To remove all the CPUs:: + + # /bin/echo "" > cpuset.cpus -> clear cpus list + +2.3 Setting flags +----------------- + +The syntax is very simple:: + + # /bin/echo 1 > cpuset.cpu_exclusive -> set flag 'cpuset.cpu_exclusive' + # /bin/echo 0 > cpuset.cpu_exclusive -> unset flag 'cpuset.cpu_exclusive' + +2.4 Attaching processes +----------------------- + +:: + + # /bin/echo PID > tasks + +Note that it is PID, not PIDs. You can only attach ONE task at a time. +If you have several tasks to attach, you have to do it one after another:: + + # /bin/echo PID1 > tasks + # /bin/echo PID2 > tasks + ... + # /bin/echo PIDn > tasks + + +3. Questions +============ + +Q: + what's up with this '/bin/echo' ? + +A: + bash's builtin 'echo' command does not check calls to write() against + errors. If you use it in the cpuset file system, you won't be + able to tell whether a command succeeded or failed. + +Q: + When I attach processes, only the first of the line gets really attached ! + +A: + We can only return one error code per call to write(). So you should also + put only ONE pid. + +4. Contact +========== + +Web: http://www.bullopensource.org/cpuset diff --git a/Documentation/admin-guide/cgroup-v1/devices.rst b/Documentation/admin-guide/cgroup-v1/devices.rst new file mode 100644 index 000000000..e18867839 --- /dev/null +++ b/Documentation/admin-guide/cgroup-v1/devices.rst @@ -0,0 +1,132 @@ +=========================== +Device Whitelist Controller +=========================== + +1. Description +============== + +Implement a cgroup to track and enforce open and mknod restrictions +on device files. A device cgroup associates a device access +whitelist with each cgroup. A whitelist entry has 4 fields. +'type' is a (all), c (char), or b (block). 'all' means it applies +to all types and all major and minor numbers. Major and minor are +either an integer or * for all. Access is a composition of r +(read), w (write), and m (mknod). + +The root device cgroup starts with rwm to 'all'. A child device +cgroup gets a copy of the parent. Administrators can then remove +devices from the whitelist or add new entries. A child cgroup can +never receive a device access which is denied by its parent. + +2. User Interface +================= + +An entry is added using devices.allow, and removed using +devices.deny. For instance:: + + echo 'c 1:3 mr' > /sys/fs/cgroup/1/devices.allow + +allows cgroup 1 to read and mknod the device usually known as +/dev/null. Doing:: + + echo a > /sys/fs/cgroup/1/devices.deny + +will remove the default 'a *:* rwm' entry. Doing:: + + echo a > /sys/fs/cgroup/1/devices.allow + +will add the 'a *:* rwm' entry to the whitelist. + +3. Security +=========== + +Any task can move itself between cgroups. This clearly won't +suffice, but we can decide the best way to adequately restrict +movement as people get some experience with this. We may just want +to require CAP_SYS_ADMIN, which at least is a separate bit from +CAP_MKNOD. We may want to just refuse moving to a cgroup which +isn't a descendant of the current one. Or we may want to use +CAP_MAC_ADMIN, since we really are trying to lock down root. + +CAP_SYS_ADMIN is needed to modify the whitelist or move another +task to a new cgroup. (Again we'll probably want to change that). + +A cgroup may not be granted more permissions than the cgroup's +parent has. + +4. Hierarchy +============ + +device cgroups maintain hierarchy by making sure a cgroup never has more +access permissions than its parent. Every time an entry is written to +a cgroup's devices.deny file, all its children will have that entry removed +from their whitelist and all the locally set whitelist entries will be +re-evaluated. In case one of the locally set whitelist entries would provide +more access than the cgroup's parent, it'll be removed from the whitelist. + +Example:: + + A + / \ + B + + group behavior exceptions + A allow "b 8:* rwm", "c 116:1 rw" + B deny "c 1:3 rwm", "c 116:2 rwm", "b 3:* rwm" + +If a device is denied in group A:: + + # echo "c 116:* r" > A/devices.deny + +it'll propagate down and after revalidating B's entries, the whitelist entry +"c 116:2 rwm" will be removed:: + + group whitelist entries denied devices + A all "b 8:* rwm", "c 116:* rw" + B "c 1:3 rwm", "b 3:* rwm" all the rest + +In case parent's exceptions change and local exceptions are not allowed +anymore, they'll be deleted. + +Notice that new whitelist entries will not be propagated:: + + A + / \ + B + + group whitelist entries denied devices + A "c 1:3 rwm", "c 1:5 r" all the rest + B "c 1:3 rwm", "c 1:5 r" all the rest + +when adding ``c *:3 rwm``:: + + # echo "c *:3 rwm" >A/devices.allow + +the result:: + + group whitelist entries denied devices + A "c *:3 rwm", "c 1:5 r" all the rest + B "c 1:3 rwm", "c 1:5 r" all the rest + +but now it'll be possible to add new entries to B:: + + # echo "c 2:3 rwm" >B/devices.allow + # echo "c 50:3 r" >B/devices.allow + +or even:: + + # echo "c *:3 rwm" >B/devices.allow + +Allowing or denying all by writing 'a' to devices.allow or devices.deny will +not be possible once the device cgroups has children. + +4.1 Hierarchy (internal implementation) +--------------------------------------- + +device cgroups is implemented internally using a behavior (ALLOW, DENY) and a +list of exceptions. The internal state is controlled using the same user +interface to preserve compatibility with the previous whitelist-only +implementation. Removal or addition of exceptions that will reduce the access +to devices will be propagated down the hierarchy. +For every propagated exception, the effective rules will be re-evaluated based +on current parent's access rules. diff --git a/Documentation/admin-guide/cgroup-v1/freezer-subsystem.rst b/Documentation/admin-guide/cgroup-v1/freezer-subsystem.rst new file mode 100644 index 000000000..582d3427d --- /dev/null +++ b/Documentation/admin-guide/cgroup-v1/freezer-subsystem.rst @@ -0,0 +1,127 @@ +============== +Cgroup Freezer +============== + +The cgroup freezer is useful to batch job management system which start +and stop sets of tasks in order to schedule the resources of a machine +according to the desires of a system administrator. This sort of program +is often used on HPC clusters to schedule access to the cluster as a +whole. The cgroup freezer uses cgroups to describe the set of tasks to +be started/stopped by the batch job management system. It also provides +a means to start and stop the tasks composing the job. + +The cgroup freezer will also be useful for checkpointing running groups +of tasks. The freezer allows the checkpoint code to obtain a consistent +image of the tasks by attempting to force the tasks in a cgroup into a +quiescent state. Once the tasks are quiescent another task can +walk /proc or invoke a kernel interface to gather information about the +quiesced tasks. Checkpointed tasks can be restarted later should a +recoverable error occur. This also allows the checkpointed tasks to be +migrated between nodes in a cluster by copying the gathered information +to another node and restarting the tasks there. + +Sequences of SIGSTOP and SIGCONT are not always sufficient for stopping +and resuming tasks in userspace. Both of these signals are observable +from within the tasks we wish to freeze. While SIGSTOP cannot be caught, +blocked, or ignored it can be seen by waiting or ptracing parent tasks. +SIGCONT is especially unsuitable since it can be caught by the task. Any +programs designed to watch for SIGSTOP and SIGCONT could be broken by +attempting to use SIGSTOP and SIGCONT to stop and resume tasks. We can +demonstrate this problem using nested bash shells:: + + $ echo $$ + 16644 + $ bash + $ echo $$ + 16690 + + From a second, unrelated bash shell: + $ kill -SIGSTOP 16690 + $ kill -SIGCONT 16690 + + <at this point 16690 exits and causes 16644 to exit too> + +This happens because bash can observe both signals and choose how it +responds to them. + +Another example of a program which catches and responds to these +signals is gdb. In fact any program designed to use ptrace is likely to +have a problem with this method of stopping and resuming tasks. + +In contrast, the cgroup freezer uses the kernel freezer code to +prevent the freeze/unfreeze cycle from becoming visible to the tasks +being frozen. This allows the bash example above and gdb to run as +expected. + +The cgroup freezer is hierarchical. Freezing a cgroup freezes all +tasks belonging to the cgroup and all its descendant cgroups. Each +cgroup has its own state (self-state) and the state inherited from the +parent (parent-state). Iff both states are THAWED, the cgroup is +THAWED. + +The following cgroupfs files are created by cgroup freezer. + +* freezer.state: Read-write. + + When read, returns the effective state of the cgroup - "THAWED", + "FREEZING" or "FROZEN". This is the combined self and parent-states. + If any is freezing, the cgroup is freezing (FREEZING or FROZEN). + + FREEZING cgroup transitions into FROZEN state when all tasks + belonging to the cgroup and its descendants become frozen. Note that + a cgroup reverts to FREEZING from FROZEN after a new task is added + to the cgroup or one of its descendant cgroups until the new task is + frozen. + + When written, sets the self-state of the cgroup. Two values are + allowed - "FROZEN" and "THAWED". If FROZEN is written, the cgroup, + if not already freezing, enters FREEZING state along with all its + descendant cgroups. + + If THAWED is written, the self-state of the cgroup is changed to + THAWED. Note that the effective state may not change to THAWED if + the parent-state is still freezing. If a cgroup's effective state + becomes THAWED, all its descendants which are freezing because of + the cgroup also leave the freezing state. + +* freezer.self_freezing: Read only. + + Shows the self-state. 0 if the self-state is THAWED; otherwise, 1. + This value is 1 iff the last write to freezer.state was "FROZEN". + +* freezer.parent_freezing: Read only. + + Shows the parent-state. 0 if none of the cgroup's ancestors is + frozen; otherwise, 1. + +The root cgroup is non-freezable and the above interface files don't +exist. + +* Examples of usage:: + + # mkdir /sys/fs/cgroup/freezer + # mount -t cgroup -ofreezer freezer /sys/fs/cgroup/freezer + # mkdir /sys/fs/cgroup/freezer/0 + # echo $some_pid > /sys/fs/cgroup/freezer/0/tasks + +to get status of the freezer subsystem:: + + # cat /sys/fs/cgroup/freezer/0/freezer.state + THAWED + +to freeze all tasks in the container:: + + # echo FROZEN > /sys/fs/cgroup/freezer/0/freezer.state + # cat /sys/fs/cgroup/freezer/0/freezer.state + FREEZING + # cat /sys/fs/cgroup/freezer/0/freezer.state + FROZEN + +to unfreeze all tasks in the container:: + + # echo THAWED > /sys/fs/cgroup/freezer/0/freezer.state + # cat /sys/fs/cgroup/freezer/0/freezer.state + THAWED + +This is the basic mechanism which should do the right thing for user space task +in a simple scenario. diff --git a/Documentation/admin-guide/cgroup-v1/hugetlb.rst b/Documentation/admin-guide/cgroup-v1/hugetlb.rst new file mode 100644 index 000000000..0fa724d82 --- /dev/null +++ b/Documentation/admin-guide/cgroup-v1/hugetlb.rst @@ -0,0 +1,135 @@ +================== +HugeTLB Controller +================== + +HugeTLB controller can be created by first mounting the cgroup filesystem. + +# mount -t cgroup -o hugetlb none /sys/fs/cgroup + +With the above step, the initial or the parent HugeTLB group becomes +visible at /sys/fs/cgroup. At bootup, this group includes all the tasks in +the system. /sys/fs/cgroup/tasks lists the tasks in this cgroup. + +New groups can be created under the parent group /sys/fs/cgroup:: + + # cd /sys/fs/cgroup + # mkdir g1 + # echo $$ > g1/tasks + +The above steps create a new group g1 and move the current shell +process (bash) into it. + +Brief summary of control files:: + + hugetlb.<hugepagesize>.rsvd.limit_in_bytes # set/show limit of "hugepagesize" hugetlb reservations + hugetlb.<hugepagesize>.rsvd.max_usage_in_bytes # show max "hugepagesize" hugetlb reservations and no-reserve faults + hugetlb.<hugepagesize>.rsvd.usage_in_bytes # show current reservations and no-reserve faults for "hugepagesize" hugetlb + hugetlb.<hugepagesize>.rsvd.failcnt # show the number of allocation failure due to HugeTLB reservation limit + hugetlb.<hugepagesize>.limit_in_bytes # set/show limit of "hugepagesize" hugetlb faults + hugetlb.<hugepagesize>.max_usage_in_bytes # show max "hugepagesize" hugetlb usage recorded + hugetlb.<hugepagesize>.usage_in_bytes # show current usage for "hugepagesize" hugetlb + hugetlb.<hugepagesize>.failcnt # show the number of allocation failure due to HugeTLB usage limit + hugetlb.<hugepagesize>.numa_stat # show the numa information of the hugetlb memory charged to this cgroup + +For a system supporting three hugepage sizes (64k, 32M and 1G), the control +files include:: + + hugetlb.1GB.limit_in_bytes + hugetlb.1GB.max_usage_in_bytes + hugetlb.1GB.numa_stat + hugetlb.1GB.usage_in_bytes + hugetlb.1GB.failcnt + hugetlb.1GB.rsvd.limit_in_bytes + hugetlb.1GB.rsvd.max_usage_in_bytes + hugetlb.1GB.rsvd.usage_in_bytes + hugetlb.1GB.rsvd.failcnt + hugetlb.64KB.limit_in_bytes + hugetlb.64KB.max_usage_in_bytes + hugetlb.64KB.numa_stat + hugetlb.64KB.usage_in_bytes + hugetlb.64KB.failcnt + hugetlb.64KB.rsvd.limit_in_bytes + hugetlb.64KB.rsvd.max_usage_in_bytes + hugetlb.64KB.rsvd.usage_in_bytes + hugetlb.64KB.rsvd.failcnt + hugetlb.32MB.limit_in_bytes + hugetlb.32MB.max_usage_in_bytes + hugetlb.32MB.numa_stat + hugetlb.32MB.usage_in_bytes + hugetlb.32MB.failcnt + hugetlb.32MB.rsvd.limit_in_bytes + hugetlb.32MB.rsvd.max_usage_in_bytes + hugetlb.32MB.rsvd.usage_in_bytes + hugetlb.32MB.rsvd.failcnt + + +1. Page fault accounting + +hugetlb.<hugepagesize>.limit_in_bytes +hugetlb.<hugepagesize>.max_usage_in_bytes +hugetlb.<hugepagesize>.usage_in_bytes +hugetlb.<hugepagesize>.failcnt + +The HugeTLB controller allows users to limit the HugeTLB usage (page fault) per +control group and enforces the limit during page fault. Since HugeTLB +doesn't support page reclaim, enforcing the limit at page fault time implies +that, the application will get SIGBUS signal if it tries to fault in HugeTLB +pages beyond its limit. Therefore the application needs to know exactly how many +HugeTLB pages it uses before hand, and the sysadmin needs to make sure that +there are enough available on the machine for all the users to avoid processes +getting SIGBUS. + + +2. Reservation accounting + +hugetlb.<hugepagesize>.rsvd.limit_in_bytes +hugetlb.<hugepagesize>.rsvd.max_usage_in_bytes +hugetlb.<hugepagesize>.rsvd.usage_in_bytes +hugetlb.<hugepagesize>.rsvd.failcnt + +The HugeTLB controller allows to limit the HugeTLB reservations per control +group and enforces the controller limit at reservation time and at the fault of +HugeTLB memory for which no reservation exists. Since reservation limits are +enforced at reservation time (on mmap or shget), reservation limits never causes +the application to get SIGBUS signal if the memory was reserved before hand. For +MAP_NORESERVE allocations, the reservation limit behaves the same as the fault +limit, enforcing memory usage at fault time and causing the application to +receive a SIGBUS if it's crossing its limit. + +Reservation limits are superior to page fault limits described above, since +reservation limits are enforced at reservation time (on mmap or shget), and +never causes the application to get SIGBUS signal if the memory was reserved +before hand. This allows for easier fallback to alternatives such as +non-HugeTLB memory for example. In the case of page fault accounting, it's very +hard to avoid processes getting SIGBUS since the sysadmin needs precisely know +the HugeTLB usage of all the tasks in the system and make sure there is enough +pages to satisfy all requests. Avoiding tasks getting SIGBUS on overcommited +systems is practically impossible with page fault accounting. + + +3. Caveats with shared memory + +For shared HugeTLB memory, both HugeTLB reservation and page faults are charged +to the first task that causes the memory to be reserved or faulted, and all +subsequent uses of this reserved or faulted memory is done without charging. + +Shared HugeTLB memory is only uncharged when it is unreserved or deallocated. +This is usually when the HugeTLB file is deleted, and not when the task that +caused the reservation or fault has exited. + + +4. Caveats with HugeTLB cgroup offline. + +When a HugeTLB cgroup goes offline with some reservations or faults still +charged to it, the behavior is as follows: + +- The fault charges are charged to the parent HugeTLB cgroup (reparented), +- the reservation charges remain on the offline HugeTLB cgroup. + +This means that if a HugeTLB cgroup gets offlined while there is still HugeTLB +reservations charged to it, that cgroup persists as a zombie until all HugeTLB +reservations are uncharged. HugeTLB reservations behave in this manner to match +the memory controller whose cgroups also persist as zombie until all charged +memory is uncharged. Also, the tracking of HugeTLB reservations is a bit more +complex compared to the tracking of HugeTLB faults, so it is significantly +harder to reparent reservations at offline time. diff --git a/Documentation/admin-guide/cgroup-v1/index.rst b/Documentation/admin-guide/cgroup-v1/index.rst new file mode 100644 index 000000000..99fbc8a64 --- /dev/null +++ b/Documentation/admin-guide/cgroup-v1/index.rst @@ -0,0 +1,31 @@ +.. _cgroup-v1: + +======================== +Control Groups version 1 +======================== + +.. toctree:: + :maxdepth: 1 + + cgroups + + blkio-controller + cpuacct + cpusets + devices + freezer-subsystem + hugetlb + memcg_test + memory + misc + net_cls + net_prio + pids + rdma + +.. only:: subproject and html + + Indices + ======= + + * :ref:`genindex` diff --git a/Documentation/admin-guide/cgroup-v1/memcg_test.rst b/Documentation/admin-guide/cgroup-v1/memcg_test.rst new file mode 100644 index 000000000..1f128458d --- /dev/null +++ b/Documentation/admin-guide/cgroup-v1/memcg_test.rst @@ -0,0 +1,344 @@ +===================================================== +Memory Resource Controller(Memcg) Implementation Memo +===================================================== + +Last Updated: 2010/2 + +Base Kernel Version: based on 2.6.33-rc7-mm(candidate for 34). + +Because VM is getting complex (one of reasons is memcg...), memcg's behavior +is complex. This is a document for memcg's internal behavior. +Please note that implementation details can be changed. + +(*) Topics on API should be in Documentation/admin-guide/cgroup-v1/memory.rst) + +0. How to record usage ? +======================== + + 2 objects are used. + + page_cgroup ....an object per page. + + Allocated at boot or memory hotplug. Freed at memory hot removal. + + swap_cgroup ... an entry per swp_entry. + + Allocated at swapon(). Freed at swapoff(). + + The page_cgroup has USED bit and double count against a page_cgroup never + occurs. swap_cgroup is used only when a charged page is swapped-out. + +1. Charge +========= + + a page/swp_entry may be charged (usage += PAGE_SIZE) at + + mem_cgroup_try_charge() + +2. Uncharge +=========== + + a page/swp_entry may be uncharged (usage -= PAGE_SIZE) by + + mem_cgroup_uncharge() + Called when a page's refcount goes down to 0. + + mem_cgroup_uncharge_swap() + Called when swp_entry's refcnt goes down to 0. A charge against swap + disappears. + +3. charge-commit-cancel +======================= + + Memcg pages are charged in two steps: + + - mem_cgroup_try_charge() + - mem_cgroup_commit_charge() or mem_cgroup_cancel_charge() + + At try_charge(), there are no flags to say "this page is charged". + at this point, usage += PAGE_SIZE. + + At commit(), the page is associated with the memcg. + + At cancel(), simply usage -= PAGE_SIZE. + +Under below explanation, we assume CONFIG_SWAP=y. + +4. Anonymous +============ + + Anonymous page is newly allocated at + - page fault into MAP_ANONYMOUS mapping. + - Copy-On-Write. + + 4.1 Swap-in. + At swap-in, the page is taken from swap-cache. There are 2 cases. + + (a) If the SwapCache is newly allocated and read, it has no charges. + (b) If the SwapCache has been mapped by processes, it has been + charged already. + + 4.2 Swap-out. + At swap-out, typical state transition is below. + + (a) add to swap cache. (marked as SwapCache) + swp_entry's refcnt += 1. + (b) fully unmapped. + swp_entry's refcnt += # of ptes. + (c) write back to swap. + (d) delete from swap cache. (remove from SwapCache) + swp_entry's refcnt -= 1. + + + Finally, at task exit, + (e) zap_pte() is called and swp_entry's refcnt -=1 -> 0. + +5. Page Cache +============= + + Page Cache is charged at + - filemap_add_folio(). + + The logic is very clear. (About migration, see below) + + Note: + __remove_from_page_cache() is called by remove_from_page_cache() + and __remove_mapping(). + +6. Shmem(tmpfs) Page Cache +=========================== + + The best way to understand shmem's page state transition is to read + mm/shmem.c. + + But brief explanation of the behavior of memcg around shmem will be + helpful to understand the logic. + + Shmem's page (just leaf page, not direct/indirect block) can be on + + - radix-tree of shmem's inode. + - SwapCache. + - Both on radix-tree and SwapCache. This happens at swap-in + and swap-out, + + It's charged when... + + - A new page is added to shmem's radix-tree. + - A swp page is read. (move a charge from swap_cgroup to page_cgroup) + +7. Page Migration +================= + + mem_cgroup_migrate() + +8. LRU +====== + Each memcg has its own vector of LRUs (inactive anon, active anon, + inactive file, active file, unevictable) of pages from each node, + each LRU handled under a single lru_lock for that memcg and node. + +9. Typical Tests. +================= + + Tests for racy cases. + +9.1 Small limit to memcg. +------------------------- + + When you do test to do racy case, it's good test to set memcg's limit + to be very small rather than GB. Many races found in the test under + xKB or xxMB limits. + + (Memory behavior under GB and Memory behavior under MB shows very + different situation.) + +9.2 Shmem +--------- + + Historically, memcg's shmem handling was poor and we saw some amount + of troubles here. This is because shmem is page-cache but can be + SwapCache. Test with shmem/tmpfs is always good test. + +9.3 Migration +------------- + + For NUMA, migration is an another special case. To do easy test, cpuset + is useful. Following is a sample script to do migration:: + + mount -t cgroup -o cpuset none /opt/cpuset + + mkdir /opt/cpuset/01 + echo 1 > /opt/cpuset/01/cpuset.cpus + echo 0 > /opt/cpuset/01/cpuset.mems + echo 1 > /opt/cpuset/01/cpuset.memory_migrate + mkdir /opt/cpuset/02 + echo 1 > /opt/cpuset/02/cpuset.cpus + echo 1 > /opt/cpuset/02/cpuset.mems + echo 1 > /opt/cpuset/02/cpuset.memory_migrate + + In above set, when you moves a task from 01 to 02, page migration to + node 0 to node 1 will occur. Following is a script to migrate all + under cpuset.:: + + -- + move_task() + { + for pid in $1 + do + /bin/echo $pid >$2/tasks 2>/dev/null + echo -n $pid + echo -n " " + done + echo END + } + + G1_TASK=`cat ${G1}/tasks` + G2_TASK=`cat ${G2}/tasks` + move_task "${G1_TASK}" ${G2} & + -- + +9.4 Memory hotplug +------------------ + + memory hotplug test is one of good test. + + to offline memory, do following:: + + # echo offline > /sys/devices/system/memory/memoryXXX/state + + (XXX is the place of memory) + + This is an easy way to test page migration, too. + +9.5 nested cgroups +------------------ + + Use tests like the following for testing nested cgroups:: + + mkdir /opt/cgroup/01/child_a + mkdir /opt/cgroup/01/child_b + + set limit to 01. + add limit to 01/child_b + run jobs under child_a and child_b + + create/delete following groups at random while jobs are running:: + + /opt/cgroup/01/child_a/child_aa + /opt/cgroup/01/child_b/child_bb + /opt/cgroup/01/child_c + + running new jobs in new group is also good. + +9.6 Mount with other subsystems +------------------------------- + + Mounting with other subsystems is a good test because there is a + race and lock dependency with other cgroup subsystems. + + example:: + + # mount -t cgroup none /cgroup -o cpuset,memory,cpu,devices + + and do task move, mkdir, rmdir etc...under this. + +9.7 swapoff +----------- + + Besides management of swap is one of complicated parts of memcg, + call path of swap-in at swapoff is not same as usual swap-in path.. + It's worth to be tested explicitly. + + For example, test like following is good: + + (Shell-A):: + + # mount -t cgroup none /cgroup -o memory + # mkdir /cgroup/test + # echo 40M > /cgroup/test/memory.limit_in_bytes + # echo 0 > /cgroup/test/tasks + + Run malloc(100M) program under this. You'll see 60M of swaps. + + (Shell-B):: + + # move all tasks in /cgroup/test to /cgroup + # /sbin/swapoff -a + # rmdir /cgroup/test + # kill malloc task. + + Of course, tmpfs v.s. swapoff test should be tested, too. + +9.8 OOM-Killer +-------------- + + Out-of-memory caused by memcg's limit will kill tasks under + the memcg. When hierarchy is used, a task under hierarchy + will be killed by the kernel. + + In this case, panic_on_oom shouldn't be invoked and tasks + in other groups shouldn't be killed. + + It's not difficult to cause OOM under memcg as following. + + Case A) when you can swapoff:: + + #swapoff -a + #echo 50M > /memory.limit_in_bytes + + run 51M of malloc + + Case B) when you use mem+swap limitation:: + + #echo 50M > memory.limit_in_bytes + #echo 50M > memory.memsw.limit_in_bytes + + run 51M of malloc + +9.9 Move charges at task migration +---------------------------------- + + Charges associated with a task can be moved along with task migration. + + (Shell-A):: + + #mkdir /cgroup/A + #echo $$ >/cgroup/A/tasks + + run some programs which uses some amount of memory in /cgroup/A. + + (Shell-B):: + + #mkdir /cgroup/B + #echo 1 >/cgroup/B/memory.move_charge_at_immigrate + #echo "pid of the program running in group A" >/cgroup/B/tasks + + You can see charges have been moved by reading ``*.usage_in_bytes`` or + memory.stat of both A and B. + + See 8.2 of Documentation/admin-guide/cgroup-v1/memory.rst to see what value should + be written to move_charge_at_immigrate. + +9.10 Memory thresholds +---------------------- + + Memory controller implements memory thresholds using cgroups notification + API. You can use tools/cgroup/cgroup_event_listener.c to test it. + + (Shell-A) Create cgroup and run event listener:: + + # mkdir /cgroup/A + # ./cgroup_event_listener /cgroup/A/memory.usage_in_bytes 5M + + (Shell-B) Add task to cgroup and try to allocate and free memory:: + + # echo $$ >/cgroup/A/tasks + # a="$(dd if=/dev/zero bs=1M count=10)" + # a= + + You will see message from cgroup_event_listener every time you cross + the thresholds. + + Use /cgroup/A/memory.memsw.usage_in_bytes to test memsw thresholds. + + It's good idea to test root cgroup as well. diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst new file mode 100644 index 000000000..ff456871b --- /dev/null +++ b/Documentation/admin-guide/cgroup-v1/memory.rst @@ -0,0 +1,1014 @@ +========================== +Memory Resource Controller +========================== + +.. caution:: + This document is hopelessly outdated and it asks for a complete + rewrite. It still contains a useful information so we are keeping it + here but make sure to check the current code if you need a deeper + understanding. + +.. note:: + The Memory Resource Controller has generically been referred to as the + memory controller in this document. Do not confuse memory controller + used here with the memory controller that is used in hardware. + +.. hint:: + When we mention a cgroup (cgroupfs's directory) with memory controller, + we call it "memory cgroup". When you see git-log and source code, you'll + see patch's title and function names tend to use "memcg". + In this document, we avoid using it. + +Benefits and Purpose of the memory controller +============================================= + +The memory controller isolates the memory behaviour of a group of tasks +from the rest of the system. The article on LWN [12]_ mentions some probable +uses of the memory controller. The memory controller can be used to + +a. Isolate an application or a group of applications + Memory-hungry applications can be isolated and limited to a smaller + amount of memory. +b. Create a cgroup with a limited amount of memory; this can be used + as a good alternative to booting with mem=XXXX. +c. Virtualization solutions can control the amount of memory they want + to assign to a virtual machine instance. +d. A CD/DVD burner could control the amount of memory used by the + rest of the system to ensure that burning does not fail due to lack + of available memory. +e. There are several other use cases; find one or use the controller just + for fun (to learn and hack on the VM subsystem). + +Current Status: linux-2.6.34-mmotm(development version of 2010/April) + +Features: + + - accounting anonymous pages, file caches, swap caches usage and limiting them. + - pages are linked to per-memcg LRU exclusively, and there is no global LRU. + - optionally, memory+swap usage can be accounted and limited. + - hierarchical accounting + - soft limit + - moving (recharging) account at moving a task is selectable. + - usage threshold notifier + - memory pressure notifier + - oom-killer disable knob and oom-notifier + - Root cgroup has no limit controls. + + Kernel memory support is a work in progress, and the current version provides + basically functionality. (See :ref:`section 2.7 + <cgroup-v1-memory-kernel-extension>`) + +Brief summary of control files. + +==================================== ========================================== + tasks attach a task(thread) and show list of + threads + cgroup.procs show list of processes + cgroup.event_control an interface for event_fd() + This knob is not available on CONFIG_PREEMPT_RT systems. + memory.usage_in_bytes show current usage for memory + (See 5.5 for details) + memory.memsw.usage_in_bytes show current usage for memory+Swap + (See 5.5 for details) + memory.limit_in_bytes set/show limit of memory usage + memory.memsw.limit_in_bytes set/show limit of memory+Swap usage + memory.failcnt show the number of memory usage hits limits + memory.memsw.failcnt show the number of memory+Swap hits limits + memory.max_usage_in_bytes show max memory usage recorded + memory.memsw.max_usage_in_bytes show max memory+Swap usage recorded + memory.soft_limit_in_bytes set/show soft limit of memory usage + This knob is not available on CONFIG_PREEMPT_RT systems. + memory.stat show various statistics + memory.use_hierarchy set/show hierarchical account enabled + This knob is deprecated and shouldn't be + used. + memory.force_empty trigger forced page reclaim + memory.pressure_level set memory pressure notifications + memory.swappiness set/show swappiness parameter of vmscan + (See sysctl's vm.swappiness) + memory.move_charge_at_immigrate set/show controls of moving charges + This knob is deprecated and shouldn't be + used. + memory.oom_control set/show oom controls. + memory.numa_stat show the number of memory usage per numa + node + memory.kmem.limit_in_bytes Deprecated knob to set and read the kernel + memory hard limit. Kernel hard limit is not + supported since 5.16. Writing any value to + do file will not have any effect same as if + nokmem kernel parameter was specified. + Kernel memory is still charged and reported + by memory.kmem.usage_in_bytes. + memory.kmem.usage_in_bytes show current kernel memory allocation + memory.kmem.failcnt show the number of kernel memory usage + hits limits + memory.kmem.max_usage_in_bytes show max kernel memory usage recorded + + memory.kmem.tcp.limit_in_bytes set/show hard limit for tcp buf memory + memory.kmem.tcp.usage_in_bytes show current tcp buf memory allocation + memory.kmem.tcp.failcnt show the number of tcp buf memory usage + hits limits + memory.kmem.tcp.max_usage_in_bytes show max tcp buf memory usage recorded +==================================== ========================================== + +1. History +========== + +The memory controller has a long history. A request for comments for the memory +controller was posted by Balbir Singh [1]_. At the time the RFC was posted +there were several implementations for memory control. The goal of the +RFC was to build consensus and agreement for the minimal features required +for memory control. The first RSS controller was posted by Balbir Singh [2]_ +in Feb 2007. Pavel Emelianov [3]_ [4]_ [5]_ has since posted three versions +of the RSS controller. At OLS, at the resource management BoF, everyone +suggested that we handle both page cache and RSS together. Another request was +raised to allow user space handling of OOM. The current memory controller is +at version 6; it combines both mapped (RSS) and unmapped Page +Cache Control [11]_. + +2. Memory Control +================= + +Memory is a unique resource in the sense that it is present in a limited +amount. If a task requires a lot of CPU processing, the task can spread +its processing over a period of hours, days, months or years, but with +memory, the same physical memory needs to be reused to accomplish the task. + +The memory controller implementation has been divided into phases. These +are: + +1. Memory controller +2. mlock(2) controller +3. Kernel user memory accounting and slab control +4. user mappings length controller + +The memory controller is the first controller developed. + +2.1. Design +----------- + +The core of the design is a counter called the page_counter. The +page_counter tracks the current memory usage and limit of the group of +processes associated with the controller. Each cgroup has a memory controller +specific data structure (mem_cgroup) associated with it. + +2.2. Accounting +--------------- + +.. code-block:: + :caption: Figure 1: Hierarchy of Accounting + + +--------------------+ + | mem_cgroup | + | (page_counter) | + +--------------------+ + / ^ \ + / | \ + +---------------+ | +---------------+ + | mm_struct | |.... | mm_struct | + | | | | | + +---------------+ | +---------------+ + | + + --------------+ + | + +---------------+ +------+--------+ + | page +----------> page_cgroup| + | | | | + +---------------+ +---------------+ + + + +Figure 1 shows the important aspects of the controller + +1. Accounting happens per cgroup +2. Each mm_struct knows about which cgroup it belongs to +3. Each page has a pointer to the page_cgroup, which in turn knows the + cgroup it belongs to + +The accounting is done as follows: mem_cgroup_charge_common() is invoked to +set up the necessary data structures and check if the cgroup that is being +charged is over its limit. If it is, then reclaim is invoked on the cgroup. +More details can be found in the reclaim section of this document. +If everything goes well, a page meta-data-structure called page_cgroup is +updated. page_cgroup has its own LRU on cgroup. +(*) page_cgroup structure is allocated at boot/memory-hotplug time. + +2.2.1 Accounting details +------------------------ + +All mapped anon pages (RSS) and cache pages (Page Cache) are accounted. +Some pages which are never reclaimable and will not be on the LRU +are not accounted. We just account pages under usual VM management. + +RSS pages are accounted at page_fault unless they've already been accounted +for earlier. A file page will be accounted for as Page Cache when it's +inserted into inode (xarray). While it's mapped into the page tables of +processes, duplicate accounting is carefully avoided. + +An RSS page is unaccounted when it's fully unmapped. A PageCache page is +unaccounted when it's removed from xarray. Even if RSS pages are fully +unmapped (by kswapd), they may exist as SwapCache in the system until they +are really freed. Such SwapCaches are also accounted. +A swapped-in page is accounted after adding into swapcache. + +Note: The kernel does swapin-readahead and reads multiple swaps at once. +Since page's memcg recorded into swap whatever memsw enabled, the page will +be accounted after swapin. + +At page migration, accounting information is kept. + +Note: we just account pages-on-LRU because our purpose is to control amount +of used pages; not-on-LRU pages tend to be out-of-control from VM view. + +2.3 Shared Page Accounting +-------------------------- + +Shared pages are accounted on the basis of the first touch approach. The +cgroup that first touches a page is accounted for the page. The principle +behind this approach is that a cgroup that aggressively uses a shared +page will eventually get charged for it (once it is uncharged from +the cgroup that brought it in -- this will happen on memory pressure). + +But see :ref:`section 8.2 <cgroup-v1-memory-movable-charges>` when moving a +task to another cgroup, its pages may be recharged to the new cgroup, if +move_charge_at_immigrate has been chosen. + +2.4 Swap Extension +-------------------------------------- + +Swap usage is always recorded for each of cgroup. Swap Extension allows you to +read and limit it. + +When CONFIG_SWAP is enabled, following files are added. + + - memory.memsw.usage_in_bytes. + - memory.memsw.limit_in_bytes. + +memsw means memory+swap. Usage of memory+swap is limited by +memsw.limit_in_bytes. + +Example: Assume a system with 4G of swap. A task which allocates 6G of memory +(by mistake) under 2G memory limitation will use all swap. +In this case, setting memsw.limit_in_bytes=3G will prevent bad use of swap. +By using the memsw limit, you can avoid system OOM which can be caused by swap +shortage. + +2.4.1 why 'memory+swap' rather than swap +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The global LRU(kswapd) can swap out arbitrary pages. Swap-out means +to move account from memory to swap...there is no change in usage of +memory+swap. In other words, when we want to limit the usage of swap without +affecting global LRU, memory+swap limit is better than just limiting swap from +an OS point of view. + +2.4.2. What happens when a cgroup hits memory.memsw.limit_in_bytes +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +When a cgroup hits memory.memsw.limit_in_bytes, it's useless to do swap-out +in this cgroup. Then, swap-out will not be done by cgroup routine and file +caches are dropped. But as mentioned above, global LRU can do swapout memory +from it for sanity of the system's memory management state. You can't forbid +it by cgroup. + +2.5 Reclaim +----------- + +Each cgroup maintains a per cgroup LRU which has the same structure as +global VM. When a cgroup goes over its limit, we first try +to reclaim memory from the cgroup so as to make space for the new +pages that the cgroup has touched. If the reclaim is unsuccessful, +an OOM routine is invoked to select and kill the bulkiest task in the +cgroup. (See :ref:`10. OOM Control <cgroup-v1-memory-oom-control>` below.) + +The reclaim algorithm has not been modified for cgroups, except that +pages that are selected for reclaiming come from the per-cgroup LRU +list. + +.. note:: + Reclaim does not work for the root cgroup, since we cannot set any + limits on the root cgroup. + +.. note:: + When panic_on_oom is set to "2", the whole system will panic. + +When oom event notifier is registered, event will be delivered. +(See :ref:`oom_control <cgroup-v1-memory-oom-control>` section) + +2.6 Locking +----------- + +Lock order is as follows:: + + Page lock (PG_locked bit of page->flags) + mm->page_table_lock or split pte_lock + folio_memcg_lock (memcg->move_lock) + mapping->i_pages lock + lruvec->lru_lock. + +Per-node-per-memcgroup LRU (cgroup's private LRU) is guarded by +lruvec->lru_lock; PG_lru bit of page->flags is cleared before +isolating a page from its LRU under lruvec->lru_lock. + +.. _cgroup-v1-memory-kernel-extension: + +2.7 Kernel Memory Extension +----------------------------------------------- + +With the Kernel memory extension, the Memory Controller is able to limit +the amount of kernel memory used by the system. Kernel memory is fundamentally +different than user memory, since it can't be swapped out, which makes it +possible to DoS the system by consuming too much of this precious resource. + +Kernel memory accounting is enabled for all memory cgroups by default. But +it can be disabled system-wide by passing cgroup.memory=nokmem to the kernel +at boot time. In this case, kernel memory will not be accounted at all. + +Kernel memory limits are not imposed for the root cgroup. Usage for the root +cgroup may or may not be accounted. The memory used is accumulated into +memory.kmem.usage_in_bytes, or in a separate counter when it makes sense. +(currently only for tcp). + +The main "kmem" counter is fed into the main counter, so kmem charges will +also be visible from the user counter. + +Currently no soft limit is implemented for kernel memory. It is future work +to trigger slab reclaim when those limits are reached. + +2.7.1 Current Kernel Memory resources accounted +----------------------------------------------- + +stack pages: + every process consumes some stack pages. By accounting into + kernel memory, we prevent new processes from being created when the kernel + memory usage is too high. + +slab pages: + pages allocated by the SLAB or SLUB allocator are tracked. A copy + of each kmem_cache is created every time the cache is touched by the first time + from inside the memcg. The creation is done lazily, so some objects can still be + skipped while the cache is being created. All objects in a slab page should + belong to the same memcg. This only fails to hold when a task is migrated to a + different memcg during the page allocation by the cache. + +sockets memory pressure: + some sockets protocols have memory pressure + thresholds. The Memory Controller allows them to be controlled individually + per cgroup, instead of globally. + +tcp memory pressure: + sockets memory pressure for the tcp protocol. + +2.7.2 Common use cases +---------------------- + +Because the "kmem" counter is fed to the main user counter, kernel memory can +never be limited completely independently of user memory. Say "U" is the user +limit, and "K" the kernel limit. There are three possible ways limits can be +set: + +U != 0, K = unlimited: + This is the standard memcg limitation mechanism already present before kmem + accounting. Kernel memory is completely ignored. + +U != 0, K < U: + Kernel memory is a subset of the user memory. This setup is useful in + deployments where the total amount of memory per-cgroup is overcommitted. + Overcommitting kernel memory limits is definitely not recommended, since the + box can still run out of non-reclaimable memory. + In this case, the admin could set up K so that the sum of all groups is + never greater than the total memory, and freely set U at the cost of his + QoS. + + .. warning:: + In the current implementation, memory reclaim will NOT be triggered for + a cgroup when it hits K while staying below U, which makes this setup + impractical. + +U != 0, K >= U: + Since kmem charges will also be fed to the user counter and reclaim will be + triggered for the cgroup for both kinds of memory. This setup gives the + admin a unified view of memory, and it is also useful for people who just + want to track kernel memory usage. + +3. User Interface +================= + +To use the user interface: + +1. Enable CONFIG_CGROUPS and CONFIG_MEMCG options +2. Prepare the cgroups (see :ref:`Why are cgroups needed? + <cgroups-why-needed>` for the background information):: + + # mount -t tmpfs none /sys/fs/cgroup + # mkdir /sys/fs/cgroup/memory + # mount -t cgroup none /sys/fs/cgroup/memory -o memory + +3. Make the new group and move bash into it:: + + # mkdir /sys/fs/cgroup/memory/0 + # echo $$ > /sys/fs/cgroup/memory/0/tasks + +4. Since now we're in the 0 cgroup, we can alter the memory limit:: + + # echo 4M > /sys/fs/cgroup/memory/0/memory.limit_in_bytes + + The limit can now be queried:: + + # cat /sys/fs/cgroup/memory/0/memory.limit_in_bytes + 4194304 + +.. note:: + We can use a suffix (k, K, m, M, g or G) to indicate values in kilo, + mega or gigabytes. (Here, Kilo, Mega, Giga are Kibibytes, Mebibytes, + Gibibytes.) + +.. note:: + We can write "-1" to reset the ``*.limit_in_bytes(unlimited)``. + +.. note:: + We cannot set limits on the root cgroup any more. + + +We can check the usage:: + + # cat /sys/fs/cgroup/memory/0/memory.usage_in_bytes + 1216512 + +A successful write to this file does not guarantee a successful setting of +this limit to the value written into the file. This can be due to a +number of factors, such as rounding up to page boundaries or the total +availability of memory on the system. The user is required to re-read +this file after a write to guarantee the value committed by the kernel:: + + # echo 1 > memory.limit_in_bytes + # cat memory.limit_in_bytes + 4096 + +The memory.failcnt field gives the number of times that the cgroup limit was +exceeded. + +The memory.stat file gives accounting information. Now, the number of +caches, RSS and Active pages/Inactive pages are shown. + +4. Testing +========== + +For testing features and implementation, see memcg_test.txt. + +Performance test is also important. To see pure memory controller's overhead, +testing on tmpfs will give you good numbers of small overheads. +Example: do kernel make on tmpfs. + +Page-fault scalability is also important. At measuring parallel +page fault test, multi-process test may be better than multi-thread +test because it has noise of shared objects/status. + +But the above two are testing extreme situations. +Trying usual test under memory controller is always helpful. + +.. _cgroup-v1-memory-test-troubleshoot: + +4.1 Troubleshooting +------------------- + +Sometimes a user might find that the application under a cgroup is +terminated by the OOM killer. There are several causes for this: + +1. The cgroup limit is too low (just too low to do anything useful) +2. The user is using anonymous memory and swap is turned off or too low + +A sync followed by echo 1 > /proc/sys/vm/drop_caches will help get rid of +some of the pages cached in the cgroup (page cache pages). + +To know what happens, disabling OOM_Kill as per :ref:`"10. OOM Control" +<cgroup-v1-memory-oom-control>` (below) and seeing what happens will be +helpful. + +.. _cgroup-v1-memory-test-task-migration: + +4.2 Task migration +------------------ + +When a task migrates from one cgroup to another, its charge is not +carried forward by default. The pages allocated from the original cgroup still +remain charged to it, the charge is dropped when the page is freed or +reclaimed. + +You can move charges of a task along with task migration. +See :ref:`8. "Move charges at task migration" <cgroup-v1-memory-move-charges>` + +4.3 Removing a cgroup +--------------------- + +A cgroup can be removed by rmdir, but as discussed in :ref:`sections 4.1 +<cgroup-v1-memory-test-troubleshoot>` and :ref:`4.2 +<cgroup-v1-memory-test-task-migration>`, a cgroup might have some charge +associated with it, even though all tasks have migrated away from it. (because +we charge against pages, not against tasks.) + +We move the stats to parent, and no change on the charge except uncharging +from the child. + +Charges recorded in swap information is not updated at removal of cgroup. +Recorded information is discarded and a cgroup which uses swap (swapcache) +will be charged as a new owner of it. + +5. Misc. interfaces +=================== + +5.1 force_empty +--------------- + memory.force_empty interface is provided to make cgroup's memory usage empty. + When writing anything to this:: + + # echo 0 > memory.force_empty + + the cgroup will be reclaimed and as many pages reclaimed as possible. + + The typical use case for this interface is before calling rmdir(). + Though rmdir() offlines memcg, but the memcg may still stay there due to + charged file caches. Some out-of-use page caches may keep charged until + memory pressure happens. If you want to avoid that, force_empty will be useful. + +5.2 stat file +------------- + +memory.stat file includes following statistics: + + * per-memory cgroup local status + + =============== =============================================================== + cache # of bytes of page cache memory. + rss # of bytes of anonymous and swap cache memory (includes + transparent hugepages). + rss_huge # of bytes of anonymous transparent hugepages. + mapped_file # of bytes of mapped file (includes tmpfs/shmem) + pgpgin # of charging events to the memory cgroup. The charging + event happens each time a page is accounted as either mapped + anon page(RSS) or cache page(Page Cache) to the cgroup. + pgpgout # of uncharging events to the memory cgroup. The uncharging + event happens each time a page is unaccounted from the + cgroup. + swap # of bytes of swap usage + dirty # of bytes that are waiting to get written back to the disk. + writeback # of bytes of file/anon cache that are queued for syncing to + disk. + inactive_anon # of bytes of anonymous and swap cache memory on inactive + LRU list. + active_anon # of bytes of anonymous and swap cache memory on active + LRU list. + inactive_file # of bytes of file-backed memory and MADV_FREE anonymous + memory (LazyFree pages) on inactive LRU list. + active_file # of bytes of file-backed memory on active LRU list. + unevictable # of bytes of memory that cannot be reclaimed (mlocked etc). + =============== =============================================================== + + * status considering hierarchy (see memory.use_hierarchy settings): + + ========================= =================================================== + hierarchical_memory_limit # of bytes of memory limit with regard to + hierarchy + under which the memory cgroup is + hierarchical_memsw_limit # of bytes of memory+swap limit with regard to + hierarchy under which memory cgroup is. + + total_<counter> # hierarchical version of <counter>, which in + addition to the cgroup's own value includes the + sum of all hierarchical children's values of + <counter>, i.e. total_cache + ========================= =================================================== + + * additional vm parameters (depends on CONFIG_DEBUG_VM): + + ========================= ======================================== + recent_rotated_anon VM internal parameter. (see mm/vmscan.c) + recent_rotated_file VM internal parameter. (see mm/vmscan.c) + recent_scanned_anon VM internal parameter. (see mm/vmscan.c) + recent_scanned_file VM internal parameter. (see mm/vmscan.c) + ========================= ======================================== + +.. hint:: + recent_rotated means recent frequency of LRU rotation. + recent_scanned means recent # of scans to LRU. + showing for better debug please see the code for meanings. + +.. note:: + Only anonymous and swap cache memory is listed as part of 'rss' stat. + This should not be confused with the true 'resident set size' or the + amount of physical memory used by the cgroup. + + 'rss + mapped_file" will give you resident set size of cgroup. + + (Note: file and shmem may be shared among other cgroups. In that case, + mapped_file is accounted only when the memory cgroup is owner of page + cache.) + +5.3 swappiness +-------------- + +Overrides /proc/sys/vm/swappiness for the particular group. The tunable +in the root cgroup corresponds to the global swappiness setting. + +Please note that unlike during the global reclaim, limit reclaim +enforces that 0 swappiness really prevents from any swapping even if +there is a swap storage available. This might lead to memcg OOM killer +if there are no file pages to reclaim. + +5.4 failcnt +----------- + +A memory cgroup provides memory.failcnt and memory.memsw.failcnt files. +This failcnt(== failure count) shows the number of times that a usage counter +hit its limit. When a memory cgroup hits a limit, failcnt increases and +memory under it will be reclaimed. + +You can reset failcnt by writing 0 to failcnt file:: + + # echo 0 > .../memory.failcnt + +5.5 usage_in_bytes +------------------ + +For efficiency, as other kernel components, memory cgroup uses some optimization +to avoid unnecessary cacheline false sharing. usage_in_bytes is affected by the +method and doesn't show 'exact' value of memory (and swap) usage, it's a fuzz +value for efficient access. (Of course, when necessary, it's synchronized.) +If you want to know more exact memory usage, you should use RSS+CACHE(+SWAP) +value in memory.stat(see 5.2). + +5.6 numa_stat +------------- + +This is similar to numa_maps but operates on a per-memcg basis. This is +useful for providing visibility into the numa locality information within +an memcg since the pages are allowed to be allocated from any physical +node. One of the use cases is evaluating application performance by +combining this information with the application's CPU allocation. + +Each memcg's numa_stat file includes "total", "file", "anon" and "unevictable" +per-node page counts including "hierarchical_<counter>" which sums up all +hierarchical children's values in addition to the memcg's own value. + +The output format of memory.numa_stat is:: + + total=<total pages> N0=<node 0 pages> N1=<node 1 pages> ... + file=<total file pages> N0=<node 0 pages> N1=<node 1 pages> ... + anon=<total anon pages> N0=<node 0 pages> N1=<node 1 pages> ... + unevictable=<total anon pages> N0=<node 0 pages> N1=<node 1 pages> ... + hierarchical_<counter>=<counter pages> N0=<node 0 pages> N1=<node 1 pages> ... + +The "total" count is sum of file + anon + unevictable. + +6. Hierarchy support +==================== + +The memory controller supports a deep hierarchy and hierarchical accounting. +The hierarchy is created by creating the appropriate cgroups in the +cgroup filesystem. Consider for example, the following cgroup filesystem +hierarchy:: + + root + / | \ + / | \ + a b c + | \ + | \ + d e + +In the diagram above, with hierarchical accounting enabled, all memory +usage of e, is accounted to its ancestors up until the root (i.e, c and root). +If one of the ancestors goes over its limit, the reclaim algorithm reclaims +from the tasks in the ancestor and the children of the ancestor. + +6.1 Hierarchical accounting and reclaim +--------------------------------------- + +Hierarchical accounting is enabled by default. Disabling the hierarchical +accounting is deprecated. An attempt to do it will result in a failure +and a warning printed to dmesg. + +For compatibility reasons writing 1 to memory.use_hierarchy will always pass:: + + # echo 1 > memory.use_hierarchy + +7. Soft limits +============== + +Soft limits allow for greater sharing of memory. The idea behind soft limits +is to allow control groups to use as much of the memory as needed, provided + +a. There is no memory contention +b. They do not exceed their hard limit + +When the system detects memory contention or low memory, control groups +are pushed back to their soft limits. If the soft limit of each control +group is very high, they are pushed back as much as possible to make +sure that one control group does not starve the others of memory. + +Please note that soft limits is a best-effort feature; it comes with +no guarantees, but it does its best to make sure that when memory is +heavily contended for, memory is allocated based on the soft limit +hints/setup. Currently soft limit based reclaim is set up such that +it gets invoked from balance_pgdat (kswapd). + +7.1 Interface +------------- + +Soft limits can be setup by using the following commands (in this example we +assume a soft limit of 256 MiB):: + + # echo 256M > memory.soft_limit_in_bytes + +If we want to change this to 1G, we can at any time use:: + + # echo 1G > memory.soft_limit_in_bytes + +.. note:: + Soft limits take effect over a long period of time, since they involve + reclaiming memory for balancing between memory cgroups + +.. note:: + It is recommended to set the soft limit always below the hard limit, + otherwise the hard limit will take precedence. + +.. _cgroup-v1-memory-move-charges: + +8. Move charges at task migration (DEPRECATED!) +=============================================== + +THIS IS DEPRECATED! + +It's expensive and unreliable! It's better practice to launch workload +tasks directly from inside their target cgroup. Use dedicated workload +cgroups to allow fine-grained policy adjustments without having to +move physical pages between control domains. + +Users can move charges associated with a task along with task migration, that +is, uncharge task's pages from the old cgroup and charge them to the new cgroup. +This feature is not supported in !CONFIG_MMU environments because of lack of +page tables. + +8.1 Interface +------------- + +This feature is disabled by default. It can be enabled (and disabled again) by +writing to memory.move_charge_at_immigrate of the destination cgroup. + +If you want to enable it:: + + # echo (some positive value) > memory.move_charge_at_immigrate + +.. note:: + Each bits of move_charge_at_immigrate has its own meaning about what type + of charges should be moved. See :ref:`section 8.2 + <cgroup-v1-memory-movable-charges>` for details. + +.. note:: + Charges are moved only when you move mm->owner, in other words, + a leader of a thread group. + +.. note:: + If we cannot find enough space for the task in the destination cgroup, we + try to make space by reclaiming memory. Task migration may fail if we + cannot make enough space. + +.. note:: + It can take several seconds if you move charges much. + +And if you want disable it again:: + + # echo 0 > memory.move_charge_at_immigrate + +.. _cgroup-v1-memory-movable-charges: + +8.2 Type of charges which can be moved +-------------------------------------- + +Each bit in move_charge_at_immigrate has its own meaning about what type of +charges should be moved. But in any case, it must be noted that an account of +a page or a swap can be moved only when it is charged to the task's current +(old) memory cgroup. + ++---+--------------------------------------------------------------------------+ +|bit| what type of charges would be moved ? | ++===+==========================================================================+ +| 0 | A charge of an anonymous page (or swap of it) used by the target task. | +| | You must enable Swap Extension (see 2.4) to enable move of swap charges. | ++---+--------------------------------------------------------------------------+ +| 1 | A charge of file pages (normal file, tmpfs file (e.g. ipc shared memory) | +| | and swaps of tmpfs file) mmapped by the target task. Unlike the case of | +| | anonymous pages, file pages (and swaps) in the range mmapped by the task | +| | will be moved even if the task hasn't done page fault, i.e. they might | +| | not be the task's "RSS", but other task's "RSS" that maps the same file. | +| | And mapcount of the page is ignored (the page can be moved even if | +| | page_mapcount(page) > 1). You must enable Swap Extension (see 2.4) to | +| | enable move of swap charges. | ++---+--------------------------------------------------------------------------+ + +8.3 TODO +-------- + +- All of moving charge operations are done under cgroup_mutex. It's not good + behavior to hold the mutex too long, so we may need some trick. + +9. Memory thresholds +==================== + +Memory cgroup implements memory thresholds using the cgroups notification +API (see cgroups.txt). It allows to register multiple memory and memsw +thresholds and gets notifications when it crosses. + +To register a threshold, an application must: + +- create an eventfd using eventfd(2); +- open memory.usage_in_bytes or memory.memsw.usage_in_bytes; +- write string like "<event_fd> <fd of memory.usage_in_bytes> <threshold>" to + cgroup.event_control. + +Application will be notified through eventfd when memory usage crosses +threshold in any direction. + +It's applicable for root and non-root cgroup. + +.. _cgroup-v1-memory-oom-control: + +10. OOM Control +=============== + +memory.oom_control file is for OOM notification and other controls. + +Memory cgroup implements OOM notifier using the cgroup notification +API (See cgroups.txt). It allows to register multiple OOM notification +delivery and gets notification when OOM happens. + +To register a notifier, an application must: + + - create an eventfd using eventfd(2) + - open memory.oom_control file + - write string like "<event_fd> <fd of memory.oom_control>" to + cgroup.event_control + +The application will be notified through eventfd when OOM happens. +OOM notification doesn't work for the root cgroup. + +You can disable the OOM-killer by writing "1" to memory.oom_control file, as: + + #echo 1 > memory.oom_control + +If OOM-killer is disabled, tasks under cgroup will hang/sleep +in memory cgroup's OOM-waitqueue when they request accountable memory. + +For running them, you have to relax the memory cgroup's OOM status by + + * enlarge limit or reduce usage. + +To reduce usage, + + * kill some tasks. + * move some tasks to other group with account migration. + * remove some files (on tmpfs?) + +Then, stopped tasks will work again. + +At reading, current status of OOM is shown. + + - oom_kill_disable 0 or 1 + (if 1, oom-killer is disabled) + - under_oom 0 or 1 + (if 1, the memory cgroup is under OOM, tasks may be stopped.) + - oom_kill integer counter + The number of processes belonging to this cgroup killed by any + kind of OOM killer. + +11. Memory Pressure +=================== + +The pressure level notifications can be used to monitor the memory +allocation cost; based on the pressure, applications can implement +different strategies of managing their memory resources. The pressure +levels are defined as following: + +The "low" level means that the system is reclaiming memory for new +allocations. Monitoring this reclaiming activity might be useful for +maintaining cache level. Upon notification, the program (typically +"Activity Manager") might analyze vmstat and act in advance (i.e. +prematurely shutdown unimportant services). + +The "medium" level means that the system is experiencing medium memory +pressure, the system might be making swap, paging out active file caches, +etc. Upon this event applications may decide to further analyze +vmstat/zoneinfo/memcg or internal memory usage statistics and free any +resources that can be easily reconstructed or re-read from a disk. + +The "critical" level means that the system is actively thrashing, it is +about to out of memory (OOM) or even the in-kernel OOM killer is on its +way to trigger. Applications should do whatever they can to help the +system. It might be too late to consult with vmstat or any other +statistics, so it's advisable to take an immediate action. + +By default, events are propagated upward until the event is handled, i.e. the +events are not pass-through. For example, you have three cgroups: A->B->C. Now +you set up an event listener on cgroups A, B and C, and suppose group C +experiences some pressure. In this situation, only group C will receive the +notification, i.e. groups A and B will not receive it. This is done to avoid +excessive "broadcasting" of messages, which disturbs the system and which is +especially bad if we are low on memory or thrashing. Group B, will receive +notification only if there are no event listeners for group C. + +There are three optional modes that specify different propagation behavior: + + - "default": this is the default behavior specified above. This mode is the + same as omitting the optional mode parameter, preserved by backwards + compatibility. + + - "hierarchy": events always propagate up to the root, similar to the default + behavior, except that propagation continues regardless of whether there are + event listeners at each level, with the "hierarchy" mode. In the above + example, groups A, B, and C will receive notification of memory pressure. + + - "local": events are pass-through, i.e. they only receive notifications when + memory pressure is experienced in the memcg for which the notification is + registered. In the above example, group C will receive notification if + registered for "local" notification and the group experiences memory + pressure. However, group B will never receive notification, regardless if + there is an event listener for group C or not, if group B is registered for + local notification. + +The level and event notification mode ("hierarchy" or "local", if necessary) are +specified by a comma-delimited string, i.e. "low,hierarchy" specifies +hierarchical, pass-through, notification for all ancestor memcgs. Notification +that is the default, non pass-through behavior, does not specify a mode. +"medium,local" specifies pass-through notification for the medium level. + +The file memory.pressure_level is only used to setup an eventfd. To +register a notification, an application must: + +- create an eventfd using eventfd(2); +- open memory.pressure_level; +- write string as "<event_fd> <fd of memory.pressure_level> <level[,mode]>" + to cgroup.event_control. + +Application will be notified through eventfd when memory pressure is at +the specific level (or higher). Read/write operations to +memory.pressure_level are no implemented. + +Test: + + Here is a small script example that makes a new cgroup, sets up a + memory limit, sets up a notification in the cgroup and then makes child + cgroup experience a critical pressure:: + + # cd /sys/fs/cgroup/memory/ + # mkdir foo + # cd foo + # cgroup_event_listener memory.pressure_level low,hierarchy & + # echo 8000000 > memory.limit_in_bytes + # echo 8000000 > memory.memsw.limit_in_bytes + # echo $$ > tasks + # dd if=/dev/zero | read x + + (Expect a bunch of notifications, and eventually, the oom-killer will + trigger.) + +12. TODO +======== + +1. Make per-cgroup scanner reclaim not-shared pages first +2. Teach controller to account for shared-pages +3. Start reclamation in the background when the limit is + not yet hit but the usage is getting closer + +Summary +======= + +Overall, the memory controller has been a stable controller and has been +commented and discussed quite extensively in the community. + +References +========== + +.. [1] Singh, Balbir. RFC: Memory Controller, http://lwn.net/Articles/206697/ +.. [2] Singh, Balbir. Memory Controller (RSS Control), + http://lwn.net/Articles/222762/ +.. [3] Emelianov, Pavel. Resource controllers based on process cgroups + https://lore.kernel.org/r/45ED7DEC.7010403@sw.ru +.. [4] Emelianov, Pavel. RSS controller based on process cgroups (v2) + https://lore.kernel.org/r/461A3010.90403@sw.ru +.. [5] Emelianov, Pavel. RSS controller based on process cgroups (v3) + https://lore.kernel.org/r/465D9739.8070209@openvz.org + +6. Menage, Paul. Control Groups v10, http://lwn.net/Articles/236032/ +7. Vaidyanathan, Srinivasan, Control Groups: Pagecache accounting and control + subsystem (v3), http://lwn.net/Articles/235534/ +8. Singh, Balbir. RSS controller v2 test results (lmbench), + https://lore.kernel.org/r/464C95D4.7070806@linux.vnet.ibm.com +9. Singh, Balbir. RSS controller v2 AIM9 results + https://lore.kernel.org/r/464D267A.50107@linux.vnet.ibm.com +10. Singh, Balbir. Memory controller v6 test results, + https://lore.kernel.org/r/20070819094658.654.84837.sendpatchset@balbir-laptop + +.. [11] Singh, Balbir. Memory controller introduction (v6), + https://lore.kernel.org/r/20070817084228.26003.12568.sendpatchset@balbir-laptop +.. [12] Corbet, Jonathan, Controlling memory use in cgroups, + http://lwn.net/Articles/243795/ diff --git a/Documentation/admin-guide/cgroup-v1/misc.rst b/Documentation/admin-guide/cgroup-v1/misc.rst new file mode 100644 index 000000000..661614c24 --- /dev/null +++ b/Documentation/admin-guide/cgroup-v1/misc.rst @@ -0,0 +1,4 @@ +=============== +Misc controller +=============== +Please refer "Misc" documentation in Documentation/admin-guide/cgroup-v2.rst diff --git a/Documentation/admin-guide/cgroup-v1/net_cls.rst b/Documentation/admin-guide/cgroup-v1/net_cls.rst new file mode 100644 index 000000000..a2cf272af --- /dev/null +++ b/Documentation/admin-guide/cgroup-v1/net_cls.rst @@ -0,0 +1,44 @@ +========================= +Network classifier cgroup +========================= + +The Network classifier cgroup provides an interface to +tag network packets with a class identifier (classid). + +The Traffic Controller (tc) can be used to assign +different priorities to packets from different cgroups. +Also, Netfilter (iptables) can use this tag to perform +actions on such packets. + +Creating a net_cls cgroups instance creates a net_cls.classid file. +This net_cls.classid value is initialized to 0. + +You can write hexadecimal values to net_cls.classid; the format for these +values is 0xAAAABBBB; AAAA is the major handle number and BBBB +is the minor handle number. +Reading net_cls.classid yields a decimal result. + +Example:: + + mkdir /sys/fs/cgroup/net_cls + mount -t cgroup -onet_cls net_cls /sys/fs/cgroup/net_cls + mkdir /sys/fs/cgroup/net_cls/0 + echo 0x100001 > /sys/fs/cgroup/net_cls/0/net_cls.classid + +- setting a 10:1 handle:: + + cat /sys/fs/cgroup/net_cls/0/net_cls.classid + 1048577 + +- configuring tc:: + + tc qdisc add dev eth0 root handle 10: htb + tc class add dev eth0 parent 10: classid 10:1 htb rate 40mbit + +- creating traffic class 10:1:: + + tc filter add dev eth0 parent 10: protocol ip prio 10 handle 1: cgroup + +configuring iptables, basic example:: + + iptables -A OUTPUT -m cgroup ! --cgroup 0x100001 -j DROP diff --git a/Documentation/admin-guide/cgroup-v1/net_prio.rst b/Documentation/admin-guide/cgroup-v1/net_prio.rst new file mode 100644 index 000000000..b40905871 --- /dev/null +++ b/Documentation/admin-guide/cgroup-v1/net_prio.rst @@ -0,0 +1,57 @@ +======================= +Network priority cgroup +======================= + +The Network priority cgroup provides an interface to allow an administrator to +dynamically set the priority of network traffic generated by various +applications + +Nominally, an application would set the priority of its traffic via the +SO_PRIORITY socket option. This however, is not always possible because: + +1) The application may not have been coded to set this value +2) The priority of application traffic is often a site-specific administrative + decision rather than an application defined one. + +This cgroup allows an administrator to assign a process to a group which defines +the priority of egress traffic on a given interface. Network priority groups can +be created by first mounting the cgroup filesystem:: + + # mount -t cgroup -onet_prio none /sys/fs/cgroup/net_prio + +With the above step, the initial group acting as the parent accounting group +becomes visible at '/sys/fs/cgroup/net_prio'. This group includes all tasks in +the system. '/sys/fs/cgroup/net_prio/tasks' lists the tasks in this cgroup. + +Each net_prio cgroup contains two files that are subsystem specific + +net_prio.prioidx + This file is read-only, and is simply informative. It contains a unique + integer value that the kernel uses as an internal representation of this + cgroup. + +net_prio.ifpriomap + This file contains a map of the priorities assigned to traffic originating + from processes in this group and egressing the system on various interfaces. + It contains a list of tuples in the form <ifname priority>. Contents of this + file can be modified by echoing a string into the file using the same tuple + format. For example:: + + echo "eth0 5" > /sys/fs/cgroups/net_prio/iscsi/net_prio.ifpriomap + +This command would force any traffic originating from processes belonging to the +iscsi net_prio cgroup and egressing on interface eth0 to have the priority of +said traffic set to the value 5. The parent accounting group also has a +writeable 'net_prio.ifpriomap' file that can be used to set a system default +priority. + +Priorities are set immediately prior to queueing a frame to the device +queueing discipline (qdisc) so priorities will be assigned prior to the hardware +queue selection being made. + +One usage for the net_prio cgroup is with mqprio qdisc allowing application +traffic to be steered to hardware/driver based traffic classes. These mappings +can then be managed by administrators or other networking protocols such as +DCBX. + +A new net_prio cgroup inherits the parent's configuration. diff --git a/Documentation/admin-guide/cgroup-v1/pids.rst b/Documentation/admin-guide/cgroup-v1/pids.rst new file mode 100644 index 000000000..6acebd9e7 --- /dev/null +++ b/Documentation/admin-guide/cgroup-v1/pids.rst @@ -0,0 +1,92 @@ +========================= +Process Number Controller +========================= + +Abstract +-------- + +The process number controller is used to allow a cgroup hierarchy to stop any +new tasks from being fork()'d or clone()'d after a certain limit is reached. + +Since it is trivial to hit the task limit without hitting any kmemcg limits in +place, PIDs are a fundamental resource. As such, PID exhaustion must be +preventable in the scope of a cgroup hierarchy by allowing resource limiting of +the number of tasks in a cgroup. + +Usage +----- + +In order to use the `pids` controller, set the maximum number of tasks in +pids.max (this is not available in the root cgroup for obvious reasons). The +number of processes currently in the cgroup is given by pids.current. + +Organisational operations are not blocked by cgroup policies, so it is possible +to have pids.current > pids.max. This can be done by either setting the limit to +be smaller than pids.current, or attaching enough processes to the cgroup such +that pids.current > pids.max. However, it is not possible to violate a cgroup +policy through fork() or clone(). fork() and clone() will return -EAGAIN if the +creation of a new process would cause a cgroup policy to be violated. + +To set a cgroup to have no limit, set pids.max to "max". This is the default for +all new cgroups (N.B. that PID limits are hierarchical, so the most stringent +limit in the hierarchy is followed). + +pids.current tracks all child cgroup hierarchies, so parent/pids.current is a +superset of parent/child/pids.current. + +The pids.events file contains event counters: + + - max: Number of times fork failed because limit was hit. + +Example +------- + +First, we mount the pids controller:: + + # mkdir -p /sys/fs/cgroup/pids + # mount -t cgroup -o pids none /sys/fs/cgroup/pids + +Then we create a hierarchy, set limits and attach processes to it:: + + # mkdir -p /sys/fs/cgroup/pids/parent/child + # echo 2 > /sys/fs/cgroup/pids/parent/pids.max + # echo $$ > /sys/fs/cgroup/pids/parent/cgroup.procs + # cat /sys/fs/cgroup/pids/parent/pids.current + 2 + # + +It should be noted that attempts to overcome the set limit (2 in this case) will +fail:: + + # cat /sys/fs/cgroup/pids/parent/pids.current + 2 + # ( /bin/echo "Here's some processes for you." | cat ) + sh: fork: Resource temporary unavailable + # + +Even if we migrate to a child cgroup (which doesn't have a set limit), we will +not be able to overcome the most stringent limit in the hierarchy (in this case, +parent's):: + + # echo $$ > /sys/fs/cgroup/pids/parent/child/cgroup.procs + # cat /sys/fs/cgroup/pids/parent/pids.current + 2 + # cat /sys/fs/cgroup/pids/parent/child/pids.current + 2 + # cat /sys/fs/cgroup/pids/parent/child/pids.max + max + # ( /bin/echo "Here's some processes for you." | cat ) + sh: fork: Resource temporary unavailable + # + +We can set a limit that is smaller than pids.current, which will stop any new +processes from being forked at all (note that the shell itself counts towards +pids.current):: + + # echo 1 > /sys/fs/cgroup/pids/parent/pids.max + # /bin/echo "We can't even spawn a single process now." + sh: fork: Resource temporary unavailable + # echo 0 > /sys/fs/cgroup/pids/parent/pids.max + # /bin/echo "We can't even spawn a single process now." + sh: fork: Resource temporary unavailable + # diff --git a/Documentation/admin-guide/cgroup-v1/rdma.rst b/Documentation/admin-guide/cgroup-v1/rdma.rst new file mode 100644 index 000000000..e69369b72 --- /dev/null +++ b/Documentation/admin-guide/cgroup-v1/rdma.rst @@ -0,0 +1,117 @@ +=============== +RDMA Controller +=============== + +.. Contents + + 1. Overview + 1-1. What is RDMA controller? + 1-2. Why RDMA controller needed? + 1-3. How is RDMA controller implemented? + 2. Usage Examples + +1. Overview +=========== + +1-1. What is RDMA controller? +----------------------------- + +RDMA controller allows user to limit RDMA/IB specific resources that a given +set of processes can use. These processes are grouped using RDMA controller. + +RDMA controller defines two resources which can be limited for processes of a +cgroup. + +1-2. Why RDMA controller needed? +-------------------------------- + +Currently user space applications can easily take away all the rdma verb +specific resources such as AH, CQ, QP, MR etc. Due to which other applications +in other cgroup or kernel space ULPs may not even get chance to allocate any +rdma resources. This can lead to service unavailability. + +Therefore RDMA controller is needed through which resource consumption +of processes can be limited. Through this controller different rdma +resources can be accounted. + +1-3. How is RDMA controller implemented? +---------------------------------------- + +RDMA cgroup allows limit configuration of resources. Rdma cgroup maintains +resource accounting per cgroup, per device using resource pool structure. +Each such resource pool is limited up to 64 resources in given resource pool +by rdma cgroup, which can be extended later if required. + +This resource pool object is linked to the cgroup css. Typically there +are 0 to 4 resource pool instances per cgroup, per device in most use cases. +But nothing limits to have it more. At present hundreds of RDMA devices per +single cgroup may not be handled optimally, however there is no +known use case or requirement for such configuration either. + +Since RDMA resources can be allocated from any process and can be freed by any +of the child processes which shares the address space, rdma resources are +always owned by the creator cgroup css. This allows process migration from one +to other cgroup without major complexity of transferring resource ownership; +because such ownership is not really present due to shared nature of +rdma resources. Linking resources around css also ensures that cgroups can be +deleted after processes migrated. This allow progress migration as well with +active resources, even though that is not a primary use case. + +Whenever RDMA resource charging occurs, owner rdma cgroup is returned to +the caller. Same rdma cgroup should be passed while uncharging the resource. +This also allows process migrated with active RDMA resource to charge +to new owner cgroup for new resource. It also allows to uncharge resource of +a process from previously charged cgroup which is migrated to new cgroup, +even though that is not a primary use case. + +Resource pool object is created in following situations. +(a) User sets the limit and no previous resource pool exist for the device +of interest for the cgroup. +(b) No resource limits were configured, but IB/RDMA stack tries to +charge the resource. So that it correctly uncharge them when applications are +running without limits and later on when limits are enforced during uncharging, +otherwise usage count will drop to negative. + +Resource pool is destroyed if all the resource limits are set to max and +it is the last resource getting deallocated. + +User should set all the limit to max value if it intents to remove/unconfigure +the resource pool for a particular device. + +IB stack honors limits enforced by the rdma controller. When application +query about maximum resource limits of IB device, it returns minimum of +what is configured by user for a given cgroup and what is supported by +IB device. + +Following resources can be accounted by rdma controller. + + ========== ============================= + hca_handle Maximum number of HCA Handles + hca_object Maximum number of HCA Objects + ========== ============================= + +2. Usage Examples +================= + +(a) Configure resource limit:: + + echo mlx4_0 hca_handle=2 hca_object=2000 > /sys/fs/cgroup/rdma/1/rdma.max + echo ocrdma1 hca_handle=3 > /sys/fs/cgroup/rdma/2/rdma.max + +(b) Query resource limit:: + + cat /sys/fs/cgroup/rdma/2/rdma.max + #Output: + mlx4_0 hca_handle=2 hca_object=2000 + ocrdma1 hca_handle=3 hca_object=max + +(c) Query current usage:: + + cat /sys/fs/cgroup/rdma/2/rdma.current + #Output: + mlx4_0 hca_handle=1 hca_object=20 + ocrdma1 hca_handle=1 hca_object=23 + +(d) Delete resource limit:: + + echo mlx4_0 hca_handle=max hca_object=max > /sys/fs/cgroup/rdma/1/rdma.max diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst new file mode 100644 index 000000000..b26b5274e --- /dev/null +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -0,0 +1,2988 @@ +.. _cgroup-v2: + +================ +Control Group v2 +================ + +:Date: October, 2015 +:Author: Tejun Heo <tj@kernel.org> + +This is the authoritative documentation on the design, interface and +conventions of cgroup v2. It describes all userland-visible aspects +of cgroup including core and specific controller behaviors. All +future changes must be reflected in this document. Documentation for +v1 is available under :ref:`Documentation/admin-guide/cgroup-v1/index.rst <cgroup-v1>`. + +.. CONTENTS + + 1. Introduction + 1-1. Terminology + 1-2. What is cgroup? + 2. Basic Operations + 2-1. Mounting + 2-2. Organizing Processes and Threads + 2-2-1. Processes + 2-2-2. Threads + 2-3. [Un]populated Notification + 2-4. Controlling Controllers + 2-4-1. Enabling and Disabling + 2-4-2. Top-down Constraint + 2-4-3. No Internal Process Constraint + 2-5. Delegation + 2-5-1. Model of Delegation + 2-5-2. Delegation Containment + 2-6. Guidelines + 2-6-1. Organize Once and Control + 2-6-2. Avoid Name Collisions + 3. Resource Distribution Models + 3-1. Weights + 3-2. Limits + 3-3. Protections + 3-4. Allocations + 4. Interface Files + 4-1. Format + 4-2. Conventions + 4-3. Core Interface Files + 5. Controllers + 5-1. CPU + 5-1-1. CPU Interface Files + 5-2. Memory + 5-2-1. Memory Interface Files + 5-2-2. Usage Guidelines + 5-2-3. Memory Ownership + 5-3. IO + 5-3-1. IO Interface Files + 5-3-2. Writeback + 5-3-3. IO Latency + 5-3-3-1. How IO Latency Throttling Works + 5-3-3-2. IO Latency Interface Files + 5-3-4. IO Priority + 5-4. PID + 5-4-1. PID Interface Files + 5-5. Cpuset + 5.5-1. Cpuset Interface Files + 5-6. Device + 5-7. RDMA + 5-7-1. RDMA Interface Files + 5-8. HugeTLB + 5.8-1. HugeTLB Interface Files + 5-9. Misc + 5.9-1 Miscellaneous cgroup Interface Files + 5.9-2 Migration and Ownership + 5-10. Others + 5-10-1. perf_event + 5-N. Non-normative information + 5-N-1. CPU controller root cgroup process behaviour + 5-N-2. IO controller root cgroup process behaviour + 6. Namespace + 6-1. Basics + 6-2. The Root and Views + 6-3. Migration and setns(2) + 6-4. Interaction with Other Namespaces + P. Information on Kernel Programming + P-1. Filesystem Support for Writeback + D. Deprecated v1 Core Features + R. Issues with v1 and Rationales for v2 + R-1. Multiple Hierarchies + R-2. Thread Granularity + R-3. Competition Between Inner Nodes and Threads + R-4. Other Interface Issues + R-5. Controller Issues and Remedies + R-5-1. Memory + + +Introduction +============ + +Terminology +----------- + +"cgroup" stands for "control group" and is never capitalized. The +singular form is used to designate the whole feature and also as a +qualifier as in "cgroup controllers". When explicitly referring to +multiple individual control groups, the plural form "cgroups" is used. + + +What is cgroup? +--------------- + +cgroup is a mechanism to organize processes hierarchically and +distribute system resources along the hierarchy in a controlled and +configurable manner. + +cgroup is largely composed of two parts - the core and controllers. +cgroup core is primarily responsible for hierarchically organizing +processes. A cgroup controller is usually responsible for +distributing a specific type of system resource along the hierarchy +although there are utility controllers which serve purposes other than +resource distribution. + +cgroups form a tree structure and every process in the system belongs +to one and only one cgroup. All threads of a process belong to the +same cgroup. On creation, all processes are put in the cgroup that +the parent process belongs to at the time. A process can be migrated +to another cgroup. Migration of a process doesn't affect already +existing descendant processes. + +Following certain structural constraints, controllers may be enabled or +disabled selectively on a cgroup. All controller behaviors are +hierarchical - if a controller is enabled on a cgroup, it affects all +processes which belong to the cgroups consisting the inclusive +sub-hierarchy of the cgroup. When a controller is enabled on a nested +cgroup, it always restricts the resource distribution further. The +restrictions set closer to the root in the hierarchy can not be +overridden from further away. + + +Basic Operations +================ + +Mounting +-------- + +Unlike v1, cgroup v2 has only single hierarchy. The cgroup v2 +hierarchy can be mounted with the following mount command:: + + # mount -t cgroup2 none $MOUNT_POINT + +cgroup2 filesystem has the magic number 0x63677270 ("cgrp"). All +controllers which support v2 and are not bound to a v1 hierarchy are +automatically bound to the v2 hierarchy and show up at the root. +Controllers which are not in active use in the v2 hierarchy can be +bound to other hierarchies. This allows mixing v2 hierarchy with the +legacy v1 multiple hierarchies in a fully backward compatible way. + +A controller can be moved across hierarchies only after the controller +is no longer referenced in its current hierarchy. Because per-cgroup +controller states are destroyed asynchronously and controllers may +have lingering references, a controller may not show up immediately on +the v2 hierarchy after the final umount of the previous hierarchy. +Similarly, a controller should be fully disabled to be moved out of +the unified hierarchy and it may take some time for the disabled +controller to become available for other hierarchies; furthermore, due +to inter-controller dependencies, other controllers may need to be +disabled too. + +While useful for development and manual configurations, moving +controllers dynamically between the v2 and other hierarchies is +strongly discouraged for production use. It is recommended to decide +the hierarchies and controller associations before starting using the +controllers after system boot. + +During transition to v2, system management software might still +automount the v1 cgroup filesystem and so hijack all controllers +during boot, before manual intervention is possible. To make testing +and experimenting easier, the kernel parameter cgroup_no_v1= allows +disabling controllers in v1 and make them always available in v2. + +cgroup v2 currently supports the following mount options. + + nsdelegate + Consider cgroup namespaces as delegation boundaries. This + option is system wide and can only be set on mount or modified + through remount from the init namespace. The mount option is + ignored on non-init namespace mounts. Please refer to the + Delegation section for details. + + favordynmods + Reduce the latencies of dynamic cgroup modifications such as + task migrations and controller on/offs at the cost of making + hot path operations such as forks and exits more expensive. + The static usage pattern of creating a cgroup, enabling + controllers, and then seeding it with CLONE_INTO_CGROUP is + not affected by this option. + + memory_localevents + Only populate memory.events with data for the current cgroup, + and not any subtrees. This is legacy behaviour, the default + behaviour without this option is to include subtree counts. + This option is system wide and can only be set on mount or + modified through remount from the init namespace. The mount + option is ignored on non-init namespace mounts. + + memory_recursiveprot + Recursively apply memory.min and memory.low protection to + entire subtrees, without requiring explicit downward + propagation into leaf cgroups. This allows protecting entire + subtrees from one another, while retaining free competition + within those subtrees. This should have been the default + behavior but is a mount-option to avoid regressing setups + relying on the original semantics (e.g. specifying bogusly + high 'bypass' protection values at higher tree levels). + + +Organizing Processes and Threads +-------------------------------- + +Processes +~~~~~~~~~ + +Initially, only the root cgroup exists to which all processes belong. +A child cgroup can be created by creating a sub-directory:: + + # mkdir $CGROUP_NAME + +A given cgroup may have multiple child cgroups forming a tree +structure. Each cgroup has a read-writable interface file +"cgroup.procs". When read, it lists the PIDs of all processes which +belong to the cgroup one-per-line. The PIDs are not ordered and the +same PID may show up more than once if the process got moved to +another cgroup and then back or the PID got recycled while reading. + +A process can be migrated into a cgroup by writing its PID to the +target cgroup's "cgroup.procs" file. Only one process can be migrated +on a single write(2) call. If a process is composed of multiple +threads, writing the PID of any thread migrates all threads of the +process. + +When a process forks a child process, the new process is born into the +cgroup that the forking process belongs to at the time of the +operation. After exit, a process stays associated with the cgroup +that it belonged to at the time of exit until it's reaped; however, a +zombie process does not appear in "cgroup.procs" and thus can't be +moved to another cgroup. + +A cgroup which doesn't have any children or live processes can be +destroyed by removing the directory. Note that a cgroup which doesn't +have any children and is associated only with zombie processes is +considered empty and can be removed:: + + # rmdir $CGROUP_NAME + +"/proc/$PID/cgroup" lists a process's cgroup membership. If legacy +cgroup is in use in the system, this file may contain multiple lines, +one for each hierarchy. The entry for cgroup v2 is always in the +format "0::$PATH":: + + # cat /proc/842/cgroup + ... + 0::/test-cgroup/test-cgroup-nested + +If the process becomes a zombie and the cgroup it was associated with +is removed subsequently, " (deleted)" is appended to the path:: + + # cat /proc/842/cgroup + ... + 0::/test-cgroup/test-cgroup-nested (deleted) + + +Threads +~~~~~~~ + +cgroup v2 supports thread granularity for a subset of controllers to +support use cases requiring hierarchical resource distribution across +the threads of a group of processes. By default, all threads of a +process belong to the same cgroup, which also serves as the resource +domain to host resource consumptions which are not specific to a +process or thread. The thread mode allows threads to be spread across +a subtree while still maintaining the common resource domain for them. + +Controllers which support thread mode are called threaded controllers. +The ones which don't are called domain controllers. + +Marking a cgroup threaded makes it join the resource domain of its +parent as a threaded cgroup. The parent may be another threaded +cgroup whose resource domain is further up in the hierarchy. The root +of a threaded subtree, that is, the nearest ancestor which is not +threaded, is called threaded domain or thread root interchangeably and +serves as the resource domain for the entire subtree. + +Inside a threaded subtree, threads of a process can be put in +different cgroups and are not subject to the no internal process +constraint - threaded controllers can be enabled on non-leaf cgroups +whether they have threads in them or not. + +As the threaded domain cgroup hosts all the domain resource +consumptions of the subtree, it is considered to have internal +resource consumptions whether there are processes in it or not and +can't have populated child cgroups which aren't threaded. Because the +root cgroup is not subject to no internal process constraint, it can +serve both as a threaded domain and a parent to domain cgroups. + +The current operation mode or type of the cgroup is shown in the +"cgroup.type" file which indicates whether the cgroup is a normal +domain, a domain which is serving as the domain of a threaded subtree, +or a threaded cgroup. + +On creation, a cgroup is always a domain cgroup and can be made +threaded by writing "threaded" to the "cgroup.type" file. The +operation is single direction:: + + # echo threaded > cgroup.type + +Once threaded, the cgroup can't be made a domain again. To enable the +thread mode, the following conditions must be met. + +- As the cgroup will join the parent's resource domain. The parent + must either be a valid (threaded) domain or a threaded cgroup. + +- When the parent is an unthreaded domain, it must not have any domain + controllers enabled or populated domain children. The root is + exempt from this requirement. + +Topology-wise, a cgroup can be in an invalid state. Please consider +the following topology:: + + A (threaded domain) - B (threaded) - C (domain, just created) + +C is created as a domain but isn't connected to a parent which can +host child domains. C can't be used until it is turned into a +threaded cgroup. "cgroup.type" file will report "domain (invalid)" in +these cases. Operations which fail due to invalid topology use +EOPNOTSUPP as the errno. + +A domain cgroup is turned into a threaded domain when one of its child +cgroup becomes threaded or threaded controllers are enabled in the +"cgroup.subtree_control" file while there are processes in the cgroup. +A threaded domain reverts to a normal domain when the conditions +clear. + +When read, "cgroup.threads" contains the list of the thread IDs of all +threads in the cgroup. Except that the operations are per-thread +instead of per-process, "cgroup.threads" has the same format and +behaves the same way as "cgroup.procs". While "cgroup.threads" can be +written to in any cgroup, as it can only move threads inside the same +threaded domain, its operations are confined inside each threaded +subtree. + +The threaded domain cgroup serves as the resource domain for the whole +subtree, and, while the threads can be scattered across the subtree, +all the processes are considered to be in the threaded domain cgroup. +"cgroup.procs" in a threaded domain cgroup contains the PIDs of all +processes in the subtree and is not readable in the subtree proper. +However, "cgroup.procs" can be written to from anywhere in the subtree +to migrate all threads of the matching process to the cgroup. + +Only threaded controllers can be enabled in a threaded subtree. When +a threaded controller is enabled inside a threaded subtree, it only +accounts for and controls resource consumptions associated with the +threads in the cgroup and its descendants. All consumptions which +aren't tied to a specific thread belong to the threaded domain cgroup. + +Because a threaded subtree is exempt from no internal process +constraint, a threaded controller must be able to handle competition +between threads in a non-leaf cgroup and its child cgroups. Each +threaded controller defines how such competitions are handled. + + +[Un]populated Notification +-------------------------- + +Each non-root cgroup has a "cgroup.events" file which contains +"populated" field indicating whether the cgroup's sub-hierarchy has +live processes in it. Its value is 0 if there is no live process in +the cgroup and its descendants; otherwise, 1. poll and [id]notify +events are triggered when the value changes. This can be used, for +example, to start a clean-up operation after all processes of a given +sub-hierarchy have exited. The populated state updates and +notifications are recursive. Consider the following sub-hierarchy +where the numbers in the parentheses represent the numbers of processes +in each cgroup:: + + A(4) - B(0) - C(1) + \ D(0) + +A, B and C's "populated" fields would be 1 while D's 0. After the one +process in C exits, B and C's "populated" fields would flip to "0" and +file modified events will be generated on the "cgroup.events" files of +both cgroups. + + +Controlling Controllers +----------------------- + +Enabling and Disabling +~~~~~~~~~~~~~~~~~~~~~~ + +Each cgroup has a "cgroup.controllers" file which lists all +controllers available for the cgroup to enable:: + + # cat cgroup.controllers + cpu io memory + +No controller is enabled by default. Controllers can be enabled and +disabled by writing to the "cgroup.subtree_control" file:: + + # echo "+cpu +memory -io" > cgroup.subtree_control + +Only controllers which are listed in "cgroup.controllers" can be +enabled. When multiple operations are specified as above, either they +all succeed or fail. If multiple operations on the same controller +are specified, the last one is effective. + +Enabling a controller in a cgroup indicates that the distribution of +the target resource across its immediate children will be controlled. +Consider the following sub-hierarchy. The enabled controllers are +listed in parentheses:: + + A(cpu,memory) - B(memory) - C() + \ D() + +As A has "cpu" and "memory" enabled, A will control the distribution +of CPU cycles and memory to its children, in this case, B. As B has +"memory" enabled but not "CPU", C and D will compete freely on CPU +cycles but their division of memory available to B will be controlled. + +As a controller regulates the distribution of the target resource to +the cgroup's children, enabling it creates the controller's interface +files in the child cgroups. In the above example, enabling "cpu" on B +would create the "cpu." prefixed controller interface files in C and +D. Likewise, disabling "memory" from B would remove the "memory." +prefixed controller interface files from C and D. This means that the +controller interface files - anything which doesn't start with +"cgroup." are owned by the parent rather than the cgroup itself. + + +Top-down Constraint +~~~~~~~~~~~~~~~~~~~ + +Resources are distributed top-down and a cgroup can further distribute +a resource only if the resource has been distributed to it from the +parent. This means that all non-root "cgroup.subtree_control" files +can only contain controllers which are enabled in the parent's +"cgroup.subtree_control" file. A controller can be enabled only if +the parent has the controller enabled and a controller can't be +disabled if one or more children have it enabled. + + +No Internal Process Constraint +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Non-root cgroups can distribute domain resources to their children +only when they don't have any processes of their own. In other words, +only domain cgroups which don't contain any processes can have domain +controllers enabled in their "cgroup.subtree_control" files. + +This guarantees that, when a domain controller is looking at the part +of the hierarchy which has it enabled, processes are always only on +the leaves. This rules out situations where child cgroups compete +against internal processes of the parent. + +The root cgroup is exempt from this restriction. Root contains +processes and anonymous resource consumption which can't be associated +with any other cgroups and requires special treatment from most +controllers. How resource consumption in the root cgroup is governed +is up to each controller (for more information on this topic please +refer to the Non-normative information section in the Controllers +chapter). + +Note that the restriction doesn't get in the way if there is no +enabled controller in the cgroup's "cgroup.subtree_control". This is +important as otherwise it wouldn't be possible to create children of a +populated cgroup. To control resource distribution of a cgroup, the +cgroup must create children and transfer all its processes to the +children before enabling controllers in its "cgroup.subtree_control" +file. + + +Delegation +---------- + +Model of Delegation +~~~~~~~~~~~~~~~~~~~ + +A cgroup can be delegated in two ways. First, to a less privileged +user by granting write access of the directory and its "cgroup.procs", +"cgroup.threads" and "cgroup.subtree_control" files to the user. +Second, if the "nsdelegate" mount option is set, automatically to a +cgroup namespace on namespace creation. + +Because the resource control interface files in a given directory +control the distribution of the parent's resources, the delegatee +shouldn't be allowed to write to them. For the first method, this is +achieved by not granting access to these files. For the second, the +kernel rejects writes to all files other than "cgroup.procs" and +"cgroup.subtree_control" on a namespace root from inside the +namespace. + +The end results are equivalent for both delegation types. Once +delegated, the user can build sub-hierarchy under the directory, +organize processes inside it as it sees fit and further distribute the +resources it received from the parent. The limits and other settings +of all resource controllers are hierarchical and regardless of what +happens in the delegated sub-hierarchy, nothing can escape the +resource restrictions imposed by the parent. + +Currently, cgroup doesn't impose any restrictions on the number of +cgroups in or nesting depth of a delegated sub-hierarchy; however, +this may be limited explicitly in the future. + + +Delegation Containment +~~~~~~~~~~~~~~~~~~~~~~ + +A delegated sub-hierarchy is contained in the sense that processes +can't be moved into or out of the sub-hierarchy by the delegatee. + +For delegations to a less privileged user, this is achieved by +requiring the following conditions for a process with a non-root euid +to migrate a target process into a cgroup by writing its PID to the +"cgroup.procs" file. + +- The writer must have write access to the "cgroup.procs" file. + +- The writer must have write access to the "cgroup.procs" file of the + common ancestor of the source and destination cgroups. + +The above two constraints ensure that while a delegatee may migrate +processes around freely in the delegated sub-hierarchy it can't pull +in from or push out to outside the sub-hierarchy. + +For an example, let's assume cgroups C0 and C1 have been delegated to +user U0 who created C00, C01 under C0 and C10 under C1 as follows and +all processes under C0 and C1 belong to U0:: + + ~~~~~~~~~~~~~ - C0 - C00 + ~ cgroup ~ \ C01 + ~ hierarchy ~ + ~~~~~~~~~~~~~ - C1 - C10 + +Let's also say U0 wants to write the PID of a process which is +currently in C10 into "C00/cgroup.procs". U0 has write access to the +file; however, the common ancestor of the source cgroup C10 and the +destination cgroup C00 is above the points of delegation and U0 would +not have write access to its "cgroup.procs" files and thus the write +will be denied with -EACCES. + +For delegations to namespaces, containment is achieved by requiring +that both the source and destination cgroups are reachable from the +namespace of the process which is attempting the migration. If either +is not reachable, the migration is rejected with -ENOENT. + + +Guidelines +---------- + +Organize Once and Control +~~~~~~~~~~~~~~~~~~~~~~~~~ + +Migrating a process across cgroups is a relatively expensive operation +and stateful resources such as memory are not moved together with the +process. This is an explicit design decision as there often exist +inherent trade-offs between migration and various hot paths in terms +of synchronization cost. + +As such, migrating processes across cgroups frequently as a means to +apply different resource restrictions is discouraged. A workload +should be assigned to a cgroup according to the system's logical and +resource structure once on start-up. Dynamic adjustments to resource +distribution can be made by changing controller configuration through +the interface files. + + +Avoid Name Collisions +~~~~~~~~~~~~~~~~~~~~~ + +Interface files for a cgroup and its children cgroups occupy the same +directory and it is possible to create children cgroups which collide +with interface files. + +All cgroup core interface files are prefixed with "cgroup." and each +controller's interface files are prefixed with the controller name and +a dot. A controller's name is composed of lower case alphabets and +'_'s but never begins with an '_' so it can be used as the prefix +character for collision avoidance. Also, interface file names won't +start or end with terms which are often used in categorizing workloads +such as job, service, slice, unit or workload. + +cgroup doesn't do anything to prevent name collisions and it's the +user's responsibility to avoid them. + + +Resource Distribution Models +============================ + +cgroup controllers implement several resource distribution schemes +depending on the resource type and expected use cases. This section +describes major schemes in use along with their expected behaviors. + + +Weights +------- + +A parent's resource is distributed by adding up the weights of all +active children and giving each the fraction matching the ratio of its +weight against the sum. As only children which can make use of the +resource at the moment participate in the distribution, this is +work-conserving. Due to the dynamic nature, this model is usually +used for stateless resources. + +All weights are in the range [1, 10000] with the default at 100. This +allows symmetric multiplicative biases in both directions at fine +enough granularity while staying in the intuitive range. + +As long as the weight is in range, all configuration combinations are +valid and there is no reason to reject configuration changes or +process migrations. + +"cpu.weight" proportionally distributes CPU cycles to active children +and is an example of this type. + + +.. _cgroupv2-limits-distributor: + +Limits +------ + +A child can only consume up to the configured amount of the resource. +Limits can be over-committed - the sum of the limits of children can +exceed the amount of resource available to the parent. + +Limits are in the range [0, max] and defaults to "max", which is noop. + +As limits can be over-committed, all configuration combinations are +valid and there is no reason to reject configuration changes or +process migrations. + +"io.max" limits the maximum BPS and/or IOPS that a cgroup can consume +on an IO device and is an example of this type. + +.. _cgroupv2-protections-distributor: + +Protections +----------- + +A cgroup is protected up to the configured amount of the resource +as long as the usages of all its ancestors are under their +protected levels. Protections can be hard guarantees or best effort +soft boundaries. Protections can also be over-committed in which case +only up to the amount available to the parent is protected among +children. + +Protections are in the range [0, max] and defaults to 0, which is +noop. + +As protections can be over-committed, all configuration combinations +are valid and there is no reason to reject configuration changes or +process migrations. + +"memory.low" implements best-effort memory protection and is an +example of this type. + + +Allocations +----------- + +A cgroup is exclusively allocated a certain amount of a finite +resource. Allocations can't be over-committed - the sum of the +allocations of children can not exceed the amount of resource +available to the parent. + +Allocations are in the range [0, max] and defaults to 0, which is no +resource. + +As allocations can't be over-committed, some configuration +combinations are invalid and should be rejected. Also, if the +resource is mandatory for execution of processes, process migrations +may be rejected. + +"cpu.rt.max" hard-allocates realtime slices and is an example of this +type. + + +Interface Files +=============== + +Format +------ + +All interface files should be in one of the following formats whenever +possible:: + + New-line separated values + (when only one value can be written at once) + + VAL0\n + VAL1\n + ... + + Space separated values + (when read-only or multiple values can be written at once) + + VAL0 VAL1 ...\n + + Flat keyed + + KEY0 VAL0\n + KEY1 VAL1\n + ... + + Nested keyed + + KEY0 SUB_KEY0=VAL00 SUB_KEY1=VAL01... + KEY1 SUB_KEY0=VAL10 SUB_KEY1=VAL11... + ... + +For a writable file, the format for writing should generally match +reading; however, controllers may allow omitting later fields or +implement restricted shortcuts for most common use cases. + +For both flat and nested keyed files, only the values for a single key +can be written at a time. For nested keyed files, the sub key pairs +may be specified in any order and not all pairs have to be specified. + + +Conventions +----------- + +- Settings for a single feature should be contained in a single file. + +- The root cgroup should be exempt from resource control and thus + shouldn't have resource control interface files. + +- The default time unit is microseconds. If a different unit is ever + used, an explicit unit suffix must be present. + +- A parts-per quantity should use a percentage decimal with at least + two digit fractional part - e.g. 13.40. + +- If a controller implements weight based resource distribution, its + interface file should be named "weight" and have the range [1, + 10000] with 100 as the default. The values are chosen to allow + enough and symmetric bias in both directions while keeping it + intuitive (the default is 100%). + +- If a controller implements an absolute resource guarantee and/or + limit, the interface files should be named "min" and "max" + respectively. If a controller implements best effort resource + guarantee and/or limit, the interface files should be named "low" + and "high" respectively. + + In the above four control files, the special token "max" should be + used to represent upward infinity for both reading and writing. + +- If a setting has a configurable default value and keyed specific + overrides, the default entry should be keyed with "default" and + appear as the first entry in the file. + + The default value can be updated by writing either "default $VAL" or + "$VAL". + + When writing to update a specific override, "default" can be used as + the value to indicate removal of the override. Override entries + with "default" as the value must not appear when read. + + For example, a setting which is keyed by major:minor device numbers + with integer values may look like the following:: + + # cat cgroup-example-interface-file + default 150 + 8:0 300 + + The default value can be updated by:: + + # echo 125 > cgroup-example-interface-file + + or:: + + # echo "default 125" > cgroup-example-interface-file + + An override can be set by:: + + # echo "8:16 170" > cgroup-example-interface-file + + and cleared by:: + + # echo "8:0 default" > cgroup-example-interface-file + # cat cgroup-example-interface-file + default 125 + 8:16 170 + +- For events which are not very high frequency, an interface file + "events" should be created which lists event key value pairs. + Whenever a notifiable event happens, file modified event should be + generated on the file. + + +Core Interface Files +-------------------- + +All cgroup core files are prefixed with "cgroup." + + cgroup.type + A read-write single value file which exists on non-root + cgroups. + + When read, it indicates the current type of the cgroup, which + can be one of the following values. + + - "domain" : A normal valid domain cgroup. + + - "domain threaded" : A threaded domain cgroup which is + serving as the root of a threaded subtree. + + - "domain invalid" : A cgroup which is in an invalid state. + It can't be populated or have controllers enabled. It may + be allowed to become a threaded cgroup. + + - "threaded" : A threaded cgroup which is a member of a + threaded subtree. + + A cgroup can be turned into a threaded cgroup by writing + "threaded" to this file. + + cgroup.procs + A read-write new-line separated values file which exists on + all cgroups. + + When read, it lists the PIDs of all processes which belong to + the cgroup one-per-line. The PIDs are not ordered and the + same PID may show up more than once if the process got moved + to another cgroup and then back or the PID got recycled while + reading. + + A PID can be written to migrate the process associated with + the PID to the cgroup. The writer should match all of the + following conditions. + + - It must have write access to the "cgroup.procs" file. + + - It must have write access to the "cgroup.procs" file of the + common ancestor of the source and destination cgroups. + + When delegating a sub-hierarchy, write access to this file + should be granted along with the containing directory. + + In a threaded cgroup, reading this file fails with EOPNOTSUPP + as all the processes belong to the thread root. Writing is + supported and moves every thread of the process to the cgroup. + + cgroup.threads + A read-write new-line separated values file which exists on + all cgroups. + + When read, it lists the TIDs of all threads which belong to + the cgroup one-per-line. The TIDs are not ordered and the + same TID may show up more than once if the thread got moved to + another cgroup and then back or the TID got recycled while + reading. + + A TID can be written to migrate the thread associated with the + TID to the cgroup. The writer should match all of the + following conditions. + + - It must have write access to the "cgroup.threads" file. + + - The cgroup that the thread is currently in must be in the + same resource domain as the destination cgroup. + + - It must have write access to the "cgroup.procs" file of the + common ancestor of the source and destination cgroups. + + When delegating a sub-hierarchy, write access to this file + should be granted along with the containing directory. + + cgroup.controllers + A read-only space separated values file which exists on all + cgroups. + + It shows space separated list of all controllers available to + the cgroup. The controllers are not ordered. + + cgroup.subtree_control + A read-write space separated values file which exists on all + cgroups. Starts out empty. + + When read, it shows space separated list of the controllers + which are enabled to control resource distribution from the + cgroup to its children. + + Space separated list of controllers prefixed with '+' or '-' + can be written to enable or disable controllers. A controller + name prefixed with '+' enables the controller and '-' + disables. If a controller appears more than once on the list, + the last one is effective. When multiple enable and disable + operations are specified, either all succeed or all fail. + + cgroup.events + A read-only flat-keyed file which exists on non-root cgroups. + The following entries are defined. Unless specified + otherwise, a value change in this file generates a file + modified event. + + populated + 1 if the cgroup or its descendants contains any live + processes; otherwise, 0. + frozen + 1 if the cgroup is frozen; otherwise, 0. + + cgroup.max.descendants + A read-write single value files. The default is "max". + + Maximum allowed number of descent cgroups. + If the actual number of descendants is equal or larger, + an attempt to create a new cgroup in the hierarchy will fail. + + cgroup.max.depth + A read-write single value files. The default is "max". + + Maximum allowed descent depth below the current cgroup. + If the actual descent depth is equal or larger, + an attempt to create a new child cgroup will fail. + + cgroup.stat + A read-only flat-keyed file with the following entries: + + nr_descendants + Total number of visible descendant cgroups. + + nr_dying_descendants + Total number of dying descendant cgroups. A cgroup becomes + dying after being deleted by a user. The cgroup will remain + in dying state for some time undefined time (which can depend + on system load) before being completely destroyed. + + A process can't enter a dying cgroup under any circumstances, + a dying cgroup can't revive. + + A dying cgroup can consume system resources not exceeding + limits, which were active at the moment of cgroup deletion. + + cgroup.freeze + A read-write single value file which exists on non-root cgroups. + Allowed values are "0" and "1". The default is "0". + + Writing "1" to the file causes freezing of the cgroup and all + descendant cgroups. This means that all belonging processes will + be stopped and will not run until the cgroup will be explicitly + unfrozen. Freezing of the cgroup may take some time; when this action + is completed, the "frozen" value in the cgroup.events control file + will be updated to "1" and the corresponding notification will be + issued. + + A cgroup can be frozen either by its own settings, or by settings + of any ancestor cgroups. If any of ancestor cgroups is frozen, the + cgroup will remain frozen. + + Processes in the frozen cgroup can be killed by a fatal signal. + They also can enter and leave a frozen cgroup: either by an explicit + move by a user, or if freezing of the cgroup races with fork(). + If a process is moved to a frozen cgroup, it stops. If a process is + moved out of a frozen cgroup, it becomes running. + + Frozen status of a cgroup doesn't affect any cgroup tree operations: + it's possible to delete a frozen (and empty) cgroup, as well as + create new sub-cgroups. + + cgroup.kill + A write-only single value file which exists in non-root cgroups. + The only allowed value is "1". + + Writing "1" to the file causes the cgroup and all descendant cgroups to + be killed. This means that all processes located in the affected cgroup + tree will be killed via SIGKILL. + + Killing a cgroup tree will deal with concurrent forks appropriately and + is protected against migrations. + + In a threaded cgroup, writing this file fails with EOPNOTSUPP as + killing cgroups is a process directed operation, i.e. it affects + the whole thread-group. + + cgroup.pressure + A read-write single value file that allowed values are "0" and "1". + The default is "1". + + Writing "0" to the file will disable the cgroup PSI accounting. + Writing "1" to the file will re-enable the cgroup PSI accounting. + + This control attribute is not hierarchical, so disable or enable PSI + accounting in a cgroup does not affect PSI accounting in descendants + and doesn't need pass enablement via ancestors from root. + + The reason this control attribute exists is that PSI accounts stalls for + each cgroup separately and aggregates it at each level of the hierarchy. + This may cause non-negligible overhead for some workloads when under + deep level of the hierarchy, in which case this control attribute can + be used to disable PSI accounting in the non-leaf cgroups. + + irq.pressure + A read-write nested-keyed file. + + Shows pressure stall information for IRQ/SOFTIRQ. See + :ref:`Documentation/accounting/psi.rst <psi>` for details. + +Controllers +=========== + +.. _cgroup-v2-cpu: + +CPU +--- + +The "cpu" controllers regulates distribution of CPU cycles. This +controller implements weight and absolute bandwidth limit models for +normal scheduling policy and absolute bandwidth allocation model for +realtime scheduling policy. + +In all the above models, cycles distribution is defined only on a temporal +base and it does not account for the frequency at which tasks are executed. +The (optional) utilization clamping support allows to hint the schedutil +cpufreq governor about the minimum desired frequency which should always be +provided by a CPU, as well as the maximum desired frequency, which should not +be exceeded by a CPU. + +WARNING: cgroup2 doesn't yet support control of realtime processes and +the cpu controller can only be enabled when all RT processes are in +the root cgroup. Be aware that system management software may already +have placed RT processes into nonroot cgroups during the system boot +process, and these processes may need to be moved to the root cgroup +before the cpu controller can be enabled. + + +CPU Interface Files +~~~~~~~~~~~~~~~~~~~ + +All time durations are in microseconds. + + cpu.stat + A read-only flat-keyed file. + This file exists whether the controller is enabled or not. + + It always reports the following three stats: + + - usage_usec + - user_usec + - system_usec + + and the following five when the controller is enabled: + + - nr_periods + - nr_throttled + - throttled_usec + - nr_bursts + - burst_usec + + cpu.weight + A read-write single value file which exists on non-root + cgroups. The default is "100". + + The weight in the range [1, 10000]. + + cpu.weight.nice + A read-write single value file which exists on non-root + cgroups. The default is "0". + + The nice value is in the range [-20, 19]. + + This interface file is an alternative interface for + "cpu.weight" and allows reading and setting weight using the + same values used by nice(2). Because the range is smaller and + granularity is coarser for the nice values, the read value is + the closest approximation of the current weight. + + cpu.max + A read-write two value file which exists on non-root cgroups. + The default is "max 100000". + + The maximum bandwidth limit. It's in the following format:: + + $MAX $PERIOD + + which indicates that the group may consume up to $MAX in each + $PERIOD duration. "max" for $MAX indicates no limit. If only + one number is written, $MAX is updated. + + cpu.max.burst + A read-write single value file which exists on non-root + cgroups. The default is "0". + + The burst in the range [0, $MAX]. + + cpu.pressure + A read-write nested-keyed file. + + Shows pressure stall information for CPU. See + :ref:`Documentation/accounting/psi.rst <psi>` for details. + + cpu.uclamp.min + A read-write single value file which exists on non-root cgroups. + The default is "0", i.e. no utilization boosting. + + The requested minimum utilization (protection) as a percentage + rational number, e.g. 12.34 for 12.34%. + + This interface allows reading and setting minimum utilization clamp + values similar to the sched_setattr(2). This minimum utilization + value is used to clamp the task specific minimum utilization clamp. + + The requested minimum utilization (protection) is always capped by + the current value for the maximum utilization (limit), i.e. + `cpu.uclamp.max`. + + cpu.uclamp.max + A read-write single value file which exists on non-root cgroups. + The default is "max". i.e. no utilization capping + + The requested maximum utilization (limit) as a percentage rational + number, e.g. 98.76 for 98.76%. + + This interface allows reading and setting maximum utilization clamp + values similar to the sched_setattr(2). This maximum utilization + value is used to clamp the task specific maximum utilization clamp. + + + +Memory +------ + +The "memory" controller regulates distribution of memory. Memory is +stateful and implements both limit and protection models. Due to the +intertwining between memory usage and reclaim pressure and the +stateful nature of memory, the distribution model is relatively +complex. + +While not completely water-tight, all major memory usages by a given +cgroup are tracked so that the total memory consumption can be +accounted and controlled to a reasonable extent. Currently, the +following types of memory usages are tracked. + +- Userland memory - page cache and anonymous memory. + +- Kernel data structures such as dentries and inodes. + +- TCP socket buffers. + +The above list may expand in the future for better coverage. + + +Memory Interface Files +~~~~~~~~~~~~~~~~~~~~~~ + +All memory amounts are in bytes. If a value which is not aligned to +PAGE_SIZE is written, the value may be rounded up to the closest +PAGE_SIZE multiple when read back. + + memory.current + A read-only single value file which exists on non-root + cgroups. + + The total amount of memory currently being used by the cgroup + and its descendants. + + memory.min + A read-write single value file which exists on non-root + cgroups. The default is "0". + + Hard memory protection. If the memory usage of a cgroup + is within its effective min boundary, the cgroup's memory + won't be reclaimed under any conditions. If there is no + unprotected reclaimable memory available, OOM killer + is invoked. Above the effective min boundary (or + effective low boundary if it is higher), pages are reclaimed + proportionally to the overage, reducing reclaim pressure for + smaller overages. + + Effective min boundary is limited by memory.min values of + all ancestor cgroups. If there is memory.min overcommitment + (child cgroup or cgroups are requiring more protected memory + than parent will allow), then each child cgroup will get + the part of parent's protection proportional to its + actual memory usage below memory.min. + + Putting more memory than generally available under this + protection is discouraged and may lead to constant OOMs. + + If a memory cgroup is not populated with processes, + its memory.min is ignored. + + memory.low + A read-write single value file which exists on non-root + cgroups. The default is "0". + + Best-effort memory protection. If the memory usage of a + cgroup is within its effective low boundary, the cgroup's + memory won't be reclaimed unless there is no reclaimable + memory available in unprotected cgroups. + Above the effective low boundary (or + effective min boundary if it is higher), pages are reclaimed + proportionally to the overage, reducing reclaim pressure for + smaller overages. + + Effective low boundary is limited by memory.low values of + all ancestor cgroups. If there is memory.low overcommitment + (child cgroup or cgroups are requiring more protected memory + than parent will allow), then each child cgroup will get + the part of parent's protection proportional to its + actual memory usage below memory.low. + + Putting more memory than generally available under this + protection is discouraged. + + memory.high + A read-write single value file which exists on non-root + cgroups. The default is "max". + + Memory usage throttle limit. If a cgroup's usage goes + over the high boundary, the processes of the cgroup are + throttled and put under heavy reclaim pressure. + + Going over the high limit never invokes the OOM killer and + under extreme conditions the limit may be breached. The high + limit should be used in scenarios where an external process + monitors the limited cgroup to alleviate heavy reclaim + pressure. + + memory.max + A read-write single value file which exists on non-root + cgroups. The default is "max". + + Memory usage hard limit. This is the main mechanism to limit + memory usage of a cgroup. If a cgroup's memory usage reaches + this limit and can't be reduced, the OOM killer is invoked in + the cgroup. Under certain circumstances, the usage may go + over the limit temporarily. + + In default configuration regular 0-order allocations always + succeed unless OOM killer chooses current task as a victim. + + Some kinds of allocations don't invoke the OOM killer. + Caller could retry them differently, return into userspace + as -ENOMEM or silently ignore in cases like disk readahead. + + memory.reclaim + A write-only nested-keyed file which exists for all cgroups. + + This is a simple interface to trigger memory reclaim in the + target cgroup. + + This file accepts a single key, the number of bytes to reclaim. + No nested keys are currently supported. + + Example:: + + echo "1G" > memory.reclaim + + The interface can be later extended with nested keys to + configure the reclaim behavior. For example, specify the + type of memory to reclaim from (anon, file, ..). + + Please note that the kernel can over or under reclaim from + the target cgroup. If less bytes are reclaimed than the + specified amount, -EAGAIN is returned. + + Please note that the proactive reclaim (triggered by this + interface) is not meant to indicate memory pressure on the + memory cgroup. Therefore socket memory balancing triggered by + the memory reclaim normally is not exercised in this case. + This means that the networking layer will not adapt based on + reclaim induced by memory.reclaim. + + memory.peak + A read-only single value file which exists on non-root + cgroups. + + The max memory usage recorded for the cgroup and its + descendants since the creation of the cgroup. + + memory.oom.group + A read-write single value file which exists on non-root + cgroups. The default value is "0". + + Determines whether the cgroup should be treated as + an indivisible workload by the OOM killer. If set, + all tasks belonging to the cgroup or to its descendants + (if the memory cgroup is not a leaf cgroup) are killed + together or not at all. This can be used to avoid + partial kills to guarantee workload integrity. + + Tasks with the OOM protection (oom_score_adj set to -1000) + are treated as an exception and are never killed. + + If the OOM killer is invoked in a cgroup, it's not going + to kill any tasks outside of this cgroup, regardless + memory.oom.group values of ancestor cgroups. + + memory.events + A read-only flat-keyed file which exists on non-root cgroups. + The following entries are defined. Unless specified + otherwise, a value change in this file generates a file + modified event. + + Note that all fields in this file are hierarchical and the + file modified event can be generated due to an event down the + hierarchy. For the local events at the cgroup level see + memory.events.local. + + low + The number of times the cgroup is reclaimed due to + high memory pressure even though its usage is under + the low boundary. This usually indicates that the low + boundary is over-committed. + + high + The number of times processes of the cgroup are + throttled and routed to perform direct memory reclaim + because the high memory boundary was exceeded. For a + cgroup whose memory usage is capped by the high limit + rather than global memory pressure, this event's + occurrences are expected. + + max + The number of times the cgroup's memory usage was + about to go over the max boundary. If direct reclaim + fails to bring it down, the cgroup goes to OOM state. + + oom + The number of time the cgroup's memory usage was + reached the limit and allocation was about to fail. + + This event is not raised if the OOM killer is not + considered as an option, e.g. for failed high-order + allocations or if caller asked to not retry attempts. + + oom_kill + The number of processes belonging to this cgroup + killed by any kind of OOM killer. + + oom_group_kill + The number of times a group OOM has occurred. + + memory.events.local + Similar to memory.events but the fields in the file are local + to the cgroup i.e. not hierarchical. The file modified event + generated on this file reflects only the local events. + + memory.stat + A read-only flat-keyed file which exists on non-root cgroups. + + This breaks down the cgroup's memory footprint into different + types of memory, type-specific details, and other information + on the state and past events of the memory management system. + + All memory amounts are in bytes. + + The entries are ordered to be human readable, and new entries + can show up in the middle. Don't rely on items remaining in a + fixed position; use the keys to look up specific values! + + If the entry has no per-node counter (or not show in the + memory.numa_stat). We use 'npn' (non-per-node) as the tag + to indicate that it will not show in the memory.numa_stat. + + anon + Amount of memory used in anonymous mappings such as + brk(), sbrk(), and mmap(MAP_ANONYMOUS) + + file + Amount of memory used to cache filesystem data, + including tmpfs and shared memory. + + kernel (npn) + Amount of total kernel memory, including + (kernel_stack, pagetables, percpu, vmalloc, slab) in + addition to other kernel memory use cases. + + kernel_stack + Amount of memory allocated to kernel stacks. + + pagetables + Amount of memory allocated for page tables. + + sec_pagetables + Amount of memory allocated for secondary page tables, + this currently includes KVM mmu allocations on x86 + and arm64. + + percpu (npn) + Amount of memory used for storing per-cpu kernel + data structures. + + sock (npn) + Amount of memory used in network transmission buffers + + vmalloc (npn) + Amount of memory used for vmap backed memory. + + shmem + Amount of cached filesystem data that is swap-backed, + such as tmpfs, shm segments, shared anonymous mmap()s + + zswap + Amount of memory consumed by the zswap compression backend. + + zswapped + Amount of application memory swapped out to zswap. + + file_mapped + Amount of cached filesystem data mapped with mmap() + + file_dirty + Amount of cached filesystem data that was modified but + not yet written back to disk + + file_writeback + Amount of cached filesystem data that was modified and + is currently being written back to disk + + swapcached + Amount of swap cached in memory. The swapcache is accounted + against both memory and swap usage. + + anon_thp + Amount of memory used in anonymous mappings backed by + transparent hugepages + + file_thp + Amount of cached filesystem data backed by transparent + hugepages + + shmem_thp + Amount of shm, tmpfs, shared anonymous mmap()s backed by + transparent hugepages + + inactive_anon, active_anon, inactive_file, active_file, unevictable + Amount of memory, swap-backed and filesystem-backed, + on the internal memory management lists used by the + page reclaim algorithm. + + As these represent internal list state (eg. shmem pages are on anon + memory management lists), inactive_foo + active_foo may not be equal to + the value for the foo counter, since the foo counter is type-based, not + list-based. + + slab_reclaimable + Part of "slab" that might be reclaimed, such as + dentries and inodes. + + slab_unreclaimable + Part of "slab" that cannot be reclaimed on memory + pressure. + + slab (npn) + Amount of memory used for storing in-kernel data + structures. + + workingset_refault_anon + Number of refaults of previously evicted anonymous pages. + + workingset_refault_file + Number of refaults of previously evicted file pages. + + workingset_activate_anon + Number of refaulted anonymous pages that were immediately + activated. + + workingset_activate_file + Number of refaulted file pages that were immediately activated. + + workingset_restore_anon + Number of restored anonymous pages which have been detected as + an active workingset before they got reclaimed. + + workingset_restore_file + Number of restored file pages which have been detected as an + active workingset before they got reclaimed. + + workingset_nodereclaim + Number of times a shadow node has been reclaimed + + pgscan (npn) + Amount of scanned pages (in an inactive LRU list) + + pgsteal (npn) + Amount of reclaimed pages + + pgscan_kswapd (npn) + Amount of scanned pages by kswapd (in an inactive LRU list) + + pgscan_direct (npn) + Amount of scanned pages directly (in an inactive LRU list) + + pgscan_khugepaged (npn) + Amount of scanned pages by khugepaged (in an inactive LRU list) + + pgsteal_kswapd (npn) + Amount of reclaimed pages by kswapd + + pgsteal_direct (npn) + Amount of reclaimed pages directly + + pgsteal_khugepaged (npn) + Amount of reclaimed pages by khugepaged + + pgfault (npn) + Total number of page faults incurred + + pgmajfault (npn) + Number of major page faults incurred + + pgrefill (npn) + Amount of scanned pages (in an active LRU list) + + pgactivate (npn) + Amount of pages moved to the active LRU list + + pgdeactivate (npn) + Amount of pages moved to the inactive LRU list + + pglazyfree (npn) + Amount of pages postponed to be freed under memory pressure + + pglazyfreed (npn) + Amount of reclaimed lazyfree pages + + thp_fault_alloc (npn) + Number of transparent hugepages which were allocated to satisfy + a page fault. This counter is not present when CONFIG_TRANSPARENT_HUGEPAGE + is not set. + + thp_collapse_alloc (npn) + Number of transparent hugepages which were allocated to allow + collapsing an existing range of pages. This counter is not + present when CONFIG_TRANSPARENT_HUGEPAGE is not set. + + memory.numa_stat + A read-only nested-keyed file which exists on non-root cgroups. + + This breaks down the cgroup's memory footprint into different + types of memory, type-specific details, and other information + per node on the state of the memory management system. + + This is useful for providing visibility into the NUMA locality + information within an memcg since the pages are allowed to be + allocated from any physical node. One of the use case is evaluating + application performance by combining this information with the + application's CPU allocation. + + All memory amounts are in bytes. + + The output format of memory.numa_stat is:: + + type N0=<bytes in node 0> N1=<bytes in node 1> ... + + The entries are ordered to be human readable, and new entries + can show up in the middle. Don't rely on items remaining in a + fixed position; use the keys to look up specific values! + + The entries can refer to the memory.stat. + + memory.swap.current + A read-only single value file which exists on non-root + cgroups. + + The total amount of swap currently being used by the cgroup + and its descendants. + + memory.swap.high + A read-write single value file which exists on non-root + cgroups. The default is "max". + + Swap usage throttle limit. If a cgroup's swap usage exceeds + this limit, all its further allocations will be throttled to + allow userspace to implement custom out-of-memory procedures. + + This limit marks a point of no return for the cgroup. It is NOT + designed to manage the amount of swapping a workload does + during regular operation. Compare to memory.swap.max, which + prohibits swapping past a set amount, but lets the cgroup + continue unimpeded as long as other memory can be reclaimed. + + Healthy workloads are not expected to reach this limit. + + memory.swap.peak + A read-only single value file which exists on non-root + cgroups. + + The max swap usage recorded for the cgroup and its + descendants since the creation of the cgroup. + + memory.swap.max + A read-write single value file which exists on non-root + cgroups. The default is "max". + + Swap usage hard limit. If a cgroup's swap usage reaches this + limit, anonymous memory of the cgroup will not be swapped out. + + memory.swap.events + A read-only flat-keyed file which exists on non-root cgroups. + The following entries are defined. Unless specified + otherwise, a value change in this file generates a file + modified event. + + high + The number of times the cgroup's swap usage was over + the high threshold. + + max + The number of times the cgroup's swap usage was about + to go over the max boundary and swap allocation + failed. + + fail + The number of times swap allocation failed either + because of running out of swap system-wide or max + limit. + + When reduced under the current usage, the existing swap + entries are reclaimed gradually and the swap usage may stay + higher than the limit for an extended period of time. This + reduces the impact on the workload and memory management. + + memory.zswap.current + A read-only single value file which exists on non-root + cgroups. + + The total amount of memory consumed by the zswap compression + backend. + + memory.zswap.max + A read-write single value file which exists on non-root + cgroups. The default is "max". + + Zswap usage hard limit. If a cgroup's zswap pool reaches this + limit, it will refuse to take any more stores before existing + entries fault back in or are written out to disk. + + memory.pressure + A read-only nested-keyed file. + + Shows pressure stall information for memory. See + :ref:`Documentation/accounting/psi.rst <psi>` for details. + + +Usage Guidelines +~~~~~~~~~~~~~~~~ + +"memory.high" is the main mechanism to control memory usage. +Over-committing on high limit (sum of high limits > available memory) +and letting global memory pressure to distribute memory according to +usage is a viable strategy. + +Because breach of the high limit doesn't trigger the OOM killer but +throttles the offending cgroup, a management agent has ample +opportunities to monitor and take appropriate actions such as granting +more memory or terminating the workload. + +Determining whether a cgroup has enough memory is not trivial as +memory usage doesn't indicate whether the workload can benefit from +more memory. For example, a workload which writes data received from +network to a file can use all available memory but can also operate as +performant with a small amount of memory. A measure of memory +pressure - how much the workload is being impacted due to lack of +memory - is necessary to determine whether a workload needs more +memory; unfortunately, memory pressure monitoring mechanism isn't +implemented yet. + + +Memory Ownership +~~~~~~~~~~~~~~~~ + +A memory area is charged to the cgroup which instantiated it and stays +charged to the cgroup until the area is released. Migrating a process +to a different cgroup doesn't move the memory usages that it +instantiated while in the previous cgroup to the new cgroup. + +A memory area may be used by processes belonging to different cgroups. +To which cgroup the area will be charged is in-deterministic; however, +over time, the memory area is likely to end up in a cgroup which has +enough memory allowance to avoid high reclaim pressure. + +If a cgroup sweeps a considerable amount of memory which is expected +to be accessed repeatedly by other cgroups, it may make sense to use +POSIX_FADV_DONTNEED to relinquish the ownership of memory areas +belonging to the affected files to ensure correct memory ownership. + + +IO +-- + +The "io" controller regulates the distribution of IO resources. This +controller implements both weight based and absolute bandwidth or IOPS +limit distribution; however, weight based distribution is available +only if cfq-iosched is in use and neither scheme is available for +blk-mq devices. + + +IO Interface Files +~~~~~~~~~~~~~~~~~~ + + io.stat + A read-only nested-keyed file. + + Lines are keyed by $MAJ:$MIN device numbers and not ordered. + The following nested keys are defined. + + ====== ===================== + rbytes Bytes read + wbytes Bytes written + rios Number of read IOs + wios Number of write IOs + dbytes Bytes discarded + dios Number of discard IOs + ====== ===================== + + An example read output follows:: + + 8:16 rbytes=1459200 wbytes=314773504 rios=192 wios=353 dbytes=0 dios=0 + 8:0 rbytes=90430464 wbytes=299008000 rios=8950 wios=1252 dbytes=50331648 dios=3021 + + io.cost.qos + A read-write nested-keyed file which exists only on the root + cgroup. + + This file configures the Quality of Service of the IO cost + model based controller (CONFIG_BLK_CGROUP_IOCOST) which + currently implements "io.weight" proportional control. Lines + are keyed by $MAJ:$MIN device numbers and not ordered. The + line for a given device is populated on the first write for + the device on "io.cost.qos" or "io.cost.model". The following + nested keys are defined. + + ====== ===================================== + enable Weight-based control enable + ctrl "auto" or "user" + rpct Read latency percentile [0, 100] + rlat Read latency threshold + wpct Write latency percentile [0, 100] + wlat Write latency threshold + min Minimum scaling percentage [1, 10000] + max Maximum scaling percentage [1, 10000] + ====== ===================================== + + The controller is disabled by default and can be enabled by + setting "enable" to 1. "rpct" and "wpct" parameters default + to zero and the controller uses internal device saturation + state to adjust the overall IO rate between "min" and "max". + + When a better control quality is needed, latency QoS + parameters can be configured. For example:: + + 8:16 enable=1 ctrl=auto rpct=95.00 rlat=75000 wpct=95.00 wlat=150000 min=50.00 max=150.0 + + shows that on sdb, the controller is enabled, will consider + the device saturated if the 95th percentile of read completion + latencies is above 75ms or write 150ms, and adjust the overall + IO issue rate between 50% and 150% accordingly. + + The lower the saturation point, the better the latency QoS at + the cost of aggregate bandwidth. The narrower the allowed + adjustment range between "min" and "max", the more conformant + to the cost model the IO behavior. Note that the IO issue + base rate may be far off from 100% and setting "min" and "max" + blindly can lead to a significant loss of device capacity or + control quality. "min" and "max" are useful for regulating + devices which show wide temporary behavior changes - e.g. a + ssd which accepts writes at the line speed for a while and + then completely stalls for multiple seconds. + + When "ctrl" is "auto", the parameters are controlled by the + kernel and may change automatically. Setting "ctrl" to "user" + or setting any of the percentile and latency parameters puts + it into "user" mode and disables the automatic changes. The + automatic mode can be restored by setting "ctrl" to "auto". + + io.cost.model + A read-write nested-keyed file which exists only on the root + cgroup. + + This file configures the cost model of the IO cost model based + controller (CONFIG_BLK_CGROUP_IOCOST) which currently + implements "io.weight" proportional control. Lines are keyed + by $MAJ:$MIN device numbers and not ordered. The line for a + given device is populated on the first write for the device on + "io.cost.qos" or "io.cost.model". The following nested keys + are defined. + + ===== ================================ + ctrl "auto" or "user" + model The cost model in use - "linear" + ===== ================================ + + When "ctrl" is "auto", the kernel may change all parameters + dynamically. When "ctrl" is set to "user" or any other + parameters are written to, "ctrl" become "user" and the + automatic changes are disabled. + + When "model" is "linear", the following model parameters are + defined. + + ============= ======================================== + [r|w]bps The maximum sequential IO throughput + [r|w]seqiops The maximum 4k sequential IOs per second + [r|w]randiops The maximum 4k random IOs per second + ============= ======================================== + + From the above, the builtin linear model determines the base + costs of a sequential and random IO and the cost coefficient + for the IO size. While simple, this model can cover most + common device classes acceptably. + + The IO cost model isn't expected to be accurate in absolute + sense and is scaled to the device behavior dynamically. + + If needed, tools/cgroup/iocost_coef_gen.py can be used to + generate device-specific coefficients. + + io.weight + A read-write flat-keyed file which exists on non-root cgroups. + The default is "default 100". + + The first line is the default weight applied to devices + without specific override. The rest are overrides keyed by + $MAJ:$MIN device numbers and not ordered. The weights are in + the range [1, 10000] and specifies the relative amount IO time + the cgroup can use in relation to its siblings. + + The default weight can be updated by writing either "default + $WEIGHT" or simply "$WEIGHT". Overrides can be set by writing + "$MAJ:$MIN $WEIGHT" and unset by writing "$MAJ:$MIN default". + + An example read output follows:: + + default 100 + 8:16 200 + 8:0 50 + + io.max + A read-write nested-keyed file which exists on non-root + cgroups. + + BPS and IOPS based IO limit. Lines are keyed by $MAJ:$MIN + device numbers and not ordered. The following nested keys are + defined. + + ===== ================================== + rbps Max read bytes per second + wbps Max write bytes per second + riops Max read IO operations per second + wiops Max write IO operations per second + ===== ================================== + + When writing, any number of nested key-value pairs can be + specified in any order. "max" can be specified as the value + to remove a specific limit. If the same key is specified + multiple times, the outcome is undefined. + + BPS and IOPS are measured in each IO direction and IOs are + delayed if limit is reached. Temporary bursts are allowed. + + Setting read limit at 2M BPS and write at 120 IOPS for 8:16:: + + echo "8:16 rbps=2097152 wiops=120" > io.max + + Reading returns the following:: + + 8:16 rbps=2097152 wbps=max riops=max wiops=120 + + Write IOPS limit can be removed by writing the following:: + + echo "8:16 wiops=max" > io.max + + Reading now returns the following:: + + 8:16 rbps=2097152 wbps=max riops=max wiops=max + + io.pressure + A read-only nested-keyed file. + + Shows pressure stall information for IO. See + :ref:`Documentation/accounting/psi.rst <psi>` for details. + + +Writeback +~~~~~~~~~ + +Page cache is dirtied through buffered writes and shared mmaps and +written asynchronously to the backing filesystem by the writeback +mechanism. Writeback sits between the memory and IO domains and +regulates the proportion of dirty memory by balancing dirtying and +write IOs. + +The io controller, in conjunction with the memory controller, +implements control of page cache writeback IOs. The memory controller +defines the memory domain that dirty memory ratio is calculated and +maintained for and the io controller defines the io domain which +writes out dirty pages for the memory domain. Both system-wide and +per-cgroup dirty memory states are examined and the more restrictive +of the two is enforced. + +cgroup writeback requires explicit support from the underlying +filesystem. Currently, cgroup writeback is implemented on ext2, ext4, +btrfs, f2fs, and xfs. On other filesystems, all writeback IOs are +attributed to the root cgroup. + +There are inherent differences in memory and writeback management +which affects how cgroup ownership is tracked. Memory is tracked per +page while writeback per inode. For the purpose of writeback, an +inode is assigned to a cgroup and all IO requests to write dirty pages +from the inode are attributed to that cgroup. + +As cgroup ownership for memory is tracked per page, there can be pages +which are associated with different cgroups than the one the inode is +associated with. These are called foreign pages. The writeback +constantly keeps track of foreign pages and, if a particular foreign +cgroup becomes the majority over a certain period of time, switches +the ownership of the inode to that cgroup. + +While this model is enough for most use cases where a given inode is +mostly dirtied by a single cgroup even when the main writing cgroup +changes over time, use cases where multiple cgroups write to a single +inode simultaneously are not supported well. In such circumstances, a +significant portion of IOs are likely to be attributed incorrectly. +As memory controller assigns page ownership on the first use and +doesn't update it until the page is released, even if writeback +strictly follows page ownership, multiple cgroups dirtying overlapping +areas wouldn't work as expected. It's recommended to avoid such usage +patterns. + +The sysctl knobs which affect writeback behavior are applied to cgroup +writeback as follows. + + vm.dirty_background_ratio, vm.dirty_ratio + These ratios apply the same to cgroup writeback with the + amount of available memory capped by limits imposed by the + memory controller and system-wide clean memory. + + vm.dirty_background_bytes, vm.dirty_bytes + For cgroup writeback, this is calculated into ratio against + total available memory and applied the same way as + vm.dirty[_background]_ratio. + + +IO Latency +~~~~~~~~~~ + +This is a cgroup v2 controller for IO workload protection. You provide a group +with a latency target, and if the average latency exceeds that target the +controller will throttle any peers that have a lower latency target than the +protected workload. + +The limits are only applied at the peer level in the hierarchy. This means that +in the diagram below, only groups A, B, and C will influence each other, and +groups D and F will influence each other. Group G will influence nobody:: + + [root] + / | \ + A B C + / \ | + D F G + + +So the ideal way to configure this is to set io.latency in groups A, B, and C. +Generally you do not want to set a value lower than the latency your device +supports. Experiment to find the value that works best for your workload. +Start at higher than the expected latency for your device and watch the +avg_lat value in io.stat for your workload group to get an idea of the +latency you see during normal operation. Use the avg_lat value as a basis for +your real setting, setting at 10-15% higher than the value in io.stat. + +How IO Latency Throttling Works +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +io.latency is work conserving; so as long as everybody is meeting their latency +target the controller doesn't do anything. Once a group starts missing its +target it begins throttling any peer group that has a higher target than itself. +This throttling takes 2 forms: + +- Queue depth throttling. This is the number of outstanding IO's a group is + allowed to have. We will clamp down relatively quickly, starting at no limit + and going all the way down to 1 IO at a time. + +- Artificial delay induction. There are certain types of IO that cannot be + throttled without possibly adversely affecting higher priority groups. This + includes swapping and metadata IO. These types of IO are allowed to occur + normally, however they are "charged" to the originating group. If the + originating group is being throttled you will see the use_delay and delay + fields in io.stat increase. The delay value is how many microseconds that are + being added to any process that runs in this group. Because this number can + grow quite large if there is a lot of swapping or metadata IO occurring we + limit the individual delay events to 1 second at a time. + +Once the victimized group starts meeting its latency target again it will start +unthrottling any peer groups that were throttled previously. If the victimized +group simply stops doing IO the global counter will unthrottle appropriately. + +IO Latency Interface Files +~~~~~~~~~~~~~~~~~~~~~~~~~~ + + io.latency + This takes a similar format as the other controllers. + + "MAJOR:MINOR target=<target time in microseconds>" + + io.stat + If the controller is enabled you will see extra stats in io.stat in + addition to the normal ones. + + depth + This is the current queue depth for the group. + + avg_lat + This is an exponential moving average with a decay rate of 1/exp + bound by the sampling interval. The decay rate interval can be + calculated by multiplying the win value in io.stat by the + corresponding number of samples based on the win value. + + win + The sampling window size in milliseconds. This is the minimum + duration of time between evaluation events. Windows only elapse + with IO activity. Idle periods extend the most recent window. + +IO Priority +~~~~~~~~~~~ + +A single attribute controls the behavior of the I/O priority cgroup policy, +namely the blkio.prio.class attribute. The following values are accepted for +that attribute: + + no-change + Do not modify the I/O priority class. + + promote-to-rt + For requests that have a non-RT I/O priority class, change it into RT. + Also change the priority level of these requests to 4. Do not modify + the I/O priority of requests that have priority class RT. + + restrict-to-be + For requests that do not have an I/O priority class or that have I/O + priority class RT, change it into BE. Also change the priority level + of these requests to 0. Do not modify the I/O priority class of + requests that have priority class IDLE. + + idle + Change the I/O priority class of all requests into IDLE, the lowest + I/O priority class. + + none-to-rt + Deprecated. Just an alias for promote-to-rt. + +The following numerical values are associated with the I/O priority policies: + ++----------------+---+ +| no-change | 0 | ++----------------+---+ +| rt-to-be | 2 | ++----------------+---+ +| all-to-idle | 3 | ++----------------+---+ + +The numerical value that corresponds to each I/O priority class is as follows: + ++-------------------------------+---+ +| IOPRIO_CLASS_NONE | 0 | ++-------------------------------+---+ +| IOPRIO_CLASS_RT (real-time) | 1 | ++-------------------------------+---+ +| IOPRIO_CLASS_BE (best effort) | 2 | ++-------------------------------+---+ +| IOPRIO_CLASS_IDLE | 3 | ++-------------------------------+---+ + +The algorithm to set the I/O priority class for a request is as follows: + +- If I/O priority class policy is promote-to-rt, change the request I/O + priority class to IOPRIO_CLASS_RT and change the request I/O priority + level to 4. +- If I/O priorityt class is not promote-to-rt, translate the I/O priority + class policy into a number, then change the request I/O priority class + into the maximum of the I/O priority class policy number and the numerical + I/O priority class. + +PID +--- + +The process number controller is used to allow a cgroup to stop any +new tasks from being fork()'d or clone()'d after a specified limit is +reached. + +The number of tasks in a cgroup can be exhausted in ways which other +controllers cannot prevent, thus warranting its own controller. For +example, a fork bomb is likely to exhaust the number of tasks before +hitting memory restrictions. + +Note that PIDs used in this controller refer to TIDs, process IDs as +used by the kernel. + + +PID Interface Files +~~~~~~~~~~~~~~~~~~~ + + pids.max + A read-write single value file which exists on non-root + cgroups. The default is "max". + + Hard limit of number of processes. + + pids.current + A read-only single value file which exists on all cgroups. + + The number of processes currently in the cgroup and its + descendants. + +Organisational operations are not blocked by cgroup policies, so it is +possible to have pids.current > pids.max. This can be done by either +setting the limit to be smaller than pids.current, or attaching enough +processes to the cgroup such that pids.current is larger than +pids.max. However, it is not possible to violate a cgroup PID policy +through fork() or clone(). These will return -EAGAIN if the creation +of a new process would cause a cgroup policy to be violated. + + +Cpuset +------ + +The "cpuset" controller provides a mechanism for constraining +the CPU and memory node placement of tasks to only the resources +specified in the cpuset interface files in a task's current cgroup. +This is especially valuable on large NUMA systems where placing jobs +on properly sized subsets of the systems with careful processor and +memory placement to reduce cross-node memory access and contention +can improve overall system performance. + +The "cpuset" controller is hierarchical. That means the controller +cannot use CPUs or memory nodes not allowed in its parent. + + +Cpuset Interface Files +~~~~~~~~~~~~~~~~~~~~~~ + + cpuset.cpus + A read-write multiple values file which exists on non-root + cpuset-enabled cgroups. + + It lists the requested CPUs to be used by tasks within this + cgroup. The actual list of CPUs to be granted, however, is + subjected to constraints imposed by its parent and can differ + from the requested CPUs. + + The CPU numbers are comma-separated numbers or ranges. + For example:: + + # cat cpuset.cpus + 0-4,6,8-10 + + An empty value indicates that the cgroup is using the same + setting as the nearest cgroup ancestor with a non-empty + "cpuset.cpus" or all the available CPUs if none is found. + + The value of "cpuset.cpus" stays constant until the next update + and won't be affected by any CPU hotplug events. + + cpuset.cpus.effective + A read-only multiple values file which exists on all + cpuset-enabled cgroups. + + It lists the onlined CPUs that are actually granted to this + cgroup by its parent. These CPUs are allowed to be used by + tasks within the current cgroup. + + If "cpuset.cpus" is empty, the "cpuset.cpus.effective" file shows + all the CPUs from the parent cgroup that can be available to + be used by this cgroup. Otherwise, it should be a subset of + "cpuset.cpus" unless none of the CPUs listed in "cpuset.cpus" + can be granted. In this case, it will be treated just like an + empty "cpuset.cpus". + + Its value will be affected by CPU hotplug events. + + cpuset.mems + A read-write multiple values file which exists on non-root + cpuset-enabled cgroups. + + It lists the requested memory nodes to be used by tasks within + this cgroup. The actual list of memory nodes granted, however, + is subjected to constraints imposed by its parent and can differ + from the requested memory nodes. + + The memory node numbers are comma-separated numbers or ranges. + For example:: + + # cat cpuset.mems + 0-1,3 + + An empty value indicates that the cgroup is using the same + setting as the nearest cgroup ancestor with a non-empty + "cpuset.mems" or all the available memory nodes if none + is found. + + The value of "cpuset.mems" stays constant until the next update + and won't be affected by any memory nodes hotplug events. + + Setting a non-empty value to "cpuset.mems" causes memory of + tasks within the cgroup to be migrated to the designated nodes if + they are currently using memory outside of the designated nodes. + + There is a cost for this memory migration. The migration + may not be complete and some memory pages may be left behind. + So it is recommended that "cpuset.mems" should be set properly + before spawning new tasks into the cpuset. Even if there is + a need to change "cpuset.mems" with active tasks, it shouldn't + be done frequently. + + cpuset.mems.effective + A read-only multiple values file which exists on all + cpuset-enabled cgroups. + + It lists the onlined memory nodes that are actually granted to + this cgroup by its parent. These memory nodes are allowed to + be used by tasks within the current cgroup. + + If "cpuset.mems" is empty, it shows all the memory nodes from the + parent cgroup that will be available to be used by this cgroup. + Otherwise, it should be a subset of "cpuset.mems" unless none of + the memory nodes listed in "cpuset.mems" can be granted. In this + case, it will be treated just like an empty "cpuset.mems". + + Its value will be affected by memory nodes hotplug events. + + cpuset.cpus.partition + A read-write single value file which exists on non-root + cpuset-enabled cgroups. This flag is owned by the parent cgroup + and is not delegatable. + + It accepts only the following input values when written to. + + ========== ===================================== + "member" Non-root member of a partition + "root" Partition root + "isolated" Partition root without load balancing + ========== ===================================== + + The root cgroup is always a partition root and its state + cannot be changed. All other non-root cgroups start out as + "member". + + When set to "root", the current cgroup is the root of a new + partition or scheduling domain that comprises itself and all + its descendants except those that are separate partition roots + themselves and their descendants. + + When set to "isolated", the CPUs in that partition root will + be in an isolated state without any load balancing from the + scheduler. Tasks placed in such a partition with multiple + CPUs should be carefully distributed and bound to each of the + individual CPUs for optimal performance. + + The value shown in "cpuset.cpus.effective" of a partition root + is the CPUs that the partition root can dedicate to a potential + new child partition root. The new child subtracts available + CPUs from its parent "cpuset.cpus.effective". + + A partition root ("root" or "isolated") can be in one of the + two possible states - valid or invalid. An invalid partition + root is in a degraded state where some state information may + be retained, but behaves more like a "member". + + All possible state transitions among "member", "root" and + "isolated" are allowed. + + On read, the "cpuset.cpus.partition" file can show the following + values. + + ============================= ===================================== + "member" Non-root member of a partition + "root" Partition root + "isolated" Partition root without load balancing + "root invalid (<reason>)" Invalid partition root + "isolated invalid (<reason>)" Invalid isolated partition root + ============================= ===================================== + + In the case of an invalid partition root, a descriptive string on + why the partition is invalid is included within parentheses. + + For a partition root to become valid, the following conditions + must be met. + + 1) The "cpuset.cpus" is exclusive with its siblings , i.e. they + are not shared by any of its siblings (exclusivity rule). + 2) The parent cgroup is a valid partition root. + 3) The "cpuset.cpus" is not empty and must contain at least + one of the CPUs from parent's "cpuset.cpus", i.e. they overlap. + 4) The "cpuset.cpus.effective" cannot be empty unless there is + no task associated with this partition. + + External events like hotplug or changes to "cpuset.cpus" can + cause a valid partition root to become invalid and vice versa. + Note that a task cannot be moved to a cgroup with empty + "cpuset.cpus.effective". + + For a valid partition root with the sibling cpu exclusivity + rule enabled, changes made to "cpuset.cpus" that violate the + exclusivity rule will invalidate the partition as well as its + sibling partitions with conflicting cpuset.cpus values. So + care must be taking in changing "cpuset.cpus". + + A valid non-root parent partition may distribute out all its CPUs + to its child partitions when there is no task associated with it. + + Care must be taken to change a valid partition root to + "member" as all its child partitions, if present, will become + invalid causing disruption to tasks running in those child + partitions. These inactivated partitions could be recovered if + their parent is switched back to a partition root with a proper + set of "cpuset.cpus". + + Poll and inotify events are triggered whenever the state of + "cpuset.cpus.partition" changes. That includes changes caused + by write to "cpuset.cpus.partition", cpu hotplug or other + changes that modify the validity status of the partition. + This will allow user space agents to monitor unexpected changes + to "cpuset.cpus.partition" without the need to do continuous + polling. + + +Device controller +----------------- + +Device controller manages access to device files. It includes both +creation of new device files (using mknod), and access to the +existing device files. + +Cgroup v2 device controller has no interface files and is implemented +on top of cgroup BPF. To control access to device files, a user may +create bpf programs of type BPF_PROG_TYPE_CGROUP_DEVICE and attach +them to cgroups with BPF_CGROUP_DEVICE flag. On an attempt to access a +device file, corresponding BPF programs will be executed, and depending +on the return value the attempt will succeed or fail with -EPERM. + +A BPF_PROG_TYPE_CGROUP_DEVICE program takes a pointer to the +bpf_cgroup_dev_ctx structure, which describes the device access attempt: +access type (mknod/read/write) and device (type, major and minor numbers). +If the program returns 0, the attempt fails with -EPERM, otherwise it +succeeds. + +An example of BPF_PROG_TYPE_CGROUP_DEVICE program may be found in +tools/testing/selftests/bpf/progs/dev_cgroup.c in the kernel source tree. + + +RDMA +---- + +The "rdma" controller regulates the distribution and accounting of +RDMA resources. + +RDMA Interface Files +~~~~~~~~~~~~~~~~~~~~ + + rdma.max + A readwrite nested-keyed file that exists for all the cgroups + except root that describes current configured resource limit + for a RDMA/IB device. + + Lines are keyed by device name and are not ordered. + Each line contains space separated resource name and its configured + limit that can be distributed. + + The following nested keys are defined. + + ========== ============================= + hca_handle Maximum number of HCA Handles + hca_object Maximum number of HCA Objects + ========== ============================= + + An example for mlx4 and ocrdma device follows:: + + mlx4_0 hca_handle=2 hca_object=2000 + ocrdma1 hca_handle=3 hca_object=max + + rdma.current + A read-only file that describes current resource usage. + It exists for all the cgroup except root. + + An example for mlx4 and ocrdma device follows:: + + mlx4_0 hca_handle=1 hca_object=20 + ocrdma1 hca_handle=1 hca_object=23 + +HugeTLB +------- + +The HugeTLB controller allows to limit the HugeTLB usage per control group and +enforces the controller limit during page fault. + +HugeTLB Interface Files +~~~~~~~~~~~~~~~~~~~~~~~ + + hugetlb.<hugepagesize>.current + Show current usage for "hugepagesize" hugetlb. It exists for all + the cgroup except root. + + hugetlb.<hugepagesize>.max + Set/show the hard limit of "hugepagesize" hugetlb usage. + The default value is "max". It exists for all the cgroup except root. + + hugetlb.<hugepagesize>.events + A read-only flat-keyed file which exists on non-root cgroups. + + max + The number of allocation failure due to HugeTLB limit + + hugetlb.<hugepagesize>.events.local + Similar to hugetlb.<hugepagesize>.events but the fields in the file + are local to the cgroup i.e. not hierarchical. The file modified event + generated on this file reflects only the local events. + + hugetlb.<hugepagesize>.numa_stat + Similar to memory.numa_stat, it shows the numa information of the + hugetlb pages of <hugepagesize> in this cgroup. Only active in + use hugetlb pages are included. The per-node values are in bytes. + +Misc +---- + +The Miscellaneous cgroup provides the resource limiting and tracking +mechanism for the scalar resources which cannot be abstracted like the other +cgroup resources. Controller is enabled by the CONFIG_CGROUP_MISC config +option. + +A resource can be added to the controller via enum misc_res_type{} in the +include/linux/misc_cgroup.h file and the corresponding name via misc_res_name[] +in the kernel/cgroup/misc.c file. Provider of the resource must set its +capacity prior to using the resource by calling misc_cg_set_capacity(). + +Once a capacity is set then the resource usage can be updated using charge and +uncharge APIs. All of the APIs to interact with misc controller are in +include/linux/misc_cgroup.h. + +Misc Interface Files +~~~~~~~~~~~~~~~~~~~~ + +Miscellaneous controller provides 3 interface files. If two misc resources (res_a and res_b) are registered then: + + misc.capacity + A read-only flat-keyed file shown only in the root cgroup. It shows + miscellaneous scalar resources available on the platform along with + their quantities:: + + $ cat misc.capacity + res_a 50 + res_b 10 + + misc.current + A read-only flat-keyed file shown in the all cgroups. It shows + the current usage of the resources in the cgroup and its children.:: + + $ cat misc.current + res_a 3 + res_b 0 + + misc.max + A read-write flat-keyed file shown in the non root cgroups. Allowed + maximum usage of the resources in the cgroup and its children.:: + + $ cat misc.max + res_a max + res_b 4 + + Limit can be set by:: + + # echo res_a 1 > misc.max + + Limit can be set to max by:: + + # echo res_a max > misc.max + + Limits can be set higher than the capacity value in the misc.capacity + file. + + misc.events + A read-only flat-keyed file which exists on non-root cgroups. The + following entries are defined. Unless specified otherwise, a value + change in this file generates a file modified event. All fields in + this file are hierarchical. + + max + The number of times the cgroup's resource usage was + about to go over the max boundary. + +Migration and Ownership +~~~~~~~~~~~~~~~~~~~~~~~ + +A miscellaneous scalar resource is charged to the cgroup in which it is used +first, and stays charged to that cgroup until that resource is freed. Migrating +a process to a different cgroup does not move the charge to the destination +cgroup where the process has moved. + +Others +------ + +perf_event +~~~~~~~~~~ + +perf_event controller, if not mounted on a legacy hierarchy, is +automatically enabled on the v2 hierarchy so that perf events can +always be filtered by cgroup v2 path. The controller can still be +moved to a legacy hierarchy after v2 hierarchy is populated. + + +Non-normative information +------------------------- + +This section contains information that isn't considered to be a part of +the stable kernel API and so is subject to change. + + +CPU controller root cgroup process behaviour +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +When distributing CPU cycles in the root cgroup each thread in this +cgroup is treated as if it was hosted in a separate child cgroup of the +root cgroup. This child cgroup weight is dependent on its thread nice +level. + +For details of this mapping see sched_prio_to_weight array in +kernel/sched/core.c file (values from this array should be scaled +appropriately so the neutral - nice 0 - value is 100 instead of 1024). + + +IO controller root cgroup process behaviour +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Root cgroup processes are hosted in an implicit leaf child node. +When distributing IO resources this implicit child node is taken into +account as if it was a normal child cgroup of the root cgroup with a +weight value of 200. + + +Namespace +========= + +Basics +------ + +cgroup namespace provides a mechanism to virtualize the view of the +"/proc/$PID/cgroup" file and cgroup mounts. The CLONE_NEWCGROUP clone +flag can be used with clone(2) and unshare(2) to create a new cgroup +namespace. The process running inside the cgroup namespace will have +its "/proc/$PID/cgroup" output restricted to cgroupns root. The +cgroupns root is the cgroup of the process at the time of creation of +the cgroup namespace. + +Without cgroup namespace, the "/proc/$PID/cgroup" file shows the +complete path of the cgroup of a process. In a container setup where +a set of cgroups and namespaces are intended to isolate processes the +"/proc/$PID/cgroup" file may leak potential system level information +to the isolated processes. For example:: + + # cat /proc/self/cgroup + 0::/batchjobs/container_id1 + +The path '/batchjobs/container_id1' can be considered as system-data +and undesirable to expose to the isolated processes. cgroup namespace +can be used to restrict visibility of this path. For example, before +creating a cgroup namespace, one would see:: + + # ls -l /proc/self/ns/cgroup + lrwxrwxrwx 1 root root 0 2014-07-15 10:37 /proc/self/ns/cgroup -> cgroup:[4026531835] + # cat /proc/self/cgroup + 0::/batchjobs/container_id1 + +After unsharing a new namespace, the view changes:: + + # ls -l /proc/self/ns/cgroup + lrwxrwxrwx 1 root root 0 2014-07-15 10:35 /proc/self/ns/cgroup -> cgroup:[4026532183] + # cat /proc/self/cgroup + 0::/ + +When some thread from a multi-threaded process unshares its cgroup +namespace, the new cgroupns gets applied to the entire process (all +the threads). This is natural for the v2 hierarchy; however, for the +legacy hierarchies, this may be unexpected. + +A cgroup namespace is alive as long as there are processes inside or +mounts pinning it. When the last usage goes away, the cgroup +namespace is destroyed. The cgroupns root and the actual cgroups +remain. + + +The Root and Views +------------------ + +The 'cgroupns root' for a cgroup namespace is the cgroup in which the +process calling unshare(2) is running. For example, if a process in +/batchjobs/container_id1 cgroup calls unshare, cgroup +/batchjobs/container_id1 becomes the cgroupns root. For the +init_cgroup_ns, this is the real root ('/') cgroup. + +The cgroupns root cgroup does not change even if the namespace creator +process later moves to a different cgroup:: + + # ~/unshare -c # unshare cgroupns in some cgroup + # cat /proc/self/cgroup + 0::/ + # mkdir sub_cgrp_1 + # echo 0 > sub_cgrp_1/cgroup.procs + # cat /proc/self/cgroup + 0::/sub_cgrp_1 + +Each process gets its namespace-specific view of "/proc/$PID/cgroup" + +Processes running inside the cgroup namespace will be able to see +cgroup paths (in /proc/self/cgroup) only inside their root cgroup. +From within an unshared cgroupns:: + + # sleep 100000 & + [1] 7353 + # echo 7353 > sub_cgrp_1/cgroup.procs + # cat /proc/7353/cgroup + 0::/sub_cgrp_1 + +From the initial cgroup namespace, the real cgroup path will be +visible:: + + $ cat /proc/7353/cgroup + 0::/batchjobs/container_id1/sub_cgrp_1 + +From a sibling cgroup namespace (that is, a namespace rooted at a +different cgroup), the cgroup path relative to its own cgroup +namespace root will be shown. For instance, if PID 7353's cgroup +namespace root is at '/batchjobs/container_id2', then it will see:: + + # cat /proc/7353/cgroup + 0::/../container_id2/sub_cgrp_1 + +Note that the relative path always starts with '/' to indicate that +its relative to the cgroup namespace root of the caller. + + +Migration and setns(2) +---------------------- + +Processes inside a cgroup namespace can move into and out of the +namespace root if they have proper access to external cgroups. For +example, from inside a namespace with cgroupns root at +/batchjobs/container_id1, and assuming that the global hierarchy is +still accessible inside cgroupns:: + + # cat /proc/7353/cgroup + 0::/sub_cgrp_1 + # echo 7353 > batchjobs/container_id2/cgroup.procs + # cat /proc/7353/cgroup + 0::/../container_id2 + +Note that this kind of setup is not encouraged. A task inside cgroup +namespace should only be exposed to its own cgroupns hierarchy. + +setns(2) to another cgroup namespace is allowed when: + +(a) the process has CAP_SYS_ADMIN against its current user namespace +(b) the process has CAP_SYS_ADMIN against the target cgroup + namespace's userns + +No implicit cgroup changes happen with attaching to another cgroup +namespace. It is expected that the someone moves the attaching +process under the target cgroup namespace root. + + +Interaction with Other Namespaces +--------------------------------- + +Namespace specific cgroup hierarchy can be mounted by a process +running inside a non-init cgroup namespace:: + + # mount -t cgroup2 none $MOUNT_POINT + +This will mount the unified cgroup hierarchy with cgroupns root as the +filesystem root. The process needs CAP_SYS_ADMIN against its user and +mount namespaces. + +The virtualization of /proc/self/cgroup file combined with restricting +the view of cgroup hierarchy by namespace-private cgroupfs mount +provides a properly isolated cgroup view inside the container. + + +Information on Kernel Programming +================================= + +This section contains kernel programming information in the areas +where interacting with cgroup is necessary. cgroup core and +controllers are not covered. + + +Filesystem Support for Writeback +-------------------------------- + +A filesystem can support cgroup writeback by updating +address_space_operations->writepage[s]() to annotate bio's using the +following two functions. + + wbc_init_bio(@wbc, @bio) + Should be called for each bio carrying writeback data and + associates the bio with the inode's owner cgroup and the + corresponding request queue. This must be called after + a queue (device) has been associated with the bio and + before submission. + + wbc_account_cgroup_owner(@wbc, @page, @bytes) + Should be called for each data segment being written out. + While this function doesn't care exactly when it's called + during the writeback session, it's the easiest and most + natural to call it as data segments are added to a bio. + +With writeback bio's annotated, cgroup support can be enabled per +super_block by setting SB_I_CGROUPWB in ->s_iflags. This allows for +selective disabling of cgroup writeback support which is helpful when +certain filesystem features, e.g. journaled data mode, are +incompatible. + +wbc_init_bio() binds the specified bio to its cgroup. Depending on +the configuration, the bio may be executed at a lower priority and if +the writeback session is holding shared resources, e.g. a journal +entry, may lead to priority inversion. There is no one easy solution +for the problem. Filesystems can try to work around specific problem +cases by skipping wbc_init_bio() and using bio_associate_blkg() +directly. + + +Deprecated v1 Core Features +=========================== + +- Multiple hierarchies including named ones are not supported. + +- All v1 mount options are not supported. + +- The "tasks" file is removed and "cgroup.procs" is not sorted. + +- "cgroup.clone_children" is removed. + +- /proc/cgroups is meaningless for v2. Use "cgroup.controllers" file + at the root instead. + + +Issues with v1 and Rationales for v2 +==================================== + +Multiple Hierarchies +-------------------- + +cgroup v1 allowed an arbitrary number of hierarchies and each +hierarchy could host any number of controllers. While this seemed to +provide a high level of flexibility, it wasn't useful in practice. + +For example, as there is only one instance of each controller, utility +type controllers such as freezer which can be useful in all +hierarchies could only be used in one. The issue is exacerbated by +the fact that controllers couldn't be moved to another hierarchy once +hierarchies were populated. Another issue was that all controllers +bound to a hierarchy were forced to have exactly the same view of the +hierarchy. It wasn't possible to vary the granularity depending on +the specific controller. + +In practice, these issues heavily limited which controllers could be +put on the same hierarchy and most configurations resorted to putting +each controller on its own hierarchy. Only closely related ones, such +as the cpu and cpuacct controllers, made sense to be put on the same +hierarchy. This often meant that userland ended up managing multiple +similar hierarchies repeating the same steps on each hierarchy +whenever a hierarchy management operation was necessary. + +Furthermore, support for multiple hierarchies came at a steep cost. +It greatly complicated cgroup core implementation but more importantly +the support for multiple hierarchies restricted how cgroup could be +used in general and what controllers was able to do. + +There was no limit on how many hierarchies there might be, which meant +that a thread's cgroup membership couldn't be described in finite +length. The key might contain any number of entries and was unlimited +in length, which made it highly awkward to manipulate and led to +addition of controllers which existed only to identify membership, +which in turn exacerbated the original problem of proliferating number +of hierarchies. + +Also, as a controller couldn't have any expectation regarding the +topologies of hierarchies other controllers might be on, each +controller had to assume that all other controllers were attached to +completely orthogonal hierarchies. This made it impossible, or at +least very cumbersome, for controllers to cooperate with each other. + +In most use cases, putting controllers on hierarchies which are +completely orthogonal to each other isn't necessary. What usually is +called for is the ability to have differing levels of granularity +depending on the specific controller. In other words, hierarchy may +be collapsed from leaf towards root when viewed from specific +controllers. For example, a given configuration might not care about +how memory is distributed beyond a certain level while still wanting +to control how CPU cycles are distributed. + + +Thread Granularity +------------------ + +cgroup v1 allowed threads of a process to belong to different cgroups. +This didn't make sense for some controllers and those controllers +ended up implementing different ways to ignore such situations but +much more importantly it blurred the line between API exposed to +individual applications and system management interface. + +Generally, in-process knowledge is available only to the process +itself; thus, unlike service-level organization of processes, +categorizing threads of a process requires active participation from +the application which owns the target process. + +cgroup v1 had an ambiguously defined delegation model which got abused +in combination with thread granularity. cgroups were delegated to +individual applications so that they can create and manage their own +sub-hierarchies and control resource distributions along them. This +effectively raised cgroup to the status of a syscall-like API exposed +to lay programs. + +First of all, cgroup has a fundamentally inadequate interface to be +exposed this way. For a process to access its own knobs, it has to +extract the path on the target hierarchy from /proc/self/cgroup, +construct the path by appending the name of the knob to the path, open +and then read and/or write to it. This is not only extremely clunky +and unusual but also inherently racy. There is no conventional way to +define transaction across the required steps and nothing can guarantee +that the process would actually be operating on its own sub-hierarchy. + +cgroup controllers implemented a number of knobs which would never be +accepted as public APIs because they were just adding control knobs to +system-management pseudo filesystem. cgroup ended up with interface +knobs which were not properly abstracted or refined and directly +revealed kernel internal details. These knobs got exposed to +individual applications through the ill-defined delegation mechanism +effectively abusing cgroup as a shortcut to implementing public APIs +without going through the required scrutiny. + +This was painful for both userland and kernel. Userland ended up with +misbehaving and poorly abstracted interfaces and kernel exposing and +locked into constructs inadvertently. + + +Competition Between Inner Nodes and Threads +------------------------------------------- + +cgroup v1 allowed threads to be in any cgroups which created an +interesting problem where threads belonging to a parent cgroup and its +children cgroups competed for resources. This was nasty as two +different types of entities competed and there was no obvious way to +settle it. Different controllers did different things. + +The cpu controller considered threads and cgroups as equivalents and +mapped nice levels to cgroup weights. This worked for some cases but +fell flat when children wanted to be allocated specific ratios of CPU +cycles and the number of internal threads fluctuated - the ratios +constantly changed as the number of competing entities fluctuated. +There also were other issues. The mapping from nice level to weight +wasn't obvious or universal, and there were various other knobs which +simply weren't available for threads. + +The io controller implicitly created a hidden leaf node for each +cgroup to host the threads. The hidden leaf had its own copies of all +the knobs with ``leaf_`` prefixed. While this allowed equivalent +control over internal threads, it was with serious drawbacks. It +always added an extra layer of nesting which wouldn't be necessary +otherwise, made the interface messy and significantly complicated the +implementation. + +The memory controller didn't have a way to control what happened +between internal tasks and child cgroups and the behavior was not +clearly defined. There were attempts to add ad-hoc behaviors and +knobs to tailor the behavior to specific workloads which would have +led to problems extremely difficult to resolve in the long term. + +Multiple controllers struggled with internal tasks and came up with +different ways to deal with it; unfortunately, all the approaches were +severely flawed and, furthermore, the widely different behaviors +made cgroup as a whole highly inconsistent. + +This clearly is a problem which needs to be addressed from cgroup core +in a uniform way. + + +Other Interface Issues +---------------------- + +cgroup v1 grew without oversight and developed a large number of +idiosyncrasies and inconsistencies. One issue on the cgroup core side +was how an empty cgroup was notified - a userland helper binary was +forked and executed for each event. The event delivery wasn't +recursive or delegatable. The limitations of the mechanism also led +to in-kernel event delivery filtering mechanism further complicating +the interface. + +Controller interfaces were problematic too. An extreme example is +controllers completely ignoring hierarchical organization and treating +all cgroups as if they were all located directly under the root +cgroup. Some controllers exposed a large amount of inconsistent +implementation details to userland. + +There also was no consistency across controllers. When a new cgroup +was created, some controllers defaulted to not imposing extra +restrictions while others disallowed any resource usage until +explicitly configured. Configuration knobs for the same type of +control used widely differing naming schemes and formats. Statistics +and information knobs were named arbitrarily and used different +formats and units even in the same controller. + +cgroup v2 establishes common conventions where appropriate and updates +controllers so that they expose minimal and consistent interfaces. + + +Controller Issues and Remedies +------------------------------ + +Memory +~~~~~~ + +The original lower boundary, the soft limit, is defined as a limit +that is per default unset. As a result, the set of cgroups that +global reclaim prefers is opt-in, rather than opt-out. The costs for +optimizing these mostly negative lookups are so high that the +implementation, despite its enormous size, does not even provide the +basic desirable behavior. First off, the soft limit has no +hierarchical meaning. All configured groups are organized in a global +rbtree and treated like equal peers, regardless where they are located +in the hierarchy. This makes subtree delegation impossible. Second, +the soft limit reclaim pass is so aggressive that it not just +introduces high allocation latencies into the system, but also impacts +system performance due to overreclaim, to the point where the feature +becomes self-defeating. + +The memory.low boundary on the other hand is a top-down allocated +reserve. A cgroup enjoys reclaim protection when it's within its +effective low, which makes delegation of subtrees possible. It also +enjoys having reclaim pressure proportional to its overage when +above its effective low. + +The original high boundary, the hard limit, is defined as a strict +limit that can not budge, even if the OOM killer has to be called. +But this generally goes against the goal of making the most out of the +available memory. The memory consumption of workloads varies during +runtime, and that requires users to overcommit. But doing that with a +strict upper limit requires either a fairly accurate prediction of the +working set size or adding slack to the limit. Since working set size +estimation is hard and error prone, and getting it wrong results in +OOM kills, most users tend to err on the side of a looser limit and +end up wasting precious resources. + +The memory.high boundary on the other hand can be set much more +conservatively. When hit, it throttles allocations by forcing them +into direct reclaim to work off the excess, but it never invokes the +OOM killer. As a result, a high boundary that is chosen too +aggressively will not terminate the processes, but instead it will +lead to gradual performance degradation. The user can monitor this +and make corrections until the minimal memory footprint that still +gives acceptable performance is found. + +In extreme cases, with many concurrent allocations and a complete +breakdown of reclaim progress within the group, the high boundary can +be exceeded. But even then it's mostly better to satisfy the +allocation from the slack available in other groups or the rest of the +system than killing the group. Otherwise, memory.max is there to +limit this type of spillover and ultimately contain buggy or even +malicious applications. + +Setting the original memory.limit_in_bytes below the current usage was +subject to a race condition, where concurrent charges could cause the +limit setting to fail. memory.max on the other hand will first set the +limit to prevent new charges, and then reclaim and OOM kill until the +new limit is met - or the task writing to memory.max is killed. + +The combined memory+swap accounting and limiting is replaced by real +control over swap space. + +The main argument for a combined memory+swap facility in the original +cgroup design was that global or parental pressure would always be +able to swap all anonymous memory of a child group, regardless of the +child's own (possibly untrusted) configuration. However, untrusted +groups can sabotage swapping by other means - such as referencing its +anonymous memory in a tight loop - and an admin can not assume full +swappability when overcommitting untrusted jobs. + +For trusted jobs, on the other hand, a combined counter is not an +intuitive userspace interface, and it flies in the face of the idea +that cgroup controllers should account and limit specific physical +resources. Swap space is a resource like all others in the system, +and that's why unified hierarchy allows distributing it separately. diff --git a/Documentation/admin-guide/cifs/authors.rst b/Documentation/admin-guide/cifs/authors.rst new file mode 100644 index 000000000..5c1d2f0fa --- /dev/null +++ b/Documentation/admin-guide/cifs/authors.rst @@ -0,0 +1,69 @@ +======= +Authors +======= + +Original Author +--------------- + +Steve French (smfrench@gmail.com, sfrench@samba.org) + +The author wishes to express his appreciation and thanks to: +Andrew Tridgell (Samba team) for his early suggestions about SMB/CIFS VFS +improvements. Thanks to IBM for allowing me time and test resources to pursue +this project, to Jim McDonough from IBM (and the Samba Team) for his help, to +the IBM Linux JFS team for explaining many esoteric Linux filesystem features. +Jeremy Allison of the Samba team has done invaluable work in adding the server +side of the original CIFS Unix extensions and reviewing and implementing +portions of the newer CIFS POSIX extensions into the Samba 3 file server. Thank +Dave Boutcher of IBM Rochester (author of the OS/400 smb/cifs filesystem client) +for proving years ago that very good smb/cifs clients could be done on Unix-like +operating systems. Volker Lendecke, Andrew Tridgell, Urban Widmark, John +Newbigin and others for their work on the Linux smbfs module. Thanks to +the other members of the Storage Network Industry Association CIFS Technical +Workgroup for their work specifying this highly complex protocol and finally +thanks to the Samba team for their technical advice and encouragement. + +Patch Contributors +------------------ + +- Zwane Mwaikambo +- Andi Kleen +- Amrut Joshi +- Shobhit Dayal +- Sergey Vlasov +- Richard Hughes +- Yury Umanets +- Mark Hamzy (for some of the early cifs IPv6 work) +- Domen Puncer +- Jesper Juhl (in particular for lots of whitespace/formatting cleanup) +- Vince Negri and Dave Stahl (for finding an important caching bug) +- Adrian Bunk (kcalloc cleanups) +- Miklos Szeredi +- Kazeon team for various fixes especially for 2.4 version. +- Asser Ferno (Change Notify support) +- Shaggy (Dave Kleikamp) for innumerable small fs suggestions and some good cleanup +- Gunter Kukkukk (testing and suggestions for support of old servers) +- Igor Mammedov (DFS support) +- Jeff Layton (many, many fixes, as well as great work on the cifs Kerberos code) +- Scott Lovenberg +- Pavel Shilovsky (for great work adding SMB2 support, and various SMB3 features) +- Aurelien Aptel (for DFS SMB3 work and some key bug fixes) +- Ronnie Sahlberg (for SMB3 xattr work, bug fixes, and lots of great work on compounding) +- Shirish Pargaonkar (for many ACL patches over the years) +- Sachin Prabhu (many bug fixes, including for reconnect, copy offload and security) +- Paulo Alcantara (for some excellent work in DFS, and in booting from SMB3) +- Long Li (some great work on RDMA, SMB Direct) + + +Test case and Bug Report contributors +------------------------------------- +Thanks to those in the community who have submitted detailed bug reports +and debug of problems they have found: Jochen Dolze, David Blaine, +Rene Scharfe, Martin Josefsson, Alexander Wild, Anthony Liguori, +Lars Muller, Urban Widmark, Massimiliano Ferrero, Howard Owen, +Olaf Kirch, Kieron Briggs, Nick Millington and others. Also special +mention to the Stanford Checker (SWAT) which pointed out many minor +bugs in error paths. Valuable suggestions also have come from Al Viro +and Dave Miller. + +And thanks to the IBM LTC and Power test teams and SuSE and Citrix and RedHat testers for finding multiple bugs during excellent stress test runs. diff --git a/Documentation/admin-guide/cifs/changes.rst b/Documentation/admin-guide/cifs/changes.rst new file mode 100644 index 000000000..8c42c4de5 --- /dev/null +++ b/Documentation/admin-guide/cifs/changes.rst @@ -0,0 +1,9 @@ +======= +Changes +======= + +See https://wiki.samba.org/index.php/LinuxCIFSKernel for summary +information about fixes/improvements to CIFS/SMB2/SMB3 support (changes +to cifs.ko module) by kernel version (and cifs internal module version). +This may be easier to read than parsing the output of +"git log fs/smb/client" by release. diff --git a/Documentation/admin-guide/cifs/index.rst b/Documentation/admin-guide/cifs/index.rst new file mode 100644 index 000000000..fad526863 --- /dev/null +++ b/Documentation/admin-guide/cifs/index.rst @@ -0,0 +1,21 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==== +CIFS +==== + +.. toctree:: + :maxdepth: 2 + + introduction + usage + todo + changes + authors + +.. only:: subproject and html + + Indices + ======= + + * :ref:`genindex` diff --git a/Documentation/admin-guide/cifs/introduction.rst b/Documentation/admin-guide/cifs/introduction.rst new file mode 100644 index 000000000..53ea62906 --- /dev/null +++ b/Documentation/admin-guide/cifs/introduction.rst @@ -0,0 +1,53 @@ +============ +Introduction +============ + + This is the client VFS module for the SMB3 NAS protocol as well + as for older dialects such as the Common Internet File System (CIFS) + protocol which was the successor to the Server Message Block + (SMB) protocol, the native file sharing mechanism for most early + PC operating systems. New and improved versions of CIFS are now + called SMB2 and SMB3. Use of SMB3 (and later, including SMB3.1.1 + the most current dialect) is strongly preferred over using older + dialects like CIFS due to security reasons. All modern dialects, + including the most recent, SMB3.1.1, are supported by the CIFS VFS + module. The SMB3 protocol is implemented and supported by all major + file servers such as Windows (including Windows 2019 Server), as + well as by Samba (which provides excellent CIFS/SMB2/SMB3 server + support and tools for Linux and many other operating systems). + Apple systems also support SMB3 well, as do most Network Attached + Storage vendors, so this network filesystem client can mount to a + wide variety of systems. It also supports mounting to the cloud + (for example Microsoft Azure), including the necessary security + features. + + The intent of this module is to provide the most advanced network + file system function for SMB3 compliant servers, including advanced + security features, excellent parallelized high performance i/o, better + POSIX compliance, secure per-user session establishment, encryption, + high performance safe distributed caching (leases/oplocks), optional packet + signing, large files, Unicode support and other internationalization + improvements. Since both Samba server and this filesystem client support the + CIFS Unix extensions, and the Linux client also suppors SMB3 POSIX extensions, + the combination can provide a reasonable alternative to other network and + cluster file systems for fileserving in some Linux to Linux environments, + not just in Linux to Windows (or Linux to Mac) environments. + + This filesystem has a mount utility (mount.cifs) and various user space + tools (including smbinfo and setcifsacl) that can be obtained from + + https://git.samba.org/?p=cifs-utils.git + + or + + git://git.samba.org/cifs-utils.git + + mount.cifs should be installed in the directory with the other mount helpers. + + For more information on the module see the project wiki page at + + https://wiki.samba.org/index.php/LinuxCIFS + + and + + https://wiki.samba.org/index.php/LinuxCIFS_utils diff --git a/Documentation/admin-guide/cifs/todo.rst b/Documentation/admin-guide/cifs/todo.rst new file mode 100644 index 000000000..2646ed2e2 --- /dev/null +++ b/Documentation/admin-guide/cifs/todo.rst @@ -0,0 +1,135 @@ +==== +TODO +==== + +Version 2.14 December 21, 2018 + +A Partial List of Missing Features +================================== + +Contributions are welcome. There are plenty of opportunities +for visible, important contributions to this module. Here +is a partial list of the known problems and missing features: + +a) SMB3 (and SMB3.1.1) missing optional features: + + - multichannel (partially integrated), integration of multichannel with RDMA + - directory leases (improved metadata caching). Currently only implemented for root dir + - T10 copy offload ie "ODX" (copy chunk, and "Duplicate Extents" ioctl + currently the only two server side copy mechanisms supported) + +b) improved sparse file support (fiemap and SEEK_HOLE are implemented + but additional features would be supportable by the protocol such + as FALLOC_FL_COLLAPSE_RANGE and FALLOC_FL_INSERT_RANGE) + +c) Directory entry caching relies on a 1 second timer, rather than + using Directory Leases, currently only the root file handle is cached longer + by leveraging Directory Leases + +d) quota support (needs minor kernel change since quota calls otherwise + won't make it to network filesystems or deviceless filesystems). + +e) Additional use cases can be optimized to use "compounding" (e.g. + open/query/close and open/setinfo/close) to reduce the number of + roundtrips to the server and improve performance. Various cases + (stat, statfs, create, unlink, mkdir, xattrs) already have been improved by + using compounding but more can be done. In addition we could + significantly reduce redundant opens by using deferred close (with + handle caching leases) and better using reference counters on file + handles. + +f) Finish inotify support so kde and gnome file list windows + will autorefresh (partially complete by Asser). Needs minor kernel + vfs change to support removing D_NOTIFY on a file. + +g) Add GUI tool to configure /proc/fs/cifs settings and for display of + the CIFS statistics (started) + +h) implement support for security and trusted categories of xattrs + (requires minor protocol extension) to enable better support for SELINUX + +i) Add support for tree connect contexts (see MS-SMB2) a new SMB3.1.1 protocol + feature (may be especially useful for virtualization). + +j) Create UID mapping facility so server UIDs can be mapped on a per + mount or a per server basis to client UIDs or nobody if no mapping + exists. Also better integration with winbind for resolving SID owners + +k) Add tools to take advantage of more smb3 specific ioctls and features + (passthrough ioctl/fsctl is now implemented in cifs.ko to allow + sending various SMB3 fsctls and query info and set info calls + directly from user space) Add tools to make setting various non-POSIX + metadata attributes easier from tools (e.g. extending what was done + in smb-info tool). + +l) encrypted file support (currently the attribute showing the file is + encrypted on the server is reported, but changing the attribute is not + supported). + +m) improved stats gathering tools (perhaps integration with nfsometer?) + to extend and make easier to use what is currently in /proc/fs/cifs/Stats + +n) Add support for claims based ACLs ("DAC") + +o) mount helper GUI (to simplify the various configuration options on mount) + +p) Expand support for witness protocol to allow for notification of share + move, and server network adapter changes. Currently only notifications by + the witness protocol for server move is supported by the Linux client. + +q) Allow mount.cifs to be more verbose in reporting errors with dialect + or unsupported feature errors. This would now be easier due to the + implementation of the new mount API. + +r) updating cifs documentation, and user guide. + +s) Addressing bugs found by running a broader set of xfstests in standard + file system xfstest suite. + +t) split cifs and smb3 support into separate modules so legacy (and less + secure) CIFS dialect can be disabled in environments that don't need it + and simplify the code. + +v) Additional testing of POSIX Extensions for SMB3.1.1 + +w) Add support for additional strong encryption types, and additional spnego + authentication mechanisms (see MS-SMB2). GCM-256 is now partially implemented. + +x) Finish support for SMB3.1.1 compression + +Known Bugs +========== + +See https://bugzilla.samba.org - search on product "CifsVFS" for +current bug list. Also check http://bugzilla.kernel.org (Product = File System, Component = CIFS) + +1) existing symbolic links (Windows reparse points) are recognized but + can not be created remotely. They are implemented for Samba and those that + support the CIFS Unix extensions, although earlier versions of Samba + overly restrict the pathnames. +2) follow_link and readdir code does not follow dfs junctions + but recognizes them + +Misc testing to do +================== +1) check out max path names and max path name components against various server + types. Try nested symlinks (8 deep). Return max path name in stat -f information + +2) Improve xfstest's cifs/smb3 enablement and adapt xfstests where needed to test + cifs/smb3 better + +3) Additional performance testing and optimization using iozone and similar - + there are some easy changes that can be done to parallelize sequential writes, + and when signing is disabled to request larger read sizes (larger than + negotiated size) and send larger write sizes to modern servers. + +4) More exhaustively test against less common servers + +5) Continue to extend the smb3 "buildbot" which does automated xfstesting + against Windows, Samba and Azure currently - to add additional tests and + to allow the buildbot to execute the tests faster. The URL for the + buildbot is: http://smb3-test-rhel-75.southcentralus.cloudapp.azure.com + +6) Address various coverity warnings (most are not bugs per-se, but + the more warnings are addressed, the easier it is to spot real + problems that static analyzers will point out in the future). diff --git a/Documentation/admin-guide/cifs/usage.rst b/Documentation/admin-guide/cifs/usage.rst new file mode 100644 index 000000000..5f936b4b6 --- /dev/null +++ b/Documentation/admin-guide/cifs/usage.rst @@ -0,0 +1,870 @@ +===== +Usage +===== + +This module supports the SMB3 family of advanced network protocols (as well +as older dialects, originally called "CIFS" or SMB1). + +The CIFS VFS module for Linux supports many advanced network filesystem +features such as hierarchical DFS like namespace, hardlinks, locking and more. +It was designed to comply with the SNIA CIFS Technical Reference (which +supersedes the 1992 X/Open SMB Standard) as well as to perform best practice +practical interoperability with Windows 2000, Windows XP, Samba and equivalent +servers. This code was developed in participation with the Protocol Freedom +Information Foundation. CIFS and now SMB3 has now become a defacto +standard for interoperating between Macs and Windows and major NAS appliances. + +Please see +MS-SMB2 (for detailed SMB2/SMB3/SMB3.1.1 protocol specification) +or https://samba.org/samba/PFIF/ +for more details. + + +For questions or bug reports please contact: + + smfrench@gmail.com + +See the project page at: https://wiki.samba.org/index.php/LinuxCIFS_utils + +Build instructions +================== + +For Linux: + +1) Download the kernel (e.g. from https://www.kernel.org) + and change directory into the top of the kernel directory tree + (e.g. /usr/src/linux-2.5.73) +2) make menuconfig (or make xconfig) +3) select cifs from within the network filesystem choices +4) save and exit +5) make + + +Installation instructions +========================= + +If you have built the CIFS vfs as module (successfully) simply +type ``make modules_install`` (or if you prefer, manually copy the file to +the modules directory e.g. /lib/modules/6.3.0-060300-generic/kernel/fs/smb/client/cifs.ko). + +If you have built the CIFS vfs into the kernel itself, follow the instructions +for your distribution on how to install a new kernel (usually you +would simply type ``make install``). + +If you do not have the utility mount.cifs (in the Samba 4.x source tree and on +the CIFS VFS web site) copy it to the same directory in which mount helpers +reside (usually /sbin). Although the helper software is not +required, mount.cifs is recommended. Most distros include a ``cifs-utils`` +package that includes this utility so it is recommended to install this. + +Note that running the Winbind pam/nss module (logon service) on all of your +Linux clients is useful in mapping Uids and Gids consistently across the +domain to the proper network user. The mount.cifs mount helper can be +found at cifs-utils.git on git.samba.org + +If cifs is built as a module, then the size and number of network buffers +and maximum number of simultaneous requests to one server can be configured. +Changing these from their defaults is not recommended. By executing modinfo:: + + modinfo <path to cifs.ko> + +on kernel/fs/smb/client/cifs.ko the list of configuration changes that can be made +at module initialization time (by running insmod cifs.ko) can be seen. + +Recommendations +=============== + +To improve security the SMB2.1 dialect or later (usually will get SMB3.1.1) is now +the new default. To use old dialects (e.g. to mount Windows XP) use "vers=1.0" +on mount (or vers=2.0 for Windows Vista). Note that the CIFS (vers=1.0) is +much older and less secure than the default dialect SMB3 which includes +many advanced security features such as downgrade attack detection +and encrypted shares and stronger signing and authentication algorithms. +There are additional mount options that may be helpful for SMB3 to get +improved POSIX behavior (NB: can use vers=3.0 to force only SMB3, never 2.1): + + ``mfsymlinks`` and either ``cifsacl`` or ``modefromsid`` (usually with ``idsfromsid``) + +Allowing User Mounts +==================== + +To permit users to mount and unmount over directories they own is possible +with the cifs vfs. A way to enable such mounting is to mark the mount.cifs +utility as suid (e.g. ``chmod +s /sbin/mount.cifs``). To enable users to +umount shares they mount requires + +1) mount.cifs version 1.4 or later +2) an entry for the share in /etc/fstab indicating that a user may + unmount it e.g.:: + + //server/usersharename /mnt/username cifs user 0 0 + +Note that when the mount.cifs utility is run suid (allowing user mounts), +in order to reduce risks, the ``nosuid`` mount flag is passed in on mount to +disallow execution of an suid program mounted on the remote target. +When mount is executed as root, nosuid is not passed in by default, +and execution of suid programs on the remote target would be enabled +by default. This can be changed, as with nfs and other filesystems, +by simply specifying ``nosuid`` among the mount options. For user mounts +though to be able to pass the suid flag to mount requires rebuilding +mount.cifs with the following flag: CIFS_ALLOW_USR_SUID + +There is a corresponding manual page for cifs mounting in the Samba 3.0 and +later source tree in docs/manpages/mount.cifs.8 + +Allowing User Unmounts +====================== + +To permit users to unmount directories that they have user mounted (see above), +the utility umount.cifs may be used. It may be invoked directly, or if +umount.cifs is placed in /sbin, umount can invoke the cifs umount helper +(at least for most versions of the umount utility) for umount of cifs +mounts, unless umount is invoked with -i (which will avoid invoking a umount +helper). As with mount.cifs, to enable user unmounts umount.cifs must be marked +as suid (e.g. ``chmod +s /sbin/umount.cifs``) or equivalent (some distributions +allow adding entries to a file to the /etc/permissions file to achieve the +equivalent suid effect). For this utility to succeed the target path +must be a cifs mount, and the uid of the current user must match the uid +of the user who mounted the resource. + +Also note that the customary way of allowing user mounts and unmounts is +(instead of using mount.cifs and unmount.cifs as suid) to add a line +to the file /etc/fstab for each //server/share you wish to mount, but +this can become unwieldy when potential mount targets include many +or unpredictable UNC names. + +Samba Considerations +==================== + +Most current servers support SMB2.1 and SMB3 which are more secure, +but there are useful protocol extensions for the older less secure CIFS +dialect, so to get the maximum benefit if mounting using the older dialect +(CIFS/SMB1), we recommend using a server that supports the SNIA CIFS +Unix Extensions standard (e.g. almost any version of Samba ie version +2.2.5 or later) but the CIFS vfs works fine with a wide variety of CIFS servers. +Note that uid, gid and file permissions will display default values if you do +not have a server that supports the Unix extensions for CIFS (such as Samba +2.2.5 or later). To enable the Unix CIFS Extensions in the Samba server, add +the line:: + + unix extensions = yes + +to your smb.conf file on the server. Note that the following smb.conf settings +are also useful (on the Samba server) when the majority of clients are Unix or +Linux:: + + case sensitive = yes + delete readonly = yes + ea support = yes + +Note that server ea support is required for supporting xattrs from the Linux +cifs client, and that EA support is present in later versions of Samba (e.g. +3.0.6 and later (also EA support works in all versions of Windows, at least to +shares on NTFS filesystems). Extended Attribute (xattr) support is an optional +feature of most Linux filesystems which may require enabling via +make menuconfig. Client support for extended attributes (user xattr) can be +disabled on a per-mount basis by specifying ``nouser_xattr`` on mount. + +The CIFS client can get and set POSIX ACLs (getfacl, setfacl) to Samba servers +version 3.10 and later. Setting POSIX ACLs requires enabling both XATTR and +then POSIX support in the CIFS configuration options when building the cifs +module. POSIX ACL support can be disabled on a per mount basic by specifying +``noacl`` on mount. + +Some administrators may want to change Samba's smb.conf ``map archive`` and +``create mask`` parameters from the default. Unless the create mask is changed +newly created files can end up with an unnecessarily restrictive default mode, +which may not be what you want, although if the CIFS Unix extensions are +enabled on the server and client, subsequent setattr calls (e.g. chmod) can +fix the mode. Note that creating special devices (mknod) remotely +may require specifying a mkdev function to Samba if you are not using +Samba 3.0.6 or later. For more information on these see the manual pages +(``man smb.conf``) on the Samba server system. Note that the cifs vfs, +unlike the smbfs vfs, does not read the smb.conf on the client system +(the few optional settings are passed in on mount via -o parameters instead). +Note that Samba 2.2.7 or later includes a fix that allows the CIFS VFS to delete +open files (required for strict POSIX compliance). Windows Servers already +supported this feature. Samba server does not allow symlinks that refer to files +outside of the share, so in Samba versions prior to 3.0.6, most symlinks to +files with absolute paths (ie beginning with slash) such as:: + + ln -s /mnt/foo bar + +would be forbidden. Samba 3.0.6 server or later includes the ability to create +such symlinks safely by converting unsafe symlinks (ie symlinks to server +files that are outside of the share) to a samba specific format on the server +that is ignored by local server applications and non-cifs clients and that will +not be traversed by the Samba server). This is opaque to the Linux client +application using the cifs vfs. Absolute symlinks will work to Samba 3.0.5 or +later, but only for remote clients using the CIFS Unix extensions, and will +be invisible to Windows clients and typically will not affect local +applications running on the same server as Samba. + +Use instructions +================ + +Once the CIFS VFS support is built into the kernel or installed as a module +(cifs.ko), you can use mount syntax like the following to access Samba or +Mac or Windows servers:: + + mount -t cifs //9.53.216.11/e$ /mnt -o username=myname,password=mypassword + +Before -o the option -v may be specified to make the mount.cifs +mount helper display the mount steps more verbosely. +After -o the following commonly used cifs vfs specific options +are supported:: + + username=<username> + password=<password> + domain=<domain name> + +Other cifs mount options are described below. Use of TCP names (in addition to +ip addresses) is available if the mount helper (mount.cifs) is installed. If +you do not trust the server to which are mounted, or if you do not have +cifs signing enabled (and the physical network is insecure), consider use +of the standard mount options ``noexec`` and ``nosuid`` to reduce the risk of +running an altered binary on your local system (downloaded from a hostile server +or altered by a hostile router). + +Although mounting using format corresponding to the CIFS URL specification is +not possible in mount.cifs yet, it is possible to use an alternate format +for the server and sharename (which is somewhat similar to NFS style mount +syntax) instead of the more widely used UNC format (i.e. \\server\share):: + + mount -t cifs tcp_name_of_server:share_name /mnt -o user=myname,pass=mypasswd + +When using the mount helper mount.cifs, passwords may be specified via alternate +mechanisms, instead of specifying it after -o using the normal ``pass=`` syntax +on the command line: +1) By including it in a credential file. Specify credentials=filename as one +of the mount options. Credential files contain two lines:: + + username=someuser + password=your_password + +2) By specifying the password in the PASSWD environment variable (similarly + the user name can be taken from the USER environment variable). +3) By specifying the password in a file by name via PASSWD_FILE +4) By specifying the password in a file by file descriptor via PASSWD_FD + +If no password is provided, mount.cifs will prompt for password entry + +Restrictions +============ + +Servers must support either "pure-TCP" (port 445 TCP/IP CIFS connections) or RFC +1001/1002 support for "Netbios-Over-TCP/IP." This is not likely to be a +problem as most servers support this. + +Valid filenames differ between Windows and Linux. Windows typically restricts +filenames which contain certain reserved characters (e.g.the character : +which is used to delimit the beginning of a stream name by Windows), while +Linux allows a slightly wider set of valid characters in filenames. Windows +servers can remap such characters when an explicit mapping is specified in +the Server's registry. Samba starting with version 3.10 will allow such +filenames (ie those which contain valid Linux characters, which normally +would be forbidden for Windows/CIFS semantics) as long as the server is +configured for Unix Extensions (and the client has not disabled +/proc/fs/cifs/LinuxExtensionsEnabled). In addition the mount option +``mapposix`` can be used on CIFS (vers=1.0) to force the mapping of +illegal Windows/NTFS/SMB characters to a remap range (this mount parameter +is the default for SMB3). This remap (``mapposix``) range is also +compatible with Mac (and "Services for Mac" on some older Windows). + +CIFS VFS Mount Options +====================== +A partial list of the supported mount options follows: + + username + The user name to use when trying to establish + the CIFS session. + password + The user password. If the mount helper is + installed, the user will be prompted for password + if not supplied. + ip + The ip address of the target server + unc + The target server Universal Network Name (export) to + mount. + domain + Set the SMB/CIFS workgroup name prepended to the + username during CIFS session establishment + forceuid + Set the default uid for inodes to the uid + passed in on mount. For mounts to servers + which do support the CIFS Unix extensions, such as a + properly configured Samba server, the server provides + the uid, gid and mode so this parameter should not be + specified unless the server and clients uid and gid + numbering differ. If the server and client are in the + same domain (e.g. running winbind or nss_ldap) and + the server supports the Unix Extensions then the uid + and gid can be retrieved from the server (and uid + and gid would not have to be specified on the mount. + For servers which do not support the CIFS Unix + extensions, the default uid (and gid) returned on lookup + of existing files will be the uid (gid) of the person + who executed the mount (root, except when mount.cifs + is configured setuid for user mounts) unless the ``uid=`` + (gid) mount option is specified. Also note that permission + checks (authorization checks) on accesses to a file occur + at the server, but there are cases in which an administrator + may want to restrict at the client as well. For those + servers which do not report a uid/gid owner + (such as Windows), permissions can also be checked at the + client, and a crude form of client side permission checking + can be enabled by specifying file_mode and dir_mode on + the client. (default) + forcegid + (similar to above but for the groupid instead of uid) (default) + noforceuid + Fill in file owner information (uid) by requesting it from + the server if possible. With this option, the value given in + the uid= option (on mount) will only be used if the server + can not support returning uids on inodes. + noforcegid + (similar to above but for the group owner, gid, instead of uid) + uid + Set the default uid for inodes, and indicate to the + cifs kernel driver which local user mounted. If the server + supports the unix extensions the default uid is + not used to fill in the owner fields of inodes (files) + unless the ``forceuid`` parameter is specified. + gid + Set the default gid for inodes (similar to above). + file_mode + If CIFS Unix extensions are not supported by the server + this overrides the default mode for file inodes. + fsc + Enable local disk caching using FS-Cache (off by default). This + option could be useful to improve performance on a slow link, + heavily loaded server and/or network where reading from the + disk is faster than reading from the server (over the network). + This could also impact scalability positively as the + number of calls to the server are reduced. However, local + caching is not suitable for all workloads for e.g. read-once + type workloads. So, you need to consider carefully your + workload/scenario before using this option. Currently, local + disk caching is functional for CIFS files opened as read-only. + dir_mode + If CIFS Unix extensions are not supported by the server + this overrides the default mode for directory inodes. + port + attempt to contact the server on this tcp port, before + trying the usual ports (port 445, then 139). + iocharset + Codepage used to convert local path names to and from + Unicode. Unicode is used by default for network path + names if the server supports it. If iocharset is + not specified then the nls_default specified + during the local client kernel build will be used. + If server does not support Unicode, this parameter is + unused. + rsize + default read size (usually 16K). The client currently + can not use rsize larger than CIFSMaxBufSize. CIFSMaxBufSize + defaults to 16K and may be changed (from 8K to the maximum + kmalloc size allowed by your kernel) at module install time + for cifs.ko. Setting CIFSMaxBufSize to a very large value + will cause cifs to use more memory and may reduce performance + in some cases. To use rsize greater than 127K (the original + cifs protocol maximum) also requires that the server support + a new Unix Capability flag (for very large read) which some + newer servers (e.g. Samba 3.0.26 or later) do. rsize can be + set from a minimum of 2048 to a maximum of 130048 (127K or + CIFSMaxBufSize, whichever is smaller) + wsize + default write size (default 57344) + maximum wsize currently allowed by CIFS is 57344 (fourteen + 4096 byte pages) + actimeo=n + attribute cache timeout in seconds (default 1 second). + After this timeout, the cifs client requests fresh attribute + information from the server. This option allows to tune the + attribute cache timeout to suit the workload needs. Shorter + timeouts mean better the cache coherency, but increased number + of calls to the server. Longer timeouts mean reduced number + of calls to the server at the expense of less stricter cache + coherency checks (i.e. incorrect attribute cache for a short + period of time). + rw + mount the network share read-write (note that the + server may still consider the share read-only) + ro + mount network share read-only + version + used to distinguish different versions of the + mount helper utility (not typically needed) + sep + if first mount option (after the -o), overrides + the comma as the separator between the mount + parameters. e.g.:: + + -o user=myname,password=mypassword,domain=mydom + + could be passed instead with period as the separator by:: + + -o sep=.user=myname.password=mypassword.domain=mydom + + this might be useful when comma is contained within username + or password or domain. This option is less important + when the cifs mount helper cifs.mount (version 1.1 or later) + is used. + nosuid + Do not allow remote executables with the suid bit + program to be executed. This is only meaningful for mounts + to servers such as Samba which support the CIFS Unix Extensions. + If you do not trust the servers in your network (your mount + targets) it is recommended that you specify this option for + greater security. + exec + Permit execution of binaries on the mount. + noexec + Do not permit execution of binaries on the mount. + dev + Recognize block devices on the remote mount. + nodev + Do not recognize devices on the remote mount. + suid + Allow remote files on this mountpoint with suid enabled to + be executed (default for mounts when executed as root, + nosuid is default for user mounts). + credentials + Although ignored by the cifs kernel component, it is used by + the mount helper, mount.cifs. When mount.cifs is installed it + opens and reads the credential file specified in order + to obtain the userid and password arguments which are passed to + the cifs vfs. + guest + Although ignored by the kernel component, the mount.cifs + mount helper will not prompt the user for a password + if guest is specified on the mount options. If no + password is specified a null password will be used. + perm + Client does permission checks (vfs_permission check of uid + and gid of the file against the mode and desired operation), + Note that this is in addition to the normal ACL check on the + target machine done by the server software. + Client permission checking is enabled by default. + noperm + Client does not do permission checks. This can expose + files on this mount to access by other users on the local + client system. It is typically only needed when the server + supports the CIFS Unix Extensions but the UIDs/GIDs on the + client and server system do not match closely enough to allow + access by the user doing the mount, but it may be useful with + non CIFS Unix Extension mounts for cases in which the default + mode is specified on the mount but is not to be enforced on the + client (e.g. perhaps when MultiUserMount is enabled) + Note that this does not affect the normal ACL check on the + target machine done by the server software (of the server + ACL against the user name provided at mount time). + serverino + Use server's inode numbers instead of generating automatically + incrementing inode numbers on the client. Although this will + make it easier to spot hardlinked files (as they will have + the same inode numbers) and inode numbers may be persistent, + note that the server does not guarantee that the inode numbers + are unique if multiple server side mounts are exported under a + single share (since inode numbers on the servers might not + be unique if multiple filesystems are mounted under the same + shared higher level directory). Note that some older + (e.g. pre-Windows 2000) do not support returning UniqueIDs + or the CIFS Unix Extensions equivalent and for those + this mount option will have no effect. Exporting cifs mounts + under nfsd requires this mount option on the cifs mount. + This is now the default if server supports the + required network operation. + noserverino + Client generates inode numbers (rather than using the actual one + from the server). These inode numbers will vary after + unmount or reboot which can confuse some applications, + but not all server filesystems support unique inode + numbers. + setuids + If the CIFS Unix extensions are negotiated with the server + the client will attempt to set the effective uid and gid of + the local process on newly created files, directories, and + devices (create, mkdir, mknod). If the CIFS Unix Extensions + are not negotiated, for newly created files and directories + instead of using the default uid and gid specified on + the mount, cache the new file's uid and gid locally which means + that the uid for the file can change when the inode is + reloaded (or the user remounts the share). + nosetuids + The client will not attempt to set the uid and gid on + on newly created files, directories, and devices (create, + mkdir, mknod) which will result in the server setting the + uid and gid to the default (usually the server uid of the + user who mounted the share). Letting the server (rather than + the client) set the uid and gid is the default. If the CIFS + Unix Extensions are not negotiated then the uid and gid for + new files will appear to be the uid (gid) of the mounter or the + uid (gid) parameter specified on the mount. + netbiosname + When mounting to servers via port 139, specifies the RFC1001 + source name to use to represent the client netbios machine + name when doing the RFC1001 netbios session initialize. + direct + Do not do inode data caching on files opened on this mount. + This precludes mmapping files on this mount. In some cases + with fast networks and little or no caching benefits on the + client (e.g. when the application is doing large sequential + reads bigger than page size without rereading the same data) + this can provide better performance than the default + behavior which caches reads (readahead) and writes + (writebehind) through the local Linux client pagecache + if oplock (caching token) is granted and held. Note that + direct allows write operations larger than page size + to be sent to the server. + strictcache + Use for switching on strict cache mode. In this mode the + client read from the cache all the time it has Oplock Level II, + otherwise - read from the server. All written data are stored + in the cache, but if the client doesn't have Exclusive Oplock, + it writes the data to the server. + rwpidforward + Forward pid of a process who opened a file to any read or write + operation on that file. This prevent applications like WINE + from failing on read and write if we use mandatory brlock style. + acl + Allow setfacl and getfacl to manage posix ACLs if server + supports them. (default) + noacl + Do not allow setfacl and getfacl calls on this mount + user_xattr + Allow getting and setting user xattrs (those attributes whose + name begins with ``user.`` or ``os2.``) as OS/2 EAs (extended + attributes) to the server. This allows support of the + setfattr and getfattr utilities. (default) + nouser_xattr + Do not allow getfattr/setfattr to get/set/list xattrs + mapchars + Translate six of the seven reserved characters (not backslash):: + + *?<>|: + + to the remap range (above 0xF000), which also + allows the CIFS client to recognize files created with + such characters by Windows's POSIX emulation. This can + also be useful when mounting to most versions of Samba + (which also forbids creating and opening files + whose names contain any of these seven characters). + This has no effect if the server does not support + Unicode on the wire. + nomapchars + Do not translate any of these seven characters (default). + nocase + Request case insensitive path name matching (case + sensitive is the default if the server supports it). + (mount option ``ignorecase`` is identical to ``nocase``) + posixpaths + If CIFS Unix extensions are supported, attempt to + negotiate posix path name support which allows certain + characters forbidden in typical CIFS filenames, without + requiring remapping. (default) + noposixpaths + If CIFS Unix extensions are supported, do not request + posix path name support (this may cause servers to + reject creatingfile with certain reserved characters). + nounix + Disable the CIFS Unix Extensions for this mount (tree + connection). This is rarely needed, but it may be useful + in order to turn off multiple settings all at once (ie + posix acls, posix locks, posix paths, symlink support + and retrieving uids/gids/mode from the server) or to + work around a bug in server which implement the Unix + Extensions. + nobrl + Do not send byte range lock requests to the server. + This is necessary for certain applications that break + with cifs style mandatory byte range locks (and most + cifs servers do not yet support requesting advisory + byte range locks). + forcemandatorylock + Even if the server supports posix (advisory) byte range + locking, send only mandatory lock requests. For some + (presumably rare) applications, originally coded for + DOS/Windows, which require Windows style mandatory byte range + locking, they may be able to take advantage of this option, + forcing the cifs client to only send mandatory locks + even if the cifs server would support posix advisory locks. + ``forcemand`` is accepted as a shorter form of this mount + option. + nostrictsync + If this mount option is set, when an application does an + fsync call then the cifs client does not send an SMB Flush + to the server (to force the server to write all dirty data + for this file immediately to disk), although cifs still sends + all dirty (cached) file data to the server and waits for the + server to respond to the write. Since SMB Flush can be + very slow, and some servers may be reliable enough (to risk + delaying slightly flushing the data to disk on the server), + turning on this option may be useful to improve performance for + applications that fsync too much, at a small risk of server + crash. If this mount option is not set, by default cifs will + send an SMB flush request (and wait for a response) on every + fsync call. + nodfs + Disable DFS (global name space support) even if the + server claims to support it. This can help work around + a problem with parsing of DFS paths with Samba server + versions 3.0.24 and 3.0.25. + remount + remount the share (often used to change from ro to rw mounts + or vice versa) + cifsacl + Report mode bits (e.g. on stat) based on the Windows ACL for + the file. (EXPERIMENTAL) + servern + Specify the server 's netbios name (RFC1001 name) to use + when attempting to setup a session to the server. + This is needed for mounting to some older servers (such + as OS/2 or Windows 98 and Windows ME) since they do not + support a default server name. A server name can be up + to 15 characters long and is usually uppercased. + sfu + When the CIFS Unix Extensions are not negotiated, attempt to + create device files and fifos in a format compatible with + Services for Unix (SFU). In addition retrieve bits 10-12 + of the mode via the SETFILEBITS extended attribute (as + SFU does). In the future the bottom 9 bits of the + mode also will be emulated using queries of the security + descriptor (ACL). + mfsymlinks + Enable support for Minshall+French symlinks + (see http://wiki.samba.org/index.php/UNIX_Extensions#Minshall.2BFrench_symlinks) + This option is ignored when specified together with the + 'sfu' option. Minshall+French symlinks are used even if + the server supports the CIFS Unix Extensions. + sign + Must use packet signing (helps avoid unwanted data modification + by intermediate systems in the route). Note that signing + does not work with lanman or plaintext authentication. + seal + Must seal (encrypt) all data on this mounted share before + sending on the network. Requires support for Unix Extensions. + Note that this differs from the sign mount option in that it + causes encryption of data sent over this mounted share but other + shares mounted to the same server are unaffected. + locallease + This option is rarely needed. Fcntl F_SETLEASE is + used by some applications such as Samba and NFSv4 server to + check to see whether a file is cacheable. CIFS has no way + to explicitly request a lease, but can check whether a file + is cacheable (oplocked). Unfortunately, even if a file + is not oplocked, it could still be cacheable (ie cifs client + could grant fcntl leases if no other local processes are using + the file) for cases for example such as when the server does not + support oplocks and the user is sure that the only updates to + the file will be from this client. Specifying this mount option + will allow the cifs client to check for leases (only) locally + for files which are not oplocked instead of denying leases + in that case. (EXPERIMENTAL) + sec + Security mode. Allowed values are: + + none + attempt to connection as a null user (no name) + krb5 + Use Kerberos version 5 authentication + krb5i + Use Kerberos authentication and packet signing + ntlm + Use NTLM password hashing (default) + ntlmi + Use NTLM password hashing with signing (if + /proc/fs/cifs/PacketSigningEnabled on or if + server requires signing also can be the default) + ntlmv2 + Use NTLMv2 password hashing + ntlmv2i + Use NTLMv2 password hashing with packet signing + lanman + (if configured in kernel config) use older + lanman hash + hard + Retry file operations if server is not responding + soft + Limit retries to unresponsive servers (usually only + one retry) before returning an error. (default) + +The mount.cifs mount helper also accepts a few mount options before -o +including: + +=============== =============================================================== + -S take password from stdin (equivalent to setting the environment + variable ``PASSWD_FD=0`` + -V print mount.cifs version + -? display simple usage information +=============== =============================================================== + +With most 2.6 kernel versions of modutils, the version of the cifs kernel +module can be displayed via modinfo. + +Misc /proc/fs/cifs Flags and Debug Info +======================================= + +Informational pseudo-files: + +======================= ======================================================= +DebugData Displays information about active CIFS sessions and + shares, features enabled as well as the cifs.ko + version. +Stats Lists summary resource usage information as well as per + share statistics. +open_files List all the open file handles on all active SMB sessions. +======================= ======================================================= + +Configuration pseudo-files: + +======================= ======================================================= +SecurityFlags Flags which control security negotiation and + also packet signing. Authentication (may/must) + flags (e.g. for NTLM and/or NTLMv2) may be combined with + the signing flags. Specifying two different password + hashing mechanisms (as "must use") on the other hand + does not make much sense. Default flags are:: + + 0x07007 + + (NTLM, NTLMv2 and packet signing allowed). The maximum + allowable flags if you want to allow mounts to servers + using weaker password hashes is 0x37037 (lanman, + plaintext, ntlm, ntlmv2, signing allowed). Some + SecurityFlags require the corresponding menuconfig + options to be enabled. Enabling plaintext + authentication currently requires also enabling + lanman authentication in the security flags + because the cifs module only supports sending + laintext passwords using the older lanman dialect + form of the session setup SMB. (e.g. for authentication + using plain text passwords, set the SecurityFlags + to 0x30030):: + + may use packet signing 0x00001 + must use packet signing 0x01001 + may use NTLM (most common password hash) 0x00002 + must use NTLM 0x02002 + may use NTLMv2 0x00004 + must use NTLMv2 0x04004 + may use Kerberos security 0x00008 + must use Kerberos 0x08008 + may use lanman (weak) password hash 0x00010 + must use lanman password hash 0x10010 + may use plaintext passwords 0x00020 + must use plaintext passwords 0x20020 + (reserved for future packet encryption) 0x00040 + +cifsFYI If set to non-zero value, additional debug information + will be logged to the system error log. This field + contains three flags controlling different classes of + debugging entries. The maximum value it can be set + to is 7 which enables all debugging points (default 0). + Some debugging statements are not compiled into the + cifs kernel unless CONFIG_CIFS_DEBUG2 is enabled in the + kernel configuration. cifsFYI may be set to one or + more of the following flags (7 sets them all):: + + +-----------------------------------------------+------+ + | log cifs informational messages | 0x01 | + +-----------------------------------------------+------+ + | log return codes from cifs entry points | 0x02 | + +-----------------------------------------------+------+ + | log slow responses | 0x04 | + | (ie which take longer than 1 second) | | + | | | + | CONFIG_CIFS_STATS2 must be enabled in .config | | + +-----------------------------------------------+------+ + +traceSMB If set to one, debug information is logged to the + system error log with the start of smb requests + and responses (default 0) +LookupCacheEnable If set to one, inode information is kept cached + for one second improving performance of lookups + (default 1) +LinuxExtensionsEnabled If set to one then the client will attempt to + use the CIFS "UNIX" extensions which are optional + protocol enhancements that allow CIFS servers + to return accurate UID/GID information as well + as support symbolic links. If you use servers + such as Samba that support the CIFS Unix + extensions but do not want to use symbolic link + support and want to map the uid and gid fields + to values supplied at mount (rather than the + actual values, then set this to zero. (default 1) +dfscache List the content of the DFS cache. + If set to 0, the client will clear the cache. +======================= ======================================================= + +These experimental features and tracing can be enabled by changing flags in +/proc/fs/cifs (after the cifs module has been installed or built into the +kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable +tracing to the kernel message log type:: + + echo 7 > /proc/fs/cifs/cifsFYI + +cifsFYI functions as a bit mask. Setting it to 1 enables additional kernel +logging of various informational messages. 2 enables logging of non-zero +SMB return codes while 4 enables logging of requests that take longer +than one second to complete (except for byte range lock requests). +Setting it to 4 requires CONFIG_CIFS_STATS2 to be set in kernel configuration +(.config). Setting it to seven enables all three. Finally, tracing +the start of smb requests and responses can be enabled via:: + + echo 1 > /proc/fs/cifs/traceSMB + +Per share (per client mount) statistics are available in /proc/fs/cifs/Stats. +Additional information is available if CONFIG_CIFS_STATS2 is enabled in the +kernel configuration (.config). The statistics returned include counters which +represent the number of attempted and failed (ie non-zero return code from the +server) SMB3 (or cifs) requests grouped by request type (read, write, close etc.). +Also recorded is the total bytes read and bytes written to the server for +that share. Note that due to client caching effects this can be less than the +number of bytes read and written by the application running on the client. +Statistics can be reset to zero by ``echo 0 > /proc/fs/cifs/Stats`` which may be +useful if comparing performance of two different scenarios. + +Also note that ``cat /proc/fs/cifs/DebugData`` will display information about +the active sessions and the shares that are mounted. + +Enabling Kerberos (extended security) works but requires version 1.2 or later +of the helper program cifs.upcall to be present and to be configured in the +/etc/request-key.conf file. The cifs.upcall helper program is from the Samba +project(https://www.samba.org). NTLM and NTLMv2 and LANMAN support do not +require this helper. Note that NTLMv2 security (which does not require the +cifs.upcall helper program), instead of using Kerberos, is sufficient for +some use cases. + +DFS support allows transparent redirection to shares in an MS-DFS name space. +In addition, DFS support for target shares which are specified as UNC +names which begin with host names (rather than IP addresses) requires +a user space helper (such as cifs.upcall) to be present in order to +translate host names to ip address, and the user space helper must also +be configured in the file /etc/request-key.conf. Samba, Windows servers and +many NAS appliances support DFS as a way of constructing a global name +space to ease network configuration and improve reliability. + +To use cifs Kerberos and DFS support, the Linux keyutils package should be +installed and something like the following lines should be added to the +/etc/request-key.conf file:: + + create cifs.spnego * * /usr/local/sbin/cifs.upcall %k + create dns_resolver * * /usr/local/sbin/cifs.upcall %k + +CIFS kernel module parameters +============================= +These module parameters can be specified or modified either during the time of +module loading or during the runtime by using the interface:: + + /sys/module/cifs/parameters/<param> + +i.e.:: + + echo "value" > /sys/module/cifs/parameters/<param> + +================= ========================================================== +1. enable_oplocks Enable or disable oplocks. Oplocks are enabled by default. + [Y/y/1]. To disable use any of [N/n/0]. +================= ========================================================== diff --git a/Documentation/admin-guide/cifs/winucase_convert.pl b/Documentation/admin-guide/cifs/winucase_convert.pl new file mode 100755 index 000000000..993186bee --- /dev/null +++ b/Documentation/admin-guide/cifs/winucase_convert.pl @@ -0,0 +1,62 @@ +#!/usr/bin/perl -w +# +# winucase_convert.pl -- convert "Windows 8 Upper Case Mapping Table.txt" to +# a two-level set of C arrays. +# +# Copyright 2013: Jeff Layton <jlayton@redhat.com> +# +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <https://www.gnu.org/licenses/>. +# + +while(<>) { + next if (!/^0x(..)(..)\t0x(....)\t/); + $firstchar = hex($1); + $secondchar = hex($2); + $uppercase = hex($3); + + $top[$firstchar][$secondchar] = $uppercase; +} + +for ($i = 0; $i < 256; $i++) { + next if (!$top[$i]); + + printf("static const wchar_t t2_%2.2x[256] = {", $i); + for ($j = 0; $j < 256; $j++) { + if (($j % 8) == 0) { + print "\n\t"; + } else { + print " "; + } + printf("0x%4.4x,", $top[$i][$j] ? $top[$i][$j] : 0); + } + print "\n};\n\n"; +} + +printf("static const wchar_t *const toplevel[256] = {", $i); +for ($i = 0; $i < 256; $i++) { + if (($i % 8) == 0) { + print "\n\t"; + } elsif ($top[$i]) { + print " "; + } else { + print " "; + } + + if ($top[$i]) { + printf("t2_%2.2x,", $i); + } else { + print "NULL,"; + } +} +print "\n};\n\n"; diff --git a/Documentation/admin-guide/clearing-warn-once.rst b/Documentation/admin-guide/clearing-warn-once.rst new file mode 100644 index 000000000..211fd926c --- /dev/null +++ b/Documentation/admin-guide/clearing-warn-once.rst @@ -0,0 +1,9 @@ +Clearing WARN_ONCE +------------------ + +WARN_ONCE / WARN_ON_ONCE / printk_once only emit a message once. + +echo 1 > /sys/kernel/debug/clear_warn_once + +clears the state and allows the warnings to print once again. +This can be useful after test suite runs to reproduce problems. diff --git a/Documentation/admin-guide/cpu-load.rst b/Documentation/admin-guide/cpu-load.rst new file mode 100644 index 000000000..21a984337 --- /dev/null +++ b/Documentation/admin-guide/cpu-load.rst @@ -0,0 +1,117 @@ +======== +CPU load +======== + +Linux exports various bits of information via ``/proc/stat`` and +``/proc/uptime`` that userland tools, such as top(1), use to calculate +the average time system spent in a particular state, for example:: + + $ iostat + Linux 2.6.18.3-exp (linmac) 02/20/2007 + + avg-cpu: %user %nice %system %iowait %steal %idle + 10.01 0.00 2.92 5.44 0.00 81.63 + + ... + +Here the system thinks that over the default sampling period the +system spent 10.01% of the time doing work in user space, 2.92% in the +kernel, and was overall 81.63% of the time idle. + +In most cases the ``/proc/stat`` information reflects the reality quite +closely, however due to the nature of how/when the kernel collects +this data sometimes it can not be trusted at all. + +So how is this information collected? Whenever timer interrupt is +signalled the kernel looks what kind of task was running at this +moment and increments the counter that corresponds to this tasks +kind/state. The problem with this is that the system could have +switched between various states multiple times between two timer +interrupts yet the counter is incremented only for the last state. + + +Example +------- + +If we imagine the system with one task that periodically burns cycles +in the following manner:: + + time line between two timer interrupts + |--------------------------------------| + ^ ^ + |_ something begins working | + |_ something goes to sleep + (only to be awaken quite soon) + +In the above situation the system will be 0% loaded according to the +``/proc/stat`` (since the timer interrupt will always happen when the +system is executing the idle handler), but in reality the load is +closer to 99%. + +One can imagine many more situations where this behavior of the kernel +will lead to quite erratic information inside ``/proc/stat``:: + + + /* gcc -o hog smallhog.c */ + #include <time.h> + #include <limits.h> + #include <signal.h> + #include <sys/time.h> + #define HIST 10 + + static volatile sig_atomic_t stop; + + static void sighandler(int signr) + { + (void) signr; + stop = 1; + } + + static unsigned long hog (unsigned long niters) + { + stop = 0; + while (!stop && --niters); + return niters; + } + + int main (void) + { + int i; + struct itimerval it = { + .it_interval = { .tv_sec = 0, .tv_usec = 1 }, + .it_value = { .tv_sec = 0, .tv_usec = 1 } }; + sigset_t set; + unsigned long v[HIST]; + double tmp = 0.0; + unsigned long n; + signal(SIGALRM, &sighandler); + setitimer(ITIMER_REAL, &it, NULL); + + hog (ULONG_MAX); + for (i = 0; i < HIST; ++i) v[i] = ULONG_MAX - hog(ULONG_MAX); + for (i = 0; i < HIST; ++i) tmp += v[i]; + tmp /= HIST; + n = tmp - (tmp / 3.0); + + sigemptyset(&set); + sigaddset(&set, SIGALRM); + + for (;;) { + hog(n); + sigwait(&set, &i); + } + return 0; + } + + +References +---------- + +- https://lore.kernel.org/r/loom.20070212T063225-663@post.gmane.org +- Documentation/filesystems/proc.rst (1.8) + + +Thanks +------ + +Con Kolivas, Pavel Machek diff --git a/Documentation/admin-guide/cputopology.rst b/Documentation/admin-guide/cputopology.rst new file mode 100644 index 000000000..d29cacc9b --- /dev/null +++ b/Documentation/admin-guide/cputopology.rst @@ -0,0 +1,101 @@ +=========================================== +How CPU topology info is exported via sysfs +=========================================== + +CPU topology info is exported via sysfs. Items (attributes) are similar +to /proc/cpuinfo output of some architectures. They reside in +/sys/devices/system/cpu/cpuX/topology/. Please refer to the ABI file: +Documentation/ABI/stable/sysfs-devices-system-cpu. + +Architecture-neutral, drivers/base/topology.c, exports these attributes. +However the die, cluster, book, and drawer hierarchy related sysfs files will +only be created if an architecture provides the related macros as described +below. + +For an architecture to support this feature, it must define some of +these macros in include/asm-XXX/topology.h:: + + #define topology_physical_package_id(cpu) + #define topology_die_id(cpu) + #define topology_cluster_id(cpu) + #define topology_core_id(cpu) + #define topology_book_id(cpu) + #define topology_drawer_id(cpu) + #define topology_sibling_cpumask(cpu) + #define topology_core_cpumask(cpu) + #define topology_cluster_cpumask(cpu) + #define topology_die_cpumask(cpu) + #define topology_book_cpumask(cpu) + #define topology_drawer_cpumask(cpu) + +The type of ``**_id macros`` is int. +The type of ``**_cpumask macros`` is ``(const) struct cpumask *``. The latter +correspond with appropriate ``**_siblings`` sysfs attributes (except for +topology_sibling_cpumask() which corresponds with thread_siblings). + +To be consistent on all architectures, include/linux/topology.h +provides default definitions for any of the above macros that are +not defined by include/asm-XXX/topology.h: + +1) topology_physical_package_id: -1 +2) topology_die_id: -1 +3) topology_cluster_id: -1 +4) topology_core_id: 0 +5) topology_book_id: -1 +6) topology_drawer_id: -1 +7) topology_sibling_cpumask: just the given CPU +8) topology_core_cpumask: just the given CPU +9) topology_cluster_cpumask: just the given CPU +10) topology_die_cpumask: just the given CPU +11) topology_book_cpumask: just the given CPU +12) topology_drawer_cpumask: just the given CPU + +Additionally, CPU topology information is provided under +/sys/devices/system/cpu and includes these files. The internal +source for the output is in brackets ("[]"). + + =========== ========================================================== + kernel_max: the maximum CPU index allowed by the kernel configuration. + [NR_CPUS-1] + + offline: CPUs that are not online because they have been + HOTPLUGGED off or exceed the limit of CPUs allowed by the + kernel configuration (kernel_max above). + [~cpu_online_mask + cpus >= NR_CPUS] + + online: CPUs that are online and being scheduled [cpu_online_mask] + + possible: CPUs that have been allocated resources and can be + brought online if they are present. [cpu_possible_mask] + + present: CPUs that have been identified as being present in the + system. [cpu_present_mask] + =========== ========================================================== + +The format for the above output is compatible with cpulist_parse() +[see <linux/cpumask.h>]. Some examples follow. + +In this example, there are 64 CPUs in the system but cpus 32-63 exceed +the kernel max which is limited to 0..31 by the NR_CPUS config option +being 32. Note also that CPUs 2 and 4-31 are not online but could be +brought online as they are both present and possible:: + + kernel_max: 31 + offline: 2,4-31,32-63 + online: 0-1,3 + possible: 0-31 + present: 0-31 + +In this example, the NR_CPUS config option is 128, but the kernel was +started with possible_cpus=144. There are 4 CPUs in the system and cpu2 +was manually taken offline (and is the only CPU that can be brought +online.):: + + kernel_max: 127 + offline: 2,4-127,128-143 + online: 0-1,3 + possible: 0-127 + present: 0-3 + +See Documentation/core-api/cpu_hotplug.rst for the possible_cpus=NUM +kernel start parameter as well as more information on the various cpumasks. diff --git a/Documentation/admin-guide/dell_rbu.rst b/Documentation/admin-guide/dell_rbu.rst new file mode 100644 index 000000000..2196caf1b --- /dev/null +++ b/Documentation/admin-guide/dell_rbu.rst @@ -0,0 +1,128 @@ +========================================= +Dell Remote BIOS Update driver (dell_rbu) +========================================= + +Purpose +======= + +Document demonstrating the use of the Dell Remote BIOS Update driver +for updating BIOS images on Dell servers and desktops. + +Scope +===== + +This document discusses the functionality of the rbu driver only. +It does not cover the support needed from applications to enable the BIOS to +update itself with the image downloaded in to the memory. + +Overview +======== + +This driver works with Dell OpenManage or Dell Update Packages for updating +the BIOS on Dell servers (starting from servers sold since 1999), desktops +and notebooks (starting from those sold in 2005). + +Please go to http://support.dell.com register and you can find info on +OpenManage and Dell Update packages (DUP). + +Libsmbios can also be used to update BIOS on Dell systems go to +https://linux.dell.com/libsmbios/ for details. + +Dell_RBU driver supports BIOS update using the monolithic image and packetized +image methods. In case of monolithic the driver allocates a contiguous chunk +of physical pages having the BIOS image. In case of packetized the app +using the driver breaks the image in to packets of fixed sizes and the driver +would place each packet in contiguous physical memory. The driver also +maintains a link list of packets for reading them back. + +If the dell_rbu driver is unloaded all the allocated memory is freed. + +The rbu driver needs to have an application (as mentioned above) which will +inform the BIOS to enable the update in the next system reboot. + +The user should not unload the rbu driver after downloading the BIOS image +or updating. + +The driver load creates the following directories under the /sys file system:: + + /sys/class/firmware/dell_rbu/loading + /sys/class/firmware/dell_rbu/data + /sys/devices/platform/dell_rbu/image_type + /sys/devices/platform/dell_rbu/data + /sys/devices/platform/dell_rbu/packet_size + +The driver supports two types of update mechanism; monolithic and packetized. +These update mechanism depends upon the BIOS currently running on the system. +Most of the Dell systems support a monolithic update where the BIOS image is +copied to a single contiguous block of physical memory. + +In case of packet mechanism the single memory can be broken in smaller chunks +of contiguous memory and the BIOS image is scattered in these packets. + +By default the driver uses monolithic memory for the update type. This can be +changed to packets during the driver load time by specifying the load +parameter image_type=packet. This can also be changed later as below:: + + echo packet > /sys/devices/platform/dell_rbu/image_type + +In packet update mode the packet size has to be given before any packets can +be downloaded. It is done as below:: + + echo XXXX > /sys/devices/platform/dell_rbu/packet_size + +In the packet update mechanism, the user needs to create a new file having +packets of data arranged back to back. It can be done as follows: +The user creates packets header, gets the chunk of the BIOS image and +places it next to the packetheader; now, the packetheader + BIOS image chunk +added together should match the specified packet_size. This makes one +packet, the user needs to create more such packets out of the entire BIOS +image file and then arrange all these packets back to back in to one single +file. + +This file is then copied to /sys/class/firmware/dell_rbu/data. +Once this file gets to the driver, the driver extracts packet_size data from +the file and spreads it across the physical memory in contiguous packet_sized +space. + +This method makes sure that all the packets get to the driver in a single operation. + +In monolithic update the user simply get the BIOS image (.hdr file) and copies +to the data file as is without any change to the BIOS image itself. + +Do the steps below to download the BIOS image. + +1) echo 1 > /sys/class/firmware/dell_rbu/loading +2) cp bios_image.hdr /sys/class/firmware/dell_rbu/data +3) echo 0 > /sys/class/firmware/dell_rbu/loading + +The /sys/class/firmware/dell_rbu/ entries will remain till the following is +done. + +:: + + echo -1 > /sys/class/firmware/dell_rbu/loading + +Until this step is completed the driver cannot be unloaded. + +Also echoing either mono, packet or init in to image_type will free up the +memory allocated by the driver. + +If a user by accident executes steps 1 and 3 above without executing step 2; +it will make the /sys/class/firmware/dell_rbu/ entries disappear. + +The entries can be recreated by doing the following:: + + echo init > /sys/devices/platform/dell_rbu/image_type + +.. note:: echoing init in image_type does not change its original value. + +Also the driver provides /sys/devices/platform/dell_rbu/data readonly file to +read back the image downloaded. + +.. note:: + + After updating the BIOS image a user mode application needs to execute + code which sends the BIOS update request to the BIOS. So on the next reboot + the BIOS knows about the new image downloaded and it updates itself. + Also don't unload the rbu driver if the image has to be updated. + diff --git a/Documentation/admin-guide/device-mapper/cache-policies.rst b/Documentation/admin-guide/device-mapper/cache-policies.rst new file mode 100644 index 000000000..13da4d831 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/cache-policies.rst @@ -0,0 +1,131 @@ +============================= +Guidance for writing policies +============================= + +Try to keep transactionality out of it. The core is careful to +avoid asking about anything that is migrating. This is a pain, but +makes it easier to write the policies. + +Mappings are loaded into the policy at construction time. + +Every bio that is mapped by the target is referred to the policy. +The policy can return a simple HIT or MISS or issue a migration. + +Currently there's no way for the policy to issue background work, +e.g. to start writing back dirty blocks that are going to be evicted +soon. + +Because we map bios, rather than requests it's easy for the policy +to get fooled by many small bios. For this reason the core target +issues periodic ticks to the policy. It's suggested that the policy +doesn't update states (eg, hit counts) for a block more than once +for each tick. The core ticks by watching bios complete, and so +trying to see when the io scheduler has let the ios run. + + +Overview of supplied cache replacement policies +=============================================== + +multiqueue (mq) +--------------- + +This policy is now an alias for smq (see below). + +The following tunables are accepted, but have no effect:: + + 'sequential_threshold <#nr_sequential_ios>' + 'random_threshold <#nr_random_ios>' + 'read_promote_adjustment <value>' + 'write_promote_adjustment <value>' + 'discard_promote_adjustment <value>' + +Stochastic multiqueue (smq) +--------------------------- + +This policy is the default. + +The stochastic multi-queue (smq) policy addresses some of the problems +with the multiqueue (mq) policy. + +The smq policy (vs mq) offers the promise of less memory utilization, +improved performance and increased adaptability in the face of changing +workloads. smq also does not have any cumbersome tuning knobs. + +Users may switch from "mq" to "smq" simply by appropriately reloading a +DM table that is using the cache target. Doing so will cause all of the +mq policy's hints to be dropped. Also, performance of the cache may +degrade slightly until smq recalculates the origin device's hotspots +that should be cached. + +Memory usage +^^^^^^^^^^^^ + +The mq policy used a lot of memory; 88 bytes per cache block on a 64 +bit machine. + +smq uses 28bit indexes to implement its data structures rather than +pointers. It avoids storing an explicit hit count for each block. It +has a 'hotspot' queue, rather than a pre-cache, which uses a quarter of +the entries (each hotspot block covers a larger area than a single +cache block). + +All this means smq uses ~25bytes per cache block. Still a lot of +memory, but a substantial improvement nonetheless. + +Level balancing +^^^^^^^^^^^^^^^ + +mq placed entries in different levels of the multiqueue structures +based on their hit count (~ln(hit count)). This meant the bottom +levels generally had the most entries, and the top ones had very +few. Having unbalanced levels like this reduced the efficacy of the +multiqueue. + +smq does not maintain a hit count, instead it swaps hit entries with +the least recently used entry from the level above. The overall +ordering being a side effect of this stochastic process. With this +scheme we can decide how many entries occupy each multiqueue level, +resulting in better promotion/demotion decisions. + +Adaptability: +The mq policy maintained a hit count for each cache block. For a +different block to get promoted to the cache its hit count has to +exceed the lowest currently in the cache. This meant it could take a +long time for the cache to adapt between varying IO patterns. + +smq doesn't maintain hit counts, so a lot of this problem just goes +away. In addition it tracks performance of the hotspot queue, which +is used to decide which blocks to promote. If the hotspot queue is +performing badly then it starts moving entries more quickly between +levels. This lets it adapt to new IO patterns very quickly. + +Performance +^^^^^^^^^^^ + +Testing smq shows substantially better performance than mq. + +cleaner +------- + +The cleaner writes back all dirty blocks in a cache to decommission it. + +Examples +======== + +The syntax for a table is:: + + cache <metadata dev> <cache dev> <origin dev> <block size> + <#feature_args> [<feature arg>]* + <policy> <#policy_args> [<policy arg>]* + +The syntax to send a message using the dmsetup command is:: + + dmsetup message <mapped device> 0 sequential_threshold 1024 + dmsetup message <mapped device> 0 random_threshold 8 + +Using dmsetup:: + + dmsetup create blah --table "0 268435456 cache /dev/sdb /dev/sdc \ + /dev/sdd 512 0 mq 4 sequential_threshold 1024 random_threshold 8" + creates a 128GB large mapped device named 'blah' with the + sequential threshold set to 1024 and the random_threshold set to 8. diff --git a/Documentation/admin-guide/device-mapper/cache.rst b/Documentation/admin-guide/device-mapper/cache.rst new file mode 100644 index 000000000..f15e5254d --- /dev/null +++ b/Documentation/admin-guide/device-mapper/cache.rst @@ -0,0 +1,337 @@ +===== +Cache +===== + +Introduction +============ + +dm-cache is a device mapper target written by Joe Thornber, Heinz +Mauelshagen, and Mike Snitzer. + +It aims to improve performance of a block device (eg, a spindle) by +dynamically migrating some of its data to a faster, smaller device +(eg, an SSD). + +This device-mapper solution allows us to insert this caching at +different levels of the dm stack, for instance above the data device for +a thin-provisioning pool. Caching solutions that are integrated more +closely with the virtual memory system should give better performance. + +The target reuses the metadata library used in the thin-provisioning +library. + +The decision as to what data to migrate and when is left to a plug-in +policy module. Several of these have been written as we experiment, +and we hope other people will contribute others for specific io +scenarios (eg. a vm image server). + +Glossary +======== + + Migration + Movement of the primary copy of a logical block from one + device to the other. + Promotion + Migration from slow device to fast device. + Demotion + Migration from fast device to slow device. + +The origin device always contains a copy of the logical block, which +may be out of date or kept in sync with the copy on the cache device +(depending on policy). + +Design +====== + +Sub-devices +----------- + +The target is constructed by passing three devices to it (along with +other parameters detailed later): + +1. An origin device - the big, slow one. + +2. A cache device - the small, fast one. + +3. A small metadata device - records which blocks are in the cache, + which are dirty, and extra hints for use by the policy object. + This information could be put on the cache device, but having it + separate allows the volume manager to configure it differently, + e.g. as a mirror for extra robustness. This metadata device may only + be used by a single cache device. + +Fixed block size +---------------- + +The origin is divided up into blocks of a fixed size. This block size +is configurable when you first create the cache. Typically we've been +using block sizes of 256KB - 1024KB. The block size must be between 64 +sectors (32KB) and 2097152 sectors (1GB) and a multiple of 64 sectors (32KB). + +Having a fixed block size simplifies the target a lot. But it is +something of a compromise. For instance, a small part of a block may be +getting hit a lot, yet the whole block will be promoted to the cache. +So large block sizes are bad because they waste cache space. And small +block sizes are bad because they increase the amount of metadata (both +in core and on disk). + +Cache operating modes +--------------------- + +The cache has three operating modes: writeback, writethrough and +passthrough. + +If writeback, the default, is selected then a write to a block that is +cached will go only to the cache and the block will be marked dirty in +the metadata. + +If writethrough is selected then a write to a cached block will not +complete until it has hit both the origin and cache devices. Clean +blocks should remain clean. + +If passthrough is selected, useful when the cache contents are not known +to be coherent with the origin device, then all reads are served from +the origin device (all reads miss the cache) and all writes are +forwarded to the origin device; additionally, write hits cause cache +block invalidates. To enable passthrough mode the cache must be clean. +Passthrough mode allows a cache device to be activated without having to +worry about coherency. Coherency that exists is maintained, although +the cache will gradually cool as writes take place. If the coherency of +the cache can later be verified, or established through use of the +"invalidate_cblocks" message, the cache device can be transitioned to +writethrough or writeback mode while still warm. Otherwise, the cache +contents can be discarded prior to transitioning to the desired +operating mode. + +A simple cleaner policy is provided, which will clean (write back) all +dirty blocks in a cache. Useful for decommissioning a cache or when +shrinking a cache. Shrinking the cache's fast device requires all cache +blocks, in the area of the cache being removed, to be clean. If the +area being removed from the cache still contains dirty blocks the resize +will fail. Care must be taken to never reduce the volume used for the +cache's fast device until the cache is clean. This is of particular +importance if writeback mode is used. Writethrough and passthrough +modes already maintain a clean cache. Future support to partially clean +the cache, above a specified threshold, will allow for keeping the cache +warm and in writeback mode during resize. + +Migration throttling +-------------------- + +Migrating data between the origin and cache device uses bandwidth. +The user can set a throttle to prevent more than a certain amount of +migration occurring at any one time. Currently we're not taking any +account of normal io traffic going to the devices. More work needs +doing here to avoid migrating during those peak io moments. + +For the time being, a message "migration_threshold <#sectors>" +can be used to set the maximum number of sectors being migrated, +the default being 2048 sectors (1MB). + +Updating on-disk metadata +------------------------- + +On-disk metadata is committed every time a FLUSH or FUA bio is written. +If no such requests are made then commits will occur every second. This +means the cache behaves like a physical disk that has a volatile write +cache. If power is lost you may lose some recent writes. The metadata +should always be consistent in spite of any crash. + +The 'dirty' state for a cache block changes far too frequently for us +to keep updating it on the fly. So we treat it as a hint. In normal +operation it will be written when the dm device is suspended. If the +system crashes all cache blocks will be assumed dirty when restarted. + +Per-block policy hints +---------------------- + +Policy plug-ins can store a chunk of data per cache block. It's up to +the policy how big this chunk is, but it should be kept small. Like the +dirty flags this data is lost if there's a crash so a safe fallback +value should always be possible. + +Policy hints affect performance, not correctness. + +Policy messaging +---------------- + +Policies will have different tunables, specific to each one, so we +need a generic way of getting and setting these. Device-mapper +messages are used. Refer to cache-policies.txt. + +Discard bitset resolution +------------------------- + +We can avoid copying data during migration if we know the block has +been discarded. A prime example of this is when mkfs discards the +whole block device. We store a bitset tracking the discard state of +blocks. However, we allow this bitset to have a different block size +from the cache blocks. This is because we need to track the discard +state for all of the origin device (compare with the dirty bitset +which is just for the smaller cache device). + +Target interface +================ + +Constructor +----------- + + :: + + cache <metadata dev> <cache dev> <origin dev> <block size> + <#feature args> [<feature arg>]* + <policy> <#policy args> [policy args]* + + ================ ======================================================= + metadata dev fast device holding the persistent metadata + cache dev fast device holding cached data blocks + origin dev slow device holding original data blocks + block size cache unit size in sectors + + #feature args number of feature arguments passed + feature args writethrough or passthrough (The default is writeback.) + + policy the replacement policy to use + #policy args an even number of arguments corresponding to + key/value pairs passed to the policy + policy args key/value pairs passed to the policy + E.g. 'sequential_threshold 1024' + See cache-policies.txt for details. + ================ ======================================================= + +Optional feature arguments are: + + + ==================== ======================================================== + writethrough write through caching that prohibits cache block + content from being different from origin block content. + Without this argument, the default behaviour is to write + back cache block contents later for performance reasons, + so they may differ from the corresponding origin blocks. + + passthrough a degraded mode useful for various cache coherency + situations (e.g., rolling back snapshots of + underlying storage). Reads and writes always go to + the origin. If a write goes to a cached origin + block, then the cache block is invalidated. + To enable passthrough mode the cache must be clean. + + metadata2 use version 2 of the metadata. This stores the dirty + bits in a separate btree, which improves speed of + shutting down the cache. + + no_discard_passdown disable passing down discards from the cache + to the origin's data device. + ==================== ======================================================== + +A policy called 'default' is always registered. This is an alias for +the policy we currently think is giving best all round performance. + +As the default policy could vary between kernels, if you are relying on +the characteristics of a specific policy, always request it by name. + +Status +------ + +:: + + <metadata block size> <#used metadata blocks>/<#total metadata blocks> + <cache block size> <#used cache blocks>/<#total cache blocks> + <#read hits> <#read misses> <#write hits> <#write misses> + <#demotions> <#promotions> <#dirty> <#features> <features>* + <#core args> <core args>* <policy name> <#policy args> <policy args>* + <cache metadata mode> + + +========================= ===================================================== +metadata block size Fixed block size for each metadata block in + sectors +#used metadata blocks Number of metadata blocks used +#total metadata blocks Total number of metadata blocks +cache block size Configurable block size for the cache device + in sectors +#used cache blocks Number of blocks resident in the cache +#total cache blocks Total number of cache blocks +#read hits Number of times a READ bio has been mapped + to the cache +#read misses Number of times a READ bio has been mapped + to the origin +#write hits Number of times a WRITE bio has been mapped + to the cache +#write misses Number of times a WRITE bio has been + mapped to the origin +#demotions Number of times a block has been removed + from the cache +#promotions Number of times a block has been moved to + the cache +#dirty Number of blocks in the cache that differ + from the origin +#feature args Number of feature args to follow +feature args 'writethrough' (optional) +#core args Number of core arguments (must be even) +core args Key/value pairs for tuning the core + e.g. migration_threshold +policy name Name of the policy +#policy args Number of policy arguments to follow (must be even) +policy args Key/value pairs e.g. sequential_threshold +cache metadata mode ro if read-only, rw if read-write + + In serious cases where even a read-only mode is + deemed unsafe no further I/O will be permitted and + the status will just contain the string 'Fail'. + The userspace recovery tools should then be used. +needs_check 'needs_check' if set, '-' if not set + A metadata operation has failed, resulting in the + needs_check flag being set in the metadata's + superblock. The metadata device must be + deactivated and checked/repaired before the + cache can be made fully operational again. + '-' indicates needs_check is not set. +========================= ===================================================== + +Messages +-------- + +Policies will have different tunables, specific to each one, so we +need a generic way of getting and setting these. Device-mapper +messages are used. (A sysfs interface would also be possible.) + +The message format is:: + + <key> <value> + +E.g.:: + + dmsetup message my_cache 0 sequential_threshold 1024 + + +Invalidation is removing an entry from the cache without writing it +back. Cache blocks can be invalidated via the invalidate_cblocks +message, which takes an arbitrary number of cblock ranges. Each cblock +range's end value is "one past the end", meaning 5-10 expresses a range +of values from 5 to 9. Each cblock must be expressed as a decimal +value, in the future a variant message that takes cblock ranges +expressed in hexadecimal may be needed to better support efficient +invalidation of larger caches. The cache must be in passthrough mode +when invalidate_cblocks is used:: + + invalidate_cblocks [<cblock>|<cblock begin>-<cblock end>]* + +E.g.:: + + dmsetup message my_cache 0 invalidate_cblocks 2345 3456-4567 5678-6789 + +Examples +======== + +The test suite can be found here: + +https://github.com/jthornber/device-mapper-test-suite + +:: + + dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \ + /dev/mapper/ssd /dev/mapper/origin 512 1 writeback default 0' + dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \ + /dev/mapper/ssd /dev/mapper/origin 1024 1 writeback \ + mq 4 sequential_threshold 1024 random_threshold 8' diff --git a/Documentation/admin-guide/device-mapper/delay.rst b/Documentation/admin-guide/device-mapper/delay.rst new file mode 100644 index 000000000..917ba8c33 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/delay.rst @@ -0,0 +1,31 @@ +======== +dm-delay +======== + +Device-Mapper's "delay" target delays reads and/or writes +and maps them to different devices. + +Parameters:: + + <device> <offset> <delay> [<write_device> <write_offset> <write_delay> + [<flush_device> <flush_offset> <flush_delay>]] + +With separate write parameters, the first set is only used for reads. +Offsets are specified in sectors. +Delays are specified in milliseconds. + +Example scripts +=============== + +:: + + #!/bin/sh + # Create device delaying rw operation for 500ms + echo "0 `blockdev --getsz $1` delay $1 0 500" | dmsetup create delayed + +:: + + #!/bin/sh + # Create device delaying only write operation for 500ms and + # splitting reads and writes to different devices $1 $2 + echo "0 `blockdev --getsz $1` delay $1 0 0 $2 0 500" | dmsetup create delayed diff --git a/Documentation/admin-guide/device-mapper/dm-clone.rst b/Documentation/admin-guide/device-mapper/dm-clone.rst new file mode 100644 index 000000000..b43a34c14 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-clone.rst @@ -0,0 +1,333 @@ +.. SPDX-License-Identifier: GPL-2.0-only + +======== +dm-clone +======== + +Introduction +============ + +dm-clone is a device mapper target which produces a one-to-one copy of an +existing, read-only source device into a writable destination device: It +presents a virtual block device which makes all data appear immediately, and +redirects reads and writes accordingly. + +The main use case of dm-clone is to clone a potentially remote, high-latency, +read-only, archival-type block device into a writable, fast, primary-type device +for fast, low-latency I/O. The cloned device is visible/mountable immediately +and the copy of the source device to the destination device happens in the +background, in parallel with user I/O. + +For example, one could restore an application backup from a read-only copy, +accessible through a network storage protocol (NBD, Fibre Channel, iSCSI, AoE, +etc.), into a local SSD or NVMe device, and start using the device immediately, +without waiting for the restore to complete. + +When the cloning completes, the dm-clone table can be removed altogether and be +replaced, e.g., by a linear table, mapping directly to the destination device. + +The dm-clone target reuses the metadata library used by the thin-provisioning +target. + +Glossary +======== + + Hydration + The process of filling a region of the destination device with data from + the same region of the source device, i.e., copying the region from the + source to the destination device. + +Once a region gets hydrated we redirect all I/O regarding it to the destination +device. + +Design +====== + +Sub-devices +----------- + +The target is constructed by passing three devices to it (along with other +parameters detailed later): + +1. A source device - the read-only device that gets cloned and source of the + hydration. + +2. A destination device - the destination of the hydration, which will become a + clone of the source device. + +3. A small metadata device - it records which regions are already valid in the + destination device, i.e., which regions have already been hydrated, or have + been written to directly, via user I/O. + +The size of the destination device must be at least equal to the size of the +source device. + +Regions +------- + +dm-clone divides the source and destination devices in fixed sized regions. +Regions are the unit of hydration, i.e., the minimum amount of data copied from +the source to the destination device. + +The region size is configurable when you first create the dm-clone device. The +recommended region size is the same as the file system block size, which usually +is 4KB. The region size must be between 8 sectors (4KB) and 2097152 sectors +(1GB) and a power of two. + +Reads and writes from/to hydrated regions are serviced from the destination +device. + +A read to a not yet hydrated region is serviced directly from the source device. + +A write to a not yet hydrated region will be delayed until the corresponding +region has been hydrated and the hydration of the region starts immediately. + +Note that a write request with size equal to region size will skip copying of +the corresponding region from the source device and overwrite the region of the +destination device directly. + +Discards +-------- + +dm-clone interprets a discard request to a range that hasn't been hydrated yet +as a hint to skip hydration of the regions covered by the request, i.e., it +skips copying the region's data from the source to the destination device, and +only updates its metadata. + +If the destination device supports discards, then by default dm-clone will pass +down discard requests to it. + +Background Hydration +-------------------- + +dm-clone copies continuously from the source to the destination device, until +all of the device has been copied. + +Copying data from the source to the destination device uses bandwidth. The user +can set a throttle to prevent more than a certain amount of copying occurring at +any one time. Moreover, dm-clone takes into account user I/O traffic going to +the devices and pauses the background hydration when there is I/O in-flight. + +A message `hydration_threshold <#regions>` can be used to set the maximum number +of regions being copied, the default being 1 region. + +dm-clone employs dm-kcopyd for copying portions of the source device to the +destination device. By default, we issue copy requests of size equal to the +region size. A message `hydration_batch_size <#regions>` can be used to tune the +size of these copy requests. Increasing the hydration batch size results in +dm-clone trying to batch together contiguous regions, so we copy the data in +batches of this many regions. + +When the hydration of the destination device finishes, a dm event will be sent +to user space. + +Updating on-disk metadata +------------------------- + +On-disk metadata is committed every time a FLUSH or FUA bio is written. If no +such requests are made then commits will occur every second. This means the +dm-clone device behaves like a physical disk that has a volatile write cache. If +power is lost you may lose some recent writes. The metadata should always be +consistent in spite of any crash. + +Target Interface +================ + +Constructor +----------- + + :: + + clone <metadata dev> <destination dev> <source dev> <region size> + [<#feature args> [<feature arg>]* [<#core args> [<core arg>]*]] + + ================ ============================================================== + metadata dev Fast device holding the persistent metadata + destination dev The destination device, where the source will be cloned + source dev Read only device containing the data that gets cloned + region size The size of a region in sectors + + #feature args Number of feature arguments passed + feature args no_hydration or no_discard_passdown + + #core args An even number of arguments corresponding to key/value pairs + passed to dm-clone + core args Key/value pairs passed to dm-clone, e.g. `hydration_threshold + 256` + ================ ============================================================== + +Optional feature arguments are: + + ==================== ========================================================= + no_hydration Create a dm-clone instance with background hydration + disabled + no_discard_passdown Disable passing down discards to the destination device + ==================== ========================================================= + +Optional core arguments are: + + ================================ ============================================== + hydration_threshold <#regions> Maximum number of regions being copied from + the source to the destination device at any + one time, during background hydration. + hydration_batch_size <#regions> During background hydration, try to batch + together contiguous regions, so we copy data + from the source to the destination device in + batches of this many regions. + ================================ ============================================== + +Status +------ + + :: + + <metadata block size> <#used metadata blocks>/<#total metadata blocks> + <region size> <#hydrated regions>/<#total regions> <#hydrating regions> + <#feature args> <feature args>* <#core args> <core args>* + <clone metadata mode> + + ======================= ======================================================= + metadata block size Fixed block size for each metadata block in sectors + #used metadata blocks Number of metadata blocks used + #total metadata blocks Total number of metadata blocks + region size Configurable region size for the device in sectors + #hydrated regions Number of regions that have finished hydrating + #total regions Total number of regions to hydrate + #hydrating regions Number of regions currently hydrating + #feature args Number of feature arguments to follow + feature args Feature arguments, e.g. `no_hydration` + #core args Even number of core arguments to follow + core args Key/value pairs for tuning the core, e.g. + `hydration_threshold 256` + clone metadata mode ro if read-only, rw if read-write + + In serious cases where even a read-only mode is deemed + unsafe no further I/O will be permitted and the status + will just contain the string 'Fail'. If the metadata + mode changes, a dm event will be sent to user space. + ======================= ======================================================= + +Messages +-------- + + `disable_hydration` + Disable the background hydration of the destination device. + + `enable_hydration` + Enable the background hydration of the destination device. + + `hydration_threshold <#regions>` + Set background hydration threshold. + + `hydration_batch_size <#regions>` + Set background hydration batch size. + +Examples +======== + +Clone a device containing a file system +--------------------------------------- + +1. Create the dm-clone device. + + :: + + dmsetup create clone --table "0 1048576000 clone $metadata_dev $dest_dev \ + $source_dev 8 1 no_hydration" + +2. Mount the device and trim the file system. dm-clone interprets the discards + sent by the file system and it will not hydrate the unused space. + + :: + + mount /dev/mapper/clone /mnt/cloned-fs + fstrim /mnt/cloned-fs + +3. Enable background hydration of the destination device. + + :: + + dmsetup message clone 0 enable_hydration + +4. When the hydration finishes, we can replace the dm-clone table with a linear + table. + + :: + + dmsetup suspend clone + dmsetup load clone --table "0 1048576000 linear $dest_dev 0" + dmsetup resume clone + + The metadata device is no longer needed and can be safely discarded or reused + for other purposes. + +Known issues +============ + +1. We redirect reads, to not-yet-hydrated regions, to the source device. If + reading the source device has high latency and the user repeatedly reads from + the same regions, this behaviour could degrade performance. We should use + these reads as hints to hydrate the relevant regions sooner. Currently, we + rely on the page cache to cache these regions, so we hopefully don't end up + reading them multiple times from the source device. + +2. Release in-core resources, i.e., the bitmaps tracking which regions are + hydrated, after the hydration has finished. + +3. During background hydration, if we fail to read the source or write to the + destination device, we print an error message, but the hydration process + continues indefinitely, until it succeeds. We should stop the background + hydration after a number of failures and emit a dm event for user space to + notice. + +Why not...? +=========== + +We explored the following alternatives before implementing dm-clone: + +1. Use dm-cache with cache size equal to the source device and implement a new + cloning policy: + + * The resulting cache device is not a one-to-one mirror of the source device + and thus we cannot remove the cache device once cloning completes. + + * dm-cache writes to the source device, which violates our requirement that + the source device must be treated as read-only. + + * Caching is semantically different from cloning. + +2. Use dm-snapshot with a COW device equal to the source device: + + * dm-snapshot stores its metadata in the COW device, so the resulting device + is not a one-to-one mirror of the source device. + + * No background copying mechanism. + + * dm-snapshot needs to commit its metadata whenever a pending exception + completes, to ensure snapshot consistency. In the case of cloning, we don't + need to be so strict and can rely on committing metadata every time a FLUSH + or FUA bio is written, or periodically, like dm-thin and dm-cache do. This + improves the performance significantly. + +3. Use dm-mirror: The mirror target has a background copying/mirroring + mechanism, but it writes to all mirrors, thus violating our requirement that + the source device must be treated as read-only. + +4. Use dm-thin's external snapshot functionality. This approach is the most + promising among all alternatives, as the thinly-provisioned volume is a + one-to-one mirror of the source device and handles reads and writes to + un-provisioned/not-yet-cloned areas the same way as dm-clone does. + + Still: + + * There is no background copying mechanism, though one could be implemented. + + * Most importantly, we want to support arbitrary block devices as the + destination of the cloning process and not restrict ourselves to + thinly-provisioned volumes. Thin-provisioning has an inherent metadata + overhead, for maintaining the thin volume mappings, which significantly + degrades performance. + + Moreover, cloning a device shouldn't force the use of thin-provisioning. On + the other hand, if we wish to use thin provisioning, we can just use a thin + LV as dm-clone's destination device. diff --git a/Documentation/admin-guide/device-mapper/dm-crypt.rst b/Documentation/admin-guide/device-mapper/dm-crypt.rst new file mode 100644 index 000000000..aa2d04d95 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-crypt.rst @@ -0,0 +1,181 @@ +======== +dm-crypt +======== + +Device-Mapper's "crypt" target provides transparent encryption of block devices +using the kernel crypto API. + +For a more detailed description of supported parameters see: +https://gitlab.com/cryptsetup/cryptsetup/wikis/DMCrypt + +Parameters:: + + <cipher> <key> <iv_offset> <device path> \ + <offset> [<#opt_params> <opt_params>] + +<cipher> + Encryption cipher, encryption mode and Initial Vector (IV) generator. + + The cipher specifications format is:: + + cipher[:keycount]-chainmode-ivmode[:ivopts] + + Examples:: + + aes-cbc-essiv:sha256 + aes-xts-plain64 + serpent-xts-plain64 + + Cipher format also supports direct specification with kernel crypt API + format (selected by capi: prefix). The IV specification is the same + as for the first format type. + This format is mainly used for specification of authenticated modes. + + The crypto API cipher specifications format is:: + + capi:cipher_api_spec-ivmode[:ivopts] + + Examples:: + + capi:cbc(aes)-essiv:sha256 + capi:xts(aes)-plain64 + + Examples of authenticated modes:: + + capi:gcm(aes)-random + capi:authenc(hmac(sha256),xts(aes))-random + capi:rfc7539(chacha20,poly1305)-random + + The /proc/crypto contains a list of currently loaded crypto modes. + +<key> + Key used for encryption. It is encoded either as a hexadecimal number + or it can be passed as <key_string> prefixed with single colon + character (':') for keys residing in kernel keyring service. + You can only use key sizes that are valid for the selected cipher + in combination with the selected iv mode. + Note that for some iv modes the key string can contain additional + keys (for example IV seed) so the key contains more parts concatenated + into a single string. + +<key_string> + The kernel keyring key is identified by string in following format: + <key_size>:<key_type>:<key_description>. + +<key_size> + The encryption key size in bytes. The kernel key payload size must match + the value passed in <key_size>. + +<key_type> + Either 'logon', 'user', 'encrypted' or 'trusted' kernel key type. + +<key_description> + The kernel keyring key description crypt target should look for + when loading key of <key_type>. + +<keycount> + Multi-key compatibility mode. You can define <keycount> keys and + then sectors are encrypted according to their offsets (sector 0 uses key0; + sector 1 uses key1 etc.). <keycount> must be a power of two. + +<iv_offset> + The IV offset is a sector count that is added to the sector number + before creating the IV. + +<device path> + This is the device that is going to be used as backend and contains the + encrypted data. You can specify it as a path like /dev/xxx or a device + number <major>:<minor>. + +<offset> + Starting sector within the device where the encrypted data begins. + +<#opt_params> + Number of optional parameters. If there are no optional parameters, + the optional parameters section can be skipped or #opt_params can be zero. + Otherwise #opt_params is the number of following arguments. + + Example of optional parameters section: + 3 allow_discards same_cpu_crypt submit_from_crypt_cpus + +allow_discards + Block discard requests (a.k.a. TRIM) are passed through the crypt device. + The default is to ignore discard requests. + + WARNING: Assess the specific security risks carefully before enabling this + option. For example, allowing discards on encrypted devices may lead to + the leak of information about the ciphertext device (filesystem type, + used space etc.) if the discarded blocks can be located easily on the + device later. + +same_cpu_crypt + Perform encryption using the same cpu that IO was submitted on. + The default is to use an unbound workqueue so that encryption work + is automatically balanced between available CPUs. + +submit_from_crypt_cpus + Disable offloading writes to a separate thread after encryption. + There are some situations where offloading write bios from the + encryption threads to a single thread degrades performance + significantly. The default is to offload write bios to the same + thread because it benefits CFQ to have writes submitted using the + same context. + +no_read_workqueue + Bypass dm-crypt internal workqueue and process read requests synchronously. + +no_write_workqueue + Bypass dm-crypt internal workqueue and process write requests synchronously. + This option is automatically enabled for host-managed zoned block devices + (e.g. host-managed SMR hard-disks). + +integrity:<bytes>:<type> + The device requires additional <bytes> metadata per-sector stored + in per-bio integrity structure. This metadata must by provided + by underlying dm-integrity target. + + The <type> can be "none" if metadata is used only for persistent IV. + + For Authenticated Encryption with Additional Data (AEAD) + the <type> is "aead". An AEAD mode additionally calculates and verifies + integrity for the encrypted device. The additional space is then + used for storing authentication tag (and persistent IV if needed). + +sector_size:<bytes> + Use <bytes> as the encryption unit instead of 512 bytes sectors. + This option can be in range 512 - 4096 bytes and must be power of two. + Virtual device will announce this size as a minimal IO and logical sector. + +iv_large_sectors + IV generators will use sector number counted in <sector_size> units + instead of default 512 bytes sectors. + + For example, if <sector_size> is 4096 bytes, plain64 IV for the second + sector will be 8 (without flag) and 1 if iv_large_sectors is present. + The <iv_offset> must be multiple of <sector_size> (in 512 bytes units) + if this flag is specified. + +Example scripts +=============== +LUKS (Linux Unified Key Setup) is now the preferred way to set up disk +encryption with dm-crypt using the 'cryptsetup' utility, see +https://gitlab.com/cryptsetup/cryptsetup + +:: + + #!/bin/sh + # Create a crypt device using dmsetup + dmsetup create crypt1 --table "0 `blockdev --getsz $1` crypt aes-cbc-essiv:sha256 babebabebabebabebabebabebabebabe 0 $1 0" + +:: + + #!/bin/sh + # Create a crypt device using dmsetup when encryption key is stored in keyring service + dmsetup create crypt2 --table "0 `blockdev --getsize $1` crypt aes-cbc-essiv:sha256 :32:logon:my_prefix:my_key 0 $1 0" + +:: + + #!/bin/sh + # Create a crypt device using cryptsetup and LUKS header with default cipher + cryptsetup luksFormat $1 + cryptsetup luksOpen $1 crypt1 diff --git a/Documentation/admin-guide/device-mapper/dm-dust.rst b/Documentation/admin-guide/device-mapper/dm-dust.rst new file mode 100644 index 000000000..e35ec8cd2 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-dust.rst @@ -0,0 +1,305 @@ +dm-dust +======= + +This target emulates the behavior of bad sectors at arbitrary +locations, and the ability to enable the emulation of the failures +at an arbitrary time. + +This target behaves similarly to a linear target. At a given time, +the user can send a message to the target to start failing read +requests on specific blocks (to emulate the behavior of a hard disk +drive with bad sectors). + +When the failure behavior is enabled (i.e.: when the output of +"dmsetup status" displays "fail_read_on_bad_block"), reads of blocks +in the "bad block list" will fail with EIO ("Input/output error"). + +Writes of blocks in the "bad block list will result in the following: + +1. Remove the block from the "bad block list". +2. Successfully complete the write. + +This emulates the "remapped sector" behavior of a drive with bad +sectors. + +Normally, a drive that is encountering bad sectors will most likely +encounter more bad sectors, at an unknown time or location. +With dm-dust, the user can use the "addbadblock" and "removebadblock" +messages to add arbitrary bad blocks at new locations, and the +"enable" and "disable" messages to modulate the state of whether the +configured "bad blocks" will be treated as bad, or bypassed. +This allows the pre-writing of test data and metadata prior to +simulating a "failure" event where bad sectors start to appear. + +Table parameters +---------------- +<device_path> <offset> <blksz> + +Mandatory parameters: + <device_path>: + Path to the block device. + + <offset>: + Offset to data area from start of device_path + + <blksz>: + Block size in bytes + + (minimum 512, maximum 1073741824, must be a power of 2) + +Usage instructions +------------------ + +First, find the size (in 512-byte sectors) of the device to be used:: + + $ sudo blockdev --getsz /dev/vdb1 + 33552384 + +Create the dm-dust device: +(For a device with a block size of 512 bytes) + +:: + + $ sudo dmsetup create dust1 --table '0 33552384 dust /dev/vdb1 0 512' + +(For a device with a block size of 4096 bytes) + +:: + + $ sudo dmsetup create dust1 --table '0 33552384 dust /dev/vdb1 0 4096' + +Check the status of the read behavior ("bypass" indicates that all I/O +will be passed through to the underlying device; "verbose" indicates that +bad block additions, removals, and remaps will be verbosely logged):: + + $ sudo dmsetup status dust1 + 0 33552384 dust 252:17 bypass verbose + + $ sudo dd if=/dev/mapper/dust1 of=/dev/null bs=512 count=128 iflag=direct + 128+0 records in + 128+0 records out + + $ sudo dd if=/dev/zero of=/dev/mapper/dust1 bs=512 count=128 oflag=direct + 128+0 records in + 128+0 records out + +Adding and removing bad blocks +------------------------------ + +At any time (i.e.: whether the device has the "bad block" emulation +enabled or disabled), bad blocks may be added or removed from the +device via the "addbadblock" and "removebadblock" messages:: + + $ sudo dmsetup message dust1 0 addbadblock 60 + kernel: device-mapper: dust: badblock added at block 60 + + $ sudo dmsetup message dust1 0 addbadblock 67 + kernel: device-mapper: dust: badblock added at block 67 + + $ sudo dmsetup message dust1 0 addbadblock 72 + kernel: device-mapper: dust: badblock added at block 72 + +These bad blocks will be stored in the "bad block list". +While the device is in "bypass" mode, reads and writes will succeed:: + + $ sudo dmsetup status dust1 + 0 33552384 dust 252:17 bypass + +Enabling block read failures +---------------------------- + +To enable the "fail read on bad block" behavior, send the "enable" message:: + + $ sudo dmsetup message dust1 0 enable + kernel: device-mapper: dust: enabling read failures on bad sectors + + $ sudo dmsetup status dust1 + 0 33552384 dust 252:17 fail_read_on_bad_block + +With the device in "fail read on bad block" mode, attempting to read a +block will encounter an "Input/output error":: + + $ sudo dd if=/dev/mapper/dust1 of=/dev/null bs=512 count=1 skip=67 iflag=direct + dd: error reading '/dev/mapper/dust1': Input/output error + 0+0 records in + 0+0 records out + 0 bytes copied, 0.00040651 s, 0.0 kB/s + +...and writing to the bad blocks will remove the blocks from the list, +therefore emulating the "remap" behavior of hard disk drives:: + + $ sudo dd if=/dev/zero of=/dev/mapper/dust1 bs=512 count=128 oflag=direct + 128+0 records in + 128+0 records out + + kernel: device-mapper: dust: block 60 removed from badblocklist by write + kernel: device-mapper: dust: block 67 removed from badblocklist by write + kernel: device-mapper: dust: block 72 removed from badblocklist by write + kernel: device-mapper: dust: block 87 removed from badblocklist by write + +Bad block add/remove error handling +----------------------------------- + +Attempting to add a bad block that already exists in the list will +result in an "Invalid argument" error, as well as a helpful message:: + + $ sudo dmsetup message dust1 0 addbadblock 88 + device-mapper: message ioctl on dust1 failed: Invalid argument + kernel: device-mapper: dust: block 88 already in badblocklist + +Attempting to remove a bad block that doesn't exist in the list will +result in an "Invalid argument" error, as well as a helpful message:: + + $ sudo dmsetup message dust1 0 removebadblock 87 + device-mapper: message ioctl on dust1 failed: Invalid argument + kernel: device-mapper: dust: block 87 not found in badblocklist + +Counting the number of bad blocks in the bad block list +------------------------------------------------------- + +To count the number of bad blocks configured in the device, run the +following message command:: + + $ sudo dmsetup message dust1 0 countbadblocks + +A message will print with the number of bad blocks currently +configured on the device:: + + countbadblocks: 895 badblock(s) found + +Querying for specific bad blocks +-------------------------------- + +To find out if a specific block is in the bad block list, run the +following message command:: + + $ sudo dmsetup message dust1 0 queryblock 72 + +The following message will print if the block is in the list:: + + dust_query_block: block 72 found in badblocklist + +The following message will print if the block is not in the list:: + + dust_query_block: block 72 not found in badblocklist + +The "queryblock" message command will work in both the "enabled" +and "disabled" modes, allowing the verification of whether a block +will be treated as "bad" without having to issue I/O to the device, +or having to "enable" the bad block emulation. + +Clearing the bad block list +--------------------------- + +To clear the bad block list (without needing to individually run +a "removebadblock" message command for every block), run the +following message command:: + + $ sudo dmsetup message dust1 0 clearbadblocks + +After clearing the bad block list, the following message will appear:: + + dust_clear_badblocks: badblocks cleared + +If there were no bad blocks to clear, the following message will +appear:: + + dust_clear_badblocks: no badblocks found + +Listing the bad block list +-------------------------- + +To list all bad blocks in the bad block list (using an example device +with blocks 1 and 2 in the bad block list), run the following message +command:: + + $ sudo dmsetup message dust1 0 listbadblocks + 1 + 2 + +If there are no bad blocks in the bad block list, the command will +execute with no output:: + + $ sudo dmsetup message dust1 0 listbadblocks + +Message commands list +--------------------- + +Below is a list of the messages that can be sent to a dust device: + +Operations on blocks (requires a <blknum> argument):: + + addbadblock <blknum> + queryblock <blknum> + removebadblock <blknum> + +...where <blknum> is a block number within range of the device +(corresponding to the block size of the device.) + +Single argument message commands:: + + countbadblocks + clearbadblocks + listbadblocks + disable + enable + quiet + +Device removal +-------------- + +When finished, remove the device via the "dmsetup remove" command:: + + $ sudo dmsetup remove dust1 + +Quiet mode +---------- + +On test runs with many bad blocks, it may be desirable to avoid +excessive logging (from bad blocks added, removed, or "remapped"). +This can be done by enabling "quiet mode" via the following message:: + + $ sudo dmsetup message dust1 0 quiet + +This will suppress log messages from add / remove / removed by write +operations. Log messages from "countbadblocks" or "queryblock" +message commands will still print in quiet mode. + +The status of quiet mode can be seen by running "dmsetup status":: + + $ sudo dmsetup status dust1 + 0 33552384 dust 252:17 fail_read_on_bad_block quiet + +To disable quiet mode, send the "quiet" message again:: + + $ sudo dmsetup message dust1 0 quiet + + $ sudo dmsetup status dust1 + 0 33552384 dust 252:17 fail_read_on_bad_block verbose + +(The presence of "verbose" indicates normal logging.) + +"Why not...?" +------------- + +scsi_debug has a "medium error" mode that can fail reads on one +specified sector (sector 0x1234, hardcoded in the source code), but +it uses RAM for the persistent storage, which drastically decreases +the potential device size. + +dm-flakey fails all I/O from all block locations at a specified time +frequency, and not a given point in time. + +When a bad sector occurs on a hard disk drive, reads to that sector +are failed by the device, usually resulting in an error code of EIO +("I/O error") or ENODATA ("No data available"). However, a write to +the sector may succeed, and result in the sector becoming readable +after the device controller no longer experiences errors reading the +sector (or after a reallocation of the sector). However, there may +be bad sectors that occur on the device in the future, in a different, +unpredictable location. + +This target seeks to provide a device that can exhibit the behavior +of a bad sector at a known sector location, at a known time, based +on a large storage device (at least tens of gigabytes, not occupying +system memory). diff --git a/Documentation/admin-guide/device-mapper/dm-ebs.rst b/Documentation/admin-guide/device-mapper/dm-ebs.rst new file mode 100644 index 000000000..c09f66db5 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-ebs.rst @@ -0,0 +1,51 @@ +====== +dm-ebs +====== + + +This target is similar to the linear target except that it emulates +a smaller logical block size on a device with a larger logical block +size. Its main purpose is to provide emulation of 512 byte sectors on +devices that do not provide this emulation (i.e. 4K native disks). + +Supported emulated logical block sizes 512, 1024, 2048 and 4096. + +Underlying block size can be set to > 4K to test buffering larger units. + + +Table parameters +---------------- + <dev path> <offset> <emulated sectors> [<underlying sectors>] + +Mandatory parameters: + + <dev path>: + Full pathname to the underlying block-device, + or a "major:minor" device-number. + <offset>: + Starting sector within the device; + has to be a multiple of <emulated sectors>. + <emulated sectors>: + Number of sectors defining the logical block size to be emulated; + 1, 2, 4, 8 sectors of 512 bytes supported. + +Optional parameter: + + <underlying sectors>: + Number of sectors defining the logical block size of <dev path>. + 2^N supported, e.g. 8 = emulate 8 sectors of 512 bytes = 4KiB. + If not provided, the logical block size of <dev path> will be used. + + +Examples: + +Emulate 1 sector = 512 bytes logical block size on /dev/sda starting at +offset 1024 sectors with underlying devices block size automatically set: + +ebs /dev/sda 1024 1 + +Emulate 2 sector = 1KiB logical block size on /dev/sda starting at +offset 128 sectors, enforce 2KiB underlying device block size. +This presumes 2KiB logical blocksize on /dev/sda or less to work: + +ebs /dev/sda 128 2 4 diff --git a/Documentation/admin-guide/device-mapper/dm-flakey.rst b/Documentation/admin-guide/device-mapper/dm-flakey.rst new file mode 100644 index 000000000..f967c5fea --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-flakey.rst @@ -0,0 +1,88 @@ +========= +dm-flakey +========= + +This target is the same as the linear target except that it exhibits +unreliable behaviour periodically. It's been found useful in simulating +failing devices for testing purposes. + +Starting from the time the table is loaded, the device is available for +<up interval> seconds, then exhibits unreliable behaviour for <down +interval> seconds, and then this cycle repeats. + +Also, consider using this in combination with the dm-delay target too, +which can delay reads and writes and/or send them to different +underlying devices. + +Table parameters +---------------- + +:: + + <dev path> <offset> <up interval> <down interval> \ + [<num_features> [<feature arguments>]] + +Mandatory parameters: + + <dev path>: + Full pathname to the underlying block-device, or a + "major:minor" device-number. + <offset>: + Starting sector within the device. + <up interval>: + Number of seconds device is available. + <down interval>: + Number of seconds device returns errors. + +Optional feature parameters: + + If no feature parameters are present, during the periods of + unreliability, all I/O returns errors. + + error_reads: + All read I/O is failed with an error signalled. + Write I/O is handled correctly. + + drop_writes: + All write I/O is silently ignored. + Read I/O is handled correctly. + + error_writes: + All write I/O is failed with an error signalled. + Read I/O is handled correctly. + + corrupt_bio_byte <Nth_byte> <direction> <value> <flags>: + During <down interval>, replace <Nth_byte> of the data of + each matching bio with <value>. + + <Nth_byte>: + The offset of the byte to replace. + Counting starts at 1, to replace the first byte. + <direction>: + Either 'r' to corrupt reads or 'w' to corrupt writes. + 'w' is incompatible with drop_writes. + <value>: + The value (from 0-255) to write. + <flags>: + Perform the replacement only if bio->bi_opf has all the + selected flags set. + + random_read_corrupt <probability> + During <down interval>, replace random byte in a read bio + with a random value. probability is an integer between + 0 and 1000000000 meaning 0% to 100% probability of corruption. + + random_write_corrupt <probability> + During <down interval>, replace random byte in a write bio + with a random value. probability is an integer between + 0 and 1000000000 meaning 0% to 100% probability of corruption. + +Examples: + +Replaces the 32nd byte of READ bios with the value 1:: + + corrupt_bio_byte 32 r 1 0 + +Replaces the 224th byte of REQ_META (=32) bios with the value 0:: + + corrupt_bio_byte 224 w 0 32 diff --git a/Documentation/admin-guide/device-mapper/dm-ima.rst b/Documentation/admin-guide/device-mapper/dm-ima.rst new file mode 100644 index 000000000..a4aa50a82 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-ima.rst @@ -0,0 +1,715 @@ +====== +dm-ima +====== + +For a given system, various external services/infrastructure tools +(including the attestation service) interact with it - both during the +setup and during rest of the system run-time. They share sensitive data +and/or execute critical workload on that system. The external services +may want to verify the current run-time state of the relevant kernel +subsystems before fully trusting the system with business-critical +data/workload. + +Device mapper plays a critical role on a given system by providing +various important functionalities to the block devices using various +target types like crypt, verity, integrity etc. Each of these target +types’ functionalities can be configured with various attributes. +The attributes chosen to configure these target types can significantly +impact the security profile of the block device, and in-turn, of the +system itself. For instance, the type of encryption algorithm and the +key size determines the strength of encryption for a given block device. + +Therefore, verifying the current state of various block devices as well +as their various target attributes is crucial for external services before +fully trusting the system with business-critical data/workload. + +IMA kernel subsystem provides the necessary functionality for +device mapper to measure the state and configuration of +various block devices - + +- by device mapper itself, from within the kernel, +- in a tamper resistant way, +- and re-measured - triggered on state/configuration change. + +Setting the IMA Policy: +======================= +For IMA to measure the data on a given system, the IMA policy on the +system needs to be updated to have following line, and the system needs +to be restarted for the measurements to take effect. + +:: + + /etc/ima/ima-policy + measure func=CRITICAL_DATA label=device-mapper template=ima-buf + +The measurements will be reflected in the IMA logs, which are located at: + +:: + + /sys/kernel/security/integrity/ima/ascii_runtime_measurements + /sys/kernel/security/integrity/ima/binary_runtime_measurements + +Then IMA ASCII measurement log has the following format: + +:: + + <PCR> <TEMPLATE_DATA_DIGEST> <TEMPLATE_NAME> <TEMPLATE_DATA> + + PCR := Platform Configuration Register, in which the values are registered. + This is applicable if TPM chip is in use. + + TEMPLATE_DATA_DIGEST := Template data digest of the IMA record. + TEMPLATE_NAME := Template name that registered the integrity value (e.g. ima-buf). + + TEMPLATE_DATA := <ALG> ":" <EVENT_DIGEST> <EVENT_NAME> <EVENT_DATA> + It contains data for the specific event to be measured, + in a given template data format. + + ALG := Algorithm to compute event digest + EVENT_DIGEST := Digest of the event data + EVENT_NAME := Description of the event (e.g. 'dm_table_load'). + EVENT_DATA := The event data to be measured. + +| + +| *NOTE #1:* +| The DM target data measured by IMA subsystem can alternatively + be queried from userspace by setting DM_IMA_MEASUREMENT_FLAG with + DM_TABLE_STATUS_CMD. + +| + +| *NOTE #2:* +| The Kernel configuration CONFIG_IMA_DISABLE_HTABLE allows measurement of duplicate records. +| To support recording duplicate IMA events in the IMA log, the Kernel needs to be configured with + CONFIG_IMA_DISABLE_HTABLE=y. + +Supported Device States: +======================== +Following device state changes will trigger IMA measurements: + + 1. Table load + #. Device resume + #. Device remove + #. Table clear + #. Device rename + +1. Table load: +--------------- +When a new table is loaded in a device's inactive table slot, +the device information and target specific details from the +targets in the table are measured. + +The IMA measurement log has the following format for 'dm_table_load': + +:: + + EVENT_NAME := "dm_table_load" + EVENT_DATA := <dm_version_str> ";" <device_metadata> ";" <table_load_data> + + dm_version_str := "dm_version=" <N> "." <N> "." <N> + Same as Device Mapper driver version. + device_metadata := <device_name> "," <device_uuid> "," <device_major> "," <device_minor> "," + <minor_count> "," <num_device_targets> ";" + + device_name := "name=" <dm-device-name> + device_uuid := "uuid=" <dm-device-uuid> + device_major := "major=" <N> + device_minor := "minor=" <N> + minor_count := "minor_count=" <N> + num_device_targets := "num_targets=" <N> + dm-device-name := Name of the device. If it contains special characters like '\', ',', ';', + they are prefixed with '\'. + dm-device-uuid := UUID of the device. If it contains special characters like '\', ',', ';', + they are prefixed with '\'. + + table_load_data := <target_data> + Represents the data (as name=value pairs) from various targets in the table, + which is being loaded into the DM device's inactive table slot. + target_data := <target_data_row> | <target_data><target_data_row> + + target_data_row := <target_index> "," <target_begin> "," <target_len> "," <target_name> "," + <target_version> "," <target_attributes> ";" + target_index := "target_index=" <N> + Represents nth target in the table (from 0 to N-1 targets specified in <num_device_targets>) + If all the data for N targets doesn't fit in the given buffer - then the data that fits + in the buffer (say from target 0 to x) is measured in a given IMA event. + The remaining data from targets x+1 to N-1 is measured in the subsequent IMA events, + with the same format as that of 'dm_table_load' + i.e. <dm_version_str> ";" <device_metadata> ";" <table_load_data>. + + target_begin := "target_begin=" <N> + target_len := "target_len=" <N> + target_name := Name of the target. 'linear', 'crypt', 'integrity' etc. + The targets that are supported for IMA measurements are documented below in the + 'Supported targets' section. + target_version := "target_version=" <N> "." <N> "." <N> + target_attributes := Data containing comma separated list of name=value pairs of target specific attributes. + + For instance, if a linear device is created with the following table entries, + # dmsetup create linear1 + 0 2 linear /dev/loop0 512 + 2 2 linear /dev/loop0 512 + 4 2 linear /dev/loop0 512 + 6 2 linear /dev/loop0 512 + + Then IMA ASCII measurement log will have the following entry: + (converted from ASCII to text for readability) + + 10 a8c5ff755561c7a28146389d1514c318592af49a ima-buf sha256:4d73481ecce5eadba8ab084640d85bb9ca899af4d0a122989252a76efadc5b72 + dm_table_load + dm_version=4.45.0; + name=linear1,uuid=,major=253,minor=0,minor_count=1,num_targets=4; + target_index=0,target_begin=0,target_len=2,target_name=linear,target_version=1.4.0,device_name=7:0,start=512; + target_index=1,target_begin=2,target_len=2,target_name=linear,target_version=1.4.0,device_name=7:0,start=512; + target_index=2,target_begin=4,target_len=2,target_name=linear,target_version=1.4.0,device_name=7:0,start=512; + target_index=3,target_begin=6,target_len=2,target_name=linear,target_version=1.4.0,device_name=7:0,start=512; + +2. Device resume: +------------------ +When a suspended device is resumed, the device information and the hash of the +data from previous load of an active table are measured. + +The IMA measurement log has the following format for 'dm_device_resume': + +:: + + EVENT_NAME := "dm_device_resume" + EVENT_DATA := <dm_version_str> ";" <device_metadata> ";" <active_table_hash> ";" <current_device_capacity> ";" + + dm_version_str := As described in the 'Table load' section above. + device_metadata := As described in the 'Table load' section above. + active_table_hash := "active_table_hash=" <table_hash_alg> ":" <table_hash> + Rerpresents the hash of the IMA data being measured for the + active table for the device. + table_hash_alg := Algorithm used to compute the hash. + table_hash := Hash of the (<dm_version_str> ";" <device_metadata> ";" <table_load_data> ";") + as described in the 'dm_table_load' above. + Note: If the table_load data spans across multiple IMA 'dm_table_load' + events for a given device, the hash is computed combining all the event data + i.e. (<dm_version_str> ";" <device_metadata> ";" <table_load_data> ";") + across all those events. + current_device_capacity := "current_device_capacity=" <N> + + For instance, if a linear device is resumed with the following command, + #dmsetup resume linear1 + + then IMA ASCII measurement log will have an entry with: + (converted from ASCII to text for readability) + + 10 56c00cc062ffc24ccd9ac2d67d194af3282b934e ima-buf sha256:e7d12c03b958b4e0e53e7363a06376be88d98a1ac191fdbd3baf5e4b77f329b6 + dm_device_resume + dm_version=4.45.0; + name=linear1,uuid=,major=253,minor=0,minor_count=1,num_targets=4; + active_table_hash=sha256:4d73481ecce5eadba8ab084640d85bb9ca899af4d0a122989252a76efadc5b72;current_device_capacity=8; + +3. Device remove: +------------------ +When a device is removed, the device information and a sha256 hash of the +data from an active and inactive table are measured. + +The IMA measurement log has the following format for 'dm_device_remove': + +:: + + EVENT_NAME := "dm_device_remove" + EVENT_DATA := <dm_version_str> ";" <device_active_metadata> ";" <device_inactive_metadata> ";" + <active_table_hash> "," <inactive_table_hash> "," <remove_all> ";" <current_device_capacity> ";" + + dm_version_str := As described in the 'Table load' section above. + device_active_metadata := Device metadata that reflects the currently loaded active table. + The format is same as 'device_metadata' described in the 'Table load' section above. + device_inactive_metadata := Device metadata that reflects the inactive table. + The format is same as 'device_metadata' described in the 'Table load' section above. + active_table_hash := Hash of the currently loaded active table. + The format is same as 'active_table_hash' described in the 'Device resume' section above. + inactive_table_hash := Hash of the inactive table. + The format is same as 'active_table_hash' described in the 'Device resume' section above. + remove_all := "remove_all=" <yes_no> + yes_no := "y" | "n" + current_device_capacity := "current_device_capacity=" <N> + + For instance, if a linear device is removed with the following command, + #dmsetup remove l1 + + then IMA ASCII measurement log will have the following entry: + (converted from ASCII to text for readability) + + 10 790e830a3a7a31590824ac0642b3b31c2d0e8b38 ima-buf sha256:ab9f3c959367a8f5d4403d6ce9c3627dadfa8f9f0e7ec7899299782388de3840 + dm_device_remove + dm_version=4.45.0; + device_active_metadata=name=l1,uuid=,major=253,minor=2,minor_count=1,num_targets=2; + device_inactive_metadata=name=l1,uuid=,major=253,minor=2,minor_count=1,num_targets=1; + active_table_hash=sha256:4a7e62efaebfc86af755831998b7db6f59b60d23c9534fb16a4455907957953a, + inactive_table_hash=sha256:9d79c175bc2302d55a183e8f50ad4bafd60f7692fd6249e5fd213e2464384b86,remove_all=n; + current_device_capacity=2048; + +4. Table clear: +---------------- +When an inactive table is cleared from the device, the device information and a sha256 hash of the +data from an inactive table are measured. + +The IMA measurement log has the following format for 'dm_table_clear': + +:: + + EVENT_NAME := "dm_table_clear" + EVENT_DATA := <dm_version_str> ";" <device_inactive_metadata> ";" <inactive_table_hash> ";" <current_device_capacity> ";" + + dm_version_str := As described in the 'Table load' section above. + device_inactive_metadata := Device metadata that was captured during the load time inactive table being cleared. + The format is same as 'device_metadata' described in the 'Table load' section above. + inactive_table_hash := Hash of the inactive table being cleared from the device. + The format is same as 'active_table_hash' described in the 'Device resume' section above. + current_device_capacity := "current_device_capacity=" <N> + + For instance, if a linear device's inactive table is cleared, + #dmsetup clear l1 + + then IMA ASCII measurement log will have an entry with: + (converted from ASCII to text for readability) + + 10 77d347408f557f68f0041acb0072946bb2367fe5 ima-buf sha256:42f9ca22163fdfa548e6229dece2959bc5ce295c681644240035827ada0e1db5 + dm_table_clear + dm_version=4.45.0; + name=l1,uuid=,major=253,minor=2,minor_count=1,num_targets=1; + inactive_table_hash=sha256:75c0dc347063bf474d28a9907037eba060bfe39d8847fc0646d75e149045d545;current_device_capacity=1024; + +5. Device rename: +------------------ +When an device's NAME or UUID is changed, the device information and the new NAME and UUID +are measured. + +The IMA measurement log has the following format for 'dm_device_rename': + +:: + + EVENT_NAME := "dm_device_rename" + EVENT_DATA := <dm_version_str> ";" <device_active_metadata> ";" <new_device_name> "," <new_device_uuid> ";" <current_device_capacity> ";" + + dm_version_str := As described in the 'Table load' section above. + device_active_metadata := Device metadata that reflects the currently loaded active table. + The format is same as 'device_metadata' described in the 'Table load' section above. + new_device_name := "new_name=" <dm-device-name> + dm-device-name := Same as <dm-device-name> described in 'Table load' section above + new_device_uuid := "new_uuid=" <dm-device-uuid> + dm-device-uuid := Same as <dm-device-uuid> described in 'Table load' section above + current_device_capacity := "current_device_capacity=" <N> + + E.g 1: if a linear device's name is changed with the following command, + #dmsetup rename linear1 --setuuid 1234-5678 + + then IMA ASCII measurement log will have an entry with: + (converted from ASCII to text for readability) + + 10 8b0423209b4c66ac1523f4c9848c9b51ee332f48 ima-buf sha256:6847b7258134189531db593e9230b257c84f04038b5a18fd2e1473860e0569ac + dm_device_rename + dm_version=4.45.0; + name=linear1,uuid=,major=253,minor=2,minor_count=1,num_targets=1;new_name=linear1,new_uuid=1234-5678; + current_device_capacity=1024; + + E.g 2: if a linear device's name is changed with the following command, + # dmsetup rename linear1 linear=2 + + then IMA ASCII measurement log will have an entry with: + (converted from ASCII to text for readability) + + 10 bef70476b99c2bdf7136fae033aa8627da1bf76f ima-buf sha256:8c6f9f53b9ef9dc8f92a2f2cca8910e622543d0f0d37d484870cb16b95111402 + dm_device_rename + dm_version=4.45.0; + name=linear1,uuid=1234-5678,major=253,minor=2,minor_count=1,num_targets=1; + new_name=linear\=2,new_uuid=1234-5678; + current_device_capacity=1024; + +Supported targets: +================== + +Following targets are supported to measure their data using IMA: + + 1. cache + #. crypt + #. integrity + #. linear + #. mirror + #. multipath + #. raid + #. snapshot + #. striped + #. verity + +1. cache +--------- +The 'target_attributes' (described as part of EVENT_DATA in 'Table load' +section above) has the following data format for 'cache' target. + +:: + + target_attributes := <target_name> "," <target_version> "," <metadata_mode> "," <cache_metadata_device> "," + <cache_device> "," <cache_origin_device> "," <writethrough> "," <writeback> "," + <passthrough> "," <no_discard_passdown> ";" + + target_name := "target_name=cache" + target_version := "target_version=" <N> "." <N> "." <N> + metadata_mode := "metadata_mode=" <cache_metadata_mode> + cache_metadata_mode := "fail" | "ro" | "rw" + cache_device := "cache_device=" <cache_device_name_string> + cache_origin_device := "cache_origin_device=" <cache_origin_device_string> + writethrough := "writethrough=" <yes_no> + writeback := "writeback=" <yes_no> + passthrough := "passthrough=" <yes_no> + no_discard_passdown := "no_discard_passdown=" <yes_no> + yes_no := "y" | "n" + + E.g. + When a 'cache' target is loaded, then IMA ASCII measurement log will have an entry + similar to the following, depicting what 'cache' attributes are measured in EVENT_DATA + for 'dm_table_load' event. + (converted from ASCII to text for readability) + + dm_version=4.45.0;name=cache1,uuid=cache_uuid,major=253,minor=2,minor_count=1,num_targets=1; + target_index=0,target_begin=0,target_len=28672,target_name=cache,target_version=2.2.0,metadata_mode=rw, + cache_metadata_device=253:4,cache_device=253:3,cache_origin_device=253:5,writethrough=y,writeback=n, + passthrough=n,metadata2=y,no_discard_passdown=n; + + +2. crypt +--------- +The 'target_attributes' (described as part of EVENT_DATA in 'Table load' +section above) has the following data format for 'crypt' target. + +:: + + target_attributes := <target_name> "," <target_version> "," <allow_discards> "," <same_cpu_crypt> "," + <submit_from_crypt_cpus> "," <no_read_workqueue> "," <no_write_workqueue> "," + <iv_large_sectors> "," <iv_large_sectors> "," [<integrity_tag_size> ","] [<cipher_auth> ","] + [<sector_size> ","] [<cipher_string> ","] <key_size> "," <key_parts> "," + <key_extra_size> "," <key_mac_size> ";" + + target_name := "target_name=crypt" + target_version := "target_version=" <N> "." <N> "." <N> + allow_discards := "allow_discards=" <yes_no> + same_cpu_crypt := "same_cpu_crypt=" <yes_no> + submit_from_crypt_cpus := "submit_from_crypt_cpus=" <yes_no> + no_read_workqueue := "no_read_workqueue=" <yes_no> + no_write_workqueue := "no_write_workqueue=" <yes_no> + iv_large_sectors := "iv_large_sectors=" <yes_no> + integrity_tag_size := "integrity_tag_size=" <N> + cipher_auth := "cipher_auth=" <string> + sector_size := "sector_size=" <N> + cipher_string := "cipher_string=" + key_size := "key_size=" <N> + key_parts := "key_parts=" <N> + key_extra_size := "key_extra_size=" <N> + key_mac_size := "key_mac_size=" <N> + yes_no := "y" | "n" + + E.g. + When a 'crypt' target is loaded, then IMA ASCII measurement log will have an entry + similar to the following, depicting what 'crypt' attributes are measured in EVENT_DATA + for 'dm_table_load' event. + (converted from ASCII to text for readability) + + dm_version=4.45.0; + name=crypt1,uuid=crypt_uuid1,major=253,minor=0,minor_count=1,num_targets=1; + target_index=0,target_begin=0,target_len=1953125,target_name=crypt,target_version=1.23.0, + allow_discards=y,same_cpu=n,submit_from_crypt_cpus=n,no_read_workqueue=n,no_write_workqueue=n, + iv_large_sectors=n,cipher_string=aes-xts-plain64,key_size=32,key_parts=1,key_extra_size=0,key_mac_size=0; + +3. integrity +------------- +The 'target_attributes' (described as part of EVENT_DATA in 'Table load' +section above) has the following data format for 'integrity' target. + +:: + + target_attributes := <target_name> "," <target_version> "," <dev_name> "," <start> + <tag_size> "," <mode> "," [<meta_device> ","] [<block_size> ","] <recalculate> "," + <allow_discards> "," <fix_padding> "," <fix_hmac> "," <legacy_recalculate> "," + <journal_sectors> "," <interleave_sectors> "," <buffer_sectors> ";" + + target_name := "target_name=integrity" + target_version := "target_version=" <N> "." <N> "." <N> + dev_name := "dev_name=" <device_name_str> + start := "start=" <N> + tag_size := "tag_size=" <N> + mode := "mode=" <integrity_mode_str> + integrity_mode_str := "J" | "B" | "D" | "R" + meta_device := "meta_device=" <meta_device_str> + block_size := "block_size=" <N> + recalculate := "recalculate=" <yes_no> + allow_discards := "allow_discards=" <yes_no> + fix_padding := "fix_padding=" <yes_no> + fix_hmac := "fix_hmac=" <yes_no> + legacy_recalculate := "legacy_recalculate=" <yes_no> + journal_sectors := "journal_sectors=" <N> + interleave_sectors := "interleave_sectors=" <N> + buffer_sectors := "buffer_sectors=" <N> + yes_no := "y" | "n" + + E.g. + When a 'integrity' target is loaded, then IMA ASCII measurement log will have an entry + similar to the following, depicting what 'integrity' attributes are measured in EVENT_DATA + for 'dm_table_load' event. + (converted from ASCII to text for readability) + + dm_version=4.45.0; + name=integrity1,uuid=,major=253,minor=1,minor_count=1,num_targets=1; + target_index=0,target_begin=0,target_len=7856,target_name=integrity,target_version=1.10.0, + dev_name=253:0,start=0,tag_size=32,mode=J,recalculate=n,allow_discards=n,fix_padding=n, + fix_hmac=n,legacy_recalculate=n,journal_sectors=88,interleave_sectors=32768,buffer_sectors=128; + + +4. linear +---------- +The 'target_attributes' (described as part of EVENT_DATA in 'Table load' +section above) has the following data format for 'linear' target. + +:: + + target_attributes := <target_name> "," <target_version> "," <device_name> <,> <start> ";" + + target_name := "target_name=linear" + target_version := "target_version=" <N> "." <N> "." <N> + device_name := "device_name=" <linear_device_name_str> + start := "start=" <N> + + E.g. + When a 'linear' target is loaded, then IMA ASCII measurement log will have an entry + similar to the following, depicting what 'linear' attributes are measured in EVENT_DATA + for 'dm_table_load' event. + (converted from ASCII to text for readability) + + dm_version=4.45.0; + name=linear1,uuid=linear_uuid1,major=253,minor=2,minor_count=1,num_targets=1; + target_index=0,target_begin=0,target_len=28672,target_name=linear,target_version=1.4.0, + device_name=253:1,start=2048; + +5. mirror +---------- +The 'target_attributes' (described as part of EVENT_DATA in 'Table load' +section above) has the following data format for 'mirror' target. + +:: + + target_attributes := <target_name> "," <target_version> "," <nr_mirrors> "," + <mirror_device_data> "," <handle_errors> "," <keep_log> "," <log_type_status> ";" + + target_name := "target_name=mirror" + target_version := "target_version=" <N> "." <N> "." <N> + nr_mirrors := "nr_mirrors=" <NR> + mirror_device_data := <mirror_device_row> | <mirror_device_data><mirror_device_row> + mirror_device_row is repeated <NR> times - for <NR> described in <nr_mirrors>. + mirror_device_row := <mirror_device_name> "," <mirror_device_status> + mirror_device_name := "mirror_device_" <X> "=" <mirror_device_name_str> + where <X> ranges from 0 to (<NR> -1) - for <NR> described in <nr_mirrors>. + mirror_device_status := "mirror_device_" <X> "_status=" <mirror_device_status_char> + where <X> ranges from 0 to (<NR> -1) - for <NR> described in <nr_mirrors>. + mirror_device_status_char := "A" | "F" | "D" | "S" | "R" | "U" + handle_errors := "handle_errors=" <yes_no> + keep_log := "keep_log=" <yes_no> + log_type_status := "log_type_status=" <log_type_status_str> + yes_no := "y" | "n" + + E.g. + When a 'mirror' target is loaded, then IMA ASCII measurement log will have an entry + similar to the following, depicting what 'mirror' attributes are measured in EVENT_DATA + for 'dm_table_load' event. + (converted from ASCII to text for readability) + + dm_version=4.45.0; + name=mirror1,uuid=mirror_uuid1,major=253,minor=6,minor_count=1,num_targets=1; + target_index=0,target_begin=0,target_len=2048,target_name=mirror,target_version=1.14.0,nr_mirrors=2, + mirror_device_0=253:4,mirror_device_0_status=A, + mirror_device_1=253:5,mirror_device_1_status=A, + handle_errors=y,keep_log=n,log_type_status=; + +6. multipath +------------- +The 'target_attributes' (described as part of EVENT_DATA in 'Table load' +section above) has the following data format for 'multipath' target. + +:: + + target_attributes := <target_name> "," <target_version> "," <nr_priority_groups> + ["," <pg_state> "," <priority_groups> "," <priority_group_paths>] ";" + + target_name := "target_name=multipath" + target_version := "target_version=" <N> "." <N> "." <N> + nr_priority_groups := "nr_priority_groups=" <NPG> + priority_groups := <priority_groups_row>|<priority_groups_row><priority_groups> + priority_groups_row := "pg_state_" <X> "=" <pg_state_str> "," "nr_pgpaths_" <X> "=" <NPGP> "," + "path_selector_name_" <X> "=" <string> "," <priority_group_paths> + where <X> ranges from 0 to (<NPG> -1) - for <NPG> described in <nr_priority_groups>. + pg_state_str := "E" | "A" | "D" + <priority_group_paths> := <priority_group_paths_row> | <priority_group_paths_row><priority_group_paths> + priority_group_paths_row := "path_name_" <X> "_" <Y> "=" <string> "," "is_active_" <X> "_" <Y> "=" <is_active_str> + "fail_count_" <X> "_" <Y> "=" <N> "," "path_selector_status_" <X> "_" <Y> "=" <path_selector_status_str> + where <X> ranges from 0 to (<NPG> -1) - for <NPG> described in <nr_priority_groups>, + and <Y> ranges from 0 to (<NPGP> -1) - for <NPGP> described in <priority_groups_row>. + is_active_str := "A" | "F" + + E.g. + When a 'multipath' target is loaded, then IMA ASCII measurement log will have an entry + similar to the following, depicting what 'multipath' attributes are measured in EVENT_DATA + for 'dm_table_load' event. + (converted from ASCII to text for readability) + + dm_version=4.45.0; + name=mp,uuid=,major=253,minor=0,minor_count=1,num_targets=1; + target_index=0,target_begin=0,target_len=2097152,target_name=multipath,target_version=1.14.0,nr_priority_groups=2, + pg_state_0=E,nr_pgpaths_0=2,path_selector_name_0=queue-length, + path_name_0_0=8:16,is_active_0_0=A,fail_count_0_0=0,path_selector_status_0_0=, + path_name_0_1=8:32,is_active_0_1=A,fail_count_0_1=0,path_selector_status_0_1=, + pg_state_1=E,nr_pgpaths_1=2,path_selector_name_1=queue-length, + path_name_1_0=8:48,is_active_1_0=A,fail_count_1_0=0,path_selector_status_1_0=, + path_name_1_1=8:64,is_active_1_1=A,fail_count_1_1=0,path_selector_status_1_1=; + +7. raid +-------- +The 'target_attributes' (described as part of EVENT_DATA in 'Table load' +section above) has the following data format for 'raid' target. + +:: + + target_attributes := <target_name> "," <target_version> "," <raid_type> "," <raid_disks> "," <raid_state> + <raid_device_status> ["," journal_dev_mode] ";" + + target_name := "target_name=raid" + target_version := "target_version=" <N> "." <N> "." <N> + raid_type := "raid_type=" <raid_type_str> + raid_disks := "raid_disks=" <NRD> + raid_state := "raid_state=" <raid_state_str> + raid_state_str := "frozen" | "reshape" |"resync" | "check" | "repair" | "recover" | "idle" |"undef" + raid_device_status := <raid_device_status_row> | <raid_device_status_row><raid_device_status> + <raid_device_status_row> is repeated <NRD> times - for <NRD> described in <raid_disks>. + raid_device_status_row := "raid_device_" <X> "_status=" <raid_device_status_str> + where <X> ranges from 0 to (<NRD> -1) - for <NRD> described in <raid_disks>. + raid_device_status_str := "A" | "D" | "a" | "-" + journal_dev_mode := "journal_dev_mode=" <journal_dev_mode_str> + journal_dev_mode_str := "writethrough" | "writeback" | "invalid" + + E.g. + When a 'raid' target is loaded, then IMA ASCII measurement log will have an entry + similar to the following, depicting what 'raid' attributes are measured in EVENT_DATA + for 'dm_table_load' event. + (converted from ASCII to text for readability) + + dm_version=4.45.0; + name=raid_LV1,uuid=uuid_raid_LV1,major=253,minor=12,minor_count=1,num_targets=1; + target_index=0,target_begin=0,target_len=2048,target_name=raid,target_version=1.15.1, + raid_type=raid10,raid_disks=4,raid_state=idle, + raid_device_0_status=A, + raid_device_1_status=A, + raid_device_2_status=A, + raid_device_3_status=A; + + +8. snapshot +------------ +The 'target_attributes' (described as part of EVENT_DATA in 'Table load' +section above) has the following data format for 'snapshot' target. + +:: + + target_attributes := <target_name> "," <target_version> "," <snap_origin_name> "," + <snap_cow_name> "," <snap_valid> "," <snap_merge_failed> "," <snapshot_overflowed> ";" + + target_name := "target_name=snapshot" + target_version := "target_version=" <N> "." <N> "." <N> + snap_origin_name := "snap_origin_name=" <string> + snap_cow_name := "snap_cow_name=" <string> + snap_valid := "snap_valid=" <yes_no> + snap_merge_failed := "snap_merge_failed=" <yes_no> + snapshot_overflowed := "snapshot_overflowed=" <yes_no> + yes_no := "y" | "n" + + E.g. + When a 'snapshot' target is loaded, then IMA ASCII measurement log will have an entry + similar to the following, depicting what 'snapshot' attributes are measured in EVENT_DATA + for 'dm_table_load' event. + (converted from ASCII to text for readability) + + dm_version=4.45.0; + name=snap1,uuid=snap_uuid1,major=253,minor=13,minor_count=1,num_targets=1; + target_index=0,target_begin=0,target_len=4096,target_name=snapshot,target_version=1.16.0, + snap_origin_name=253:11,snap_cow_name=253:12,snap_valid=y,snap_merge_failed=n,snapshot_overflowed=n; + +9. striped +----------- +The 'target_attributes' (described as part of EVENT_DATA in 'Table load' +section above) has the following data format for 'striped' target. + +:: + + target_attributes := <target_name> "," <target_version> "," <stripes> "," <chunk_size> "," + <stripe_data> ";" + + target_name := "target_name=striped" + target_version := "target_version=" <N> "." <N> "." <N> + stripes := "stripes=" <NS> + chunk_size := "chunk_size=" <N> + stripe_data := <stripe_data_row>|<stripe_data><stripe_data_row> + stripe_data_row := <stripe_device_name> "," <stripe_physical_start> "," <stripe_status> + stripe_device_name := "stripe_" <X> "_device_name=" <stripe_device_name_str> + where <X> ranges from 0 to (<NS> -1) - for <NS> described in <stripes>. + stripe_physical_start := "stripe_" <X> "_physical_start=" <N> + where <X> ranges from 0 to (<NS> -1) - for <NS> described in <stripes>. + stripe_status := "stripe_" <X> "_status=" <stripe_status_str> + where <X> ranges from 0 to (<NS> -1) - for <NS> described in <stripes>. + stripe_status_str := "D" | "A" + + E.g. + When a 'striped' target is loaded, then IMA ASCII measurement log will have an entry + similar to the following, depicting what 'striped' attributes are measured in EVENT_DATA + for 'dm_table_load' event. + (converted from ASCII to text for readability) + + dm_version=4.45.0; + name=striped1,uuid=striped_uuid1,major=253,minor=5,minor_count=1,num_targets=1; + target_index=0,target_begin=0,target_len=640,target_name=striped,target_version=1.6.0,stripes=2,chunk_size=64, + stripe_0_device_name=253:0,stripe_0_physical_start=2048,stripe_0_status=A, + stripe_1_device_name=253:3,stripe_1_physical_start=2048,stripe_1_status=A; + +10. verity +---------- +The 'target_attributes' (described as part of EVENT_DATA in 'Table load' +section above) has the following data format for 'verity' target. + +:: + + target_attributes := <target_name> "," <target_version> "," <hash_failed> "," <verity_version> "," + <data_device_name> "," <hash_device_name> "," <verity_algorithm> "," <root_digest> "," + <salt> "," <ignore_zero_blocks> "," <check_at_most_once> ["," <root_hash_sig_key_desc>] + ["," <verity_mode>] ";" + + target_name := "target_name=verity" + target_version := "target_version=" <N> "." <N> "." <N> + hash_failed := "hash_failed=" <hash_failed_str> + hash_failed_str := "C" | "V" + verity_version := "verity_version=" <verity_version_str> + data_device_name := "data_device_name=" <data_device_name_str> + hash_device_name := "hash_device_name=" <hash_device_name_str> + verity_algorithm := "verity_algorithm=" <verity_algorithm_str> + root_digest := "root_digest=" <root_digest_str> + salt := "salt=" <salt_str> + salt_str := "-" <verity_salt_str> + ignore_zero_blocks := "ignore_zero_blocks=" <yes_no> + check_at_most_once := "check_at_most_once=" <yes_no> + root_hash_sig_key_desc := "root_hash_sig_key_desc=" + verity_mode := "verity_mode=" <verity_mode_str> + verity_mode_str := "ignore_corruption" | "restart_on_corruption" | "panic_on_corruption" | "invalid" + yes_no := "y" | "n" + + E.g. + When a 'verity' target is loaded, then IMA ASCII measurement log will have an entry + similar to the following, depicting what 'verity' attributes are measured in EVENT_DATA + for 'dm_table_load' event. + (converted from ASCII to text for readability) + + dm_version=4.45.0; + name=test-verity,uuid=,major=253,minor=2,minor_count=1,num_targets=1; + target_index=0,target_begin=0,target_len=1953120,target_name=verity,target_version=1.8.0,hash_failed=V, + verity_version=1,data_device_name=253:1,hash_device_name=253:0,verity_algorithm=sha256, + root_digest=29cb87e60ce7b12b443ba6008266f3e41e93e403d7f298f8e3f316b29ff89c5e, + salt=e48da609055204e89ae53b655ca2216dd983cf3cb829f34f63a297d106d53e2d, + ignore_zero_blocks=n,check_at_most_once=n; diff --git a/Documentation/admin-guide/device-mapper/dm-init.rst b/Documentation/admin-guide/device-mapper/dm-init.rst new file mode 100644 index 000000000..981d6a907 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-init.rst @@ -0,0 +1,133 @@ +================================ +Early creation of mapped devices +================================ + +It is possible to configure a device-mapper device to act as the root device for +your system in two ways. + +The first is to build an initial ramdisk which boots to a minimal userspace +which configures the device, then pivot_root(8) in to it. + +The second is to create one or more device-mappers using the module parameter +"dm-mod.create=" through the kernel boot command line argument. + +The format is specified as a string of data separated by commas and optionally +semi-colons, where: + + - a comma is used to separate fields like name, uuid, flags and table + (specifies one device) + - a semi-colon is used to separate devices. + +So the format will look like this:: + + dm-mod.create=<name>,<uuid>,<minor>,<flags>,<table>[,<table>+][;<name>,<uuid>,<minor>,<flags>,<table>[,<table>+]+] + +Where:: + + <name> ::= The device name. + <uuid> ::= xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx | "" + <minor> ::= The device minor number | "" + <flags> ::= "ro" | "rw" + <table> ::= <start_sector> <num_sectors> <target_type> <target_args> + <target_type> ::= "verity" | "linear" | ... (see list below) + +The dm line should be equivalent to the one used by the dmsetup tool with the +`--concise` argument. + +Target types +============ + +Not all target types are available as there are serious risks in allowing +activation of certain DM targets without first using userspace tools to check +the validity of associated metadata. + +======================= ======================================================= +`cache` constrained, userspace should verify cache device +`crypt` allowed +`delay` allowed +`era` constrained, userspace should verify metadata device +`flakey` constrained, meant for test +`linear` allowed +`log-writes` constrained, userspace should verify metadata device +`mirror` constrained, userspace should verify main/mirror device +`raid` constrained, userspace should verify metadata device +`snapshot` constrained, userspace should verify src/dst device +`snapshot-origin` allowed +`snapshot-merge` constrained, userspace should verify src/dst device +`striped` allowed +`switch` constrained, userspace should verify dev path +`thin` constrained, requires dm target message from userspace +`thin-pool` constrained, requires dm target message from userspace +`verity` allowed +`writecache` constrained, userspace should verify cache device +`zero` constrained, not meant for rootfs +======================= ======================================================= + +If the target is not listed above, it is constrained by default (not tested). + +Examples +======== +An example of booting to a linear array made up of user-mode linux block +devices:: + + dm-mod.create="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0 + +This will boot to a rw dm-linear target of 8192 sectors split across two block +devices identified by their major:minor numbers. After boot, udev will rename +this target to /dev/mapper/lroot (depending on the rules). No uuid was assigned. + +An example of multiple device-mappers, with the dm-mod.create="..." contents +is shown here split on multiple lines for readability:: + + dm-linear,,1,rw, + 0 32768 linear 8:1 0, + 32768 1024000 linear 8:2 0; + dm-verity,,3,ro, + 0 1638400 verity 1 /dev/sdc1 /dev/sdc2 4096 4096 204800 1 sha256 + ac87db56303c9c1da433d7209b5a6ef3e4779df141200cbd7c157dcb8dd89c42 + 5ebfe87f7df3235b80a117ebc4078e44f55045487ad4a96581d1adb564615b51 + +Other examples (per target): + +"crypt":: + + dm-crypt,,8,ro, + 0 1048576 crypt aes-xts-plain64 + babebabebabebabebabebabebabebabebabebabebabebabebabebabebabebabe 0 + /dev/sda 0 1 allow_discards + +"delay":: + + dm-delay,,4,ro,0 409600 delay /dev/sda1 0 500 + +"linear":: + + dm-linear,,,rw, + 0 32768 linear /dev/sda1 0, + 32768 1024000 linear /dev/sda2 0, + 1056768 204800 linear /dev/sda3 0, + 1261568 512000 linear /dev/sda4 0 + +"snapshot-origin":: + + dm-snap-orig,,4,ro,0 409600 snapshot-origin 8:2 + +"striped":: + + dm-striped,,4,ro,0 1638400 striped 4 4096 + /dev/sda1 0 /dev/sda2 0 /dev/sda3 0 /dev/sda4 0 + +"verity":: + + dm-verity,,4,ro, + 0 1638400 verity 1 8:1 8:2 4096 4096 204800 1 sha256 + fb1a5a0f00deb908d8b53cb270858975e76cf64105d412ce764225d53b8f3cfd + 51934789604d1b92399c52e7cb149d1b3a1b74bbbcb103b2a0aaacbed5c08584 + +For setups using device-mapper on top of asynchronously probed block +devices (MMC, USB, ..), it may be necessary to tell dm-init to +explicitly wait for them to become available before setting up the +device-mapper tables. This can be done with the "dm-mod.waitfor=" +module parameter, which takes a list of devices to wait for:: + + dm-mod.waitfor=<device1>[,..,<deviceN>] diff --git a/Documentation/admin-guide/device-mapper/dm-integrity.rst b/Documentation/admin-guide/device-mapper/dm-integrity.rst new file mode 100644 index 000000000..d8a5f14d0 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-integrity.rst @@ -0,0 +1,303 @@ +============ +dm-integrity +============ + +The dm-integrity target emulates a block device that has additional +per-sector tags that can be used for storing integrity information. + +A general problem with storing integrity tags with every sector is that +writing the sector and the integrity tag must be atomic - i.e. in case of +crash, either both sector and integrity tag or none of them is written. + +To guarantee write atomicity, the dm-integrity target uses journal, it +writes sector data and integrity tags into a journal, commits the journal +and then copies the data and integrity tags to their respective location. + +The dm-integrity target can be used with the dm-crypt target - in this +situation the dm-crypt target creates the integrity data and passes them +to the dm-integrity target via bio_integrity_payload attached to the bio. +In this mode, the dm-crypt and dm-integrity targets provide authenticated +disk encryption - if the attacker modifies the encrypted device, an I/O +error is returned instead of random data. + +The dm-integrity target can also be used as a standalone target, in this +mode it calculates and verifies the integrity tag internally. In this +mode, the dm-integrity target can be used to detect silent data +corruption on the disk or in the I/O path. + +There's an alternate mode of operation where dm-integrity uses a bitmap +instead of a journal. If a bit in the bitmap is 1, the corresponding +region's data and integrity tags are not synchronized - if the machine +crashes, the unsynchronized regions will be recalculated. The bitmap mode +is faster than the journal mode, because we don't have to write the data +twice, but it is also less reliable, because if data corruption happens +when the machine crashes, it may not be detected. + +When loading the target for the first time, the kernel driver will format +the device. But it will only format the device if the superblock contains +zeroes. If the superblock is neither valid nor zeroed, the dm-integrity +target can't be loaded. + +Accesses to the on-disk metadata area containing checksums (aka tags) are +buffered using dm-bufio. When an access to any given metadata area +occurs, each unique metadata area gets its own buffer(s). The buffer size +is capped at the size of the metadata area, but may be smaller, thereby +requiring multiple buffers to represent the full metadata area. A smaller +buffer size will produce a smaller resulting read/write operation to the +metadata area for small reads/writes. The metadata is still read even in +a full write to the data covered by a single buffer. + +To use the target for the first time: + +1. overwrite the superblock with zeroes +2. load the dm-integrity target with one-sector size, the kernel driver + will format the device +3. unload the dm-integrity target +4. read the "provided_data_sectors" value from the superblock +5. load the dm-integrity target with the target size + "provided_data_sectors" +6. if you want to use dm-integrity with dm-crypt, load the dm-crypt target + with the size "provided_data_sectors" + + +Target arguments: + +1. the underlying block device + +2. the number of reserved sector at the beginning of the device - the + dm-integrity won't read of write these sectors + +3. the size of the integrity tag (if "-" is used, the size is taken from + the internal-hash algorithm) + +4. mode: + + D - direct writes (without journal) + in this mode, journaling is + not used and data sectors and integrity tags are written + separately. In case of crash, it is possible that the data + and integrity tag doesn't match. + J - journaled writes + data and integrity tags are written to the + journal and atomicity is guaranteed. In case of crash, + either both data and tag or none of them are written. The + journaled mode degrades write throughput twice because the + data have to be written twice. + B - bitmap mode - data and metadata are written without any + synchronization, the driver maintains a bitmap of dirty + regions where data and metadata don't match. This mode can + only be used with internal hash. + R - recovery mode - in this mode, journal is not replayed, + checksums are not checked and writes to the device are not + allowed. This mode is useful for data recovery if the + device cannot be activated in any of the other standard + modes. + +5. the number of additional arguments + +Additional arguments: + +journal_sectors:number + The size of journal, this argument is used only if formatting the + device. If the device is already formatted, the value from the + superblock is used. + +interleave_sectors:number (default 32768) + The number of interleaved sectors. This values is rounded down to + a power of two. If the device is already formatted, the value from + the superblock is used. + +meta_device:device + Don't interleave the data and metadata on the device. Use a + separate device for metadata. + +buffer_sectors:number (default 128) + The number of sectors in one metadata buffer. The value is rounded + down to a power of two. + +journal_watermark:number (default 50) + The journal watermark in percents. When the size of the journal + exceeds this watermark, the thread that flushes the journal will + be started. + +commit_time:number (default 10000) + Commit time in milliseconds. When this time passes, the journal is + written. The journal is also written immediately if the FLUSH + request is received. + +internal_hash:algorithm(:key) (the key is optional) + Use internal hash or crc. + When this argument is used, the dm-integrity target won't accept + integrity tags from the upper target, but it will automatically + generate and verify the integrity tags. + + You can use a crc algorithm (such as crc32), then integrity target + will protect the data against accidental corruption. + You can also use a hmac algorithm (for example + "hmac(sha256):0123456789abcdef"), in this mode it will provide + cryptographic authentication of the data without encryption. + + When this argument is not used, the integrity tags are accepted + from an upper layer target, such as dm-crypt. The upper layer + target should check the validity of the integrity tags. + +recalculate + Recalculate the integrity tags automatically. It is only valid + when using internal hash. + +journal_crypt:algorithm(:key) (the key is optional) + Encrypt the journal using given algorithm to make sure that the + attacker can't read the journal. You can use a block cipher here + (such as "cbc(aes)") or a stream cipher (for example "chacha20" + or "ctr(aes)"). + + The journal contains history of last writes to the block device, + an attacker reading the journal could see the last sector numbers + that were written. From the sector numbers, the attacker can infer + the size of files that were written. To protect against this + situation, you can encrypt the journal. + +journal_mac:algorithm(:key) (the key is optional) + Protect sector numbers in the journal from accidental or malicious + modification. To protect against accidental modification, use a + crc algorithm, to protect against malicious modification, use a + hmac algorithm with a key. + + This option is not needed when using internal-hash because in this + mode, the integrity of journal entries is checked when replaying + the journal. Thus, modified sector number would be detected at + this stage. + +block_size:number (default 512) + The size of a data block in bytes. The larger the block size the + less overhead there is for per-block integrity metadata. + Supported values are 512, 1024, 2048 and 4096 bytes. + +sectors_per_bit:number + In the bitmap mode, this parameter specifies the number of + 512-byte sectors that corresponds to one bitmap bit. + +bitmap_flush_interval:number + The bitmap flush interval in milliseconds. The metadata buffers + are synchronized when this interval expires. + +allow_discards + Allow block discard requests (a.k.a. TRIM) for the integrity device. + Discards are only allowed to devices using internal hash. + +fix_padding + Use a smaller padding of the tag area that is more + space-efficient. If this option is not present, large padding is + used - that is for compatibility with older kernels. + +fix_hmac + Improve security of internal_hash and journal_mac: + + - the section number is mixed to the mac, so that an attacker can't + copy sectors from one journal section to another journal section + - the superblock is protected by journal_mac + - a 16-byte salt stored in the superblock is mixed to the mac, so + that the attacker can't detect that two disks have the same hmac + key and also to disallow the attacker to move sectors from one + disk to another + +legacy_recalculate + Allow recalculating of volumes with HMAC keys. This is disabled by + default for security reasons - an attacker could modify the volume, + set recalc_sector to zero, and the kernel would not detect the + modification. + +The journal mode (D/J), buffer_sectors, journal_watermark, commit_time and +allow_discards can be changed when reloading the target (load an inactive +table and swap the tables with suspend and resume). The other arguments +should not be changed when reloading the target because the layout of disk +data depend on them and the reloaded target would be non-functional. + +For example, on a device using the default interleave_sectors of 32768, a +block_size of 512, and an internal_hash of crc32c with a tag size of 4 +bytes, it will take 128 KiB of tags to track a full data area, requiring +256 sectors of metadata per data area. With the default buffer_sectors of +128, that means there will be 2 buffers per metadata area, or 2 buffers +per 16 MiB of data. + +Status line: + +1. the number of integrity mismatches +2. provided data sectors - that is the number of sectors that the user + could use +3. the current recalculating position (or '-' if we didn't recalculate) + + +The layout of the formatted block device: + +* reserved sectors + (they are not used by this target, they can be used for + storing LUKS metadata or for other purpose), the size of the reserved + area is specified in the target arguments + +* superblock (4kiB) + * magic string - identifies that the device was formatted + * version + * log2(interleave sectors) + * integrity tag size + * the number of journal sections + * provided data sectors - the number of sectors that this target + provides (i.e. the size of the device minus the size of all + metadata and padding). The user of this target should not send + bios that access data beyond the "provided data sectors" limit. + * flags + SB_FLAG_HAVE_JOURNAL_MAC + - a flag is set if journal_mac is used + SB_FLAG_RECALCULATING + - recalculating is in progress + SB_FLAG_DIRTY_BITMAP + - journal area contains the bitmap of dirty + blocks + * log2(sectors per block) + * a position where recalculating finished +* journal + The journal is divided into sections, each section contains: + + * metadata area (4kiB), it contains journal entries + + - every journal entry contains: + + * logical sector (specifies where the data and tag should + be written) + * last 8 bytes of data + * integrity tag (the size is specified in the superblock) + + - every metadata sector ends with + + * mac (8-bytes), all the macs in 8 metadata sectors form a + 64-byte value. It is used to store hmac of sector + numbers in the journal section, to protect against a + possibility that the attacker tampers with sector + numbers in the journal. + * commit id + + * data area (the size is variable; it depends on how many journal + entries fit into the metadata area) + + - every sector in the data area contains: + + * data (504 bytes of data, the last 8 bytes are stored in + the journal entry) + * commit id + + To test if the whole journal section was written correctly, every + 512-byte sector of the journal ends with 8-byte commit id. If the + commit id matches on all sectors in a journal section, then it is + assumed that the section was written correctly. If the commit id + doesn't match, the section was written partially and it should not + be replayed. + +* one or more runs of interleaved tags and data. + Each run contains: + + * tag area - it contains integrity tags. There is one tag for each + sector in the data area. The size of this area is always 4KiB or + greater. + * data area - it contains data sectors. The number of data sectors + in one run must be a power of two. log2 of this value is stored + in the superblock. diff --git a/Documentation/admin-guide/device-mapper/dm-io.rst b/Documentation/admin-guide/device-mapper/dm-io.rst new file mode 100644 index 000000000..d2492917a --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-io.rst @@ -0,0 +1,75 @@ +===== +dm-io +===== + +Dm-io provides synchronous and asynchronous I/O services. There are three +types of I/O services available, and each type has a sync and an async +version. + +The user must set up an io_region structure to describe the desired location +of the I/O. Each io_region indicates a block-device along with the starting +sector and size of the region:: + + struct io_region { + struct block_device *bdev; + sector_t sector; + sector_t count; + }; + +Dm-io can read from one io_region or write to one or more io_regions. Writes +to multiple regions are specified by an array of io_region structures. + +The first I/O service type takes a list of memory pages as the data buffer for +the I/O, along with an offset into the first page:: + + struct page_list { + struct page_list *next; + struct page *page; + }; + + int dm_io_sync(unsigned int num_regions, struct io_region *where, int rw, + struct page_list *pl, unsigned int offset, + unsigned long *error_bits); + int dm_io_async(unsigned int num_regions, struct io_region *where, int rw, + struct page_list *pl, unsigned int offset, + io_notify_fn fn, void *context); + +The second I/O service type takes an array of bio vectors as the data buffer +for the I/O. This service can be handy if the caller has a pre-assembled bio, +but wants to direct different portions of the bio to different devices:: + + int dm_io_sync_bvec(unsigned int num_regions, struct io_region *where, + int rw, struct bio_vec *bvec, + unsigned long *error_bits); + int dm_io_async_bvec(unsigned int num_regions, struct io_region *where, + int rw, struct bio_vec *bvec, + io_notify_fn fn, void *context); + +The third I/O service type takes a pointer to a vmalloc'd memory buffer as the +data buffer for the I/O. This service can be handy if the caller needs to do +I/O to a large region but doesn't want to allocate a large number of individual +memory pages:: + + int dm_io_sync_vm(unsigned int num_regions, struct io_region *where, int rw, + void *data, unsigned long *error_bits); + int dm_io_async_vm(unsigned int num_regions, struct io_region *where, int rw, + void *data, io_notify_fn fn, void *context); + +Callers of the asynchronous I/O services must include the name of a completion +callback routine and a pointer to some context data for the I/O:: + + typedef void (*io_notify_fn)(unsigned long error, void *context); + +The "error" parameter in this callback, as well as the `*error` parameter in +all of the synchronous versions, is a bitset (instead of a simple error value). +In the case of an write-I/O to multiple regions, this bitset allows dm-io to +indicate success or failure on each individual region. + +Before using any of the dm-io services, the user should call dm_io_get() +and specify the number of pages they expect to perform I/O on concurrently. +Dm-io will attempt to resize its mempool to make sure enough pages are +always available in order to avoid unnecessary waiting while performing I/O. + +When the user is finished using the dm-io services, they should call +dm_io_put() and specify the same number of pages that were given on the +dm_io_get() call. diff --git a/Documentation/admin-guide/device-mapper/dm-log.rst b/Documentation/admin-guide/device-mapper/dm-log.rst new file mode 100644 index 000000000..ba4fce39b --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-log.rst @@ -0,0 +1,57 @@ +===================== +Device-Mapper Logging +===================== +The device-mapper logging code is used by some of the device-mapper +RAID targets to track regions of the disk that are not consistent. +A region (or portion of the address space) of the disk may be +inconsistent because a RAID stripe is currently being operated on or +a machine died while the region was being altered. In the case of +mirrors, a region would be considered dirty/inconsistent while you +are writing to it because the writes need to be replicated for all +the legs of the mirror and may not reach the legs at the same time. +Once all writes are complete, the region is considered clean again. + +There is a generic logging interface that the device-mapper RAID +implementations use to perform logging operations (see +dm_dirty_log_type in include/linux/dm-dirty-log.h). Various different +logging implementations are available and provide different +capabilities. The list includes: + +============== ============================================================== +Type Files +============== ============================================================== +disk drivers/md/dm-log.c +core drivers/md/dm-log.c +userspace drivers/md/dm-log-userspace* include/linux/dm-log-userspace.h +============== ============================================================== + +The "disk" log type +------------------- +This log implementation commits the log state to disk. This way, the +logging state survives reboots/crashes. + +The "core" log type +------------------- +This log implementation keeps the log state in memory. The log state +will not survive a reboot or crash, but there may be a small boost in +performance. This method can also be used if no storage device is +available for storing log state. + +The "userspace" log type +------------------------ +This log type simply provides a way to export the log API to userspace, +so log implementations can be done there. This is done by forwarding most +logging requests to userspace, where a daemon receives and processes the +request. + +The structure used for communication between kernel and userspace are +located in include/linux/dm-log-userspace.h. Due to the frequency, +diversity, and 2-way communication nature of the exchanges between +kernel and userspace, 'connector' is used as the interface for +communication. + +There are currently two userspace log implementations that leverage this +framework - "clustered-disk" and "clustered-core". These implementations +provide a cluster-coherent log for shared-storage. Device-mapper mirroring +can be used in a shared-storage environment when the cluster log implementations +are employed. diff --git a/Documentation/admin-guide/device-mapper/dm-queue-length.rst b/Documentation/admin-guide/device-mapper/dm-queue-length.rst new file mode 100644 index 000000000..d8e381c1c --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-queue-length.rst @@ -0,0 +1,48 @@ +=============== +dm-queue-length +=============== + +dm-queue-length is a path selector module for device-mapper targets, +which selects a path with the least number of in-flight I/Os. +The path selector name is 'queue-length'. + +Table parameters for each path: [<repeat_count>] + +:: + + <repeat_count>: The number of I/Os to dispatch using the selected + path before switching to the next path. + If not given, internal default is used. To check + the default value, see the activated table. + +Status for each path: <status> <fail-count> <in-flight> + +:: + + <status>: 'A' if the path is active, 'F' if the path is failed. + <fail-count>: The number of path failures. + <in-flight>: The number of in-flight I/Os on the path. + + +Algorithm +========= + +dm-queue-length increments/decrements 'in-flight' when an I/O is +dispatched/completed respectively. +dm-queue-length selects a path with the minimum 'in-flight'. + + +Examples +======== +In case that 2 paths (sda and sdb) are used with repeat_count == 128. + +:: + + # echo "0 10 multipath 0 0 1 1 queue-length 0 2 1 8:0 128 8:16 128" \ + dmsetup create test + # + # dmsetup table + test: 0 10 multipath 0 0 1 1 queue-length 0 2 1 8:0 128 8:16 128 + # + # dmsetup status + test: 0 10 multipath 2 0 0 0 1 1 E 0 2 1 8:0 A 0 0 8:16 A 0 0 diff --git a/Documentation/admin-guide/device-mapper/dm-raid.rst b/Documentation/admin-guide/device-mapper/dm-raid.rst new file mode 100644 index 000000000..bb17e26e3 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-raid.rst @@ -0,0 +1,423 @@ +======= +dm-raid +======= + +The device-mapper RAID (dm-raid) target provides a bridge from DM to MD. +It allows the MD RAID drivers to be accessed using a device-mapper +interface. + + +Mapping Table Interface +----------------------- +The target is named "raid" and it accepts the following parameters:: + + <raid_type> <#raid_params> <raid_params> \ + <#raid_devs> <metadata_dev0> <dev0> [.. <metadata_devN> <devN>] + +<raid_type>: + + ============= =============================================================== + raid0 RAID0 striping (no resilience) + raid1 RAID1 mirroring + raid4 RAID4 with dedicated last parity disk + raid5_n RAID5 with dedicated last parity disk supporting takeover + Same as raid4 + + - Transitory layout + raid5_la RAID5 left asymmetric + + - rotating parity 0 with data continuation + raid5_ra RAID5 right asymmetric + + - rotating parity N with data continuation + raid5_ls RAID5 left symmetric + + - rotating parity 0 with data restart + raid5_rs RAID5 right symmetric + + - rotating parity N with data restart + raid6_zr RAID6 zero restart + + - rotating parity zero (left-to-right) with data restart + raid6_nr RAID6 N restart + + - rotating parity N (right-to-left) with data restart + raid6_nc RAID6 N continue + + - rotating parity N (right-to-left) with data continuation + raid6_n_6 RAID6 with dedicate parity disks + + - parity and Q-syndrome on the last 2 disks; + layout for takeover from/to raid4/raid5_n + raid6_la_6 Same as "raid_la" plus dedicated last Q-syndrome disk + + - layout for takeover from raid5_la from/to raid6 + raid6_ra_6 Same as "raid5_ra" dedicated last Q-syndrome disk + + - layout for takeover from raid5_ra from/to raid6 + raid6_ls_6 Same as "raid5_ls" dedicated last Q-syndrome disk + + - layout for takeover from raid5_ls from/to raid6 + raid6_rs_6 Same as "raid5_rs" dedicated last Q-syndrome disk + + - layout for takeover from raid5_rs from/to raid6 + raid10 Various RAID10 inspired algorithms chosen by additional params + (see raid10_format and raid10_copies below) + + - RAID10: Striped Mirrors (aka 'Striping on top of mirrors') + - RAID1E: Integrated Adjacent Stripe Mirroring + - RAID1E: Integrated Offset Stripe Mirroring + - and other similar RAID10 variants + ============= =============================================================== + + Reference: Chapter 4 of + https://www.snia.org/sites/default/files/SNIA_DDF_Technical_Position_v2.0.pdf + +<#raid_params>: The number of parameters that follow. + +<raid_params> consists of + + Mandatory parameters: + <chunk_size>: + Chunk size in sectors. This parameter is often known as + "stripe size". It is the only mandatory parameter and + is placed first. + + followed by optional parameters (in any order): + [sync|nosync] + Force or prevent RAID initialization. + + [rebuild <idx>] + Rebuild drive number 'idx' (first drive is 0). + + [daemon_sleep <ms>] + Interval between runs of the bitmap daemon that + clear bits. A longer interval means less bitmap I/O but + resyncing after a failure is likely to take longer. + + [min_recovery_rate <kB/sec/disk>] + Throttle RAID initialization + [max_recovery_rate <kB/sec/disk>] + Throttle RAID initialization + [write_mostly <idx>] + Mark drive index 'idx' write-mostly. + [max_write_behind <sectors>] + See '--write-behind=' (man mdadm) + [stripe_cache <sectors>] + Stripe cache size (RAID 4/5/6 only) + [region_size <sectors>] + The region_size multiplied by the number of regions is the + logical size of the array. The bitmap records the device + synchronisation state for each region. + + [raid10_copies <# copies>], [raid10_format <near|far|offset>] + These two options are used to alter the default layout of + a RAID10 configuration. The number of copies is can be + specified, but the default is 2. There are also three + variations to how the copies are laid down - the default + is "near". Near copies are what most people think of with + respect to mirroring. If these options are left unspecified, + or 'raid10_copies 2' and/or 'raid10_format near' are given, + then the layouts for 2, 3 and 4 devices are: + + ======== ========== ============== + 2 drives 3 drives 4 drives + ======== ========== ============== + A1 A1 A1 A1 A2 A1 A1 A2 A2 + A2 A2 A2 A3 A3 A3 A3 A4 A4 + A3 A3 A4 A4 A5 A5 A5 A6 A6 + A4 A4 A5 A6 A6 A7 A7 A8 A8 + .. .. .. .. .. .. .. .. .. + ======== ========== ============== + + The 2-device layout is equivalent 2-way RAID1. The 4-device + layout is what a traditional RAID10 would look like. The + 3-device layout is what might be called a 'RAID1E - Integrated + Adjacent Stripe Mirroring'. + + If 'raid10_copies 2' and 'raid10_format far', then the layouts + for 2, 3 and 4 devices are: + + ======== ============ =================== + 2 drives 3 drives 4 drives + ======== ============ =================== + A1 A2 A1 A2 A3 A1 A2 A3 A4 + A3 A4 A4 A5 A6 A5 A6 A7 A8 + A5 A6 A7 A8 A9 A9 A10 A11 A12 + .. .. .. .. .. .. .. .. .. + A2 A1 A3 A1 A2 A2 A1 A4 A3 + A4 A3 A6 A4 A5 A6 A5 A8 A7 + A6 A5 A9 A7 A8 A10 A9 A12 A11 + .. .. .. .. .. .. .. .. .. + ======== ============ =================== + + If 'raid10_copies 2' and 'raid10_format offset', then the + layouts for 2, 3 and 4 devices are: + + ======== ========== ================ + 2 drives 3 drives 4 drives + ======== ========== ================ + A1 A2 A1 A2 A3 A1 A2 A3 A4 + A2 A1 A3 A1 A2 A2 A1 A4 A3 + A3 A4 A4 A5 A6 A5 A6 A7 A8 + A4 A3 A6 A4 A5 A6 A5 A8 A7 + A5 A6 A7 A8 A9 A9 A10 A11 A12 + A6 A5 A9 A7 A8 A10 A9 A12 A11 + .. .. .. .. .. .. .. .. .. + ======== ========== ================ + + Here we see layouts closely akin to 'RAID1E - Integrated + Offset Stripe Mirroring'. + + [delta_disks <N>] + The delta_disks option value (-251 < N < +251) triggers + device removal (negative value) or device addition (positive + value) to any reshape supporting raid levels 4/5/6 and 10. + RAID levels 4/5/6 allow for addition of devices (metadata + and data device tuple), raid10_near and raid10_offset only + allow for device addition. raid10_far does not support any + reshaping at all. + A minimum of devices have to be kept to enforce resilience, + which is 3 devices for raid4/5 and 4 devices for raid6. + + [data_offset <sectors>] + This option value defines the offset into each data device + where the data starts. This is used to provide out-of-place + reshaping space to avoid writing over data while + changing the layout of stripes, hence an interruption/crash + may happen at any time without the risk of losing data. + E.g. when adding devices to an existing raid set during + forward reshaping, the out-of-place space will be allocated + at the beginning of each raid device. The kernel raid4/5/6/10 + MD personalities supporting such device addition will read the data from + the existing first stripes (those with smaller number of stripes) + starting at data_offset to fill up a new stripe with the larger + number of stripes, calculate the redundancy blocks (CRC/Q-syndrome) + and write that new stripe to offset 0. Same will be applied to all + N-1 other new stripes. This out-of-place scheme is used to change + the RAID type (i.e. the allocation algorithm) as well, e.g. + changing from raid5_ls to raid5_n. + + [journal_dev <dev>] + This option adds a journal device to raid4/5/6 raid sets and + uses it to close the 'write hole' caused by the non-atomic updates + to the component devices which can cause data loss during recovery. + The journal device is used as writethrough thus causing writes to + be throttled versus non-journaled raid4/5/6 sets. + Takeover/reshape is not possible with a raid4/5/6 journal device; + it has to be deconfigured before requesting these. + + [journal_mode <mode>] + This option sets the caching mode on journaled raid4/5/6 raid sets + (see 'journal_dev <dev>' above) to 'writethrough' or 'writeback'. + If 'writeback' is selected the journal device has to be resilient + and must not suffer from the 'write hole' problem itself (e.g. use + raid1 or raid10) to avoid a single point of failure. + +<#raid_devs>: The number of devices composing the array. + Each device consists of two entries. The first is the device + containing the metadata (if any); the second is the one containing the + data. A Maximum of 64 metadata/data device entries are supported + up to target version 1.8.0. + 1.9.0 supports up to 253 which is enforced by the used MD kernel runtime. + + If a drive has failed or is missing at creation time, a '-' can be + given for both the metadata and data drives for a given position. + + +Example Tables +-------------- + +:: + + # RAID4 - 4 data drives, 1 parity (no metadata devices) + # No metadata devices specified to hold superblock/bitmap info + # Chunk size of 1MiB + # (Lines separated for easy reading) + + 0 1960893648 raid \ + raid4 1 2048 \ + 5 - 8:17 - 8:33 - 8:49 - 8:65 - 8:81 + + # RAID4 - 4 data drives, 1 parity (with metadata devices) + # Chunk size of 1MiB, force RAID initialization, + # min recovery rate at 20 kiB/sec/disk + + 0 1960893648 raid \ + raid4 4 2048 sync min_recovery_rate 20 \ + 5 8:17 8:18 8:33 8:34 8:49 8:50 8:65 8:66 8:81 8:82 + + +Status Output +------------- +'dmsetup table' displays the table used to construct the mapping. +The optional parameters are always printed in the order listed +above with "sync" or "nosync" always output ahead of the other +arguments, regardless of the order used when originally loading the table. +Arguments that can be repeated are ordered by value. + + +'dmsetup status' yields information on the state and health of the array. +The output is as follows (normally a single line, but expanded here for +clarity):: + + 1: <s> <l> raid \ + 2: <raid_type> <#devices> <health_chars> \ + 3: <sync_ratio> <sync_action> <mismatch_cnt> + +Line 1 is the standard output produced by device-mapper. + +Line 2 & 3 are produced by the raid target and are best explained by example:: + + 0 1960893648 raid raid4 5 AAAAA 2/490221568 init 0 + +Here we can see the RAID type is raid4, there are 5 devices - all of +which are 'A'live, and the array is 2/490221568 complete with its initial +recovery. Here is a fuller description of the individual fields: + + =============== ========================================================= + <raid_type> Same as the <raid_type> used to create the array. + <health_chars> One char for each device, indicating: + + - 'A' = alive and in-sync + - 'a' = alive but not in-sync + - 'D' = dead/failed. + <sync_ratio> The ratio indicating how much of the array has undergone + the process described by 'sync_action'. If the + 'sync_action' is "check" or "repair", then the process + of "resync" or "recover" can be considered complete. + <sync_action> One of the following possible states: + + idle + - No synchronization action is being performed. + frozen + - The current action has been halted. + resync + - Array is undergoing its initial synchronization + or is resynchronizing after an unclean shutdown + (possibly aided by a bitmap). + recover + - A device in the array is being rebuilt or + replaced. + check + - A user-initiated full check of the array is + being performed. All blocks are read and + checked for consistency. The number of + discrepancies found are recorded in + <mismatch_cnt>. No changes are made to the + array by this action. + repair + - The same as "check", but discrepancies are + corrected. + reshape + - The array is undergoing a reshape. + <mismatch_cnt> The number of discrepancies found between mirror copies + in RAID1/10 or wrong parity values found in RAID4/5/6. + This value is valid only after a "check" of the array + is performed. A healthy array has a 'mismatch_cnt' of 0. + <data_offset> The current data offset to the start of the user data on + each component device of a raid set (see the respective + raid parameter to support out-of-place reshaping). + <journal_char> - 'A' - active write-through journal device. + - 'a' - active write-back journal device. + - 'D' - dead journal device. + - '-' - no journal device. + =============== ========================================================= + + +Message Interface +----------------- +The dm-raid target will accept certain actions through the 'message' interface. +('man dmsetup' for more information on the message interface.) These actions +include: + + ========= ================================================ + "idle" Halt the current sync action. + "frozen" Freeze the current sync action. + "resync" Initiate/continue a resync. + "recover" Initiate/continue a recover process. + "check" Initiate a check (i.e. a "scrub") of the array. + "repair" Initiate a repair of the array. + ========= ================================================ + + +Discard Support +--------------- +The implementation of discard support among hardware vendors varies. +When a block is discarded, some storage devices will return zeroes when +the block is read. These devices set the 'discard_zeroes_data' +attribute. Other devices will return random data. Confusingly, some +devices that advertise 'discard_zeroes_data' will not reliably return +zeroes when discarded blocks are read! Since RAID 4/5/6 uses blocks +from a number of devices to calculate parity blocks and (for performance +reasons) relies on 'discard_zeroes_data' being reliable, it is important +that the devices be consistent. Blocks may be discarded in the middle +of a RAID 4/5/6 stripe and if subsequent read results are not +consistent, the parity blocks may be calculated differently at any time; +making the parity blocks useless for redundancy. It is important to +understand how your hardware behaves with discards if you are going to +enable discards with RAID 4/5/6. + +Since the behavior of storage devices is unreliable in this respect, +even when reporting 'discard_zeroes_data', by default RAID 4/5/6 +discard support is disabled -- this ensures data integrity at the +expense of losing some performance. + +Storage devices that properly support 'discard_zeroes_data' are +increasingly whitelisted in the kernel and can thus be trusted. + +For trusted devices, the following dm-raid module parameter can be set +to safely enable discard support for RAID 4/5/6: + + 'devices_handle_discards_safely' + + +Version History +--------------- + +:: + + 1.0.0 Initial version. Support for RAID 4/5/6 + 1.1.0 Added support for RAID 1 + 1.2.0 Handle creation of arrays that contain failed devices. + 1.3.0 Added support for RAID 10 + 1.3.1 Allow device replacement/rebuild for RAID 10 + 1.3.2 Fix/improve redundancy checking for RAID10 + 1.4.0 Non-functional change. Removes arg from mapping function. + 1.4.1 RAID10 fix redundancy validation checks (commit 55ebbb5). + 1.4.2 Add RAID10 "far" and "offset" algorithm support. + 1.5.0 Add message interface to allow manipulation of the sync_action. + New status (STATUSTYPE_INFO) fields: sync_action and mismatch_cnt. + 1.5.1 Add ability to restore transiently failed devices on resume. + 1.5.2 'mismatch_cnt' is zero unless [last_]sync_action is "check". + 1.6.0 Add discard support (and devices_handle_discard_safely module param). + 1.7.0 Add support for MD RAID0 mappings. + 1.8.0 Explicitly check for compatible flags in the superblock metadata + and reject to start the raid set if any are set by a newer + target version, thus avoiding data corruption on a raid set + with a reshape in progress. + 1.9.0 Add support for RAID level takeover/reshape/region size + and set size reduction. + 1.9.1 Fix activation of existing RAID 4/10 mapped devices + 1.9.2 Don't emit '- -' on the status table line in case the constructor + fails reading a superblock. Correctly emit 'maj:min1 maj:min2' and + 'D' on the status line. If '- -' is passed into the constructor, emit + '- -' on the table line and '-' as the status line health character. + 1.10.0 Add support for raid4/5/6 journal device + 1.10.1 Fix data corruption on reshape request + 1.11.0 Fix table line argument order + (wrong raid10_copies/raid10_format sequence) + 1.11.1 Add raid4/5/6 journal write-back support via journal_mode option + 1.12.1 Fix for MD deadlock between mddev_suspend() and md_write_start() available + 1.13.0 Fix dev_health status at end of "recover" (was 'a', now 'A') + 1.13.1 Fix deadlock caused by early md_stop_writes(). Also fix size an + state races. + 1.13.2 Fix raid redundancy validation and avoid keeping raid set frozen + 1.14.0 Fix reshape race on small devices. Fix stripe adding reshape + deadlock/potential data corruption. Update superblock when + specific devices are requested via rebuild. Fix RAID leg + rebuild errors. + 1.15.0 Fix size extensions not being synchronized in case of new MD bitmap + pages allocated; also fix those not occurring after previous reductions + 1.15.1 Fix argument count and arguments for rebuild/write_mostly/journal_(dev|mode) + on the status line. diff --git a/Documentation/admin-guide/device-mapper/dm-service-time.rst b/Documentation/admin-guide/device-mapper/dm-service-time.rst new file mode 100644 index 000000000..facf277fc --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-service-time.rst @@ -0,0 +1,101 @@ +=============== +dm-service-time +=============== + +dm-service-time is a path selector module for device-mapper targets, +which selects a path with the shortest estimated service time for +the incoming I/O. + +The service time for each path is estimated by dividing the total size +of in-flight I/Os on a path with the performance value of the path. +The performance value is a relative throughput value among all paths +in a path-group, and it can be specified as a table argument. + +The path selector name is 'service-time'. + +Table parameters for each path: + + [<repeat_count> [<relative_throughput>]] + <repeat_count>: + The number of I/Os to dispatch using the selected + path before switching to the next path. + If not given, internal default is used. To check + the default value, see the activated table. + <relative_throughput>: + The relative throughput value of the path + among all paths in the path-group. + The valid range is 0-100. + If not given, minimum value '1' is used. + If '0' is given, the path isn't selected while + other paths having a positive value are available. + +Status for each path: + + <status> <fail-count> <in-flight-size> <relative_throughput> + <status>: + 'A' if the path is active, 'F' if the path is failed. + <fail-count>: + The number of path failures. + <in-flight-size>: + The size of in-flight I/Os on the path. + <relative_throughput>: + The relative throughput value of the path + among all paths in the path-group. + + +Algorithm +========= + +dm-service-time adds the I/O size to 'in-flight-size' when the I/O is +dispatched and subtracts when completed. +Basically, dm-service-time selects a path having minimum service time +which is calculated by:: + + ('in-flight-size' + 'size-of-incoming-io') / 'relative_throughput' + +However, some optimizations below are used to reduce the calculation +as much as possible. + + 1. If the paths have the same 'relative_throughput', skip + the division and just compare the 'in-flight-size'. + + 2. If the paths have the same 'in-flight-size', skip the division + and just compare the 'relative_throughput'. + + 3. If some paths have non-zero 'relative_throughput' and others + have zero 'relative_throughput', ignore those paths with zero + 'relative_throughput'. + +If such optimizations can't be applied, calculate service time, and +compare service time. +If calculated service time is equal, the path having maximum +'relative_throughput' may be better. So compare 'relative_throughput' +then. + + +Examples +======== +In case that 2 paths (sda and sdb) are used with repeat_count == 128 +and sda has an average throughput 1GB/s and sdb has 4GB/s, +'relative_throughput' value may be '1' for sda and '4' for sdb:: + + # echo "0 10 multipath 0 0 1 1 service-time 0 2 2 8:0 128 1 8:16 128 4" \ + dmsetup create test + # + # dmsetup table + test: 0 10 multipath 0 0 1 1 service-time 0 2 2 8:0 128 1 8:16 128 4 + # + # dmsetup status + test: 0 10 multipath 2 0 0 0 1 1 E 0 2 2 8:0 A 0 0 1 8:16 A 0 0 4 + + +Or '2' for sda and '8' for sdb would be also true:: + + # echo "0 10 multipath 0 0 1 1 service-time 0 2 2 8:0 128 2 8:16 128 8" \ + dmsetup create test + # + # dmsetup table + test: 0 10 multipath 0 0 1 1 service-time 0 2 2 8:0 128 2 8:16 128 8 + # + # dmsetup status + test: 0 10 multipath 2 0 0 0 1 1 E 0 2 2 8:0 A 0 0 2 8:16 A 0 0 8 diff --git a/Documentation/admin-guide/device-mapper/dm-uevent.rst b/Documentation/admin-guide/device-mapper/dm-uevent.rst new file mode 100644 index 000000000..4a8ee8d06 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-uevent.rst @@ -0,0 +1,110 @@ +==================== +device-mapper uevent +==================== + +The device-mapper uevent code adds the capability to device-mapper to create +and send kobject uevents (uevents). Previously device-mapper events were only +available through the ioctl interface. The advantage of the uevents interface +is the event contains environment attributes providing increased context for +the event avoiding the need to query the state of the device-mapper device after +the event is received. + +There are two functions currently for device-mapper events. The first function +listed creates the event and the second function sends the event(s):: + + void dm_path_uevent(enum dm_uevent_type event_type, struct dm_target *ti, + const char *path, unsigned nr_valid_paths) + + void dm_send_uevents(struct list_head *events, struct kobject *kobj) + + +The variables added to the uevent environment are: + +Variable Name: DM_TARGET +------------------------ +:Uevent Action(s): KOBJ_CHANGE +:Type: string +:Description: +:Value: Name of device-mapper target that generated the event. + +Variable Name: DM_ACTION +------------------------ +:Uevent Action(s): KOBJ_CHANGE +:Type: string +:Description: +:Value: Device-mapper specific action that caused the uevent action. + PATH_FAILED - A path has failed; + PATH_REINSTATED - A path has been reinstated. + +Variable Name: DM_SEQNUM +------------------------ +:Uevent Action(s): KOBJ_CHANGE +:Type: unsigned integer +:Description: A sequence number for this specific device-mapper device. +:Value: Valid unsigned integer range. + +Variable Name: DM_PATH +---------------------- +:Uevent Action(s): KOBJ_CHANGE +:Type: string +:Description: Major and minor number of the path device pertaining to this + event. +:Value: Path name in the form of "Major:Minor" + +Variable Name: DM_NR_VALID_PATHS +-------------------------------- +:Uevent Action(s): KOBJ_CHANGE +:Type: unsigned integer +:Description: +:Value: Valid unsigned integer range. + +Variable Name: DM_NAME +---------------------- +:Uevent Action(s): KOBJ_CHANGE +:Type: string +:Description: Name of the device-mapper device. +:Value: Name + +Variable Name: DM_UUID +---------------------- +:Uevent Action(s): KOBJ_CHANGE +:Type: string +:Description: UUID of the device-mapper device. +:Value: UUID. (Empty string if there isn't one.) + +An example of the uevents generated as captured by udevmonitor is shown +below + +1.) Path failure:: + + UEVENT[1192521009.711215] change@/block/dm-3 + ACTION=change + DEVPATH=/block/dm-3 + SUBSYSTEM=block + DM_TARGET=multipath + DM_ACTION=PATH_FAILED + DM_SEQNUM=1 + DM_PATH=8:32 + DM_NR_VALID_PATHS=0 + DM_NAME=mpath2 + DM_UUID=mpath-35333333000002328 + MINOR=3 + MAJOR=253 + SEQNUM=1130 + +2.) Path reinstate:: + + UEVENT[1192521132.989927] change@/block/dm-3 + ACTION=change + DEVPATH=/block/dm-3 + SUBSYSTEM=block + DM_TARGET=multipath + DM_ACTION=PATH_REINSTATED + DM_SEQNUM=2 + DM_PATH=8:32 + DM_NR_VALID_PATHS=1 + DM_NAME=mpath2 + DM_UUID=mpath-35333333000002328 + MINOR=3 + MAJOR=253 + SEQNUM=1131 diff --git a/Documentation/admin-guide/device-mapper/dm-zoned.rst b/Documentation/admin-guide/device-mapper/dm-zoned.rst new file mode 100644 index 000000000..932383fe6 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-zoned.rst @@ -0,0 +1,194 @@ +======== +dm-zoned +======== + +The dm-zoned device mapper target exposes a zoned block device (ZBC and +ZAC compliant devices) as a regular block device without any write +pattern constraints. In effect, it implements a drive-managed zoned +block device which hides from the user (a file system or an application +doing raw block device accesses) the sequential write constraints of +host-managed zoned block devices and can mitigate the potential +device-side performance degradation due to excessive random writes on +host-aware zoned block devices. + +For a more detailed description of the zoned block device models and +their constraints see (for SCSI devices): + +https://www.t10.org/drafts.htm#ZBC_Family + +and (for ATA devices): + +http://www.t13.org/Documents/UploadedDocuments/docs2015/di537r05-Zoned_Device_ATA_Command_Set_ZAC.pdf + +The dm-zoned implementation is simple and minimizes system overhead (CPU +and memory usage as well as storage capacity loss). For a 10TB +host-managed disk with 256 MB zones, dm-zoned memory usage per disk +instance is at most 4.5 MB and as little as 5 zones will be used +internally for storing metadata and performing reclaim operations. + +dm-zoned target devices are formatted and checked using the dmzadm +utility available at: + +https://github.com/hgst/dm-zoned-tools + +Algorithm +========= + +dm-zoned implements an on-disk buffering scheme to handle non-sequential +write accesses to the sequential zones of a zoned block device. +Conventional zones are used for caching as well as for storing internal +metadata. It can also use a regular block device together with the zoned +block device; in that case the regular block device will be split logically +in zones with the same size as the zoned block device. These zones will be +placed in front of the zones from the zoned block device and will be handled +just like conventional zones. + +The zones of the device(s) are separated into 2 types: + +1) Metadata zones: these are conventional zones used to store metadata. +Metadata zones are not reported as usable capacity to the user. + +2) Data zones: all remaining zones, the vast majority of which will be +sequential zones used exclusively to store user data. The conventional +zones of the device may be used also for buffering user random writes. +Data in these zones may be directly mapped to the conventional zone, but +later moved to a sequential zone so that the conventional zone can be +reused for buffering incoming random writes. + +dm-zoned exposes a logical device with a sector size of 4096 bytes, +irrespective of the physical sector size of the backend zoned block +device being used. This allows reducing the amount of metadata needed to +manage valid blocks (blocks written). + +The on-disk metadata format is as follows: + +1) The first block of the first conventional zone found contains the +super block which describes the on disk amount and position of metadata +blocks. + +2) Following the super block, a set of blocks is used to describe the +mapping of the logical device blocks. The mapping is done per chunk of +blocks, with the chunk size equal to the zoned block device size. The +mapping table is indexed by chunk number and each mapping entry +indicates the zone number of the device storing the chunk of data. Each +mapping entry may also indicate if the zone number of a conventional +zone used to buffer random modification to the data zone. + +3) A set of blocks used to store bitmaps indicating the validity of +blocks in the data zones follows the mapping table. A valid block is +defined as a block that was written and not discarded. For a buffered +data chunk, a block is always valid only in the data zone mapping the +chunk or in the buffer zone of the chunk. + +For a logical chunk mapped to a conventional zone, all write operations +are processed by directly writing to the zone. If the mapping zone is a +sequential zone, the write operation is processed directly only if the +write offset within the logical chunk is equal to the write pointer +offset within of the sequential data zone (i.e. the write operation is +aligned on the zone write pointer). Otherwise, write operations are +processed indirectly using a buffer zone. In that case, an unused +conventional zone is allocated and assigned to the chunk being +accessed. Writing a block to the buffer zone of a chunk will +automatically invalidate the same block in the sequential zone mapping +the chunk. If all blocks of the sequential zone become invalid, the zone +is freed and the chunk buffer zone becomes the primary zone mapping the +chunk, resulting in native random write performance similar to a regular +block device. + +Read operations are processed according to the block validity +information provided by the bitmaps. Valid blocks are read either from +the sequential zone mapping a chunk, or if the chunk is buffered, from +the buffer zone assigned. If the accessed chunk has no mapping, or the +accessed blocks are invalid, the read buffer is zeroed and the read +operation terminated. + +After some time, the limited number of conventional zones available may +be exhausted (all used to map chunks or buffer sequential zones) and +unaligned writes to unbuffered chunks become impossible. To avoid this +situation, a reclaim process regularly scans used conventional zones and +tries to reclaim the least recently used zones by copying the valid +blocks of the buffer zone to a free sequential zone. Once the copy +completes, the chunk mapping is updated to point to the sequential zone +and the buffer zone freed for reuse. + +Metadata Protection +=================== + +To protect metadata against corruption in case of sudden power loss or +system crash, 2 sets of metadata zones are used. One set, the primary +set, is used as the main metadata region, while the secondary set is +used as a staging area. Modified metadata is first written to the +secondary set and validated by updating the super block in the secondary +set, a generation counter is used to indicate that this set contains the +newest metadata. Once this operation completes, in place of metadata +block updates can be done in the primary metadata set. This ensures that +one of the set is always consistent (all modifications committed or none +at all). Flush operations are used as a commit point. Upon reception of +a flush request, metadata modification activity is temporarily blocked +(for both incoming BIO processing and reclaim process) and all dirty +metadata blocks are staged and updated. Normal operation is then +resumed. Flushing metadata thus only temporarily delays write and +discard requests. Read requests can be processed concurrently while +metadata flush is being executed. + +If a regular device is used in conjunction with the zoned block device, +a third set of metadata (without the zone bitmaps) is written to the +start of the zoned block device. This metadata has a generation counter of +'0' and will never be updated during normal operation; it just serves for +identification purposes. The first and second copy of the metadata +are located at the start of the regular block device. + +Usage +===== + +A zoned block device must first be formatted using the dmzadm tool. This +will analyze the device zone configuration, determine where to place the +metadata sets on the device and initialize the metadata sets. + +Ex:: + + dmzadm --format /dev/sdxx + + +If two drives are to be used, both devices must be specified, with the +regular block device as the first device. + +Ex:: + + dmzadm --format /dev/sdxx /dev/sdyy + + +Formatted device(s) can be started with the dmzadm utility, too.: + +Ex:: + + dmzadm --start /dev/sdxx /dev/sdyy + + +Information about the internal layout and current usage of the zones can +be obtained with the 'status' callback from dmsetup: + +Ex:: + + dmsetup status /dev/dm-X + +will return a line + + 0 <size> zoned <nr_zones> zones <nr_unmap_rnd>/<nr_rnd> random <nr_unmap_seq>/<nr_seq> sequential + +where <nr_zones> is the total number of zones, <nr_unmap_rnd> is the number +of unmapped (ie free) random zones, <nr_rnd> the total number of zones, +<nr_unmap_seq> the number of unmapped sequential zones, and <nr_seq> the +total number of sequential zones. + +Normally the reclaim process will be started once there are less than 50 +percent free random zones. In order to start the reclaim process manually +even before reaching this threshold the 'dmsetup message' function can be +used: + +Ex:: + + dmsetup message /dev/dm-X 0 reclaim + +will start the reclaim process and random zones will be moved to sequential +zones. diff --git a/Documentation/admin-guide/device-mapper/era.rst b/Documentation/admin-guide/device-mapper/era.rst new file mode 100644 index 000000000..90dd5c670 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/era.rst @@ -0,0 +1,116 @@ +====== +dm-era +====== + +Introduction +============ + +dm-era is a target that behaves similar to the linear target. In +addition it keeps track of which blocks were written within a user +defined period of time called an 'era'. Each era target instance +maintains the current era as a monotonically increasing 32-bit +counter. + +Use cases include tracking changed blocks for backup software, and +partially invalidating the contents of a cache to restore cache +coherency after rolling back a vendor snapshot. + +Constructor +=========== + +era <metadata dev> <origin dev> <block size> + + ================ ====================================================== + metadata dev fast device holding the persistent metadata + origin dev device holding data blocks that may change + block size block size of origin data device, granularity that is + tracked by the target + ================ ====================================================== + +Messages +======== + +None of the dm messages take any arguments. + +checkpoint +---------- + +Possibly move to a new era. You shouldn't assume the era has +incremented. After sending this message, you should check the +current era via the status line. + +take_metadata_snap +------------------ + +Create a clone of the metadata, to allow a userland process to read it. + +drop_metadata_snap +------------------ + +Drop the metadata snapshot. + +Status +====== + +<metadata block size> <#used metadata blocks>/<#total metadata blocks> +<current era> <held metadata root | '-'> + +========================= ============================================== +metadata block size Fixed block size for each metadata block in + sectors +#used metadata blocks Number of metadata blocks used +#total metadata blocks Total number of metadata blocks +current era The current era +held metadata root The location, in blocks, of the metadata root + that has been 'held' for userspace read + access. '-' indicates there is no held root +========================= ============================================== + +Detailed use case +================= + +The scenario of invalidating a cache when rolling back a vendor +snapshot was the primary use case when developing this target: + +Taking a vendor snapshot +------------------------ + +- Send a checkpoint message to the era target +- Make a note of the current era in its status line +- Take vendor snapshot (the era and snapshot should be forever + associated now). + +Rolling back to an vendor snapshot +---------------------------------- + +- Cache enters passthrough mode (see: dm-cache's docs in cache.txt) +- Rollback vendor storage +- Take metadata snapshot +- Ascertain which blocks have been written since the snapshot was taken + by checking each block's era +- Invalidate those blocks in the caching software +- Cache returns to writeback/writethrough mode + +Memory usage +============ + +The target uses a bitset to record writes in the current era. It also +has a spare bitset ready for switching over to a new era. Other than +that it uses a few 4k blocks for updating metadata:: + + (4 * nr_blocks) bytes + buffers + +Resilience +========== + +Metadata is updated on disk before a write to a previously unwritten +block is performed. As such dm-era should not be effected by a hard +crash such as power failure. + +Userland tools +============== + +Userland tools are found in the increasingly poorly named +thin-provisioning-tools project: + + https://github.com/jthornber/thin-provisioning-tools diff --git a/Documentation/admin-guide/device-mapper/index.rst b/Documentation/admin-guide/device-mapper/index.rst new file mode 100644 index 000000000..cde52cc09 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/index.rst @@ -0,0 +1,46 @@ +============= +Device Mapper +============= + +.. toctree:: + :maxdepth: 1 + + cache-policies + cache + delay + dm-clone + dm-crypt + dm-dust + dm-ebs + dm-flakey + dm-ima + dm-init + dm-integrity + dm-io + dm-log + dm-queue-length + dm-raid + dm-service-time + dm-uevent + dm-zoned + era + kcopyd + linear + log-writes + persistent-data + snapshot + statistics + striped + switch + thin-provisioning + unstriped + verity + writecache + zero + +.. only:: subproject and html + + Indices + ======= + + * :ref:`genindex` diff --git a/Documentation/admin-guide/device-mapper/kcopyd.rst b/Documentation/admin-guide/device-mapper/kcopyd.rst new file mode 100644 index 000000000..7651d3951 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/kcopyd.rst @@ -0,0 +1,47 @@ +====== +kcopyd +====== + +Kcopyd provides the ability to copy a range of sectors from one block-device +to one or more other block-devices, with an asynchronous completion +notification. It is used by dm-snapshot and dm-mirror. + +Users of kcopyd must first create a client and indicate how many memory pages +to set aside for their copy jobs. This is done with a call to +kcopyd_client_create():: + + int kcopyd_client_create(unsigned int num_pages, + struct kcopyd_client **result); + +To start a copy job, the user must set up io_region structures to describe +the source and destinations of the copy. Each io_region indicates a +block-device along with the starting sector and size of the region. The source +of the copy is given as one io_region structure, and the destinations of the +copy are given as an array of io_region structures:: + + struct io_region { + struct block_device *bdev; + sector_t sector; + sector_t count; + }; + +To start the copy, the user calls kcopyd_copy(), passing in the client +pointer, pointers to the source and destination io_regions, the name of a +completion callback routine, and a pointer to some context data for the copy:: + + int kcopyd_copy(struct kcopyd_client *kc, struct io_region *from, + unsigned int num_dests, struct io_region *dests, + unsigned int flags, kcopyd_notify_fn fn, void *context); + + typedef void (*kcopyd_notify_fn)(int read_err, unsigned int write_err, + void *context); + +When the copy completes, kcopyd will call the user's completion routine, +passing back the user's context pointer. It will also indicate if a read or +write error occurred during the copy. + +When a user is done with all their copy jobs, they should call +kcopyd_client_destroy() to delete the kcopyd client, which will release the +associated memory pages:: + + void kcopyd_client_destroy(struct kcopyd_client *kc); diff --git a/Documentation/admin-guide/device-mapper/linear.rst b/Documentation/admin-guide/device-mapper/linear.rst new file mode 100644 index 000000000..9d17fc6e6 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/linear.rst @@ -0,0 +1,63 @@ +========= +dm-linear +========= + +Device-Mapper's "linear" target maps a linear range of the Device-Mapper +device onto a linear range of another device. This is the basic building +block of logical volume managers. + +Parameters: <dev path> <offset> + <dev path>: + Full pathname to the underlying block-device, or a + "major:minor" device-number. + <offset>: + Starting sector within the device. + + +Example scripts +=============== + +:: + + #!/bin/sh + # Create an identity mapping for a device + echo "0 `blockdev --getsz $1` linear $1 0" | dmsetup create identity + +:: + + #!/bin/sh + # Join 2 devices together + size1=`blockdev --getsz $1` + size2=`blockdev --getsz $2` + echo "0 $size1 linear $1 0 + $size1 $size2 linear $2 0" | dmsetup create joined + +:: + + #!/usr/bin/perl -w + # Split a device into 4M chunks and then join them together in reverse order. + + my $name = "reverse"; + my $extent_size = 4 * 1024 * 2; + my $dev = $ARGV[0]; + my $table = ""; + my $count = 0; + + if (!defined($dev)) { + die("Please specify a device.\n"); + } + + my $dev_size = `blockdev --getsz $dev`; + my $extents = int($dev_size / $extent_size) - + (($dev_size % $extent_size) ? 1 : 0); + + while ($extents > 0) { + my $this_start = $count * $extent_size; + $extents--; + $count++; + my $this_offset = $extents * $extent_size; + + $table .= "$this_start $extent_size linear $dev $this_offset\n"; + } + + `echo \"$table\" | dmsetup create $name`; diff --git a/Documentation/admin-guide/device-mapper/log-writes.rst b/Documentation/admin-guide/device-mapper/log-writes.rst new file mode 100644 index 000000000..23141f2ff --- /dev/null +++ b/Documentation/admin-guide/device-mapper/log-writes.rst @@ -0,0 +1,145 @@ +============= +dm-log-writes +============= + +This target takes 2 devices, one to pass all IO to normally, and one to log all +of the write operations to. This is intended for file system developers wishing +to verify the integrity of metadata or data as the file system is written to. +There is a log_write_entry written for every WRITE request and the target is +able to take arbitrary data from userspace to insert into the log. The data +that is in the WRITE requests is copied into the log to make the replay happen +exactly as it happened originally. + +Log Ordering +============ + +We log things in order of completion once we are sure the write is no longer in +cache. This means that normal WRITE requests are not actually logged until the +next REQ_PREFLUSH request. This is to make it easier for userspace to replay +the log in a way that correlates to what is on disk and not what is in cache, +to make it easier to detect improper waiting/flushing. + +This works by attaching all WRITE requests to a list once the write completes. +Once we see a REQ_PREFLUSH request we splice this list onto the request and once +the FLUSH request completes we log all of the WRITEs and then the FLUSH. Only +completed WRITEs, at the time the REQ_PREFLUSH is issued, are added in order to +simulate the worst case scenario with regard to power failures. Consider the +following example (W means write, C means complete): + + W1,W2,W3,C3,C2,Wflush,C1,Cflush + +The log would show the following: + + W3,W2,flush,W1.... + +Again this is to simulate what is actually on disk, this allows us to detect +cases where a power failure at a particular point in time would create an +inconsistent file system. + +Any REQ_FUA requests bypass this flushing mechanism and are logged as soon as +they complete as those requests will obviously bypass the device cache. + +Any REQ_OP_DISCARD requests are treated like WRITE requests. Otherwise we would +have all the DISCARD requests, and then the WRITE requests and then the FLUSH +request. Consider the following example: + + WRITE block 1, DISCARD block 1, FLUSH + +If we logged DISCARD when it completed, the replay would look like this: + + DISCARD 1, WRITE 1, FLUSH + +which isn't quite what happened and wouldn't be caught during the log replay. + +Target interface +================ + +i) Constructor + + log-writes <dev_path> <log_dev_path> + + ============= ============================================== + dev_path Device that all of the IO will go to normally. + log_dev_path Device where the log entries are written to. + ============= ============================================== + +ii) Status + + <#logged entries> <highest allocated sector> + + =========================== ======================== + #logged entries Number of logged entries + highest allocated sector Highest allocated sector + =========================== ======================== + +iii) Messages + + mark <description> + + You can use a dmsetup message to set an arbitrary mark in a log. + For example say you want to fsck a file system after every + write, but first you need to replay up to the mkfs to make sure + we're fsck'ing something reasonable, you would do something like + this:: + + mkfs.btrfs -f /dev/mapper/log + dmsetup message log 0 mark mkfs + <run test> + + This would allow you to replay the log up to the mkfs mark and + then replay from that point on doing the fsck check in the + interval that you want. + + Every log has a mark at the end labeled "dm-log-writes-end". + +Userspace component +=================== + +There is a userspace tool that will replay the log for you in various ways. +It can be found here: https://github.com/josefbacik/log-writes + +Example usage +============= + +Say you want to test fsync on your file system. You would do something like +this:: + + TABLE="0 $(blockdev --getsz /dev/sdb) log-writes /dev/sdb /dev/sdc" + dmsetup create log --table "$TABLE" + mkfs.btrfs -f /dev/mapper/log + dmsetup message log 0 mark mkfs + + mount /dev/mapper/log /mnt/btrfs-test + <some test that does fsync at the end> + dmsetup message log 0 mark fsync + md5sum /mnt/btrfs-test/foo + umount /mnt/btrfs-test + + dmsetup remove log + replay-log --log /dev/sdc --replay /dev/sdb --end-mark fsync + mount /dev/sdb /mnt/btrfs-test + md5sum /mnt/btrfs-test/foo + <verify md5sum's are correct> + + Another option is to do a complicated file system operation and verify the file + system is consistent during the entire operation. You could do this with: + + TABLE="0 $(blockdev --getsz /dev/sdb) log-writes /dev/sdb /dev/sdc" + dmsetup create log --table "$TABLE" + mkfs.btrfs -f /dev/mapper/log + dmsetup message log 0 mark mkfs + + mount /dev/mapper/log /mnt/btrfs-test + <fsstress to dirty the fs> + btrfs filesystem balance /mnt/btrfs-test + umount /mnt/btrfs-test + dmsetup remove log + + replay-log --log /dev/sdc --replay /dev/sdb --end-mark mkfs + btrfsck /dev/sdb + replay-log --log /dev/sdc --replay /dev/sdb --start-mark mkfs \ + --fsck "btrfsck /dev/sdb" --check fua + +And that will replay the log until it sees a FUA request, run the fsck command +and if the fsck passes it will replay to the next FUA, until it is completed or +the fsck command exists abnormally. diff --git a/Documentation/admin-guide/device-mapper/persistent-data.rst b/Documentation/admin-guide/device-mapper/persistent-data.rst new file mode 100644 index 000000000..2065c3c5a --- /dev/null +++ b/Documentation/admin-guide/device-mapper/persistent-data.rst @@ -0,0 +1,88 @@ +=============== +Persistent data +=============== + +Introduction +============ + +The more-sophisticated device-mapper targets require complex metadata +that is managed in kernel. In late 2010 we were seeing that various +different targets were rolling their own data structures, for example: + +- Mikulas Patocka's multisnap implementation +- Heinz Mauelshagen's thin provisioning target +- Another btree-based caching target posted to dm-devel +- Another multi-snapshot target based on a design of Daniel Phillips + +Maintaining these data structures takes a lot of work, so if possible +we'd like to reduce the number. + +The persistent-data library is an attempt to provide a re-usable +framework for people who want to store metadata in device-mapper +targets. It's currently used by the thin-provisioning target and an +upcoming hierarchical storage target. + +Overview +======== + +The main documentation is in the header files which can all be found +under drivers/md/persistent-data. + +The block manager +----------------- + +dm-block-manager.[hc] + +This provides access to the data on disk in fixed sized-blocks. There +is a read/write locking interface to prevent concurrent accesses, and +keep data that is being used in the cache. + +Clients of persistent-data are unlikely to use this directly. + +The transaction manager +----------------------- + +dm-transaction-manager.[hc] + +This restricts access to blocks and enforces copy-on-write semantics. +The only way you can get hold of a writable block through the +transaction manager is by shadowing an existing block (ie. doing +copy-on-write) or allocating a fresh one. Shadowing is elided within +the same transaction so performance is reasonable. The commit method +ensures that all data is flushed before it writes the superblock. +On power failure your metadata will be as it was when last committed. + +The Space Maps +-------------- + +dm-space-map.h +dm-space-map-metadata.[hc] +dm-space-map-disk.[hc] + +On-disk data structures that keep track of reference counts of blocks. +Also acts as the allocator of new blocks. Currently two +implementations: a simpler one for managing blocks on a different +device (eg. thinly-provisioned data blocks); and one for managing +the metadata space. The latter is complicated by the need to store +its own data within the space it's managing. + +The data structures +------------------- + +dm-btree.[hc] +dm-btree-remove.c +dm-btree-spine.c +dm-btree-internal.h + +Currently there is only one data structure, a hierarchical btree. +There are plans to add more. For example, something with an +array-like interface would see a lot of use. + +The btree is 'hierarchical' in that you can define it to be composed +of nested btrees, and take multiple keys. For example, the +thin-provisioning target uses a btree with two levels of nesting. +The first maps a device id to a mapping tree, and that in turn maps a +virtual block to a physical block. + +Values stored in the btrees can have arbitrary size. Keys are always +64bits, although nesting allows you to use multiple keys. diff --git a/Documentation/admin-guide/device-mapper/snapshot.rst b/Documentation/admin-guide/device-mapper/snapshot.rst new file mode 100644 index 000000000..ccdd8b587 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/snapshot.rst @@ -0,0 +1,196 @@ +============================== +Device-mapper snapshot support +============================== + +Device-mapper allows you, without massive data copying: + +- To create snapshots of any block device i.e. mountable, saved states of + the block device which are also writable without interfering with the + original content; +- To create device "forks", i.e. multiple different versions of the + same data stream. +- To merge a snapshot of a block device back into the snapshot's origin + device. + +In the first two cases, dm copies only the chunks of data that get +changed and uses a separate copy-on-write (COW) block device for +storage. + +For snapshot merge the contents of the COW storage are merged back into +the origin device. + + +There are three dm targets available: +snapshot, snapshot-origin, and snapshot-merge. + +- snapshot-origin <origin> + +which will normally have one or more snapshots based on it. +Reads will be mapped directly to the backing device. For each write, the +original data will be saved in the <COW device> of each snapshot to keep +its visible content unchanged, at least until the <COW device> fills up. + + +- snapshot <origin> <COW device> <persistent?> <chunksize> + [<# feature args> [<arg>]*] + +A snapshot of the <origin> block device is created. Changed chunks of +<chunksize> sectors will be stored on the <COW device>. Writes will +only go to the <COW device>. Reads will come from the <COW device> or +from <origin> for unchanged data. <COW device> will often be +smaller than the origin and if it fills up the snapshot will become +useless and be disabled, returning errors. So it is important to monitor +the amount of free space and expand the <COW device> before it fills up. + +<persistent?> is P (Persistent) or N (Not persistent - will not survive +after reboot). O (Overflow) can be added as a persistent store option +to allow userspace to advertise its support for seeing "Overflow" in the +snapshot status. So supported store types are "P", "PO" and "N". + +The difference between persistent and transient is with transient +snapshots less metadata must be saved on disk - they can be kept in +memory by the kernel. + +When loading or unloading the snapshot target, the corresponding +snapshot-origin or snapshot-merge target must be suspended. A failure to +suspend the origin target could result in data corruption. + +Optional features: + + discard_zeroes_cow - a discard issued to the snapshot device that + maps to entire chunks to will zero the corresponding exception(s) in + the snapshot's exception store. + + discard_passdown_origin - a discard to the snapshot device is passed + down to the snapshot-origin's underlying device. This doesn't cause + copy-out to the snapshot exception store because the snapshot-origin + target is bypassed. + + The discard_passdown_origin feature depends on the discard_zeroes_cow + feature being enabled. + + +- snapshot-merge <origin> <COW device> <persistent> <chunksize> + [<# feature args> [<arg>]*] + +takes the same table arguments as the snapshot target except it only +works with persistent snapshots. This target assumes the role of the +"snapshot-origin" target and must not be loaded if the "snapshot-origin" +is still present for <origin>. + +Creates a merging snapshot that takes control of the changed chunks +stored in the <COW device> of an existing snapshot, through a handover +procedure, and merges these chunks back into the <origin>. Once merging +has started (in the background) the <origin> may be opened and the merge +will continue while I/O is flowing to it. Changes to the <origin> are +deferred until the merging snapshot's corresponding chunk(s) have been +merged. Once merging has started the snapshot device, associated with +the "snapshot" target, will return -EIO when accessed. + + +How snapshot is used by LVM2 +============================ +When you create the first LVM2 snapshot of a volume, four dm devices are used: + +1) a device containing the original mapping table of the source volume; +2) a device used as the <COW device>; +3) a "snapshot" device, combining #1 and #2, which is the visible snapshot + volume; +4) the "original" volume (which uses the device number used by the original + source volume), whose table is replaced by a "snapshot-origin" mapping + from device #1. + +A fixed naming scheme is used, so with the following commands:: + + lvcreate -L 1G -n base volumeGroup + lvcreate -L 100M --snapshot -n snap volumeGroup/base + +we'll have this situation (with volumes in above order):: + + # dmsetup table|grep volumeGroup + + volumeGroup-base-real: 0 2097152 linear 8:19 384 + volumeGroup-snap-cow: 0 204800 linear 8:19 2097536 + volumeGroup-snap: 0 2097152 snapshot 254:11 254:12 P 16 + volumeGroup-base: 0 2097152 snapshot-origin 254:11 + + # ls -lL /dev/mapper/volumeGroup-* + brw------- 1 root root 254, 11 29 ago 18:15 /dev/mapper/volumeGroup-base-real + brw------- 1 root root 254, 12 29 ago 18:15 /dev/mapper/volumeGroup-snap-cow + brw------- 1 root root 254, 13 29 ago 18:15 /dev/mapper/volumeGroup-snap + brw------- 1 root root 254, 10 29 ago 18:14 /dev/mapper/volumeGroup-base + + +How snapshot-merge is used by LVM2 +================================== +A merging snapshot assumes the role of the "snapshot-origin" while +merging. As such the "snapshot-origin" is replaced with +"snapshot-merge". The "-real" device is not changed and the "-cow" +device is renamed to <origin name>-cow to aid LVM2's cleanup of the +merging snapshot after it completes. The "snapshot" that hands over its +COW device to the "snapshot-merge" is deactivated (unless using lvchange +--refresh); but if it is left active it will simply return I/O errors. + +A snapshot will merge into its origin with the following command:: + + lvconvert --merge volumeGroup/snap + +we'll now have this situation:: + + # dmsetup table|grep volumeGroup + + volumeGroup-base-real: 0 2097152 linear 8:19 384 + volumeGroup-base-cow: 0 204800 linear 8:19 2097536 + volumeGroup-base: 0 2097152 snapshot-merge 254:11 254:12 P 16 + + # ls -lL /dev/mapper/volumeGroup-* + brw------- 1 root root 254, 11 29 ago 18:15 /dev/mapper/volumeGroup-base-real + brw------- 1 root root 254, 12 29 ago 18:16 /dev/mapper/volumeGroup-base-cow + brw------- 1 root root 254, 10 29 ago 18:16 /dev/mapper/volumeGroup-base + + +How to determine when a merging is complete +=========================================== +The snapshot-merge and snapshot status lines end with: + + <sectors_allocated>/<total_sectors> <metadata_sectors> + +Both <sectors_allocated> and <total_sectors> include both data and metadata. +During merging, the number of sectors allocated gets smaller and +smaller. Merging has finished when the number of sectors holding data +is zero, in other words <sectors_allocated> == <metadata_sectors>. + +Here is a practical example (using a hybrid of lvm and dmsetup commands):: + + # lvs + LV VG Attr LSize Origin Snap% Move Log Copy% Convert + base volumeGroup owi-a- 4.00g + snap volumeGroup swi-a- 1.00g base 18.97 + + # dmsetup status volumeGroup-snap + 0 8388608 snapshot 397896/2097152 1560 + ^^^^ metadata sectors + + # lvconvert --merge -b volumeGroup/snap + Merging of volume snap started. + + # lvs volumeGroup/snap + LV VG Attr LSize Origin Snap% Move Log Copy% Convert + base volumeGroup Owi-a- 4.00g 17.23 + + # dmsetup status volumeGroup-base + 0 8388608 snapshot-merge 281688/2097152 1104 + + # dmsetup status volumeGroup-base + 0 8388608 snapshot-merge 180480/2097152 712 + + # dmsetup status volumeGroup-base + 0 8388608 snapshot-merge 16/2097152 16 + +Merging has finished. + +:: + + # lvs + LV VG Attr LSize Origin Snap% Move Log Copy% Convert + base volumeGroup owi-a- 4.00g diff --git a/Documentation/admin-guide/device-mapper/statistics.rst b/Documentation/admin-guide/device-mapper/statistics.rst new file mode 100644 index 000000000..41ded0bc5 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/statistics.rst @@ -0,0 +1,225 @@ +============= +DM statistics +============= + +Device Mapper supports the collection of I/O statistics on user-defined +regions of a DM device. If no regions are defined no statistics are +collected so there isn't any performance impact. Only bio-based DM +devices are currently supported. + +Each user-defined region specifies a starting sector, length and step. +Individual statistics will be collected for each step-sized area within +the range specified. + +The I/O statistics counters for each step-sized area of a region are +in the same format as `/sys/block/*/stat` or `/proc/diskstats` (see: +Documentation/admin-guide/iostats.rst). But two extra counters (12 and 13) are +provided: total time spent reading and writing. When the histogram +argument is used, the 14th parameter is reported that represents the +histogram of latencies. All these counters may be accessed by sending +the @stats_print message to the appropriate DM device via dmsetup. + +The reported times are in milliseconds and the granularity depends on +the kernel ticks. When the option precise_timestamps is used, the +reported times are in nanoseconds. + +Each region has a corresponding unique identifier, which we call a +region_id, that is assigned when the region is created. The region_id +must be supplied when querying statistics about the region, deleting the +region, etc. Unique region_ids enable multiple userspace programs to +request and process statistics for the same DM device without stepping +on each other's data. + +The creation of DM statistics will allocate memory via kmalloc or +fallback to using vmalloc space. At most, 1/4 of the overall system +memory may be allocated by DM statistics. The admin can see how much +memory is used by reading: + + /sys/module/dm_mod/parameters/stats_current_allocated_bytes + +Messages +======== + + @stats_create <range> <step> [<number_of_optional_arguments> <optional_arguments>...] [<program_id> [<aux_data>]] + Create a new region and return the region_id. + + <range> + "-" + whole device + "<start_sector>+<length>" + a range of <length> 512-byte sectors + starting with <start_sector>. + + <step> + "<area_size>" + the range is subdivided into areas each containing + <area_size> sectors. + "/<number_of_areas>" + the range is subdivided into the specified + number of areas. + + <number_of_optional_arguments> + The number of optional arguments + + <optional_arguments> + The following optional arguments are supported: + + precise_timestamps + use precise timer with nanosecond resolution + instead of the "jiffies" variable. When this argument is + used, the resulting times are in nanoseconds instead of + milliseconds. Precise timestamps are a little bit slower + to obtain than jiffies-based timestamps. + histogram:n1,n2,n3,n4,... + collect histogram of latencies. The + numbers n1, n2, etc are times that represent the boundaries + of the histogram. If precise_timestamps is not used, the + times are in milliseconds, otherwise they are in + nanoseconds. For each range, the kernel will report the + number of requests that completed within this range. For + example, if we use "histogram:10,20,30", the kernel will + report four numbers a:b:c:d. a is the number of requests + that took 0-10 ms to complete, b is the number of requests + that took 10-20 ms to complete, c is the number of requests + that took 20-30 ms to complete and d is the number of + requests that took more than 30 ms to complete. + + <program_id> + An optional parameter. A name that uniquely identifies + the userspace owner of the range. This groups ranges together + so that userspace programs can identify the ranges they + created and ignore those created by others. + The kernel returns this string back in the output of + @stats_list message, but it doesn't use it for anything else. + If we omit the number of optional arguments, program id must not + be a number, otherwise it would be interpreted as the number of + optional arguments. + + <aux_data> + An optional parameter. A word that provides auxiliary data + that is useful to the client program that created the range. + The kernel returns this string back in the output of + @stats_list message, but it doesn't use this value for anything. + + @stats_delete <region_id> + Delete the region with the specified id. + + <region_id> + region_id returned from @stats_create + + @stats_clear <region_id> + Clear all the counters except the in-flight i/o counters. + + <region_id> + region_id returned from @stats_create + + @stats_list [<program_id>] + List all regions registered with @stats_create. + + <program_id> + An optional parameter. + If this parameter is specified, only matching regions + are returned. + If it is not specified, all regions are returned. + + Output format: + <region_id>: <start_sector>+<length> <step> <program_id> <aux_data> + precise_timestamps histogram:n1,n2,n3,... + + The strings "precise_timestamps" and "histogram" are printed only + if they were specified when creating the region. + + @stats_print <region_id> [<starting_line> <number_of_lines>] + Print counters for each step-sized area of a region. + + <region_id> + region_id returned from @stats_create + + <starting_line> + The index of the starting line in the output. + If omitted, all lines are returned. + + <number_of_lines> + The number of lines to include in the output. + If omitted, all lines are returned. + + Output format for each step-sized area of a region: + + <start_sector>+<length> + counters + + The first 11 counters have the same meaning as + `/sys/block/*/stat or /proc/diskstats`. + + Please refer to Documentation/admin-guide/iostats.rst for details. + + 1. the number of reads completed + 2. the number of reads merged + 3. the number of sectors read + 4. the number of milliseconds spent reading + 5. the number of writes completed + 6. the number of writes merged + 7. the number of sectors written + 8. the number of milliseconds spent writing + 9. the number of I/Os currently in progress + 10. the number of milliseconds spent doing I/Os + 11. the weighted number of milliseconds spent doing I/Os + + Additional counters: + + 12. the total time spent reading in milliseconds + 13. the total time spent writing in milliseconds + + @stats_print_clear <region_id> [<starting_line> <number_of_lines>] + Atomically print and then clear all the counters except the + in-flight i/o counters. Useful when the client consuming the + statistics does not want to lose any statistics (those updated + between printing and clearing). + + <region_id> + region_id returned from @stats_create + + <starting_line> + The index of the starting line in the output. + If omitted, all lines are printed and then cleared. + + <number_of_lines> + The number of lines to process. + If omitted, all lines are printed and then cleared. + + @stats_set_aux <region_id> <aux_data> + Store auxiliary data aux_data for the specified region. + + <region_id> + region_id returned from @stats_create + + <aux_data> + The string that identifies data which is useful to the client + program that created the range. The kernel returns this + string back in the output of @stats_list message, but it + doesn't use this value for anything. + +Examples +======== + +Subdivide the DM device 'vol' into 100 pieces and start collecting +statistics on them:: + + dmsetup message vol 0 @stats_create - /100 + +Set the auxiliary data string to "foo bar baz" (the escape for each +space must also be escaped, otherwise the shell will consume them):: + + dmsetup message vol 0 @stats_set_aux 0 foo\\ bar\\ baz + +List the statistics:: + + dmsetup message vol 0 @stats_list + +Print the statistics:: + + dmsetup message vol 0 @stats_print 0 + +Delete the statistics:: + + dmsetup message vol 0 @stats_delete 0 diff --git a/Documentation/admin-guide/device-mapper/striped.rst b/Documentation/admin-guide/device-mapper/striped.rst new file mode 100644 index 000000000..e9a8da192 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/striped.rst @@ -0,0 +1,61 @@ +========= +dm-stripe +========= + +Device-Mapper's "striped" target is used to create a striped (i.e. RAID-0) +device across one or more underlying devices. Data is written in "chunks", +with consecutive chunks rotating among the underlying devices. This can +potentially provide improved I/O throughput by utilizing several physical +devices in parallel. + +Parameters: <num devs> <chunk size> [<dev path> <offset>]+ + <num devs>: + Number of underlying devices. + <chunk size>: + Size of each chunk of data. Must be at least as + large as the system's PAGE_SIZE. + <dev path>: + Full pathname to the underlying block-device, or a + "major:minor" device-number. + <offset>: + Starting sector within the device. + +One or more underlying devices can be specified. The striped device size must +be a multiple of the chunk size multiplied by the number of underlying devices. + + +Example scripts +=============== + +:: + + #!/usr/bin/perl -w + # Create a striped device across any number of underlying devices. The device + # will be called "stripe_dev" and have a chunk-size of 128k. + + my $chunk_size = 128 * 2; + my $dev_name = "stripe_dev"; + my $num_devs = @ARGV; + my @devs = @ARGV; + my ($min_dev_size, $stripe_dev_size, $i); + + if (!$num_devs) { + die("Specify at least one device\n"); + } + + $min_dev_size = `blockdev --getsz $devs[0]`; + for ($i = 1; $i < $num_devs; $i++) { + my $this_size = `blockdev --getsz $devs[$i]`; + $min_dev_size = ($min_dev_size < $this_size) ? + $min_dev_size : $this_size; + } + + $stripe_dev_size = $min_dev_size * $num_devs; + $stripe_dev_size -= $stripe_dev_size % ($chunk_size * $num_devs); + + $table = "0 $stripe_dev_size striped $num_devs $chunk_size"; + for ($i = 0; $i < $num_devs; $i++) { + $table .= " $devs[$i] 0"; + } + + `echo $table | dmsetup create $dev_name`; diff --git a/Documentation/admin-guide/device-mapper/switch.rst b/Documentation/admin-guide/device-mapper/switch.rst new file mode 100644 index 000000000..7dde06be1 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/switch.rst @@ -0,0 +1,141 @@ +========= +dm-switch +========= + +The device-mapper switch target creates a device that supports an +arbitrary mapping of fixed-size regions of I/O across a fixed set of +paths. The path used for any specific region can be switched +dynamically by sending the target a message. + +It maps I/O to underlying block devices efficiently when there is a large +number of fixed-sized address regions but there is no simple pattern +that would allow for a compact representation of the mapping such as +dm-stripe. + +Background +---------- + +Dell EqualLogic and some other iSCSI storage arrays use a distributed +frameless architecture. In this architecture, the storage group +consists of a number of distinct storage arrays ("members") each having +independent controllers, disk storage and network adapters. When a LUN +is created it is spread across multiple members. The details of the +spreading are hidden from initiators connected to this storage system. +The storage group exposes a single target discovery portal, no matter +how many members are being used. When iSCSI sessions are created, each +session is connected to an eth port on a single member. Data to a LUN +can be sent on any iSCSI session, and if the blocks being accessed are +stored on another member the I/O will be forwarded as required. This +forwarding is invisible to the initiator. The storage layout is also +dynamic, and the blocks stored on disk may be moved from member to +member as needed to balance the load. + +This architecture simplifies the management and configuration of both +the storage group and initiators. In a multipathing configuration, it +is possible to set up multiple iSCSI sessions to use multiple network +interfaces on both the host and target to take advantage of the +increased network bandwidth. An initiator could use a simple round +robin algorithm to send I/O across all paths and let the storage array +members forward it as necessary, but there is a performance advantage to +sending data directly to the correct member. + +A device-mapper table already lets you map different regions of a +device onto different targets. However in this architecture the LUN is +spread with an address region size on the order of 10s of MBs, which +means the resulting table could have more than a million entries and +consume far too much memory. + +Using this device-mapper switch target we can now build a two-layer +device hierarchy: + + Upper Tier - Determine which array member the I/O should be sent to. + Lower Tier - Load balance amongst paths to a particular member. + +The lower tier consists of a single dm multipath device for each member. +Each of these multipath devices contains the set of paths directly to +the array member in one priority group, and leverages existing path +selectors to load balance amongst these paths. We also build a +non-preferred priority group containing paths to other array members for +failover reasons. + +The upper tier consists of a single dm-switch device. This device uses +a bitmap to look up the location of the I/O and choose the appropriate +lower tier device to route the I/O. By using a bitmap we are able to +use 4 bits for each address range in a 16 member group (which is very +large for us). This is a much denser representation than the dm table +b-tree can achieve. + +Construction Parameters +======================= + + <num_paths> <region_size> <num_optional_args> [<optional_args>...] [<dev_path> <offset>]+ + <num_paths> + The number of paths across which to distribute the I/O. + + <region_size> + The number of 512-byte sectors in a region. Each region can be redirected + to any of the available paths. + + <num_optional_args> + The number of optional arguments. Currently, no optional arguments + are supported and so this must be zero. + + <dev_path> + The block device that represents a specific path to the device. + + <offset> + The offset of the start of data on the specific <dev_path> (in units + of 512-byte sectors). This number is added to the sector number when + forwarding the request to the specific path. Typically it is zero. + +Messages +======== + +set_region_mappings <index>:<path_nr> [<index>]:<path_nr> [<index>]:<path_nr>... + +Modify the region table by specifying which regions are redirected to +which paths. + +<index> + The region number (region size was specified in constructor parameters). + If index is omitted, the next region (previous index + 1) is used. + Expressed in hexadecimal (WITHOUT any prefix like 0x). + +<path_nr> + The path number in the range 0 ... (<num_paths> - 1). + Expressed in hexadecimal (WITHOUT any prefix like 0x). + +R<n>,<m> + This parameter allows repetitive patterns to be loaded quickly. <n> and <m> + are hexadecimal numbers. The last <n> mappings are repeated in the next <m> + slots. + +Status +====== + +No status line is reported. + +Example +======= + +Assume that you have volumes vg1/switch0 vg1/switch1 vg1/switch2 with +the same size. + +Create a switch device with 64kB region size:: + + dmsetup create switch --table "0 `blockdev --getsz /dev/vg1/switch0` + switch 3 128 0 /dev/vg1/switch0 0 /dev/vg1/switch1 0 /dev/vg1/switch2 0" + +Set mappings for the first 7 entries to point to devices switch0, switch1, +switch2, switch0, switch1, switch2, switch1:: + + dmsetup message switch 0 set_region_mappings 0:0 :1 :2 :0 :1 :2 :1 + +Set repetitive mapping. This command:: + + dmsetup message switch 0 set_region_mappings 1000:1 :2 R2,10 + +is equivalent to:: + + dmsetup message switch 0 set_region_mappings 1000:1 :2 :1 :2 :1 :2 :1 :2 \ + :1 :2 :1 :2 :1 :2 :1 :2 :1 :2 diff --git a/Documentation/admin-guide/device-mapper/thin-provisioning.rst b/Documentation/admin-guide/device-mapper/thin-provisioning.rst new file mode 100644 index 000000000..bafebf79d --- /dev/null +++ b/Documentation/admin-guide/device-mapper/thin-provisioning.rst @@ -0,0 +1,427 @@ +================= +Thin provisioning +================= + +Introduction +============ + +This document describes a collection of device-mapper targets that +between them implement thin-provisioning and snapshots. + +The main highlight of this implementation, compared to the previous +implementation of snapshots, is that it allows many virtual devices to +be stored on the same data volume. This simplifies administration and +allows the sharing of data between volumes, thus reducing disk usage. + +Another significant feature is support for an arbitrary depth of +recursive snapshots (snapshots of snapshots of snapshots ...). The +previous implementation of snapshots did this by chaining together +lookup tables, and so performance was O(depth). This new +implementation uses a single data structure to avoid this degradation +with depth. Fragmentation may still be an issue, however, in some +scenarios. + +Metadata is stored on a separate device from data, giving the +administrator some freedom, for example to: + +- Improve metadata resilience by storing metadata on a mirrored volume + but data on a non-mirrored one. + +- Improve performance by storing the metadata on SSD. + +Status +====== + +These targets are considered safe for production use. But different use +cases will have different performance characteristics, for example due +to fragmentation of the data volume. + +If you find this software is not performing as expected please mail +dm-devel@redhat.com with details and we'll try our best to improve +things for you. + +Userspace tools for checking and repairing the metadata have been fully +developed and are available as 'thin_check' and 'thin_repair'. The name +of the package that provides these utilities varies by distribution (on +a Red Hat distribution it is named 'device-mapper-persistent-data'). + +Cookbook +======== + +This section describes some quick recipes for using thin provisioning. +They use the dmsetup program to control the device-mapper driver +directly. End users will be advised to use a higher-level volume +manager such as LVM2 once support has been added. + +Pool device +----------- + +The pool device ties together the metadata volume and the data volume. +It maps I/O linearly to the data volume and updates the metadata via +two mechanisms: + +- Function calls from the thin targets + +- Device-mapper 'messages' from userspace which control the creation of new + virtual devices amongst other things. + +Setting up a fresh pool device +------------------------------ + +Setting up a pool device requires a valid metadata device, and a +data device. If you do not have an existing metadata device you can +make one by zeroing the first 4k to indicate empty metadata. + + dd if=/dev/zero of=$metadata_dev bs=4096 count=1 + +The amount of metadata you need will vary according to how many blocks +are shared between thin devices (i.e. through snapshots). If you have +less sharing than average you'll need a larger-than-average metadata device. + +As a guide, we suggest you calculate the number of bytes to use in the +metadata device as 48 * $data_dev_size / $data_block_size but round it up +to 2MB if the answer is smaller. If you're creating large numbers of +snapshots which are recording large amounts of change, you may find you +need to increase this. + +The largest size supported is 16GB: If the device is larger, +a warning will be issued and the excess space will not be used. + +Reloading a pool table +---------------------- + +You may reload a pool's table, indeed this is how the pool is resized +if it runs out of space. (N.B. While specifying a different metadata +device when reloading is not forbidden at the moment, things will go +wrong if it does not route I/O to exactly the same on-disk location as +previously.) + +Using an existing pool device +----------------------------- + +:: + + dmsetup create pool \ + --table "0 20971520 thin-pool $metadata_dev $data_dev \ + $data_block_size $low_water_mark" + +$data_block_size gives the smallest unit of disk space that can be +allocated at a time expressed in units of 512-byte sectors. +$data_block_size must be between 128 (64KB) and 2097152 (1GB) and a +multiple of 128 (64KB). $data_block_size cannot be changed after the +thin-pool is created. People primarily interested in thin provisioning +may want to use a value such as 1024 (512KB). People doing lots of +snapshotting may want a smaller value such as 128 (64KB). If you are +not zeroing newly-allocated data, a larger $data_block_size in the +region of 256000 (128MB) is suggested. + +$low_water_mark is expressed in blocks of size $data_block_size. If +free space on the data device drops below this level then a dm event +will be triggered which a userspace daemon should catch allowing it to +extend the pool device. Only one such event will be sent. + +No special event is triggered if a just resumed device's free space is below +the low water mark. However, resuming a device always triggers an +event; a userspace daemon should verify that free space exceeds the low +water mark when handling this event. + +A low water mark for the metadata device is maintained in the kernel and +will trigger a dm event if free space on the metadata device drops below +it. + +Updating on-disk metadata +------------------------- + +On-disk metadata is committed every time a FLUSH or FUA bio is written. +If no such requests are made then commits will occur every second. This +means the thin-provisioning target behaves like a physical disk that has +a volatile write cache. If power is lost you may lose some recent +writes. The metadata should always be consistent in spite of any crash. + +If data space is exhausted the pool will either error or queue IO +according to the configuration (see: error_if_no_space). If metadata +space is exhausted or a metadata operation fails: the pool will error IO +until the pool is taken offline and repair is performed to 1) fix any +potential inconsistencies and 2) clear the flag that imposes repair. +Once the pool's metadata device is repaired it may be resized, which +will allow the pool to return to normal operation. Note that if a pool +is flagged as needing repair, the pool's data and metadata devices +cannot be resized until repair is performed. It should also be noted +that when the pool's metadata space is exhausted the current metadata +transaction is aborted. Given that the pool will cache IO whose +completion may have already been acknowledged to upper IO layers +(e.g. filesystem) it is strongly suggested that consistency checks +(e.g. fsck) be performed on those layers when repair of the pool is +required. + +Thin provisioning +----------------- + +i) Creating a new thinly-provisioned volume. + + To create a new thinly- provisioned volume you must send a message to an + active pool device, /dev/mapper/pool in this example:: + + dmsetup message /dev/mapper/pool 0 "create_thin 0" + + Here '0' is an identifier for the volume, a 24-bit number. It's up + to the caller to allocate and manage these identifiers. If the + identifier is already in use, the message will fail with -EEXIST. + +ii) Using a thinly-provisioned volume. + + Thinly-provisioned volumes are activated using the 'thin' target:: + + dmsetup create thin --table "0 2097152 thin /dev/mapper/pool 0" + + The last parameter is the identifier for the thinp device. + +Internal snapshots +------------------ + +i) Creating an internal snapshot. + + Snapshots are created with another message to the pool. + + N.B. If the origin device that you wish to snapshot is active, you + must suspend it before creating the snapshot to avoid corruption. + This is NOT enforced at the moment, so please be careful! + + :: + + dmsetup suspend /dev/mapper/thin + dmsetup message /dev/mapper/pool 0 "create_snap 1 0" + dmsetup resume /dev/mapper/thin + + Here '1' is the identifier for the volume, a 24-bit number. '0' is the + identifier for the origin device. + +ii) Using an internal snapshot. + + Once created, the user doesn't have to worry about any connection + between the origin and the snapshot. Indeed the snapshot is no + different from any other thinly-provisioned device and can be + snapshotted itself via the same method. It's perfectly legal to + have only one of them active, and there's no ordering requirement on + activating or removing them both. (This differs from conventional + device-mapper snapshots.) + + Activate it exactly the same way as any other thinly-provisioned volume:: + + dmsetup create snap --table "0 2097152 thin /dev/mapper/pool 1" + +External snapshots +------------------ + +You can use an external **read only** device as an origin for a +thinly-provisioned volume. Any read to an unprovisioned area of the +thin device will be passed through to the origin. Writes trigger +the allocation of new blocks as usual. + +One use case for this is VM hosts that want to run guests on +thinly-provisioned volumes but have the base image on another device +(possibly shared between many VMs). + +You must not write to the origin device if you use this technique! +Of course, you may write to the thin device and take internal snapshots +of the thin volume. + +i) Creating a snapshot of an external device + + This is the same as creating a thin device. + You don't mention the origin at this stage. + + :: + + dmsetup message /dev/mapper/pool 0 "create_thin 0" + +ii) Using a snapshot of an external device. + + Append an extra parameter to the thin target specifying the origin:: + + dmsetup create snap --table "0 2097152 thin /dev/mapper/pool 0 /dev/image" + + N.B. All descendants (internal snapshots) of this snapshot require the + same extra origin parameter. + +Deactivation +------------ + +All devices using a pool must be deactivated before the pool itself +can be. + +:: + + dmsetup remove thin + dmsetup remove snap + dmsetup remove pool + +Reference +========= + +'thin-pool' target +------------------ + +i) Constructor + + :: + + thin-pool <metadata dev> <data dev> <data block size (sectors)> \ + <low water mark (blocks)> [<number of feature args> [<arg>]*] + + Optional feature arguments: + + skip_block_zeroing: + Skip the zeroing of newly-provisioned blocks. + + ignore_discard: + Disable discard support. + + no_discard_passdown: + Don't pass discards down to the underlying + data device, but just remove the mapping. + + read_only: + Don't allow any changes to be made to the pool + metadata. This mode is only available after the + thin-pool has been created and first used in full + read/write mode. It cannot be specified on initial + thin-pool creation. + + error_if_no_space: + Error IOs, instead of queueing, if no space. + + Data block size must be between 64KB (128 sectors) and 1GB + (2097152 sectors) inclusive. + + +ii) Status + + :: + + <transaction id> <used metadata blocks>/<total metadata blocks> + <used data blocks>/<total data blocks> <held metadata root> + ro|rw|out_of_data_space [no_]discard_passdown [error|queue]_if_no_space + needs_check|- metadata_low_watermark + + transaction id: + A 64-bit number used by userspace to help synchronise with metadata + from volume managers. + + used data blocks / total data blocks + If the number of free blocks drops below the pool's low water mark a + dm event will be sent to userspace. This event is edge-triggered and + it will occur only once after each resume so volume manager writers + should register for the event and then check the target's status. + + held metadata root: + The location, in blocks, of the metadata root that has been + 'held' for userspace read access. '-' indicates there is no + held root. + + discard_passdown|no_discard_passdown + Whether or not discards are actually being passed down to the + underlying device. When this is enabled when loading the table, + it can get disabled if the underlying device doesn't support it. + + ro|rw|out_of_data_space + If the pool encounters certain types of device failures it will + drop into a read-only metadata mode in which no changes to + the pool metadata (like allocating new blocks) are permitted. + + In serious cases where even a read-only mode is deemed unsafe + no further I/O will be permitted and the status will just + contain the string 'Fail'. The userspace recovery tools + should then be used. + + error_if_no_space|queue_if_no_space + If the pool runs out of data or metadata space, the pool will + either queue or error the IO destined to the data device. The + default is to queue the IO until more space is added or the + 'no_space_timeout' expires. The 'no_space_timeout' dm-thin-pool + module parameter can be used to change this timeout -- it + defaults to 60 seconds but may be disabled using a value of 0. + + needs_check + A metadata operation has failed, resulting in the needs_check + flag being set in the metadata's superblock. The metadata + device must be deactivated and checked/repaired before the + thin-pool can be made fully operational again. '-' indicates + needs_check is not set. + + metadata_low_watermark: + Value of metadata low watermark in blocks. The kernel sets this + value internally but userspace needs to know this value to + determine if an event was caused by crossing this threshold. + +iii) Messages + + create_thin <dev id> + Create a new thinly-provisioned device. + <dev id> is an arbitrary unique 24-bit identifier chosen by + the caller. + + create_snap <dev id> <origin id> + Create a new snapshot of another thinly-provisioned device. + <dev id> is an arbitrary unique 24-bit identifier chosen by + the caller. + <origin id> is the identifier of the thinly-provisioned device + of which the new device will be a snapshot. + + delete <dev id> + Deletes a thin device. Irreversible. + + set_transaction_id <current id> <new id> + Userland volume managers, such as LVM, need a way to + synchronise their external metadata with the internal metadata of the + pool target. The thin-pool target offers to store an + arbitrary 64-bit transaction id and return it on the target's + status line. To avoid races you must provide what you think + the current transaction id is when you change it with this + compare-and-swap message. + + reserve_metadata_snap + Reserve a copy of the data mapping btree for use by userland. + This allows userland to inspect the mappings as they were when + this message was executed. Use the pool's status command to + get the root block associated with the metadata snapshot. + + release_metadata_snap + Release a previously reserved copy of the data mapping btree. + +'thin' target +------------- + +i) Constructor + + :: + + thin <pool dev> <dev id> [<external origin dev>] + + pool dev: + the thin-pool device, e.g. /dev/mapper/my_pool or 253:0 + + dev id: + the internal device identifier of the device to be + activated. + + external origin dev: + an optional block device outside the pool to be treated as a + read-only snapshot origin: reads to unprovisioned areas of the + thin target will be mapped to this device. + +The pool doesn't store any size against the thin devices. If you +load a thin target that is smaller than you've been using previously, +then you'll have no access to blocks mapped beyond the end. If you +load a target that is bigger than before, then extra blocks will be +provisioned as and when needed. + +ii) Status + + <nr mapped sectors> <highest mapped sector> + If the pool has encountered device errors and failed, the status + will just contain the string 'Fail'. The userspace recovery + tools should then be used. + + In the case where <nr mapped sectors> is 0, there is no highest + mapped sector and the value of <highest mapped sector> is unspecified. diff --git a/Documentation/admin-guide/device-mapper/unstriped.rst b/Documentation/admin-guide/device-mapper/unstriped.rst new file mode 100644 index 000000000..5772ccdd1 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/unstriped.rst @@ -0,0 +1,135 @@ +================================ +Device-mapper "unstriped" target +================================ + +Introduction +============ + +The device-mapper "unstriped" target provides a transparent mechanism to +unstripe a device-mapper "striped" target to access the underlying disks +without having to touch the true backing block-device. It can also be +used to unstripe a hardware RAID-0 to access backing disks. + +Parameters: +<number of stripes> <chunk size> <stripe #> <dev_path> <offset> + +<number of stripes> + The number of stripes in the RAID 0. + +<chunk size> + The amount of 512B sectors in the chunk striping. + +<dev_path> + The block device you wish to unstripe. + +<stripe #> + The stripe number within the device that corresponds to physical + drive you wish to unstripe. This must be 0 indexed. + + +Why use this module? +==================== + +An example of undoing an existing dm-stripe +------------------------------------------- + +This small bash script will setup 4 loop devices and use the existing +striped target to combine the 4 devices into one. It then will use +the unstriped target on top of the striped device to access the +individual backing loop devices. We write data to the newly exposed +unstriped devices and verify the data written matches the correct +underlying device on the striped array:: + + #!/bin/bash + + MEMBER_SIZE=$((128 * 1024 * 1024)) + NUM=4 + SEQ_END=$((${NUM}-1)) + CHUNK=256 + BS=4096 + + RAID_SIZE=$((${MEMBER_SIZE}*${NUM}/512)) + DM_PARMS="0 ${RAID_SIZE} striped ${NUM} ${CHUNK}" + COUNT=$((${MEMBER_SIZE} / ${BS})) + + for i in $(seq 0 ${SEQ_END}); do + dd if=/dev/zero of=member-${i} bs=${MEMBER_SIZE} count=1 oflag=direct + losetup /dev/loop${i} member-${i} + DM_PARMS+=" /dev/loop${i} 0" + done + + echo $DM_PARMS | dmsetup create raid0 + for i in $(seq 0 ${SEQ_END}); do + echo "0 1 unstriped ${NUM} ${CHUNK} ${i} /dev/mapper/raid0 0" | dmsetup create set-${i} + done; + + for i in $(seq 0 ${SEQ_END}); do + dd if=/dev/urandom of=/dev/mapper/set-${i} bs=${BS} count=${COUNT} oflag=direct + diff /dev/mapper/set-${i} member-${i} + done; + + for i in $(seq 0 ${SEQ_END}); do + dmsetup remove set-${i} + done + + dmsetup remove raid0 + + for i in $(seq 0 ${SEQ_END}); do + losetup -d /dev/loop${i} + rm -f member-${i} + done + +Another example +--------------- + +Intel NVMe drives contain two cores on the physical device. +Each core of the drive has segregated access to its LBA range. +The current LBA model has a RAID 0 128k chunk on each core, resulting +in a 256k stripe across the two cores:: + + Core 0: Core 1: + __________ __________ + | LBA 512| | LBA 768| + | LBA 0 | | LBA 256| + ---------- ---------- + +The purpose of this unstriping is to provide better QoS in noisy +neighbor environments. When two partitions are created on the +aggregate drive without this unstriping, reads on one partition +can affect writes on another partition. This is because the partitions +are striped across the two cores. When we unstripe this hardware RAID 0 +and make partitions on each new exposed device the two partitions are now +physically separated. + +With the dm-unstriped target we're able to segregate an fio script that +has read and write jobs that are independent of each other. Compared to +when we run the test on a combined drive with partitions, we were able +to get a 92% reduction in read latency using this device mapper target. + + +Example dmsetup usage +===================== + +unstriped on top of Intel NVMe device that has 2 cores +------------------------------------------------------ + +:: + + dmsetup create nvmset0 --table '0 512 unstriped 2 256 0 /dev/nvme0n1 0' + dmsetup create nvmset1 --table '0 512 unstriped 2 256 1 /dev/nvme0n1 0' + +There will now be two devices that expose Intel NVMe core 0 and 1 +respectively:: + + /dev/mapper/nvmset0 + /dev/mapper/nvmset1 + +unstriped on top of striped with 4 drives using 128K chunk size +--------------------------------------------------------------- + +:: + + dmsetup create raid_disk0 --table '0 512 unstriped 4 256 0 /dev/mapper/striped 0' + dmsetup create raid_disk1 --table '0 512 unstriped 4 256 1 /dev/mapper/striped 0' + dmsetup create raid_disk2 --table '0 512 unstriped 4 256 2 /dev/mapper/striped 0' + dmsetup create raid_disk3 --table '0 512 unstriped 4 256 3 /dev/mapper/striped 0' diff --git a/Documentation/admin-guide/device-mapper/verity.rst b/Documentation/admin-guide/device-mapper/verity.rst new file mode 100644 index 000000000..a65c1602c --- /dev/null +++ b/Documentation/admin-guide/device-mapper/verity.rst @@ -0,0 +1,249 @@ +========= +dm-verity +========= + +Device-Mapper's "verity" target provides transparent integrity checking of +block devices using a cryptographic digest provided by the kernel crypto API. +This target is read-only. + +Construction Parameters +======================= + +:: + + <version> <dev> <hash_dev> + <data_block_size> <hash_block_size> + <num_data_blocks> <hash_start_block> + <algorithm> <digest> <salt> + [<#opt_params> <opt_params>] + +<version> + This is the type of the on-disk hash format. + + 0 is the original format used in the Chromium OS. + The salt is appended when hashing, digests are stored continuously and + the rest of the block is padded with zeroes. + + 1 is the current format that should be used for new devices. + The salt is prepended when hashing and each digest is + padded with zeroes to the power of two. + +<dev> + This is the device containing data, the integrity of which needs to be + checked. It may be specified as a path, like /dev/sdaX, or a device number, + <major>:<minor>. + +<hash_dev> + This is the device that supplies the hash tree data. It may be + specified similarly to the device path and may be the same device. If the + same device is used, the hash_start should be outside the configured + dm-verity device. + +<data_block_size> + The block size on a data device in bytes. + Each block corresponds to one digest on the hash device. + +<hash_block_size> + The size of a hash block in bytes. + +<num_data_blocks> + The number of data blocks on the data device. Additional blocks are + inaccessible. You can place hashes to the same partition as data, in this + case hashes are placed after <num_data_blocks>. + +<hash_start_block> + This is the offset, in <hash_block_size>-blocks, from the start of hash_dev + to the root block of the hash tree. + +<algorithm> + The cryptographic hash algorithm used for this device. This should + be the name of the algorithm, like "sha1". + +<digest> + The hexadecimal encoding of the cryptographic hash of the root hash block + and the salt. This hash should be trusted as there is no other authenticity + beyond this point. + +<salt> + The hexadecimal encoding of the salt value. + +<#opt_params> + Number of optional parameters. If there are no optional parameters, + the optional parameters section can be skipped or #opt_params can be zero. + Otherwise #opt_params is the number of following arguments. + + Example of optional parameters section: + 1 ignore_corruption + +ignore_corruption + Log corrupted blocks, but allow read operations to proceed normally. + +restart_on_corruption + Restart the system when a corrupted block is discovered. This option is + not compatible with ignore_corruption and requires user space support to + avoid restart loops. + +panic_on_corruption + Panic the device when a corrupted block is discovered. This option is + not compatible with ignore_corruption and restart_on_corruption. + +ignore_zero_blocks + Do not verify blocks that are expected to contain zeroes and always return + zeroes instead. This may be useful if the partition contains unused blocks + that are not guaranteed to contain zeroes. + +use_fec_from_device <fec_dev> + Use forward error correction (FEC) to recover from corruption if hash + verification fails. Use encoding data from the specified device. This + may be the same device where data and hash blocks reside, in which case + fec_start must be outside data and hash areas. + + If the encoding data covers additional metadata, it must be accessible + on the hash device after the hash blocks. + + Note: block sizes for data and hash devices must match. Also, if the + verity <dev> is encrypted the <fec_dev> should be too. + +fec_roots <num> + Number of generator roots. This equals to the number of parity bytes in + the encoding data. For example, in RS(M, N) encoding, the number of roots + is M-N. + +fec_blocks <num> + The number of encoding data blocks on the FEC device. The block size for + the FEC device is <data_block_size>. + +fec_start <offset> + This is the offset, in <data_block_size> blocks, from the start of the + FEC device to the beginning of the encoding data. + +check_at_most_once + Verify data blocks only the first time they are read from the data device, + rather than every time. This reduces the overhead of dm-verity so that it + can be used on systems that are memory and/or CPU constrained. However, it + provides a reduced level of security because only offline tampering of the + data device's content will be detected, not online tampering. + + Hash blocks are still verified each time they are read from the hash device, + since verification of hash blocks is less performance critical than data + blocks, and a hash block will not be verified any more after all the data + blocks it covers have been verified anyway. + +root_hash_sig_key_desc <key_description> + This is the description of the USER_KEY that the kernel will lookup to get + the pkcs7 signature of the roothash. The pkcs7 signature is used to validate + the root hash during the creation of the device mapper block device. + Verification of roothash depends on the config DM_VERITY_VERIFY_ROOTHASH_SIG + being set in the kernel. The signatures are checked against the builtin + trusted keyring by default, or the secondary trusted keyring if + DM_VERITY_VERIFY_ROOTHASH_SIG_SECONDARY_KEYRING is set. The secondary + trusted keyring includes by default the builtin trusted keyring, and it can + also gain new certificates at run time if they are signed by a certificate + already in the secondary trusted keyring. + +try_verify_in_tasklet + If verity hashes are in cache, verify data blocks in kernel tasklet instead + of workqueue. This option can reduce IO latency. + +Theory of operation +=================== + +dm-verity is meant to be set up as part of a verified boot path. This +may be anything ranging from a boot using tboot or trustedgrub to just +booting from a known-good device (like a USB drive or CD). + +When a dm-verity device is configured, it is expected that the caller +has been authenticated in some way (cryptographic signatures, etc). +After instantiation, all hashes will be verified on-demand during +disk access. If they cannot be verified up to the root node of the +tree, the root hash, then the I/O will fail. This should detect +tampering with any data on the device and the hash data. + +Cryptographic hashes are used to assert the integrity of the device on a +per-block basis. This allows for a lightweight hash computation on first read +into the page cache. Block hashes are stored linearly, aligned to the nearest +block size. + +If forward error correction (FEC) support is enabled any recovery of +corrupted data will be verified using the cryptographic hash of the +corresponding data. This is why combining error correction with +integrity checking is essential. + +Hash Tree +--------- + +Each node in the tree is a cryptographic hash. If it is a leaf node, the hash +of some data block on disk is calculated. If it is an intermediary node, +the hash of a number of child nodes is calculated. + +Each entry in the tree is a collection of neighboring nodes that fit in one +block. The number is determined based on block_size and the size of the +selected cryptographic digest algorithm. The hashes are linearly-ordered in +this entry and any unaligned trailing space is ignored but included when +calculating the parent node. + +The tree looks something like: + + alg = sha256, num_blocks = 32768, block_size = 4096 + +:: + + [ root ] + / . . . \ + [entry_0] [entry_1] + / . . . \ . . . \ + [entry_0_0] . . . [entry_0_127] . . . . [entry_1_127] + / ... \ / . . . \ / \ + blk_0 ... blk_127 blk_16256 blk_16383 blk_32640 . . . blk_32767 + + +On-disk format +============== + +The verity kernel code does not read the verity metadata on-disk header. +It only reads the hash blocks which directly follow the header. +It is expected that a user-space tool will verify the integrity of the +verity header. + +Alternatively, the header can be omitted and the dmsetup parameters can +be passed via the kernel command-line in a rooted chain of trust where +the command-line is verified. + +Directly following the header (and with sector number padded to the next hash +block boundary) are the hash blocks which are stored a depth at a time +(starting from the root), sorted in order of increasing index. + +The full specification of kernel parameters and on-disk metadata format +is available at the cryptsetup project's wiki page + + https://gitlab.com/cryptsetup/cryptsetup/wikis/DMVerity + +Status +====== +V (for Valid) is returned if every check performed so far was valid. +If any check failed, C (for Corruption) is returned. + +Example +======= +Set up a device:: + + # dmsetup create vroot --readonly --table \ + "0 2097152 verity 1 /dev/sda1 /dev/sda2 4096 4096 262144 1 sha256 "\ + "4392712ba01368efdf14b05c76f9e4df0d53664630b5d48632ed17a137f39076 "\ + "1234000000000000000000000000000000000000000000000000000000000000" + +A command line tool veritysetup is available to compute or verify +the hash tree or activate the kernel device. This is available from +the cryptsetup upstream repository https://gitlab.com/cryptsetup/cryptsetup/ +(as a libcryptsetup extension). + +Create hash on the device:: + + # veritysetup format /dev/sda1 /dev/sda2 + ... + Root hash: 4392712ba01368efdf14b05c76f9e4df0d53664630b5d48632ed17a137f39076 + +Activate the device:: + + # veritysetup create vroot /dev/sda1 /dev/sda2 \ + 4392712ba01368efdf14b05c76f9e4df0d53664630b5d48632ed17a137f39076 diff --git a/Documentation/admin-guide/device-mapper/writecache.rst b/Documentation/admin-guide/device-mapper/writecache.rst new file mode 100644 index 000000000..60c16b7fd --- /dev/null +++ b/Documentation/admin-guide/device-mapper/writecache.rst @@ -0,0 +1,114 @@ +================= +Writecache target +================= + +The writecache target caches writes on persistent memory or on SSD. It +doesn't cache reads because reads are supposed to be cached in page cache +in normal RAM. + +When the device is constructed, the first sector should be zeroed or the +first sector should contain valid superblock from previous invocation. + +Constructor parameters: + +1. type of the cache device - "p" or "s" + - p - persistent memory + - s - SSD +2. the underlying device that will be cached +3. the cache device +4. block size (4096 is recommended; the maximum block size is the page + size) +5. the number of optional parameters (the parameters with an argument + count as two) + + start_sector n (default: 0) + offset from the start of cache device in 512-byte sectors + high_watermark n (default: 50) + start writeback when the number of used blocks reach this + watermark + low_watermark x (default: 45) + stop writeback when the number of used blocks drops below + this watermark + writeback_jobs n (default: unlimited) + limit the number of blocks that are in flight during + writeback. Setting this value reduces writeback + throughput, but it may improve latency of read requests + autocommit_blocks n (default: 64 for pmem, 65536 for ssd) + when the application writes this amount of blocks without + issuing the FLUSH request, the blocks are automatically + committed + autocommit_time ms (default: 1000) + autocommit time in milliseconds. The data is automatically + committed if this time passes and no FLUSH request is + received + fua (by default on) + applicable only to persistent memory - use the FUA flag + when writing data from persistent memory back to the + underlying device + nofua + applicable only to persistent memory - don't use the FUA + flag when writing back data and send the FLUSH request + afterwards + + - some underlying devices perform better with fua, some + with nofua. The user should test it + cleaner + when this option is activated (either in the constructor + arguments or by a message), the cache will not promote + new writes (however, writes to already cached blocks are + promoted, to avoid data corruption due to misordered + writes) and it will gradually writeback any cached + data. The userspace can then monitor the cleaning + process with "dmsetup status". When the number of cached + blocks drops to zero, userspace can unload the + dm-writecache target and replace it with dm-linear or + other targets. + max_age n + specifies the maximum age of a block in milliseconds. If + a block is stored in the cache for too long, it will be + written to the underlying device and cleaned up. + metadata_only + only metadata is promoted to the cache. This option + improves performance for heavier REQ_META workloads. + pause_writeback n (default: 3000) + pause writeback if there was some write I/O redirected to + the origin volume in the last n milliseconds + +Status: + +1. error indicator - 0 if there was no error, otherwise error number +2. the number of blocks +3. the number of free blocks +4. the number of blocks under writeback +5. the number of read blocks +6. the number of read blocks that hit the cache +7. the number of write blocks +8. the number of write blocks that hit uncommitted block +9. the number of write blocks that hit committed block +10. the number of write blocks that bypass the cache +11. the number of write blocks that are allocated in the cache +12. the number of write requests that are blocked on the freelist +13. the number of flush requests +14. the number of discarded blocks + +Messages: + flush + Flush the cache device. The message returns successfully + if the cache device was flushed without an error + flush_on_suspend + Flush the cache device on next suspend. Use this message + when you are going to remove the cache device. The proper + sequence for removing the cache device is: + + 1. send the "flush_on_suspend" message + 2. load an inactive table with a linear target that maps + to the underlying device + 3. suspend the device + 4. ask for status and verify that there are no errors + 5. resume the device, so that it will use the linear + target + 6. the cache device is now inactive and it can be deleted + cleaner + See above "cleaner" constructor documentation. + clear_stats + Clear the statistics that are reported on the status line diff --git a/Documentation/admin-guide/device-mapper/zero.rst b/Documentation/admin-guide/device-mapper/zero.rst new file mode 100644 index 000000000..11fb5cf45 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/zero.rst @@ -0,0 +1,37 @@ +======= +dm-zero +======= + +Device-Mapper's "zero" target provides a block-device that always returns +zero'd data on reads and silently drops writes. This is similar behavior to +/dev/zero, but as a block-device instead of a character-device. + +Dm-zero has no target-specific parameters. + +One very interesting use of dm-zero is for creating "sparse" devices in +conjunction with dm-snapshot. A sparse device reports a device-size larger +than the amount of actual storage space available for that device. A user can +write data anywhere within the sparse device and read it back like a normal +device. Reads to previously unwritten areas will return a zero'd buffer. When +enough data has been written to fill up the actual storage space, the sparse +device is deactivated. This can be very useful for testing device and +filesystem limitations. + +To create a sparse device, start by creating a dm-zero device that's the +desired size of the sparse device. For this example, we'll assume a 10TB +sparse device:: + + TEN_TERABYTES=`expr 10 \* 1024 \* 1024 \* 1024 \* 2` # 10 TB in sectors + echo "0 $TEN_TERABYTES zero" | dmsetup create zero1 + +Then create a snapshot of the zero device, using any available block-device as +the COW device. The size of the COW device will determine the amount of real +space available to the sparse device. For this example, we'll assume /dev/sdb1 +is an available 10GB partition:: + + echo "0 $TEN_TERABYTES snapshot /dev/mapper/zero1 /dev/sdb1 p 128" | \ + dmsetup create sparse1 + +This will create a 10TB sparse device called /dev/mapper/sparse1 that has +10GB of actual storage space available. If more than 10GB of data is written +to this device, it will start returning I/O errors. diff --git a/Documentation/admin-guide/devices.rst b/Documentation/admin-guide/devices.rst new file mode 100644 index 000000000..e3776d773 --- /dev/null +++ b/Documentation/admin-guide/devices.rst @@ -0,0 +1,268 @@ +.. _admin_devices: + +Linux allocated devices (4.x+ version) +====================================== + +This list is the Linux Device List, the official registry of allocated +device numbers and ``/dev`` directory nodes for the Linux operating +system. + +The version of this document at lanana.org is no longer maintained. This +version in the mainline Linux kernel is the master document. Updates +shall be sent as patches to the kernel maintainers (see the +:ref:`Documentation/process/submitting-patches.rst <submittingpatches>` document). +Specifically explore the sections titled "CHAR and MISC DRIVERS", and +"BLOCK LAYER" in the MAINTAINERS file to find the right maintainers +to involve for character and block devices. + +This document is included by reference into the Filesystem Hierarchy +Standard (FHS). The FHS is available from https://www.pathname.com/fhs/. + +Allocations marked (68k/Amiga) apply to Linux/68k on the Amiga +platform only. Allocations marked (68k/Atari) apply to Linux/68k on +the Atari platform only. + +This document is in the public domain. The authors requests, however, +that semantically altered versions are not distributed without +permission of the authors, assuming the authors can be contacted without +an unreasonable effort. + + +.. attention:: + + DEVICE DRIVERS AUTHORS PLEASE READ THIS + + Linux now has extensive support for dynamic allocation of device numbering + and can use ``sysfs`` and ``udev`` (``systemd``) to handle the naming needs. + There are still some exceptions in the serial and boot device area. Before + asking for a device number make sure you actually need one. + + To have a major number allocated, or a minor number in situations + where that applies (e.g. busmice), please submit a patch and send to + the authors as indicated above. + + Keep the description of the device *in the same format + as this list*. The reason for this is that it is the only way we have + found to ensure we have all the requisite information to publish your + device and avoid conflicts. + + Finally, sometimes we have to play "namespace police." Please don't be + offended. We often get submissions for ``/dev`` names that would be bound + to cause conflicts down the road. We are trying to avoid getting in a + situation where we would have to suffer an incompatible forward + change. Therefore, please consult with us **before** you make your + device names and numbers in any way public, at least to the point + where it would be at all difficult to get them changed. + + Your cooperation is appreciated. + +.. include:: devices.txt + :literal: + +Additional ``/dev/`` directory entries +-------------------------------------- + +This section details additional entries that should or may exist in +the /dev directory. It is preferred that symbolic links use the same +form (absolute or relative) as is indicated here. Links are +classified as "hard" or "symbolic" depending on the preferred type of +link; if possible, the indicated type of link should be used. + +Compulsory links +++++++++++++++++ + +These links should exist on all systems: + +=============== =============== =============== =============================== +/dev/fd /proc/self/fd symbolic File descriptors +/dev/stdin fd/0 symbolic stdin file descriptor +/dev/stdout fd/1 symbolic stdout file descriptor +/dev/stderr fd/2 symbolic stderr file descriptor +/dev/nfsd socksys symbolic Required by iBCS-2 +/dev/X0R null symbolic Required by iBCS-2 +=============== =============== =============== =============================== + +Note: ``/dev/X0R`` is <letter X>-<digit 0>-<letter R>. + +Recommended links ++++++++++++++++++ + +It is recommended that these links exist on all systems: + + +=============== =============== =============== =============================== +/dev/core /proc/kcore symbolic Backward compatibility +/dev/ramdisk ram0 symbolic Backward compatibility +/dev/ftape qft0 symbolic Backward compatibility +/dev/bttv0 video0 symbolic Backward compatibility +/dev/radio radio0 symbolic Backward compatibility +/dev/i2o* /dev/i2o/* symbolic Backward compatibility +/dev/scd? sr? hard Alternate SCSI CD-ROM name +=============== =============== =============== =============================== + +Locally defined links ++++++++++++++++++++++ + +The following links may be established locally to conform to the +configuration of the system. This is merely a tabulation of existing +practice, and does not constitute a recommendation. However, if they +exist, they should have the following uses. + +=============== =============== =============== =============================== +/dev/mouse mouse port symbolic Current mouse device +/dev/tape tape device symbolic Current tape device +/dev/cdrom CD-ROM device symbolic Current CD-ROM device +/dev/cdwriter CD-writer symbolic Current CD-writer device +/dev/scanner scanner symbolic Current scanner device +/dev/modem modem port symbolic Current dialout device +/dev/root root device symbolic Current root filesystem +/dev/swap swap device symbolic Current swap device +=============== =============== =============== =============================== + +``/dev/modem`` should not be used for a modem which supports dialin as +well as dialout, as it tends to cause lock file problems. If it +exists, ``/dev/modem`` should point to the appropriate primary TTY device +(the use of the alternate callout devices is deprecated). + +For SCSI devices, ``/dev/tape`` and ``/dev/cdrom`` should point to the +*cooked* devices (``/dev/st*`` and ``/dev/sr*``, respectively), whereas +``/dev/cdwriter`` and /dev/scanner should point to the appropriate generic +SCSI devices (/dev/sg*). + +``/dev/mouse`` may point to a primary serial TTY device, a hardware mouse +device, or a socket for a mouse driver program (e.g. ``/dev/gpmdata``). + +Sockets and pipes ++++++++++++++++++ + +Non-transient sockets and named pipes may exist in /dev. Common entries are: + +=============== =============== =============================================== +/dev/printer socket lpd local socket +/dev/log socket syslog local socket +/dev/gpmdata socket gpm mouse multiplexer +=============== =============== =============================================== + +Mount points +++++++++++++ + +The following names are reserved for mounting special filesystems +under /dev. These special filesystems provide kernel interfaces that +cannot be provided with standard device nodes. + +=============== =============== =============================================== +/dev/pts devpts PTY slave filesystem +/dev/shm tmpfs POSIX shared memory maintenance access +=============== =============== =============================================== + +Terminal devices +---------------- + +Terminal, or TTY devices are a special class of character devices. A +terminal device is any device that could act as a controlling terminal +for a session; this includes virtual consoles, serial ports, and +pseudoterminals (PTYs). + +All terminal devices share a common set of capabilities known as line +disciplines; these include the common terminal line discipline as well +as SLIP and PPP modes. + +All terminal devices are named similarly; this section explains the +naming and use of the various types of TTYs. Note that the naming +conventions include several historical warts; some of these are +Linux-specific, some were inherited from other systems, and some +reflect Linux outgrowing a borrowed convention. + +A hash mark (``#``) in a device name is used here to indicate a decimal +number without leading zeroes. + +Virtual consoles and the console device ++++++++++++++++++++++++++++++++++++++++ + +Virtual consoles are full-screen terminal displays on the system video +monitor. Virtual consoles are named ``/dev/tty#``, with numbering +starting at ``/dev/tty1``; ``/dev/tty0`` is the current virtual console. +``/dev/tty0`` is the device that should be used to access the system video +card on those architectures for which the frame buffer devices +(``/dev/fb*``) are not applicable. Do not use ``/dev/console`` +for this purpose. + +The console device, ``/dev/console``, is the device to which system +messages should be sent, and on which logins should be permitted in +single-user mode. Starting with Linux 2.1.71, ``/dev/console`` is managed +by the kernel; for previous versions it should be a symbolic link to +either ``/dev/tty0``, a specific virtual console such as ``/dev/tty1``, or to +a serial port primary (``tty*``, not ``cu*``) device, depending on the +configuration of the system. + +Serial ports +++++++++++++ + +Serial ports are RS-232 serial ports and any device which simulates +one, either in hardware (such as internal modems) or in software (such +as the ISDN driver.) Under Linux, each serial ports has two device +names, the primary or callin device and the alternate or callout one. +Each kind of device is indicated by a different letter. For any +letter X, the names of the devices are ``/dev/ttyX#`` and ``/dev/cux#``, +respectively; for historical reasons, ``/dev/ttyS#`` and ``/dev/ttyC#`` +correspond to ``/dev/cua#`` and ``/dev/cub#``. In the future, it should be +expected that multiple letters will be used; all letters will be upper +case for the "tty" device (e.g. ``/dev/ttyDP#``) and lower case for the +"cu" device (e.g. ``/dev/cudp#``). + +The names ``/dev/ttyQ#`` and ``/dev/cuq#`` are reserved for local use. + +The alternate devices provide for kernel-based exclusion and somewhat +different defaults than the primary devices. Their main purpose is to +allow the use of serial ports with programs with no inherent or broken +support for serial ports. Their use is deprecated, and they may be +removed from a future version of Linux. + +Arbitration of serial ports is provided by the use of lock files with +the names ``/var/lock/LCK..ttyX#``. The contents of the lock file should +be the PID of the locking process as an ASCII number. + +It is common practice to install links such as /dev/modem +which point to serial ports. In order to ensure proper locking in the +presence of these links, it is recommended that software chase +symlinks and lock all possible names; additionally, it is recommended +that a lock file be installed with the corresponding alternate +device. In order to avoid deadlocks, it is recommended that the locks +are acquired in the following order, and released in the reverse: + + 1. The symbolic link name, if any (``/var/lock/LCK..modem``) + 2. The "tty" name (``/var/lock/LCK..ttyS2``) + 3. The alternate device name (``/var/lock/LCK..cua2``) + +In the case of nested symbolic links, the lock files should be +installed in the order the symlinks are resolved. + +Under no circumstances should an application hold a lock while waiting +for another to be released. In addition, applications which attempt +to create lock files for the corresponding alternate device names +should take into account the possibility of being used on a non-serial +port TTY, for which no alternate device would exist. + +Pseudoterminals (PTYs) +++++++++++++++++++++++ + +Pseudoterminals, or PTYs, are used to create login sessions or provide +other capabilities requiring a TTY line discipline (including SLIP or +PPP capability) to arbitrary data-generation processes. Each PTY has +a master side, named ``/dev/pty[p-za-e][0-9a-f]``, and a slave side, named +``/dev/tty[p-za-e][0-9a-f]``. The kernel arbitrates the use of PTYs by +allowing each master side to be opened only once. + +Once the master side has been opened, the corresponding slave device +can be used in the same manner as any TTY device. The master and +slave devices are connected by the kernel, generating the equivalent +of a bidirectional pipe with TTY capabilities. + +Recent versions of the Linux kernels and GNU libc contain support for +the System V/Unix98 naming scheme for PTYs, which assigns a common +device, ``/dev/ptmx``, to all the masters (opening it will automatically +give you a previously unassigned PTY) and a subdirectory, ``/dev/pts``, +for the slaves; the slaves are named with decimal integers (``/dev/pts/#`` +in our notation). This removes the problem of exhausting the +namespace and enables the kernel to automatically create the device +nodes for the slaves on demand using the "devpts" filesystem. diff --git a/Documentation/admin-guide/devices.txt b/Documentation/admin-guide/devices.txt new file mode 100644 index 000000000..839054923 --- /dev/null +++ b/Documentation/admin-guide/devices.txt @@ -0,0 +1,3079 @@ + 0 Unnamed devices (e.g. non-device mounts) + 0 = reserved as null device number + See block major 144, 145, 146 for expansion areas. + + 1 char Memory devices + 1 = /dev/mem Physical memory access + 2 = /dev/kmem OBSOLETE - replaced by /proc/kcore + 3 = /dev/null Null device + 4 = /dev/port I/O port access + 5 = /dev/zero Null byte source + 6 = /dev/core OBSOLETE - replaced by /proc/kcore + 7 = /dev/full Returns ENOSPC on write + 8 = /dev/random Nondeterministic random number gen. + 9 = /dev/urandom Faster, less secure random number gen. + 10 = /dev/aio Asynchronous I/O notification interface + 11 = /dev/kmsg Writes to this come out as printk's, reads + export the buffered printk records. + 12 = /dev/oldmem OBSOLETE - replaced by /proc/vmcore + + 1 block RAM disk + 0 = /dev/ram0 First RAM disk + 1 = /dev/ram1 Second RAM disk + ... + 250 = /dev/initrd Initial RAM disk + + Older kernels had /dev/ramdisk (1, 1) here. + /dev/initrd refers to a RAM disk which was preloaded + by the boot loader; newer kernels use /dev/ram0 for + the initrd. + + 2 char Pseudo-TTY masters + 0 = /dev/ptyp0 First PTY master + 1 = /dev/ptyp1 Second PTY master + ... + 255 = /dev/ptyef 256th PTY master + + Pseudo-tty's are named as follows: + * Masters are "pty", slaves are "tty"; + * the fourth letter is one of pqrstuvwxyzabcde indicating + the 1st through 16th series of 16 pseudo-ttys each, and + * the fifth letter is one of 0123456789abcdef indicating + the position within the series. + + These are the old-style (BSD) PTY devices; Unix98 + devices are on major 128 and above and use the PTY + master multiplex (/dev/ptmx) to acquire a PTY on + demand. + + 2 block Floppy disks + 0 = /dev/fd0 Controller 0, drive 0, autodetect + 1 = /dev/fd1 Controller 0, drive 1, autodetect + 2 = /dev/fd2 Controller 0, drive 2, autodetect + 3 = /dev/fd3 Controller 0, drive 3, autodetect + 128 = /dev/fd4 Controller 1, drive 0, autodetect + 129 = /dev/fd5 Controller 1, drive 1, autodetect + 130 = /dev/fd6 Controller 1, drive 2, autodetect + 131 = /dev/fd7 Controller 1, drive 3, autodetect + + To specify format, add to the autodetect device number: + 0 = /dev/fd? Autodetect format + 4 = /dev/fd?d360 5.25" 360K in a 360K drive(1) + 20 = /dev/fd?h360 5.25" 360K in a 1200K drive(1) + 48 = /dev/fd?h410 5.25" 410K in a 1200K drive + 64 = /dev/fd?h420 5.25" 420K in a 1200K drive + 24 = /dev/fd?h720 5.25" 720K in a 1200K drive + 80 = /dev/fd?h880 5.25" 880K in a 1200K drive(1) + 8 = /dev/fd?h1200 5.25" 1200K in a 1200K drive(1) + 40 = /dev/fd?h1440 5.25" 1440K in a 1200K drive(1) + 56 = /dev/fd?h1476 5.25" 1476K in a 1200K drive + 72 = /dev/fd?h1494 5.25" 1494K in a 1200K drive + 92 = /dev/fd?h1600 5.25" 1600K in a 1200K drive(1) + + 12 = /dev/fd?u360 3.5" 360K Double Density(2) + 16 = /dev/fd?u720 3.5" 720K Double Density(1) + 120 = /dev/fd?u800 3.5" 800K Double Density(2) + 52 = /dev/fd?u820 3.5" 820K Double Density + 68 = /dev/fd?u830 3.5" 830K Double Density + 84 = /dev/fd?u1040 3.5" 1040K Double Density(1) + 88 = /dev/fd?u1120 3.5" 1120K Double Density(1) + 28 = /dev/fd?u1440 3.5" 1440K High Density(1) + 124 = /dev/fd?u1600 3.5" 1600K High Density(1) + 44 = /dev/fd?u1680 3.5" 1680K High Density(3) + 60 = /dev/fd?u1722 3.5" 1722K High Density + 76 = /dev/fd?u1743 3.5" 1743K High Density + 96 = /dev/fd?u1760 3.5" 1760K High Density + 116 = /dev/fd?u1840 3.5" 1840K High Density(3) + 100 = /dev/fd?u1920 3.5" 1920K High Density(1) + 32 = /dev/fd?u2880 3.5" 2880K Extra Density(1) + 104 = /dev/fd?u3200 3.5" 3200K Extra Density + 108 = /dev/fd?u3520 3.5" 3520K Extra Density + 112 = /dev/fd?u3840 3.5" 3840K Extra Density(1) + + 36 = /dev/fd?CompaQ Compaq 2880K drive; obsolete? + + (1) Autodetectable format + (2) Autodetectable format in a Double Density (720K) drive only + (3) Autodetectable format in a High Density (1440K) drive only + + NOTE: The letter in the device name (d, q, h or u) + signifies the type of drive: 5.25" Double Density (d), + 5.25" Quad Density (q), 5.25" High Density (h) or 3.5" + (any model, u). The use of the capital letters D, H + and E for the 3.5" models have been deprecated, since + the drive type is insignificant for these devices. + + 3 char Pseudo-TTY slaves + 0 = /dev/ttyp0 First PTY slave + 1 = /dev/ttyp1 Second PTY slave + ... + 255 = /dev/ttyef 256th PTY slave + + These are the old-style (BSD) PTY devices; Unix98 + devices are on major 136 and above. + + 3 block First MFM, RLL and IDE hard disk/CD-ROM interface + 0 = /dev/hda Master: whole disk (or CD-ROM) + 64 = /dev/hdb Slave: whole disk (or CD-ROM) + + For partitions, add to the whole disk device number: + 0 = /dev/hd? Whole disk + 1 = /dev/hd?1 First partition + 2 = /dev/hd?2 Second partition + ... + 63 = /dev/hd?63 63rd partition + + For Linux/i386, partitions 1-4 are the primary + partitions, and 5 and above are logical partitions. + Other versions of Linux use partitioning schemes + appropriate to their respective architectures. + + 4 char TTY devices + 0 = /dev/tty0 Current virtual console + + 1 = /dev/tty1 First virtual console + ... + 63 = /dev/tty63 63rd virtual console + 64 = /dev/ttyS0 First UART serial port + ... + 255 = /dev/ttyS191 192nd UART serial port + + UART serial ports refer to 8250/16450/16550 series devices. + + Older versions of the Linux kernel used this major + number for BSD PTY devices. As of Linux 2.1.115, this + is no longer supported. Use major numbers 2 and 3. + + 4 block Aliases for dynamically allocated major devices to be used + when its not possible to create the real device nodes + because the root filesystem is mounted read-only. + + 0 = /dev/root + + 5 char Alternate TTY devices + 0 = /dev/tty Current TTY device + 1 = /dev/console System console + 2 = /dev/ptmx PTY master multiplex + 3 = /dev/ttyprintk User messages via printk TTY device + 64 = /dev/cua0 Callout device for ttyS0 + ... + 255 = /dev/cua191 Callout device for ttyS191 + + (5,1) is /dev/console starting with Linux 2.1.71. See + the section on terminal devices for more information + on /dev/console. + + 6 char Parallel printer devices + 0 = /dev/lp0 Parallel printer on parport0 + 1 = /dev/lp1 Parallel printer on parport1 + ... + + Current Linux kernels no longer have a fixed mapping + between parallel ports and I/O addresses. Instead, + they are redirected through the parport multiplex layer. + + 7 char Virtual console capture devices + 0 = /dev/vcs Current vc text (glyph) contents + 1 = /dev/vcs1 tty1 text (glyph) contents + ... + 63 = /dev/vcs63 tty63 text (glyph) contents + 64 = /dev/vcsu Current vc text (unicode) contents + 65 = /dev/vcsu1 tty1 text (unicode) contents + ... + 127 = /dev/vcsu63 tty63 text (unicode) contents + 128 = /dev/vcsa Current vc text/attribute (glyph) contents + 129 = /dev/vcsa1 tty1 text/attribute (glyph) contents + ... + 191 = /dev/vcsa63 tty63 text/attribute (glyph) contents + + NOTE: These devices permit both read and write access. + + 7 block Loopback devices + 0 = /dev/loop0 First loop device + 1 = /dev/loop1 Second loop device + ... + + The loop devices are used to mount filesystems not + associated with block devices. The binding to the + loop devices is handled by mount(8) or losetup(8). + + 8 block SCSI disk devices (0-15) + 0 = /dev/sda First SCSI disk whole disk + 16 = /dev/sdb Second SCSI disk whole disk + 32 = /dev/sdc Third SCSI disk whole disk + ... + 240 = /dev/sdp Sixteenth SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 9 char SCSI tape devices + 0 = /dev/st0 First SCSI tape, mode 0 + 1 = /dev/st1 Second SCSI tape, mode 0 + ... + 32 = /dev/st0l First SCSI tape, mode 1 + 33 = /dev/st1l Second SCSI tape, mode 1 + ... + 64 = /dev/st0m First SCSI tape, mode 2 + 65 = /dev/st1m Second SCSI tape, mode 2 + ... + 96 = /dev/st0a First SCSI tape, mode 3 + 97 = /dev/st1a Second SCSI tape, mode 3 + ... + 128 = /dev/nst0 First SCSI tape, mode 0, no rewind + 129 = /dev/nst1 Second SCSI tape, mode 0, no rewind + ... + 160 = /dev/nst0l First SCSI tape, mode 1, no rewind + 161 = /dev/nst1l Second SCSI tape, mode 1, no rewind + ... + 192 = /dev/nst0m First SCSI tape, mode 2, no rewind + 193 = /dev/nst1m Second SCSI tape, mode 2, no rewind + ... + 224 = /dev/nst0a First SCSI tape, mode 3, no rewind + 225 = /dev/nst1a Second SCSI tape, mode 3, no rewind + ... + + "No rewind" refers to the omission of the default + automatic rewind on device close. The MTREW or MTOFFL + ioctl()'s can be used to rewind the tape regardless of + the device used to access it. + + 9 block Metadisk (RAID) devices + 0 = /dev/md0 First metadisk group + 1 = /dev/md1 Second metadisk group + ... + + The metadisk driver is used to span a + filesystem across multiple physical disks. + + 10 char Non-serial mice, misc features + 0 = /dev/logibm Logitech bus mouse + 1 = /dev/psaux PS/2-style mouse port + 2 = /dev/inportbm Microsoft Inport bus mouse + 3 = /dev/atibm ATI XL bus mouse + 4 = /dev/jbm J-mouse + 4 = /dev/amigamouse Amiga mouse (68k/Amiga) + 5 = /dev/atarimouse Atari mouse + 6 = /dev/sunmouse Sun mouse + 7 = /dev/amigamouse1 Second Amiga mouse + 8 = /dev/smouse Simple serial mouse driver + 9 = /dev/pc110pad IBM PC-110 digitizer pad + 10 = /dev/adbmouse Apple Desktop Bus mouse + 11 = /dev/vrtpanel Vr41xx embedded touch panel + 13 = /dev/vpcmouse Connectix Virtual PC Mouse + 14 = /dev/touchscreen/ucb1x00 UCB 1x00 touchscreen + 15 = /dev/touchscreen/mk712 MK712 touchscreen + 128 = /dev/beep Fancy beep device + 129 = + 130 = /dev/watchdog Watchdog timer port + 131 = /dev/temperature Machine internal temperature + 132 = /dev/hwtrap Hardware fault trap + 133 = /dev/exttrp External device trap + 134 = /dev/apm_bios Advanced Power Management BIOS + 135 = /dev/rtc Real Time Clock + 137 = /dev/vhci Bluetooth virtual HCI driver + 139 = /dev/openprom SPARC OpenBoot PROM + 140 = /dev/relay8 Berkshire Products Octal relay card + 141 = /dev/relay16 Berkshire Products ISO-16 relay card + 142 = + 143 = /dev/pciconf PCI configuration space + 144 = /dev/nvram Non-volatile configuration RAM + 145 = /dev/hfmodem Soundcard shortwave modem control + 146 = /dev/graphics Linux/SGI graphics device + 147 = /dev/opengl Linux/SGI OpenGL pipe + 148 = /dev/gfx Linux/SGI graphics effects device + 149 = /dev/input/mouse Linux/SGI Irix emulation mouse + 150 = /dev/input/keyboard Linux/SGI Irix emulation keyboard + 151 = /dev/led Front panel LEDs + 152 = /dev/kpoll Kernel Poll Driver + 153 = /dev/mergemem Memory merge device + 154 = /dev/pmu Macintosh PowerBook power manager + 155 = + 156 = /dev/lcd Front panel LCD display + 157 = /dev/ac Applicom Intl Profibus card + 158 = /dev/nwbutton Netwinder external button + 159 = /dev/nwdebug Netwinder debug interface + 160 = /dev/nwflash Netwinder flash memory + 161 = /dev/userdma User-space DMA access + 162 = /dev/smbus System Management Bus + 163 = /dev/lik Logitech Internet Keyboard + 164 = /dev/ipmo Intel Intelligent Platform Management + 165 = /dev/vmmon VMware virtual machine monitor + 166 = /dev/i2o/ctl I2O configuration manager + 167 = /dev/specialix_sxctl Specialix serial control + 168 = /dev/tcldrv Technology Concepts serial control + 169 = /dev/specialix_rioctl Specialix RIO serial control + 170 = /dev/thinkpad/thinkpad IBM Thinkpad devices + 171 = /dev/srripc QNX4 API IPC manager + 172 = /dev/usemaclone Semaphore clone device + 173 = /dev/ipmikcs Intelligent Platform Management + 174 = /dev/uctrl SPARCbook 3 microcontroller + 175 = /dev/agpgart AGP Graphics Address Remapping Table + 176 = /dev/gtrsc Gorgy Timing radio clock + 177 = /dev/cbm Serial CBM bus + 178 = /dev/jsflash JavaStation OS flash SIMM + 179 = /dev/xsvc High-speed shared-mem/semaphore service + 180 = /dev/vrbuttons Vr41xx button input device + 181 = /dev/toshiba Toshiba laptop SMM support + 182 = /dev/perfctr Performance-monitoring counters + 183 = /dev/hwrng Generic random number generator + 184 = /dev/cpu/microcode CPU microcode update interface + 186 = /dev/atomicps Atomic snapshot of process state data + 187 = /dev/irnet IrNET device + 188 = /dev/smbusbios SMBus BIOS + 189 = /dev/ussp_ctl User space serial port control + 190 = /dev/crash Mission Critical Linux crash dump facility + 191 = /dev/pcl181 <information missing> + 192 = /dev/nas_xbus NAS xbus LCD/buttons access + 193 = /dev/d7s SPARC 7-segment display + 194 = /dev/zkshim Zero-Knowledge network shim control + 195 = /dev/elographics/e2201 Elographics touchscreen E271-2201 + 196 = /dev/vfio/vfio VFIO userspace driver interface + 197 = /dev/pxa3xx-gcu PXA3xx graphics controller unit driver + 198 = /dev/sexec Signed executable interface + 199 = /dev/scanners/cuecat :CueCat barcode scanner + 200 = /dev/net/tun TAP/TUN network device + 201 = /dev/button/gulpb Transmeta GULP-B buttons + 202 = /dev/emd/ctl Enhanced Metadisk RAID (EMD) control + 203 = /dev/cuse Cuse (character device in user-space) + 204 = /dev/video/em8300 EM8300 DVD decoder control + 205 = /dev/video/em8300_mv EM8300 DVD decoder video + 206 = /dev/video/em8300_ma EM8300 DVD decoder audio + 207 = /dev/video/em8300_sp EM8300 DVD decoder subpicture + 208 = /dev/compaq/cpqphpc Compaq PCI Hot Plug Controller + 209 = /dev/compaq/cpqrid Compaq Remote Insight Driver + 210 = /dev/impi/bt IMPI coprocessor block transfer + 211 = /dev/impi/smic IMPI coprocessor stream interface + 212 = /dev/watchdogs/0 First watchdog device + 213 = /dev/watchdogs/1 Second watchdog device + 214 = /dev/watchdogs/2 Third watchdog device + 215 = /dev/watchdogs/3 Fourth watchdog device + 216 = /dev/fujitsu/apanel Fujitsu/Siemens application panel + 217 = /dev/ni/natmotn National Instruments Motion + 218 = /dev/kchuid Inter-process chuid control + 219 = /dev/modems/mwave MWave modem firmware upload + 220 = /dev/mptctl Message passing technology (MPT) control + 221 = /dev/mvista/hssdsi Montavista PICMG hot swap system driver + 222 = /dev/mvista/hasi Montavista PICMG high availability + 223 = /dev/input/uinput User level driver support for input + 224 = /dev/tpm TCPA TPM driver + 225 = /dev/pps Pulse Per Second driver + 226 = /dev/systrace Systrace device + 227 = /dev/mcelog X86_64 Machine Check Exception driver + 228 = /dev/hpet HPET driver + 229 = /dev/fuse Fuse (virtual filesystem in user-space) + 230 = /dev/midishare MidiShare driver + 231 = /dev/snapshot System memory snapshot device + 232 = /dev/kvm Kernel-based virtual machine (hardware virtualization extensions) + 233 = /dev/kmview View-OS A process with a view + 234 = /dev/btrfs-control Btrfs control device + 235 = /dev/autofs Autofs control device + 236 = /dev/mapper/control Device-Mapper control device + 237 = /dev/loop-control Loopback control device + 238 = /dev/vhost-net Host kernel accelerator for virtio net + 239 = /dev/uhid User-space I/O driver support for HID subsystem + 240 = /dev/userio Serio driver testing device + 241 = /dev/vhost-vsock Host kernel driver for virtio vsock + 242 = /dev/rfkill Turning off radio transmissions (rfkill) + + 243-254 Reserved for local use + 255 Reserved for MISC_DYNAMIC_MINOR + + 11 char Raw keyboard device (Linux/SPARC only) + 0 = /dev/kbd Raw keyboard device + + 11 char Serial Mux device (Linux/PA-RISC only) + 0 = /dev/ttyB0 First mux port + 1 = /dev/ttyB1 Second mux port + ... + + 11 block SCSI CD-ROM devices + 0 = /dev/scd0 First SCSI CD-ROM + 1 = /dev/scd1 Second SCSI CD-ROM + ... + + The prefix /dev/sr (instead of /dev/scd) has been deprecated. + + 12 char QIC-02 tape + 2 = /dev/ntpqic11 QIC-11, no rewind-on-close + 3 = /dev/tpqic11 QIC-11, rewind-on-close + 4 = /dev/ntpqic24 QIC-24, no rewind-on-close + 5 = /dev/tpqic24 QIC-24, rewind-on-close + 6 = /dev/ntpqic120 QIC-120, no rewind-on-close + 7 = /dev/tpqic120 QIC-120, rewind-on-close + 8 = /dev/ntpqic150 QIC-150, no rewind-on-close + 9 = /dev/tpqic150 QIC-150, rewind-on-close + + The device names specified are proposed -- if there + are "standard" names for these devices, please let me know. + + 12 block + + 13 char Input core + 0 = /dev/input/js0 First joystick + 1 = /dev/input/js1 Second joystick + ... + 32 = /dev/input/mouse0 First mouse + 33 = /dev/input/mouse1 Second mouse + ... + 63 = /dev/input/mice Unified mouse + 64 = /dev/input/event0 First event queue + 65 = /dev/input/event1 Second event queue + ... + + Each device type has 5 bits (32 minors). + + 13 block Previously used for the XT disk (/dev/xdN) + Deleted in kernel v3.9. + + 14 char Open Sound System (OSS) + 0 = /dev/mixer Mixer control + 1 = /dev/sequencer Audio sequencer + 2 = /dev/midi00 First MIDI port + 3 = /dev/dsp Digital audio + 4 = /dev/audio Sun-compatible digital audio + 6 = + 7 = /dev/audioctl SPARC audio control device + 8 = /dev/sequencer2 Sequencer -- alternate device + 16 = /dev/mixer1 Second soundcard mixer control + 17 = /dev/patmgr0 Sequencer patch manager + 18 = /dev/midi01 Second MIDI port + 19 = /dev/dsp1 Second soundcard digital audio + 20 = /dev/audio1 Second soundcard Sun digital audio + 33 = /dev/patmgr1 Sequencer patch manager + 34 = /dev/midi02 Third MIDI port + 50 = /dev/midi03 Fourth MIDI port + + 14 block + + 15 char Joystick + 0 = /dev/js0 First analog joystick + 1 = /dev/js1 Second analog joystick + ... + 128 = /dev/djs0 First digital joystick + 129 = /dev/djs1 Second digital joystick + ... + 15 block Sony CDU-31A/CDU-33A CD-ROM + 0 = /dev/sonycd Sony CDU-31a CD-ROM + + 16 char Non-SCSI scanners + 0 = /dev/gs4500 Genius 4500 handheld scanner + + 16 block GoldStar CD-ROM + 0 = /dev/gscd GoldStar CD-ROM + + 17 char OBSOLETE (was Chase serial card) + 0 = /dev/ttyH0 First Chase port + 1 = /dev/ttyH1 Second Chase port + ... + 17 block Optics Storage CD-ROM + 0 = /dev/optcd Optics Storage CD-ROM + + 18 char OBSOLETE (was Chase serial card - alternate devices) + 0 = /dev/cuh0 Callout device for ttyH0 + 1 = /dev/cuh1 Callout device for ttyH1 + ... + 18 block Sanyo CD-ROM + 0 = /dev/sjcd Sanyo CD-ROM + + 19 block "Double" compressed disk + 0 = /dev/double0 First compressed disk + ... + 7 = /dev/double7 Eighth compressed disk + 128 = /dev/cdouble0 Mirror of first compressed disk + ... + 135 = /dev/cdouble7 Mirror of eighth compressed disk + + See the Double documentation for the meaning of the + mirror devices. + + 20 block Hitachi CD-ROM (under development) + 0 = /dev/hitcd Hitachi CD-ROM + + 21 char Generic SCSI access + 0 = /dev/sg0 First generic SCSI device + 1 = /dev/sg1 Second generic SCSI device + ... + + Most distributions name these /dev/sga, /dev/sgb...; + this sets an unnecessary limit of 26 SCSI devices in + the system and is counter to standard Linux + device-naming practice. + + 21 block Acorn MFM hard drive interface + 0 = /dev/mfma First MFM drive whole disk + 64 = /dev/mfmb Second MFM drive whole disk + + This device is used on the ARM-based Acorn RiscPC. + Partitions are handled the same way as for IDE disks + (see major number 3). + + 22 char Digiboard serial card + 0 = /dev/ttyD0 First Digiboard port + 1 = /dev/ttyD1 Second Digiboard port + ... + 22 block Second IDE hard disk/CD-ROM interface + 0 = /dev/hdc Master: whole disk (or CD-ROM) + 64 = /dev/hdd Slave: whole disk (or CD-ROM) + + Partitions are handled the same way as for the first + interface (see major number 3). + + 23 char Digiboard serial card - alternate devices + 0 = /dev/cud0 Callout device for ttyD0 + 1 = /dev/cud1 Callout device for ttyD1 + ... + 23 block Mitsumi proprietary CD-ROM + 0 = /dev/mcd Mitsumi CD-ROM + + 24 char Stallion serial card + 0 = /dev/ttyE0 Stallion port 0 card 0 + 1 = /dev/ttyE1 Stallion port 1 card 0 + ... + 64 = /dev/ttyE64 Stallion port 0 card 1 + 65 = /dev/ttyE65 Stallion port 1 card 1 + ... + 128 = /dev/ttyE128 Stallion port 0 card 2 + 129 = /dev/ttyE129 Stallion port 1 card 2 + ... + 192 = /dev/ttyE192 Stallion port 0 card 3 + 193 = /dev/ttyE193 Stallion port 1 card 3 + ... + 24 block Sony CDU-535 CD-ROM + 0 = /dev/cdu535 Sony CDU-535 CD-ROM + + 25 char Stallion serial card - alternate devices + 0 = /dev/cue0 Callout device for ttyE0 + 1 = /dev/cue1 Callout device for ttyE1 + ... + 64 = /dev/cue64 Callout device for ttyE64 + 65 = /dev/cue65 Callout device for ttyE65 + ... + 128 = /dev/cue128 Callout device for ttyE128 + 129 = /dev/cue129 Callout device for ttyE129 + ... + 192 = /dev/cue192 Callout device for ttyE192 + 193 = /dev/cue193 Callout device for ttyE193 + ... + 25 block First Matsushita (Panasonic/SoundBlaster) CD-ROM + 0 = /dev/sbpcd0 Panasonic CD-ROM controller 0 unit 0 + 1 = /dev/sbpcd1 Panasonic CD-ROM controller 0 unit 1 + 2 = /dev/sbpcd2 Panasonic CD-ROM controller 0 unit 2 + 3 = /dev/sbpcd3 Panasonic CD-ROM controller 0 unit 3 + + 26 char + + 26 block Second Matsushita (Panasonic/SoundBlaster) CD-ROM + 0 = /dev/sbpcd4 Panasonic CD-ROM controller 1 unit 0 + 1 = /dev/sbpcd5 Panasonic CD-ROM controller 1 unit 1 + 2 = /dev/sbpcd6 Panasonic CD-ROM controller 1 unit 2 + 3 = /dev/sbpcd7 Panasonic CD-ROM controller 1 unit 3 + + 27 char QIC-117 tape + 0 = /dev/qft0 Unit 0, rewind-on-close + 1 = /dev/qft1 Unit 1, rewind-on-close + 2 = /dev/qft2 Unit 2, rewind-on-close + 3 = /dev/qft3 Unit 3, rewind-on-close + 4 = /dev/nqft0 Unit 0, no rewind-on-close + 5 = /dev/nqft1 Unit 1, no rewind-on-close + 6 = /dev/nqft2 Unit 2, no rewind-on-close + 7 = /dev/nqft3 Unit 3, no rewind-on-close + 16 = /dev/zqft0 Unit 0, rewind-on-close, compression + 17 = /dev/zqft1 Unit 1, rewind-on-close, compression + 18 = /dev/zqft2 Unit 2, rewind-on-close, compression + 19 = /dev/zqft3 Unit 3, rewind-on-close, compression + 20 = /dev/nzqft0 Unit 0, no rewind-on-close, compression + 21 = /dev/nzqft1 Unit 1, no rewind-on-close, compression + 22 = /dev/nzqft2 Unit 2, no rewind-on-close, compression + 23 = /dev/nzqft3 Unit 3, no rewind-on-close, compression + 32 = /dev/rawqft0 Unit 0, rewind-on-close, no file marks + 33 = /dev/rawqft1 Unit 1, rewind-on-close, no file marks + 34 = /dev/rawqft2 Unit 2, rewind-on-close, no file marks + 35 = /dev/rawqft3 Unit 3, rewind-on-close, no file marks + 36 = /dev/nrawqft0 Unit 0, no rewind-on-close, no file marks + 37 = /dev/nrawqft1 Unit 1, no rewind-on-close, no file marks + 38 = /dev/nrawqft2 Unit 2, no rewind-on-close, no file marks + 39 = /dev/nrawqft3 Unit 3, no rewind-on-close, no file marks + + 27 block Third Matsushita (Panasonic/SoundBlaster) CD-ROM + 0 = /dev/sbpcd8 Panasonic CD-ROM controller 2 unit 0 + 1 = /dev/sbpcd9 Panasonic CD-ROM controller 2 unit 1 + 2 = /dev/sbpcd10 Panasonic CD-ROM controller 2 unit 2 + 3 = /dev/sbpcd11 Panasonic CD-ROM controller 2 unit 3 + + 28 char Stallion serial card - card programming + 0 = /dev/staliomem0 First Stallion card I/O memory + 1 = /dev/staliomem1 Second Stallion card I/O memory + 2 = /dev/staliomem2 Third Stallion card I/O memory + 3 = /dev/staliomem3 Fourth Stallion card I/O memory + + 28 char Atari SLM ACSI laser printer (68k/Atari) + 0 = /dev/slm0 First SLM laser printer + 1 = /dev/slm1 Second SLM laser printer + ... + 28 block Fourth Matsushita (Panasonic/SoundBlaster) CD-ROM + 0 = /dev/sbpcd12 Panasonic CD-ROM controller 3 unit 0 + 1 = /dev/sbpcd13 Panasonic CD-ROM controller 3 unit 1 + 2 = /dev/sbpcd14 Panasonic CD-ROM controller 3 unit 2 + 3 = /dev/sbpcd15 Panasonic CD-ROM controller 3 unit 3 + + 28 block ACSI disk (68k/Atari) + 0 = /dev/ada First ACSI disk whole disk + 16 = /dev/adb Second ACSI disk whole disk + 32 = /dev/adc Third ACSI disk whole disk + ... + 240 = /dev/adp 16th ACSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15, like SCSI. + + 29 char Universal frame buffer + 0 = /dev/fb0 First frame buffer + 1 = /dev/fb1 Second frame buffer + ... + 31 = /dev/fb31 32nd frame buffer + + 29 block Aztech/Orchid/Okano/Wearnes CD-ROM + 0 = /dev/aztcd Aztech CD-ROM + + 30 char iBCS-2 compatibility devices + 0 = /dev/socksys Socket access + 1 = /dev/spx SVR3 local X interface + 32 = /dev/inet/ip Network access + 33 = /dev/inet/icmp + 34 = /dev/inet/ggp + 35 = /dev/inet/ipip + 36 = /dev/inet/tcp + 37 = /dev/inet/egp + 38 = /dev/inet/pup + 39 = /dev/inet/udp + 40 = /dev/inet/idp + 41 = /dev/inet/rawip + + Additionally, iBCS-2 requires the following links: + + /dev/ip -> /dev/inet/ip + /dev/icmp -> /dev/inet/icmp + /dev/ggp -> /dev/inet/ggp + /dev/ipip -> /dev/inet/ipip + /dev/tcp -> /dev/inet/tcp + /dev/egp -> /dev/inet/egp + /dev/pup -> /dev/inet/pup + /dev/udp -> /dev/inet/udp + /dev/idp -> /dev/inet/idp + /dev/rawip -> /dev/inet/rawip + /dev/inet/arp -> /dev/inet/udp + /dev/inet/rip -> /dev/inet/udp + /dev/nfsd -> /dev/socksys + /dev/X0R -> /dev/null (? apparently not required ?) + + 30 block Philips LMS CM-205 CD-ROM + 0 = /dev/cm205cd Philips LMS CM-205 CD-ROM + + /dev/lmscd is an older name for this device. This + driver does not work with the CM-205MS CD-ROM. + + 31 char MPU-401 MIDI + 0 = /dev/mpu401data MPU-401 data port + 1 = /dev/mpu401stat MPU-401 status port + + 31 block ROM/flash memory card + 0 = /dev/rom0 First ROM card (rw) + ... + 7 = /dev/rom7 Eighth ROM card (rw) + 8 = /dev/rrom0 First ROM card (ro) + ... + 15 = /dev/rrom7 Eighth ROM card (ro) + 16 = /dev/flash0 First flash memory card (rw) + ... + 23 = /dev/flash7 Eighth flash memory card (rw) + 24 = /dev/rflash0 First flash memory card (ro) + ... + 31 = /dev/rflash7 Eighth flash memory card (ro) + + The read-write (rw) devices support back-caching + written data in RAM, as well as writing to flash RAM + devices. The read-only devices (ro) support reading + only. + + 32 char Specialix serial card + 0 = /dev/ttyX0 First Specialix port + 1 = /dev/ttyX1 Second Specialix port + ... + 32 block Philips LMS CM-206 CD-ROM + 0 = /dev/cm206cd Philips LMS CM-206 CD-ROM + + 33 char Specialix serial card - alternate devices + 0 = /dev/cux0 Callout device for ttyX0 + 1 = /dev/cux1 Callout device for ttyX1 + ... + 33 block Third IDE hard disk/CD-ROM interface + 0 = /dev/hde Master: whole disk (or CD-ROM) + 64 = /dev/hdf Slave: whole disk (or CD-ROM) + + Partitions are handled the same way as for the first + interface (see major number 3). + + 34 char Z8530 HDLC driver + 0 = /dev/scc0 First Z8530, first port + 1 = /dev/scc1 First Z8530, second port + 2 = /dev/scc2 Second Z8530, first port + 3 = /dev/scc3 Second Z8530, second port + ... + + In a previous version these devices were named + /dev/sc1 for /dev/scc0, /dev/sc2 for /dev/scc1, and so + on. + + 34 block Fourth IDE hard disk/CD-ROM interface + 0 = /dev/hdg Master: whole disk (or CD-ROM) + 64 = /dev/hdh Slave: whole disk (or CD-ROM) + + Partitions are handled the same way as for the first + interface (see major number 3). + + 35 char tclmidi MIDI driver + 0 = /dev/midi0 First MIDI port, kernel timed + 1 = /dev/midi1 Second MIDI port, kernel timed + 2 = /dev/midi2 Third MIDI port, kernel timed + 3 = /dev/midi3 Fourth MIDI port, kernel timed + 64 = /dev/rmidi0 First MIDI port, untimed + 65 = /dev/rmidi1 Second MIDI port, untimed + 66 = /dev/rmidi2 Third MIDI port, untimed + 67 = /dev/rmidi3 Fourth MIDI port, untimed + 128 = /dev/smpte0 First MIDI port, SMPTE timed + 129 = /dev/smpte1 Second MIDI port, SMPTE timed + 130 = /dev/smpte2 Third MIDI port, SMPTE timed + 131 = /dev/smpte3 Fourth MIDI port, SMPTE timed + + 35 block Slow memory ramdisk + 0 = /dev/slram Slow memory ramdisk + + 36 char Netlink support + 0 = /dev/route Routing, device updates, kernel to user + 1 = /dev/skip enSKIP security cache control + 3 = /dev/fwmonitor Firewall packet copies + 16 = /dev/tap0 First Ethertap device + ... + 31 = /dev/tap15 16th Ethertap device + + 36 block OBSOLETE (was MCA ESDI hard disk) + + 37 char IDE tape + 0 = /dev/ht0 First IDE tape + 1 = /dev/ht1 Second IDE tape + ... + 128 = /dev/nht0 First IDE tape, no rewind-on-close + 129 = /dev/nht1 Second IDE tape, no rewind-on-close + ... + + Currently, only one IDE tape drive is supported. + + 37 block Zorro II ramdisk + 0 = /dev/z2ram Zorro II ramdisk + + 38 char Myricom PCI Myrinet board + 0 = /dev/mlanai0 First Myrinet board + 1 = /dev/mlanai1 Second Myrinet board + ... + + This device is used for status query, board control + and "user level packet I/O." This board is also + accessible as a standard networking "eth" device. + + 38 block OBSOLETE (was Linux/AP+) + + 39 char ML-16P experimental I/O board + 0 = /dev/ml16pa-a0 First card, first analog channel + 1 = /dev/ml16pa-a1 First card, second analog channel + ... + 15 = /dev/ml16pa-a15 First card, 16th analog channel + 16 = /dev/ml16pa-d First card, digital lines + 17 = /dev/ml16pa-c0 First card, first counter/timer + 18 = /dev/ml16pa-c1 First card, second counter/timer + 19 = /dev/ml16pa-c2 First card, third counter/timer + 32 = /dev/ml16pb-a0 Second card, first analog channel + 33 = /dev/ml16pb-a1 Second card, second analog channel + ... + 47 = /dev/ml16pb-a15 Second card, 16th analog channel + 48 = /dev/ml16pb-d Second card, digital lines + 49 = /dev/ml16pb-c0 Second card, first counter/timer + 50 = /dev/ml16pb-c1 Second card, second counter/timer + 51 = /dev/ml16pb-c2 Second card, third counter/timer + ... + 39 block + + 40 char + + 40 block + + 41 char Yet Another Micro Monitor + 0 = /dev/yamm Yet Another Micro Monitor + + 41 block + + 42 char Demo/sample use + + 42 block Demo/sample use + + This number is intended for use in sample code, as + well as a general "example" device number. It + should never be used for a device driver that is being + distributed; either obtain an official number or use + the local/experimental range. The sudden addition or + removal of a driver with this number should not cause + ill effects to the system (bugs excepted.) + + IN PARTICULAR, ANY DISTRIBUTION WHICH CONTAINS A + DEVICE DRIVER USING MAJOR NUMBER 42 IS NONCOMPLIANT. + + 43 char isdn4linux virtual modem + 0 = /dev/ttyI0 First virtual modem + ... + 63 = /dev/ttyI63 64th virtual modem + + 43 block Network block devices + 0 = /dev/nb0 First network block device + 1 = /dev/nb1 Second network block device + ... + + Network Block Device is somehow similar to loopback + devices: If you read from it, it sends packet across + network asking server for data. If you write to it, it + sends packet telling server to write. It could be used + to mounting filesystems over the net, swapping over + the net, implementing block device in userland etc. + + 44 char isdn4linux virtual modem - alternate devices + 0 = /dev/cui0 Callout device for ttyI0 + ... + 63 = /dev/cui63 Callout device for ttyI63 + + 44 block Flash Translation Layer (FTL) filesystems + 0 = /dev/ftla FTL on first Memory Technology Device + 16 = /dev/ftlb FTL on second Memory Technology Device + 32 = /dev/ftlc FTL on third Memory Technology Device + ... + 240 = /dev/ftlp FTL on 16th Memory Technology Device + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the partition + limit is 15 rather than 63 per disk (same as SCSI.) + + 45 char isdn4linux ISDN BRI driver + 0 = /dev/isdn0 First virtual B channel raw data + ... + 63 = /dev/isdn63 64th virtual B channel raw data + 64 = /dev/isdnctrl0 First channel control/debug + ... + 127 = /dev/isdnctrl63 64th channel control/debug + + 128 = /dev/ippp0 First SyncPPP device + ... + 191 = /dev/ippp63 64th SyncPPP device + + 255 = /dev/isdninfo ISDN monitor interface + + 45 block Parallel port IDE disk devices + 0 = /dev/pda First parallel port IDE disk + 16 = /dev/pdb Second parallel port IDE disk + 32 = /dev/pdc Third parallel port IDE disk + 48 = /dev/pdd Fourth parallel port IDE disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the partition + limit is 15 rather than 63 per disk. + + 46 char Comtrol Rocketport serial card + 0 = /dev/ttyR0 First Rocketport port + 1 = /dev/ttyR1 Second Rocketport port + ... + 46 block Parallel port ATAPI CD-ROM devices + 0 = /dev/pcd0 First parallel port ATAPI CD-ROM + 1 = /dev/pcd1 Second parallel port ATAPI CD-ROM + 2 = /dev/pcd2 Third parallel port ATAPI CD-ROM + 3 = /dev/pcd3 Fourth parallel port ATAPI CD-ROM + + 47 char Comtrol Rocketport serial card - alternate devices + 0 = /dev/cur0 Callout device for ttyR0 + 1 = /dev/cur1 Callout device for ttyR1 + ... + 47 block Parallel port ATAPI disk devices + 0 = /dev/pf0 First parallel port ATAPI disk + 1 = /dev/pf1 Second parallel port ATAPI disk + 2 = /dev/pf2 Third parallel port ATAPI disk + 3 = /dev/pf3 Fourth parallel port ATAPI disk + + This driver is intended for floppy disks and similar + devices and hence does not support partitioning. + + 48 char SDL RISCom serial card + 0 = /dev/ttyL0 First RISCom port + 1 = /dev/ttyL1 Second RISCom port + ... + 48 block Mylex DAC960 PCI RAID controller; first controller + 0 = /dev/rd/c0d0 First disk, whole disk + 8 = /dev/rd/c0d1 Second disk, whole disk + ... + 248 = /dev/rd/c0d31 32nd disk, whole disk + + For partitions add: + 0 = /dev/rd/c?d? Whole disk + 1 = /dev/rd/c?d?p1 First partition + ... + 7 = /dev/rd/c?d?p7 Seventh partition + + 49 char SDL RISCom serial card - alternate devices + 0 = /dev/cul0 Callout device for ttyL0 + 1 = /dev/cul1 Callout device for ttyL1 + ... + 49 block Mylex DAC960 PCI RAID controller; second controller + 0 = /dev/rd/c1d0 First disk, whole disk + 8 = /dev/rd/c1d1 Second disk, whole disk + ... + 248 = /dev/rd/c1d31 32nd disk, whole disk + + Partitions are handled as for major 48. + + 50 char Reserved for GLINT + + 50 block Mylex DAC960 PCI RAID controller; third controller + 0 = /dev/rd/c2d0 First disk, whole disk + 8 = /dev/rd/c2d1 Second disk, whole disk + ... + 248 = /dev/rd/c2d31 32nd disk, whole disk + + 51 char Baycom radio modem OR Radio Tech BIM-XXX-RS232 radio modem + 0 = /dev/bc0 First Baycom radio modem + 1 = /dev/bc1 Second Baycom radio modem + ... + 51 block Mylex DAC960 PCI RAID controller; fourth controller + 0 = /dev/rd/c3d0 First disk, whole disk + 8 = /dev/rd/c3d1 Second disk, whole disk + ... + 248 = /dev/rd/c3d31 32nd disk, whole disk + + Partitions are handled as for major 48. + + 52 char Spellcaster DataComm/BRI ISDN card + 0 = /dev/dcbri0 First DataComm card + 1 = /dev/dcbri1 Second DataComm card + 2 = /dev/dcbri2 Third DataComm card + 3 = /dev/dcbri3 Fourth DataComm card + + 52 block Mylex DAC960 PCI RAID controller; fifth controller + 0 = /dev/rd/c4d0 First disk, whole disk + 8 = /dev/rd/c4d1 Second disk, whole disk + ... + 248 = /dev/rd/c4d31 32nd disk, whole disk + + Partitions are handled as for major 48. + + 53 char BDM interface for remote debugging MC683xx microcontrollers + 0 = /dev/pd_bdm0 PD BDM interface on lp0 + 1 = /dev/pd_bdm1 PD BDM interface on lp1 + 2 = /dev/pd_bdm2 PD BDM interface on lp2 + 4 = /dev/icd_bdm0 ICD BDM interface on lp0 + 5 = /dev/icd_bdm1 ICD BDM interface on lp1 + 6 = /dev/icd_bdm2 ICD BDM interface on lp2 + + This device is used for the interfacing to the MC683xx + microcontrollers via Background Debug Mode by use of a + Parallel Port interface. PD is the Motorola Public + Domain Interface and ICD is the commercial interface + by P&E. + + 53 block Mylex DAC960 PCI RAID controller; sixth controller + 0 = /dev/rd/c5d0 First disk, whole disk + 8 = /dev/rd/c5d1 Second disk, whole disk + ... + 248 = /dev/rd/c5d31 32nd disk, whole disk + + Partitions are handled as for major 48. + + 54 char Electrocardiognosis Holter serial card + 0 = /dev/holter0 First Holter port + 1 = /dev/holter1 Second Holter port + 2 = /dev/holter2 Third Holter port + + A custom serial card used by Electrocardiognosis SRL + <mseritan@ottonel.pub.ro> to transfer data from Holter + 24-hour heart monitoring equipment. + + 54 block Mylex DAC960 PCI RAID controller; seventh controller + 0 = /dev/rd/c6d0 First disk, whole disk + 8 = /dev/rd/c6d1 Second disk, whole disk + ... + 248 = /dev/rd/c6d31 32nd disk, whole disk + + Partitions are handled as for major 48. + + 55 char DSP56001 digital signal processor + 0 = /dev/dsp56k First DSP56001 + + 55 block Mylex DAC960 PCI RAID controller; eighth controller + 0 = /dev/rd/c7d0 First disk, whole disk + 8 = /dev/rd/c7d1 Second disk, whole disk + ... + 248 = /dev/rd/c7d31 32nd disk, whole disk + + Partitions are handled as for major 48. + + 56 char Apple Desktop Bus + 0 = /dev/adb ADB bus control + + Additional devices will be added to this number, all + starting with /dev/adb. + + 56 block Fifth IDE hard disk/CD-ROM interface + 0 = /dev/hdi Master: whole disk (or CD-ROM) + 64 = /dev/hdj Slave: whole disk (or CD-ROM) + + Partitions are handled the same way as for the first + interface (see major number 3). + + 57 char Hayes ESP serial card + 0 = /dev/ttyP0 First ESP port + 1 = /dev/ttyP1 Second ESP port + ... + + 57 block Sixth IDE hard disk/CD-ROM interface + 0 = /dev/hdk Master: whole disk (or CD-ROM) + 64 = /dev/hdl Slave: whole disk (or CD-ROM) + + Partitions are handled the same way as for the first + interface (see major number 3). + + 58 char Hayes ESP serial card - alternate devices + 0 = /dev/cup0 Callout device for ttyP0 + 1 = /dev/cup1 Callout device for ttyP1 + ... + + 58 block Reserved for logical volume manager + + 59 char sf firewall package + 0 = /dev/firewall Communication with sf kernel module + + 59 block Generic PDA filesystem device + 0 = /dev/pda0 First PDA device + 1 = /dev/pda1 Second PDA device + ... + + The pda devices are used to mount filesystems on + remote pda's (basically slow handheld machines with + proprietary OS's and limited memory and storage + running small fs translation drivers) through serial / + IRDA / parallel links. + + NAMING CONFLICT -- PROPOSED REVISED NAME /dev/rpda0 etc + + 60-63 char LOCAL/EXPERIMENTAL USE + + 60-63 block LOCAL/EXPERIMENTAL USE + Allocated for local/experimental use. For devices not + assigned official numbers, these ranges should be + used in order to avoid conflicting with future assignments. + + 64 char ENskip kernel encryption package + 0 = /dev/enskip Communication with ENskip kernel module + + 64 block Scramdisk/DriveCrypt encrypted devices + 0 = /dev/scramdisk/master Master node for ioctls + 1 = /dev/scramdisk/1 First encrypted device + 2 = /dev/scramdisk/2 Second encrypted device + ... + 255 = /dev/scramdisk/255 255th encrypted device + + The filename of the encrypted container and the passwords + are sent via ioctls (using the sdmount tool) to the master + node which then activates them via one of the + /dev/scramdisk/x nodes for loop mounting (all handled + through the sdmount tool). + + Requested by: andy@scramdisklinux.org + + 65 char Sundance "plink" Transputer boards (obsolete, unused) + 0 = /dev/plink0 First plink device + 1 = /dev/plink1 Second plink device + 2 = /dev/plink2 Third plink device + 3 = /dev/plink3 Fourth plink device + 64 = /dev/rplink0 First plink device, raw + 65 = /dev/rplink1 Second plink device, raw + 66 = /dev/rplink2 Third plink device, raw + 67 = /dev/rplink3 Fourth plink device, raw + 128 = /dev/plink0d First plink device, debug + 129 = /dev/plink1d Second plink device, debug + 130 = /dev/plink2d Third plink device, debug + 131 = /dev/plink3d Fourth plink device, debug + 192 = /dev/rplink0d First plink device, raw, debug + 193 = /dev/rplink1d Second plink device, raw, debug + 194 = /dev/rplink2d Third plink device, raw, debug + 195 = /dev/rplink3d Fourth plink device, raw, debug + + This is a commercial driver; contact James Howes + <jth@prosig.demon.co.uk> for information. + + 65 block SCSI disk devices (16-31) + 0 = /dev/sdq 17th SCSI disk whole disk + 16 = /dev/sdr 18th SCSI disk whole disk + 32 = /dev/sds 19th SCSI disk whole disk + ... + 240 = /dev/sdaf 32nd SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 66 char YARC PowerPC PCI coprocessor card + 0 = /dev/yppcpci0 First YARC card + 1 = /dev/yppcpci1 Second YARC card + ... + + 66 block SCSI disk devices (32-47) + 0 = /dev/sdag 33th SCSI disk whole disk + 16 = /dev/sdah 34th SCSI disk whole disk + 32 = /dev/sdai 35th SCSI disk whole disk + ... + 240 = /dev/sdav 48nd SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 67 char Coda network file system + 0 = /dev/cfs0 Coda cache manager + + See http://www.coda.cs.cmu.edu for information about Coda. + + 67 block SCSI disk devices (48-63) + 0 = /dev/sdaw 49th SCSI disk whole disk + 16 = /dev/sdax 50th SCSI disk whole disk + 32 = /dev/sday 51st SCSI disk whole disk + ... + 240 = /dev/sdbl 64th SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 68 char CAPI 2.0 interface + 0 = /dev/capi20 Control device + 1 = /dev/capi20.00 First CAPI 2.0 application + 2 = /dev/capi20.01 Second CAPI 2.0 application + ... + 20 = /dev/capi20.19 19th CAPI 2.0 application + + ISDN CAPI 2.0 driver for use with CAPI 2.0 + applications; currently supports the AVM B1 card. + + 68 block SCSI disk devices (64-79) + 0 = /dev/sdbm 65th SCSI disk whole disk + 16 = /dev/sdbn 66th SCSI disk whole disk + 32 = /dev/sdbo 67th SCSI disk whole disk + ... + 240 = /dev/sdcb 80th SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 69 char MA16 numeric accelerator card + 0 = /dev/ma16 Board memory access + + 69 block SCSI disk devices (80-95) + 0 = /dev/sdcc 81st SCSI disk whole disk + 16 = /dev/sdcd 82nd SCSI disk whole disk + 32 = /dev/sdce 83th SCSI disk whole disk + ... + 240 = /dev/sdcr 96th SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 70 char SpellCaster Protocol Services Interface + 0 = /dev/apscfg Configuration interface + 1 = /dev/apsauth Authentication interface + 2 = /dev/apslog Logging interface + 3 = /dev/apsdbg Debugging interface + 64 = /dev/apsisdn ISDN command interface + 65 = /dev/apsasync Async command interface + 128 = /dev/apsmon Monitor interface + + 70 block SCSI disk devices (96-111) + 0 = /dev/sdcs 97th SCSI disk whole disk + 16 = /dev/sdct 98th SCSI disk whole disk + 32 = /dev/sdcu 99th SCSI disk whole disk + ... + 240 = /dev/sddh 112nd SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 71 char Computone IntelliPort II serial card + 0 = /dev/ttyF0 IntelliPort II board 0, port 0 + 1 = /dev/ttyF1 IntelliPort II board 0, port 1 + ... + 63 = /dev/ttyF63 IntelliPort II board 0, port 63 + 64 = /dev/ttyF64 IntelliPort II board 1, port 0 + 65 = /dev/ttyF65 IntelliPort II board 1, port 1 + ... + 127 = /dev/ttyF127 IntelliPort II board 1, port 63 + 128 = /dev/ttyF128 IntelliPort II board 2, port 0 + 129 = /dev/ttyF129 IntelliPort II board 2, port 1 + ... + 191 = /dev/ttyF191 IntelliPort II board 2, port 63 + 192 = /dev/ttyF192 IntelliPort II board 3, port 0 + 193 = /dev/ttyF193 IntelliPort II board 3, port 1 + ... + 255 = /dev/ttyF255 IntelliPort II board 3, port 63 + + 71 block SCSI disk devices (112-127) + 0 = /dev/sddi 113th SCSI disk whole disk + 16 = /dev/sddj 114th SCSI disk whole disk + 32 = /dev/sddk 115th SCSI disk whole disk + ... + 240 = /dev/sddx 128th SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 72 char Computone IntelliPort II serial card - alternate devices + 0 = /dev/cuf0 Callout device for ttyF0 + 1 = /dev/cuf1 Callout device for ttyF1 + ... + 63 = /dev/cuf63 Callout device for ttyF63 + 64 = /dev/cuf64 Callout device for ttyF64 + 65 = /dev/cuf65 Callout device for ttyF65 + ... + 127 = /dev/cuf127 Callout device for ttyF127 + 128 = /dev/cuf128 Callout device for ttyF128 + 129 = /dev/cuf129 Callout device for ttyF129 + ... + 191 = /dev/cuf191 Callout device for ttyF191 + 192 = /dev/cuf192 Callout device for ttyF192 + 193 = /dev/cuf193 Callout device for ttyF193 + ... + 255 = /dev/cuf255 Callout device for ttyF255 + + 72 block Compaq Intelligent Drive Array, first controller + 0 = /dev/ida/c0d0 First logical drive whole disk + 16 = /dev/ida/c0d1 Second logical drive whole disk + ... + 240 = /dev/ida/c0d15 16th logical drive whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + 73 char Computone IntelliPort II serial card - control devices + 0 = /dev/ip2ipl0 Loadware device for board 0 + 1 = /dev/ip2stat0 Status device for board 0 + 4 = /dev/ip2ipl1 Loadware device for board 1 + 5 = /dev/ip2stat1 Status device for board 1 + 8 = /dev/ip2ipl2 Loadware device for board 2 + 9 = /dev/ip2stat2 Status device for board 2 + 12 = /dev/ip2ipl3 Loadware device for board 3 + 13 = /dev/ip2stat3 Status device for board 3 + + 73 block Compaq Intelligent Drive Array, second controller + 0 = /dev/ida/c1d0 First logical drive whole disk + 16 = /dev/ida/c1d1 Second logical drive whole disk + ... + 240 = /dev/ida/c1d15 16th logical drive whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + 74 char SCI bridge + 0 = /dev/SCI/0 SCI device 0 + 1 = /dev/SCI/1 SCI device 1 + ... + + Currently for Dolphin Interconnect Solutions' PCI-SCI + bridge. + + 74 block Compaq Intelligent Drive Array, third controller + 0 = /dev/ida/c2d0 First logical drive whole disk + 16 = /dev/ida/c2d1 Second logical drive whole disk + ... + 240 = /dev/ida/c2d15 16th logical drive whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + 75 char Specialix IO8+ serial card + 0 = /dev/ttyW0 First IO8+ port, first card + 1 = /dev/ttyW1 Second IO8+ port, first card + ... + 8 = /dev/ttyW8 First IO8+ port, second card + ... + + 75 block Compaq Intelligent Drive Array, fourth controller + 0 = /dev/ida/c3d0 First logical drive whole disk + 16 = /dev/ida/c3d1 Second logical drive whole disk + ... + 240 = /dev/ida/c3d15 16th logical drive whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + 76 char Specialix IO8+ serial card - alternate devices + 0 = /dev/cuw0 Callout device for ttyW0 + 1 = /dev/cuw1 Callout device for ttyW1 + ... + 8 = /dev/cuw8 Callout device for ttyW8 + ... + + 76 block Compaq Intelligent Drive Array, fifth controller + 0 = /dev/ida/c4d0 First logical drive whole disk + 16 = /dev/ida/c4d1 Second logical drive whole disk + ... + 240 = /dev/ida/c4d15 16th logical drive whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + + 77 char ComScire Quantum Noise Generator + 0 = /dev/qng ComScire Quantum Noise Generator + + 77 block Compaq Intelligent Drive Array, sixth controller + 0 = /dev/ida/c5d0 First logical drive whole disk + 16 = /dev/ida/c5d1 Second logical drive whole disk + ... + 240 = /dev/ida/c5d15 16th logical drive whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + 78 char PAM Software's multimodem boards + 0 = /dev/ttyM0 First PAM modem + 1 = /dev/ttyM1 Second PAM modem + ... + + 78 block Compaq Intelligent Drive Array, seventh controller + 0 = /dev/ida/c6d0 First logical drive whole disk + 16 = /dev/ida/c6d1 Second logical drive whole disk + ... + 240 = /dev/ida/c6d15 16th logical drive whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + 79 char PAM Software's multimodem boards - alternate devices + 0 = /dev/cum0 Callout device for ttyM0 + 1 = /dev/cum1 Callout device for ttyM1 + ... + + 79 block Compaq Intelligent Drive Array, eighth controller + 0 = /dev/ida/c7d0 First logical drive whole disk + 16 = /dev/ida/c7d1 Second logical drive whole disk + ... + 240 = /dev/ida/c715 16th logical drive whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + 80 char Photometrics AT200 CCD camera + 0 = /dev/at200 Photometrics AT200 CCD camera + + 80 block I2O hard disk + 0 = /dev/i2o/hda First I2O hard disk, whole disk + 16 = /dev/i2o/hdb Second I2O hard disk, whole disk + ... + 240 = /dev/i2o/hdp 16th I2O hard disk, whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 81 char video4linux + 0 = /dev/video0 Video capture/overlay device + ... + 63 = /dev/video63 Video capture/overlay device + 64 = /dev/radio0 Radio device + ... + 127 = /dev/radio63 Radio device + 128 = /dev/swradio0 Software Defined Radio device + ... + 191 = /dev/swradio63 Software Defined Radio device + 224 = /dev/vbi0 Vertical blank interrupt + ... + 255 = /dev/vbi31 Vertical blank interrupt + + Minor numbers are allocated dynamically unless + CONFIG_VIDEO_FIXED_MINOR_RANGES (default n) + configuration option is set. + + 81 block I2O hard disk + 0 = /dev/i2o/hdq 17th I2O hard disk, whole disk + 16 = /dev/i2o/hdr 18th I2O hard disk, whole disk + ... + 240 = /dev/i2o/hdaf 32nd I2O hard disk, whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 82 char WiNRADiO communications receiver card + 0 = /dev/winradio0 First WiNRADiO card + 1 = /dev/winradio1 Second WiNRADiO card + ... + + The driver and documentation may be obtained from + https://www.winradio.com/ + + 82 block I2O hard disk + 0 = /dev/i2o/hdag 33rd I2O hard disk, whole disk + 16 = /dev/i2o/hdah 34th I2O hard disk, whole disk + ... + 240 = /dev/i2o/hdav 48th I2O hard disk, whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 83 char Matrox mga_vid video driver + 0 = /dev/mga_vid0 1st video card + 1 = /dev/mga_vid1 2nd video card + 2 = /dev/mga_vid2 3rd video card + ... + 15 = /dev/mga_vid15 16th video card + + 83 block I2O hard disk + 0 = /dev/i2o/hdaw 49th I2O hard disk, whole disk + 16 = /dev/i2o/hdax 50th I2O hard disk, whole disk + ... + 240 = /dev/i2o/hdbl 64th I2O hard disk, whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 84 char Ikon 1011[57] Versatec Greensheet Interface + 0 = /dev/ihcp0 First Greensheet port + 1 = /dev/ihcp1 Second Greensheet port + + 84 block I2O hard disk + 0 = /dev/i2o/hdbm 65th I2O hard disk, whole disk + 16 = /dev/i2o/hdbn 66th I2O hard disk, whole disk + ... + 240 = /dev/i2o/hdcb 80th I2O hard disk, whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 85 char Linux/SGI shared memory input queue + 0 = /dev/shmiq Master shared input queue + 1 = /dev/qcntl0 First device pushed + 2 = /dev/qcntl1 Second device pushed + ... + + 85 block I2O hard disk + 0 = /dev/i2o/hdcc 81st I2O hard disk, whole disk + 16 = /dev/i2o/hdcd 82nd I2O hard disk, whole disk + ... + 240 = /dev/i2o/hdcr 96th I2O hard disk, whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 86 char SCSI media changer + 0 = /dev/sch0 First SCSI media changer + 1 = /dev/sch1 Second SCSI media changer + ... + + 86 block I2O hard disk + 0 = /dev/i2o/hdcs 97th I2O hard disk, whole disk + 16 = /dev/i2o/hdct 98th I2O hard disk, whole disk + ... + 240 = /dev/i2o/hddh 112th I2O hard disk, whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 87 char Sony Control-A1 stereo control bus + 0 = /dev/controla0 First device on chain + 1 = /dev/controla1 Second device on chain + ... + + 87 block I2O hard disk + 0 = /dev/i2o/hddi 113rd I2O hard disk, whole disk + 16 = /dev/i2o/hddj 114th I2O hard disk, whole disk + ... + 240 = /dev/i2o/hddx 128th I2O hard disk, whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 88 char COMX synchronous serial card + 0 = /dev/comx0 COMX channel 0 + 1 = /dev/comx1 COMX channel 1 + ... + + 88 block Seventh IDE hard disk/CD-ROM interface + 0 = /dev/hdm Master: whole disk (or CD-ROM) + 64 = /dev/hdn Slave: whole disk (or CD-ROM) + + Partitions are handled the same way as for the first + interface (see major number 3). + + 89 char I2C bus interface + 0 = /dev/i2c-0 First I2C adapter + 1 = /dev/i2c-1 Second I2C adapter + ... + + 89 block Eighth IDE hard disk/CD-ROM interface + 0 = /dev/hdo Master: whole disk (or CD-ROM) + 64 = /dev/hdp Slave: whole disk (or CD-ROM) + + Partitions are handled the same way as for the first + interface (see major number 3). + + 90 char Memory Technology Device (RAM, ROM, Flash) + 0 = /dev/mtd0 First MTD (rw) + 1 = /dev/mtdr0 First MTD (ro) + ... + 30 = /dev/mtd15 16th MTD (rw) + 31 = /dev/mtdr15 16th MTD (ro) + + 90 block Ninth IDE hard disk/CD-ROM interface + 0 = /dev/hdq Master: whole disk (or CD-ROM) + 64 = /dev/hdr Slave: whole disk (or CD-ROM) + + Partitions are handled the same way as for the first + interface (see major number 3). + + 91 char CAN-Bus devices + 0 = /dev/can0 First CAN-Bus controller + 1 = /dev/can1 Second CAN-Bus controller + ... + + 91 block Tenth IDE hard disk/CD-ROM interface + 0 = /dev/hds Master: whole disk (or CD-ROM) + 64 = /dev/hdt Slave: whole disk (or CD-ROM) + + Partitions are handled the same way as for the first + interface (see major number 3). + + 92 char Reserved for ith Kommunikationstechnik MIC ISDN card + + 92 block PPDD encrypted disk driver + 0 = /dev/ppdd0 First encrypted disk + 1 = /dev/ppdd1 Second encrypted disk + ... + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 93 char + + 93 block NAND Flash Translation Layer filesystem + 0 = /dev/nftla First NFTL layer + 16 = /dev/nftlb Second NFTL layer + ... + 240 = /dev/nftlp 16th NTFL layer + + 94 char + + 94 block IBM S/390 DASD block storage + 0 = /dev/dasda First DASD device, major + 1 = /dev/dasda1 First DASD device, block 1 + 2 = /dev/dasda2 First DASD device, block 2 + 3 = /dev/dasda3 First DASD device, block 3 + 4 = /dev/dasdb Second DASD device, major + 5 = /dev/dasdb1 Second DASD device, block 1 + 6 = /dev/dasdb2 Second DASD device, block 2 + 7 = /dev/dasdb3 Second DASD device, block 3 + ... + + 95 char IP filter + 0 = /dev/ipl Filter control device/log file + 1 = /dev/ipnat NAT control device/log file + 2 = /dev/ipstate State information log file + 3 = /dev/ipauth Authentication control device/log file + ... + + 96 char Parallel port ATAPI tape devices + 0 = /dev/pt0 First parallel port ATAPI tape + 1 = /dev/pt1 Second parallel port ATAPI tape + ... + 128 = /dev/npt0 First p.p. ATAPI tape, no rewind + 129 = /dev/npt1 Second p.p. ATAPI tape, no rewind + ... + + 96 block Inverse NAND Flash Translation Layer + 0 = /dev/inftla First INFTL layer + 16 = /dev/inftlb Second INFTL layer + ... + 240 = /dev/inftlp 16th INTFL layer + + 97 char Parallel port generic ATAPI interface + 0 = /dev/pg0 First parallel port ATAPI device + 1 = /dev/pg1 Second parallel port ATAPI device + 2 = /dev/pg2 Third parallel port ATAPI device + 3 = /dev/pg3 Fourth parallel port ATAPI device + + These devices support the same API as the generic SCSI + devices. + + 98 char Control and Measurement Device (comedi) + 0 = /dev/comedi0 First comedi device + 1 = /dev/comedi1 Second comedi device + ... + 47 = /dev/comedi47 48th comedi device + + Minors 48 to 255 are reserved for comedi subdevices with + pathnames of the form "/dev/comediX_subdY", where "X" is the + minor number of the associated comedi device and "Y" is the + subdevice number. These subdevice minors are assigned + dynamically, so there is no fixed mapping from subdevice + pathnames to minor numbers. + + See https://www.comedi.org/ for information about the Comedi + project. + + 98 block User-mode virtual block device + 0 = /dev/ubda First user-mode block device + 16 = /dev/ubdb Second user-mode block device + ... + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + This device is used by the user-mode virtual kernel port. + + 99 char Raw parallel ports + 0 = /dev/parport0 First parallel port + 1 = /dev/parport1 Second parallel port + ... + + 99 block JavaStation flash disk + 0 = /dev/jsfd JavaStation flash disk + + 100 char Telephony for Linux + 0 = /dev/phone0 First telephony device + 1 = /dev/phone1 Second telephony device + ... + + 101 char Motorola DSP 56xxx board + 0 = /dev/mdspstat Status information + 1 = /dev/mdsp1 First DSP board I/O controls + ... + 16 = /dev/mdsp16 16th DSP board I/O controls + + 101 block AMI HyperDisk RAID controller + 0 = /dev/amiraid/ar0 First array whole disk + 16 = /dev/amiraid/ar1 Second array whole disk + ... + 240 = /dev/amiraid/ar15 16th array whole disk + + For each device, partitions are added as: + 0 = /dev/amiraid/ar? Whole disk + 1 = /dev/amiraid/ar?p1 First partition + 2 = /dev/amiraid/ar?p2 Second partition + ... + 15 = /dev/amiraid/ar?p15 15th partition + + 102 char + + 102 block Compressed block device + 0 = /dev/cbd/a First compressed block device, whole device + 16 = /dev/cbd/b Second compressed block device, whole device + ... + 240 = /dev/cbd/p 16th compressed block device, whole device + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 103 char Arla network file system + 0 = /dev/nnpfs0 First NNPFS device + 1 = /dev/nnpfs1 Second NNPFS device + + Arla is a free clone of the Andrew File System, AFS. + The NNPFS device gives user mode filesystem + implementations a kernel presence for caching and easy + mounting. For more information about the project, + write to <arla-drinkers@stacken.kth.se> or see + https://www.stacken.kth.se/project/arla/ + + 103 block Audit device + 0 = /dev/audit Audit device + + 104 char Flash BIOS support + + 104 block Compaq Next Generation Drive Array, first controller + 0 = /dev/cciss/c0d0 First logical drive, whole disk + 16 = /dev/cciss/c0d1 Second logical drive, whole disk + ... + 240 = /dev/cciss/c0d15 16th logical drive, whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + 105 char Comtrol VS-1000 serial controller + 0 = /dev/ttyV0 First VS-1000 port + 1 = /dev/ttyV1 Second VS-1000 port + ... + + 105 block Compaq Next Generation Drive Array, second controller + 0 = /dev/cciss/c1d0 First logical drive, whole disk + 16 = /dev/cciss/c1d1 Second logical drive, whole disk + ... + 240 = /dev/cciss/c1d15 16th logical drive, whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + 106 char Comtrol VS-1000 serial controller - alternate devices + 0 = /dev/cuv0 First VS-1000 port + 1 = /dev/cuv1 Second VS-1000 port + ... + + 106 block Compaq Next Generation Drive Array, third controller + 0 = /dev/cciss/c2d0 First logical drive, whole disk + 16 = /dev/cciss/c2d1 Second logical drive, whole disk + ... + 240 = /dev/cciss/c2d15 16th logical drive, whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + 107 char 3Dfx Voodoo Graphics device + 0 = /dev/3dfx Primary 3Dfx graphics device + + 107 block Compaq Next Generation Drive Array, fourth controller + 0 = /dev/cciss/c3d0 First logical drive, whole disk + 16 = /dev/cciss/c3d1 Second logical drive, whole disk + ... + 240 = /dev/cciss/c3d15 16th logical drive, whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + 108 char Device independent PPP interface + 0 = /dev/ppp Device independent PPP interface + + 108 block Compaq Next Generation Drive Array, fifth controller + 0 = /dev/cciss/c4d0 First logical drive, whole disk + 16 = /dev/cciss/c4d1 Second logical drive, whole disk + ... + 240 = /dev/cciss/c4d15 16th logical drive, whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + 109 char Reserved for logical volume manager + + 109 block Compaq Next Generation Drive Array, sixth controller + 0 = /dev/cciss/c5d0 First logical drive, whole disk + 16 = /dev/cciss/c5d1 Second logical drive, whole disk + ... + 240 = /dev/cciss/c5d15 16th logical drive, whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + 110 char miroMEDIA Surround board + 0 = /dev/srnd0 First miroMEDIA Surround board + 1 = /dev/srnd1 Second miroMEDIA Surround board + ... + + 110 block Compaq Next Generation Drive Array, seventh controller + 0 = /dev/cciss/c6d0 First logical drive, whole disk + 16 = /dev/cciss/c6d1 Second logical drive, whole disk + ... + 240 = /dev/cciss/c6d15 16th logical drive, whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + 111 char + + 111 block Compaq Next Generation Drive Array, eighth controller + 0 = /dev/cciss/c7d0 First logical drive, whole disk + 16 = /dev/cciss/c7d1 Second logical drive, whole disk + ... + 240 = /dev/cciss/c7d15 16th logical drive, whole disk + + Partitions are handled the same way as for Mylex + DAC960 (see major number 48) except that the limit on + partitions is 15. + + 112 char ISI serial card + 0 = /dev/ttyM0 First ISI port + 1 = /dev/ttyM1 Second ISI port + ... + + There is currently a device-naming conflict between + these and PAM multimodems (major 78). + + 112 block IBM iSeries virtual disk + 0 = /dev/iseries/vda First virtual disk, whole disk + 8 = /dev/iseries/vdb Second virtual disk, whole disk + ... + 200 = /dev/iseries/vdz 26th virtual disk, whole disk + 208 = /dev/iseries/vdaa 27th virtual disk, whole disk + ... + 248 = /dev/iseries/vdaf 32nd virtual disk, whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 7. + + 113 char ISI serial card - alternate devices + 0 = /dev/cum0 Callout device for ttyM0 + 1 = /dev/cum1 Callout device for ttyM1 + ... + + 113 block IBM iSeries virtual CD-ROM + 0 = /dev/iseries/vcda First virtual CD-ROM + 1 = /dev/iseries/vcdb Second virtual CD-ROM + ... + + 114 char Picture Elements ISE board + 0 = /dev/ise0 First ISE board + 1 = /dev/ise1 Second ISE board + ... + 128 = /dev/isex0 Control node for first ISE board + 129 = /dev/isex1 Control node for second ISE board + ... + + The ISE board is an embedded computer, optimized for + image processing. The /dev/iseN nodes are the general + I/O access to the board, the /dev/isex0 nodes command + nodes used to control the board. + + 114 block IDE BIOS powered software RAID interfaces such as the + Promise Fastrak + + 0 = /dev/ataraid/d0 + 1 = /dev/ataraid/d0p1 + 2 = /dev/ataraid/d0p2 + ... + 16 = /dev/ataraid/d1 + 17 = /dev/ataraid/d1p1 + 18 = /dev/ataraid/d1p2 + ... + 255 = /dev/ataraid/d15p15 + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 115 char TI link cable devices (115 was formerly the console driver speaker) + 0 = /dev/tipar0 Parallel cable on first parallel port + ... + 7 = /dev/tipar7 Parallel cable on seventh parallel port + + 8 = /dev/tiser0 Serial cable on first serial port + ... + 15 = /dev/tiser7 Serial cable on seventh serial port + + 16 = /dev/tiusb0 First USB cable + ... + 47 = /dev/tiusb31 32nd USB cable + + 115 block NetWare (NWFS) Devices (0-255) + + The NWFS (NetWare) devices are used to present a + collection of NetWare Mirror Groups or NetWare + Partitions as a logical storage segment for + use in mounting NetWare volumes. A maximum of + 256 NetWare volumes can be supported in a single + machine. + + http://cgfa.telepac.pt/ftp2/kernel.org/linux/kernel/people/jmerkey/nwfs/ + + 0 = /dev/nwfs/v0 First NetWare (NWFS) Logical Volume + 1 = /dev/nwfs/v1 Second NetWare (NWFS) Logical Volume + 2 = /dev/nwfs/v2 Third NetWare (NWFS) Logical Volume + ... + 255 = /dev/nwfs/v255 Last NetWare (NWFS) Logical Volume + + 116 char Advanced Linux Sound Driver (ALSA) + + 116 block MicroMemory battery backed RAM adapter (NVRAM) + Supports 16 boards, 15 partitions each. + Requested by neilb at cse.unsw.edu.au. + + 0 = /dev/umem/d0 Whole of first board + 1 = /dev/umem/d0p1 First partition of first board + 2 = /dev/umem/d0p2 Second partition of first board + 15 = /dev/umem/d0p15 15th partition of first board + + 16 = /dev/umem/d1 Whole of second board + 17 = /dev/umem/d1p1 First partition of second board + ... + 255= /dev/umem/d15p15 15th partition of 16th board. + + 117 char [REMOVED] COSA/SRP synchronous serial card + 0 = /dev/cosa0c0 1st board, 1st channel + 1 = /dev/cosa0c1 1st board, 2nd channel + ... + 16 = /dev/cosa1c0 2nd board, 1st channel + 17 = /dev/cosa1c1 2nd board, 2nd channel + ... + + 117 block Enterprise Volume Management System (EVMS) + + The EVMS driver uses a layered, plug-in model to provide + unparalleled flexibility and extensibility in managing + storage. This allows for easy expansion or customization + of various levels of volume management. Requested by + Mark Peloquin (peloquin at us.ibm.com). + + Note: EVMS populates and manages all the devnodes in + /dev/evms. + + http://sf.net/projects/evms + + 0 = /dev/evms/block_device EVMS block device + 1 = /dev/evms/legacyname1 First EVMS legacy device + 2 = /dev/evms/legacyname2 Second EVMS legacy device + ... + Both ranges can grow (down or up) until they meet. + ... + 254 = /dev/evms/EVMSname2 Second EVMS native device + 255 = /dev/evms/EVMSname1 First EVMS native device + + Note: legacyname(s) are derived from the normal legacy + device names. For example, /dev/hda5 would become + /dev/evms/hda5. + + 118 char IBM Cryptographic Accelerator + 0 = /dev/ica Virtual interface to all IBM Crypto Accelerators + 1 = /dev/ica0 IBMCA Device 0 + 2 = /dev/ica1 IBMCA Device 1 + ... + + 119 char VMware virtual network control + 0 = /dev/vnet0 1st virtual network + 1 = /dev/vnet1 2nd virtual network + ... + + 120-127 char LOCAL/EXPERIMENTAL USE + + 120-127 block LOCAL/EXPERIMENTAL USE + Allocated for local/experimental use. For devices not + assigned official numbers, these ranges should be + used in order to avoid conflicting with future assignments. + + 128-135 char Unix98 PTY masters + + These devices should not have corresponding device + nodes; instead they should be accessed through the + /dev/ptmx cloning interface. + + 128 block SCSI disk devices (128-143) + 0 = /dev/sddy 129th SCSI disk whole disk + 16 = /dev/sddz 130th SCSI disk whole disk + 32 = /dev/sdea 131th SCSI disk whole disk + ... + 240 = /dev/sden 144th SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 129 block SCSI disk devices (144-159) + 0 = /dev/sdeo 145th SCSI disk whole disk + 16 = /dev/sdep 146th SCSI disk whole disk + 32 = /dev/sdeq 147th SCSI disk whole disk + ... + 240 = /dev/sdfd 160th SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 130 char (Misc devices) + + 130 block SCSI disk devices (160-175) + 0 = /dev/sdfe 161st SCSI disk whole disk + 16 = /dev/sdff 162nd SCSI disk whole disk + 32 = /dev/sdfg 163rd SCSI disk whole disk + ... + 240 = /dev/sdft 176th SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 131 block SCSI disk devices (176-191) + 0 = /dev/sdfu 177th SCSI disk whole disk + 16 = /dev/sdfv 178th SCSI disk whole disk + 32 = /dev/sdfw 179th SCSI disk whole disk + ... + 240 = /dev/sdgj 192nd SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 132 block SCSI disk devices (192-207) + 0 = /dev/sdgk 193rd SCSI disk whole disk + 16 = /dev/sdgl 194th SCSI disk whole disk + 32 = /dev/sdgm 195th SCSI disk whole disk + ... + 240 = /dev/sdgz 208th SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 133 block SCSI disk devices (208-223) + 0 = /dev/sdha 209th SCSI disk whole disk + 16 = /dev/sdhb 210th SCSI disk whole disk + 32 = /dev/sdhc 211th SCSI disk whole disk + ... + 240 = /dev/sdhp 224th SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 134 block SCSI disk devices (224-239) + 0 = /dev/sdhq 225th SCSI disk whole disk + 16 = /dev/sdhr 226th SCSI disk whole disk + 32 = /dev/sdhs 227th SCSI disk whole disk + ... + 240 = /dev/sdif 240th SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 135 block SCSI disk devices (240-255) + 0 = /dev/sdig 241st SCSI disk whole disk + 16 = /dev/sdih 242nd SCSI disk whole disk + 32 = /dev/sdih 243rd SCSI disk whole disk + ... + 240 = /dev/sdiv 256th SCSI disk whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 136-143 char Unix98 PTY slaves + 0 = /dev/pts/0 First Unix98 pseudo-TTY + 1 = /dev/pts/1 Second Unix98 pseudo-TTY + ... + + These device nodes are automatically generated with + the proper permissions and modes by mounting the + devpts filesystem onto /dev/pts with the appropriate + mount options (distribution dependent, however, on + *most* distributions the appropriate options are + "mode=0620,gid=<gid of the "tty" group>".) + + 136 block Mylex DAC960 PCI RAID controller; ninth controller + 0 = /dev/rd/c8d0 First disk, whole disk + 8 = /dev/rd/c8d1 Second disk, whole disk + ... + 248 = /dev/rd/c8d31 32nd disk, whole disk + + Partitions are handled as for major 48. + + 137 block Mylex DAC960 PCI RAID controller; tenth controller + 0 = /dev/rd/c9d0 First disk, whole disk + 8 = /dev/rd/c9d1 Second disk, whole disk + ... + 248 = /dev/rd/c9d31 32nd disk, whole disk + + Partitions are handled as for major 48. + + 138 block Mylex DAC960 PCI RAID controller; eleventh controller + 0 = /dev/rd/c10d0 First disk, whole disk + 8 = /dev/rd/c10d1 Second disk, whole disk + ... + 248 = /dev/rd/c10d31 32nd disk, whole disk + + Partitions are handled as for major 48. + + 139 block Mylex DAC960 PCI RAID controller; twelfth controller + 0 = /dev/rd/c11d0 First disk, whole disk + 8 = /dev/rd/c11d1 Second disk, whole disk + ... + 248 = /dev/rd/c11d31 32nd disk, whole disk + + Partitions are handled as for major 48. + + 140 block Mylex DAC960 PCI RAID controller; thirteenth controller + 0 = /dev/rd/c12d0 First disk, whole disk + 8 = /dev/rd/c12d1 Second disk, whole disk + ... + 248 = /dev/rd/c12d31 32nd disk, whole disk + + Partitions are handled as for major 48. + + 141 block Mylex DAC960 PCI RAID controller; fourteenth controller + 0 = /dev/rd/c13d0 First disk, whole disk + 8 = /dev/rd/c13d1 Second disk, whole disk + ... + 248 = /dev/rd/c13d31 32nd disk, whole disk + + Partitions are handled as for major 48. + + 142 block Mylex DAC960 PCI RAID controller; fifteenth controller + 0 = /dev/rd/c14d0 First disk, whole disk + 8 = /dev/rd/c14d1 Second disk, whole disk + ... + 248 = /dev/rd/c14d31 32nd disk, whole disk + + Partitions are handled as for major 48. + + 143 block Mylex DAC960 PCI RAID controller; sixteenth controller + 0 = /dev/rd/c15d0 First disk, whole disk + 8 = /dev/rd/c15d1 Second disk, whole disk + ... + 248 = /dev/rd/c15d31 32nd disk, whole disk + + Partitions are handled as for major 48. + + 144 char Encapsulated PPP + 0 = /dev/pppox0 First PPP over Ethernet + ... + 63 = /dev/pppox63 64th PPP over Ethernet + + This is primarily used for ADSL. + + The SST 5136-DN DeviceNet interface driver has been + relocated to major 183 due to an unfortunate conflict. + + 144 block Expansion Area #1 for more non-device (e.g. NFS) mounts + 0 = mounted device 256 + 255 = mounted device 511 + + 145 char SAM9407-based soundcard + 0 = /dev/sam0_mixer + 1 = /dev/sam0_sequencer + 2 = /dev/sam0_midi00 + 3 = /dev/sam0_dsp + 4 = /dev/sam0_audio + 6 = /dev/sam0_sndstat + 18 = /dev/sam0_midi01 + 34 = /dev/sam0_midi02 + 50 = /dev/sam0_midi03 + 64 = /dev/sam1_mixer + ... + 128 = /dev/sam2_mixer + ... + 192 = /dev/sam3_mixer + ... + + Device functions match OSS, but offer a number of + addons, which are sam9407 specific. OSS can be + operated simultaneously, taking care of the codec. + + 145 block Expansion Area #2 for more non-device (e.g. NFS) mounts + 0 = mounted device 512 + 255 = mounted device 767 + + 146 char SYSTRAM SCRAMNet mirrored-memory network + 0 = /dev/scramnet0 First SCRAMNet device + 1 = /dev/scramnet1 Second SCRAMNet device + ... + + 146 block Expansion Area #3 for more non-device (e.g. NFS) mounts + 0 = mounted device 768 + 255 = mounted device 1023 + + 147 char Aureal Semiconductor Vortex Audio device + 0 = /dev/aureal0 First Aureal Vortex + 1 = /dev/aureal1 Second Aureal Vortex + ... + + 147 block Distributed Replicated Block Device (DRBD) + 0 = /dev/drbd0 First DRBD device + 1 = /dev/drbd1 Second DRBD device + ... + + 148 char Technology Concepts serial card + 0 = /dev/ttyT0 First TCL port + 1 = /dev/ttyT1 Second TCL port + ... + + 149 char Technology Concepts serial card - alternate devices + 0 = /dev/cut0 Callout device for ttyT0 + 1 = /dev/cut0 Callout device for ttyT1 + ... + + 150 char Real-Time Linux FIFOs + 0 = /dev/rtf0 First RTLinux FIFO + 1 = /dev/rtf1 Second RTLinux FIFO + ... + + 151 char DPT I2O SmartRaid V controller + 0 = /dev/dpti0 First DPT I2O adapter + 1 = /dev/dpti1 Second DPT I2O adapter + ... + + 152 char EtherDrive Control Device + 0 = /dev/etherd/ctl Connect/Disconnect an EtherDrive + 1 = /dev/etherd/err Monitor errors + 2 = /dev/etherd/raw Raw AoE packet monitor + + 152 block EtherDrive Block Devices + 0 = /dev/etherd/0 EtherDrive 0 + ... + 255 = /dev/etherd/255 EtherDrive 255 + + 153 char SPI Bus Interface (sometimes referred to as MicroWire) + 0 = /dev/spi0 First SPI device on the bus + 1 = /dev/spi1 Second SPI device on the bus + ... + 15 = /dev/spi15 Sixteenth SPI device on the bus + + 153 block Enhanced Metadisk RAID (EMD) storage units + 0 = /dev/emd/0 First unit + 1 = /dev/emd/0p1 Partition 1 on First unit + 2 = /dev/emd/0p2 Partition 2 on First unit + ... + 15 = /dev/emd/0p15 Partition 15 on First unit + + 16 = /dev/emd/1 Second unit + 32 = /dev/emd/2 Third unit + ... + 240 = /dev/emd/15 Sixteenth unit + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 154 char Specialix RIO serial card + 0 = /dev/ttySR0 First RIO port + ... + 255 = /dev/ttySR255 256th RIO port + + 155 char Specialix RIO serial card - alternate devices + 0 = /dev/cusr0 Callout device for ttySR0 + ... + 255 = /dev/cusr255 Callout device for ttySR255 + + 156 char Specialix RIO serial card + 0 = /dev/ttySR256 257th RIO port + ... + 255 = /dev/ttySR511 512th RIO port + + 157 char Specialix RIO serial card - alternate devices + 0 = /dev/cusr256 Callout device for ttySR256 + ... + 255 = /dev/cusr511 Callout device for ttySR511 + + 158 char Dialogic GammaLink fax driver + 0 = /dev/gfax0 GammaLink channel 0 + 1 = /dev/gfax1 GammaLink channel 1 + ... + + 159 char RESERVED + + 159 block RESERVED + + 160 char General Purpose Instrument Bus (GPIB) + 0 = /dev/gpib0 First GPIB bus + 1 = /dev/gpib1 Second GPIB bus + ... + + 160 block Carmel 8-port SATA Disks on First Controller + 0 = /dev/carmel/0 SATA disk 0 whole disk + 1 = /dev/carmel/0p1 SATA disk 0 partition 1 + ... + 31 = /dev/carmel/0p31 SATA disk 0 partition 31 + + 32 = /dev/carmel/1 SATA disk 1 whole disk + 64 = /dev/carmel/2 SATA disk 2 whole disk + ... + 224 = /dev/carmel/7 SATA disk 7 whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 31. + + 161 char IrCOMM devices (IrDA serial/parallel emulation) + 0 = /dev/ircomm0 First IrCOMM device + 1 = /dev/ircomm1 Second IrCOMM device + ... + 16 = /dev/irlpt0 First IrLPT device + 17 = /dev/irlpt1 Second IrLPT device + ... + + 161 block Carmel 8-port SATA Disks on Second Controller + 0 = /dev/carmel/8 SATA disk 8 whole disk + 1 = /dev/carmel/8p1 SATA disk 8 partition 1 + ... + 31 = /dev/carmel/8p31 SATA disk 8 partition 31 + + 32 = /dev/carmel/9 SATA disk 9 whole disk + 64 = /dev/carmel/10 SATA disk 10 whole disk + ... + 224 = /dev/carmel/15 SATA disk 15 whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 31. + + 162 char Used for (now removed) raw block device interface + + 163 char + + 164 char Chase Research AT/PCI-Fast serial card + 0 = /dev/ttyCH0 AT/PCI-Fast board 0, port 0 + ... + 15 = /dev/ttyCH15 AT/PCI-Fast board 0, port 15 + 16 = /dev/ttyCH16 AT/PCI-Fast board 1, port 0 + ... + 31 = /dev/ttyCH31 AT/PCI-Fast board 1, port 15 + 32 = /dev/ttyCH32 AT/PCI-Fast board 2, port 0 + ... + 47 = /dev/ttyCH47 AT/PCI-Fast board 2, port 15 + 48 = /dev/ttyCH48 AT/PCI-Fast board 3, port 0 + ... + 63 = /dev/ttyCH63 AT/PCI-Fast board 3, port 15 + + 165 char Chase Research AT/PCI-Fast serial card - alternate devices + 0 = /dev/cuch0 Callout device for ttyCH0 + ... + 63 = /dev/cuch63 Callout device for ttyCH63 + + 166 char ACM USB modems + 0 = /dev/ttyACM0 First ACM modem + 1 = /dev/ttyACM1 Second ACM modem + ... + + 167 char ACM USB modems - alternate devices + 0 = /dev/cuacm0 Callout device for ttyACM0 + 1 = /dev/cuacm1 Callout device for ttyACM1 + ... + + 168 char Eracom CSA7000 PCI encryption adaptor + 0 = /dev/ecsa0 First CSA7000 + 1 = /dev/ecsa1 Second CSA7000 + ... + + 169 char Eracom CSA8000 PCI encryption adaptor + 0 = /dev/ecsa8-0 First CSA8000 + 1 = /dev/ecsa8-1 Second CSA8000 + ... + + 170 char AMI MegaRAC remote access controller + 0 = /dev/megarac0 First MegaRAC card + 1 = /dev/megarac1 Second MegaRAC card + ... + + 171 char Reserved for IEEE 1394 (Firewire) + + 172 char Moxa Intellio serial card + 0 = /dev/ttyMX0 First Moxa port + 1 = /dev/ttyMX1 Second Moxa port + ... + 127 = /dev/ttyMX127 128th Moxa port + 128 = /dev/moxactl Moxa control port + + 173 char Moxa Intellio serial card - alternate devices + 0 = /dev/cumx0 Callout device for ttyMX0 + 1 = /dev/cumx1 Callout device for ttyMX1 + ... + 127 = /dev/cumx127 Callout device for ttyMX127 + + 174 char SmartIO serial card + 0 = /dev/ttySI0 First SmartIO port + 1 = /dev/ttySI1 Second SmartIO port + ... + + 175 char SmartIO serial card - alternate devices + 0 = /dev/cusi0 Callout device for ttySI0 + 1 = /dev/cusi1 Callout device for ttySI1 + ... + + 176 char nCipher nFast PCI crypto accelerator + 0 = /dev/nfastpci0 First nFast PCI device + 1 = /dev/nfastpci1 First nFast PCI device + ... + + 177 char TI PCILynx memory spaces + 0 = /dev/pcilynx/aux0 AUX space of first PCILynx card + ... + 15 = /dev/pcilynx/aux15 AUX space of 16th PCILynx card + 16 = /dev/pcilynx/rom0 ROM space of first PCILynx card + ... + 31 = /dev/pcilynx/rom15 ROM space of 16th PCILynx card + 32 = /dev/pcilynx/ram0 RAM space of first PCILynx card + ... + 47 = /dev/pcilynx/ram15 RAM space of 16th PCILynx card + + 178 char Giganet cLAN1xxx virtual interface adapter + 0 = /dev/clanvi0 First cLAN adapter + 1 = /dev/clanvi1 Second cLAN adapter + ... + + 179 block MMC block devices + 0 = /dev/mmcblk0 First SD/MMC card + 1 = /dev/mmcblk0p1 First partition on first MMC card + 8 = /dev/mmcblk1 Second SD/MMC card + ... + + The start of next SD/MMC card can be configured with + CONFIG_MMC_BLOCK_MINORS, or overridden at boot/modprobe + time using the mmcblk.perdev_minors option. That would + bump the offset between each card to be the configured + value instead of the default 8. + + 179 char CCube DVXChip-based PCI products + 0 = /dev/dvxirq0 First DVX device + 1 = /dev/dvxirq1 Second DVX device + ... + + 180 char USB devices + 0 = /dev/usb/lp0 First USB printer + ... + 15 = /dev/usb/lp15 16th USB printer + 48 = /dev/usb/scanner0 First USB scanner + ... + 63 = /dev/usb/scanner15 16th USB scanner + 64 = /dev/usb/rio500 Diamond Rio 500 + 65 = /dev/usb/usblcd USBLCD Interface (info@usblcd.de) + 66 = /dev/usb/cpad0 Synaptics cPad (mouse/LCD) + 96 = /dev/usb/hiddev0 1st USB HID device + ... + 111 = /dev/usb/hiddev15 16th USB HID device + 112 = /dev/usb/auer0 1st auerswald ISDN device + ... + 127 = /dev/usb/auer15 16th auerswald ISDN device + 128 = /dev/usb/brlvgr0 First Braille Voyager device + ... + 131 = /dev/usb/brlvgr3 Fourth Braille Voyager device + 132 = /dev/usb/idmouse ID Mouse (fingerprint scanner) device + 133 = /dev/usb/sisusbvga1 First SiSUSB VGA device + ... + 140 = /dev/usb/sisusbvga8 Eighth SISUSB VGA device + 144 = /dev/usb/lcd USB LCD device + 160 = /dev/usb/legousbtower0 1st USB Legotower device + ... + 175 = /dev/usb/legousbtower15 16th USB Legotower device + 176 = /dev/usb/usbtmc1 First USB TMC device + ... + 191 = /dev/usb/usbtmc16 16th USB TMC device + 192 = /dev/usb/yurex1 First USB Yurex device + ... + 209 = /dev/usb/yurex16 16th USB Yurex device + + 180 block USB block devices + 0 = /dev/uba First USB block device + 8 = /dev/ubb Second USB block device + 16 = /dev/ubc Third USB block device + ... + + 181 char Conrad Electronic parallel port radio clocks + 0 = /dev/pcfclock0 First Conrad radio clock + 1 = /dev/pcfclock1 Second Conrad radio clock + ... + + 182 char Picture Elements THR2 binarizer + 0 = /dev/pethr0 First THR2 board + 1 = /dev/pethr1 Second THR2 board + ... + + 183 char SST 5136-DN DeviceNet interface + 0 = /dev/ss5136dn0 First DeviceNet interface + 1 = /dev/ss5136dn1 Second DeviceNet interface + ... + + This device used to be assigned to major number 144. + It had to be moved due to an unfortunate conflict. + + 184 char Picture Elements' video simulator/sender + 0 = /dev/pevss0 First sender board + 1 = /dev/pevss1 Second sender board + ... + + 185 char InterMezzo high availability file system + 0 = /dev/intermezzo0 First cache manager + 1 = /dev/intermezzo1 Second cache manager + ... + + See http://web.archive.org/web/20080115195241/ + http://inter-mezzo.org/index.html + + 186 char Object-based storage control device + 0 = /dev/obd0 First obd control device + 1 = /dev/obd1 Second obd control device + ... + + See ftp://ftp.lustre.org/pub/obd for code and information. + + 187 char DESkey hardware encryption device + 0 = /dev/deskey0 First DES key + 1 = /dev/deskey1 Second DES key + ... + + 188 char USB serial converters + 0 = /dev/ttyUSB0 First USB serial converter + 1 = /dev/ttyUSB1 Second USB serial converter + ... + + 189 char USB serial converters - alternate devices + 0 = /dev/cuusb0 Callout device for ttyUSB0 + 1 = /dev/cuusb1 Callout device for ttyUSB1 + ... + + 190 char Kansas City tracker/tuner card + 0 = /dev/kctt0 First KCT/T card + 1 = /dev/kctt1 Second KCT/T card + ... + + 191 char Reserved for PCMCIA + + 192 char Kernel profiling interface + 0 = /dev/profile Profiling control device + 1 = /dev/profile0 Profiling device for CPU 0 + 2 = /dev/profile1 Profiling device for CPU 1 + ... + + 193 char Kernel event-tracing interface + 0 = /dev/trace Tracing control device + 1 = /dev/trace0 Tracing device for CPU 0 + 2 = /dev/trace1 Tracing device for CPU 1 + ... + + 194 char linVideoStreams (LINVS) + 0 = /dev/mvideo/status0 Video compression status + 1 = /dev/mvideo/stream0 Video stream + 2 = /dev/mvideo/frame0 Single compressed frame + 3 = /dev/mvideo/rawframe0 Raw uncompressed frame + 4 = /dev/mvideo/codec0 Direct codec access + 5 = /dev/mvideo/video4linux0 Video4Linux compatibility + + 16 = /dev/mvideo/status1 Second device + ... + 32 = /dev/mvideo/status2 Third device + ... + ... + 240 = /dev/mvideo/status15 16th device + ... + + 195 char Nvidia graphics devices + 0 = /dev/nvidia0 First Nvidia card + 1 = /dev/nvidia1 Second Nvidia card + ... + 255 = /dev/nvidiactl Nvidia card control device + + 196 char Tormenta T1 card + 0 = /dev/tor/0 Master control channel for all cards + 1 = /dev/tor/1 First DS0 + 2 = /dev/tor/2 Second DS0 + ... + 48 = /dev/tor/48 48th DS0 + 49 = /dev/tor/49 First pseudo-channel + 50 = /dev/tor/50 Second pseudo-channel + ... + + 197 char OpenTNF tracing facility + 0 = /dev/tnf/t0 Trace 0 data extraction + 1 = /dev/tnf/t1 Trace 1 data extraction + ... + 128 = /dev/tnf/status Tracing facility status + 130 = /dev/tnf/trace Tracing device + + 198 char Total Impact TPMP2 quad coprocessor PCI card + 0 = /dev/tpmp2/0 First card + 1 = /dev/tpmp2/1 Second card + ... + + 199 char Veritas volume manager (VxVM) volumes + 0 = /dev/vx/rdsk/*/* First volume + 1 = /dev/vx/rdsk/*/* Second volume + ... + + 199 block Veritas volume manager (VxVM) volumes + 0 = /dev/vx/dsk/*/* First volume + 1 = /dev/vx/dsk/*/* Second volume + ... + + The namespace in these directories is maintained by + the user space VxVM software. + + 200 char Veritas VxVM configuration interface + 0 = /dev/vx/config Configuration access node + 1 = /dev/vx/trace Volume i/o trace access node + 2 = /dev/vx/iod Volume i/o daemon access node + 3 = /dev/vx/info Volume information access node + 4 = /dev/vx/task Volume tasks access node + 5 = /dev/vx/taskmon Volume tasks monitor daemon + + 201 char Veritas VxVM dynamic multipathing driver + 0 = /dev/vx/rdmp/* First multipath device + 1 = /dev/vx/rdmp/* Second multipath device + ... + 201 block Veritas VxVM dynamic multipathing driver + 0 = /dev/vx/dmp/* First multipath device + 1 = /dev/vx/dmp/* Second multipath device + ... + + The namespace in these directories is maintained by + the user space VxVM software. + + 202 char CPU model-specific registers + 0 = /dev/cpu/0/msr MSRs on CPU 0 + 1 = /dev/cpu/1/msr MSRs on CPU 1 + ... + + 202 block Xen Virtual Block Device + 0 = /dev/xvda First Xen VBD whole disk + 16 = /dev/xvdb Second Xen VBD whole disk + 32 = /dev/xvdc Third Xen VBD whole disk + ... + 240 = /dev/xvdp Sixteenth Xen VBD whole disk + + Partitions are handled in the same way as for IDE + disks (see major number 3) except that the limit on + partitions is 15. + + 203 char CPU CPUID information + 0 = /dev/cpu/0/cpuid CPUID on CPU 0 + 1 = /dev/cpu/1/cpuid CPUID on CPU 1 + ... + + 204 char Low-density serial ports + 0 = /dev/ttyLU0 LinkUp Systems L72xx UART - port 0 + 1 = /dev/ttyLU1 LinkUp Systems L72xx UART - port 1 + 2 = /dev/ttyLU2 LinkUp Systems L72xx UART - port 2 + 3 = /dev/ttyLU3 LinkUp Systems L72xx UART - port 3 + 4 = /dev/ttyFB0 Intel Footbridge (ARM) + 5 = /dev/ttySA0 StrongARM builtin serial port 0 + 6 = /dev/ttySA1 StrongARM builtin serial port 1 + 7 = /dev/ttySA2 StrongARM builtin serial port 2 + 8 = /dev/ttySC0 SCI serial port (SuperH) - port 0 + 9 = /dev/ttySC1 SCI serial port (SuperH) - port 1 + 10 = /dev/ttySC2 SCI serial port (SuperH) - port 2 + 11 = /dev/ttySC3 SCI serial port (SuperH) - port 3 + 12 = /dev/ttyFW0 Firmware console - port 0 + 13 = /dev/ttyFW1 Firmware console - port 1 + 14 = /dev/ttyFW2 Firmware console - port 2 + 15 = /dev/ttyFW3 Firmware console - port 3 + 16 = /dev/ttyAM0 ARM "AMBA" serial port 0 + ... + 31 = /dev/ttyAM15 ARM "AMBA" serial port 15 + 32 = /dev/ttyDB0 DataBooster serial port 0 + ... + 39 = /dev/ttyDB7 DataBooster serial port 7 + 40 = /dev/ttySG0 SGI Altix console port + 41 = /dev/ttySMX0 Motorola i.MX - port 0 + 42 = /dev/ttySMX1 Motorola i.MX - port 1 + 43 = /dev/ttySMX2 Motorola i.MX - port 2 + 44 = /dev/ttyMM0 Marvell MPSC - port 0 (obsolete unused) + 45 = /dev/ttyMM1 Marvell MPSC - port 1 (obsolete unused) + 46 = /dev/ttyCPM0 PPC CPM (SCC or SMC) - port 0 + ... + 51 = /dev/ttyCPM5 PPC CPM (SCC or SMC) - port 5 + 82 = /dev/ttyVR0 NEC VR4100 series SIU + 83 = /dev/ttyVR1 NEC VR4100 series DSIU + 148 = /dev/ttyPSC0 PPC PSC - port 0 + ... + 153 = /dev/ttyPSC5 PPC PSC - port 5 + 154 = /dev/ttyAT0 ATMEL serial port 0 + ... + 169 = /dev/ttyAT15 ATMEL serial port 15 + 170 = /dev/ttyNX0 Hilscher netX serial port 0 + ... + 185 = /dev/ttyNX15 Hilscher netX serial port 15 + 186 = /dev/ttyJ0 JTAG1 DCC protocol based serial port emulation + 187 = /dev/ttyUL0 Xilinx uartlite - port 0 + ... + 190 = /dev/ttyUL3 Xilinx uartlite - port 3 + 191 = /dev/xvc0 Xen virtual console - port 0 + 192 = /dev/ttyPZ0 pmac_zilog - port 0 + ... + 195 = /dev/ttyPZ3 pmac_zilog - port 3 + 196 = /dev/ttyTX0 TX39/49 serial port 0 + ... + 204 = /dev/ttyTX7 TX39/49 serial port 7 + 205 = /dev/ttySC0 SC26xx serial port 0 + 206 = /dev/ttySC1 SC26xx serial port 1 + 207 = /dev/ttySC2 SC26xx serial port 2 + 208 = /dev/ttySC3 SC26xx serial port 3 + 209 = /dev/ttyMAX0 MAX3100 serial port 0 + 210 = /dev/ttyMAX1 MAX3100 serial port 1 + 211 = /dev/ttyMAX2 MAX3100 serial port 2 + 212 = /dev/ttyMAX3 MAX3100 serial port 3 + + 205 char Low-density serial ports (alternate device) + 0 = /dev/culu0 Callout device for ttyLU0 + 1 = /dev/culu1 Callout device for ttyLU1 + 2 = /dev/culu2 Callout device for ttyLU2 + 3 = /dev/culu3 Callout device for ttyLU3 + 4 = /dev/cufb0 Callout device for ttyFB0 + 5 = /dev/cusa0 Callout device for ttySA0 + 6 = /dev/cusa1 Callout device for ttySA1 + 7 = /dev/cusa2 Callout device for ttySA2 + 8 = /dev/cusc0 Callout device for ttySC0 + 9 = /dev/cusc1 Callout device for ttySC1 + 10 = /dev/cusc2 Callout device for ttySC2 + 11 = /dev/cusc3 Callout device for ttySC3 + 12 = /dev/cufw0 Callout device for ttyFW0 + 13 = /dev/cufw1 Callout device for ttyFW1 + 14 = /dev/cufw2 Callout device for ttyFW2 + 15 = /dev/cufw3 Callout device for ttyFW3 + 16 = /dev/cuam0 Callout device for ttyAM0 + ... + 31 = /dev/cuam15 Callout device for ttyAM15 + 32 = /dev/cudb0 Callout device for ttyDB0 + ... + 39 = /dev/cudb7 Callout device for ttyDB7 + 40 = /dev/cusg0 Callout device for ttySG0 + 41 = /dev/ttycusmx0 Callout device for ttySMX0 + 42 = /dev/ttycusmx1 Callout device for ttySMX1 + 43 = /dev/ttycusmx2 Callout device for ttySMX2 + 46 = /dev/cucpm0 Callout device for ttyCPM0 + ... + 51 = /dev/cucpm5 Callout device for ttyCPM5 + 82 = /dev/cuvr0 Callout device for ttyVR0 + 83 = /dev/cuvr1 Callout device for ttyVR1 + + 206 char OnStream SC-x0 tape devices + 0 = /dev/osst0 First OnStream SCSI tape, mode 0 + 1 = /dev/osst1 Second OnStream SCSI tape, mode 0 + ... + 32 = /dev/osst0l First OnStream SCSI tape, mode 1 + 33 = /dev/osst1l Second OnStream SCSI tape, mode 1 + ... + 64 = /dev/osst0m First OnStream SCSI tape, mode 2 + 65 = /dev/osst1m Second OnStream SCSI tape, mode 2 + ... + 96 = /dev/osst0a First OnStream SCSI tape, mode 3 + 97 = /dev/osst1a Second OnStream SCSI tape, mode 3 + ... + 128 = /dev/nosst0 No rewind version of /dev/osst0 + 129 = /dev/nosst1 No rewind version of /dev/osst1 + ... + 160 = /dev/nosst0l No rewind version of /dev/osst0l + 161 = /dev/nosst1l No rewind version of /dev/osst1l + ... + 192 = /dev/nosst0m No rewind version of /dev/osst0m + 193 = /dev/nosst1m No rewind version of /dev/osst1m + ... + 224 = /dev/nosst0a No rewind version of /dev/osst0a + 225 = /dev/nosst1a No rewind version of /dev/osst1a + ... + + The OnStream SC-x0 SCSI tapes do not support the + standard SCSI SASD command set and therefore need + their own driver "osst". Note that the IDE, USB (and + maybe ParPort) versions may be driven via ide-scsi or + usb-storage SCSI emulation and this osst device and + driver as well. The ADR-x0 drives are QIC-157 + compliant and don't need osst. + + 207 char Compaq ProLiant health feature indicate + 0 = /dev/cpqhealth/cpqw Redirector interface + 1 = /dev/cpqhealth/crom EISA CROM + 2 = /dev/cpqhealth/cdt Data Table + 3 = /dev/cpqhealth/cevt Event Log + 4 = /dev/cpqhealth/casr Automatic Server Recovery + 5 = /dev/cpqhealth/cecc ECC Memory + 6 = /dev/cpqhealth/cmca Machine Check Architecture + 7 = /dev/cpqhealth/ccsm Deprecated CDT + 8 = /dev/cpqhealth/cnmi NMI Handling + 9 = /dev/cpqhealth/css Sideshow Management + 10 = /dev/cpqhealth/cram CMOS interface + 11 = /dev/cpqhealth/cpci PCI IRQ interface + + 208 char User space serial ports + 0 = /dev/ttyU0 First user space serial port + 1 = /dev/ttyU1 Second user space serial port + ... + + 209 char User space serial ports (alternate devices) + 0 = /dev/cuu0 Callout device for ttyU0 + 1 = /dev/cuu1 Callout device for ttyU1 + ... + + 210 char SBE, Inc. sync/async serial card + 0 = /dev/sbei/wxcfg0 Configuration device for board 0 + 1 = /dev/sbei/dld0 Download device for board 0 + 2 = /dev/sbei/wan00 WAN device, port 0, board 0 + 3 = /dev/sbei/wan01 WAN device, port 1, board 0 + 4 = /dev/sbei/wan02 WAN device, port 2, board 0 + 5 = /dev/sbei/wan03 WAN device, port 3, board 0 + 6 = /dev/sbei/wanc00 WAN clone device, port 0, board 0 + 7 = /dev/sbei/wanc01 WAN clone device, port 1, board 0 + 8 = /dev/sbei/wanc02 WAN clone device, port 2, board 0 + 9 = /dev/sbei/wanc03 WAN clone device, port 3, board 0 + 10 = /dev/sbei/wxcfg1 Configuration device for board 1 + 11 = /dev/sbei/dld1 Download device for board 1 + 12 = /dev/sbei/wan10 WAN device, port 0, board 1 + 13 = /dev/sbei/wan11 WAN device, port 1, board 1 + 14 = /dev/sbei/wan12 WAN device, port 2, board 1 + 15 = /dev/sbei/wan13 WAN device, port 3, board 1 + 16 = /dev/sbei/wanc10 WAN clone device, port 0, board 1 + 17 = /dev/sbei/wanc11 WAN clone device, port 1, board 1 + 18 = /dev/sbei/wanc12 WAN clone device, port 2, board 1 + 19 = /dev/sbei/wanc13 WAN clone device, port 3, board 1 + ... + + Yes, each board is really spaced 10 (decimal) apart. + + 211 char Addinum CPCI1500 digital I/O card + 0 = /dev/addinum/cpci1500/0 First CPCI1500 card + 1 = /dev/addinum/cpci1500/1 Second CPCI1500 card + ... + + 212 char LinuxTV.org DVB driver subsystem + 0 = /dev/dvb/adapter0/video0 first video decoder of first card + 1 = /dev/dvb/adapter0/audio0 first audio decoder of first card + 2 = /dev/dvb/adapter0/sec0 (obsolete/unused) + 3 = /dev/dvb/adapter0/frontend0 first frontend device of first card + 4 = /dev/dvb/adapter0/demux0 first demux device of first card + 5 = /dev/dvb/adapter0/dvr0 first digital video recoder device of first card + 6 = /dev/dvb/adapter0/ca0 first common access port of first card + 7 = /dev/dvb/adapter0/net0 first network device of first card + 8 = /dev/dvb/adapter0/osd0 first on-screen-display device of first card + 9 = /dev/dvb/adapter0/video1 second video decoder of first card + ... + 64 = /dev/dvb/adapter1/video0 first video decoder of second card + ... + 128 = /dev/dvb/adapter2/video0 first video decoder of third card + ... + 196 = /dev/dvb/adapter3/video0 first video decoder of fourth card + + 216 char Bluetooth RFCOMM TTY devices + 0 = /dev/rfcomm0 First Bluetooth RFCOMM TTY device + 1 = /dev/rfcomm1 Second Bluetooth RFCOMM TTY device + ... + + 217 char Bluetooth RFCOMM TTY devices (alternate devices) + 0 = /dev/curf0 Callout device for rfcomm0 + 1 = /dev/curf1 Callout device for rfcomm1 + ... + + 218 char The Logical Company bus Unibus/Qbus adapters + 0 = /dev/logicalco/bci/0 First bus adapter + 1 = /dev/logicalco/bci/1 First bus adapter + ... + + 219 char The Logical Company DCI-1300 digital I/O card + 0 = /dev/logicalco/dci1300/0 First DCI-1300 card + 1 = /dev/logicalco/dci1300/1 Second DCI-1300 card + ... + + 220 char Myricom Myrinet "GM" board + 0 = /dev/myricom/gm0 First Myrinet GM board + 1 = /dev/myricom/gmp0 First board "root access" + 2 = /dev/myricom/gm1 Second Myrinet GM board + 3 = /dev/myricom/gmp1 Second board "root access" + ... + + 221 char VME bus + 0 = /dev/bus/vme/m0 First master image + 1 = /dev/bus/vme/m1 Second master image + 2 = /dev/bus/vme/m2 Third master image + 3 = /dev/bus/vme/m3 Fourth master image + 4 = /dev/bus/vme/s0 First slave image + 5 = /dev/bus/vme/s1 Second slave image + 6 = /dev/bus/vme/s2 Third slave image + 7 = /dev/bus/vme/s3 Fourth slave image + 8 = /dev/bus/vme/ctl Control + + It is expected that all VME bus drivers will use the + same interface. For interface documentation see + http://www.vmelinux.org/. + + 224 char A2232 serial card + 0 = /dev/ttyY0 First A2232 port + 1 = /dev/ttyY1 Second A2232 port + ... + + 225 char A2232 serial card (alternate devices) + 0 = /dev/cuy0 Callout device for ttyY0 + 1 = /dev/cuy1 Callout device for ttyY1 + ... + + 226 char Direct Rendering Infrastructure (DRI) + 0 = /dev/dri/card0 First graphics card + 1 = /dev/dri/card1 Second graphics card + ... + + 227 char IBM 3270 terminal Unix tty access + 1 = /dev/3270/tty1 First 3270 terminal + 2 = /dev/3270/tty2 Seconds 3270 terminal + ... + + 228 char IBM 3270 terminal block-mode access + 0 = /dev/3270/tub Controlling interface + 1 = /dev/3270/tub1 First 3270 terminal + 2 = /dev/3270/tub2 Second 3270 terminal + ... + + 229 char IBM iSeries/pSeries virtual console + 0 = /dev/hvc0 First console port + 1 = /dev/hvc1 Second console port + ... + + 230 char IBM iSeries virtual tape + 0 = /dev/iseries/vt0 First virtual tape, mode 0 + 1 = /dev/iseries/vt1 Second virtual tape, mode 0 + ... + 32 = /dev/iseries/vt0l First virtual tape, mode 1 + 33 = /dev/iseries/vt1l Second virtual tape, mode 1 + ... + 64 = /dev/iseries/vt0m First virtual tape, mode 2 + 65 = /dev/iseries/vt1m Second virtual tape, mode 2 + ... + 96 = /dev/iseries/vt0a First virtual tape, mode 3 + 97 = /dev/iseries/vt1a Second virtual tape, mode 3 + ... + 128 = /dev/iseries/nvt0 First virtual tape, mode 0, no rewind + 129 = /dev/iseries/nvt1 Second virtual tape, mode 0, no rewind + ... + 160 = /dev/iseries/nvt0l First virtual tape, mode 1, no rewind + 161 = /dev/iseries/nvt1l Second virtual tape, mode 1, no rewind + ... + 192 = /dev/iseries/nvt0m First virtual tape, mode 2, no rewind + 193 = /dev/iseries/nvt1m Second virtual tape, mode 2, no rewind + ... + 224 = /dev/iseries/nvt0a First virtual tape, mode 3, no rewind + 225 = /dev/iseries/nvt1a Second virtual tape, mode 3, no rewind + ... + + "No rewind" refers to the omission of the default + automatic rewind on device close. The MTREW or MTOFFL + ioctl()'s can be used to rewind the tape regardless of + the device used to access it. + + 231 char InfiniBand + 0 = /dev/infiniband/umad0 + 1 = /dev/infiniband/umad1 + ... + 63 = /dev/infiniband/umad63 63rd InfiniBandMad device + 64 = /dev/infiniband/issm0 First InfiniBand IsSM device + 65 = /dev/infiniband/issm1 Second InfiniBand IsSM device + ... + 127 = /dev/infiniband/issm63 63rd InfiniBand IsSM device + 192 = /dev/infiniband/uverbs0 First InfiniBand verbs device + 193 = /dev/infiniband/uverbs1 Second InfiniBand verbs device + ... + 223 = /dev/infiniband/uverbs31 31st InfiniBand verbs device + + 232 char Biometric Devices + 0 = /dev/biometric/sensor0/fingerprint first fingerprint sensor on first device + 1 = /dev/biometric/sensor0/iris first iris sensor on first device + 2 = /dev/biometric/sensor0/retina first retina sensor on first device + 3 = /dev/biometric/sensor0/voiceprint first voiceprint sensor on first device + 4 = /dev/biometric/sensor0/facial first facial sensor on first device + 5 = /dev/biometric/sensor0/hand first hand sensor on first device + ... + 10 = /dev/biometric/sensor1/fingerprint first fingerprint sensor on second device + ... + 20 = /dev/biometric/sensor2/fingerprint first fingerprint sensor on third device + ... + + 233 char PathScale InfiniPath interconnect + 0 = /dev/ipath Primary device for programs (any unit) + 1 = /dev/ipath0 Access specifically to unit 0 + 2 = /dev/ipath1 Access specifically to unit 1 + ... + 4 = /dev/ipath3 Access specifically to unit 3 + 129 = /dev/ipath_sma Device used by Subnet Management Agent + 130 = /dev/ipath_diag Device used by diagnostics programs + + 234-254 char RESERVED FOR DYNAMIC ASSIGNMENT + Character devices that request a dynamic allocation of major number will + take numbers starting from 254 and downward. + + 240-254 block LOCAL/EXPERIMENTAL USE + Allocated for local/experimental use. For devices not + assigned official numbers, these ranges should be + used in order to avoid conflicting with future assignments. + + 255 char RESERVED + + 255 block RESERVED + + This major is reserved to assist the expansion to a + larger number space. No device nodes with this major + should ever be created on the filesystem. + (This is probably not true anymore, but I'll leave it + for now /Torben) + + ---LARGE MAJORS!!!!!--- + + 256 char Equinox SST multi-port serial boards + 0 = /dev/ttyEQ0 First serial port on first Equinox SST board + 127 = /dev/ttyEQ127 Last serial port on first Equinox SST board + 128 = /dev/ttyEQ128 First serial port on second Equinox SST board + ... + 1027 = /dev/ttyEQ1027 Last serial port on eighth Equinox SST board + + 256 block Resident Flash Disk Flash Translation Layer + 0 = /dev/rfda First RFD FTL layer + 16 = /dev/rfdb Second RFD FTL layer + ... + 240 = /dev/rfdp 16th RFD FTL layer + + 257 char Phoenix Technologies Cryptographic Services Driver + 0 = /dev/ptlsec Crypto Services Driver + + 257 block SSFDC Flash Translation Layer filesystem + 0 = /dev/ssfdca First SSFDC layer + 8 = /dev/ssfdcb Second SSFDC layer + 16 = /dev/ssfdcc Third SSFDC layer + 24 = /dev/ssfdcd 4th SSFDC layer + 32 = /dev/ssfdce 5th SSFDC layer + 40 = /dev/ssfdcf 6th SSFDC layer + 48 = /dev/ssfdcg 7th SSFDC layer + 56 = /dev/ssfdch 8th SSFDC layer + + 258 block ROM/Flash read-only translation layer + 0 = /dev/blockrom0 First ROM card's translation layer interface + 1 = /dev/blockrom1 Second ROM card's translation layer interface + ... + + 259 block Block Extended Major + Used dynamically to hold additional partition minor + numbers and allow large numbers of partitions per device + + 259 char FPGA configuration interfaces + 0 = /dev/icap0 First Xilinx internal configuration + 1 = /dev/icap1 Second Xilinx internal configuration + + 260 char OSD (Object-based-device) SCSI Device + 0 = /dev/osd0 First OSD Device + 1 = /dev/osd1 Second OSD Device + ... + 255 = /dev/osd255 256th OSD Device + + 261 char Compute Acceleration Devices + 0 = /dev/accel/accel0 First acceleration device + 1 = /dev/accel/accel1 Second acceleration device + ... + + 384-511 char RESERVED FOR DYNAMIC ASSIGNMENT + Character devices that request a dynamic allocation of major + number will take numbers starting from 511 and downward, + once the 234-254 range is full. diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst new file mode 100644 index 000000000..0b3d39c61 --- /dev/null +++ b/Documentation/admin-guide/dynamic-debug-howto.rst @@ -0,0 +1,377 @@ +Dynamic debug ++++++++++++++ + + +Introduction +============ + +Dynamic debug allows you to dynamically enable/disable kernel +debug-print code to obtain additional kernel information. + +If ``/proc/dynamic_debug/control`` exists, your kernel has dynamic +debug. You'll need root access (sudo su) to use this. + +Dynamic debug provides: + + * a Catalog of all *prdbgs* in your kernel. + ``cat /proc/dynamic_debug/control`` to see them. + + * a Simple query/command language to alter *prdbgs* by selecting on + any combination of 0 or 1 of: + + - source filename + - function name + - line number (including ranges of line numbers) + - module name + - format string + - class name (as known/declared by each module) + +Viewing Dynamic Debug Behaviour +=============================== + +You can view the currently configured behaviour in the *prdbg* catalog:: + + :#> head -n7 /proc/dynamic_debug/control + # filename:lineno [module]function flags format + init/main.c:1179 [main]initcall_blacklist =_ "blacklisting initcall %s\012 + init/main.c:1218 [main]initcall_blacklisted =_ "initcall %s blacklisted\012" + init/main.c:1424 [main]run_init_process =_ " with arguments:\012" + init/main.c:1426 [main]run_init_process =_ " %s\012" + init/main.c:1427 [main]run_init_process =_ " with environment:\012" + init/main.c:1429 [main]run_init_process =_ " %s\012" + +The 3rd space-delimited column shows the current flags, preceded by +a ``=`` for easy use with grep/cut. ``=p`` shows enabled callsites. + +Controlling dynamic debug Behaviour +=================================== + +The behaviour of *prdbg* sites are controlled by writing +query/commands to the control file. Example:: + + # grease the interface + :#> alias ddcmd='echo $* > /proc/dynamic_debug/control' + + :#> ddcmd '-p; module main func run* +p' + :#> grep =p /proc/dynamic_debug/control + init/main.c:1424 [main]run_init_process =p " with arguments:\012" + init/main.c:1426 [main]run_init_process =p " %s\012" + init/main.c:1427 [main]run_init_process =p " with environment:\012" + init/main.c:1429 [main]run_init_process =p " %s\012" + +Error messages go to console/syslog:: + + :#> ddcmd mode foo +p + dyndbg: unknown keyword "mode" + dyndbg: query parse failed + bash: echo: write error: Invalid argument + +If debugfs is also enabled and mounted, ``dynamic_debug/control`` is +also under the mount-dir, typically ``/sys/kernel/debug/``. + +Command Language Reference +========================== + +At the basic lexical level, a command is a sequence of words separated +by spaces or tabs. So these are all equivalent:: + + :#> ddcmd file svcsock.c line 1603 +p + :#> ddcmd "file svcsock.c line 1603 +p" + :#> ddcmd ' file svcsock.c line 1603 +p ' + +Command submissions are bounded by a write() system call. +Multiple commands can be written together, separated by ``;`` or ``\n``:: + + :#> ddcmd "func pnpacpi_get_resources +p; func pnp_assign_mem +p" + :#> ddcmd <<"EOC" + func pnpacpi_get_resources +p + func pnp_assign_mem +p + EOC + :#> cat query-batch-file > /proc/dynamic_debug/control + +You can also use wildcards in each query term. The match rule supports +``*`` (matches zero or more characters) and ``?`` (matches exactly one +character). For example, you can match all usb drivers:: + + :#> ddcmd file "drivers/usb/*" +p # "" to suppress shell expansion + +Syntactically, a command is pairs of keyword values, followed by a +flags change or setting:: + + command ::= match-spec* flags-spec + +The match-spec's select *prdbgs* from the catalog, upon which to apply +the flags-spec, all constraints are ANDed together. An absent keyword +is the same as keyword "*". + + +A match specification is a keyword, which selects the attribute of +the callsite to be compared, and a value to compare against. Possible +keywords are::: + + match-spec ::= 'func' string | + 'file' string | + 'module' string | + 'format' string | + 'class' string | + 'line' line-range + + line-range ::= lineno | + '-'lineno | + lineno'-' | + lineno'-'lineno + + lineno ::= unsigned-int + +.. note:: + + ``line-range`` cannot contain space, e.g. + "1-30" is valid range but "1 - 30" is not. + + +The meanings of each keyword are: + +func + The given string is compared against the function name + of each callsite. Example:: + + func svc_tcp_accept + func *recv* # in rfcomm, bluetooth, ping, tcp + +file + The given string is compared against either the src-root relative + pathname, or the basename of the source file of each callsite. + Examples:: + + file svcsock.c + file kernel/freezer.c # ie column 1 of control file + file drivers/usb/* # all callsites under it + file inode.c:start_* # parse :tail as a func (above) + file inode.c:1-100 # parse :tail as a line-range (above) + +module + The given string is compared against the module name + of each callsite. The module name is the string as + seen in ``lsmod``, i.e. without the directory or the ``.ko`` + suffix and with ``-`` changed to ``_``. Examples:: + + module sunrpc + module nfsd + module drm* # both drm, drm_kms_helper + +format + The given string is searched for in the dynamic debug format + string. Note that the string does not need to match the + entire format, only some part. Whitespace and other + special characters can be escaped using C octal character + escape ``\ooo`` notation, e.g. the space character is ``\040``. + Alternatively, the string can be enclosed in double quote + characters (``"``) or single quote characters (``'``). + Examples:: + + format svcrdma: // many of the NFS/RDMA server pr_debugs + format readahead // some pr_debugs in the readahead cache + format nfsd:\040SETATTR // one way to match a format with whitespace + format "nfsd: SETATTR" // a neater way to match a format with whitespace + format 'nfsd: SETATTR' // yet another way to match a format with whitespace + +class + The given class_name is validated against each module, which may + have declared a list of known class_names. If the class_name is + found for a module, callsite & class matching and adjustment + proceeds. Examples:: + + class DRM_UT_KMS # a DRM.debug category + class JUNK # silent non-match + // class TLD_* # NOTICE: no wildcard in class names + +line + The given line number or range of line numbers is compared + against the line number of each ``pr_debug()`` callsite. A single + line number matches the callsite line number exactly. A + range of line numbers matches any callsite between the first + and last line number inclusive. An empty first number means + the first line in the file, an empty last line number means the + last line number in the file. Examples:: + + line 1603 // exactly line 1603 + line 1600-1605 // the six lines from line 1600 to line 1605 + line -1605 // the 1605 lines from line 1 to line 1605 + line 1600- // all lines from line 1600 to the end of the file + +The flags specification comprises a change operation followed +by one or more flag characters. The change operation is one +of the characters:: + + - remove the given flags + + add the given flags + = set the flags to the given flags + +The flags are:: + + p enables the pr_debug() callsite. + _ enables no flags. + + Decorator flags add to the message-prefix, in order: + t Include thread ID, or <intr> + m Include module name + f Include the function name + s Include the source file name + l Include line number + +For ``print_hex_dump_debug()`` and ``print_hex_dump_bytes()``, only +the ``p`` flag has meaning, other flags are ignored. + +Note the regexp ``^[-+=][fslmpt_]+$`` matches a flags specification. +To clear all flags at once, use ``=_`` or ``-fslmpt``. + + +Debug messages during Boot Process +================================== + +To activate debug messages for core code and built-in modules during +the boot process, even before userspace and debugfs exists, use +``dyndbg="QUERY"`` or ``module.dyndbg="QUERY"``. QUERY follows +the syntax described above, but must not exceed 1023 characters. Your +bootloader may impose lower limits. + +These ``dyndbg`` params are processed just after the ddebug tables are +processed, as part of the early_initcall. Thus you can enable debug +messages in all code run after this early_initcall via this boot +parameter. + +On an x86 system for example ACPI enablement is a subsys_initcall and:: + + dyndbg="file ec.c +p" + +will show early Embedded Controller transactions during ACPI setup if +your machine (typically a laptop) has an Embedded Controller. +PCI (or other devices) initialization also is a hot candidate for using +this boot parameter for debugging purposes. + +If ``foo`` module is not built-in, ``foo.dyndbg`` will still be processed at +boot time, without effect, but will be reprocessed when module is +loaded later. Bare ``dyndbg=`` is only processed at boot. + + +Debug Messages at Module Initialization Time +============================================ + +When ``modprobe foo`` is called, modprobe scans ``/proc/cmdline`` for +``foo.params``, strips ``foo.``, and passes them to the kernel along with +params given in modprobe args or ``/etc/modprob.d/*.conf`` files, +in the following order: + +1. parameters given via ``/etc/modprobe.d/*.conf``:: + + options foo dyndbg=+pt + options foo dyndbg # defaults to +p + +2. ``foo.dyndbg`` as given in boot args, ``foo.`` is stripped and passed:: + + foo.dyndbg=" func bar +p; func buz +mp" + +3. args to modprobe:: + + modprobe foo dyndbg==pmf # override previous settings + +These ``dyndbg`` queries are applied in order, with last having final say. +This allows boot args to override or modify those from ``/etc/modprobe.d`` +(sensible, since 1 is system wide, 2 is kernel or boot specific), and +modprobe args to override both. + +In the ``foo.dyndbg="QUERY"`` form, the query must exclude ``module foo``. +``foo`` is extracted from the param-name, and applied to each query in +``QUERY``, and only 1 match-spec of each type is allowed. + +The ``dyndbg`` option is a "fake" module parameter, which means: + +- modules do not need to define it explicitly +- every module gets it tacitly, whether they use pr_debug or not +- it doesn't appear in ``/sys/module/$module/parameters/`` + To see it, grep the control file, or inspect ``/proc/cmdline.`` + +For ``CONFIG_DYNAMIC_DEBUG`` kernels, any settings given at boot-time (or +enabled by ``-DDEBUG`` flag during compilation) can be disabled later via +the debugfs interface if the debug messages are no longer needed:: + + echo "module module_name -p" > /proc/dynamic_debug/control + +Examples +======== + +:: + + // enable the message at line 1603 of file svcsock.c + :#> ddcmd 'file svcsock.c line 1603 +p' + + // enable all the messages in file svcsock.c + :#> ddcmd 'file svcsock.c +p' + + // enable all the messages in the NFS server module + :#> ddcmd 'module nfsd +p' + + // enable all 12 messages in the function svc_process() + :#> ddcmd 'func svc_process +p' + + // disable all 12 messages in the function svc_process() + :#> ddcmd 'func svc_process -p' + + // enable messages for NFS calls READ, READLINK, READDIR and READDIR+. + :#> ddcmd 'format "nfsd: READ" +p' + + // enable messages in files of which the paths include string "usb" + :#> ddcmd 'file *usb* +p' > /proc/dynamic_debug/control + + // enable all messages + :#> ddcmd '+p' > /proc/dynamic_debug/control + + // add module, function to all enabled messages + :#> ddcmd '+mf' > /proc/dynamic_debug/control + + // boot-args example, with newlines and comments for readability + Kernel command line: ... + // see what's going on in dyndbg=value processing + dynamic_debug.verbose=3 + // enable pr_debugs in the btrfs module (can be builtin or loadable) + btrfs.dyndbg="+p" + // enable pr_debugs in all files under init/ + // and the function parse_one, #cmt is stripped + dyndbg="file init/* +p #cmt ; func parse_one +p" + // enable pr_debugs in 2 functions in a module loaded later + pc87360.dyndbg="func pc87360_init_device +p; func pc87360_find +p" + +Kernel Configuration +==================== + +Dynamic Debug is enabled via kernel config items:: + + CONFIG_DYNAMIC_DEBUG=y # build catalog, enables CORE + CONFIG_DYNAMIC_DEBUG_CORE=y # enable mechanics only, skip catalog + +If you do not want to enable dynamic debug globally (i.e. in some embedded +system), you may set ``CONFIG_DYNAMIC_DEBUG_CORE`` as basic support of dynamic +debug and add ``ccflags := -DDYNAMIC_DEBUG_MODULE`` into the Makefile of any +modules which you'd like to dynamically debug later. + + +Kernel *prdbg* API +================== + +The following functions are cataloged and controllable when dynamic +debug is enabled:: + + pr_debug() + dev_dbg() + print_hex_dump_debug() + print_hex_dump_bytes() + +Otherwise, they are off by default; ``ccflags += -DDEBUG`` or +``#define DEBUG`` in a source file will enable them appropriately. + +If ``CONFIG_DYNAMIC_DEBUG`` is not set, ``print_hex_dump_debug()`` is +just a shortcut for ``print_hex_dump(KERN_DEBUG)``. + +For ``print_hex_dump_debug()``/``print_hex_dump_bytes()``, format string is +its ``prefix_str`` argument, if it is constant string; or ``hexdump`` +in case ``prefix_str`` is built dynamically. diff --git a/Documentation/admin-guide/edid.rst b/Documentation/admin-guide/edid.rst new file mode 100644 index 000000000..80deeb21a --- /dev/null +++ b/Documentation/admin-guide/edid.rst @@ -0,0 +1,60 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==== +EDID +==== + +In the good old days when graphics parameters were configured explicitly +in a file called xorg.conf, even broken hardware could be managed. + +Today, with the advent of Kernel Mode Setting, a graphics board is +either correctly working because all components follow the standards - +or the computer is unusable, because the screen remains dark after +booting or it displays the wrong area. Cases when this happens are: + +- The graphics board does not recognize the monitor. +- The graphics board is unable to detect any EDID data. +- The graphics board incorrectly forwards EDID data to the driver. +- The monitor sends no or bogus EDID data. +- A KVM sends its own EDID data instead of querying the connected monitor. + +Adding the kernel parameter "nomodeset" helps in most cases, but causes +restrictions later on. + +As a remedy for such situations, the kernel configuration item +CONFIG_DRM_LOAD_EDID_FIRMWARE was introduced. It allows to provide an +individually prepared or corrected EDID data set in the /lib/firmware +directory from where it is loaded via the firmware interface. The code +(see drivers/gpu/drm/drm_edid_load.c) contains built-in data sets for +commonly used screen resolutions (800x600, 1024x768, 1280x1024, 1600x1200, +1680x1050, 1920x1080) as binary blobs, but the kernel source tree does +not contain code to create these data. In order to elucidate the origin +of the built-in binary EDID blobs and to facilitate the creation of +individual data for a specific misbehaving monitor, commented sources +and a Makefile environment are given here. + +To create binary EDID and C source code files from the existing data +material, simply type "make" in tools/edid/. + +If you want to create your own EDID file, copy the file 1024x768.S, +replace the settings with your own data and add a new target to the +Makefile. Please note that the EDID data structure expects the timing +values in a different way as compared to the standard X11 format. + +X11: + HTimings: + hdisp hsyncstart hsyncend htotal + VTimings: + vdisp vsyncstart vsyncend vtotal + +EDID:: + + #define XPIX hdisp + #define XBLANK htotal-hdisp + #define XOFFSET hsyncstart-hdisp + #define XPULSE hsyncend-hsyncstart + + #define YPIX vdisp + #define YBLANK vtotal-vdisp + #define YOFFSET vsyncstart-vdisp + #define YPULSE vsyncend-vsyncstart diff --git a/Documentation/admin-guide/efi-stub.rst b/Documentation/admin-guide/efi-stub.rst new file mode 100644 index 000000000..b24e7c40d --- /dev/null +++ b/Documentation/admin-guide/efi-stub.rst @@ -0,0 +1,100 @@ +================= +The EFI Boot Stub +================= + +On the x86 and ARM platforms, a kernel zImage/bzImage can masquerade +as a PE/COFF image, thereby convincing EFI firmware loaders to load +it as an EFI executable. The code that modifies the bzImage header, +along with the EFI-specific entry point that the firmware loader +jumps to are collectively known as the "EFI boot stub", and live in +arch/x86/boot/header.S and drivers/firmware/efi/libstub/x86-stub.c, +respectively. For ARM the EFI stub is implemented in +arch/arm/boot/compressed/efi-header.S and +drivers/firmware/efi/libstub/arm32-stub.c. EFI stub code that is shared +between architectures is in drivers/firmware/efi/libstub. + +For arm64, there is no compressed kernel support, so the Image itself +masquerades as a PE/COFF image and the EFI stub is linked into the +kernel. The arm64 EFI stub lives in arch/arm64/kernel/efi-entry.S +and drivers/firmware/efi/libstub/arm64-stub.c. + +By using the EFI boot stub it's possible to boot a Linux kernel +without the use of a conventional EFI boot loader, such as grub or +elilo. Since the EFI boot stub performs the jobs of a boot loader, in +a certain sense it *IS* the boot loader. + +The EFI boot stub is enabled with the CONFIG_EFI_STUB kernel option. + + +How to install bzImage.efi +-------------------------- + +The bzImage located in arch/x86/boot/bzImage must be copied to the EFI +System Partition (ESP) and renamed with the extension ".efi". Without +the extension the EFI firmware loader will refuse to execute it. It's +not possible to execute bzImage.efi from the usual Linux file systems +because EFI firmware doesn't have support for them. For ARM the +arch/arm/boot/zImage should be copied to the system partition, and it +may not need to be renamed. Similarly for arm64, arch/arm64/boot/Image +should be copied but not necessarily renamed. + + +Passing kernel parameters from the EFI shell +-------------------------------------------- + +Arguments to the kernel can be passed after bzImage.efi, e.g.:: + + fs0:> bzImage.efi console=ttyS0 root=/dev/sda4 + + +The "initrd=" option +-------------------- + +Like most boot loaders, the EFI stub allows the user to specify +multiple initrd files using the "initrd=" option. This is the only EFI +stub-specific command line parameter, everything else is passed to the +kernel when it boots. + +The path to the initrd file must be an absolute path from the +beginning of the ESP, relative path names do not work. Also, the path +is an EFI-style path and directory elements must be separated with +backslashes (\). For example, given the following directory layout:: + + fs0:> + Kernels\ + bzImage.efi + initrd-large.img + + Ramdisks\ + initrd-small.img + initrd-medium.img + +to boot with the initrd-large.img file if the current working +directory is fs0:\Kernels, the following command must be used:: + + fs0:\Kernels> bzImage.efi initrd=\Kernels\initrd-large.img + +Notice how bzImage.efi can be specified with a relative path. That's +because the image we're executing is interpreted by the EFI shell, +which understands relative paths, whereas the rest of the command line +is passed to bzImage.efi. + + +The "dtb=" option +----------------- + +For the ARM and arm64 architectures, a device tree must be provided to +the kernel. Normally firmware shall supply the device tree via the +EFI CONFIGURATION TABLE. However, the "dtb=" command line option can +be used to override the firmware supplied device tree, or to supply +one when firmware is unable to. + +Please note: Firmware adds runtime configuration information to the +device tree before booting the kernel. If dtb= is used to override +the device tree, then any runtime data provided by firmware will be +lost. The dtb= option should only be used either as a debug tool, or +as a last resort when a device tree is not provided in the EFI +CONFIGURATION TABLE. + +"dtb=" is processed in the same manner as the "initrd=" option that is +described above. diff --git a/Documentation/admin-guide/ext4.rst b/Documentation/admin-guide/ext4.rst new file mode 100644 index 000000000..5740d8543 --- /dev/null +++ b/Documentation/admin-guide/ext4.rst @@ -0,0 +1,624 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================== +ext4 General Information +======================== + +Ext4 is an advanced level of the ext3 filesystem which incorporates +scalability and reliability enhancements for supporting large filesystems +(64 bit) in keeping with increasing disk capacities and state-of-the-art +feature requirements. + +Mailing list: linux-ext4@vger.kernel.org +Web site: http://ext4.wiki.kernel.org + + +Quick usage instructions +======================== + +Note: More extensive information for getting started with ext4 can be +found at the ext4 wiki site at the URL: +http://ext4.wiki.kernel.org/index.php/Ext4_Howto + + - The latest version of e2fsprogs can be found at: + + https://www.kernel.org/pub/linux/kernel/people/tytso/e2fsprogs/ + + or + + http://sourceforge.net/project/showfiles.php?group_id=2406 + + or grab the latest git repository from: + + https://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git + + - Create a new filesystem using the ext4 filesystem type: + + # mke2fs -t ext4 /dev/hda1 + + Or to configure an existing ext3 filesystem to support extents: + + # tune2fs -O extents /dev/hda1 + + If the filesystem was created with 128 byte inodes, it can be + converted to use 256 byte for greater efficiency via: + + # tune2fs -I 256 /dev/hda1 + + - Mounting: + + # mount -t ext4 /dev/hda1 /wherever + + - When comparing performance with other filesystems, it's always + important to try multiple workloads; very often a subtle change in a + workload parameter can completely change the ranking of which + filesystems do well compared to others. When comparing versus ext3, + note that ext4 enables write barriers by default, while ext3 does + not enable write barriers by default. So it is useful to use + explicitly specify whether barriers are enabled or not when via the + '-o barriers=[0|1]' mount option for both ext3 and ext4 filesystems + for a fair comparison. When tuning ext3 for best benchmark numbers, + it is often worthwhile to try changing the data journaling mode; '-o + data=writeback' can be faster for some workloads. (Note however that + running mounted with data=writeback can potentially leave stale data + exposed in recently written files in case of an unclean shutdown, + which could be a security exposure in some situations.) Configuring + the filesystem with a large journal can also be helpful for + metadata-intensive workloads. + +Features +======== + +Currently Available +------------------- + +* ability to use filesystems > 16TB (e2fsprogs support not available yet) +* extent format reduces metadata overhead (RAM, IO for access, transactions) +* extent format more robust in face of on-disk corruption due to magics, +* internal redundancy in tree +* improved file allocation (multi-block alloc) +* lift 32000 subdirectory limit imposed by i_links_count[1] +* nsec timestamps for mtime, atime, ctime, create time +* inode version field on disk (NFSv4, Lustre) +* reduced e2fsck time via uninit_bg feature +* journal checksumming for robustness, performance +* persistent file preallocation (e.g for streaming media, databases) +* ability to pack bitmaps and inode tables into larger virtual groups via the + flex_bg feature +* large file support +* inode allocation using large virtual block groups via flex_bg +* delayed allocation +* large block (up to pagesize) support +* efficient new ordered mode in JBD2 and ext4 (avoid using buffer head to force + the ordering) +* Case-insensitive file name lookups +* file-based encryption support (fscrypt) +* file-based verity support (fsverity) + +[1] Filesystems with a block size of 1k may see a limit imposed by the +directory hash tree having a maximum depth of two. + +case-insensitive file name lookups +====================================================== + +The case-insensitive file name lookup feature is supported on a +per-directory basis, allowing the user to mix case-insensitive and +case-sensitive directories in the same filesystem. It is enabled by +flipping the +F inode attribute of an empty directory. The +case-insensitive string match operation is only defined when we know how +text in encoded in a byte sequence. For that reason, in order to enable +case-insensitive directories, the filesystem must have the +casefold feature, which stores the filesystem-wide encoding +model used. By default, the charset adopted is the latest version of +Unicode (12.1.0, by the time of this writing), encoded in the UTF-8 +form. The comparison algorithm is implemented by normalizing the +strings to the Canonical decomposition form, as defined by Unicode, +followed by a byte per byte comparison. + +The case-awareness is name-preserving on the disk, meaning that the file +name provided by userspace is a byte-per-byte match to what is actually +written in the disk. The Unicode normalization format used by the +kernel is thus an internal representation, and not exposed to the +userspace nor to the disk, with the important exception of disk hashes, +used on large case-insensitive directories with DX feature. On DX +directories, the hash must be calculated using the casefolded version of +the filename, meaning that the normalization format used actually has an +impact on where the directory entry is stored. + +When we change from viewing filenames as opaque byte sequences to seeing +them as encoded strings we need to address what happens when a program +tries to create a file with an invalid name. The Unicode subsystem +within the kernel leaves the decision of what to do in this case to the +filesystem, which select its preferred behavior by enabling/disabling +the strict mode. When Ext4 encounters one of those strings and the +filesystem did not require strict mode, it falls back to considering the +entire string as an opaque byte sequence, which still allows the user to +operate on that file, but the case-insensitive lookups won't work. + +Options +======= + +When mounting an ext4 filesystem, the following option are accepted: +(*) == default + + ro + Mount filesystem read only. Note that ext4 will replay the journal (and + thus write to the partition) even when mounted "read only". The mount + options "ro,noload" can be used to prevent writes to the filesystem. + + journal_checksum + Enable checksumming of the journal transactions. This will allow the + recovery code in e2fsck and the kernel to detect corruption in the + kernel. It is a compatible change and will be ignored by older + kernels. + + journal_async_commit + Commit block can be written to disk without waiting for descriptor + blocks. If enabled older kernels cannot mount the device. This will + enable 'journal_checksum' internally. + + journal_path=path, journal_dev=devnum + When the external journal device's major/minor numbers have changed, + these options allow the user to specify the new journal location. The + journal device is identified through either its new major/minor numbers + encoded in devnum, or via a path to the device. + + norecovery, noload + Don't load the journal on mounting. Note that if the filesystem was + not unmounted cleanly, skipping the journal replay will lead to the + filesystem containing inconsistencies that can lead to any number of + problems. + + data=journal + All data are committed into the journal prior to being written into the + main file system. Enabling this mode will disable delayed allocation + and O_DIRECT support. + + data=ordered (*) + All data are forced directly out to the main file system prior to its + metadata being committed to the journal. + + data=writeback + Data ordering is not preserved, data may be written into the main file + system after its metadata has been committed to the journal. + + commit=nrsec (*) + This setting limits the maximum age of the running transaction to + 'nrsec' seconds. The default value is 5 seconds. This means that if + you lose your power, you will lose as much as the latest 5 seconds of + metadata changes (your filesystem will not be damaged though, thanks + to the journaling). This default value (or any low value) will hurt + performance, but it's good for data-safety. Setting it to 0 will have + the same effect as leaving it at the default (5 seconds). Setting it + to very large values will improve performance. Note that due to + delayed allocation even older data can be lost on power failure since + writeback of those data begins only after time set in + /proc/sys/vm/dirty_expire_centisecs. + + barrier=<0|1(*)>, barrier(*), nobarrier + This enables/disables the use of write barriers in the jbd code. + barrier=0 disables, barrier=1 enables. This also requires an IO stack + which can support barriers, and if jbd gets an error on a barrier + write, it will disable again with a warning. Write barriers enforce + proper on-disk ordering of journal commits, making volatile disk write + caches safe to use, at some performance penalty. If your disks are + battery-backed in one way or another, disabling barriers may safely + improve performance. The mount options "barrier" and "nobarrier" can + also be used to enable or disable barriers, for consistency with other + ext4 mount options. + + inode_readahead_blks=n + This tuning parameter controls the maximum number of inode table blocks + that ext4's inode table readahead algorithm will pre-read into the + buffer cache. The default value is 32 blocks. + + nouser_xattr + Disables Extended User Attributes. See the attr(5) manual page for + more information about extended attributes. + + noacl + This option disables POSIX Access Control List support. If ACL support + is enabled in the kernel configuration (CONFIG_EXT4_FS_POSIX_ACL), ACL + is enabled by default on mount. See the acl(5) manual page for more + information about acl. + + bsddf (*) + Make 'df' act like BSD. + + minixdf + Make 'df' act like Minix. + + debug + Extra debugging information is sent to syslog. + + abort + Simulate the effects of calling ext4_abort() for debugging purposes. + This is normally used while remounting a filesystem which is already + mounted. + + errors=remount-ro + Remount the filesystem read-only on an error. + + errors=continue + Keep going on a filesystem error. + + errors=panic + Panic and halt the machine if an error occurs. (These mount options + override the errors behavior specified in the superblock, which can be + configured using tune2fs) + + data_err=ignore(*) + Just print an error message if an error occurs in a file data buffer in + ordered mode. + data_err=abort + Abort the journal if an error occurs in a file data buffer in ordered + mode. + + grpid | bsdgroups + New objects have the group ID of their parent. + + nogrpid (*) | sysvgroups + New objects have the group ID of their creator. + + resgid=n + The group ID which may use the reserved blocks. + + resuid=n + The user ID which may use the reserved blocks. + + sb= + Use alternate superblock at this location. + + quota, noquota, grpquota, usrquota + These options are ignored by the filesystem. They are used only by + quota tools to recognize volumes where quota should be turned on. See + documentation in the quota-tools package for more details + (http://sourceforge.net/projects/linuxquota). + + jqfmt=<quota type>, usrjquota=<file>, grpjquota=<file> + These options tell filesystem details about quota so that quota + information can be properly updated during journal replay. They replace + the above quota options. See documentation in the quota-tools package + for more details (http://sourceforge.net/projects/linuxquota). + + stripe=n + Number of filesystem blocks that mballoc will try to use for allocation + size and alignment. For RAID5/6 systems this should be the number of + data disks * RAID chunk size in file system blocks. + + delalloc (*) + Defer block allocation until just before ext4 writes out the block(s) + in question. This allows ext4 to better allocation decisions more + efficiently. + + nodelalloc + Disable delayed allocation. Blocks are allocated when the data is + copied from userspace to the page cache, either via the write(2) system + call or when an mmap'ed page which was previously unallocated is + written for the first time. + + max_batch_time=usec + Maximum amount of time ext4 should wait for additional filesystem + operations to be batch together with a synchronous write operation. + Since a synchronous write operation is going to force a commit and then + a wait for the I/O complete, it doesn't cost much, and can be a huge + throughput win, we wait for a small amount of time to see if any other + transactions can piggyback on the synchronous write. The algorithm + used is designed to automatically tune for the speed of the disk, by + measuring the amount of time (on average) that it takes to finish + committing a transaction. Call this time the "commit time". If the + time that the transaction has been running is less than the commit + time, ext4 will try sleeping for the commit time to see if other + operations will join the transaction. The commit time is capped by + the max_batch_time, which defaults to 15000us (15ms). This + optimization can be turned off entirely by setting max_batch_time to 0. + + min_batch_time=usec + This parameter sets the commit time (as described above) to be at least + min_batch_time. It defaults to zero microseconds. Increasing this + parameter may improve the throughput of multi-threaded, synchronous + workloads on very fast disks, at the cost of increasing latency. + + journal_ioprio=prio + The I/O priority (from 0 to 7, where 0 is the highest priority) which + should be used for I/O operations submitted by kjournald2 during a + commit operation. This defaults to 3, which is a slightly higher + priority than the default I/O priority. + + auto_da_alloc(*), noauto_da_alloc + Many broken applications don't use fsync() when replacing existing + files via patterns such as fd = open("foo.new")/write(fd,..)/close(fd)/ + rename("foo.new", "foo"), or worse yet, fd = open("foo", + O_TRUNC)/write(fd,..)/close(fd). If auto_da_alloc is enabled, ext4 + will detect the replace-via-rename and replace-via-truncate patterns + and force that any delayed allocation blocks are allocated such that at + the next journal commit, in the default data=ordered mode, the data + blocks of the new file are forced to disk before the rename() operation + is committed. This provides roughly the same level of guarantees as + ext3, and avoids the "zero-length" problem that can happen when a + system crashes before the delayed allocation blocks are forced to disk. + + noinit_itable + Do not initialize any uninitialized inode table blocks in the + background. This feature may be used by installation CD's so that the + install process can complete as quickly as possible; the inode table + initialization process would then be deferred until the next time the + file system is unmounted. + + init_itable=n + The lazy itable init code will wait n times the number of milliseconds + it took to zero out the previous block group's inode table. This + minimizes the impact on the system performance while file system's + inode table is being initialized. + + discard, nodiscard(*) + Controls whether ext4 should issue discard/TRIM commands to the + underlying block device when blocks are freed. This is useful for SSD + devices and sparse/thinly-provisioned LUNs, but it is off by default + until sufficient testing has been done. + + nouid32 + Disables 32-bit UIDs and GIDs. This is for interoperability with + older kernels which only store and expect 16-bit values. + + block_validity(*), noblock_validity + These options enable or disable the in-kernel facility for tracking + filesystem metadata blocks within internal data structures. This + allows multi- block allocator and other routines to notice bugs or + corrupted allocation bitmaps which cause blocks to be allocated which + overlap with filesystem metadata blocks. + + dioread_lock, dioread_nolock + Controls whether or not ext4 should use the DIO read locking. If the + dioread_nolock option is specified ext4 will allocate uninitialized + extent before buffer write and convert the extent to initialized after + IO completes. This approach allows ext4 code to avoid using inode + mutex, which improves scalability on high speed storages. However this + does not work with data journaling and dioread_nolock option will be + ignored with kernel warning. Note that dioread_nolock code path is only + used for extent-based files. Because of the restrictions this options + comprises it is off by default (e.g. dioread_lock). + + max_dir_size_kb=n + This limits the size of directories so that any attempt to expand them + beyond the specified limit in kilobytes will cause an ENOSPC error. + This is useful in memory constrained environments, where a very large + directory can cause severe performance problems or even provoke the Out + Of Memory killer. (For example, if there is only 512mb memory + available, a 176mb directory may seriously cramp the system's style.) + + i_version + Enable 64-bit inode version support. This option is off by default. + + dax + Use direct access (no page cache). See + Documentation/filesystems/dax.rst. Note that this option is + incompatible with data=journal. + + inlinecrypt + When possible, encrypt/decrypt the contents of encrypted files using the + blk-crypto framework rather than filesystem-layer encryption. This + allows the use of inline encryption hardware. The on-disk format is + unaffected. For more details, see + Documentation/block/inline-encryption.rst. + +Data Mode +========= +There are 3 different data modes: + +* writeback mode + + In data=writeback mode, ext4 does not journal data at all. This mode provides + a similar level of journaling as that of XFS, JFS, and ReiserFS in its default + mode - metadata journaling. A crash+recovery can cause incorrect data to + appear in files which were written shortly before the crash. This mode will + typically provide the best ext4 performance. + +* ordered mode + + In data=ordered mode, ext4 only officially journals metadata, but it logically + groups metadata information related to data changes with the data blocks into + a single unit called a transaction. When it's time to write the new metadata + out to disk, the associated data blocks are written first. In general, this + mode performs slightly slower than writeback but significantly faster than + journal mode. + +* journal mode + + data=journal mode provides full data and metadata journaling. All new data is + written to the journal first, and then to its final location. In the event of + a crash, the journal can be replayed, bringing both data and metadata into a + consistent state. This mode is the slowest except when data needs to be read + from and written to disk at the same time where it outperforms all others + modes. Enabling this mode will disable delayed allocation and O_DIRECT + support. + +/proc entries +============= + +Information about mounted ext4 file systems can be found in +/proc/fs/ext4. Each mounted filesystem will have a directory in +/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or +/proc/fs/ext4/dm-0). The files in each per-device directory are shown +in table below. + +Files in /proc/fs/ext4/<devname> + + mb_groups + details of multiblock allocator buddy cache of free blocks + +/sys entries +============ + +Information about mounted ext4 file systems can be found in +/sys/fs/ext4. Each mounted filesystem will have a directory in +/sys/fs/ext4 based on its device name (i.e., /sys/fs/ext4/hdc or +/sys/fs/ext4/dm-0). The files in each per-device directory are shown +in table below. + +Files in /sys/fs/ext4/<devname>: + +(see also Documentation/ABI/testing/sysfs-fs-ext4) + + delayed_allocation_blocks + This file is read-only and shows the number of blocks that are dirty in + the page cache, but which do not have their location in the filesystem + allocated yet. + + inode_goal + Tuning parameter which (if non-zero) controls the goal inode used by + the inode allocator in preference to all other allocation heuristics. + This is intended for debugging use only, and should be 0 on production + systems. + + inode_readahead_blks + Tuning parameter which controls the maximum number of inode table + blocks that ext4's inode table readahead algorithm will pre-read into + the buffer cache. + + lifetime_write_kbytes + This file is read-only and shows the number of kilobytes of data that + have been written to this filesystem since it was created. + + max_writeback_mb_bump + The maximum number of megabytes the writeback code will try to write + out before move on to another inode. + + mb_group_prealloc + The multiblock allocator will round up allocation requests to a + multiple of this tuning parameter if the stripe size is not set in the + ext4 superblock + + mb_max_to_scan + The maximum number of extents the multiblock allocator will search to + find the best extent. + + mb_min_to_scan + The minimum number of extents the multiblock allocator will search to + find the best extent. + + mb_order2_req + Tuning parameter which controls the minimum size for requests (as a + power of 2) where the buddy cache is used. + + mb_stats + Controls whether the multiblock allocator should collect statistics, + which are shown during the unmount. 1 means to collect statistics, 0 + means not to collect statistics. + + mb_stream_req + Files which have fewer blocks than this tunable parameter will have + their blocks allocated out of a block group specific preallocation + pool, so that small files are packed closely together. Each large file + will have its blocks allocated out of its own unique preallocation + pool. + + session_write_kbytes + This file is read-only and shows the number of kilobytes of data that + have been written to this filesystem since it was mounted. + + reserved_clusters + This is RW file and contains number of reserved clusters in the file + system which will be used in the specific situations to avoid costly + zeroout, unexpected ENOSPC, or possible data loss. The default is 2% or + 4096 clusters, whichever is smaller and this can be changed however it + can never exceed number of clusters in the file system. If there is not + enough space for the reserved space when mounting the file mount will + _not_ fail. + +Ioctls +====== + +Ext4 implements various ioctls which can be used by applications to access +ext4-specific functionality. An incomplete list of these ioctls is shown in the +table below. This list includes truly ext4-specific ioctls (``EXT4_IOC_*``) as +well as ioctls that may have been ext4-specific originally but are now supported +by some other filesystem(s) too (``FS_IOC_*``). + +Table of Ext4 ioctls + + FS_IOC_GETFLAGS + Get additional attributes associated with inode. The ioctl argument is + an integer bitfield, with bit values described in ext4.h. + + FS_IOC_SETFLAGS + Set additional attributes associated with inode. The ioctl argument is + an integer bitfield, with bit values described in ext4.h. + + EXT4_IOC_GETVERSION, EXT4_IOC_GETVERSION_OLD + Get the inode i_generation number stored for each inode. The + i_generation number is normally changed only when new inode is created + and it is particularly useful for network filesystems. The '_OLD' + version of this ioctl is an alias for FS_IOC_GETVERSION. + + EXT4_IOC_SETVERSION, EXT4_IOC_SETVERSION_OLD + Set the inode i_generation number stored for each inode. The '_OLD' + version of this ioctl is an alias for FS_IOC_SETVERSION. + + EXT4_IOC_GROUP_EXTEND + This ioctl has the same purpose as the resize mount option. It allows + to resize filesystem to the end of the last existing block group, + further resize has to be done with resize2fs, either online, or + offline. The argument points to the unsigned logn number representing + the filesystem new block count. + + EXT4_IOC_MOVE_EXT + Move the block extents from orig_fd (the one this ioctl is pointing to) + to the donor_fd (the one specified in move_extent structure passed as + an argument to this ioctl). Then, exchange inode metadata between + orig_fd and donor_fd. This is especially useful for online + defragmentation, because the allocator has the opportunity to allocate + moved blocks better, ideally into one contiguous extent. + + EXT4_IOC_GROUP_ADD + Add a new group descriptor to an existing or new group descriptor + block. The new group descriptor is described by ext4_new_group_input + structure, which is passed as an argument to this ioctl. This is + especially useful in conjunction with EXT4_IOC_GROUP_EXTEND, which + allows online resize of the filesystem to the end of the last existing + block group. Those two ioctls combined is used in userspace online + resize tool (e.g. resize2fs). + + EXT4_IOC_MIGRATE + This ioctl operates on the filesystem itself. It converts (migrates) + ext3 indirect block mapped inode to ext4 extent mapped inode by walking + through indirect block mapping of the original inode and converting + contiguous block ranges into ext4 extents of the temporary inode. Then, + inodes are swapped. This ioctl might help, when migrating from ext3 to + ext4 filesystem, however suggestion is to create fresh ext4 filesystem + and copy data from the backup. Note, that filesystem has to support + extents for this ioctl to work. + + EXT4_IOC_ALLOC_DA_BLKS + Force all of the delay allocated blocks to be allocated to preserve + application-expected ext3 behaviour. Note that this will also start + triggering a write of the data blocks, but this behaviour may change in + the future as it is not necessary and has been done this way only for + sake of simplicity. + + EXT4_IOC_RESIZE_FS + Resize the filesystem to a new size. The number of blocks of resized + filesystem is passed in via 64 bit integer argument. The kernel + allocates bitmaps and inode table, the userspace tool thus just passes + the new number of blocks. + + EXT4_IOC_SWAP_BOOT + Swap i_blocks and associated attributes (like i_blocks, i_size, + i_flags, ...) from the specified inode with inode EXT4_BOOT_LOADER_INO + (#5). This is typically used to store a boot loader in a secure part of + the filesystem, where it can't be changed by a normal user by accident. + The data blocks of the previous boot loader will be associated with the + given inode. + +References +========== + +kernel source: <file:fs/ext4/> + <file:fs/jbd2/> + +programs: http://e2fsprogs.sourceforge.net/ + +useful links: https://fedoraproject.org/wiki/ext3-devel + http://www.bullopensource.org/ext4/ + http://ext4.wiki.kernel.org/index.php/Main_Page + https://fedoraproject.org/wiki/Features/Ext4 diff --git a/Documentation/admin-guide/features.rst b/Documentation/admin-guide/features.rst new file mode 100644 index 000000000..7651eca38 --- /dev/null +++ b/Documentation/admin-guide/features.rst @@ -0,0 +1,3 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. kernel-feat:: features diff --git a/Documentation/admin-guide/filesystem-monitoring.rst b/Documentation/admin-guide/filesystem-monitoring.rst new file mode 100644 index 000000000..ab8dba762 --- /dev/null +++ b/Documentation/admin-guide/filesystem-monitoring.rst @@ -0,0 +1,78 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==================================== +File system Monitoring with fanotify +==================================== + +File system Error Reporting +=========================== + +Fanotify supports the FAN_FS_ERROR event type for file system-wide error +reporting. It is meant to be used by file system health monitoring +daemons, which listen for these events and take actions (notify +sysadmin, start recovery) when a file system problem is detected. + +By design, a FAN_FS_ERROR notification exposes sufficient information +for a monitoring tool to know a problem in the file system has happened. +It doesn't necessarily provide a user space application with semantics +to verify an IO operation was successfully executed. That is out of +scope for this feature. Instead, it is only meant as a framework for +early file system problem detection and reporting recovery tools. + +When a file system operation fails, it is common for dozens of kernel +errors to cascade after the initial failure, hiding the original failure +log, which is usually the most useful debug data to troubleshoot the +problem. For this reason, FAN_FS_ERROR tries to report only the first +error that occurred for a file system since the last notification, and +it simply counts additional errors. This ensures that the most +important pieces of information are never lost. + +FAN_FS_ERROR requires the fanotify group to be setup with the +FAN_REPORT_FID flag. + +At the time of this writing, the only file system that emits FAN_FS_ERROR +notifications is Ext4. + +A FAN_FS_ERROR Notification has the following format:: + + :: + + [ Notification Metadata (Mandatory) ] + [ Generic Error Record (Mandatory) ] + [ FID record (Mandatory) ] + +The order of records is not guaranteed, and new records might be added +in the future. Therefore, applications must not rely on the order and +must be prepared to skip over unknown records. Please refer to +``samples/fanotify/fs-monitor.c`` for an example parser. + +Generic error record +-------------------- + +The generic error record provides enough information for a file system +agnostic tool to learn about a problem in the file system, without +providing any additional details about the problem. This record is +identified by ``struct fanotify_event_info_header.info_type`` being set +to FAN_EVENT_INFO_TYPE_ERROR. + + :: + + struct fanotify_event_info_error { + struct fanotify_event_info_header hdr; + __s32 error; + __u32 error_count; + }; + +The `error` field identifies the type of error using errno values. +`error_count` tracks the number of errors that occurred and were +suppressed to preserve the original error information, since the last +notification. + +FID record +---------- + +The FID record can be used to uniquely identify the inode that triggered +the error through the combination of fsid and file handle. A file system +specific application can use that information to attempt a recovery +procedure. Errors that are not related to an inode are reported with an +empty file handle of type FILEID_INVALID. diff --git a/Documentation/admin-guide/gpio/gpio-aggregator.rst b/Documentation/admin-guide/gpio/gpio-aggregator.rst new file mode 100644 index 000000000..5cd1e7221 --- /dev/null +++ b/Documentation/admin-guide/gpio/gpio-aggregator.rst @@ -0,0 +1,111 @@ +.. SPDX-License-Identifier: GPL-2.0-only + +GPIO Aggregator +=============== + +The GPIO Aggregator provides a mechanism to aggregate GPIOs, and expose them as +a new gpio_chip. This supports the following use cases. + + +Aggregating GPIOs using Sysfs +----------------------------- + +GPIO controllers are exported to userspace using /dev/gpiochip* character +devices. Access control to these devices is provided by standard UNIX file +system permissions, on an all-or-nothing basis: either a GPIO controller is +accessible for a user, or it is not. + +The GPIO Aggregator provides access control for a set of one or more GPIOs, by +aggregating them into a new gpio_chip, which can be assigned to a group or user +using standard UNIX file ownership and permissions. Furthermore, this +simplifies and hardens exporting GPIOs to a virtual machine, as the VM can just +grab the full GPIO controller, and no longer needs to care about which GPIOs to +grab and which not, reducing the attack surface. + +Aggregated GPIO controllers are instantiated and destroyed by writing to +write-only attribute files in sysfs. + + /sys/bus/platform/drivers/gpio-aggregator/ + + "new_device" ... + Userspace may ask the kernel to instantiate an aggregated GPIO + controller by writing a string describing the GPIOs to + aggregate to the "new_device" file, using the format + + .. code-block:: none + + [<gpioA>] [<gpiochipB> <offsets>] ... + + Where: + + "<gpioA>" ... + is a GPIO line name, + + "<gpiochipB>" ... + is a GPIO chip label, and + + "<offsets>" ... + is a comma-separated list of GPIO offsets and/or + GPIO offset ranges denoted by dashes. + + Example: Instantiate a new GPIO aggregator by aggregating GPIO + line 19 of "e6052000.gpio" and GPIO lines 20-21 of + "e6050000.gpio" into a new gpio_chip: + + .. code-block:: sh + + $ echo 'e6052000.gpio 19 e6050000.gpio 20-21' > new_device + + "delete_device" ... + Userspace may ask the kernel to destroy an aggregated GPIO + controller after use by writing its device name to the + "delete_device" file. + + Example: Destroy the previously-created aggregated GPIO + controller, assumed to be "gpio-aggregator.0": + + .. code-block:: sh + + $ echo gpio-aggregator.0 > delete_device + + +Generic GPIO Driver +------------------- + +The GPIO Aggregator can also be used as a generic driver for a simple +GPIO-operated device described in DT, without a dedicated in-kernel driver. +This is useful in industrial control, and is not unlike e.g. spidev, which +allows the user to communicate with an SPI device from userspace. + +Binding a device to the GPIO Aggregator is performed either by modifying the +gpio-aggregator driver, or by writing to the "driver_override" file in Sysfs. + +Example: If "door" is a GPIO-operated device described in DT, using its own +compatible value:: + + door { + compatible = "myvendor,mydoor"; + + gpios = <&gpio2 19 GPIO_ACTIVE_HIGH>, + <&gpio2 20 GPIO_ACTIVE_LOW>; + gpio-line-names = "open", "lock"; + }; + +it can be bound to the GPIO Aggregator by either: + +1. Adding its compatible value to ``gpio_aggregator_dt_ids[]``, +2. Binding manually using "driver_override": + +.. code-block:: sh + + $ echo gpio-aggregator > /sys/bus/platform/devices/door/driver_override + $ echo door > /sys/bus/platform/drivers/gpio-aggregator/bind + +After that, a new gpiochip "door" has been created: + +.. code-block:: sh + + $ gpioinfo door + gpiochip12 - 2 lines: + line 0: "open" unused input active-high + line 1: "lock" unused input active-high diff --git a/Documentation/admin-guide/gpio/gpio-mockup.rst b/Documentation/admin-guide/gpio/gpio-mockup.rst new file mode 100644 index 000000000..493071da1 --- /dev/null +++ b/Documentation/admin-guide/gpio/gpio-mockup.rst @@ -0,0 +1,51 @@ +.. SPDX-License-Identifier: GPL-2.0-only + +GPIO Testing Driver +=================== + +The GPIO Testing Driver (gpio-mockup) provides a way to create simulated GPIO +chips for testing purposes. The lines exposed by these chips can be accessed +using the standard GPIO character device interface as well as manipulated +using the dedicated debugfs directory structure. + +Creating simulated chips using module params +-------------------------------------------- + +When loading the gpio-mockup driver a number of parameters can be passed to the +module. + + gpio_mockup_ranges + + This parameter takes an argument in the form of an array of integer + pairs. Each pair defines the base GPIO number (non-negative integer) + and the first number after the last of this chip. If the base GPIO + is -1, the gpiolib will assign it automatically. while the following + parameter is the number of lines exposed by the chip. + + Example: gpio_mockup_ranges=-1,8,-1,16,405,409 + + The line above creates three chips. The first one will expose 8 lines, + the second 16 and the third 4. The base GPIO for the third chip is set + to 405 while for two first chips it will be assigned automatically. + + gpio_mockup_named_lines + + This parameter doesn't take any arguments. It lets the driver know that + GPIO lines exposed by it should be named. + + The name format is: gpio-mockup-X-Y where X is mockup chip's ID + and Y is the line offset. + +Manipulating simulated lines +---------------------------- + +Each mockup chip creates its own subdirectory in /sys/kernel/debug/gpio-mockup/. +The directory is named after the chip's label. A symlink is also created, named +after the chip's name, which points to the label directory. + +Inside each subdirectory, there's a separate attribute for each GPIO line. The +name of the attribute represents the line's offset in the chip. + +Reading from a line attribute returns the current value. Writing to it (0 or 1) +changes the configuration of the simulated pull-up/pull-down resistor +(1 - pull-up, 0 - pull-down). diff --git a/Documentation/admin-guide/gpio/gpio-sim.rst b/Documentation/admin-guide/gpio/gpio-sim.rst new file mode 100644 index 000000000..1cc5567a4 --- /dev/null +++ b/Documentation/admin-guide/gpio/gpio-sim.rst @@ -0,0 +1,134 @@ +.. SPDX-License-Identifier: GPL-2.0-or-later + +Configfs GPIO Simulator +======================= + +The configfs GPIO Simulator (gpio-sim) provides a way to create simulated GPIO +chips for testing purposes. The lines exposed by these chips can be accessed +using the standard GPIO character device interface as well as manipulated +using sysfs attributes. + +Creating simulated chips +------------------------ + +The gpio-sim module registers a configfs subsystem called ``'gpio-sim'``. For +details of the configfs filesystem, please refer to the configfs documentation. + +The user can create a hierarchy of configfs groups and items as well as modify +values of exposed attributes. Once the chip is instantiated, this hierarchy +will be translated to appropriate device properties. The general structure is: + +**Group:** ``/config/gpio-sim`` + +This is the top directory of the gpio-sim configfs tree. + +**Group:** ``/config/gpio-sim/gpio-device`` + +**Attribute:** ``/config/gpio-sim/gpio-device/dev_name`` + +**Attribute:** ``/config/gpio-sim/gpio-device/live`` + +This is a directory representing a GPIO platform device. The ``'dev_name'`` +attribute is read-only and allows the user-space to read the platform device +name (e.g. ``'gpio-sim.0'``). The ``'live'`` attribute allows to trigger the +actual creation of the device once it's fully configured. The accepted values +are: ``'1'`` to enable the simulated device and ``'0'`` to disable and tear +it down. + +**Group:** ``/config/gpio-sim/gpio-device/gpio-bankX`` + +**Attribute:** ``/config/gpio-sim/gpio-device/gpio-bankX/chip_name`` + +**Attribute:** ``/config/gpio-sim/gpio-device/gpio-bankX/num_lines`` + +This group represents a bank of GPIOs under the top platform device. The +``'chip_name'`` attribute is read-only and allows the user-space to read the +device name of the bank device. The ``'num_lines'`` attribute allows to specify +the number of lines exposed by this bank. + +**Group:** ``/config/gpio-sim/gpio-device/gpio-bankX/lineY`` + +**Attribute:** ``/config/gpio-sim/gpio-device/gpio-bankX/lineY/name`` + +This group represents a single line at the offset Y. The 'name' attribute +allows to set the line name as represented by the 'gpio-line-names' property. + +**Item:** ``/config/gpio-sim/gpio-device/gpio-bankX/lineY/hog`` + +**Attribute:** ``/config/gpio-sim/gpio-device/gpio-bankX/lineY/hog/name`` + +**Attribute:** ``/config/gpio-sim/gpio-device/gpio-bankX/lineY/hog/direction`` + +This item makes the gpio-sim module hog the associated line. The ``'name'`` +attribute specifies the in-kernel consumer name to use. The ``'direction'`` +attribute specifies the hog direction and must be one of: ``'input'``, +``'output-high'`` and ``'output-low'``. + +Inside each bank directory, there's a set of attributes that can be used to +configure the new chip. Additionally the user can ``mkdir()`` subdirectories +inside the chip's directory that allow to pass additional configuration for +specific lines. The name of those subdirectories must take the form of: +``'line<offset>'`` (e.g. ``'line0'``, ``'line20'``, etc.) as the name will be +used by the module to assign the config to the specific line at given offset. + +Once the confiuration is complete, the ``'live'`` attribute must be set to 1 in +order to instantiate the chip. It can be set back to 0 to destroy the simulated +chip. The module will synchronously wait for the new simulated device to be +successfully probed and if this doesn't happen, writing to ``'live'`` will +result in an error. + +Simulated GPIO chips can also be defined in device-tree. The compatible string +must be: ``"gpio-simulator"``. Supported properties are: + + ``"gpio-sim,label"`` - chip label + +Other standard GPIO properties (like ``"gpio-line-names"``, ``"ngpios"`` or +``"gpio-hog"``) are also supported. Please refer to the GPIO documentation for +details. + +An example device-tree code defining a GPIO simulator: + +.. code-block :: none + + gpio-sim { + compatible = "gpio-simulator"; + + bank0 { + gpio-controller; + #gpio-cells = <2>; + ngpios = <16>; + gpio-sim,label = "dt-bank0"; + gpio-line-names = "", "sim-foo", "", "sim-bar"; + }; + + bank1 { + gpio-controller; + #gpio-cells = <2>; + ngpios = <8>; + gpio-sim,label = "dt-bank1"; + + line3 { + gpio-hog; + gpios = <3 0>; + output-high; + line-name = "sim-hog-from-dt"; + }; + }; + }; + +Manipulating simulated lines +---------------------------- + +Each simulated GPIO chip creates a separate sysfs group under its device +directory for each exposed line +(e.g. ``/sys/devices/platform/gpio-sim.X/gpiochipY/``). The name of each group +is of the form: ``'sim_gpioX'`` where X is the offset of the line. Inside each +group there are two attributes: + + ``pull`` - allows to read and set the current simulated pull setting for + every line, when writing the value must be one of: ``'pull-up'``, + ``'pull-down'`` + + ``value`` - allows to read the current value of the line which may be + different from the pull if the line is being driven from + user-space diff --git a/Documentation/admin-guide/gpio/index.rst b/Documentation/admin-guide/gpio/index.rst new file mode 100644 index 000000000..f6861ca16 --- /dev/null +++ b/Documentation/admin-guide/gpio/index.rst @@ -0,0 +1,20 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==== +gpio +==== + +.. toctree:: + :maxdepth: 1 + + gpio-aggregator + sysfs + gpio-mockup + gpio-sim + +.. only:: subproject and html + + Indices + ======= + + * :ref:`genindex` diff --git a/Documentation/admin-guide/gpio/sysfs.rst b/Documentation/admin-guide/gpio/sysfs.rst new file mode 100644 index 000000000..35171d15f --- /dev/null +++ b/Documentation/admin-guide/gpio/sysfs.rst @@ -0,0 +1,167 @@ +GPIO Sysfs Interface for Userspace +================================== + +.. warning:: + + THIS ABI IS DEPRECATED, THE ABI DOCUMENTATION HAS BEEN MOVED TO + Documentation/ABI/obsolete/sysfs-gpio AND NEW USERSPACE CONSUMERS + ARE SUPPOSED TO USE THE CHARACTER DEVICE ABI. THIS OLD SYSFS ABI WILL + NOT BE DEVELOPED (NO NEW FEATURES), IT WILL JUST BE MAINTAINED. + +Refer to the examples in tools/gpio/* for an introduction to the new +character device ABI. Also see the userspace header in +include/uapi/linux/gpio.h + +The deprecated sysfs ABI +------------------------ +Platforms which use the "gpiolib" implementors framework may choose to +configure a sysfs user interface to GPIOs. This is different from the +debugfs interface, since it provides control over GPIO direction and +value instead of just showing a gpio state summary. Plus, it could be +present on production systems without debugging support. + +Given appropriate hardware documentation for the system, userspace could +know for example that GPIO #23 controls the write protect line used to +protect boot loader segments in flash memory. System upgrade procedures +may need to temporarily remove that protection, first importing a GPIO, +then changing its output state, then updating the code before re-enabling +the write protection. In normal use, GPIO #23 would never be touched, +and the kernel would have no need to know about it. + +Again depending on appropriate hardware documentation, on some systems +userspace GPIO can be used to determine system configuration data that +standard kernels won't know about. And for some tasks, simple userspace +GPIO drivers could be all that the system really needs. + +DO NOT ABUSE SYSFS TO CONTROL HARDWARE THAT HAS PROPER KERNEL DRIVERS. +PLEASE READ THE DOCUMENT AT Documentation/driver-api/gpio/drivers-on-gpio.rst +TO AVOID REINVENTING KERNEL WHEELS IN USERSPACE. I MEAN IT. REALLY. + +Paths in Sysfs +-------------- +There are three kinds of entries in /sys/class/gpio: + + - Control interfaces used to get userspace control over GPIOs; + + - GPIOs themselves; and + + - GPIO controllers ("gpio_chip" instances). + +That's in addition to standard files including the "device" symlink. + +The control interfaces are write-only: + + /sys/class/gpio/ + + "export" ... + Userspace may ask the kernel to export control of + a GPIO to userspace by writing its number to this file. + + Example: "echo 19 > export" will create a "gpio19" node + for GPIO #19, if that's not requested by kernel code. + + "unexport" ... + Reverses the effect of exporting to userspace. + + Example: "echo 19 > unexport" will remove a "gpio19" + node exported using the "export" file. + +GPIO signals have paths like /sys/class/gpio/gpio42/ (for GPIO #42) +and have the following read/write attributes: + + /sys/class/gpio/gpioN/ + + "direction" ... + reads as either "in" or "out". This value may + normally be written. Writing as "out" defaults to + initializing the value as low. To ensure glitch free + operation, values "low" and "high" may be written to + configure the GPIO as an output with that initial value. + + Note that this attribute *will not exist* if the kernel + doesn't support changing the direction of a GPIO, or + it was exported by kernel code that didn't explicitly + allow userspace to reconfigure this GPIO's direction. + + "value" ... + reads as either 0 (low) or 1 (high). If the GPIO + is configured as an output, this value may be written; + any nonzero value is treated as high. + + If the pin can be configured as interrupt-generating interrupt + and if it has been configured to generate interrupts (see the + description of "edge"), you can poll(2) on that file and + poll(2) will return whenever the interrupt was triggered. If + you use poll(2), set the events POLLPRI and POLLERR. If you + use select(2), set the file descriptor in exceptfds. After + poll(2) returns, either lseek(2) to the beginning of the sysfs + file and read the new value or close the file and re-open it + to read the value. + + "edge" ... + reads as either "none", "rising", "falling", or + "both". Write these strings to select the signal edge(s) + that will make poll(2) on the "value" file return. + + This file exists only if the pin can be configured as an + interrupt generating input pin. + + "active_low" ... + reads as either 0 (false) or 1 (true). Write + any nonzero value to invert the value attribute both + for reading and writing. Existing and subsequent + poll(2) support configuration via the edge attribute + for "rising" and "falling" edges will follow this + setting. + +GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the +controller implementing GPIOs starting at #42) and have the following +read-only attributes: + + /sys/class/gpio/gpiochipN/ + + "base" ... + same as N, the first GPIO managed by this chip + + "label" ... + provided for diagnostics (not always unique) + + "ngpio" ... + how many GPIOs this manages (N to N + ngpio - 1) + +Board documentation should in most cases cover what GPIOs are used for +what purposes. However, those numbers are not always stable; GPIOs on +a daughtercard might be different depending on the base board being used, +or other cards in the stack. In such cases, you may need to use the +gpiochip nodes (possibly in conjunction with schematics) to determine +the correct GPIO number to use for a given signal. + + +Exporting from Kernel code +-------------------------- +Kernel code can explicitly manage exports of GPIOs which have already been +requested using gpio_request():: + + /* export the GPIO to userspace */ + int gpiod_export(struct gpio_desc *desc, bool direction_may_change); + + /* reverse gpiod_export() */ + void gpiod_unexport(struct gpio_desc *desc); + + /* create a sysfs link to an exported GPIO node */ + int gpiod_export_link(struct device *dev, const char *name, + struct gpio_desc *desc); + +After a kernel driver requests a GPIO, it may only be made available in +the sysfs interface by gpiod_export(). The driver can control whether the +signal direction may change. This helps drivers prevent userspace code +from accidentally clobbering important system state. + +This explicit exporting can help with debugging (by making some kinds +of experiments easier), or can provide an always-there interface that's +suitable for documenting as part of a board support package. + +After the GPIO has been exported, gpiod_export_link() allows creating +symlinks from elsewhere in sysfs to the GPIO sysfs node. Drivers can +use this to provide the interface under their own device in sysfs with +a descriptive name. diff --git a/Documentation/admin-guide/highuid.rst b/Documentation/admin-guide/highuid.rst new file mode 100644 index 000000000..6ee70465c --- /dev/null +++ b/Documentation/admin-guide/highuid.rst @@ -0,0 +1,80 @@ +=================================================== +Notes on the change from 16-bit UIDs to 32-bit UIDs +=================================================== + +:Author: Chris Wing <wingc@umich.edu> +:Last updated: January 11, 2000 + +- kernel code MUST take into account __kernel_uid_t and __kernel_uid32_t + when communicating between user and kernel space in an ioctl or data + structure. + +- kernel code should use uid_t and gid_t in kernel-private structures and + code. + +What's left to be done for 32-bit UIDs on all Linux architectures: + +- Disk quotas have an interesting limitation that is not related to the + maximum UID/GID. They are limited by the maximum file size on the + underlying filesystem, because quota records are written at offsets + corresponding to the UID in question. + Further investigation is needed to see if the quota system can cope + properly with huge UIDs. If it can deal with 64-bit file offsets on all + architectures, this should not be a problem. + +- Decide whether or not to keep backwards compatibility with the system + accounting file, or if we should break it as the comments suggest + (currently, the old 16-bit UID and GID are still written to disk, and + part of the former pad space is used to store separate 32-bit UID and + GID) + +- Need to validate that OS emulation calls the 16-bit UID + compatibility syscalls, if the OS being emulated used 16-bit UIDs, or + uses the 32-bit UID system calls properly otherwise. + + This affects at least: + + - iBCS on Intel + + - sparc32 emulation on sparc64 + (need to support whatever new 32-bit UID system calls are added to + sparc32) + +- Validate that all filesystems behave properly. + + At present, 32-bit UIDs _should_ work for: + + - ext2 + - ufs + - isofs + - nfs + - coda + - udf + + Ioctl() fixups have been made for: + + - ncpfs + - smbfs + + Filesystems with simple fixups to prevent 16-bit UID wraparound: + + - minix + - sysv + - qnx4 + + Other filesystems have not been checked yet. + +- The ncpfs and smpfs filesystems cannot presently use 32-bit UIDs in + all ioctl()s. Some new ioctl()s have been added with 32-bit UIDs, but + more are needed. (as well as new user<->kernel data structures) + +- The ELF core dump format only supports 16-bit UIDs on arm, i386, m68k, + sh, and sparc32. Fixing this is probably not that important, but would + require adding a new ELF section. + +- The ioctl()s used to control the in-kernel NFS server only support + 16-bit UIDs on arm, i386, m68k, sh, and sparc32. + +- make sure that the UID mapping feature of AX25 networking works properly + (it should be safe because it's always used a 32-bit integer to + communicate between user and kernel) diff --git a/Documentation/admin-guide/hw-vuln/core-scheduling.rst b/Documentation/admin-guide/hw-vuln/core-scheduling.rst new file mode 100644 index 000000000..cf1eeefdf --- /dev/null +++ b/Documentation/admin-guide/hw-vuln/core-scheduling.rst @@ -0,0 +1,226 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============== +Core Scheduling +=============== +Core scheduling support allows userspace to define groups of tasks that can +share a core. These groups can be specified either for security usecases (one +group of tasks don't trust another), or for performance usecases (some +workloads may benefit from running on the same core as they don't need the same +hardware resources of the shared core, or may prefer different cores if they +do share hardware resource needs). This document only describes the security +usecase. + +Security usecase +---------------- +A cross-HT attack involves the attacker and victim running on different Hyper +Threads of the same core. MDS and L1TF are examples of such attacks. The only +full mitigation of cross-HT attacks is to disable Hyper Threading (HT). Core +scheduling is a scheduler feature that can mitigate some (not all) cross-HT +attacks. It allows HT to be turned on safely by ensuring that only tasks in a +user-designated trusted group can share a core. This increase in core sharing +can also improve performance, however it is not guaranteed that performance +will always improve, though that is seen to be the case with a number of real +world workloads. In theory, core scheduling aims to perform at least as good as +when Hyper Threading is disabled. In practice, this is mostly the case though +not always: as synchronizing scheduling decisions across 2 or more CPUs in a +core involves additional overhead - especially when the system is lightly +loaded. When ``total_threads <= N_CPUS/2``, the extra overhead may cause core +scheduling to perform more poorly compared to SMT-disabled, where N_CPUS is the +total number of CPUs. Please measure the performance of your workloads always. + +Usage +----- +Core scheduling support is enabled via the ``CONFIG_SCHED_CORE`` config option. +Using this feature, userspace defines groups of tasks that can be co-scheduled +on the same core. The core scheduler uses this information to make sure that +tasks that are not in the same group never run simultaneously on a core, while +doing its best to satisfy the system's scheduling requirements. + +Core scheduling can be enabled via the ``PR_SCHED_CORE`` prctl interface. +This interface provides support for the creation of core scheduling groups, as +well as admission and removal of tasks from created groups:: + + #include <sys/prctl.h> + + int prctl(int option, unsigned long arg2, unsigned long arg3, + unsigned long arg4, unsigned long arg5); + +option: + ``PR_SCHED_CORE`` + +arg2: + Command for operation, must be one off: + + - ``PR_SCHED_CORE_GET`` -- get core_sched cookie of ``pid``. + - ``PR_SCHED_CORE_CREATE`` -- create a new unique cookie for ``pid``. + - ``PR_SCHED_CORE_SHARE_TO`` -- push core_sched cookie to ``pid``. + - ``PR_SCHED_CORE_SHARE_FROM`` -- pull core_sched cookie from ``pid``. + +arg3: + ``pid`` of the task for which the operation applies. + +arg4: + ``pid_type`` for which the operation applies. It is one of + ``PR_SCHED_CORE_SCOPE_``-prefixed macro constants. For example, if arg4 + is ``PR_SCHED_CORE_SCOPE_THREAD_GROUP``, then the operation of this command + will be performed for all tasks in the task group of ``pid``. + +arg5: + userspace pointer to an unsigned long for storing the cookie returned by + ``PR_SCHED_CORE_GET`` command. Should be 0 for all other commands. + +In order for a process to push a cookie to, or pull a cookie from a process, it +is required to have the ptrace access mode: `PTRACE_MODE_READ_REALCREDS` to the +process. + +Building hierarchies of tasks +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The simplest way to build hierarchies of threads/processes which share a +cookie and thus a core is to rely on the fact that the core-sched cookie is +inherited across forks/clones and execs, thus setting a cookie for the +'initial' script/executable/daemon will place every spawned child in the +same core-sched group. + +Cookie Transferral +~~~~~~~~~~~~~~~~~~ +Transferring a cookie between the current and other tasks is possible using +PR_SCHED_CORE_SHARE_FROM and PR_SCHED_CORE_SHARE_TO to inherit a cookie from a +specified task or a share a cookie with a task. In combination this allows a +simple helper program to pull a cookie from a task in an existing core +scheduling group and share it with already running tasks. + +Design/Implementation +--------------------- +Each task that is tagged is assigned a cookie internally in the kernel. As +mentioned in `Usage`_, tasks with the same cookie value are assumed to trust +each other and share a core. + +The basic idea is that, every schedule event tries to select tasks for all the +siblings of a core such that all the selected tasks running on a core are +trusted (same cookie) at any point in time. Kernel threads are assumed trusted. +The idle task is considered special, as it trusts everything and everything +trusts it. + +During a schedule() event on any sibling of a core, the highest priority task on +the sibling's core is picked and assigned to the sibling calling schedule(), if +the sibling has the task enqueued. For rest of the siblings in the core, +highest priority task with the same cookie is selected if there is one runnable +in their individual run queues. If a task with same cookie is not available, +the idle task is selected. Idle task is globally trusted. + +Once a task has been selected for all the siblings in the core, an IPI is sent to +siblings for whom a new task was selected. Siblings on receiving the IPI will +switch to the new task immediately. If an idle task is selected for a sibling, +then the sibling is considered to be in a `forced idle` state. I.e., it may +have tasks on its on runqueue to run, however it will still have to run idle. +More on this in the next section. + +Forced-idling of hyperthreads +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The scheduler tries its best to find tasks that trust each other such that all +tasks selected to be scheduled are of the highest priority in a core. However, +it is possible that some runqueues had tasks that were incompatible with the +highest priority ones in the core. Favoring security over fairness, one or more +siblings could be forced to select a lower priority task if the highest +priority task is not trusted with respect to the core wide highest priority +task. If a sibling does not have a trusted task to run, it will be forced idle +by the scheduler (idle thread is scheduled to run). + +When the highest priority task is selected to run, a reschedule-IPI is sent to +the sibling to force it into idle. This results in 4 cases which need to be +considered depending on whether a VM or a regular usermode process was running +on either HT:: + + HT1 (attack) HT2 (victim) + A idle -> user space user space -> idle + B idle -> user space guest -> idle + C idle -> guest user space -> idle + D idle -> guest guest -> idle + +Note that for better performance, we do not wait for the destination CPU +(victim) to enter idle mode. This is because the sending of the IPI would bring +the destination CPU immediately into kernel mode from user space, or VMEXIT +in the case of guests. At best, this would only leak some scheduler metadata +which may not be worth protecting. It is also possible that the IPI is received +too late on some architectures, but this has not been observed in the case of +x86. + +Trust model +~~~~~~~~~~~ +Core scheduling maintains trust relationships amongst groups of tasks by +assigning them a tag that is the same cookie value. +When a system with core scheduling boots, all tasks are considered to trust +each other. This is because the core scheduler does not have information about +trust relationships until userspace uses the above mentioned interfaces, to +communicate them. In other words, all tasks have a default cookie value of 0. +and are considered system-wide trusted. The forced-idling of siblings running +cookie-0 tasks is also avoided. + +Once userspace uses the above mentioned interfaces to group sets of tasks, tasks +within such groups are considered to trust each other, but do not trust those +outside. Tasks outside the group also don't trust tasks within. + +Limitations of core-scheduling +------------------------------ +Core scheduling tries to guarantee that only trusted tasks run concurrently on a +core. But there could be small window of time during which untrusted tasks run +concurrently or kernel could be running concurrently with a task not trusted by +kernel. + +IPI processing delays +~~~~~~~~~~~~~~~~~~~~~ +Core scheduling selects only trusted tasks to run together. IPI is used to notify +the siblings to switch to the new task. But there could be hardware delays in +receiving of the IPI on some arch (on x86, this has not been observed). This may +cause an attacker task to start running on a CPU before its siblings receive the +IPI. Even though cache is flushed on entry to user mode, victim tasks on siblings +may populate data in the cache and micro architectural buffers after the attacker +starts to run and this is a possibility for data leak. + +Open cross-HT issues that core scheduling does not solve +-------------------------------------------------------- +1. For MDS +~~~~~~~~~~ +Core scheduling cannot protect against MDS attacks between the siblings +running in user mode and the others running in kernel mode. Even though all +siblings run tasks which trust each other, when the kernel is executing +code on behalf of a task, it cannot trust the code running in the +sibling. Such attacks are possible for any combination of sibling CPU modes +(host or guest mode). + +2. For L1TF +~~~~~~~~~~~ +Core scheduling cannot protect against an L1TF guest attacker exploiting a +guest or host victim. This is because the guest attacker can craft invalid +PTEs which are not inverted due to a vulnerable guest kernel. The only +solution is to disable EPT (Extended Page Tables). + +For both MDS and L1TF, if the guest vCPU is configured to not trust each +other (by tagging separately), then the guest to guest attacks would go away. +Or it could be a system admin policy which considers guest to guest attacks as +a guest problem. + +Another approach to resolve these would be to make every untrusted task on the +system to not trust every other untrusted task. While this could reduce +parallelism of the untrusted tasks, it would still solve the above issues while +allowing system processes (trusted tasks) to share a core. + +3. Protecting the kernel (IRQ, syscall, VMEXIT) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Unfortunately, core scheduling does not protect kernel contexts running on +sibling hyperthreads from one another. Prototypes of mitigations have been posted +to LKML to solve this, but it is debatable whether such windows are practically +exploitable, and whether the performance overhead of the prototypes are worth +it (not to mention, the added code complexity). + +Other Use cases +--------------- +The main use case for Core scheduling is mitigating the cross-HT vulnerabilities +with SMT enabled. There are other use cases where this feature could be used: + +- Isolating tasks that needs a whole core: Examples include realtime tasks, tasks + that uses SIMD instructions etc. +- Gang scheduling: Requirements for a group of tasks that needs to be scheduled + together could also be realized using core scheduling. One example is vCPUs of + a VM. diff --git a/Documentation/admin-guide/hw-vuln/cross-thread-rsb.rst b/Documentation/admin-guide/hw-vuln/cross-thread-rsb.rst new file mode 100644 index 000000000..875616d67 --- /dev/null +++ b/Documentation/admin-guide/hw-vuln/cross-thread-rsb.rst @@ -0,0 +1,91 @@ + +.. SPDX-License-Identifier: GPL-2.0 + +Cross-Thread Return Address Predictions +======================================= + +Certain AMD and Hygon processors are subject to a cross-thread return address +predictions vulnerability. When running in SMT mode and one sibling thread +transitions out of C0 state, the other sibling thread could use return target +predictions from the sibling thread that transitioned out of C0. + +The Spectre v2 mitigations protect the Linux kernel, as it fills the return +address prediction entries with safe targets when context switching to the idle +thread. However, KVM does allow a VMM to prevent exiting guest mode when +transitioning out of C0. This could result in a guest-controlled return target +being consumed by the sibling thread. + +Affected processors +------------------- + +The following CPUs are vulnerable: + + - AMD Family 17h processors + - Hygon Family 18h processors + +Related CVEs +------------ + +The following CVE entry is related to this issue: + + ============== ======================================= + CVE-2022-27672 Cross-Thread Return Address Predictions + ============== ======================================= + +Problem +------- + +Affected SMT-capable processors support 1T and 2T modes of execution when SMT +is enabled. In 2T mode, both threads in a core are executing code. For the +processor core to enter 1T mode, it is required that one of the threads +requests to transition out of the C0 state. This can be communicated with the +HLT instruction or with an MWAIT instruction that requests non-C0. +When the thread re-enters the C0 state, the processor transitions back +to 2T mode, assuming the other thread is also still in C0 state. + +In affected processors, the return address predictor (RAP) is partitioned +depending on the SMT mode. For instance, in 2T mode each thread uses a private +16-entry RAP, but in 1T mode, the active thread uses a 32-entry RAP. Upon +transition between 1T/2T mode, the RAP contents are not modified but the RAP +pointers (which control the next return target to use for predictions) may +change. This behavior may result in return targets from one SMT thread being +used by RET predictions in the sibling thread following a 1T/2T switch. In +particular, a RET instruction executed immediately after a transition to 1T may +use a return target from the thread that just became idle. In theory, this +could lead to information disclosure if the return targets used do not come +from trustworthy code. + +Attack scenarios +---------------- + +An attack can be mounted on affected processors by performing a series of CALL +instructions with targeted return locations and then transitioning out of C0 +state. + +Mitigation mechanism +-------------------- + +Before entering idle state, the kernel context switches to the idle thread. The +context switch fills the RAP entries (referred to as the RSB in Linux) with safe +targets by performing a sequence of CALL instructions. + +Prevent a guest VM from directly putting the processor into an idle state by +intercepting HLT and MWAIT instructions. + +Both mitigations are required to fully address this issue. + +Mitigation control on the kernel command line +--------------------------------------------- + +Use existing Spectre v2 mitigations that will fill the RSB on context switch. + +Mitigation control for KVM - module parameter +--------------------------------------------- + +By default, the KVM hypervisor mitigates this issue by intercepting guest +attempts to transition out of C0. A VMM can use the KVM_CAP_X86_DISABLE_EXITS +capability to override those interceptions, but since this is not common, the +mitigation that covers this path is not enabled by default. + +The mitigation for the KVM_CAP_X86_DISABLE_EXITS capability can be turned on +using the boolean module parameter mitigate_smt_rsb, e.g. ``kvm.mitigate_smt_rsb=1``. diff --git a/Documentation/admin-guide/hw-vuln/gather_data_sampling.rst b/Documentation/admin-guide/hw-vuln/gather_data_sampling.rst new file mode 100644 index 000000000..264bfa937 --- /dev/null +++ b/Documentation/admin-guide/hw-vuln/gather_data_sampling.rst @@ -0,0 +1,109 @@ +.. SPDX-License-Identifier: GPL-2.0 + +GDS - Gather Data Sampling +========================== + +Gather Data Sampling is a hardware vulnerability which allows unprivileged +speculative access to data which was previously stored in vector registers. + +Problem +------- +When a gather instruction performs loads from memory, different data elements +are merged into the destination vector register. However, when a gather +instruction that is transiently executed encounters a fault, stale data from +architectural or internal vector registers may get transiently forwarded to the +destination vector register instead. This will allow a malicious attacker to +infer stale data using typical side channel techniques like cache timing +attacks. GDS is a purely sampling-based attack. + +The attacker uses gather instructions to infer the stale vector register data. +The victim does not need to do anything special other than use the vector +registers. The victim does not need to use gather instructions to be +vulnerable. + +Because the buffers are shared between Hyper-Threads cross Hyper-Thread attacks +are possible. + +Attack scenarios +---------------- +Without mitigation, GDS can infer stale data across virtually all +permission boundaries: + + Non-enclaves can infer SGX enclave data + Userspace can infer kernel data + Guests can infer data from hosts + Guest can infer guest from other guests + Users can infer data from other users + +Because of this, it is important to ensure that the mitigation stays enabled in +lower-privilege contexts like guests and when running outside SGX enclaves. + +The hardware enforces the mitigation for SGX. Likewise, VMMs should ensure +that guests are not allowed to disable the GDS mitigation. If a host erred and +allowed this, a guest could theoretically disable GDS mitigation, mount an +attack, and re-enable it. + +Mitigation mechanism +-------------------- +This issue is mitigated in microcode. The microcode defines the following new +bits: + + ================================ === ============================ + IA32_ARCH_CAPABILITIES[GDS_CTRL] R/O Enumerates GDS vulnerability + and mitigation support. + IA32_ARCH_CAPABILITIES[GDS_NO] R/O Processor is not vulnerable. + IA32_MCU_OPT_CTRL[GDS_MITG_DIS] R/W Disables the mitigation + 0 by default. + IA32_MCU_OPT_CTRL[GDS_MITG_LOCK] R/W Locks GDS_MITG_DIS=0. Writes + to GDS_MITG_DIS are ignored + Can't be cleared once set. + ================================ === ============================ + +GDS can also be mitigated on systems that don't have updated microcode by +disabling AVX. This can be done by setting gather_data_sampling="force" or +"clearcpuid=avx" on the kernel command-line. + +If used, these options will disable AVX use by turning off XSAVE YMM support. +However, the processor will still enumerate AVX support. Userspace that +does not follow proper AVX enumeration to check both AVX *and* XSAVE YMM +support will break. + +Mitigation control on the kernel command line +--------------------------------------------- +The mitigation can be disabled by setting "gather_data_sampling=off" or +"mitigations=off" on the kernel command line. Not specifying either will default +to the mitigation being enabled. Specifying "gather_data_sampling=force" will +use the microcode mitigation when available or disable AVX on affected systems +where the microcode hasn't been updated to include the mitigation. + +GDS System Information +------------------------ +The kernel provides vulnerability status information through sysfs. For +GDS this can be accessed by the following sysfs file: + +/sys/devices/system/cpu/vulnerabilities/gather_data_sampling + +The possible values contained in this file are: + + ============================== ============================================= + Not affected Processor not vulnerable. + Vulnerable Processor vulnerable and mitigation disabled. + Vulnerable: No microcode Processor vulnerable and microcode is missing + mitigation. + Mitigation: AVX disabled, + no microcode Processor is vulnerable and microcode is missing + mitigation. AVX disabled as mitigation. + Mitigation: Microcode Processor is vulnerable and mitigation is in + effect. + Mitigation: Microcode (locked) Processor is vulnerable and mitigation is in + effect and cannot be disabled. + Unknown: Dependent on + hypervisor status Running on a virtual guest processor that is + affected but with no way to know if host + processor is mitigated or vulnerable. + ============================== ============================================= + +GDS Default mitigation +---------------------- +The updated microcode will enable the mitigation by default. The kernel's +default action is to leave the mitigation enabled. diff --git a/Documentation/admin-guide/hw-vuln/index.rst b/Documentation/admin-guide/hw-vuln/index.rst new file mode 100644 index 000000000..de99caabf --- /dev/null +++ b/Documentation/admin-guide/hw-vuln/index.rst @@ -0,0 +1,23 @@ +======================== +Hardware vulnerabilities +======================== + +This section describes CPU vulnerabilities and provides an overview of the +possible mitigations along with guidance for selecting mitigations if they +are configurable at compile, boot or run time. + +.. toctree:: + :maxdepth: 1 + + spectre + l1tf + mds + tsx_async_abort + multihit + special-register-buffer-data-sampling + core-scheduling + l1d_flush + processor_mmio_stale_data + cross-thread-rsb + srso + gather_data_sampling diff --git a/Documentation/admin-guide/hw-vuln/l1d_flush.rst b/Documentation/admin-guide/hw-vuln/l1d_flush.rst new file mode 100644 index 000000000..210020bc3 --- /dev/null +++ b/Documentation/admin-guide/hw-vuln/l1d_flush.rst @@ -0,0 +1,69 @@ +L1D Flushing +============ + +With an increasing number of vulnerabilities being reported around data +leaks from the Level 1 Data cache (L1D) the kernel provides an opt-in +mechanism to flush the L1D cache on context switch. + +This mechanism can be used to address e.g. CVE-2020-0550. For applications +the mechanism keeps them safe from vulnerabilities, related to leaks +(snooping of) from the L1D cache. + + +Related CVEs +------------ +The following CVEs can be addressed by this +mechanism + + ============= ======================== ================== + CVE-2020-0550 Improper Data Forwarding OS related aspects + ============= ======================== ================== + +Usage Guidelines +---------------- + +Please see document: :ref:`Documentation/userspace-api/spec_ctrl.rst +<set_spec_ctrl>` for details. + +**NOTE**: The feature is disabled by default, applications need to +specifically opt into the feature to enable it. + +Mitigation +---------- + +When PR_SET_L1D_FLUSH is enabled for a task a flush of the L1D cache is +performed when the task is scheduled out and the incoming task belongs to a +different process and therefore to a different address space. + +If the underlying CPU supports L1D flushing in hardware, the hardware +mechanism is used, software fallback for the mitigation, is not supported. + +Mitigation control on the kernel command line +--------------------------------------------- + +The kernel command line allows to control the L1D flush mitigations at boot +time with the option "l1d_flush=". The valid arguments for this option are: + + ============ ============================================================= + on Enables the prctl interface, applications trying to use + the prctl() will fail with an error if l1d_flush is not + enabled + ============ ============================================================= + +By default the mechanism is disabled. + +Limitations +----------- + +The mechanism does not mitigate L1D data leaks between tasks belonging to +different processes which are concurrently executing on sibling threads of +a physical CPU core when SMT is enabled on the system. + +This can be addressed by controlled placement of processes on physical CPU +cores or by disabling SMT. See the relevant chapter in the L1TF mitigation +document: :ref:`Documentation/admin-guide/hw-vuln/l1tf.rst <smt_control>`. + +**NOTE** : The opt-in of a task for L1D flushing works only when the task's +affinity is limited to cores running in non-SMT mode. If a task which +requested L1D flushing is scheduled on a SMT-enabled core the kernel sends +a SIGBUS to the task. diff --git a/Documentation/admin-guide/hw-vuln/l1tf.rst b/Documentation/admin-guide/hw-vuln/l1tf.rst new file mode 100644 index 000000000..3eeeb488d --- /dev/null +++ b/Documentation/admin-guide/hw-vuln/l1tf.rst @@ -0,0 +1,615 @@ +L1TF - L1 Terminal Fault +======================== + +L1 Terminal Fault is a hardware vulnerability which allows unprivileged +speculative access to data which is available in the Level 1 Data Cache +when the page table entry controlling the virtual address, which is used +for the access, has the Present bit cleared or other reserved bits set. + +Affected processors +------------------- + +This vulnerability affects a wide range of Intel processors. The +vulnerability is not present on: + + - Processors from AMD, Centaur and other non Intel vendors + + - Older processor models, where the CPU family is < 6 + + - A range of Intel ATOM processors (Cedarview, Cloverview, Lincroft, + Penwell, Pineview, Silvermont, Airmont, Merrifield) + + - The Intel XEON PHI family + + - Intel processors which have the ARCH_CAP_RDCL_NO bit set in the + IA32_ARCH_CAPABILITIES MSR. If the bit is set the CPU is not affected + by the Meltdown vulnerability either. These CPUs should become + available by end of 2018. + +Whether a processor is affected or not can be read out from the L1TF +vulnerability file in sysfs. See :ref:`l1tf_sys_info`. + +Related CVEs +------------ + +The following CVE entries are related to the L1TF vulnerability: + + ============= ================= ============================== + CVE-2018-3615 L1 Terminal Fault SGX related aspects + CVE-2018-3620 L1 Terminal Fault OS, SMM related aspects + CVE-2018-3646 L1 Terminal Fault Virtualization related aspects + ============= ================= ============================== + +Problem +------- + +If an instruction accesses a virtual address for which the relevant page +table entry (PTE) has the Present bit cleared or other reserved bits set, +then speculative execution ignores the invalid PTE and loads the referenced +data if it is present in the Level 1 Data Cache, as if the page referenced +by the address bits in the PTE was still present and accessible. + +While this is a purely speculative mechanism and the instruction will raise +a page fault when it is retired eventually, the pure act of loading the +data and making it available to other speculative instructions opens up the +opportunity for side channel attacks to unprivileged malicious code, +similar to the Meltdown attack. + +While Meltdown breaks the user space to kernel space protection, L1TF +allows to attack any physical memory address in the system and the attack +works across all protection domains. It allows an attack of SGX and also +works from inside virtual machines because the speculation bypasses the +extended page table (EPT) protection mechanism. + + +Attack scenarios +---------------- + +1. Malicious user space +^^^^^^^^^^^^^^^^^^^^^^^ + + Operating Systems store arbitrary information in the address bits of a + PTE which is marked non present. This allows a malicious user space + application to attack the physical memory to which these PTEs resolve. + In some cases user-space can maliciously influence the information + encoded in the address bits of the PTE, thus making attacks more + deterministic and more practical. + + The Linux kernel contains a mitigation for this attack vector, PTE + inversion, which is permanently enabled and has no performance + impact. The kernel ensures that the address bits of PTEs, which are not + marked present, never point to cacheable physical memory space. + + A system with an up to date kernel is protected against attacks from + malicious user space applications. + +2. Malicious guest in a virtual machine +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + The fact that L1TF breaks all domain protections allows malicious guest + OSes, which can control the PTEs directly, and malicious guest user + space applications, which run on an unprotected guest kernel lacking the + PTE inversion mitigation for L1TF, to attack physical host memory. + + A special aspect of L1TF in the context of virtualization is symmetric + multi threading (SMT). The Intel implementation of SMT is called + HyperThreading. The fact that Hyperthreads on the affected processors + share the L1 Data Cache (L1D) is important for this. As the flaw allows + only to attack data which is present in L1D, a malicious guest running + on one Hyperthread can attack the data which is brought into the L1D by + the context which runs on the sibling Hyperthread of the same physical + core. This context can be host OS, host user space or a different guest. + + If the processor does not support Extended Page Tables, the attack is + only possible, when the hypervisor does not sanitize the content of the + effective (shadow) page tables. + + While solutions exist to mitigate these attack vectors fully, these + mitigations are not enabled by default in the Linux kernel because they + can affect performance significantly. The kernel provides several + mechanisms which can be utilized to address the problem depending on the + deployment scenario. The mitigations, their protection scope and impact + are described in the next sections. + + The default mitigations and the rationale for choosing them are explained + at the end of this document. See :ref:`default_mitigations`. + +.. _l1tf_sys_info: + +L1TF system information +----------------------- + +The Linux kernel provides a sysfs interface to enumerate the current L1TF +status of the system: whether the system is vulnerable, and which +mitigations are active. The relevant sysfs file is: + +/sys/devices/system/cpu/vulnerabilities/l1tf + +The possible values in this file are: + + =========================== =============================== + 'Not affected' The processor is not vulnerable + 'Mitigation: PTE Inversion' The host protection is active + =========================== =============================== + +If KVM/VMX is enabled and the processor is vulnerable then the following +information is appended to the 'Mitigation: PTE Inversion' part: + + - SMT status: + + ===================== ================ + 'VMX: SMT vulnerable' SMT is enabled + 'VMX: SMT disabled' SMT is disabled + ===================== ================ + + - L1D Flush mode: + + ================================ ==================================== + 'L1D vulnerable' L1D flushing is disabled + + 'L1D conditional cache flushes' L1D flush is conditionally enabled + + 'L1D cache flushes' L1D flush is unconditionally enabled + ================================ ==================================== + +The resulting grade of protection is discussed in the following sections. + + +Host mitigation mechanism +------------------------- + +The kernel is unconditionally protected against L1TF attacks from malicious +user space running on the host. + + +Guest mitigation mechanisms +--------------------------- + +.. _l1d_flush: + +1. L1D flush on VMENTER +^^^^^^^^^^^^^^^^^^^^^^^ + + To make sure that a guest cannot attack data which is present in the L1D + the hypervisor flushes the L1D before entering the guest. + + Flushing the L1D evicts not only the data which should not be accessed + by a potentially malicious guest, it also flushes the guest + data. Flushing the L1D has a performance impact as the processor has to + bring the flushed guest data back into the L1D. Depending on the + frequency of VMEXIT/VMENTER and the type of computations in the guest + performance degradation in the range of 1% to 50% has been observed. For + scenarios where guest VMEXIT/VMENTER are rare the performance impact is + minimal. Virtio and mechanisms like posted interrupts are designed to + confine the VMEXITs to a bare minimum, but specific configurations and + application scenarios might still suffer from a high VMEXIT rate. + + The kernel provides two L1D flush modes: + - conditional ('cond') + - unconditional ('always') + + The conditional mode avoids L1D flushing after VMEXITs which execute + only audited code paths before the corresponding VMENTER. These code + paths have been verified that they cannot expose secrets or other + interesting data to an attacker, but they can leak information about the + address space layout of the hypervisor. + + Unconditional mode flushes L1D on all VMENTER invocations and provides + maximum protection. It has a higher overhead than the conditional + mode. The overhead cannot be quantified correctly as it depends on the + workload scenario and the resulting number of VMEXITs. + + The general recommendation is to enable L1D flush on VMENTER. The kernel + defaults to conditional mode on affected processors. + + **Note**, that L1D flush does not prevent the SMT problem because the + sibling thread will also bring back its data into the L1D which makes it + attackable again. + + L1D flush can be controlled by the administrator via the kernel command + line and sysfs control files. See :ref:`mitigation_control_command_line` + and :ref:`mitigation_control_kvm`. + +.. _guest_confinement: + +2. Guest VCPU confinement to dedicated physical cores +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + To address the SMT problem, it is possible to make a guest or a group of + guests affine to one or more physical cores. The proper mechanism for + that is to utilize exclusive cpusets to ensure that no other guest or + host tasks can run on these cores. + + If only a single guest or related guests run on sibling SMT threads on + the same physical core then they can only attack their own memory and + restricted parts of the host memory. + + Host memory is attackable, when one of the sibling SMT threads runs in + host OS (hypervisor) context and the other in guest context. The amount + of valuable information from the host OS context depends on the context + which the host OS executes, i.e. interrupts, soft interrupts and kernel + threads. The amount of valuable data from these contexts cannot be + declared as non-interesting for an attacker without deep inspection of + the code. + + **Note**, that assigning guests to a fixed set of physical cores affects + the ability of the scheduler to do load balancing and might have + negative effects on CPU utilization depending on the hosting + scenario. Disabling SMT might be a viable alternative for particular + scenarios. + + For further information about confining guests to a single or to a group + of cores consult the cpusets documentation: + + https://www.kernel.org/doc/Documentation/admin-guide/cgroup-v1/cpusets.rst + +.. _interrupt_isolation: + +3. Interrupt affinity +^^^^^^^^^^^^^^^^^^^^^ + + Interrupts can be made affine to logical CPUs. This is not universally + true because there are types of interrupts which are truly per CPU + interrupts, e.g. the local timer interrupt. Aside of that multi queue + devices affine their interrupts to single CPUs or groups of CPUs per + queue without allowing the administrator to control the affinities. + + Moving the interrupts, which can be affinity controlled, away from CPUs + which run untrusted guests, reduces the attack vector space. + + Whether the interrupts with are affine to CPUs, which run untrusted + guests, provide interesting data for an attacker depends on the system + configuration and the scenarios which run on the system. While for some + of the interrupts it can be assumed that they won't expose interesting + information beyond exposing hints about the host OS memory layout, there + is no way to make general assumptions. + + Interrupt affinity can be controlled by the administrator via the + /proc/irq/$NR/smp_affinity[_list] files. Limited documentation is + available at: + + https://www.kernel.org/doc/Documentation/core-api/irq/irq-affinity.rst + +.. _smt_control: + +4. SMT control +^^^^^^^^^^^^^^ + + To prevent the SMT issues of L1TF it might be necessary to disable SMT + completely. Disabling SMT can have a significant performance impact, but + the impact depends on the hosting scenario and the type of workloads. + The impact of disabling SMT needs also to be weighted against the impact + of other mitigation solutions like confining guests to dedicated cores. + + The kernel provides a sysfs interface to retrieve the status of SMT and + to control it. It also provides a kernel command line interface to + control SMT. + + The kernel command line interface consists of the following options: + + =========== ========================================================== + nosmt Affects the bring up of the secondary CPUs during boot. The + kernel tries to bring all present CPUs online during the + boot process. "nosmt" makes sure that from each physical + core only one - the so called primary (hyper) thread is + activated. Due to a design flaw of Intel processors related + to Machine Check Exceptions the non primary siblings have + to be brought up at least partially and are then shut down + again. "nosmt" can be undone via the sysfs interface. + + nosmt=force Has the same effect as "nosmt" but it does not allow to + undo the SMT disable via the sysfs interface. + =========== ========================================================== + + The sysfs interface provides two files: + + - /sys/devices/system/cpu/smt/control + - /sys/devices/system/cpu/smt/active + + /sys/devices/system/cpu/smt/control: + + This file allows to read out the SMT control state and provides the + ability to disable or (re)enable SMT. The possible states are: + + ============== =================================================== + on SMT is supported by the CPU and enabled. All + logical CPUs can be onlined and offlined without + restrictions. + + off SMT is supported by the CPU and disabled. Only + the so called primary SMT threads can be onlined + and offlined without restrictions. An attempt to + online a non-primary sibling is rejected + + forceoff Same as 'off' but the state cannot be controlled. + Attempts to write to the control file are rejected. + + notsupported The processor does not support SMT. It's therefore + not affected by the SMT implications of L1TF. + Attempts to write to the control file are rejected. + ============== =================================================== + + The possible states which can be written into this file to control SMT + state are: + + - on + - off + - forceoff + + /sys/devices/system/cpu/smt/active: + + This file reports whether SMT is enabled and active, i.e. if on any + physical core two or more sibling threads are online. + + SMT control is also possible at boot time via the l1tf kernel command + line parameter in combination with L1D flush control. See + :ref:`mitigation_control_command_line`. + +5. Disabling EPT +^^^^^^^^^^^^^^^^ + + Disabling EPT for virtual machines provides full mitigation for L1TF even + with SMT enabled, because the effective page tables for guests are + managed and sanitized by the hypervisor. Though disabling EPT has a + significant performance impact especially when the Meltdown mitigation + KPTI is enabled. + + EPT can be disabled in the hypervisor via the 'kvm-intel.ept' parameter. + +There is ongoing research and development for new mitigation mechanisms to +address the performance impact of disabling SMT or EPT. + +.. _mitigation_control_command_line: + +Mitigation control on the kernel command line +--------------------------------------------- + +The kernel command line allows to control the L1TF mitigations at boot +time with the option "l1tf=". The valid arguments for this option are: + + ============ ============================================================= + full Provides all available mitigations for the L1TF + vulnerability. Disables SMT and enables all mitigations in + the hypervisors, i.e. unconditional L1D flushing + + SMT control and L1D flush control via the sysfs interface + is still possible after boot. Hypervisors will issue a + warning when the first VM is started in a potentially + insecure configuration, i.e. SMT enabled or L1D flush + disabled. + + full,force Same as 'full', but disables SMT and L1D flush runtime + control. Implies the 'nosmt=force' command line option. + (i.e. sysfs control of SMT is disabled.) + + flush Leaves SMT enabled and enables the default hypervisor + mitigation, i.e. conditional L1D flushing + + SMT control and L1D flush control via the sysfs interface + is still possible after boot. Hypervisors will issue a + warning when the first VM is started in a potentially + insecure configuration, i.e. SMT enabled or L1D flush + disabled. + + flush,nosmt Disables SMT and enables the default hypervisor mitigation, + i.e. conditional L1D flushing. + + SMT control and L1D flush control via the sysfs interface + is still possible after boot. Hypervisors will issue a + warning when the first VM is started in a potentially + insecure configuration, i.e. SMT enabled or L1D flush + disabled. + + flush,nowarn Same as 'flush', but hypervisors will not warn when a VM is + started in a potentially insecure configuration. + + off Disables hypervisor mitigations and doesn't emit any + warnings. + It also drops the swap size and available RAM limit restrictions + on both hypervisor and bare metal. + + ============ ============================================================= + +The default is 'flush'. For details about L1D flushing see :ref:`l1d_flush`. + + +.. _mitigation_control_kvm: + +Mitigation control for KVM - module parameter +------------------------------------------------------------- + +The KVM hypervisor mitigation mechanism, flushing the L1D cache when +entering a guest, can be controlled with a module parameter. + +The option/parameter is "kvm-intel.vmentry_l1d_flush=". It takes the +following arguments: + + ============ ============================================================== + always L1D cache flush on every VMENTER. + + cond Flush L1D on VMENTER only when the code between VMEXIT and + VMENTER can leak host memory which is considered + interesting for an attacker. This still can leak host memory + which allows e.g. to determine the hosts address space layout. + + never Disables the mitigation + ============ ============================================================== + +The parameter can be provided on the kernel command line, as a module +parameter when loading the modules and at runtime modified via the sysfs +file: + +/sys/module/kvm_intel/parameters/vmentry_l1d_flush + +The default is 'cond'. If 'l1tf=full,force' is given on the kernel command +line, then 'always' is enforced and the kvm-intel.vmentry_l1d_flush +module parameter is ignored and writes to the sysfs file are rejected. + +.. _mitigation_selection: + +Mitigation selection guide +-------------------------- + +1. No virtualization in use +^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + The system is protected by the kernel unconditionally and no further + action is required. + +2. Virtualization with trusted guests +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + If the guest comes from a trusted source and the guest OS kernel is + guaranteed to have the L1TF mitigations in place the system is fully + protected against L1TF and no further action is required. + + To avoid the overhead of the default L1D flushing on VMENTER the + administrator can disable the flushing via the kernel command line and + sysfs control files. See :ref:`mitigation_control_command_line` and + :ref:`mitigation_control_kvm`. + + +3. Virtualization with untrusted guests +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +3.1. SMT not supported or disabled +"""""""""""""""""""""""""""""""""" + + If SMT is not supported by the processor or disabled in the BIOS or by + the kernel, it's only required to enforce L1D flushing on VMENTER. + + Conditional L1D flushing is the default behaviour and can be tuned. See + :ref:`mitigation_control_command_line` and :ref:`mitigation_control_kvm`. + +3.2. EPT not supported or disabled +"""""""""""""""""""""""""""""""""" + + If EPT is not supported by the processor or disabled in the hypervisor, + the system is fully protected. SMT can stay enabled and L1D flushing on + VMENTER is not required. + + EPT can be disabled in the hypervisor via the 'kvm-intel.ept' parameter. + +3.3. SMT and EPT supported and active +""""""""""""""""""""""""""""""""""""" + + If SMT and EPT are supported and active then various degrees of + mitigations can be employed: + + - L1D flushing on VMENTER: + + L1D flushing on VMENTER is the minimal protection requirement, but it + is only potent in combination with other mitigation methods. + + Conditional L1D flushing is the default behaviour and can be tuned. See + :ref:`mitigation_control_command_line` and :ref:`mitigation_control_kvm`. + + - Guest confinement: + + Confinement of guests to a single or a group of physical cores which + are not running any other processes, can reduce the attack surface + significantly, but interrupts, soft interrupts and kernel threads can + still expose valuable data to a potential attacker. See + :ref:`guest_confinement`. + + - Interrupt isolation: + + Isolating the guest CPUs from interrupts can reduce the attack surface + further, but still allows a malicious guest to explore a limited amount + of host physical memory. This can at least be used to gain knowledge + about the host address space layout. The interrupts which have a fixed + affinity to the CPUs which run the untrusted guests can depending on + the scenario still trigger soft interrupts and schedule kernel threads + which might expose valuable information. See + :ref:`interrupt_isolation`. + +The above three mitigation methods combined can provide protection to a +certain degree, but the risk of the remaining attack surface has to be +carefully analyzed. For full protection the following methods are +available: + + - Disabling SMT: + + Disabling SMT and enforcing the L1D flushing provides the maximum + amount of protection. This mitigation is not depending on any of the + above mitigation methods. + + SMT control and L1D flushing can be tuned by the command line + parameters 'nosmt', 'l1tf', 'kvm-intel.vmentry_l1d_flush' and at run + time with the matching sysfs control files. See :ref:`smt_control`, + :ref:`mitigation_control_command_line` and + :ref:`mitigation_control_kvm`. + + - Disabling EPT: + + Disabling EPT provides the maximum amount of protection as well. It is + not depending on any of the above mitigation methods. SMT can stay + enabled and L1D flushing is not required, but the performance impact is + significant. + + EPT can be disabled in the hypervisor via the 'kvm-intel.ept' + parameter. + +3.4. Nested virtual machines +"""""""""""""""""""""""""""" + +When nested virtualization is in use, three operating systems are involved: +the bare metal hypervisor, the nested hypervisor and the nested virtual +machine. VMENTER operations from the nested hypervisor into the nested +guest will always be processed by the bare metal hypervisor. If KVM is the +bare metal hypervisor it will: + + - Flush the L1D cache on every switch from the nested hypervisor to the + nested virtual machine, so that the nested hypervisor's secrets are not + exposed to the nested virtual machine; + + - Flush the L1D cache on every switch from the nested virtual machine to + the nested hypervisor; this is a complex operation, and flushing the L1D + cache avoids that the bare metal hypervisor's secrets are exposed to the + nested virtual machine; + + - Instruct the nested hypervisor to not perform any L1D cache flush. This + is an optimization to avoid double L1D flushing. + + +.. _default_mitigations: + +Default mitigations +------------------- + + The kernel default mitigations for vulnerable processors are: + + - PTE inversion to protect against malicious user space. This is done + unconditionally and cannot be controlled. The swap storage is limited + to ~16TB. + + - L1D conditional flushing on VMENTER when EPT is enabled for + a guest. + + The kernel does not by default enforce the disabling of SMT, which leaves + SMT systems vulnerable when running untrusted guests with EPT enabled. + + The rationale for this choice is: + + - Force disabling SMT can break existing setups, especially with + unattended updates. + + - If regular users run untrusted guests on their machine, then L1TF is + just an add on to other malware which might be embedded in an untrusted + guest, e.g. spam-bots or attacks on the local network. + + There is no technical way to prevent a user from running untrusted code + on their machines blindly. + + - It's technically extremely unlikely and from today's knowledge even + impossible that L1TF can be exploited via the most popular attack + mechanisms like JavaScript because these mechanisms have no way to + control PTEs. If this would be possible and not other mitigation would + be possible, then the default might be different. + + - The administrators of cloud and hosting setups have to carefully + analyze the risk for their scenarios and make the appropriate + mitigation choices, which might even vary across their deployed + machines and also result in other changes of their overall setup. + There is no way for the kernel to provide a sensible default for this + kind of scenarios. diff --git a/Documentation/admin-guide/hw-vuln/mds.rst b/Documentation/admin-guide/hw-vuln/mds.rst new file mode 100644 index 000000000..48ca0bd85 --- /dev/null +++ b/Documentation/admin-guide/hw-vuln/mds.rst @@ -0,0 +1,311 @@ +MDS - Microarchitectural Data Sampling +====================================== + +Microarchitectural Data Sampling is a hardware vulnerability which allows +unprivileged speculative access to data which is available in various CPU +internal buffers. + +Affected processors +------------------- + +This vulnerability affects a wide range of Intel processors. The +vulnerability is not present on: + + - Processors from AMD, Centaur and other non Intel vendors + + - Older processor models, where the CPU family is < 6 + + - Some Atoms (Bonnell, Saltwell, Goldmont, GoldmontPlus) + + - Intel processors which have the ARCH_CAP_MDS_NO bit set in the + IA32_ARCH_CAPABILITIES MSR. + +Whether a processor is affected or not can be read out from the MDS +vulnerability file in sysfs. See :ref:`mds_sys_info`. + +Not all processors are affected by all variants of MDS, but the mitigation +is identical for all of them so the kernel treats them as a single +vulnerability. + +Related CVEs +------------ + +The following CVE entries are related to the MDS vulnerability: + + ============== ===== =================================================== + CVE-2018-12126 MSBDS Microarchitectural Store Buffer Data Sampling + CVE-2018-12130 MFBDS Microarchitectural Fill Buffer Data Sampling + CVE-2018-12127 MLPDS Microarchitectural Load Port Data Sampling + CVE-2019-11091 MDSUM Microarchitectural Data Sampling Uncacheable Memory + ============== ===== =================================================== + +Problem +------- + +When performing store, load, L1 refill operations, processors write data +into temporary microarchitectural structures (buffers). The data in the +buffer can be forwarded to load operations as an optimization. + +Under certain conditions, usually a fault/assist caused by a load +operation, data unrelated to the load memory address can be speculatively +forwarded from the buffers. Because the load operation causes a fault or +assist and its result will be discarded, the forwarded data will not cause +incorrect program execution or state changes. But a malicious operation +may be able to forward this speculative data to a disclosure gadget which +allows in turn to infer the value via a cache side channel attack. + +Because the buffers are potentially shared between Hyper-Threads cross +Hyper-Thread attacks are possible. + +Deeper technical information is available in the MDS specific x86 +architecture section: :ref:`Documentation/arch/x86/mds.rst <mds>`. + + +Attack scenarios +---------------- + +Attacks against the MDS vulnerabilities can be mounted from malicious non- +privileged user space applications running on hosts or guest. Malicious +guest OSes can obviously mount attacks as well. + +Contrary to other speculation based vulnerabilities the MDS vulnerability +does not allow the attacker to control the memory target address. As a +consequence the attacks are purely sampling based, but as demonstrated with +the TLBleed attack samples can be postprocessed successfully. + +Web-Browsers +^^^^^^^^^^^^ + + It's unclear whether attacks through Web-Browsers are possible at + all. The exploitation through Java-Script is considered very unlikely, + but other widely used web technologies like Webassembly could possibly be + abused. + + +.. _mds_sys_info: + +MDS system information +----------------------- + +The Linux kernel provides a sysfs interface to enumerate the current MDS +status of the system: whether the system is vulnerable, and which +mitigations are active. The relevant sysfs file is: + +/sys/devices/system/cpu/vulnerabilities/mds + +The possible values in this file are: + + .. list-table:: + + * - 'Not affected' + - The processor is not vulnerable + * - 'Vulnerable' + - The processor is vulnerable, but no mitigation enabled + * - 'Vulnerable: Clear CPU buffers attempted, no microcode' + - The processor is vulnerable but microcode is not updated. + + The mitigation is enabled on a best effort basis. See :ref:`vmwerv` + * - 'Mitigation: Clear CPU buffers' + - The processor is vulnerable and the CPU buffer clearing mitigation is + enabled. + +If the processor is vulnerable then the following information is appended +to the above information: + + ======================== ============================================ + 'SMT vulnerable' SMT is enabled + 'SMT mitigated' SMT is enabled and mitigated + 'SMT disabled' SMT is disabled + 'SMT Host state unknown' Kernel runs in a VM, Host SMT state unknown + ======================== ============================================ + +.. _vmwerv: + +Best effort mitigation mode +^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + If the processor is vulnerable, but the availability of the microcode based + mitigation mechanism is not advertised via CPUID the kernel selects a best + effort mitigation mode. This mode invokes the mitigation instructions + without a guarantee that they clear the CPU buffers. + + This is done to address virtualization scenarios where the host has the + microcode update applied, but the hypervisor is not yet updated to expose + the CPUID to the guest. If the host has updated microcode the protection + takes effect otherwise a few cpu cycles are wasted pointlessly. + + The state in the mds sysfs file reflects this situation accordingly. + + +Mitigation mechanism +------------------------- + +The kernel detects the affected CPUs and the presence of the microcode +which is required. + +If a CPU is affected and the microcode is available, then the kernel +enables the mitigation by default. The mitigation can be controlled at boot +time via a kernel command line option. See +:ref:`mds_mitigation_control_command_line`. + +.. _cpu_buffer_clear: + +CPU buffer clearing +^^^^^^^^^^^^^^^^^^^ + + The mitigation for MDS clears the affected CPU buffers on return to user + space and when entering a guest. + + If SMT is enabled it also clears the buffers on idle entry when the CPU + is only affected by MSBDS and not any other MDS variant, because the + other variants cannot be protected against cross Hyper-Thread attacks. + + For CPUs which are only affected by MSBDS the user space, guest and idle + transition mitigations are sufficient and SMT is not affected. + +.. _virt_mechanism: + +Virtualization mitigation +^^^^^^^^^^^^^^^^^^^^^^^^^ + + The protection for host to guest transition depends on the L1TF + vulnerability of the CPU: + + - CPU is affected by L1TF: + + If the L1D flush mitigation is enabled and up to date microcode is + available, the L1D flush mitigation is automatically protecting the + guest transition. + + If the L1D flush mitigation is disabled then the MDS mitigation is + invoked explicit when the host MDS mitigation is enabled. + + For details on L1TF and virtualization see: + :ref:`Documentation/admin-guide/hw-vuln//l1tf.rst <mitigation_control_kvm>`. + + - CPU is not affected by L1TF: + + CPU buffers are flushed before entering the guest when the host MDS + mitigation is enabled. + + The resulting MDS protection matrix for the host to guest transition: + + ============ ===== ============= ============ ================= + L1TF MDS VMX-L1FLUSH Host MDS MDS-State + + Don't care No Don't care N/A Not affected + + Yes Yes Disabled Off Vulnerable + + Yes Yes Disabled Full Mitigated + + Yes Yes Enabled Don't care Mitigated + + No Yes N/A Off Vulnerable + + No Yes N/A Full Mitigated + ============ ===== ============= ============ ================= + + This only covers the host to guest transition, i.e. prevents leakage from + host to guest, but does not protect the guest internally. Guests need to + have their own protections. + +.. _xeon_phi: + +XEON PHI specific considerations +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + The XEON PHI processor family is affected by MSBDS which can be exploited + cross Hyper-Threads when entering idle states. Some XEON PHI variants allow + to use MWAIT in user space (Ring 3) which opens an potential attack vector + for malicious user space. The exposure can be disabled on the kernel + command line with the 'ring3mwait=disable' command line option. + + XEON PHI is not affected by the other MDS variants and MSBDS is mitigated + before the CPU enters a idle state. As XEON PHI is not affected by L1TF + either disabling SMT is not required for full protection. + +.. _mds_smt_control: + +SMT control +^^^^^^^^^^^ + + All MDS variants except MSBDS can be attacked cross Hyper-Threads. That + means on CPUs which are affected by MFBDS or MLPDS it is necessary to + disable SMT for full protection. These are most of the affected CPUs; the + exception is XEON PHI, see :ref:`xeon_phi`. + + Disabling SMT can have a significant performance impact, but the impact + depends on the type of workloads. + + See the relevant chapter in the L1TF mitigation documentation for details: + :ref:`Documentation/admin-guide/hw-vuln/l1tf.rst <smt_control>`. + + +.. _mds_mitigation_control_command_line: + +Mitigation control on the kernel command line +--------------------------------------------- + +The kernel command line allows to control the MDS mitigations at boot +time with the option "mds=". The valid arguments for this option are: + + ============ ============================================================= + full If the CPU is vulnerable, enable all available mitigations + for the MDS vulnerability, CPU buffer clearing on exit to + userspace and when entering a VM. Idle transitions are + protected as well if SMT is enabled. + + It does not automatically disable SMT. + + full,nosmt The same as mds=full, with SMT disabled on vulnerable + CPUs. This is the complete mitigation. + + off Disables MDS mitigations completely. + + ============ ============================================================= + +Not specifying this option is equivalent to "mds=full". For processors +that are affected by both TAA (TSX Asynchronous Abort) and MDS, +specifying just "mds=off" without an accompanying "tsx_async_abort=off" +will have no effect as the same mitigation is used for both +vulnerabilities. + +Mitigation selection guide +-------------------------- + +1. Trusted userspace +^^^^^^^^^^^^^^^^^^^^ + + If all userspace applications are from a trusted source and do not + execute untrusted code which is supplied externally, then the mitigation + can be disabled. + + +2. Virtualization with trusted guests +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + The same considerations as above versus trusted user space apply. + +3. Virtualization with untrusted guests +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + The protection depends on the state of the L1TF mitigations. + See :ref:`virt_mechanism`. + + If the MDS mitigation is enabled and SMT is disabled, guest to host and + guest to guest attacks are prevented. + +.. _mds_default_mitigations: + +Default mitigations +------------------- + + The kernel default mitigations for vulnerable processors are: + + - Enable CPU buffer clearing + + The kernel does not by default enforce the disabling of SMT, which leaves + SMT systems vulnerable when running untrusted code. The same rationale as + for L1TF applies. + See :ref:`Documentation/admin-guide/hw-vuln//l1tf.rst <default_mitigations>`. diff --git a/Documentation/admin-guide/hw-vuln/multihit.rst b/Documentation/admin-guide/hw-vuln/multihit.rst new file mode 100644 index 000000000..140e4cec3 --- /dev/null +++ b/Documentation/admin-guide/hw-vuln/multihit.rst @@ -0,0 +1,167 @@ +iTLB multihit +============= + +iTLB multihit is an erratum where some processors may incur a machine check +error, possibly resulting in an unrecoverable CPU lockup, when an +instruction fetch hits multiple entries in the instruction TLB. This can +occur when the page size is changed along with either the physical address +or cache type. A malicious guest running on a virtualized system can +exploit this erratum to perform a denial of service attack. + + +Affected processors +------------------- + +Variations of this erratum are present on most Intel Core and Xeon processor +models. The erratum is not present on: + + - non-Intel processors + + - Some Atoms (Airmont, Bonnell, Goldmont, GoldmontPlus, Saltwell, Silvermont) + + - Intel processors that have the PSCHANGE_MC_NO bit set in the + IA32_ARCH_CAPABILITIES MSR. + + +Related CVEs +------------ + +The following CVE entry is related to this issue: + + ============== ================================================= + CVE-2018-12207 Machine Check Error Avoidance on Page Size Change + ============== ================================================= + + +Problem +------- + +Privileged software, including OS and virtual machine managers (VMM), are in +charge of memory management. A key component in memory management is the control +of the page tables. Modern processors use virtual memory, a technique that creates +the illusion of a very large memory for processors. This virtual space is split +into pages of a given size. Page tables translate virtual addresses to physical +addresses. + +To reduce latency when performing a virtual to physical address translation, +processors include a structure, called TLB, that caches recent translations. +There are separate TLBs for instruction (iTLB) and data (dTLB). + +Under this errata, instructions are fetched from a linear address translated +using a 4 KB translation cached in the iTLB. Privileged software modifies the +paging structure so that the same linear address using large page size (2 MB, 4 +MB, 1 GB) with a different physical address or memory type. After the page +structure modification but before the software invalidates any iTLB entries for +the linear address, a code fetch that happens on the same linear address may +cause a machine-check error which can result in a system hang or shutdown. + + +Attack scenarios +---------------- + +Attacks against the iTLB multihit erratum can be mounted from malicious +guests in a virtualized system. + + +iTLB multihit system information +-------------------------------- + +The Linux kernel provides a sysfs interface to enumerate the current iTLB +multihit status of the system:whether the system is vulnerable and which +mitigations are active. The relevant sysfs file is: + +/sys/devices/system/cpu/vulnerabilities/itlb_multihit + +The possible values in this file are: + +.. list-table:: + + * - Not affected + - The processor is not vulnerable. + * - KVM: Mitigation: Split huge pages + - Software changes mitigate this issue. + * - KVM: Mitigation: VMX unsupported + - KVM is not vulnerable because Virtual Machine Extensions (VMX) is not supported. + * - KVM: Mitigation: VMX disabled + - KVM is not vulnerable because Virtual Machine Extensions (VMX) is disabled. + * - KVM: Vulnerable + - The processor is vulnerable, but no mitigation enabled + + +Enumeration of the erratum +-------------------------------- + +A new bit has been allocated in the IA32_ARCH_CAPABILITIES (PSCHANGE_MC_NO) msr +and will be set on CPU's which are mitigated against this issue. + + ======================================= =========== =============================== + IA32_ARCH_CAPABILITIES MSR Not present Possibly vulnerable,check model + IA32_ARCH_CAPABILITIES[PSCHANGE_MC_NO] '0' Likely vulnerable,check model + IA32_ARCH_CAPABILITIES[PSCHANGE_MC_NO] '1' Not vulnerable + ======================================= =========== =============================== + + +Mitigation mechanism +------------------------- + +This erratum can be mitigated by restricting the use of large page sizes to +non-executable pages. This forces all iTLB entries to be 4K, and removes +the possibility of multiple hits. + +In order to mitigate the vulnerability, KVM initially marks all huge pages +as non-executable. If the guest attempts to execute in one of those pages, +the page is broken down into 4K pages, which are then marked executable. + +If EPT is disabled or not available on the host, KVM is in control of TLB +flushes and the problematic situation cannot happen. However, the shadow +EPT paging mechanism used by nested virtualization is vulnerable, because +the nested guest can trigger multiple iTLB hits by modifying its own +(non-nested) page tables. For simplicity, KVM will make large pages +non-executable in all shadow paging modes. + +Mitigation control on the kernel command line and KVM - module parameter +------------------------------------------------------------------------ + +The KVM hypervisor mitigation mechanism for marking huge pages as +non-executable can be controlled with a module parameter "nx_huge_pages=". +The kernel command line allows to control the iTLB multihit mitigations at +boot time with the option "kvm.nx_huge_pages=". + +The valid arguments for these options are: + + ========== ================================================================ + force Mitigation is enabled. In this case, the mitigation implements + non-executable huge pages in Linux kernel KVM module. All huge + pages in the EPT are marked as non-executable. + If a guest attempts to execute in one of those pages, the page is + broken down into 4K pages, which are then marked executable. + + off Mitigation is disabled. + + auto Enable mitigation only if the platform is affected and the kernel + was not booted with the "mitigations=off" command line parameter. + This is the default option. + ========== ================================================================ + + +Mitigation selection guide +-------------------------- + +1. No virtualization in use +^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + The system is protected by the kernel unconditionally and no further + action is required. + +2. Virtualization with trusted guests +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + If the guest comes from a trusted source, you may assume that the guest will + not attempt to maliciously exploit these errata and no further action is + required. + +3. Virtualization with untrusted guests +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + If the guest comes from an untrusted source, the guest host kernel will need + to apply iTLB multihit mitigation via the kernel command line or kvm + module parameter. diff --git a/Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst b/Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst new file mode 100644 index 000000000..c98fd1190 --- /dev/null +++ b/Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst @@ -0,0 +1,260 @@ +========================================= +Processor MMIO Stale Data Vulnerabilities +========================================= + +Processor MMIO Stale Data Vulnerabilities are a class of memory-mapped I/O +(MMIO) vulnerabilities that can expose data. The sequences of operations for +exposing data range from simple to very complex. Because most of the +vulnerabilities require the attacker to have access to MMIO, many environments +are not affected. System environments using virtualization where MMIO access is +provided to untrusted guests may need mitigation. These vulnerabilities are +not transient execution attacks. However, these vulnerabilities may propagate +stale data into core fill buffers where the data can subsequently be inferred +by an unmitigated transient execution attack. Mitigation for these +vulnerabilities includes a combination of microcode update and software +changes, depending on the platform and usage model. Some of these mitigations +are similar to those used to mitigate Microarchitectural Data Sampling (MDS) or +those used to mitigate Special Register Buffer Data Sampling (SRBDS). + +Data Propagators +================ +Propagators are operations that result in stale data being copied or moved from +one microarchitectural buffer or register to another. Processor MMIO Stale Data +Vulnerabilities are operations that may result in stale data being directly +read into an architectural, software-visible state or sampled from a buffer or +register. + +Fill Buffer Stale Data Propagator (FBSDP) +----------------------------------------- +Stale data may propagate from fill buffers (FB) into the non-coherent portion +of the uncore on some non-coherent writes. Fill buffer propagation by itself +does not make stale data architecturally visible. Stale data must be propagated +to a location where it is subject to reading or sampling. + +Sideband Stale Data Propagator (SSDP) +------------------------------------- +The sideband stale data propagator (SSDP) is limited to the client (including +Intel Xeon server E3) uncore implementation. The sideband response buffer is +shared by all client cores. For non-coherent reads that go to sideband +destinations, the uncore logic returns 64 bytes of data to the core, including +both requested data and unrequested stale data, from a transaction buffer and +the sideband response buffer. As a result, stale data from the sideband +response and transaction buffers may now reside in a core fill buffer. + +Primary Stale Data Propagator (PSDP) +------------------------------------ +The primary stale data propagator (PSDP) is limited to the client (including +Intel Xeon server E3) uncore implementation. Similar to the sideband response +buffer, the primary response buffer is shared by all client cores. For some +processors, MMIO primary reads will return 64 bytes of data to the core fill +buffer including both requested data and unrequested stale data. This is +similar to the sideband stale data propagator. + +Vulnerabilities +=============== +Device Register Partial Write (DRPW) (CVE-2022-21166) +----------------------------------------------------- +Some endpoint MMIO registers incorrectly handle writes that are smaller than +the register size. Instead of aborting the write or only copying the correct +subset of bytes (for example, 2 bytes for a 2-byte write), more bytes than +specified by the write transaction may be written to the register. On +processors affected by FBSDP, this may expose stale data from the fill buffers +of the core that created the write transaction. + +Shared Buffers Data Sampling (SBDS) (CVE-2022-21125) +---------------------------------------------------- +After propagators may have moved data around the uncore and copied stale data +into client core fill buffers, processors affected by MFBDS can leak data from +the fill buffer. It is limited to the client (including Intel Xeon server E3) +uncore implementation. + +Shared Buffers Data Read (SBDR) (CVE-2022-21123) +------------------------------------------------ +It is similar to Shared Buffer Data Sampling (SBDS) except that the data is +directly read into the architectural software-visible state. It is limited to +the client (including Intel Xeon server E3) uncore implementation. + +Affected Processors +=================== +Not all the CPUs are affected by all the variants. For instance, most +processors for the server market (excluding Intel Xeon E3 processors) are +impacted by only Device Register Partial Write (DRPW). + +Below is the list of affected Intel processors [#f1]_: + + =================== ============ ========= + Common name Family_Model Steppings + =================== ============ ========= + HASWELL_X 06_3FH 2,4 + SKYLAKE_L 06_4EH 3 + BROADWELL_X 06_4FH All + SKYLAKE_X 06_55H 3,4,6,7,11 + BROADWELL_D 06_56H 3,4,5 + SKYLAKE 06_5EH 3 + ICELAKE_X 06_6AH 4,5,6 + ICELAKE_D 06_6CH 1 + ICELAKE_L 06_7EH 5 + ATOM_TREMONT_D 06_86H All + LAKEFIELD 06_8AH 1 + KABYLAKE_L 06_8EH 9 to 12 + ATOM_TREMONT 06_96H 1 + ATOM_TREMONT_L 06_9CH 0 + KABYLAKE 06_9EH 9 to 13 + COMETLAKE 06_A5H 2,3,5 + COMETLAKE_L 06_A6H 0,1 + ROCKETLAKE 06_A7H 1 + =================== ============ ========= + +If a CPU is in the affected processor list, but not affected by a variant, it +is indicated by new bits in MSR IA32_ARCH_CAPABILITIES. As described in a later +section, mitigation largely remains the same for all the variants, i.e. to +clear the CPU fill buffers via VERW instruction. + +New bits in MSRs +================ +Newer processors and microcode update on existing affected processors added new +bits to IA32_ARCH_CAPABILITIES MSR. These bits can be used to enumerate +specific variants of Processor MMIO Stale Data vulnerabilities and mitigation +capability. + +MSR IA32_ARCH_CAPABILITIES +-------------------------- +Bit 13 - SBDR_SSDP_NO - When set, processor is not affected by either the + Shared Buffers Data Read (SBDR) vulnerability or the sideband stale + data propagator (SSDP). +Bit 14 - FBSDP_NO - When set, processor is not affected by the Fill Buffer + Stale Data Propagator (FBSDP). +Bit 15 - PSDP_NO - When set, processor is not affected by Primary Stale Data + Propagator (PSDP). +Bit 17 - FB_CLEAR - When set, VERW instruction will overwrite CPU fill buffer + values as part of MD_CLEAR operations. Processors that do not + enumerate MDS_NO (meaning they are affected by MDS) but that do + enumerate support for both L1D_FLUSH and MD_CLEAR implicitly enumerate + FB_CLEAR as part of their MD_CLEAR support. +Bit 18 - FB_CLEAR_CTRL - Processor supports read and write to MSR + IA32_MCU_OPT_CTRL[FB_CLEAR_DIS]. On such processors, the FB_CLEAR_DIS + bit can be set to cause the VERW instruction to not perform the + FB_CLEAR action. Not all processors that support FB_CLEAR will support + FB_CLEAR_CTRL. + +MSR IA32_MCU_OPT_CTRL +--------------------- +Bit 3 - FB_CLEAR_DIS - When set, VERW instruction does not perform the FB_CLEAR +action. This may be useful to reduce the performance impact of FB_CLEAR in +cases where system software deems it warranted (for example, when performance +is more critical, or the untrusted software has no MMIO access). Note that +FB_CLEAR_DIS has no impact on enumeration (for example, it does not change +FB_CLEAR or MD_CLEAR enumeration) and it may not be supported on all processors +that enumerate FB_CLEAR. + +Mitigation +========== +Like MDS, all variants of Processor MMIO Stale Data vulnerabilities have the +same mitigation strategy to force the CPU to clear the affected buffers before +an attacker can extract the secrets. + +This is achieved by using the otherwise unused and obsolete VERW instruction in +combination with a microcode update. The microcode clears the affected CPU +buffers when the VERW instruction is executed. + +Kernel reuses the MDS function to invoke the buffer clearing: + + mds_clear_cpu_buffers() + +On MDS affected CPUs, the kernel already invokes CPU buffer clear on +kernel/userspace, hypervisor/guest and C-state (idle) transitions. No +additional mitigation is needed on such CPUs. + +For CPUs not affected by MDS or TAA, mitigation is needed only for the attacker +with MMIO capability. Therefore, VERW is not required for kernel/userspace. For +virtualization case, VERW is only needed at VMENTER for a guest with MMIO +capability. + +Mitigation points +----------------- +Return to user space +^^^^^^^^^^^^^^^^^^^^ +Same mitigation as MDS when affected by MDS/TAA, otherwise no mitigation +needed. + +C-State transition +^^^^^^^^^^^^^^^^^^ +Control register writes by CPU during C-state transition can propagate data +from fill buffer to uncore buffers. Execute VERW before C-state transition to +clear CPU fill buffers. + +Guest entry point +^^^^^^^^^^^^^^^^^ +Same mitigation as MDS when processor is also affected by MDS/TAA, otherwise +execute VERW at VMENTER only for MMIO capable guests. On CPUs not affected by +MDS/TAA, guest without MMIO access cannot extract secrets using Processor MMIO +Stale Data vulnerabilities, so there is no need to execute VERW for such guests. + +Mitigation control on the kernel command line +--------------------------------------------- +The kernel command line allows to control the Processor MMIO Stale Data +mitigations at boot time with the option "mmio_stale_data=". The valid +arguments for this option are: + + ========== ================================================================= + full If the CPU is vulnerable, enable mitigation; CPU buffer clearing + on exit to userspace and when entering a VM. Idle transitions are + protected as well. It does not automatically disable SMT. + full,nosmt Same as full, with SMT disabled on vulnerable CPUs. This is the + complete mitigation. + off Disables mitigation completely. + ========== ================================================================= + +If the CPU is affected and mmio_stale_data=off is not supplied on the kernel +command line, then the kernel selects the appropriate mitigation. + +Mitigation status information +----------------------------- +The Linux kernel provides a sysfs interface to enumerate the current +vulnerability status of the system: whether the system is vulnerable, and +which mitigations are active. The relevant sysfs file is: + + /sys/devices/system/cpu/vulnerabilities/mmio_stale_data + +The possible values in this file are: + + .. list-table:: + + * - 'Not affected' + - The processor is not vulnerable + * - 'Vulnerable' + - The processor is vulnerable, but no mitigation enabled + * - 'Vulnerable: Clear CPU buffers attempted, no microcode' + - The processor is vulnerable, but microcode is not updated. The + mitigation is enabled on a best effort basis. + * - 'Mitigation: Clear CPU buffers' + - The processor is vulnerable and the CPU buffer clearing mitigation is + enabled. + * - 'Unknown: No mitigations' + - The processor vulnerability status is unknown because it is + out of Servicing period. Mitigation is not attempted. + +Definitions: +------------ + +Servicing period: The process of providing functional and security updates to +Intel processors or platforms, utilizing the Intel Platform Update (IPU) +process or other similar mechanisms. + +End of Servicing Updates (ESU): ESU is the date at which Intel will no +longer provide Servicing, such as through IPU or other similar update +processes. ESU dates will typically be aligned to end of quarter. + +If the processor is vulnerable then the following information is appended to +the above information: + + ======================== =========================================== + 'SMT vulnerable' SMT is enabled + 'SMT disabled' SMT is disabled + 'SMT Host state unknown' Kernel runs in a VM, Host SMT state unknown + ======================== =========================================== + +References +---------- +.. [#f1] Affected Processors + https://www.intel.com/content/www/us/en/developer/topic-technology/software-security-guidance/processors-affected-consolidated-product-cpu-model.html diff --git a/Documentation/admin-guide/hw-vuln/special-register-buffer-data-sampling.rst b/Documentation/admin-guide/hw-vuln/special-register-buffer-data-sampling.rst new file mode 100644 index 000000000..966c9b329 --- /dev/null +++ b/Documentation/admin-guide/hw-vuln/special-register-buffer-data-sampling.rst @@ -0,0 +1,150 @@ +.. SPDX-License-Identifier: GPL-2.0 + +SRBDS - Special Register Buffer Data Sampling +============================================= + +SRBDS is a hardware vulnerability that allows MDS +Documentation/admin-guide/hw-vuln/mds.rst techniques to +infer values returned from special register accesses. Special register +accesses are accesses to off core registers. According to Intel's evaluation, +the special register reads that have a security expectation of privacy are +RDRAND, RDSEED and SGX EGETKEY. + +When RDRAND, RDSEED and EGETKEY instructions are used, the data is moved +to the core through the special register mechanism that is susceptible +to MDS attacks. + +Affected processors +------------------- +Core models (desktop, mobile, Xeon-E3) that implement RDRAND and/or RDSEED may +be affected. + +A processor is affected by SRBDS if its Family_Model and stepping is +in the following list, with the exception of the listed processors +exporting MDS_NO while Intel TSX is available yet not enabled. The +latter class of processors are only affected when Intel TSX is enabled +by software using TSX_CTRL_MSR otherwise they are not affected. + + ============= ============ ======== + common name Family_Model Stepping + ============= ============ ======== + IvyBridge 06_3AH All + + Haswell 06_3CH All + Haswell_L 06_45H All + Haswell_G 06_46H All + + Broadwell_G 06_47H All + Broadwell 06_3DH All + + Skylake_L 06_4EH All + Skylake 06_5EH All + + Kabylake_L 06_8EH <= 0xC + Kabylake 06_9EH <= 0xD + ============= ============ ======== + +Related CVEs +------------ + +The following CVE entry is related to this SRBDS issue: + + ============== ===== ===================================== + CVE-2020-0543 SRBDS Special Register Buffer Data Sampling + ============== ===== ===================================== + +Attack scenarios +---------------- +An unprivileged user can extract values returned from RDRAND and RDSEED +executed on another core or sibling thread using MDS techniques. + + +Mitigation mechanism +-------------------- +Intel will release microcode updates that modify the RDRAND, RDSEED, and +EGETKEY instructions to overwrite secret special register data in the shared +staging buffer before the secret data can be accessed by another logical +processor. + +During execution of the RDRAND, RDSEED, or EGETKEY instructions, off-core +accesses from other logical processors will be delayed until the special +register read is complete and the secret data in the shared staging buffer is +overwritten. + +This has three effects on performance: + +#. RDRAND, RDSEED, or EGETKEY instructions have higher latency. + +#. Executing RDRAND at the same time on multiple logical processors will be + serialized, resulting in an overall reduction in the maximum RDRAND + bandwidth. + +#. Executing RDRAND, RDSEED or EGETKEY will delay memory accesses from other + logical processors that miss their core caches, with an impact similar to + legacy locked cache-line-split accesses. + +The microcode updates provide an opt-out mechanism (RNGDS_MITG_DIS) to disable +the mitigation for RDRAND and RDSEED instructions executed outside of Intel +Software Guard Extensions (Intel SGX) enclaves. On logical processors that +disable the mitigation using this opt-out mechanism, RDRAND and RDSEED do not +take longer to execute and do not impact performance of sibling logical +processors memory accesses. The opt-out mechanism does not affect Intel SGX +enclaves (including execution of RDRAND or RDSEED inside an enclave, as well +as EGETKEY execution). + +IA32_MCU_OPT_CTRL MSR Definition +-------------------------------- +Along with the mitigation for this issue, Intel added a new thread-scope +IA32_MCU_OPT_CTRL MSR, (address 0x123). The presence of this MSR and +RNGDS_MITG_DIS (bit 0) is enumerated by CPUID.(EAX=07H,ECX=0).EDX[SRBDS_CTRL = +9]==1. This MSR is introduced through the microcode update. + +Setting IA32_MCU_OPT_CTRL[0] (RNGDS_MITG_DIS) to 1 for a logical processor +disables the mitigation for RDRAND and RDSEED executed outside of an Intel SGX +enclave on that logical processor. Opting out of the mitigation for a +particular logical processor does not affect the RDRAND and RDSEED mitigations +for other logical processors. + +Note that inside of an Intel SGX enclave, the mitigation is applied regardless +of the value of RNGDS_MITG_DS. + +Mitigation control on the kernel command line +--------------------------------------------- +The kernel command line allows control over the SRBDS mitigation at boot time +with the option "srbds=". The option for this is: + + ============= ============================================================= + off This option disables SRBDS mitigation for RDRAND and RDSEED on + affected platforms. + ============= ============================================================= + +SRBDS System Information +------------------------ +The Linux kernel provides vulnerability status information through sysfs. For +SRBDS this can be accessed by the following sysfs file: +/sys/devices/system/cpu/vulnerabilities/srbds + +The possible values contained in this file are: + + ============================== ============================================= + Not affected Processor not vulnerable + Vulnerable Processor vulnerable and mitigation disabled + Vulnerable: No microcode Processor vulnerable and microcode is missing + mitigation + Mitigation: Microcode Processor is vulnerable and mitigation is in + effect. + Mitigation: TSX disabled Processor is only vulnerable when TSX is + enabled while this system was booted with TSX + disabled. + Unknown: Dependent on + hypervisor status Running on virtual guest processor that is + affected but with no way to know if host + processor is mitigated or vulnerable. + ============================== ============================================= + +SRBDS Default mitigation +------------------------ +This new microcode serializes processor access during execution of RDRAND, +RDSEED ensures that the shared buffer is overwritten before it is released for +reuse. Use the "srbds=off" kernel command line to disable the mitigation for +RDRAND and RDSEED. diff --git a/Documentation/admin-guide/hw-vuln/spectre.rst b/Documentation/admin-guide/hw-vuln/spectre.rst new file mode 100644 index 000000000..32a8893e5 --- /dev/null +++ b/Documentation/admin-guide/hw-vuln/spectre.rst @@ -0,0 +1,759 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Spectre Side Channels +===================== + +Spectre is a class of side channel attacks that exploit branch prediction +and speculative execution on modern CPUs to read memory, possibly +bypassing access controls. Speculative execution side channel exploits +do not modify memory but attempt to infer privileged data in the memory. + +This document covers Spectre variant 1 and Spectre variant 2. + +Affected processors +------------------- + +Speculative execution side channel methods affect a wide range of modern +high performance processors, since most modern high speed processors +use branch prediction and speculative execution. + +The following CPUs are vulnerable: + + - Intel Core, Atom, Pentium, and Xeon processors + + - AMD Phenom, EPYC, and Zen processors + + - IBM POWER and zSeries processors + + - Higher end ARM processors + + - Apple CPUs + + - Higher end MIPS CPUs + + - Likely most other high performance CPUs. Contact your CPU vendor for details. + +Whether a processor is affected or not can be read out from the Spectre +vulnerability files in sysfs. See :ref:`spectre_sys_info`. + +Related CVEs +------------ + +The following CVE entries describe Spectre variants: + + ============= ======================= ========================== + CVE-2017-5753 Bounds check bypass Spectre variant 1 + CVE-2017-5715 Branch target injection Spectre variant 2 + CVE-2019-1125 Spectre v1 swapgs Spectre variant 1 (swapgs) + ============= ======================= ========================== + +Problem +------- + +CPUs use speculative operations to improve performance. That may leave +traces of memory accesses or computations in the processor's caches, +buffers, and branch predictors. Malicious software may be able to +influence the speculative execution paths, and then use the side effects +of the speculative execution in the CPUs' caches and buffers to infer +privileged data touched during the speculative execution. + +Spectre variant 1 attacks take advantage of speculative execution of +conditional branches, while Spectre variant 2 attacks use speculative +execution of indirect branches to leak privileged memory. +See :ref:`[1] <spec_ref1>` :ref:`[5] <spec_ref5>` :ref:`[6] <spec_ref6>` +:ref:`[7] <spec_ref7>` :ref:`[10] <spec_ref10>` :ref:`[11] <spec_ref11>`. + +Spectre variant 1 (Bounds Check Bypass) +--------------------------------------- + +The bounds check bypass attack :ref:`[2] <spec_ref2>` takes advantage +of speculative execution that bypasses conditional branch instructions +used for memory access bounds check (e.g. checking if the index of an +array results in memory access within a valid range). This results in +memory accesses to invalid memory (with out-of-bound index) that are +done speculatively before validation checks resolve. Such speculative +memory accesses can leave side effects, creating side channels which +leak information to the attacker. + +There are some extensions of Spectre variant 1 attacks for reading data +over the network, see :ref:`[12] <spec_ref12>`. However such attacks +are difficult, low bandwidth, fragile, and are considered low risk. + +Note that, despite "Bounds Check Bypass" name, Spectre variant 1 is not +only about user-controlled array bounds checks. It can affect any +conditional checks. The kernel entry code interrupt, exception, and NMI +handlers all have conditional swapgs checks. Those may be problematic +in the context of Spectre v1, as kernel code can speculatively run with +a user GS. + +Spectre variant 2 (Branch Target Injection) +------------------------------------------- + +The branch target injection attack takes advantage of speculative +execution of indirect branches :ref:`[3] <spec_ref3>`. The indirect +branch predictors inside the processor used to guess the target of +indirect branches can be influenced by an attacker, causing gadget code +to be speculatively executed, thus exposing sensitive data touched by +the victim. The side effects left in the CPU's caches during speculative +execution can be measured to infer data values. + +.. _poison_btb: + +In Spectre variant 2 attacks, the attacker can steer speculative indirect +branches in the victim to gadget code by poisoning the branch target +buffer of a CPU used for predicting indirect branch addresses. Such +poisoning could be done by indirect branching into existing code, +with the address offset of the indirect branch under the attacker's +control. Since the branch prediction on impacted hardware does not +fully disambiguate branch address and uses the offset for prediction, +this could cause privileged code's indirect branch to jump to a gadget +code with the same offset. + +The most useful gadgets take an attacker-controlled input parameter (such +as a register value) so that the memory read can be controlled. Gadgets +without input parameters might be possible, but the attacker would have +very little control over what memory can be read, reducing the risk of +the attack revealing useful data. + +One other variant 2 attack vector is for the attacker to poison the +return stack buffer (RSB) :ref:`[13] <spec_ref13>` to cause speculative +subroutine return instruction execution to go to a gadget. An attacker's +imbalanced subroutine call instructions might "poison" entries in the +return stack buffer which are later consumed by a victim's subroutine +return instructions. This attack can be mitigated by flushing the return +stack buffer on context switch, or virtual machine (VM) exit. + +On systems with simultaneous multi-threading (SMT), attacks are possible +from the sibling thread, as level 1 cache and branch target buffer +(BTB) may be shared between hardware threads in a CPU core. A malicious +program running on the sibling thread may influence its peer's BTB to +steer its indirect branch speculations to gadget code, and measure the +speculative execution's side effects left in level 1 cache to infer the +victim's data. + +Yet another variant 2 attack vector is for the attacker to poison the +Branch History Buffer (BHB) to speculatively steer an indirect branch +to a specific Branch Target Buffer (BTB) entry, even if the entry isn't +associated with the source address of the indirect branch. Specifically, +the BHB might be shared across privilege levels even in the presence of +Enhanced IBRS. + +Currently the only known real-world BHB attack vector is via +unprivileged eBPF. Therefore, it's highly recommended to not enable +unprivileged eBPF, especially when eIBRS is used (without retpolines). +For a full mitigation against BHB attacks, it's recommended to use +retpolines (or eIBRS combined with retpolines). + +Attack scenarios +---------------- + +The following list of attack scenarios have been anticipated, but may +not cover all possible attack vectors. + +1. A user process attacking the kernel +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Spectre variant 1 +~~~~~~~~~~~~~~~~~ + + The attacker passes a parameter to the kernel via a register or + via a known address in memory during a syscall. Such parameter may + be used later by the kernel as an index to an array or to derive + a pointer for a Spectre variant 1 attack. The index or pointer + is invalid, but bound checks are bypassed in the code branch taken + for speculative execution. This could cause privileged memory to be + accessed and leaked. + + For kernel code that has been identified where data pointers could + potentially be influenced for Spectre attacks, new "nospec" accessor + macros are used to prevent speculative loading of data. + +Spectre variant 1 (swapgs) +~~~~~~~~~~~~~~~~~~~~~~~~~~ + + An attacker can train the branch predictor to speculatively skip the + swapgs path for an interrupt or exception. If they initialize + the GS register to a user-space value, if the swapgs is speculatively + skipped, subsequent GS-related percpu accesses in the speculation + window will be done with the attacker-controlled GS value. This + could cause privileged memory to be accessed and leaked. + + For example: + + :: + + if (coming from user space) + swapgs + mov %gs:<percpu_offset>, %reg + mov (%reg), %reg1 + + When coming from user space, the CPU can speculatively skip the + swapgs, and then do a speculative percpu load using the user GS + value. So the user can speculatively force a read of any kernel + value. If a gadget exists which uses the percpu value as an address + in another load/store, then the contents of the kernel value may + become visible via an L1 side channel attack. + + A similar attack exists when coming from kernel space. The CPU can + speculatively do the swapgs, causing the user GS to get used for the + rest of the speculative window. + +Spectre variant 2 +~~~~~~~~~~~~~~~~~ + + A spectre variant 2 attacker can :ref:`poison <poison_btb>` the branch + target buffer (BTB) before issuing syscall to launch an attack. + After entering the kernel, the kernel could use the poisoned branch + target buffer on indirect jump and jump to gadget code in speculative + execution. + + If an attacker tries to control the memory addresses leaked during + speculative execution, he would also need to pass a parameter to the + gadget, either through a register or a known address in memory. After + the gadget has executed, he can measure the side effect. + + The kernel can protect itself against consuming poisoned branch + target buffer entries by using return trampolines (also known as + "retpoline") :ref:`[3] <spec_ref3>` :ref:`[9] <spec_ref9>` for all + indirect branches. Return trampolines trap speculative execution paths + to prevent jumping to gadget code during speculative execution. + x86 CPUs with Enhanced Indirect Branch Restricted Speculation + (Enhanced IBRS) available in hardware should use the feature to + mitigate Spectre variant 2 instead of retpoline. Enhanced IBRS is + more efficient than retpoline. + + There may be gadget code in firmware which could be exploited with + Spectre variant 2 attack by a rogue user process. To mitigate such + attacks on x86, Indirect Branch Restricted Speculation (IBRS) feature + is turned on before the kernel invokes any firmware code. + +2. A user process attacking another user process +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + A malicious user process can try to attack another user process, + either via a context switch on the same hardware thread, or from the + sibling hyperthread sharing a physical processor core on simultaneous + multi-threading (SMT) system. + + Spectre variant 1 attacks generally require passing parameters + between the processes, which needs a data passing relationship, such + as remote procedure calls (RPC). Those parameters are used in gadget + code to derive invalid data pointers accessing privileged memory in + the attacked process. + + Spectre variant 2 attacks can be launched from a rogue process by + :ref:`poisoning <poison_btb>` the branch target buffer. This can + influence the indirect branch targets for a victim process that either + runs later on the same hardware thread, or running concurrently on + a sibling hardware thread sharing the same physical core. + + A user process can protect itself against Spectre variant 2 attacks + by using the prctl() syscall to disable indirect branch speculation + for itself. An administrator can also cordon off an unsafe process + from polluting the branch target buffer by disabling the process's + indirect branch speculation. This comes with a performance cost + from not using indirect branch speculation and clearing the branch + target buffer. When SMT is enabled on x86, for a process that has + indirect branch speculation disabled, Single Threaded Indirect Branch + Predictors (STIBP) :ref:`[4] <spec_ref4>` are turned on to prevent the + sibling thread from controlling branch target buffer. In addition, + the Indirect Branch Prediction Barrier (IBPB) is issued to clear the + branch target buffer when context switching to and from such process. + + On x86, the return stack buffer is stuffed on context switch. + This prevents the branch target buffer from being used for branch + prediction when the return stack buffer underflows while switching to + a deeper call stack. Any poisoned entries in the return stack buffer + left by the previous process will also be cleared. + + User programs should use address space randomization to make attacks + more difficult (Set /proc/sys/kernel/randomize_va_space = 1 or 2). + +3. A virtualized guest attacking the host +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + The attack mechanism is similar to how user processes attack the + kernel. The kernel is entered via hyper-calls or other virtualization + exit paths. + + For Spectre variant 1 attacks, rogue guests can pass parameters + (e.g. in registers) via hyper-calls to derive invalid pointers to + speculate into privileged memory after entering the kernel. For places + where such kernel code has been identified, nospec accessor macros + are used to stop speculative memory access. + + For Spectre variant 2 attacks, rogue guests can :ref:`poison + <poison_btb>` the branch target buffer or return stack buffer, causing + the kernel to jump to gadget code in the speculative execution paths. + + To mitigate variant 2, the host kernel can use return trampolines + for indirect branches to bypass the poisoned branch target buffer, + and flushing the return stack buffer on VM exit. This prevents rogue + guests from affecting indirect branching in the host kernel. + + To protect host processes from rogue guests, host processes can have + indirect branch speculation disabled via prctl(). The branch target + buffer is cleared before context switching to such processes. + +4. A virtualized guest attacking other guest +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + A rogue guest may attack another guest to get data accessible by the + other guest. + + Spectre variant 1 attacks are possible if parameters can be passed + between guests. This may be done via mechanisms such as shared memory + or message passing. Such parameters could be used to derive data + pointers to privileged data in guest. The privileged data could be + accessed by gadget code in the victim's speculation paths. + + Spectre variant 2 attacks can be launched from a rogue guest by + :ref:`poisoning <poison_btb>` the branch target buffer or the return + stack buffer. Such poisoned entries could be used to influence + speculation execution paths in the victim guest. + + Linux kernel mitigates attacks to other guests running in the same + CPU hardware thread by flushing the return stack buffer on VM exit, + and clearing the branch target buffer before switching to a new guest. + + If SMT is used, Spectre variant 2 attacks from an untrusted guest + in the sibling hyperthread can be mitigated by the administrator, + by turning off the unsafe guest's indirect branch speculation via + prctl(). A guest can also protect itself by turning on microcode + based mitigations (such as IBPB or STIBP on x86) within the guest. + +.. _spectre_sys_info: + +Spectre system information +-------------------------- + +The Linux kernel provides a sysfs interface to enumerate the current +mitigation status of the system for Spectre: whether the system is +vulnerable, and which mitigations are active. + +The sysfs file showing Spectre variant 1 mitigation status is: + + /sys/devices/system/cpu/vulnerabilities/spectre_v1 + +The possible values in this file are: + + .. list-table:: + + * - 'Not affected' + - The processor is not vulnerable. + * - 'Vulnerable: __user pointer sanitization and usercopy barriers only; no swapgs barriers' + - The swapgs protections are disabled; otherwise it has + protection in the kernel on a case by case base with explicit + pointer sanitation and usercopy LFENCE barriers. + * - 'Mitigation: usercopy/swapgs barriers and __user pointer sanitization' + - Protection in the kernel on a case by case base with explicit + pointer sanitation, usercopy LFENCE barriers, and swapgs LFENCE + barriers. + +However, the protections are put in place on a case by case basis, +and there is no guarantee that all possible attack vectors for Spectre +variant 1 are covered. + +The spectre_v2 kernel file reports if the kernel has been compiled with +retpoline mitigation or if the CPU has hardware mitigation, and if the +CPU has support for additional process-specific mitigation. + +This file also reports CPU features enabled by microcode to mitigate +attack between user processes: + +1. Indirect Branch Prediction Barrier (IBPB) to add additional + isolation between processes of different users. +2. Single Thread Indirect Branch Predictors (STIBP) to add additional + isolation between CPU threads running on the same core. + +These CPU features may impact performance when used and can be enabled +per process on a case-by-case base. + +The sysfs file showing Spectre variant 2 mitigation status is: + + /sys/devices/system/cpu/vulnerabilities/spectre_v2 + +The possible values in this file are: + + - Kernel status: + + ======================================== ================================= + 'Not affected' The processor is not vulnerable + 'Mitigation: None' Vulnerable, no mitigation + 'Mitigation: Retpolines' Use Retpoline thunks + 'Mitigation: LFENCE' Use LFENCE instructions + 'Mitigation: Enhanced IBRS' Hardware-focused mitigation + 'Mitigation: Enhanced IBRS + Retpolines' Hardware-focused + Retpolines + 'Mitigation: Enhanced IBRS + LFENCE' Hardware-focused + LFENCE + ======================================== ================================= + + - Firmware status: Show if Indirect Branch Restricted Speculation (IBRS) is + used to protect against Spectre variant 2 attacks when calling firmware (x86 only). + + ========== ============================================================= + 'IBRS_FW' Protection against user program attacks when calling firmware + ========== ============================================================= + + - Indirect branch prediction barrier (IBPB) status for protection between + processes of different users. This feature can be controlled through + prctl() per process, or through kernel command line options. This is + an x86 only feature. For more details see below. + + =================== ======================================================== + 'IBPB: disabled' IBPB unused + 'IBPB: always-on' Use IBPB on all tasks + 'IBPB: conditional' Use IBPB on SECCOMP or indirect branch restricted tasks + =================== ======================================================== + + - Single threaded indirect branch prediction (STIBP) status for protection + between different hyper threads. This feature can be controlled through + prctl per process, or through kernel command line options. This is x86 + only feature. For more details see below. + + ==================== ======================================================== + 'STIBP: disabled' STIBP unused + 'STIBP: forced' Use STIBP on all tasks + 'STIBP: conditional' Use STIBP on SECCOMP or indirect branch restricted tasks + ==================== ======================================================== + + - Return stack buffer (RSB) protection status: + + ============= =========================================== + 'RSB filling' Protection of RSB on context switch enabled + ============= =========================================== + + - EIBRS Post-barrier Return Stack Buffer (PBRSB) protection status: + + =========================== ======================================================= + 'PBRSB-eIBRS: SW sequence' CPU is affected and protection of RSB on VMEXIT enabled + 'PBRSB-eIBRS: Vulnerable' CPU is vulnerable + 'PBRSB-eIBRS: Not affected' CPU is not affected by PBRSB + =========================== ======================================================= + +Full mitigation might require a microcode update from the CPU +vendor. When the necessary microcode is not available, the kernel will +report vulnerability. + +Turning on mitigation for Spectre variant 1 and Spectre variant 2 +----------------------------------------------------------------- + +1. Kernel mitigation +^^^^^^^^^^^^^^^^^^^^ + +Spectre variant 1 +~~~~~~~~~~~~~~~~~ + + For the Spectre variant 1, vulnerable kernel code (as determined + by code audit or scanning tools) is annotated on a case by case + basis to use nospec accessor macros for bounds clipping :ref:`[2] + <spec_ref2>` to avoid any usable disclosure gadgets. However, it may + not cover all attack vectors for Spectre variant 1. + + Copy-from-user code has an LFENCE barrier to prevent the access_ok() + check from being mis-speculated. The barrier is done by the + barrier_nospec() macro. + + For the swapgs variant of Spectre variant 1, LFENCE barriers are + added to interrupt, exception and NMI entry where needed. These + barriers are done by the FENCE_SWAPGS_KERNEL_ENTRY and + FENCE_SWAPGS_USER_ENTRY macros. + +Spectre variant 2 +~~~~~~~~~~~~~~~~~ + + For Spectre variant 2 mitigation, the compiler turns indirect calls or + jumps in the kernel into equivalent return trampolines (retpolines) + :ref:`[3] <spec_ref3>` :ref:`[9] <spec_ref9>` to go to the target + addresses. Speculative execution paths under retpolines are trapped + in an infinite loop to prevent any speculative execution jumping to + a gadget. + + To turn on retpoline mitigation on a vulnerable CPU, the kernel + needs to be compiled with a gcc compiler that supports the + -mindirect-branch=thunk-extern -mindirect-branch-register options. + If the kernel is compiled with a Clang compiler, the compiler needs + to support -mretpoline-external-thunk option. The kernel config + CONFIG_RETPOLINE needs to be turned on, and the CPU needs to run with + the latest updated microcode. + + On Intel Skylake-era systems the mitigation covers most, but not all, + cases. See :ref:`[3] <spec_ref3>` for more details. + + On CPUs with hardware mitigation for Spectre variant 2 (e.g. IBRS + or enhanced IBRS on x86), retpoline is automatically disabled at run time. + + Systems which support enhanced IBRS (eIBRS) enable IBRS protection once at + boot, by setting the IBRS bit, and they're automatically protected against + Spectre v2 variant attacks. + + On Intel's enhanced IBRS systems, this includes cross-thread branch target + injections on SMT systems (STIBP). In other words, Intel eIBRS enables + STIBP, too. + + AMD Automatic IBRS does not protect userspace, and Legacy IBRS systems clear + the IBRS bit on exit to userspace, therefore both explicitly enable STIBP. + + The retpoline mitigation is turned on by default on vulnerable + CPUs. It can be forced on or off by the administrator + via the kernel command line and sysfs control files. See + :ref:`spectre_mitigation_control_command_line`. + + On x86, indirect branch restricted speculation is turned on by default + before invoking any firmware code to prevent Spectre variant 2 exploits + using the firmware. + + Using kernel address space randomization (CONFIG_RANDOMIZE_BASE=y + and CONFIG_SLAB_FREELIST_RANDOM=y in the kernel configuration) makes + attacks on the kernel generally more difficult. + +2. User program mitigation +^^^^^^^^^^^^^^^^^^^^^^^^^^ + + User programs can mitigate Spectre variant 1 using LFENCE or "bounds + clipping". For more details see :ref:`[2] <spec_ref2>`. + + For Spectre variant 2 mitigation, individual user programs + can be compiled with return trampolines for indirect branches. + This protects them from consuming poisoned entries in the branch + target buffer left by malicious software. + + On legacy IBRS systems, at return to userspace, implicit STIBP is disabled + because the kernel clears the IBRS bit. In this case, the userspace programs + can disable indirect branch speculation via prctl() (See + :ref:`Documentation/userspace-api/spec_ctrl.rst <set_spec_ctrl>`). + On x86, this will turn on STIBP to guard against attacks from the + sibling thread when the user program is running, and use IBPB to + flush the branch target buffer when switching to/from the program. + + Restricting indirect branch speculation on a user program will + also prevent the program from launching a variant 2 attack + on x86. Administrators can change that behavior via the kernel + command line and sysfs control files. + See :ref:`spectre_mitigation_control_command_line`. + + Programs that disable their indirect branch speculation will have + more overhead and run slower. + + User programs should use address space randomization + (/proc/sys/kernel/randomize_va_space = 1 or 2) to make attacks more + difficult. + +3. VM mitigation +^^^^^^^^^^^^^^^^ + + Within the kernel, Spectre variant 1 attacks from rogue guests are + mitigated on a case by case basis in VM exit paths. Vulnerable code + uses nospec accessor macros for "bounds clipping", to avoid any + usable disclosure gadgets. However, this may not cover all variant + 1 attack vectors. + + For Spectre variant 2 attacks from rogue guests to the kernel, the + Linux kernel uses retpoline or Enhanced IBRS to prevent consumption of + poisoned entries in branch target buffer left by rogue guests. It also + flushes the return stack buffer on every VM exit to prevent a return + stack buffer underflow so poisoned branch target buffer could be used, + or attacker guests leaving poisoned entries in the return stack buffer. + + To mitigate guest-to-guest attacks in the same CPU hardware thread, + the branch target buffer is sanitized by flushing before switching + to a new guest on a CPU. + + The above mitigations are turned on by default on vulnerable CPUs. + + To mitigate guest-to-guest attacks from sibling thread when SMT is + in use, an untrusted guest running in the sibling thread can have + its indirect branch speculation disabled by administrator via prctl(). + + The kernel also allows guests to use any microcode based mitigation + they choose to use (such as IBPB or STIBP on x86) to protect themselves. + +.. _spectre_mitigation_control_command_line: + +Mitigation control on the kernel command line +--------------------------------------------- + +Spectre variant 2 mitigation can be disabled or force enabled at the +kernel command line. + + nospectre_v1 + + [X86,PPC] Disable mitigations for Spectre Variant 1 + (bounds check bypass). With this option data leaks are + possible in the system. + + nospectre_v2 + + [X86] Disable all mitigations for the Spectre variant 2 + (indirect branch prediction) vulnerability. System may + allow data leaks with this option, which is equivalent + to spectre_v2=off. + + + spectre_v2= + + [X86] Control mitigation of Spectre variant 2 + (indirect branch speculation) vulnerability. + The default operation protects the kernel from + user space attacks. + + on + unconditionally enable, implies + spectre_v2_user=on + off + unconditionally disable, implies + spectre_v2_user=off + auto + kernel detects whether your CPU model is + vulnerable + + Selecting 'on' will, and 'auto' may, choose a + mitigation method at run time according to the + CPU, the available microcode, the setting of the + CONFIG_RETPOLINE configuration option, and the + compiler with which the kernel was built. + + Selecting 'on' will also enable the mitigation + against user space to user space task attacks. + + Selecting 'off' will disable both the kernel and + the user space protections. + + Specific mitigations can also be selected manually: + + retpoline auto pick between generic,lfence + retpoline,generic Retpolines + retpoline,lfence LFENCE; indirect branch + retpoline,amd alias for retpoline,lfence + eibrs Enhanced/Auto IBRS + eibrs,retpoline Enhanced/Auto IBRS + Retpolines + eibrs,lfence Enhanced/Auto IBRS + LFENCE + ibrs use IBRS to protect kernel + + Not specifying this option is equivalent to + spectre_v2=auto. + + In general the kernel by default selects + reasonable mitigations for the current CPU. To + disable Spectre variant 2 mitigations, boot with + spectre_v2=off. Spectre variant 1 mitigations + cannot be disabled. + +For spectre_v2_user see Documentation/admin-guide/kernel-parameters.txt + +Mitigation selection guide +-------------------------- + +1. Trusted userspace +^^^^^^^^^^^^^^^^^^^^ + + If all userspace applications are from trusted sources and do not + execute externally supplied untrusted code, then the mitigations can + be disabled. + +2. Protect sensitive programs +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + For security-sensitive programs that have secrets (e.g. crypto + keys), protection against Spectre variant 2 can be put in place by + disabling indirect branch speculation when the program is running + (See :ref:`Documentation/userspace-api/spec_ctrl.rst <set_spec_ctrl>`). + +3. Sandbox untrusted programs +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + Untrusted programs that could be a source of attacks can be cordoned + off by disabling their indirect branch speculation when they are run + (See :ref:`Documentation/userspace-api/spec_ctrl.rst <set_spec_ctrl>`). + This prevents untrusted programs from polluting the branch target + buffer. This behavior can be changed via the kernel command line + and sysfs control files. See + :ref:`spectre_mitigation_control_command_line`. + +3. High security mode +^^^^^^^^^^^^^^^^^^^^^ + + All Spectre variant 2 mitigations can be forced on + at boot time for all programs (See the "on" option in + :ref:`spectre_mitigation_control_command_line`). This will add + overhead as indirect branch speculations for all programs will be + restricted. + + On x86, branch target buffer will be flushed with IBPB when switching + to a new program. STIBP is left on all the time to protect programs + against variant 2 attacks originating from programs running on + sibling threads. + + Alternatively, STIBP can be used only when running programs + whose indirect branch speculation is explicitly disabled, + while IBPB is still used all the time when switching to a new + program to clear the branch target buffer (See "ibpb" option in + :ref:`spectre_mitigation_control_command_line`). This "ibpb" option + has less performance cost than the "on" option, which leaves STIBP + on all the time. + +References on Spectre +--------------------- + +Intel white papers: + +.. _spec_ref1: + +[1] `Intel analysis of speculative execution side channels <https://newsroom.intel.com/wp-content/uploads/sites/11/2018/01/Intel-Analysis-of-Speculative-Execution-Side-Channels.pdf>`_. + +.. _spec_ref2: + +[2] `Bounds check bypass <https://software.intel.com/security-software-guidance/software-guidance/bounds-check-bypass>`_. + +.. _spec_ref3: + +[3] `Deep dive: Retpoline: A branch target injection mitigation <https://software.intel.com/security-software-guidance/insights/deep-dive-retpoline-branch-target-injection-mitigation>`_. + +.. _spec_ref4: + +[4] `Deep Dive: Single Thread Indirect Branch Predictors <https://software.intel.com/security-software-guidance/insights/deep-dive-single-thread-indirect-branch-predictors>`_. + +AMD white papers: + +.. _spec_ref5: + +[5] `AMD64 technology indirect branch control extension <https://developer.amd.com/wp-content/resources/Architecture_Guidelines_Update_Indirect_Branch_Control.pdf>`_. + +.. _spec_ref6: + +[6] `Software techniques for managing speculation on AMD processors <https://developer.amd.com/wp-content/resources/Managing-Speculation-on-AMD-Processors.pdf>`_. + +ARM white papers: + +.. _spec_ref7: + +[7] `Cache speculation side-channels <https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability/download-the-whitepaper>`_. + +.. _spec_ref8: + +[8] `Cache speculation issues update <https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability/latest-updates/cache-speculation-issues-update>`_. + +Google white paper: + +.. _spec_ref9: + +[9] `Retpoline: a software construct for preventing branch-target-injection <https://support.google.com/faqs/answer/7625886>`_. + +MIPS white paper: + +.. _spec_ref10: + +[10] `MIPS: response on speculative execution and side channel vulnerabilities <https://www.mips.com/blog/mips-response-on-speculative-execution-and-side-channel-vulnerabilities/>`_. + +Academic papers: + +.. _spec_ref11: + +[11] `Spectre Attacks: Exploiting Speculative Execution <https://spectreattack.com/spectre.pdf>`_. + +.. _spec_ref12: + +[12] `NetSpectre: Read Arbitrary Memory over Network <https://arxiv.org/abs/1807.10535>`_. + +.. _spec_ref13: + +[13] `Spectre Returns! Speculation Attacks using the Return Stack Buffer <https://www.usenix.org/system/files/conference/woot18/woot18-paper-koruyeh.pdf>`_. diff --git a/Documentation/admin-guide/hw-vuln/srso.rst b/Documentation/admin-guide/hw-vuln/srso.rst new file mode 100644 index 000000000..e715bfc09 --- /dev/null +++ b/Documentation/admin-guide/hw-vuln/srso.rst @@ -0,0 +1,160 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Speculative Return Stack Overflow (SRSO) +======================================== + +This is a mitigation for the speculative return stack overflow (SRSO) +vulnerability found on AMD processors. The mechanism is by now the well +known scenario of poisoning CPU functional units - the Branch Target +Buffer (BTB) and Return Address Predictor (RAP) in this case - and then +tricking the elevated privilege domain (the kernel) into leaking +sensitive data. + +AMD CPUs predict RET instructions using a Return Address Predictor (aka +Return Address Stack/Return Stack Buffer). In some cases, a non-architectural +CALL instruction (i.e., an instruction predicted to be a CALL but is +not actually a CALL) can create an entry in the RAP which may be used +to predict the target of a subsequent RET instruction. + +The specific circumstances that lead to this varies by microarchitecture +but the concern is that an attacker can mis-train the CPU BTB to predict +non-architectural CALL instructions in kernel space and use this to +control the speculative target of a subsequent kernel RET, potentially +leading to information disclosure via a speculative side-channel. + +The issue is tracked under CVE-2023-20569. + +Affected processors +------------------- + +AMD Zen, generations 1-4. That is, all families 0x17 and 0x19. Older +processors have not been investigated. + +System information and options +------------------------------ + +First of all, it is required that the latest microcode be loaded for +mitigations to be effective. + +The sysfs file showing SRSO mitigation status is: + + /sys/devices/system/cpu/vulnerabilities/spec_rstack_overflow + +The possible values in this file are: + + * 'Not affected': + + The processor is not vulnerable + +* 'Vulnerable': + + The processor is vulnerable and no mitigations have been applied. + + * 'Vulnerable: No microcode': + + The processor is vulnerable, no microcode extending IBPB + functionality to address the vulnerability has been applied. + + * 'Vulnerable: Safe RET, no microcode': + + The "Safe RET" mitigation (see below) has been applied to protect the + kernel, but the IBPB-extending microcode has not been applied. User + space tasks may still be vulnerable. + + * 'Vulnerable: Microcode, no safe RET': + + Extended IBPB functionality microcode patch has been applied. It does + not address User->Kernel and Guest->Host transitions protection but it + does address User->User and VM->VM attack vectors. + + Note that User->User mitigation is controlled by how the IBPB aspect in + the Spectre v2 mitigation is selected: + + * conditional IBPB: + + where each process can select whether it needs an IBPB issued + around it PR_SPEC_DISABLE/_ENABLE etc, see :doc:`spectre` + + * strict: + + i.e., always on - by supplying spectre_v2_user=on on the kernel + command line + + (spec_rstack_overflow=microcode) + + * 'Mitigation: Safe RET': + + Combined microcode/software mitigation. It complements the + extended IBPB microcode patch functionality by addressing + User->Kernel and Guest->Host transitions protection. + + Selected by default or by spec_rstack_overflow=safe-ret + + * 'Mitigation: IBPB': + + Similar protection as "safe RET" above but employs an IBPB barrier on + privilege domain crossings (User->Kernel, Guest->Host). + + (spec_rstack_overflow=ibpb) + + * 'Mitigation: IBPB on VMEXIT': + + Mitigation addressing the cloud provider scenario - the Guest->Host + transitions only. + + (spec_rstack_overflow=ibpb-vmexit) + + + +In order to exploit vulnerability, an attacker needs to: + + - gain local access on the machine + + - break kASLR + + - find gadgets in the running kernel in order to use them in the exploit + + - potentially create and pin an additional workload on the sibling + thread, depending on the microarchitecture (not necessary on fam 0x19) + + - run the exploit + +Considering the performance implications of each mitigation type, the +default one is 'Mitigation: safe RET' which should take care of most +attack vectors, including the local User->Kernel one. + +As always, the user is advised to keep her/his system up-to-date by +applying software updates regularly. + +The default setting will be reevaluated when needed and especially when +new attack vectors appear. + +As one can surmise, 'Mitigation: safe RET' does come at the cost of some +performance depending on the workload. If one trusts her/his userspace +and does not want to suffer the performance impact, one can always +disable the mitigation with spec_rstack_overflow=off. + +Similarly, 'Mitigation: IBPB' is another full mitigation type employing +an indrect branch prediction barrier after having applied the required +microcode patch for one's system. This mitigation comes also at +a performance cost. + +Mitigation: Safe RET +-------------------- + +The mitigation works by ensuring all RET instructions speculate to +a controlled location, similar to how speculation is controlled in the +retpoline sequence. To accomplish this, the __x86_return_thunk forces +the CPU to mispredict every function return using a 'safe return' +sequence. + +To ensure the safety of this mitigation, the kernel must ensure that the +safe return sequence is itself free from attacker interference. In Zen3 +and Zen4, this is accomplished by creating a BTB alias between the +untraining function srso_alias_untrain_ret() and the safe return +function srso_alias_safe_ret() which results in evicting a potentially +poisoned BTB entry and using that safe one for all function returns. + +In older Zen1 and Zen2, this is accomplished using a reinterpretation +technique similar to Retbleed one: srso_untrain_ret() and +srso_safe_ret(). diff --git a/Documentation/admin-guide/hw-vuln/tsx_async_abort.rst b/Documentation/admin-guide/hw-vuln/tsx_async_abort.rst new file mode 100644 index 000000000..014167ef8 --- /dev/null +++ b/Documentation/admin-guide/hw-vuln/tsx_async_abort.rst @@ -0,0 +1,277 @@ +.. SPDX-License-Identifier: GPL-2.0 + +TAA - TSX Asynchronous Abort +====================================== + +TAA is a hardware vulnerability that allows unprivileged speculative access to +data which is available in various CPU internal buffers by using asynchronous +aborts within an Intel TSX transactional region. + +Affected processors +------------------- + +This vulnerability only affects Intel processors that support Intel +Transactional Synchronization Extensions (TSX) when the TAA_NO bit (bit 8) +is 0 in the IA32_ARCH_CAPABILITIES MSR. On processors where the MDS_NO bit +(bit 5) is 0 in the IA32_ARCH_CAPABILITIES MSR, the existing MDS mitigations +also mitigate against TAA. + +Whether a processor is affected or not can be read out from the TAA +vulnerability file in sysfs. See :ref:`tsx_async_abort_sys_info`. + +Related CVEs +------------ + +The following CVE entry is related to this TAA issue: + + ============== ===== =================================================== + CVE-2019-11135 TAA TSX Asynchronous Abort (TAA) condition on some + microprocessors utilizing speculative execution may + allow an authenticated user to potentially enable + information disclosure via a side channel with + local access. + ============== ===== =================================================== + +Problem +------- + +When performing store, load or L1 refill operations, processors write +data into temporary microarchitectural structures (buffers). The data in +those buffers can be forwarded to load operations as an optimization. + +Intel TSX is an extension to the x86 instruction set architecture that adds +hardware transactional memory support to improve performance of multi-threaded +software. TSX lets the processor expose and exploit concurrency hidden in an +application due to dynamically avoiding unnecessary synchronization. + +TSX supports atomic memory transactions that are either committed (success) or +aborted. During an abort, operations that happened within the transactional region +are rolled back. An asynchronous abort takes place, among other options, when a +different thread accesses a cache line that is also used within the transactional +region when that access might lead to a data race. + +Immediately after an uncompleted asynchronous abort, certain speculatively +executed loads may read data from those internal buffers and pass it to dependent +operations. This can be then used to infer the value via a cache side channel +attack. + +Because the buffers are potentially shared between Hyper-Threads cross +Hyper-Thread attacks are possible. + +The victim of a malicious actor does not need to make use of TSX. Only the +attacker needs to begin a TSX transaction and raise an asynchronous abort +which in turn potentially leaks data stored in the buffers. + +More detailed technical information is available in the TAA specific x86 +architecture section: :ref:`Documentation/arch/x86/tsx_async_abort.rst <tsx_async_abort>`. + + +Attack scenarios +---------------- + +Attacks against the TAA vulnerability can be implemented from unprivileged +applications running on hosts or guests. + +As for MDS, the attacker has no control over the memory addresses that can +be leaked. Only the victim is responsible for bringing data to the CPU. As +a result, the malicious actor has to sample as much data as possible and +then postprocess it to try to infer any useful information from it. + +A potential attacker only has read access to the data. Also, there is no direct +privilege escalation by using this technique. + + +.. _tsx_async_abort_sys_info: + +TAA system information +----------------------- + +The Linux kernel provides a sysfs interface to enumerate the current TAA status +of mitigated systems. The relevant sysfs file is: + +/sys/devices/system/cpu/vulnerabilities/tsx_async_abort + +The possible values in this file are: + +.. list-table:: + + * - 'Vulnerable' + - The CPU is affected by this vulnerability and the microcode and kernel mitigation are not applied. + * - 'Vulnerable: Clear CPU buffers attempted, no microcode' + - The system tries to clear the buffers but the microcode might not support the operation. + * - 'Mitigation: Clear CPU buffers' + - The microcode has been updated to clear the buffers. TSX is still enabled. + * - 'Mitigation: TSX disabled' + - TSX is disabled. + * - 'Not affected' + - The CPU is not affected by this issue. + +.. _ucode_needed: + +Best effort mitigation mode +^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +If the processor is vulnerable, but the availability of the microcode-based +mitigation mechanism is not advertised via CPUID the kernel selects a best +effort mitigation mode. This mode invokes the mitigation instructions +without a guarantee that they clear the CPU buffers. + +This is done to address virtualization scenarios where the host has the +microcode update applied, but the hypervisor is not yet updated to expose the +CPUID to the guest. If the host has updated microcode the protection takes +effect; otherwise a few CPU cycles are wasted pointlessly. + +The state in the tsx_async_abort sysfs file reflects this situation +accordingly. + + +Mitigation mechanism +-------------------- + +The kernel detects the affected CPUs and the presence of the microcode which is +required. If a CPU is affected and the microcode is available, then the kernel +enables the mitigation by default. + + +The mitigation can be controlled at boot time via a kernel command line option. +See :ref:`taa_mitigation_control_command_line`. + +Virtualization mitigation +^^^^^^^^^^^^^^^^^^^^^^^^^ + +Affected systems where the host has TAA microcode and TAA is mitigated by +having disabled TSX previously, are not vulnerable regardless of the status +of the VMs. + +In all other cases, if the host either does not have the TAA microcode or +the kernel is not mitigated, the system might be vulnerable. + + +.. _taa_mitigation_control_command_line: + +Mitigation control on the kernel command line +--------------------------------------------- + +The kernel command line allows to control the TAA mitigations at boot time with +the option "tsx_async_abort=". The valid arguments for this option are: + + ============ ============================================================= + off This option disables the TAA mitigation on affected platforms. + If the system has TSX enabled (see next parameter) and the CPU + is affected, the system is vulnerable. + + full TAA mitigation is enabled. If TSX is enabled, on an affected + system it will clear CPU buffers on ring transitions. On + systems which are MDS-affected and deploy MDS mitigation, + TAA is also mitigated. Specifying this option on those + systems will have no effect. + + full,nosmt The same as tsx_async_abort=full, with SMT disabled on + vulnerable CPUs that have TSX enabled. This is the complete + mitigation. When TSX is disabled, SMT is not disabled because + CPU is not vulnerable to cross-thread TAA attacks. + ============ ============================================================= + +Not specifying this option is equivalent to "tsx_async_abort=full". For +processors that are affected by both TAA and MDS, specifying just +"tsx_async_abort=off" without an accompanying "mds=off" will have no +effect as the same mitigation is used for both vulnerabilities. + +The kernel command line also allows to control the TSX feature using the +parameter "tsx=" on CPUs which support TSX control. MSR_IA32_TSX_CTRL is used +to control the TSX feature and the enumeration of the TSX feature bits (RTM +and HLE) in CPUID. + +The valid options are: + + ============ ============================================================= + off Disables TSX on the system. + + Note that this option takes effect only on newer CPUs which are + not vulnerable to MDS, i.e., have MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 + and which get the new IA32_TSX_CTRL MSR through a microcode + update. This new MSR allows for the reliable deactivation of + the TSX functionality. + + on Enables TSX. + + Although there are mitigations for all known security + vulnerabilities, TSX has been known to be an accelerator for + several previous speculation-related CVEs, and so there may be + unknown security risks associated with leaving it enabled. + + auto Disables TSX if X86_BUG_TAA is present, otherwise enables TSX + on the system. + ============ ============================================================= + +Not specifying this option is equivalent to "tsx=off". + +The following combinations of the "tsx_async_abort" and "tsx" are possible. For +affected platforms tsx=auto is equivalent to tsx=off and the result will be: + + ========= ========================== ========================================= + tsx=on tsx_async_abort=full The system will use VERW to clear CPU + buffers. Cross-thread attacks are still + possible on SMT machines. + tsx=on tsx_async_abort=full,nosmt As above, cross-thread attacks on SMT + mitigated. + tsx=on tsx_async_abort=off The system is vulnerable. + tsx=off tsx_async_abort=full TSX might be disabled if microcode + provides a TSX control MSR. If so, + system is not vulnerable. + tsx=off tsx_async_abort=full,nosmt Ditto + tsx=off tsx_async_abort=off ditto + ========= ========================== ========================================= + + +For unaffected platforms "tsx=on" and "tsx_async_abort=full" does not clear CPU +buffers. For platforms without TSX control (MSR_IA32_ARCH_CAPABILITIES.MDS_NO=0) +"tsx" command line argument has no effect. + +For the affected platforms below table indicates the mitigation status for the +combinations of CPUID bit MD_CLEAR and IA32_ARCH_CAPABILITIES MSR bits MDS_NO +and TSX_CTRL_MSR. + + ======= ========= ============= ======================================== + MDS_NO MD_CLEAR TSX_CTRL_MSR Status + ======= ========= ============= ======================================== + 0 0 0 Vulnerable (needs microcode) + 0 1 0 MDS and TAA mitigated via VERW + 1 1 0 MDS fixed, TAA vulnerable if TSX enabled + because MD_CLEAR has no meaning and + VERW is not guaranteed to clear buffers + 1 X 1 MDS fixed, TAA can be mitigated by + VERW or TSX_CTRL_MSR + ======= ========= ============= ======================================== + +Mitigation selection guide +-------------------------- + +1. Trusted userspace and guests +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +If all user space applications are from a trusted source and do not execute +untrusted code which is supplied externally, then the mitigation can be +disabled. The same applies to virtualized environments with trusted guests. + + +2. Untrusted userspace and guests +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +If there are untrusted applications or guests on the system, enabling TSX +might allow a malicious actor to leak data from the host or from other +processes running on the same physical core. + +If the microcode is available and the TSX is disabled on the host, attacks +are prevented in a virtualized environment as well, even if the VMs do not +explicitly enable the mitigation. + + +.. _taa_default_mitigations: + +Default mitigations +------------------- + +The kernel's default action for vulnerable processors is: + + - Deploy TSX disable mitigation (tsx_async_abort=full tsx=off). diff --git a/Documentation/admin-guide/hw_random.rst b/Documentation/admin-guide/hw_random.rst new file mode 100644 index 000000000..d49460171 --- /dev/null +++ b/Documentation/admin-guide/hw_random.rst @@ -0,0 +1,105 @@ +================================= +Hardware random number generators +================================= + +Introduction +============ + +The hw_random framework is software that makes use of a +special hardware feature on your CPU or motherboard, +a Random Number Generator (RNG). The software has two parts: +a core providing the /dev/hwrng character device and its +sysfs support, plus a hardware-specific driver that plugs +into that core. + +To make the most effective use of these mechanisms, you +should download the support software as well. Download the +latest version of the "rng-tools" package from the +hw_random driver's official Web site: + + http://sourceforge.net/projects/gkernel/ + +Those tools use /dev/hwrng to fill the kernel entropy pool, +which is used internally and exported by the /dev/urandom and +/dev/random special files. + +Theory of operation +=================== + +CHARACTER DEVICE. Using the standard open() +and read() system calls, you can read random data from +the hardware RNG device. This data is NOT CHECKED by any +fitness tests, and could potentially be bogus (if the +hardware is faulty or has been tampered with). Data is only +output if the hardware "has-data" flag is set, but nevertheless +a security-conscious person would run fitness tests on the +data before assuming it is truly random. + +The rng-tools package uses such tests in "rngd", and lets you +run them by hand with a "rngtest" utility. + +/dev/hwrng is char device major 10, minor 183. + +CLASS DEVICE. There is a /sys/class/misc/hw_random node with +two unique attributes, "rng_available" and "rng_current". The +"rng_available" attribute lists the hardware-specific drivers +available, while "rng_current" lists the one which is currently +connected to /dev/hwrng. If your system has more than one +RNG available, you may change the one used by writing a name from +the list in "rng_available" into "rng_current". + +========================================================================== + + +Hardware driver for Intel/AMD/VIA Random Number Generators (RNG) + - Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com> + - Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com> + + +About the Intel RNG hardware, from the firmware hub datasheet +============================================================= + +The Firmware Hub integrates a Random Number Generator (RNG) +using thermal noise generated from inherently random quantum +mechanical properties of silicon. When not generating new random +bits the RNG circuitry will enter a low power state. Intel will +provide a binary software driver to give third party software +access to our RNG for use as a security feature. At this time, +the RNG is only to be used with a system in an OS-present state. + +Intel RNG Driver notes +====================== + +FIXME: support poll(2) + +.. note:: + + request_mem_region was removed, for three reasons: + + 1) Only one RNG is supported by this driver; + 2) The location used by the RNG is a fixed location in + MMIO-addressable memory; + 3) users with properly working BIOS e820 handling will always + have the region in which the RNG is located reserved, so + request_mem_region calls always fail for proper setups. + However, for people who use mem=XX, BIOS e820 information is + **not** in /proc/iomem, and request_mem_region(RNG_ADDR) can + succeed. + +Driver details +============== + +Based on: + Intel 82802AB/82802AC Firmware Hub (FWH) Datasheet + May 1999 Order Number: 290658-002 R + +Intel 82802 Firmware Hub: + Random Number Generator + Programmer's Reference Manual + December 1999 Order Number: 298029-001 R + +Intel 82802 Firmware HUB Random Number Generator Driver + Copyright (c) 2000 Matt Sottek <msottek@quiknet.com> + +Special thanks to Matt Sottek. I did the "guts", he +did the "brains" and all the testing. diff --git a/Documentation/admin-guide/index.rst b/Documentation/admin-guide/index.rst new file mode 100644 index 000000000..43ea35613 --- /dev/null +++ b/Documentation/admin-guide/index.rst @@ -0,0 +1,143 @@ +The Linux kernel user's and administrator's guide +================================================= + +The following is a collection of user-oriented documents that have been +added to the kernel over time. There is, as yet, little overall order or +organization here — this material was not written to be a single, coherent +document! With luck things will improve quickly over time. + +This initial section contains overall information, including the README +file describing the kernel as a whole, documentation on kernel parameters, +etc. + +.. toctree:: + :maxdepth: 1 + + README + kernel-parameters + devices + sysctl/index + + abi + features + +This section describes CPU vulnerabilities and their mitigations. + +.. toctree:: + :maxdepth: 1 + + hw-vuln/index + +Here is a set of documents aimed at users who are trying to track down +problems and bugs in particular. + +.. toctree:: + :maxdepth: 1 + + reporting-issues + reporting-regressions + quickly-build-trimmed-linux + bug-hunting + bug-bisect + tainted-kernels + ramoops + dynamic-debug-howto + init + kdump/index + perf/index + pstore-blk + +This is the beginning of a section with information of interest to +application developers. Documents covering various aspects of the kernel +ABI will be found here. + +.. toctree:: + :maxdepth: 1 + + sysfs-rules + +This is the beginning of a section with information of interest to +application developers and system integrators doing analysis of the +Linux kernel for safety critical applications. Documents supporting +analysis of kernel interactions with applications, and key kernel +subsystems expectations will be found here. + +.. toctree:: + :maxdepth: 1 + + workload-tracing + +The rest of this manual consists of various unordered guides on how to +configure specific aspects of kernel behavior to your liking. + +.. toctree:: + :maxdepth: 1 + + acpi/index + aoe/index + auxdisplay/index + bcache + binderfs + binfmt-misc + blockdev/index + bootconfig + braille-console + btmrvl + cgroup-v1/index + cgroup-v2 + cifs/index + clearing-warn-once + cpu-load + cputopology + dell_rbu + device-mapper/index + edid + efi-stub + ext4 + filesystem-monitoring + nfs/index + gpio/index + highuid + hw_random + initrd + iostats + java + jfs + kernel-per-CPU-kthreads + laptops/index + lcd-panel-cgram + ldm + lockup-watchdogs + LSM/index + md + media/index + mm/index + module-signing + mono + namespaces/index + numastat + parport + perf-security + pm/index + pnp + rapidio + ras + rtc + serial-console + svga + syscall-user-dispatch + sysrq + thermal/index + thunderbolt + ufs + unicode + vga-softcursor + video-output + xfs + +.. only:: subproject and html + + Indices + ======= + + * :ref:`genindex` diff --git a/Documentation/admin-guide/init.rst b/Documentation/admin-guide/init.rst new file mode 100644 index 000000000..41f06a091 --- /dev/null +++ b/Documentation/admin-guide/init.rst @@ -0,0 +1,48 @@ +Explaining the "No working init found." boot hang message +========================================================= +:Authors: Andreas Mohr <andi at lisas period de> + Cristian Souza <cristianmsbr at gmail period com> + +This document provides some high-level reasons for failure +(listed roughly in order of execution) to load the init binary. + +1) **Unable to mount root FS**: Set "debug" kernel parameter (in bootloader + config file or CONFIG_CMDLINE) to get more detailed kernel messages. + +2) **init binary doesn't exist on rootfs**: Make sure you have the correct + root FS type (and ``root=`` kernel parameter points to the correct + partition), required drivers such as storage hardware (such as SCSI or + USB!) and filesystem (ext3, jffs2, etc.) are builtin (alternatively as + modules, to be pre-loaded by an initrd). + +3) **Broken console device**: Possibly a conflict in ``console= setup`` + --> initial console unavailable. E.g. some serial consoles are unreliable + due to serial IRQ issues (e.g. missing interrupt-based configuration). + Try using a different ``console= device`` or e.g. ``netconsole=``. + +4) **Binary exists but dependencies not available**: E.g. required library + dependencies of the init binary such as ``/lib/ld-linux.so.2`` missing or + broken. Use ``readelf -d <INIT>|grep NEEDED`` to find out which libraries + are required. + +5) **Binary cannot be loaded**: Make sure the binary's architecture matches + your hardware. E.g. i386 vs. x86_64 mismatch, or trying to load x86 on ARM + hardware. In case you tried loading a non-binary file here (shell script?), + you should make sure that the script specifies an interpreter in its + shebang header line (``#!/...``) that is fully working (including its + library dependencies). And before tackling scripts, better first test a + simple non-script binary such as ``/bin/sh`` and confirm its successful + execution. To find out more, add code ``to init/main.c`` to display + kernel_execve()s return values. + +Please extend this explanation whenever you find new failure causes +(after all loading the init binary is a CRITICAL and hard transition step +which needs to be made as painless as possible), then submit a patch to LKML. +Further TODOs: + +- Implement the various ``run_init_process()`` invocations via a struct array + which can then store the ``kernel_execve()`` result value and on failure + log it all by iterating over **all** results (very important usability fix). +- Try to make the implementation itself more helpful in general, e.g. by + providing additional error messages at affected places. + diff --git a/Documentation/admin-guide/initrd.rst b/Documentation/admin-guide/initrd.rst new file mode 100644 index 000000000..67bbad880 --- /dev/null +++ b/Documentation/admin-guide/initrd.rst @@ -0,0 +1,383 @@ +Using the initial RAM disk (initrd) +=================================== + +Written 1996,2000 by Werner Almesberger <werner.almesberger@epfl.ch> and +Hans Lermen <lermen@fgan.de> + + +initrd provides the capability to load a RAM disk by the boot loader. +This RAM disk can then be mounted as the root file system and programs +can be run from it. Afterwards, a new root file system can be mounted +from a different device. The previous root (from initrd) is then moved +to a directory and can be subsequently unmounted. + +initrd is mainly designed to allow system startup to occur in two phases, +where the kernel comes up with a minimum set of compiled-in drivers, and +where additional modules are loaded from initrd. + +This document gives a brief overview of the use of initrd. A more detailed +discussion of the boot process can be found in [#f1]_. + + +Operation +--------- + +When using initrd, the system typically boots as follows: + + 1) the boot loader loads the kernel and the initial RAM disk + 2) the kernel converts initrd into a "normal" RAM disk and + frees the memory used by initrd + 3) if the root device is not ``/dev/ram0``, the old (deprecated) + change_root procedure is followed. see the "Obsolete root change + mechanism" section below. + 4) root device is mounted. if it is ``/dev/ram0``, the initrd image is + then mounted as root + 5) /sbin/init is executed (this can be any valid executable, including + shell scripts; it is run with uid 0 and can do basically everything + init can do). + 6) init mounts the "real" root file system + 7) init places the root file system at the root directory using the + pivot_root system call + 8) init execs the ``/sbin/init`` on the new root filesystem, performing + the usual boot sequence + 9) the initrd file system is removed + +Note that changing the root directory does not involve unmounting it. +It is therefore possible to leave processes running on initrd during that +procedure. Also note that file systems mounted under initrd continue to +be accessible. + + +Boot command-line options +------------------------- + +initrd adds the following new options:: + + initrd=<path> (e.g. LOADLIN) + + Loads the specified file as the initial RAM disk. When using LILO, you + have to specify the RAM disk image file in /etc/lilo.conf, using the + INITRD configuration variable. + + noinitrd + + initrd data is preserved but it is not converted to a RAM disk and + the "normal" root file system is mounted. initrd data can be read + from /dev/initrd. Note that the data in initrd can have any structure + in this case and doesn't necessarily have to be a file system image. + This option is used mainly for debugging. + + Note: /dev/initrd is read-only and it can only be used once. As soon + as the last process has closed it, all data is freed and /dev/initrd + can't be opened anymore. + + root=/dev/ram0 + + initrd is mounted as root, and the normal boot procedure is followed, + with the RAM disk mounted as root. + +Compressed cpio images +---------------------- + +Recent kernels have support for populating a ramdisk from a compressed cpio +archive. On such systems, the creation of a ramdisk image doesn't need to +involve special block devices or loopbacks; you merely create a directory on +disk with the desired initrd content, cd to that directory, and run (as an +example):: + + find . | cpio --quiet -H newc -o | gzip -9 -n > /boot/imagefile.img + +Examining the contents of an existing image file is just as simple:: + + mkdir /tmp/imagefile + cd /tmp/imagefile + gzip -cd /boot/imagefile.img | cpio -imd --quiet + +Installation +------------ + +First, a directory for the initrd file system has to be created on the +"normal" root file system, e.g.:: + + # mkdir /initrd + +The name is not relevant. More details can be found on the +:manpage:`pivot_root(2)` man page. + +If the root file system is created during the boot procedure (i.e. if +you're building an install floppy), the root file system creation +procedure should create the ``/initrd`` directory. + +If initrd will not be mounted in some cases, its content is still +accessible if the following device has been created:: + + # mknod /dev/initrd b 1 250 + # chmod 400 /dev/initrd + +Second, the kernel has to be compiled with RAM disk support and with +support for the initial RAM disk enabled. Also, at least all components +needed to execute programs from initrd (e.g. executable format and file +system) must be compiled into the kernel. + +Third, you have to create the RAM disk image. This is done by creating a +file system on a block device, copying files to it as needed, and then +copying the content of the block device to the initrd file. With recent +kernels, at least three types of devices are suitable for that: + + - a floppy disk (works everywhere but it's painfully slow) + - a RAM disk (fast, but allocates physical memory) + - a loopback device (the most elegant solution) + +We'll describe the loopback device method: + + 1) make sure loopback block devices are configured into the kernel + 2) create an empty file system of the appropriate size, e.g.:: + + # dd if=/dev/zero of=initrd bs=300k count=1 + # mke2fs -F -m0 initrd + + (if space is critical, you may want to use the Minix FS instead of Ext2) + 3) mount the file system, e.g.:: + + # mount -t ext2 -o loop initrd /mnt + + 4) create the console device:: + + # mkdir /mnt/dev + # mknod /mnt/dev/console c 5 1 + + 5) copy all the files that are needed to properly use the initrd + environment. Don't forget the most important file, ``/sbin/init`` + + .. note:: ``/sbin/init`` permissions must include "x" (execute). + + 6) correct operation the initrd environment can frequently be tested + even without rebooting with the command:: + + # chroot /mnt /sbin/init + + This is of course limited to initrds that do not interfere with the + general system state (e.g. by reconfiguring network interfaces, + overwriting mounted devices, trying to start already running demons, + etc. Note however that it is usually possible to use pivot_root in + such a chroot'ed initrd environment.) + 7) unmount the file system:: + + # umount /mnt + + 8) the initrd is now in the file "initrd". Optionally, it can now be + compressed:: + + # gzip -9 initrd + +For experimenting with initrd, you may want to take a rescue floppy and +only add a symbolic link from ``/sbin/init`` to ``/bin/sh``. Alternatively, you +can try the experimental newlib environment [#f2]_ to create a small +initrd. + +Finally, you have to boot the kernel and load initrd. Almost all Linux +boot loaders support initrd. Since the boot process is still compatible +with an older mechanism, the following boot command line parameters +have to be given:: + + root=/dev/ram0 rw + +(rw is only necessary if writing to the initrd file system.) + +With LOADLIN, you simply execute:: + + LOADLIN <kernel> initrd=<disk_image> + +e.g.:: + + LOADLIN C:\LINUX\BZIMAGE initrd=C:\LINUX\INITRD.GZ root=/dev/ram0 rw + +With LILO, you add the option ``INITRD=<path>`` to either the global section +or to the section of the respective kernel in ``/etc/lilo.conf``, and pass +the options using APPEND, e.g.:: + + image = /bzImage + initrd = /boot/initrd.gz + append = "root=/dev/ram0 rw" + +and run ``/sbin/lilo`` + +For other boot loaders, please refer to the respective documentation. + +Now you can boot and enjoy using initrd. + + +Changing the root device +------------------------ + +When finished with its duties, init typically changes the root device +and proceeds with starting the Linux system on the "real" root device. + +The procedure involves the following steps: + - mounting the new root file system + - turning it into the root file system + - removing all accesses to the old (initrd) root file system + - unmounting the initrd file system and de-allocating the RAM disk + +Mounting the new root file system is easy: it just needs to be mounted on +a directory under the current root. Example:: + + # mkdir /new-root + # mount -o ro /dev/hda1 /new-root + +The root change is accomplished with the pivot_root system call, which +is also available via the ``pivot_root`` utility (see :manpage:`pivot_root(8)` +man page; ``pivot_root`` is distributed with util-linux version 2.10h or higher +[#f3]_). ``pivot_root`` moves the current root to a directory under the new +root, and puts the new root at its place. The directory for the old root +must exist before calling ``pivot_root``. Example:: + + # cd /new-root + # mkdir initrd + # pivot_root . initrd + +Now, the init process may still access the old root via its +executable, shared libraries, standard input/output/error, and its +current root directory. All these references are dropped by the +following command:: + + # exec chroot . what-follows <dev/console >dev/console 2>&1 + +Where what-follows is a program under the new root, e.g. ``/sbin/init`` +If the new root file system will be used with udev and has no valid +``/dev`` directory, udev must be initialized before invoking chroot in order +to provide ``/dev/console``. + +Note: implementation details of pivot_root may change with time. In order +to ensure compatibility, the following points should be observed: + + - before calling pivot_root, the current directory of the invoking + process should point to the new root directory + - use . as the first argument, and the _relative_ path of the directory + for the old root as the second argument + - a chroot program must be available under the old and the new root + - chroot to the new root afterwards + - use relative paths for dev/console in the exec command + +Now, the initrd can be unmounted and the memory allocated by the RAM +disk can be freed:: + + # umount /initrd + # blockdev --flushbufs /dev/ram0 + +It is also possible to use initrd with an NFS-mounted root, see the +:manpage:`pivot_root(8)` man page for details. + + +Usage scenarios +--------------- + +The main motivation for implementing initrd was to allow for modular +kernel configuration at system installation. The procedure would work +as follows: + + 1) system boots from floppy or other media with a minimal kernel + (e.g. support for RAM disks, initrd, a.out, and the Ext2 FS) and + loads initrd + 2) ``/sbin/init`` determines what is needed to (1) mount the "real" root FS + (i.e. device type, device drivers, file system) and (2) the + distribution media (e.g. CD-ROM, network, tape, ...). This can be + done by asking the user, by auto-probing, or by using a hybrid + approach. + 3) ``/sbin/init`` loads the necessary kernel modules + 4) ``/sbin/init`` creates and populates the root file system (this doesn't + have to be a very usable system yet) + 5) ``/sbin/init`` invokes ``pivot_root`` to change the root file system and + execs - via chroot - a program that continues the installation + 6) the boot loader is installed + 7) the boot loader is configured to load an initrd with the set of + modules that was used to bring up the system (e.g. ``/initrd`` can be + modified, then unmounted, and finally, the image is written from + ``/dev/ram0`` or ``/dev/rd/0`` to a file) + 8) now the system is bootable and additional installation tasks can be + performed + +The key role of initrd here is to re-use the configuration data during +normal system operation without requiring the use of a bloated "generic" +kernel or re-compiling or re-linking the kernel. + +A second scenario is for installations where Linux runs on systems with +different hardware configurations in a single administrative domain. In +such cases, it is desirable to generate only a small set of kernels +(ideally only one) and to keep the system-specific part of configuration +information as small as possible. In this case, a common initrd could be +generated with all the necessary modules. Then, only ``/sbin/init`` or a file +read by it would have to be different. + +A third scenario is more convenient recovery disks, because information +like the location of the root FS partition doesn't have to be provided at +boot time, but the system loaded from initrd can invoke a user-friendly +dialog and it can also perform some sanity checks (or even some form of +auto-detection). + +Last not least, CD-ROM distributors may use it for better installation +from CD, e.g. by using a boot floppy and bootstrapping a bigger RAM disk +via initrd from CD; or by booting via a loader like ``LOADLIN`` or directly +from the CD-ROM, and loading the RAM disk from CD without need of +floppies. + + +Obsolete root change mechanism +------------------------------ + +The following mechanism was used before the introduction of pivot_root. +Current kernels still support it, but you should _not_ rely on its +continued availability. + +It works by mounting the "real" root device (i.e. the one set with rdev +in the kernel image or with root=... at the boot command line) as the +root file system when linuxrc exits. The initrd file system is then +unmounted, or, if it is still busy, moved to a directory ``/initrd``, if +such a directory exists on the new root file system. + +In order to use this mechanism, you do not have to specify the boot +command options root, init, or rw. (If specified, they will affect +the real root file system, not the initrd environment.) + +If /proc is mounted, the "real" root device can be changed from within +linuxrc by writing the number of the new root FS device to the special +file /proc/sys/kernel/real-root-dev, e.g.:: + + # echo 0x301 >/proc/sys/kernel/real-root-dev + +Note that the mechanism is incompatible with NFS and similar file +systems. + +This old, deprecated mechanism is commonly called ``change_root``, while +the new, supported mechanism is called ``pivot_root``. + + +Mixed change_root and pivot_root mechanism +------------------------------------------ + +In case you did not want to use ``root=/dev/ram0`` to trigger the pivot_root +mechanism, you may create both ``/linuxrc`` and ``/sbin/init`` in your initrd +image. + +``/linuxrc`` would contain only the following:: + + #! /bin/sh + mount -n -t proc proc /proc + echo 0x0100 >/proc/sys/kernel/real-root-dev + umount -n /proc + +Once linuxrc exited, the kernel would mount again your initrd as root, +this time executing ``/sbin/init``. Again, it would be the duty of this init +to build the right environment (maybe using the ``root= device`` passed on +the cmdline) before the final execution of the real ``/sbin/init``. + + +Resources +--------- + +.. [#f1] Almesberger, Werner; "Booting Linux: The History and the Future" + https://www.almesberger.net/cv/papers/ols2k-9.ps.gz +.. [#f2] newlib package (experimental), with initrd example + https://www.sourceware.org/newlib/ +.. [#f3] util-linux: Miscellaneous utilities for Linux + https://www.kernel.org/pub/linux/utils/util-linux/ diff --git a/Documentation/admin-guide/iostats.rst b/Documentation/admin-guide/iostats.rst new file mode 100644 index 000000000..609a3201f --- /dev/null +++ b/Documentation/admin-guide/iostats.rst @@ -0,0 +1,210 @@ +===================== +I/O statistics fields +===================== + +Since 2.4.20 (and some versions before, with patches), and 2.5.45, +more extensive disk statistics have been introduced to help measure disk +activity. Tools such as ``sar`` and ``iostat`` typically interpret these and do +the work for you, but in case you are interested in creating your own +tools, the fields are explained here. + +In 2.4 now, the information is found as additional fields in +``/proc/partitions``. In 2.6 and upper, the same information is found in two +places: one is in the file ``/proc/diskstats``, and the other is within +the sysfs file system, which must be mounted in order to obtain +the information. Throughout this document we'll assume that sysfs +is mounted on ``/sys``, although of course it may be mounted anywhere. +Both ``/proc/diskstats`` and sysfs use the same source for the information +and so should not differ. + +Here are examples of these different formats:: + + 2.4: + 3 0 39082680 hda 446216 784926 9550688 4382310 424847 312726 5922052 19310380 0 3376340 23705160 + 3 1 9221278 hda1 35486 0 35496 38030 0 0 0 0 0 38030 38030 + + 2.6+ sysfs: + 446216 784926 9550688 4382310 424847 312726 5922052 19310380 0 3376340 23705160 + 35486 38030 38030 38030 + + 2.6+ diskstats: + 3 0 hda 446216 784926 9550688 4382310 424847 312726 5922052 19310380 0 3376340 23705160 + 3 1 hda1 35486 38030 38030 38030 + + 4.18+ diskstats: + 3 0 hda 446216 784926 9550688 4382310 424847 312726 5922052 19310380 0 3376340 23705160 0 0 0 0 + +On 2.4 you might execute ``grep 'hda ' /proc/partitions``. On 2.6+, you have +a choice of ``cat /sys/block/hda/stat`` or ``grep 'hda ' /proc/diskstats``. + +The advantage of one over the other is that the sysfs choice works well +if you are watching a known, small set of disks. ``/proc/diskstats`` may +be a better choice if you are watching a large number of disks because +you'll avoid the overhead of 50, 100, or 500 or more opens/closes with +each snapshot of your disk statistics. + +In 2.4, the statistics fields are those after the device name. In +the above example, the first field of statistics would be 446216. +By contrast, in 2.6+ if you look at ``/sys/block/hda/stat``, you'll +find just the 15 fields, beginning with 446216. If you look at +``/proc/diskstats``, the 15 fields will be preceded by the major and +minor device numbers, and device name. Each of these formats provides +15 fields of statistics, each meaning exactly the same things. +All fields except field 9 are cumulative since boot. Field 9 should +go to zero as I/Os complete; all others only increase (unless they +overflow and wrap). Wrapping might eventually occur on a very busy +or long-lived system; so applications should be prepared to deal with +it. Regarding wrapping, the types of the fields are either unsigned +int (32 bit) or unsigned long (32-bit or 64-bit, depending on your +machine) as noted per-field below. Unless your observations are very +spread in time, these fields should not wrap twice before you notice it. + +Each set of stats only applies to the indicated device; if you want +system-wide stats you'll have to find all the devices and sum them all up. + +Field 1 -- # of reads completed (unsigned long) + This is the total number of reads completed successfully. + +Field 2 -- # of reads merged, field 6 -- # of writes merged (unsigned long) + Reads and writes which are adjacent to each other may be merged for + efficiency. Thus two 4K reads may become one 8K read before it is + ultimately handed to the disk, and so it will be counted (and queued) + as only one I/O. This field lets you know how often this was done. + +Field 3 -- # of sectors read (unsigned long) + This is the total number of sectors read successfully. + +Field 4 -- # of milliseconds spent reading (unsigned int) + This is the total number of milliseconds spent by all reads (as + measured from blk_mq_alloc_request() to __blk_mq_end_request()). + +Field 5 -- # of writes completed (unsigned long) + This is the total number of writes completed successfully. + +Field 6 -- # of writes merged (unsigned long) + See the description of field 2. + +Field 7 -- # of sectors written (unsigned long) + This is the total number of sectors written successfully. + +Field 8 -- # of milliseconds spent writing (unsigned int) + This is the total number of milliseconds spent by all writes (as + measured from blk_mq_alloc_request() to __blk_mq_end_request()). + +Field 9 -- # of I/Os currently in progress (unsigned int) + The only field that should go to zero. Incremented as requests are + given to appropriate struct request_queue and decremented as they finish. + +Field 10 -- # of milliseconds spent doing I/Os (unsigned int) + This field increases so long as field 9 is nonzero. + + Since 5.0 this field counts jiffies when at least one request was + started or completed. If request runs more than 2 jiffies then some + I/O time might be not accounted in case of concurrent requests. + +Field 11 -- weighted # of milliseconds spent doing I/Os (unsigned int) + This field is incremented at each I/O start, I/O completion, I/O + merge, or read of these stats by the number of I/Os in progress + (field 9) times the number of milliseconds spent doing I/O since the + last update of this field. This can provide an easy measure of both + I/O completion time and the backlog that may be accumulating. + +Field 12 -- # of discards completed (unsigned long) + This is the total number of discards completed successfully. + +Field 13 -- # of discards merged (unsigned long) + See the description of field 2 + +Field 14 -- # of sectors discarded (unsigned long) + This is the total number of sectors discarded successfully. + +Field 15 -- # of milliseconds spent discarding (unsigned int) + This is the total number of milliseconds spent by all discards (as + measured from blk_mq_alloc_request() to __blk_mq_end_request()). + +Field 16 -- # of flush requests completed + This is the total number of flush requests completed successfully. + + Block layer combines flush requests and executes at most one at a time. + This counts flush requests executed by disk. Not tracked for partitions. + +Field 17 -- # of milliseconds spent flushing + This is the total number of milliseconds spent by all flush requests. + +To avoid introducing performance bottlenecks, no locks are held while +modifying these counters. This implies that minor inaccuracies may be +introduced when changes collide, so (for instance) adding up all the +read I/Os issued per partition should equal those made to the disks ... +but due to the lack of locking it may only be very close. + +In 2.6+, there are counters for each CPU, which make the lack of locking +almost a non-issue. When the statistics are read, the per-CPU counters +are summed (possibly overflowing the unsigned long variable they are +summed to) and the result given to the user. There is no convenient +user interface for accessing the per-CPU counters themselves. + +Since 4.19 request times are measured with nanoseconds precision and +truncated to milliseconds before showing in this interface. + +Disks vs Partitions +------------------- + +There were significant changes between 2.4 and 2.6+ in the I/O subsystem. +As a result, some statistic information disappeared. The translation from +a disk address relative to a partition to the disk address relative to +the host disk happens much earlier. All merges and timings now happen +at the disk level rather than at both the disk and partition level as +in 2.4. Consequently, you'll see a different statistics output on 2.6+ for +partitions from that for disks. There are only *four* fields available +for partitions on 2.6+ machines. This is reflected in the examples above. + +Field 1 -- # of reads issued + This is the total number of reads issued to this partition. + +Field 2 -- # of sectors read + This is the total number of sectors requested to be read from this + partition. + +Field 3 -- # of writes issued + This is the total number of writes issued to this partition. + +Field 4 -- # of sectors written + This is the total number of sectors requested to be written to + this partition. + +Note that since the address is translated to a disk-relative one, and no +record of the partition-relative address is kept, the subsequent success +or failure of the read cannot be attributed to the partition. In other +words, the number of reads for partitions is counted slightly before time +of queuing for partitions, and at completion for whole disks. This is +a subtle distinction that is probably uninteresting for most cases. + +More significant is the error induced by counting the numbers of +reads/writes before merges for partitions and after for disks. Since a +typical workload usually contains a lot of successive and adjacent requests, +the number of reads/writes issued can be several times higher than the +number of reads/writes completed. + +In 2.6.25, the full statistic set is again available for partitions and +disk and partition statistics are consistent again. Since we still don't +keep record of the partition-relative address, an operation is attributed to +the partition which contains the first sector of the request after the +eventual merges. As requests can be merged across partition, this could lead +to some (probably insignificant) inaccuracy. + +Additional notes +---------------- + +In 2.6+, sysfs is not mounted by default. If your distribution of +Linux hasn't added it already, here's the line you'll want to add to +your ``/etc/fstab``:: + + none /sys sysfs defaults 0 0 + + +In 2.6+, all disk statistics were removed from ``/proc/stat``. In 2.4, they +appear in both ``/proc/partitions`` and ``/proc/stat``, although the ones in +``/proc/stat`` take a very different format from those in ``/proc/partitions`` +(see proc(5), if your system has it.) + +-- ricklind@us.ibm.com diff --git a/Documentation/admin-guide/java.rst b/Documentation/admin-guide/java.rst new file mode 100644 index 000000000..8744e272e --- /dev/null +++ b/Documentation/admin-guide/java.rst @@ -0,0 +1,423 @@ +Java(tm) Binary Kernel Support for Linux v1.03 +---------------------------------------------- + +Linux beats them ALL! While all other OS's are TALKING about direct +support of Java Binaries in the OS, Linux is doing it! + +You can execute Java applications and Java Applets just like any +other program after you have done the following: + +1) You MUST FIRST install the Java Developers Kit for Linux. + The Java on Linux HOWTO gives the details on getting and + installing this. This HOWTO can be found at: + + ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO/Java-HOWTO + + You should also set up a reasonable CLASSPATH environment + variable to use Java applications that make use of any + nonstandard classes (not included in the same directory + as the application itself). + +2) You have to compile BINFMT_MISC either as a module or into + the kernel (``CONFIG_BINFMT_MISC``) and set it up properly. + If you choose to compile it as a module, you will have + to insert it manually with modprobe/insmod, as kmod + cannot easily be supported with binfmt_misc. + Read the file 'binfmt_misc.txt' in this directory to know + more about the configuration process. + +3) Add the following configuration items to binfmt_misc + (you should really have read ``binfmt_misc.txt`` now): + support for Java applications:: + + ':Java:M::\xca\xfe\xba\xbe::/usr/local/bin/javawrapper:' + + support for executable Jar files:: + + ':ExecutableJAR:E::jar::/usr/local/bin/jarwrapper:' + + support for Java Applets:: + + ':Applet:E::html::/usr/bin/appletviewer:' + + or the following, if you want to be more selective:: + + ':Applet:M::<!--applet::/usr/bin/appletviewer:' + + Of course you have to fix the path names. The path/file names given in this + document match the Debian 2.1 system. (i.e. jdk installed in ``/usr``, + custom wrappers from this document in ``/usr/local``) + + Note, that for the more selective applet support you have to modify + existing html-files to contain ``<!--applet-->`` in the first line + (``<`` has to be the first character!) to let this work! + + For the compiled Java programs you need a wrapper script like the + following (this is because Java is broken in case of the filename + handling), again fix the path names, both in the script and in the + above given configuration string. + + You, too, need the little program after the script. Compile like:: + + gcc -O2 -o javaclassname javaclassname.c + + and stick it to ``/usr/local/bin``. + + Both the javawrapper shellscript and the javaclassname program + were supplied by Colin J. Watson <cjw44@cam.ac.uk>. + +Javawrapper shell script: + +.. code-block:: sh + + #!/bin/bash + # /usr/local/bin/javawrapper - the wrapper for binfmt_misc/java + + if [ -z "$1" ]; then + exec 1>&2 + echo Usage: $0 class-file + exit 1 + fi + + CLASS=$1 + FQCLASS=`/usr/local/bin/javaclassname $1` + FQCLASSN=`echo $FQCLASS | sed -e 's/^.*\.\([^.]*\)$/\1/'` + FQCLASSP=`echo $FQCLASS | sed -e 's-\.-/-g' -e 's-^[^/]*$--' -e 's-/[^/]*$--'` + + # for example: + # CLASS=Test.class + # FQCLASS=foo.bar.Test + # FQCLASSN=Test + # FQCLASSP=foo/bar + + unset CLASSBASE + + declare -i LINKLEVEL=0 + + while :; do + if [ "`basename $CLASS .class`" == "$FQCLASSN" ]; then + # See if this directory works straight off + cd -L `dirname $CLASS` + CLASSDIR=$PWD + cd $OLDPWD + if echo $CLASSDIR | grep -q "$FQCLASSP$"; then + CLASSBASE=`echo $CLASSDIR | sed -e "s.$FQCLASSP$.."` + break; + fi + # Try dereferencing the directory name + cd -P `dirname $CLASS` + CLASSDIR=$PWD + cd $OLDPWD + if echo $CLASSDIR | grep -q "$FQCLASSP$"; then + CLASSBASE=`echo $CLASSDIR | sed -e "s.$FQCLASSP$.."` + break; + fi + # If no other possible filename exists + if [ ! -L $CLASS ]; then + exec 1>&2 + echo $0: + echo " $CLASS should be in a" \ + "directory tree called $FQCLASSP" + exit 1 + fi + fi + if [ ! -L $CLASS ]; then break; fi + # Go down one more level of symbolic links + let LINKLEVEL+=1 + if [ $LINKLEVEL -gt 5 ]; then + exec 1>&2 + echo $0: + echo " Too many symbolic links encountered" + exit 1 + fi + CLASS=`ls --color=no -l $CLASS | sed -e 's/^.* \([^ ]*\)$/\1/'` + done + + if [ -z "$CLASSBASE" ]; then + if [ -z "$FQCLASSP" ]; then + GOODNAME=$FQCLASSN.class + else + GOODNAME=$FQCLASSP/$FQCLASSN.class + fi + exec 1>&2 + echo $0: + echo " $FQCLASS should be in a file called $GOODNAME" + exit 1 + fi + + if ! echo $CLASSPATH | grep -q "^\(.*:\)*$CLASSBASE\(:.*\)*"; then + # class is not in CLASSPATH, so prepend dir of class to CLASSPATH + if [ -z "${CLASSPATH}" ] ; then + export CLASSPATH=$CLASSBASE + else + export CLASSPATH=$CLASSBASE:$CLASSPATH + fi + fi + + shift + /usr/bin/java $FQCLASS "$@" + +javaclassname.c: + +.. code-block:: c + + /* javaclassname.c + * + * Extracts the class name from a Java class file; intended for use in a Java + * wrapper of the type supported by the binfmt_misc option in the Linux kernel. + * + * Copyright (C) 1999 Colin J. Watson <cjw44@cam.ac.uk>. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + */ + + #include <stdlib.h> + #include <stdio.h> + #include <stdarg.h> + #include <sys/types.h> + + /* From Sun's Java VM Specification, as tag entries in the constant pool. */ + + #define CP_UTF8 1 + #define CP_INTEGER 3 + #define CP_FLOAT 4 + #define CP_LONG 5 + #define CP_DOUBLE 6 + #define CP_CLASS 7 + #define CP_STRING 8 + #define CP_FIELDREF 9 + #define CP_METHODREF 10 + #define CP_INTERFACEMETHODREF 11 + #define CP_NAMEANDTYPE 12 + #define CP_METHODHANDLE 15 + #define CP_METHODTYPE 16 + #define CP_INVOKEDYNAMIC 18 + + /* Define some commonly used error messages */ + + #define seek_error() error("%s: Cannot seek\n", program) + #define corrupt_error() error("%s: Class file corrupt\n", program) + #define eof_error() error("%s: Unexpected end of file\n", program) + #define utf8_error() error("%s: Only ASCII 1-255 supported\n", program); + + char *program; + + long *pool; + + u_int8_t read_8(FILE *classfile); + u_int16_t read_16(FILE *classfile); + void skip_constant(FILE *classfile, u_int16_t *cur); + void error(const char *format, ...); + int main(int argc, char **argv); + + /* Reads in an unsigned 8-bit integer. */ + u_int8_t read_8(FILE *classfile) + { + int b = fgetc(classfile); + if(b == EOF) + eof_error(); + return (u_int8_t)b; + } + + /* Reads in an unsigned 16-bit integer. */ + u_int16_t read_16(FILE *classfile) + { + int b1, b2; + b1 = fgetc(classfile); + if(b1 == EOF) + eof_error(); + b2 = fgetc(classfile); + if(b2 == EOF) + eof_error(); + return (u_int16_t)((b1 << 8) | b2); + } + + /* Reads in a value from the constant pool. */ + void skip_constant(FILE *classfile, u_int16_t *cur) + { + u_int16_t len; + int seekerr = 1; + pool[*cur] = ftell(classfile); + switch(read_8(classfile)) + { + case CP_UTF8: + len = read_16(classfile); + seekerr = fseek(classfile, len, SEEK_CUR); + break; + case CP_CLASS: + case CP_STRING: + case CP_METHODTYPE: + seekerr = fseek(classfile, 2, SEEK_CUR); + break; + case CP_METHODHANDLE: + seekerr = fseek(classfile, 3, SEEK_CUR); + break; + case CP_INTEGER: + case CP_FLOAT: + case CP_FIELDREF: + case CP_METHODREF: + case CP_INTERFACEMETHODREF: + case CP_NAMEANDTYPE: + case CP_INVOKEDYNAMIC: + seekerr = fseek(classfile, 4, SEEK_CUR); + break; + case CP_LONG: + case CP_DOUBLE: + seekerr = fseek(classfile, 8, SEEK_CUR); + ++(*cur); + break; + default: + corrupt_error(); + } + if(seekerr) + seek_error(); + } + + void error(const char *format, ...) + { + va_list ap; + va_start(ap, format); + vfprintf(stderr, format, ap); + va_end(ap); + exit(1); + } + + int main(int argc, char **argv) + { + FILE *classfile; + u_int16_t cp_count, i, this_class, classinfo_ptr; + u_int8_t length; + + program = argv[0]; + + if(!argv[1]) + error("%s: Missing input file\n", program); + classfile = fopen(argv[1], "rb"); + if(!classfile) + error("%s: Error opening %s\n", program, argv[1]); + + if(fseek(classfile, 8, SEEK_SET)) /* skip magic and version numbers */ + seek_error(); + cp_count = read_16(classfile); + pool = calloc(cp_count, sizeof(long)); + if(!pool) + error("%s: Out of memory for constant pool\n", program); + + for(i = 1; i < cp_count; ++i) + skip_constant(classfile, &i); + if(fseek(classfile, 2, SEEK_CUR)) /* skip access flags */ + seek_error(); + + this_class = read_16(classfile); + if(this_class < 1 || this_class >= cp_count) + corrupt_error(); + if(!pool[this_class] || pool[this_class] == -1) + corrupt_error(); + if(fseek(classfile, pool[this_class] + 1, SEEK_SET)) + seek_error(); + + classinfo_ptr = read_16(classfile); + if(classinfo_ptr < 1 || classinfo_ptr >= cp_count) + corrupt_error(); + if(!pool[classinfo_ptr] || pool[classinfo_ptr] == -1) + corrupt_error(); + if(fseek(classfile, pool[classinfo_ptr] + 1, SEEK_SET)) + seek_error(); + + length = read_16(classfile); + for(i = 0; i < length; ++i) + { + u_int8_t x = read_8(classfile); + if((x & 0x80) || !x) + { + if((x & 0xE0) == 0xC0) + { + u_int8_t y = read_8(classfile); + if((y & 0xC0) == 0x80) + { + int c = ((x & 0x1f) << 6) + (y & 0x3f); + if(c) putchar(c); + else utf8_error(); + } + else utf8_error(); + } + else utf8_error(); + } + else if(x == '/') putchar('.'); + else putchar(x); + } + putchar('\n'); + free(pool); + fclose(classfile); + return 0; + } + +jarwrapper:: + + #!/bin/bash + # /usr/local/java/bin/jarwrapper - the wrapper for binfmt_misc/jar + + java -jar $1 + + +Now simply ``chmod +x`` the ``.class``, ``.jar`` and/or ``.html`` files you +want to execute. + +To add a Java program to your path best put a symbolic link to the main +.class file into /usr/bin (or another place you like) omitting the .class +extension. The directory containing the original .class file will be +added to your CLASSPATH during execution. + + +To test your new setup, enter in the following simple Java app, and name +it "HelloWorld.java": + +.. code-block:: java + + class HelloWorld { + public static void main(String args[]) { + System.out.println("Hello World!"); + } + } + +Now compile the application with:: + + javac HelloWorld.java + +Set the executable permissions of the binary file, with:: + + chmod 755 HelloWorld.class + +And then execute it:: + + ./HelloWorld.class + + +To execute Java Jar files, simple chmod the ``*.jar`` files to include +the execution bit, then just do:: + + ./Application.jar + + +To execute Java Applets, simple chmod the ``*.html`` files to include +the execution bit, then just do:: + + ./Applet.html + + +originally by Brian A. Lantz, brian@lantz.com +heavily edited for binfmt_misc by Richard Günther +new scripts by Colin J. Watson <cjw44@cam.ac.uk> +added executable Jar file support by Kurt Huwig <kurt@iku-netz.de> diff --git a/Documentation/admin-guide/jfs.rst b/Documentation/admin-guide/jfs.rst new file mode 100644 index 000000000..9e12d936b --- /dev/null +++ b/Documentation/admin-guide/jfs.rst @@ -0,0 +1,66 @@ +=========================================== +IBM's Journaled File System (JFS) for Linux +=========================================== + +JFS Homepage: http://jfs.sourceforge.net/ + +The following mount options are supported: + +(*) == default + +iocharset=name + Character set to use for converting from Unicode to + ASCII. The default is to do no conversion. Use + iocharset=utf8 for UTF-8 translations. This requires + CONFIG_NLS_UTF8 to be set in the kernel .config file. + iocharset=none specifies the default behavior explicitly. + +resize=value + Resize the volume to <value> blocks. JFS only supports + growing a volume, not shrinking it. This option is only + valid during a remount, when the volume is mounted + read-write. The resize keyword with no value will grow + the volume to the full size of the partition. + +nointegrity + Do not write to the journal. The primary use of this option + is to allow for higher performance when restoring a volume + from backup media. The integrity of the volume is not + guaranteed if the system abnormally abends. + +integrity(*) + Commit metadata changes to the journal. Use this option to + remount a volume where the nointegrity option was + previously specified in order to restore normal behavior. + +errors=continue + Keep going on a filesystem error. +errors=remount-ro(*) + Remount the filesystem read-only on an error. +errors=panic + Panic and halt the machine if an error occurs. + +uid=value + Override on-disk uid with specified value +gid=value + Override on-disk gid with specified value +umask=value + Override on-disk umask with specified octal value. For + directories, the execute bit will be set if the corresponding + read bit is set. + +discard=minlen, discard/nodiscard(*) + This enables/disables the use of discard/TRIM commands. + The discard/TRIM commands are sent to the underlying + block device when blocks are freed. This is useful for SSD + devices and sparse/thinly-provisioned LUNs. The FITRIM ioctl + command is also available together with the nodiscard option. + The value of minlen specifies the minimum blockcount, when + a TRIM command to the block device is considered useful. + When no value is given to the discard option, it defaults to + 64 blocks, which means 256KiB in JFS. + The minlen value of discard overrides the minlen value given + on an FITRIM ioctl(). + +The JFS mailing list can be subscribed to by using the link labeled +"Mail list Subscribe" at our web page http://jfs.sourceforge.net/ diff --git a/Documentation/admin-guide/kdump/gdbmacros.txt b/Documentation/admin-guide/kdump/gdbmacros.txt new file mode 100644 index 000000000..030de95e3 --- /dev/null +++ b/Documentation/admin-guide/kdump/gdbmacros.txt @@ -0,0 +1,323 @@ +# +# This file contains a few gdb macros (user defined commands) to extract +# useful information from kernel crashdump (kdump) like stack traces of +# all the processes or a particular process and trapinfo. +# +# These macros can be used by copying this file in .gdbinit (put in home +# directory or current directory) or by invoking gdb command with +# --command=<command-file-name> option +# +# Credits: +# Alexander Nyberg <alexn@telia.com> +# V Srivatsa <vatsa@in.ibm.com> +# Maneesh Soni <maneesh@in.ibm.com> +# + +define bttnobp + set $tasks_off=((size_t)&((struct task_struct *)0)->tasks) + set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next) + set $init_t=&init_task + set $next_t=(((char *)($init_t->tasks).next) - $tasks_off) + set var $stacksize = sizeof(union thread_union) + while ($next_t != $init_t) + set $next_t=(struct task_struct *)$next_t + printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm + printf "===================\n" + set var $stackp = $next_t.thread.sp + set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize + + while ($stackp < $stack_top) + if (*($stackp) > _stext && *($stackp) < _sinittext) + info symbol *($stackp) + end + set $stackp += 4 + end + set $next_th=(((char *)$next_t->thread_group.next) - $pid_off) + while ($next_th != $next_t) + set $next_th=(struct task_struct *)$next_th + printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm + printf "===================\n" + set var $stackp = $next_t.thread.sp + set var $stack_top = ($stackp & ~($stacksize - 1)) + stacksize + + while ($stackp < $stack_top) + if (*($stackp) > _stext && *($stackp) < _sinittext) + info symbol *($stackp) + end + set $stackp += 4 + end + set $next_th=(((char *)$next_th->thread_group.next) - $pid_off) + end + set $next_t=(char *)($next_t->tasks.next) - $tasks_off + end +end +document bttnobp + dump all thread stack traces on a kernel compiled with !CONFIG_FRAME_POINTER +end + +define btthreadstack + set var $pid_task = $arg0 + + printf "\npid %d; comm %s:\n", $pid_task.pid, $pid_task.comm + printf "task struct: " + print $pid_task + printf "===================\n" + set var $stackp = $pid_task.thread.sp + set var $stacksize = sizeof(union thread_union) + set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize + set var $stack_bot = ($stackp & ~($stacksize - 1)) + + set $stackp = *((unsigned long *) $stackp) + while (($stackp < $stack_top) && ($stackp > $stack_bot)) + set var $addr = *(((unsigned long *) $stackp) + 1) + info symbol $addr + set $stackp = *((unsigned long *) $stackp) + end +end +document btthreadstack + dump a thread stack using the given task structure pointer +end + + +define btt + set $tasks_off=((size_t)&((struct task_struct *)0)->tasks) + set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next) + set $init_t=&init_task + set $next_t=(((char *)($init_t->tasks).next) - $tasks_off) + while ($next_t != $init_t) + set $next_t=(struct task_struct *)$next_t + btthreadstack $next_t + + set $next_th=(((char *)$next_t->thread_group.next) - $pid_off) + while ($next_th != $next_t) + set $next_th=(struct task_struct *)$next_th + btthreadstack $next_th + set $next_th=(((char *)$next_th->thread_group.next) - $pid_off) + end + set $next_t=(char *)($next_t->tasks.next) - $tasks_off + end +end +document btt + dump all thread stack traces on a kernel compiled with CONFIG_FRAME_POINTER +end + +define btpid + set var $pid = $arg0 + set $tasks_off=((size_t)&((struct task_struct *)0)->tasks) + set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next) + set $init_t=&init_task + set $next_t=(((char *)($init_t->tasks).next) - $tasks_off) + set var $pid_task = 0 + + while ($next_t != $init_t) + set $next_t=(struct task_struct *)$next_t + + if ($next_t.pid == $pid) + set $pid_task = $next_t + end + + set $next_th=(((char *)$next_t->thread_group.next) - $pid_off) + while ($next_th != $next_t) + set $next_th=(struct task_struct *)$next_th + if ($next_th.pid == $pid) + set $pid_task = $next_th + end + set $next_th=(((char *)$next_th->thread_group.next) - $pid_off) + end + set $next_t=(char *)($next_t->tasks.next) - $tasks_off + end + + btthreadstack $pid_task +end +document btpid + backtrace of pid +end + + +define trapinfo + set var $pid = $arg0 + set $tasks_off=((size_t)&((struct task_struct *)0)->tasks) + set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next) + set $init_t=&init_task + set $next_t=(((char *)($init_t->tasks).next) - $tasks_off) + set var $pid_task = 0 + + while ($next_t != $init_t) + set $next_t=(struct task_struct *)$next_t + + if ($next_t.pid == $pid) + set $pid_task = $next_t + end + + set $next_th=(((char *)$next_t->thread_group.next) - $pid_off) + while ($next_th != $next_t) + set $next_th=(struct task_struct *)$next_th + if ($next_th.pid == $pid) + set $pid_task = $next_th + end + set $next_th=(((char *)$next_th->thread_group.next) - $pid_off) + end + set $next_t=(char *)($next_t->tasks.next) - $tasks_off + end + + printf "Trapno %ld, cr2 0x%lx, error_code %ld\n", $pid_task.thread.trap_no, \ + $pid_task.thread.cr2, $pid_task.thread.error_code + +end +document trapinfo + Run info threads and lookup pid of thread #1 + 'trapinfo <pid>' will tell you by which trap & possibly + address the kernel panicked. +end + +define dump_record + set var $desc = $arg0 + set var $info = $arg1 + if ($argc > 2) + set var $prev_flags = $arg2 + else + set var $prev_flags = 0 + end + + set var $prefix = 1 + set var $newline = 1 + + set var $begin = $desc->text_blk_lpos.begin % (1U << prb->text_data_ring.size_bits) + set var $next = $desc->text_blk_lpos.next % (1U << prb->text_data_ring.size_bits) + + # handle data-less record + if ($begin & 1) + set var $text_len = 0 + set var $log = "" + else + # handle wrapping data block + if ($begin > $next) + set var $begin = 0 + end + + # skip over descriptor id + set var $begin = $begin + sizeof(long) + + # handle truncated message + if ($next - $begin < $info->text_len) + set var $text_len = $next - $begin + else + set var $text_len = $info->text_len + end + + set var $log = &prb->text_data_ring.data[$begin] + end + + # prev & LOG_CONT && !(info->flags & LOG_PREIX) + if (($prev_flags & 8) && !($info->flags & 4)) + set var $prefix = 0 + end + + # info->flags & LOG_CONT + if ($info->flags & 8) + # (prev & LOG_CONT && !(prev & LOG_NEWLINE)) + if (($prev_flags & 8) && !($prev_flags & 2)) + set var $prefix = 0 + end + # (!(info->flags & LOG_NEWLINE)) + if (!($info->flags & 2)) + set var $newline = 0 + end + end + + if ($prefix) + printf "[%5lu.%06lu] ", $info->ts_nsec / 1000000000, $info->ts_nsec % 1000000000 + end + if ($text_len) + eval "printf \"%%%d.%ds\", $log", $text_len, $text_len + end + if ($newline) + printf "\n" + end + + # handle dictionary data + + set var $dict = &$info->dev_info.subsystem[0] + set var $dict_len = sizeof($info->dev_info.subsystem) + if ($dict[0] != '\0') + printf " SUBSYSTEM=" + set var $idx = 0 + while ($idx < $dict_len) + set var $c = $dict[$idx] + if ($c == '\0') + loop_break + else + if ($c < ' ' || $c >= 127 || $c == '\\') + printf "\\x%02x", $c + else + printf "%c", $c + end + end + set var $idx = $idx + 1 + end + printf "\n" + end + + set var $dict = &$info->dev_info.device[0] + set var $dict_len = sizeof($info->dev_info.device) + if ($dict[0] != '\0') + printf " DEVICE=" + set var $idx = 0 + while ($idx < $dict_len) + set var $c = $dict[$idx] + if ($c == '\0') + loop_break + else + if ($c < ' ' || $c >= 127 || $c == '\\') + printf "\\x%02x", $c + else + printf "%c", $c + end + end + set var $idx = $idx + 1 + end + printf "\n" + end +end +document dump_record + Dump a single record. The first parameter is the descriptor, + the second parameter is the info, the third parameter is + optional and specifies the previous record's flags, used for + properly formatting continued lines. +end + +define dmesg + # definitions from kernel/printk/printk_ringbuffer.h + set var $desc_committed = 1 + set var $desc_finalized = 2 + set var $desc_sv_bits = sizeof(long) * 8 + set var $desc_flags_shift = $desc_sv_bits - 2 + set var $desc_flags_mask = 3 << $desc_flags_shift + set var $id_mask = ~$desc_flags_mask + + set var $desc_count = 1U << prb->desc_ring.count_bits + set var $prev_flags = 0 + + set var $id = prb->desc_ring.tail_id.counter + set var $end_id = prb->desc_ring.head_id.counter + + while (1) + set var $desc = &prb->desc_ring.descs[$id % $desc_count] + set var $info = &prb->desc_ring.infos[$id % $desc_count] + + # skip non-committed record + set var $state = 3 & ($desc->state_var.counter >> $desc_flags_shift) + if ($state == $desc_committed || $state == $desc_finalized) + dump_record $desc $info $prev_flags + set var $prev_flags = $info->flags + end + + if ($id == $end_id) + loop_break + end + set var $id = ($id + 1) & $id_mask + end +end +document dmesg + print the kernel ring buffer +end diff --git a/Documentation/admin-guide/kdump/index.rst b/Documentation/admin-guide/kdump/index.rst new file mode 100644 index 000000000..8e2ebd038 --- /dev/null +++ b/Documentation/admin-guide/kdump/index.rst @@ -0,0 +1,20 @@ + +================================================================ +Documentation for Kdump - The kexec-based Crash Dumping Solution +================================================================ + +This document includes overview, setup and installation, and analysis +information. + +.. toctree:: + :maxdepth: 1 + + kdump + vmcoreinfo + +.. only:: subproject and html + + Indices + ======= + + * :ref:`genindex` diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst new file mode 100644 index 000000000..a748e7eb4 --- /dev/null +++ b/Documentation/admin-guide/kdump/kdump.rst @@ -0,0 +1,597 @@ +================================================================ +Documentation for Kdump - The kexec-based Crash Dumping Solution +================================================================ + +This document includes overview, setup, installation, and analysis +information. + +Overview +======== + +Kdump uses kexec to quickly boot to a dump-capture kernel whenever a +dump of the system kernel's memory needs to be taken (for example, when +the system panics). The system kernel's memory image is preserved across +the reboot and is accessible to the dump-capture kernel. + +You can use common commands, such as cp, scp or makedumpfile to copy +the memory image to a dump file on the local disk, or across the network +to a remote system. + +Kdump and kexec are currently supported on the x86, x86_64, ppc64, ia64, +s390x, arm and arm64 architectures. + +When the system kernel boots, it reserves a small section of memory for +the dump-capture kernel. This ensures that ongoing Direct Memory Access +(DMA) from the system kernel does not corrupt the dump-capture kernel. +The kexec -p command loads the dump-capture kernel into this reserved +memory. + +On x86 machines, the first 640 KB of physical memory is needed for boot, +regardless of where the kernel loads. For simpler handling, the whole +low 1M is reserved to avoid any later kernel or device driver writing +data into this area. Like this, the low 1M can be reused as system RAM +by kdump kernel without extra handling. + +On PPC64 machines first 32KB of physical memory is needed for booting +regardless of where the kernel is loaded and to support 64K page size +kexec backs up the first 64KB memory. + +For s390x, when kdump is triggered, the crashkernel region is exchanged +with the region [0, crashkernel region size] and then the kdump kernel +runs in [0, crashkernel region size]. Therefore no relocatable kernel is +needed for s390x. + +All of the necessary information about the system kernel's core image is +encoded in the ELF format, and stored in a reserved area of memory +before a crash. The physical address of the start of the ELF header is +passed to the dump-capture kernel through the elfcorehdr= boot +parameter. Optionally the size of the ELF header can also be passed +when using the elfcorehdr=[size[KMG]@]offset[KMG] syntax. + +With the dump-capture kernel, you can access the memory image through +/proc/vmcore. This exports the dump as an ELF-format file that you can +write out using file copy commands such as cp or scp. You can also use +makedumpfile utility to analyze and write out filtered contents with +options, e.g with '-d 31' it will only write out kernel data. Further, +you can use analysis tools such as the GNU Debugger (GDB) and the Crash +tool to debug the dump file. This method ensures that the dump pages are +correctly ordered. + +Setup and Installation +====================== + +Install kexec-tools +------------------- + +1) Login as the root user. + +2) Download the kexec-tools user-space package from the following URL: + +http://kernel.org/pub/linux/utils/kernel/kexec/kexec-tools.tar.gz + +This is a symlink to the latest version. + +The latest kexec-tools git tree is available at: + +- git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git +- http://www.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git + +There is also a gitweb interface available at +http://www.kernel.org/git/?p=utils/kernel/kexec/kexec-tools.git + +More information about kexec-tools can be found at +http://horms.net/projects/kexec/ + +3) Unpack the tarball with the tar command, as follows:: + + tar xvpzf kexec-tools.tar.gz + +4) Change to the kexec-tools directory, as follows:: + + cd kexec-tools-VERSION + +5) Configure the package, as follows:: + + ./configure + +6) Compile the package, as follows:: + + make + +7) Install the package, as follows:: + + make install + + +Build the system and dump-capture kernels +----------------------------------------- +There are two possible methods of using Kdump. + +1) Build a separate custom dump-capture kernel for capturing the + kernel core dump. + +2) Or use the system kernel binary itself as dump-capture kernel and there is + no need to build a separate dump-capture kernel. This is possible + only with the architectures which support a relocatable kernel. As + of today, i386, x86_64, ppc64, ia64, arm and arm64 architectures support + relocatable kernel. + +Building a relocatable kernel is advantageous from the point of view that +one does not have to build a second kernel for capturing the dump. But +at the same time one might want to build a custom dump capture kernel +suitable to his needs. + +Following are the configuration setting required for system and +dump-capture kernels for enabling kdump support. + +System kernel config options +---------------------------- + +1) Enable "kexec system call" or "kexec file based system call" in + "Processor type and features.":: + + CONFIG_KEXEC=y or CONFIG_KEXEC_FILE=y + + And both of them will select KEXEC_CORE:: + + CONFIG_KEXEC_CORE=y + + Subsequently, CRASH_CORE is selected by KEXEC_CORE:: + + CONFIG_CRASH_CORE=y + +2) Enable "sysfs file system support" in "Filesystem" -> "Pseudo + filesystems." This is usually enabled by default:: + + CONFIG_SYSFS=y + + Note that "sysfs file system support" might not appear in the "Pseudo + filesystems" menu if "Configure standard kernel features (expert users)" + is not enabled in "General Setup." In this case, check the .config file + itself to ensure that sysfs is turned on, as follows:: + + grep 'CONFIG_SYSFS' .config + +3) Enable "Compile the kernel with debug info" in "Kernel hacking.":: + + CONFIG_DEBUG_INFO=Y + + This causes the kernel to be built with debug symbols. The dump + analysis tools require a vmlinux with debug symbols in order to read + and analyze a dump file. + +Dump-capture kernel config options (Arch Independent) +----------------------------------------------------- + +1) Enable "kernel crash dumps" support under "Processor type and + features":: + + CONFIG_CRASH_DUMP=y + +2) Enable "/proc/vmcore support" under "Filesystems" -> "Pseudo filesystems":: + + CONFIG_PROC_VMCORE=y + + (CONFIG_PROC_VMCORE is set by default when CONFIG_CRASH_DUMP is selected.) + +Dump-capture kernel config options (Arch Dependent, i386 and x86_64) +-------------------------------------------------------------------- + +1) On i386, enable high memory support under "Processor type and + features":: + + CONFIG_HIGHMEM64G=y + + or:: + + CONFIG_HIGHMEM4G + +2) With CONFIG_SMP=y, usually nr_cpus=1 need specified on the kernel + command line when loading the dump-capture kernel because one + CPU is enough for kdump kernel to dump vmcore on most of systems. + + However, you can also specify nr_cpus=X to enable multiple processors + in kdump kernel. In this case, "disable_cpu_apicid=" is needed to + tell kdump kernel which cpu is 1st kernel's BSP. Please refer to + admin-guide/kernel-parameters.txt for more details. + + With CONFIG_SMP=n, the above things are not related. + +3) A relocatable kernel is suggested to be built by default. If not yet, + enable "Build a relocatable kernel" support under "Processor type and + features":: + + CONFIG_RELOCATABLE=y + +4) Use a suitable value for "Physical address where the kernel is + loaded" (under "Processor type and features"). This only appears when + "kernel crash dumps" is enabled. A suitable value depends upon + whether kernel is relocatable or not. + + If you are using a relocatable kernel use CONFIG_PHYSICAL_START=0x100000 + This will compile the kernel for physical address 1MB, but given the fact + kernel is relocatable, it can be run from any physical address hence + kexec boot loader will load it in memory region reserved for dump-capture + kernel. + + Otherwise it should be the start of memory region reserved for + second kernel using boot parameter "crashkernel=Y@X". Here X is + start of memory region reserved for dump-capture kernel. + Generally X is 16MB (0x1000000). So you can set + CONFIG_PHYSICAL_START=0x1000000 + +5) Make and install the kernel and its modules. DO NOT add this kernel + to the boot loader configuration files. + +Dump-capture kernel config options (Arch Dependent, ppc64) +---------------------------------------------------------- + +1) Enable "Build a kdump crash kernel" support under "Kernel" options:: + + CONFIG_CRASH_DUMP=y + +2) Enable "Build a relocatable kernel" support:: + + CONFIG_RELOCATABLE=y + + Make and install the kernel and its modules. + +Dump-capture kernel config options (Arch Dependent, ia64) +---------------------------------------------------------- + +- No specific options are required to create a dump-capture kernel + for ia64, other than those specified in the arch independent section + above. This means that it is possible to use the system kernel + as a dump-capture kernel if desired. + + The crashkernel region can be automatically placed by the system + kernel at runtime. This is done by specifying the base address as 0, + or omitting it all together:: + + crashkernel=256M@0 + + or:: + + crashkernel=256M + +Dump-capture kernel config options (Arch Dependent, arm) +---------------------------------------------------------- + +- To use a relocatable kernel, + Enable "AUTO_ZRELADDR" support under "Boot" options:: + + AUTO_ZRELADDR=y + +Dump-capture kernel config options (Arch Dependent, arm64) +---------------------------------------------------------- + +- Please note that kvm of the dump-capture kernel will not be enabled + on non-VHE systems even if it is configured. This is because the CPU + will not be reset to EL2 on panic. + +crashkernel syntax +=========================== +1) crashkernel=size@offset + + Here 'size' specifies how much memory to reserve for the dump-capture kernel + and 'offset' specifies the beginning of this reserved memory. For example, + "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory + starting at physical address 0x01000000 (16MB) for the dump-capture kernel. + + The crashkernel region can be automatically placed by the system + kernel at run time. This is done by specifying the base address as 0, + or omitting it all together:: + + crashkernel=256M@0 + + or:: + + crashkernel=256M + + If the start address is specified, note that the start address of the + kernel will be aligned to a value (which is Arch dependent), so if the + start address is not then any space below the alignment point will be + wasted. + +2) range1:size1[,range2:size2,...][@offset] + + While the "crashkernel=size[@offset]" syntax is sufficient for most + configurations, sometimes it's handy to have the reserved memory dependent + on the value of System RAM -- that's mostly for distributors that pre-setup + the kernel command line to avoid a unbootable system after some memory has + been removed from the machine. + + The syntax is:: + + crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset] + range=start-[end] + + For example:: + + crashkernel=512M-2G:64M,2G-:128M + + This would mean: + + 1) if the RAM is smaller than 512M, then don't reserve anything + (this is the "rescue" case) + 2) if the RAM size is between 512M and 2G (exclusive), then reserve 64M + 3) if the RAM size is larger than 2G, then reserve 128M + +3) crashkernel=size,high and crashkernel=size,low + + If memory above 4G is preferred, crashkernel=size,high can be used to + fulfill that. With it, physical memory is allowed to be allocated from top, + so could be above 4G if system has more than 4G RAM installed. Otherwise, + memory region will be allocated below 4G if available. + + When crashkernel=X,high is passed, kernel could allocate physical memory + region above 4G, low memory under 4G is needed in this case. There are + three ways to get low memory: + + 1) Kernel will allocate at least 256M memory below 4G automatically + if crashkernel=Y,low is not specified. + 2) Let user specify low memory size instead. + 3) Specified value 0 will disable low memory allocation:: + + crashkernel=0,low + +Boot into System Kernel +----------------------- +1) Update the boot loader (such as grub, yaboot, or lilo) configuration + files as necessary. + +2) Boot the system kernel with the boot parameter "crashkernel=Y@X". + + On x86 and x86_64, use "crashkernel=Y[@X]". Most of the time, the + start address 'X' is not necessary, kernel will search a suitable + area. Unless an explicit start address is expected. + + On ppc64, use "crashkernel=128M@32M". + + On ia64, 256M@256M is a generous value that typically works. + The region may be automatically placed on ia64, see the + dump-capture kernel config option notes above. + If use sparse memory, the size should be rounded to GRANULE boundaries. + + On s390x, typically use "crashkernel=xxM". The value of xx is dependent + on the memory consumption of the kdump system. In general this is not + dependent on the memory size of the production system. + + On arm, the use of "crashkernel=Y@X" is no longer necessary; the + kernel will automatically locate the crash kernel image within the + first 512MB of RAM if X is not given. + + On arm64, use "crashkernel=Y[@X]". Note that the start address of + the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000). + +Load the Dump-capture Kernel +============================ + +After booting to the system kernel, dump-capture kernel needs to be +loaded. + +Based on the architecture and type of image (relocatable or not), one +can choose to load the uncompressed vmlinux or compressed bzImage/vmlinuz +of dump-capture kernel. Following is the summary. + +For i386 and x86_64: + + - Use bzImage/vmlinuz if kernel is relocatable. + - Use vmlinux if kernel is not relocatable. + +For ppc64: + + - Use vmlinux + +For ia64: + + - Use vmlinux or vmlinuz.gz + +For s390x: + + - Use image or bzImage + +For arm: + + - Use zImage + +For arm64: + + - Use vmlinux or Image + +If you are using an uncompressed vmlinux image then use following command +to load dump-capture kernel:: + + kexec -p <dump-capture-kernel-vmlinux-image> \ + --initrd=<initrd-for-dump-capture-kernel> --args-linux \ + --append="root=<root-dev> <arch-specific-options>" + +If you are using a compressed bzImage/vmlinuz, then use following command +to load dump-capture kernel:: + + kexec -p <dump-capture-kernel-bzImage> \ + --initrd=<initrd-for-dump-capture-kernel> \ + --append="root=<root-dev> <arch-specific-options>" + +If you are using a compressed zImage, then use following command +to load dump-capture kernel:: + + kexec --type zImage -p <dump-capture-kernel-bzImage> \ + --initrd=<initrd-for-dump-capture-kernel> \ + --dtb=<dtb-for-dump-capture-kernel> \ + --append="root=<root-dev> <arch-specific-options>" + +If you are using an uncompressed Image, then use following command +to load dump-capture kernel:: + + kexec -p <dump-capture-kernel-Image> \ + --initrd=<initrd-for-dump-capture-kernel> \ + --append="root=<root-dev> <arch-specific-options>" + +Please note, that --args-linux does not need to be specified for ia64. +It is planned to make this a no-op on that architecture, but for now +it should be omitted + +Following are the arch specific command line options to be used while +loading dump-capture kernel. + +For i386, x86_64 and ia64: + + "1 irqpoll nr_cpus=1 reset_devices" + +For ppc64: + + "1 maxcpus=1 noirqdistrib reset_devices" + +For s390x: + + "1 nr_cpus=1 cgroup_disable=memory" + +For arm: + + "1 maxcpus=1 reset_devices" + +For arm64: + + "1 nr_cpus=1 reset_devices" + +Notes on loading the dump-capture kernel: + +* By default, the ELF headers are stored in ELF64 format to support + systems with more than 4GB memory. On i386, kexec automatically checks if + the physical RAM size exceeds the 4 GB limit and if not, uses ELF32. + So, on non-PAE systems, ELF32 is always used. + + The --elf32-core-headers option can be used to force the generation of ELF32 + headers. This is necessary because GDB currently cannot open vmcore files + with ELF64 headers on 32-bit systems. + +* The "irqpoll" boot parameter reduces driver initialization failures + due to shared interrupts in the dump-capture kernel. + +* You must specify <root-dev> in the format corresponding to the root + device name in the output of mount command. + +* Boot parameter "1" boots the dump-capture kernel into single-user + mode without networking. If you want networking, use "3". + +* We generally don't have to bring up a SMP kernel just to capture the + dump. Hence generally it is useful either to build a UP dump-capture + kernel or specify maxcpus=1 option while loading dump-capture kernel. + Note, though maxcpus always works, you had better replace it with + nr_cpus to save memory if supported by the current ARCH, such as x86. + +* You should enable multi-cpu support in dump-capture kernel if you intend + to use multi-thread programs with it, such as parallel dump feature of + makedumpfile. Otherwise, the multi-thread program may have a great + performance degradation. To enable multi-cpu support, you should bring up an + SMP dump-capture kernel and specify maxcpus/nr_cpus, disable_cpu_apicid=[X] + options while loading it. + +* For s390x there are two kdump modes: If a ELF header is specified with + the elfcorehdr= kernel parameter, it is used by the kdump kernel as it + is done on all other architectures. If no elfcorehdr= kernel parameter is + specified, the s390x kdump kernel dynamically creates the header. The + second mode has the advantage that for CPU and memory hotplug, kdump has + not to be reloaded with kexec_load(). + +* For s390x systems with many attached devices the "cio_ignore" kernel + parameter should be used for the kdump kernel in order to prevent allocation + of kernel memory for devices that are not relevant for kdump. The same + applies to systems that use SCSI/FCP devices. In that case the + "allow_lun_scan" zfcp module parameter should be set to zero before + setting FCP devices online. + +Kernel Panic +============ + +After successfully loading the dump-capture kernel as previously +described, the system will reboot into the dump-capture kernel if a +system crash is triggered. Trigger points are located in panic(), +die(), die_nmi() and in the sysrq handler (ALT-SysRq-c). + +The following conditions will execute a crash trigger point: + +If a hard lockup is detected and "NMI watchdog" is configured, the system +will boot into the dump-capture kernel ( die_nmi() ). + +If die() is called, and it happens to be a thread with pid 0 or 1, or die() +is called inside interrupt context or die() is called and panic_on_oops is set, +the system will boot into the dump-capture kernel. + +On powerpc systems when a soft-reset is generated, die() is called by all cpus +and the system will boot into the dump-capture kernel. + +For testing purposes, you can trigger a crash by using "ALT-SysRq-c", +"echo c > /proc/sysrq-trigger" or write a module to force the panic. + +Write Out the Dump File +======================= + +After the dump-capture kernel is booted, write out the dump file with +the following command:: + + cp /proc/vmcore <dump-file> + +or use scp to write out the dump file between hosts on a network, e.g:: + + scp /proc/vmcore remote_username@remote_ip:<dump-file> + +You can also use makedumpfile utility to write out the dump file +with specified options to filter out unwanted contents, e.g:: + + makedumpfile -l --message-level 1 -d 31 /proc/vmcore <dump-file> + +Analysis +======== + +Before analyzing the dump image, you should reboot into a stable kernel. + +You can do limited analysis using GDB on the dump file copied out of +/proc/vmcore. Use the debug vmlinux built with -g and run the following +command:: + + gdb vmlinux <dump-file> + +Stack trace for the task on processor 0, register display, and memory +display work fine. + +Note: GDB cannot analyze core files generated in ELF64 format for x86. +On systems with a maximum of 4GB of memory, you can generate +ELF32-format headers using the --elf32-core-headers kernel option on the +dump kernel. + +You can also use the Crash utility to analyze dump files in Kdump +format. Crash is available at the following URL: + + https://github.com/crash-utility/crash + +Crash document can be found at: + https://crash-utility.github.io/ + +Trigger Kdump on WARN() +======================= + +The kernel parameter, panic_on_warn, calls panic() in all WARN() paths. This +will cause a kdump to occur at the panic() call. In cases where a user wants +to specify this during runtime, /proc/sys/kernel/panic_on_warn can be set to 1 +to achieve the same behaviour. + +Trigger Kdump on add_taint() +============================ + +The kernel parameter panic_on_taint facilitates a conditional call to panic() +from within add_taint() whenever the value set in this bitmask matches with the +bit flag being set by add_taint(). +This will cause a kdump to occur at the add_taint()->panic() call. + +Contact +======= + +- kexec@lists.infradead.org + +GDB macros +========== + +.. include:: gdbmacros.txt + :literal: diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst new file mode 100644 index 000000000..599e8d3bc --- /dev/null +++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst @@ -0,0 +1,626 @@ +========== +VMCOREINFO +========== + +What is it? +=========== + +VMCOREINFO is a special ELF note section. It contains various +information from the kernel like structure size, page size, symbol +values, field offsets, etc. These data are packed into an ELF note +section and used by user-space tools like crash and makedumpfile to +analyze a kernel's memory layout. + +Common variables +================ + +init_uts_ns.name.release +------------------------ + +The version of the Linux kernel. Used to find the corresponding source +code from which the kernel has been built. For example, crash uses it to +find the corresponding vmlinux in order to process vmcore. + +PAGE_SIZE +--------- + +The size of a page. It is the smallest unit of data used by the memory +management facilities. It is usually 4096 bytes of size and a page is +aligned on 4096 bytes. Used for computing page addresses. + +init_uts_ns +----------- + +The UTS namespace which is used to isolate two specific elements of the +system that relate to the uname(2) system call. It is named after the +data structure used to store information returned by the uname(2) system +call. + +User-space tools can get the kernel name, host name, kernel release +number, kernel version, architecture name and OS type from it. + +(uts_namespace, name) +--------------------- + +Offset of the name's member. Crash Utility and Makedumpfile get +the start address of the init_uts_ns.name from this. + +node_online_map +--------------- + +An array node_states[N_ONLINE] which represents the set of online nodes +in a system, one bit position per node number. Used to keep track of +which nodes are in the system and online. + +swapper_pg_dir +-------------- + +The global page directory pointer of the kernel. Used to translate +virtual to physical addresses. + +_stext +------ + +Defines the beginning of the text section. In general, _stext indicates +the kernel start address. Used to convert a virtual address from the +direct kernel map to a physical address. + +vmap_area_list +-------------- + +Stores the virtual area list. makedumpfile gets the vmalloc start value +from this variable and its value is necessary for vmalloc translation. + +mem_map +------- + +Physical addresses are translated to struct pages by treating them as +an index into the mem_map array. Right-shifting a physical address +PAGE_SHIFT bits converts it into a page frame number which is an index +into that mem_map array. + +Used to map an address to the corresponding struct page. + +contig_page_data +---------------- + +Makedumpfile gets the pglist_data structure from this symbol, which is +used to describe the memory layout. + +User-space tools use this to exclude free pages when dumping memory. + +mem_section|(mem_section, NR_SECTION_ROOTS)|(mem_section, section_mem_map) +-------------------------------------------------------------------------- + +The address of the mem_section array, its length, structure size, and +the section_mem_map offset. + +It exists in the sparse memory mapping model, and it is also somewhat +similar to the mem_map variable, both of them are used to translate an +address. + +MAX_PHYSMEM_BITS +---------------- + +Defines the maximum supported physical address space memory. + +page +---- + +The size of a page structure. struct page is an important data structure +and it is widely used to compute contiguous memory. + +pglist_data +----------- + +The size of a pglist_data structure. This value is used to check if the +pglist_data structure is valid. It is also used for checking the memory +type. + +zone +---- + +The size of a zone structure. This value is used to check if the zone +structure has been found. It is also used for excluding free pages. + +free_area +--------- + +The size of a free_area structure. It indicates whether the free_area +structure is valid or not. Useful when excluding free pages. + +list_head +--------- + +The size of a list_head structure. Used when iterating lists in a +post-mortem analysis session. + +nodemask_t +---------- + +The size of a nodemask_t type. Used to compute the number of online +nodes. + +(page, flags|_refcount|mapping|lru|_mapcount|private|compound_order|compound_head) +---------------------------------------------------------------------------------- + +User-space tools compute their values based on the offset of these +variables. The variables are used when excluding unnecessary pages. + +(pglist_data, node_zones|nr_zones|node_mem_map|node_start_pfn|node_spanned_pages|node_id) +----------------------------------------------------------------------------------------- + +On NUMA machines, each NUMA node has a pg_data_t to describe its memory +layout. On UMA machines there is a single pglist_data which describes the +whole memory. + +These values are used to check the memory type and to compute the +virtual address for memory map. + +(zone, free_area|vm_stat|spanned_pages) +--------------------------------------- + +Each node is divided into a number of blocks called zones which +represent ranges within memory. A zone is described by a structure zone. + +User-space tools compute required values based on the offset of these +variables. + +(free_area, free_list) +---------------------- + +Offset of the free_list's member. This value is used to compute the number +of free pages. + +Each zone has a free_area structure array called free_area[MAX_ORDER + 1]. +The free_list represents a linked list of free page blocks. + +(list_head, next|prev) +---------------------- + +Offsets of the list_head's members. list_head is used to define a +circular linked list. User-space tools need these in order to traverse +lists. + +(vmap_area, va_start|list) +-------------------------- + +Offsets of the vmap_area's members. They carry vmalloc-specific +information. Makedumpfile gets the start address of the vmalloc region +from this. + +(zone.free_area, MAX_ORDER + 1) +------------------------------- + +Free areas descriptor. User-space tools use this value to iterate the +free_area ranges. MAX_ORDER is used by the zone buddy allocator. + +prb +--- + +A pointer to the printk ringbuffer (struct printk_ringbuffer). This +may be pointing to the static boot ringbuffer or the dynamically +allocated ringbuffer, depending on when the core dump occurred. +Used by user-space tools to read the active kernel log buffer. + +printk_rb_static +---------------- + +A pointer to the static boot printk ringbuffer. If @prb has a +different value, this is useful for viewing the initial boot messages, +which may have been overwritten in the dynamically allocated +ringbuffer. + +clear_seq +--------- + +The sequence number of the printk() record after the last clear +command. It indicates the first record after the last +SYSLOG_ACTION_CLEAR, like issued by 'dmesg -c'. Used by user-space +tools to dump a subset of the dmesg log. + +printk_ringbuffer +----------------- + +The size of a printk_ringbuffer structure. This structure contains all +information required for accessing the various components of the +kernel log buffer. + +(printk_ringbuffer, desc_ring|text_data_ring|dict_data_ring|fail) +----------------------------------------------------------------- + +Offsets for the various components of the printk ringbuffer. Used by +user-space tools to view the kernel log buffer without requiring the +declaration of the structure. + +prb_desc_ring +------------- + +The size of the prb_desc_ring structure. This structure contains +information about the set of record descriptors. + +(prb_desc_ring, count_bits|descs|head_id|tail_id) +------------------------------------------------- + +Offsets for the fields describing the set of record descriptors. Used +by user-space tools to be able to traverse the descriptors without +requiring the declaration of the structure. + +prb_desc +-------- + +The size of the prb_desc structure. This structure contains +information about a single record descriptor. + +(prb_desc, info|state_var|text_blk_lpos|dict_blk_lpos) +------------------------------------------------------ + +Offsets for the fields describing a record descriptors. Used by +user-space tools to be able to read descriptors without requiring +the declaration of the structure. + +prb_data_blk_lpos +----------------- + +The size of the prb_data_blk_lpos structure. This structure contains +information about where the text or dictionary data (data block) is +located within the respective data ring. + +(prb_data_blk_lpos, begin|next) +------------------------------- + +Offsets for the fields describing the location of a data block. Used +by user-space tools to be able to locate data blocks without +requiring the declaration of the structure. + +printk_info +----------- + +The size of the printk_info structure. This structure contains all +the meta-data for a record. + +(printk_info, seq|ts_nsec|text_len|dict_len|caller_id) +------------------------------------------------------ + +Offsets for the fields providing the meta-data for a record. Used by +user-space tools to be able to read the information without requiring +the declaration of the structure. + +prb_data_ring +------------- + +The size of the prb_data_ring structure. This structure contains +information about a set of data blocks. + +(prb_data_ring, size_bits|data|head_lpos|tail_lpos) +--------------------------------------------------- + +Offsets for the fields describing a set of data blocks. Used by +user-space tools to be able to access the data blocks without +requiring the declaration of the structure. + +atomic_long_t +------------- + +The size of the atomic_long_t structure. Used by user-space tools to +be able to copy the full structure, regardless of its +architecture-specific implementation. + +(atomic_long_t, counter) +------------------------ + +Offset for the long value of an atomic_long_t variable. Used by +user-space tools to access the long value without requiring the +architecture-specific declaration. + +(free_area.free_list, MIGRATE_TYPES) +------------------------------------ + +The number of migrate types for pages. The free_list is described by the +array. Used by tools to compute the number of free pages. + +NR_FREE_PAGES +------------- + +On linux-2.6.21 or later, the number of free pages is in +vm_stat[NR_FREE_PAGES]. Used to get the number of free pages. + +PG_lru|PG_private|PG_swapcache|PG_swapbacked|PG_slab|PG_hwpoision|PG_head_mask|PG_hugetlb +----------------------------------------------------------------------------------------- + +Page attributes. These flags are used to filter various unnecessary for +dumping pages. + +PAGE_BUDDY_MAPCOUNT_VALUE(~PG_buddy)|PAGE_OFFLINE_MAPCOUNT_VALUE(~PG_offline) +----------------------------------------------------------------------------- + +More page attributes. These flags are used to filter various unnecessary for +dumping pages. + + +x86_64 +====== + +phys_base +--------- + +Used to convert the virtual address of an exported kernel symbol to its +corresponding physical address. + +init_top_pgt +------------ + +Used to walk through the whole page table and convert virtual addresses +to physical addresses. The init_top_pgt is somewhat similar to +swapper_pg_dir, but it is only used in x86_64. + +pgtable_l5_enabled +------------------ + +User-space tools need to know whether the crash kernel was in 5-level +paging mode. + +node_data +--------- + +This is a struct pglist_data array and stores all NUMA nodes +information. Makedumpfile gets the pglist_data structure from it. + +(node_data, MAX_NUMNODES) +------------------------- + +The maximum number of nodes in system. + +KERNELOFFSET +------------ + +The kernel randomization offset. Used to compute the page offset. If +KASLR is disabled, this value is zero. + +KERNEL_IMAGE_SIZE +----------------- + +Currently unused by Makedumpfile. Used to compute the module virtual +address by Crash. + +sme_mask +-------- + +AMD-specific with SME support: it indicates the secure memory encryption +mask. Makedumpfile tools need to know whether the crash kernel was +encrypted. If SME is enabled in the first kernel, the crash kernel's +page table entries (pgd/pud/pmd/pte) contain the memory encryption +mask. This is used to remove the SME mask and obtain the true physical +address. + +Currently, sme_mask stores the value of the C-bit position. If needed, +additional SME-relevant info can be placed in that variable. + +For example:: + + [ misc ][ enc bit ][ other misc SME info ] + 0000_0000_0000_0000_1000_0000_0000_0000_0000_0000_..._0000 + 63 59 55 51 47 43 39 35 31 27 ... 3 + +x86_32 +====== + +X86_PAE +------- + +Denotes whether physical address extensions are enabled. It has the cost +of a higher page table lookup overhead, and also consumes more page +table space per process. Used to check whether PAE was enabled in the +crash kernel when converting virtual addresses to physical addresses. + +ia64 +==== + +pgdat_list|(pgdat_list, MAX_NUMNODES) +------------------------------------- + +pg_data_t array storing all NUMA nodes information. MAX_NUMNODES +indicates the number of the nodes. + +node_memblk|(node_memblk, NR_NODE_MEMBLKS) +------------------------------------------ + +List of node memory chunks. Filled when parsing the SRAT table to obtain +information about memory nodes. NR_NODE_MEMBLKS indicates the number of +node memory chunks. + +These values are used to compute the number of nodes the crashed kernel used. + +node_memblk_s|(node_memblk_s, start_paddr)|(node_memblk_s, size) +---------------------------------------------------------------- + +The size of a struct node_memblk_s and the offsets of the +node_memblk_s's members. Used to compute the number of nodes. + +PGTABLE_3|PGTABLE_4 +------------------- + +User-space tools need to know whether the crash kernel was in 3-level or +4-level paging mode. Used to distinguish the page table. + +ARM64 +===== + +VA_BITS +------- + +The maximum number of bits for virtual addresses. Used to compute the +virtual memory ranges. + +kimage_voffset +-------------- + +The offset between the kernel virtual and physical mappings. Used to +translate virtual to physical addresses. + +PHYS_OFFSET +----------- + +Indicates the physical address of the start of memory. Similar to +kimage_voffset, which is used to translate virtual to physical +addresses. + +KERNELOFFSET +------------ + +The kernel randomization offset. Used to compute the page offset. If +KASLR is disabled, this value is zero. + +KERNELPACMASK +------------- + +The mask to extract the Pointer Authentication Code from a kernel virtual +address. + +TCR_EL1.T1SZ +------------ + +Indicates the size offset of the memory region addressed by TTBR1_EL1. +The region size is 2^(64-T1SZ) bytes. + +TTBR1_EL1 is the table base address register specified by ARMv8-A +architecture which is used to lookup the page-tables for the Virtual +addresses in the higher VA range (refer to ARMv8 ARM document for +more details). + +MODULES_VADDR|MODULES_END|VMALLOC_START|VMALLOC_END|VMEMMAP_START|VMEMMAP_END +----------------------------------------------------------------------------- + +Used to get the correct ranges: + MODULES_VADDR ~ MODULES_END-1 : Kernel module space. + VMALLOC_START ~ VMALLOC_END-1 : vmalloc() / ioremap() space. + VMEMMAP_START ~ VMEMMAP_END-1 : vmemmap region, used for struct page array. + +arm +=== + +ARM_LPAE +-------- + +It indicates whether the crash kernel supports large physical address +extensions. Used to translate virtual to physical addresses. + +s390 +==== + +lowcore_ptr +----------- + +An array with a pointer to the lowcore of every CPU. Used to print the +psw and all registers information. + +high_memory +----------- + +Used to get the vmalloc_start address from the high_memory symbol. + +(lowcore_ptr, NR_CPUS) +---------------------- + +The maximum number of CPUs. + +powerpc +======= + + +node_data|(node_data, MAX_NUMNODES) +----------------------------------- + +See above. + +contig_page_data +---------------- + +See above. + +vmemmap_list +------------ + +The vmemmap_list maintains the entire vmemmap physical mapping. Used +to get vmemmap list count and populated vmemmap regions info. If the +vmemmap address translation information is stored in the crash kernel, +it is used to translate vmemmap kernel virtual addresses. + +mmu_vmemmap_psize +----------------- + +The size of a page. Used to translate virtual to physical addresses. + +mmu_psize_defs +-------------- + +Page size definitions, i.e. 4k, 64k, or 16M. + +Used to make vtop translations. + +vmemmap_backing|(vmemmap_backing, list)|(vmemmap_backing, phys)|(vmemmap_backing, virt_addr) +-------------------------------------------------------------------------------------------- + +The vmemmap virtual address space management does not have a traditional +page table to track which virtual struct pages are backed by a physical +mapping. The virtual to physical mappings are tracked in a simple linked +list format. + +User-space tools need to know the offset of list, phys and virt_addr +when computing the count of vmemmap regions. + +mmu_psize_def|(mmu_psize_def, shift) +------------------------------------ + +The size of a struct mmu_psize_def and the offset of mmu_psize_def's +member. + +Used in vtop translations. + +sh +== + +node_data|(node_data, MAX_NUMNODES) +----------------------------------- + +See above. + +X2TLB +----- + +Indicates whether the crashed kernel enabled SH extended mode. + +RISCV64 +======= + +VA_BITS +------- + +The maximum number of bits for virtual addresses. Used to compute the +virtual memory ranges. + +PAGE_OFFSET +----------- + +Indicates the virtual kernel start address of the direct-mapped RAM region. + +phys_ram_base +------------- + +Indicates the start physical RAM address. + +MODULES_VADDR|MODULES_END|VMALLOC_START|VMALLOC_END|VMEMMAP_START|VMEMMAP_END|KERNEL_LINK_ADDR +---------------------------------------------------------------------------------------------- + +Used to get the correct ranges: + + * MODULES_VADDR ~ MODULES_END : Kernel module space. + * VMALLOC_START ~ VMALLOC_END : vmalloc() / ioremap() space. + * VMEMMAP_START ~ VMEMMAP_END : vmemmap space, used for struct page array. + * KERNEL_LINK_ADDR : start address of Kernel link and BPF + +va_kernel_pa_offset +------------------- + +Indicates the offset between the kernel virtual and physical mappings. +Used to translate virtual to physical addresses. diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst new file mode 100644 index 000000000..102937bc8 --- /dev/null +++ b/Documentation/admin-guide/kernel-parameters.rst @@ -0,0 +1,225 @@ +.. _kernelparameters: + +The kernel's command-line parameters +==================================== + +The following is a consolidated list of the kernel parameters as implemented +by the __setup(), early_param(), core_param() and module_param() macros +and sorted into English Dictionary order (defined as ignoring all +punctuation and sorting digits before letters in a case insensitive +manner), and with descriptions where known. + +The kernel parses parameters from the kernel command line up to "``--``"; +if it doesn't recognize a parameter and it doesn't contain a '.', the +parameter gets passed to init: parameters with '=' go into init's +environment, others are passed as command line arguments to init. +Everything after "``--``" is passed as an argument to init. + +Module parameters can be specified in two ways: via the kernel command +line with a module name prefix, or via modprobe, e.g.:: + + (kernel command line) usbcore.blinkenlights=1 + (modprobe command line) modprobe usbcore blinkenlights=1 + +Parameters for modules which are built into the kernel need to be +specified on the kernel command line. modprobe looks through the +kernel command line (/proc/cmdline) and collects module parameters +when it loads a module, so the kernel command line can be used for +loadable modules too. + +Hyphens (dashes) and underscores are equivalent in parameter names, so:: + + log_buf_len=1M print-fatal-signals=1 + +can also be entered as:: + + log-buf-len=1M print_fatal_signals=1 + +Double-quotes can be used to protect spaces in values, e.g.:: + + param="spaces in here" + +cpu lists: +---------- + +Some kernel parameters take a list of CPUs as a value, e.g. isolcpus, +nohz_full, irqaffinity, rcu_nocbs. The format of this list is: + + <cpu number>,...,<cpu number> + +or + + <cpu number>-<cpu number> + (must be a positive range in ascending order) + +or a mixture + +<cpu number>,...,<cpu number>-<cpu number> + +Note that for the special case of a range one can split the range into equal +sized groups and for each group use some amount from the beginning of that +group: + + <cpu number>-<cpu number>:<used size>/<group size> + +For example one can add to the command line following parameter: + + isolcpus=1,2,10-20,100-2000:2/25 + +where the final item represents CPUs 100,101,125,126,150,151,... + +The value "N" can be used to represent the numerically last CPU on the system, +i.e "foo_cpus=16-N" would be equivalent to "16-31" on a 32 core system. + +Keep in mind that "N" is dynamic, so if system changes cause the bitmap width +to change, such as less cores in the CPU list, then N and any ranges using N +will also change. Use the same on a small 4 core system, and "16-N" becomes +"16-3" and now the same boot input will be flagged as invalid (start > end). + +The special case-tolerant group name "all" has a meaning of selecting all CPUs, +so that "nohz_full=all" is the equivalent of "nohz_full=0-N". + +The semantics of "N" and "all" is supported on a level of bitmaps and holds for +all users of bitmap_parselist(). + +This document may not be entirely up to date and comprehensive. The command +"modinfo -p ${modulename}" shows a current list of all parameters of a loadable +module. Loadable modules, after being loaded into the running kernel, also +reveal their parameters in /sys/module/${modulename}/parameters/. Some of these +parameters may be changed at runtime by the command +``echo -n ${value} > /sys/module/${modulename}/parameters/${parm}``. + +The parameters listed below are only valid if certain kernel build options +were enabled and if respective hardware is present. This list should be kept +in alphabetical order. The text in square brackets at the beginning +of each description states the restrictions within which a parameter +is applicable:: + + ACPI ACPI support is enabled. + AGP AGP (Accelerated Graphics Port) is enabled. + ALSA ALSA sound support is enabled. + APIC APIC support is enabled. + APM Advanced Power Management support is enabled. + APPARMOR AppArmor support is enabled. + ARM ARM architecture is enabled. + ARM64 ARM64 architecture is enabled. + AX25 Appropriate AX.25 support is enabled. + CLK Common clock infrastructure is enabled. + CMA Contiguous Memory Area support is enabled. + DRM Direct Rendering Management support is enabled. + DYNAMIC_DEBUG Build in debug messages and enable them at runtime + EDD BIOS Enhanced Disk Drive Services (EDD) is enabled + EFI EFI Partitioning (GPT) is enabled + EVM Extended Verification Module + FB The frame buffer device is enabled. + FTRACE Function tracing enabled. + GCOV GCOV profiling is enabled. + HIBERNATION HIBERNATION is enabled. + HW Appropriate hardware is enabled. + HYPER_V HYPERV support is enabled. + IA-64 IA-64 architecture is enabled. + IMA Integrity measurement architecture is enabled. + IP_PNP IP DHCP, BOOTP, or RARP is enabled. + IPV6 IPv6 support is enabled. + ISAPNP ISA PnP code is enabled. + ISDN Appropriate ISDN support is enabled. + ISOL CPU Isolation is enabled. + JOY Appropriate joystick support is enabled. + KGDB Kernel debugger support is enabled. + KVM Kernel Virtual Machine support is enabled. + LIBATA Libata driver is enabled + LOONGARCH LoongArch architecture is enabled. + LOOP Loopback device support is enabled. + LP Printer support is enabled. + M68k M68k architecture is enabled. + These options have more detailed description inside of + Documentation/arch/m68k/kernel-options.rst. + MDA MDA console support is enabled. + MIPS MIPS architecture is enabled. + MOUSE Appropriate mouse support is enabled. + MSI Message Signaled Interrupts (PCI). + MTD MTD (Memory Technology Device) support is enabled. + NET Appropriate network support is enabled. + NFS Appropriate NFS support is enabled. + NUMA NUMA support is enabled. + OF Devicetree is enabled. + PARISC The PA-RISC architecture is enabled. + PCI PCI bus support is enabled. + PCIE PCI Express support is enabled. + PCMCIA The PCMCIA subsystem is enabled. + PNP Plug & Play support is enabled. + PPC PowerPC architecture is enabled. + PPT Parallel port support is enabled. + PS2 Appropriate PS/2 support is enabled. + PV_OPS A paravirtualized kernel is enabled. + RAM RAM disk support is enabled. + RDT Intel Resource Director Technology. + RISCV RISCV architecture is enabled. + S390 S390 architecture is enabled. + SCSI Appropriate SCSI support is enabled. + A lot of drivers have their options described inside + the Documentation/scsi/ sub-directory. + SECURITY Different security models are enabled. + SELINUX SELinux support is enabled. + SERIAL Serial support is enabled. + SH SuperH architecture is enabled. + SMP The kernel is an SMP kernel. + SPARC Sparc architecture is enabled. + SUSPEND System suspend states are enabled. + SWSUSP Software suspend (hibernation) is enabled. + TPM TPM drivers are enabled. + UMS USB Mass Storage support is enabled. + USB USB support is enabled. + USBHID USB Human Interface Device support is enabled. + V4L Video For Linux support is enabled. + VGA The VGA console has been enabled. + VMMIO Driver for memory mapped virtio devices is enabled. + VT Virtual terminal support is enabled. + WDT Watchdog support is enabled. + X86-32 X86-32, aka i386 architecture is enabled. + X86-64 X86-64 architecture is enabled. + More X86-64 boot options can be found in + Documentation/arch/x86/x86_64/boot-options.rst. + X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64) + X86_UV SGI UV support is enabled. + XEN Xen support is enabled + XTENSA xtensa architecture is enabled. + +In addition, the following text indicates that the option:: + + BOOT Is a boot loader parameter. + BUGS= Relates to possible processor bugs on the said processor. + KNL Is a kernel start-up parameter. + +Parameters denoted with BOOT are actually interpreted by the boot +loader, and have no meaning to the kernel directly. +Do not modify the syntax of boot loader parameters without extreme +need or coordination with <Documentation/arch/x86/boot.rst>. + +There are also arch-specific kernel-parameters not documented here. +See for example <Documentation/arch/x86/x86_64/boot-options.rst>. + +Note that ALL kernel parameters listed below are CASE SENSITIVE, and that +a trailing = on the name of any parameter states that that parameter will +be entered as an environment variable, whereas its absence indicates that +it will appear as a kernel argument readable via /proc/cmdline by programs +running once the system is up. + +The number of kernel parameters is not limited, but the length of the +complete command line (parameters including spaces etc.) is limited to +a fixed number of characters. This limit depends on the architecture +and is between 256 and 4096 characters. It is defined in the file +./include/uapi/asm-generic/setup.h as COMMAND_LINE_SIZE. + +Finally, the [KMG] suffix is commonly described after a number of kernel +parameter values. These 'K', 'M', and 'G' letters represent the _binary_ +multipliers 'Kilo', 'Mega', and 'Giga', equaling 2^10, 2^20, and 2^30 +bytes respectively. Such letter suffixes can also be entirely omitted: + +.. include:: kernel-parameters.txt + :literal: + +Todo +---- + + Add more DRM drivers. diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt new file mode 100644 index 000000000..41644336e --- /dev/null +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -0,0 +1,7283 @@ + acpi= [HW,ACPI,X86,ARM64,RISCV64] + Advanced Configuration and Power Interface + Format: { force | on | off | strict | noirq | rsdt | + copy_dsdt } + force -- enable ACPI if default was off + on -- enable ACPI but allow fallback to DT [arm64,riscv64] + off -- disable ACPI if default was on + noirq -- do not use ACPI for IRQ routing + strict -- Be less tolerant of platforms that are not + strictly ACPI specification compliant. + rsdt -- prefer RSDT over (default) XSDT + copy_dsdt -- copy DSDT to memory + For ARM64 and RISCV64, ONLY "acpi=off", "acpi=on" or + "acpi=force" are available + + See also Documentation/power/runtime_pm.rst, pci=noacpi + + acpi_apic_instance= [ACPI, IOAPIC] + Format: <int> + 2: use 2nd APIC table, if available + 1,0: use 1st APIC table + default: 0 + + acpi_backlight= [HW,ACPI] + { vendor | video | native | none } + If set to vendor, prefer vendor-specific driver + (e.g. thinkpad_acpi, sony_acpi, etc.) instead + of the ACPI video.ko driver. + If set to video, use the ACPI video.ko driver. + If set to native, use the device's native backlight mode. + If set to none, disable the ACPI backlight interface. + + acpi_force_32bit_fadt_addr + force FADT to use 32 bit addresses rather than the + 64 bit X_* addresses. Some firmware have broken 64 + bit addresses for force ACPI ignore these and use + the older legacy 32 bit addresses. + + acpica_no_return_repair [HW, ACPI] + Disable AML predefined validation mechanism + This mechanism can repair the evaluation result to make + the return objects more ACPI specification compliant. + This option is useful for developers to identify the + root cause of an AML interpreter issue when the issue + has something to do with the repair mechanism. + + acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] + acpi.debug_level= [HW,ACPI,ACPI_DEBUG] + Format: <int> + CONFIG_ACPI_DEBUG must be enabled to produce any ACPI + debug output. Bits in debug_layer correspond to a + _COMPONENT in an ACPI source file, e.g., + #define _COMPONENT ACPI_EVENTS + Bits in debug_level correspond to a level in + ACPI_DEBUG_PRINT statements, e.g., + ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... + The debug_level mask defaults to "info". See + Documentation/firmware-guide/acpi/debug.rst for more information about + debug layers and levels. + + Enable processor driver info messages: + acpi.debug_layer=0x20000000 + Enable AML "Debug" output, i.e., stores to the Debug + object while interpreting AML: + acpi.debug_layer=0xffffffff acpi.debug_level=0x2 + Enable all messages related to ACPI hardware: + acpi.debug_layer=0x2 acpi.debug_level=0xffffffff + + Some values produce so much output that the system is + unusable. The "log_buf_len" parameter may be useful + if you need to capture more output. + + acpi_enforce_resources= [ACPI] + { strict | lax | no } + Check for resource conflicts between native drivers + and ACPI OperationRegions (SystemIO and SystemMemory + only). IO ports and memory declared in ACPI might be + used by the ACPI subsystem in arbitrary AML code and + can interfere with legacy drivers. + strict (default): access to resources claimed by ACPI + is denied; legacy drivers trying to access reserved + resources will fail to bind to device using them. + lax: access to resources claimed by ACPI is allowed; + legacy drivers trying to access reserved resources + will bind successfully but a warning message is logged. + no: ACPI OperationRegions are not marked as reserved, + no further checks are performed. + + acpi_force_table_verification [HW,ACPI] + Enable table checksum verification during early stage. + By default, this is disabled due to x86 early mapping + size limitation. + + acpi_irq_balance [HW,ACPI] + ACPI will balance active IRQs + default in APIC mode + + acpi_irq_nobalance [HW,ACPI] + ACPI will not move active IRQs (default) + default in PIC mode + + acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA + Format: <irq>,<irq>... + + acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for + use by PCI + Format: <irq>,<irq>... + + acpi_mask_gpe= [HW,ACPI] + Due to the existence of _Lxx/_Exx, some GPEs triggered + by unsupported hardware/firmware features can result in + GPE floodings that cannot be automatically disabled by + the GPE dispatcher. + This facility can be used to prevent such uncontrolled + GPE floodings. + Format: <byte> or <bitmap-list> + + acpi_no_auto_serialize [HW,ACPI] + Disable auto-serialization of AML methods + AML control methods that contain the opcodes to create + named objects will be marked as "Serialized" by the + auto-serialization feature. + This feature is enabled by default. + This option allows to turn off the feature. + + acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump + kernels. + + acpi_no_static_ssdt [HW,ACPI] + Disable installation of static SSDTs at early boot time + By default, SSDTs contained in the RSDT/XSDT will be + installed automatically and they will appear under + /sys/firmware/acpi/tables. + This option turns off this feature. + Note that specifying this option does not affect + dynamic table installation which will install SSDT + tables to /sys/firmware/acpi/tables/dynamic. + + acpi_no_watchdog [HW,ACPI,WDT] + Ignore the ACPI-based watchdog interface (WDAT) and let + a native driver control the watchdog device instead. + + acpi_rsdp= [ACPI,EFI,KEXEC] + Pass the RSDP address to the kernel, mostly used + on machines running EFI runtime service to boot the + second kernel for kdump. + + acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS + Format: To spoof as Windows 98: ="Microsoft Windows" + + acpi_rev_override [ACPI] Override the _REV object to return 5 (instead + of 2 which is mandated by ACPI 6) as the supported ACPI + specification revision (when using this switch, it may + be necessary to carry out a cold reboot _twice_ in a + row to make it take effect on the platform firmware). + + acpi_osi= [HW,ACPI] Modify list of supported OS interface strings + acpi_osi="string1" # add string1 + acpi_osi="!string2" # remove string2 + acpi_osi=!* # remove all strings + acpi_osi=! # disable all built-in OS vendor + strings + acpi_osi=!! # enable all built-in OS vendor + strings + acpi_osi= # disable all strings + + 'acpi_osi=!' can be used in combination with single or + multiple 'acpi_osi="string1"' to support specific OS + vendor string(s). Note that such command can only + affect the default state of the OS vendor strings, thus + it cannot affect the default state of the feature group + strings and the current state of the OS vendor strings, + specifying it multiple times through kernel command line + is meaningless. This command is useful when one do not + care about the state of the feature group strings which + should be controlled by the OSPM. + Examples: + 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent + to 'acpi_osi="Windows 2000" acpi_osi=!', they all + can make '_OSI("Windows 2000")' TRUE. + + 'acpi_osi=' cannot be used in combination with other + 'acpi_osi=' command lines, the _OSI method will not + exist in the ACPI namespace. NOTE that such command can + only affect the _OSI support state, thus specifying it + multiple times through kernel command line is also + meaningless. + Examples: + 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)' + FALSE. + + 'acpi_osi=!*' can be used in combination with single or + multiple 'acpi_osi="string1"' to support specific + string(s). Note that such command can affect the + current state of both the OS vendor strings and the + feature group strings, thus specifying it multiple times + through kernel command line is meaningful. But it may + still not able to affect the final state of a string if + there are quirks related to this string. This command + is useful when one want to control the state of the + feature group strings to debug BIOS issues related to + the OSPM features. + Examples: + 1. 'acpi_osi="Module Device" acpi_osi=!*' can make + '_OSI("Module Device")' FALSE. + 2. 'acpi_osi=!* acpi_osi="Module Device"' can make + '_OSI("Module Device")' TRUE. + 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is + equivalent to + 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"' + and + 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!', + they all will make '_OSI("Windows 2000")' TRUE. + + acpi_pm_good [X86] + Override the pmtimer bug detection: force the kernel + to assume that this machine's pmtimer latches its value + and always returns good values. + + acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode + Format: { level | edge | high | low } + + acpi_skip_timer_override [HW,ACPI] + Recognize and ignore IRQ0/pin2 Interrupt Override. + For broken nForce2 BIOS resulting in XT-PIC timer. + + acpi_sleep= [HW,ACPI] Sleep options + Format: { s3_bios, s3_mode, s3_beep, s4_hwsig, + s4_nohwsig, old_ordering, nonvs, + sci_force_enable, nobl } + See Documentation/power/video.rst for information on + s3_bios and s3_mode. + s3_beep is for debugging; it makes the PC's speaker beep + as soon as the kernel's real-mode entry point is called. + s4_hwsig causes the kernel to check the ACPI hardware + signature during resume from hibernation, and gracefully + refuse to resume if it has changed. This complies with + the ACPI specification but not with reality, since + Windows does not do this and many laptops do change it + on docking. So the default behaviour is to allow resume + and simply warn when the signature changes, unless the + s4_hwsig option is enabled. + s4_nohwsig prevents ACPI hardware signature from being + used (or even warned about) during resume. + old_ordering causes the ACPI 1.0 ordering of the _PTS + control method, with respect to putting devices into + low power states, to be enforced (the ACPI 2.0 ordering + of _PTS is used by default). + nonvs prevents the kernel from saving/restoring the + ACPI NVS memory during suspend/hibernation and resume. + sci_force_enable causes the kernel to set SCI_EN directly + on resume from S1/S3 (which is against the ACPI spec, + but some broken systems don't work without it). + nobl causes the internal blacklist of systems known to + behave incorrectly in some ways with respect to system + suspend and resume to be ignored (use wisely). + + acpi_use_timer_override [HW,ACPI] + Use timer override. For some broken Nvidia NF5 boards + that require a timer override, but don't have HPET + + add_efi_memmap [EFI; X86] Include EFI memory map in + kernel's map of available physical RAM. + + agp= [AGP] + { off | try_unsupported } + off: disable AGP support + try_unsupported: try to drive unsupported chipsets + (may crash computer or cause data corruption) + + ALSA [HW,ALSA] + See Documentation/sound/alsa-configuration.rst + + alignment= [KNL,ARM] + Allow the default userspace alignment fault handler + behaviour to be specified. Bit 0 enables warnings, + bit 1 enables fixups, and bit 2 sends a segfault. + + align_va_addr= [X86-64] + Align virtual addresses by clearing slice [14:12] when + allocating a VMA at process creation time. This option + gives you up to 3% performance improvement on AMD F15h + machines (where it is enabled by default) for a + CPU-intensive style benchmark, and it can vary highly in + a microbenchmark depending on workload and compiler. + + 32: only for 32-bit processes + 64: only for 64-bit processes + on: enable for both 32- and 64-bit processes + off: disable for both 32- and 64-bit processes + + alloc_snapshot [FTRACE] + Allocate the ftrace snapshot buffer on boot up when the + main buffer is allocated. This is handy if debugging + and you need to use tracing_snapshot() on boot up, and + do not want to use tracing_snapshot_alloc() as it needs + to be done where GFP_KERNEL allocations are allowed. + + allow_mismatched_32bit_el0 [ARM64] + Allow execve() of 32-bit applications and setting of the + PER_LINUX32 personality on systems where only a strict + subset of the CPUs support 32-bit EL0. When this + parameter is present, the set of CPUs supporting 32-bit + EL0 is indicated by /sys/devices/system/cpu/aarch32_el0 + and hot-unplug operations may be restricted. + + See Documentation/arch/arm64/asymmetric-32bit.rst for more + information. + + amd_iommu= [HW,X86-64] + Pass parameters to the AMD IOMMU driver in the system. + Possible values are: + fullflush - Deprecated, equivalent to iommu.strict=1 + off - do not initialize any AMD IOMMU found in + the system + force_isolation - Force device isolation for all + devices. The IOMMU driver is not + allowed anymore to lift isolation + requirements as needed. This option + does not override iommu=pt + force_enable - Force enable the IOMMU on platforms known + to be buggy with IOMMU enabled. Use this + option with care. + pgtbl_v1 - Use v1 page table for DMA-API (Default). + pgtbl_v2 - Use v2 page table for DMA-API. + irtcachedis - Disable Interrupt Remapping Table (IRT) caching. + + amd_iommu_dump= [HW,X86-64] + Enable AMD IOMMU driver option to dump the ACPI table + for AMD IOMMU. With this option enabled, AMD IOMMU + driver will print ACPI tables for AMD IOMMU during + IOMMU initialization. + + amd_iommu_intr= [HW,X86-64] + Specifies one of the following AMD IOMMU interrupt + remapping modes: + legacy - Use legacy interrupt remapping mode. + vapic - Use virtual APIC mode, which allows IOMMU + to inject interrupts directly into guest. + This mode requires kvm-amd.avic=1. + (Default when IOMMU HW support is present.) + + amd_pstate= [X86] + disable + Do not enable amd_pstate as the default + scaling driver for the supported processors + passive + Use amd_pstate with passive mode as a scaling driver. + In this mode autonomous selection is disabled. + Driver requests a desired performance level and platform + tries to match the same performance level if it is + satisfied by guaranteed performance level. + active + Use amd_pstate_epp driver instance as the scaling driver, + driver provides a hint to the hardware if software wants + to bias toward performance (0x0) or energy efficiency (0xff) + to the CPPC firmware. then CPPC power algorithm will + calculate the runtime workload and adjust the realtime cores + frequency. + guided + Activate guided autonomous mode. Driver requests minimum and + maximum performance level and the platform autonomously + selects a performance level in this range and appropriate + to the current workload. + + amijoy.map= [HW,JOY] Amiga joystick support + Map of devices attached to JOY0DAT and JOY1DAT + Format: <a>,<b> + See also Documentation/input/joydev/joystick.rst + + analog.map= [HW,JOY] Analog joystick and gamepad support + Specifies type or capabilities of an analog joystick + connected to one of 16 gameports + Format: <type1>,<type2>,..<type16> + + apc= [HW,SPARC] + Power management functions (SPARCstation-4/5 + deriv.) + Format: noidle + Disable APC CPU standby support. SPARCstation-Fox does + not play well with APC CPU idle - disable it if you have + APC and your system crashes randomly. + + apic= [APIC,X86] Advanced Programmable Interrupt Controller + Change the output verbosity while booting + Format: { quiet (default) | verbose | debug } + Change the amount of debugging information output + when initialising the APIC and IO-APIC components. + For X86-32, this can also be used to specify an APIC + driver name. + Format: apic=driver_name + Examples: apic=bigsmp + + apic_extnmi= [APIC,X86] External NMI delivery setting + Format: { bsp (default) | all | none } + bsp: External NMI is delivered only to CPU 0 + all: External NMIs are broadcast to all CPUs as a + backup of CPU 0 + none: External NMI is masked for all CPUs. This is + useful so that a dump capture kernel won't be + shot down by NMI + + autoconf= [IPV6] + See Documentation/networking/ipv6.rst. + + apm= [APM] Advanced Power Management + See header of arch/x86/kernel/apm_32.c. + + apparmor= [APPARMOR] Disable or enable AppArmor at boot time + Format: { "0" | "1" } + See security/apparmor/Kconfig help text + 0 -- disable. + 1 -- enable. + Default value is set via kernel config option. + + arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards + Format: <io>,<irq>,<nodeID> + + arm64.nobti [ARM64] Unconditionally disable Branch Target + Identification support + + arm64.nomops [ARM64] Unconditionally disable Memory Copy and Memory + Set instructions support + + arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension + support + + arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication + support + + arm64.nosme [ARM64] Unconditionally disable Scalable Matrix + Extension support + + arm64.nosve [ARM64] Unconditionally disable Scalable Vector + Extension support + + ataflop= [HW,M68k] + + atarimouse= [HW,MOUSE] Atari Mouse + + atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, + EzKey and similar keyboards + + atkbd.reset= [HW] Reset keyboard during initialization + + atkbd.set= [HW] Select keyboard code set + Format: <int> (2 = AT (default), 3 = PS/2) + + atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar + keyboards + + atkbd.softraw= [HW] Choose between synthetic and real raw mode + Format: <bool> (0 = real, 1 = synthetic (default)) + + atkbd.softrepeat= [HW] + Use software keyboard repeat + + audit= [KNL] Enable the audit sub-system + Format: { "0" | "1" | "off" | "on" } + 0 | off - kernel audit is disabled and can not be + enabled until the next reboot + unset - kernel audit is initialized but disabled and + will be fully enabled by the userspace auditd. + 1 | on - kernel audit is initialized and partially + enabled, storing at most audit_backlog_limit + messages in RAM until it is fully enabled by the + userspace auditd. + Default: unset + + audit_backlog_limit= [KNL] Set the audit queue size limit. + Format: <int> (must be >=0) + Default: 64 + + bau= [X86_UV] Enable the BAU on SGI UV. The default + behavior is to disable the BAU (i.e. bau=0). + Format: { "0" | "1" } + 0 - Disable the BAU. + 1 - Enable the BAU. + unset - Disable the BAU. + + baycom_epp= [HW,AX25] + Format: <io>,<mode> + + baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem + Format: <io>,<mode> + See header of drivers/net/hamradio/baycom_par.c. + + baycom_ser_fdx= [HW,AX25] + BayCom Serial Port AX.25 Modem (Full Duplex Mode) + Format: <io>,<irq>,<mode>[,<baud>] + See header of drivers/net/hamradio/baycom_ser_fdx.c. + + baycom_ser_hdx= [HW,AX25] + BayCom Serial Port AX.25 Modem (Half Duplex Mode) + Format: <io>,<irq>,<mode> + See header of drivers/net/hamradio/baycom_ser_hdx.c. + + bert_disable [ACPI] + Disable BERT OS support on buggy BIOSes. + + bgrt_disable [ACPI][X86] + Disable BGRT to avoid flickering OEM logo. + + blkdevparts= Manual partition parsing of block device(s) for + embedded devices based on command line input. + See Documentation/block/cmdline-partition.rst + + boot_delay= Milliseconds to delay each printk during boot. + Only works if CONFIG_BOOT_PRINTK_DELAY is enabled, + and you may also have to specify "lpj=". Boot_delay + values larger than 10 seconds (10000) are assumed + erroneous and ignored. + Format: integer + + bootconfig [KNL] + Extended command line options can be added to an initrd + and this will cause the kernel to look for it. + + See Documentation/admin-guide/bootconfig.rst + + bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) + bttv.radio= Most important insmod options are available as + kernel args too. + bttv.pll= See Documentation/admin-guide/media/bttv.rst + bttv.tuner= + + bulk_remove=off [PPC] This parameter disables the use of the pSeries + firmware feature for flushing multiple hpte entries + at a time. + + c101= [NET] Moxa C101 synchronous serial card + + cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. + Sometimes CPU hardware bugs make them report the cache + size incorrectly. The kernel will attempt work arounds + to fix known problems, but for some CPUs it is not + possible to determine what the correct size should be. + This option provides an override for these situations. + + carrier_timeout= + [NET] Specifies amount of time (in seconds) that + the kernel should wait for a network carrier. By default + it waits 120 seconds. + + ca_keys= [KEYS] This parameter identifies a specific key(s) on + the system trusted keyring to be used for certificate + trust validation. + format: { id:<keyid> | builtin } + + cca= [MIPS] Override the kernel pages' cache coherency + algorithm. Accepted values range from 0 to 7 + inclusive. See arch/mips/include/asm/pgtable-bits.h + for platform specific values (SB1, Loongson3 and + others). + + ccw_timeout_log [S390] + See Documentation/arch/s390/common_io.rst for details. + + cgroup_disable= [KNL] Disable a particular controller or optional feature + Format: {name of the controller(s) or feature(s) to disable} + The effects of cgroup_disable=foo are: + - foo isn't auto-mounted if you mount all cgroups in + a single hierarchy + - foo isn't visible as an individually mountable + subsystem + - if foo is an optional feature then the feature is + disabled and corresponding cgroup files are not + created + {Currently only "memory" controller deal with this and + cut the overhead, others just disable the usage. So + only cgroup_disable=memory is actually worthy} + Specifying "pressure" disables per-cgroup pressure + stall information accounting feature + + cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1 + Format: { { controller | "all" | "named" } + [,{ controller | "all" | "named" }...] } + Like cgroup_disable, but only applies to cgroup v1; + the blacklisted controllers remain available in cgroup2. + "all" blacklists all controllers and "named" disables + named mounts. Specifying both "all" and "named" disables + all v1 hierarchies. + + cgroup.memory= [KNL] Pass options to the cgroup memory controller. + Format: <string> + nosocket -- Disable socket memory accounting. + nokmem -- Disable kernel memory accounting. + nobpf -- Disable BPF memory accounting. + + checkreqprot= [SELINUX] Set initial checkreqprot flag value. + Format: { "0" | "1" } + See security/selinux/Kconfig help text. + 0 -- check protection applied by kernel (includes + any implied execute protection). + 1 -- check protection requested by application. + Default value is set via a kernel config option. + Value can be changed at runtime via + /sys/fs/selinux/checkreqprot. + Setting checkreqprot to 1 is deprecated. + + cio_ignore= [S390] + See Documentation/arch/s390/common_io.rst for details. + + clearcpuid=X[,X...] [X86] + Disable CPUID feature X for the kernel. See + arch/x86/include/asm/cpufeatures.h for the valid bit + numbers X. Note the Linux-specific bits are not necessarily + stable over kernel options, but the vendor-specific + ones should be. + X can also be a string as appearing in the flags: line + in /proc/cpuinfo which does not have the above + instability issue. However, not all features have names + in /proc/cpuinfo. + Note that using this option will taint your kernel. + Also note that user programs calling CPUID directly + or using the feature without checking anything + will still see it. This just prevents it from + being used by the kernel or shown in /proc/cpuinfo. + Also note the kernel might malfunction if you disable + some critical bits. + + clk_ignore_unused + [CLK] + Prevents the clock framework from automatically gating + clocks that have not been explicitly enabled by a Linux + device driver but are enabled in hardware at reset or + by the bootloader/firmware. Note that this does not + force such clocks to be always-on nor does it reserve + those clocks in any way. This parameter is useful for + debug and development, but should not be needed on a + platform with proper driver support. For more + information, see Documentation/driver-api/clk.rst. + + clock= [BUGS=X86-32, HW] gettimeofday clocksource override. + [Deprecated] + Forces specified clocksource (if available) to be used + when calculating gettimeofday(). If specified + clocksource is not available, it defaults to PIT. + Format: { pit | tsc | cyclone | pmtmr } + + clocksource= Override the default clocksource + Format: <string> + Override the default clocksource and use the clocksource + with the name specified. + Some clocksource names to choose from, depending on + the platform: + [all] jiffies (this is the base, fallback clocksource) + [ACPI] acpi_pm + [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, + pxa_timer,timer3,32k_counter,timer0_1 + [X86-32] pit,hpet,tsc; + scx200_hrt on Geode; cyclone on IBM x440 + [MIPS] MIPS + [PARISC] cr16 + [S390] tod + [SH] SuperH + [SPARC64] tick + [X86-64] hpet,tsc + + clocksource.arm_arch_timer.evtstrm= + [ARM,ARM64] + Format: <bool> + Enable/disable the eventstream feature of the ARM + architected timer so that code using WFE-based polling + loops can be debugged more effectively on production + systems. + + clocksource.max_cswd_read_retries= [KNL] + Number of clocksource_watchdog() retries due to + external delays before the clock will be marked + unstable. Defaults to two retries, that is, + three attempts to read the clock under test. + + clocksource.verify_n_cpus= [KNL] + Limit the number of CPUs checked for clocksources + marked with CLOCK_SOURCE_VERIFY_PERCPU that + are marked unstable due to excessive skew. + A negative value says to check all CPUs, while + zero says not to check any. Values larger than + nr_cpu_ids are silently truncated to nr_cpu_ids. + The actual CPUs are chosen randomly, with + no replacement if the same CPU is chosen twice. + + clocksource-wdtest.holdoff= [KNL] + Set the time in seconds that the clocksource + watchdog test waits before commencing its tests. + Defaults to zero when built as a module and to + 10 seconds when built into the kernel. + + cma=nn[MG]@[start[MG][-end[MG]]] + [KNL,CMA] + Sets the size of kernel global memory area for + contiguous memory allocations and optionally the + placement constraint by the physical address range of + memory allocations. A value of 0 disables CMA + altogether. For more information, see + kernel/dma/contiguous.c + + cma_pernuma=nn[MG] + [KNL,CMA] + Sets the size of kernel per-numa memory area for + contiguous memory allocations. A value of 0 disables + per-numa CMA altogether. And If this option is not + specified, the default value is 0. + With per-numa CMA enabled, DMA users on node nid will + first try to allocate buffer from the pernuma area + which is located in node nid, if the allocation fails, + they will fallback to the global default memory area. + + numa_cma=<node>:nn[MG][,<node>:nn[MG]] + [KNL,CMA] + Sets the size of kernel numa memory area for + contiguous memory allocations. It will reserve CMA + area for the specified node. + + With numa CMA enabled, DMA users on node nid will + first try to allocate buffer from the numa area + which is located in node nid, if the allocation fails, + they will fallback to the global default memory area. + + cmo_free_hint= [PPC] Format: { yes | no } + Specify whether pages are marked as being inactive + when they are freed. This is used in CMO environments + to determine OS memory pressure for page stealing by + a hypervisor. + Default: yes + + coherent_pool=nn[KMG] [ARM,KNL] + Sets the size of memory pool for coherent, atomic dma + allocations, by default set to 256K. + + com20020= [HW,NET] ARCnet - COM20020 chipset + Format: + <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] + + com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) + Format: <io>[,<irq>] + + com90xx= [HW,NET] + ARCnet - COM90xx chipset (memory-mapped buffers) + Format: <io>[,<irq>[,<memstart>]] + + condev= [HW,S390] console device + conmode= + + con3215_drop= [S390] 3215 console drop mode. + Format: y|n|Y|N|1|0 + When set to true, drop data on the 3215 console when + the console buffer is full. In this case the + operator using a 3270 terminal emulator (for example + x3270) does not have to enter the clear key for the + console output to advance and the kernel to continue. + This leads to a much faster boot time when a 3270 + terminal emulator is active. If no 3270 terminal + emulator is used, this parameter has no effect. + + console= [KNL] Output console device and options. + + tty<n> Use the virtual console device <n>. + + ttyS<n>[,options] + ttyUSB0[,options] + Use the specified serial port. The options are of + the form "bbbbpnf", where "bbbb" is the baud rate, + "p" is parity ("n", "o", or "e"), "n" is number of + bits, and "f" is flow control ("r" for RTS or + omit it). Default is "9600n8". + + See Documentation/admin-guide/serial-console.rst for more + information. See + Documentation/networking/netconsole.rst for an + alternative. + + uart[8250],io,<addr>[,options] + uart[8250],mmio,<addr>[,options] + uart[8250],mmio16,<addr>[,options] + uart[8250],mmio32,<addr>[,options] + uart[8250],0x<addr>[,options] + Start an early, polled-mode console on the 8250/16550 + UART at the specified I/O port or MMIO address, + switching to the matching ttyS device later. + MMIO inter-register address stride is either 8-bit + (mmio), 16-bit (mmio16), or 32-bit (mmio32). + If none of [io|mmio|mmio16|mmio32], <addr> is assumed + to be equivalent to 'mmio'. 'options' are specified in + the same format described for ttyS above; if unspecified, + the h/w is not re-initialized. + + hvc<n> Use the hypervisor console device <n>. This is for + both Xen and PowerPC hypervisors. + + { null | "" } + Use to disable console output, i.e., to have kernel + console messages discarded. + This must be the only console= parameter used on the + kernel command line. + + If the device connected to the port is not a TTY but a braille + device, prepend "brl," before the device type, for instance + console=brl,ttyS0 + For now, only VisioBraille is supported. + + console_msg_format= + [KNL] Change console messages format + default + By default we print messages on consoles in + "[time stamp] text\n" format (time stamp may not be + printed, depending on CONFIG_PRINTK_TIME or + `printk_time' param). + syslog + Switch to syslog format: "<%u>[time stamp] text\n" + IOW, each message will have a facility and loglevel + prefix. The format is similar to one used by syslog() + syscall, or to executing "dmesg -S --raw" or to reading + from /proc/kmsg. + + consoleblank= [KNL] The console blank (screen saver) timeout in + seconds. A value of 0 disables the blank timer. + Defaults to 0. + + coredump_filter= + [KNL] Change the default value for + /proc/<pid>/coredump_filter. + See also Documentation/filesystems/proc.rst. + + coresight_cpu_debug.enable + [ARM,ARM64] + Format: <bool> + Enable/disable the CPU sampling based debugging. + 0: default value, disable debugging + 1: enable debugging at boot time + + cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver + Format: + <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] + + cpuidle.off=1 [CPU_IDLE] + disable the cpuidle sub-system + + cpuidle.governor= + [CPU_IDLE] Name of the cpuidle governor to use. + + cpufreq.off=1 [CPU_FREQ] + disable the cpufreq sub-system + + cpufreq.default_governor= + [CPU_FREQ] Name of the default cpufreq governor or + policy to use. This governor must be registered in the + kernel before the cpufreq driver probes. + + cpu_init_udelay=N + [X86] Delay for N microsec between assert and de-assert + of APIC INIT to start processors. This delay occurs + on every CPU online, such as boot, and resume from suspend. + Default: 10000 + + cpuhp.parallel= + [SMP] Enable/disable parallel bringup of secondary CPUs + Format: <bool> + Default is enabled if CONFIG_HOTPLUG_PARALLEL=y. Otherwise + the parameter has no effect. + + crash_kexec_post_notifiers + Run kdump after running panic-notifiers and dumping + kmsg. This only for the users who doubt kdump always + succeeds in any situation. + Note that this also increases risks of kdump failure, + because some panic notifiers can make the crashed + kernel more unstable. + + crashkernel=size[KMG][@offset[KMG]] + [KNL] Using kexec, Linux can switch to a 'crash kernel' + upon panic. This parameter reserves the physical + memory region [offset, offset + size] for that kernel + image. If '@offset' is omitted, then a suitable offset + is selected automatically. + [KNL, X86-64, ARM64, RISCV] Select a region under 4G first, and + fall back to reserve region above 4G when '@offset' + hasn't been specified. + See Documentation/admin-guide/kdump/kdump.rst for further details. + + crashkernel=range1:size1[,range2:size2,...][@offset] + [KNL] Same as above, but depends on the memory + in the running system. The syntax of range is + start-[end] where start and end are both + a memory unit (amount[KMG]). See also + Documentation/admin-guide/kdump/kdump.rst for an example. + + crashkernel=size[KMG],high + [KNL, X86-64, ARM64, RISCV] range could be above 4G. + Allow kernel to allocate physical memory region from top, + so could be above 4G if system have more than 4G ram + installed. Otherwise memory region will be allocated + below 4G, if available. + It will be ignored if crashkernel=X is specified. + crashkernel=size[KMG],low + [KNL, X86-64, ARM64, RISCV] range under 4G. When crashkernel=X,high + is passed, kernel could allocate physical memory region + above 4G, that cause second kernel crash on system + that require some amount of low memory, e.g. swiotlb + requires at least 64M+32K low memory, also enough extra + low memory is needed to make sure DMA buffers for 32-bit + devices won't run out. Kernel would try to allocate + default size of memory below 4G automatically. The default + size is platform dependent. + --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB) + --> arm64: 128MiB + --> riscv: 128MiB + This one lets the user specify own low range under 4G + for second kernel instead. + 0: to disable low allocation. + It will be ignored when crashkernel=X,high is not used + or memory reserved is below 4G. + + cryptomgr.notests + [KNL] Disable crypto self-tests + + cs89x0_dma= [HW,NET] + Format: <dma> + + cs89x0_media= [HW,NET] + Format: { rj45 | aui | bnc } + + csdlock_debug= [KNL] Enable or disable debug add-ons of cross-CPU + function call handling. When switched on, + additional debug data is printed to the console + in case a hanging CPU is detected, and that + CPU is pinged again in order to try to resolve + the hang situation. The default value of this + option depends on the CSD_LOCK_WAIT_DEBUG_DEFAULT + Kconfig option. + + dasd= [HW,NET] + See header of drivers/s390/block/dasd_devmap.c. + + db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port + (one device per port) + Format: <port#>,<type> + See also Documentation/input/devices/joystick-parport.rst + + debug [KNL] Enable kernel debugging (events log level). + + debug_boot_weak_hash + [KNL] Enable printing [hashed] pointers early in the + boot sequence. If enabled, we use a weak hash instead + of siphash to hash pointers. Use this option if you are + seeing instances of '(___ptrval___)') and need to see a + value (hashed pointer) instead. Cryptographically + insecure, please do not use on production kernels. + + debug_locks_verbose= + [KNL] verbose locking self-tests + Format: <int> + Print debugging info while doing the locking API + self-tests. + Bitmask for the various LOCKTYPE_ tests. Defaults to 0 + (no extra messages), setting it to -1 (all bits set) + will print _a_lot_ more information - normally only + useful to lockdep developers. + + debug_objects [KNL] Enable object debugging + + debug_guardpage_minorder= + [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this + parameter allows control of the order of pages that will + be intentionally kept free (and hence protected) by the + buddy allocator. Bigger value increase the probability + of catching random memory corruption, but reduce the + amount of memory for normal system use. The maximum + possible value is MAX_ORDER/2. Setting this parameter + to 1 or 2 should be enough to identify most random + memory corruption problems caused by bugs in kernel or + driver code when a CPU writes to (or reads from) a + random memory location. Note that there exists a class + of memory corruptions problems caused by buggy H/W or + F/W or by drivers badly programming DMA (basically when + memory is written at bus level and the CPU MMU is + bypassed) which are not detectable by + CONFIG_DEBUG_PAGEALLOC, hence this option will not help + tracking down these problems. + + debug_pagealloc= + [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter + enables the feature at boot time. By default, it is + disabled and the system will work mostly the same as a + kernel built without CONFIG_DEBUG_PAGEALLOC. + Note: to get most of debug_pagealloc error reports, it's + useful to also enable the page_owner functionality. + on: enable the feature + + debugfs= [KNL] This parameter enables what is exposed to userspace + and debugfs internal clients. + Format: { on, no-mount, off } + on: All functions are enabled. + no-mount: + Filesystem is not registered but kernel clients can + access APIs and a crashkernel can be used to read + its content. There is nothing to mount. + off: Filesystem is not registered and clients + get a -EPERM as result when trying to register files + or directories within debugfs. + This is equivalent of the runtime functionality if + debugfs was not enabled in the kernel at all. + Default value is set in build-time with a kernel configuration. + + debugpat [X86] Enable PAT debugging + + default_hugepagesz= + [HW] The size of the default HugeTLB page. This is + the size represented by the legacy /proc/ hugepages + APIs. In addition, this is the default hugetlb size + used for shmget(), mmap() and mounting hugetlbfs + filesystems. If not specified, defaults to the + architecture's default huge page size. Huge page + sizes are architecture dependent. See also + Documentation/admin-guide/mm/hugetlbpage.rst. + Format: size[KMG] + + deferred_probe_timeout= + [KNL] Debugging option to set a timeout in seconds for + deferred probe to give up waiting on dependencies to + probe. Only specific dependencies (subsystems or + drivers) that have opted in will be ignored. A timeout + of 0 will timeout at the end of initcalls. If the time + out hasn't expired, it'll be restarted by each + successful driver registration. This option will also + dump out devices still on the deferred probe list after + retrying. + + delayacct [KNL] Enable per-task delay accounting + + dell_smm_hwmon.ignore_dmi= + [HW] Continue probing hardware even if DMI data + indicates that the driver is running on unsupported + hardware. + + dell_smm_hwmon.force= + [HW] Activate driver even if SMM BIOS signature does + not match list of supported models and enable otherwise + blacklisted features. + + dell_smm_hwmon.power_status= + [HW] Report power status in /proc/i8k + (disabled by default). + + dell_smm_hwmon.restricted= + [HW] Allow controlling fans only if SYS_ADMIN + capability is set. + + dell_smm_hwmon.fan_mult= + [HW] Factor to multiply fan speed with. + + dell_smm_hwmon.fan_max= + [HW] Maximum configurable fan speed. + + dfltcc= [HW,S390] + Format: { on | off | def_only | inf_only | always } + on: s390 zlib hardware support for compression on + level 1 and decompression (default) + off: No s390 zlib hardware support + def_only: s390 zlib hardware support for deflate + only (compression on level 1) + inf_only: s390 zlib hardware support for inflate + only (decompression) + always: Same as 'on' but ignores the selected compression + level always using hardware support (used for debugging) + + dhash_entries= [KNL] + Set number of hash buckets for dentry cache. + + disable_1tb_segments [PPC] + Disables the use of 1TB hash page table segments. This + causes the kernel to fall back to 256MB segments which + can be useful when debugging issues that require an SLB + miss to occur. + + disable= [IPV6] + See Documentation/networking/ipv6.rst. + + disable_radix [PPC] + Disable RADIX MMU mode on POWER9 + + disable_tlbie [PPC] + Disable TLBIE instruction. Currently does not work + with KVM, with HASH MMU, or with coherent accelerators. + + disable_cpu_apicid= [X86,APIC,SMP] + Format: <int> + The number of initial APIC ID for the + corresponding CPU to be disabled at boot, + mostly used for the kdump 2nd kernel to + disable BSP to wake up multiple CPUs without + causing system reset or hang due to sending + INIT from AP to BSP. + + disable_ddw [PPC/PSERIES] + Disable Dynamic DMA Window support. Use this + to workaround buggy firmware. + + disable_ipv6= [IPV6] + See Documentation/networking/ipv6.rst. + + disable_mtrr_cleanup [X86] + The kernel tries to adjust MTRR layout from continuous + to discrete, to make X server driver able to add WB + entry later. This parameter disables that. + + disable_mtrr_trim [X86, Intel and AMD only] + By default the kernel will trim any uncacheable + memory out of your available memory pool based on + MTRR settings. This parameter disables that behavior, + possibly causing your machine to run very slowly. + + disable_timer_pin_1 [X86] + Disable PIN 1 of APIC timer + Can be useful to work around chipset bugs. + + dis_ucode_ldr [X86] Disable the microcode loader. + + dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, + this option disables the debugging code at boot. + + dma_debug_entries=<number> + This option allows to tune the number of preallocated + entries for DMA-API debugging code. One entry is + required per DMA-API allocation. Use this if the + DMA-API debugging code disables itself because the + architectural default is too low. + + dma_debug_driver=<driver_name> + With this option the DMA-API debugging driver + filter feature can be enabled at boot time. Just + pass the driver to filter for as the parameter. + The filter can be disabled or changed to another + driver later using sysfs. + + driver_async_probe= [KNL] + List of driver names to be probed asynchronously. * + matches with all driver names. If * is specified, the + rest of the listed driver names are those that will NOT + match the *. + Format: <driver_name1>,<driver_name2>... + + drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>] + Broken monitors, graphic adapters, KVMs and EDIDless + panels may send no or incorrect EDID data sets. + This parameter allows to specify an EDID data sets + in the /lib/firmware directory that are used instead. + Generic built-in EDID data sets are used, if one of + edid/1024x768.bin, edid/1280x1024.bin, + edid/1680x1050.bin, or edid/1920x1080.bin is given + and no file with the same name exists. Details and + instructions how to build your own EDID data are + available in Documentation/admin-guide/edid.rst. An EDID + data set will only be used for a particular connector, + if its name and a colon are prepended to the EDID + name. Each connector may use a unique EDID data + set by separating the files with a comma. An EDID + data set with no connector name will be used for + any connectors not explicitly specified. + + dscc4.setup= [NET] + + dt_cpu_ftrs= [PPC] + Format: {"off" | "known"} + Control how the dt_cpu_ftrs device-tree binding is + used for CPU feature discovery and setup (if it + exists). + off: Do not use it, fall back to legacy cpu table. + known: Do not pass through unknown features to guests + or userspace, only those that the kernel is aware of. + + dump_apple_properties [X86] + Dump name and content of EFI device properties on + x86 Macs. Useful for driver authors to determine + what data is available or for reverse-engineering. + + dyndbg[="val"] [KNL,DYNAMIC_DEBUG] + <module>.dyndbg[="val"] + Enable debug messages at boot time. See + Documentation/admin-guide/dynamic-debug-howto.rst + for details. + + early_ioremap_debug [KNL] + Enable debug messages in early_ioremap support. This + is useful for tracking down temporary early mappings + which are not unmapped. + + earlycon= [KNL] Output early console device and options. + + When used with no options, the early console is + determined by stdout-path property in device tree's + chosen node or the ACPI SPCR table if supported by + the platform. + + cdns,<addr>[,options] + Start an early, polled-mode console on a Cadence + (xuartps) serial port at the specified address. Only + supported option is baud rate. If baud rate is not + specified, the serial port must already be setup and + configured. + + uart[8250],io,<addr>[,options[,uartclk]] + uart[8250],mmio,<addr>[,options[,uartclk]] + uart[8250],mmio32,<addr>[,options[,uartclk]] + uart[8250],mmio32be,<addr>[,options[,uartclk]] + uart[8250],0x<addr>[,options] + Start an early, polled-mode console on the 8250/16550 + UART at the specified I/O port or MMIO address. + MMIO inter-register address stride is either 8-bit + (mmio) or 32-bit (mmio32 or mmio32be). + If none of [io|mmio|mmio32|mmio32be], <addr> is assumed + to be equivalent to 'mmio'. 'options' are specified + in the same format described for "console=ttyS<n>"; if + unspecified, the h/w is not initialized. 'uartclk' is + the uart clock frequency; if unspecified, it is set + to 'BASE_BAUD' * 16. + + pl011,<addr> + pl011,mmio32,<addr> + Start an early, polled-mode console on a pl011 serial + port at the specified address. The pl011 serial port + must already be setup and configured. Options are not + yet supported. If 'mmio32' is specified, then only + the driver will use only 32-bit accessors to read/write + the device registers. + + liteuart,<addr> + Start an early console on a litex serial port at the + specified address. The serial port must already be + setup and configured. Options are not yet supported. + + meson,<addr> + Start an early, polled-mode console on a meson serial + port at the specified address. The serial port must + already be setup and configured. Options are not yet + supported. + + msm_serial,<addr> + Start an early, polled-mode console on an msm serial + port at the specified address. The serial port + must already be setup and configured. Options are not + yet supported. + + msm_serial_dm,<addr> + Start an early, polled-mode console on an msm serial + dm port at the specified address. The serial port + must already be setup and configured. Options are not + yet supported. + + owl,<addr> + Start an early, polled-mode console on a serial port + of an Actions Semi SoC, such as S500 or S900, at the + specified address. The serial port must already be + setup and configured. Options are not yet supported. + + rda,<addr> + Start an early, polled-mode console on a serial port + of an RDA Micro SoC, such as RDA8810PL, at the + specified address. The serial port must already be + setup and configured. Options are not yet supported. + + sbi + Use RISC-V SBI (Supervisor Binary Interface) for early + console. + + smh Use ARM semihosting calls for early console. + + s3c2410,<addr> + s3c2412,<addr> + s3c2440,<addr> + s3c6400,<addr> + s5pv210,<addr> + exynos4210,<addr> + Use early console provided by serial driver available + on Samsung SoCs, requires selecting proper type and + a correct base address of the selected UART port. The + serial port must already be setup and configured. + Options are not yet supported. + + lantiq,<addr> + Start an early, polled-mode console on a lantiq serial + (lqasc) port at the specified address. The serial port + must already be setup and configured. Options are not + yet supported. + + lpuart,<addr> + lpuart32,<addr> + Use early console provided by Freescale LP UART driver + found on Freescale Vybrid and QorIQ LS1021A processors. + A valid base address must be provided, and the serial + port must already be setup and configured. + + ec_imx21,<addr> + ec_imx6q,<addr> + Start an early, polled-mode, output-only console on the + Freescale i.MX UART at the specified address. The UART + must already be setup and configured. + + ar3700_uart,<addr> + Start an early, polled-mode console on the + Armada 3700 serial port at the specified + address. The serial port must already be setup + and configured. Options are not yet supported. + + qcom_geni,<addr> + Start an early, polled-mode console on a Qualcomm + Generic Interface (GENI) based serial port at the + specified address. The serial port must already be + setup and configured. Options are not yet supported. + + efifb,[options] + Start an early, unaccelerated console on the EFI + memory mapped framebuffer (if available). On cache + coherent non-x86 systems that use system memory for + the framebuffer, pass the 'ram' option so that it is + mapped with the correct attributes. + + linflex,<addr> + Use early console provided by Freescale LINFlexD UART + serial driver for NXP S32V234 SoCs. A valid base + address must be provided, and the serial port must + already be setup and configured. + + earlyprintk= [X86,SH,ARM,M68k,S390] + earlyprintk=vga + earlyprintk=sclp + earlyprintk=xen + earlyprintk=serial[,ttySn[,baudrate]] + earlyprintk=serial[,0x...[,baudrate]] + earlyprintk=ttySn[,baudrate] + earlyprintk=dbgp[debugController#] + earlyprintk=pciserial[,force],bus:device.function[,baudrate] + earlyprintk=xdbc[xhciController#] + + earlyprintk is useful when the kernel crashes before + the normal console is initialized. It is not enabled by + default because it has some cosmetic problems. + + Append ",keep" to not disable it when the real console + takes over. + + Only one of vga, serial, or usb debug port can + be used at a time. + + Currently only ttyS0 and ttyS1 may be specified by + name. Other I/O ports may be explicitly specified + on some architectures (x86 and arm at least) by + replacing ttySn with an I/O port address, like this: + earlyprintk=serial,0x1008,115200 + You can find the port for a given device in + /proc/tty/driver/serial: + 2: uart:ST16650V2 port:00001008 irq:18 ... + + Interaction with the standard serial driver is not + very good. + + The VGA output is eventually overwritten by + the real console. + + The xen option can only be used in Xen domains. + + The sclp output can only be used on s390. + + The optional "force" to "pciserial" enables use of a + PCI device even when its classcode is not of the + UART class. + + edac_report= [HW,EDAC] Control how to report EDAC event + Format: {"on" | "off" | "force"} + on: enable EDAC to report H/W event. May be overridden + by other higher priority error reporting module. + off: disable H/W event reporting through EDAC. + force: enforce the use of EDAC to report H/W event. + default: on. + + edd= [EDD] + Format: {"off" | "on" | "skip[mbr]"} + + efi= [EFI] + Format: { "debug", "disable_early_pci_dma", + "nochunk", "noruntime", "nosoftreserve", + "novamap", "no_disable_early_pci_dma" } + debug: enable misc debug output. + disable_early_pci_dma: disable the busmaster bit on all + PCI bridges while in the EFI boot stub. + nochunk: disable reading files in "chunks" in the EFI + boot stub, as chunking can cause problems with some + firmware implementations. + noruntime : disable EFI runtime services support + nosoftreserve: The EFI_MEMORY_SP (Specific Purpose) + attribute may cause the kernel to reserve the + memory range for a memory mapping driver to + claim. Specify efi=nosoftreserve to disable this + reservation and treat the memory by its base type + (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM"). + novamap: do not call SetVirtualAddressMap(). + no_disable_early_pci_dma: Leave the busmaster bit set + on all PCI bridges while in the EFI boot stub + + efi_no_storage_paranoia [EFI; X86] + Using this parameter you can use more than 50% of + your efi variable storage. Use this parameter only if + you are really sure that your UEFI does sane gc and + fulfills the spec otherwise your board may brick. + + efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86] + Add arbitrary attribute to specific memory range by + updating original EFI memory map. + Region of memory which aa attribute is added to is + from ss to ss+nn. + + If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000 + is specified, EFI_MEMORY_MORE_RELIABLE(0x10000) + attribute is added to range 0x100000000-0x180000000 and + 0x10a0000000-0x1120000000. + + If efi_fake_mem=8G@9G:0x40000 is specified, the + EFI_MEMORY_SP(0x40000) attribute is added to + range 0x240000000-0x43fffffff. + + Using this parameter you can do debugging of EFI memmap + related features. For example, you can do debugging of + Address Range Mirroring feature even if your box + doesn't support it, or mark specific memory as + "soft reserved". + + efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT + that is to be dynamically loaded by Linux. If there are + multiple variables with the same name but with different + vendor GUIDs, all of them will be loaded. See + Documentation/admin-guide/acpi/ssdt-overlays.rst for details. + + + eisa_irq_edge= [PARISC,HW] + See header of drivers/parisc/eisa.c. + + ekgdboc= [X86,KGDB] Allow early kernel console debugging + Format: ekgdboc=kbd + + This is designed to be used in conjunction with + the boot argument: earlyprintk=vga + + This parameter works in place of the kgdboc parameter + but can only be used if the backing tty is available + very early in the boot process. For early debugging + via a serial port see kgdboc_earlycon instead. + + elanfreq= [X86-32] + See comment before function elanfreq_setup() in + arch/x86/kernel/cpu/cpufreq/elanfreq.c. + + elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390] + Specifies physical address of start of kernel core + image elf header and optionally the size. Generally + kexec loader will pass this option to capture kernel. + See Documentation/admin-guide/kdump/kdump.rst for details. + + enable_mtrr_cleanup [X86] + The kernel tries to adjust MTRR layout from continuous + to discrete, to make X server driver able to add WB + entry later. This parameter enables that. + + enable_timer_pin_1 [X86] + Enable PIN 1 of APIC timer + Can be useful to work around chipset bugs + (in particular on some ATI chipsets). + The kernel tries to set a reasonable default. + + enforcing= [SELINUX] Set initial enforcing status. + Format: {"0" | "1"} + See security/selinux/Kconfig help text. + 0 -- permissive (log only, no denials). + 1 -- enforcing (deny and log). + Default value is 0. + Value can be changed at runtime via + /sys/fs/selinux/enforce. + + erst_disable [ACPI] + Disable Error Record Serialization Table (ERST) + support. + + ether= [HW,NET] Ethernet cards parameters + This option is obsoleted by the "netdev=" option, which + has equivalent usage. See its documentation for details. + + evm= [EVM] + Format: { "fix" } + Permit 'security.evm' to be updated regardless of + current integrity status. + + early_page_ext [KNL] Enforces page_ext initialization to earlier + stages so cover more early boot allocations. + Please note that as side effect some optimizations + might be disabled to achieve that (e.g. parallelized + memory initialization is disabled) so the boot process + might take longer, especially on systems with a lot of + memory. Available with CONFIG_PAGE_EXTENSION=y. + + failslab= + fail_usercopy= + fail_page_alloc= + fail_make_request=[KNL] + General fault injection mechanism. + Format: <interval>,<probability>,<space>,<times> + See also Documentation/fault-injection/. + + fb_tunnels= [NET] + Format: { initns | none } + See Documentation/admin-guide/sysctl/net.rst for + fb_tunnels_only_for_init_ns + + floppy= [HW] + See Documentation/admin-guide/blockdev/floppy.rst. + + force_pal_cache_flush + [IA-64] Avoid check_sal_cache_flush which may hang on + buggy SAL_CACHE_FLUSH implementations. Using this + parameter will force ia64_sal_cache_flush to call + ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. + + forcepae [X86-32] + Forcefully enable Physical Address Extension (PAE). + Many Pentium M systems disable PAE but may have a + functionally usable PAE implementation. + Warning: use of this parameter will taint the kernel + and may cause unknown problems. + + ftrace=[tracer] + [FTRACE] will set and start the specified tracer + as early as possible in order to facilitate early + boot debugging. + + ftrace_boot_snapshot + [FTRACE] On boot up, a snapshot will be taken of the + ftrace ring buffer that can be read at: + /sys/kernel/tracing/snapshot. + This is useful if you need tracing information from kernel + boot up that is likely to be overridden by user space + start up functionality. + + Optionally, the snapshot can also be defined for a tracing + instance that was created by the trace_instance= command + line parameter. + + trace_instance=foo,sched_switch ftrace_boot_snapshot=foo + + The above will cause the "foo" tracing instance to trigger + a snapshot at the end of boot up. + + ftrace_dump_on_oops[=orig_cpu] + [FTRACE] will dump the trace buffers on oops. + If no parameter is passed, ftrace will dump + buffers of all CPUs, but if you pass orig_cpu, it will + dump only the buffer of the CPU that triggered the + oops. + + ftrace_filter=[function-list] + [FTRACE] Limit the functions traced by the function + tracer at boot up. function-list is a comma-separated + list of functions. This list can be changed at run + time by the set_ftrace_filter file in the debugfs + tracing directory. + + ftrace_notrace=[function-list] + [FTRACE] Do not trace the functions specified in + function-list. This list can be changed at run time + by the set_ftrace_notrace file in the debugfs + tracing directory. + + ftrace_graph_filter=[function-list] + [FTRACE] Limit the top level callers functions traced + by the function graph tracer at boot up. + function-list is a comma-separated list of functions + that can be changed at run time by the + set_graph_function file in the debugfs tracing directory. + + ftrace_graph_notrace=[function-list] + [FTRACE] Do not trace from the functions specified in + function-list. This list is a comma-separated list of + functions that can be changed at run time by the + set_graph_notrace file in the debugfs tracing directory. + + ftrace_graph_max_depth=<uint> + [FTRACE] Used with the function graph tracer. This is + the max depth it will trace into a function. This value + can be changed at run time by the max_graph_depth file + in the tracefs tracing directory. default: 0 (no limit) + + fw_devlink= [KNL] Create device links between consumer and supplier + devices by scanning the firmware to infer the + consumer/supplier relationships. This feature is + especially useful when drivers are loaded as modules as + it ensures proper ordering of tasks like device probing + (suppliers first, then consumers), supplier boot state + clean up (only after all consumers have probed), + suspend/resume & runtime PM (consumers first, then + suppliers). + Format: { off | permissive | on | rpm } + off -- Don't create device links from firmware info. + permissive -- Create device links from firmware info + but use it only for ordering boot state clean + up (sync_state() calls). + on -- Create device links from firmware info and use it + to enforce probe and suspend/resume ordering. + rpm -- Like "on", but also use to order runtime PM. + + fw_devlink.strict=<bool> + [KNL] Treat all inferred dependencies as mandatory + dependencies. This only applies for fw_devlink=on|rpm. + Format: <bool> + + fw_devlink.sync_state = + [KNL] When all devices that could probe have finished + probing, this parameter controls what to do with + devices that haven't yet received their sync_state() + calls. + Format: { strict | timeout } + strict -- Default. Continue waiting on consumers to + probe successfully. + timeout -- Give up waiting on consumers and call + sync_state() on any devices that haven't yet + received their sync_state() calls after + deferred_probe_timeout has expired or by + late_initcall() if !CONFIG_MODULES. + + gamecon.map[2|3]= + [HW,JOY] Multisystem joystick and NES/SNES/PSX pad + support via parallel port (up to 5 devices per port) + Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> + See also Documentation/input/devices/joystick-parport.rst + + gamma= [HW,DRM] + + gart_fix_e820= [X86-64] disable the fix e820 for K8 GART + Format: off | on + default: on + + gather_data_sampling= + [X86,INTEL] Control the Gather Data Sampling (GDS) + mitigation. + + Gather Data Sampling is a hardware vulnerability which + allows unprivileged speculative access to data which was + previously stored in vector registers. + + This issue is mitigated by default in updated microcode. + The mitigation may have a performance impact but can be + disabled. On systems without the microcode mitigation + disabling AVX serves as a mitigation. + + force: Disable AVX to mitigate systems without + microcode mitigation. No effect if the microcode + mitigation is present. Known to cause crashes in + userspace with buggy AVX enumeration. + + off: Disable GDS mitigation. + + gcov_persist= [GCOV] When non-zero (default), profiling data for + kernel modules is saved and remains accessible via + debugfs, even when the module is unloaded/reloaded. + When zero, profiling data is discarded and associated + debugfs files are removed at module unload time. + + goldfish [X86] Enable the goldfish android emulator platform. + Don't use this when you are not running on the + android emulator + + gpio-mockup.gpio_mockup_ranges + [HW] Sets the ranges of gpiochip of for this device. + Format: <start1>,<end1>,<start2>,<end2>... + gpio-mockup.gpio_mockup_named_lines + [HW] Let the driver know GPIO lines should be named. + + gpt [EFI] Forces disk with valid GPT signature but + invalid Protective MBR to be treated as GPT. If the + primary GPT is corrupted, it enables the backup/alternate + GPT to be used instead. + + grcan.enable0= [HW] Configuration of physical interface 0. Determines + the "Enable 0" bit of the configuration register. + Format: 0 | 1 + Default: 0 + grcan.enable1= [HW] Configuration of physical interface 1. Determines + the "Enable 0" bit of the configuration register. + Format: 0 | 1 + Default: 0 + grcan.select= [HW] Select which physical interface to use. + Format: 0 | 1 + Default: 0 + grcan.txsize= [HW] Sets the size of the tx buffer. + Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0. + Default: 1024 + grcan.rxsize= [HW] Sets the size of the rx buffer. + Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0. + Default: 1024 + + hardened_usercopy= + [KNL] Under CONFIG_HARDENED_USERCOPY, whether + hardening is enabled for this boot. Hardened + usercopy checking is used to protect the kernel + from reading or writing beyond known memory + allocation boundaries as a proactive defense + against bounds-checking flaws in the kernel's + copy_to_user()/copy_from_user() interface. + on Perform hardened usercopy checks (default). + off Disable hardened usercopy checks. + + hardlockup_all_cpu_backtrace= + [KNL] Should the hard-lockup detector generate + backtraces on all cpus. + Format: 0 | 1 + + hashdist= [KNL,NUMA] Large hashes allocated during boot + are distributed across NUMA nodes. Defaults on + for 64-bit NUMA, off otherwise. + Format: 0 | 1 (for off | on) + + hcl= [IA-64] SGI's Hardware Graph compatibility layer + + hd= [EIDE] (E)IDE hard drive subsystem geometry + Format: <cyl>,<head>,<sect> + + hest_disable [ACPI] + Disable Hardware Error Source Table (HEST) support; + corresponding firmware-first mode error processing + logic will be disabled. + + hibernate= [HIBERNATION] + noresume Don't check if there's a hibernation image + present during boot. + nocompress Don't compress/decompress hibernation images. + no Disable hibernation and resume. + protect_image Turn on image protection during restoration + (that will set all pages holding image data + during restoration read-only). + + highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact + size of <nn>. This works even on boxes that have no + highmem otherwise. This also works to reduce highmem + size on bigger boxes. + + highres= [KNL] Enable/disable high resolution timer mode. + Valid parameters: "on", "off" + Default: "on" + + hlt [BUGS=ARM,SH] + + hostname= [KNL] Set the hostname (aka UTS nodename). + Format: <string> + This allows setting the system's hostname during early + startup. This sets the name returned by gethostname. + Using this parameter to set the hostname makes it + possible to ensure the hostname is correctly set before + any userspace processes run, avoiding the possibility + that a process may call gethostname before the hostname + has been explicitly set, resulting in the calling + process getting an incorrect result. The string must + not exceed the maximum allowed hostname length (usually + 64 characters) and will be truncated otherwise. + + hpet= [X86-32,HPET] option to control HPET usage + Format: { enable (default) | disable | force | + verbose } + disable: disable HPET and use PIT instead + force: allow force enabled of undocumented chips (ICH4, + VIA, nVidia) + verbose: show contents of HPET registers during setup + + hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET + registers. Default set by CONFIG_HPET_MMAP_DEFAULT. + + hugepages= [HW] Number of HugeTLB pages to allocate at boot. + If this follows hugepagesz (below), it specifies + the number of pages of hugepagesz to be allocated. + If this is the first HugeTLB parameter on the command + line, it specifies the number of pages to allocate for + the default huge page size. If using node format, the + number of pages to allocate per-node can be specified. + See also Documentation/admin-guide/mm/hugetlbpage.rst. + Format: <integer> or (node format) + <node>:<integer>[,<node>:<integer>] + + hugepagesz= + [HW] The size of the HugeTLB pages. This is used in + conjunction with hugepages (above) to allocate huge + pages of a specific size at boot. The pair + hugepagesz=X hugepages=Y can be specified once for + each supported huge page size. Huge page sizes are + architecture dependent. See also + Documentation/admin-guide/mm/hugetlbpage.rst. + Format: size[KMG] + + hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation + of gigantic hugepages. Or using node format, the size + of a CMA area per node can be specified. + Format: nn[KMGTPE] or (node format) + <node>:nn[KMGTPE][,<node>:nn[KMGTPE]] + + Reserve a CMA area of given size and allocate gigantic + hugepages using the CMA allocator. If enabled, the + boot-time allocation of gigantic hugepages is skipped. + + hugetlb_free_vmemmap= + [KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP + enabled. + Control if HugeTLB Vmemmap Optimization (HVO) is enabled. + Allows heavy hugetlb users to free up some more + memory (7 * PAGE_SIZE for each 2MB hugetlb page). + Format: { on | off (default) } + + on: enable HVO + off: disable HVO + + Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y, + the default is on. + + Note that the vmemmap pages may be allocated from the added + memory block itself when memory_hotplug.memmap_on_memory is + enabled, those vmemmap pages cannot be optimized even if this + feature is enabled. Other vmemmap pages not allocated from + the added memory block itself do not be affected. + + hung_task_panic= + [KNL] Should the hung task detector generate panics. + Format: 0 | 1 + + A value of 1 instructs the kernel to panic when a + hung task is detected. The default value is controlled + by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time + option. The value selected by this boot parameter can + be changed later by the kernel.hung_task_panic sysctl. + + hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) + terminal devices. Valid values: 0..8 + hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. + If specified, z/VM IUCV HVC accepts connections + from listed z/VM user IDs only. + + hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations + which allow the hypervisor to 'idle' the + guest on lock contention. + + i2c_bus= [HW] Override the default board specific I2C bus speed + or register an additional I2C bus that is not + registered from board initialization code. + Format: + <bus_id>,<clkrate> + + i8042.debug [HW] Toggle i8042 debug mode + i8042.unmask_kbd_data + [HW] Enable printing of interrupt data from the KBD port + (disabled by default, and as a pre-condition + requires that i8042.debug=1 be enabled) + i8042.direct [HW] Put keyboard port into non-translated mode + i8042.dumbkbd [HW] Pretend that controller can only read data from + keyboard and cannot control its state + (Don't attempt to blink the leds) + i8042.noaux [HW] Don't check for auxiliary (== mouse) port + i8042.nokbd [HW] Don't check/create keyboard port + i8042.noloop [HW] Disable the AUX Loopback command while probing + for the AUX port + i8042.nomux [HW] Don't check presence of an active multiplexing + controller + i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX + controllers + i8042.notimeout [HW] Ignore timeout condition signalled by controller + i8042.reset [HW] Reset the controller during init, cleanup and + suspend-to-ram transitions, only during s2r + transitions, or never reset + Format: { 1 | Y | y | 0 | N | n } + 1, Y, y: always reset controller + 0, N, n: don't ever reset controller + Default: only on s2r transitions on x86; most other + architectures force reset to be always executed + i8042.unlock [HW] Unlock (ignore) the keylock + i8042.kbdreset [HW] Reset device connected to KBD port + i8042.probe_defer + [HW] Allow deferred probing upon i8042 probe errors + + i810= [HW,DRM] + + i915.invert_brightness= + [DRM] Invert the sense of the variable that is used to + set the brightness of the panel backlight. Normally a + brightness value of 0 indicates backlight switched off, + and the maximum of the brightness value sets the backlight + to maximum brightness. If this parameter is set to 0 + (default) and the machine requires it, or this parameter + is set to 1, a brightness value of 0 sets the backlight + to maximum brightness, and the maximum of the brightness + value switches the backlight off. + -1 -- never invert brightness + 0 -- machine default + 1 -- force brightness inversion + + icn= [HW,ISDN] + Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] + + + idle= [X86] + Format: idle=poll, idle=halt, idle=nomwait + Poll forces a polling idle loop that can slightly + improve the performance of waking up a idle CPU, but + will use a lot of power and make the system run hot. + Not recommended. + idle=halt: Halt is forced to be used for CPU idle. + In such case C2/C3 won't be used again. + idle=nomwait: Disable mwait for CPU C-states + + idxd.sva= [HW] + Format: <bool> + Allow force disabling of Shared Virtual Memory (SVA) + support for the idxd driver. By default it is set to + true (1). + + idxd.tc_override= [HW] + Format: <bool> + Allow override of default traffic class configuration + for the device. By default it is set to false (0). + + ieee754= [MIPS] Select IEEE Std 754 conformance mode + Format: { strict | legacy | 2008 | relaxed } + Default: strict + + Choose which programs will be accepted for execution + based on the IEEE 754 NaN encoding(s) supported by + the FPU and the NaN encoding requested with the value + of an ELF file header flag individually set by each + binary. Hardware implementations are permitted to + support either or both of the legacy and the 2008 NaN + encoding mode. + + Available settings are as follows: + strict accept binaries that request a NaN encoding + supported by the FPU + legacy only accept legacy-NaN binaries, if supported + by the FPU + 2008 only accept 2008-NaN binaries, if supported + by the FPU + relaxed accept any binaries regardless of whether + supported by the FPU + + The FPU emulator is always able to support both NaN + encodings, so if no FPU hardware is present or it has + been disabled with 'nofpu', then the settings of + 'legacy' and '2008' strap the emulator accordingly, + 'relaxed' straps the emulator for both legacy-NaN and + 2008-NaN, whereas 'strict' enables legacy-NaN only on + legacy processors and both NaN encodings on MIPS32 or + MIPS64 CPUs. + + The setting for ABS.fmt/NEG.fmt instruction execution + mode generally follows that for the NaN encoding, + except where unsupported by hardware. + + ignore_loglevel [KNL] + Ignore loglevel setting - this will print /all/ + kernel messages to the console. Useful for debugging. + We also add it as printk module parameter, so users + could change it dynamically, usually by + /sys/module/printk/parameters/ignore_loglevel. + + ignore_rlimit_data + Ignore RLIMIT_DATA setting for data mappings, + print warning at first misuse. Can be changed via + /sys/module/kernel/parameters/ignore_rlimit_data. + + ihash_entries= [KNL] + Set number of hash buckets for inode cache. + + ima_appraise= [IMA] appraise integrity measurements + Format: { "off" | "enforce" | "fix" | "log" } + default: "enforce" + + ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead. + The builtin appraise policy appraises all files + owned by uid=0. + + ima_canonical_fmt [IMA] + Use the canonical format for the binary runtime + measurements, instead of host native format. + + ima_hash= [IMA] + Format: { md5 | sha1 | rmd160 | sha256 | sha384 + | sha512 | ... } + default: "sha1" + + The list of supported hash algorithms is defined + in crypto/hash_info.h. + + ima_policy= [IMA] + The builtin policies to load during IMA setup. + Format: "tcb | appraise_tcb | secure_boot | + fail_securely | critical_data" + + The "tcb" policy measures all programs exec'd, files + mmap'd for exec, and all files opened with the read + mode bit set by either the effective uid (euid=0) or + uid=0. + + The "appraise_tcb" policy appraises the integrity of + all files owned by root. + + The "secure_boot" policy appraises the integrity + of files (eg. kexec kernel image, kernel modules, + firmware, policy, etc) based on file signatures. + + The "fail_securely" policy forces file signature + verification failure also on privileged mounted + filesystems with the SB_I_UNVERIFIABLE_SIGNATURE + flag. + + The "critical_data" policy measures kernel integrity + critical data. + + ima_tcb [IMA] Deprecated. Use ima_policy= instead. + Load a policy which meets the needs of the Trusted + Computing Base. This means IMA will measure all + programs exec'd, files mmap'd for exec, and all files + opened for read by uid=0. + + ima_template= [IMA] + Select one of defined IMA measurements template formats. + Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" | + "ima-sigv2" } + Default: "ima-ng" + + ima_template_fmt= + [IMA] Define a custom template format. + Format: { "field1|...|fieldN" } + + ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage + Format: <min_file_size> + Set the minimal file size for using asynchronous hash. + If left unspecified, ahash usage is disabled. + + ahash performance varies for different data sizes on + different crypto accelerators. This option can be used + to achieve the best performance for a particular HW. + + ima.ahash_bufsize= [IMA] Asynchronous hash buffer size + Format: <bufsize> + Set hashing buffer size. Default: 4k. + + ahash performance varies for different chunk sizes on + different crypto accelerators. This option can be used + to achieve best performance for particular HW. + + init= [KNL] + Format: <full_path> + Run specified binary instead of /sbin/init as init + process. + + initcall_debug [KNL] Trace initcalls as they are executed. Useful + for working out where the kernel is dying during + startup. + + initcall_blacklist= [KNL] Do not execute a comma-separated list of + initcall functions. Useful for debugging built-in + modules and initcalls. + + initramfs_async= [KNL] + Format: <bool> + Default: 1 + This parameter controls whether the initramfs + image is unpacked asynchronously, concurrently + with devices being probed and + initialized. This should normally just work, + but as a debugging aid, one can get the + historical behaviour of the initramfs + unpacking being completed before device_ and + late_ initcalls. + + initrd= [BOOT] Specify the location of the initial ramdisk + + initrdmem= [KNL] Specify a physical address and size from which to + load the initrd. If an initrd is compiled in or + specified in the bootparams, it takes priority over this + setting. + Format: ss[KMG],nn[KMG] + Default is 0, 0 + + init_on_alloc= [MM] Fill newly allocated pages and heap objects with + zeroes. + Format: 0 | 1 + Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON. + + init_on_free= [MM] Fill freed pages and heap objects with zeroes. + Format: 0 | 1 + Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON. + + init_pkru= [X86] Specify the default memory protection keys rights + register contents for all processes. 0x55555554 by + default (disallow access to all but pkey 0). Can + override in debugfs after boot. + + inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver + Format: <irq> + + int_pln_enable [X86] Enable power limit notification interrupt + + integrity_audit=[IMA] + Format: { "0" | "1" } + 0 -- basic integrity auditing messages. (Default) + 1 -- additional integrity auditing messages. + + intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option + on + Enable intel iommu driver. + off + Disable intel iommu driver. + igfx_off [Default Off] + By default, gfx is mapped as normal device. If a gfx + device has a dedicated DMAR unit, the DMAR unit is + bypassed by not enabling DMAR with this option. In + this case, gfx device will use physical address for + DMA. + strict [Default Off] + Deprecated, equivalent to iommu.strict=1. + sp_off [Default Off] + By default, super page will be supported if Intel IOMMU + has the capability. With this option, super page will + not be supported. + sm_on + Enable the Intel IOMMU scalable mode if the hardware + advertises that it has support for the scalable mode + translation. + sm_off + Disallow use of the Intel IOMMU scalable mode. + tboot_noforce [Default Off] + Do not force the Intel IOMMU enabled under tboot. + By default, tboot will force Intel IOMMU on, which + could harm performance of some high-throughput + devices like 40GBit network cards, even if identity + mapping is enabled. + Note that using this option lowers the security + provided by tboot because it makes the system + vulnerable to DMA attacks. + + intel_idle.max_cstate= [KNL,HW,ACPI,X86] + 0 disables intel_idle and fall back on acpi_idle. + 1 to 9 specify maximum depth of C-state. + + intel_pstate= [X86] + disable + Do not enable intel_pstate as the default + scaling driver for the supported processors + active + Use intel_pstate driver to bypass the scaling + governors layer of cpufreq and provides it own + algorithms for p-state selection. There are two + P-state selection algorithms provided by + intel_pstate in the active mode: powersave and + performance. The way they both operate depends + on whether or not the hardware managed P-states + (HWP) feature has been enabled in the processor + and possibly on the processor model. + passive + Use intel_pstate as a scaling driver, but configure it + to work with generic cpufreq governors (instead of + enabling its internal governor). This mode cannot be + used along with the hardware-managed P-states (HWP) + feature. + force + Enable intel_pstate on systems that prohibit it by default + in favor of acpi-cpufreq. Forcing the intel_pstate driver + instead of acpi-cpufreq may disable platform features, such + as thermal controls and power capping, that rely on ACPI + P-States information being indicated to OSPM and therefore + should be used with caution. This option does not work with + processors that aren't supported by the intel_pstate driver + or on platforms that use pcc-cpufreq instead of acpi-cpufreq. + no_hwp + Do not enable hardware P state control (HWP) + if available. + hwp_only + Only load intel_pstate on systems which support + hardware P state control (HWP) if available. + support_acpi_ppc + Enforce ACPI _PPC performance limits. If the Fixed ACPI + Description Table, specifies preferred power management + profile as "Enterprise Server" or "Performance Server", + then this feature is turned on by default. + per_cpu_perf_limits + Allow per-logical-CPU P-State performance control limits using + cpufreq sysfs interface + + intremap= [X86-64, Intel-IOMMU] + on enable Interrupt Remapping (default) + off disable Interrupt Remapping + nosid disable Source ID checking + no_x2apic_optout + BIOS x2APIC opt-out request will be ignored + nopost disable Interrupt Posting + + iomem= Disable strict checking of access to MMIO memory + strict regions from userspace. + relaxed + + iommu= [X86] + off + force + noforce + biomerge + panic + nopanic + merge + nomerge + soft + pt [X86] + nopt [X86] + nobypass [PPC/POWERNV] + Disable IOMMU bypass, using IOMMU for PCI devices. + + iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices. + Format: { "0" | "1" } + 0 - Try to allocate a 32-bit DMA address first, before + falling back to the full range if needed. + 1 - Allocate directly from the full usable range, + forcing Dual Address Cycle for PCI cards supporting + greater than 32-bit addressing. + + iommu.strict= [ARM64, X86] Configure TLB invalidation behaviour + Format: { "0" | "1" } + 0 - Lazy mode. + Request that DMA unmap operations use deferred + invalidation of hardware TLBs, for increased + throughput at the cost of reduced device isolation. + Will fall back to strict mode if not supported by + the relevant IOMMU driver. + 1 - Strict mode. + DMA unmap operations invalidate IOMMU hardware TLBs + synchronously. + unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}. + Note: on x86, strict mode specified via one of the + legacy driver-specific options takes precedence. + + iommu.passthrough= + [ARM64, X86] Configure DMA to bypass the IOMMU by default. + Format: { "0" | "1" } + 0 - Use IOMMU translation for DMA. + 1 - Bypass the IOMMU for DMA. + unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH. + + io7= [HW] IO7 for Marvel-based Alpha systems + See comment before marvel_specify_io7 in + arch/alpha/kernel/core_marvel.c. + + io_delay= [X86] I/O delay method + 0x80 + Standard port 0x80 based delay + 0xed + Alternate port 0xed based delay (needed on some systems) + udelay + Simple two microseconds delay + none + No delay + + ip= [IP_PNP] + See Documentation/admin-guide/nfs/nfsroot.rst. + + ipcmni_extend [KNL] Extend the maximum number of unique System V + IPC identifiers from 32,768 to 16,777,216. + + irqaffinity= [SMP] Set the default irq affinity mask + The argument is a cpu list, as described above. + + irqchip.gicv2_force_probe= + [ARM, ARM64] + Format: <bool> + Force the kernel to look for the second 4kB page + of a GICv2 controller even if the memory range + exposed by the device tree is too small. + + irqchip.gicv3_nolpi= + [ARM, ARM64] + Force the kernel to ignore the availability of + LPIs (and by consequence ITSs). Intended for system + that use the kernel as a bootloader, and thus want + to let secondary kernels in charge of setting up + LPIs. + + irqchip.gicv3_pseudo_nmi= [ARM64] + Enables support for pseudo-NMIs in the kernel. This + requires the kernel to be built with + CONFIG_ARM64_PSEUDO_NMI. + + irqfixup [HW] + When an interrupt is not handled search all handlers + for it. Intended to get systems with badly broken + firmware running. + + irqpoll [HW] + When an interrupt is not handled search all handlers + for it. Also check all handlers each timer + interrupt. Intended to get systems with badly broken + firmware running. + + isapnp= [ISAPNP] + Format: <RDP>,<reset>,<pci_scan>,<verbosity> + + isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance. + [Deprecated - use cpusets instead] + Format: [flag-list,]<cpu-list> + + Specify one or more CPUs to isolate from disturbances + specified in the flag list (default: domain): + + nohz + Disable the tick when a single task runs. + + A residual 1Hz tick is offloaded to workqueues, which you + need to affine to housekeeping through the global + workqueue's affinity configured via the + /sys/devices/virtual/workqueue/cpumask sysfs file, or + by using the 'domain' flag described below. + + NOTE: by default the global workqueue runs on all CPUs, + so to protect individual CPUs the 'cpumask' file has to + be configured manually after bootup. + + domain + Isolate from the general SMP balancing and scheduling + algorithms. Note that performing domain isolation this way + is irreversible: it's not possible to bring back a CPU to + the domains once isolated through isolcpus. It's strongly + advised to use cpusets instead to disable scheduler load + balancing through the "cpuset.sched_load_balance" file. + It offers a much more flexible interface where CPUs can + move in and out of an isolated set anytime. + + You can move a process onto or off an "isolated" CPU via + the CPU affinity syscalls or cpuset. + <cpu number> begins at 0 and the maximum value is + "number of CPUs in system - 1". + + managed_irq + + Isolate from being targeted by managed interrupts + which have an interrupt mask containing isolated + CPUs. The affinity of managed interrupts is + handled by the kernel and cannot be changed via + the /proc/irq/* interfaces. + + This isolation is best effort and only effective + if the automatically assigned interrupt mask of a + device queue contains isolated and housekeeping + CPUs. If housekeeping CPUs are online then such + interrupts are directed to the housekeeping CPU + so that IO submitted on the housekeeping CPU + cannot disturb the isolated CPU. + + If a queue's affinity mask contains only isolated + CPUs then this parameter has no effect on the + interrupt routing decision, though interrupts are + only delivered when tasks running on those + isolated CPUs submit IO. IO submitted on + housekeeping CPUs has no influence on those + queues. + + The format of <cpu-list> is described above. + + iucv= [HW,NET] + + ivrs_ioapic [HW,X86-64] + Provide an override to the IOAPIC-ID<->DEVICE-ID + mapping provided in the IVRS ACPI table. + By default, PCI segment is 0, and can be omitted. + + For example, to map IOAPIC-ID decimal 10 to + PCI segment 0x1 and PCI device 00:14.0, + write the parameter as: + ivrs_ioapic=10@0001:00:14.0 + + Deprecated formats: + * To map IOAPIC-ID decimal 10 to PCI device 00:14.0 + write the parameter as: + ivrs_ioapic[10]=00:14.0 + * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and + PCI device 00:14.0 write the parameter as: + ivrs_ioapic[10]=0001:00:14.0 + + ivrs_hpet [HW,X86-64] + Provide an override to the HPET-ID<->DEVICE-ID + mapping provided in the IVRS ACPI table. + By default, PCI segment is 0, and can be omitted. + + For example, to map HPET-ID decimal 10 to + PCI segment 0x1 and PCI device 00:14.0, + write the parameter as: + ivrs_hpet=10@0001:00:14.0 + + Deprecated formats: + * To map HPET-ID decimal 0 to PCI device 00:14.0 + write the parameter as: + ivrs_hpet[0]=00:14.0 + * To map HPET-ID decimal 10 to PCI segment 0x1 and + PCI device 00:14.0 write the parameter as: + ivrs_ioapic[10]=0001:00:14.0 + + ivrs_acpihid [HW,X86-64] + Provide an override to the ACPI-HID:UID<->DEVICE-ID + mapping provided in the IVRS ACPI table. + By default, PCI segment is 0, and can be omitted. + + For example, to map UART-HID:UID AMD0020:0 to + PCI segment 0x1 and PCI device ID 00:14.5, + write the parameter as: + ivrs_acpihid=AMD0020:0@0001:00:14.5 + + Deprecated formats: + * To map UART-HID:UID AMD0020:0 to PCI segment is 0, + PCI device ID 00:14.5, write the parameter as: + ivrs_acpihid[00:14.5]=AMD0020:0 + * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and + PCI device ID 00:14.5, write the parameter as: + ivrs_acpihid[0001:00:14.5]=AMD0020:0 + + js= [HW,JOY] Analog joystick + See Documentation/input/joydev/joystick.rst. + + kasan_multi_shot + [KNL] Enforce KASAN (Kernel Address Sanitizer) to print + report on every invalid memory access. Without this + parameter KASAN will print report only for the first + invalid access. + + keep_bootcon [KNL] + Do not unregister boot console at start. This is only + useful for debugging when something happens in the window + between unregistering the boot console and initializing + the real console. + + keepinitrd [HW,ARM] + + kernelcore= [KNL,X86,IA-64,PPC] + Format: nn[KMGTPE] | nn% | "mirror" + This parameter specifies the amount of memory usable by + the kernel for non-movable allocations. The requested + amount is spread evenly throughout all nodes in the + system as ZONE_NORMAL. The remaining memory is used for + movable memory in its own zone, ZONE_MOVABLE. In the + event, a node is too small to have both ZONE_NORMAL and + ZONE_MOVABLE, kernelcore memory will take priority and + other nodes will have a larger ZONE_MOVABLE. + + ZONE_MOVABLE is used for the allocation of pages that + may be reclaimed or moved by the page migration + subsystem. Note that allocations like PTEs-from-HighMem + still use the HighMem zone if it exists, and the Normal + zone if it does not. + + It is possible to specify the exact amount of memory in + the form of "nn[KMGTPE]", a percentage of total system + memory in the form of "nn%", or "mirror". If "mirror" + option is specified, mirrored (reliable) memory is used + for non-movable allocations and remaining memory is used + for Movable pages. "nn[KMGTPE]", "nn%", and "mirror" + are exclusive, so you cannot specify multiple forms. + + kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. + Format: <Controller#>[,poll interval] + The controller # is the number of the ehci usb debug + port as it is probed via PCI. The poll interval is + optional and is the number seconds in between + each poll cycle to the debug port in case you need + the functionality for interrupting the kernel with + gdb or control-c on the dbgp connection. When + not using this parameter you use sysrq-g to break into + the kernel debugger. + + kgdboc= [KGDB,HW] kgdb over consoles. + Requires a tty driver that supports console polling, + or a supported polling keyboard driver (non-usb). + Serial only format: <serial_device>[,baud] + keyboard only format: kbd + keyboard and serial format: kbd,<serial_device>[,baud] + Optional Kernel mode setting: + kms, kbd format: kms,kbd + kms, kbd and serial format: kms,kbd,<ser_dev>[,baud] + + kgdboc_earlycon= [KGDB,HW] + If the boot console provides the ability to read + characters and can work in polling mode, you can use + this parameter to tell kgdb to use it as a backend + until the normal console is registered. Intended to + be used together with the kgdboc parameter which + specifies the normal console to transition to. + + The name of the early console should be specified + as the value of this parameter. Note that the name of + the early console might be different than the tty + name passed to kgdboc. It's OK to leave the value + blank and the first boot console that implements + read() will be picked. + + kgdbwait [KGDB] Stop kernel execution and enter the + kernel debugger at the earliest opportunity. + + kmac= [MIPS] Korina ethernet MAC address. + Configure the RouterBoard 532 series on-chip + Ethernet adapter MAC address. + + kmemleak= [KNL] Boot-time kmemleak enable/disable + Valid arguments: on, off + Default: on + Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, + the default is off. + + kprobe_event=[probe-list] + [FTRACE] Add kprobe events and enable at boot time. + The probe-list is a semicolon delimited list of probe + definitions. Each definition is same as kprobe_events + interface, but the parameters are comma delimited. + For example, to add a kprobe event on vfs_read with + arg1 and arg2, add to the command line; + + kprobe_event=p,vfs_read,$arg1,$arg2 + + See also Documentation/trace/kprobetrace.rst "Kernel + Boot Parameter" section. + + kpti= [ARM64] Control page table isolation of user + and kernel address spaces. + Default: enabled on cores which need mitigation. + 0: force disabled + 1: force enabled + + kunit.enable= [KUNIT] Enable executing KUnit tests. Requires + CONFIG_KUNIT to be set to be fully enabled. The + default value can be overridden via + KUNIT_DEFAULT_ENABLED. + Default is 1 (enabled) + + kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. + Default is 0 (don't ignore, but inject #GP) + + kvm.eager_page_split= + [KVM,X86] Controls whether or not KVM will try to + proactively split all huge pages during dirty logging. + Eager page splitting reduces interruptions to vCPU + execution by eliminating the write-protection faults + and MMU lock contention that would otherwise be + required to split huge pages lazily. + + VM workloads that rarely perform writes or that write + only to a small region of VM memory may benefit from + disabling eager page splitting to allow huge pages to + still be used for reads. + + The behavior of eager page splitting depends on whether + KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If + disabled, all huge pages in a memslot will be eagerly + split when dirty logging is enabled on that memslot. If + enabled, eager page splitting will be performed during + the KVM_CLEAR_DIRTY ioctl, and only for the pages being + cleared. + + Eager page splitting is only supported when kvm.tdp_mmu=Y. + + Default is Y (on). + + kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface. + Default is false (don't support). + + kvm.nx_huge_pages= + [KVM] Controls the software workaround for the + X86_BUG_ITLB_MULTIHIT bug. + force : Always deploy workaround. + off : Never deploy workaround. + auto : Deploy workaround based on the presence of + X86_BUG_ITLB_MULTIHIT. + + Default is 'auto'. + + If the software workaround is enabled for the host, + guests do need not to enable it for nested guests. + + kvm.nx_huge_pages_recovery_ratio= + [KVM] Controls how many 4KiB pages are periodically zapped + back to huge pages. 0 disables the recovery, otherwise if + the value is N KVM will zap 1/Nth of the 4KiB pages every + period (see below). The default is 60. + + kvm.nx_huge_pages_recovery_period_ms= + [KVM] Controls the time period at which KVM zaps 4KiB pages + back to huge pages. If the value is a non-zero N, KVM will + zap a portion (see ratio above) of the pages every N msecs. + If the value is 0 (the default), KVM will pick a period based + on the ratio, such that a page is zapped after 1 hour on average. + + kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in + KVM/SVM. Default is 1 (enabled). + + kvm-amd.npt= [KVM,AMD] Control KVM's use of Nested Page Tables, + a.k.a. Two-Dimensional Page Tables. Default is 1 + (enabled). Disable by KVM if hardware lacks support + for NPT. + + kvm-arm.mode= + [KVM,ARM] Select one of KVM/arm64's modes of operation. + + none: Forcefully disable KVM. + + nvhe: Standard nVHE-based mode, without support for + protected guests. + + protected: nVHE-based mode with support for guests whose + state is kept private from the host. + + nested: VHE-based mode with support for nested + virtualization. Requires at least ARMv8.3 + hardware. + + Defaults to VHE/nVHE based on hardware support. Setting + mode to "protected" will disable kexec and hibernation + for the host. "nested" is experimental and should be + used with extreme caution. + + kvm-arm.vgic_v3_group0_trap= + [KVM,ARM] Trap guest accesses to GICv3 group-0 + system registers + + kvm-arm.vgic_v3_group1_trap= + [KVM,ARM] Trap guest accesses to GICv3 group-1 + system registers + + kvm-arm.vgic_v3_common_trap= + [KVM,ARM] Trap guest accesses to GICv3 common + system registers + + kvm-arm.vgic_v4_enable= + [KVM,ARM] Allow use of GICv4 for direct injection of + LPIs. + + kvm_cma_resv_ratio=n [PPC] + Reserves given percentage from system memory area for + contiguous memory allocation for KVM hash pagetable + allocation. + By default it reserves 5% of total system memory. + Format: <integer> + Default: 5 + + kvm-intel.ept= [KVM,Intel] Control KVM's use of Extended Page Tables, + a.k.a. Two-Dimensional Page Tables. Default is 1 + (enabled). Disable by KVM if hardware lacks support + for EPT. + + kvm-intel.emulate_invalid_guest_state= + [KVM,Intel] Control whether to emulate invalid guest + state. Ignored if kvm-intel.enable_unrestricted_guest=1, + as guest state is never invalid for unrestricted + guests. This param doesn't apply to nested guests (L2), + as KVM never emulates invalid L2 guest state. + Default is 1 (enabled). + + kvm-intel.flexpriority= + [KVM,Intel] Control KVM's use of FlexPriority feature + (TPR shadow). Default is 1 (enabled). Disable by KVM if + hardware lacks support for it. + + kvm-intel.nested= + [KVM,Intel] Control nested virtualization feature in + KVM/VMX. Default is 1 (enabled). + + kvm-intel.unrestricted_guest= + [KVM,Intel] Control KVM's use of unrestricted guest + feature (virtualized real and unpaged mode). Default + is 1 (enabled). Disable by KVM if EPT is disabled or + hardware lacks support for it. + + kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault + CVE-2018-3620. + + Valid arguments: never, cond, always + + always: L1D cache flush on every VMENTER. + cond: Flush L1D on VMENTER only when the code between + VMEXIT and VMENTER can leak host memory. + never: Disables the mitigation + + Default is cond (do L1 cache flush in specific instances) + + kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor + Identification feature (tagged TLBs). Default is 1 + (enabled). Disable by KVM if hardware lacks support + for it. + + l1d_flush= [X86,INTEL] + Control mitigation for L1D based snooping vulnerability. + + Certain CPUs are vulnerable to an exploit against CPU + internal buffers which can forward information to a + disclosure gadget under certain conditions. + + In vulnerable processors, the speculatively + forwarded data can be used in a cache side channel + attack, to access data to which the attacker does + not have direct access. + + This parameter controls the mitigation. The + options are: + + on - enable the interface for the mitigation + + l1tf= [X86] Control mitigation of the L1TF vulnerability on + affected CPUs + + The kernel PTE inversion protection is unconditionally + enabled and cannot be disabled. + + full + Provides all available mitigations for the + L1TF vulnerability. Disables SMT and + enables all mitigations in the + hypervisors, i.e. unconditional L1D flush. + + SMT control and L1D flush control via the + sysfs interface is still possible after + boot. Hypervisors will issue a warning + when the first VM is started in a + potentially insecure configuration, + i.e. SMT enabled or L1D flush disabled. + + full,force + Same as 'full', but disables SMT and L1D + flush runtime control. Implies the + 'nosmt=force' command line option. + (i.e. sysfs control of SMT is disabled.) + + flush + Leaves SMT enabled and enables the default + hypervisor mitigation, i.e. conditional + L1D flush. + + SMT control and L1D flush control via the + sysfs interface is still possible after + boot. Hypervisors will issue a warning + when the first VM is started in a + potentially insecure configuration, + i.e. SMT enabled or L1D flush disabled. + + flush,nosmt + + Disables SMT and enables the default + hypervisor mitigation. + + SMT control and L1D flush control via the + sysfs interface is still possible after + boot. Hypervisors will issue a warning + when the first VM is started in a + potentially insecure configuration, + i.e. SMT enabled or L1D flush disabled. + + flush,nowarn + Same as 'flush', but hypervisors will not + warn when a VM is started in a potentially + insecure configuration. + + off + Disables hypervisor mitigations and doesn't + emit any warnings. + It also drops the swap size and available + RAM limit restriction on both hypervisor and + bare metal. + + Default is 'flush'. + + For details see: Documentation/admin-guide/hw-vuln/l1tf.rst + + l2cr= [PPC] + + l3cr= [PPC] + + lapic [X86-32,APIC] Enable the local APIC even if BIOS + disabled it. + + lapic= [X86,APIC] Do not use TSC deadline + value for LAPIC timer one-shot implementation. Default + back to the programmable timer unit in the LAPIC. + Format: notscdeadline + + lapic_timer_c2_ok [X86,APIC] trust the local apic timer + in C2 power state. + + libata.dma= [LIBATA] DMA control + libata.dma=0 Disable all PATA and SATA DMA + libata.dma=1 PATA and SATA Disk DMA only + libata.dma=2 ATAPI (CDROM) DMA only + libata.dma=4 Compact Flash DMA only + Combinations also work, so libata.dma=3 enables DMA + for disks and CDROMs, but not CFs. + + libata.ignore_hpa= [LIBATA] Ignore HPA limit + libata.ignore_hpa=0 keep BIOS limits (default) + libata.ignore_hpa=1 ignore limits, using full disk + + libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume + when set. + Format: <int> + + libata.force= [LIBATA] Force configurations. The format is a comma- + separated list of "[ID:]VAL" where ID is PORT[.DEVICE]. + PORT and DEVICE are decimal numbers matching port, link + or device. Basically, it matches the ATA ID string + printed on console by libata. If the whole ID part is + omitted, the last PORT and DEVICE values are used. If + ID hasn't been specified yet, the configuration applies + to all ports, links and devices. + + If only DEVICE is omitted, the parameter applies to + the port and all links and devices behind it. DEVICE + number of 0 either selects the first device or the + first fan-out link behind PMP device. It does not + select the host link. DEVICE number of 15 selects the + host link and device attached to it. + + The VAL specifies the configuration to force. As long + as there is no ambiguity, shortcut notation is allowed. + For example, both 1.5 and 1.5G would work for 1.5Gbps. + The following configurations can be forced. + + * Cable type: 40c, 80c, short40c, unk, ign or sata. + Any ID with matching PORT is used. + + * SATA link speed limit: 1.5Gbps or 3.0Gbps. + + * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. + udma[/][16,25,33,44,66,100,133] notation is also + allowed. + + * nohrst, nosrst, norst: suppress hard, soft and both + resets. + + * rstonce: only attempt one reset during hot-unplug + link recovery. + + * [no]dbdelay: Enable or disable the extra 200ms delay + before debouncing a link PHY and device presence + detection. + + * [no]ncq: Turn on or off NCQ. + + * [no]ncqtrim: Enable or disable queued DSM TRIM. + + * [no]ncqati: Enable or disable NCQ trim on ATI chipset. + + * [no]trim: Enable or disable (unqueued) TRIM. + + * trim_zero: Indicate that TRIM command zeroes data. + + * max_trim_128m: Set 128M maximum trim size limit. + + * [no]dma: Turn on or off DMA transfers. + + * atapi_dmadir: Enable ATAPI DMADIR bridge support. + + * atapi_mod16_dma: Enable the use of ATAPI DMA for + commands that are not a multiple of 16 bytes. + + * [no]dmalog: Enable or disable the use of the + READ LOG DMA EXT command to access logs. + + * [no]iddevlog: Enable or disable access to the + identify device data log. + + * [no]logdir: Enable or disable access to the general + purpose log directory. + + * max_sec_128: Set transfer size limit to 128 sectors. + + * max_sec_1024: Set or clear transfer size limit to + 1024 sectors. + + * max_sec_lba48: Set or clear transfer size limit to + 65535 sectors. + + * [no]lpm: Enable or disable link power management. + + * [no]setxfer: Indicate if transfer speed mode setting + should be skipped. + + * [no]fua: Disable or enable FUA (Force Unit Access) + support for devices supporting this feature. + + * dump_id: Dump IDENTIFY data. + + * disable: Disable this device. + + If there are multiple matching configurations changing + the same attribute, the last one is used. + + load_ramdisk= [RAM] [Deprecated] + + lockd.nlm_grace_period=P [NFS] Assign grace period. + Format: <integer> + + lockd.nlm_tcpport=N [NFS] Assign TCP port. + Format: <integer> + + lockd.nlm_timeout=T [NFS] Assign timeout value. + Format: <integer> + + lockd.nlm_udpport=M [NFS] Assign UDP port. + Format: <integer> + + lockdown= [SECURITY] + { integrity | confidentiality } + Enable the kernel lockdown feature. If set to + integrity, kernel features that allow userland to + modify the running kernel are disabled. If set to + confidentiality, kernel features that allow userland + to extract confidential information from the kernel + are also disabled. + + locktorture.nreaders_stress= [KNL] + Set the number of locking read-acquisition kthreads. + Defaults to being automatically set based on the + number of online CPUs. + + locktorture.nwriters_stress= [KNL] + Set the number of locking write-acquisition kthreads. + + locktorture.onoff_holdoff= [KNL] + Set time (s) after boot for CPU-hotplug testing. + + locktorture.onoff_interval= [KNL] + Set time (s) between CPU-hotplug operations, or + zero to disable CPU-hotplug testing. + + locktorture.shuffle_interval= [KNL] + Set task-shuffle interval (jiffies). Shuffling + tasks allows some CPUs to go into dyntick-idle + mode during the locktorture test. + + locktorture.shutdown_secs= [KNL] + Set time (s) after boot system shutdown. This + is useful for hands-off automated testing. + + locktorture.stat_interval= [KNL] + Time (s) between statistics printk()s. + + locktorture.stutter= [KNL] + Time (s) to stutter testing, for example, + specifying five seconds causes the test to run for + five seconds, wait for five seconds, and so on. + This tests the locking primitive's ability to + transition abruptly to and from idle. + + locktorture.torture_type= [KNL] + Specify the locking implementation to test. + + locktorture.writer_fifo= [KNL] + Run the write-side locktorture kthreads at + sched_set_fifo() real-time priority. + + locktorture.verbose= [KNL] + Enable additional printk() statements. + + logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver + Format: <irq> + + loglevel= All Kernel Messages with a loglevel smaller than the + console loglevel will be printed to the console. It can + also be changed with klogd or other programs. The + loglevels are defined as follows: + + 0 (KERN_EMERG) system is unusable + 1 (KERN_ALERT) action must be taken immediately + 2 (KERN_CRIT) critical conditions + 3 (KERN_ERR) error conditions + 4 (KERN_WARNING) warning conditions + 5 (KERN_NOTICE) normal but significant condition + 6 (KERN_INFO) informational + 7 (KERN_DEBUG) debug-level messages + + log_buf_len=n[KMG] Sets the size of the printk ring buffer, + in bytes. n must be a power of two and greater + than the minimal size. The minimal size is defined + by LOG_BUF_SHIFT kernel config parameter. There is + also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter + that allows to increase the default size depending on + the number of CPUs. See init/Kconfig for more details. + + logo.nologo [FB] Disables display of the built-in Linux logo. + This may be used to provide more screen space for + kernel log messages and is useful when debugging + kernel boot problems. + + lp=0 [LP] Specify parallel ports to use, e.g, + lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses + lp=reset first parallel port). 'lp=0' disables the + lp=auto printer driver. 'lp=reset' (which can be + specified in addition to the ports) causes + attached printers to be reset. Using + lp=port1,port2,... specifies the parallel ports + to associate lp devices with, starting with + lp0. A port specification may be 'none' to skip + that lp device, or a parport name such as + 'parport0'. Specifying 'lp=auto' instead of a + port specification list means that device IDs + from each port should be examined, to see if + an IEEE 1284-compliant printer is attached; if + so, the driver will manage that printer. + See also header of drivers/char/lp.c. + + lpj=n [KNL] + Sets loops_per_jiffy to given constant, thus avoiding + time-consuming boot-time autodetection (up to 250 ms per + CPU). 0 enables autodetection (default). To determine + the correct value for your kernel, boot with normal + autodetection and see what value is printed. Note that + on SMP systems the preset will be applied to all CPUs, + which is likely to cause problems if your CPUs need + significantly divergent settings. An incorrect value + will cause delays in the kernel to be wrong, leading to + unpredictable I/O errors and other breakage. Although + unlikely, in the extreme case this might damage your + hardware. + + ltpc= [NET] + Format: <io>,<irq>,<dma> + + lsm.debug [SECURITY] Enable LSM initialization debugging output. + + lsm=lsm1,...,lsmN + [SECURITY] Choose order of LSM initialization. This + overrides CONFIG_LSM, and the "security=" parameter. + + machvec= [IA-64] Force the use of a particular machine-vector + (machvec) in a generic kernel. + Example: machvec=hpzx1 + + machtype= [Loongson] Share the same kernel image file between + different yeeloong laptops. + Example: machtype=lemote-yeeloong-2f-7inch + + max_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory greater + than or equal to this physical address is ignored. + + maxcpus= [SMP] Maximum number of processors that an SMP kernel + will bring up during bootup. maxcpus=n : n >= 0 limits + the kernel to bring up 'n' processors. Surely after + bootup you can bring up the other plugged cpu by executing + "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus + only takes effect during system bootup. + While n=0 is a special case, it is equivalent to "nosmp", + which also disables the IO APIC. + + max_loop= [LOOP] The number of loop block devices that get + (loop.max_loop) unconditionally pre-created at init time. The default + number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead + of statically allocating a predefined number, loop + devices can be requested on-demand with the + /dev/loop-control interface. + + mce [X86-32] Machine Check Exception + + mce=option [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst + + md= [HW] RAID subsystems devices and level + See Documentation/admin-guide/md.rst. + + mdacon= [MDA] + Format: <first>,<last> + Specifies range of consoles to be captured by the MDA. + + mds= [X86,INTEL] + Control mitigation for the Micro-architectural Data + Sampling (MDS) vulnerability. + + Certain CPUs are vulnerable to an exploit against CPU + internal buffers which can forward information to a + disclosure gadget under certain conditions. + + In vulnerable processors, the speculatively + forwarded data can be used in a cache side channel + attack, to access data to which the attacker does + not have direct access. + + This parameter controls the MDS mitigation. The + options are: + + full - Enable MDS mitigation on vulnerable CPUs + full,nosmt - Enable MDS mitigation and disable + SMT on vulnerable CPUs + off - Unconditionally disable MDS mitigation + + On TAA-affected machines, mds=off can be prevented by + an active TAA mitigation as both vulnerabilities are + mitigated with the same mechanism so in order to disable + this mitigation, you need to specify tsx_async_abort=off + too. + + Not specifying this option is equivalent to + mds=full. + + For details see: Documentation/admin-guide/hw-vuln/mds.rst + + mem=nn[KMG] [HEXAGON] Set the memory size. + Must be specified, otherwise memory size will be 0. + + mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory + Amount of memory to be used in cases as follows: + + 1 for test; + 2 when the kernel is not able to see the whole system memory; + 3 memory that lies after 'mem=' boundary is excluded from + the hypervisor, then assigned to KVM guests. + 4 to limit the memory available for kdump kernel. + + [ARC,MICROBLAZE] - the limit applies only to low memory, + high memory is not affected. + + [ARM64] - only limits memory covered by the linear + mapping. The NOMAP regions are not affected. + + [X86] Work as limiting max address. Use together + with memmap= to avoid physical address space collisions. + Without memmap= PCI devices could be placed at addresses + belonging to unused RAM. + + Note that this only takes effects during boot time since + in above case 3, memory may need be hot added after boot + if system memory of hypervisor is not sufficient. + + mem=nn[KMG]@ss[KMG] + [ARM,MIPS] - override the memory layout reported by + firmware. + Define a memory region of size nn[KMG] starting at + ss[KMG]. + Multiple different regions can be specified with + multiple mem= parameters on the command line. + + mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel + memory. + + memblock=debug [KNL] Enable memblock debug messages. + + memchunk=nn[KMG] + [KNL,SH] Allow user to override the default size for + per-device physically contiguous DMA buffers. + + memhp_default_state=online/offline/online_kernel/online_movable + [KNL] Set the initial state for the memory hotplug + onlining policy. If not specified, the default value is + set according to the + CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config + option. + See Documentation/admin-guide/mm/memory-hotplug.rst. + + memmap=exactmap [KNL,X86] Enable setting of an exact + E820 memory map, as specified by the user. + Such memmap=exactmap lines can be constructed based on + BIOS output or other requirements. See the memmap=nn@ss + option description. + + memmap=nn[KMG]@ss[KMG] + [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory. + Region of memory to be used is from ss to ss+nn. + If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG], + which limits max address to nn[KMG]. + Multiple different regions can be specified, + comma delimited. + Example: + memmap=100M@2G,100M#3G,1G!1024G + + memmap=nn[KMG]#ss[KMG] + [KNL,ACPI] Mark specific memory as ACPI data. + Region of memory to be marked is from ss to ss+nn. + + memmap=nn[KMG]$ss[KMG] + [KNL,ACPI] Mark specific memory as reserved. + Region of memory to be reserved is from ss to ss+nn. + Example: Exclude memory from 0x18690000-0x1869ffff + memmap=64K$0x18690000 + or + memmap=0x10000$0x18690000 + Some bootloaders may need an escape character before '$', + like Grub2, otherwise '$' and the following number + will be eaten. + + memmap=nn[KMG]!ss[KMG] + [KNL,X86] Mark specific memory as protected. + Region of memory to be used, from ss to ss+nn. + The memory region may be marked as e820 type 12 (0xc) + and is NVDIMM or ADR memory. + + memmap=<size>%<offset>-<oldtype>+<newtype> + [KNL,ACPI] Convert memory within the specified region + from <oldtype> to <newtype>. If "-<oldtype>" is left + out, the whole region will be marked as <newtype>, + even if previously unavailable. If "+<newtype>" is left + out, matching memory will be removed. Types are + specified as e820 types, e.g., 1 = RAM, 2 = reserved, + 3 = ACPI, 12 = PRAM. + + memory_corruption_check=0/1 [X86] + Some BIOSes seem to corrupt the first 64k of + memory when doing things like suspend/resume. + Setting this option will scan the memory + looking for corruption. Enabling this will + both detect corruption and prevent the kernel + from using the memory being corrupted. + However, its intended as a diagnostic tool; if + repeatable BIOS-originated corruption always + affects the same memory, you can use memmap= + to prevent the kernel from using that memory. + + memory_corruption_check_size=size [X86] + By default it checks for corruption in the low + 64k, making this memory unavailable for normal + use. Use this parameter to scan for + corruption in more or less memory. + + memory_corruption_check_period=seconds [X86] + By default it checks for corruption every 60 + seconds. Use this parameter to check at some + other rate. 0 disables periodic checking. + + memory_hotplug.memmap_on_memory + [KNL,X86,ARM] Boolean flag to enable this feature. + Format: {on | off (default)} + When enabled, runtime hotplugged memory will + allocate its internal metadata (struct pages, + those vmemmap pages cannot be optimized even + if hugetlb_free_vmemmap is enabled) from the + hotadded memory which will allow to hotadd a + lot of memory without requiring additional + memory to do so. + This feature is disabled by default because it + has some implication on large (e.g. GB) + allocations in some configurations (e.g. small + memory blocks). + The state of the flag can be read in + /sys/module/memory_hotplug/parameters/memmap_on_memory. + Note that even when enabled, there are a few cases where + the feature is not effective. + + memtest= [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest + Format: <integer> + default : 0 <disable> + Specifies the number of memtest passes to be + performed. Each pass selects another test + pattern from a given set of patterns. Memtest + fills the memory with this pattern, validates + memory contents and reserves bad memory + regions that are detected. + + mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control + Valid arguments: on, off + Default (depends on kernel configuration option): + on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y) + off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n) + mem_encrypt=on: Activate SME + mem_encrypt=off: Do not activate SME + + Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst + for details on when memory encryption can be activated. + + mem_sleep_default= [SUSPEND] Default system suspend mode: + s2idle - Suspend-To-Idle + shallow - Power-On Suspend or equivalent (if supported) + deep - Suspend-To-RAM or equivalent (if supported) + See Documentation/admin-guide/pm/sleep-states.rst. + + mfgpt_irq= [IA-32] Specify the IRQ to use for the + Multi-Function General Purpose Timers on AMD Geode + platforms. + + mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when + the BIOS has incorrectly applied a workaround. TinyBIOS + version 0.98 is known to be affected, 0.99 fixes the + problem by letting the user disable the workaround. + + mga= [HW,DRM] + + min_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory below this + physical address is ignored. + + mini2440= [ARM,HW,KNL] + Format:[0..2][b][c][t] + Default: "0tb" + MINI2440 configuration specification: + 0 - The attached screen is the 3.5" TFT + 1 - The attached screen is the 7" TFT + 2 - The VGA Shield is attached (1024x768) + Leaving out the screen size parameter will not load + the TFT driver, and the framebuffer will be left + unconfigured. + b - Enable backlight. The TFT backlight pin will be + linked to the kernel VESA blanking code and a GPIO + LED. This parameter is not necessary when using the + VGA shield. + c - Enable the s3c camera interface. + t - Reserved for enabling touchscreen support. The + touchscreen support is not enabled in the mainstream + kernel as of 2.6.30, a preliminary port can be found + in the "bleeding edge" mini2440 support kernel at + https://repo.or.cz/w/linux-2.6/mini2440.git + + mitigations= + [X86,PPC,S390,ARM64] Control optional mitigations for + CPU vulnerabilities. This is a set of curated, + arch-independent options, each of which is an + aggregation of existing arch-specific options. + + off + Disable all optional CPU mitigations. This + improves system performance, but it may also + expose users to several CPU vulnerabilities. + Equivalent to: if nokaslr then kpti=0 [ARM64] + gather_data_sampling=off [X86] + kvm.nx_huge_pages=off [X86] + l1tf=off [X86] + mds=off [X86] + mmio_stale_data=off [X86] + no_entry_flush [PPC] + no_uaccess_flush [PPC] + nobp=0 [S390] + nopti [X86,PPC] + nospectre_bhb [ARM64] + nospectre_v1 [X86,PPC] + nospectre_v2 [X86,PPC,S390,ARM64] + retbleed=off [X86] + spec_store_bypass_disable=off [X86,PPC] + spectre_v2_user=off [X86] + srbds=off [X86,INTEL] + ssbd=force-off [ARM64] + tsx_async_abort=off [X86] + + Exceptions: + This does not have any effect on + kvm.nx_huge_pages when + kvm.nx_huge_pages=force. + + auto (default) + Mitigate all CPU vulnerabilities, but leave SMT + enabled, even if it's vulnerable. This is for + users who don't want to be surprised by SMT + getting disabled across kernel upgrades, or who + have other ways of avoiding SMT-based attacks. + Equivalent to: (default behavior) + + auto,nosmt + Mitigate all CPU vulnerabilities, disabling SMT + if needed. This is for users who always want to + be fully mitigated, even if it means losing SMT. + Equivalent to: l1tf=flush,nosmt [X86] + mds=full,nosmt [X86] + tsx_async_abort=full,nosmt [X86] + mmio_stale_data=full,nosmt [X86] + retbleed=auto,nosmt [X86] + + mminit_loglevel= + [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this + parameter allows control of the logging verbosity for + the additional memory initialisation checks. A value + of 0 disables mminit logging and a level of 4 will + log everything. Information is printed at KERN_DEBUG + so loglevel=8 may also need to be specified. + + mmio_stale_data= + [X86,INTEL] Control mitigation for the Processor + MMIO Stale Data vulnerabilities. + + Processor MMIO Stale Data is a class of + vulnerabilities that may expose data after an MMIO + operation. Exposed data could originate or end in + the same CPU buffers as affected by MDS and TAA. + Therefore, similar to MDS and TAA, the mitigation + is to clear the affected CPU buffers. + + This parameter controls the mitigation. The + options are: + + full - Enable mitigation on vulnerable CPUs + + full,nosmt - Enable mitigation and disable SMT on + vulnerable CPUs. + + off - Unconditionally disable mitigation + + On MDS or TAA affected machines, + mmio_stale_data=off can be prevented by an active + MDS or TAA mitigation as these vulnerabilities are + mitigated with the same mechanism so in order to + disable this mitigation, you need to specify + mds=off and tsx_async_abort=off too. + + Not specifying this option is equivalent to + mmio_stale_data=full. + + For details see: + Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst + + <module>.async_probe[=<bool>] [KNL] + If no <bool> value is specified or if the value + specified is not a valid <bool>, enable asynchronous + probe on this module. Otherwise, enable/disable + asynchronous probe on this module as indicated by the + <bool> value. See also: module.async_probe + + module.async_probe=<bool> + [KNL] When set to true, modules will use async probing + by default. To enable/disable async probing for a + specific module, use the module specific control that + is documented under <module>.async_probe. When both + module.async_probe and <module>.async_probe are + specified, <module>.async_probe takes precedence for + the specific module. + + module.enable_dups_trace + [KNL] When CONFIG_MODULE_DEBUG_AUTOLOAD_DUPS is set, + this means that duplicate request_module() calls will + trigger a WARN_ON() instead of a pr_warn(). Note that + if MODULE_DEBUG_AUTOLOAD_DUPS_TRACE is set, WARN_ON()s + will always be issued and this option does nothing. + module.sig_enforce + [KNL] When CONFIG_MODULE_SIG is set, this means that + modules without (valid) signatures will fail to load. + Note that if CONFIG_MODULE_SIG_FORCE is set, that + is always true, so this option does nothing. + + module_blacklist= [KNL] Do not load a comma-separated list of + modules. Useful for debugging problem modules. + + mousedev.tap_time= + [MOUSE] Maximum time between finger touching and + leaving touchpad surface for touch to be considered + a tap and be reported as a left button click (for + touchpads working in absolute mode only). + Format: <msecs> + mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices + reporting absolute coordinates, such as tablets + mousedev.yres= [MOUSE] Vertical screen resolution, used for devices + reporting absolute coordinates, such as tablets + + movablecore= [KNL,X86,IA-64,PPC] + Format: nn[KMGTPE] | nn% + This parameter is the complement to kernelcore=, it + specifies the amount of memory used for migratable + allocations. If both kernelcore and movablecore is + specified, then kernelcore will be at *least* the + specified value but may be more. If movablecore on its + own is specified, the administrator must be careful + that the amount of memory usable for all allocations + is not too small. + + movable_node [KNL] Boot-time switch to make hotplugable memory + NUMA nodes to be movable. This means that the memory + of such nodes will be usable only for movable + allocations which rules out almost all kernel + allocations. Use with caution! + + MTD_Partition= [MTD] + Format: <name>,<region-number>,<size>,<offset> + + MTD_Region= [MTD] Format: + <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] + + mtdparts= [MTD] + See drivers/mtd/parsers/cmdlinepart.c + + mtdset= [ARM] + ARM/S3C2412 JIVE boot control + + See arch/arm/mach-s3c/mach-jive.c + + mtouchusb.raw_coordinates= + [HW] Make the MicroTouch USB driver use raw coordinates + ('y', default) or cooked coordinates ('n') + + mtrr=debug [X86] + Enable printing debug information related to MTRR + registers at boot time. + + mtrr_chunk_size=nn[KMG] [X86] + used for mtrr cleanup. It is largest continuous chunk + that could hold holes aka. UC entries. + + mtrr_gran_size=nn[KMG] [X86] + Used for mtrr cleanup. It is granularity of mtrr block. + Default is 1. + Large value could prevent small alignment from + using up MTRRs. + + mtrr_spare_reg_nr=n [X86] + Format: <integer> + Range: 0,7 : spare reg number + Default : 1 + Used for mtrr cleanup. It is spare mtrr entries number. + Set to 2 or more if your graphical card needs more. + + multitce=off [PPC] This parameter disables the use of the pSeries + firmware feature for updating multiple TCE entries + at a time. + + n2= [NET] SDL Inc. RISCom/N2 synchronous serial card + + netdev= [NET] Network devices parameters + Format: <irq>,<io>,<mem_start>,<mem_end>,<name> + Note that mem_start is often overloaded to mean + something different and driver-specific. + This usage is only documented in each driver source + file if at all. + + netpoll.carrier_timeout= + [NET] Specifies amount of time (in seconds) that + netpoll should wait for a carrier. By default netpoll + waits 4 seconds. + + nf_conntrack.acct= + [NETFILTER] Enable connection tracking flow accounting + 0 to disable accounting + 1 to enable accounting + Default value is 0. + + nfs.cache_getent= + [NFS] sets the pathname to the program which is used + to update the NFS client cache entries. + + nfs.cache_getent_timeout= + [NFS] sets the timeout after which an attempt to + update a cache entry is deemed to have failed. + + nfs.callback_nr_threads= + [NFSv4] set the total number of threads that the + NFS client will assign to service NFSv4 callback + requests. + + nfs.callback_tcpport= + [NFS] set the TCP port on which the NFSv4 callback + channel should listen. + + nfs.enable_ino64= + [NFS] enable 64-bit inode numbers. + If zero, the NFS client will fake up a 32-bit inode + number for the readdir() and stat() syscalls instead + of returning the full 64-bit number. + The default is to return 64-bit inode numbers. + + nfs.idmap_cache_timeout= + [NFS] set the maximum lifetime for idmapper cache + entries. + + nfs.max_session_cb_slots= + [NFSv4.1] Sets the maximum number of session + slots the client will assign to the callback + channel. This determines the maximum number of + callbacks the client will process in parallel for + a particular server. + + nfs.max_session_slots= + [NFSv4.1] Sets the maximum number of session slots + the client will attempt to negotiate with the server. + This limits the number of simultaneous RPC requests + that the client can send to the NFSv4.1 server. + Note that there is little point in setting this + value higher than the max_tcp_slot_table_limit. + + nfs.nfs4_disable_idmapping= + [NFSv4] When set to the default of '1', this option + ensures that both the RPC level authentication + scheme and the NFS level operations agree to use + numeric uids/gids if the mount is using the + 'sec=sys' security flavour. In effect it is + disabling idmapping, which can make migration from + legacy NFSv2/v3 systems to NFSv4 easier. + Servers that do not support this mode of operation + will be autodetected by the client, and it will fall + back to using the idmapper. + To turn off this behaviour, set the value to '0'. + + nfs.nfs4_unique_id= + [NFS4] Specify an additional fixed unique ident- + ification string that NFSv4 clients can insert into + their nfs_client_id4 string. This is typically a + UUID that is generated at system install time. + + nfs.recover_lost_locks= + [NFSv4] Attempt to recover locks that were lost due + to a lease timeout on the server. Please note that + doing this risks data corruption, since there are + no guarantees that the file will remain unchanged + after the locks are lost. + If you want to enable the kernel legacy behaviour of + attempting to recover these locks, then set this + parameter to '1'. + The default parameter value of '0' causes the kernel + not to attempt recovery of lost locks. + + nfs.send_implementation_id= + [NFSv4.1] Send client implementation identification + information in exchange_id requests. + If zero, no implementation identification information + will be sent. + The default is to send the implementation identification + information. + + nfs4.layoutstats_timer= + [NFSv4.2] Change the rate at which the kernel sends + layoutstats to the pNFS metadata server. + + Setting this to value to 0 causes the kernel to use + whatever value is the default set by the layout + driver. A non-zero value sets the minimum interval + in seconds between layoutstats transmissions. + + nfsd.inter_copy_offload_enable= + [NFSv4.2] When set to 1, the server will support + server-to-server copies for which this server is + the destination of the copy. + + nfsd.nfs4_disable_idmapping= + [NFSv4] When set to the default of '1', the NFSv4 + server will return only numeric uids and gids to + clients using auth_sys, and will accept numeric uids + and gids from such clients. This is intended to ease + migration from NFSv2/v3. + + nfsd.nfsd4_ssc_umount_timeout= + [NFSv4.2] When used as the destination of a + server-to-server copy, knfsd temporarily mounts + the source server. It caches the mount in case + it will be needed again, and discards it if not + used for the number of milliseconds specified by + this parameter. + + nfsaddrs= [NFS] Deprecated. Use ip= instead. + See Documentation/admin-guide/nfs/nfsroot.rst. + + nfsroot= [NFS] nfs root filesystem for disk-less boxes. + See Documentation/admin-guide/nfs/nfsroot.rst. + + nfsrootdebug [NFS] enable nfsroot debugging messages. + See Documentation/admin-guide/nfs/nfsroot.rst. + + nmi_backtrace.backtrace_idle [KNL] + Dump stacks even of idle CPUs in response to an + NMI stack-backtrace request. + + nmi_debug= [KNL,SH] Specify one or more actions to take + when a NMI is triggered. + Format: [state][,regs][,debounce][,die] + + nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels + Format: [panic,][nopanic,][num] + Valid num: 0 or 1 + 0 - turn hardlockup detector in nmi_watchdog off + 1 - turn hardlockup detector in nmi_watchdog on + When panic is specified, panic when an NMI watchdog + timeout occurs (or 'nopanic' to not panic on an NMI + watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set) + To disable both hard and soft lockup detectors, + please see 'nowatchdog'. + This is useful when you use a panic=... timeout and + need the box quickly up again. + + These settings can be accessed at runtime via + the nmi_watchdog and hardlockup_panic sysctls. + + no387 [BUGS=X86-32] Tells the kernel to use the 387 maths + emulation library even if a 387 maths coprocessor + is present. + + no4lvl [RISCV] Disable 4-level and 5-level paging modes. Forces + kernel to use 3-level paging instead. + + no5lvl [X86-64,RISCV] Disable 5-level paging mode. Forces + kernel to use 4-level paging instead. + + noaliencache [MM, NUMA, SLAB] Disables the allocation of alien + caches in the slab allocator. Saves per-node memory, + but will impact performance. + + noalign [KNL,ARM] + + noaltinstr [S390] Disables alternative instructions patching + (CPU alternatives feature). + + noapic [SMP,APIC] Tells the kernel to not make use of any + IOAPICs that may be present in the system. + + noautogroup Disable scheduler automatic task group creation. + + nocache [ARM] + + no_console_suspend + [HW] Never suspend the console + Disable suspending of consoles during suspend and + hibernate operations. Once disabled, debugging + messages can reach various consoles while the rest + of the system is being put to sleep (ie, while + debugging driver suspend/resume hooks). This may + not work reliably with all consoles, but is known + to work with serial and VGA consoles. + To facilitate more flexible debugging, we also add + console_suspend, a printk module parameter to control + it. Users could use console_suspend (usually + /sys/module/printk/parameters/console_suspend) to + turn on/off it dynamically. + + no_debug_objects + [KNL] Disable object debugging + + nodsp [SH] Disable hardware DSP at boot time. + + noefi Disable EFI runtime services support. + + no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel. + + noexec [IA-64] + + noexec32 [X86-64] + This affects only 32-bit executables. + noexec32=on: enable non-executable mappings (default) + read doesn't imply executable mappings + noexec32=off: disable non-executable mappings + read implies executable mappings + + no_file_caps Tells the kernel not to honor file capabilities. The + only way then for a file to be executed with privilege + is to be setuid root or executed by root. + + nofpu [MIPS,SH] Disable hardware FPU at boot time. + + nofsgsbase [X86] Disables FSGSBASE instructions. + + nofxsr [BUGS=X86-32] Disables x86 floating point extended + register save and restore. The kernel will only save + legacy floating-point registers on task switch. + + nohalt [IA-64] Tells the kernel not to use the power saving + function PAL_HALT_LIGHT when idle. This increases + power-consumption. On the positive side, it reduces + interrupt wake-up latency, which may improve performance + in certain environments such as networked servers or + real-time systems. + + no_hash_pointers + Force pointers printed to the console or buffers to be + unhashed. By default, when a pointer is printed via %p + format string, that pointer is "hashed", i.e. obscured + by hashing the pointer value. This is a security feature + that hides actual kernel addresses from unprivileged + users, but it also makes debugging the kernel more + difficult since unequal pointers can no longer be + compared. However, if this command-line option is + specified, then all normal pointers will have their true + value printed. This option should only be specified when + debugging the kernel. Please do not use on production + kernels. + + nohibernate [HIBERNATION] Disable hibernation and resume. + + nohlt [ARM,ARM64,MICROBLAZE,MIPS,PPC,SH] Forces the kernel to + busy wait in do_idle() and not use the arch_cpu_idle() + implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP + to be effective. This is useful on platforms where the + sleep(SH) or wfi(ARM,ARM64) instructions do not work + correctly or when doing power measurements to evaluate + the impact of the sleep instructions. This is also + useful when using JTAG debugger. + + nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings. + + nohugevmalloc [KNL,X86,PPC,ARM64] Disable kernel huge vmalloc mappings. + + nohz= [KNL] Boottime enable/disable dynamic ticks + Valid arguments: on, off + Default: on + + nohz_full= [KNL,BOOT,SMP,ISOL] + The argument is a cpu list, as described above. + In kernels built with CONFIG_NO_HZ_FULL=y, set + the specified list of CPUs whose tick will be stopped + whenever possible. The boot CPU will be forced outside + the range to maintain the timekeeping. Any CPUs + in this list will have their RCU callbacks offloaded, + just as if they had also been called out in the + rcu_nocbs= boot parameter. + + Note that this argument takes precedence over + the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option. + + noinitrd [RAM] Tells the kernel not to load any configured + initial RAM disk. + + nointremap [X86-64, Intel-IOMMU] Do not enable interrupt + remapping. + [Deprecated - use intremap=off] + + nointroute [IA-64] + + noinvpcid [X86] Disable the INVPCID cpu feature. + + noiotrap [SH] Disables trapped I/O port accesses. + + noirqdebug [X86-32] Disables the code which attempts to detect and + disable unhandled interrupt sources. + + noisapnp [ISAPNP] Disables ISA PnP code. + + nojitter [IA-64] Disables jitter checking for ITC timers. + + nokaslr [KNL] + When CONFIG_RANDOMIZE_BASE is set, this disables + kernel and module base offset ASLR (Address Space + Layout Randomization). + + no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page + fault handling. + + no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver + + nolapic [X86-32,APIC] Do not enable or use the local APIC. + + nolapic_timer [X86-32,APIC] Do not use the local APIC timer. + + nomca [IA-64] Disable machine check abort handling + + nomce [X86-32] Disable Machine Check Exception + + nomfgpt [X86-32] Disable Multi-Function General Purpose + Timer usage (for AMD Geode machines). + + nomodeset Disable kernel modesetting. Most systems' firmware + sets up a display mode and provides framebuffer memory + for output. With nomodeset, DRM and fbdev drivers will + not load if they could possibly displace the pre- + initialized output. Only the system framebuffer will + be available for use. The respective drivers will not + perform display-mode changes or accelerated rendering. + + Useful as error fallback, or for testing and debugging. + + nomodule Disable module load + + nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to + shutdown the other cpus. Instead use the REBOOT_VECTOR + irq. + + nopat [X86] Disable PAT (page attribute table extension of + pagetables) support. + + nopcid [X86-64] Disable the PCID cpu feature. + + nopku [X86] Disable Memory Protection Keys CPU feature found + in some Intel CPUs. + + nopti [X86-64] + Equivalent to pti=off + + nopv= [X86,XEN,KVM,HYPER_V,VMWARE] + Disables the PV optimizations forcing the guest to run + as generic guest with no PV drivers. Currently support + XEN HVM, KVM, HYPER_V and VMWARE guest. + + nopvspin [X86,XEN,KVM] + Disables the qspinlock slow path using PV optimizations + which allow the hypervisor to 'idle' the guest on lock + contention. + + norandmaps Don't use address space randomization. Equivalent to + echo 0 > /proc/sys/kernel/randomize_va_space + + noreplace-smp [X86-32,SMP] Don't replace SMP instructions + with UP alternatives + + noresume [SWSUSP] Disables resume and restores original swap + space. + + nosbagart [IA-64] + + no-scroll [VGA] Disables scrollback. + This is required for the Braillex ib80-piezo Braille + reader made by F.H. Papenmeier (Germany). + + nosgx [X86-64,SGX] Disables Intel SGX kernel support. + + nosmap [PPC] + Disable SMAP (Supervisor Mode Access Prevention) + even if it is supported by processor. + + nosmep [PPC64s] + Disable SMEP (Supervisor Mode Execution Prevention) + even if it is supported by processor. + + nosmp [SMP] Tells an SMP kernel to act as a UP kernel, + and disable the IO APIC. legacy for "maxcpus=0". + + nosmt [KNL,MIPS,PPC,S390] Disable symmetric multithreading (SMT). + Equivalent to smt=1. + + [KNL,X86,PPC] Disable symmetric multithreading (SMT). + nosmt=force: Force disable SMT, cannot be undone + via the sysfs control file. + + nosoftlockup [KNL] Disable the soft-lockup detector. + + nospec_store_bypass_disable + [HW] Disable all mitigations for the Speculative Store Bypass vulnerability + + nospectre_bhb [ARM64] Disable all mitigations for Spectre-BHB (branch + history injection) vulnerability. System may allow data leaks + with this option. + + nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1 + (bounds check bypass). With this option data leaks are + possible in the system. + + nospectre_v2 [X86,PPC_E500,ARM64] Disable all mitigations for + the Spectre variant 2 (indirect branch prediction) + vulnerability. System may allow data leaks with this + option. + + no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES] Disable paravirtualized + steal time accounting. steal time is computed, but + won't influence scheduler behaviour + + nosync [HW,M68K] Disables sync negotiation for all devices. + + no_timer_check [X86,APIC] Disables the code which tests for + broken timer IRQ sources. + + no_uaccess_flush + [PPC] Don't flush the L1-D cache after accessing user data. + + novmcoredd [KNL,KDUMP] + Disable device dump. Device dump allows drivers to + append dump data to vmcore so you can collect driver + specified debug info. Drivers can append the data + without any limit and this data is stored in memory, + so this may cause significant memory stress. Disabling + device dump can help save memory but the driver debug + data will be no longer available. This parameter + is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP + is set. + + no-vmw-sched-clock + [X86,PV_OPS] Disable paravirtualized VMware scheduler + clock and use the default one. + + nowatchdog [KNL] Disable both lockup detectors, i.e. + soft-lockup and NMI watchdog (hard-lockup). + + nowb [ARM] + + nox2apic [X86-64,APIC] Do not enable x2APIC mode. + + NOTE: this parameter will be ignored on systems with the + LEGACY_XAPIC_DISABLED bit set in the + IA32_XAPIC_DISABLE_STATUS MSR. + + noxsave [BUGS=X86] Disables x86 extended register state save + and restore using xsave. The kernel will fallback to + enabling legacy floating-point and sse state. + + noxsaveopt [X86] Disables xsaveopt used in saving x86 extended + register states. The kernel will fall back to use + xsave to save the states. By using this parameter, + performance of saving the states is degraded because + xsave doesn't support modified optimization while + xsaveopt supports it on xsaveopt enabled systems. + + noxsaves [X86] Disables xsaves and xrstors used in saving and + restoring x86 extended register state in compacted + form of xsave area. The kernel will fall back to use + xsaveopt and xrstor to save and restore the states + in standard form of xsave area. By using this + parameter, xsave area per process might occupy more + memory on xsaves enabled systems. + + nps_mtm_hs_ctr= [KNL,ARC] + This parameter sets the maximum duration, in + cycles, each HW thread of the CTOP can run + without interruptions, before HW switches it. + The actual maximum duration is 16 times this + parameter's value. + Format: integer between 1 and 255 + Default: 255 + + nptcg= [IA-64] Override max number of concurrent global TLB + purges which is reported from either PAL_VM_SUMMARY or + SAL PALO. + + nr_cpus= [SMP] Maximum number of processors that an SMP kernel + could support. nr_cpus=n : n >= 1 limits the kernel to + support 'n' processors. It could be larger than the + number of already plugged CPU during bootup, later in + runtime you can physically add extra cpu until it reaches + n. So during boot up some boot time memory for per-cpu + variables need be pre-allocated for later physical cpu + hot plugging. + + nr_uarts= [SERIAL] maximum number of UARTs to be registered. + + numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only + set up a single NUMA node spanning all memory. + + numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic + NUMA balancing. + Allowed values are enable and disable + + numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. + 'node', 'default' can be specified + This can be set from sysctl after boot. + See Documentation/admin-guide/sysctl/vm.rst for details. + + ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. + See Documentation/core-api/debugging-via-ohci1394.rst for more + info. + + olpc_ec_timeout= [OLPC] ms delay when issuing EC commands + Rather than timing out after 20 ms if an EC + command is not properly ACKed, override the length + of the timeout. We have interrupts disabled while + waiting for the ACK, so if this is set too high + interrupts *may* be lost! + + omap_mux= [OMAP] Override bootloader pin multiplexing. + Format: <mux_mode0.mode_name=value>... + For example, to override I2C bus2: + omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 + + onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration + + Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] + + boundary - index of last SLC block on Flex-OneNAND. + The remaining blocks are configured as MLC blocks. + lock - Configure if Flex-OneNAND boundary should be locked. + Once locked, the boundary cannot be changed. + 1 indicates lock status, 0 indicates unlock status. + + oops=panic Always panic on oopses. Default is to just kill the + process, but there is a small probability of + deadlocking the machine. + This will also cause panics on machine check exceptions. + Useful together with panic=30 to trigger a reboot. + + page_alloc.shuffle= + [KNL] Boolean flag to control whether the page allocator + should randomize its free lists. The randomization may + be automatically enabled if the kernel detects it is + running on a platform with a direct-mapped memory-side + cache, and this parameter can be used to + override/disable that behavior. The state of the flag + can be read from sysfs at: + /sys/module/page_alloc/parameters/shuffle. + + page_owner= [KNL] Boot-time page_owner enabling option. + Storage of the information about who allocated + each page is disabled in default. With this switch, + we can turn it on. + on: enable the feature + + page_poison= [KNL] Boot-time parameter changing the state of + poisoning on the buddy allocator, available with + CONFIG_PAGE_POISONING=y. + off: turn off poisoning (default) + on: turn on poisoning + + page_reporting.page_reporting_order= + [KNL] Minimal page reporting order + Format: <integer> + Adjust the minimal page reporting order. The page + reporting is disabled when it exceeds MAX_ORDER. + + panic= [KNL] Kernel behaviour on panic: delay <timeout> + timeout > 0: seconds before rebooting + timeout = 0: wait forever + timeout < 0: reboot immediately + Format: <timeout> + + panic_on_taint= Bitmask for conditionally calling panic() in add_taint() + Format: <hex>[,nousertaint] + Hexadecimal bitmask representing the set of TAINT flags + that will cause the kernel to panic when add_taint() is + called with any of the flags in this set. + The optional switch "nousertaint" can be utilized to + prevent userspace forced crashes by writing to sysctl + /proc/sys/kernel/tainted any flagset matching with the + bitmask set on panic_on_taint. + See Documentation/admin-guide/tainted-kernels.rst for + extra details on the taint flags that users can pick + to compose the bitmask to assign to panic_on_taint. + + panic_on_warn=1 panic() instead of WARN(). Useful to cause kdump + on a WARN(). + + panic_print= Bitmask for printing system info when panic happens. + User can chose combination of the following bits: + bit 0: print all tasks info + bit 1: print system memory info + bit 2: print timer info + bit 3: print locks info if CONFIG_LOCKDEP is on + bit 4: print ftrace buffer + bit 5: print all printk messages in buffer + bit 6: print all CPUs backtrace (if available in the arch) + *Be aware* that this option may print a _lot_ of lines, + so there are risks of losing older messages in the log. + Use this option carefully, maybe worth to setup a + bigger log buffer with "log_buf_len" along with this. + + parkbd.port= [HW] Parallel port number the keyboard adapter is + connected to, default is 0. + Format: <parport#> + parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, + 0 for XT, 1 for AT (default is AT). + Format: <mode> + + parport= [HW,PPT] Specify parallel ports. 0 disables. + Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } + Use 'auto' to force the driver to use any + IRQ/DMA settings detected (the default is to + ignore detected IRQ/DMA settings because of + possible conflicts). You can specify the base + address, IRQ, and DMA settings; IRQ and DMA + should be numbers, or 'auto' (for using detected + settings on that particular port), or 'nofifo' + (to avoid using a FIFO even if it is detected). + Parallel ports are assigned in the order they + are specified on the command line, starting + with parport0. + + parport_init_mode= [HW,PPT] + Configure VIA parallel port to operate in + a specific mode. This is necessary on Pegasos + computer where firmware has no options for setting + up parallel port mode and sets it to spp. + Currently this function knows 686a and 8231 chips. + Format: [spp|ps2|epp|ecp|ecpepp] + + pata_legacy.all= [HW,LIBATA] + Format: <int> + Set to non-zero to probe primary and secondary ISA + port ranges on PCI systems where no PCI PATA device + has been found at either range. Disabled by default. + + pata_legacy.autospeed= [HW,LIBATA] + Format: <int> + Set to non-zero if a chip is present that snoops speed + changes. Disabled by default. + + pata_legacy.ht6560a= [HW,LIBATA] + Format: <int> + Set to 1, 2, or 3 for HT 6560A on the primary channel, + the secondary channel, or both channels respectively. + Disabled by default. + + pata_legacy.ht6560b= [HW,LIBATA] + Format: <int> + Set to 1, 2, or 3 for HT 6560B on the primary channel, + the secondary channel, or both channels respectively. + Disabled by default. + + pata_legacy.iordy_mask= [HW,LIBATA] + Format: <int> + IORDY enable mask. Set individual bits to allow IORDY + for the respective channel. Bit 0 is for the first + legacy channel handled by this driver, bit 1 is for + the second channel, and so on. The sequence will often + correspond to the primary legacy channel, the secondary + legacy channel, and so on, but the handling of a PCI + bus and the use of other driver options may interfere + with the sequence. By default IORDY is allowed across + all channels. + + pata_legacy.opti82c46x= [HW,LIBATA] + Format: <int> + Set to 1, 2, or 3 for Opti 82c611A on the primary + channel, the secondary channel, or both channels + respectively. Disabled by default. + + pata_legacy.opti82c611a= [HW,LIBATA] + Format: <int> + Set to 1, 2, or 3 for Opti 82c465MV on the primary + channel, the secondary channel, or both channels + respectively. Disabled by default. + + pata_legacy.pio_mask= [HW,LIBATA] + Format: <int> + PIO mode mask for autospeed devices. Set individual + bits to allow the use of the respective PIO modes. + Bit 0 is for mode 0, bit 1 is for mode 1, and so on. + All modes allowed by default. + + pata_legacy.probe_all= [HW,LIBATA] + Format: <int> + Set to non-zero to probe tertiary and further ISA + port ranges on PCI systems. Disabled by default. + + pata_legacy.probe_mask= [HW,LIBATA] + Format: <int> + Probe mask for legacy ISA PATA ports. Depending on + platform configuration and the use of other driver + options up to 6 legacy ports are supported: 0x1f0, + 0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing + of individual ports can be disabled by setting the + corresponding bits in the mask to 1. Bit 0 is for + the first port in the list above (0x1f0), and so on. + By default all supported ports are probed. + + pata_legacy.qdi= [HW,LIBATA] + Format: <int> + Set to non-zero to probe QDI controllers. By default + set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise. + + pata_legacy.winbond= [HW,LIBATA] + Format: <int> + Set to non-zero to probe Winbond controllers. Use + the standard I/O port (0x130) if 1, otherwise the + value given is the I/O port to use (typically 0x1b0). + By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE, + 0 otherwise. + + pata_platform.pio_mask= [HW,LIBATA] + Format: <int> + Supported PIO mode mask. Set individual bits to allow + the use of the respective PIO modes. Bit 0 is for + mode 0, bit 1 is for mode 1, and so on. Mode 0 only + allowed by default. + + pause_on_oops=<int> + Halt all CPUs after the first oops has been printed for + the specified number of seconds. This is to be used if + your oopses keep scrolling off the screen. + + pcbit= [HW,ISDN] + + pci=option[,option...] [PCI] various PCI subsystem options. + + Some options herein operate on a specific device + or a set of devices (<pci_dev>). These are + specified in one of the following formats: + + [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]* + pci:<vendor>:<device>[:<subvendor>:<subdevice>] + + Note: the first format specifies a PCI + bus/device/function address which may change + if new hardware is inserted, if motherboard + firmware changes, or due to changes caused + by other kernel parameters. If the + domain is left unspecified, it is + taken to be zero. Optionally, a path + to a device through multiple device/function + addresses can be specified after the base + address (this is more robust against + renumbering issues). The second format + selects devices using IDs from the + configuration space which may match multiple + devices in the system. + + earlydump dump PCI config space before the kernel + changes anything + off [X86] don't probe for the PCI bus + bios [X86-32] force use of PCI BIOS, don't access + the hardware directly. Use this if your machine + has a non-standard PCI host bridge. + nobios [X86-32] disallow use of PCI BIOS, only direct + hardware access methods are allowed. Use this + if you experience crashes upon bootup and you + suspect they are caused by the BIOS. + conf1 [X86] Force use of PCI Configuration Access + Mechanism 1 (config address in IO port 0xCF8, + data in IO port 0xCFC, both 32-bit). + conf2 [X86] Force use of PCI Configuration Access + Mechanism 2 (IO port 0xCF8 is an 8-bit port for + the function, IO port 0xCFA, also 8-bit, sets + bus number. The config space is then accessed + through ports 0xC000-0xCFFF). + See http://wiki.osdev.org/PCI for more info + on the configuration access mechanisms. + noaer [PCIE] If the PCIEAER kernel config parameter is + enabled, this kernel boot option can be used to + disable the use of PCIE advanced error reporting. + nodomains [PCI] Disable support for multiple PCI + root domains (aka PCI segments, in ACPI-speak). + nommconf [X86] Disable use of MMCONFIG for PCI + Configuration + check_enable_amd_mmconf [X86] check for and enable + properly configured MMIO access to PCI + config space on AMD family 10h CPU + nomsi [MSI] If the PCI_MSI kernel config parameter is + enabled, this kernel boot option can be used to + disable the use of MSI interrupts system-wide. + noioapicquirk [APIC] Disable all boot interrupt quirks. + Safety option to keep boot IRQs enabled. This + should never be necessary. + ioapicreroute [APIC] Enable rerouting of boot IRQs to the + primary IO-APIC for bridges that cannot disable + boot IRQs. This fixes a source of spurious IRQs + when the system masks IRQs. + noioapicreroute [APIC] Disable workaround that uses the + boot IRQ equivalent of an IRQ that connects to + a chipset where boot IRQs cannot be disabled. + The opposite of ioapicreroute. + biosirq [X86-32] Use PCI BIOS calls to get the interrupt + routing table. These calls are known to be buggy + on several machines and they hang the machine + when used, but on other computers it's the only + way to get the interrupt routing table. Try + this option if the kernel is unable to allocate + IRQs or discover secondary PCI buses on your + motherboard. + rom [X86] Assign address space to expansion ROMs. + Use with caution as certain devices share + address decoders between ROMs and other + resources. + norom [X86] Do not assign address space to + expansion ROMs that do not already have + BIOS assigned address ranges. + nobar [X86] Do not assign address space to the + BARs that weren't assigned by the BIOS. + irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be + assigned automatically to PCI devices. You can + make the kernel exclude IRQs of your ISA cards + this way. + pirqaddr=0xAAAAA [X86] Specify the physical address + of the PIRQ table (normally generated + by the BIOS) if it is outside the + F0000h-100000h range. + lastbus=N [X86] Scan all buses thru bus #N. Can be + useful if the kernel is unable to find your + secondary buses and you want to tell it + explicitly which ones they are. + assign-busses [X86] Always assign all PCI bus + numbers ourselves, overriding + whatever the firmware may have done. + usepirqmask [X86] Honor the possible IRQ mask stored + in the BIOS $PIR table. This is needed on + some systems with broken BIOSes, notably + some HP Pavilion N5400 and Omnibook XE3 + notebooks. This will have no effect if ACPI + IRQ routing is enabled. + noacpi [X86] Do not use ACPI for IRQ routing + or for PCI scanning. + use_crs [X86] Use PCI host bridge window information + from ACPI. On BIOSes from 2008 or later, this + is enabled by default. If you need to use this, + please report a bug. + nocrs [X86] Ignore PCI host bridge windows from ACPI. + If you need to use this, please report a bug. + use_e820 [X86] Use E820 reservations to exclude parts of + PCI host bridge windows. This is a workaround + for BIOS defects in host bridge _CRS methods. + If you need to use this, please report a bug to + <linux-pci@vger.kernel.org>. + no_e820 [X86] Ignore E820 reservations for PCI host + bridge windows. This is the default on modern + hardware. If you need to use this, please report + a bug to <linux-pci@vger.kernel.org>. + routeirq Do IRQ routing for all PCI devices. + This is normally done in pci_enable_device(), + so this option is a temporary workaround + for broken drivers that don't call it. + skip_isa_align [X86] do not align io start addr, so can + handle more pci cards + noearly [X86] Don't do any early type 1 scanning. + This might help on some broken boards which + machine check when some devices' config space + is read. But various workarounds are disabled + and some IOMMU drivers will not work. + bfsort Sort PCI devices into breadth-first order. + This sorting is done to get a device + order compatible with older (<= 2.4) kernels. + nobfsort Don't sort PCI devices into breadth-first order. + pcie_bus_tune_off Disable PCIe MPS (Max Payload Size) + tuning and use the BIOS-configured MPS defaults. + pcie_bus_safe Set every device's MPS to the largest value + supported by all devices below the root complex. + pcie_bus_perf Set device MPS to the largest allowable MPS + based on its parent bus. Also set MRRS (Max + Read Request Size) to the largest supported + value (no larger than the MPS that the device + or bus can support) for best performance. + pcie_bus_peer2peer Set every device's MPS to 128B, which + every device is guaranteed to support. This + configuration allows peer-to-peer DMA between + any pair of devices, possibly at the cost of + reduced performance. This also guarantees + that hot-added devices will work. + cbiosize=nn[KMG] The fixed amount of bus space which is + reserved for the CardBus bridge's IO window. + The default value is 256 bytes. + cbmemsize=nn[KMG] The fixed amount of bus space which is + reserved for the CardBus bridge's memory + window. The default value is 64 megabytes. + resource_alignment= + Format: + [<order of align>@]<pci_dev>[; ...] + Specifies alignment and device to reassign + aligned memory resources. How to + specify the device is described above. + If <order of align> is not specified, + PAGE_SIZE is used as alignment. + A PCI-PCI bridge can be specified if resource + windows need to be expanded. + To specify the alignment for several + instances of a device, the PCI vendor, + device, subvendor, and subdevice may be + specified, e.g., 12@pci:8086:9c22:103c:198f + for 4096-byte alignment. + ecrc= Enable/disable PCIe ECRC (transaction layer + end-to-end CRC checking). Only effective if + OS has native AER control (either granted by + ACPI _OSC or forced via "pcie_ports=native") + bios: Use BIOS/firmware settings. This is the + the default. + off: Turn ECRC off + on: Turn ECRC on. + hpiosize=nn[KMG] The fixed amount of bus space which is + reserved for hotplug bridge's IO window. + Default size is 256 bytes. + hpmmiosize=nn[KMG] The fixed amount of bus space which is + reserved for hotplug bridge's MMIO window. + Default size is 2 megabytes. + hpmmioprefsize=nn[KMG] The fixed amount of bus space which is + reserved for hotplug bridge's MMIO_PREF window. + Default size is 2 megabytes. + hpmemsize=nn[KMG] The fixed amount of bus space which is + reserved for hotplug bridge's MMIO and + MMIO_PREF window. + Default size is 2 megabytes. + hpbussize=nn The minimum amount of additional bus numbers + reserved for buses below a hotplug bridge. + Default is 1. + realloc= Enable/disable reallocating PCI bridge resources + if allocations done by BIOS are too small to + accommodate resources required by all child + devices. + off: Turn realloc off + on: Turn realloc on + realloc same as realloc=on + noari do not use PCIe ARI. + noats [PCIE, Intel-IOMMU, AMD-IOMMU] + do not use PCIe ATS (and IOMMU device IOTLB). + pcie_scan_all Scan all possible PCIe devices. Otherwise we + only look for one device below a PCIe downstream + port. + big_root_window Try to add a big 64bit memory window to the PCIe + root complex on AMD CPUs. Some GFX hardware + can resize a BAR to allow access to all VRAM. + Adding the window is slightly risky (it may + conflict with unreported devices), so this + taints the kernel. + disable_acs_redir=<pci_dev>[; ...] + Specify one or more PCI devices (in the format + specified above) separated by semicolons. + Each device specified will have the PCI ACS + redirect capabilities forced off which will + allow P2P traffic between devices through + bridges without forcing it upstream. Note: + this removes isolation between devices and + may put more devices in an IOMMU group. + force_floating [S390] Force usage of floating interrupts. + nomio [S390] Do not use MIO instructions. + norid [S390] ignore the RID field and force use of + one PCI domain per PCI function + + pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power + Management. + off Disable ASPM. + force Enable ASPM even on devices that claim not to support it. + WARNING: Forcing ASPM on may cause system lockups. + + pcie_ports= [PCIE] PCIe port services handling: + native Use native PCIe services (PME, AER, DPC, PCIe hotplug) + even if the platform doesn't give the OS permission to + use them. This may cause conflicts if the platform + also tries to use these services. + dpc-native Use native PCIe service for DPC only. May + cause conflicts if firmware uses AER or DPC. + compat Disable native PCIe services (PME, AER, DPC, PCIe + hotplug). + + pcie_port_pm= [PCIE] PCIe port power management handling: + off Disable power management of all PCIe ports + force Forcibly enable power management of all PCIe ports + + pcie_pme= [PCIE,PM] Native PCIe PME signaling options: + nomsi Do not use MSI for native PCIe PME signaling (this makes + all PCIe root ports use INTx for all services). + + pcmv= [HW,PCMCIA] BadgePAD 4 + + pd_ignore_unused + [PM] + Keep all power-domains already enabled by bootloader on, + even if no driver has claimed them. This is useful + for debug and development, but should not be + needed on a platform with proper driver support. + + pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at + boot time. + Format: { 0 | 1 } + See arch/parisc/kernel/pdc_chassis.c + + percpu_alloc= Select which percpu first chunk allocator to use. + Currently supported values are "embed" and "page". + Archs may support subset or none of the selections. + See comments in mm/percpu.c for details on each + allocator. This parameter is primarily for debugging + and performance comparison. + + pirq= [SMP,APIC] Manual mp-table setup + See Documentation/arch/x86/i386/IO-APIC.rst. + + plip= [PPT,NET] Parallel port network link + Format: { parport<nr> | timid | 0 } + See also Documentation/admin-guide/parport.rst. + + pmtmr= [X86] Manual setup of pmtmr I/O Port. + Override pmtimer IOPort with a hex value. + e.g. pmtmr=0x508 + + pmu_override= [PPC] Override the PMU. + This option takes over the PMU facility, so it is no + longer usable by perf. Setting this option starts the + PMU counters by setting MMCR0 to 0 (the FC bit is + cleared). If a number is given, then MMCR1 is set to + that number, otherwise (e.g., 'pmu_override=on'), MMCR1 + remains 0. + + pm_debug_messages [SUSPEND,KNL] + Enable suspend/resume debug messages during boot up. + + pnp.debug=1 [PNP] + Enable PNP debug messages (depends on the + CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time + via /sys/module/pnp/parameters/debug. We always show + current resource usage; turning this on also shows + possible settings and some assignment information. + + pnpacpi= [ACPI] + { off } + + pnpbios= [ISAPNP] + { on | off | curr | res | no-curr | no-res } + + pnp_reserve_irq= + [ISAPNP] Exclude IRQs for the autoconfiguration + + pnp_reserve_dma= + [ISAPNP] Exclude DMAs for the autoconfiguration + + pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration + Ranges are in pairs (I/O port base and size). + + pnp_reserve_mem= + [ISAPNP] Exclude memory regions for the + autoconfiguration. + Ranges are in pairs (memory base and size). + + ports= [IP_VS_FTP] IPVS ftp helper module + Default is 21. + Up to 8 (IP_VS_APP_MAX_PORTS) ports + may be specified. + Format: <port>,<port>.... + + powersave=off [PPC] This option disables power saving features. + It specifically disables cpuidle and sets the + platform machine description specific power_save + function to NULL. On Idle the CPU just reduces + execution priority. + + ppc_strict_facility_enable + [PPC] This option catches any kernel floating point, + Altivec, VSX and SPE outside of regions specifically + allowed (eg kernel_enable_fpu()/kernel_disable_fpu()). + There is some performance impact when enabling this. + + ppc_tm= [PPC] + Format: {"off"} + Disable Hardware Transactional Memory + + preempt= [KNL] + Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC + none - Limited to cond_resched() calls + voluntary - Limited to cond_resched() and might_sleep() calls + full - Any section that isn't explicitly preempt disabled + can be preempted anytime. + + print-fatal-signals= + [KNL] debug: print fatal signals + + If enabled, warn about various signal handling + related application anomalies: too many signals, + too many POSIX.1 timers, fatal signals causing a + coredump - etc. + + If you hit the warning due to signal overflow, + you might want to try "ulimit -i unlimited". + + default: off. + + printk.always_kmsg_dump= + Trigger kmsg_dump for cases other than kernel oops or + panics + Format: <bool> (1/Y/y=enable, 0/N/n=disable) + default: disabled + + printk.console_no_auto_verbose= + Disable console loglevel raise on oops, panic + or lockdep-detected issues (only if lock debug is on). + With an exception to setups with low baudrate on + serial console, keeping this 0 is a good choice + in order to provide more debug information. + Format: <bool> + default: 0 (auto_verbose is enabled) + + printk.devkmsg={on,off,ratelimit} + Control writing to /dev/kmsg. + on - unlimited logging to /dev/kmsg from userspace + off - logging to /dev/kmsg disabled + ratelimit - ratelimit the logging + Default: ratelimit + + printk.time= Show timing data prefixed to each printk message line + Format: <bool> (1/Y/y=enable, 0/N/n=disable) + + processor.max_cstate= [HW,ACPI] + Limit processor to maximum C-state + max_cstate=9 overrides any DMI blacklist limit. + + processor.nocst [HW,ACPI] + Ignore the _CST method to determine C-states, + instead using the legacy FADT method + + profile= [KNL] Enable kernel profiling via /proc/profile + Format: [<profiletype>,]<number> + Param: <profiletype>: "schedule", "sleep", or "kvm" + [defaults to kernel profiling] + Param: "schedule" - profile schedule points. + Param: "sleep" - profile D-state sleeping (millisecs). + Requires CONFIG_SCHEDSTATS + Param: "kvm" - profile VM exits. + Param: <number> - step/bucket size as a power of 2 for + statistical time based profiling. + + prompt_ramdisk= [RAM] [Deprecated] + + prot_virt= [S390] enable hosting protected virtual machines + isolated from the hypervisor (if hardware supports + that). + Format: <bool> + + psi= [KNL] Enable or disable pressure stall information + tracking. + Format: <bool> + + psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to + probe for; one of (bare|imps|exps|lifebook|any). + psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports + per second. + psmouse.resetafter= [HW,MOUSE] + Try to reset the device after so many bad packets + (0 = never). + psmouse.resolution= + [HW,MOUSE] Set desired mouse resolution, in dpi. + psmouse.smartscroll= + [HW,MOUSE] Controls Logitech smartscroll autorepeat. + 0 = disabled, 1 = enabled (default). + + pstore.backend= Specify the name of the pstore backend to use + + pti= [X86-64] Control Page Table Isolation of user and + kernel address spaces. Disabling this feature + removes hardening, but improves performance of + system calls and interrupts. + + on - unconditionally enable + off - unconditionally disable + auto - kernel detects whether your CPU model is + vulnerable to issues that PTI mitigates + + Not specifying this option is equivalent to pti=auto. + + pty.legacy_count= + [KNL] Number of legacy pty's. Overwrites compiled-in + default number. + + quiet [KNL] Disable most log messages + + r128= [HW,DRM] + + radix_hcall_invalidate=on [PPC/PSERIES] + Disable RADIX GTSE feature and use hcall for TLB + invalidate. + + raid= [HW,RAID] + See Documentation/admin-guide/md.rst. + + ramdisk_size= [RAM] Sizes of RAM disks in kilobytes + See Documentation/admin-guide/blockdev/ramdisk.rst. + + ramdisk_start= [RAM] RAM disk image start address + + random.trust_cpu=off + [KNL] Disable trusting the use of the CPU's + random number generator (if available) to + initialize the kernel's RNG. + + random.trust_bootloader=off + [KNL] Disable trusting the use of the a seed + passed by the bootloader (if available) to + initialize the kernel's RNG. + + randomize_kstack_offset= + [KNL] Enable or disable kernel stack offset + randomization, which provides roughly 5 bits of + entropy, frustrating memory corruption attacks + that depend on stack address determinism or + cross-syscall address exposures. This is only + available on architectures that have defined + CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET. + Format: <bool> (1/Y/y=enable, 0/N/n=disable) + Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT. + + ras=option[,option,...] [KNL] RAS-specific options + + cec_disable [X86] + Disable the Correctable Errors Collector, + see CONFIG_RAS_CEC help text. + + rcu_nocbs[=cpu-list] + [KNL] The optional argument is a cpu list, + as described above. + + In kernels built with CONFIG_RCU_NOCB_CPU=y, + enable the no-callback CPU mode, which prevents + such CPUs' callbacks from being invoked in + softirq context. Invocation of such CPUs' RCU + callbacks will instead be offloaded to "rcuox/N" + kthreads created for that purpose, where "x" is + "p" for RCU-preempt, "s" for RCU-sched, and "g" + for the kthreads that mediate grace periods; and + "N" is the CPU number. This reduces OS jitter on + the offloaded CPUs, which can be useful for HPC + and real-time workloads. It can also improve + energy efficiency for asymmetric multiprocessors. + + If a cpulist is passed as an argument, the specified + list of CPUs is set to no-callback mode from boot. + + Otherwise, if the '=' sign and the cpulist + arguments are omitted, no CPU will be set to + no-callback mode from boot but the mode may be + toggled at runtime via cpusets. + + Note that this argument takes precedence over + the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option. + + rcu_nocb_poll [KNL] + Rather than requiring that offloaded CPUs + (specified by rcu_nocbs= above) explicitly + awaken the corresponding "rcuoN" kthreads, + make these kthreads poll for callbacks. + This improves the real-time response for the + offloaded CPUs by relieving them of the need to + wake up the corresponding kthread, but degrades + energy efficiency by requiring that the kthreads + periodically wake up to do the polling. + + rcutree.blimit= [KNL] + Set maximum number of finished RCU callbacks to + process in one batch. + + rcutree.dump_tree= [KNL] + Dump the structure of the rcu_node combining tree + out at early boot. This is used for diagnostic + purposes, to verify correct tree setup. + + rcutree.gp_cleanup_delay= [KNL] + Set the number of jiffies to delay each step of + RCU grace-period cleanup. + + rcutree.gp_init_delay= [KNL] + Set the number of jiffies to delay each step of + RCU grace-period initialization. + + rcutree.gp_preinit_delay= [KNL] + Set the number of jiffies to delay each step of + RCU grace-period pre-initialization, that is, + the propagation of recent CPU-hotplug changes up + the rcu_node combining tree. + + rcutree.jiffies_till_first_fqs= [KNL] + Set delay from grace-period initialization to + first attempt to force quiescent states. + Units are jiffies, minimum value is zero, + and maximum value is HZ. + + rcutree.jiffies_till_next_fqs= [KNL] + Set delay between subsequent attempts to force + quiescent states. Units are jiffies, minimum + value is one, and maximum value is HZ. + + rcutree.jiffies_till_sched_qs= [KNL] + Set required age in jiffies for a + given grace period before RCU starts + soliciting quiescent-state help from + rcu_note_context_switch() and cond_resched(). + If not specified, the kernel will calculate + a value based on the most recent settings + of rcutree.jiffies_till_first_fqs + and rcutree.jiffies_till_next_fqs. + This calculated value may be viewed in + rcutree.jiffies_to_sched_qs. Any attempt to set + rcutree.jiffies_to_sched_qs will be cheerfully + overwritten. + + rcutree.kthread_prio= [KNL,BOOT] + Set the SCHED_FIFO priority of the RCU per-CPU + kthreads (rcuc/N). This value is also used for + the priority of the RCU boost threads (rcub/N) + and for the RCU grace-period kthreads (rcu_bh, + rcu_preempt, and rcu_sched). If RCU_BOOST is + set, valid values are 1-99 and the default is 1 + (the least-favored priority). Otherwise, when + RCU_BOOST is not set, valid values are 0-99 and + the default is zero (non-realtime operation). + When RCU_NOCB_CPU is set, also adjust the + priority of NOCB callback kthreads. + + rcutree.nocb_nobypass_lim_per_jiffy= [KNL] + On callback-offloaded (rcu_nocbs) CPUs, + RCU reduces the lock contention that would + otherwise be caused by callback floods through + use of the ->nocb_bypass list. However, in the + common non-flooded case, RCU queues directly to + the main ->cblist in order to avoid the extra + overhead of the ->nocb_bypass list and its lock. + But if there are too many callbacks queued during + a single jiffy, RCU pre-queues the callbacks into + the ->nocb_bypass queue. The definition of "too + many" is supplied by this kernel boot parameter. + + rcutree.qhimark= [KNL] + Set threshold of queued RCU callbacks beyond which + batch limiting is disabled. + + rcutree.qlowmark= [KNL] + Set threshold of queued RCU callbacks below which + batch limiting is re-enabled. + + rcutree.qovld= [KNL] + Set threshold of queued RCU callbacks beyond which + RCU's force-quiescent-state scan will aggressively + enlist help from cond_resched() and sched IPIs to + help CPUs more quickly reach quiescent states. + Set to less than zero to make this be set based + on rcutree.qhimark at boot time and to zero to + disable more aggressive help enlistment. + + rcutree.rcu_delay_page_cache_fill_msec= [KNL] + Set the page-cache refill delay (in milliseconds) + in response to low-memory conditions. The range + of permitted values is in the range 0:100000. + + rcutree.rcu_divisor= [KNL] + Set the shift-right count to use to compute + the callback-invocation batch limit bl from + the number of callbacks queued on this CPU. + The result will be bounded below by the value of + the rcutree.blimit kernel parameter. Every bl + callbacks, the softirq handler will exit in + order to allow the CPU to do other work. + + Please note that this callback-invocation batch + limit applies only to non-offloaded callback + invocation. Offloaded callbacks are instead + invoked in the context of an rcuoc kthread, which + scheduler will preempt as it does any other task. + + rcutree.rcu_fanout_exact= [KNL] + Disable autobalancing of the rcu_node combining + tree. This is used by rcutorture, and might + possibly be useful for architectures having high + cache-to-cache transfer latencies. + + rcutree.rcu_fanout_leaf= [KNL] + Change the number of CPUs assigned to each + leaf rcu_node structure. Useful for very + large systems, which will choose the value 64, + and for NUMA systems with large remote-access + latencies, which will choose a value aligned + with the appropriate hardware boundaries. + + rcutree.rcu_min_cached_objs= [KNL] + Minimum number of objects which are cached and + maintained per one CPU. Object size is equal + to PAGE_SIZE. The cache allows to reduce the + pressure to page allocator, also it makes the + whole algorithm to behave better in low memory + condition. + + rcutree.rcu_nocb_gp_stride= [KNL] + Set the number of NOCB callback kthreads in + each group, which defaults to the square root + of the number of CPUs. Larger numbers reduce + the wakeup overhead on the global grace-period + kthread, but increases that same overhead on + each group's NOCB grace-period kthread. + + rcutree.rcu_kick_kthreads= [KNL] + Cause the grace-period kthread to get an extra + wake_up() if it sleeps three times longer than + it should at force-quiescent-state time. + This wake_up() will be accompanied by a + WARN_ONCE() splat and an ftrace_dump(). + + rcutree.rcu_resched_ns= [KNL] + Limit the time spend invoking a batch of RCU + callbacks to the specified number of nanoseconds. + By default, this limit is checked only once + every 32 callbacks in order to limit the pain + inflicted by local_clock() overhead. + + rcutree.rcu_unlock_delay= [KNL] + In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels, + this specifies an rcu_read_unlock()-time delay + in microseconds. This defaults to zero. + Larger delays increase the probability of + catching RCU pointer leaks, that is, buggy use + of RCU-protected pointers after the relevant + rcu_read_unlock() has completed. + + rcutree.sysrq_rcu= [KNL] + Commandeer a sysrq key to dump out Tree RCU's + rcu_node tree with an eye towards determining + why a new grace period has not yet started. + + rcutree.use_softirq= [KNL] + If set to zero, move all RCU_SOFTIRQ processing to + per-CPU rcuc kthreads. Defaults to a non-zero + value, meaning that RCU_SOFTIRQ is used by default. + Specify rcutree.use_softirq=0 to use rcuc kthreads. + + But note that CONFIG_PREEMPT_RT=y kernels disable + this kernel boot parameter, forcibly setting it + to zero. + + rcuscale.gp_async= [KNL] + Measure performance of asynchronous + grace-period primitives such as call_rcu(). + + rcuscale.gp_async_max= [KNL] + Specify the maximum number of outstanding + callbacks per writer thread. When a writer + thread exceeds this limit, it invokes the + corresponding flavor of rcu_barrier() to allow + previously posted callbacks to drain. + + rcuscale.gp_exp= [KNL] + Measure performance of expedited synchronous + grace-period primitives. + + rcuscale.holdoff= [KNL] + Set test-start holdoff period. The purpose of + this parameter is to delay the start of the + test until boot completes in order to avoid + interference. + + rcuscale.kfree_by_call_rcu= [KNL] + In kernels built with CONFIG_RCU_LAZY=y, test + call_rcu() instead of kfree_rcu(). + + rcuscale.kfree_mult= [KNL] + Instead of allocating an object of size kfree_obj, + allocate one of kfree_mult * sizeof(kfree_obj). + Defaults to 1. + + rcuscale.kfree_rcu_test= [KNL] + Set to measure performance of kfree_rcu() flooding. + + rcuscale.kfree_rcu_test_double= [KNL] + Test the double-argument variant of kfree_rcu(). + If this parameter has the same value as + rcuscale.kfree_rcu_test_single, both the single- + and double-argument variants are tested. + + rcuscale.kfree_rcu_test_single= [KNL] + Test the single-argument variant of kfree_rcu(). + If this parameter has the same value as + rcuscale.kfree_rcu_test_double, both the single- + and double-argument variants are tested. + + rcuscale.kfree_nthreads= [KNL] + The number of threads running loops of kfree_rcu(). + + rcuscale.kfree_alloc_num= [KNL] + Number of allocations and frees done in an iteration. + + rcuscale.kfree_loops= [KNL] + Number of loops doing rcuscale.kfree_alloc_num number + of allocations and frees. + + rcuscale.minruntime= [KNL] + Set the minimum test run time in seconds. This + does not affect the data-collection interval, + but instead allows better measurement of things + like CPU consumption. + + rcuscale.nreaders= [KNL] + Set number of RCU readers. The value -1 selects + N, where N is the number of CPUs. A value + "n" less than -1 selects N-n+1, where N is again + the number of CPUs. For example, -2 selects N + (the number of CPUs), -3 selects N+1, and so on. + A value of "n" less than or equal to -N selects + a single reader. + + rcuscale.nwriters= [KNL] + Set number of RCU writers. The values operate + the same as for rcuscale.nreaders. + N, where N is the number of CPUs + + rcuscale.scale_type= [KNL] + Specify the RCU implementation to test. + + rcuscale.shutdown= [KNL] + Shut the system down after performance tests + complete. This is useful for hands-off automated + testing. + + rcuscale.verbose= [KNL] + Enable additional printk() statements. + + rcuscale.writer_holdoff= [KNL] + Write-side holdoff between grace periods, + in microseconds. The default of zero says + no holdoff. + + rcuscale.writer_holdoff_jiffies= [KNL] + Additional write-side holdoff between grace + periods, but in jiffies. The default of zero + says no holdoff. + + rcutorture.fqs_duration= [KNL] + Set duration of force_quiescent_state bursts + in microseconds. + + rcutorture.fqs_holdoff= [KNL] + Set holdoff time within force_quiescent_state bursts + in microseconds. + + rcutorture.fqs_stutter= [KNL] + Set wait time between force_quiescent_state bursts + in seconds. + + rcutorture.fwd_progress= [KNL] + Specifies the number of kthreads to be used + for RCU grace-period forward-progress testing + for the types of RCU supporting this notion. + Defaults to 1 kthread, values less than zero or + greater than the number of CPUs cause the number + of CPUs to be used. + + rcutorture.fwd_progress_div= [KNL] + Specify the fraction of a CPU-stall-warning + period to do tight-loop forward-progress testing. + + rcutorture.fwd_progress_holdoff= [KNL] + Number of seconds to wait between successive + forward-progress tests. + + rcutorture.fwd_progress_need_resched= [KNL] + Enclose cond_resched() calls within checks for + need_resched() during tight-loop forward-progress + testing. + + rcutorture.gp_cond= [KNL] + Use conditional/asynchronous update-side + primitives, if available. + + rcutorture.gp_exp= [KNL] + Use expedited update-side primitives, if available. + + rcutorture.gp_normal= [KNL] + Use normal (non-expedited) asynchronous + update-side primitives, if available. + + rcutorture.gp_sync= [KNL] + Use normal (non-expedited) synchronous + update-side primitives, if available. If all + of rcutorture.gp_cond=, rcutorture.gp_exp=, + rcutorture.gp_normal=, and rcutorture.gp_sync= + are zero, rcutorture acts as if is interpreted + they are all non-zero. + + rcutorture.irqreader= [KNL] + Run RCU readers from irq handlers, or, more + accurately, from a timer handler. Not all RCU + flavors take kindly to this sort of thing. + + rcutorture.leakpointer= [KNL] + Leak an RCU-protected pointer out of the reader. + This can of course result in splats, and is + intended to test the ability of things like + CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect + such leaks. + + rcutorture.n_barrier_cbs= [KNL] + Set callbacks/threads for rcu_barrier() testing. + + rcutorture.nfakewriters= [KNL] + Set number of concurrent RCU writers. These just + stress RCU, they don't participate in the actual + test, hence the "fake". + + rcutorture.nocbs_nthreads= [KNL] + Set number of RCU callback-offload togglers. + Zero (the default) disables toggling. + + rcutorture.nocbs_toggle= [KNL] + Set the delay in milliseconds between successive + callback-offload toggling attempts. + + rcutorture.nreaders= [KNL] + Set number of RCU readers. The value -1 selects + N-1, where N is the number of CPUs. A value + "n" less than -1 selects N-n-2, where N is again + the number of CPUs. For example, -2 selects N + (the number of CPUs), -3 selects N+1, and so on. + + rcutorture.object_debug= [KNL] + Enable debug-object double-call_rcu() testing. + + rcutorture.onoff_holdoff= [KNL] + Set time (s) after boot for CPU-hotplug testing. + + rcutorture.onoff_interval= [KNL] + Set time (jiffies) between CPU-hotplug operations, + or zero to disable CPU-hotplug testing. + + rcutorture.read_exit= [KNL] + Set the number of read-then-exit kthreads used + to test the interaction of RCU updaters and + task-exit processing. + + rcutorture.read_exit_burst= [KNL] + The number of times in a given read-then-exit + episode that a set of read-then-exit kthreads + is spawned. + + rcutorture.read_exit_delay= [KNL] + The delay, in seconds, between successive + read-then-exit testing episodes. + + rcutorture.shuffle_interval= [KNL] + Set task-shuffle interval (s). Shuffling tasks + allows some CPUs to go into dyntick-idle mode + during the rcutorture test. + + rcutorture.shutdown_secs= [KNL] + Set time (s) after boot system shutdown. This + is useful for hands-off automated testing. + + rcutorture.stall_cpu= [KNL] + Duration of CPU stall (s) to test RCU CPU stall + warnings, zero to disable. + + rcutorture.stall_cpu_block= [KNL] + Sleep while stalling if set. This will result + in warnings from preemptible RCU in addition to + any other stall-related activity. Note that + in kernels built with CONFIG_PREEMPTION=n and + CONFIG_PREEMPT_COUNT=y, this parameter will + cause the CPU to pass through a quiescent state. + Given CONFIG_PREEMPTION=n, this will suppress + RCU CPU stall warnings, but will instead result + in scheduling-while-atomic splats. + + Use of this module parameter results in splats. + + + rcutorture.stall_cpu_holdoff= [KNL] + Time to wait (s) after boot before inducing stall. + + rcutorture.stall_cpu_irqsoff= [KNL] + Disable interrupts while stalling if set. + + rcutorture.stall_gp_kthread= [KNL] + Duration (s) of forced sleep within RCU + grace-period kthread to test RCU CPU stall + warnings, zero to disable. If both stall_cpu + and stall_gp_kthread are specified, the + kthread is starved first, then the CPU. + + rcutorture.stat_interval= [KNL] + Time (s) between statistics printk()s. + + rcutorture.stutter= [KNL] + Time (s) to stutter testing, for example, specifying + five seconds causes the test to run for five seconds, + wait for five seconds, and so on. This tests RCU's + ability to transition abruptly to and from idle. + + rcutorture.test_boost= [KNL] + Test RCU priority boosting? 0=no, 1=maybe, 2=yes. + "Maybe" means test if the RCU implementation + under test support RCU priority boosting. + + rcutorture.test_boost_duration= [KNL] + Duration (s) of each individual boost test. + + rcutorture.test_boost_interval= [KNL] + Interval (s) between each boost test. + + rcutorture.test_no_idle_hz= [KNL] + Test RCU's dyntick-idle handling. See also the + rcutorture.shuffle_interval parameter. + + rcutorture.torture_type= [KNL] + Specify the RCU implementation to test. + + rcutorture.verbose= [KNL] + Enable additional printk() statements. + + rcupdate.rcu_cpu_stall_ftrace_dump= [KNL] + Dump ftrace buffer after reporting RCU CPU + stall warning. + + rcupdate.rcu_cpu_stall_suppress= [KNL] + Suppress RCU CPU stall warning messages. + + rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL] + Suppress RCU CPU stall warning messages and + rcutorture writer stall warnings that occur + during early boot, that is, during the time + before the init task is spawned. + + rcupdate.rcu_cpu_stall_timeout= [KNL] + Set timeout for RCU CPU stall warning messages. + The value is in seconds and the maximum allowed + value is 300 seconds. + + rcupdate.rcu_exp_cpu_stall_timeout= [KNL] + Set timeout for expedited RCU CPU stall warning + messages. The value is in milliseconds + and the maximum allowed value is 21000 + milliseconds. Please note that this value is + adjusted to an arch timer tick resolution. + Setting this to zero causes the value from + rcupdate.rcu_cpu_stall_timeout to be used (after + conversion from seconds to milliseconds). + + rcupdate.rcu_cpu_stall_cputime= [KNL] + Provide statistics on the cputime and count of + interrupts and tasks during the sampling period. For + multiple continuous RCU stalls, all sampling periods + begin at half of the first RCU stall timeout. + + rcupdate.rcu_exp_stall_task_details= [KNL] + Print stack dumps of any tasks blocking the + current expedited RCU grace period during an + expedited RCU CPU stall warning. + + rcupdate.rcu_expedited= [KNL] + Use expedited grace-period primitives, for + example, synchronize_rcu_expedited() instead + of synchronize_rcu(). This reduces latency, + but can increase CPU utilization, degrade + real-time latency, and degrade energy efficiency. + No effect on CONFIG_TINY_RCU kernels. + + rcupdate.rcu_normal= [KNL] + Use only normal grace-period primitives, + for example, synchronize_rcu() instead of + synchronize_rcu_expedited(). This improves + real-time latency, CPU utilization, and + energy efficiency, but can expose users to + increased grace-period latency. This parameter + overrides rcupdate.rcu_expedited. No effect on + CONFIG_TINY_RCU kernels. + + rcupdate.rcu_normal_after_boot= [KNL] + Once boot has completed (that is, after + rcu_end_inkernel_boot() has been invoked), use + only normal grace-period primitives. No effect + on CONFIG_TINY_RCU kernels. + + But note that CONFIG_PREEMPT_RT=y kernels enables + this kernel boot parameter, forcibly setting + it to the value one, that is, converting any + post-boot attempt at an expedited RCU grace + period to instead use normal non-expedited + grace-period processing. + + rcupdate.rcu_task_collapse_lim= [KNL] + Set the maximum number of callbacks present + at the beginning of a grace period that allows + the RCU Tasks flavors to collapse back to using + a single callback queue. This switching only + occurs when rcupdate.rcu_task_enqueue_lim is + set to the default value of -1. + + rcupdate.rcu_task_contend_lim= [KNL] + Set the minimum number of callback-queuing-time + lock-contention events per jiffy required to + cause the RCU Tasks flavors to switch to per-CPU + callback queuing. This switching only occurs + when rcupdate.rcu_task_enqueue_lim is set to + the default value of -1. + + rcupdate.rcu_task_enqueue_lim= [KNL] + Set the number of callback queues to use for the + RCU Tasks family of RCU flavors. The default + of -1 allows this to be automatically (and + dynamically) adjusted. This parameter is intended + for use in testing. + + rcupdate.rcu_task_ipi_delay= [KNL] + Set time in jiffies during which RCU tasks will + avoid sending IPIs, starting with the beginning + of a given grace period. Setting a large + number avoids disturbing real-time workloads, + but lengthens grace periods. + + rcupdate.rcu_task_lazy_lim= [KNL] + Number of callbacks on a given CPU that will + cancel laziness on that CPU. Use -1 to disable + cancellation of laziness, but be advised that + doing so increases the danger of OOM due to + callback flooding. + + rcupdate.rcu_task_stall_info= [KNL] + Set initial timeout in jiffies for RCU task stall + informational messages, which give some indication + of the problem for those not patient enough to + wait for ten minutes. Informational messages are + only printed prior to the stall-warning message + for a given grace period. Disable with a value + less than or equal to zero. Defaults to ten + seconds. A change in value does not take effect + until the beginning of the next grace period. + + rcupdate.rcu_task_stall_info_mult= [KNL] + Multiplier for time interval between successive + RCU task stall informational messages for a given + RCU tasks grace period. This value is clamped + to one through ten, inclusive. It defaults to + the value three, so that the first informational + message is printed 10 seconds into the grace + period, the second at 40 seconds, the third at + 160 seconds, and then the stall warning at 600 + seconds would prevent a fourth at 640 seconds. + + rcupdate.rcu_task_stall_timeout= [KNL] + Set timeout in jiffies for RCU task stall + warning messages. Disable with a value less + than or equal to zero. Defaults to ten minutes. + A change in value does not take effect until + the beginning of the next grace period. + + rcupdate.rcu_tasks_lazy_ms= [KNL] + Set timeout in milliseconds RCU Tasks asynchronous + callback batching for call_rcu_tasks(). + A negative value will take the default. A value + of zero will disable batching. Batching is + always disabled for synchronize_rcu_tasks(). + + rcupdate.rcu_tasks_rude_lazy_ms= [KNL] + Set timeout in milliseconds RCU Tasks + Rude asynchronous callback batching for + call_rcu_tasks_rude(). A negative value + will take the default. A value of zero will + disable batching. Batching is always disabled + for synchronize_rcu_tasks_rude(). + + rcupdate.rcu_tasks_trace_lazy_ms= [KNL] + Set timeout in milliseconds RCU Tasks + Trace asynchronous callback batching for + call_rcu_tasks_trace(). A negative value + will take the default. A value of zero will + disable batching. Batching is always disabled + for synchronize_rcu_tasks_trace(). + + rcupdate.rcu_self_test= [KNL] + Run the RCU early boot self tests + + rdinit= [KNL] + Format: <full_path> + Run specified binary instead of /init from the ramdisk, + used for early userspace startup. See initrd. + + rdrand= [X86] + force - Override the decision by the kernel to hide the + advertisement of RDRAND support (this affects + certain AMD processors because of buggy BIOS + support, specifically around the suspend/resume + path). + + rdt= [HW,X86,RDT] + Turn on/off individual RDT features. List is: + cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp, + mba, smba, bmec. + E.g. to turn on cmt and turn off mba use: + rdt=cmt,!mba + + reboot= [KNL] + Format (x86 or x86_64): + [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \ + [[,]s[mp]#### \ + [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \ + [[,]f[orce] + Where reboot_mode is one of warm (soft) or cold (hard) or gpio + (prefix with 'panic_' to set mode for panic + reboot only), + reboot_type is one of bios, acpi, kbd, triple, efi, or pci, + reboot_force is either force or not specified, + reboot_cpu is s[mp]#### with #### being the processor + to be used for rebooting. + + refscale.holdoff= [KNL] + Set test-start holdoff period. The purpose of + this parameter is to delay the start of the + test until boot completes in order to avoid + interference. + + refscale.loops= [KNL] + Set the number of loops over the synchronization + primitive under test. Increasing this number + reduces noise due to loop start/end overhead, + but the default has already reduced the per-pass + noise to a handful of picoseconds on ca. 2020 + x86 laptops. + + refscale.nreaders= [KNL] + Set number of readers. The default value of -1 + selects N, where N is roughly 75% of the number + of CPUs. A value of zero is an interesting choice. + + refscale.nruns= [KNL] + Set number of runs, each of which is dumped onto + the console log. + + refscale.readdelay= [KNL] + Set the read-side critical-section duration, + measured in microseconds. + + refscale.scale_type= [KNL] + Specify the read-protection implementation to test. + + refscale.shutdown= [KNL] + Shut down the system at the end of the performance + test. This defaults to 1 (shut it down) when + refscale is built into the kernel and to 0 (leave + it running) when refscale is built as a module. + + refscale.verbose= [KNL] + Enable additional printk() statements. + + refscale.verbose_batched= [KNL] + Batch the additional printk() statements. If zero + (the default) or negative, print everything. Otherwise, + print every Nth verbose statement, where N is the value + specified. + + relax_domain_level= + [KNL, SMP] Set scheduler's default relax_domain_level. + See Documentation/admin-guide/cgroup-v1/cpusets.rst. + + reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory + Format: <base1>,<size1>[,<base2>,<size2>,...] + Reserve I/O ports or memory so the kernel won't use + them. If <base> is less than 0x10000, the region + is assumed to be I/O ports; otherwise it is memory. + + reservetop= [X86-32] + Format: nn[KMG] + Reserves a hole at the top of the kernel virtual + address space. + + reset_devices [KNL] Force drivers to reset the underlying device + during initialization. + + resume= [SWSUSP] + Specify the partition device for software suspend + Format: + {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>} + + resume_offset= [SWSUSP] + Specify the offset from the beginning of the partition + given by "resume=" at which the swap header is located, + in <PAGE_SIZE> units (needed only for swap files). + See Documentation/power/swsusp-and-swap-files.rst + + resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to + read the resume files + + resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up. + Useful for devices that are detected asynchronously + (e.g. USB and MMC devices). + + retain_initrd [RAM] Keep initrd memory after extraction + + retbleed= [X86] Control mitigation of RETBleed (Arbitrary + Speculative Code Execution with Return Instructions) + vulnerability. + + AMD-based UNRET and IBPB mitigations alone do not stop + sibling threads from influencing the predictions of other + sibling threads. For that reason, STIBP is used on pro- + cessors that support it, and mitigate SMT on processors + that don't. + + off - no mitigation + auto - automatically select a migitation + auto,nosmt - automatically select a mitigation, + disabling SMT if necessary for + the full mitigation (only on Zen1 + and older without STIBP). + ibpb - On AMD, mitigate short speculation + windows on basic block boundaries too. + Safe, highest perf impact. It also + enables STIBP if present. Not suitable + on Intel. + ibpb,nosmt - Like "ibpb" above but will disable SMT + when STIBP is not available. This is + the alternative for systems which do not + have STIBP. + unret - Force enable untrained return thunks, + only effective on AMD f15h-f17h based + systems. + unret,nosmt - Like unret, but will disable SMT when STIBP + is not available. This is the alternative for + systems which do not have STIBP. + + Selecting 'auto' will choose a mitigation method at run + time according to the CPU. + + Not specifying this option is equivalent to retbleed=auto. + + rfkill.default_state= + 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm, + etc. communication is blocked by default. + 1 Unblocked. + + rfkill.master_switch_mode= + 0 The "airplane mode" button does nothing. + 1 The "airplane mode" button toggles between everything + blocked and the previous configuration. + 2 The "airplane mode" button toggles between everything + blocked and everything unblocked. + + rhash_entries= [KNL,NET] + Set number of hash buckets for route cache + + ring3mwait=disable + [KNL] Disable ring 3 MONITOR/MWAIT feature on supported + CPUs. + + riscv_isa_fallback [RISCV] + When CONFIG_RISCV_ISA_FALLBACK is not enabled, permit + falling back to detecting extension support by parsing + "riscv,isa" property on devicetree systems when the + replacement properties are not found. See the Kconfig + entry for RISCV_ISA_FALLBACK. + + ro [KNL] Mount root device read-only on boot + + rodata= [KNL] + on Mark read-only kernel memory as read-only (default). + off Leave read-only kernel memory writable for debugging. + full Mark read-only kernel memory and aliases as read-only + [arm64] + + rockchip.usb_uart + Enable the uart passthrough on the designated usb port + on Rockchip SoCs. When active, the signals of the + debug-uart get routed to the D+ and D- pins of the usb + port and the regular usb controller gets disabled. + + root= [KNL] Root filesystem + Usually this a a block device specifier of some kind, + see the early_lookup_bdev comment in + block/early-lookup.c for details. + Alternatively this can be "ram" for the legacy initial + ramdisk, "nfs" and "cifs" for root on a network file + system, or "mtd" and "ubi" for mounting from raw flash. + + rootdelay= [KNL] Delay (in seconds) to pause before attempting to + mount the root filesystem + + rootflags= [KNL] Set root filesystem mount option string + + rootfstype= [KNL] Set root filesystem type + + rootwait [KNL] Wait (indefinitely) for root device to show up. + Useful for devices that are detected asynchronously + (e.g. USB and MMC devices). + + rootwait= [KNL] Maximum time (in seconds) to wait for root device + to show up before attempting to mount the root + filesystem. + + rproc_mem=nn[KMG][@address] + [KNL,ARM,CMA] Remoteproc physical memory block. + Memory area to be used by remote processor image, + managed by CMA. + + rw [KNL] Mount root device read-write on boot + + S [KNL] Run init in single mode + + s390_iommu= [HW,S390] + Set s390 IOTLB flushing mode + strict + With strict flushing every unmap operation will result in + an IOTLB flush. Default is lazy flushing before reuse, + which is faster. + + s390_iommu_aperture= [KNL,S390] + Specifies the size of the per device DMA address space + accessible through the DMA and IOMMU APIs as a decimal + factor of the size of main memory. + The default is 1 meaning that one can concurrently use + as many DMA addresses as physical memory is installed, + if supported by hardware, and thus map all of memory + once. With a value of 2 one can map all of memory twice + and so on. As a special case a factor of 0 imposes no + restrictions other than those given by hardware at the + cost of significant additional memory use for tables. + + sa1100ir [NET] + See drivers/net/irda/sa1100_ir.c. + + sched_verbose [KNL] Enables verbose scheduler debug messages. + + schedstats= [KNL,X86] Enable or disable scheduled statistics. + Allowed values are enable and disable. This feature + incurs a small amount of overhead in the scheduler + but is useful for debugging and performance tuning. + + sched_thermal_decay_shift= + [KNL, SMP] Set a decay shift for scheduler thermal + pressure signal. Thermal pressure signal follows the + default decay period of other scheduler pelt + signals(usually 32 ms but configurable). Setting + sched_thermal_decay_shift will left shift the decay + period for the thermal pressure signal by the shift + value. + i.e. with the default pelt decay period of 32 ms + sched_thermal_decay_shift thermal pressure decay pr + 1 64 ms + 2 128 ms + and so on. + Format: integer between 0 and 10 + Default is 0. + + scftorture.holdoff= [KNL] + Number of seconds to hold off before starting + test. Defaults to zero for module insertion and + to 10 seconds for built-in smp_call_function() + tests. + + scftorture.longwait= [KNL] + Request ridiculously long waits randomly selected + up to the chosen limit in seconds. Zero (the + default) disables this feature. Please note + that requesting even small non-zero numbers of + seconds can result in RCU CPU stall warnings, + softlockup complaints, and so on. + + scftorture.nthreads= [KNL] + Number of kthreads to spawn to invoke the + smp_call_function() family of functions. + The default of -1 specifies a number of kthreads + equal to the number of CPUs. + + scftorture.onoff_holdoff= [KNL] + Number seconds to wait after the start of the + test before initiating CPU-hotplug operations. + + scftorture.onoff_interval= [KNL] + Number seconds to wait between successive + CPU-hotplug operations. Specifying zero (which + is the default) disables CPU-hotplug operations. + + scftorture.shutdown_secs= [KNL] + The number of seconds following the start of the + test after which to shut down the system. The + default of zero avoids shutting down the system. + Non-zero values are useful for automated tests. + + scftorture.stat_interval= [KNL] + The number of seconds between outputting the + current test statistics to the console. A value + of zero disables statistics output. + + scftorture.stutter_cpus= [KNL] + The number of jiffies to wait between each change + to the set of CPUs under test. + + scftorture.use_cpus_read_lock= [KNL] + Use use_cpus_read_lock() instead of the default + preempt_disable() to disable CPU hotplug + while invoking one of the smp_call_function*() + functions. + + scftorture.verbose= [KNL] + Enable additional printk() statements. + + scftorture.weight_single= [KNL] + The probability weighting to use for the + smp_call_function_single() function with a zero + "wait" parameter. A value of -1 selects the + default if all other weights are -1. However, + if at least one weight has some other value, a + value of -1 will instead select a weight of zero. + + scftorture.weight_single_wait= [KNL] + The probability weighting to use for the + smp_call_function_single() function with a + non-zero "wait" parameter. See weight_single. + + scftorture.weight_many= [KNL] + The probability weighting to use for the + smp_call_function_many() function with a zero + "wait" parameter. See weight_single. + Note well that setting a high probability for + this weighting can place serious IPI load + on the system. + + scftorture.weight_many_wait= [KNL] + The probability weighting to use for the + smp_call_function_many() function with a + non-zero "wait" parameter. See weight_single + and weight_many. + + scftorture.weight_all= [KNL] + The probability weighting to use for the + smp_call_function_all() function with a zero + "wait" parameter. See weight_single and + weight_many. + + scftorture.weight_all_wait= [KNL] + The probability weighting to use for the + smp_call_function_all() function with a + non-zero "wait" parameter. See weight_single + and weight_many. + + skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate + xtime_lock contention on larger systems, and/or RCU lock + contention on all systems with CONFIG_MAXSMP set. + Format: { "0" | "1" } + 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1" + 1 -- enable. + Note: increases power consumption, thus should only be + enabled if running jitter sensitive (HPC/RT) workloads. + + security= [SECURITY] Choose a legacy "major" security module to + enable at boot. This has been deprecated by the + "lsm=" parameter. + + selinux= [SELINUX] Disable or enable SELinux at boot time. + Format: { "0" | "1" } + See security/selinux/Kconfig help text. + 0 -- disable. + 1 -- enable. + Default value is 1. + + serialnumber [BUGS=X86-32] + + sev=option[,option...] [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst + + shapers= [NET] + Maximal number of shapers. + + show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller + Limit apic dumping. The parameter defines the maximal + number of local apics being dumped. Also it is possible + to set it to "all" by meaning -- no limit here. + Format: { 1 (default) | 2 | ... | all }. + The parameter valid if only apic=debug or + apic=verbose is specified. + Example: apic=debug show_lapic=all + + simeth= [IA-64] + simscsi= + + slram= [HW,MTD] + + slab_merge [MM] + Enable merging of slabs with similar size when the + kernel is built without CONFIG_SLAB_MERGE_DEFAULT. + + slab_nomerge [MM] + Disable merging of slabs with similar size. May be + necessary if there is some reason to distinguish + allocs to different slabs, especially in hardened + environments where the risk of heap overflows and + layout control by attackers can usually be + frustrated by disabling merging. This will reduce + most of the exposure of a heap attack to a single + cache (risks via metadata attacks are mostly + unchanged). Debug options disable merging on their + own. + For more information see Documentation/mm/slub.rst. + + slab_max_order= [MM, SLAB] + Determines the maximum allowed order for slabs. + A high setting may cause OOMs due to memory + fragmentation. Defaults to 1 for systems with + more than 32MB of RAM, 0 otherwise. + + slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB] + Enabling slub_debug allows one to determine the + culprit if slab objects become corrupted. Enabling + slub_debug can create guard zones around objects and + may poison objects when not in use. Also tracks the + last alloc / free. For more information see + Documentation/mm/slub.rst. + + slub_max_order= [MM, SLUB] + Determines the maximum allowed order for slabs. + A high setting may cause OOMs due to memory + fragmentation. For more information see + Documentation/mm/slub.rst. + + slub_min_objects= [MM, SLUB] + The minimum number of objects per slab. SLUB will + increase the slab order up to slub_max_order to + generate a sufficiently large slab able to contain + the number of objects indicated. The higher the number + of objects the smaller the overhead of tracking slabs + and the less frequently locks need to be acquired. + For more information see Documentation/mm/slub.rst. + + slub_min_order= [MM, SLUB] + Determines the minimum page order for slabs. Must be + lower than slub_max_order. + For more information see Documentation/mm/slub.rst. + + slub_merge [MM, SLUB] + Same with slab_merge. + + slub_nomerge [MM, SLUB] + Same with slab_nomerge. This is supported for legacy. + See slab_nomerge for more information. + + smart2= [HW] + Format: <io1>[,<io2>[,...,<io8>]] + + smp.csd_lock_timeout= [KNL] + Specify the period of time in milliseconds + that smp_call_function() and friends will wait + for a CPU to release the CSD lock. This is + useful when diagnosing bugs involving CPUs + disabling interrupts for extended periods + of time. Defaults to 5,000 milliseconds, and + setting a value of zero disables this feature. + This feature may be more efficiently disabled + using the csdlock_debug- kernel parameter. + + smp.panic_on_ipistall= [KNL] + If a csd_lock_timeout extends for more than + the specified number of milliseconds, panic the + system. By default, let CSD-lock acquisition + take as long as they take. Specifying 300,000 + for this value provides a 5-minute timeout. + + smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices + smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port + smsc-ircc2.ircc_sir= [HW] SIR base I/O port + smsc-ircc2.ircc_fir= [HW] FIR base I/O port + smsc-ircc2.ircc_irq= [HW] IRQ line + smsc-ircc2.ircc_dma= [HW] DMA channel + smsc-ircc2.ircc_transceiver= [HW] Transceiver type: + 0: Toshiba Satellite 1800 (GP data pin select) + 1: Fast pin select (default) + 2: ATC IRMode + + smt= [KNL,MIPS,S390] Set the maximum number of threads (logical + CPUs) to use per physical CPU on systems capable of + symmetric multithreading (SMT). Will be capped to the + actual hardware limit. + Format: <integer> + Default: -1 (no limit) + + softlockup_panic= + [KNL] Should the soft-lockup detector generate panics. + Format: 0 | 1 + + A value of 1 instructs the soft-lockup detector + to panic the machine when a soft-lockup occurs. It is + also controlled by the kernel.softlockup_panic sysctl + and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the + respective build-time switch to that functionality. + + softlockup_all_cpu_backtrace= + [KNL] Should the soft-lockup detector generate + backtraces on all cpus. + Format: 0 | 1 + + sonypi.*= [HW] Sony Programmable I/O Control Device driver + See Documentation/admin-guide/laptops/sonypi.rst + + spectre_v2= [X86] Control mitigation of Spectre variant 2 + (indirect branch speculation) vulnerability. + The default operation protects the kernel from + user space attacks. + + on - unconditionally enable, implies + spectre_v2_user=on + off - unconditionally disable, implies + spectre_v2_user=off + auto - kernel detects whether your CPU model is + vulnerable + + Selecting 'on' will, and 'auto' may, choose a + mitigation method at run time according to the + CPU, the available microcode, the setting of the + CONFIG_RETPOLINE configuration option, and the + compiler with which the kernel was built. + + Selecting 'on' will also enable the mitigation + against user space to user space task attacks. + + Selecting 'off' will disable both the kernel and + the user space protections. + + Specific mitigations can also be selected manually: + + retpoline - replace indirect branches + retpoline,generic - Retpolines + retpoline,lfence - LFENCE; indirect branch + retpoline,amd - alias for retpoline,lfence + eibrs - Enhanced/Auto IBRS + eibrs,retpoline - Enhanced/Auto IBRS + Retpolines + eibrs,lfence - Enhanced/Auto IBRS + LFENCE + ibrs - use IBRS to protect kernel + + Not specifying this option is equivalent to + spectre_v2=auto. + + spectre_v2_user= + [X86] Control mitigation of Spectre variant 2 + (indirect branch speculation) vulnerability between + user space tasks + + on - Unconditionally enable mitigations. Is + enforced by spectre_v2=on + + off - Unconditionally disable mitigations. Is + enforced by spectre_v2=off + + prctl - Indirect branch speculation is enabled, + but mitigation can be enabled via prctl + per thread. The mitigation control state + is inherited on fork. + + prctl,ibpb + - Like "prctl" above, but only STIBP is + controlled per thread. IBPB is issued + always when switching between different user + space processes. + + seccomp + - Same as "prctl" above, but all seccomp + threads will enable the mitigation unless + they explicitly opt out. + + seccomp,ibpb + - Like "seccomp" above, but only STIBP is + controlled per thread. IBPB is issued + always when switching between different + user space processes. + + auto - Kernel selects the mitigation depending on + the available CPU features and vulnerability. + + Default mitigation: "prctl" + + Not specifying this option is equivalent to + spectre_v2_user=auto. + + spec_rstack_overflow= + [X86] Control RAS overflow mitigation on AMD Zen CPUs + + off - Disable mitigation + microcode - Enable microcode mitigation only + safe-ret - Enable sw-only safe RET mitigation (default) + ibpb - Enable mitigation by issuing IBPB on + kernel entry + ibpb-vmexit - Issue IBPB only on VMEXIT + (cloud-specific mitigation) + + spec_store_bypass_disable= + [HW] Control Speculative Store Bypass (SSB) Disable mitigation + (Speculative Store Bypass vulnerability) + + Certain CPUs are vulnerable to an exploit against a + a common industry wide performance optimization known + as "Speculative Store Bypass" in which recent stores + to the same memory location may not be observed by + later loads during speculative execution. The idea + is that such stores are unlikely and that they can + be detected prior to instruction retirement at the + end of a particular speculation execution window. + + In vulnerable processors, the speculatively forwarded + store can be used in a cache side channel attack, for + example to read memory to which the attacker does not + directly have access (e.g. inside sandboxed code). + + This parameter controls whether the Speculative Store + Bypass optimization is used. + + On x86 the options are: + + on - Unconditionally disable Speculative Store Bypass + off - Unconditionally enable Speculative Store Bypass + auto - Kernel detects whether the CPU model contains an + implementation of Speculative Store Bypass and + picks the most appropriate mitigation. If the + CPU is not vulnerable, "off" is selected. If the + CPU is vulnerable the default mitigation is + architecture and Kconfig dependent. See below. + prctl - Control Speculative Store Bypass per thread + via prctl. Speculative Store Bypass is enabled + for a process by default. The state of the control + is inherited on fork. + seccomp - Same as "prctl" above, but all seccomp threads + will disable SSB unless they explicitly opt out. + + Default mitigations: + X86: "prctl" + + On powerpc the options are: + + on,auto - On Power8 and Power9 insert a store-forwarding + barrier on kernel entry and exit. On Power7 + perform a software flush on kernel entry and + exit. + off - No action. + + Not specifying this option is equivalent to + spec_store_bypass_disable=auto. + + spia_io_base= [HW,MTD] + spia_fio_base= + spia_pedr= + spia_peddr= + + split_lock_detect= + [X86] Enable split lock detection or bus lock detection + + When enabled (and if hardware support is present), atomic + instructions that access data across cache line + boundaries will result in an alignment check exception + for split lock detection or a debug exception for + bus lock detection. + + off - not enabled + + warn - the kernel will emit rate-limited warnings + about applications triggering the #AC + exception or the #DB exception. This mode is + the default on CPUs that support split lock + detection or bus lock detection. Default + behavior is by #AC if both features are + enabled in hardware. + + fatal - the kernel will send SIGBUS to applications + that trigger the #AC exception or the #DB + exception. Default behavior is by #AC if + both features are enabled in hardware. + + ratelimit:N - + Set system wide rate limit to N bus locks + per second for bus lock detection. + 0 < N <= 1000. + + N/A for split lock detection. + + + If an #AC exception is hit in the kernel or in + firmware (i.e. not while executing in user mode) + the kernel will oops in either "warn" or "fatal" + mode. + + #DB exception for bus lock is triggered only when + CPL > 0. + + srbds= [X86,INTEL] + Control the Special Register Buffer Data Sampling + (SRBDS) mitigation. + + Certain CPUs are vulnerable to an MDS-like + exploit which can leak bits from the random + number generator. + + By default, this issue is mitigated by + microcode. However, the microcode fix can cause + the RDRAND and RDSEED instructions to become + much slower. Among other effects, this will + result in reduced throughput from /dev/urandom. + + The microcode mitigation can be disabled with + the following option: + + off: Disable mitigation and remove + performance impact to RDRAND and RDSEED + + srcutree.big_cpu_lim [KNL] + Specifies the number of CPUs constituting a + large system, such that srcu_struct structures + should immediately allocate an srcu_node array. + This kernel-boot parameter defaults to 128, + but takes effect only when the low-order four + bits of srcutree.convert_to_big is equal to 3 + (decide at boot). + + srcutree.convert_to_big [KNL] + Specifies under what conditions an SRCU tree + srcu_struct structure will be converted to big + form, that is, with an rcu_node tree: + + 0: Never. + 1: At init_srcu_struct() time. + 2: When rcutorture decides to. + 3: Decide at boot time (default). + 0x1X: Above plus if high contention. + + Either way, the srcu_node tree will be sized based + on the actual runtime number of CPUs (nr_cpu_ids) + instead of the compile-time CONFIG_NR_CPUS. + + srcutree.counter_wrap_check [KNL] + Specifies how frequently to check for + grace-period sequence counter wrap for the + srcu_data structure's ->srcu_gp_seq_needed field. + The greater the number of bits set in this kernel + parameter, the less frequently counter wrap will + be checked for. Note that the bottom two bits + are ignored. + + srcutree.exp_holdoff [KNL] + Specifies how many nanoseconds must elapse + since the end of the last SRCU grace period for + a given srcu_struct until the next normal SRCU + grace period will be considered for automatic + expediting. Set to zero to disable automatic + expediting. + + srcutree.srcu_max_nodelay [KNL] + Specifies the number of no-delay instances + per jiffy for which the SRCU grace period + worker thread will be rescheduled with zero + delay. Beyond this limit, worker thread will + be rescheduled with a sleep delay of one jiffy. + + srcutree.srcu_max_nodelay_phase [KNL] + Specifies the per-grace-period phase, number of + non-sleeping polls of readers. Beyond this limit, + grace period worker thread will be rescheduled + with a sleep delay of one jiffy, between each + rescan of the readers, for a grace period phase. + + srcutree.srcu_retry_check_delay [KNL] + Specifies number of microseconds of non-sleeping + delay between each non-sleeping poll of readers. + + srcutree.small_contention_lim [KNL] + Specifies the number of update-side contention + events per jiffy will be tolerated before + initiating a conversion of an srcu_struct + structure to big form. Note that the value of + srcutree.convert_to_big must have the 0x10 bit + set for contention-based conversions to occur. + + ssbd= [ARM64,HW] + Speculative Store Bypass Disable control + + On CPUs that are vulnerable to the Speculative + Store Bypass vulnerability and offer a + firmware based mitigation, this parameter + indicates how the mitigation should be used: + + force-on: Unconditionally enable mitigation for + for both kernel and userspace + force-off: Unconditionally disable mitigation for + for both kernel and userspace + kernel: Always enable mitigation in the + kernel, and offer a prctl interface + to allow userspace to register its + interest in being mitigated too. + + stack_guard_gap= [MM] + override the default stack gap protection. The value + is in page units and it defines how many pages prior + to (for stacks growing down) resp. after (for stacks + growing up) the main stack are reserved for no other + mapping. Default value is 256 pages. + + stack_depot_disable= [KNL] + Setting this to true through kernel command line will + disable the stack depot thereby saving the static memory + consumed by the stack hash table. By default this is set + to false. + + stacktrace [FTRACE] + Enabled the stack tracer on boot up. + + stacktrace_filter=[function-list] + [FTRACE] Limit the functions that the stack tracer + will trace at boot up. function-list is a comma-separated + list of functions. This list can be changed at run + time by the stack_trace_filter file in the debugfs + tracing directory. Note, this enables stack tracing + and the stacktrace above is not needed. + + sti= [PARISC,HW] + Format: <num> + Set the STI (builtin display/keyboard on the HP-PARISC + machines) console (graphic card) which should be used + as the initial boot-console. + See also comment in drivers/video/console/sticore.c. + + sti_font= [HW] + See comment in drivers/video/console/sticore.c. + + stifb= [HW] + Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] + + strict_sas_size= + [X86] + Format: <bool> + Enable or disable strict sigaltstack size checks + against the required signal frame size which + depends on the supported FPU features. This can + be used to filter out binaries which have + not yet been made aware of AT_MINSIGSTKSZ. + + stress_hpt [PPC] + Limits the number of kernel HPT entries in the hash + page table to increase the rate of hash page table + faults on kernel addresses. + + stress_slb [PPC] + Limits the number of kernel SLB entries, and flushes + them frequently to increase the rate of SLB faults + on kernel addresses. + + sunrpc.min_resvport= + sunrpc.max_resvport= + [NFS,SUNRPC] + SunRPC servers often require that client requests + originate from a privileged port (i.e. a port in the + range 0 < portnr < 1024). + An administrator who wishes to reserve some of these + ports for other uses may adjust the range that the + kernel's sunrpc client considers to be privileged + using these two parameters to set the minimum and + maximum port values. + + sunrpc.svc_rpc_per_connection_limit= + [NFS,SUNRPC] + Limit the number of requests that the server will + process in parallel from a single connection. + The default value is 0 (no limit). + + sunrpc.pool_mode= + [NFS] + Control how the NFS server code allocates CPUs to + service thread pools. Depending on how many NICs + you have and where their interrupts are bound, this + option will affect which CPUs will do NFS serving. + Note: this parameter cannot be changed while the + NFS server is running. + + auto the server chooses an appropriate mode + automatically using heuristics + global a single global pool contains all CPUs + percpu one pool for each CPU + pernode one pool for each NUMA node (equivalent + to global on non-NUMA machines) + + sunrpc.tcp_slot_table_entries= + sunrpc.udp_slot_table_entries= + [NFS,SUNRPC] + Sets the upper limit on the number of simultaneous + RPC calls that can be sent from the client to a + server. Increasing these values may allow you to + improve throughput, but will also increase the + amount of memory reserved for use by the client. + + suspend.pm_test_delay= + [SUSPEND] + Sets the number of seconds to remain in a suspend test + mode before resuming the system (see + /sys/power/pm_test). Only available when CONFIG_PM_DEBUG + is set. Default value is 5. + + svm= [PPC] + Format: { on | off | y | n | 1 | 0 } + This parameter controls use of the Protected + Execution Facility on pSeries. + + swiotlb= [ARM,IA-64,PPC,MIPS,X86] + Format: { <int> [,<int>] | force | noforce } + <int> -- Number of I/O TLB slabs + <int> -- Second integer after comma. Number of swiotlb + areas with their own lock. Will be rounded up + to a power of 2. + force -- force using of bounce buffers even if they + wouldn't be automatically used by the kernel + noforce -- Never use bounce buffers (for debugging) + + switches= [HW,M68k] + + sysctl.*= [KNL] + Set a sysctl parameter, right before loading the init + process, as if the value was written to the respective + /proc/sys/... file. Both '.' and '/' are recognized as + separators. Unrecognized parameters and invalid values + are reported in the kernel log. Sysctls registered + later by a loaded module cannot be set this way. + Example: sysctl.vm.swappiness=40 + + sysrq_always_enabled + [KNL] + Ignore sysrq setting - this boot parameter will + neutralize any effect of /proc/sys/kernel/sysrq. + Useful for debugging. + + tcpmhash_entries= [KNL,NET] + Set the number of tcp_metrics_hash slots. + Default value is 8192 or 16384 depending on total + ram pages. This is used to specify the TCP metrics + cache size. See Documentation/networking/ip-sysctl.rst + "tcp_no_metrics_save" section for more details. + + tdfx= [HW,DRM] + + test_suspend= [SUSPEND] + Format: { "mem" | "standby" | "freeze" }[,N] + Specify "mem" (for Suspend-to-RAM) or "standby" (for + standby suspend) or "freeze" (for suspend type freeze) + as the system sleep state during system startup with + the optional capability to repeat N number of times. + The system is woken from this state using a + wakeup-capable RTC alarm. + + thash_entries= [KNL,NET] + Set number of hash buckets for TCP connection + + thermal.act= [HW,ACPI] + -1: disable all active trip points in all thermal zones + <degrees C>: override all lowest active trip points + + thermal.crt= [HW,ACPI] + -1: disable all critical trip points in all thermal zones + <degrees C>: override all critical trip points + + thermal.off= [HW,ACPI] + 1: disable ACPI thermal control + + thermal.psv= [HW,ACPI] + -1: disable all passive trip points + <degrees C>: override all passive trip points to this + value + + thermal.tzp= [HW,ACPI] + Specify global default ACPI thermal zone polling rate + <deci-seconds>: poll all this frequency + 0: no polling (default) + + threadirqs [KNL] + Force threading of all interrupt handlers except those + marked explicitly IRQF_NO_THREAD. + + topology= [S390] + Format: {off | on} + Specify if the kernel should make use of the cpu + topology information if the hardware supports this. + The scheduler will make use of this information and + e.g. base its process migration decisions on it. + Default is on. + + topology_updates= [KNL, PPC, NUMA] + Format: {off} + Specify if the kernel should ignore (off) + topology updates sent by the hypervisor to this + LPAR. + + torture.disable_onoff_at_boot= [KNL] + Prevent the CPU-hotplug component of torturing + until after init has spawned. + + torture.ftrace_dump_at_shutdown= [KNL] + Dump the ftrace buffer at torture-test shutdown, + even if there were no errors. This can be a + very costly operation when many torture tests + are running concurrently, especially on systems + with rotating-rust storage. + + torture.verbose_sleep_frequency= [KNL] + Specifies how many verbose printk()s should be + emitted between each sleep. The default of zero + disables verbose-printk() sleeping. + + torture.verbose_sleep_duration= [KNL] + Duration of each verbose-printk() sleep in jiffies. + + tp720= [HW,PS2] + + tpm_suspend_pcr=[HW,TPM] + Format: integer pcr id + Specify that at suspend time, the tpm driver + should extend the specified pcr with zeros, + as a workaround for some chips which fail to + flush the last written pcr on TPM_SaveState. + This will guarantee that all the other pcrs + are saved. + + tpm_tis.interrupts= [HW,TPM] + Enable interrupts for the MMIO based physical layer + for the FIFO interface. By default it is set to false + (0). For more information about TPM hardware interfaces + defined by Trusted Computing Group (TCG) see + https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/ + + tp_printk [FTRACE] + Have the tracepoints sent to printk as well as the + tracing ring buffer. This is useful for early boot up + where the system hangs or reboots and does not give the + option for reading the tracing buffer or performing a + ftrace_dump_on_oops. + + To turn off having tracepoints sent to printk, + echo 0 > /proc/sys/kernel/tracepoint_printk + Note, echoing 1 into this file without the + tracepoint_printk kernel cmdline option has no effect. + + The tp_printk_stop_on_boot (see below) can also be used + to stop the printing of events to console at + late_initcall_sync. + + ** CAUTION ** + + Having tracepoints sent to printk() and activating high + frequency tracepoints such as irq or sched, can cause + the system to live lock. + + tp_printk_stop_on_boot [FTRACE] + When tp_printk (above) is set, it can cause a lot of noise + on the console. It may be useful to only include the + printing of events during boot up, as user space may + make the system inoperable. + + This command line option will stop the printing of events + to console at the late_initcall_sync() time frame. + + trace_buf_size=nn[KMG] + [FTRACE] will set tracing buffer size on each cpu. + + trace_clock= [FTRACE] Set the clock used for tracing events + at boot up. + local - Use the per CPU time stamp counter + (converted into nanoseconds). Fast, but + depending on the architecture, may not be + in sync between CPUs. + global - Event time stamps are synchronize across + CPUs. May be slower than the local clock, + but better for some race conditions. + counter - Simple counting of events (1, 2, ..) + note, some counts may be skipped due to the + infrastructure grabbing the clock more than + once per event. + uptime - Use jiffies as the time stamp. + perf - Use the same clock that perf uses. + mono - Use ktime_get_mono_fast_ns() for time stamps. + mono_raw - Use ktime_get_raw_fast_ns() for time + stamps. + boot - Use ktime_get_boot_fast_ns() for time stamps. + Architectures may add more clocks. See + Documentation/trace/ftrace.rst for more details. + + trace_event=[event-list] + [FTRACE] Set and start specified trace events in order + to facilitate early boot debugging. The event-list is a + comma-separated list of trace events to enable. See + also Documentation/trace/events.rst + + trace_instance=[instance-info] + [FTRACE] Create a ring buffer instance early in boot up. + This will be listed in: + + /sys/kernel/tracing/instances + + Events can be enabled at the time the instance is created + via: + + trace_instance=<name>,<system1>:<event1>,<system2>:<event2> + + Note, the "<system*>:" portion is optional if the event is + unique. + + trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall + + will enable the "sched_switch" event (note, the "sched:" is optional, and + the same thing would happen if it was left off). The irq_handler_entry + event, and all events under the "initcall" system. + + trace_options=[option-list] + [FTRACE] Enable or disable tracer options at boot. + The option-list is a comma delimited list of options + that can be enabled or disabled just as if you were + to echo the option name into + + /sys/kernel/tracing/trace_options + + For example, to enable stacktrace option (to dump the + stack trace of each event), add to the command line: + + trace_options=stacktrace + + See also Documentation/trace/ftrace.rst "trace options" + section. + + trace_trigger=[trigger-list] + [FTRACE] Add a event trigger on specific events. + Set a trigger on top of a specific event, with an optional + filter. + + The format is is "trace_trigger=<event>.<trigger>[ if <filter>],..." + Where more than one trigger may be specified that are comma deliminated. + + For example: + + trace_trigger="sched_switch.stacktrace if prev_state == 2" + + The above will enable the "stacktrace" trigger on the "sched_switch" + event but only trigger it if the "prev_state" of the "sched_switch" + event is "2" (TASK_UNINTERUPTIBLE). + + See also "Event triggers" in Documentation/trace/events.rst + + + traceoff_on_warning + [FTRACE] enable this option to disable tracing when a + warning is hit. This turns off "tracing_on". Tracing can + be enabled again by echoing '1' into the "tracing_on" + file located in /sys/kernel/tracing/ + + This option is useful, as it disables the trace before + the WARNING dump is called, which prevents the trace to + be filled with content caused by the warning output. + + This option can also be set at run time via the sysctl + option: kernel/traceoff_on_warning + + transparent_hugepage= + [KNL] + Format: [always|madvise|never] + Can be used to control the default behavior of the system + with respect to transparent hugepages. + See Documentation/admin-guide/mm/transhuge.rst + for more details. + + trusted.source= [KEYS] + Format: <string> + This parameter identifies the trust source as a backend + for trusted keys implementation. Supported trust + sources: + - "tpm" + - "tee" + - "caam" + If not specified then it defaults to iterating through + the trust source list starting with TPM and assigns the + first trust source as a backend which is initialized + successfully during iteration. + + trusted.rng= [KEYS] + Format: <string> + The RNG used to generate key material for trusted keys. + Can be one of: + - "kernel" + - the same value as trusted.source: "tpm" or "tee" + - "default" + If not specified, "default" is used. In this case, + the RNG's choice is left to each individual trust source. + + tsc= Disable clocksource stability checks for TSC. + Format: <string> + [x86] reliable: mark tsc clocksource as reliable, this + disables clocksource verification at runtime, as well + as the stability checks done at bootup. Used to enable + high-resolution timer mode on older hardware, and in + virtualized environment. + [x86] noirqtime: Do not use TSC to do irq accounting. + Used to run time disable IRQ_TIME_ACCOUNTING on any + platforms where RDTSC is slow and this accounting + can add overhead. + [x86] unstable: mark the TSC clocksource as unstable, this + marks the TSC unconditionally unstable at bootup and + avoids any further wobbles once the TSC watchdog notices. + [x86] nowatchdog: disable clocksource watchdog. Used + in situations with strict latency requirements (where + interruptions from clocksource watchdog are not + acceptable). + [x86] recalibrate: force recalibration against a HW timer + (HPET or PM timer) on systems whose TSC frequency was + obtained from HW or FW using either an MSR or CPUID(0x15). + Warn if the difference is more than 500 ppm. + [x86] watchdog: Use TSC as the watchdog clocksource with + which to check other HW timers (HPET or PM timer), but + only on systems where TSC has been deemed trustworthy. + This will be suppressed by an earlier tsc=nowatchdog and + can be overridden by a later tsc=nowatchdog. A console + message will flag any such suppression or overriding. + + tsc_early_khz= [X86] Skip early TSC calibration and use the given + value instead. Useful when the early TSC frequency discovery + procedure is not reliable, such as on overclocked systems + with CPUID.16h support and partial CPUID.15h support. + Format: <unsigned int> + + tsx= [X86] Control Transactional Synchronization + Extensions (TSX) feature in Intel processors that + support TSX control. + + This parameter controls the TSX feature. The options are: + + on - Enable TSX on the system. Although there are + mitigations for all known security vulnerabilities, + TSX has been known to be an accelerator for + several previous speculation-related CVEs, and + so there may be unknown security risks associated + with leaving it enabled. + + off - Disable TSX on the system. (Note that this + option takes effect only on newer CPUs which are + not vulnerable to MDS, i.e., have + MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get + the new IA32_TSX_CTRL MSR through a microcode + update. This new MSR allows for the reliable + deactivation of the TSX functionality.) + + auto - Disable TSX if X86_BUG_TAA is present, + otherwise enable TSX on the system. + + Not specifying this option is equivalent to tsx=off. + + See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst + for more details. + + tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async + Abort (TAA) vulnerability. + + Similar to Micro-architectural Data Sampling (MDS) + certain CPUs that support Transactional + Synchronization Extensions (TSX) are vulnerable to an + exploit against CPU internal buffers which can forward + information to a disclosure gadget under certain + conditions. + + In vulnerable processors, the speculatively forwarded + data can be used in a cache side channel attack, to + access data to which the attacker does not have direct + access. + + This parameter controls the TAA mitigation. The + options are: + + full - Enable TAA mitigation on vulnerable CPUs + if TSX is enabled. + + full,nosmt - Enable TAA mitigation and disable SMT on + vulnerable CPUs. If TSX is disabled, SMT + is not disabled because CPU is not + vulnerable to cross-thread TAA attacks. + off - Unconditionally disable TAA mitigation + + On MDS-affected machines, tsx_async_abort=off can be + prevented by an active MDS mitigation as both vulnerabilities + are mitigated with the same mechanism so in order to disable + this mitigation, you need to specify mds=off too. + + Not specifying this option is equivalent to + tsx_async_abort=full. On CPUs which are MDS affected + and deploy MDS mitigation, TAA mitigation is not + required and doesn't provide any additional + mitigation. + + For details see: + Documentation/admin-guide/hw-vuln/tsx_async_abort.rst + + turbografx.map[2|3]= [HW,JOY] + TurboGraFX parallel port interface + Format: + <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> + See also Documentation/input/devices/joystick-parport.rst + + udbg-immortal [PPC] When debugging early kernel crashes that + happen after console_init() and before a proper + console driver takes over, this boot options might + help "seeing" what's going on. + + uhash_entries= [KNL,NET] + Set number of hash buckets for UDP/UDP-Lite connections + + uhci-hcd.ignore_oc= + [USB] Ignore overcurrent events (default N). + Some badly-designed motherboards generate lots of + bogus events, for ports that aren't wired to + anything. Set this parameter to avoid log spamming. + Note that genuine overcurrent events won't be + reported either. + + unknown_nmi_panic + [X86] Cause panic on unknown NMI. + + unwind_debug [X86-64] + Enable unwinder debug output. This can be + useful for debugging certain unwinder error + conditions, including corrupt stacks and + bad/missing unwinder metadata. + + usbcore.authorized_default= + [USB] Default USB device authorization: + (default -1 = authorized (same as 1), + 0 = not authorized, 1 = authorized, 2 = authorized + if device connected to internal port) + + usbcore.autosuspend= + [USB] The autosuspend time delay (in seconds) used + for newly-detected USB devices (default 2). This + is the time required before an idle device will be + autosuspended. Devices for which the delay is set + to a negative value won't be autosuspended at all. + + usbcore.usbfs_snoop= + [USB] Set to log all usbfs traffic (default 0 = off). + + usbcore.usbfs_snoop_max= + [USB] Maximum number of bytes to snoop in each URB + (default = 65536). + + usbcore.blinkenlights= + [USB] Set to cycle leds on hubs (default 0 = off). + + usbcore.old_scheme_first= + [USB] Start with the old device initialization + scheme (default 0 = off). + + usbcore.usbfs_memory_mb= + [USB] Memory limit (in MB) for buffers allocated by + usbfs (default = 16, 0 = max = 2047). + + usbcore.use_both_schemes= + [USB] Try the other device initialization scheme + if the first one fails (default 1 = enabled). + + usbcore.initial_descriptor_timeout= + [USB] Specifies timeout for the initial 64-byte + USB_REQ_GET_DESCRIPTOR request in milliseconds + (default 5000 = 5.0 seconds). + + usbcore.nousb [USB] Disable the USB subsystem + + usbcore.quirks= + [USB] A list of quirk entries to augment the built-in + usb core quirk list. List entries are separated by + commas. Each entry has the form + VendorID:ProductID:Flags. The IDs are 4-digit hex + numbers and Flags is a set of letters. Each letter + will change the built-in quirk; setting it if it is + clear and clearing it if it is set. The letters have + the following meanings: + a = USB_QUIRK_STRING_FETCH_255 (string + descriptors must not be fetched using + a 255-byte read); + b = USB_QUIRK_RESET_RESUME (device can't resume + correctly so reset it instead); + c = USB_QUIRK_NO_SET_INTF (device can't handle + Set-Interface requests); + d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't + handle its Configuration or Interface + strings); + e = USB_QUIRK_RESET (device can't be reset + (e.g morph devices), don't use reset); + f = USB_QUIRK_HONOR_BNUMINTERFACES (device has + more interface descriptions than the + bNumInterfaces count, and can't handle + talking to these interfaces); + g = USB_QUIRK_DELAY_INIT (device needs a pause + during initialization, after we read + the device descriptor); + h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For + high speed and super speed interrupt + endpoints, the USB 2.0 and USB 3.0 spec + require the interval in microframes (1 + microframe = 125 microseconds) to be + calculated as interval = 2 ^ + (bInterval-1). + Devices with this quirk report their + bInterval as the result of this + calculation instead of the exponent + variable used in the calculation); + i = USB_QUIRK_DEVICE_QUALIFIER (device can't + handle device_qualifier descriptor + requests); + j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device + generates spurious wakeup, ignore + remote wakeup capability); + k = USB_QUIRK_NO_LPM (device can't handle Link + Power Management); + l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL + (Device reports its bInterval as linear + frames instead of the USB 2.0 + calculation); + m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs + to be disconnected before suspend to + prevent spurious wakeup); + n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a + pause after every control message); + o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra + delay after resetting its port); + Example: quirks=0781:5580:bk,0a5c:5834:gij + + usbhid.mousepoll= + [USBHID] The interval which mice are to be polled at. + + usbhid.jspoll= + [USBHID] The interval which joysticks are to be polled at. + + usbhid.kbpoll= + [USBHID] The interval which keyboards are to be polled at. + + usb-storage.delay_use= + [UMS] The delay in seconds before a new device is + scanned for Logical Units (default 1). + + usb-storage.quirks= + [UMS] A list of quirks entries to supplement or + override the built-in unusual_devs list. List + entries are separated by commas. Each entry has + the form VID:PID:Flags where VID and PID are Vendor + and Product ID values (4-digit hex numbers) and + Flags is a set of characters, each corresponding + to a common usb-storage quirk flag as follows: + a = SANE_SENSE (collect more than 18 bytes + of sense data, not on uas); + b = BAD_SENSE (don't collect more than 18 + bytes of sense data, not on uas); + c = FIX_CAPACITY (decrease the reported + device capacity by one sector); + d = NO_READ_DISC_INFO (don't use + READ_DISC_INFO command, not on uas); + e = NO_READ_CAPACITY_16 (don't use + READ_CAPACITY_16 command); + f = NO_REPORT_OPCODES (don't use report opcodes + command, uas only); + g = MAX_SECTORS_240 (don't transfer more than + 240 sectors at a time, uas only); + h = CAPACITY_HEURISTICS (decrease the + reported device capacity by one + sector if the number is odd); + i = IGNORE_DEVICE (don't bind to this + device); + j = NO_REPORT_LUNS (don't use report luns + command, uas only); + k = NO_SAME (do not use WRITE_SAME, uas only) + l = NOT_LOCKABLE (don't try to lock and + unlock ejectable media, not on uas); + m = MAX_SECTORS_64 (don't transfer more + than 64 sectors = 32 KB at a time, + not on uas); + n = INITIAL_READ10 (force a retry of the + initial READ(10) command, not on uas); + o = CAPACITY_OK (accept the capacity + reported by the device, not on uas); + p = WRITE_CACHE (the device cache is ON + by default, not on uas); + r = IGNORE_RESIDUE (the device reports + bogus residue values, not on uas); + s = SINGLE_LUN (the device has only one + Logical Unit); + t = NO_ATA_1X (don't allow ATA(12) and ATA(16) + commands, uas only); + u = IGNORE_UAS (don't bind to the uas driver); + w = NO_WP_DETECT (don't test whether the + medium is write-protected). + y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE + even if the device claims no cache, + not on uas) + Example: quirks=0419:aaf5:rl,0421:0433:rc + + user_debug= [KNL,ARM] + Format: <int> + See arch/arm/Kconfig.debug help text. + 1 - undefined instruction events + 2 - system calls + 4 - invalid data aborts + 8 - SIGSEGV faults + 16 - SIGBUS faults + Example: user_debug=31 + + userpte= + [X86] Flags controlling user PTE allocations. + + nohigh = do not allocate PTE pages in + HIGHMEM regardless of setting + of CONFIG_HIGHPTE. + + vdso= [X86,SH,SPARC] + On X86_32, this is an alias for vdso32=. Otherwise: + + vdso=1: enable VDSO (the default) + vdso=0: disable VDSO mapping + + vdso32= [X86] Control the 32-bit vDSO + vdso32=1: enable 32-bit VDSO + vdso32=0 or vdso32=2: disable 32-bit VDSO + + See the help text for CONFIG_COMPAT_VDSO for more + details. If CONFIG_COMPAT_VDSO is set, the default is + vdso32=0; otherwise, the default is vdso32=1. + + For compatibility with older kernels, vdso32=2 is an + alias for vdso32=0. + + Try vdso32=0 if you encounter an error that says: + dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed! + + vector= [IA-64,SMP] + vector=percpu: enable percpu vector domain + + video= [FB] Frame buffer configuration + See Documentation/fb/modedb.rst. + + video.brightness_switch_enabled= [ACPI] + Format: [0|1] + If set to 1, on receiving an ACPI notify event + generated by hotkey, video driver will adjust brightness + level and then send out the event to user space through + the allocated input device. If set to 0, video driver + will only send out the event without touching backlight + brightness level. + default: 1 + + virtio_mmio.device= + [VMMIO] Memory mapped virtio (platform) device. + + <size>@<baseaddr>:<irq>[:<id>] + where: + <size> := size (can use standard suffixes + like K, M and G) + <baseaddr> := physical base address + <irq> := interrupt number (as passed to + request_irq()) + <id> := (optional) platform device id + example: + virtio_mmio.device=1K@0x100b0000:48:7 + + Can be used multiple times for multiple devices. + + vga= [BOOT,X86-32] Select a particular video mode + See Documentation/arch/x86/boot.rst and + Documentation/admin-guide/svga.rst. + Use vga=ask for menu. + This is actually a boot loader parameter; the value is + passed to the kernel using a special protocol. + + vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y. + May slow down system boot speed, especially when + enabled on systems with a large amount of memory. + All options are enabled by default, and this + interface is meant to allow for selectively + enabling or disabling specific virtual memory + debugging features. + + Available options are: + P Enable page structure init time poisoning + - Disable all of the above options + + vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact + size of <nn>. This can be used to increase the + minimum size (128MB on x86). It can also be used to + decrease the size and leave more room for directly + mapped kernel RAM. + + vmcp_cma=nn[MG] [KNL,S390] + Sets the memory size reserved for contiguous memory + allocations for the vmcp device driver. + + vmhalt= [KNL,S390] Perform z/VM CP command after system halt. + Format: <command> + + vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. + Format: <command> + + vmpoff= [KNL,S390] Perform z/VM CP command after power off. + Format: <command> + + vsyscall= [X86-64] + Controls the behavior of vsyscalls (i.e. calls to + fixed addresses of 0xffffffffff600x00 from legacy + code). Most statically-linked binaries and older + versions of glibc use these calls. Because these + functions are at fixed addresses, they make nice + targets for exploits that can control RIP. + + emulate Vsyscalls turn into traps and are emulated + reasonably safely. The vsyscall page is + readable. + + xonly [default] Vsyscalls turn into traps and are + emulated reasonably safely. The vsyscall + page is not readable. + + none Vsyscalls don't work at all. This makes + them quite hard to use for exploits but + might break your system. + + vt.color= [VT] Default text color. + Format: 0xYX, X = foreground, Y = background. + Default: 0x07 = light gray on black. + + vt.cur_default= [VT] Default cursor shape. + Format: 0xCCBBAA, where AA, BB, and CC are the same as + the parameters of the <Esc>[?A;B;Cc escape sequence; + see VGA-softcursor.txt. Default: 2 = underline. + + vt.default_blu= [VT] + Format: <blue0>,<blue1>,<blue2>,...,<blue15> + Change the default blue palette of the console. + This is a 16-member array composed of values + ranging from 0-255. + + vt.default_grn= [VT] + Format: <green0>,<green1>,<green2>,...,<green15> + Change the default green palette of the console. + This is a 16-member array composed of values + ranging from 0-255. + + vt.default_red= [VT] + Format: <red0>,<red1>,<red2>,...,<red15> + Change the default red palette of the console. + This is a 16-member array composed of values + ranging from 0-255. + + vt.default_utf8= + [VT] + Format=<0|1> + Set system-wide default UTF-8 mode for all tty's. + Default is 1, i.e. UTF-8 mode is enabled for all + newly opened terminals. + + vt.global_cursor_default= + [VT] + Format=<-1|0|1> + Set system-wide default for whether a cursor + is shown on new VTs. Default is -1, + i.e. cursors will be created by default unless + overridden by individual drivers. 0 will hide + cursors, 1 will display them. + + vt.italic= [VT] Default color for italic text; 0-15. + Default: 2 = green. + + vt.underline= [VT] Default color for underlined text; 0-15. + Default: 3 = cyan. + + watchdog timers [HW,WDT] For information on watchdog timers, + see Documentation/watchdog/watchdog-parameters.rst + or other driver-specific files in the + Documentation/watchdog/ directory. + + watchdog_thresh= + [KNL] + Set the hard lockup detector stall duration + threshold in seconds. The soft lockup detector + threshold is set to twice the value. A value of 0 + disables both lockup detectors. Default is 10 + seconds. + + workqueue.unbound_cpus= + [KNL,SMP] Specify to constrain one or some CPUs + to use in unbound workqueues. + Format: <cpu-list> + By default, all online CPUs are available for + unbound workqueues. + + workqueue.watchdog_thresh= + If CONFIG_WQ_WATCHDOG is configured, workqueue can + warn stall conditions and dump internal state to + help debugging. 0 disables workqueue stall + detection; otherwise, it's the stall threshold + duration in seconds. The default value is 30 and + it can be updated at runtime by writing to the + corresponding sysfs file. + + workqueue.cpu_intensive_thresh_us= + Per-cpu work items which run for longer than this + threshold are automatically considered CPU intensive + and excluded from concurrency management to prevent + them from noticeably delaying other per-cpu work + items. Default is 10000 (10ms). + + If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel + will report the work functions which violate this + threshold repeatedly. They are likely good + candidates for using WQ_UNBOUND workqueues instead. + + workqueue.power_efficient + Per-cpu workqueues are generally preferred because + they show better performance thanks to cache + locality; unfortunately, per-cpu workqueues tend to + be more power hungry than unbound workqueues. + + Enabling this makes the per-cpu workqueues which + were observed to contribute significantly to power + consumption unbound, leading to measurably lower + power usage at the cost of small performance + overhead. + + The default value of this parameter is determined by + the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT. + + workqueue.default_affinity_scope= + Select the default affinity scope to use for unbound + workqueues. Can be one of "cpu", "smt", "cache", + "numa" and "system". Default is "cache". For more + information, see the Affinity Scopes section in + Documentation/core-api/workqueue.rst. + + This can be changed after boot by writing to the + matching /sys/module/workqueue/parameters file. All + workqueues with the "default" affinity scope will be + updated accordignly. + + workqueue.debug_force_rr_cpu + Workqueue used to implicitly guarantee that work + items queued without explicit CPU specified are put + on the local CPU. This guarantee is no longer true + and while local CPU is still preferred work items + may be put on foreign CPUs. This debug option + forces round-robin CPU selection to flush out + usages which depend on the now broken guarantee. + When enabled, memory and cache locality will be + impacted. + + writecombine= [LOONGARCH] Control the MAT (Memory Access Type) of + ioremap_wc(). + + on - Enable writecombine, use WUC for ioremap_wc() + off - Disable writecombine, use SUC for ioremap_wc() + + x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of + default x2apic cluster mode on platforms + supporting x2apic. + + xen_512gb_limit [KNL,X86-64,XEN] + Restricts the kernel running paravirtualized under Xen + to use only up to 512 GB of RAM. The reason to do so is + crash analysis tools and Xen tools for doing domain + save/restore/migration must be enabled to handle larger + domains. + + xen_emul_unplug= [HW,X86,XEN] + Unplug Xen emulated devices + Format: [unplug0,][unplug1] + ide-disks -- unplug primary master IDE devices + aux-ide-disks -- unplug non-primary-master IDE devices + nics -- unplug network devices + all -- unplug all emulated devices (NICs and IDE disks) + unnecessary -- unplugging emulated devices is + unnecessary even if the host did not respond to + the unplug protocol + never -- do not unplug even if version check succeeds + + xen_legacy_crash [X86,XEN] + Crash from Xen panic notifier, without executing late + panic() code such as dumping handler. + + xen_msr_safe= [X86,XEN] + Format: <bool> + Select whether to always use non-faulting (safe) MSR + access functions when running as Xen PV guest. The + default value is controlled by CONFIG_XEN_PV_MSR_SAFE. + + xen_nopvspin [X86,XEN] + Disables the qspinlock slowpath using Xen PV optimizations. + This parameter is obsoleted by "nopvspin" parameter, which + has equivalent effect for XEN platform. + + xen_nopv [X86] + Disables the PV optimizations forcing the HVM guest to + run as generic HVM guest with no PV drivers. + This option is obsoleted by the "nopv" option, which + has equivalent effect for XEN platform. + + xen_no_vector_callback + [KNL,X86,XEN] Disable the vector callback for Xen + event channel interrupts. + + xen_scrub_pages= [XEN] + Boolean option to control scrubbing pages before giving them back + to Xen, for use by other domains. Can be also changed at runtime + with /sys/devices/system/xen_memory/xen_memory0/scrub_pages. + Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT. + + xen_timer_slop= [X86-64,XEN] + Set the timer slop (in nanoseconds) for the virtual Xen + timers (default is 100000). This adjusts the minimum + delta of virtualized Xen timers, where lower values + improve timer resolution at the expense of processing + more timer interrupts. + + xen.balloon_boot_timeout= [XEN] + The time (in seconds) to wait before giving up to boot + in case initial ballooning fails to free enough memory. + Applies only when running as HVM or PVH guest and + started with less memory configured than allowed at + max. Default is 180. + + xen.event_eoi_delay= [XEN] + How long to delay EOI handling in case of event + storms (jiffies). Default is 10. + + xen.event_loop_timeout= [XEN] + After which time (jiffies) the event handling loop + should start to delay EOI handling. Default is 2. + + xen.fifo_events= [XEN] + Boolean parameter to disable using fifo event handling + even if available. Normally fifo event handling is + preferred over the 2-level event handling, as it is + fairer and the number of possible event channels is + much higher. Default is on (use fifo events). + + xirc2ps_cs= [NET,PCMCIA] + Format: + <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] + + xive= [PPC] + By default on POWER9 and above, the kernel will + natively use the XIVE interrupt controller. This option + allows the fallback firmware mode to be used: + + off Fallback to firmware control of XIVE interrupt + controller on both pseries and powernv + platforms. Only useful on POWER9 and above. + + xive.store-eoi=off [PPC] + By default on POWER10 and above, the kernel will use + stores for EOI handling when the XIVE interrupt mode + is active. This option allows the XIVE driver to use + loads instead, as on POWER9. + + xhci-hcd.quirks [USB,KNL] + A hex value specifying bitmask with supplemental xhci + host controller quirks. Meaning of each bit can be + consulted in header drivers/usb/host/xhci.h. + + xmon [PPC] + Format: { early | on | rw | ro | off } + Controls if xmon debugger is enabled. Default is off. + Passing only "xmon" is equivalent to "xmon=early". + early Call xmon as early as possible on boot; xmon + debugger is called from setup_arch(). + on xmon debugger hooks will be installed so xmon + is only called on a kernel crash. Default mode, + i.e. either "ro" or "rw" mode, is controlled + with CONFIG_XMON_DEFAULT_RO_MODE. + rw xmon debugger hooks will be installed so xmon + is called only on a kernel crash, mode is write, + meaning SPR registers, memory and, other data + can be written using xmon commands. + ro same as "rw" option above but SPR registers, + memory, and other data can't be written using + xmon commands. + off xmon is disabled. + diff --git a/Documentation/admin-guide/kernel-per-CPU-kthreads.rst b/Documentation/admin-guide/kernel-per-CPU-kthreads.rst new file mode 100644 index 000000000..993c2a05f --- /dev/null +++ b/Documentation/admin-guide/kernel-per-CPU-kthreads.rst @@ -0,0 +1,334 @@ +========================================== +Reducing OS jitter due to per-cpu kthreads +========================================== + +This document lists per-CPU kthreads in the Linux kernel and presents +options to control their OS jitter. Note that non-per-CPU kthreads are +not listed here. To reduce OS jitter from non-per-CPU kthreads, bind +them to a "housekeeping" CPU dedicated to such work. + +References +========== + +- Documentation/core-api/irq/irq-affinity.rst: Binding interrupts to sets of CPUs. + +- Documentation/admin-guide/cgroup-v1: Using cgroups to bind tasks to sets of CPUs. + +- man taskset: Using the taskset command to bind tasks to sets + of CPUs. + +- man sched_setaffinity: Using the sched_setaffinity() system + call to bind tasks to sets of CPUs. + +- /sys/devices/system/cpu/cpuN/online: Control CPU N's hotplug state, + writing "0" to offline and "1" to online. + +- In order to locate kernel-generated OS jitter on CPU N: + + cd /sys/kernel/tracing + echo 1 > max_graph_depth # Increase the "1" for more detail + echo function_graph > current_tracer + # run workload + cat per_cpu/cpuN/trace + +kthreads +======== + +Name: + ehca_comp/%u + +Purpose: + Periodically process Infiniband-related work. + +To reduce its OS jitter, do any of the following: + +1. Don't use eHCA Infiniband hardware, instead choosing hardware + that does not require per-CPU kthreads. This will prevent these + kthreads from being created in the first place. (This will + work for most people, as this hardware, though important, is + relatively old and is produced in relatively low unit volumes.) +2. Do all eHCA-Infiniband-related work on other CPUs, including + interrupts. +3. Rework the eHCA driver so that its per-CPU kthreads are + provisioned only on selected CPUs. + + +Name: + irq/%d-%s + +Purpose: + Handle threaded interrupts. + +To reduce its OS jitter, do the following: + +1. Use irq affinity to force the irq threads to execute on + some other CPU. + +Name: + kcmtpd_ctr_%d + +Purpose: + Handle Bluetooth work. + +To reduce its OS jitter, do one of the following: + +1. Don't use Bluetooth, in which case these kthreads won't be + created in the first place. +2. Use irq affinity to force Bluetooth-related interrupts to + occur on some other CPU and furthermore initiate all + Bluetooth activity on some other CPU. + +Name: + ksoftirqd/%u + +Purpose: + Execute softirq handlers when threaded or when under heavy load. + +To reduce its OS jitter, each softirq vector must be handled +separately as follows: + +TIMER_SOFTIRQ +------------- + +Do all of the following: + +1. To the extent possible, keep the CPU out of the kernel when it + is non-idle, for example, by avoiding system calls and by forcing + both kernel threads and interrupts to execute elsewhere. +2. Build with CONFIG_HOTPLUG_CPU=y. After boot completes, force + the CPU offline, then bring it back online. This forces + recurring timers to migrate elsewhere. If you are concerned + with multiple CPUs, force them all offline before bringing the + first one back online. Once you have onlined the CPUs in question, + do not offline any other CPUs, because doing so could force the + timer back onto one of the CPUs in question. + +NET_TX_SOFTIRQ and NET_RX_SOFTIRQ +--------------------------------- + +Do all of the following: + +1. Force networking interrupts onto other CPUs. +2. Initiate any network I/O on other CPUs. +3. Once your application has started, prevent CPU-hotplug operations + from being initiated from tasks that might run on the CPU to + be de-jittered. (It is OK to force this CPU offline and then + bring it back online before you start your application.) + +BLOCK_SOFTIRQ +------------- + +Do all of the following: + +1. Force block-device interrupts onto some other CPU. +2. Initiate any block I/O on other CPUs. +3. Once your application has started, prevent CPU-hotplug operations + from being initiated from tasks that might run on the CPU to + be de-jittered. (It is OK to force this CPU offline and then + bring it back online before you start your application.) + +IRQ_POLL_SOFTIRQ +---------------- + +Do all of the following: + +1. Force block-device interrupts onto some other CPU. +2. Initiate any block I/O and block-I/O polling on other CPUs. +3. Once your application has started, prevent CPU-hotplug operations + from being initiated from tasks that might run on the CPU to + be de-jittered. (It is OK to force this CPU offline and then + bring it back online before you start your application.) + +TASKLET_SOFTIRQ +--------------- + +Do one or more of the following: + +1. Avoid use of drivers that use tasklets. (Such drivers will contain + calls to things like tasklet_schedule().) +2. Convert all drivers that you must use from tasklets to workqueues. +3. Force interrupts for drivers using tasklets onto other CPUs, + and also do I/O involving these drivers on other CPUs. + +SCHED_SOFTIRQ +------------- + +Do all of the following: + +1. Avoid sending scheduler IPIs to the CPU to be de-jittered, + for example, ensure that at most one runnable kthread is present + on that CPU. If a thread that expects to run on the de-jittered + CPU awakens, the scheduler will send an IPI that can result in + a subsequent SCHED_SOFTIRQ. +2. CONFIG_NO_HZ_FULL=y and ensure that the CPU to be de-jittered + is marked as an adaptive-ticks CPU using the "nohz_full=" + boot parameter. This reduces the number of scheduler-clock + interrupts that the de-jittered CPU receives, minimizing its + chances of being selected to do the load balancing work that + runs in SCHED_SOFTIRQ context. +3. To the extent possible, keep the CPU out of the kernel when it + is non-idle, for example, by avoiding system calls and by + forcing both kernel threads and interrupts to execute elsewhere. + This further reduces the number of scheduler-clock interrupts + received by the de-jittered CPU. + +HRTIMER_SOFTIRQ +--------------- + +Do all of the following: + +1. To the extent possible, keep the CPU out of the kernel when it + is non-idle. For example, avoid system calls and force both + kernel threads and interrupts to execute elsewhere. +2. Build with CONFIG_HOTPLUG_CPU=y. Once boot completes, force the + CPU offline, then bring it back online. This forces recurring + timers to migrate elsewhere. If you are concerned with multiple + CPUs, force them all offline before bringing the first one + back online. Once you have onlined the CPUs in question, do not + offline any other CPUs, because doing so could force the timer + back onto one of the CPUs in question. + +RCU_SOFTIRQ +----------- + +Do at least one of the following: + +1. Offload callbacks and keep the CPU in either dyntick-idle or + adaptive-ticks state by doing all of the following: + + a. CONFIG_NO_HZ_FULL=y and ensure that the CPU to be + de-jittered is marked as an adaptive-ticks CPU using the + "nohz_full=" boot parameter. Bind the rcuo kthreads to + housekeeping CPUs, which can tolerate OS jitter. + b. To the extent possible, keep the CPU out of the kernel + when it is non-idle, for example, by avoiding system + calls and by forcing both kernel threads and interrupts + to execute elsewhere. + +2. Enable RCU to do its processing remotely via dyntick-idle by + doing all of the following: + + a. Build with CONFIG_NO_HZ=y. + b. Ensure that the CPU goes idle frequently, allowing other + CPUs to detect that it has passed through an RCU quiescent + state. If the kernel is built with CONFIG_NO_HZ_FULL=y, + userspace execution also allows other CPUs to detect that + the CPU in question has passed through a quiescent state. + c. To the extent possible, keep the CPU out of the kernel + when it is non-idle, for example, by avoiding system + calls and by forcing both kernel threads and interrupts + to execute elsewhere. + +Name: + kworker/%u:%d%s (cpu, id, priority) + +Purpose: + Execute workqueue requests + +To reduce its OS jitter, do any of the following: + +1. Run your workload at a real-time priority, which will allow + preempting the kworker daemons. +2. A given workqueue can be made visible in the sysfs filesystem + by passing the WQ_SYSFS to that workqueue's alloc_workqueue(). + Such a workqueue can be confined to a given subset of the + CPUs using the ``/sys/devices/virtual/workqueue/*/cpumask`` sysfs + files. The set of WQ_SYSFS workqueues can be displayed using + "ls /sys/devices/virtual/workqueue". That said, the workqueues + maintainer would like to caution people against indiscriminately + sprinkling WQ_SYSFS across all the workqueues. The reason for + caution is that it is easy to add WQ_SYSFS, but because sysfs is + part of the formal user/kernel API, it can be nearly impossible + to remove it, even if its addition was a mistake. +3. Do any of the following needed to avoid jitter that your + application cannot tolerate: + + a. Build your kernel with CONFIG_SLUB=y rather than + CONFIG_SLAB=y, thus avoiding the slab allocator's periodic + use of each CPU's workqueues to run its cache_reap() + function. + b. Avoid using oprofile, thus avoiding OS jitter from + wq_sync_buffer(). + c. Limit your CPU frequency so that a CPU-frequency + governor is not required, possibly enlisting the aid of + special heatsinks or other cooling technologies. If done + correctly, and if you CPU architecture permits, you should + be able to build your kernel with CONFIG_CPU_FREQ=n to + avoid the CPU-frequency governor periodically running + on each CPU, including cs_dbs_timer() and od_dbs_timer(). + + WARNING: Please check your CPU specifications to + make sure that this is safe on your particular system. + d. As of v3.18, Christoph Lameter's on-demand vmstat workers + commit prevents OS jitter due to vmstat_update() on + CONFIG_SMP=y systems. Before v3.18, is not possible + to entirely get rid of the OS jitter, but you can + decrease its frequency by writing a large value to + /proc/sys/vm/stat_interval. The default value is HZ, + for an interval of one second. Of course, larger values + will make your virtual-memory statistics update more + slowly. Of course, you can also run your workload at + a real-time priority, thus preempting vmstat_update(), + but if your workload is CPU-bound, this is a bad idea. + However, there is an RFC patch from Christoph Lameter + (based on an earlier one from Gilad Ben-Yossef) that + reduces or even eliminates vmstat overhead for some + workloads at https://lore.kernel.org/r/00000140e9dfd6bd-40db3d4f-c1be-434f-8132-7820f81bb586-000000@email.amazonses.com. + e. If running on high-end powerpc servers, build with + CONFIG_PPC_RTAS_DAEMON=n. This prevents the RTAS + daemon from running on each CPU every second or so. + (This will require editing Kconfig files and will defeat + this platform's RAS functionality.) This avoids jitter + due to the rtas_event_scan() function. + WARNING: Please check your CPU specifications to + make sure that this is safe on your particular system. + f. If running on Cell Processor, build your kernel with + CBE_CPUFREQ_SPU_GOVERNOR=n to avoid OS jitter from + spu_gov_work(). + WARNING: Please check your CPU specifications to + make sure that this is safe on your particular system. + g. If running on PowerMAC, build your kernel with + CONFIG_PMAC_RACKMETER=n to disable the CPU-meter, + avoiding OS jitter from rackmeter_do_timer(). + +Name: + rcuc/%u + +Purpose: + Execute RCU callbacks in CONFIG_RCU_BOOST=y kernels. + +To reduce its OS jitter, do at least one of the following: + +1. Build the kernel with CONFIG_PREEMPT=n. This prevents these + kthreads from being created in the first place, and also obviates + the need for RCU priority boosting. This approach is feasible + for workloads that do not require high degrees of responsiveness. +2. Build the kernel with CONFIG_RCU_BOOST=n. This prevents these + kthreads from being created in the first place. This approach + is feasible only if your workload never requires RCU priority + boosting, for example, if you ensure frequent idle time on all + CPUs that might execute within the kernel. +3. Build with CONFIG_RCU_NOCB_CPU=y and boot with the rcu_nocbs= + boot parameter offloading RCU callbacks from all CPUs susceptible + to OS jitter. This approach prevents the rcuc/%u kthreads from + having any work to do, so that they are never awakened. +4. Ensure that the CPU never enters the kernel, and, in particular, + avoid initiating any CPU hotplug operations on this CPU. This is + another way of preventing any callbacks from being queued on the + CPU, again preventing the rcuc/%u kthreads from having any work + to do. + +Name: + rcuop/%d and rcuos/%d + +Purpose: + Offload RCU callbacks from the corresponding CPU. + +To reduce its OS jitter, do at least one of the following: + +1. Use affinity, cgroups, or other mechanism to force these kthreads + to execute on some other CPU. +2. Build with CONFIG_RCU_NOCB_CPU=n, which will prevent these + kthreads from being created in the first place. However, please + note that this will not eliminate OS jitter, but will instead + shift it to RCU_SOFTIRQ. diff --git a/Documentation/admin-guide/laptops/asus-laptop.rst b/Documentation/admin-guide/laptops/asus-laptop.rst new file mode 100644 index 000000000..95176321a --- /dev/null +++ b/Documentation/admin-guide/laptops/asus-laptop.rst @@ -0,0 +1,271 @@ +================== +Asus Laptop Extras +================== + +Version 0.1 + +August 6, 2009 + +Corentin Chary <corentincj@iksaif.net> +http://acpi4asus.sf.net/ + + This driver provides support for extra features of ACPI-compatible ASUS laptops. + It may also support some MEDION, JVC or VICTOR laptops (such as MEDION 9675 or + VICTOR XP7210 for example). It makes all the extra buttons generate input + events (like keyboards). + + On some models adds support for changing the display brightness and output, + switching the LCD backlight on and off, and most importantly, allows you to + blink those fancy LEDs intended for reporting mail and wireless status. + +This driver supersedes the old asus_acpi driver. + +Requirements +------------ + + Kernel 2.6.X sources, configured for your computer, with ACPI support. + You also need CONFIG_INPUT and CONFIG_ACPI. + +Status +------ + + The features currently supported are the following (see below for + detailed description): + + - Fn key combinations + - Bluetooth enable and disable + - Wlan enable and disable + - GPS enable and disable + - Video output switching + - Ambient Light Sensor on and off + - LED control + - LED Display control + - LCD brightness control + - LCD on and off + + A compatibility table by model and feature is maintained on the web + site, http://acpi4asus.sf.net/. + +Usage +----- + + Try "modprobe asus-laptop". Check your dmesg (simply type dmesg). You should + see some lines like this : + + Asus Laptop Extras version 0.42 + - L2D model detected. + + If it is not the output you have on your laptop, send it (and the laptop's + DSDT) to me. + + That's all, now, all the events generated by the hotkeys of your laptop + should be reported via netlink events. You can check with + "acpi_genl monitor" (part of the acpica project). + + Hotkeys are also reported as input keys (like keyboards) you can check + which key are supported using "xev" under X11. + + You can get information on the version of your DSDT table by reading the + /sys/devices/platform/asus-laptop/infos entry. If you have a question or a + bug report to do, please include the output of this entry. + +LEDs +---- + + You can modify LEDs be echoing values to `/sys/class/leds/asus/*/brightness`:: + + echo 1 > /sys/class/leds/asus::mail/brightness + + will switch the mail LED on. + + You can also know if they are on/off by reading their content and use + kernel triggers like disk-activity or heartbeat. + +Backlight +--------- + + You can control lcd backlight power and brightness with + /sys/class/backlight/asus-laptop/. Brightness Values are between 0 and 15. + +Wireless devices +---------------- + + You can turn the internal Bluetooth adapter on/off with the bluetooth entry + (only on models with Bluetooth). This usually controls the associated LED. + Same for Wlan adapter. + +Display switching +----------------- + + Note: the display switching code is currently considered EXPERIMENTAL. + + Switching works for the following models: + + - L3800C + - A2500H + - L5800C + - M5200N + - W1000N (albeit with some glitches) + - M6700R + - A6JC + - F3J + + Switching doesn't work for the following: + + - M3700N + - L2X00D (locks the laptop under certain conditions) + + To switch the displays, echo values from 0 to 15 to + /sys/devices/platform/asus-laptop/display. The significance of those values + is as follows: + + +-------+-----+-----+-----+-----+-----+ + | Bin | Val | DVI | TV | CRT | LCD | + +-------+-----+-----+-----+-----+-----+ + | 0000 | 0 | | | | | + +-------+-----+-----+-----+-----+-----+ + | 0001 | 1 | | | | X | + +-------+-----+-----+-----+-----+-----+ + | 0010 | 2 | | | X | | + +-------+-----+-----+-----+-----+-----+ + | 0011 | 3 | | | X | X | + +-------+-----+-----+-----+-----+-----+ + | 0100 | 4 | | X | | | + +-------+-----+-----+-----+-----+-----+ + | 0101 | 5 | | X | | X | + +-------+-----+-----+-----+-----+-----+ + | 0110 | 6 | | X | X | | + +-------+-----+-----+-----+-----+-----+ + | 0111 | 7 | | X | X | X | + +-------+-----+-----+-----+-----+-----+ + | 1000 | 8 | X | | | | + +-------+-----+-----+-----+-----+-----+ + | 1001 | 9 | X | | | X | + +-------+-----+-----+-----+-----+-----+ + | 1010 | 10 | X | | X | | + +-------+-----+-----+-----+-----+-----+ + | 1011 | 11 | X | | X | X | + +-------+-----+-----+-----+-----+-----+ + | 1100 | 12 | X | X | | | + +-------+-----+-----+-----+-----+-----+ + | 1101 | 13 | X | X | | X | + +-------+-----+-----+-----+-----+-----+ + | 1110 | 14 | X | X | X | | + +-------+-----+-----+-----+-----+-----+ + | 1111 | 15 | X | X | X | X | + +-------+-----+-----+-----+-----+-----+ + + In most cases, the appropriate displays must be plugged in for the above + combinations to work. TV-Out may need to be initialized at boot time. + + Debugging: + + 1) Check whether the Fn+F8 key: + + a) does not lock the laptop (try a boot with noapic / nolapic if it does) + b) generates events (0x6n, where n is the value corresponding to the + configuration above) + c) actually works + + Record the disp value at every configuration. + 2) Echo values from 0 to 15 to /sys/devices/platform/asus-laptop/display. + Record its value, note any change. If nothing changes, try a broader range, + up to 65535. + 3) Send ANY output (both positive and negative reports are needed, unless your + machine is already listed above) to the acpi4asus-user mailing list. + + Note: on some machines (e.g. L3C), after the module has been loaded, only 0x6n + events are generated and no actual switching occurs. In such a case, a line + like:: + + echo $((10#$arg-60)) > /sys/devices/platform/asus-laptop/display + + will usually do the trick ($arg is the 0000006n-like event passed to acpid). + + Note: there is currently no reliable way to read display status on xxN + (Centrino) models. + +LED display +----------- + + Some models like the W1N have a LED display that can be used to display + several items of information. + + LED display works for the following models: + + - W1000N + - W1J + + To control the LED display, use the following:: + + echo 0x0T000DDD > /sys/devices/platform/asus-laptop/ + + where T control the 3 letters display, and DDD the 3 digits display, + according to the tables below:: + + DDD (digits) + 000 to 999 = display digits + AAA = --- + BBB to FFF = turn-off + + T (type) + 0 = off + 1 = dvd + 2 = vcd + 3 = mp3 + 4 = cd + 5 = tv + 6 = cpu + 7 = vol + + For example "echo 0x01000001 >/sys/devices/platform/asus-laptop/ledd" + would display "DVD001". + +Driver options +-------------- + + Options can be passed to the asus-laptop driver using the standard + module argument syntax (<param>=<value> when passing the option to the + module or asus-laptop.<param>=<value> on the kernel boot line when + asus-laptop is statically linked into the kernel). + + wapf: WAPF defines the behavior of the Fn+Fx wlan key + The significance of values is yet to be found, but + most of the time: + + - 0x0 should do nothing + - 0x1 should allow to control the device with Fn+Fx key. + - 0x4 should send an ACPI event (0x88) while pressing the Fn+Fx key + - 0x5 like 0x1 or 0x4 + + The default value is 0x1. + +Unsupported models +------------------ + + These models will never be supported by this module, as they use a completely + different mechanism to handle LEDs and extra stuff (meaning we have no clue + how it works): + + - ASUS A1300 (A1B), A1370D + - ASUS L7300G + - ASUS L8400 + +Patches, Errors, Questions +-------------------------- + + I appreciate any success or failure + reports, especially if they add to or correct the compatibility table. + Please include the following information in your report: + + - Asus model name + - a copy of your ACPI tables, using the "acpidump" utility + - a copy of /sys/devices/platform/asus-laptop/infos + - which driver features work and which don't + - the observed behavior of non-working features + + Any other comments or patches are also more than welcome. + + acpi4asus-user@lists.sourceforge.net + + http://sourceforge.net/projects/acpi4asus diff --git a/Documentation/admin-guide/laptops/disk-shock-protection.rst b/Documentation/admin-guide/laptops/disk-shock-protection.rst new file mode 100644 index 000000000..22c7ec3e8 --- /dev/null +++ b/Documentation/admin-guide/laptops/disk-shock-protection.rst @@ -0,0 +1,151 @@ +========================== +Hard disk shock protection +========================== + +Author: Elias Oltmanns <eo@nebensachen.de> + +Last modified: 2008-10-03 + + +.. 0. Contents + + 1. Intro + 2. The interface + 3. References + 4. CREDITS + + +1. Intro +-------- + +ATA/ATAPI-7 specifies the IDLE IMMEDIATE command with unload feature. +Issuing this command should cause the drive to switch to idle mode and +unload disk heads. This feature is being used in modern laptops in +conjunction with accelerometers and appropriate software to implement +a shock protection facility. The idea is to stop all I/O operations on +the internal hard drive and park its heads on the ramp when critical +situations are anticipated. The desire to have such a feature +available on GNU/Linux systems has been the original motivation to +implement a generic disk head parking interface in the Linux kernel. +Please note, however, that other components have to be set up on your +system in order to get disk shock protection working (see +section 3. References below for pointers to more information about +that). + + +2. The interface +---------------- + +For each ATA device, the kernel exports the file +`block/*/device/unload_heads` in sysfs (here assumed to be mounted under +/sys). Access to `/sys/block/*/device/unload_heads` is denied with +-EOPNOTSUPP if the device does not support the unload feature. +Otherwise, writing an integer value to this file will take the heads +of the respective drive off the platter and block all I/O operations +for the specified number of milliseconds. When the timeout expires and +no further disk head park request has been issued in the meantime, +normal operation will be resumed. The maximal value accepted for a +timeout is 30000 milliseconds. Exceeding this limit will return +-EOVERFLOW, but heads will be parked anyway and the timeout will be +set to 30 seconds. However, you can always change a timeout to any +value between 0 and 30000 by issuing a subsequent head park request +before the timeout of the previous one has expired. In particular, the +total timeout can exceed 30 seconds and, more importantly, you can +cancel a previously set timeout and resume normal operation +immediately by specifying a timeout of 0. Values below -2 are rejected +with -EINVAL (see below for the special meaning of -1 and -2). If the +timeout specified for a recent head park request has not yet expired, +reading from `/sys/block/*/device/unload_heads` will report the number +of milliseconds remaining until normal operation will be resumed; +otherwise, reading the unload_heads attribute will return 0. + +For example, do the following in order to park the heads of drive +/dev/sda and stop all I/O operations for five seconds:: + + # echo 5000 > /sys/block/sda/device/unload_heads + +A simple:: + + # cat /sys/block/sda/device/unload_heads + +will show you how many milliseconds are left before normal operation +will be resumed. + +A word of caution: The fact that the interface operates on a basis of +milliseconds may raise expectations that cannot be satisfied in +reality. In fact, the ATA specs clearly state that the time for an +unload operation to complete is vendor specific. The hint in ATA-7 +that this will typically be within 500 milliseconds apparently has +been dropped in ATA-8. + +There is a technical detail of this implementation that may cause some +confusion and should be discussed here. When a head park request has +been issued to a device successfully, all I/O operations on the +controller port this device is attached to will be deferred. That is +to say, any other device that may be connected to the same port will +be affected too. The only exception is that a subsequent head unload +request to that other device will be executed immediately. Further +operations on that port will be deferred until the timeout specified +for either device on the port has expired. As far as PATA (old style +IDE) configurations are concerned, there can only be two devices +attached to any single port. In SATA world we have port multipliers +which means that a user-issued head parking request to one device may +actually result in stopping I/O to a whole bunch of devices. However, +since this feature is supposed to be used on laptops and does not seem +to be very useful in any other environment, there will be mostly one +device per port. Even if the CD/DVD writer happens to be connected to +the same port as the hard drive, it generally *should* recover just +fine from the occasional buffer under-run incurred by a head park +request to the HD. Actually, when you are using an ide driver rather +than its libata counterpart (i.e. your disk is called /dev/hda +instead of /dev/sda), then parking the heads of one drive (drive X) +will generally not affect the mode of operation of another drive +(drive Y) on the same port as described above. It is only when a port +reset is required to recover from an exception on drive Y that further +I/O operations on that drive (and the reset itself) will be delayed +until drive X is no longer in the parked state. + +Finally, there are some hard drives that only comply with an earlier +version of the ATA standard than ATA-7, but do support the unload +feature nonetheless. Unfortunately, there is no safe way Linux can +detect these devices, so you won't be able to write to the +unload_heads attribute. If you know that your device really does +support the unload feature (for instance, because the vendor of your +laptop or the hard drive itself told you so), then you can tell the +kernel to enable the usage of this feature for that drive by writing +the special value -1 to the unload_heads attribute:: + + # echo -1 > /sys/block/sda/device/unload_heads + +will enable the feature for /dev/sda, and giving -2 instead of -1 will +disable it again. + + +3. References +------------- + +There are several laptops from different vendors featuring shock +protection capabilities. As manufacturers have refused to support open +source development of the required software components so far, Linux +support for shock protection varies considerably between different +hardware implementations. Ideally, this section should contain a list +of pointers at different projects aiming at an implementation of shock +protection on different systems. Unfortunately, I only know of a +single project which, although still considered experimental, is fit +for use. Please feel free to add projects that have been the victims +of my ignorance. + +- https://www.thinkwiki.org/wiki/HDAPS + + See this page for information about Linux support of the hard disk + active protection system as implemented in IBM/Lenovo Thinkpads. + + +4. CREDITS +---------- + +This implementation of disk head parking has been inspired by a patch +originally published by Jon Escombe <lists@dresco.co.uk>. My efforts +to develop an implementation of this feature that is fit to be merged +into mainline have been aided by various kernel developers, in +particular by Tejun Heo and Bartlomiej Zolnierkiewicz. diff --git a/Documentation/admin-guide/laptops/index.rst b/Documentation/admin-guide/laptops/index.rst new file mode 100644 index 000000000..cd9a1c269 --- /dev/null +++ b/Documentation/admin-guide/laptops/index.rst @@ -0,0 +1,17 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============== +Laptop Drivers +============== + +.. toctree:: + :maxdepth: 1 + + asus-laptop + disk-shock-protection + laptop-mode + lg-laptop + sony-laptop + sonypi + thinkpad-acpi + toshiba_haps diff --git a/Documentation/admin-guide/laptops/laptop-mode.rst b/Documentation/admin-guide/laptops/laptop-mode.rst new file mode 100644 index 000000000..b61cc601d --- /dev/null +++ b/Documentation/admin-guide/laptops/laptop-mode.rst @@ -0,0 +1,770 @@ +=============================================== +How to conserve battery power using laptop-mode +=============================================== + +Document Author: Bart Samwel (bart@samwel.tk) + +Date created: January 2, 2004 + +Last modified: December 06, 2004 + +Introduction +------------ + +Laptop mode is used to minimize the time that the hard disk needs to be spun up, +to conserve battery power on laptops. It has been reported to cause significant +power savings. + +.. Contents + + * Introduction + * Installation + * Caveats + * The Details + * Tips & Tricks + * Control script + * ACPI integration + * Monitoring tool + + +Installation +------------ + +To use laptop mode, you don't need to set any kernel configuration options +or anything. Simply install all the files included in this document, and +laptop mode will automatically be started when you're on battery. For +your convenience, a tarball containing an installer can be downloaded at: + + http://www.samwel.tk/laptop_mode/laptop_mode/ + +To configure laptop mode, you need to edit the configuration file, which is +located in /etc/default/laptop-mode on Debian-based systems, or in +/etc/sysconfig/laptop-mode on other systems. + +Unfortunately, automatic enabling of laptop mode does not work for +laptops that don't have ACPI. On those laptops, you need to start laptop +mode manually. To start laptop mode, run "laptop_mode start", and to +stop it, run "laptop_mode stop". (Note: The laptop mode tools package now +has experimental support for APM, you might want to try that first.) + + +Caveats +------- + +* The downside of laptop mode is that you have a chance of losing up to 10 + minutes of work. If you cannot afford this, don't use it! The supplied ACPI + scripts automatically turn off laptop mode when the battery almost runs out, + so that you won't lose any data at the end of your battery life. + +* Most desktop hard drives have a very limited lifetime measured in spindown + cycles, typically about 50.000 times (it's usually listed on the spec sheet). + Check your drive's rating, and don't wear down your drive's lifetime if you + don't need to. + +* If you mount some of your ext3/reiserfs filesystems with the -n option, then + the control script will not be able to remount them correctly. You must set + DO_REMOUNTS=0 in the control script, otherwise it will remount them with the + wrong options -- or it will fail because it cannot write to /etc/mtab. + +* If you have your filesystems listed as type "auto" in fstab, like I did, then + the control script will not recognize them as filesystems that need remounting. + You must list the filesystems with their true type instead. + +* It has been reported that some versions of the mutt mail client use file access + times to determine whether a folder contains new mail. If you use mutt and + experience this, you must disable the noatime remounting by setting the option + DO_REMOUNT_NOATIME to 0 in the configuration file. + + +The Details +----------- + +Laptop mode is controlled by the knob /proc/sys/vm/laptop_mode. This knob is +present for all kernels that have the laptop mode patch, regardless of any +configuration options. When the knob is set, any physical disk I/O (that might +have caused the hard disk to spin up) causes Linux to flush all dirty blocks. The +result of this is that after a disk has spun down, it will not be spun up +anymore to write dirty blocks, because those blocks had already been written +immediately after the most recent read operation. The value of the laptop_mode +knob determines the time between the occurrence of disk I/O and when the flush +is triggered. A sensible value for the knob is 5 seconds. Setting the knob to +0 disables laptop mode. + +To increase the effectiveness of the laptop_mode strategy, the laptop_mode +control script increases dirty_expire_centisecs and dirty_writeback_centisecs in +/proc/sys/vm to about 10 minutes (by default), which means that pages that are +dirtied are not forced to be written to disk as often. The control script also +changes the dirty background ratio, so that background writeback of dirty pages +is not done anymore. Combined with a higher commit value (also 10 minutes) for +ext3 or ReiserFS filesystems (also done automatically by the control script), +this results in concentration of disk activity in a small time interval which +occurs only once every 10 minutes, or whenever the disk is forced to spin up by +a cache miss. The disk can then be spun down in the periods of inactivity. + + +Configuration +------------- + +The laptop mode configuration file is located in /etc/default/laptop-mode on +Debian-based systems, or in /etc/sysconfig/laptop-mode on other systems. It +contains the following options: + +MAX_AGE: + +Maximum time, in seconds, of hard drive spindown time that you are +comfortable with. Worst case, it's possible that you could lose this +amount of work if your battery fails while you're in laptop mode. + +MINIMUM_BATTERY_MINUTES: + +Automatically disable laptop mode if the remaining number of minutes of +battery power is less than this value. Default is 10 minutes. + +AC_HD/BATT_HD: + +The idle timeout that should be set on your hard drive when laptop mode +is active (BATT_HD) and when it is not active (AC_HD). The defaults are +20 seconds (value 4) for BATT_HD and 2 hours (value 244) for AC_HD. The +possible values are those listed in the manual page for "hdparm" for the +"-S" option. + +HD: + +The devices for which the spindown timeout should be adjusted by laptop mode. +Default is /dev/hda. If you specify multiple devices, separate them by a space. + +READAHEAD: + +Disk readahead, in 512-byte sectors, while laptop mode is active. A large +readahead can prevent disk accesses for things like executable pages (which are +loaded on demand while the application executes) and sequentially accessed data +(MP3s). + +DO_REMOUNTS: + +The control script automatically remounts any mounted journaled filesystems +with appropriate commit interval options. When this option is set to 0, this +feature is disabled. + +DO_REMOUNT_NOATIME: + +When remounting, should the filesystems be remounted with the noatime option? +Normally, this is set to "1" (enabled), but there may be programs that require +access time recording. + +DIRTY_RATIO: + +The percentage of memory that is allowed to contain "dirty" or unsaved data +before a writeback is forced, while laptop mode is active. Corresponds to +the /proc/sys/vm/dirty_ratio sysctl. + +DIRTY_BACKGROUND_RATIO: + +The percentage of memory that is allowed to contain "dirty" or unsaved data +after a forced writeback is done due to an exceeding of DIRTY_RATIO. Set +this nice and low. This corresponds to the /proc/sys/vm/dirty_background_ratio +sysctl. + +Note that the behaviour of dirty_background_ratio is quite different +when laptop mode is active and when it isn't. When laptop mode is inactive, +dirty_background_ratio is the threshold percentage at which background writeouts +start taking place. When laptop mode is active, however, background writeouts +are disabled, and the dirty_background_ratio only determines how much writeback +is done when dirty_ratio is reached. + +DO_CPU: + +Enable CPU frequency scaling when in laptop mode. (Requires CPUFreq to be setup. +See Documentation/admin-guide/pm/cpufreq.rst for more info. Disabled by default.) + +CPU_MAXFREQ: + +When on battery, what is the maximum CPU speed that the system should use? Legal +values are "slowest" for the slowest speed that your CPU is able to operate at, +or a value listed in /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies. + + +Tips & Tricks +------------- + +* Bartek Kania reports getting up to 50 minutes of extra battery life (on top + of his regular 3 to 3.5 hours) using a spindown time of 5 seconds (BATT_HD=1). + +* You can spin down the disk while playing MP3, by setting disk readahead + to 8MB (READAHEAD=16384). Effectively, the disk will read a complete MP3 at + once, and will then spin down while the MP3 is playing. (Thanks to Bartek + Kania.) + +* Drew Scott Daniels observed: "I don't know why, but when I decrease the number + of colours that my display uses it consumes less battery power. I've seen + this on powerbooks too. I hope that this is a piece of information that + might be useful to the Laptop Mode patch or its users." + +* In syslog.conf, you can prefix entries with a dash `-` to omit syncing the + file after every logging. When you're using laptop-mode and your disk doesn't + spin down, this is a likely culprit. + +* Richard Atterer observed that laptop mode does not work well with noflushd + (http://noflushd.sourceforge.net/), it seems that noflushd prevents laptop-mode + from doing its thing. + +* If you're worried about your data, you might want to consider using a USB + memory stick or something like that as a "working area". (Be aware though + that flash memory can only handle a limited number of writes, and overuse + may wear out your memory stick pretty quickly. Do _not_ use journalling + filesystems on flash memory sticks.) + + +Configuration file for control and ACPI battery scripts +------------------------------------------------------- + +This allows the tunables to be changed for the scripts via an external +configuration file + +It should be installed as /etc/default/laptop-mode on Debian, and as +/etc/sysconfig/laptop-mode on Red Hat, SUSE, Mandrake, and other work-alikes. + +Config file:: + + # Maximum time, in seconds, of hard drive spindown time that you are + # comfortable with. Worst case, it's possible that you could lose this + # amount of work if your battery fails you while in laptop mode. + #MAX_AGE=600 + + # Automatically disable laptop mode when the number of minutes of battery + # that you have left goes below this threshold. + MINIMUM_BATTERY_MINUTES=10 + + # Read-ahead, in 512-byte sectors. You can spin down the disk while playing MP3/OGG + # by setting the disk readahead to 8MB (READAHEAD=16384). Effectively, the disk + # will read a complete MP3 at once, and will then spin down while the MP3/OGG is + # playing. + #READAHEAD=4096 + + # Shall we remount journaled fs. with appropriate commit interval? (1=yes) + #DO_REMOUNTS=1 + + # And shall we add the "noatime" option to that as well? (1=yes) + #DO_REMOUNT_NOATIME=1 + + # Dirty synchronous ratio. At this percentage of dirty pages the process + # which + # calls write() does its own writeback + #DIRTY_RATIO=40 + + # + # Allowed dirty background ratio, in percent. Once DIRTY_RATIO has been + # exceeded, the kernel will wake flusher threads which will then reduce the + # amount of dirty memory to dirty_background_ratio. Set this nice and low, + # so once some writeout has commenced, we do a lot of it. + # + #DIRTY_BACKGROUND_RATIO=5 + + # kernel default dirty buffer age + #DEF_AGE=30 + #DEF_UPDATE=5 + #DEF_DIRTY_BACKGROUND_RATIO=10 + #DEF_DIRTY_RATIO=40 + #DEF_XFS_AGE_BUFFER=15 + #DEF_XFS_SYNC_INTERVAL=30 + #DEF_XFS_BUFD_INTERVAL=1 + + # This must be adjusted manually to the value of HZ in the running kernel + # on 2.4, until the XFS people change their 2.4 external interfaces to work in + # centisecs. This can be automated, but it's a work in progress that still + # needs# some fixes. On 2.6 kernels, XFS uses USER_HZ instead of HZ for + # external interfaces, and that is currently always set to 100. So you don't + # need to change this on 2.6. + #XFS_HZ=100 + + # Should the maximum CPU frequency be adjusted down while on battery? + # Requires CPUFreq to be setup. + # See Documentation/admin-guide/pm/cpufreq.rst for more info + #DO_CPU=0 + + # When on battery what is the maximum CPU speed that the system should + # use? Legal values are "slowest" for the slowest speed that your + # CPU is able to operate at, or a value listed in: + # /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies + # Only applicable if DO_CPU=1. + #CPU_MAXFREQ=slowest + + # Idle timeout for your hard drive (man hdparm for valid values, -S option) + # Default is 2 hours on AC (AC_HD=244) and 20 seconds for battery (BATT_HD=4). + #AC_HD=244 + #BATT_HD=4 + + # The drives for which to adjust the idle timeout. Separate them by a space, + # e.g. HD="/dev/hda /dev/hdb". + #HD="/dev/hda" + + # Set the spindown timeout on a hard drive? + #DO_HD=1 + + +Control script +-------------- + +Please note that this control script works for the Linux 2.4 and 2.6 series (thanks +to Kiko Piris). + +Control script:: + + #!/bin/bash + + # start or stop laptop_mode, best run by a power management daemon when + # ac gets connected/disconnected from a laptop + # + # install as /sbin/laptop_mode + # + # Contributors to this script: Kiko Piris + # Bart Samwel + # Micha Feigin + # Andrew Morton + # Herve Eychenne + # Dax Kelson + # + # Original Linux 2.4 version by: Jens Axboe + + ############################################################################# + + # Source config + if [ -f /etc/default/laptop-mode ] ; then + # Debian + . /etc/default/laptop-mode + elif [ -f /etc/sysconfig/laptop-mode ] ; then + # Others + . /etc/sysconfig/laptop-mode + fi + + # Don't raise an error if the config file is incomplete + # set defaults instead: + + # Maximum time, in seconds, of hard drive spindown time that you are + # comfortable with. Worst case, it's possible that you could lose this + # amount of work if your battery fails you while in laptop mode. + MAX_AGE=${MAX_AGE:-'600'} + + # Read-ahead, in kilobytes + READAHEAD=${READAHEAD:-'4096'} + + # Shall we remount journaled fs. with appropriate commit interval? (1=yes) + DO_REMOUNTS=${DO_REMOUNTS:-'1'} + + # And shall we add the "noatime" option to that as well? (1=yes) + DO_REMOUNT_NOATIME=${DO_REMOUNT_NOATIME:-'1'} + + # Shall we adjust the idle timeout on a hard drive? + DO_HD=${DO_HD:-'1'} + + # Adjust idle timeout on which hard drive? + HD="${HD:-'/dev/hda'}" + + # spindown time for HD (hdparm -S values) + AC_HD=${AC_HD:-'244'} + BATT_HD=${BATT_HD:-'4'} + + # Dirty synchronous ratio. At this percentage of dirty pages the process which + # calls write() does its own writeback + DIRTY_RATIO=${DIRTY_RATIO:-'40'} + + # cpu frequency scaling + # See Documentation/admin-guide/pm/cpufreq.rst for more info + DO_CPU=${CPU_MANAGE:-'0'} + CPU_MAXFREQ=${CPU_MAXFREQ:-'slowest'} + + # + # Allowed dirty background ratio, in percent. Once DIRTY_RATIO has been + # exceeded, the kernel will wake flusher threads which will then reduce the + # amount of dirty memory to dirty_background_ratio. Set this nice and low, + # so once some writeout has commenced, we do a lot of it. + # + DIRTY_BACKGROUND_RATIO=${DIRTY_BACKGROUND_RATIO:-'5'} + + # kernel default dirty buffer age + DEF_AGE=${DEF_AGE:-'30'} + DEF_UPDATE=${DEF_UPDATE:-'5'} + DEF_DIRTY_BACKGROUND_RATIO=${DEF_DIRTY_BACKGROUND_RATIO:-'10'} + DEF_DIRTY_RATIO=${DEF_DIRTY_RATIO:-'40'} + DEF_XFS_AGE_BUFFER=${DEF_XFS_AGE_BUFFER:-'15'} + DEF_XFS_SYNC_INTERVAL=${DEF_XFS_SYNC_INTERVAL:-'30'} + DEF_XFS_BUFD_INTERVAL=${DEF_XFS_BUFD_INTERVAL:-'1'} + + # This must be adjusted manually to the value of HZ in the running kernel + # on 2.4, until the XFS people change their 2.4 external interfaces to work in + # centisecs. This can be automated, but it's a work in progress that still needs + # some fixes. On 2.6 kernels, XFS uses USER_HZ instead of HZ for external + # interfaces, and that is currently always set to 100. So you don't need to + # change this on 2.6. + XFS_HZ=${XFS_HZ:-'100'} + + ############################################################################# + + KLEVEL="$(uname -r | + { + IFS='.' read a b c + echo $a.$b + } + )" + case "$KLEVEL" in + "2.4"|"2.6") + ;; + *) + echo "Unhandled kernel version: $KLEVEL ('uname -r' = '$(uname -r)')" >&2 + exit 1 + ;; + esac + + if [ ! -e /proc/sys/vm/laptop_mode ] ; then + echo "Kernel is not patched with laptop_mode patch." >&2 + exit 1 + fi + + if [ ! -w /proc/sys/vm/laptop_mode ] ; then + echo "You do not have enough privileges to enable laptop_mode." >&2 + exit 1 + fi + + # Remove an option (the first parameter) of the form option=<number> from + # a mount options string (the rest of the parameters). + parse_mount_opts () { + OPT="$1" + shift + echo ",$*," | sed \ + -e 's/,'"$OPT"'=[0-9]*,/,/g' \ + -e 's/,,*/,/g' \ + -e 's/^,//' \ + -e 's/,$//' + } + + # Remove an option (the first parameter) without any arguments from + # a mount option string (the rest of the parameters). + parse_nonumber_mount_opts () { + OPT="$1" + shift + echo ",$*," | sed \ + -e 's/,'"$OPT"',/,/g' \ + -e 's/,,*/,/g' \ + -e 's/^,//' \ + -e 's/,$//' + } + + # Find out the state of a yes/no option (e.g. "atime"/"noatime") in + # fstab for a given filesystem, and use this state to replace the + # value of the option in another mount options string. The device + # is the first argument, the option name the second, and the default + # value the third. The remainder is the mount options string. + # + # Example: + # parse_yesno_opts_wfstab /dev/hda1 atime atime defaults,noatime + # + # If fstab contains, say, "rw" for this filesystem, then the result + # will be "defaults,atime". + parse_yesno_opts_wfstab () { + L_DEV="$1" + OPT="$2" + DEF_OPT="$3" + shift 3 + L_OPTS="$*" + PARSEDOPTS1="$(parse_nonumber_mount_opts $OPT $L_OPTS)" + PARSEDOPTS1="$(parse_nonumber_mount_opts no$OPT $PARSEDOPTS1)" + # Watch for a default atime in fstab + FSTAB_OPTS="$(awk '$1 == "'$L_DEV'" { print $4 }' /etc/fstab)" + if echo "$FSTAB_OPTS" | grep "$OPT" > /dev/null ; then + # option specified in fstab: extract the value and use it + if echo "$FSTAB_OPTS" | grep "no$OPT" > /dev/null ; then + echo "$PARSEDOPTS1,no$OPT" + else + # no$OPT not found -- so we must have $OPT. + echo "$PARSEDOPTS1,$OPT" + fi + else + # option not specified in fstab -- choose the default. + echo "$PARSEDOPTS1,$DEF_OPT" + fi + } + + # Find out the state of a numbered option (e.g. "commit=NNN") in + # fstab for a given filesystem, and use this state to replace the + # value of the option in another mount options string. The device + # is the first argument, and the option name the second. The + # remainder is the mount options string in which the replacement + # must be done. + # + # Example: + # parse_mount_opts_wfstab /dev/hda1 commit defaults,commit=7 + # + # If fstab contains, say, "commit=3,rw" for this filesystem, then the + # result will be "rw,commit=3". + parse_mount_opts_wfstab () { + L_DEV="$1" + OPT="$2" + shift 2 + L_OPTS="$*" + PARSEDOPTS1="$(parse_mount_opts $OPT $L_OPTS)" + # Watch for a default commit in fstab + FSTAB_OPTS="$(awk '$1 == "'$L_DEV'" { print $4 }' /etc/fstab)" + if echo "$FSTAB_OPTS" | grep "$OPT=" > /dev/null ; then + # option specified in fstab: extract the value, and use it + echo -n "$PARSEDOPTS1,$OPT=" + echo ",$FSTAB_OPTS," | sed \ + -e 's/.*,'"$OPT"'=//' \ + -e 's/,.*//' + else + # option not specified in fstab: set it to 0 + echo "$PARSEDOPTS1,$OPT=0" + fi + } + + deduce_fstype () { + MP="$1" + # My root filesystem unfortunately has + # type "unknown" in /etc/mtab. If we encounter + # "unknown", we try to get the type from fstab. + cat /etc/fstab | + grep -v '^#' | + while read FSTAB_DEV FSTAB_MP FSTAB_FST FSTAB_OPTS FSTAB_DUMP FSTAB_DUMP ; do + if [ "$FSTAB_MP" = "$MP" ]; then + echo $FSTAB_FST + exit 0 + fi + done + } + + if [ $DO_REMOUNT_NOATIME -eq 1 ] ; then + NOATIME_OPT=",noatime" + fi + + case "$1" in + start) + AGE=$((100*$MAX_AGE)) + XFS_AGE=$(($XFS_HZ*$MAX_AGE)) + echo -n "Starting laptop_mode" + + if [ -d /proc/sys/vm/pagebuf ] ; then + # (For 2.4 and early 2.6.) + # This only needs to be set, not reset -- it is only used when + # laptop mode is enabled. + echo $XFS_AGE > /proc/sys/vm/pagebuf/lm_flush_age + echo $XFS_AGE > /proc/sys/fs/xfs/lm_sync_interval + elif [ -f /proc/sys/fs/xfs/lm_age_buffer ] ; then + # (A couple of early 2.6 laptop mode patches had these.) + # The same goes for these. + echo $XFS_AGE > /proc/sys/fs/xfs/lm_age_buffer + echo $XFS_AGE > /proc/sys/fs/xfs/lm_sync_interval + elif [ -f /proc/sys/fs/xfs/age_buffer ] ; then + # (2.6.6) + # But not for these -- they are also used in normal + # operation. + echo $XFS_AGE > /proc/sys/fs/xfs/age_buffer + echo $XFS_AGE > /proc/sys/fs/xfs/sync_interval + elif [ -f /proc/sys/fs/xfs/age_buffer_centisecs ] ; then + # (2.6.7 upwards) + # And not for these either. These are in centisecs, + # not USER_HZ, so we have to use $AGE, not $XFS_AGE. + echo $AGE > /proc/sys/fs/xfs/age_buffer_centisecs + echo $AGE > /proc/sys/fs/xfs/xfssyncd_centisecs + echo 3000 > /proc/sys/fs/xfs/xfsbufd_centisecs + fi + + case "$KLEVEL" in + "2.4") + echo 1 > /proc/sys/vm/laptop_mode + echo "30 500 0 0 $AGE $AGE 60 20 0" > /proc/sys/vm/bdflush + ;; + "2.6") + echo 5 > /proc/sys/vm/laptop_mode + echo "$AGE" > /proc/sys/vm/dirty_writeback_centisecs + echo "$AGE" > /proc/sys/vm/dirty_expire_centisecs + echo "$DIRTY_RATIO" > /proc/sys/vm/dirty_ratio + echo "$DIRTY_BACKGROUND_RATIO" > /proc/sys/vm/dirty_background_ratio + ;; + esac + if [ $DO_REMOUNTS -eq 1 ]; then + cat /etc/mtab | while read DEV MP FST OPTS DUMP PASS ; do + PARSEDOPTS="$(parse_mount_opts "$OPTS")" + if [ "$FST" = 'unknown' ]; then + FST=$(deduce_fstype $MP) + fi + case "$FST" in + "ext3"|"reiserfs") + PARSEDOPTS="$(parse_mount_opts commit "$OPTS")" + mount $DEV -t $FST $MP -o remount,$PARSEDOPTS,commit=$MAX_AGE$NOATIME_OPT + ;; + "xfs") + mount $DEV -t $FST $MP -o remount,$OPTS$NOATIME_OPT + ;; + esac + if [ -b $DEV ] ; then + blockdev --setra $(($READAHEAD * 2)) $DEV + fi + done + fi + if [ $DO_HD -eq 1 ] ; then + for THISHD in $HD ; do + /sbin/hdparm -S $BATT_HD $THISHD > /dev/null 2>&1 + /sbin/hdparm -B 1 $THISHD > /dev/null 2>&1 + done + fi + if [ $DO_CPU -eq 1 -a -e /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq ]; then + if [ $CPU_MAXFREQ = 'slowest' ]; then + CPU_MAXFREQ=`cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq` + fi + echo $CPU_MAXFREQ > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq + fi + echo "." + ;; + stop) + U_AGE=$((100*$DEF_UPDATE)) + B_AGE=$((100*$DEF_AGE)) + echo -n "Stopping laptop_mode" + echo 0 > /proc/sys/vm/laptop_mode + if [ -f /proc/sys/fs/xfs/age_buffer -a ! -f /proc/sys/fs/xfs/lm_age_buffer ] ; then + # These need to be restored, if there are no lm_*. + echo $(($XFS_HZ*$DEF_XFS_AGE_BUFFER)) > /proc/sys/fs/xfs/age_buffer + echo $(($XFS_HZ*$DEF_XFS_SYNC_INTERVAL)) > /proc/sys/fs/xfs/sync_interval + elif [ -f /proc/sys/fs/xfs/age_buffer_centisecs ] ; then + # These need to be restored as well. + echo $((100*$DEF_XFS_AGE_BUFFER)) > /proc/sys/fs/xfs/age_buffer_centisecs + echo $((100*$DEF_XFS_SYNC_INTERVAL)) > /proc/sys/fs/xfs/xfssyncd_centisecs + echo $((100*$DEF_XFS_BUFD_INTERVAL)) > /proc/sys/fs/xfs/xfsbufd_centisecs + fi + case "$KLEVEL" in + "2.4") + echo "30 500 0 0 $U_AGE $B_AGE 60 20 0" > /proc/sys/vm/bdflush + ;; + "2.6") + echo "$U_AGE" > /proc/sys/vm/dirty_writeback_centisecs + echo "$B_AGE" > /proc/sys/vm/dirty_expire_centisecs + echo "$DEF_DIRTY_RATIO" > /proc/sys/vm/dirty_ratio + echo "$DEF_DIRTY_BACKGROUND_RATIO" > /proc/sys/vm/dirty_background_ratio + ;; + esac + if [ $DO_REMOUNTS -eq 1 ] ; then + cat /etc/mtab | while read DEV MP FST OPTS DUMP PASS ; do + # Reset commit and atime options to defaults. + if [ "$FST" = 'unknown' ]; then + FST=$(deduce_fstype $MP) + fi + case "$FST" in + "ext3"|"reiserfs") + PARSEDOPTS="$(parse_mount_opts_wfstab $DEV commit $OPTS)" + PARSEDOPTS="$(parse_yesno_opts_wfstab $DEV atime atime $PARSEDOPTS)" + mount $DEV -t $FST $MP -o remount,$PARSEDOPTS + ;; + "xfs") + PARSEDOPTS="$(parse_yesno_opts_wfstab $DEV atime atime $OPTS)" + mount $DEV -t $FST $MP -o remount,$PARSEDOPTS + ;; + esac + if [ -b $DEV ] ; then + blockdev --setra 256 $DEV + fi + done + fi + if [ $DO_HD -eq 1 ] ; then + for THISHD in $HD ; do + /sbin/hdparm -S $AC_HD $THISHD > /dev/null 2>&1 + /sbin/hdparm -B 255 $THISHD > /dev/null 2>&1 + done + fi + if [ $DO_CPU -eq 1 -a -e /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq ]; then + echo `cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq` > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq + fi + echo "." + ;; + *) + echo "Usage: $0 {start|stop}" 2>&1 + exit 1 + ;; + + esac + + exit 0 + + +ACPI integration +---------------- + +Dax Kelson submitted this so that the ACPI acpid daemon will +kick off the laptop_mode script and run hdparm. The part that +automatically disables laptop mode when the battery is low was +written by Jan Topinski. + +/etc/acpi/events/ac_adapter:: + + event=ac_adapter + action=/etc/acpi/actions/ac.sh %e + +/etc/acpi/events/battery:: + + event=battery.* + action=/etc/acpi/actions/battery.sh %e + +/etc/acpi/actions/ac.sh:: + + #!/bin/bash + + # ac on/offline event handler + + status=`awk '/^state: / { print $2 }' /proc/acpi/ac_adapter/$2/state` + + case $status in + "on-line") + /sbin/laptop_mode stop + exit 0 + ;; + "off-line") + /sbin/laptop_mode start + exit 0 + ;; + esac + + +/etc/acpi/actions/battery.sh:: + + #! /bin/bash + + # Automatically disable laptop mode when the battery almost runs out. + + BATT_INFO=/proc/acpi/battery/$2/state + + if [[ -f /proc/sys/vm/laptop_mode ]] + then + LM=`cat /proc/sys/vm/laptop_mode` + if [[ $LM -gt 0 ]] + then + if [[ -f $BATT_INFO ]] + then + # Source the config file only now that we know we need + if [ -f /etc/default/laptop-mode ] ; then + # Debian + . /etc/default/laptop-mode + elif [ -f /etc/sysconfig/laptop-mode ] ; then + # Others + . /etc/sysconfig/laptop-mode + fi + MINIMUM_BATTERY_MINUTES=${MINIMUM_BATTERY_MINUTES:-'10'} + + ACTION="`cat $BATT_INFO | grep charging | cut -c 26-`" + if [[ ACTION -eq "discharging" ]] + then + PRESENT_RATE=`cat $BATT_INFO | grep "present rate:" | sed "s/.* \([0-9][0-9]* \).*/\1/" ` + REMAINING=`cat $BATT_INFO | grep "remaining capacity:" | sed "s/.* \([0-9][0-9]* \).*/\1/" ` + fi + if (($REMAINING * 60 / $PRESENT_RATE < $MINIMUM_BATTERY_MINUTES)) + then + /sbin/laptop_mode stop + fi + else + logger -p daemon.warning "You are using laptop mode and your battery interface $BATT_INFO is missing. This may lead to loss of data when the battery runs out. Check kernel ACPI support and /proc/acpi/battery folder, and edit /etc/acpi/battery.sh to set BATT_INFO to the correct path." + fi + fi + fi + + +Monitoring tool +--------------- + +Bartek Kania submitted this, it can be used to measure how much time your disk +spends spun up/down. See tools/laptop/dslm/dslm.c diff --git a/Documentation/admin-guide/laptops/lg-laptop.rst b/Documentation/admin-guide/laptops/lg-laptop.rst new file mode 100644 index 000000000..67fd6932c --- /dev/null +++ b/Documentation/admin-guide/laptops/lg-laptop.rst @@ -0,0 +1,82 @@ +.. SPDX-License-Identifier: GPL-2.0+ + + +LG Gram laptop extra features +============================= + +By Matan Ziv-Av <matan@svgalib.org> + + +Hotkeys +------- + +The following FN keys are ignored by the kernel without this driver: + +- FN-F1 (LG control panel) - Generates F15 +- FN-F5 (Touchpad toggle) - Generates F21 +- FN-F6 (Airplane mode) - Generates RFKILL +- FN-F9 (Reader mode) - Generates F14 + +The rest of the FN keys work without a need for a special driver. + + +Reader mode +----------- + +Writing 0/1 to /sys/devices/platform/lg-laptop/reader_mode disables/enables +reader mode. In this mode the screen colors change (blue color reduced), +and the reader mode indicator LED (on F9 key) turns on. + + +FN Lock +------- + +Writing 0/1 to /sys/devices/platform/lg-laptop/fn_lock disables/enables +FN lock. + + +Battery care limit +------------------ + +Writing 80/100 to /sys/class/power_supply/CMB0/charge_control_end_threshold +sets the maximum capacity to charge the battery. Limiting the charge +reduces battery capacity loss over time. + +This value is reset to 100 when the kernel boots. + + +Fan mode +-------- + +Writing 1/0 to /sys/devices/platform/lg-laptop/fan_mode disables/enables +the fan silent mode. + + +USB charge +---------- + +Writing 0/1 to /sys/devices/platform/lg-laptop/usb_charge disables/enables +charging another device from the USB port while the device is turned off. + +This value is reset to 0 when the kernel boots. + + +LEDs +~~~~ + +The are two LED devices supported by the driver: + +Keyboard backlight +------------------ + +A led device named kbd_led controls the keyboard backlight. There are three +lighting level: off (0), low (127) and high (255). + +The keyboard backlight is also controlled by the key combination FN-F8 +which cycles through those levels. + + +Touchpad indicator LED +---------------------- + +On the F5 key. Controlled by led device names tpad_led. diff --git a/Documentation/admin-guide/laptops/sony-laptop.rst b/Documentation/admin-guide/laptops/sony-laptop.rst new file mode 100644 index 000000000..9edcc7f66 --- /dev/null +++ b/Documentation/admin-guide/laptops/sony-laptop.rst @@ -0,0 +1,174 @@ +========================================= +Sony Notebook Control Driver (SNC) Readme +========================================= + + - Copyright (C) 2004- 2005 Stelian Pop <stelian@popies.net> + - Copyright (C) 2007 Mattia Dongili <malattia@linux.it> + +This mini-driver drives the SNC and SPIC device present in the ACPI BIOS of the +Sony Vaio laptops. This driver mixes both devices functions under the same +(hopefully consistent) interface. This also means that the sonypi driver is +obsoleted by sony-laptop now. + +Fn keys (hotkeys): +------------------ + +Some models report hotkeys through the SNC or SPIC devices, such events are +reported both through the ACPI subsystem as acpi events and through the INPUT +subsystem. See the logs of /proc/bus/input/devices to find out what those +events are and which input devices are created by the driver. +Additionally, loading the driver with the debug option will report all events +in the kernel log. + +The "scancodes" passed to the input system (that can be remapped with udev) +are indexes to the table "sony_laptop_input_keycode_map" in the sony-laptop.c +module. For example the "FN/E" key combination (EJECTCD on some models) +generates the scancode 20 (0x14). + +Backlight control: +------------------ +If your laptop model supports it, you will find sysfs files in the +/sys/class/backlight/sony/ +directory. You will be able to query and set the current screen +brightness: + + ====================== ========================================= + brightness get/set screen brightness (an integer + between 0 and 7) + actual_brightness reading from this file will query the HW + to get real brightness value + max_brightness the maximum brightness value + ====================== ========================================= + + +Platform specific: +------------------ +Loading the sony-laptop module will create a +/sys/devices/platform/sony-laptop/ +directory populated with some files. + +You then read/write integer values from/to those files by using +standard UNIX tools. + +The files are: + + ====================== ========================================== + brightness_default screen brightness which will be set + when the laptop will be rebooted + cdpower power on/off the internal CD drive + audiopower power on/off the internal sound card + lanpower power on/off the internal ethernet card + (only in debug mode) + bluetoothpower power on/off the internal bluetooth device + fanspeed get/set the fan speed + ====================== ========================================== + +Note that some files may be missing if they are not supported +by your particular laptop model. + +Example usage:: + + # echo "1" > /sys/devices/platform/sony-laptop/brightness_default + +sets the lowest screen brightness for the next and later reboots + +:: + + # echo "8" > /sys/devices/platform/sony-laptop/brightness_default + +sets the highest screen brightness for the next and later reboots + +:: + + # cat /sys/devices/platform/sony-laptop/brightness_default + +retrieves the value + +:: + + # echo "0" > /sys/devices/platform/sony-laptop/audiopower + +powers off the sound card + +:: + + # echo "1" > /sys/devices/platform/sony-laptop/audiopower + +powers on the sound card. + + +RFkill control: +--------------- +More recent Vaio models expose a consistent set of ACPI methods to +control radio frequency emitting devices. If you are a lucky owner of +such a laptop you will find the necessary rfkill devices under +/sys/class/rfkill. Check those starting with sony-* in:: + + # grep . /sys/class/rfkill/*/{state,name} + + +Development: +------------ + +If you want to help with the development of this driver (and +you are not afraid of any side effects doing strange things with +your ACPI BIOS could have on your laptop), load the driver and +pass the option 'debug=1'. + +REPEAT: + **DON'T DO THIS IF YOU DON'T LIKE RISKY BUSINESS.** + +In your kernel logs you will find the list of all ACPI methods +the SNC device has on your laptop. + +* For new models you will see a long list of meaningless method names, + reading the DSDT table source should reveal that: + +(1) the SNC device uses an internal capability lookup table +(2) SN00 is used to find values in the lookup table +(3) SN06 and SN07 are used to call into the real methods based on + offsets you can obtain iterating the table using SN00 +(4) SN02 used to enable events. + +Some values in the capability lookup table are more or less known, see +the code for all sony_call_snc_handle calls, others are more obscure. + +* For old models you can see the GCDP/GCDP methods used to pwer on/off + the CD drive, but there are others and they are usually different from + model to model. + +**I HAVE NO IDEA WHAT THOSE METHODS DO.** + +The sony-laptop driver creates, for some of those methods (the most +current ones found on several Vaio models), an entry under +/sys/devices/platform/sony-laptop, just like the 'cdpower' one. +You can create other entries corresponding to your own laptop methods by +further editing the source (see the 'sony_nc_values' table, and add a new +entry to this table with your get/set method names using the +SNC_HANDLE_NAMES macro). + +Your mission, should you accept it, is to try finding out what +those entries are for, by reading/writing random values from/to those +files and find out what is the impact on your laptop. + +Should you find anything interesting, please report it back to me, +I will not disavow all knowledge of your actions :) + +See also http://www.linux.it/~malattia/wiki/index.php/Sony_drivers for other +useful info. + +Bugs/Limitations: +----------------- + +* This driver is not based on official documentation from Sony + (because there is none), so there is no guarantee this driver + will work at all, or do the right thing. Although this hasn't + happened to me, this driver could do very bad things to your + laptop, including permanent damage. + +* The sony-laptop and sonypi drivers do not interact at all. In the + future, sonypi will be removed and replaced by sony-laptop. + +* spicctrl, which is the userspace tool used to communicate with the + sonypi driver (through /dev/sonypi) is deprecated as well since all + its features are now available under the sysfs tree via sony-laptop. diff --git a/Documentation/admin-guide/laptops/sonypi.rst b/Documentation/admin-guide/laptops/sonypi.rst new file mode 100644 index 000000000..190da1234 --- /dev/null +++ b/Documentation/admin-guide/laptops/sonypi.rst @@ -0,0 +1,158 @@ +================================================== +Sony Programmable I/O Control Device Driver Readme +================================================== + + - Copyright (C) 2001-2004 Stelian Pop <stelian@popies.net> + - Copyright (C) 2001-2002 Alcôve <www.alcove.com> + - Copyright (C) 2001 Michael Ashley <m.ashley@unsw.edu.au> + - Copyright (C) 2001 Junichi Morita <jun1m@mars.dti.ne.jp> + - Copyright (C) 2000 Takaya Kinjo <t-kinjo@tc4.so-net.ne.jp> + - Copyright (C) 2000 Andrew Tridgell <tridge@samba.org> + +This driver enables access to the Sony Programmable I/O Control Device which +can be found in many Sony Vaio laptops. Some newer Sony laptops (seems to be +limited to new FX series laptops, at least the FX501 and the FX702) lack a +sonypi device and are not supported at all by this driver. + +It will give access (through a user space utility) to some events those laptops +generate, like: + + - jogdial events (the small wheel on the side of Vaios) + - capture button events (only on Vaio Picturebook series) + - Fn keys + - bluetooth button (only on C1VR model) + - programmable keys, back, help, zoom, thumbphrase buttons, etc. + (when available) + +Those events (see linux/sonypi.h) can be polled using the character device node +/dev/sonypi (major 10, minor auto allocated or specified as a option). +A simple daemon which translates the jogdial movements into mouse wheel events +can be downloaded at: <http://popies.net/sonypi/> + +Another option to intercept the events is to get them directly through the +input layer. + +This driver supports also some ioctl commands for setting the LCD screen +brightness and querying the batteries charge information (some more +commands may be added in the future). + +This driver can also be used to set the camera controls on Picturebook series +(brightness, contrast etc), and is used by the video4linux driver for the +Motion Eye camera. + +Please note that this driver was created by reverse engineering the Windows +driver and the ACPI BIOS, because Sony doesn't agree to release any programming +specs for its laptops. If someone convinces them to do so, drop me a note. + +Driver options: +--------------- + +Several options can be passed to the sonypi driver using the standard +module argument syntax (<param>=<value> when passing the option to the +module or sonypi.<param>=<value> on the kernel boot line when sonypi is +statically linked into the kernel). Those options are: + + =============== ======================================================= + minor: minor number of the misc device /dev/sonypi, + default is -1 (automatic allocation, see /proc/misc + or kernel logs) + + camera: if you have a PictureBook series Vaio (with the + integrated MotionEye camera), set this parameter to 1 + in order to let the driver access to the camera + + fnkeyinit: on some Vaios (C1VE, C1VR etc), the Fn key events don't + get enabled unless you set this parameter to 1. + Do not use this option unless it's actually necessary, + some Vaio models don't deal well with this option. + This option is available only if the kernel is + compiled without ACPI support (since it conflicts + with it and it shouldn't be required anyway if + ACPI is already enabled). + + verbose: set to 1 to print unknown events received from the + sonypi device. + set to 2 to print all events received from the + sonypi device. + + compat: uses some compatibility code for enabling the sonypi + events. If the driver worked for you in the past + (prior to version 1.5) and does not work anymore, + add this option and report to the author. + + mask: event mask telling the driver what events will be + reported to the user. This parameter is required for + some Vaio models where the hardware reuses values + used in other Vaio models (like the FX series who does + not have a jogdial but reuses the jogdial events for + programmable keys events). The default event mask is + set to 0xffffffff, meaning that all possible events + will be tried. You can use the following bits to + construct your own event mask (from + drivers/char/sonypi.h):: + + SONYPI_JOGGER_MASK 0x0001 + SONYPI_CAPTURE_MASK 0x0002 + SONYPI_FNKEY_MASK 0x0004 + SONYPI_BLUETOOTH_MASK 0x0008 + SONYPI_PKEY_MASK 0x0010 + SONYPI_BACK_MASK 0x0020 + SONYPI_HELP_MASK 0x0040 + SONYPI_LID_MASK 0x0080 + SONYPI_ZOOM_MASK 0x0100 + SONYPI_THUMBPHRASE_MASK 0x0200 + SONYPI_MEYE_MASK 0x0400 + SONYPI_MEMORYSTICK_MASK 0x0800 + SONYPI_BATTERY_MASK 0x1000 + SONYPI_WIRELESS_MASK 0x2000 + + useinput: if set (which is the default) two input devices are + created, one which interprets the jogdial events as + mouse events, the other one which acts like a + keyboard reporting the pressing of the special keys. + =============== ======================================================= + +Module use: +----------- + +In order to automatically load the sonypi module on use, you can put those +lines a configuration file in /etc/modprobe.d/:: + + alias char-major-10-250 sonypi + options sonypi minor=250 + +This supposes the use of minor 250 for the sonypi device:: + + # mknod /dev/sonypi c 10 250 + +Bugs: +----- + + - several users reported that this driver disables the BIOS-managed + Fn-keys which put the laptop in sleeping state, or switch the + external monitor on/off. There is no workaround yet, since this + driver disables all APM management for those keys, by enabling the + ACPI management (and the ACPI core stuff is not complete yet). If + you have one of those laptops with working Fn keys and want to + continue to use them, don't use this driver. + + - some users reported that the laptop speed is lower (dhrystone + tested) when using the driver with the fnkeyinit parameter. I cannot + reproduce it on my laptop and not all users have this problem. + This happens because the fnkeyinit parameter enables the ACPI + mode (but without additional ACPI control, like processor + speed handling etc). Use ACPI instead of APM if it works on your + laptop. + + - sonypi lacks the ability to distinguish between certain key + events on some models. + + - some models with the nvidia card (geforce go 6200 tc) uses a + different way to adjust the backlighting of the screen. There + is a userspace utility to adjust the brightness on those models, + which can be downloaded from + https://www.acc.umu.se/~erikw/program/smartdimmer-0.1.tar.bz2 + + - since all development was done by reverse engineering, there is + *absolutely no guarantee* that this driver will not crash your + laptop. Permanently. diff --git a/Documentation/admin-guide/laptops/thinkpad-acpi.rst b/Documentation/admin-guide/laptops/thinkpad-acpi.rst new file mode 100644 index 000000000..e27a1c3f6 --- /dev/null +++ b/Documentation/admin-guide/laptops/thinkpad-acpi.rst @@ -0,0 +1,1662 @@ +=========================== +ThinkPad ACPI Extras Driver +=========================== + +Version 0.25 + +October 16th, 2013 + +- Borislav Deianov <borislav@users.sf.net> +- Henrique de Moraes Holschuh <hmh@hmh.eng.br> + +http://ibm-acpi.sf.net/ + +This is a Linux driver for the IBM and Lenovo ThinkPad laptops. It +supports various features of these laptops which are accessible +through the ACPI and ACPI EC framework, but not otherwise fully +supported by the generic Linux ACPI drivers. + +This driver used to be named ibm-acpi until kernel 2.6.21 and release +0.13-20070314. It used to be in the drivers/acpi tree, but it was +moved to the drivers/misc tree and renamed to thinkpad-acpi for kernel +2.6.22, and release 0.14. It was moved to drivers/platform/x86 for +kernel 2.6.29 and release 0.22. + +The driver is named "thinkpad-acpi". In some places, like module +names and log messages, "thinkpad_acpi" is used because of userspace +issues. + +"tpacpi" is used as a shorthand where "thinkpad-acpi" would be too +long due to length limitations on some Linux kernel versions. + +Status +------ + +The features currently supported are the following (see below for +detailed description): + + - Fn key combinations + - Bluetooth enable and disable + - video output switching, expansion control + - ThinkLight on and off + - CMOS/UCMS control + - LED control + - ACPI sounds + - temperature sensors + - Experimental: embedded controller register dump + - LCD brightness control + - Volume control + - Fan control and monitoring: fan speed, fan enable/disable + - WAN enable and disable + - UWB enable and disable + - LCD Shadow (PrivacyGuard) enable and disable + - Lap mode sensor + - Setting keyboard language + - WWAN Antenna type + +A compatibility table by model and feature is maintained on the web +site, http://ibm-acpi.sf.net/. I appreciate any success or failure +reports, especially if they add to or correct the compatibility table. +Please include the following information in your report: + + - ThinkPad model name + - a copy of your ACPI tables, using the "acpidump" utility + - a copy of the output of dmidecode, with serial numbers + and UUIDs masked off + - which driver features work and which don't + - the observed behavior of non-working features + +Any other comments or patches are also more than welcome. + + +Installation +------------ + +If you are compiling this driver as included in the Linux kernel +sources, look for the CONFIG_THINKPAD_ACPI Kconfig option. +It is located on the menu path: "Device Drivers" -> "X86 Platform +Specific Device Drivers" -> "ThinkPad ACPI Laptop Extras". + + +Features +-------- + +The driver exports two different interfaces to userspace, which can be +used to access the features it provides. One is a legacy procfs-based +interface, which will be removed at some time in the future. The other +is a new sysfs-based interface which is not complete yet. + +The procfs interface creates the /proc/acpi/ibm directory. There is a +file under that directory for each feature it supports. The procfs +interface is mostly frozen, and will change very little if at all: it +will not be extended to add any new functionality in the driver, instead +all new functionality will be implemented on the sysfs interface. + +The sysfs interface tries to blend in the generic Linux sysfs subsystems +and classes as much as possible. Since some of these subsystems are not +yet ready or stabilized, it is expected that this interface will change, +and any and all userspace programs must deal with it. + + +Notes about the sysfs interface +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Unlike what was done with the procfs interface, correctness when talking +to the sysfs interfaces will be enforced, as will correctness in the +thinkpad-acpi's implementation of sysfs interfaces. + +Also, any bugs in the thinkpad-acpi sysfs driver code or in the +thinkpad-acpi's implementation of the sysfs interfaces will be fixed for +maximum correctness, even if that means changing an interface in +non-compatible ways. As these interfaces mature both in the kernel and +in thinkpad-acpi, such changes should become quite rare. + +Applications interfacing to the thinkpad-acpi sysfs interfaces must +follow all sysfs guidelines and correctly process all errors (the sysfs +interface makes extensive use of errors). File descriptors and open / +close operations to the sysfs inodes must also be properly implemented. + +The version of thinkpad-acpi's sysfs interface is exported by the driver +as a driver attribute (see below). + +Sysfs driver attributes are on the driver's sysfs attribute space, +for 2.6.23+ this is /sys/bus/platform/drivers/thinkpad_acpi/ and +/sys/bus/platform/drivers/thinkpad_hwmon/ + +Sysfs device attributes are on the thinkpad_acpi device sysfs attribute +space, for 2.6.23+ this is /sys/devices/platform/thinkpad_acpi/. + +Sysfs device attributes for the sensors and fan are on the +thinkpad_hwmon device's sysfs attribute space, but you should locate it +looking for a hwmon device with the name attribute of "thinkpad", or +better yet, through libsensors. For 4.14+ sysfs attributes were moved to the +hwmon device (/sys/bus/platform/devices/thinkpad_hwmon/hwmon/hwmon? or +/sys/class/hwmon/hwmon?). + +Driver version +-------------- + +procfs: /proc/acpi/ibm/driver + +sysfs driver attribute: version + +The driver name and version. No commands can be written to this file. + + +Sysfs interface version +----------------------- + +sysfs driver attribute: interface_version + +Version of the thinkpad-acpi sysfs interface, as an unsigned long +(output in hex format: 0xAAAABBCC), where: + + AAAA + - major revision + BB + - minor revision + CC + - bugfix revision + +The sysfs interface version changelog for the driver can be found at the +end of this document. Changes to the sysfs interface done by the kernel +subsystems are not documented here, nor are they tracked by this +attribute. + +Changes to the thinkpad-acpi sysfs interface are only considered +non-experimental when they are submitted to Linux mainline, at which +point the changes in this interface are documented and interface_version +may be updated. If you are using any thinkpad-acpi features not yet +sent to mainline for merging, you do so on your own risk: these features +may disappear, or be implemented in a different and incompatible way by +the time they are merged in Linux mainline. + +Changes that are backwards-compatible by nature (e.g. the addition of +attributes that do not change the way the other attributes work) do not +always warrant an update of interface_version. Therefore, one must +expect that an attribute might not be there, and deal with it properly +(an attribute not being there *is* a valid way to make it clear that a +feature is not available in sysfs). + + +Hot keys +-------- + +procfs: /proc/acpi/ibm/hotkey + +sysfs device attribute: hotkey_* + +In a ThinkPad, the ACPI HKEY handler is responsible for communicating +some important events and also keyboard hot key presses to the operating +system. Enabling the hotkey functionality of thinkpad-acpi signals the +firmware that such a driver is present, and modifies how the ThinkPad +firmware will behave in many situations. + +The driver enables the HKEY ("hot key") event reporting automatically +when loaded, and disables it when it is removed. + +The driver will report HKEY events in the following format:: + + ibm/hotkey HKEY 00000080 0000xxxx + +Some of these events refer to hot key presses, but not all of them. + +The driver will generate events over the input layer for hot keys and +radio switches, and over the ACPI netlink layer for other events. The +input layer support accepts the standard IOCTLs to remap the keycodes +assigned to each hot key. + +The hot key bit mask allows some control over which hot keys generate +events. If a key is "masked" (bit set to 0 in the mask), the firmware +will handle it. If it is "unmasked", it signals the firmware that +thinkpad-acpi would prefer to handle it, if the firmware would be so +kind to allow it (and it often doesn't!). + +Not all bits in the mask can be modified. Not all bits that can be +modified do anything. Not all hot keys can be individually controlled +by the mask. Some models do not support the mask at all. The behaviour +of the mask is, therefore, highly dependent on the ThinkPad model. + +The driver will filter out any unmasked hotkeys, so even if the firmware +doesn't allow disabling an specific hotkey, the driver will not report +events for unmasked hotkeys. + +Note that unmasking some keys prevents their default behavior. For +example, if Fn+F5 is unmasked, that key will no longer enable/disable +Bluetooth by itself in firmware. + +Note also that not all Fn key combinations are supported through ACPI +depending on the ThinkPad model and firmware version. On those +ThinkPads, it is still possible to support some extra hotkeys by +polling the "CMOS NVRAM" at least 10 times per second. The driver +attempts to enables this functionality automatically when required. + +procfs notes +^^^^^^^^^^^^ + +The following commands can be written to the /proc/acpi/ibm/hotkey file:: + + echo 0xffffffff > /proc/acpi/ibm/hotkey -- enable all hot keys + echo 0 > /proc/acpi/ibm/hotkey -- disable all possible hot keys + ... any other 8-hex-digit mask ... + echo reset > /proc/acpi/ibm/hotkey -- restore the recommended mask + +The following commands have been deprecated and will cause the kernel +to log a warning:: + + echo enable > /proc/acpi/ibm/hotkey -- does nothing + echo disable > /proc/acpi/ibm/hotkey -- returns an error + +The procfs interface does not support NVRAM polling control. So as to +maintain maximum bug-to-bug compatibility, it does not report any masks, +nor does it allow one to manipulate the hot key mask when the firmware +does not support masks at all, even if NVRAM polling is in use. + +sysfs notes +^^^^^^^^^^^ + + hotkey_bios_enabled: + DEPRECATED, WILL BE REMOVED SOON. + + Returns 0. + + hotkey_bios_mask: + DEPRECATED, DON'T USE, WILL BE REMOVED IN THE FUTURE. + + Returns the hot keys mask when thinkpad-acpi was loaded. + Upon module unload, the hot keys mask will be restored + to this value. This is always 0x80c, because those are + the hotkeys that were supported by ancient firmware + without mask support. + + hotkey_enable: + DEPRECATED, WILL BE REMOVED SOON. + + 0: returns -EPERM + 1: does nothing + + hotkey_mask: + bit mask to enable reporting (and depending on + the firmware, ACPI event generation) for each hot key + (see above). Returns the current status of the hot keys + mask, and allows one to modify it. + + hotkey_all_mask: + bit mask that should enable event reporting for all + supported hot keys, when echoed to hotkey_mask above. + Unless you know which events need to be handled + passively (because the firmware *will* handle them + anyway), do *not* use hotkey_all_mask. Use + hotkey_recommended_mask, instead. You have been warned. + + hotkey_recommended_mask: + bit mask that should enable event reporting for all + supported hot keys, except those which are always + handled by the firmware anyway. Echo it to + hotkey_mask above, to use. This is the default mask + used by the driver. + + hotkey_source_mask: + bit mask that selects which hot keys will the driver + poll the NVRAM for. This is auto-detected by the driver + based on the capabilities reported by the ACPI firmware, + but it can be overridden at runtime. + + Hot keys whose bits are set in hotkey_source_mask are + polled for in NVRAM, and reported as hotkey events if + enabled in hotkey_mask. Only a few hot keys are + available through CMOS NVRAM polling. + + Warning: when in NVRAM mode, the volume up/down/mute + keys are synthesized according to changes in the mixer, + which uses a single volume up or volume down hotkey + press to unmute, as per the ThinkPad volume mixer user + interface. When in ACPI event mode, volume up/down/mute + events are reported by the firmware and can behave + differently (and that behaviour changes with firmware + version -- not just with firmware models -- as well as + OSI(Linux) state). + + hotkey_poll_freq: + frequency in Hz for hot key polling. It must be between + 0 and 25 Hz. Polling is only carried out when strictly + needed. + + Setting hotkey_poll_freq to zero disables polling, and + will cause hot key presses that require NVRAM polling + to never be reported. + + Setting hotkey_poll_freq too low may cause repeated + pressings of the same hot key to be misreported as a + single key press, or to not even be detected at all. + The recommended polling frequency is 10Hz. + + hotkey_radio_sw: + If the ThinkPad has a hardware radio switch, this + attribute will read 0 if the switch is in the "radios + disabled" position, and 1 if the switch is in the + "radios enabled" position. + + This attribute has poll()/select() support. + + hotkey_tablet_mode: + If the ThinkPad has tablet capabilities, this attribute + will read 0 if the ThinkPad is in normal mode, and + 1 if the ThinkPad is in tablet mode. + + This attribute has poll()/select() support. + + wakeup_reason: + Set to 1 if the system is waking up because the user + requested a bay ejection. Set to 2 if the system is + waking up because the user requested the system to + undock. Set to zero for normal wake-ups or wake-ups + due to unknown reasons. + + This attribute has poll()/select() support. + + wakeup_hotunplug_complete: + Set to 1 if the system was waken up because of an + undock or bay ejection request, and that request + was successfully completed. At this point, it might + be useful to send the system back to sleep, at the + user's choice. Refer to HKEY events 0x4003 and + 0x3003, below. + + This attribute has poll()/select() support. + +input layer notes +^^^^^^^^^^^^^^^^^ + +A Hot key is mapped to a single input layer EV_KEY event, possibly +followed by an EV_MSC MSC_SCAN event that shall contain that key's scan +code. An EV_SYN event will always be generated to mark the end of the +event block. + +Do not use the EV_MSC MSC_SCAN events to process keys. They are to be +used as a helper to remap keys, only. They are particularly useful when +remapping KEY_UNKNOWN keys. + +The events are available in an input device, with the following id: + + ============== ============================== + Bus BUS_HOST + vendor 0x1014 (PCI_VENDOR_ID_IBM) or + 0x17aa (PCI_VENDOR_ID_LENOVO) + product 0x5054 ("TP") + version 0x4101 + ============== ============================== + +The version will have its LSB incremented if the keymap changes in a +backwards-compatible way. The MSB shall always be 0x41 for this input +device. If the MSB is not 0x41, do not use the device as described in +this section, as it is either something else (e.g. another input device +exported by a thinkpad driver, such as HDAPS) or its functionality has +been changed in a non-backwards compatible way. + +Adding other event types for other functionalities shall be considered a +backwards-compatible change for this input device. + +Thinkpad-acpi Hot Key event map (version 0x4101): + +======= ======= ============== ============================================== +ACPI Scan +event code Key Notes +======= ======= ============== ============================================== +0x1001 0x00 FN+F1 - + +0x1002 0x01 FN+F2 IBM: battery (rare) + Lenovo: Screen lock + +0x1003 0x02 FN+F3 Many IBM models always report + this hot key, even with hot keys + disabled or with Fn+F3 masked + off + IBM: screen lock, often turns + off the ThinkLight as side-effect + Lenovo: battery + +0x1004 0x03 FN+F4 Sleep button (ACPI sleep button + semantics, i.e. sleep-to-RAM). + It always generates some kind + of event, either the hot key + event or an ACPI sleep button + event. The firmware may + refuse to generate further FN+F4 + key presses until a S3 or S4 ACPI + sleep cycle is performed or some + time passes. + +0x1005 0x04 FN+F5 Radio. Enables/disables + the internal Bluetooth hardware + and W-WAN card if left in control + of the firmware. Does not affect + the WLAN card. + Should be used to turn on/off all + radios (Bluetooth+W-WAN+WLAN), + really. + +0x1006 0x05 FN+F6 - + +0x1007 0x06 FN+F7 Video output cycle. + Do you feel lucky today? + +0x1008 0x07 FN+F8 IBM: toggle screen expand + Lenovo: configure UltraNav, + or toggle screen expand + +0x1009 0x08 FN+F9 - + +... ... ... ... + +0x100B 0x0A FN+F11 - + +0x100C 0x0B FN+F12 Sleep to disk. You are always + supposed to handle it yourself, + either through the ACPI event, + or through a hotkey event. + The firmware may refuse to + generate further FN+F12 key + press events until a S3 or S4 + ACPI sleep cycle is performed, + or some time passes. + +0x100D 0x0C FN+BACKSPACE - +0x100E 0x0D FN+INSERT - +0x100F 0x0E FN+DELETE - + +0x1010 0x0F FN+HOME Brightness up. This key is + always handled by the firmware + in IBM ThinkPads, even when + unmasked. Just leave it alone. + For Lenovo ThinkPads with a new + BIOS, it has to be handled either + by the ACPI OSI, or by userspace. + The driver does the right thing, + never mess with this. +0x1011 0x10 FN+END Brightness down. See brightness + up for details. + +0x1012 0x11 FN+PGUP ThinkLight toggle. This key is + always handled by the firmware, + even when unmasked. + +0x1013 0x12 FN+PGDOWN - + +0x1014 0x13 FN+SPACE Zoom key + +0x1015 0x14 VOLUME UP Internal mixer volume up. This + key is always handled by the + firmware, even when unmasked. + NOTE: Lenovo seems to be changing + this. +0x1016 0x15 VOLUME DOWN Internal mixer volume up. This + key is always handled by the + firmware, even when unmasked. + NOTE: Lenovo seems to be changing + this. +0x1017 0x16 MUTE Mute internal mixer. This + key is always handled by the + firmware, even when unmasked. + +0x1018 0x17 THINKPAD ThinkPad/Access IBM/Lenovo key + +0x1019 0x18 unknown + +... ... ... + +0x1020 0x1F unknown +======= ======= ============== ============================================== + +The ThinkPad firmware does not allow one to differentiate when most hot +keys are pressed or released (either that, or we don't know how to, yet). +For these keys, the driver generates a set of events for a key press and +immediately issues the same set of events for a key release. It is +unknown by the driver if the ThinkPad firmware triggered these events on +hot key press or release, but the firmware will do it for either one, not +both. + +If a key is mapped to KEY_RESERVED, it generates no input events at all. +If a key is mapped to KEY_UNKNOWN, it generates an input event that +includes an scan code. If a key is mapped to anything else, it will +generate input device EV_KEY events. + +In addition to the EV_KEY events, thinkpad-acpi may also issue EV_SW +events for switches: + +============== ============================================== +SW_RFKILL_ALL T60 and later hardware rfkill rocker switch +SW_TABLET_MODE Tablet ThinkPads HKEY events 0x5009 and 0x500A +============== ============================================== + +Non hotkey ACPI HKEY event map +------------------------------ + +Events that are never propagated by the driver: + +====== ================================================== +0x2304 System is waking up from suspend to undock +0x2305 System is waking up from suspend to eject bay +0x2404 System is waking up from hibernation to undock +0x2405 System is waking up from hibernation to eject bay +0x5001 Lid closed +0x5002 Lid opened +0x5009 Tablet swivel: switched to tablet mode +0x500A Tablet swivel: switched to normal mode +0x5010 Brightness level changed/control event +0x6000 KEYBOARD: Numlock key pressed +0x6005 KEYBOARD: Fn key pressed (TO BE VERIFIED) +0x7000 Radio Switch may have changed state +====== ================================================== + + +Events that are propagated by the driver to userspace: + +====== ===================================================== +0x2313 ALARM: System is waking up from suspend because + the battery is nearly empty +0x2413 ALARM: System is waking up from hibernation because + the battery is nearly empty +0x3003 Bay ejection (see 0x2x05) complete, can sleep again +0x3006 Bay hotplug request (hint to power up SATA link when + the optical drive tray is ejected) +0x4003 Undocked (see 0x2x04), can sleep again +0x4010 Docked into hotplug port replicator (non-ACPI dock) +0x4011 Undocked from hotplug port replicator (non-ACPI dock) +0x500B Tablet pen inserted into its storage bay +0x500C Tablet pen removed from its storage bay +0x6011 ALARM: battery is too hot +0x6012 ALARM: battery is extremely hot +0x6021 ALARM: a sensor is too hot +0x6022 ALARM: a sensor is extremely hot +0x6030 System thermal table changed +0x6032 Thermal Control command set completion (DYTC, Windows) +0x6040 Nvidia Optimus/AC adapter related (TO BE VERIFIED) +0x60C0 X1 Yoga 2016, Tablet mode status changed +0x60F0 Thermal Transformation changed (GMTS, Windows) +====== ===================================================== + +Battery nearly empty alarms are a last resort attempt to get the +operating system to hibernate or shutdown cleanly (0x2313), or shutdown +cleanly (0x2413) before power is lost. They must be acted upon, as the +wake up caused by the firmware will have negated most safety nets... + +When any of the "too hot" alarms happen, according to Lenovo the user +should suspend or hibernate the laptop (and in the case of battery +alarms, unplug the AC adapter) to let it cool down. These alarms do +signal that something is wrong, they should never happen on normal +operating conditions. + +The "extremely hot" alarms are emergencies. According to Lenovo, the +operating system is to force either an immediate suspend or hibernate +cycle, or a system shutdown. Obviously, something is very wrong if this +happens. + + +Brightness hotkey notes +^^^^^^^^^^^^^^^^^^^^^^^ + +Don't mess with the brightness hotkeys in a Thinkpad. If you want +notifications for OSD, use the sysfs backlight class event support. + +The driver will issue KEY_BRIGHTNESS_UP and KEY_BRIGHTNESS_DOWN events +automatically for the cases were userspace has to do something to +implement brightness changes. When you override these events, you will +either fail to handle properly the ThinkPads that require explicit +action to change backlight brightness, or the ThinkPads that require +that no action be taken to work properly. + + +Bluetooth +--------- + +procfs: /proc/acpi/ibm/bluetooth + +sysfs device attribute: bluetooth_enable (deprecated) + +sysfs rfkill class: switch "tpacpi_bluetooth_sw" + +This feature shows the presence and current state of a ThinkPad +Bluetooth device in the internal ThinkPad CDC slot. + +If the ThinkPad supports it, the Bluetooth state is stored in NVRAM, +so it is kept across reboots and power-off. + +Procfs notes +^^^^^^^^^^^^ + +If Bluetooth is installed, the following commands can be used:: + + echo enable > /proc/acpi/ibm/bluetooth + echo disable > /proc/acpi/ibm/bluetooth + +Sysfs notes +^^^^^^^^^^^ + + If the Bluetooth CDC card is installed, it can be enabled / + disabled through the "bluetooth_enable" thinkpad-acpi device + attribute, and its current status can also be queried. + + enable: + + - 0: disables Bluetooth / Bluetooth is disabled + - 1: enables Bluetooth / Bluetooth is enabled. + + Note: this interface has been superseded by the generic rfkill + class. It has been deprecated, and it will be removed in year + 2010. + + rfkill controller switch "tpacpi_bluetooth_sw": refer to + Documentation/driver-api/rfkill.rst for details. + + +Video output control -- /proc/acpi/ibm/video +-------------------------------------------- + +This feature allows control over the devices used for video output - +LCD, CRT or DVI (if available). The following commands are available:: + + echo lcd_enable > /proc/acpi/ibm/video + echo lcd_disable > /proc/acpi/ibm/video + echo crt_enable > /proc/acpi/ibm/video + echo crt_disable > /proc/acpi/ibm/video + echo dvi_enable > /proc/acpi/ibm/video + echo dvi_disable > /proc/acpi/ibm/video + echo auto_enable > /proc/acpi/ibm/video + echo auto_disable > /proc/acpi/ibm/video + echo expand_toggle > /proc/acpi/ibm/video + echo video_switch > /proc/acpi/ibm/video + +NOTE: + Access to this feature is restricted to processes owning the + CAP_SYS_ADMIN capability for safety reasons, as it can interact badly + enough with some versions of X.org to crash it. + +Each video output device can be enabled or disabled individually. +Reading /proc/acpi/ibm/video shows the status of each device. + +Automatic video switching can be enabled or disabled. When automatic +video switching is enabled, certain events (e.g. opening the lid, +docking or undocking) cause the video output device to change +automatically. While this can be useful, it also causes flickering +and, on the X40, video corruption. By disabling automatic switching, +the flickering or video corruption can be avoided. + +The video_switch command cycles through the available video outputs +(it simulates the behavior of Fn-F7). + +Video expansion can be toggled through this feature. This controls +whether the display is expanded to fill the entire LCD screen when a +mode with less than full resolution is used. Note that the current +video expansion status cannot be determined through this feature. + +Note that on many models (particularly those using Radeon graphics +chips) the X driver configures the video card in a way which prevents +Fn-F7 from working. This also disables the video output switching +features of this driver, as it uses the same ACPI methods as +Fn-F7. Video switching on the console should still work. + +UPDATE: refer to https://bugs.freedesktop.org/show_bug.cgi?id=2000 + + +ThinkLight control +------------------ + +procfs: /proc/acpi/ibm/light + +sysfs attributes: as per LED class, for the "tpacpi::thinklight" LED + +procfs notes +^^^^^^^^^^^^ + +The ThinkLight status can be read and set through the procfs interface. A +few models which do not make the status available will show the ThinkLight +status as "unknown". The available commands are:: + + echo on > /proc/acpi/ibm/light + echo off > /proc/acpi/ibm/light + +sysfs notes +^^^^^^^^^^^ + +The ThinkLight sysfs interface is documented by the LED class +documentation, in Documentation/leds/leds-class.rst. The ThinkLight LED name +is "tpacpi::thinklight". + +Due to limitations in the sysfs LED class, if the status of the ThinkLight +cannot be read or if it is unknown, thinkpad-acpi will report it as "off". +It is impossible to know if the status returned through sysfs is valid. + + +CMOS/UCMS control +----------------- + +procfs: /proc/acpi/ibm/cmos + +sysfs device attribute: cmos_command + +This feature is mostly used internally by the ACPI firmware to keep the legacy +CMOS NVRAM bits in sync with the current machine state, and to record this +state so that the ThinkPad will retain such settings across reboots. + +Some of these commands actually perform actions in some ThinkPad models, but +this is expected to disappear more and more in newer models. As an example, in +a T43 and in a X40, commands 12 and 13 still control the ThinkLight state for +real, but commands 0 to 2 don't control the mixer anymore (they have been +phased out) and just update the NVRAM. + +The range of valid cmos command numbers is 0 to 21, but not all have an +effect and the behavior varies from model to model. Here is the behavior +on the X40 (tpb is the ThinkPad Buttons utility): + + - 0 - Related to "Volume down" key press + - 1 - Related to "Volume up" key press + - 2 - Related to "Mute on" key press + - 3 - Related to "Access IBM" key press + - 4 - Related to "LCD brightness up" key press + - 5 - Related to "LCD brightness down" key press + - 11 - Related to "toggle screen expansion" key press/function + - 12 - Related to "ThinkLight on" + - 13 - Related to "ThinkLight off" + - 14 - Related to "ThinkLight" key press (toggle ThinkLight) + +The cmos command interface is prone to firmware split-brain problems, as +in newer ThinkPads it is just a compatibility layer. Do not use it, it is +exported just as a debug tool. + + +LED control +----------- + +procfs: /proc/acpi/ibm/led +sysfs attributes: as per LED class, see below for names + +Some of the LED indicators can be controlled through this feature. On +some older ThinkPad models, it is possible to query the status of the +LED indicators as well. Newer ThinkPads cannot query the real status +of the LED indicators. + +Because misuse of the LEDs could induce an unaware user to perform +dangerous actions (like undocking or ejecting a bay device while the +buses are still active), or mask an important alarm (such as a nearly +empty battery, or a broken battery), access to most LEDs is +restricted. + +Unrestricted access to all LEDs requires that thinkpad-acpi be +compiled with the CONFIG_THINKPAD_ACPI_UNSAFE_LEDS option enabled. +Distributions must never enable this option. Individual users that +are aware of the consequences are welcome to enabling it. + +Audio mute and microphone mute LEDs are supported, but currently not +visible to userspace. They are used by the snd-hda-intel audio driver. + +procfs notes +^^^^^^^^^^^^ + +The available commands are:: + + echo '<LED number> on' >/proc/acpi/ibm/led + echo '<LED number> off' >/proc/acpi/ibm/led + echo '<LED number> blink' >/proc/acpi/ibm/led + +The <LED number> range is 0 to 15. The set of LEDs that can be +controlled varies from model to model. Here is the common ThinkPad +mapping: + + - 0 - power + - 1 - battery (orange) + - 2 - battery (green) + - 3 - UltraBase/dock + - 4 - UltraBay + - 5 - UltraBase battery slot + - 6 - (unknown) + - 7 - standby + - 8 - dock status 1 + - 9 - dock status 2 + - 10, 11 - (unknown) + - 12 - thinkvantage + - 13, 14, 15 - (unknown) + +All of the above can be turned on and off and can be made to blink. + +sysfs notes +^^^^^^^^^^^ + +The ThinkPad LED sysfs interface is described in detail by the LED class +documentation, in Documentation/leds/leds-class.rst. + +The LEDs are named (in LED ID order, from 0 to 12): +"tpacpi::power", "tpacpi:orange:batt", "tpacpi:green:batt", +"tpacpi::dock_active", "tpacpi::bay_active", "tpacpi::dock_batt", +"tpacpi::unknown_led", "tpacpi::standby", "tpacpi::dock_status1", +"tpacpi::dock_status2", "tpacpi::unknown_led2", "tpacpi::unknown_led3", +"tpacpi::thinkvantage". + +Due to limitations in the sysfs LED class, if the status of the LED +indicators cannot be read due to an error, thinkpad-acpi will report it as +a brightness of zero (same as LED off). + +If the thinkpad firmware doesn't support reading the current status, +trying to read the current LED brightness will just return whatever +brightness was last written to that attribute. + +These LEDs can blink using hardware acceleration. To request that a +ThinkPad indicator LED should blink in hardware accelerated mode, use the +"timer" trigger, and leave the delay_on and delay_off parameters set to +zero (to request hardware acceleration autodetection). + +LEDs that are known not to exist in a given ThinkPad model are not +made available through the sysfs interface. If you have a dock and you +notice there are LEDs listed for your ThinkPad that do not exist (and +are not in the dock), or if you notice that there are missing LEDs, +a report to ibm-acpi-devel@lists.sourceforge.net is appreciated. + + +ACPI sounds -- /proc/acpi/ibm/beep +---------------------------------- + +The BEEP method is used internally by the ACPI firmware to provide +audible alerts in various situations. This feature allows the same +sounds to be triggered manually. + +The commands are non-negative integer numbers:: + + echo <number> >/proc/acpi/ibm/beep + +The valid <number> range is 0 to 17. Not all numbers trigger sounds +and the sounds vary from model to model. Here is the behavior on the +X40: + + - 0 - stop a sound in progress (but use 17 to stop 16) + - 2 - two beeps, pause, third beep ("low battery") + - 3 - single beep + - 4 - high, followed by low-pitched beep ("unable") + - 5 - single beep + - 6 - very high, followed by high-pitched beep ("AC/DC") + - 7 - high-pitched beep + - 9 - three short beeps + - 10 - very long beep + - 12 - low-pitched beep + - 15 - three high-pitched beeps repeating constantly, stop with 0 + - 16 - one medium-pitched beep repeating constantly, stop with 17 + - 17 - stop 16 + + +Temperature sensors +------------------- + +procfs: /proc/acpi/ibm/thermal + +sysfs device attributes: (hwmon "thinkpad") temp*_input + +Most ThinkPads include six or more separate temperature sensors but only +expose the CPU temperature through the standard ACPI methods. This +feature shows readings from up to eight different sensors on older +ThinkPads, and up to sixteen different sensors on newer ThinkPads. + +For example, on the X40, a typical output may be: + +temperatures: + 42 42 45 41 36 -128 33 -128 + +On the T43/p, a typical output may be: + +temperatures: + 48 48 36 52 38 -128 31 -128 48 52 48 -128 -128 -128 -128 -128 + +The mapping of thermal sensors to physical locations varies depending on +system-board model (and thus, on ThinkPad model). + +https://thinkwiki.org/wiki/Thermal_Sensors is a public wiki page that +tries to track down these locations for various models. + +Most (newer?) models seem to follow this pattern: + +- 1: CPU +- 2: (depends on model) +- 3: (depends on model) +- 4: GPU +- 5: Main battery: main sensor +- 6: Bay battery: main sensor +- 7: Main battery: secondary sensor +- 8: Bay battery: secondary sensor +- 9-15: (depends on model) + +For the R51 (source: Thomas Gruber): + +- 2: Mini-PCI +- 3: Internal HDD + +For the T43, T43/p (source: Shmidoax/Thinkwiki.org) +https://thinkwiki.org/wiki/Thermal_Sensors#ThinkPad_T43.2C_T43p + +- 2: System board, left side (near PCMCIA slot), reported as HDAPS temp +- 3: PCMCIA slot +- 9: MCH (northbridge) to DRAM Bus +- 10: Clock-generator, mini-pci card and ICH (southbridge), under Mini-PCI + card, under touchpad +- 11: Power regulator, underside of system board, below F2 key + +The A31 has a very atypical layout for the thermal sensors +(source: Milos Popovic, https://thinkwiki.org/wiki/Thermal_Sensors#ThinkPad_A31) + +- 1: CPU +- 2: Main Battery: main sensor +- 3: Power Converter +- 4: Bay Battery: main sensor +- 5: MCH (northbridge) +- 6: PCMCIA/ambient +- 7: Main Battery: secondary sensor +- 8: Bay Battery: secondary sensor + + +Procfs notes +^^^^^^^^^^^^ + + Readings from sensors that are not available return -128. + No commands can be written to this file. + +Sysfs notes +^^^^^^^^^^^ + + Sensors that are not available return the ENXIO error. This + status may change at runtime, as there are hotplug thermal + sensors, like those inside the batteries and docks. + + thinkpad-acpi thermal sensors are reported through the hwmon + subsystem, and follow all of the hwmon guidelines at + Documentation/hwmon. + +EXPERIMENTAL: Embedded controller register dump +----------------------------------------------- + +This feature is not included in the thinkpad driver anymore. +Instead the EC can be accessed through /sys/kernel/debug/ec with +a userspace tool which can be found here: +ftp://ftp.suse.com/pub/people/trenn/sources/ec + +Use it to determine the register holding the fan +speed on some models. To do that, do the following: + + - make sure the battery is fully charged + - make sure the fan is running + - use above mentioned tool to read out the EC + +Often fan and temperature values vary between +readings. Since temperatures don't change vary fast, you can take +several quick dumps to eliminate them. + +You can use a similar method to figure out the meaning of other +embedded controller registers - e.g. make sure nothing else changes +except the charging or discharging battery to determine which +registers contain the current battery capacity, etc. If you experiment +with this, do send me your results (including some complete dumps with +a description of the conditions when they were taken.) + + +LCD brightness control +---------------------- + +procfs: /proc/acpi/ibm/brightness + +sysfs backlight device "thinkpad_screen" + +This feature allows software control of the LCD brightness on ThinkPad +models which don't have a hardware brightness slider. + +It has some limitations: the LCD backlight cannot be actually turned +on or off by this interface, it just controls the backlight brightness +level. + +On IBM (and some of the earlier Lenovo) ThinkPads, the backlight control +has eight brightness levels, ranging from 0 to 7. Some of the levels +may not be distinct. Later Lenovo models that implement the ACPI +display backlight brightness control methods have 16 levels, ranging +from 0 to 15. + +For IBM ThinkPads, there are two interfaces to the firmware for direct +brightness control, EC and UCMS (or CMOS). To select which one should be +used, use the brightness_mode module parameter: brightness_mode=1 selects +EC mode, brightness_mode=2 selects UCMS mode, brightness_mode=3 selects EC +mode with NVRAM backing (so that brightness changes are remembered across +shutdown/reboot). + +The driver tries to select which interface to use from a table of +defaults for each ThinkPad model. If it makes a wrong choice, please +report this as a bug, so that we can fix it. + +Lenovo ThinkPads only support brightness_mode=2 (UCMS). + +When display backlight brightness controls are available through the +standard ACPI interface, it is best to use it instead of this direct +ThinkPad-specific interface. The driver will disable its native +backlight brightness control interface if it detects that the standard +ACPI interface is available in the ThinkPad. + +If you want to use the thinkpad-acpi backlight brightness control +instead of the generic ACPI video backlight brightness control for some +reason, you should use the acpi_backlight=vendor kernel parameter. + +The brightness_enable module parameter can be used to control whether +the LCD brightness control feature will be enabled when available. +brightness_enable=0 forces it to be disabled. brightness_enable=1 +forces it to be enabled when available, even if the standard ACPI +interface is also available. + +Procfs notes +^^^^^^^^^^^^ + +The available commands are:: + + echo up >/proc/acpi/ibm/brightness + echo down >/proc/acpi/ibm/brightness + echo 'level <level>' >/proc/acpi/ibm/brightness + +Sysfs notes +^^^^^^^^^^^ + +The interface is implemented through the backlight sysfs class, which is +poorly documented at this time. + +Locate the thinkpad_screen device under /sys/class/backlight, and inside +it there will be the following attributes: + + max_brightness: + Reads the maximum brightness the hardware can be set to. + The minimum is always zero. + + actual_brightness: + Reads what brightness the screen is set to at this instant. + + brightness: + Writes request the driver to change brightness to the + given value. Reads will tell you what brightness the + driver is trying to set the display to when "power" is set + to zero and the display has not been dimmed by a kernel + power management event. + + power: + power management mode, where 0 is "display on", and 1 to 3 + will dim the display backlight to brightness level 0 + because thinkpad-acpi cannot really turn the backlight + off. Kernel power management events can temporarily + increase the current power management level, i.e. they can + dim the display. + + +WARNING: + + Whatever you do, do NOT ever call thinkpad-acpi backlight-level change + interface and the ACPI-based backlight level change interface + (available on newer BIOSes, and driven by the Linux ACPI video driver) + at the same time. The two will interact in bad ways, do funny things, + and maybe reduce the life of the backlight lamps by needlessly kicking + its level up and down at every change. + + +Volume control (Console Audio control) +-------------------------------------- + +procfs: /proc/acpi/ibm/volume + +ALSA: "ThinkPad Console Audio Control", default ID: "ThinkPadEC" + +NOTE: by default, the volume control interface operates in read-only +mode, as it is supposed to be used for on-screen-display purposes. +The read/write mode can be enabled through the use of the +"volume_control=1" module parameter. + +NOTE: distros are urged to not enable volume_control by default, this +should be done by the local admin only. The ThinkPad UI is for the +console audio control to be done through the volume keys only, and for +the desktop environment to just provide on-screen-display feedback. +Software volume control should be done only in the main AC97/HDA +mixer. + + +About the ThinkPad Console Audio control +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +ThinkPads have a built-in amplifier and muting circuit that drives the +console headphone and speakers. This circuit is after the main AC97 +or HDA mixer in the audio path, and under exclusive control of the +firmware. + +ThinkPads have three special hotkeys to interact with the console +audio control: volume up, volume down and mute. + +It is worth noting that the normal way the mute function works (on +ThinkPads that do not have a "mute LED") is: + +1. Press mute to mute. It will *always* mute, you can press it as + many times as you want, and the sound will remain mute. + +2. Press either volume key to unmute the ThinkPad (it will _not_ + change the volume, it will just unmute). + +This is a very superior design when compared to the cheap software-only +mute-toggle solution found on normal consumer laptops: you can be +absolutely sure the ThinkPad will not make noise if you press the mute +button, no matter the previous state. + +The IBM ThinkPads, and the earlier Lenovo ThinkPads have variable-gain +amplifiers driving the speakers and headphone output, and the firmware +also handles volume control for the headphone and speakers on these +ThinkPads without any help from the operating system (this volume +control stage exists after the main AC97 or HDA mixer in the audio +path). + +The newer Lenovo models only have firmware mute control, and depend on +the main HDA mixer to do volume control (which is done by the operating +system). In this case, the volume keys are filtered out for unmute +key press (there are some firmware bugs in this area) and delivered as +normal key presses to the operating system (thinkpad-acpi is not +involved). + + +The ThinkPad-ACPI volume control +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The preferred way to interact with the Console Audio control is the +ALSA interface. + +The legacy procfs interface allows one to read the current state, +and if volume control is enabled, accepts the following commands:: + + echo up >/proc/acpi/ibm/volume + echo down >/proc/acpi/ibm/volume + echo mute >/proc/acpi/ibm/volume + echo unmute >/proc/acpi/ibm/volume + echo 'level <level>' >/proc/acpi/ibm/volume + +The <level> number range is 0 to 14 although not all of them may be +distinct. To unmute the volume after the mute command, use either the +up or down command (the level command will not unmute the volume), or +the unmute command. + +You can use the volume_capabilities parameter to tell the driver +whether your thinkpad has volume control or mute-only control: +volume_capabilities=1 for mixers with mute and volume control, +volume_capabilities=2 for mixers with only mute control. + +If the driver misdetects the capabilities for your ThinkPad model, +please report this to ibm-acpi-devel@lists.sourceforge.net, so that we +can update the driver. + +There are two strategies for volume control. To select which one +should be used, use the volume_mode module parameter: volume_mode=1 +selects EC mode, and volume_mode=3 selects EC mode with NVRAM backing +(so that volume/mute changes are remembered across shutdown/reboot). + +The driver will operate in volume_mode=3 by default. If that does not +work well on your ThinkPad model, please report this to +ibm-acpi-devel@lists.sourceforge.net. + +The driver supports the standard ALSA module parameters. If the ALSA +mixer is disabled, the driver will disable all volume functionality. + + +Fan control and monitoring: fan speed, fan enable/disable +--------------------------------------------------------- + +procfs: /proc/acpi/ibm/fan + +sysfs device attributes: (hwmon "thinkpad") fan1_input, pwm1, pwm1_enable, fan2_input + +sysfs hwmon driver attributes: fan_watchdog + +NOTE NOTE NOTE: + fan control operations are disabled by default for + safety reasons. To enable them, the module parameter "fan_control=1" + must be given to thinkpad-acpi. + +This feature attempts to show the current fan speed, control mode and +other fan data that might be available. The speed is read directly +from the hardware registers of the embedded controller. This is known +to work on later R, T, X and Z series ThinkPads but may show a bogus +value on other models. + +Some Lenovo ThinkPads support a secondary fan. This fan cannot be +controlled separately, it shares the main fan control. + +Fan levels +^^^^^^^^^^ + +Most ThinkPad fans work in "levels" at the firmware interface. Level 0 +stops the fan. The higher the level, the higher the fan speed, although +adjacent levels often map to the same fan speed. 7 is the highest +level, where the fan reaches the maximum recommended speed. + +Level "auto" means the EC changes the fan level according to some +internal algorithm, usually based on readings from the thermal sensors. + +There is also a "full-speed" level, also known as "disengaged" level. +In this level, the EC disables the speed-locked closed-loop fan control, +and drives the fan as fast as it can go, which might exceed hardware +limits, so use this level with caution. + +The fan usually ramps up or down slowly from one speed to another, and +it is normal for the EC to take several seconds to react to fan +commands. The full-speed level may take up to two minutes to ramp up to +maximum speed, and in some ThinkPads, the tachometer readings go stale +while the EC is transitioning to the full-speed level. + +WARNING WARNING WARNING: do not leave the fan disabled unless you are +monitoring all of the temperature sensor readings and you are ready to +enable it if necessary to avoid overheating. + +An enabled fan in level "auto" may stop spinning if the EC decides the +ThinkPad is cool enough and doesn't need the extra airflow. This is +normal, and the EC will spin the fan up if the various thermal readings +rise too much. + +On the X40, this seems to depend on the CPU and HDD temperatures. +Specifically, the fan is turned on when either the CPU temperature +climbs to 56 degrees or the HDD temperature climbs to 46 degrees. The +fan is turned off when the CPU temperature drops to 49 degrees and the +HDD temperature drops to 41 degrees. These thresholds cannot +currently be controlled. + +The ThinkPad's ACPI DSDT code will reprogram the fan on its own when +certain conditions are met. It will override any fan programming done +through thinkpad-acpi. + +The thinkpad-acpi kernel driver can be programmed to revert the fan +level to a safe setting if userspace does not issue one of the procfs +fan commands: "enable", "disable", "level" or "watchdog", or if there +are no writes to pwm1_enable (or to pwm1 *if and only if* pwm1_enable is +set to 1, manual mode) within a configurable amount of time of up to +120 seconds. This functionality is called fan safety watchdog. + +Note that the watchdog timer stops after it enables the fan. It will be +rearmed again automatically (using the same interval) when one of the +above mentioned fan commands is received. The fan watchdog is, +therefore, not suitable to protect against fan mode changes made through +means other than the "enable", "disable", and "level" procfs fan +commands, or the hwmon fan control sysfs interface. + +Procfs notes +^^^^^^^^^^^^ + +The fan may be enabled or disabled with the following commands:: + + echo enable >/proc/acpi/ibm/fan + echo disable >/proc/acpi/ibm/fan + +Placing a fan on level 0 is the same as disabling it. Enabling a fan +will try to place it in a safe level if it is too slow or disabled. + +The fan level can be controlled with the command:: + + echo 'level <level>' > /proc/acpi/ibm/fan + +Where <level> is an integer from 0 to 7, or one of the words "auto" or +"full-speed" (without the quotes). Not all ThinkPads support the "auto" +and "full-speed" levels. The driver accepts "disengaged" as an alias for +"full-speed", and reports it as "disengaged" for backwards +compatibility. + +On the X31 and X40 (and ONLY on those models), the fan speed can be +controlled to a certain degree. Once the fan is running, it can be +forced to run faster or slower with the following command:: + + echo 'speed <speed>' > /proc/acpi/ibm/fan + +The sustainable range of fan speeds on the X40 appears to be from about +3700 to about 7350. Values outside this range either do not have any +effect or the fan speed eventually settles somewhere in that range. The +fan cannot be stopped or started with this command. This functionality +is incomplete, and not available through the sysfs interface. + +To program the safety watchdog, use the "watchdog" command:: + + echo 'watchdog <interval in seconds>' > /proc/acpi/ibm/fan + +If you want to disable the watchdog, use 0 as the interval. + +Sysfs notes +^^^^^^^^^^^ + +The sysfs interface follows the hwmon subsystem guidelines for the most +part, and the exception is the fan safety watchdog. + +Writes to any of the sysfs attributes may return the EINVAL error if +that operation is not supported in a given ThinkPad or if the parameter +is out-of-bounds, and EPERM if it is forbidden. They may also return +EINTR (interrupted system call), and EIO (I/O error while trying to talk +to the firmware). + +Features not yet implemented by the driver return ENOSYS. + +hwmon device attribute pwm1_enable: + - 0: PWM offline (fan is set to full-speed mode) + - 1: Manual PWM control (use pwm1 to set fan level) + - 2: Hardware PWM control (EC "auto" mode) + - 3: reserved (Software PWM control, not implemented yet) + + Modes 0 and 2 are not supported by all ThinkPads, and the + driver is not always able to detect this. If it does know a + mode is unsupported, it will return -EINVAL. + +hwmon device attribute pwm1: + Fan level, scaled from the firmware values of 0-7 to the hwmon + scale of 0-255. 0 means fan stopped, 255 means highest normal + speed (level 7). + + This attribute only commands the fan if pmw1_enable is set to 1 + (manual PWM control). + +hwmon device attribute fan1_input: + Fan tachometer reading, in RPM. May go stale on certain + ThinkPads while the EC transitions the PWM to offline mode, + which can take up to two minutes. May return rubbish on older + ThinkPads. + +hwmon device attribute fan2_input: + Fan tachometer reading, in RPM, for the secondary fan. + Available only on some ThinkPads. If the secondary fan is + not installed, will always read 0. + +hwmon driver attribute fan_watchdog: + Fan safety watchdog timer interval, in seconds. Minimum is + 1 second, maximum is 120 seconds. 0 disables the watchdog. + +To stop the fan: set pwm1 to zero, and pwm1_enable to 1. + +To start the fan in a safe mode: set pwm1_enable to 2. If that fails +with EINVAL, try to set pwm1_enable to 1 and pwm1 to at least 128 (255 +would be the safest choice, though). + + +WAN +--- + +procfs: /proc/acpi/ibm/wan + +sysfs device attribute: wwan_enable (deprecated) + +sysfs rfkill class: switch "tpacpi_wwan_sw" + +This feature shows the presence and current state of the built-in +Wireless WAN device. + +If the ThinkPad supports it, the WWAN state is stored in NVRAM, +so it is kept across reboots and power-off. + +It was tested on a Lenovo ThinkPad X60. It should probably work on other +ThinkPad models which come with this module installed. + +Procfs notes +^^^^^^^^^^^^ + +If the W-WAN card is installed, the following commands can be used:: + + echo enable > /proc/acpi/ibm/wan + echo disable > /proc/acpi/ibm/wan + +Sysfs notes +^^^^^^^^^^^ + + If the W-WAN card is installed, it can be enabled / + disabled through the "wwan_enable" thinkpad-acpi device + attribute, and its current status can also be queried. + + enable: + - 0: disables WWAN card / WWAN card is disabled + - 1: enables WWAN card / WWAN card is enabled. + + Note: this interface has been superseded by the generic rfkill + class. It has been deprecated, and it will be removed in year + 2010. + + rfkill controller switch "tpacpi_wwan_sw": refer to + Documentation/driver-api/rfkill.rst for details. + + +LCD Shadow control +------------------ + +procfs: /proc/acpi/ibm/lcdshadow + +Some newer T480s and T490s ThinkPads provide a feature called +PrivacyGuard. By turning this feature on, the usable vertical and +horizontal viewing angles of the LCD can be limited (as if some privacy +screen was applied manually in front of the display). + +procfs notes +^^^^^^^^^^^^ + +The available commands are:: + + echo '0' >/proc/acpi/ibm/lcdshadow + echo '1' >/proc/acpi/ibm/lcdshadow + +The first command ensures the best viewing angle and the latter one turns +on the feature, restricting the viewing angles. + + +DYTC Lapmode sensor +------------------- + +sysfs: dytc_lapmode + +Newer thinkpads and mobile workstations have the ability to determine if +the device is in deskmode or lapmode. This feature is used by user space +to decide if WWAN transmission can be increased to maximum power and is +also useful for understanding the different thermal modes available as +they differ between desk and lap mode. + +The property is read-only. If the platform doesn't have support the sysfs +class is not created. + +EXPERIMENTAL: UWB +----------------- + +This feature is considered EXPERIMENTAL because it has not been extensively +tested and validated in various ThinkPad models yet. The feature may not +work as expected. USE WITH CAUTION! To use this feature, you need to supply +the experimental=1 parameter when loading the module. + +sysfs rfkill class: switch "tpacpi_uwb_sw" + +This feature exports an rfkill controller for the UWB device, if one is +present and enabled in the BIOS. + +Sysfs notes +^^^^^^^^^^^ + + rfkill controller switch "tpacpi_uwb_sw": refer to + Documentation/driver-api/rfkill.rst for details. + + +Setting keyboard language +------------------------- + +sysfs: keyboard_lang + +This feature is used to set keyboard language to ECFW using ASL interface. +Fewer thinkpads models like T580 , T590 , T15 Gen 1 etc.. has "=", "(', +")" numeric keys, which are not displaying correctly, when keyboard language +is other than "english". This is because the default keyboard language in ECFW +is set as "english". Hence using this sysfs, user can set the correct keyboard +language to ECFW and then these key's will work correctly. + +Example of command to set keyboard language is mentioned below:: + + echo jp > /sys/devices/platform/thinkpad_acpi/keyboard_lang + +Text corresponding to keyboard layout to be set in sysfs are: be(Belgian), +cz(Czech), da(Danish), de(German), en(English), es(Spain), et(Estonian), +fr(French), fr-ch(French(Switzerland)), hu(Hungarian), it(Italy), jp (Japan), +nl(Dutch), nn(Norway), pl(Polish), pt(portuguese), sl(Slovenian), sv(Sweden), +tr(Turkey) + +WWAN Antenna type +----------------- + +sysfs: wwan_antenna_type + +On some newer Thinkpads we need to set SAR value based on the antenna +type. This interface will be used by userspace to get the antenna type +and set the corresponding SAR value, as is required for FCC certification. + +The available commands are:: + + cat /sys/devices/platform/thinkpad_acpi/wwan_antenna_type + +Currently 2 antenna types are supported as mentioned below: +- type a +- type b + +The property is read-only. If the platform doesn't have support the sysfs +class is not created. + +Adaptive keyboard +----------------- + +sysfs device attribute: adaptive_kbd_mode + +This sysfs attribute controls the keyboard "face" that will be shown on the +Lenovo X1 Carbon 2nd gen (2014)'s adaptive keyboard. The value can be read +and set. + +- 0 = Home mode +- 1 = Web-browser mode +- 2 = Web-conference mode +- 3 = Function mode +- 4 = Layflat mode + +For more details about which buttons will appear depending on the mode, please +review the laptop's user guide: +https://download.lenovo.com/ibmdl/pub/pc/pccbbs/mobiles_pdf/x1carbon_2_ug_en.pdf + +Battery charge control +---------------------- + +sysfs attributes: +/sys/class/power_supply/BAT*/charge_control_{start,end}_threshold + +These two attributes are created for those batteries that are supported by the +driver. They enable the user to control the battery charge thresholds of the +given battery. Both values may be read and set. `charge_control_start_threshold` +accepts an integer between 0 and 99 (inclusive); this value represents a battery +percentage level, below which charging will begin. `charge_control_end_threshold` +accepts an integer between 1 and 100 (inclusive); this value represents a battery +percentage level, above which charging will stop. + +The exact semantics of the attributes may be found in +Documentation/ABI/testing/sysfs-class-power. + +Multiple Commands, Module Parameters +------------------------------------ + +Multiple commands can be written to the proc files in one shot by +separating them with commas, for example:: + + echo enable,0xffff > /proc/acpi/ibm/hotkey + echo lcd_disable,crt_enable > /proc/acpi/ibm/video + +Commands can also be specified when loading the thinkpad-acpi module, +for example:: + + modprobe thinkpad_acpi hotkey=enable,0xffff video=auto_disable + + +Enabling debugging output +------------------------- + +The module takes a debug parameter which can be used to selectively +enable various classes of debugging output, for example:: + + modprobe thinkpad_acpi debug=0xffff + +will enable all debugging output classes. It takes a bitmask, so +to enable more than one output class, just add their values. + + ============= ====================================== + Debug bitmask Description + ============= ====================================== + 0x8000 Disclose PID of userspace programs + accessing some functions of the driver + 0x0001 Initialization and probing + 0x0002 Removal + 0x0004 RF Transmitter control (RFKILL) + (bluetooth, WWAN, UWB...) + 0x0008 HKEY event interface, hotkeys + 0x0010 Fan control + 0x0020 Backlight brightness + 0x0040 Audio mixer/volume control + ============= ====================================== + +There is also a kernel build option to enable more debugging +information, which may be necessary to debug driver problems. + +The level of debugging information output by the driver can be changed +at runtime through sysfs, using the driver attribute debug_level. The +attribute takes the same bitmask as the debug module parameter above. + + +Force loading of module +----------------------- + +If thinkpad-acpi refuses to detect your ThinkPad, you can try to specify +the module parameter force_load=1. Regardless of whether this works or +not, please contact ibm-acpi-devel@lists.sourceforge.net with a report. + + +Sysfs interface changelog +^^^^^^^^^^^^^^^^^^^^^^^^^ + +========= =============================================================== +0x000100: Initial sysfs support, as a single platform driver and + device. +0x000200: Hot key support for 32 hot keys, and radio slider switch + support. +0x010000: Hot keys are now handled by default over the input + layer, the radio switch generates input event EV_RADIO, + and the driver enables hot key handling by default in + the firmware. + +0x020000: ABI fix: added a separate hwmon platform device and + driver, which must be located by name (thinkpad) + and the hwmon class for libsensors4 (lm-sensors 3) + compatibility. Moved all hwmon attributes to this + new platform device. + +0x020100: Marker for thinkpad-acpi with hot key NVRAM polling + support. If you must, use it to know you should not + start a userspace NVRAM poller (allows to detect when + NVRAM is compiled out by the user because it is + unneeded/undesired in the first place). +0x020101: Marker for thinkpad-acpi with hot key NVRAM polling + and proper hotkey_mask semantics (version 8 of the + NVRAM polling patch). Some development snapshots of + 0.18 had an earlier version that did strange things + to hotkey_mask. + +0x020200: Add poll()/select() support to the following attributes: + hotkey_radio_sw, wakeup_hotunplug_complete, wakeup_reason + +0x020300: hotkey enable/disable support removed, attributes + hotkey_bios_enabled and hotkey_enable deprecated and + marked for removal. + +0x020400: Marker for 16 LEDs support. Also, LEDs that are known + to not exist in a given model are not registered with + the LED sysfs class anymore. + +0x020500: Updated hotkey driver, hotkey_mask is always available + and it is always able to disable hot keys. Very old + thinkpads are properly supported. hotkey_bios_mask + is deprecated and marked for removal. + +0x020600: Marker for backlight change event support. + +0x020700: Support for mute-only mixers. + Volume control in read-only mode by default. + Marker for ALSA mixer support. + +0x030000: Thermal and fan sysfs attributes were moved to the hwmon + device instead of being attached to the backing platform + device. +========= =============================================================== diff --git a/Documentation/admin-guide/laptops/toshiba_haps.rst b/Documentation/admin-guide/laptops/toshiba_haps.rst new file mode 100644 index 000000000..d28b6c3f2 --- /dev/null +++ b/Documentation/admin-guide/laptops/toshiba_haps.rst @@ -0,0 +1,87 @@ +==================================== +Toshiba HDD Active Protection Sensor +==================================== + +Kernel driver: toshiba_haps + +Author: Azael Avalos <coproscefalo@gmail.com> + + +.. 0. Contents + + 1. Description + 2. Interface + 3. Accelerometer axes + 4. Supported devices + 5. Usage + + +1. Description +-------------- + +This driver provides support for the accelerometer found in various Toshiba +laptops, being called "Toshiba HDD Protection - Shock Sensor" officially, +and detects laptops automatically with this device. +On Windows, Toshiba provided software monitors this device and provides +automatic HDD protection (head unload) on sudden moves or harsh vibrations, +however, this driver only provides a notification via a sysfs file to let +userspace tools or daemons act accordingly, as well as providing a sysfs +file to set the desired protection level or sensor sensibility. + + +2. Interface +------------ + +This device comes with 3 methods: + +==== ===================================================================== +_STA Checks existence of the device, returning Zero if the device does not + exists or is not supported. +PTLV Sets the desired protection level. +RSSS Shuts down the HDD protection interface for a few seconds, + then restores normal operation. +==== ===================================================================== + +Note: + The presence of Solid State Drives (SSD) can make this driver to fail loading, + given the fact that such drives have no movable parts, and thus, not requiring + any "protection" as well as failing during the evaluation of the _STA method + found under this device. + + +3. Accelerometer axes +--------------------- + +This device does not report any axes, however, to query the sensor position +a couple HCI (Hardware Configuration Interface) calls (0x6D and 0xA6) are +provided to query such information, handled by the kernel module toshiba_acpi +since kernel version 3.15. + + +4. Supported devices +-------------------- + +This driver binds itself to the ACPI device TOS620A, and any Toshiba laptop +with this device is supported, given the fact that they have the presence of +conventional HDD and not only SSD, or a combination of both HDD and SSD. + + +5. Usage +-------- + +The sysfs files under /sys/devices/LNXSYSTM:00/LNXSYBUS:00/TOS620A:00/ are: + +================ ============================================================ +protection_level The protection_level is readable and writeable, and + provides a way to let userspace query the current protection + level, as well as set the desired protection level, the + available protection levels are:: + + ============ ======= ========== ======== + 0 - Disabled 1 - Low 2 - Medium 3 - High + ============ ======= ========== ======== + +reset_protection The reset_protection entry is writeable only, being "1" + the only parameter it accepts, it is used to trigger + a reset of the protection interface. +================ ============================================================ diff --git a/Documentation/admin-guide/lcd-panel-cgram.rst b/Documentation/admin-guide/lcd-panel-cgram.rst new file mode 100644 index 000000000..a3eb00c62 --- /dev/null +++ b/Documentation/admin-guide/lcd-panel-cgram.rst @@ -0,0 +1,27 @@ +====================================== +Parallel port LCD/Keypad Panel support +====================================== + +Some LCDs allow you to define up to 8 characters, mapped to ASCII +characters 0 to 7. The escape code to define a new character is +'\e[LG' followed by one digit from 0 to 7, representing the character +number, and up to 8 couples of hex digits terminated by a semi-colon +(';'). Each couple of digits represents a line, with 1-bits for each +illuminated pixel with LSB on the right. Lines are numbered from the +top of the character to the bottom. On a 5x7 matrix, only the 5 lower +bits of the 7 first bytes are used for each character. If the string +is incomplete, only complete lines will be redefined. Here are some +examples:: + + printf "\e[LG0010101050D1F0C04;" => 0 = [enter] + printf "\e[LG1040E1F0000000000;" => 1 = [up] + printf "\e[LG2000000001F0E0400;" => 2 = [down] + printf "\e[LG3040E1F001F0E0400;" => 3 = [up-down] + printf "\e[LG40002060E1E0E0602;" => 4 = [left] + printf "\e[LG500080C0E0F0E0C08;" => 5 = [right] + printf "\e[LG60016051516141400;" => 6 = "IP" + + printf "\e[LG00103071F1F070301;" => big speaker + printf "\e[LG00002061E1E060200;" => small speaker + +Willy diff --git a/Documentation/admin-guide/ldm.rst b/Documentation/admin-guide/ldm.rst new file mode 100644 index 000000000..12c571368 --- /dev/null +++ b/Documentation/admin-guide/ldm.rst @@ -0,0 +1,121 @@ +========================================== +LDM - Logical Disk Manager (Dynamic Disks) +========================================== + +:Author: Originally Written by FlatCap - Richard Russon <ldm@flatcap.org>. +:Last Updated: Anton Altaparmakov on 30 March 2007 for Windows Vista. + +Overview +-------- + +Windows 2000, XP, and Vista use a new partitioning scheme. It is a complete +replacement for the MSDOS style partitions. It stores its information in a +1MiB journalled database at the end of the physical disk. The size of +partitions is limited only by disk space. The maximum number of partitions is +nearly 2000. + +Any partitions created under the LDM are called "Dynamic Disks". There are no +longer any primary or extended partitions. Normal MSDOS style partitions are +now known as Basic Disks. + +If you wish to use Spanned, Striped, Mirrored or RAID 5 Volumes, you must use +Dynamic Disks. The journalling allows Windows to make changes to these +partitions and filesystems without the need to reboot. + +Once the LDM driver has divided up the disk, you can use the MD driver to +assemble any multi-partition volumes, e.g. Stripes, RAID5. + +To prevent legacy applications from repartitioning the disk, the LDM creates a +dummy MSDOS partition containing one disk-sized partition. This is what is +supported with the Linux LDM driver. + +A newer approach that has been implemented with Vista is to put LDM on top of a +GPT label disk. This is not supported by the Linux LDM driver yet. + + +Example +------- + +Below we have a 50MiB disk, divided into seven partitions. + +.. note:: + + The missing 1MiB at the end of the disk is where the LDM database is + stored. + ++-------++--------------+---------+-----++--------------+---------+----+ +|Device || Offset Bytes | Sectors | MiB || Size Bytes | Sectors | MiB| ++=======++==============+=========+=====++==============+=========+====+ +|hda || 0 | 0 | 0 || 52428800 | 102400 | 50| ++-------++--------------+---------+-----++--------------+---------+----+ +|hda1 || 51380224 | 100352 | 49 || 1048576 | 2048 | 1| ++-------++--------------+---------+-----++--------------+---------+----+ +|hda2 || 16384 | 32 | 0 || 6979584 | 13632 | 6| ++-------++--------------+---------+-----++--------------+---------+----+ +|hda3 || 6995968 | 13664 | 6 || 10485760 | 20480 | 10| ++-------++--------------+---------+-----++--------------+---------+----+ +|hda4 || 17481728 | 34144 | 16 || 4194304 | 8192 | 4| ++-------++--------------+---------+-----++--------------+---------+----+ +|hda5 || 21676032 | 42336 | 20 || 5242880 | 10240 | 5| ++-------++--------------+---------+-----++--------------+---------+----+ +|hda6 || 26918912 | 52576 | 25 || 10485760 | 20480 | 10| ++-------++--------------+---------+-----++--------------+---------+----+ +|hda7 || 37404672 | 73056 | 35 || 13959168 | 27264 | 13| ++-------++--------------+---------+-----++--------------+---------+----+ + +The LDM Database may not store the partitions in the order that they appear on +disk, but the driver will sort them. + +When Linux boots, you will see something like:: + + hda: 102400 sectors w/32KiB Cache, CHS=50/64/32 + hda: [LDM] hda1 hda2 hda3 hda4 hda5 hda6 hda7 + + +Compiling LDM Support +--------------------- + +To enable LDM, choose the following two options: + + - "Advanced partition selection" CONFIG_PARTITION_ADVANCED + - "Windows Logical Disk Manager (Dynamic Disk) support" CONFIG_LDM_PARTITION + +If you believe the driver isn't working as it should, you can enable the extra +debugging code. This will produce a LOT of output. The option is: + + - "Windows LDM extra logging" CONFIG_LDM_DEBUG + +N.B. The partition code cannot be compiled as a module. + +As with all the partition code, if the driver doesn't see signs of its type of +partition, it will pass control to another driver, so there is no harm in +enabling it. + +If you have Dynamic Disks but don't enable the driver, then all you will see +is a dummy MSDOS partition filling the whole disk. You won't be able to mount +any of the volumes on the disk. + + +Booting +------- + +If you enable LDM support, then lilo is capable of booting from any of the +discovered partitions. However, grub does not understand the LDM partitioning +and cannot boot from a Dynamic Disk. + + +More Documentation +------------------ + +There is an Overview of the LDM together with complete Technical Documentation. +It is available for download. + + http://www.linux-ntfs.org/ + +If you have any LDM questions that aren't answered in the documentation, email +me. + +Cheers, + FlatCap - Richard Russon + ldm@flatcap.org + diff --git a/Documentation/admin-guide/lockup-watchdogs.rst b/Documentation/admin-guide/lockup-watchdogs.rst new file mode 100644 index 000000000..3e09284a8 --- /dev/null +++ b/Documentation/admin-guide/lockup-watchdogs.rst @@ -0,0 +1,83 @@ +=============================================================== +Softlockup detector and hardlockup detector (aka nmi_watchdog) +=============================================================== + +The Linux kernel can act as a watchdog to detect both soft and hard +lockups. + +A 'softlockup' is defined as a bug that causes the kernel to loop in +kernel mode for more than 20 seconds (see "Implementation" below for +details), without giving other tasks a chance to run. The current +stack trace is displayed upon detection and, by default, the system +will stay locked up. Alternatively, the kernel can be configured to +panic; a sysctl, "kernel.softlockup_panic", a kernel parameter, +"softlockup_panic" (see "Documentation/admin-guide/kernel-parameters.rst" for +details), and a compile option, "BOOTPARAM_SOFTLOCKUP_PANIC", are +provided for this. + +A 'hardlockup' is defined as a bug that causes the CPU to loop in +kernel mode for more than 10 seconds (see "Implementation" below for +details), without letting other interrupts have a chance to run. +Similarly to the softlockup case, the current stack trace is displayed +upon detection and the system will stay locked up unless the default +behavior is changed, which can be done through a sysctl, +'hardlockup_panic', a compile time knob, "BOOTPARAM_HARDLOCKUP_PANIC", +and a kernel parameter, "nmi_watchdog" +(see "Documentation/admin-guide/kernel-parameters.rst" for details). + +The panic option can be used in combination with panic_timeout (this +timeout is set through the confusingly named "kernel.panic" sysctl), +to cause the system to reboot automatically after a specified amount +of time. + +Implementation +============== + +The soft and hard lockup detectors are built on top of the hrtimer and +perf subsystems, respectively. A direct consequence of this is that, +in principle, they should work in any architecture where these +subsystems are present. + +A periodic hrtimer runs to generate interrupts and kick the watchdog +job. An NMI perf event is generated every "watchdog_thresh" +(compile-time initialized to 10 and configurable through sysctl of the +same name) seconds to check for hardlockups. If any CPU in the system +does not receive any hrtimer interrupt during that time the +'hardlockup detector' (the handler for the NMI perf event) will +generate a kernel warning or call panic, depending on the +configuration. + +The watchdog job runs in a stop scheduling thread that updates a +timestamp every time it is scheduled. If that timestamp is not updated +for 2*watchdog_thresh seconds (the softlockup threshold) the +'softlockup detector' (coded inside the hrtimer callback function) +will dump useful debug information to the system log, after which it +will call panic if it was instructed to do so or resume execution of +other kernel code. + +The period of the hrtimer is 2*watchdog_thresh/5, which means it has +two or three chances to generate an interrupt before the hardlockup +detector kicks in. + +As explained above, a kernel knob is provided that allows +administrators to configure the period of the hrtimer and the perf +event. The right value for a particular environment is a trade-off +between fast response to lockups and detection overhead. + +By default, the watchdog runs on all online cores. However, on a +kernel configured with NO_HZ_FULL, by default the watchdog runs only +on the housekeeping cores, not the cores specified in the "nohz_full" +boot argument. If we allowed the watchdog to run by default on +the "nohz_full" cores, we would have to run timer ticks to activate +the scheduler, which would prevent the "nohz_full" functionality +from protecting the user code on those cores from the kernel. +Of course, disabling it by default on the nohz_full cores means that +when those cores do enter the kernel, by default we will not be +able to detect if they lock up. However, allowing the watchdog +to continue to run on the housekeeping (non-tickless) cores means +that we will continue to detect lockups properly on those cores. + +In either case, the set of cores excluded from running the watchdog +may be adjusted via the kernel.watchdog_cpumask sysctl. For +nohz_full cores, this may be useful for debugging a case where the +kernel seems to be hanging on the nohz_full cores. diff --git a/Documentation/admin-guide/md.rst b/Documentation/admin-guide/md.rst new file mode 100644 index 000000000..4ff2cc291 --- /dev/null +++ b/Documentation/admin-guide/md.rst @@ -0,0 +1,765 @@ +RAID arrays +=========== + +Boot time assembly of RAID arrays +--------------------------------- + +Tools that manage md devices can be found at + https://www.kernel.org/pub/linux/utils/raid/ + + +You can boot with your md device with the following kernel command +lines: + +for old raid arrays without persistent superblocks:: + + md=<md device no.>,<raid level>,<chunk size factor>,<fault level>,dev0,dev1,...,devn + +for raid arrays with persistent superblocks:: + + md=<md device no.>,dev0,dev1,...,devn + +or, to assemble a partitionable array:: + + md=d<md device no.>,dev0,dev1,...,devn + +``md device no.`` ++++++++++++++++++ + +The number of the md device + +================= ========= +``md device no.`` device +================= ========= + 0 md0 + 1 md1 + 2 md2 + 3 md3 + 4 md4 +================= ========= + +``raid level`` +++++++++++++++ + +level of the RAID array + +=============== ============= +``raid level`` level +=============== ============= +-1 linear mode +0 striped mode +=============== ============= + +other modes are only supported with persistent super blocks + +``chunk size factor`` ++++++++++++++++++++++ + +(raid-0 and raid-1 only) + +Set the chunk size as 4k << n. + +``fault level`` ++++++++++++++++ + +Totally ignored + +``dev0`` to ``devn`` +++++++++++++++++++++ + +e.g. ``/dev/hda1``, ``/dev/hdc1``, ``/dev/sda1``, ``/dev/sdb1`` + +A possible loadlin line (Harald Hoyer <HarryH@Royal.Net>) looks like this:: + + e:\loadlin\loadlin e:\zimage root=/dev/md0 md=0,0,4,0,/dev/hdb2,/dev/hdc3 ro + + +Boot time autodetection of RAID arrays +-------------------------------------- + +When md is compiled into the kernel (not as module), partitions of +type 0xfd are scanned and automatically assembled into RAID arrays. +This autodetection may be suppressed with the kernel parameter +``raid=noautodetect``. As of kernel 2.6.9, only drives with a type 0 +superblock can be autodetected and run at boot time. + +The kernel parameter ``raid=partitionable`` (or ``raid=part``) means +that all auto-detected arrays are assembled as partitionable. + +Boot time assembly of degraded/dirty arrays +------------------------------------------- + +If a raid5 or raid6 array is both dirty and degraded, it could have +undetectable data corruption. This is because the fact that it is +``dirty`` means that the parity cannot be trusted, and the fact that it +is degraded means that some datablocks are missing and cannot reliably +be reconstructed (due to no parity). + +For this reason, md will normally refuse to start such an array. This +requires the sysadmin to take action to explicitly start the array +despite possible corruption. This is normally done with:: + + mdadm --assemble --force .... + +This option is not really available if the array has the root +filesystem on it. In order to support this booting from such an +array, md supports a module parameter ``start_dirty_degraded`` which, +when set to 1, bypassed the checks and will allows dirty degraded +arrays to be started. + +So, to boot with a root filesystem of a dirty degraded raid 5 or 6, use:: + + md-mod.start_dirty_degraded=1 + + +Superblock formats +------------------ + +The md driver can support a variety of different superblock formats. +Currently, it supports superblock formats ``0.90.0`` and the ``md-1`` format +introduced in the 2.5 development series. + +The kernel will autodetect which format superblock is being used. + +Superblock format ``0`` is treated differently to others for legacy +reasons - it is the original superblock format. + + +General Rules - apply for all superblock formats +------------------------------------------------ + +An array is ``created`` by writing appropriate superblocks to all +devices. + +It is ``assembled`` by associating each of these devices with an +particular md virtual device. Once it is completely assembled, it can +be accessed. + +An array should be created by a user-space tool. This will write +superblocks to all devices. It will usually mark the array as +``unclean``, or with some devices missing so that the kernel md driver +can create appropriate redundancy (copying in raid 1, parity +calculation in raid 4/5). + +When an array is assembled, it is first initialized with the +SET_ARRAY_INFO ioctl. This contains, in particular, a major and minor +version number. The major version number selects which superblock +format is to be used. The minor number might be used to tune handling +of the format, such as suggesting where on each device to look for the +superblock. + +Then each device is added using the ADD_NEW_DISK ioctl. This +provides, in particular, a major and minor number identifying the +device to add. + +The array is started with the RUN_ARRAY ioctl. + +Once started, new devices can be added. They should have an +appropriate superblock written to them, and then be passed in with +ADD_NEW_DISK. + +Devices that have failed or are not yet active can be detached from an +array using HOT_REMOVE_DISK. + + +Specific Rules that apply to format-0 super block arrays, and arrays with no superblock (non-persistent) +-------------------------------------------------------------------------------------------------------- + +An array can be ``created`` by describing the array (level, chunksize +etc) in a SET_ARRAY_INFO ioctl. This must have ``major_version==0`` and +``raid_disks != 0``. + +Then uninitialized devices can be added with ADD_NEW_DISK. The +structure passed to ADD_NEW_DISK must specify the state of the device +and its role in the array. + +Once started with RUN_ARRAY, uninitialized spares can be added with +HOT_ADD_DISK. + + +MD devices in sysfs +------------------- + +md devices appear in sysfs (``/sys``) as regular block devices, +e.g.:: + + /sys/block/md0 + +Each ``md`` device will contain a subdirectory called ``md`` which +contains further md-specific information about the device. + +All md devices contain: + + level + a text file indicating the ``raid level``. e.g. raid0, raid1, + raid5, linear, multipath, faulty. + If no raid level has been set yet (array is still being + assembled), the value will reflect whatever has been written + to it, which may be a name like the above, or may be a number + such as ``0``, ``5``, etc. + + raid_disks + a text file with a simple number indicating the number of devices + in a fully functional array. If this is not yet known, the file + will be empty. If an array is being resized this will contain + the new number of devices. + Some raid levels allow this value to be set while the array is + active. This will reconfigure the array. Otherwise it can only + be set while assembling an array. + A change to this attribute will not be permitted if it would + reduce the size of the array. To reduce the number of drives + in an e.g. raid5, the array size must first be reduced by + setting the ``array_size`` attribute. + + chunk_size + This is the size in bytes for ``chunks`` and is only relevant to + raid levels that involve striping (0,4,5,6,10). The address space + of the array is conceptually divided into chunks and consecutive + chunks are striped onto neighbouring devices. + The size should be at least PAGE_SIZE (4k) and should be a power + of 2. This can only be set while assembling an array + + layout + The ``layout`` for the array for the particular level. This is + simply a number that is interpreted differently by different + levels. It can be written while assembling an array. + + array_size + This can be used to artificially constrain the available space in + the array to be less than is actually available on the combined + devices. Writing a number (in Kilobytes) which is less than + the available size will set the size. Any reconfiguration of the + array (e.g. adding devices) will not cause the size to change. + Writing the word ``default`` will cause the effective size of the + array to be whatever size is actually available based on + ``level``, ``chunk_size`` and ``component_size``. + + This can be used to reduce the size of the array before reducing + the number of devices in a raid4/5/6, or to support external + metadata formats which mandate such clipping. + + reshape_position + This is either ``none`` or a sector number within the devices of + the array where ``reshape`` is up to. If this is set, the three + attributes mentioned above (raid_disks, chunk_size, layout) can + potentially have 2 values, an old and a new value. If these + values differ, reading the attribute returns:: + + new (old) + + and writing will effect the ``new`` value, leaving the ``old`` + unchanged. + + component_size + For arrays with data redundancy (i.e. not raid0, linear, faulty, + multipath), all components must be the same size - or at least + there must a size that they all provide space for. This is a key + part or the geometry of the array. It is measured in sectors + and can be read from here. Writing to this value may resize + the array if the personality supports it (raid1, raid5, raid6), + and if the component drives are large enough. + + metadata_version + This indicates the format that is being used to record metadata + about the array. It can be 0.90 (traditional format), 1.0, 1.1, + 1.2 (newer format in varying locations) or ``none`` indicating that + the kernel isn't managing metadata at all. + Alternately it can be ``external:`` followed by a string which + is set by user-space. This indicates that metadata is managed + by a user-space program. Any device failure or other event that + requires a metadata update will cause array activity to be + suspended until the event is acknowledged. + + resync_start + The point at which resync should start. If no resync is needed, + this will be a very large number (or ``none`` since 2.6.30-rc1). At + array creation it will default to 0, though starting the array as + ``clean`` will set it much larger. + + new_dev + This file can be written but not read. The value written should + be a block device number as major:minor. e.g. 8:0 + This will cause that device to be attached to the array, if it is + available. It will then appear at md/dev-XXX (depending on the + name of the device) and further configuration is then possible. + + safe_mode_delay + When an md array has seen no write requests for a certain period + of time, it will be marked as ``clean``. When another write + request arrives, the array is marked as ``dirty`` before the write + commences. This is known as ``safe_mode``. + The ``certain period`` is controlled by this file which stores the + period as a number of seconds. The default is 200msec (0.200). + Writing a value of 0 disables safemode. + + array_state + This file contains a single word which describes the current + state of the array. In many cases, the state can be set by + writing the word for the desired state, however some states + cannot be explicitly set, and some transitions are not allowed. + + Select/poll works on this file. All changes except between + Active_idle and active (which can be frequent and are not + very interesting) are notified. active->active_idle is + reported if the metadata is externally managed. + + clear + No devices, no size, no level + + Writing is equivalent to STOP_ARRAY ioctl + + inactive + May have some settings, but array is not active + all IO results in error + + When written, doesn't tear down array, but just stops it + + suspended (not supported yet) + All IO requests will block. The array can be reconfigured. + + Writing this, if accepted, will block until array is quiescent + + readonly + no resync can happen. no superblocks get written. + + Write requests fail + + read-auto + like readonly, but behaves like ``clean`` on a write request. + + clean + no pending writes, but otherwise active. + + When written to inactive array, starts without resync + + If a write request arrives then + if metadata is known, mark ``dirty`` and switch to ``active``. + if not known, block and switch to write-pending + + If written to an active array that has pending writes, then fails. + active + fully active: IO and resync can be happening. + When written to inactive array, starts with resync + + write-pending + clean, but writes are blocked waiting for ``active`` to be written. + + active-idle + like active, but no writes have been seen for a while (safe_mode_delay). + + bitmap/location + This indicates where the write-intent bitmap for the array is + stored. + + It can be one of ``none``, ``file`` or ``[+-]N``. + ``file`` may later be extended to ``file:/file/name`` + ``[+-]N`` means that many sectors from the start of the metadata. + + This is replicated on all devices. For arrays with externally + managed metadata, the offset is from the beginning of the + device. + + bitmap/chunksize + The size, in bytes, of the chunk which will be represented by a + single bit. For RAID456, it is a portion of an individual + device. For RAID10, it is a portion of the array. For RAID1, it + is both (they come to the same thing). + + bitmap/time_base + The time, in seconds, between looking for bits in the bitmap to + be cleared. In the current implementation, a bit will be cleared + between 2 and 3 times ``time_base`` after all the covered blocks + are known to be in-sync. + + bitmap/backlog + When write-mostly devices are active in a RAID1, write requests + to those devices proceed in the background - the filesystem (or + other user of the device) does not have to wait for them. + ``backlog`` sets a limit on the number of concurrent background + writes. If there are more than this, new writes will by + synchronous. + + bitmap/metadata + This can be either ``internal`` or ``external``. + + ``internal`` + is the default and means the metadata for the bitmap + is stored in the first 256 bytes of the allocated space and is + managed by the md module. + + ``external`` + means that bitmap metadata is managed externally to + the kernel (i.e. by some userspace program) + + bitmap/can_clear + This is either ``true`` or ``false``. If ``true``, then bits in the + bitmap will be cleared when the corresponding blocks are thought + to be in-sync. If ``false``, bits will never be cleared. + This is automatically set to ``false`` if a write happens on a + degraded array, or if the array becomes degraded during a write. + When metadata is managed externally, it should be set to true + once the array becomes non-degraded, and this fact has been + recorded in the metadata. + + consistency_policy + This indicates how the array maintains consistency in case of unexpected + shutdown. It can be: + + none + Array has no redundancy information, e.g. raid0, linear. + + resync + Full resync is performed and all redundancy is regenerated when the + array is started after unclean shutdown. + + bitmap + Resync assisted by a write-intent bitmap. + + journal + For raid4/5/6, journal device is used to log transactions and replay + after unclean shutdown. + + ppl + For raid5 only, Partial Parity Log is used to close the write hole and + eliminate resync. + + The accepted values when writing to this file are ``ppl`` and ``resync``, + used to enable and disable PPL. + + uuid + This indicates the UUID of the array in the following format: + xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx + + +As component devices are added to an md array, they appear in the ``md`` +directory as new directories named:: + + dev-XXX + +where ``XXX`` is a name that the kernel knows for the device, e.g. hdb1. +Each directory contains: + + block + a symlink to the block device in /sys/block, e.g.:: + + /sys/block/md0/md/dev-hdb1/block -> ../../../../block/hdb/hdb1 + + super + A file containing an image of the superblock read from, or + written to, that device. + + state + A file recording the current state of the device in the array + which can be a comma separated list of: + + faulty + device has been kicked from active use due to + a detected fault, or it has unacknowledged bad + blocks + + in_sync + device is a fully in-sync member of the array + + writemostly + device will only be subject to read + requests if there are no other options. + + This applies only to raid1 arrays. + + blocked + device has failed, and the failure hasn't been + acknowledged yet by the metadata handler. + + Writes that would write to this device if + it were not faulty are blocked. + + spare + device is working, but not a full member. + + This includes spares that are in the process + of being recovered to + + write_error + device has ever seen a write error. + + want_replacement + device is (mostly) working but probably + should be replaced, either due to errors or + due to user request. + + replacement + device is a replacement for another active + device with same raid_disk. + + + This list may grow in future. + + This can be written to. + + Writing ``faulty`` simulates a failure on the device. + + Writing ``remove`` removes the device from the array. + + Writing ``writemostly`` sets the writemostly flag. + + Writing ``-writemostly`` clears the writemostly flag. + + Writing ``blocked`` sets the ``blocked`` flag. + + Writing ``-blocked`` clears the ``blocked`` flags and allows writes + to complete and possibly simulates an error. + + Writing ``in_sync`` sets the in_sync flag. + + Writing ``write_error`` sets writeerrorseen flag. + + Writing ``-write_error`` clears writeerrorseen flag. + + Writing ``want_replacement`` is allowed at any time except to a + replacement device or a spare. It sets the flag. + + Writing ``-want_replacement`` is allowed at any time. It clears + the flag. + + Writing ``replacement`` or ``-replacement`` is only allowed before + starting the array. It sets or clears the flag. + + + This file responds to select/poll. Any change to ``faulty`` + or ``blocked`` causes an event. + + errors + An approximate count of read errors that have been detected on + this device but have not caused the device to be evicted from + the array (either because they were corrected or because they + happened while the array was read-only). When using version-1 + metadata, this value persists across restarts of the array. + + This value can be written while assembling an array thus + providing an ongoing count for arrays with metadata managed by + userspace. + + slot + This gives the role that the device has in the array. It will + either be ``none`` if the device is not active in the array + (i.e. is a spare or has failed) or an integer less than the + ``raid_disks`` number for the array indicating which position + it currently fills. This can only be set while assembling an + array. A device for which this is set is assumed to be working. + + offset + This gives the location in the device (in sectors from the + start) where data from the array will be stored. Any part of + the device before this offset is not touched, unless it is + used for storing metadata (Formats 1.1 and 1.2). + + size + The amount of the device, after the offset, that can be used + for storage of data. This will normally be the same as the + component_size. This can be written while assembling an + array. If a value less than the current component_size is + written, it will be rejected. + + recovery_start + When the device is not ``in_sync``, this records the number of + sectors from the start of the device which are known to be + correct. This is normally zero, but during a recovery + operation it will steadily increase, and if the recovery is + interrupted, restoring this value can cause recovery to + avoid repeating the earlier blocks. With v1.x metadata, this + value is saved and restored automatically. + + This can be set whenever the device is not an active member of + the array, either before the array is activated, or before + the ``slot`` is set. + + Setting this to ``none`` is equivalent to setting ``in_sync``. + Setting to any other value also clears the ``in_sync`` flag. + + bad_blocks + This gives the list of all known bad blocks in the form of + start address and length (in sectors respectively). If output + is too big to fit in a page, it will be truncated. Writing + ``sector length`` to this file adds new acknowledged (i.e. + recorded to disk safely) bad blocks. + + unacknowledged_bad_blocks + This gives the list of known-but-not-yet-saved-to-disk bad + blocks in the same form of ``bad_blocks``. If output is too big + to fit in a page, it will be truncated. Writing to this file + adds bad blocks without acknowledging them. This is largely + for testing. + + ppl_sector, ppl_size + Location and size (in sectors) of the space used for Partial Parity Log + on this device. + + +An active md device will also contain an entry for each active device +in the array. These are named:: + + rdNN + +where ``NN`` is the position in the array, starting from 0. +So for a 3 drive array there will be rd0, rd1, rd2. +These are symbolic links to the appropriate ``dev-XXX`` entry. +Thus, for example:: + + cat /sys/block/md*/md/rd*/state + +will show ``in_sync`` on every line. + + + +Active md devices for levels that support data redundancy (1,4,5,6,10) +also have + + sync_action + a text file that can be used to monitor and control the rebuild + process. It contains one word which can be one of: + + resync + redundancy is being recalculated after unclean + shutdown or creation + + recover + a hot spare is being built to replace a + failed/missing device + + idle + nothing is happening + check + A full check of redundancy was requested and is + happening. This reads all blocks and checks + them. A repair may also happen for some raid + levels. + + repair + A full check and repair is happening. This is + similar to ``resync``, but was requested by the + user, and the write-intent bitmap is NOT used to + optimise the process. + + This file is writable, and each of the strings that could be + read are meaningful for writing. + + ``idle`` will stop an active resync/recovery etc. There is no + guarantee that another resync/recovery may not be automatically + started again, though some event will be needed to trigger + this. + + ``resync`` or ``recovery`` can be used to restart the + corresponding operation if it was stopped with ``idle``. + + ``check`` and ``repair`` will start the appropriate process + providing the current state is ``idle``. + + This file responds to select/poll. Any important change in the value + triggers a poll event. Sometimes the value will briefly be + ``recover`` if a recovery seems to be needed, but cannot be + achieved. In that case, the transition to ``recover`` isn't + notified, but the transition away is. + + degraded + This contains a count of the number of devices by which the + arrays is degraded. So an optimal array will show ``0``. A + single failed/missing drive will show ``1``, etc. + + This file responds to select/poll, any increase or decrease + in the count of missing devices will trigger an event. + + mismatch_count + When performing ``check`` and ``repair``, and possibly when + performing ``resync``, md will count the number of errors that are + found. The count in ``mismatch_cnt`` is the number of sectors + that were re-written, or (for ``check``) would have been + re-written. As most raid levels work in units of pages rather + than sectors, this may be larger than the number of actual errors + by a factor of the number of sectors in a page. + + bitmap_set_bits + If the array has a write-intent bitmap, then writing to this + attribute can set bits in the bitmap, indicating that a resync + would need to check the corresponding blocks. Either individual + numbers or start-end pairs can be written. Multiple numbers + can be separated by a space. + + Note that the numbers are ``bit`` numbers, not ``block`` numbers. + They should be scaled by the bitmap_chunksize. + + sync_speed_min, sync_speed_max + This are similar to ``/proc/sys/dev/raid/speed_limit_{min,max}`` + however they only apply to the particular array. + + If no value has been written to these, or if the word ``system`` + is written, then the system-wide value is used. If a value, + in kibibytes-per-second is written, then it is used. + + When the files are read, they show the currently active value + followed by ``(local)`` or ``(system)`` depending on whether it is + a locally set or system-wide value. + + sync_completed + This shows the number of sectors that have been completed of + whatever the current sync_action is, followed by the number of + sectors in total that could need to be processed. The two + numbers are separated by a ``/`` thus effectively showing one + value, a fraction of the process that is complete. + + A ``select`` on this attribute will return when resync completes, + when it reaches the current sync_max (below) and possibly at + other times. + + sync_speed + This shows the current actual speed, in K/sec, of the current + sync_action. It is averaged over the last 30 seconds. + + suspend_lo, suspend_hi + The two values, given as numbers of sectors, indicate a range + within the array where IO will be blocked. This is currently + only supported for raid4/5/6. + + sync_min, sync_max + The two values, given as numbers of sectors, indicate a range + within the array where ``check``/``repair`` will operate. Must be + a multiple of chunk_size. When it reaches ``sync_max`` it will + pause, rather than complete. + You can use ``select`` or ``poll`` on ``sync_completed`` to wait for + that number to reach sync_max. Then you can either increase + ``sync_max``, or can write ``idle`` to ``sync_action``. + + The value of ``max`` for ``sync_max`` effectively disables the limit. + When a resync is active, the value can only ever be increased, + never decreased. + The value of ``0`` is the minimum for ``sync_min``. + + + +Each active md device may also have attributes specific to the +personality module that manages it. +These are specific to the implementation of the module and could +change substantially if the implementation changes. + +These currently include: + + stripe_cache_size (currently raid5 only) + number of entries in the stripe cache. This is writable, but + there are upper and lower limits (32768, 17). Default is 256. + + strip_cache_active (currently raid5 only) + number of active entries in the stripe cache + + preread_bypass_threshold (currently raid5 only) + number of times a stripe requiring preread will be bypassed by + a stripe that does not require preread. For fairness defaults + to 1. Setting this to 0 disables bypass accounting and + requires preread stripes to wait until all full-width stripe- + writes are complete. Valid values are 0 to stripe_cache_size. + + journal_mode (currently raid5 only) + The cache mode for raid5. raid5 could include an extra disk for + caching. The mode can be "write-throuth" and "write-back". The + default is "write-through". + + ppl_write_hint + NVMe stream ID to be set for each PPL write request. diff --git a/Documentation/admin-guide/media/au0828-cardlist.rst b/Documentation/admin-guide/media/au0828-cardlist.rst new file mode 100644 index 000000000..aaaadc934 --- /dev/null +++ b/Documentation/admin-guide/media/au0828-cardlist.rst @@ -0,0 +1,39 @@ +.. SPDX-License-Identifier: GPL-2.0 + +AU0828 cards list +================= + +.. tabularcolumns:: |p{1.4cm}|p{6.5cm}|p{10.0cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 2 19 18 + :stub-columns: 0 + + * - Card number + - Card name + - USB IDs + + * - 0 + - Unknown board + - + + * - 1 + - Hauppauge HVR950Q + - 2040:7200, 2040:7210, 2040:7217, 2040:721b, 2040:721e, 2040:721f, 2040:7280, 0fd9:0008, 2040:7260, 2040:7213, 2040:7270 + + * - 2 + - Hauppauge HVR850 + - 2040:7240 + + * - 3 + - DViCO FusionHDTV USB + - 0fe9:d620 + + * - 4 + - Hauppauge HVR950Q rev xxF8 + - 2040:7201, 2040:7211, 2040:7281 + + * - 5 + - Hauppauge Woodbury + - 05e1:0480, 2040:8200 diff --git a/Documentation/admin-guide/media/avermedia.rst b/Documentation/admin-guide/media/avermedia.rst new file mode 100644 index 000000000..93ff74002 --- /dev/null +++ b/Documentation/admin-guide/media/avermedia.rst @@ -0,0 +1,94 @@ +.. SPDX-License-Identifier: GPL-2.0 + +====================================== +Avermedia DVB-T on BT878 Release Notes +====================================== + +February 14th 2006 + +.. note:: + + Several other Avermedia devices are supported. For a more + broader and updated content about that, please check: + + https://linuxtv.org/wiki/index.php/AVerMedia + +The Avermedia DVB-T +~~~~~~~~~~~~~~~~~~~ + +The Avermedia DVB-T is a budget PCI DVB card. It has 3 inputs: + +* RF Tuner Input +* Composite Video Input (RCA Jack) +* SVIDEO Input (Mini-DIN) + +The RF Tuner Input is the input to the tuner module of the +card. The Tuner is otherwise known as the "Frontend" . The +Frontend of the Avermedia DVB-T is a Microtune 7202D. A timely +post to the linux-dvb mailing list ascertained that the +Microtune 7202D is supported by the sp887x driver which is +found in the dvb-hw CVS module. + +The DVB-T card is based around the BT878 chip which is a very +common multimedia bridge and often found on Analogue TV cards. +There is no on-board MPEG2 decoder, which means that all MPEG2 +decoding must be done in software, or if you have one, on an +MPEG2 hardware decoding card or chipset. + + +Getting the card going +~~~~~~~~~~~~~~~~~~~~~~ + +At this stage, it has not been able to ascertain the +functionality of the remaining device nodes in respect of the +Avermedia DVBT. However, full functionality in respect of +tuning, receiving and supplying the MPEG2 data stream is +possible with the currently available versions of the driver. +It may be possible that additional functionality is available +from the card (i.e. viewing the additional analogue inputs +that the card presents), but this has not been tested yet. If +I get around to this, I'll update the document with whatever I +find. + +To power up the card, load the following modules in the +following order: + +* modprobe bttv (normally loaded automatically) +* modprobe dvb-bt8xx (or place dvb-bt8xx in /etc/modules) + +Insertion of these modules into the running kernel will +activate the appropriate DVB device nodes. It is then possible +to start accessing the card with utilities such as scan, tzap, +dvbstream etc. + +The frontend module sp887x.o, requires an external firmware. +Please use the command "get_dvb_firmware sp887x" to download +it. Then copy it to /usr/lib/hotplug/firmware or /lib/firmware/ +(depending on configuration of firmware hotplug). + +Known Limitations +~~~~~~~~~~~~~~~~~ + +At present I can say with confidence that the frontend tunes +via /dev/dvb/adapter{x}/frontend0 and supplies an MPEG2 stream +via /dev/dvb/adapter{x}/dvr0. I have not tested the +functionality of any other part of the card yet. I will do so +over time and update this document. + +There are some limitations in the i2c layer due to a returned +error message inconsistency. Although this generates errors in +dmesg and the system logs, it does not appear to affect the +ability of the frontend to function correctly. + +Further Update +~~~~~~~~~~~~~~ + +dvbstream and VideoLAN Client on windows works a treat with +DVB, in fact this is currently serving as my main way of +viewing DVB-T at the moment. Additionally, VLC is happily +decoding HDTV signals, although the PC is dropping the odd +frame here and there - I assume due to processing capability - +as all the decoding is being done under windows in software. + +Many thanks to Nigel Pearson for the updates to this document +since the recent revision of the driver. diff --git a/Documentation/admin-guide/media/bt8xx.rst b/Documentation/admin-guide/media/bt8xx.rst new file mode 100644 index 000000000..3589f6ab7 --- /dev/null +++ b/Documentation/admin-guide/media/bt8xx.rst @@ -0,0 +1,157 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================================== +How to get the bt8xx cards working +================================== + +Authors: + Richard Walker, + Jamie Honan, + Michael Hunold, + Manu Abraham, + Uwe Bugla, + Michael Krufky + +General information +------------------- + +This class of cards has a bt878a as the PCI interface, and require the bttv +driver for accessing the i2c bus and the gpio pins of the bt8xx chipset. + +Please see Documentation/admin-guide/media/bttv-cardlist.rst for a complete +list of Cards based on the Conexant Bt8xx PCI bridge supported by the +Linux Kernel. + +In order to be able to compile the kernel, some config options should be +enabled:: + + ./scripts/config -e PCI + ./scripts/config -e INPUT + ./scripts/config -m I2C + ./scripts/config -m MEDIA_SUPPORT + ./scripts/config -e MEDIA_PCI_SUPPORT + ./scripts/config -e MEDIA_ANALOG_TV_SUPPORT + ./scripts/config -e MEDIA_DIGITAL_TV_SUPPORT + ./scripts/config -e MEDIA_RADIO_SUPPORT + ./scripts/config -e RC_CORE + ./scripts/config -m VIDEO_BT848 + ./scripts/config -m DVB_BT8XX + +If you want to automatically support all possible variants of the Bt8xx +cards, you should also do:: + + ./scripts/config -e MEDIA_SUBDRV_AUTOSELECT + +.. note:: + + Please use the following options with care as deselection of drivers which + are in fact necessary may result in DVB devices that cannot be tuned due + to lack of driver support. + +If your goal is to just support an specific board, you may, instead, +disable MEDIA_SUBDRV_AUTOSELECT and manually select the frontend drivers +required by your board. With that, you can save some RAM. + +You can do that by calling make xconfig/qconfig/menuconfig and look at +the options on those menu options (only enabled if +``Autoselect ancillary drivers`` is disabled: + +#) ``Device drivers`` => ``Multimedia support`` => ``Customize TV tuners`` +#) ``Device drivers`` => ``Multimedia support`` => ``Customize DVB frontends`` + +Then, on each of the above menu, please select your card-specific +frontend and tuner modules. + + +Loading Modules +--------------- + +Regular case: If the bttv driver detects a bt8xx-based DVB card, all +frontend and backend modules will be loaded automatically. + +Exceptions are: + +- Old TV cards without EEPROMs, sharing a common PCI subsystem ID; +- Old TwinHan DST cards or clones with or without CA slot and not + containing an Eeprom. + +In the following cases overriding the PCI type detection for bttv and +for dvb-bt8xx drivers by passing modprobe parameters may be necessary. + +Running TwinHan and Clones +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +As shown at Documentation/admin-guide/media/bttv-cardlist.rst, TwinHan and +clones use ``card=113`` modprobe parameter. So, in order to properly +detect it for devices without EEPROM, you should use:: + + $ modprobe bttv card=113 + $ modprobe dst + +Useful parameters for verbosity level and debugging the dst module:: + + verbose=0: messages are disabled + 1: only error messages are displayed + 2: notifications are displayed + 3: other useful messages are displayed + 4: debug setting + dst_addons=0: card is a free to air (FTA) card only + 0x20: card has a conditional access slot for scrambled channels + dst_algo=0: (default) Software tuning algorithm + 1: Hardware tuning algorithm + + +The autodetected values are determined by the cards' "response string". + +In your logs see f. ex.: dst_get_device_id: Recognize [DSTMCI]. + +For bug reports please send in a complete log with verbose=4 activated. +Please also see Documentation/admin-guide/media/ci.rst. + +Running multiple cards +~~~~~~~~~~~~~~~~~~~~~~ + +See Documentation/admin-guide/media/bttv-cardlist.rst for a complete list of +Card ID. Some examples: + + =========================== === + Brand name ID + =========================== === + Pinnacle PCTV Sat 94 + Nebula Electronics Digi TV 104 + pcHDTV HD-2000 TV 112 + Twinhan DST and clones 113 + Avermedia AverTV DVB-T 77: 123 + Avermedia AverTV DVB-T 761 124 + DViCO FusionHDTV DVB-T Lite 128 + DViCO FusionHDTV 5 Lite 135 + =========================== === + +.. note:: + + When you have multiple cards, the order of the card ID should + match the order where they're detected by the system. Please notice + that removing/inserting other PCI cards may change the detection + order. + +Example:: + + $ modprobe bttv card=113 card=135 + +In case of further problems please subscribe and send questions to +the mailing list: linux-media@vger.kernel.org. + +Probing the cards with broken PCI subsystem ID +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +There are some TwinHan cards whose EEPROM has become corrupted for some +reason. The cards do not have a correct PCI subsystem ID. +Still, it is possible to force probing the cards with:: + + $ echo 109e 0878 $subvendor $subdevice > \ + /sys/bus/pci/drivers/bt878/new_id + +The two numbers there are:: + + 109e: PCI_VENDOR_ID_BROOKTREE + 0878: PCI_DEVICE_ID_BROOKTREE_878 diff --git a/Documentation/admin-guide/media/bttv-cardlist.rst b/Documentation/admin-guide/media/bttv-cardlist.rst new file mode 100644 index 000000000..8671d4f7b --- /dev/null +++ b/Documentation/admin-guide/media/bttv-cardlist.rst @@ -0,0 +1,683 @@ +.. SPDX-License-Identifier: GPL-2.0 + +BTTV cards list +=============== + +.. tabularcolumns:: |p{1.4cm}|p{11.1cm}|p{4.2cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 2 19 18 + :stub-columns: 0 + + * - Card number + - Card name + - PCI subsystem IDs + + * - 0 + - *** UNKNOWN/GENERIC *** + - + + * - 1 + - MIRO PCTV + - + + * - 2 + - Hauppauge (bt848) + - + + * - 3 + - STB, Gateway P/N 6000699 (bt848) + - + + * - 4 + - Intel Create and Share PCI/ Smart Video Recorder III + - + + * - 5 + - Diamond DTV2000 + - + + * - 6 + - AVerMedia TVPhone + - + + * - 7 + - MATRIX-Vision MV-Delta + - + + * - 8 + - Lifeview FlyVideo II (Bt848) LR26 / MAXI TV Video PCI2 LR26 + - + + * - 9 + - IMS/IXmicro TurboTV + - + + * - 10 + - Hauppauge (bt878) + - 0070:13eb, 0070:3900, 2636:10b4 + + * - 11 + - MIRO PCTV pro + - + + * - 12 + - ADS Technologies Channel Surfer TV (bt848) + - + + * - 13 + - AVerMedia TVCapture 98 + - 1461:0002, 1461:0004, 1461:0300 + + * - 14 + - Aimslab Video Highway Xtreme (VHX) + - + + * - 15 + - Zoltrix TV-Max + - a1a0:a0fc + + * - 16 + - Prolink Pixelview PlayTV (bt878) + - + + * - 17 + - Leadtek WinView 601 + - + + * - 18 + - AVEC Intercapture + - + + * - 19 + - Lifeview FlyVideo II EZ /FlyKit LR38 Bt848 (capture only) + - + + * - 20 + - CEI Raffles Card + - + + * - 21 + - Lifeview FlyVideo 98/ Lucky Star Image World ConferenceTV LR50 + - + + * - 22 + - Askey CPH050/ Phoebe Tv Master + FM + - 14ff:3002 + + * - 23 + - Modular Technology MM201/MM202/MM205/MM210/MM215 PCTV, bt878 + - 14c7:0101 + + * - 24 + - Askey CPH05X/06X (bt878) [many vendors] + - 144f:3002, 144f:3005, 144f:5000, 14ff:3000 + + * - 25 + - Terratec TerraTV+ Version 1.0 (Bt848)/ Terra TValue Version 1.0/ Vobis TV-Boostar + - + + * - 26 + - Hauppauge WinCam newer (bt878) + - + + * - 27 + - Lifeview FlyVideo 98/ MAXI TV Video PCI2 LR50 + - + + * - 28 + - Terratec TerraTV+ Version 1.1 (bt878) + - 153b:1127, 1852:1852 + + * - 29 + - Imagenation PXC200 + - 1295:200a + + * - 30 + - Lifeview FlyVideo 98 LR50 + - 1f7f:1850 + + * - 31 + - Formac iProTV, Formac ProTV I (bt848) + - + + * - 32 + - Intel Create and Share PCI/ Smart Video Recorder III + - + + * - 33 + - Terratec TerraTValue Version Bt878 + - 153b:1117, 153b:1118, 153b:1119, 153b:111a, 153b:1134, 153b:5018 + + * - 34 + - Leadtek WinFast 2000/ WinFast 2000 XP + - 107d:6606, 107d:6609, 6606:217d, f6ff:fff6 + + * - 35 + - Lifeview FlyVideo 98 LR50 / Chronos Video Shuttle II + - 1851:1850, 1851:a050 + + * - 36 + - Lifeview FlyVideo 98FM LR50 / Typhoon TView TV/FM Tuner + - 1852:1852 + + * - 37 + - Prolink PixelView PlayTV pro + - + + * - 38 + - Askey CPH06X TView99 + - 144f:3000, 144f:a005, a04f:a0fc + + * - 39 + - Pinnacle PCTV Studio/Rave + - 11bd:0012, bd11:1200, bd11:ff00, 11bd:ff12 + + * - 40 + - STB TV PCI FM, Gateway P/N 6000704 (bt878), 3Dfx VoodooTV 100 + - 10b4:2636, 10b4:2645, 121a:3060 + + * - 41 + - AVerMedia TVPhone 98 + - 1461:0001, 1461:0003 + + * - 42 + - ProVideo PV951 + - aa0c:146c + + * - 43 + - Little OnAir TV + - + + * - 44 + - Sigma TVII-FM + - + + * - 45 + - MATRIX-Vision MV-Delta 2 + - + + * - 46 + - Zoltrix Genie TV/FM + - 15b0:4000, 15b0:400a, 15b0:400d, 15b0:4010, 15b0:4016 + + * - 47 + - Terratec TV/Radio+ + - 153b:1123 + + * - 48 + - Askey CPH03x/ Dynalink Magic TView + - + + * - 49 + - IODATA GV-BCTV3/PCI + - 10fc:4020 + + * - 50 + - Prolink PV-BT878P+4E / PixelView PlayTV PAK / Lenco MXTV-9578 CP + - + + * - 51 + - Eagle Wireless Capricorn2 (bt878A) + - + + * - 52 + - Pinnacle PCTV Studio Pro + - + + * - 53 + - Typhoon TView RDS + FM Stereo / KNC1 TV Station RDS + - + + * - 54 + - Lifeview FlyVideo 2000 /FlyVideo A2/ Lifetec LT 9415 TV [LR90] + - + + * - 55 + - Askey CPH031/ BESTBUY Easy TV + - + + * - 56 + - Lifeview FlyVideo 98FM LR50 + - a051:41a0 + + * - 57 + - GrandTec 'Grand Video Capture' (Bt848) + - 4344:4142 + + * - 58 + - Askey CPH060/ Phoebe TV Master Only (No FM) + - + + * - 59 + - Askey CPH03x TV Capturer + - + + * - 60 + - Modular Technology MM100PCTV + - + + * - 61 + - AG Electronics GMV1 + - 15cb:0101 + + * - 62 + - Askey CPH061/ BESTBUY Easy TV (bt878) + - + + * - 63 + - ATI TV-Wonder + - 1002:0001 + + * - 64 + - ATI TV-Wonder VE + - 1002:0003 + + * - 65 + - Lifeview FlyVideo 2000S LR90 + - + + * - 66 + - Terratec TValueRadio + - 153b:1135, 153b:ff3b + + * - 67 + - IODATA GV-BCTV4/PCI + - 10fc:4050 + + * - 68 + - 3Dfx VoodooTV FM (Euro) + - 10b4:2637 + + * - 69 + - Active Imaging AIMMS + - + + * - 70 + - Prolink Pixelview PV-BT878P+ (Rev.4C,8E) + - + + * - 71 + - Lifeview FlyVideo 98EZ (capture only) LR51 + - 1851:1851 + + * - 72 + - Prolink Pixelview PV-BT878P+9B (PlayTV Pro rev.9B FM+NICAM) + - 1554:4011 + + * - 73 + - Sensoray 311/611 + - 6000:0311, 6000:0611 + + * - 74 + - RemoteVision MX (RV605) + - + + * - 75 + - Powercolor MTV878/ MTV878R/ MTV878F + - + + * - 76 + - Canopus WinDVR PCI (COMPAQ Presario 3524JP, 5112JP) + - 0e11:0079 + + * - 77 + - GrandTec Multi Capture Card (Bt878) + - + + * - 78 + - Jetway TV/Capture JW-TV878-FBK, Kworld KW-TV878RF + - 0a01:17de + + * - 79 + - DSP Design TCVIDEO + - + + * - 80 + - Hauppauge WinTV PVR + - 0070:4500 + + * - 81 + - IODATA GV-BCTV5/PCI + - 10fc:4070, 10fc:d018 + + * - 82 + - Osprey 100/150 (878) + - 0070:ff00 + + * - 83 + - Osprey 100/150 (848) + - + + * - 84 + - Osprey 101 (848) + - + + * - 85 + - Osprey 101/151 + - + + * - 86 + - Osprey 101/151 w/ svid + - + + * - 87 + - Osprey 200/201/250/251 + - + + * - 88 + - Osprey 200/250 + - 0070:ff01 + + * - 89 + - Osprey 210/220/230 + - + + * - 90 + - Osprey 500 + - 0070:ff02 + + * - 91 + - Osprey 540 + - 0070:ff04 + + * - 92 + - Osprey 2000 + - 0070:ff03 + + * - 93 + - IDS Eagle + - + + * - 94 + - Pinnacle PCTV Sat + - 11bd:001c + + * - 95 + - Formac ProTV II (bt878) + - + + * - 96 + - MachTV + - + + * - 97 + - Euresys Picolo + - + + * - 98 + - ProVideo PV150 + - aa00:1460, aa01:1461, aa02:1462, aa03:1463, aa04:1464, aa05:1465, aa06:1466, aa07:1467 + + * - 99 + - AD-TVK503 + - + + * - 100 + - Hercules Smart TV Stereo + - + + * - 101 + - Pace TV & Radio Card + - + + * - 102 + - IVC-200 + - 0000:a155, 0001:a155, 0002:a155, 0003:a155, 0100:a155, 0101:a155, 0102:a155, 0103:a155, 0800:a155, 0801:a155, 0802:a155, 0803:a155 + + * - 103 + - Grand X-Guard / Trust 814PCI + - 0304:0102 + + * - 104 + - Nebula Electronics DigiTV + - 0071:0101 + + * - 105 + - ProVideo PV143 + - aa00:1430, aa00:1431, aa00:1432, aa00:1433, aa03:1433 + + * - 106 + - PHYTEC VD-009-X1 VD-011 MiniDIN (bt878) + - + + * - 107 + - PHYTEC VD-009-X1 VD-011 Combi (bt878) + - + + * - 108 + - PHYTEC VD-009 MiniDIN (bt878) + - + + * - 109 + - PHYTEC VD-009 Combi (bt878) + - + + * - 110 + - IVC-100 + - ff00:a132 + + * - 111 + - IVC-120G + - ff00:a182, ff01:a182, ff02:a182, ff03:a182, ff04:a182, ff05:a182, ff06:a182, ff07:a182, ff08:a182, ff09:a182, ff0a:a182, ff0b:a182, ff0c:a182, ff0d:a182, ff0e:a182, ff0f:a182 + + * - 112 + - pcHDTV HD-2000 TV + - 7063:2000 + + * - 113 + - Twinhan DST + clones + - 11bd:0026, 1822:0001, 270f:fc00, 1822:0026 + + * - 114 + - Winfast VC100 + - 107d:6607 + + * - 115 + - Teppro TEV-560/InterVision IV-560 + - + + * - 116 + - SIMUS GVC1100 + - aa6a:82b2 + + * - 117 + - NGS NGSTV+ + - + + * - 118 + - LMLBT4 + - + + * - 119 + - Tekram M205 PRO + - + + * - 120 + - Conceptronic CONTVFMi + - + + * - 121 + - Euresys Picolo Tetra + - 1805:0105, 1805:0106, 1805:0107, 1805:0108 + + * - 122 + - Spirit TV Tuner + - + + * - 123 + - AVerMedia AVerTV DVB-T 771 + - 1461:0771 + + * - 124 + - AverMedia AverTV DVB-T 761 + - 1461:0761 + + * - 125 + - MATRIX Vision Sigma-SQ + - + + * - 126 + - MATRIX Vision Sigma-SLC + - + + * - 127 + - APAC Viewcomp 878(AMAX) + - + + * - 128 + - DViCO FusionHDTV DVB-T Lite + - 18ac:db10, 18ac:db11 + + * - 129 + - V-Gear MyVCD + - + + * - 130 + - Super TV Tuner + - + + * - 131 + - Tibet Systems 'Progress DVR' CS16 + - + + * - 132 + - Kodicom 4400R (master) + - + + * - 133 + - Kodicom 4400R (slave) + - + + * - 134 + - Adlink RTV24 + - + + * - 135 + - DViCO FusionHDTV 5 Lite + - 18ac:d500 + + * - 136 + - Acorp Y878F + - 9511:1540 + + * - 137 + - Conceptronic CTVFMi v2 + - 036e:109e + + * - 138 + - Prolink Pixelview PV-BT878P+ (Rev.2E) + - + + * - 139 + - Prolink PixelView PlayTV MPEG2 PV-M4900 + - + + * - 140 + - Osprey 440 + - 0070:ff07 + + * - 141 + - Asound Skyeye PCTV + - + + * - 142 + - Sabrent TV-FM (bttv version) + - + + * - 143 + - Hauppauge ImpactVCB (bt878) + - 0070:13eb + + * - 144 + - MagicTV + - + + * - 145 + - SSAI Security Video Interface + - 4149:5353 + + * - 146 + - SSAI Ultrasound Video Interface + - 414a:5353 + + * - 147 + - VoodooTV 200 (USA) + - 121a:3000 + + * - 148 + - DViCO FusionHDTV 2 + - dbc0:d200 + + * - 149 + - Typhoon TV-Tuner PCI (50684) + - + + * - 150 + - Geovision GV-600 + - 008a:763c + + * - 151 + - Kozumi KTV-01C + - + + * - 152 + - Encore ENL TV-FM-2 + - 1000:1801 + + * - 153 + - PHYTEC VD-012 (bt878) + - + + * - 154 + - PHYTEC VD-012-X1 (bt878) + - + + * - 155 + - PHYTEC VD-012-X2 (bt878) + - + + * - 156 + - IVCE-8784 + - 0000:f050, 0001:f050, 0002:f050, 0003:f050 + + * - 157 + - Geovision GV-800(S) (master) + - 800a:763d + + * - 158 + - Geovision GV-800(S) (slave) + - 800b:763d, 800c:763d, 800d:763d + + * - 159 + - ProVideo PV183 + - 1830:1540, 1831:1540, 1832:1540, 1833:1540, 1834:1540, 1835:1540, 1836:1540, 1837:1540 + + * - 160 + - Tongwei Video Technology TD-3116 + - f200:3116 + + * - 161 + - Aposonic W-DVR + - 0279:0228 + + * - 162 + - Adlink MPG24 + - + + * - 163 + - Bt848 Capture 14MHz + - + + * - 164 + - CyberVision CV06 (SV) + - + + * - 165 + - Kworld V-Stream Xpert TV PVR878 + - + + * - 166 + - PCI-8604PW + - diff --git a/Documentation/admin-guide/media/bttv.rst b/Documentation/admin-guide/media/bttv.rst new file mode 100644 index 000000000..58cbaf6df --- /dev/null +++ b/Documentation/admin-guide/media/bttv.rst @@ -0,0 +1,1762 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============== +The bttv driver +=============== + +Release notes for bttv +---------------------- + +You'll need at least these config options for bttv:: + + ./scripts/config -e PCI + ./scripts/config -m I2C + ./scripts/config -m INPUT + ./scripts/config -m MEDIA_SUPPORT + ./scripts/config -e MEDIA_PCI_SUPPORT + ./scripts/config -e MEDIA_ANALOG_TV_SUPPORT + ./scripts/config -e MEDIA_DIGITAL_TV_SUPPORT + ./scripts/config -e MEDIA_RADIO_SUPPORT + ./scripts/config -e RC_CORE + ./scripts/config -m VIDEO_BT848 + +If your board has digital TV, you'll also need:: + + ./scripts/config -m DVB_BT8XX + +In this case, please see Documentation/admin-guide/media/bt8xx.rst +for additional notes. + +Make bttv work with your card +----------------------------- + +If you have bttv compiled and installed, just booting the Kernel +should be enough for it to try probing it. However, depending +on the model, the Kernel may require additional information about +the hardware, as the device may not be able to provide such info +directly to the Kernel. + +If it doesn't bttv likely could not autodetect your card and needs some +insmod options. The most important insmod option for bttv is "card=n" +to select the correct card type. If you get video but no sound you've +very likely specified the wrong (or no) card type. A list of supported +cards is in Documentation/admin-guide/media/bttv-cardlist.rst. + +If bttv takes very long to load (happens sometimes with the cheap +cards which have no tuner), try adding this to your modules configuration +file (usually, it is either ``/etc/modules.conf`` or some file at +``/etc/modules-load.d/``, but the actual place depends on your +distribution):: + + options i2c-algo-bit bit_test=1 + +Some cards may require an extra firmware file to work. For example, +for the WinTV/PVR you need one firmware file from its driver CD, +called: ``hcwamc.rbf``. It is inside a self-extracting zip file +called ``pvr45xxx.exe``. Just placing it at the ``/etc/firmware`` +directory should be enough for it to be autoload during the driver's +probing mode (e. g. when the Kernel boots or when the driver is +manually loaded via ``modprobe`` command). + +If your card isn't listed in Documentation/admin-guide/media/bttv-cardlist.rst +or if you have trouble making audio work, please read :ref:`still_doesnt_work`. + + +Autodetecting cards +------------------- + +bttv uses the PCI Subsystem ID to autodetect the card type. lspci lists +the Subsystem ID in the second line, looks like this: + +.. code-block:: none + + 00:0a.0 Multimedia video controller: Brooktree Corporation Bt878 (rev 02) + Subsystem: Hauppauge computer works Inc. WinTV/GO + Flags: bus master, medium devsel, latency 32, IRQ 5 + Memory at e2000000 (32-bit, prefetchable) [size=4K] + +only bt878-based cards can have a subsystem ID (which does not mean +that every card really has one). bt848 cards can't have a Subsystem +ID and therefore can't be autodetected. There is a list with the ID's +at Documentation/admin-guide/media/bttv-cardlist.rst +(in case you are interested or want to mail patches with updates). + + +.. _still_doesnt_work: + +Still doesn't work? +------------------- + +I do NOT have a lab with 30+ different grabber boards and a +PAL/NTSC/SECAM test signal generator at home, so I often can't +reproduce your problems. This makes debugging very difficult for me. + +If you have some knowledge and spare time, please try to fix this +yourself (patches very welcome of course...) You know: The linux +slogan is "Do it yourself". + +There is a mailing list at +http://vger.kernel.org/vger-lists.html#linux-media + +If you have trouble with some specific TV card, try to ask there +instead of mailing me directly. The chance that someone with the +same card listens there is much higher... + +For problems with sound: There are a lot of different systems used +for TV sound all over the world. And there are also different chips +which decode the audio signal. Reports about sound problems ("stereo +doesn't work") are pretty useless unless you include some details +about your hardware and the TV sound scheme used in your country (or +at least the country you are living in). + +Modprobe options +---------------- + +.. note:: + + + The following argument list can be outdated, as we might add more + options if ever needed. In case of doubt, please check with + ``modinfo <module>``. + + This command prints various information about a kernel + module, among them a complete and up-to-date list of insmod options. + + + +bttv + The bt848/878 (grabber chip) driver + + insmod args:: + + card=n card type, see CARDLIST for a list. + tuner=n tuner type, see CARDLIST for a list. + radio=0/1 card supports radio + pll=0/1/2 pll settings + + 0: don't use PLL + 1: 28 MHz crystal installed + 2: 35 MHz crystal installed + + triton1=0/1 for Triton1 (+others) compatibility + vsfx=0/1 yet another chipset bug compatibility bit + see README.quirks for details on these two. + + bigendian=n Set the endianness of the gfx framebuffer. + Default is native endian. + fieldnr=0/1 Count fields. Some TV descrambling software + needs this, for others it only generates + 50 useless IRQs/sec. default is 0 (off). + autoload=0/1 autoload helper modules (tuner, audio). + default is 1 (on). + bttv_verbose=0/1/2 verbose level (at insmod time, while + looking at the hardware). default is 1. + bttv_debug=0/1 debug messages (for capture). + default is 0 (off). + irq_debug=0/1 irq handler debug messages. + default is 0 (off). + gbuffers=2-32 number of capture buffers for mmap'ed capture. + default is 4. + gbufsize= size of capture buffers. default and + maximum value is 0x208000 (~2MB) + no_overlay=0 Enable overlay on broken hardware. There + are some chipsets (SIS for example) which + are known to have problems with the PCI DMA + push used by bttv. bttv will disable overlay + by default on this hardware to avoid crashes. + With this insmod option you can override this. + no_overlay=1 Disable overlay. It should be used by broken + hardware that doesn't support PCI2PCI direct + transfers. + automute=0/1 Automatically mutes the sound if there is + no TV signal, on by default. You might try + to disable this if you have bad input signal + quality which leading to unwanted sound + dropouts. + chroma_agc=0/1 AGC of chroma signal, off by default. + adc_crush=0/1 Luminance ADC crush, on by default. + i2c_udelay= Allow reduce I2C speed. Default is 5 usecs + (meaning 66,67 Kbps). The default is the + maximum supported speed by kernel bitbang + algorithm. You may use lower numbers, if I2C + messages are lost (16 is known to work on + all supported cards). + + bttv_gpio=0/1 + gpiomask= + audioall= + audiomux= + See Sound-FAQ for a detailed description. + + remap, card, radio and pll accept up to four comma-separated arguments + (for multiple boards). + +tuner + The tuner driver. You need this unless you want to use only + with a camera or the board doesn't provide analog TV tuning. + + insmod args:: + + debug=1 print some debug info to the syslog + type=n type of the tuner chip. n as follows: + see CARDLIST for a complete list. + pal=[bdgil] select PAL variant (used for some tuners + only, important for the audio carrier). + +tvaudio + Provide a single driver for all simple i2c audio control + chips (tda/tea*). + + insmod args:: + + tda8425 = 1 enable/disable the support for the + tda9840 = 1 various chips. + tda9850 = 1 The tea6300 can't be autodetected and is + tda9855 = 1 therefore off by default, if you have + tda9873 = 1 this one on your card (STB uses these) + tda9874a = 1 you have to enable it explicitly. + tea6300 = 0 The two tda985x chips use the same i2c + tea6420 = 1 address and can't be disturgished from + pic16c54 = 1 each other, you might have to disable + the wrong one. + debug = 1 print debug messages + +msp3400 + The driver for the msp34xx sound processor chips. If you have a + stereo card, you probably want to insmod this one. + + insmod args:: + + debug=1/2 print some debug info to the syslog, + 2 is more verbose. + simple=1 Use the "short programming" method. Newer + msp34xx versions support this. You need this + for dbx stereo. Default is on if supported by + the chip. + once=1 Don't check the TV-stations Audio mode + every few seconds, but only once after + channel switches. + amsound=1 Audio carrier is AM/NICAM at 6.5 Mhz. This + should improve things for french people, the + carrier autoscan seems to work with FM only... + +If the box freezes hard with bttv +--------------------------------- + +It might be a bttv driver bug. It also might be bad hardware. It also +might be something else ... + +Just mailing me "bttv freezes" isn't going to help much. This README +has a few hints how you can help to pin down the problem. + + +bttv bugs +~~~~~~~~~ + +If some version works and another doesn't it is likely to be a driver +bug. It is very helpful if you can tell where exactly it broke +(i.e. the last working and the first broken version). + +With a hard freeze you probably doesn't find anything in the logfiles. +The only way to capture any kernel messages is to hook up a serial +console and let some terminal application log the messages. /me uses +screen. See Documentation/admin-guide/serial-console.rst for details on +setting up a serial console. + +Read Documentation/admin-guide/bug-hunting.rst to learn how to get any useful +information out of a register+stack dump printed by the kernel on +protection faults (so-called "kernel oops"). + +If you run into some kind of deadlock, you can try to dump a call trace +for each process using sysrq-t (see Documentation/admin-guide/sysrq.rst). +This way it is possible to figure where *exactly* some process in "D" +state is stuck. + +I've seen reports that bttv 0.7.x crashes whereas 0.8.x works rock solid +for some people. Thus probably a small buglet left somewhere in bttv +0.7.x. I have no idea where exactly, it works stable for me and a lot of +other people. But in case you have problems with the 0.7.x versions you +can give 0.8.x a try ... + + +hardware bugs +~~~~~~~~~~~~~ + +Some hardware can't deal with PCI-PCI transfers (i.e. grabber => vga). +Sometimes problems show up with bttv just because of the high load on +the PCI bus. The bt848/878 chips have a few workarounds for known +incompatibilities, see README.quirks. + +Some folks report that increasing the pci latency helps too, +althrought I'm not sure whenever this really fixes the problems or +only makes it less likely to happen. Both bttv and btaudio have a +insmod option to set the PCI latency of the device. + +Some mainboard have problems to deal correctly with multiple devices +doing DMA at the same time. bttv + ide seems to cause this sometimes, +if this is the case you likely see freezes only with video and hard disk +access at the same time. Updating the IDE driver to get the latest and +greatest workarounds for hardware bugs might fix these problems. + + +other +~~~~~ + +If you use some binary-only yunk (like nvidia module) try to reproduce +the problem without. + +IRQ sharing is known to cause problems in some cases. It works just +fine in theory and many configurations. Neverless it might be worth a +try to shuffle around the PCI cards to give bttv another IRQ or make +it share the IRQ with some other piece of hardware. IRQ sharing with +VGA cards seems to cause trouble sometimes. I've also seen funny +effects with bttv sharing the IRQ with the ACPI bridge (and +apci-enabled kernel). + +Bttv quirks +----------- + +Below is what the bt878 data book says about the PCI bug compatibility +modes of the bt878 chip. + +The triton1 insmod option sets the EN_TBFX bit in the control register. +The vsfx insmod option does the same for EN_VSFX bit. If you have +stability problems you can try if one of these options makes your box +work solid. + +drivers/pci/quirks.c knows about these issues, this way these bits are +enabled automagically for known-buggy chipsets (look at the kernel +messages, bttv tells you). + +Normal PCI Mode +~~~~~~~~~~~~~~~ + +The PCI REQ signal is the logical-or of the incoming function requests. +The inter-nal GNT[0:1] signals are gated asynchronously with GNT and +demultiplexed by the audio request signal. Thus the arbiter defaults to +the video function at power-up and parks there during no requests for +bus access. This is desirable since the video will request the bus more +often. However, the audio will have highest bus access priority. Thus +the audio will have first access to the bus even when issuing a request +after the video request but before the PCI external arbiter has granted +access to the Bt879. Neither function can preempt the other once on the +bus. The duration to empty the entire video PCI FIFO onto the PCI bus is +very short compared to the bus access latency the audio PCI FIFO can +tolerate. + + +430FX Compatibility Mode +~~~~~~~~~~~~~~~~~~~~~~~~ + +When using the 430FX PCI, the following rules will ensure +compatibility: + + (1) Deassert REQ at the same time as asserting FRAME. + (2) Do not reassert REQ to request another bus transaction until after + finish-ing the previous transaction. + +Since the individual bus masters do not have direct control of REQ, a +simple logical-or of video and audio requests would violate the rules. +Thus, both the arbiter and the initiator contain 430FX compatibility +mode logic. To enable 430FX mode, set the EN_TBFX bit as indicated in +Device Control Register on page 104. + +When EN_TBFX is enabled, the arbiter ensures that the two compatibility +rules are satisfied. Before GNT is asserted by the PCI arbiter, this +internal arbiter may still logical-or the two requests. However, once +the GNT is issued, this arbiter must lock in its decision and now route +only the granted request to the REQ pin. The arbiter decision lock +happens regardless of the state of FRAME because it does not know when +FRAME will be asserted (typically - each initiator will assert FRAME on +the cycle following GNT). When FRAME is asserted, it is the initiator s +responsibility to remove its request at the same time. It is the +arbiters responsibility to allow this request to flow through to REQ and +not allow the other request to hold REQ asserted. The decision lock may +be removed at the end of the transaction: for example, when the bus is +idle (FRAME and IRDY). The arbiter decision may then continue +asynchronously until GNT is again asserted. + + +Interfacing with Non-PCI 2.1 Compliant Core Logic +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +A small percentage of core logic devices may start a bus transaction +during the same cycle that GNT is de-asserted. This is non PCI 2.1 +compliant. To ensure compatibility when using PCs with these PCI +controllers, the EN_VSFX bit must be enabled (refer to Device Control +Register on page 104). When in this mode, the arbiter does not pass GNT +to the internal functions unless REQ is asserted. This prevents a bus +transaction from starting the same cycle as GNT is de-asserted. This +also has the side effect of not being able to take advantage of bus +parking, thus lowering arbitration performance. The Bt879 drivers must +query for these non-compliant devices, and set the EN_VSFX bit only if +required. + + +Other elements of the tvcards array +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +If you are trying to make a new card work you might find it useful to +know what the other elements in the tvcards array are good for:: + + video_inputs - # of video inputs the card has + audio_inputs - historical cruft, not used any more. + tuner - which input is the tuner + svhs - which input is svhs (all others are labeled composite) + muxsel - video mux, input->registervalue mapping + pll - same as pll= insmod option + tuner_type - same as tuner= insmod option + *_modulename - hint whenever some card needs this or that audio + module loaded to work properly. + has_radio - whenever this TV card has a radio tuner. + no_msp34xx - "1" disables loading of msp3400.o module + no_tda9875 - "1" disables loading of tda9875.o module + needs_tvaudio - set to "1" to load tvaudio.o module + +If some config item is specified both from the tvcards array and as +insmod option, the insmod option takes precedence. + +Cards +----- + +.. note:: + + For a more updated list, please check + https://linuxtv.org/wiki/index.php/Hardware_Device_Information + +Supported cards: Bt848/Bt848a/Bt849/Bt878/Bt879 cards +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +All cards with Bt848/Bt848a/Bt849/Bt878/Bt879 and normal +Composite/S-VHS inputs are supported. Teletext and Intercast support +(PAL only) for ALL cards via VBI sample decoding in software. + +Some cards with additional multiplexing of inputs or other additional +fancy chips are only partially supported (unless specifications by the +card manufacturer are given). When a card is listed here it isn't +necessarily fully supported. + +All other cards only differ by additional components as tuners, sound +decoders, EEPROMs, teletext decoders ... + + +MATRIX Vision +~~~~~~~~~~~~~ + +MV-Delta +- Bt848A +- 4 Composite inputs, 1 S-VHS input (shared with 4th composite) +- EEPROM + +http://www.matrix-vision.de/ + +This card has no tuner but supports all 4 composite (1 shared with an +S-VHS input) of the Bt848A. +Very nice card if you only have satellite TV but several tuners connected +to the card via composite. + +Many thanks to Matrix-Vision for giving us 2 cards for free which made +Bt848a/Bt849 single crystal operation support possible!!! + + + +Miro/Pinnacle PCTV +~~~~~~~~~~~~~~~~~~ + +- Bt848 + some (all??) come with 2 crystals for PAL/SECAM and NTSC +- PAL, SECAM or NTSC TV tuner (Philips or TEMIC) +- MSP34xx sound decoder on add on board + decoder is supported but AFAIK does not yet work + (other sound MUX setting in GPIO port needed??? somebody who fixed this???) +- 1 tuner, 1 composite and 1 S-VHS input +- tuner type is autodetected + +http://www.miro.de/ +http://www.miro.com/ + + +Many thanks for the free card which made first NTSC support possible back +in 1997! + + +Hauppauge Win/TV pci +~~~~~~~~~~~~~~~~~~~~ + +There are many different versions of the Hauppauge cards with different +tuners (TV+Radio ...), teletext decoders. +Note that even cards with same model numbers have (depending on the revision) +different chips on it. + +- Bt848 (and others but always in 2 crystal operation???) + newer cards have a Bt878 + +- PAL, SECAM, NTSC or tuner with or without Radio support + +e.g.: + +- PAL: + + - TDA5737: VHF, hyperband and UHF mixer/oscillator for TV and VCR 3-band tuners + - TSA5522: 1.4 GHz I2C-bus controlled synthesizer, I2C 0xc2-0xc3 + +- NTSC: + + - TDA5731: VHF, hyperband and UHF mixer/oscillator for TV and VCR 3-band tuners + - TSA5518: no datasheet available on Philips site + +- Philips SAA5246 or SAA5284 ( or no) Teletext decoder chip + with buffer RAM (e.g. Winbond W24257AS-35: 32Kx8 CMOS static RAM) + SAA5246 (I2C 0x22) is supported + +- 256 bytes EEPROM: Microchip 24LC02B or Philips 8582E2Y + with configuration information + I2C address 0xa0 (24LC02B also responds to 0xa2-0xaf) + +- 1 tuner, 1 composite and (depending on model) 1 S-VHS input + +- 14052B: mux for selection of sound source + +- sound decoder: TDA9800, MSP34xx (stereo cards) + + +Askey CPH-Series +~~~~~~~~~~~~~~~~ +Developed by TelSignal(?), OEMed by many vendors (Typhoon, Anubis, Dynalink) + +- Card series: + - CPH01x: BT848 capture only + - CPH03x: BT848 + - CPH05x: BT878 with FM + - CPH06x: BT878 (w/o FM) + - CPH07x: BT878 capture only + +- TV standards: + - CPH0x0: NTSC-M/M + - CPH0x1: PAL-B/G + - CPH0x2: PAL-I/I + - CPH0x3: PAL-D/K + - CPH0x4: SECAM-L/L + - CPH0x5: SECAM-B/G + - CPH0x6: SECAM-D/K + - CPH0x7: PAL-N/N + - CPH0x8: PAL-B/H + - CPH0x9: PAL-M/M + +- CPH03x was often sold as "TV capturer". + +Identifying: + + #) 878 cards can be identified by PCI Subsystem-ID: + - 144f:3000 = CPH06x + - 144F:3002 = CPH05x w/ FM + - 144F:3005 = CPH06x_LC (w/o remote control) + #) The cards have a sticker with "CPH"-model on the back. + #) These cards have a number printed on the PCB just above the tuner metal box: + - "80-CP2000300-x" = CPH03X + - "80-CP2000500-x" = CPH05X + - "80-CP2000600-x" = CPH06X / CPH06x_LC + + Askey sells these cards as "Magic TView series", Brand "MagicXpress". + Other OEM often call these "Tview", "TView99" or else. + +Lifeview Flyvideo Series: +~~~~~~~~~~~~~~~~~~~~~~~~~ + +The naming of these series differs in time and space. + +Identifying: + #) Some models can be identified by PCI subsystem ID: + + - 1852:1852 = Flyvideo 98 FM + - 1851:1850 = Flyvideo 98 + - 1851:1851 = Flyvideo 98 EZ (capture only) + + #) There is a print on the PCB: + + - LR25 = Flyvideo (Zoran ZR36120, SAA7110A) + - LR26 Rev.N = Flyvideo II (Bt848) + - LR26 Rev.O = Flyvideo II (Bt878) + - LR37 Rev.C = Flyvideo EZ (Capture only, ZR36120 + SAA7110) + - LR38 Rev.A1= Flyvideo II EZ (Bt848 capture only) + - LR50 Rev.Q = Flyvideo 98 (w/eeprom and PCI subsystem ID) + - LR50 Rev.W = Flyvideo 98 (no eeprom) + - LR51 Rev.E = Flyvideo 98 EZ (capture only) + - LR90 = Flyvideo 2000 (Bt878) + - LR90 Flyvideo 2000S (Bt878) w/Stereo TV (Package incl. LR91 daughterboard) + - LR91 = Stereo daughter card for LR90 + - LR97 = Flyvideo DVBS + - LR99 Rev.E = Low profile card for OEM integration (only internal audio!) bt878 + - LR136 = Flyvideo 2100/3100 (Low profile, SAA7130/SAA7134) + - LR137 = Flyvideo DV2000/DV3000 (SAA7130/SAA7134 + IEEE1394) + - LR138 Rev.C= Flyvideo 2000 (SAA7130) + - LR138 Flyvideo 3000 (SAA7134) w/Stereo TV + + - These exist in variations w/FM and w/Remote sometimes denoted + by suffixes "FM" and "R". + + #) You have a laptop (miniPCI card): + + - Product = FlyTV Platinum Mini + - Model/Chip = LR212/saa7135 + + - Lifeview.com.tw states (Feb. 2002): + "The FlyVideo2000 and FlyVideo2000s product name have renamed to FlyVideo98." + Their Bt8x8 cards are listed as discontinued. + - Flyvideo 2000S was probably sold as Flyvideo 3000 in some countries(Europe?). + The new Flyvideo 2000/3000 are SAA7130/SAA7134 based. + +"Flyvideo II" had been the name for the 848 cards, nowadays (in Germany) +this name is re-used for LR50 Rev.W. + +The Lifeview website mentioned Flyvideo III at some time, but such a card +has not yet been seen (perhaps it was the german name for LR90 [stereo]). +These cards are sold by many OEMs too. + +FlyVideo A2 (Elta 8680)= LR90 Rev.F (w/Remote, w/o FM, stereo TV by tda9821) {Germany} + +Lifeview 3000 (Elta 8681) as sold by Plus(April 2002), Germany = LR138 w/ saa7134 + +lifeview config coding on gpio pins 0-9 +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +- LR50 rev. Q ("PARTS: 7031505116), Tuner wurde als Nr. 5 erkannt, Eingänge + SVideo, TV, Composite, Audio, Remote: + + - CP9..1=100001001 (1: 0-Ohm-Widerstand gegen GND unbestückt; 0: bestückt) + + +Typhoon TV card series: +~~~~~~~~~~~~~~~~~~~~~~~ + +These can be CPH, Flyvideo, Pixelview or KNC1 series. + +Typhoon is the brand of Anubis. + +Model 50680 got re-used, some model no. had different contents over time. + +Models: + + - 50680 "TV Tuner PCI Pal BG"(old,red package)=can be CPH03x(bt848) or CPH06x(bt878) + - 50680 "TV Tuner Pal BG" (blue package)= Pixelview PV-BT878P+ (Rev 9B) + - 50681 "TV Tuner PCI Pal I" (variant of 50680) + - 50682 "TView TV/FM Tuner Pal BG" = Flyvideo 98FM (LR50 Rev.Q) + + .. note:: + + The package has a picture of CPH05x (which would be a real TView) + + - 50683 "TV Tuner PCI SECAM" (variant of 50680) + - 50684 "TV Tuner Pal BG" = Pixelview 878TV(Rev.3D) + - 50686 "TV Tuner" = KNC1 TV Station + - 50687 "TV Tuner stereo" = KNC1 TV Station pro + - 50688 "TV Tuner RDS" (black package) = KNC1 TV Station RDS + - 50689 TV SAT DVB-S CARD CI PCI (SAA7146AH, SU1278?) = "KNC1 TV Station DVB-S" + - 50692 "TV/FM Tuner" (small PCB) + - 50694 TV TUNER CARD RDS (PHILIPS CHIPSET SAA7134HL) + - 50696 TV TUNER STEREO (PHILIPS CHIPSET SAA7134HL, MK3ME Tuner) + - 50804 PC-SAT TV/Audio Karte = Techni-PC-Sat (ZORAN 36120PQC, Tuner:Alps) + - 50866 TVIEW SAT RECEIVER+ADR + - 50868 "TV/FM Tuner Pal I" (variant of 50682) + - 50999 "TV/FM Tuner Secam" (variant of 50682) + +Guillemot +~~~~~~~~~ + +Models: + +- Maxi-TV PCI (ZR36120) +- Maxi TV Video 2 = LR50 Rev.Q (FI1216MF, PAL BG+SECAM) +- Maxi TV Video 3 = CPH064 (PAL BG + SECAM) + +Mentor +~~~~~~ + +Mentor TV card ("55-878TV-U1") = Pixelview 878TV(Rev.3F) (w/FM w/Remote) + +Prolink +~~~~~~~ + +- TV cards: + + - PixelView Play TV pro - (Model: PV-BT878P+ REV 8E) + - PixelView Play TV pro - (Model: PV-BT878P+ REV 9D) + - PixelView Play TV pro - (Model: PV-BT878P+ REV 4C / 8D / 10A ) + - PixelView Play TV - (Model: PV-BT848P+) + - 878TV - (Model: PV-BT878TV) + +- Multimedia TV packages (card + software pack): + + - PixelView Play TV Theater - (Model: PV-M4200) = PixelView Play TV pro + Software + - PixelView Play TV PAK - (Model: PV-BT878P+ REV 4E) + - PixelView Play TV/VCR - (Model: PV-M3200 REV 4C / 8D / 10A ) + - PixelView Studio PAK - (Model: M2200 REV 4C / 8D / 10A ) + - PixelView PowerStudio PAK - (Model: PV-M3600 REV 4E) + - PixelView DigitalVCR PAK - (Model: PV-M2400 REV 4C / 8D / 10A ) + - PixelView PlayTV PAK II (TV/FM card + usb camera) PV-M3800 + - PixelView PlayTV XP PV-M4700,PV-M4700(w/FM) + - PixelView PlayTV DVR PV-M4600 package contents:PixelView PlayTV pro, windvr & videoMail s/w + +- Further Cards: + + - PV-BT878P+rev.9B (Play TV Pro, opt. w/FM w/NICAM) + - PV-BT878P+rev.2F + - PV-BT878P Rev.1D (bt878, capture only) + + - XCapture PV-CX881P (cx23881) + - PlayTV HD PV-CX881PL+, PV-CX881PL+(w/FM) (cx23881) + + - DTV3000 PV-DTV3000P+ DVB-S CI = Twinhan VP-1030 + - DTV2000 DVB-S = Twinhan VP-1020 + +- Video Conferencing: + + - PixelView Meeting PAK - (Model: PV-BT878P) + - PixelView Meeting PAK Lite - (Model: PV-BT878P) + - PixelView Meeting PAK plus - (Model: PV-BT878P+rev 4C/8D/10A) + - PixelView Capture - (Model: PV-BT848P) + - PixelView PlayTV USB pro + - Model No. PV-NT1004+, PV-NT1004+ (w/FM) = NT1004 USB decoder chip + SAA7113 video decoder chip + +Dynalink +~~~~~~~~ + +These are CPH series. + +Phoebemicro +~~~~~~~~~~~ + +- TV Master = CPH030 or CPH060 +- TV Master FM = CPH050 + +Genius/Kye +~~~~~~~~~~ + +- Video Wonder/Genius Internet Video Kit = LR37 Rev.C +- Video Wonder Pro II (848 or 878) = LR26 + +Tekram +~~~~~~ + +- VideoCap C205 (Bt848) +- VideoCap C210 (zr36120 +Philips) +- CaptureTV M200 (ISA) +- CaptureTV M205 (Bt848) + +Lucky Star +~~~~~~~~~~ + +- Image World Conference TV = LR50 Rev. Q + +Leadtek +~~~~~~~ + +- WinView 601 (Bt848) +- WinView 610 (Zoran) +- WinFast2000 +- WinFast2000 XP + +Support for the Leadtek WinView 601 TV/FM +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Author of this section: Jon Tombs <jon@gte.esi.us.es> + +This card is basically the same as all the rest (Bt484A, Philips tuner), +the main difference is that they have attached a programmable attenuator to 3 +GPIO lines in order to give some volume control. They have also stuck an +infra-red remote control decoded on the board, I will add support for this +when I get time (it simple generates an interrupt for each key press, with +the key code is placed in the GPIO port). + +I don't yet have any application to test the radio support. The tuner +frequency setting should work but it is possible that the audio multiplexer +is wrong. If it doesn't work, send me email. + + +- No Thanks to Leadtek they refused to answer any questions about their + hardware. The driver was written by visual inspection of the card. If you + use this driver, send an email insult to them, and tell them you won't + continue buying their hardware unless they support Linux. + +- Little thanks to Princeton Technology Corp (http://www.princeton.com.tw) + who make the audio attenuator. Their publicly available data-sheet available + on their web site doesn't include the chip programming information! Hidden + on their server are the full data-sheets, but don't ask how I found it. + +To use the driver I use the following options, the tuner and pll settings might +be different in your country. You can force it via modprobe parameters. +For example:: + + modprobe bttv tuner=1 pll=28 radio=1 card=17 + +Sets tuner type 1 (Philips PAL_I), PLL with a 28 MHz crystal, enables +FM radio and selects bttv card ID 17 (Leadtek WinView 601). + + +KNC One +~~~~~~~ + +- TV-Station +- TV-Station SE (+Software Bundle) +- TV-Station pro (+TV stereo) +- TV-Station FM (+Radio) +- TV-Station RDS (+RDS) +- TV Station SAT (analog satellite) +- TV-Station DVB-S + +.. note:: newer Cards have saa7134, but model name stayed the same? + +Provideo +~~~~~~~~ + +- PV951 or PV-951, now named PV-951T + (also are sold as: + Boeder TV-FM Video Capture Card, + Titanmedia Supervision TV-2400, + Provideo PV951 TF, + 3DeMon PV951, + MediaForte TV-Vision PV951, + Yoko PV951, + Vivanco Tuner Card PCI Art.-Nr.: 68404 + ) + +- Surveillance Series: + + - PV-141 + - PV-143 + - PV-147 + - PV-148 (capture only) + - PV-150 + - PV-151 + +- TV-FM Tuner Series: + + - PV-951TDV (tv tuner + 1394) + - PV-951T/TF + - PV-951PT/TF + - PV-956T/TF Low Profile + - PV-911 + +Highscreen +~~~~~~~~~~ + +Models: + +- TV Karte = LR50 Rev.S +- TV-Boostar = Terratec Terra TV+ Version 1.0 (Bt848, tda9821) "ceb105.pcb" + +Zoltrix +~~~~~~~ + +Models: + +- Face to Face Capture (Bt848 capture only) (PCB "VP-2848") +- Face To Face TV MAX (Bt848) (PCB "VP-8482 Rev1.3") +- Genie TV (Bt878) (PCB "VP-8790 Rev 2.1") +- Genie Wonder Pro + +AVerMedia +~~~~~~~~~ + +- AVer FunTV Lite (ISA, AV3001 chipset) "M101.C" +- AVerTV +- AVerTV Stereo +- AVerTV Studio (w/FM) +- AVerMedia TV98 with Remote +- AVerMedia TV/FM98 Stereo +- AVerMedia TVCAM98 +- TVCapture (Bt848) +- TVPhone (Bt848) +- TVCapture98 (="AVerMedia TV98" in USA) (Bt878) +- TVPhone98 (Bt878, w/FM) + +======== =========== =============== ======= ====== ======== ======================= +PCB PCI-ID Model-Name Eeprom Tuner Sound Country +======== =========== =============== ======= ====== ======== ======================= +M101.C ISA ! +M108-B Bt848 -- FR1236 US [#f2]_, [#f3]_ +M1A8-A Bt848 AVer TV-Phone FM1216 -- +M168-T 1461:0003 AVerTV Studio 48:17 FM1216 TDA9840T D [#f1]_ w/FM w/Remote +M168-U 1461:0004 TVCapture98 40:11 FI1216 -- D w/Remote +M168II-B 1461:0003 Medion MD9592 48:16 FM1216 TDA9873H D w/FM +======== =========== =============== ======= ====== ======== ======================= + +.. [#f1] Daughterboard MB68-A with TDA9820T and TDA9840T +.. [#f2] Sony NE41S soldered (stereo sound?) +.. [#f3] Daughterboard M118-A w/ pic 16c54 and 4 MHz quartz + +- US site has different drivers for (as of 09/2002): + + - EZ Capture/InterCam PCI (BT-848 chip) + - EZ Capture/InterCam PCI (BT-878 chip) + - TV-Phone (BT-848 chip) + - TV98 (BT-848 chip) + - TV98 With Remote (BT-848 chip) + - TV98 (BT-878 chip) + - TV98 With Remote (BT-878) + - TV/FM98 (BT-878 chip) + - AVerTV + - AverTV Stereo + - AVerTV Studio + +DE hat diverse Treiber fuer diese Modelle (Stand 09/2002): + + - TVPhone (848) mit Philips tuner FR12X6 (w/ FM radio) + - TVPhone (848) mit Philips tuner FM12X6 (w/ FM radio) + - TVCapture (848) w/Philips tuner FI12X6 + - TVCapture (848) non-Philips tuner + - TVCapture98 (Bt878) + - TVPhone98 (Bt878) + - AVerTV und TVCapture98 w/VCR (Bt 878) + - AVerTVStudio und TVPhone98 w/VCR (Bt878) + - AVerTV GO Series (Kein SVideo Input) + - AVerTV98 (BT-878 chip) + - AVerTV98 mit Fernbedienung (BT-878 chip) + - AVerTV/FM98 (BT-878 chip) + + - VDOmate (www.averm.com.cn) = M168U ? + +Aimslab +~~~~~~~ + +Models: + +- Video Highway or "Video Highway TR200" (ISA) +- Video Highway Xtreme (aka "VHX") (Bt848, FM w/ TEA5757) + +IXMicro (former: IMS=Integrated Micro Solutions) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Models: + +- IXTV BT848 (=TurboTV) +- IXTV BT878 +- IMS TurboTV (Bt848) + +Lifetec/Medion/Tevion/Aldi +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Models: + +- LT9306/MD9306 = CPH061 +- LT9415/MD9415 = LR90 Rev.F or Rev.G +- MD9592 = Avermedia TVphone98 (PCI_ID=1461:0003), PCB-Rev=M168II-B (w/TDA9873H) +- MD9717 = KNC One (Rev D4, saa7134, FM1216 MK2 tuner) +- MD5044 = KNC One (Rev D4, saa7134, FM1216ME MK3 tuner) + +Modular Technologies (www.modulartech.com) UK +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Models: + +- MM100 PCTV (Bt848) +- MM201 PCTV (Bt878, Bt832) w/ Quartzsight camera +- MM202 PCTV (Bt878, Bt832, tda9874) +- MM205 PCTV (Bt878) +- MM210 PCTV (Bt878) (Galaxy TV, Galaxymedia ?) + +Terratec +~~~~~~~~ + +Models: + +- Terra TV+ Version 1.0 (Bt848), "ceb105.PCB" printed on the PCB, TDA9821 +- Terra TV+ Version 1.1 (Bt878), "LR74 Rev.E" printed on the PCB, TDA9821 +- Terra TValueRadio, "LR102 Rev.C" printed on the PCB +- Terra TV/Radio+ Version 1.0, "80-CP2830100-0" TTTV3 printed on the PCB, + "CPH010-E83" on the back, SAA6588T, TDA9873H +- Terra TValue Version BT878, "80-CP2830110-0 TTTV4" printed on the PCB, + "CPH011-D83" on back +- Terra TValue Version 1.0 "ceb105.PCB" (really identical to Terra TV+ Version 1.0) +- Terra TValue New Revision "LR102 Rec.C" +- Terra Active Radio Upgrade (tea5757h, saa6588t) + +- LR74 is a newer PCB revision of ceb105 (both incl. connector for Active Radio Upgrade) + +- Cinergy 400 (saa7134), "E877 11(S)", "PM820092D" printed on PCB +- Cinergy 600 (saa7134) + +Technisat +~~~~~~~~~ + +Models: + +- Discos ADR PC-Karte ISA (no TV!) +- Discos ADR PC-Karte PCI (probably no TV?) +- Techni-PC-Sat (Sat. analog) + Rev 1.2 (zr36120, vpx3220, stv0030, saa5246, BSJE3-494A) +- Mediafocus I (zr36120/zr36125, drp3510, Sat. analog + ADR Radio) +- Mediafocus II (saa7146, Sat. analog) +- SatADR Rev 2.1 (saa7146a, saa7113h, stv0056a, msp3400c, drp3510a, BSKE3-307A) +- SkyStar 1 DVB (AV7110) = Technotrend Premium +- SkyStar 2 DVB (B2C2) (=Sky2PC) + +Siemens +~~~~~~~ + +Multimedia eXtension Board (MXB) (SAA7146, SAA7111) + +Powercolor +~~~~~~~~~~ + +Models: + +- MTV878 + Package comes with different contents: + + a) pcb "MTV878" (CARD=75) + b) Pixelview Rev. 4\_ + +- MTV878R w/Remote Control +- MTV878F w/Remote Control w/FM radio + +Pinnacle +~~~~~~~~ + +PCTV models: + +- Mirovideo PCTV (Bt848) +- Mirovideo PCTV SE (Bt848) +- Mirovideo PCTV Pro (Bt848 + Daughterboard for TV Stereo and FM) +- Studio PCTV Rave (Bt848 Version = Mirovideo PCTV) +- Studio PCTV Rave (Bt878 package w/o infrared) +- Studio PCTV (Bt878) +- Studio PCTV Pro (Bt878 stereo w/ FM) +- Pinnacle PCTV (Bt878, MT2032) +- Pinnacle PCTV Pro (Bt878, MT2032) +- Pinncale PCTV Sat (bt878a, HM1821/1221) ["Conexant CX24110 with CX24108 tuner, aka HM1221/HM1811"] +- Pinnacle PCTV Sat XE + +M(J)PEG capture and playback models: + +- DC1+ (ISA) +- DC10 (zr36057, zr36060, saa7110, adv7176) +- DC10+ (zr36067, zr36060, saa7110, adv7176) +- DC20 (ql16x24b,zr36050, zr36016, saa7110, saa7187 ...) +- DC30 (zr36057, zr36050, zr36016, vpx3220, adv7176, ad1843, tea6415, miro FST97A1) +- DC30+ (zr36067, zr36050, zr36016, vpx3220, adv7176) +- DC50 (zr36067, zr36050, zr36016, saa7112, adv7176 (2 pcs.?), ad1843, miro FST97A1, Lattice ???) + +Lenco +~~~~~ + +Models: + +- MXR-9565 (=Technisat Mediafocus?) +- MXR-9571 (Bt848) (=CPH031?) +- MXR-9575 +- MXR-9577 (Bt878) (=Prolink 878TV Rev.3x) +- MXTV-9578CP (Bt878) (= Prolink PV-BT878P+4E) + +Iomega +~~~~~~ + +Buz (zr36067, zr36060, saa7111, saa7185) + +LML +~~~ + LML33 (zr36067, zr36060, bt819, bt856) + +Grandtec +~~~~~~~~ + +Models: + +- Grand Video Capture (Bt848) +- Multi Capture Card (Bt878) + +Koutech +~~~~~~~ + +Models: + +- KW-606 (Bt848) +- KW-607 (Bt848 capture only) +- KW-606RSF +- KW-607A (capture only) +- KW-608 (Zoran capture only) + +IODATA (jp) +~~~~~~~~~~~ + +Models: + +- GV-BCTV/PCI +- GV-BCTV2/PCI +- GV-BCTV3/PCI +- GV-BCTV4/PCI +- GV-VCP/PCI (capture only) +- GV-VCP2/PCI (capture only) + +Canopus (jp) +~~~~~~~~~~~~ + +WinDVR = Kworld "KW-TVL878RF" + +www.sigmacom.co.kr +~~~~~~~~~~~~~~~~~~ + +Sigma Cyber TV II + +www.sasem.co.kr +~~~~~~~~~~~~~~~ + +Litte OnAir TV + +hama +~~~~ + +TV/Radio-Tuner Card, PCI (Model 44677) = CPH051 + +Sigma Designs +~~~~~~~~~~~~~ + +Hollywood plus (em8300, em9010, adv7175), (PCB "M340-10") MPEG DVD decoder + +Formac +~~~~~~ + +Models: + +- iProTV (Card for iMac Mezzanine slot, Bt848+SCSI) +- ProTV (Bt848) +- ProTV II = ProTV Stereo (Bt878) ["stereo" means FM stereo, tv is still mono] + +ATI +~~~ + +Models: + +- TV-Wonder +- TV-Wonder VE + +Diamond Multimedia +~~~~~~~~~~~~~~~~~~ + +DTV2000 (Bt848, tda9875) + +Aopen +~~~~~ + +- VA1000 Plus (w/ Stereo) +- VA1000 Lite +- VA1000 (=LR90) + +Intel +~~~~~ + +Models: + +- Smart Video Recorder (ISA full-length) +- Smart Video Recorder pro (ISA half-length) +- Smart Video Recorder III (Bt848) + +STB +~~~ + +Models: + +- STB Gateway 6000704 (bt878) +- STB Gateway 6000699 (bt848) +- STB Gateway 6000402 (bt848) +- STB TV130 PCI + +Videologic +~~~~~~~~~~ + +Models: + +- Captivator Pro/TV (ISA?) +- Captivator PCI/VC (Bt848 bundled with camera) (capture only) + +Technotrend +~~~~~~~~~~~~ + +Models: + +- TT-SAT PCI (PCB "Sat-PCI Rev.:1.3.1"; zr36125, vpx3225d, stc0056a, Tuner:BSKE6-155A +- TT-DVB-Sat + - revisions 1.1, 1.3, 1.5, 1.6 and 2.1 + - This card is sold as OEM from: + + - Siemens DVB-s Card + - Hauppauge WinTV DVB-S + - Technisat SkyStar 1 DVB + - Galaxis DVB Sat + + - Now this card is called TT-PCline Premium Family + - TT-Budget (saa7146, bsru6-701a) + This card is sold as OEM from: + + - Hauppauge WinTV Nova + - Satelco Standard PCI (DVB-S) + - TT-DVB-C PCI + +Teles +~~~~~ + + DVB-s (Rev. 2.2, BSRV2-301A, data only?) + +Remote Vision +~~~~~~~~~~~~~ + +MX RV605 (Bt848 capture only) + +Boeder +~~~~~~ + +Models: + +- PC ChatCam (Model 68252) (Bt848 capture only) +- Tv/Fm Capture Card (Model 68404) = PV951 + +Media-Surfer (esc-kathrein.de) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Models: + +- Sat-Surfer (ISA) +- Sat-Surfer PCI = Techni-PC-Sat +- Cable-Surfer 1 +- Cable-Surfer 2 +- Cable-Surfer PCI (zr36120) +- Audio-Surfer (ISA Radio card) + +Jetway (www.jetway.com.tw) +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Models: + +- JW-TV 878M +- JW-TV 878 = KWorld KW-TV878RF + +Galaxis +~~~~~~~ + +Models: + +- Galaxis DVB Card S CI +- Galaxis DVB Card C CI +- Galaxis DVB Card S +- Galaxis DVB Card C +- Galaxis plug.in S [neuer Name: Galaxis DVB Card S CI + +Hauppauge +~~~~~~~~~ + +Models: + +- many many WinTV models ... +- WinTV DVBs = Technotrend Premium 1.3 +- WinTV NOVA = Technotrend Budget 1.1 "S-DVB DATA" +- WinTV NOVA-CI "SDVBACI" +- WinTV Nova USB (=Technotrend USB 1.0) +- WinTV-Nexus-s (=Technotrend Premium 2.1 or 2.2) +- WinTV PVR +- WinTV PVR 250 +- WinTV PVR 450 + +US models + +-990 WinTV-PVR-350 (249USD) (iTVC15 chipset + radio) +-980 WinTV-PVR-250 (149USD) (iTVC15 chipset) +-880 WinTV-PVR-PCI (199USD) (KFIR chipset + bt878) +-881 WinTV-PVR-USB +-190 WinTV-GO +-191 WinTV-GO-FM +-404 WinTV +-401 WinTV-radio +-495 WinTV-Theater +-602 WinTV-USB +-621 WinTV-USB-FM +-600 USB-Live +-698 WinTV-HD +-697 WinTV-D +-564 WinTV-Nexus-S + +Deutsche Modelle: + +-603 WinTV GO +-719 WinTV Primio-FM +-718 WinTV PCI-FM +-497 WinTV Theater +-569 WinTV USB +-568 WinTV USB-FM +-882 WinTV PVR +-981 WinTV PVR 250 +-891 WinTV-PVR-USB +-541 WinTV Nova +-488 WinTV Nova-Ci +-564 WinTV-Nexus-s +-727 WinTV-DVB-c +-545 Common Interface +-898 WinTV-Nova-USB + +UK models: + +-607 WinTV Go +-693,793 WinTV Primio FM +-647,747 WinTV PCI FM +-498 WinTV Theater +-883 WinTV PVR +-893 WinTV PVR USB (Duplicate entry) +-566 WinTV USB (UK) +-573 WinTV USB FM +-429 Impact VCB (bt848) +-600 USB Live (Video-In 1x Comp, 1xSVHS) +-542 WinTV Nova +-717 WinTV DVB-S +-909 Nova-t PCI +-893 Nova-t USB (Duplicate entry) +-802 MyTV +-804 MyView +-809 MyVideo +-872 MyTV2Go FM +-546 WinTV Nova-S CI +-543 WinTV Nova +-907 Nova-S USB +-908 Nova-T USB +-717 WinTV Nexus-S +-157 DEC3000-s Standalone + USB + +Spain: + +-685 WinTV-Go +-690 WinTV-PrimioFM +-416 WinTV-PCI Nicam Estereo +-677 WinTV-PCI-FM +-699 WinTV-Theater +-683 WinTV-USB +-678 WinTV-USB-FM +-983 WinTV-PVR-250 +-883 WinTV-PVR-PCI +-993 WinTV-PVR-350 +-893 WinTV-PVR-USB +-728 WinTV-DVB-C PCI +-832 MyTV2Go +-869 MyTV2Go-FM +-805 MyVideo (USB) + + +Matrix-Vision +~~~~~~~~~~~~~ + +Models: + +- MATRIX-Vision MV-Delta +- MATRIX-Vision MV-Delta 2 +- MVsigma-SLC (Bt848) + +Conceptronic (.net) +~~~~~~~~~~~~~~~~~~~ + +Models: + +- TVCON FM, TV card w/ FM = CPH05x +- TVCON = CPH06x + +BestData +~~~~~~~~ + +Models: + +- HCC100 = VCC100rev1 + camera +- VCC100 rev1 (bt848) +- VCC100 rev2 (bt878) + +Gallant (www.gallantcom.com) www.minton.com.tw +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Models: + +- Intervision IV-510 (capture only bt8x8) +- Intervision IV-550 (bt8x8) +- Intervision IV-100 (zoran) +- Intervision IV-1000 (bt8x8) + +Asonic (www.asonic.com.cn) (website down) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +SkyEye tv 878 + +Hoontech +~~~~~~~~ + +878TV/FM + +Teppro (www.itcteppro.com.tw) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Models: + +- ITC PCITV (Card Ver 1.0) "Teppro TV1/TVFM1 Card" +- ITC PCITV (Card Ver 2.0) +- ITC PCITV (Card Ver 3.0) = "PV-BT878P+ (REV.9D)" +- ITC PCITV (Card Ver 4.0) +- TEPPRO IV-550 (For BT848 Main Chip) +- ITC DSTTV (bt878, satellite) +- ITC VideoMaker (saa7146, StreamMachine sm2110, tvtuner) "PV-SM2210P+ (REV:1C)" + +Kworld (www.kworld.com.tw) +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +PC TV Station: + +- KWORLD KW-TV878R TV (no radio) +- KWORLD KW-TV878RF TV (w/ radio) +- KWORLD KW-TVL878RF (low profile) +- KWORLD KW-TV713XRF (saa7134) + + + MPEG TV Station (same cards as above plus WinDVR Software MPEG en/decoder) + +- KWORLD KW-TV878R -Pro TV (no Radio) +- KWORLD KW-TV878RF-Pro TV (w/ Radio) +- KWORLD KW-TV878R -Ultra TV (no Radio) +- KWORLD KW-TV878RF-Ultra TV (w/ Radio) + +JTT/ Justy Corp.(http://www.jtt.ne.jp/) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +JTT-02 (JTT TV) "TV watchmate pro" (bt848) + +ADS www.adstech.com +~~~~~~~~~~~~~~~~~~~ + +Models: + +- Channel Surfer TV ( CHX-950 ) +- Channel Surfer TV+FM ( CHX-960FM ) + +AVEC www.prochips.com +~~~~~~~~~~~~~~~~~~~~~ + +AVEC Intercapture (bt848, tea6320) + +NoBrand +~~~~~~~ + +TV Excel = Australian Name for "PV-BT878P+ 8E" or "878TV Rev.3\_" + +Mach www.machspeed.com +~~~~~~~~~~~~~~~~~~~~~~ + +Mach TV 878 + +Eline www.eline-net.com/ +~~~~~~~~~~~~~~~~~~~~~~~~ + +Models: + +- Eline Vision TVMaster / TVMaster FM (ELV-TVM/ ELV-TVM-FM) = LR26 (bt878) +- Eline Vision TVMaster-2000 (ELV-TVM-2000, ELV-TVM-2000-FM)= LR138 (saa713x) + +Spirit +~~~~~~ + +- Spirit TV Tuner/Video Capture Card (bt848) + +Boser www.boser.com.tw +~~~~~~~~~~~~~~~~~~~~~~ + +Models: + +- HS-878 Mini PCI Capture Add-on Card +- HS-879 Mini PCI 3D Audio and Capture Add-on Card (w/ ES1938 Solo-1) + +Satelco www.citycom-gmbh.de, www.satelco.de +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Models: + +- TV-FM =KNC1 saa7134 +- Standard PCI (DVB-S) = Technotrend Budget +- Standard PCI (DVB-S) w/ CI +- Satelco Highend PCI (DVB-S) = Technotrend Premium + + +Sensoray www.sensoray.com +~~~~~~~~~~~~~~~~~~~~~~~~~ + +Models: + +- Sensoray 311 (PC/104 bus) +- Sensoray 611 (PCI) + +CEI (Chartered Electronics Industries Pte Ltd [CEI] [FCC ID HBY]) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Models: + +- TV Tuner - HBY-33A-RAFFLES Brooktree Bt848KPF + Philips +- TV Tuner MG9910 - HBY33A-TVO CEI + Philips SAA7110 + OKI M548262 + ST STV8438CV +- Primetime TV (ISA) + + - acquired by Singapore Technologies + - now operating as Chartered Semiconductor Manufacturing + - Manufacturer of video cards is listed as: + + - Cogent Electronics Industries [CEI] + +AITech +~~~~~~ + +Models: + +- Wavewatcher TV (ISA) +- AITech WaveWatcher TV-PCI = can be LR26 (Bt848) or LR50 (BT878) +- WaveWatcher TVR-202 TV/FM Radio Card (ISA) + +MAXRON +~~~~~~ + +Maxron MaxTV/FM Radio (KW-TV878-FNT) = Kworld or JW-TV878-FBK + +www.ids-imaging.de +~~~~~~~~~~~~~~~~~~ + +Models: + +- Falcon Series (capture only) + +In USA: http://www.theimagingsource.com/ +- DFG/LC1 + +www.sknet-web.co.jp +~~~~~~~~~~~~~~~~~~~ + +SKnet Monster TV (saa7134) + +A-Max www.amaxhk.com (Colormax, Amax, Napa) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +APAC Viewcomp 878 + +Cybertainment +~~~~~~~~~~~~~ + +Models: + +- CyberMail AV Video Email Kit w/ PCI Capture Card (capture only) +- CyberMail Xtreme + +These are Flyvideo + +VCR (http://www.vcrinc.com/) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Video Catcher 16 + +Twinhan +~~~~~~~ + +Models: + +- DST Card/DST-IP (bt878, twinhan asic) VP-1020 + - Sold as: + + - KWorld DVBS Satellite TV-Card + - Powercolor DSTV Satellite Tuner Card + - Prolink Pixelview DTV2000 + - Provideo PV-911 Digital Satellite TV Tuner Card With Common Interface ? + +- DST-CI Card (DVB Satellite) VP-1030 +- DCT Card (DVB cable) + +MSI +~~~ + +Models: + +- MSI TV@nywhere Tuner Card (MS-8876) (CX23881/883) Not Bt878 compatible. +- MS-8401 DVB-S + +Focus www.focusinfo.com +~~~~~~~~~~~~~~~~~~~~~~~ + +InVideo PCI (bt878) + +Sdisilk www.sdisilk.com/ +~~~~~~~~~~~~~~~~~~~~~~~~ + +Models: + +- SDI Silk 100 +- SDI Silk 200 SDI Input Card + +www.euresys.com +~~~~~~~~~~~~~~~ + +PICOLO series + +PMC/Pace +~~~~~~~~ + +www.pacecom.co.uk website closed + +Mercury www.kobian.com (UK and FR) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Models: + +- LR50 +- LR138RBG-Rx == LR138 + +TEC sound +~~~~~~~~~ + +TV-Mate = Zoltrix VP-8482 + +Though educated googling found: www.techmakers.com + +(package and manuals don't have any other manufacturer info) TecSound + +Lorenzen www.lorenzen.de +~~~~~~~~~~~~~~~~~~~~~~~~ + +SL DVB-S PCI = Technotrend Budget PCI (su1278 or bsru version) + +Origo (.uk) www.origo2000.com +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +PC TV Card = LR50 + +I/O Magic www.iomagic.com +~~~~~~~~~~~~~~~~~~~~~~~~~ + +PC PVR - Desktop TV Personal Video Recorder DR-PCTV100 = Pinnacle ROB2D-51009464 4.0 + Cyberlink PowerVCR II + +Arowana +~~~~~~~ + +TV-Karte / Poso Power TV (?) = Zoltrix VP-8482 (?) + +iTVC15 boards +~~~~~~~~~~~~~ + +kuroutoshikou.com ITVC15 +yuan.com MPG160 PCI TV (Internal PCI MPEG2 encoder card plus TV-tuner) + +Asus www.asuscom.com +~~~~~~~~~~~~~~~~~~~~ + +Models: + +- Asus TV Tuner Card 880 NTSC (low profile, cx23880) +- Asus TV (saa7134) + +Hoontech +~~~~~~~~ + +http://www.hoontech.de/ + +- HART Vision 848 (H-ART Vision 848) +- HART Vision 878 (H-Art Vision 878) + + + +Chips used at bttv devices +-------------------------- + +- all boards: + + - Brooktree Bt848/848A/849/878/879: video capture chip + +- Board specific + + - Miro PCTV: + + - Philips or Temic Tuner + + - Hauppauge Win/TV pci (version 405): + + - Microchip 24LC02B or Philips 8582E2Y: + + - 256 Byte EEPROM with configuration information + - I2C 0xa0-0xa1, (24LC02B also responds to 0xa2-0xaf) + + - Philips SAA5246AGP/E: Videotext decoder chip, I2C 0x22-0x23 + + - TDA9800: sound decoder + + - Winbond W24257AS-35: 32Kx8 CMOS static RAM (Videotext buffer mem) + + - 14052B: analog switch for selection of sound source + +- PAL: + + - TDA5737: VHF, hyperband and UHF mixer/oscillator for TV and VCR 3-band tuners + - TSA5522: 1.4 GHz I2C-bus controlled synthesizer, I2C 0xc2-0xc3 + +- NTSC: + + - TDA5731: VHF, hyperband and UHF mixer/oscillator for TV and VCR 3-band tuners + - TSA5518: no datasheet available on Philips site + +- STB TV pci: + + - ??? + - if you want better support for STB cards send me info! + Look at the board! What chips are on it? + + + + +Specs +----- + +Philips http://www.Semiconductors.COM/pip/ + +Conexant http://www.conexant.com/ + +Micronas http://www.micronas.com/en/home/index.html + +Thanks +------ + +Many thanks to: + +- Markus Schroeder <schroedm@uni-duesseldorf.de> for information on the Bt848 + and tuner programming and his control program xtvc. + +- Martin Buck <martin-2.buck@student.uni-ulm.de> for his great Videotext + package. + +- Gerd Hoffmann for the MSP3400 support and the modular + I2C, tuner, ... support. + + +- MATRIX Vision for giving us 2 cards for free, which made support of + single crystal operation possible. + +- MIRO for providing a free PCTV card and detailed information about the + components on their cards. (E.g. how the tuner type is detected) + Without their card I could not have debugged the NTSC mode. + +- Hauppauge for telling how the sound input is selected and what components + they do and will use on their radio cards. + Also many thanks for faxing me the FM1216 data sheet. + +Contributors +------------ + +Michael Chu <mmchu@pobox.com> + AverMedia fix and more flexible card recognition + +Alan Cox <alan@lxorguk.ukuu.org.uk> + Video4Linux interface and 2.1.x kernel adaptation + +Chris Kleitsch + Hardware I2C + +Gerd Hoffmann + Radio card (ITT sound processor) + +bigfoot <bigfoot@net-way.net> + +Ragnar Hojland Espinosa <ragnar@macula.net> + ConferenceTV card + + ++ many more (please mail me if you are missing in this list and would + like to be mentioned) diff --git a/Documentation/admin-guide/media/building.rst b/Documentation/admin-guide/media/building.rst new file mode 100644 index 000000000..a06473429 --- /dev/null +++ b/Documentation/admin-guide/media/building.rst @@ -0,0 +1,357 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=================================== +Building support for a media device +=================================== + +The first step is to download the Kernel's source code, either via a +distribution-specific source file or via the Kernel's main git tree\ [1]_. + +Please notice, however, that, if: + +- you're a braveheart and want to experiment with new stuff; +- if you want to report a bug; +- if you're developing new patches + +you should use the main media development tree ``master`` branch: + + https://git.linuxtv.org/media_tree.git/ + +In this case, you may find some useful information at the +`LinuxTv wiki pages <https://linuxtv.org/wiki>`_: + + https://linuxtv.org/wiki/index.php/How_to_Obtain,_Build_and_Install_V4L-DVB_Device_Drivers + +.. [1] The upstream Linux Kernel development tree is located at + + https://git.kernel.org/pub/scm/li nux/kernel/git/torvalds/linux.git/ + +Configuring the Linux Kernel +============================ + +You can access a menu of Kernel building options with:: + + $ make menuconfig + +Then, select all desired options and exit it, saving the configuration. + +The changed configuration will be at the ``.config`` file. It would +look like:: + + ... + # CONFIG_RC_CORE is not set + # CONFIG_CEC_CORE is not set + CONFIG_MEDIA_SUPPORT=m + CONFIG_MEDIA_SUPPORT_FILTER=y + ... + +The media subsystem is controlled by those menu configuration options:: + + Device Drivers ---> + <M> Remote Controller support ---> + [ ] HDMI CEC RC integration + [ ] Enable CEC error injection support + [*] HDMI CEC drivers ---> + <*> Multimedia support ---> + +The ``Remote Controller support`` option enables the core support for +remote controllers\ [2]_. + +The ``HDMI CEC RC integration`` option enables integration of HDMI CEC +with Linux, allowing to receive data via HDMI CEC as if it were produced +by a remote controller directly connected to the machine. + +The ``HDMI CEC drivers`` option allow selecting platform and USB drivers +that receives and/or transmits CEC codes via HDMI interfaces\ [3]_. + +The last option (``Multimedia support``) enables support for cameras, +audio/video grabbers and TV. + +The media subsystem support can either be built together with the main +Kernel or as a module. For most use cases, it is preferred to have it +built as modules. + +.. note:: + + Instead of using a menu, the Kernel provides a script with allows + enabling configuration options directly. To enable media support + and remote controller support using Kernel modules, you could use:: + + $ scripts/config -m RC_CORE + $ scripts/config -m MEDIA_SUPPORT + +.. [2] ``Remote Controller support`` should also be enabled if you + want to use some TV card drivers that may depend on the remote + controller core support. + +.. [3] Please notice that the DRM subsystem also have drivers for GPUs + that use the media HDMI CEC support. + + Those GPU-specific drivers are selected via the ``Graphics support`` + menu, under ``Device Drivers``. + + When a GPU driver supports HDMI CEC, it will automatically + enable the CEC core support at the media subsystem. + +Media dependencies +------------------ + +It should be noticed that enabling the above from a clean config is +usually not enough. The media subsystem depends on several other Linux +core support in order to work. + +For example, most media devices use a serial communication bus in +order to talk with some peripherals. Such bus is called I²C +(Inter-Integrated Circuit). In order to be able to build support +for such hardware, the I²C bus support should be enabled, either via +menu or with:: + + ./scripts/config -m I2C + +Another example: the remote controller core requires support for +input devices, with can be enabled with:: + + ./scripts/config -m INPUT + +Other core functionality may also be needed (like PCI and/or USB support), +depending on the specific driver(s) you would like to enable. + +Enabling Remote Controller Support +---------------------------------- + +The remote controller menu allows selecting drivers for specific devices. +It's menu looks like this:: + + --- Remote Controller support + <M> Compile Remote Controller keymap modules + [*] LIRC user interface + [*] Support for eBPF programs attached to lirc devices + [*] Remote controller decoders ---> + [*] Remote Controller devices ---> + +The ``Compile Remote Controller keymap modules`` option creates key maps for +several popular remote controllers. + +The ``LIRC user interface`` option adds enhanced functionality when using the +``lirc`` program, by enabling an API that allows userspace to receive raw data +from remote controllers. + +The ``Support for eBPF programs attached to lirc devices`` option allows +the usage of special programs (called eBPF) that would allow applications +to add extra remote controller decoding functionality to the Linux Kernel. + +The ``Remote controller decoders`` option allows selecting the +protocols that will be recognized by the Linux Kernel. Except if you +want to disable some specific decoder, it is suggested to keep all +sub-options enabled. + +The ``Remote Controller devices`` allows you to select the drivers +that would be needed to support your device. + +The same configuration can also be set via the ``script/config`` +script. So, for instance, in order to support the ITE remote controller +driver (found on Intel NUCs and on some ASUS x86 desktops), you could do:: + + $ scripts/config -e INPUT + $ scripts/config -e ACPI + $ scripts/config -e MODULES + $ scripts/config -m RC_CORE + $ scripts/config -e RC_DEVICES + $ scripts/config -e RC_DECODERS + $ scripts/config -m IR_RC5_DECODER + $ scripts/config -m IR_ITE_CIR + +Enabling HDMI CEC Support +------------------------- + +The HDMI CEC support is set automatically when a driver requires it. So, +all you need to do is to enable support either for a graphics card +that needs it or by one of the existing HDMI drivers. + +The HDMI-specific drivers are available at the ``HDMI CEC drivers`` +menu\ [4]_:: + + --- HDMI CEC drivers + < > ChromeOS EC CEC driver + < > Amlogic Meson AO CEC driver + < > Amlogic Meson G12A AO CEC driver + < > Generic GPIO-based CEC driver + < > Samsung S5P CEC driver + < > STMicroelectronics STiH4xx HDMI CEC driver + < > STMicroelectronics STM32 HDMI CEC driver + < > Tegra HDMI CEC driver + < > SECO Boards HDMI CEC driver + [ ] SECO Boards IR RC5 support + < > Pulse Eight HDMI CEC + < > RainShadow Tech HDMI CEC + +.. [4] The above contents is just an example. The actual options for + HDMI devices depends on the system's architecture and may vary + on new Kernels. + +Enabling Media Support +---------------------- + +The Media menu has a lot more options than the remote controller menu. +Once selected, you should see the following options:: + + --- Media support + [ ] Filter media drivers + [*] Autoselect ancillary drivers + Media device types ---> + Media core support ---> + Video4Linux options ---> + Media controller options ---> + Digital TV options ---> + HDMI CEC options ---> + Media drivers ---> + Media ancillary drivers ---> + +Except if you know exactly what you're doing, or if you want to build +a driver for a SoC platform, it is strongly recommended to keep the +``Autoselect ancillary drivers`` option turned on, as it will auto-select +the needed I²C ancillary drivers. + +There are now two ways to select media device drivers, as described +below. + +``Filter media drivers`` menu +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +This menu is meant to easy setup for PC and Laptop hardware. It works +by letting the user to specify what kind of media drivers are desired, +with those options:: + + [ ] Cameras and video grabbers + [ ] Analog TV + [ ] Digital TV + [ ] AM/FM radio receivers/transmitters + [ ] Software defined radio + [ ] Platform-specific devices + [ ] Test drivers + +So, if you want to add support to a camera or video grabber only, +select just the first option. Multiple options are allowed. + +Once the options on this menu are selected, the building system will +auto-select the needed core drivers in order to support the selected +functionality. + +.. note:: + + Most TV cards are hybrid: they support both Analog TV and Digital TV. + + If you have an hybrid card, you may need to enable both ``Analog TV`` + and ``Digital TV`` at the menu. + +When using this option, the defaults for the media support core +functionality are usually good enough to provide the basic functionality +for the driver. Yet, you could manually enable some desired extra (optional) +functionality using the settings under each of the following +``Media support`` sub-menus:: + + Media core support ---> + Video4Linux options ---> + Media controller options ---> + Digital TV options ---> + HDMI CEC options ---> + +Once you select the desired filters, the drivers that matches the filtering +criteria will be available at the ``Media support->Media drivers`` sub-menu. + +``Media Core Support`` menu without filtering +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +If you disable the ``Filter media drivers`` menu, all drivers available +for your system whose dependencies are met should be shown at the +``Media drivers`` menu. + +Please notice, however, that you should first ensure that the +``Media Core Support`` menu has all the core functionality your drivers +would need, as otherwise the corresponding device drivers won't be shown. + +Example +------- + +In order to enable modular support for one of the boards listed on +:doc:`this table <cx231xx-cardlist>`, with modular media core modules, the +``.config`` file should contain those lines:: + + CONFIG_MODULES=y + CONFIG_USB=y + CONFIG_I2C=y + CONFIG_INPUT=y + CONFIG_RC_CORE=m + CONFIG_MEDIA_SUPPORT=m + CONFIG_MEDIA_SUPPORT_FILTER=y + CONFIG_MEDIA_ANALOG_TV_SUPPORT=y + CONFIG_MEDIA_DIGITAL_TV_SUPPORT=y + CONFIG_MEDIA_USB_SUPPORT=y + CONFIG_VIDEO_CX231XX=y + CONFIG_VIDEO_CX231XX_DVB=y + +Building and installing a new Kernel +==================================== + +Once the ``.config`` file has everything needed, all it takes to build +is to run the ``make`` command:: + + $ make + +And then install the new Kernel and its modules:: + + $ sudo make modules_install + $ sudo make install + +Building just the new media drivers and core +============================================ + +Running a new development Kernel from the development tree is usually risky, +because it may have experimental changes that may have bugs. So, there are +some ways to build just the new drivers, using alternative trees. + +There is the `Linux Kernel backports project +<https://backports.wiki.kernel.org/index.php/Main_Page>`_, with contains +newer drivers meant to be compiled against stable Kernels. + +The LinuxTV developers, with are responsible for maintaining the media +subsystem also maintains a backport tree, with just the media drivers +daily updated from the newest kernel. Such tree is available at: + +https://git.linuxtv.org/media_build.git/ + +It should be noticed that, while it should be relatively safe to use the +``media_build`` tree for testing purposes, there are not warranties that +it would work (or even build) on a random Kernel. This tree is maintained +using a "best-efforts" principle, as time permits us to fix issues there. + +If you notice anything wrong on it, feel free to submit patches at the +Linux media subsystem's mailing list: media@vger.kernel.org. Please +add ``[PATCH media-build]`` at the e-mail's subject if you submit a new +patch for the media-build. + +Before using it, you should run:: + + $ ./build + +.. note:: + + 1) you may need to run it twice if the ``media-build`` tree gets + updated; + 2) you may need to do a ``make distclean`` if you had built it + in the past for a different Kernel version than the one you're + currently using; + 3) by default, it will use the same config options for media as + the ones defined on the Kernel you're running. + +In order to select different drivers or different config options, +use:: + + $ make menuconfig + +Then, you can build and install the new drivers:: + + $ make && sudo make install + +This will override the previous media drivers that your Kernel were +using. diff --git a/Documentation/admin-guide/media/cafe_ccic.rst b/Documentation/admin-guide/media/cafe_ccic.rst new file mode 100644 index 000000000..ff7fbce13 --- /dev/null +++ b/Documentation/admin-guide/media/cafe_ccic.rst @@ -0,0 +1,62 @@ +.. SPDX-License-Identifier: GPL-2.0 + +The cafe_ccic driver +==================== + +Author: Jonathan Corbet <corbet@lwn.net> + +Introduction +------------ + +"cafe_ccic" is a driver for the Marvell 88ALP01 "cafe" CMOS camera +controller. This is the controller found in first-generation OLPC systems, +and this driver was written with support from the OLPC project. + +Current status: the core driver works. It can generate data in YUV422, +RGB565, and RGB444 formats. (Anybody looking at the code will see RGB32 as +well, but that is a debugging aid which will be removed shortly). VGA and +QVGA modes work; CIF is there but the colors remain funky. Only the OV7670 +sensor is known to work with this controller at this time. + +To try it out: either of these commands will work: + +.. code-block:: none + + $ mplayer tv:// -tv driver=v4l2:width=640:height=480 -nosound + $ mplayer tv:// -tv driver=v4l2:width=640:height=480:outfmt=bgr16 -nosound + +The "xawtv" utility also works; gqcam does not, for unknown reasons. + +Load time options +----------------- + +There are a few load-time options, most of which can be changed after +loading via sysfs as well: + + - alloc_bufs_at_load: Normally, the driver will not allocate any DMA + buffers until the time comes to transfer data. If this option is set, + then worst-case-sized buffers will be allocated at module load time. + This option nails down the memory for the life of the module, but + perhaps decreases the chances of an allocation failure later on. + + - dma_buf_size: The size of DMA buffers to allocate. Note that this + option is only consulted for load-time allocation; when buffers are + allocated at run time, they will be sized appropriately for the current + camera settings. + + - n_dma_bufs: The controller can cycle through either two or three DMA + buffers. Normally, the driver tries to use three buffers; on faster + systems, however, it will work well with only two. + + - min_buffers: The minimum number of streaming I/O buffers that the driver + will consent to work with. Default is one, but, on slower systems, + better behavior with mplayer can be achieved by setting to a higher + value (like six). + + - max_buffers: The maximum number of streaming I/O buffers; default is + ten. That number was carefully picked out of a hat and should not be + assumed to actually mean much of anything. + + - flip: If this boolean parameter is set, the sensor will be instructed to + invert the video image. Whether it makes sense is determined by how + your particular camera is mounted. diff --git a/Documentation/admin-guide/media/cardlist.rst b/Documentation/admin-guide/media/cardlist.rst new file mode 100644 index 000000000..5b38bfd6a --- /dev/null +++ b/Documentation/admin-guide/media/cardlist.rst @@ -0,0 +1,29 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========== +Cards List +========== + +The media subsystem provide support for lots of PCI and USB drivers, plus +platform-specific drivers. It also contains several ancillary I²C drivers. + +The platform-specific drivers are usually present on embedded systems, +or are supported by the main board. Usually, setting them is done via +OpenFirmware or ACPI. + +The PCI and USB drivers, however, are independent of the system's board, +and may be added/removed by the user. + +You may also take a look at +https://linuxtv.org/wiki/index.php/Hardware_Device_Information +for more details about supported cards. + +.. toctree:: + :maxdepth: 2 + + usb-cardlist + pci-cardlist + platform-cardlist + radio-cardlist + i2c-cardlist + misc-cardlist diff --git a/Documentation/admin-guide/media/cec.rst b/Documentation/admin-guide/media/cec.rst new file mode 100644 index 000000000..6b30e355c --- /dev/null +++ b/Documentation/admin-guide/media/cec.rst @@ -0,0 +1,380 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======== +HDMI CEC +======== + +Supported hardware in mainline +============================== + +HDMI Transmitters: + +- Exynos4 +- Exynos5 +- STIH4xx HDMI CEC +- V4L2 adv7511 (same HW, but a different driver from the drm adv7511) +- stm32 +- Allwinner A10 (sun4i) +- Raspberry Pi +- dw-hdmi (Synopsis IP) +- amlogic (meson ao-cec and ao-cec-g12a) +- drm adv7511/adv7533 +- omap4 +- tegra +- rk3288, rk3399 +- tda998x +- DisplayPort CEC-Tunneling-over-AUX on i915, nouveau and amdgpu +- ChromeOS EC CEC +- CEC for SECO boards (UDOO x86). +- Chrontel CH7322 + + +HDMI Receivers: + +- adv7604/11/12 +- adv7842 +- tc358743 + +USB Dongles (see below for additional information on how to use these +dongles): + +- Pulse-Eight: the pulse8-cec driver implements the following module option: + ``persistent_config``: by default this is off, but when set to 1 the driver + will store the current settings to the device's internal eeprom and restore + it the next time the device is connected to the USB port. +- RainShadow Tech. Note: this driver does not support the persistent_config + module option of the Pulse-Eight driver. The hardware supports it, but I + have no plans to add this feature. But I accept patches :-) + +Miscellaneous: + +- vivid: emulates a CEC receiver and CEC transmitter. + Can be used to test CEC applications without actual CEC hardware. + +- cec-gpio. If the CEC pin is hooked up to a GPIO pin then + you can control the CEC line through this driver. This supports error + injection as well. + +- cec-gpio and Allwinner A10 (or any other driver that uses the CEC pin + framework to drive the CEC pin directly): the CEC pin framework uses + high-resolution timers. These timers are affected by NTP daemons that + speed up or slow down the clock to sync with the official time. The + chronyd server will by default increase or decrease the clock by + 1/12th. This will cause the CEC timings to go out of spec. To fix this, + add a 'maxslewrate 40000' line to chronyd.conf. This limits the clock + frequency change to 1/25th, which keeps the CEC timings within spec. + + +Utilities +========= + +Utilities are available here: https://git.linuxtv.org/v4l-utils.git + +``utils/cec-ctl``: control a CEC device + +``utils/cec-compliance``: test compliance of a remote CEC device + +``utils/cec-follower``: emulate a CEC follower device + +Note that ``cec-ctl`` has support for the CEC Hospitality Profile as is +used in some hotel displays. See http://www.htng.org. + +Note that the libcec library (https://github.com/Pulse-Eight/libcec) supports +the linux CEC framework. + +If you want to get the CEC specification, then look at the References of +the HDMI wikipedia page: https://en.wikipedia.org/wiki/HDMI. CEC is part +of the HDMI specification. HDMI 1.3 is freely available (very similar to +HDMI 1.4 w.r.t. CEC) and should be good enough for most things. + + +DisplayPort to HDMI Adapters with working CEC +============================================= + +Background: most adapters do not support the CEC Tunneling feature, +and of those that do many did not actually connect the CEC pin. +Unfortunately, this means that while a CEC device is created, it +is actually all alone in the world and will never be able to see other +CEC devices. + +This is a list of known working adapters that have CEC Tunneling AND +that properly connected the CEC pin. If you find adapters that work +but are not in this list, then drop me a note. + +To test: hook up your DP-to-HDMI adapter to a CEC capable device +(typically a TV), then run:: + + cec-ctl --playback # Configure the PC as a CEC Playback device + cec-ctl -S # Show the CEC topology + +The ``cec-ctl -S`` command should show at least two CEC devices, +ourselves and the CEC device you are connected to (i.e. typically the TV). + +General note: I have only seen this work with the Parade PS175, PS176 and +PS186 chipsets and the MegaChips 2900. While MegaChips 28x0 claims CEC support, +I have never seen it work. + +USB-C to HDMI +------------- + +Samsung Multiport Adapter EE-PW700: https://www.samsung.com/ie/support/model/EE-PW700BBEGWW/ + +Kramer ADC-U31C/HF: https://www.kramerav.com/product/ADC-U31C/HF + +Club3D CAC-2504: https://www.club-3d.com/en/detail/2449/usb_3.1_type_c_to_hdmi_2.0_uhd_4k_60hz_active_adapter/ + +DisplayPort to HDMI +------------------- + +Club3D CAC-1080: https://www.club-3d.com/en/detail/2442/displayport_1.4_to_hdmi_2.0b_hdr/ + +CableCreation (SKU: CD0712): https://www.cablecreation.com/products/active-displayport-to-hdmi-adapter-4k-hdr + +HP DisplayPort to HDMI True 4k Adapter (P/N 2JA63AA): https://www.hp.com/us-en/shop/pdp/hp-displayport-to-hdmi-true-4k-adapter + +Mini-DisplayPort to HDMI +------------------------ + +Club3D CAC-1180: https://www.club-3d.com/en/detail/2443/mini_displayport_1.4_to_hdmi_2.0b_hdr/ + +Note that passive adapters will never work, you need an active adapter. + +The Club3D adapters in this list are all MegaChips 2900 based. Other Club3D adapters +are PS176 based and do NOT have the CEC pin hooked up, so only the three Club3D +adapters above are known to work. + +I suspect that MegaChips 2900 based designs in general are likely to work +whereas with the PS176 it is more hit-and-miss (mostly miss). The PS186 is +likely to have the CEC pin hooked up, it looks like they changed the reference +design for that chipset. + + +USB CEC Dongles +=============== + +These dongles appear as ``/dev/ttyACMX`` devices and need the ``inputattach`` +utility to create the ``/dev/cecX`` devices. Support for the Pulse-Eight +has been added to ``inputattach`` 1.6.0. Support for the Rainshadow Tech has +been added to ``inputattach`` 1.6.1. + +You also need udev rules to automatically start systemd services:: + + SUBSYSTEM=="tty", KERNEL=="ttyACM[0-9]*", ATTRS{idVendor}=="2548", ATTRS{idProduct}=="1002", ACTION=="add", TAG+="systemd", ENV{SYSTEMD_WANTS}+="pulse8-cec-inputattach@%k.service" + SUBSYSTEM=="tty", KERNEL=="ttyACM[0-9]*", ATTRS{idVendor}=="2548", ATTRS{idProduct}=="1001", ACTION=="add", TAG+="systemd", ENV{SYSTEMD_WANTS}+="pulse8-cec-inputattach@%k.service" + SUBSYSTEM=="tty", KERNEL=="ttyACM[0-9]*", ATTRS{idVendor}=="04d8", ATTRS{idProduct}=="ff59", ACTION=="add", TAG+="systemd", ENV{SYSTEMD_WANTS}+="rainshadow-cec-inputattach@%k.service" + +and these systemd services: + +For Pulse-Eight make /lib/systemd/system/pulse8-cec-inputattach@.service:: + + [Unit] + Description=inputattach for pulse8-cec device on %I + + [Service] + Type=simple + ExecStart=/usr/bin/inputattach --pulse8-cec /dev/%I + +For the RainShadow Tech make /lib/systemd/system/rainshadow-cec-inputattach@.service:: + + [Unit] + Description=inputattach for rainshadow-cec device on %I + + [Service] + Type=simple + ExecStart=/usr/bin/inputattach --rainshadow-cec /dev/%I + + +For proper suspend/resume support create: /lib/systemd/system/restart-cec-inputattach.service:: + + [Unit] + Description=restart inputattach for cec devices + After=suspend.target + + [Service] + Type=forking + ExecStart=/bin/bash -c 'for d in /dev/serial/by-id/usb-Pulse-Eight*; do /usr/bin/inputattach --daemon --pulse8-cec $d; done; for d in /dev/serial/by-id/usb-RainShadow_Tech*; do /usr/bin/inputattach --daemon --rainshadow-cec $d; done' + + [Install] + WantedBy=suspend.target + +And run ``systemctl enable restart-cec-inputattach``. + +To automatically set the physical address of the CEC device whenever the +EDID changes, you can use ``cec-ctl`` with the ``-E`` option:: + + cec-ctl -E /sys/class/drm/card0-DP-1/edid + +This assumes the dongle is connected to the card0-DP-1 output (``xrandr`` will tell +you which output is used) and it will poll for changes to the EDID and update +the Physical Address whenever they occur. + +To automatically run this command you can use cron. Edit crontab with +``crontab -e`` and add this line:: + + @reboot /usr/local/bin/cec-ctl -E /sys/class/drm/card0-DP-1/edid + +This only works for display drivers that expose the EDID in ``/sys/class/drm``, +such as the i915 driver. + + +CEC Without HPD +=============== + +Some displays when in standby mode have no HDMI Hotplug Detect signal, but +CEC is still enabled so connected devices can send an <Image View On> CEC +message in order to wake up such displays. Unfortunately, not all CEC +adapters can support this. An example is the Odroid-U3 SBC that has a +level-shifter that is powered off when the HPD signal is low, thus +blocking the CEC pin. Even though the SoC can use CEC without a HPD, +the level-shifter will prevent this from functioning. + +There is a CEC capability flag to signal this: ``CEC_CAP_NEEDS_HPD``. +If set, then the hardware cannot wake up displays with this behavior. + +Note for CEC application implementers: the <Image View On> message must +be the first message you send, don't send any other messages before. +Certain very bad but unfortunately not uncommon CEC implementations +get very confused if they receive anything else but this message and +they won't wake up. + +When writing a driver it can be tricky to test this. There are two +ways to do this: + +1) Get a Pulse-Eight USB CEC dongle, connect an HDMI cable from your + device to the Pulse-Eight, but do not connect the Pulse-Eight to + the display. + + Now configure the Pulse-Eight dongle:: + + cec-ctl -p0.0.0.0 --tv + + and start monitoring:: + + sudo cec-ctl -M + + On the device you are testing run:: + + cec-ctl --playback + + It should report a physical address of f.f.f.f. Now run this + command:: + + cec-ctl -t0 --image-view-on + + The Pulse-Eight should see the <Image View On> message. If not, + then something (hardware and/or software) is preventing the CEC + message from going out. + + To make sure you have the wiring correct just connect the + Pulse-Eight to a CEC-enabled display and run the same command + on your device: now there is a HPD, so you should see the command + arriving at the Pulse-Eight. + +2) If you have another linux device supporting CEC without HPD, then + you can just connect your device to that device. Yes, you can connect + two HDMI outputs together. You won't have a HPD (which is what we + want for this test), but the second device can monitor the CEC pin. + + Otherwise use the same commands as in 1. + +If CEC messages do not come through when there is no HPD, then you +need to figure out why. Typically it is either a hardware restriction +or the software powers off the CEC core when the HPD goes low. The +first cannot be corrected of course, the second will likely required +driver changes. + + +Microcontrollers & CEC +====================== + +We have seen some CEC implementations in displays that use a microcontroller +to sample the bus. This does not have to be a problem, but some implementations +have timing issues. This is hard to discover unless you can hook up a low-level +CEC debugger (see the next section). + +You will see cases where the CEC transmitter holds the CEC line high or low for +a longer time than is allowed. For directed messages this is not a problem since +if that happens the message will not be Acked and it will be retransmitted. +For broadcast messages no such mechanism exists. + +It's not clear what to do about this. It is probably wise to transmit some +broadcast messages twice to reduce the chance of them being lost. Specifically +<Standby> and <Active Source> are candidates for that. + + +Making a CEC debugger +===================== + +By using a Raspberry Pi 4B and some cheap components you can make +your own low-level CEC debugger. + +The critical component is one of these HDMI female-female passthrough connectors +(full soldering type 1): + +https://elabbay.myshopify.com/collections/camera/products/hdmi-af-af-v1a-hdmi-type-a-female-to-hdmi-type-a-female-pass-through-adapter-breakout-board?variant=45533926147 + +The video quality is variable and certainly not enough to pass-through 4kp60 +(594 MHz) video. You might be able to support 4kp30, but more likely you will +be limited to 1080p60 (148.5 MHz). But for CEC testing that is fine. + +You need a breadboard and some breadboard wires: + +http://www.dx.com/p/diy-40p-male-to-female-male-to-male-female-to-female-dupont-line-wire-3pcs-356089#.WYLOOXWGN7I + +If you want to monitor the HPD and/or 5V lines as well, then you need one of +these 5V to 3.3V level shifters: + +https://www.adafruit.com/product/757 + +(This is just where I got these components, there are many other places you +can get similar things). + +The ground pin of the HDMI connector needs to be connected to a ground +pin of the Raspberry Pi, of course. + +The CEC pin of the HDMI connector needs to be connected to these pins: +GPIO 6 and GPIO 7. The optional HPD pin of the HDMI connector should +be connected via the level shifter to these pins: GPIO 23 and GPIO 12. +The optional 5V pin of the HDMI connector should be connected via the +level shifter to these pins: GPIO 25 and GPIO 22. Monitoring the HPD and +5V lines is not necessary, but it is helpful. + +This device tree addition in ``arch/arm/boot/dts/bcm2711-rpi-4-b.dts`` +will hook up the cec-gpio driver correctly:: + + cec@6 { + compatible = "cec-gpio"; + cec-gpios = <&gpio 6 (GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN)>; + hpd-gpios = <&gpio 23 GPIO_ACTIVE_HIGH>; + v5-gpios = <&gpio 25 GPIO_ACTIVE_HIGH>; + }; + + cec@7 { + compatible = "cec-gpio"; + cec-gpios = <&gpio 7 (GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN)>; + hpd-gpios = <&gpio 12 GPIO_ACTIVE_HIGH>; + v5-gpios = <&gpio 22 GPIO_ACTIVE_HIGH>; + }; + +If you haven't hooked up the HPD and/or 5V lines, then just delete those +lines. + +This dts change will enable two cec GPIO devices: I typically use one to +send/receive CEC commands and the other to monitor. If you monitor using +an unconfigured CEC adapter then it will use GPIO interrupts which makes +monitoring very accurate. + +If you just want to monitor traffic, then a single instance is sufficient. +The minimum configuration is one HDMI female-female passthrough connector +and two female-female breadboard wires: one for connecting the HDMI ground +pin to a ground pin on the Raspberry Pi, and the other to connect the HDMI +CEC pin to GPIO 6 on the Raspberry Pi. + +The documentation on how to use the error injection is here: :ref:`cec_pin_error_inj`. + +``cec-ctl --monitor-pin`` will do low-level CEC bus sniffing and analysis. +You can also store the CEC traffic to file using ``--store-pin`` and analyze +it later using ``--analyze-pin``. + +You can also use this as a full-fledged CEC device by configuring it +using ``cec-ctl --tv -p0.0.0.0`` or ``cec-ctl --playback -p1.0.0.0``. diff --git a/Documentation/admin-guide/media/ci.rst b/Documentation/admin-guide/media/ci.rst new file mode 100644 index 000000000..ded4d8fbb --- /dev/null +++ b/Documentation/admin-guide/media/ci.rst @@ -0,0 +1,77 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Digital TV Conditional Access Interface +======================================= + + +.. note:: + + This documentation is outdated. + +This document describes the usage of the high level CI API as +in accordance to the Linux DVB API. This is a not a documentation for the, +existing low level CI API. + +.. note:: + + For the Twinhan/Twinhan clones, the dst_ca module handles the CI + hardware handling. This module is loaded automatically if a CI + (Common Interface, that holds the CAM (Conditional Access Module) + is detected. + +ca_zap +~~~~~~ + +A userspace application, like ``ca_zap`` is required to handle encrypted +MPEG-TS streams. + +The ``ca_zap`` userland application is in charge of sending the +descrambling related information to the Conditional Access Module (CAM). + +This application requires the following to function properly as of now. + +a) Tune to a valid channel, with szap. + + eg: $ szap -c channels.conf -r "TMC" -x + +b) a channels.conf containing a valid PMT PID + + eg: TMC:11996:h:0:27500:278:512:650:321 + + here 278 is a valid PMT PID. the rest of the values are the + same ones that szap uses. + +c) after running a szap, you have to run ca_zap, for the + descrambler to function, + + eg: $ ca_zap channels.conf "TMC" + +d) Hopefully enjoy your favourite subscribed channel as you do with + a FTA card. + +.. note:: + + Currently ca_zap, and dst_test, both are meant for demonstration + purposes only, they can become full fledged applications if necessary. + + +Cards that fall in this category +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +At present the cards that fall in this category are the Twinhan and its +clones, these cards are available as VVMER, Tomato, Hercules, Orange and +so on. + +CI modules that are supported +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The CI module support is largely dependent upon the firmware on the cards +Some cards do support almost all of the available CI modules. There is +nothing much that can be done in order to make additional CI modules +working with these cards. + +Modules that have been tested by this driver at present are + +(1) Irdeto 1 and 2 from SCM +(2) Viaccess from SCM +(3) Dragoncam diff --git a/Documentation/admin-guide/media/cx18-cardlist.rst b/Documentation/admin-guide/media/cx18-cardlist.rst new file mode 100644 index 000000000..26f2da9aa --- /dev/null +++ b/Documentation/admin-guide/media/cx18-cardlist.rst @@ -0,0 +1,17 @@ +.. SPDX-License-Identifier: GPL-2.0 + +CX18 cards list +=============== + +Those cards are supported by cx18 driver: + +- Hauppauge HVR-1600 (ESMT memory) +- Hauppauge HVR-1600 (Samsung memory) +- Compro VideoMate H900 +- Yuan MPC718 MiniPCI DVB-T/Analog +- Conexant Raptor PAL/SECAM +- Toshiba Qosmio DVB-T/Analog +- Leadtek WinFast PVR2100 +- Leadtek WinFast DVR3100 +- GoTView PCI DVD3 Hybrid +- Hauppauge HVR-1600 (s5h1411/tda18271) diff --git a/Documentation/admin-guide/media/cx231xx-cardlist.rst b/Documentation/admin-guide/media/cx231xx-cardlist.rst new file mode 100644 index 000000000..d374101be --- /dev/null +++ b/Documentation/admin-guide/media/cx231xx-cardlist.rst @@ -0,0 +1,99 @@ +.. SPDX-License-Identifier: GPL-2.0 + +cx231xx cards list +================== + +.. tabularcolumns:: |p{1.4cm}|p{10.0cm}|p{6.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 2 12 19 + :stub-columns: 0 + + * - Card number + - Card name + - USB IDs + * - 0 + - Unknown CX231xx video grabber + - 0572:5A3C + * - 1 + - Conexant Hybrid TV - CARRAERA + - 0572:58A2 + * - 2 + - Conexant Hybrid TV - SHELBY + - 0572:58A1 + * - 3 + - Conexant Hybrid TV - RDE253S + - 0572:58A4 + * - 4 + - Conexant Hybrid TV - RDU253S + - 0572:58A5 + * - 5 + - Conexant VIDEO GRABBER + - 0572:58A6, 07ca:c039 + * - 6 + - Conexant Hybrid TV - rde 250 + - 0572:589E + * - 7 + - Conexant Hybrid TV - RDU 250 + - 0572:58A0 + * - 8 + - Hauppauge EXETER + - 2040:b120, 2040:b140 + * - 9 + - Hauppauge USB Live 2 + - 2040:c200 + * - 10 + - Pixelview PlayTV USB Hybrid + - 4000:4001 + * - 11 + - Pixelview Xcapture USB + - 1D19:6109, 4000:4001 + * - 12 + - Kworld UB430 USB Hybrid + - 1b80:e424 + * - 13 + - Iconbit Analog Stick U100 FM + - 1f4d:0237 + * - 14 + - Hauppauge WinTV USB2 FM (PAL) + - 2040:b110 + * - 15 + - Hauppauge WinTV USB2 FM (NTSC) + - 2040:b111 + * - 16 + - Elgato Video Capture V2 + - 0fd9:0037 + * - 17 + - Geniatech OTG102 + - 1f4d:0102 + * - 18 + - Kworld UB445 USB Hybrid + - 1b80:e421 + * - 19 + - Hauppauge WinTV 930C-HD (1113xx) / HVR-900H (111xxx) / PCTV QuatroStick 521e + - 2040:b130, 2040:b138, 2013:0259 + * - 20 + - Hauppauge WinTV 930C-HD (1114xx) / HVR-901H (1114xx) / PCTV QuatroStick 522e + - 2040:b131, 2040:b139, 2013:025e + * - 21 + - Hauppauge WinTV-HVR-955Q (111401) + - 2040:b123, 2040:b124 + * - 22 + - Terratec Grabby + - 1f4d:0102 + * - 23 + - Evromedia USB Full Hybrid Full HD + - 1b80:d3b2 + * - 24 + - Astrometa T2hybrid + - 15f4:0135 + * - 25 + - The Imaging Source DFG/USB2pro + - 199e:8002 + * - 26 + - Hauppauge WinTV-HVR-935C + - 2040:b151 + * - 27 + - Hauppauge WinTV-HVR-975 + - 2040:b150 diff --git a/Documentation/admin-guide/media/cx23885-cardlist.rst b/Documentation/admin-guide/media/cx23885-cardlist.rst new file mode 100644 index 000000000..c47514fea --- /dev/null +++ b/Documentation/admin-guide/media/cx23885-cardlist.rst @@ -0,0 +1,267 @@ +.. SPDX-License-Identifier: GPL-2.0 + +cx23885 cards list +================== + +.. tabularcolumns:: |p{1.4cm}|p{11.1cm}|p{4.2cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 2 19 18 + :stub-columns: 0 + + * - Card number + - Card name + - PCI subsystem IDs + + * - 0 + - UNKNOWN/GENERIC + - 0070:3400 + + * - 1 + - Hauppauge WinTV-HVR1800lp + - 0070:7600 + + * - 2 + - Hauppauge WinTV-HVR1800 + - 0070:7800, 0070:7801, 0070:7809 + + * - 3 + - Hauppauge WinTV-HVR1250 + - 0070:7911 + + * - 4 + - DViCO FusionHDTV5 Express + - 18ac:d500 + + * - 5 + - Hauppauge WinTV-HVR1500Q + - 0070:7790, 0070:7797 + + * - 6 + - Hauppauge WinTV-HVR1500 + - 0070:7710, 0070:7717 + + * - 7 + - Hauppauge WinTV-HVR1200 + - 0070:71d1, 0070:71d3 + + * - 8 + - Hauppauge WinTV-HVR1700 + - 0070:8101 + + * - 9 + - Hauppauge WinTV-HVR1400 + - 0070:8010 + + * - 10 + - DViCO FusionHDTV7 Dual Express + - 18ac:d618 + + * - 11 + - DViCO FusionHDTV DVB-T Dual Express + - 18ac:db78 + + * - 12 + - Leadtek Winfast PxDVR3200 H + - 107d:6681 + + * - 13 + - Compro VideoMate E650F + - 185b:e800 + + * - 14 + - TurboSight TBS 6920 + - 6920:8888 + + * - 15 + - TeVii S470 + - d470:9022 + + * - 16 + - DVBWorld DVB-S2 2005 + - 0001:2005 + + * - 17 + - NetUP Dual DVB-S2 CI + - 1b55:2a2c + + * - 18 + - Hauppauge WinTV-HVR1270 + - 0070:2211 + + * - 19 + - Hauppauge WinTV-HVR1275 + - 0070:2215, 0070:221d, 0070:22f2 + + * - 20 + - Hauppauge WinTV-HVR1255 + - 0070:2251, 0070:22f1 + + * - 21 + - Hauppauge WinTV-HVR1210 + - 0070:2291, 0070:2295, 0070:2299, 0070:229d, 0070:22f0, 0070:22f3, 0070:22f4, 0070:22f5 + + * - 22 + - Mygica X8506 DMB-TH + - 14f1:8651 + + * - 23 + - Magic-Pro ProHDTV Extreme 2 + - 14f1:8657 + + * - 24 + - Hauppauge WinTV-HVR1850 + - 0070:8541 + + * - 25 + - Compro VideoMate E800 + - 1858:e800 + + * - 26 + - Hauppauge WinTV-HVR1290 + - 0070:8551 + + * - 27 + - Mygica X8558 PRO DMB-TH + - 14f1:8578 + + * - 28 + - LEADTEK WinFast PxTV1200 + - 107d:6f22 + + * - 29 + - GoTView X5 3D Hybrid + - 5654:2390 + + * - 30 + - NetUP Dual DVB-T/C-CI RF + - 1b55:e2e4 + + * - 31 + - Leadtek Winfast PxDVR3200 H XC4000 + - 107d:6f39 + + * - 32 + - MPX-885 + - + + * - 33 + - Mygica X8502/X8507 ISDB-T + - 14f1:8502 + + * - 34 + - TerraTec Cinergy T PCIe Dual + - 153b:117e + + * - 35 + - TeVii S471 + - d471:9022 + + * - 36 + - Hauppauge WinTV-HVR1255 + - 0070:2259 + + * - 37 + - Prof Revolution DVB-S2 8000 + - 8000:3034 + + * - 38 + - Hauppauge WinTV-HVR4400/HVR5500 + - 0070:c108, 0070:c138, 0070:c1f8 + + * - 39 + - AVerTV Hybrid Express Slim HC81R + - 1461:d939 + + * - 40 + - TurboSight TBS 6981 + - 6981:8888 + + * - 41 + - TurboSight TBS 6980 + - 6980:8888 + + * - 42 + - Leadtek Winfast PxPVR2200 + - 107d:6f21 + + * - 43 + - Hauppauge ImpactVCB-e + - 0070:7133, 0070:7137 + + * - 44 + - DViCO FusionHDTV DVB-T Dual Express2 + - 18ac:db98 + + * - 45 + - DVBSky T9580 + - 4254:9580 + + * - 46 + - DVBSky T980C + - 4254:980c + + * - 47 + - DVBSky S950C + - 4254:950c + + * - 48 + - Technotrend TT-budget CT2-4500 CI + - 13c2:3013 + + * - 49 + - DVBSky S950 + - 4254:0950 + + * - 50 + - DVBSky S952 + - 4254:0952 + + * - 51 + - DVBSky T982 + - 4254:0982 + + * - 52 + - Hauppauge WinTV-HVR5525 + - 0070:f038 + + * - 53 + - Hauppauge WinTV Starburst + - 0070:c12a + + * - 54 + - ViewCast 260e + - 1576:0260 + + * - 55 + - ViewCast 460e + - 1576:0460 + + * - 56 + - Hauppauge WinTV-QuadHD-DVB + - 0070:6a28, 0070:6b28 + + * - 57 + - Hauppauge WinTV-QuadHD-ATSC + - 0070:6a18, 0070:6b18 + + * - 58 + - Hauppauge WinTV-HVR-1265(161111) + - 0070:2a18 + + * - 59 + - Hauppauge WinTV-Starburst2 + - 0070:f02a + + * - 60 + - Hauppauge WinTV-QuadHD-DVB(885) + - + + * - 61 + - Hauppauge WinTV-QuadHD-ATSC(885) + - + + * - 62 + - AVerMedia CE310B + - 1461:3100 diff --git a/Documentation/admin-guide/media/cx88-cardlist.rst b/Documentation/admin-guide/media/cx88-cardlist.rst new file mode 100644 index 000000000..76dc9a14c --- /dev/null +++ b/Documentation/admin-guide/media/cx88-cardlist.rst @@ -0,0 +1,383 @@ +.. SPDX-License-Identifier: GPL-2.0 + +CX88 cards list +=============== + +.. tabularcolumns:: |p{1.4cm}|p{11.1cm}|p{4.2cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 2 19 18 + :stub-columns: 0 + + * - Card number + - Card name + - PCI subsystem IDs + + * - 0 + - UNKNOWN/GENERIC + - + + * - 1 + - Hauppauge WinTV 34xxx models + - 0070:3400, 0070:3401 + + * - 2 + - GDI Black Gold + - 14c7:0106, 14c7:0107 + + * - 3 + - PixelView + - 1554:4811 + + * - 4 + - ATI TV Wonder Pro + - 1002:00f8, 1002:00f9 + + * - 5 + - Leadtek Winfast 2000XP Expert + - 107d:6611, 107d:6613 + + * - 6 + - AverTV Studio 303 (M126) + - 1461:000b + + * - 7 + - MSI TV-@nywhere Master + - 1462:8606 + + * - 8 + - Leadtek Winfast DV2000 + - 107d:6620, 107d:6621 + + * - 9 + - Leadtek PVR 2000 + - 107d:663b, 107d:663c, 107d:6632, 107d:6630, 107d:6638, 107d:6631, 107d:6637, 107d:663d + + * - 10 + - IODATA GV-VCP3/PCI + - 10fc:d003 + + * - 11 + - Prolink PlayTV PVR + - + + * - 12 + - ASUS PVR-416 + - 1043:4823, 1461:c111 + + * - 13 + - MSI TV-@nywhere + - + + * - 14 + - KWorld/VStream XPert DVB-T + - 17de:08a6 + + * - 15 + - DViCO FusionHDTV DVB-T1 + - 18ac:db00 + + * - 16 + - KWorld LTV883RF + - + + * - 17 + - DViCO FusionHDTV 3 Gold-Q + - 18ac:d810, 18ac:d800 + + * - 18 + - Hauppauge Nova-T DVB-T + - 0070:9002, 0070:9001, 0070:9000 + + * - 19 + - Conexant DVB-T reference design + - 14f1:0187 + + * - 20 + - Provideo PV259 + - 1540:2580 + + * - 21 + - DViCO FusionHDTV DVB-T Plus + - 18ac:db10, 18ac:db11 + + * - 22 + - pcHDTV HD3000 HDTV + - 7063:3000 + + * - 23 + - digitalnow DNTV Live! DVB-T + - 17de:a8a6 + + * - 24 + - Hauppauge WinTV 28xxx (Roslyn) models + - 0070:2801 + + * - 25 + - Digital-Logic MICROSPACE Entertainment Center (MEC) + - 14f1:0342 + + * - 26 + - IODATA GV/BCTV7E + - 10fc:d035 + + * - 27 + - PixelView PlayTV Ultra Pro (Stereo) + - + + * - 28 + - DViCO FusionHDTV 3 Gold-T + - 18ac:d820 + + * - 29 + - ADS Tech Instant TV DVB-T PCI + - 1421:0334 + + * - 30 + - TerraTec Cinergy 1400 DVB-T + - 153b:1166 + + * - 31 + - DViCO FusionHDTV 5 Gold + - 18ac:d500 + + * - 32 + - AverMedia UltraTV Media Center PCI 550 + - 1461:8011 + + * - 33 + - Kworld V-Stream Xpert DVD + - + + * - 34 + - ATI HDTV Wonder + - 1002:a101 + + * - 35 + - WinFast DTV1000-T + - 107d:665f + + * - 36 + - AVerTV 303 (M126) + - 1461:000a + + * - 37 + - Hauppauge Nova-S-Plus DVB-S + - 0070:9201, 0070:9202 + + * - 38 + - Hauppauge Nova-SE2 DVB-S + - 0070:9200 + + * - 39 + - KWorld DVB-S 100 + - 17de:08b2, 1421:0341 + + * - 40 + - Hauppauge WinTV-HVR1100 DVB-T/Hybrid + - 0070:9400, 0070:9402 + + * - 41 + - Hauppauge WinTV-HVR1100 DVB-T/Hybrid (Low Profile) + - 0070:9800, 0070:9802 + + * - 42 + - digitalnow DNTV Live! DVB-T Pro + - 1822:0025, 1822:0019 + + * - 43 + - KWorld/VStream XPert DVB-T with cx22702 + - 17de:08a1, 12ab:2300 + + * - 44 + - DViCO FusionHDTV DVB-T Dual Digital + - 18ac:db50, 18ac:db54 + + * - 45 + - KWorld HardwareMpegTV XPert + - 17de:0840, 1421:0305 + + * - 46 + - DViCO FusionHDTV DVB-T Hybrid + - 18ac:db40, 18ac:db44 + + * - 47 + - pcHDTV HD5500 HDTV + - 7063:5500 + + * - 48 + - Kworld MCE 200 Deluxe + - 17de:0841 + + * - 49 + - PixelView PlayTV P7000 + - 1554:4813 + + * - 50 + - NPG Tech Real TV FM Top 10 + - 14f1:0842 + + * - 51 + - WinFast DTV2000 H + - 107d:665e + + * - 52 + - Geniatech DVB-S + - 14f1:0084 + + * - 53 + - Hauppauge WinTV-HVR3000 TriMode Analog/DVB-S/DVB-T + - 0070:1404, 0070:1400, 0070:1401, 0070:1402 + + * - 54 + - Norwood Micro TV Tuner + - + + * - 55 + - Shenzhen Tungsten Ages Tech TE-DTV-250 / Swann OEM + - c180:c980 + + * - 56 + - Hauppauge WinTV-HVR1300 DVB-T/Hybrid MPEG Encoder + - 0070:9600, 0070:9601, 0070:9602 + + * - 57 + - ADS Tech Instant Video PCI + - 1421:0390 + + * - 58 + - Pinnacle PCTV HD 800i + - 11bd:0051 + + * - 59 + - DViCO FusionHDTV 5 PCI nano + - 18ac:d530 + + * - 60 + - Pinnacle Hybrid PCTV + - 12ab:1788 + + * - 61 + - Leadtek TV2000 XP Global + - 107d:6f18, 107d:6618, 107d:6619 + + * - 62 + - PowerColor RA330 + - 14f1:ea3d + + * - 63 + - Geniatech X8000-MT DVBT + - 14f1:8852 + + * - 64 + - DViCO FusionHDTV DVB-T PRO + - 18ac:db30 + + * - 65 + - DViCO FusionHDTV 7 Gold + - 18ac:d610 + + * - 66 + - Prolink Pixelview MPEG 8000GT + - 1554:4935 + + * - 67 + - Kworld PlusTV HD PCI 120 (ATSC 120) + - 17de:08c1 + + * - 68 + - Hauppauge WinTV-HVR4000 DVB-S/S2/T/Hybrid + - 0070:6900, 0070:6904, 0070:6902 + + * - 69 + - Hauppauge WinTV-HVR4000(Lite) DVB-S/S2 + - 0070:6905, 0070:6906 + + * - 70 + - TeVii S460 DVB-S/S2 + - d460:9022 + + * - 71 + - Omicom SS4 DVB-S/S2 PCI + - A044:2011 + + * - 72 + - TBS 8920 DVB-S/S2 + - 8920:8888 + + * - 73 + - TeVii S420 DVB-S + - d420:9022 + + * - 74 + - Prolink Pixelview Global Extreme + - 1554:4976 + + * - 75 + - PROF 7300 DVB-S/S2 + - B033:3033 + + * - 76 + - SATTRADE ST4200 DVB-S/S2 + - b200:4200 + + * - 77 + - TBS 8910 DVB-S + - 8910:8888 + + * - 78 + - Prof 6200 DVB-S + - b022:3022 + + * - 79 + - Terratec Cinergy HT PCI MKII + - 153b:1177 + + * - 80 + - Hauppauge WinTV-IR Only + - 0070:9290 + + * - 81 + - Leadtek WinFast DTV1800 Hybrid + - 107d:6654 + + * - 82 + - WinFast DTV2000 H rev. J + - 107d:6f2b + + * - 83 + - Prof 7301 DVB-S/S2 + - b034:3034 + + * - 84 + - Samsung SMT 7020 DVB-S + - 18ac:dc00, 18ac:dccd + + * - 85 + - Twinhan VP-1027 DVB-S + - 1822:0023 + + * - 86 + - TeVii S464 DVB-S/S2 + - d464:9022 + + * - 87 + - Leadtek WinFast DTV2000 H PLUS + - 107d:6f42 + + * - 88 + - Leadtek WinFast DTV1800 H (XC4000) + - 107d:6f38 + + * - 89 + - Leadtek TV2000 XP Global (SC4100) + - 107d:6f36 + + * - 90 + - Leadtek TV2000 XP Global (XC4100) + - 107d:6f43 + + * - 91 + - NotOnlyTV LV3H + - diff --git a/Documentation/admin-guide/media/cx88.rst b/Documentation/admin-guide/media/cx88.rst new file mode 100644 index 000000000..e4badb181 --- /dev/null +++ b/Documentation/admin-guide/media/cx88.rst @@ -0,0 +1,58 @@ +.. SPDX-License-Identifier: GPL-2.0 + +The cx88 driver +=============== + +Author: Gerd Hoffmann + +This is a v4l2 device driver for the cx2388x chip. + + +Current status +-------------- + +video + - Works. + - Overlay isn't supported. + +audio + - Works. The TV standard detection is made by the driver, as the + hardware has bugs to auto-detect. + - audio data dma (i.e. recording without loopback cable to the + sound card) is supported via cx88-alsa. + +vbi + - Works. + + +How to add support for new cards +-------------------------------- + +The driver needs some config info for the TV cards. This stuff is in +cx88-cards.c. If the driver doesn't work well you likely need a new +entry for your card in that file. Check the kernel log (using dmesg) +to see whenever the driver knows your card or not. There is a line +like this one: + +.. code-block:: none + + cx8800[0]: subsystem: 0070:3400, board: Hauppauge WinTV \ + 34xxx models [card=1,autodetected] + +If your card is listed as "board: UNKNOWN/GENERIC" it is unknown to +the driver. What to do then? + +1) Try upgrading to the latest snapshot, maybe it has been added + meanwhile. +2) You can try to create a new entry yourself, have a look at + cx88-cards.c. If that worked, mail me your changes as unified + diff ("diff -u"). +3) Or you can mail me the config information. We need at least the + following information to add the card: + + - the PCI Subsystem ID ("0070:3400" from the line above, + "lspci -v" output is fine too). + - the tuner type used by the card. You can try to find one by + trial-and-error using the tuner=<n> insmod option. If you + know which one the card has you can also have a look at the + list in CARDLIST.tuner diff --git a/Documentation/admin-guide/media/dvb-drivers.rst b/Documentation/admin-guide/media/dvb-drivers.rst new file mode 100644 index 000000000..66fa4edd0 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-drivers.rst @@ -0,0 +1,15 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================================== +Digital TV driver-specific documentation +======================================== + +.. toctree:: + :maxdepth: 2 + + avermedia + bt8xx + lmedm04 + opera-firmware + technisat + ttusb-dec diff --git a/Documentation/admin-guide/media/dvb-usb-a800-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-a800-cardlist.rst new file mode 100644 index 000000000..2ec8bb823 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-a800-cardlist.rst @@ -0,0 +1,16 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-a800 cards list +======================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - AVerMedia AverTV DVB-T USB 2.0 (A800) + - 07ca:a800, 07ca:a801 diff --git a/Documentation/admin-guide/media/dvb-usb-af9005-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-af9005-cardlist.rst new file mode 100644 index 000000000..285160ee8 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-af9005-cardlist.rst @@ -0,0 +1,20 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-af9005 cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - Afatech DVB-T USB1.1 stick + - 15a4:9020 + * - Ansonic DVB-T USB1.1 stick + - 10b9:6000 + * - TerraTec Cinergy T USB XE + - 0ccd:0055 diff --git a/Documentation/admin-guide/media/dvb-usb-af9015-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-af9015-cardlist.rst new file mode 100644 index 000000000..c557994f7 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-af9015-cardlist.rst @@ -0,0 +1,80 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-af9015 cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - AVerMedia A309 + - 07ca:a309 + * - AVerMedia AVerTV DVB-T Volar X + - 07ca:a815 + * - Afatech AF9015 reference design + - 15a4:9015, 15a4:9016 + * - AverMedia AVerTV Red HD+ (A850T) + - 07ca:850b + * - AverMedia AVerTV Volar Black HD (A850) + - 07ca:850a + * - AverMedia AVerTV Volar GPS 805 (A805) + - 07ca:a805 + * - AverMedia AVerTV Volar M (A815Mac) + - 07ca:815a + * - Conceptronic USB2.0 DVB-T CTVDIGRCU V3.0 + - 1b80:e397 + * - DigitalNow TinyTwin + - 13d3:3226 + * - DigitalNow TinyTwin v2 + - 1b80:e402 + * - DigitalNow TinyTwin v3 + - 1f4d:9016 + * - Fujitsu-Siemens Slim Mobile USB DVB-T + - 07ca:8150 + * - Genius TVGo DVB-T03 + - 0458:4012 + * - KWorld Digital MC-810 + - 1b80:c810 + * - KWorld PlusTV DVB-T PCI Pro Card (DVB-T PC160-T) + - 1b80:c161 + * - KWorld PlusTV Dual DVB-T PCI (DVB-T PC160-2T) + - 1b80:c160 + * - KWorld PlusTV Dual DVB-T Stick (DVB-T 399U) + - 1b80:e399, 1b80:e400 + * - KWorld USB DVB-T Stick Mobile (UB383-T) + - 1b80:e383 + * - KWorld USB DVB-T TV Stick II (VS-DVB-T 395U) + - 1b80:e396, 1b80:e39b, 1b80:e395, 1b80:e39a + * - Leadtek WinFast DTV Dongle Gold + - 0413:6029 + * - Leadtek WinFast DTV2000DS + - 0413:6a04 + * - MSI DIGIVOX Duo + - 1462:8801 + * - MSI Digi VOX mini III + - 1462:8807 + * - Pinnacle PCTV 71e + - 2304:022b + * - Sveon STV20 Tuner USB DVB-T HDTV + - 1b80:e39d + * - Sveon STV22 Dual USB DVB-T Tuner HDTV + - 1b80:e401 + * - Telestar Starstick 2 + - 10b9:8000 + * - TerraTec Cinergy T Stick Dual RC + - 0ccd:0099 + * - TerraTec Cinergy T Stick RC + - 0ccd:0097 + * - TerraTec Cinergy T USB XE + - 0ccd:0069 + * - TrekStor DVB-T USB Stick + - 15a4:901b + * - TwinHan AzureWave AD-TU700(704J) + - 13d3:3237 + * - Xtensions XD-380 + - 1ae7:0381 diff --git a/Documentation/admin-guide/media/dvb-usb-af9035-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-af9035-cardlist.rst new file mode 100644 index 000000000..63e417077 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-af9035-cardlist.rst @@ -0,0 +1,74 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-af9035 cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - AVerMedia AVerTV Volar HD/PRO (A835) + - 07ca:a835, 07ca:b835 + * - AVerMedia HD Volar (A867) + - 07ca:1867, 07ca:a867, 07ca:0337 + * - AVerMedia TD310 DVB-T2 + - 07ca:1871 + * - AVerMedia Twinstar (A825) + - 07ca:0825 + * - Afatech AF9035 reference design + - 15a4:9035, 15a4:1000, 15a4:1001, 15a4:1002, 15a4:1003 + * - Asus U3100Mini Plus + - 0b05:1779 + * - Avermedia A835B(1835) + - 07ca:1835 + * - Avermedia A835B(2835) + - 07ca:2835 + * - Avermedia A835B(3835) + - 07ca:3835 + * - Avermedia A835B(4835) + - 07ca:4835 + * - Avermedia AverTV Volar HD 2 (TD110) + - 07ca:a110 + * - Avermedia H335 + - 07ca:0335 + * - Digital Dual TV Receiver CTVDIGDUAL_V2 + - 1b80:e410 + * - EVOLVEO XtraTV stick + - 1f4d:a115 + * - Hauppauge WinTV-MiniStick 2 + - 2040:f900 + * - ITE 9135 Generic + - 048d:9135 + * - ITE 9135(9005) Generic + - 048d:9005 + * - ITE 9135(9006) Generic + - 048d:9006 + * - ITE 9303 Generic + - 048d:9306 + * - Kworld UB499-2T T09 + - 1b80:e409 + * - Leadtek WinFast DTV Dongle Dual + - 0413:6a05 + * - Logilink VG0022A + - 1d19:0100 + * - PCTV AndroiDTV (78e) + - 2013:025a + * - PCTV microStick (79e) + - 2013:0262 + * - Sveon STV22 Dual DVB-T HDTV + - 1b80:e411 + * - TerraTec Cinergy T Stick + - 0ccd:0093 + * - TerraTec Cinergy T Stick (rev. 2) + - 0ccd:00aa + * - TerraTec Cinergy T Stick Dual RC (rev. 2) + - 0ccd:0099 + * - TerraTec Cinergy TC2 Stick + - 0ccd:10b2 + * - TerraTec T1 + - 0ccd:10ae diff --git a/Documentation/admin-guide/media/dvb-usb-anysee-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-anysee-cardlist.rst new file mode 100644 index 000000000..1fb5d22a0 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-anysee-cardlist.rst @@ -0,0 +1,16 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-anysee cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - Anysee + - 04b4:861f, 1c73:861f diff --git a/Documentation/admin-guide/media/dvb-usb-au6610-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-au6610-cardlist.rst new file mode 100644 index 000000000..02b2b7427 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-au6610-cardlist.rst @@ -0,0 +1,16 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-au6610 cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - Sigmatek DVB-110 + - 058f:6610 diff --git a/Documentation/admin-guide/media/dvb-usb-az6007-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-az6007-cardlist.rst new file mode 100644 index 000000000..db27eb47c --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-az6007-cardlist.rst @@ -0,0 +1,20 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-az6007 cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - Azurewave 6007 + - 13d3:0ccd + * - Technisat CableStar Combo HD CI + - 14f7:0003 + * - Terratec H7 + - 0ccd:10b4, 0ccd:10a3 diff --git a/Documentation/admin-guide/media/dvb-usb-az6027-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-az6027-cardlist.rst new file mode 100644 index 000000000..6d8575e9d --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-az6027-cardlist.rst @@ -0,0 +1,24 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-az6027 cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - AZUREWAVE DVB-S/S2 USB2.0 (AZ6027) + - 13d3:3275 + * - Elgato EyeTV Sat + - 0fd9:002a, 0fd9:0025, 0fd9:0036 + * - TERRATEC S7 + - 0ccd:10a4 + * - TERRATEC S7 MKII + - 0ccd:10ac + * - Technisat SkyStar USB 2 HD CI + - 14f7:0001, 14f7:0002 diff --git a/Documentation/admin-guide/media/dvb-usb-ce6230-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-ce6230-cardlist.rst new file mode 100644 index 000000000..09750e8ac --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-ce6230-cardlist.rst @@ -0,0 +1,18 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-ce6230 cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - AVerMedia A310 USB 2.0 DVB-T tuner + - 07ca:a310 + * - Intel CE9500 reference design + - 8086:9500 diff --git a/Documentation/admin-guide/media/dvb-usb-cinergyT2-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-cinergyT2-cardlist.rst new file mode 100644 index 000000000..0ee753929 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-cinergyT2-cardlist.rst @@ -0,0 +1,16 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-cinergyT2 cards list +============================ + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - TerraTec/qanu USB2.0 Highspeed DVB-T Receiver + - 0ccd:0x0038 diff --git a/Documentation/admin-guide/media/dvb-usb-cxusb-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-cxusb-cardlist.rst new file mode 100644 index 000000000..a73f15d1a --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-cxusb-cardlist.rst @@ -0,0 +1,40 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-cxusb cards list +======================== + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - AVerMedia AVerTVHD Volar (A868R) + - + * - Conexant DMB-TH Stick + - + * - DViCO FusionHDTV DVB-T Dual Digital 2 + - + * - DViCO FusionHDTV DVB-T Dual Digital 4 + - + * - DViCO FusionHDTV DVB-T Dual Digital 4 (rev 2) + - + * - DViCO FusionHDTV DVB-T Dual USB + - + * - DViCO FusionHDTV DVB-T NANO2 + - + * - DViCO FusionHDTV DVB-T USB (LGZ201) + - + * - DViCO FusionHDTV DVB-T USB (TH7579) + - + * - DViCO FusionHDTV5 USB Gold + - + * - DigitalNow DVB-T Dual USB + - + * - Medion MD95700 (MDUSBTV-HYBRID) + - + * - Mygica D689 DMB-TH + - diff --git a/Documentation/admin-guide/media/dvb-usb-dib0700-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-dib0700-cardlist.rst new file mode 100644 index 000000000..4b76b6f10 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-dib0700-cardlist.rst @@ -0,0 +1,162 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-dib0700 cards list +========================== + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - ASUS My Cinema U3000 Mini DVBT Tuner + - 0b05:171f + * - ASUS My Cinema U3100 Mini DVBT Tuner + - 0b05:173f + * - AVerMedia AVerTV DVB-T Express + - 07ca:b568 + * - AVerMedia AVerTV DVB-T Volar + - 07ca:a807, 07ca:b808 + * - Artec T14BR DVB-T + - 05d8:810f + * - Asus My Cinema-U3000Hybrid + - 0b05:1736 + * - Compro Videomate U500 + - 185b:1e78, 185b:1e80 + * - DiBcom NIM7090 reference design + - 10b8:1bb2 + * - DiBcom NIM8096MD reference design + - 10b8:1fa8 + * - DiBcom NIM9090MD reference design + - 10b8:2384 + * - DiBcom STK7070P reference design + - 10b8:1ebc + * - DiBcom STK7070PD reference design + - 10b8:1ebe + * - DiBcom STK7700D reference design + - 10b8:1ef0 + * - DiBcom STK7700P reference design + - 10b8:1e14, 10b8:1e78 + * - DiBcom STK7770P reference design + - 10b8:1e80 + * - DiBcom STK807xP reference design + - 10b8:1f90 + * - DiBcom STK807xPVR reference design + - 10b8:1f98 + * - DiBcom STK8096-PVR reference design + - 2013:1faa, 10b8:1faa + * - DiBcom STK8096GP reference design + - 10b8:1fa0 + * - DiBcom STK9090M reference design + - 10b8:2383 + * - DiBcom TFE7090PVR reference design + - 10b8:1bb4 + * - DiBcom TFE7790P reference design + - 10b8:1e6e + * - DiBcom TFE8096P reference design + - 10b8:1f9C + * - Elgato EyeTV DTT + - 0fd9:0021 + * - Elgato EyeTV DTT rev. 2 + - 0fd9:003f + * - Elgato EyeTV Diversity + - 0fd9:0011 + * - Elgato EyeTV Dtt Dlx PD378S + - 0fd9:0020 + * - EvolutePC TVWay+ + - 1e59:0002 + * - Gigabyte U7000 + - 1044:7001 + * - Gigabyte U8000-RH + - 1044:7002 + * - Hama DVB=T Hybrid USB Stick + - 147f:2758 + * - Hauppauge ATSC MiniCard (B200) + - 2040:b200 + * - Hauppauge ATSC MiniCard (B210) + - 2040:b210 + * - Hauppauge Nova-T 500 Dual DVB-T + - 2040:9941, 2040:9950 + * - Hauppauge Nova-T MyTV.t + - 2040:7080 + * - Hauppauge Nova-T Stick + - 2040:7050, 2040:7060, 2040:7070 + * - Hauppauge Nova-TD Stick (52009) + - 2040:5200 + * - Hauppauge Nova-TD Stick/Elgato Eye-TV Diversity + - 2040:9580 + * - Hauppauge Nova-TD-500 (84xxx) + - 2040:8400 + * - Leadtek WinFast DTV Dongle H + - 0413:60f6 + * - Leadtek Winfast DTV Dongle (STK7700P based) + - 0413:6f00, 0413:6f01 + * - Medion CTX1921 DVB-T USB + - 1660:1921 + * - Microsoft Xbox One Digital TV Tuner + - 045e:02d5 + * - PCTV 2002e + - 2013:025c + * - PCTV 2002e SE + - 2013:025d + * - Pinnacle Expresscard 320cx + - 2304:022e + * - Pinnacle PCTV 2000e + - 2304:022c + * - Pinnacle PCTV 282e + - 2013:0248, 2304:0248 + * - Pinnacle PCTV 340e HD Pro USB Stick + - 2304:023d + * - Pinnacle PCTV 72e + - 2304:0236 + * - Pinnacle PCTV 73A + - 2304:0243 + * - Pinnacle PCTV 73e + - 2304:0237 + * - Pinnacle PCTV 73e SE + - 2013:0245, 2304:0245 + * - Pinnacle PCTV DVB-T Flash Stick + - 2304:0228 + * - Pinnacle PCTV Dual DVB-T Diversity Stick + - 2304:0229 + * - Pinnacle PCTV HD Pro USB Stick + - 2304:023a + * - Pinnacle PCTV HD USB Stick + - 2304:023b + * - Pinnacle PCTV Hybrid Stick Solo + - 2304:023e + * - Prolink Pixelview SBTVD + - 1554:5010 + * - Sony PlayTV + - 1415:0003 + * - TechniSat AirStar TeleStick 2 + - 14f7:0004 + * - Terratec Cinergy DT USB XS Diversity/ T5 + - 0ccd:0081, 0ccd:10a1 + * - Terratec Cinergy DT XS Diversity + - 0ccd:005a + * - Terratec Cinergy HT Express + - 0ccd:0060 + * - Terratec Cinergy HT USB XE + - 0ccd:0058 + * - Terratec Cinergy T Express + - 0ccd:0062 + * - Terratec Cinergy T USB XXS (HD)/ T3 + - 0ccd:0078, 0ccd:10a0, 0ccd:00ab + * - Uniwill STK7700P based (Hama and others) + - 1584:6003 + * - YUAN High-Tech DiBcom STK7700D + - 1164:1e8c + * - YUAN High-Tech MC770 + - 1164:0871 + * - YUAN High-Tech STK7700D + - 1164:1efc + * - YUAN High-Tech STK7700PH + - 1164:1f08 + * - Yuan EC372S + - 1164:1edc + * - Yuan PD378S + - 1164:2edc diff --git a/Documentation/admin-guide/media/dvb-usb-dibusb-mb-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-dibusb-mb-cardlist.rst new file mode 100644 index 000000000..f25a54721 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-dibusb-mb-cardlist.rst @@ -0,0 +1,42 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-dibusb-mb cards list +============================ + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - AVerMedia AverTV DVBT USB1.1 + - 14aa:0001, 14aa:0002 + * - Artec T1 USB1.1 TVBOX with AN2135 + - 05d8:8105, 05d8:8106 + * - Artec T1 USB1.1 TVBOX with AN2235 + - 05d8:8107, 05d8:8108 + * - Artec T1 USB1.1 TVBOX with AN2235 (faulty USB IDs) + - 0547:2235 + * - Artec T1 USB2.0 + - 05d8:8109, 05d8:810a + * - Compro Videomate DVB-U2000 - DVB-T USB1.1 (please confirm to linux-dvb) + - 185b:d000, 145f:010c, 185b:d001 + * - DiBcom USB1.1 DVB-T reference design (MOD3000) + - 10b8:0bb8, 10b8:0bb9 + * - Grandtec USB1.1 DVB-T + - 5032:0fa0, 5032:0bb8, 5032:0fa1, 5032:0bb9 + * - KWorld V-Stream XPERT DTV - DVB-T USB1.1 + - eb1a:17de, eb1a:17df + * - KWorld Xpert DVB-T USB2.0 + - eb2a:17de + * - KWorld/ADSTech Instant DVB-T USB2.0 + - 06e1:a333, 06e1:a334 + * - TwinhanDTV USB-Ter USB1.1 / Magic Box I / HAMA USB1.1 DVB-T device + - 13d3:3201, 1822:3201, 13d3:3202, 1822:3202 + * - Unknown USB1.1 DVB-T device ???? please report the name to the author + - 1025:005e, 1025:005f + * - VideoWalker DVB-T USB + - 0458:701e, 0458:701f diff --git a/Documentation/admin-guide/media/dvb-usb-dibusb-mc-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-dibusb-mc-cardlist.rst new file mode 100644 index 000000000..8d03bae0e --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-dibusb-mc-cardlist.rst @@ -0,0 +1,30 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-dibusb-mc cards list +============================ + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - Artec T1 USB2.0 TVBOX (please check the warm ID) + - 05d8:8109, 05d8:810a + * - Artec T14 - USB2.0 DVB-T + - 05d8:810b, 05d8:810c + * - DiBcom USB2.0 DVB-T reference design (MOD3000P) + - 10b8:0bc6, 10b8:0bc7 + * - GRAND - USB2.0 DVB-T adapter + - 5032:0bc6, 5032:0bc7 + * - Humax/Coex DVB-T USB Stick 2.0 High Speed + - 10b9:5000, 10b9:5001 + * - LITE-ON USB2.0 DVB-T Tuner + - 04ca:f000, 04ca:f001 + * - Leadtek - USB2.0 Winfast DTV dongle + - 0413:6025, 0413:6026 + * - MSI Digivox Mini SL + - eb1a:e360, eb1a:e361 diff --git a/Documentation/admin-guide/media/dvb-usb-digitv-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-digitv-cardlist.rst new file mode 100644 index 000000000..2b4d8325e --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-digitv-cardlist.rst @@ -0,0 +1,16 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-digitv cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - Nebula Electronics uDigiTV DVB-T USB2.0) + - 0547:0201 diff --git a/Documentation/admin-guide/media/dvb-usb-dtt200u-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-dtt200u-cardlist.rst new file mode 100644 index 000000000..b4150a7bf --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-dtt200u-cardlist.rst @@ -0,0 +1,22 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-dtt200u cards list +========================== + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - WideView WT-220U PenType Receiver (Miglia) + - 18f3:0220 + * - WideView WT-220U PenType Receiver (Typhoon/Freecom) + - 14aa:0222, 14aa:0220, 14aa:0221, 14aa:0225, 14aa:0226 + * - WideView WT-220U PenType Receiver (based on ZL353) + - 14aa:022a, 14aa:022b + * - WideView/Yuan/Yakumo/Hama/Typhoon DVB-T USB2.0 (WT-200U) + - 14aa:0201, 14aa:0301 diff --git a/Documentation/admin-guide/media/dvb-usb-dtv5100-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-dtv5100-cardlist.rst new file mode 100644 index 000000000..91d6e35e6 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-dtv5100-cardlist.rst @@ -0,0 +1,16 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-dtv5100 cards list +========================== + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - AME DTV-5100 USB2.0 DVB-T + - 0x06be:0xa232 diff --git a/Documentation/admin-guide/media/dvb-usb-dvbsky-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-dvbsky-cardlist.rst new file mode 100644 index 000000000..9f7b619f3 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-dvbsky-cardlist.rst @@ -0,0 +1,42 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-dvbsky cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - DVBSky S960/S860 + - 0572:6831 + * - DVBSky S960CI + - 0572:960c + * - DVBSky T330 + - 0572:0320 + * - DVBSky T680CI + - 0572:680c + * - MyGica Mini DVB-(T/T2/C) USB Stick T230 + - 0572:c688 + * - MyGica Mini DVB-(T/T2/C) USB Stick T230C + - 0572:c689 + * - MyGica Mini DVB-(T/T2/C) USB Stick T230C Lite + - 0572:c699 + * - MyGica Mini DVB-(T/T2/C) USB Stick T230C v2 + - 0572:c68a + * - TechnoTrend TT-connect CT2-4650 CI + - 0b48:3012 + * - TechnoTrend TT-connect CT2-4650 CI v1.1 + - 0b48:3015 + * - TechnoTrend TT-connect S2-4650 CI + - 0b48:3017 + * - TechnoTrend TVStick CT2-4400 + - 0b48:3014 + * - Terratec Cinergy S2 Rev.4 + - 0ccd:0105 + * - Terratec H7 Rev.4 + - 0ccd:10a5 diff --git a/Documentation/admin-guide/media/dvb-usb-dw2102-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-dw2102-cardlist.rst new file mode 100644 index 000000000..e39bc8e4b --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-dw2102-cardlist.rst @@ -0,0 +1,56 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-dw2102 cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - DVBWorld DVB-C 3101 USB2.0 + - 04b4:3101 + * - DVBWorld DVB-S 2101 USB2.0 + - 04b4:0x2101 + * - DVBWorld DVB-S 2102 USB2.0 + - 04b4:2102 + * - DVBWorld DW2104 USB2.0 + - 04b4:2104 + * - GOTVIEW Satellite HD + - 0x1FE1:5456 + * - Geniatech T220 DVB-T/T2 USB2.0 + - 0x1f4d:0xD220 + * - SU3000HD DVB-S USB2.0 + - 0x1f4d:0x3000 + * - TeVii S482 (tuner 1) + - 0x9022:0xd483 + * - TeVii S482 (tuner 2) + - 0x9022:0xd484 + * - TeVii S630 USB + - 0x9022:d630 + * - TeVii S650 USB2.0 + - 0x9022:d650 + * - TeVii S662 + - 0x9022:d662 + * - TechnoTrend TT-connect S2-4600 + - 0b48:3011 + * - TerraTec Cinergy S USB + - 0ccd:0064 + * - Terratec Cinergy S2 PCIe Dual Port 1 + - 153b:1181 + * - Terratec Cinergy S2 PCIe Dual Port 2 + - 153b:1182 + * - Terratec Cinergy S2 USB BOX + - 0ccd:0x0105 + * - Terratec Cinergy S2 USB HD + - 0ccd:00a8 + * - Terratec Cinergy S2 USB HD Rev.2 + - 0ccd:00b0 + * - Terratec Cinergy S2 USB HD Rev.3 + - 0ccd:0102 + * - X3M TV SPC1400HD PCI + - 0x1f4d:0x3100 diff --git a/Documentation/admin-guide/media/dvb-usb-ec168-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-ec168-cardlist.rst new file mode 100644 index 000000000..a3660dfa5 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-ec168-cardlist.rst @@ -0,0 +1,16 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-ec168 cards list +======================== + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - E3C EC168 reference design + - 18b4:1689, 18b4:fffa, 18b4:fffb, 18b4:1001, 18b4:1002 diff --git a/Documentation/admin-guide/media/dvb-usb-gl861-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-gl861-cardlist.rst new file mode 100644 index 000000000..5ec62fe03 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-gl861-cardlist.rst @@ -0,0 +1,20 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-gl861 cards list +======================== + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - 774 Friio White ISDB-T USB2.0 + - 7a69:0001 + * - A-LINK DTU DVB-T USB2.0 + - 05e3:f170 + * - MSI Mega Sky 55801 DVB-T USB2.0 + - 0db0:5581 diff --git a/Documentation/admin-guide/media/dvb-usb-gp8psk-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-gp8psk-cardlist.rst new file mode 100644 index 000000000..150fa9f78 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-gp8psk-cardlist.rst @@ -0,0 +1,22 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-gp8psk cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - Genpix 8PSK-to-USB2 Rev.1 DVB-S receiver + - 09c0:0200, 09c0:0201 + * - Genpix 8PSK-to-USB2 Rev.2 DVB-S receiver + - 09c0:0202 + * - Genpix SkyWalker-1 DVB-S receiver + - 09c0:0203 + * - Genpix SkyWalker-2 DVB-S receiver + - 09c0:0206 diff --git a/Documentation/admin-guide/media/dvb-usb-lmedm04-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-lmedm04-cardlist.rst new file mode 100644 index 000000000..2050fbf03 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-lmedm04-cardlist.rst @@ -0,0 +1,20 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-lmedm04 cards list +========================== + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - DM04_LME2510C_DVB-S + - 3344:1120 + * - DM04_LME2510C_DVB-S RS2000 + - 3344:22f0 + * - DM04_LME2510_DVB-S + - 3344:1122 diff --git a/Documentation/admin-guide/media/dvb-usb-m920x-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-m920x-cardlist.rst new file mode 100644 index 000000000..73145940b --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-m920x-cardlist.rst @@ -0,0 +1,26 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-m920x cards list +======================== + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - DTV-DVB UDTT7049 + - 13d3:3219 + * - Dposh DVB-T USB2.0 + - 1498:9206, 1498:a090 + * - LifeView TV Walker Twin DVB-T USB2.0 + - 10fd:0514, 10fd:0513 + * - MSI DIGI VOX mini II DVB-T USB2.0 + - 10fd:1513 + * - MSI Mega Sky 580 DVB-T USB2.0 + - 0db0:5580 + * - Pinnacle PCTV 310e + - 13d3:3211 diff --git a/Documentation/admin-guide/media/dvb-usb-mxl111sf-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-mxl111sf-cardlist.rst new file mode 100644 index 000000000..6974801c4 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-mxl111sf-cardlist.rst @@ -0,0 +1,36 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-mxl111sf cards list +=========================== + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - HCW 117xxx + - 2040:b702 + * - HCW 126xxx + - 2040:c602, 2040:c60a + * - Hauppauge 117xxx ATSC+ + - 2040:b700, 2040:b703, 2040:b753, 2040:b763, 2040:b757, 2040:b767 + * - Hauppauge 117xxx DVBT + - 2040:b704, 2040:b764 + * - Hauppauge 126xxx + - 2040:c612, 2040:c61a + * - Hauppauge 126xxx ATSC + - 2040:c601, 2040:c609, 2040:b701 + * - Hauppauge 126xxx ATSC+ + - 2040:c600, 2040:c603, 2040:c60b, 2040:c653, 2040:c65b + * - Hauppauge 126xxx DVBT + - 2040:c604, 2040:c60c + * - Hauppauge 138xxx DVBT + - 2040:d854, 2040:d864, 2040:d8d4, 2040:d8e4 + * - Hauppauge Mercury + - 2040:d853, 2040:d863, 2040:d8d3, 2040:d8e3, 2040:d8ff + * - Hauppauge WinTV-Aero-M + - 2040:c613, 2040:c61b diff --git a/Documentation/admin-guide/media/dvb-usb-nova-t-usb2-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-nova-t-usb2-cardlist.rst new file mode 100644 index 000000000..e295f912a --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-nova-t-usb2-cardlist.rst @@ -0,0 +1,16 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-nova-t-usb2 cards list +============================== + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - Hauppauge WinTV-NOVA-T usb2 + - 2040:9300, 2040:9301 diff --git a/Documentation/admin-guide/media/dvb-usb-opera1-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-opera1-cardlist.rst new file mode 100644 index 000000000..362245f5a --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-opera1-cardlist.rst @@ -0,0 +1,16 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-opera1 cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - Opera1 DVB-S USB2.0 + - 04b4:2830, 695c:3829 diff --git a/Documentation/admin-guide/media/dvb-usb-pctv452e-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-pctv452e-cardlist.rst new file mode 100644 index 000000000..886d8cc18 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-pctv452e-cardlist.rst @@ -0,0 +1,20 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-pctv452e cards list +=========================== + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - PCTV HDTV USB + - 2304:021f + * - Technotrend TT Connect S2-3600 + - 0b48:3007 + * - Technotrend TT Connect S2-3650-CI + - 0b48:300a diff --git a/Documentation/admin-guide/media/dvb-usb-rtl28xxu-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-rtl28xxu-cardlist.rst new file mode 100644 index 000000000..9f4295331 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-rtl28xxu-cardlist.rst @@ -0,0 +1,80 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-rtl28xxu cards list +=========================== + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - ASUS My Cinema-U3100Mini Plus V2 + - 1b80:d3a8 + * - Astrometa DVB-T2 + - 15f4:0131 + * - Compro VideoMate U620F + - 185b:0620 + * - Compro VideoMate U650F + - 185b:0650 + * - Crypto ReDi PC 50 A + - 1f4d:a803 + * - Dexatek DK DVB-T Dongle + - 1d19:1101 + * - Dexatek DK mini DVB-T Dongle + - 1d19:1102 + * - DigitalNow Quad DVB-T Receiver + - 0413:6680 + * - Freecom USB2.0 DVB-T + - 14aa:0160, 14aa:0161 + * - G-Tek Electronics Group Lifeview LV5TDLX DVB-T + - 1f4d:b803 + * - GIGABYTE U7300 + - 1b80:d393 + * - Genius TVGo DVB-T03 + - 0458:707f + * - GoTView MasterHD 3 + - 5654:ca42 + * - Leadtek WinFast DTV Dongle mini + - 0413:6a03 + * - Leadtek WinFast DTV2000DS Plus + - 0413:6f12 + * - Leadtek Winfast DTV Dongle Mini D + - 0413:6f0f + * - MSI DIGIVOX Micro HD + - 1d19:1104 + * - MaxMedia HU394-T + - 1b80:d394 + * - PROlectrix DV107669 + - 1f4d:d803 + * - Peak DVB-T USB + - 1b80:d395 + * - Realtek RTL2831U reference design + - 0bda:2831 + * - Realtek RTL2832U reference design + - 0bda:2832, 0bda:2838 + * - Sveon STV20 + - 1b80:d39d + * - Sveon STV21 + - 1b80:d3b0 + * - Sveon STV27 + - 1b80:d3af + * - TURBO-X Pure TV Tuner DTT-2000 + - 1b80:d3a4 + * - TerraTec Cinergy T Stick Black + - 0ccd:00a9 + * - TerraTec Cinergy T Stick RC (Rev. 3) + - 0ccd:00d3 + * - TerraTec Cinergy T Stick+ + - 0ccd:00d7 + * - TerraTec NOXON DAB Stick + - 0ccd:00b3 + * - TerraTec NOXON DAB Stick (rev 2) + - 0ccd:00e0 + * - TerraTec NOXON DAB Stick (rev 3) + - 0ccd:00b4 + * - Trekstor DVB-T Stick Terres 2.0 + - 1f4d:C803 diff --git a/Documentation/admin-guide/media/dvb-usb-technisat-usb2-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-technisat-usb2-cardlist.rst new file mode 100644 index 000000000..30ee92ada --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-technisat-usb2-cardlist.rst @@ -0,0 +1,16 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-technisat-usb2 cards list +================================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - Technisat SkyStar USB HD (DVB-S/S2) + - 14f7:0500 diff --git a/Documentation/admin-guide/media/dvb-usb-ttusb2-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-ttusb2-cardlist.rst new file mode 100644 index 000000000..faa78e5f3 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-ttusb2-cardlist.rst @@ -0,0 +1,24 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-ttusb2 cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - Pinnacle 400e DVB-S USB2.0 + - 2304:020f + * - Pinnacle 450e DVB-S USB2.0 + - 2304:0222 + * - Technotrend TT-connect CT-3650 + - 0b48:300d + * - Technotrend TT-connect S-2400 + - 0b48:3006 + * - Technotrend TT-connect S-2400 (8kB EEPROM) + - 0b48:3009 diff --git a/Documentation/admin-guide/media/dvb-usb-umt-010-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-umt-010-cardlist.rst new file mode 100644 index 000000000..ce7ce901b --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-umt-010-cardlist.rst @@ -0,0 +1,16 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-umt-010 cards list +========================== + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - Hanftek UMT-010 DVB-T USB2.0 + - 15f4:0001, 15f4:0015 diff --git a/Documentation/admin-guide/media/dvb-usb-vp702x-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-vp702x-cardlist.rst new file mode 100644 index 000000000..101442434 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-vp702x-cardlist.rst @@ -0,0 +1,16 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-vp702x cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - TwinhanDTV StarBox DVB-S USB2.0 (VP7021) + - 13d3:3207 diff --git a/Documentation/admin-guide/media/dvb-usb-vp7045-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-vp7045-cardlist.rst new file mode 100644 index 000000000..2fc8fc4ec --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-vp7045-cardlist.rst @@ -0,0 +1,18 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-vp7045 cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - DigitalNow TinyUSB 2 DVB-t Receiver + - 13d3:3223, 13d3:3224 + * - Twinhan USB2.0 DVB-T receiver (TwinhanDTV Alpha/MagicBox II) + - 13d3:3205, 13d3:3206 diff --git a/Documentation/admin-guide/media/dvb-usb-zd1301-cardlist.rst b/Documentation/admin-guide/media/dvb-usb-zd1301-cardlist.rst new file mode 100644 index 000000000..9ca446184 --- /dev/null +++ b/Documentation/admin-guide/media/dvb-usb-zd1301-cardlist.rst @@ -0,0 +1,16 @@ +.. SPDX-License-Identifier: GPL-2.0 + +dvb-usb-zd1301 cards list +========================= + +.. tabularcolumns:: |p{7.0cm}|p{10.5cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 7 13 + :stub-columns: 0 + + * - Card name + - USB IDs + * - ZyDAS ZD1301 reference design + - 0ace:13a1 diff --git a/Documentation/admin-guide/media/dvb.rst b/Documentation/admin-guide/media/dvb.rst new file mode 100644 index 000000000..e5258bfa5 --- /dev/null +++ b/Documentation/admin-guide/media/dvb.rst @@ -0,0 +1,12 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========== +Digital TV +========== + +.. toctree:: + + dvb_intro + ci + faq + dvb_references diff --git a/Documentation/admin-guide/media/dvb_intro.rst b/Documentation/admin-guide/media/dvb_intro.rst new file mode 100644 index 000000000..44eac9b3b --- /dev/null +++ b/Documentation/admin-guide/media/dvb_intro.rst @@ -0,0 +1,616 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================== +Using the Digital TV Framework +============================== + +Introduction +~~~~~~~~~~~~ + +One significant difference between Digital TV and Analogue TV that the +unwary (like myself) should consider is that, although the component +structure of DVB-T cards are substantially similar to Analogue TV cards, +they function in substantially different ways. + +The purpose of an Analogue TV is to receive and display an Analogue +Television signal. An Analogue TV signal (otherwise known as composite +video) is an analogue encoding of a sequence of image frames (25 frames +per second in Europe) rasterised using an interlacing technique. +Interlacing takes two fields to represent one frame. Therefore, an +Analogue TV card for a PC has the following purpose: + +* Tune the receiver to receive a broadcast signal +* demodulate the broadcast signal +* demultiplex the analogue video signal and analogue audio + signal. + + .. note:: + + some countries employ a digital audio signal + embedded within the modulated composite analogue signal - + using NICAM signaling.) + +* digitize the analogue video signal and make the resulting datastream + available to the data bus. + +The digital datastream from an Analogue TV card is generated by +circuitry on the card and is often presented uncompressed. For a PAL TV +signal encoded at a resolution of 768x576 24-bit color pixels over 25 +frames per second - a fair amount of data is generated and must be +processed by the PC before it can be displayed on the video monitor +screen. Some Analogue TV cards for PCs have onboard MPEG2 encoders which +permit the raw digital data stream to be presented to the PC in an +encoded and compressed form - similar to the form that is used in +Digital TV. + +The purpose of a simple budget digital TV card (DVB-T,C or S) is to +simply: + +* Tune the received to receive a broadcast signal. * Extract the encoded + digital datastream from the broadcast signal. +* Make the encoded digital datastream (MPEG2) available to the data bus. + +The significant difference between the two is that the tuner on the +analogue TV card spits out an Analogue signal, whereas the tuner on the +digital TV card spits out a compressed encoded digital datastream. As +the signal is already digitised, it is trivial to pass this datastream +to the PC databus with minimal additional processing and then extract +the digital video and audio datastreams passing them to the appropriate +software or hardware for decoding and viewing. + +Getting the card going +~~~~~~~~~~~~~~~~~~~~~~ + +The Device Driver API for DVB under Linux will the following +device nodes via the devfs filesystem: + +* /dev/dvb/adapter0/demux0 +* /dev/dvb/adapter0/dvr0 +* /dev/dvb/adapter0/frontend0 + +The ``/dev/dvb/adapter0/dvr0`` device node is used to read the MPEG2 +Data Stream and the ``/dev/dvb/adapter0/frontend0`` device node is used +to tune the frontend tuner module. The ``/dev/dvb/adapter0/demux0`` is +used to control what programs will be received. + +Depending on the card's feature set, the Device Driver API could also +expose other device nodes: + +* /dev/dvb/adapter0/ca0 +* /dev/dvb/adapter0/audio0 +* /dev/dvb/adapter0/net0 +* /dev/dvb/adapter0/osd0 +* /dev/dvb/adapter0/video0 + +The ``/dev/dvb/adapter0/ca0`` is used to decode encrypted channels. The +other device nodes are found only on devices that use the av7110 +driver, with is now obsoleted, together with the extra API whose such +devices use. + +Receiving a digital TV channel +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +This section attempts to explain how it works and how this affects the +configuration of a Digital TV card. + +On this example, we're considering tuning into DVB-T channels in +Australia, at the Melbourne region. + +The frequencies broadcast by Mount Dandenong transmitters are, +currently: + +Table 1. Transponder Frequencies Mount Dandenong, Vic, Aus. + +=========== =========== +Broadcaster Frequency +=========== =========== +Seven 177.500 Mhz +SBS 184.500 Mhz +Nine 191.625 Mhz +Ten 219.500 Mhz +ABC 226.500 Mhz +Channel 31 557.625 Mhz +=========== =========== + +The digital TV Scan utilities (like dvbv5-scan) have use a set of +compiled-in defaults for various countries and regions. Those are +currently provided as a separate package, called dtv-scan-tables. It's +git tree is located at LinuxTV.org: + + https://git.linuxtv.org/dtv-scan-tables.git/ + +If none of the tables there suit, you can specify a data file on the +command line which contains the transponder frequencies. Here is a +sample file for the above channel transponders, in the old "channel" +format:: + + # Data file for DVB scan program + # + # C Frequency SymbolRate FEC QAM + # S Frequency Polarisation SymbolRate FEC + # T Frequency Bandwidth FEC FEC2 QAM Mode Guard Hier + + T 177500000 7MHz AUTO AUTO QAM64 8k 1/16 NONE + T 184500000 7MHz AUTO AUTO QAM64 8k 1/8 NONE + T 191625000 7MHz AUTO AUTO QAM64 8k 1/16 NONE + T 219500000 7MHz AUTO AUTO QAM64 8k 1/16 NONE + T 226500000 7MHz AUTO AUTO QAM64 8k 1/16 NONE + T 557625000 7MHz AUTO AUTO QPSK 8k 1/16 NONE + +Nowadays, we prefer to use a newer format, with is more verbose and easier +to understand. With the new format, the "Seven" channel transponder's +data is represented by:: + + [Seven] + DELIVERY_SYSTEM = DVBT + FREQUENCY = 177500000 + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = AUTO + CODE_RATE_LP = AUTO + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + INVERSION = AUTO + +For an updated version of the complete table, please see: + + https://git.linuxtv.org/dtv-scan-tables.git/tree/dvb-t/au-Melbourne + +When the Digital TV scanning utility runs, it will output a file +containing the information for all the audio and video programs that +exists into each channel's transponders which the card's frontend can +lock onto. (i.e. any whose signal is strong enough at your antenna). + +Here's the output of the dvbv5 tools from a channel scan took from +Melburne:: + + [ABC HDTV] + SERVICE_ID = 560 + VIDEO_PID = 2307 + AUDIO_PID = 0 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 226500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 3/4 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [ABC TV Melbourne] + SERVICE_ID = 561 + VIDEO_PID = 512 + AUDIO_PID = 650 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 226500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 3/4 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [ABC TV 2] + SERVICE_ID = 562 + VIDEO_PID = 512 + AUDIO_PID = 650 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 226500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 3/4 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [ABC TV 3] + SERVICE_ID = 563 + VIDEO_PID = 512 + AUDIO_PID = 650 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 226500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 3/4 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [ABC TV 4] + SERVICE_ID = 564 + VIDEO_PID = 512 + AUDIO_PID = 650 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 226500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 3/4 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [ABC DiG Radio] + SERVICE_ID = 566 + VIDEO_PID = 0 + AUDIO_PID = 2311 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 226500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 3/4 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [TEN Digital] + SERVICE_ID = 1585 + VIDEO_PID = 512 + AUDIO_PID = 650 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 219500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 1/2 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [TEN Digital 1] + SERVICE_ID = 1586 + VIDEO_PID = 512 + AUDIO_PID = 650 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 219500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 1/2 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [TEN Digital 2] + SERVICE_ID = 1587 + VIDEO_PID = 512 + AUDIO_PID = 650 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 219500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 1/2 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [TEN Digital 3] + SERVICE_ID = 1588 + VIDEO_PID = 512 + AUDIO_PID = 650 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 219500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 1/2 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [TEN Digital] + SERVICE_ID = 1589 + VIDEO_PID = 512 + AUDIO_PID = 650 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 219500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 1/2 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [TEN Digital 4] + SERVICE_ID = 1590 + VIDEO_PID = 512 + AUDIO_PID = 650 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 219500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 1/2 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [TEN Digital] + SERVICE_ID = 1591 + VIDEO_PID = 512 + AUDIO_PID = 650 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 219500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 1/2 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [TEN HD] + SERVICE_ID = 1592 + VIDEO_PID = 514 + AUDIO_PID = 0 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 219500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 1/2 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [TEN Digital] + SERVICE_ID = 1593 + VIDEO_PID = 512 + AUDIO_PID = 650 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 219500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 1/2 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [Nine Digital] + SERVICE_ID = 1072 + VIDEO_PID = 513 + AUDIO_PID = 660 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 191625000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 1/2 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [Nine Digital HD] + SERVICE_ID = 1073 + VIDEO_PID = 512 + AUDIO_PID = 0 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 191625000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 1/2 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [Nine Guide] + SERVICE_ID = 1074 + VIDEO_PID = 514 + AUDIO_PID = 670 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 191625000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 3/4 + CODE_RATE_LP = 1/2 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/16 + HIERARCHY = NONE + + [7 Digital] + SERVICE_ID = 1328 + VIDEO_PID = 769 + AUDIO_PID = 770 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 177500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 2/3 + CODE_RATE_LP = 2/3 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/8 + HIERARCHY = NONE + + [7 Digital 1] + SERVICE_ID = 1329 + VIDEO_PID = 769 + AUDIO_PID = 770 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 177500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 2/3 + CODE_RATE_LP = 2/3 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/8 + HIERARCHY = NONE + + [7 Digital 2] + SERVICE_ID = 1330 + VIDEO_PID = 769 + AUDIO_PID = 770 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 177500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 2/3 + CODE_RATE_LP = 2/3 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/8 + HIERARCHY = NONE + + [7 Digital 3] + SERVICE_ID = 1331 + VIDEO_PID = 769 + AUDIO_PID = 770 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 177500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 2/3 + CODE_RATE_LP = 2/3 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/8 + HIERARCHY = NONE + + [7 HD Digital] + SERVICE_ID = 1332 + VIDEO_PID = 833 + AUDIO_PID = 834 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 177500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 2/3 + CODE_RATE_LP = 2/3 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/8 + HIERARCHY = NONE + + [7 Program Guide] + SERVICE_ID = 1334 + VIDEO_PID = 865 + AUDIO_PID = 866 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 177500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 2/3 + CODE_RATE_LP = 2/3 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/8 + HIERARCHY = NONE + + [SBS HD] + SERVICE_ID = 784 + VIDEO_PID = 102 + AUDIO_PID = 103 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 536500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 2/3 + CODE_RATE_LP = 2/3 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/8 + HIERARCHY = NONE + + [SBS DIGITAL 1] + SERVICE_ID = 785 + VIDEO_PID = 161 + AUDIO_PID = 81 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 536500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 2/3 + CODE_RATE_LP = 2/3 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/8 + HIERARCHY = NONE + + [SBS DIGITAL 2] + SERVICE_ID = 786 + VIDEO_PID = 162 + AUDIO_PID = 83 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 536500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 2/3 + CODE_RATE_LP = 2/3 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/8 + HIERARCHY = NONE + + [SBS EPG] + SERVICE_ID = 787 + VIDEO_PID = 163 + AUDIO_PID = 85 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 536500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 2/3 + CODE_RATE_LP = 2/3 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/8 + HIERARCHY = NONE + + [SBS RADIO 1] + SERVICE_ID = 798 + VIDEO_PID = 0 + AUDIO_PID = 201 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 536500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 2/3 + CODE_RATE_LP = 2/3 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/8 + HIERARCHY = NONE + + [SBS RADIO 2] + SERVICE_ID = 799 + VIDEO_PID = 0 + AUDIO_PID = 202 + DELIVERY_SYSTEM = DVBT + FREQUENCY = 536500000 + INVERSION = OFF + BANDWIDTH_HZ = 7000000 + CODE_RATE_HP = 2/3 + CODE_RATE_LP = 2/3 + MODULATION = QAM/64 + TRANSMISSION_MODE = 8K + GUARD_INTERVAL = 1/8 + HIERARCHY = NONE diff --git a/Documentation/admin-guide/media/dvb_references.rst b/Documentation/admin-guide/media/dvb_references.rst new file mode 100644 index 000000000..4f0fd4259 --- /dev/null +++ b/Documentation/admin-guide/media/dvb_references.rst @@ -0,0 +1,29 @@ +.. SPDX-License-Identifier: GPL-2.0 + +References +========== + +The main development site and GIT repository for Digital TV +drivers is https://linuxtv.org. + +The DVB mailing list linux-dvb is hosted at vger. Please see +http://vger.kernel.org/vger-lists.html#linux-media for details. + +There are also some other old lists hosted at: +https://linuxtv.org/lists.php. If you're interested on that for historic +reasons, please check the archive at https://linuxtv.org/pipermail/linux-dvb/. + +The media subsystem Wiki is hosted at https://linuxtv.org/wiki/. +There, you'll find lots of information, from both development and usage +of media boards. Please check it before asking newbie questions on the +mailing list or IRC channels. + +The API documentation is documented at the Kernel tree. You can find it +in both html and pdf formats, together with other useful documentation at: + + - https://linuxtv.org/docs.php. + +You may also find useful material at https://linuxtv.org/downloads/. + +In order to get the needed firmware for some drivers to work, there's +a script at the kernel tree, at scripts/get_dvb_firmware. diff --git a/Documentation/admin-guide/media/em28xx-cardlist.rst b/Documentation/admin-guide/media/em28xx-cardlist.rst new file mode 100644 index 000000000..ace65718e --- /dev/null +++ b/Documentation/admin-guide/media/em28xx-cardlist.rst @@ -0,0 +1,440 @@ +.. SPDX-License-Identifier: GPL-2.0 + +EM28xx cards list +================= + +.. tabularcolumns:: |p{1.4cm}|p{10.0cm}|p{1.9cm}|p{4.2cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 2 12 3 16 + :stub-columns: 0 + + * - Card number + - Card name + - Empia Chip + - USB IDs + * - 0 + - Unknown EM2800 video grabber + - em2800 + - eb1a:2800 + * - 1 + - Unknown EM2750/28xx video grabber + - em2820 or em2840 + - eb1a:2710, eb1a:2820, eb1a:2821, eb1a:2860, eb1a:2861, eb1a:2862, eb1a:2863, eb1a:2870, eb1a:2881, eb1a:2883, eb1a:2868, eb1a:2875 + * - 2 + - Terratec Cinergy 250 USB + - em2820 or em2840 + - 0ccd:0036 + * - 3 + - Pinnacle PCTV USB 2 + - em2820 or em2840 + - 2304:0208 + * - 4 + - Hauppauge WinTV USB 2 + - em2820 or em2840 + - 2040:4200, 2040:4201 + * - 5 + - MSI VOX USB 2.0 + - em2820 or em2840 + - + * - 6 + - Terratec Cinergy 200 USB + - em2800 + - + * - 7 + - Leadtek Winfast USB II + - em2800 + - 0413:6023 + * - 8 + - Kworld USB2800 + - em2800 + - + * - 9 + - Pinnacle Dazzle DVC 90/100/101/107 / Kaiser Baas Video to DVD maker / Kworld DVD Maker 2 / Plextor ConvertX PX-AV100U + - em2820 or em2840 + - 1b80:e302, 1b80:e304, 2304:0207, 2304:021a, 093b:a003 + * - 10 + - Hauppauge WinTV HVR 900 + - em2880 + - 2040:6500 + * - 11 + - Terratec Hybrid XS + - em2880 + - + * - 12 + - Kworld PVR TV 2800 RF + - em2820 or em2840 + - + * - 13 + - Terratec Prodigy XS + - em2880 + - + * - 14 + - SIIG AVTuner-PVR / Pixelview Prolink PlayTV USB 2.0 + - em2820 or em2840 + - + * - 15 + - V-Gear PocketTV + - em2800 + - + * - 16 + - Hauppauge WinTV HVR 950 + - em2883 + - 2040:6513, 2040:6517, 2040:651b + * - 17 + - Pinnacle PCTV HD Pro Stick + - em2880 + - 2304:0227 + * - 18 + - Hauppauge WinTV HVR 900 (R2) + - em2880 + - 2040:6502 + * - 19 + - EM2860/SAA711X Reference Design + - em2860 + - + * - 20 + - AMD ATI TV Wonder HD 600 + - em2880 + - 0438:b002 + * - 21 + - eMPIA Technology, Inc. GrabBeeX+ Video Encoder + - em2800 + - eb1a:2801 + * - 22 + - EM2710/EM2750/EM2751 webcam grabber + - em2750 + - eb1a:2750, eb1a:2751 + * - 23 + - Huaqi DLCW-130 + - em2750 + - + * - 24 + - D-Link DUB-T210 TV Tuner + - em2820 or em2840 + - 2001:f112 + * - 25 + - Gadmei UTV310 + - em2820 or em2840 + - + * - 26 + - Hercules Smart TV USB 2.0 + - em2820 or em2840 + - + * - 27 + - Pinnacle PCTV USB 2 (Philips FM1216ME) + - em2820 or em2840 + - + * - 28 + - Leadtek Winfast USB II Deluxe + - em2820 or em2840 + - + * - 29 + - EM2860/TVP5150 Reference Design + - em2860 + - eb1a:5051 + * - 30 + - Videology 20K14XUSB USB2.0 + - em2820 or em2840 + - + * - 31 + - Usbgear VD204v9 + - em2821 + - + * - 32 + - Supercomp USB 2.0 TV + - em2821 + - + * - 33 + - Elgato Video Capture + - em2860 + - 0fd9:0033 + * - 34 + - Terratec Cinergy A Hybrid XS + - em2860 + - 0ccd:004f + * - 35 + - Typhoon DVD Maker + - em2860 + - + * - 36 + - NetGMBH Cam + - em2860 + - + * - 37 + - Gadmei UTV330 + - em2860 + - eb1a:50a6 + * - 38 + - Yakumo MovieMixer + - em2861 + - + * - 39 + - KWorld PVRTV 300U + - em2861 + - eb1a:e300 + * - 40 + - Plextor ConvertX PX-TV100U + - em2861 + - 093b:a005 + * - 41 + - Kworld 350 U DVB-T + - em2870 + - eb1a:e350 + * - 42 + - Kworld 355 U DVB-T + - em2870 + - eb1a:e355, eb1a:e357, eb1a:e359 + * - 43 + - Terratec Cinergy T XS + - em2870 + - + * - 44 + - Terratec Cinergy T XS (MT2060) + - em2870 + - 0ccd:0043 + * - 45 + - Pinnacle PCTV DVB-T + - em2870 + - + * - 46 + - Compro, VideoMate U3 + - em2870 + - 185b:2870 + * - 47 + - KWorld DVB-T 305U + - em2880 + - eb1a:e305 + * - 48 + - KWorld DVB-T 310U + - em2880 + - + * - 49 + - MSI DigiVox A/D + - em2880 + - eb1a:e310 + * - 50 + - MSI DigiVox A/D II + - em2880 + - eb1a:e320 + * - 51 + - Terratec Hybrid XS Secam + - em2880 + - 0ccd:004c + * - 52 + - DNT DA2 Hybrid + - em2881 + - + * - 53 + - Pinnacle Hybrid Pro + - em2881 + - + * - 54 + - Kworld VS-DVB-T 323UR + - em2882 + - eb1a:e323 + * - 55 + - Terratec Cinergy Hybrid T USB XS (em2882) + - em2882 + - 0ccd:005e, 0ccd:0042 + * - 56 + - Pinnacle Hybrid Pro (330e) + - em2882 + - 2304:0226 + * - 57 + - Kworld PlusTV HD Hybrid 330 + - em2883 + - eb1a:a316 + * - 58 + - Compro VideoMate ForYou/Stereo + - em2820 or em2840 + - 185b:2041 + * - 59 + - Pinnacle PCTV HD Mini + - em2874 + - 2304:023f + * - 60 + - Hauppauge WinTV HVR 850 + - em2883 + - 2040:651f + * - 61 + - Pixelview PlayTV Box 4 USB 2.0 + - em2820 or em2840 + - + * - 62 + - Gadmei TVR200 + - em2820 or em2840 + - + * - 63 + - Kaiomy TVnPC U2 + - em2860 + - eb1a:e303 + * - 64 + - Easy Cap Capture DC-60 + - em2860 + - 1b80:e309 + * - 65 + - IO-DATA GV-MVP/SZ + - em2820 or em2840 + - 04bb:0515 + * - 66 + - Empire dual TV + - em2880 + - + * - 67 + - Terratec Grabby + - em2860 + - 0ccd:0096, 0ccd:10AF + * - 68 + - Terratec AV350 + - em2860 + - 0ccd:0084 + * - 69 + - KWorld ATSC 315U HDTV TV Box + - em2882 + - eb1a:a313 + * - 70 + - Evga inDtube + - em2882 + - + * - 71 + - Silvercrest Webcam 1.3mpix + - em2820 or em2840 + - + * - 72 + - Gadmei UTV330+ + - em2861 + - + * - 73 + - Reddo DVB-C USB TV Box + - em2870 + - + * - 74 + - Actionmaster/LinXcel/Digitus VC211A + - em2800 + - + * - 75 + - Dikom DK300 + - em2882 + - + * - 76 + - KWorld PlusTV 340U or UB435-Q (ATSC) + - em2870 + - 1b80:a340 + * - 77 + - EM2874 Leadership ISDBT + - em2874 + - + * - 78 + - PCTV nanoStick T2 290e + - em28174 + - 2013:024f + * - 79 + - Terratec Cinergy H5 + - em2884 + - eb1a:2885, 0ccd:10a2, 0ccd:10ad, 0ccd:10b6 + * - 80 + - PCTV DVB-S2 Stick (460e) + - em28174 + - 2013:024c + * - 81 + - Hauppauge WinTV HVR 930C + - em2884 + - 2040:1605 + * - 82 + - Terratec Cinergy HTC Stick + - em2884 + - 0ccd:00b2 + * - 83 + - Honestech Vidbox NW03 + - em2860 + - eb1a:5006 + * - 84 + - MaxMedia UB425-TC + - em2874 + - 1b80:e425 + * - 85 + - PCTV QuatroStick (510e) + - em2884 + - 2304:0242 + * - 86 + - PCTV QuatroStick nano (520e) + - em2884 + - 2013:0251 + * - 87 + - Terratec Cinergy HTC USB XS + - em2884 + - 0ccd:008e, 0ccd:00ac + * - 88 + - C3 Tech Digital Duo HDTV/SDTV USB + - em2884 + - 1b80:e755 + * - 89 + - Delock 61959 + - em2874 + - 1b80:e1cc + * - 90 + - KWorld USB ATSC TV Stick UB435-Q V2 + - em2874 + - 1b80:e346 + * - 91 + - SpeedLink Vicious And Devine Laplace webcam + - em2765 + - 1ae7:9003, 1ae7:9004 + * - 92 + - PCTV DVB-S2 Stick (461e) + - em28178 + - 2013:0258 + * - 93 + - KWorld USB ATSC TV Stick UB435-Q V3 + - em2874 + - 1b80:e34c + * - 94 + - PCTV tripleStick (292e) + - em28178 + - 2013:025f, 2013:0264, 2040:0264, 2040:8264, 2040:8268 + * - 95 + - Leadtek VC100 + - em2861 + - 0413:6f07 + * - 96 + - Terratec Cinergy T2 Stick HD + - em28178 + - eb1a:8179 + * - 97 + - Elgato EyeTV Hybrid 2008 INT + - em2884 + - 0fd9:0018 + * - 98 + - PLEX PX-BCUD + - em28178 + - 3275:0085 + * - 99 + - Hauppauge WinTV-dualHD DVB + - em28174 + - 2040:0265, 2040:8265 + * - 100 + - Hauppauge WinTV-dualHD 01595 ATSC/QAM + - em28174 + - 2040:026d, 2040:826d + * - 101 + - Terratec Cinergy H6 rev. 2 + - em2884 + - 0ccd:10b2 + * - 102 + - :ZOLID HYBRID TV STICK + - em2882 + - + * - 103 + - Magix USB Videowandler-2 + - em2861 + - 1b80:e349 + * - 104 + - PCTV DVB-S2 Stick (461e v2) + - em28178 + - 2013:0461, 2013:0259 + * - 105 + - MyGica iGrabber + - em2860 + - 1f4d:1abe diff --git a/Documentation/admin-guide/media/faq.rst b/Documentation/admin-guide/media/faq.rst new file mode 100644 index 000000000..b63548b6f --- /dev/null +++ b/Documentation/admin-guide/media/faq.rst @@ -0,0 +1,216 @@ +.. SPDX-License-Identifier: GPL-2.0 + +FAQ +=== + +.. note:: + + 1. With Digital TV, a single physical channel may have different + contents inside it. The specs call each one as a *service*. + This is what a TV user would call "channel". So, in order to + avoid confusion, we're calling *transponders* as the physical + channel on this FAQ, and *services* for the logical channel. + 2. The LinuxTV community maintains some Wiki pages with contain + a lot of information related to the media subsystem. If you + don't find an answer for your needs here, it is likely that + you'll be able to get something useful there. It is hosted + at: + + https://www.linuxtv.org/wiki/ + +Some very frequently asked questions about Linux Digital TV support + +1. The signal seems to die a few seconds after tuning. + + It's not a bug, it's a feature. Because the frontends have + significant power requirements (and hence get very hot), they + are powered down if they are unused (i.e. if the frontend device + is closed). The ``dvb-core`` module parameter ``dvb_shutdown_timeout`` + allow you to change the timeout (default 5 seconds). Setting the + timeout to 0 disables the timeout feature. + +2. How can I watch TV? + + Together with the Linux Kernel, the Digital TV developers support + some simple utilities which are mainly intended for testing + and to demonstrate how the DVB API works. This is called DVB v5 + tools and are grouped together with the ``v4l-utils`` git repository: + + https://git.linuxtv.org/v4l-utils.git/ + + You can find more information at the LinuxTV wiki: + + https://www.linuxtv.org/wiki/index.php/DVBv5_Tools + + The first step is to get a list of services that are transmitted. + + This is done by using several existing tools. You can use + for example the ``dvbv5-scan`` tool. You can find more information + about it at: + + https://www.linuxtv.org/wiki/index.php/Dvbv5-scan + + There are some other applications like ``w_scan`` [#]_ that do a + blind scan, trying hard to find all possible channels, but + those consumes a large amount of time to run. + + .. [#] https://www.linuxtv.org/wiki/index.php/W_scan + + Also, some applications like ``kaffeine`` have their own code + to scan for services. So, you don't need to use an external + application to obtain such list. + + Most of such tools need a file containing a list of channel + transponders available on your area. So, LinuxTV developers + maintain tables of Digital TV channel transponders, receiving + patches from the community to keep them updated. + + This list is hosted at: + + https://git.linuxtv.org/dtv-scan-tables.git + + And packaged on several distributions. + + Kaffeine has some blind scan support for some terrestrial standards. + It also relies on DTV scan tables, although it contains a copy + of it internally (and, if requested by the user, it will download + newer versions of it). + + If you are lucky you can just use one of the supplied channel + transponders. If not, you may need to seek for such info at + the Internet and create a new file. There are several sites with + contains physical channel lists. For cable and satellite, usually + knowing how to tune into a single channel is enough for the + scanning tool to identify the other channels. On some places, + this could also work for terrestrial transmissions. + + Once you have a transponders list, you need to generate a services + list with a tool like ``dvbv5-scan``. + + Almost all modern Digital TV cards don't have built-in hardware + MPEG-decoders. So, it is up to the application to get a MPEG-TS + stream provided by the board, split it into audio, video and other + data and decode. + +3. Which Digital TV applications exist? + + Several media player applications are capable of tuning into + digital TV channels, including Kaffeine, Vlc, mplayer and MythTV. + + Kaffeine aims to be very user-friendly, and it is maintained + by one of the Kernel driver developers. + + A comprehensive list of those and other apps can be found at: + + https://www.linuxtv.org/wiki/index.php/TV_Related_Software + + Some of the most popular ones are linked below: + + https://kde.org/applications/multimedia/org.kde.kaffeine + KDE media player, focused on Digital TV support + + https://www.linuxtv.org/vdrwiki/index.php/Main_Page + Klaus Schmidinger's Video Disk Recorder + + https://linuxtv.org/downloads and https://git.linuxtv.org/ + Digital TV and other media-related applications and + Kernel drivers. The ``v4l-utils`` package there contains + several swiss knife tools for using with Digital TV. + + http://sourceforge.net/projects/dvbtools/ + Dave Chapman's dvbtools package, including + dvbstream and dvbtune + + http://www.dbox2.info/ + LinuxDVB on the dBox2 + + http://www.tuxbox.org/ + the TuxBox CVS many interesting DVB applications and the dBox2 + DVB source + + http://www.nenie.org/misc/mpsys/ + MPSYS: a MPEG2 system library and tools + + https://www.videolan.org/vlc/index.pt.html + Vlc + + http://mplayerhq.hu/ + MPlayer + + http://xine.sourceforge.net/ and http://xinehq.de/ + Xine + + http://www.mythtv.org/ + MythTV - analog TV and digital TV PVR + + http://dvbsnoop.sourceforge.net/ + DVB sniffer program to monitor, analyze, debug, dump + or view dvb/mpeg/dsm-cc/mhp stream information (TS, + PES, SECTION) + +4. Can't get a signal tuned correctly + + That could be due to a lot of problems. On my personal experience, + usually TV cards need stronger signals than TV sets, and are more + sensitive to noise. So, perhaps you just need a better antenna or + cabling. Yet, it could also be some hardware or driver issue. + + For example, if you are using a Technotrend/Hauppauge DVB-C card + *without* analog module, you might have to use module parameter + adac=-1 (dvb-ttpci.o). + + Please see the FAQ page at linuxtv.org, as it could contain some + valuable information: + + https://www.linuxtv.org/wiki/index.php/FAQ_%26_Troubleshooting + + If that doesn't work, check at the linux-media ML archives, to + see if someone else had a similar problem with your hardware + and/or digital TV service provider: + + https://lore.kernel.org/linux-media/ + + If none of this works, you can try sending an e-mail to the + linux-media ML and see if someone else could shed some light. + The e-mail is linux-media AT vger.kernel.org. + +5. The dvb_net device doesn't give me any packets at all + + Run ``tcpdump`` on the ``dvb0_0`` interface. This sets the interface + into promiscuous mode so it accepts any packets from the PID + you have configured with the ``dvbnet`` utility. Check if there + are any packets with the IP addr and MAC addr you have + configured with ``ifconfig`` or with ``ip addr``. + + If ``tcpdump`` doesn't give you any output, check the statistics + which ``ifconfig`` or ``netstat -ni`` outputs. (Note: If the MAC + address is wrong, ``dvb_net`` won't get any input; thus you have to + run ``tcpdump`` before checking the statistics.) If there are no + packets at all then maybe the PID is wrong. If there are error packets, + then either the PID is wrong or the stream does not conform to + the MPE standard (EN 301 192, http://www.etsi.org/). You can + use e.g. ``dvbsnoop`` for debugging. + +6. The ``dvb_net`` device doesn't give me any multicast packets + + Check your routes if they include the multicast address range. + Additionally make sure that "source validation by reversed path + lookup" is disabled:: + + $ "echo 0 > /proc/sys/net/ipv4/conf/dvb0/rp_filter" + +7. What are all those modules that need to be loaded? + + In order to make it more flexible and support different hardware + combinations, the media subsystem is written on a modular way. + + So, besides the Digital TV hardware module for the main chipset, + it also needs to load a frontend driver, plus the Digital TV + core. If the board also has remote controller, it will also + need the remote controller core and the remote controller tables. + The same happens if the board has support for analog TV: the + core support for video4linux need to be loaded. + + The actual module names are Linux-kernel version specific, as, + from time to time, things change, in order to make the media + support more flexible. diff --git a/Documentation/admin-guide/media/fimc.rst b/Documentation/admin-guide/media/fimc.rst new file mode 100644 index 000000000..267ef52fe --- /dev/null +++ b/Documentation/admin-guide/media/fimc.rst @@ -0,0 +1,153 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. include:: <isonum.txt> + +The Samsung S5P/Exynos4 FIMC driver +=================================== + +Copyright |copy| 2012 - 2013 Samsung Electronics Co., Ltd. + +The FIMC (Fully Interactive Mobile Camera) device available in Samsung +SoC Application Processors is an integrated camera host interface, color +space converter, image resizer and rotator. It's also capable of capturing +data from LCD controller (FIMD) through the SoC internal writeback data +path. There are multiple FIMC instances in the SoCs (up to 4), having +slightly different capabilities, like pixel alignment constraints, rotator +availability, LCD writeback support, etc. The driver is located at +drivers/media/platform/samsung/exynos4-is directory. + +Supported SoCs +-------------- + +S5PC100 (mem-to-mem only), S5PV210, Exynos4210 + +Supported features +------------------ + +- camera parallel interface capture (ITU-R.BT601/565); +- camera serial interface capture (MIPI-CSI2); +- memory-to-memory processing (color space conversion, scaling, mirror + and rotation); +- dynamic pipeline re-configuration at runtime (re-attachment of any FIMC + instance to any parallel video input or any MIPI-CSI front-end); +- runtime PM and system wide suspend/resume + +Not currently supported +----------------------- + +- LCD writeback input +- per frame clock gating (mem-to-mem) + +User space interfaces +--------------------- + +Media device interface +~~~~~~~~~~~~~~~~~~~~~~ + +The driver supports Media Controller API as defined at :ref:`media_controller`. +The media device driver name is "Samsung S5P FIMC". + +The purpose of this interface is to allow changing assignment of FIMC instances +to the SoC peripheral camera input at runtime and optionally to control internal +connections of the MIPI-CSIS device(s) to the FIMC entities. + +The media device interface allows to configure the SoC for capturing image +data from the sensor through more than one FIMC instance (e.g. for simultaneous +viewfinder and still capture setup). + +Reconfiguration is done by enabling/disabling media links created by the driver +during initialization. The internal device topology can be easily discovered +through media entity and links enumeration. + +Memory-to-memory video node +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +V4L2 memory-to-memory interface at /dev/video? device node. This is standalone +video device, it has no media pads. However please note the mem-to-mem and +capture video node operation on same FIMC instance is not allowed. The driver +detects such cases but the applications should prevent them to avoid an +undefined behaviour. + +Capture video node +~~~~~~~~~~~~~~~~~~ + +The driver supports V4L2 Video Capture Interface as defined at +:ref:`devices`. + +At the capture and mem-to-mem video nodes only the multi-planar API is +supported. For more details see: :ref:`planar-apis`. + +Camera capture subdevs +~~~~~~~~~~~~~~~~~~~~~~ + +Each FIMC instance exports a sub-device node (/dev/v4l-subdev?), a sub-device +node is also created per each available and enabled at the platform level +MIPI-CSI receiver device (currently up to two). + +sysfs +~~~~~ + +In order to enable more precise camera pipeline control through the sub-device +API the driver creates a sysfs entry associated with "s5p-fimc-md" platform +device. The entry path is: /sys/platform/devices/s5p-fimc-md/subdev_conf_mode. + +In typical use case there could be a following capture pipeline configuration: +sensor subdev -> mipi-csi subdev -> fimc subdev -> video node + +When we configure these devices through sub-device API at user space, the +configuration flow must be from left to right, and the video node is +configured as last one. + +When we don't use sub-device user space API the whole configuration of all +devices belonging to the pipeline is done at the video node driver. +The sysfs entry allows to instruct the capture node driver not to configure +the sub-devices (format, crop), to avoid resetting the subdevs' configuration +when the last configuration steps at the video node is performed. + +For full sub-device control support (subdevs configured at user space before +starting streaming): + +.. code-block:: none + + # echo "sub-dev" > /sys/platform/devices/s5p-fimc-md/subdev_conf_mode + +For V4L2 video node control only (subdevs configured internally by the host +driver): + +.. code-block:: none + + # echo "vid-dev" > /sys/platform/devices/s5p-fimc-md/subdev_conf_mode + +This is a default option. + +5. Device mapping to video and subdev device nodes +-------------------------------------------------- + +There are associated two video device nodes with each device instance in +hardware - video capture and mem-to-mem and additionally a subdev node for +more precise FIMC capture subsystem control. In addition a separate v4l2 +sub-device node is created per each MIPI-CSIS device. + +How to find out which /dev/video? or /dev/v4l-subdev? is assigned to which +device? + +You can either grep through the kernel log to find relevant information, i.e. + +.. code-block:: none + + # dmesg | grep -i fimc + +(note that udev, if present, might still have rearranged the video nodes), + +or retrieve the information from /dev/media? with help of the media-ctl tool: + +.. code-block:: none + + # media-ctl -p + +7. Build +-------- + +If the driver is built as a loadable kernel module (CONFIG_VIDEO_SAMSUNG_S5P_FIMC=m) +two modules are created (in addition to the core v4l2 modules): s5p-fimc.ko and +optional s5p-csis.ko (MIPI-CSI receiver subdev). diff --git a/Documentation/admin-guide/media/frontend-cardlist.rst b/Documentation/admin-guide/media/frontend-cardlist.rst new file mode 100644 index 000000000..ba5b7c69a --- /dev/null +++ b/Documentation/admin-guide/media/frontend-cardlist.rst @@ -0,0 +1,226 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================ +Frontend drivers +================ + +.. note:: + + #) There is no guarantee that every frontend driver works + out of the box with every card, because of different wiring. + + #) The demodulator chips can be used with a variety of + tuner/PLL chips, and not all combinations are supported. Often + the demodulator and tuner/PLL chip are inside a metal box for + shielding, and the whole metal box has its own part number. + + +Common Interface (EN50221) controller drivers +============================================= + +============== ========================================================= +Driver Name +============== ========================================================= +cxd2099 Sony CXD2099AR Common Interface driver +sp2 CIMaX SP2 +============== ========================================================= + +ATSC (North American/Korean Terrestrial/Cable DTV) frontends +============================================================ + +============== ========================================================= +Driver Name +============== ========================================================= +au8522_dig Auvitek AU8522 based DTV demod +au8522_decoder Auvitek AU8522 based ATV demod +bcm3510 Broadcom BCM3510 +lg2160 LG Electronics LG216x based +lgdt3305 LG Electronics LGDT3304 and LGDT3305 based +lgdt3306a LG Electronics LGDT3306A based +lgdt330x LG Electronics LGDT3302/LGDT3303 based +nxt200x NxtWave Communications NXT2002/NXT2004 based +or51132 Oren OR51132 based +or51211 Oren OR51211 based +s5h1409 Samsung S5H1409 based +s5h1411 Samsung S5H1411 based +============== ========================================================= + +DVB-C (cable) frontends +======================= + +============== ========================================================= +Driver Name +============== ========================================================= +stv0297 ST STV0297 based +tda10021 Philips TDA10021 based +tda10023 Philips TDA10023 based +ves1820 VLSI VES1820 based +============== ========================================================= + +DVB-S (satellite) frontends +=========================== + +============== ========================================================= +Driver Name +============== ========================================================= +cx24110 Conexant CX24110 based +cx24116 Conexant CX24116 based +cx24117 Conexant CX24117 based +cx24120 Conexant CX24120 based +cx24123 Conexant CX24123 based +ds3000 Montage Technology DS3000 based +mb86a16 Fujitsu MB86A16 based +mt312 Zarlink VP310/MT312/ZL10313 based +s5h1420 Samsung S5H1420 based +si21xx Silicon Labs SI21XX based +stb6000 ST STB6000 silicon tuner +stv0288 ST STV0288 based +stv0299 ST STV0299 based +stv0900 ST STV0900 based +stv6110 ST STV6110 silicon tuner +tda10071 NXP TDA10071 +tda10086 Philips TDA10086 based +tda8083 Philips TDA8083 based +tda8261 Philips TDA8261 based +tda826x Philips TDA826X silicon tuner +ts2020 Montage Technology TS2020 based tuners +tua6100 Infineon TUA6100 PLL +cx24113 Conexant CX24113/CX24128 tuner for DVB-S/DSS +itd1000 Integrant ITD1000 Zero IF tuner for DVB-S/DSS +ves1x93 VLSI VES1893 or VES1993 based +zl10036 Zarlink ZL10036 silicon tuner +zl10039 Zarlink ZL10039 silicon tuner +============== ========================================================= + +DVB-T (terrestrial) frontends +============================= + +============== ========================================================= +Driver Name +============== ========================================================= +af9013 Afatech AF9013 demodulator +cx22700 Conexant CX22700 based +cx22702 Conexant cx22702 demodulator (OFDM) +cxd2820r Sony CXD2820R +cxd2841er Sony CXD2841ER +cxd2880 Sony CXD2880 DVB-T2/T tuner + demodulator +dib3000mb DiBcom 3000M-B +dib3000mc DiBcom 3000P/M-C +dib7000m DiBcom 7000MA/MB/PA/PB/MC +dib7000p DiBcom 7000PC +dib9000 DiBcom 9000 +drxd Micronas DRXD driver +ec100 E3C EC100 +l64781 LSI L64781 +mt352 Zarlink MT352 based +nxt6000 NxtWave Communications NXT6000 based +rtl2830 Realtek RTL2830 DVB-T +rtl2832 Realtek RTL2832 DVB-T +rtl2832_sdr Realtek RTL2832 SDR +s5h1432 Samsung s5h1432 demodulator (OFDM) +si2168 Silicon Labs Si2168 +sp8870 Spase sp8870 based +sp887x Spase sp887x based +stv0367 ST STV0367 based +tda10048 Philips TDA10048HN based +tda1004x Philips TDA10045H/TDA10046H based +zd1301_demod ZyDAS ZD1301 +zl10353 Zarlink ZL10353 based +============== ========================================================= + +Digital terrestrial only tuners/PLL +=================================== + +============== ========================================================= +Driver Name +============== ========================================================= +dvb-pll Generic I2C PLL based tuners +dib0070 DiBcom DiB0070 silicon base-band tuner +dib0090 DiBcom DiB0090 silicon base-band tuner +============== ========================================================= + +ISDB-S (satellite) & ISDB-T (terrestrial) frontends +=================================================== + +============== ========================================================= +Driver Name +============== ========================================================= +mn88443x Socionext MN88443x +tc90522 Toshiba TC90522 +============== ========================================================= + +ISDB-T (terrestrial) frontends +============================== + +============== ========================================================= +Driver Name +============== ========================================================= +dib8000 DiBcom 8000MB/MC +mb86a20s Fujitsu mb86a20s +s921 Sharp S921 frontend +============== ========================================================= + +Multistandard (cable + terrestrial) frontends +============================================= + +============== ========================================================= +Driver Name +============== ========================================================= +drxk Micronas DRXK based +mn88472 Panasonic MN88472 +mn88473 Panasonic MN88473 +si2165 Silicon Labs si2165 based +tda18271c2dd NXP TDA18271C2 silicon tuner +============== ========================================================= + +Multistandard (satellite) frontends +=================================== + +============== ========================================================= +Driver Name +============== ========================================================= +m88ds3103 Montage Technology M88DS3103 +mxl5xx MaxLinear MxL5xx based tuner-demodulators +stb0899 STB0899 based +stb6100 STB6100 based tuners +stv090x STV0900/STV0903(A/B) based +stv0910 STV0910 based +stv6110x STV6110/(A) based tuners +stv6111 STV6111 based tuners +============== ========================================================= + +SEC control devices for DVB-S +============================= + +============== ========================================================= +Driver Name +============== ========================================================= +a8293 Allegro A8293 +af9033 Afatech AF9033 DVB-T demodulator +ascot2e Sony Ascot2E tuner +atbm8830 AltoBeam ATBM8830/8831 DMB-TH demodulator +drx39xyj Micronas DRX-J demodulator +helene Sony HELENE Sat/Ter tuner (CXD2858ER) +horus3a Sony Horus3A tuner +isl6405 ISL6405 SEC controller +isl6421 ISL6421 SEC controller +isl6423 ISL6423 SEC controller +ix2505v Sharp IX2505V silicon tuner +lgs8gl5 Silicon Legend LGS-8GL5 demodulator (OFDM) +lgs8gxx Legend Silicon LGS8913/LGS8GL5/LGS8GXX DMB-TH demodulator +lnbh25 LNBH25 SEC controller +lnbh29 LNBH29 SEC controller +lnbp21 LNBP21/LNBH24 SEC controllers +lnbp22 LNBP22 SEC controllers +m88rs2000 M88RS2000 DVB-S demodulator and tuner +tda665x TDA665x tuner +============== ========================================================= + +Tools to develop new frontends +============================== + +============== ========================================================= +Driver Name +============== ========================================================= +dvb_dummy_fe Dummy frontend driver +============== ========================================================= diff --git a/Documentation/admin-guide/media/gspca-cardlist.rst b/Documentation/admin-guide/media/gspca-cardlist.rst new file mode 100644 index 000000000..e3404d158 --- /dev/null +++ b/Documentation/admin-guide/media/gspca-cardlist.rst @@ -0,0 +1,451 @@ +.. SPDX-License-Identifier: GPL-2.0 + +The gspca cards list +==================== + +The modules for the gspca webcam drivers are: + +- gspca_main: main driver +- gspca\_\ *driver*: subdriver module with *driver* as follows + +========= ========= =================================================================== +*driver* vend:prod Device +========= ========= =================================================================== +spca501 0000:0000 MystFromOri Unknown Camera +spca508 0130:0130 Clone Digital Webcam 11043 +se401 03e8:0004 Endpoints/AoxSE401 +zc3xx 03f0:1b07 HP Premium Starter Cam +m5602 0402:5602 ALi Video Camera Controller +spca501 040a:0002 Kodak DVC-325 +spca500 040a:0300 Kodak EZ200 +zc3xx 041e:041e Creative WebCam Live! +ov519 041e:4003 Video Blaster WebCam Go Plus +stv0680 041e:4007 Go Mini +spca500 041e:400a Creative PC-CAM 300 +sunplus 041e:400b Creative PC-CAM 600 +sunplus 041e:4012 PC-Cam350 +sunplus 041e:4013 Creative Pccam750 +zc3xx 041e:4017 Creative Webcam Mobile PD1090 +spca508 041e:4018 Creative Webcam Vista (PD1100) +spca561 041e:401a Creative Webcam Vista (PD1100) +zc3xx 041e:401c Creative NX +spca505 041e:401d Creative Webcam NX ULTRA +zc3xx 041e:401e Creative Nx Pro +zc3xx 041e:401f Creative Webcam Notebook PD1171 +zc3xx 041e:4022 Webcam NX Pro +pac207 041e:4028 Creative Webcam Vista Plus +zc3xx 041e:4029 Creative WebCam Vista Pro +zc3xx 041e:4034 Creative Instant P0620 +zc3xx 041e:4035 Creative Instant P0620D +zc3xx 041e:4036 Creative Live ! +sq930x 041e:4038 Creative Joy-IT +zc3xx 041e:403a Creative Nx Pro 2 +spca561 041e:403b Creative Webcam Vista (VF0010) +sq930x 041e:403c Creative Live! Ultra +sq930x 041e:403d Creative Live! Ultra for Notebooks +sq930x 041e:4041 Creative Live! Motion +zc3xx 041e:4051 Creative Live!Cam Notebook Pro (VF0250) +ov519 041e:4052 Creative Live! VISTA IM +zc3xx 041e:4053 Creative Live!Cam Video IM +vc032x 041e:405b Creative Live! Cam Notebook Ultra (VC0130) +ov519 041e:405f Creative Live! VISTA VF0330 +ov519 041e:4060 Creative Live! VISTA VF0350 +ov519 041e:4061 Creative Live! VISTA VF0400 +ov519 041e:4064 Creative Live! VISTA VF0420 +ov519 041e:4067 Creative Live! Cam Video IM (VF0350) +ov519 041e:4068 Creative Live! VISTA VF0470 +sn9c2028 0458:7003 GeniusVideocam Live v2 +spca561 0458:7004 Genius VideoCAM Express V2 +sn9c2028 0458:7005 Genius Smart 300, version 2 +sunplus 0458:7006 Genius Dsc 1.3 Smart +zc3xx 0458:7007 Genius VideoCam V2 +zc3xx 0458:700c Genius VideoCam V3 +zc3xx 0458:700f Genius VideoCam Web V2 +sonixj 0458:7025 Genius Eye 311Q +sn9c20x 0458:7029 Genius Look 320s +sonixj 0458:702e Genius Slim 310 NB +sn9c20x 0458:7045 Genius Look 1320 V2 +sn9c20x 0458:704a Genius Slim 1320 +sn9c20x 0458:704c Genius i-Look 1321 +sn9c20x 045e:00f4 LifeCam VX-6000 (SN9C20x + OV9650) +sonixj 045e:00f5 MicroSoft VX3000 +sonixj 045e:00f7 MicroSoft VX1000 +ov519 045e:028c Micro$oft xbox cam +kinect 045e:02ae Xbox NUI Camera +kinect 045e:02bf Kinect for Windows NUI Camera +spca561 0461:0815 Micro Innovations IC200 Webcam +sunplus 0461:0821 Fujifilm MV-1 +zc3xx 0461:0a00 MicroInnovation WebCam320 +stv06xx 046D:08F0 QuickCamMessenger +stv06xx 046D:08F5 QuickCamCommunicate +stv06xx 046D:08F6 QuickCamMessenger (new) +stv06xx 046d:0840 QuickCamExpress +stv06xx 046d:0850 LEGOcam / QuickCam Web +stv06xx 046d:0870 DexxaWebCam USB +spca500 046d:0890 Logitech QuickCam traveler +vc032x 046d:0892 Logitech Orbicam +vc032x 046d:0896 Logitech Orbicam +vc032x 046d:0897 Logitech QuickCam for Dell notebooks +zc3xx 046d:089d Logitech QuickCam E2500 +zc3xx 046d:08a0 Logitech QC IM +zc3xx 046d:08a1 Logitech QC IM 0x08A1 +sound +zc3xx 046d:08a2 Labtec Webcam Pro +zc3xx 046d:08a3 Logitech QC Chat +zc3xx 046d:08a6 Logitech QCim +zc3xx 046d:08a7 Logitech QuickCam Image +zc3xx 046d:08a9 Logitech Notebook Deluxe +zc3xx 046d:08aa Labtec Webcam Notebook +zc3xx 046d:08ac Logitech QuickCam Cool +zc3xx 046d:08ad Logitech QCCommunicate STX +zc3xx 046d:08ae Logitech QuickCam for Notebooks +zc3xx 046d:08af Logitech QuickCam Cool +zc3xx 046d:08b9 Logitech QuickCam Express +zc3xx 046d:08d7 Logitech QCam STX +zc3xx 046d:08d8 Logitech Notebook Deluxe +zc3xx 046d:08d9 Logitech QuickCam IM/Connect +zc3xx 046d:08da Logitech QuickCam Messenger +zc3xx 046d:08dd Logitech QuickCam for Notebooks +spca500 046d:0900 Logitech Inc. ClickSmart 310 +spca500 046d:0901 Logitech Inc. ClickSmart 510 +sunplus 046d:0905 Logitech ClickSmart 820 +tv8532 046d:0920 Logitech QuickCam Express +tv8532 046d:0921 Labtec Webcam +spca561 046d:0928 Logitech QC Express Etch2 +spca561 046d:0929 Labtec Webcam Elch2 +spca561 046d:092a Logitech QC for Notebook +spca561 046d:092b Labtec Webcam Plus +spca561 046d:092c Logitech QC chat Elch2 +spca561 046d:092d Logitech QC Elch2 +spca561 046d:092e Logitech QC Elch2 +spca561 046d:092f Logitech QuickCam Express Plus +sunplus 046d:0960 Logitech ClickSmart 420 +nw80x 046d:d001 Logitech QuickCam Pro (dark focus ring) +se401 0471:030b PhilipsPCVC665K +sunplus 0471:0322 Philips DMVC1300K +zc3xx 0471:0325 Philips SPC 200 NC +zc3xx 0471:0326 Philips SPC 300 NC +sonixj 0471:0327 Philips SPC 600 NC +sonixj 0471:0328 Philips SPC 700 NC +zc3xx 0471:032d Philips SPC 210 NC +zc3xx 0471:032e Philips SPC 315 NC +sonixj 0471:0330 Philips SPC 710 NC +se401 047d:5001 Kensington67014 +se401 047d:5002 Kensington6701(5/7) +se401 047d:5003 Kensington67016 +spca501 0497:c001 Smile International +sunplus 04a5:3003 Benq DC 1300 +sunplus 04a5:3008 Benq DC 1500 +sunplus 04a5:300a Benq DC 3410 +spca500 04a5:300c Benq DC 1016 +benq 04a5:3035 Benq DC E300 +vicam 04c1:009d HomeConnect Webcam [vicam] +konica 04c8:0720 IntelYC 76 +finepix 04cb:0104 Fujifilm FinePix 4800 +finepix 04cb:0109 Fujifilm FinePix A202 +finepix 04cb:010b Fujifilm FinePix A203 +finepix 04cb:010f Fujifilm FinePix A204 +finepix 04cb:0111 Fujifilm FinePix A205 +finepix 04cb:0113 Fujifilm FinePix A210 +finepix 04cb:0115 Fujifilm FinePix A303 +finepix 04cb:0117 Fujifilm FinePix A310 +finepix 04cb:0119 Fujifilm FinePix F401 +finepix 04cb:011b Fujifilm FinePix F402 +finepix 04cb:011d Fujifilm FinePix F410 +finepix 04cb:0121 Fujifilm FinePix F601 +finepix 04cb:0123 Fujifilm FinePix F700 +finepix 04cb:0125 Fujifilm FinePix M603 +finepix 04cb:0127 Fujifilm FinePix S300 +finepix 04cb:0129 Fujifilm FinePix S304 +finepix 04cb:012b Fujifilm FinePix S500 +finepix 04cb:012d Fujifilm FinePix S602 +finepix 04cb:012f Fujifilm FinePix S700 +finepix 04cb:0131 Fujifilm FinePix unknown model +finepix 04cb:013b Fujifilm FinePix unknown model +finepix 04cb:013d Fujifilm FinePix unknown model +finepix 04cb:013f Fujifilm FinePix F420 +sunplus 04f1:1001 JVC GC A50 +spca561 04fc:0561 Flexcam 100 +spca1528 04fc:1528 Sunplus MD80 clone +sunplus 04fc:500c Sunplus CA500C +sunplus 04fc:504a Aiptek Mini PenCam 1.3 +sunplus 04fc:504b Maxell MaxPocket LE 1.3 +sunplus 04fc:5330 Digitrex 2110 +sunplus 04fc:5360 Sunplus Generic +spca500 04fc:7333 PalmPixDC85 +sunplus 04fc:ffff Pure DigitalDakota +nw80x 0502:d001 DVC V6 +spca501 0506:00df 3Com HomeConnect Lite +sunplus 052b:1507 Megapixel 5 Pretec DC-1007 +sunplus 052b:1513 Megapix V4 +sunplus 052b:1803 MegaImage VI +nw80x 052b:d001 EZCam Pro p35u +tv8532 0545:808b Veo Stingray +tv8532 0545:8333 Veo Stingray +sunplus 0546:3155 Polaroid PDC3070 +sunplus 0546:3191 Polaroid Ion 80 +sunplus 0546:3273 Polaroid PDC2030 +touptek 0547:6801 TTUCMOS08000KPB, AS MU800 +dtcs033 0547:7303 Anchor Chips, Inc +ov519 054c:0154 Sonny toy4 +ov519 054c:0155 Sonny toy5 +cpia1 0553:0002 CPIA CPiA (version1) based cameras +stv0680 0553:0202 STV0680 Camera +zc3xx 055f:c005 Mustek Wcam300A +spca500 055f:c200 Mustek Gsmart 300 +sunplus 055f:c211 Kowa Bs888e Microcamera +spca500 055f:c220 Gsmart Mini +sunplus 055f:c230 Mustek Digicam 330K +sunplus 055f:c232 Mustek MDC3500 +sunplus 055f:c360 Mustek DV4000 Mpeg4 +sunplus 055f:c420 Mustek gSmart Mini 2 +sunplus 055f:c430 Mustek Gsmart LCD 2 +sunplus 055f:c440 Mustek DV 3000 +sunplus 055f:c520 Mustek gSmart Mini 3 +sunplus 055f:c530 Mustek Gsmart LCD 3 +sunplus 055f:c540 Gsmart D30 +sunplus 055f:c630 Mustek MDC4000 +sunplus 055f:c650 Mustek MDC5500Z +nw80x 055f:d001 Mustek Wcam 300 mini +zc3xx 055f:d003 Mustek WCam300A +zc3xx 055f:d004 Mustek WCam300 AN +conex 0572:0041 Creative Notebook cx11646 +ov519 05a9:0511 Video Blaster WebCam 3/WebCam Plus, D-Link USB Digital Video Camera +ov519 05a9:0518 Creative WebCam +ov519 05a9:0519 OV519 Microphone +ov519 05a9:0530 OmniVision +ov534_9 05a9:1550 OmniVision VEHO Filmscanner +ov519 05a9:2800 OmniVision SuperCAM +ov519 05a9:4519 Webcam Classic +ov534_9 05a9:8065 OmniVision test kit ov538+ov9712 +ov519 05a9:8519 OmniVision +ov519 05a9:a511 D-Link USB Digital Video Camera +ov519 05a9:a518 D-Link DSB-C310 Webcam +sunplus 05da:1018 Digital Dream Enigma 1.3 +stk014 05e1:0893 Syntek DV4000 +gl860 05e3:0503 Genesys Logic PC Camera +gl860 05e3:f191 Genesys Logic PC Camera +vicam 0602:1001 ViCam Webcam +spca561 060b:a001 Maxell Compact Pc PM3 +zc3xx 0698:2003 CTX M730V built in +topro 06a2:0003 TP6800 PC Camera, CmoX CX0342 webcam +topro 06a2:6810 Creative Qmax +nw80x 06a5:0000 Typhoon Webcam 100 USB +nw80x 06a5:d001 Divio based webcams +nw80x 06a5:d800 Divio Chicony TwinkleCam, Trust SpaceCam +spca500 06bd:0404 Agfa CL20 +spca500 06be:0800 Optimedia +nw80x 06be:d001 EZCam Pro p35u +sunplus 06d6:0031 Trust 610 LCD PowerC@m Zoom +sunplus 06d6:0041 Aashima Technology B.V. +spca506 06e1:a190 ADS Instant VCD +ov534 06f8:3002 Hercules Blog Webcam +ov534_9 06f8:3003 Hercules Dualpix HD Weblog +sonixj 06f8:3004 Hercules Classic Silver +sonixj 06f8:3008 Hercules Deluxe Optical Glass +pac7302 06f8:3009 Hercules Classic Link +pac7302 06f8:301b Hercules Link +nw80x 0728:d001 AVerMedia Camguard +spca508 0733:0110 ViewQuest VQ110 +spca501 0733:0401 Intel Create and Share +spca501 0733:0402 ViewQuest M318B +spca505 0733:0430 Intel PC Camera Pro +sunplus 0733:1311 Digital Dream Epsilon 1.3 +sunplus 0733:1314 Mercury 2.1MEG Deluxe Classic Cam +sunplus 0733:2211 Jenoptik jdc 21 LCD +sunplus 0733:2221 Mercury Digital Pro 3.1p +sunplus 0733:3261 Concord 3045 spca536a +sunplus 0733:3281 Cyberpix S550V +spca506 0734:043b 3DeMon USB Capture aka +cpia1 0813:0001 QX3 camera +ov519 0813:0002 Dual Mode USB Camera Plus +spca500 084d:0003 D-Link DSC-350 +spca500 08ca:0103 Aiptek PocketDV +sunplus 08ca:0104 Aiptek PocketDVII 1.3 +sunplus 08ca:0106 Aiptek Pocket DV3100+ +mr97310a 08ca:0110 Trust Spyc@m 100 +mr97310a 08ca:0111 Aiptek PenCam VGA+ +sunplus 08ca:2008 Aiptek Mini PenCam 2 M +sunplus 08ca:2010 Aiptek PocketCam 3M +sunplus 08ca:2016 Aiptek PocketCam 2 Mega +sunplus 08ca:2018 Aiptek Pencam SD 2M +sunplus 08ca:2020 Aiptek Slim 3000F +sunplus 08ca:2022 Aiptek Slim 3200 +sunplus 08ca:2024 Aiptek DV3500 Mpeg4 +sunplus 08ca:2028 Aiptek PocketCam4M +sunplus 08ca:2040 Aiptek PocketDV4100M +sunplus 08ca:2042 Aiptek PocketDV5100 +sunplus 08ca:2050 Medion MD 41437 +sunplus 08ca:2060 Aiptek PocketDV5300 +tv8532 0923:010f ICM532 cams +mr97310a 093a:010e All known CIF cams with this ID +mr97310a 093a:010f All known VGA cams with this ID +mars 093a:050f Mars-Semi Pc-Camera +pac207 093a:2460 Qtec Webcam 100 +pac207 093a:2461 HP Webcam +pac207 093a:2463 Philips SPC 220 NC +pac207 093a:2464 Labtec Webcam 1200 +pac207 093a:2468 Webcam WB-1400T +pac207 093a:2470 Genius GF112 +pac207 093a:2471 Genius VideoCam ge111 +pac207 093a:2472 Genius VideoCam ge110 +pac207 093a:2474 Genius iLook 111 +pac207 093a:2476 Genius e-Messenger 112 +pac7311 093a:2600 PAC7311 Typhoon +pac7311 093a:2601 Philips SPC 610 NC +pac7311 093a:2603 Philips SPC 500 NC +pac7311 093a:2608 Trust WB-3300p +pac7311 093a:260e Gigaware VGA PC Camera, Trust WB-3350p, SIGMA cam 2350 +pac7311 093a:260f SnakeCam +pac7302 093a:2620 Apollo AC-905 +pac7302 093a:2621 PAC731x +pac7302 093a:2622 Genius Eye 312 +pac7302 093a:2623 Pixart Imaging, Inc. +pac7302 093a:2624 PAC7302 +pac7302 093a:2625 Genius iSlim 310 +pac7302 093a:2626 Labtec 2200 +pac7302 093a:2627 Genius FaceCam 300 +pac7302 093a:2628 Genius iLook 300 +pac7302 093a:2629 Genius iSlim 300 +pac7302 093a:262a Webcam 300k +pac7302 093a:262c Philips SPC 230 NC +jl2005bcd 0979:0227 Various brands, 19 known cameras supported +jeilinj 0979:0270 Sakar 57379 +jeilinj 0979:0280 Sportscam DV15, Sakar 57379 +zc3xx 0ac8:0301 Web Camera +zc3xx 0ac8:0302 Z-star Vimicro zc0302 +vc032x 0ac8:0321 Vimicro generic vc0321 +vc032x 0ac8:0323 Vimicro Vc0323 +vc032x 0ac8:0328 A4Tech PK-130MG +zc3xx 0ac8:301b Z-Star zc301b +zc3xx 0ac8:303b Vimicro 0x303b +zc3xx 0ac8:305b Z-star Vimicro zc0305b +zc3xx 0ac8:307b PC Camera (ZS0211) +vc032x 0ac8:c001 Sony embedded vimicro +vc032x 0ac8:c002 Sony embedded vimicro +vc032x 0ac8:c301 Samsung Q1 Ultra Premium +spca508 0af9:0010 Hama USB Sightcam 100 +spca508 0af9:0011 Hama USB Sightcam 100 +ov519 0b62:0059 iBOT2 Webcam +sonixb 0c45:6001 Genius VideoCAM NB +sonixb 0c45:6005 Microdia Sweex Mini Webcam +sonixb 0c45:6007 Sonix sn9c101 + Tas5110D +sonixb 0c45:6009 spcaCam@120 +sonixb 0c45:600d spcaCam@120 +sonixb 0c45:6011 Microdia PC Camera (SN9C102) +sonixb 0c45:6019 Generic Sonix OV7630 +sonixb 0c45:6024 Generic Sonix Tas5130c +sonixb 0c45:6025 Xcam Shanga +sonixb 0c45:6027 GeniusEye 310 +sonixb 0c45:6028 Sonix Btc Pc380 +sonixb 0c45:6029 spcaCam@150 +sonixb 0c45:602a Meade ETX-105EC Camera +sonixb 0c45:602c Generic Sonix OV7630 +sonixb 0c45:602d LIC-200 LG +sonixb 0c45:602e Genius VideoCam Messenger +sonixj 0c45:6040 Speed NVC 350K +sonixj 0c45:607c Sonix sn9c102p Hv7131R +sonixb 0c45:6083 VideoCAM Look +sonixb 0c45:608c VideoCAM Look +sonixb 0c45:608f PC Camera (SN9C103 + OV7630) +sonixb 0c45:60a8 VideoCAM Look +sonixb 0c45:60aa VideoCAM Look +sonixb 0c45:60af VideoCAM Look +sonixb 0c45:60b0 Genius VideoCam Look +sonixj 0c45:60c0 Sangha Sn535 +sonixj 0c45:60ce USB-PC-Camera-168 (TALK-5067) +sonixj 0c45:60ec SN9C105+MO4000 +sonixj 0c45:60fb Surfer NoName +sonixj 0c45:60fc LG-LIC300 +sonixj 0c45:60fe Microdia Audio +sonixj 0c45:6100 PC Camera (SN9C128) +sonixj 0c45:6102 PC Camera (SN9C128) +sonixj 0c45:610a PC Camera (SN9C128) +sonixj 0c45:610b PC Camera (SN9C128) +sonixj 0c45:610c PC Camera (SN9C128) +sonixj 0c45:610e PC Camera (SN9C128) +sonixj 0c45:6128 Microdia/Sonix SNP325 +sonixj 0c45:612a Avant Camera +sonixj 0c45:612b Speed-Link REFLECT2 +sonixj 0c45:612c Typhoon Rasy Cam 1.3MPix +sonixj 0c45:612e PC Camera (SN9C110) +sonixj 0c45:6130 Sonix Pccam +sonixj 0c45:6138 Sn9c120 Mo4000 +sonixj 0c45:613a Microdia Sonix PC Camera +sonixj 0c45:613b Surfer SN-206 +sonixj 0c45:613c Sonix Pccam168 +sonixj 0c45:613e PC Camera (SN9C120) +sonixj 0c45:6142 Hama PC-Webcam AC-150 +sonixj 0c45:6143 Sonix Pccam168 +sonixj 0c45:6148 Digitus DA-70811/ZSMC USB PC Camera ZS211/Microdia +sonixj 0c45:614a Frontech E-Ccam (JIL-2225) +sn9c20x 0c45:6240 PC Camera (SN9C201 + MT9M001) +sn9c20x 0c45:6242 PC Camera (SN9C201 + MT9M111) +sn9c20x 0c45:6248 PC Camera (SN9C201 + OV9655) +sn9c20x 0c45:624c PC Camera (SN9C201 + MT9M112) +sn9c20x 0c45:624e PC Camera (SN9C201 + SOI968) +sn9c20x 0c45:624f PC Camera (SN9C201 + OV9650) +sn9c20x 0c45:6251 PC Camera (SN9C201 + OV9650) +sn9c20x 0c45:6253 PC Camera (SN9C201 + OV9650) +sn9c20x 0c45:6260 PC Camera (SN9C201 + OV7670) +sn9c20x 0c45:6270 PC Camera (SN9C201 + MT9V011/MT9V111/MT9V112) +sn9c20x 0c45:627b PC Camera (SN9C201 + OV7660) +sn9c20x 0c45:627c PC Camera (SN9C201 + HV7131R) +sn9c20x 0c45:627f PC Camera (SN9C201 + OV9650) +sn9c20x 0c45:6280 PC Camera (SN9C202 + MT9M001) +sn9c20x 0c45:6282 PC Camera (SN9C202 + MT9M111) +sn9c20x 0c45:6288 PC Camera (SN9C202 + OV9655) +sn9c20x 0c45:628c PC Camera (SN9C201 + MT9M112) +sn9c20x 0c45:628e PC Camera (SN9C202 + SOI968) +sn9c20x 0c45:628f PC Camera (SN9C202 + OV9650) +sn9c20x 0c45:62a0 PC Camera (SN9C202 + OV7670) +sn9c20x 0c45:62b0 PC Camera (SN9C202 + MT9V011/MT9V111/MT9V112) +sn9c20x 0c45:62b3 PC Camera (SN9C202 + OV9655) +sn9c20x 0c45:62bb PC Camera (SN9C202 + OV7660) +sn9c20x 0c45:62bc PC Camera (SN9C202 + HV7131R) +sn9c2028 0c45:8001 Wild Planet Digital Spy Camera +sn9c2028 0c45:8003 Sakar #11199, #6637x, #67480 keychain cams +sn9c2028 0c45:8008 Mini-Shotz ms-350 +sn9c2028 0c45:800a Vivitar Vivicam 3350B +sunplus 0d64:0303 Sunplus FashionCam DXG +ov519 0e96:c001 TRUST 380 USB2 SPACEC@M +etoms 102c:6151 Qcam Sangha CIF +etoms 102c:6251 Qcam xxxxxx VGA +ov519 1046:9967 W9967CF/W9968CF WebCam IC, Video Blaster WebCam Go +zc3xx 10fd:0128 Typhoon Webshot II USB 300k 0x0128 +spca561 10fd:7e50 FlyCam Usb 100 +zc3xx 10fd:804d Typhoon Webshot II Webcam [zc0301] +zc3xx 10fd:8050 Typhoon Webshot II USB 300k +ov534 1415:2000 Sony HD Eye for PS3 (SLEH 00201) +pac207 145f:013a Trust WB-1300N +pac7302 145f:013c Trust +sn9c20x 145f:013d Trust WB-3600R +vc032x 15b8:6001 HP 2.0 Megapixel +vc032x 15b8:6002 HP 2.0 Megapixel rz406aa +stk1135 174f:6a31 ASUSlaptop, MT9M112 sensor +spca501 1776:501c Arowana 300K CMOS Camera +t613 17a1:0128 TASCORP JPEG Webcam, NGS Cyclops +vc032x 17ef:4802 Lenovo Vc0323+MI1310_SOC +pac7302 1ae7:2001 SpeedLinkSnappy Mic SL-6825-SBK +pac207 2001:f115 D-Link DSB-C120 +sq905c 2770:9050 Disney pix micro (CIF) +sq905c 2770:9051 Lego Bionicle +sq905c 2770:9052 Disney pix micro 2 (VGA) +sq905c 2770:905c All 11 known cameras with this ID +sq905 2770:9120 All 24 known cameras with this ID +sq905c 2770:913d All 4 known cameras with this ID +sq930x 2770:930b Sweex Motion Tracking / I-Tec iCam Tracer +sq930x 2770:930c Trust WB-3500T / NSG Robbie 2.0 +spca500 2899:012c Toptro Industrial +ov519 8020:ef04 ov519 +spca508 8086:0110 Intel Easy PC Camera +spca500 8086:0630 Intel Pocket PC Camera +spca506 99fa:8988 Grandtec V.cap +sn9c20x a168:0610 Dino-Lite Digital Microscope (SN9C201 + HV7131R) +sn9c20x a168:0611 Dino-Lite Digital Microscope (SN9C201 + HV7131R) +sn9c20x a168:0613 Dino-Lite Digital Microscope (SN9C201 + HV7131R) +sn9c20x a168:0614 Dino-Lite Digital Microscope (SN9C201 + MT9M111) +sn9c20x a168:0615 Dino-Lite Digital Microscope (SN9C201 + MT9M111) +sn9c20x a168:0617 Dino-Lite Digital Microscope (SN9C201 + MT9M111) +sn9c20x a168:0618 Dino-Lite Digital Microscope (SN9C201 + HV7131R) +spca561 abcd:cdee Petcam +========= ========= =================================================================== diff --git a/Documentation/admin-guide/media/i2c-cardlist.rst b/Documentation/admin-guide/media/i2c-cardlist.rst new file mode 100644 index 000000000..1825a0bb4 --- /dev/null +++ b/Documentation/admin-guide/media/i2c-cardlist.rst @@ -0,0 +1,288 @@ +.. SPDX-License-Identifier: GPL-2.0 + +I²C drivers +=========== + +The I²C (Inter-Integrated Circuit) bus is a three-wires bus used internally +at the media cards for communication between different chips. While the bus +is not visible to the Linux Kernel, drivers need to send and receive +commands via the bus. The Linux Kernel driver abstraction has support to +implement different drivers for each component inside an I²C bus, as if +the bus were visible to the main system board. + +One of the problems with I²C devices is that sometimes the same device may +work with different I²C hardware. This is common, for example, on devices +that comes with a tuner for North America market, and another one for +Europe. Some drivers have a ``tuner=`` modprobe parameter to allow using a +different tuner number in order to address such issue. + +The current supported of I²C drivers (not including staging drivers) are +listed below. + +Audio decoders, processors and mixers +------------------------------------- + +============ ========================================================== +Driver Name +============ ========================================================== +cs3308 Cirrus Logic CS3308 audio ADC +cs5345 Cirrus Logic CS5345 audio ADC +cs53l32a Cirrus Logic CS53L32A audio ADC +msp3400 Micronas MSP34xx audio decoders +sony-btf-mpx Sony BTF's internal MPX +tda1997x NXP TDA1997x HDMI receiver +tda7432 Philips TDA7432 audio processor +tda9840 Philips TDA9840 audio processor +tea6415c Philips TEA6415C audio processor +tea6420 Philips TEA6420 audio processor +tlv320aic23b Texas Instruments TLV320AIC23B audio codec +tvaudio Simple audio decoder chips +uda1342 Philips UDA1342 audio codec +vp27smpx Panasonic VP27's internal MPX +wm8739 Wolfson Microelectronics WM8739 stereo audio ADC +wm8775 Wolfson Microelectronics WM8775 audio ADC with input mixer +============ ========================================================== + +Audio/Video compression chips +----------------------------- + +============ ========================================================== +Driver Name +============ ========================================================== +saa6752hs Philips SAA6752HS MPEG-2 Audio/Video Encoder +============ ========================================================== + +Camera sensor devices +--------------------- + +============ ========================================================== +Driver Name +============ ========================================================== +ccs MIPI CCS compliant camera sensors (also SMIA++ and SMIA) +et8ek8 ET8EK8 camera sensor +hi556 Hynix Hi-556 sensor +hi846 Hynix Hi-846 sensor +imx208 Sony IMX208 sensor +imx214 Sony IMX214 sensor +imx219 Sony IMX219 sensor +imx258 Sony IMX258 sensor +imx274 Sony IMX274 sensor +imx290 Sony IMX290 sensor +imx319 Sony IMX319 sensor +imx334 Sony IMX334 sensor +imx355 Sony IMX355 sensor +imx412 Sony IMX412 sensor +mt9m001 mt9m001 +mt9m111 mt9m111, mt9m112 and mt9m131 +mt9p031 Aptina MT9P031 +mt9t112 Aptina MT9T111/MT9T112 +mt9v011 Micron mt9v011 sensor +mt9v032 Micron MT9V032 sensor +mt9v111 Aptina MT9V111 sensor +ov13858 OmniVision OV13858 sensor +ov13b10 OmniVision OV13B10 sensor +ov2640 OmniVision OV2640 sensor +ov2659 OmniVision OV2659 sensor +ov2680 OmniVision OV2680 sensor +ov2685 OmniVision OV2685 sensor +ov5640 OmniVision OV5640 sensor +ov5645 OmniVision OV5645 sensor +ov5647 OmniVision OV5647 sensor +ov5670 OmniVision OV5670 sensor +ov5675 OmniVision OV5675 sensor +ov5695 OmniVision OV5695 sensor +ov6650 OmniVision OV6650 sensor +ov7251 OmniVision OV7251 sensor +ov7640 OmniVision OV7640 sensor +ov7670 OmniVision OV7670 sensor +ov772x OmniVision OV772x sensor +ov7740 OmniVision OV7740 sensor +ov8856 OmniVision OV8856 sensor +ov9640 OmniVision OV9640 sensor +ov9650 OmniVision OV9650/OV9652 sensor +rj54n1cb0c Sharp RJ54N1CB0C sensor +s5c73m3 Samsung S5C73M3 sensor +s5k4ecgx Samsung S5K4ECGX sensor +s5k5baf Samsung S5K5BAF sensor +s5k6a3 Samsung S5K6A3 sensor +============ ========================================================== + +Flash devices +------------- + +============ ========================================================== +Driver Name +============ ========================================================== +adp1653 ADP1653 flash +lm3560 LM3560 dual flash driver +lm3646 LM3646 dual flash driver +============ ========================================================== + +IR I2C driver +------------- + +============ ========================================================== +Driver Name +============ ========================================================== +ir-kbd-i2c I2C module for IR +============ ========================================================== + +Lens drivers +------------ + +============ ========================================================== +Driver Name +============ ========================================================== +ad5820 AD5820 lens voice coil +ak7375 AK7375 lens voice coil +dw9714 DW9714 lens voice coil +dw9768 DW9768 lens voice coil +dw9807-vcm DW9807 lens voice coil +============ ========================================================== + +Miscellaneous helper chips +-------------------------- + +============ ========================================================== +Driver Name +============ ========================================================== +video-i2c I2C transport video +m52790 Mitsubishi M52790 A/V switch +st-mipid02 STMicroelectronics MIPID02 CSI-2 to PARALLEL bridge +ths7303 THS7303/53 Video Amplifier +============ ========================================================== + +RDS decoders +------------ + +============ ========================================================== +Driver Name +============ ========================================================== +saa6588 SAA6588 Radio Chip RDS decoder +============ ========================================================== + +SDR tuner chips +--------------- + +============ ========================================================== +Driver Name +============ ========================================================== +max2175 Maxim 2175 RF to Bits tuner +============ ========================================================== + +Video and audio decoders +------------------------ + +============ ========================================================== +Driver Name +============ ========================================================== +cx25840 Conexant CX2584x audio/video decoders +saa717x Philips SAA7171/3/4 audio/video decoders +============ ========================================================== + +Video decoders +-------------- + +============ ========================================================== +Driver Name +============ ========================================================== +adv7180 Analog Devices ADV7180 decoder +adv7183 Analog Devices ADV7183 decoder +adv748x Analog Devices ADV748x decoder +adv7604 Analog Devices ADV7604 decoder +adv7842 Analog Devices ADV7842 decoder +bt819 BT819A VideoStream decoder +bt856 BT856 VideoStream decoder +bt866 BT866 VideoStream decoder +ks0127 KS0127 video decoder +ml86v7667 OKI ML86V7667 video decoder +saa7110 Philips SAA7110 video decoder +saa7115 Philips SAA7111/3/4/5 video decoders +tc358743 Toshiba TC358743 decoder +tvp514x Texas Instruments TVP514x video decoder +tvp5150 Texas Instruments TVP5150 video decoder +tvp7002 Texas Instruments TVP7002 video decoder +tw2804 Techwell TW2804 multiple video decoder +tw9903 Techwell TW9903 video decoder +tw9906 Techwell TW9906 video decoder +tw9910 Techwell TW9910 video decoder +vpx3220 vpx3220a, vpx3216b & vpx3214c video decoders +============ ========================================================== + +Video encoders +-------------- + +============ ========================================================== +Driver Name +============ ========================================================== +adv7170 Analog Devices ADV7170 video encoder +adv7175 Analog Devices ADV7175 video encoder +adv7343 ADV7343 video encoder +adv7393 ADV7393 video encoder +adv7511-v4l2 Analog Devices ADV7511 encoder +ak881x AK8813/AK8814 video encoders +saa7127 Philips SAA7127/9 digital video encoders +saa7185 Philips SAA7185 video encoder +ths8200 Texas Instruments THS8200 video encoder +============ ========================================================== + +Video improvement chips +----------------------- + +============ ========================================================== +Driver Name +============ ========================================================== +upd64031a NEC Electronics uPD64031A Ghost Reduction +upd64083 NEC Electronics uPD64083 3-Dimensional Y/C separation +============ ========================================================== + +Tuner drivers +------------- + +============ ================================================== +Driver Name +============ ================================================== +e4000 Elonics E4000 silicon tuner +fc0011 Fitipower FC0011 silicon tuner +fc0012 Fitipower FC0012 silicon tuner +fc0013 Fitipower FC0013 silicon tuner +fc2580 FCI FC2580 silicon tuner +it913x ITE Tech IT913x silicon tuner +m88rs6000t Montage M88RS6000 internal tuner +max2165 Maxim MAX2165 silicon tuner +mc44s803 Freescale MC44S803 Low Power CMOS Broadband tuners +msi001 Mirics MSi001 +mt2060 Microtune MT2060 silicon IF tuner +mt2063 Microtune MT2063 silicon IF tuner +mt20xx Microtune 2032 / 2050 tuners +mt2131 Microtune MT2131 silicon tuner +mt2266 Microtune MT2266 silicon tuner +mxl301rf MaxLinear MxL301RF tuner +mxl5005s MaxLinear MSL5005S silicon tuner +mxl5007t MaxLinear MxL5007T silicon tuner +qm1d1b0004 Sharp QM1D1B0004 tuner +qm1d1c0042 Sharp QM1D1C0042 tuner +qt1010 Quantek QT1010 silicon tuner +r820t Rafael Micro R820T silicon tuner +si2157 Silicon Labs Si2157 silicon tuner +tuner-types Simple tuner support +tda18212 NXP TDA18212 silicon tuner +tda18218 NXP TDA18218 silicon tuner +tda18250 NXP TDA18250 silicon tuner +tda18271 NXP TDA18271 silicon tuner +tda827x Philips TDA827X silicon tuner +tda8290 TDA 8290/8295 + 8275(a)/18271 tuner combo +tda9887 TDA 9885/6/7 analog IF demodulator +tea5761 TEA 5761 radio tuner +tea5767 TEA 5767 radio tuner +tua9001 Infineon TUA9001 silicon tuner +xc2028 XCeive xc2028/xc3028 tuners +xc4000 Xceive XC4000 silicon tuner +xc5000 Xceive XC5000 silicon tuner +============ ================================================== + +.. toctree:: + :maxdepth: 1 + + tuner-cardlist + frontend-cardlist diff --git a/Documentation/admin-guide/media/imx.rst b/Documentation/admin-guide/media/imx.rst new file mode 100644 index 000000000..b8fa70f85 --- /dev/null +++ b/Documentation/admin-guide/media/imx.rst @@ -0,0 +1,714 @@ +.. SPDX-License-Identifier: GPL-2.0 + +i.MX Video Capture Driver +========================= + +Introduction +------------ + +The Freescale i.MX5/6 contains an Image Processing Unit (IPU), which +handles the flow of image frames to and from capture devices and +display devices. + +For image capture, the IPU contains the following internal subunits: + +- Image DMA Controller (IDMAC) +- Camera Serial Interface (CSI) +- Image Converter (IC) +- Sensor Multi-FIFO Controller (SMFC) +- Image Rotator (IRT) +- Video De-Interlacing or Combining Block (VDIC) + +The IDMAC is the DMA controller for transfer of image frames to and from +memory. Various dedicated DMA channels exist for both video capture and +display paths. During transfer, the IDMAC is also capable of vertical +image flip, 8x8 block transfer (see IRT description), pixel component +re-ordering (for example UYVY to YUYV) within the same colorspace, and +packed <--> planar conversion. The IDMAC can also perform a simple +de-interlacing by interweaving even and odd lines during transfer +(without motion compensation which requires the VDIC). + +The CSI is the backend capture unit that interfaces directly with +camera sensors over Parallel, BT.656/1120, and MIPI CSI-2 buses. + +The IC handles color-space conversion, resizing (downscaling and +upscaling), horizontal flip, and 90/270 degree rotation operations. + +There are three independent "tasks" within the IC that can carry out +conversions concurrently: pre-process encoding, pre-process viewfinder, +and post-processing. Within each task, conversions are split into three +sections: downsizing section, main section (upsizing, flip, colorspace +conversion, and graphics plane combining), and rotation section. + +The IPU time-shares the IC task operations. The time-slice granularity +is one burst of eight pixels in the downsizing section, one image line +in the main processing section, one image frame in the rotation section. + +The SMFC is composed of four independent FIFOs that each can transfer +captured frames from sensors directly to memory concurrently via four +IDMAC channels. + +The IRT carries out 90 and 270 degree image rotation operations. The +rotation operation is carried out on 8x8 pixel blocks at a time. This +operation is supported by the IDMAC which handles the 8x8 block transfer +along with block reordering, in coordination with vertical flip. + +The VDIC handles the conversion of interlaced video to progressive, with +support for different motion compensation modes (low, medium, and high +motion). The deinterlaced output frames from the VDIC can be sent to the +IC pre-process viewfinder task for further conversions. The VDIC also +contains a Combiner that combines two image planes, with alpha blending +and color keying. + +In addition to the IPU internal subunits, there are also two units +outside the IPU that are also involved in video capture on i.MX: + +- MIPI CSI-2 Receiver for camera sensors with the MIPI CSI-2 bus + interface. This is a Synopsys DesignWare core. +- Two video multiplexers for selecting among multiple sensor inputs + to send to a CSI. + +For more info, refer to the latest versions of the i.MX5/6 reference +manuals [#f1]_ and [#f2]_. + + +Features +-------- + +Some of the features of this driver include: + +- Many different pipelines can be configured via media controller API, + that correspond to the hardware video capture pipelines supported in + the i.MX. + +- Supports parallel, BT.565, and MIPI CSI-2 interfaces. + +- Concurrent independent streams, by configuring pipelines to multiple + video capture interfaces using independent entities. + +- Scaling, color-space conversion, horizontal and vertical flip, and + image rotation via IC task subdevs. + +- Many pixel formats supported (RGB, packed and planar YUV, partial + planar YUV). + +- The VDIC subdev supports motion compensated de-interlacing, with three + motion compensation modes: low, medium, and high motion. Pipelines are + defined that allow sending frames to the VDIC subdev directly from the + CSI. There is also support in the future for sending frames to the + VDIC from memory buffers via a output/mem2mem devices. + +- Includes a Frame Interval Monitor (FIM) that can correct vertical sync + problems with the ADV718x video decoders. + + +Topology +-------- + +The following shows the media topologies for the i.MX6Q SabreSD and +i.MX6Q SabreAuto. Refer to these diagrams in the entity descriptions +in the next section. + +The i.MX5/6 topologies can differ upstream from the IPUv3 CSI video +multiplexers, but the internal IPUv3 topology downstream from there +is common to all i.MX5/6 platforms. For example, the SabreSD, with the +MIPI CSI-2 OV5640 sensor, requires the i.MX6 MIPI CSI-2 receiver. But +the SabreAuto has only the ADV7180 decoder on a parallel bt.656 bus, and +therefore does not require the MIPI CSI-2 receiver, so it is missing in +its graph. + +.. _imx6q_topology_graph: + +.. kernel-figure:: imx6q-sabresd.dot + :alt: Diagram of the i.MX6Q SabreSD media pipeline topology + :align: center + + Media pipeline graph on i.MX6Q SabreSD + +.. kernel-figure:: imx6q-sabreauto.dot + :alt: Diagram of the i.MX6Q SabreAuto media pipeline topology + :align: center + + Media pipeline graph on i.MX6Q SabreAuto + +Entities +-------- + +imx6-mipi-csi2 +-------------- + +This is the MIPI CSI-2 receiver entity. It has one sink pad to receive +the MIPI CSI-2 stream (usually from a MIPI CSI-2 camera sensor). It has +four source pads, corresponding to the four MIPI CSI-2 demuxed virtual +channel outputs. Multiple source pads can be enabled to independently +stream from multiple virtual channels. + +This entity actually consists of two sub-blocks. One is the MIPI CSI-2 +core. This is a Synopsys Designware MIPI CSI-2 core. The other sub-block +is a "CSI-2 to IPU gasket". The gasket acts as a demultiplexer of the +four virtual channels streams, providing four separate parallel buses +containing each virtual channel that are routed to CSIs or video +multiplexers as described below. + +On i.MX6 solo/dual-lite, all four virtual channel buses are routed to +two video multiplexers. Both CSI0 and CSI1 can receive any virtual +channel, as selected by the video multiplexers. + +On i.MX6 Quad, virtual channel 0 is routed to IPU1-CSI0 (after selected +by a video mux), virtual channels 1 and 2 are hard-wired to IPU1-CSI1 +and IPU2-CSI0, respectively, and virtual channel 3 is routed to +IPU2-CSI1 (again selected by a video mux). + +ipuX_csiY_mux +------------- + +These are the video multiplexers. They have two or more sink pads to +select from either camera sensors with a parallel interface, or from +MIPI CSI-2 virtual channels from imx6-mipi-csi2 entity. They have a +single source pad that routes to a CSI (ipuX_csiY entities). + +On i.MX6 solo/dual-lite, there are two video mux entities. One sits +in front of IPU1-CSI0 to select between a parallel sensor and any of +the four MIPI CSI-2 virtual channels (a total of five sink pads). The +other mux sits in front of IPU1-CSI1, and again has five sink pads to +select between a parallel sensor and any of the four MIPI CSI-2 virtual +channels. + +On i.MX6 Quad, there are two video mux entities. One sits in front of +IPU1-CSI0 to select between a parallel sensor and MIPI CSI-2 virtual +channel 0 (two sink pads). The other mux sits in front of IPU2-CSI1 to +select between a parallel sensor and MIPI CSI-2 virtual channel 3 (two +sink pads). + +ipuX_csiY +--------- + +These are the CSI entities. They have a single sink pad receiving from +either a video mux or from a MIPI CSI-2 virtual channel as described +above. + +This entity has two source pads. The first source pad can link directly +to the ipuX_vdic entity or the ipuX_ic_prp entity, using hardware links +that require no IDMAC memory buffer transfer. + +When the direct source pad is routed to the ipuX_ic_prp entity, frames +from the CSI can be processed by one or both of the IC pre-processing +tasks. + +When the direct source pad is routed to the ipuX_vdic entity, the VDIC +will carry out motion-compensated de-interlace using "high motion" mode +(see description of ipuX_vdic entity). + +The second source pad sends video frames directly to memory buffers +via the SMFC and an IDMAC channel, bypassing IC pre-processing. This +source pad is routed to a capture device node, with a node name of the +format "ipuX_csiY capture". + +Note that since the IDMAC source pad makes use of an IDMAC channel, +pixel reordering within the same colorspace can be carried out by the +IDMAC channel. For example, if the CSI sink pad is receiving in UYVY +order, the capture device linked to the IDMAC source pad can capture +in YUYV order. Also, if the CSI sink pad is receiving a packed YUV +format, the capture device can capture a planar YUV format such as +YUV420. + +The IDMAC channel at the IDMAC source pad also supports simple +interweave without motion compensation, which is activated if the source +pad's field type is sequential top-bottom or bottom-top, and the +requested capture interface field type is set to interlaced (t-b, b-t, +or unqualified interlaced). The capture interface will enforce the same +field order as the source pad field order (interlaced-bt if source pad +is seq-bt, interlaced-tb if source pad is seq-tb). + +For events produced by ipuX_csiY, see ref:`imx_api_ipuX_csiY`. + +Cropping in ipuX_csiY +--------------------- + +The CSI supports cropping the incoming raw sensor frames. This is +implemented in the ipuX_csiY entities at the sink pad, using the +crop selection subdev API. + +The CSI also supports fixed divide-by-two downscaling independently in +width and height. This is implemented in the ipuX_csiY entities at +the sink pad, using the compose selection subdev API. + +The output rectangle at the ipuX_csiY source pad is the same as +the compose rectangle at the sink pad. So the source pad rectangle +cannot be negotiated, it must be set using the compose selection +API at sink pad (if /2 downscale is desired, otherwise source pad +rectangle is equal to incoming rectangle). + +To give an example of crop and /2 downscale, this will crop a +1280x960 input frame to 640x480, and then /2 downscale in both +dimensions to 320x240 (assumes ipu1_csi0 is linked to ipu1_csi0_mux): + +.. code-block:: none + + media-ctl -V "'ipu1_csi0_mux':2[fmt:UYVY2X8/1280x960]" + media-ctl -V "'ipu1_csi0':0[crop:(0,0)/640x480]" + media-ctl -V "'ipu1_csi0':0[compose:(0,0)/320x240]" + +Frame Skipping in ipuX_csiY +--------------------------- + +The CSI supports frame rate decimation, via frame skipping. Frame +rate decimation is specified by setting the frame intervals at +sink and source pads. The ipuX_csiY entity then applies the best +frame skip setting to the CSI to achieve the desired frame rate +at the source pad. + +The following example reduces an assumed incoming 60 Hz frame +rate by half at the IDMAC output source pad: + +.. code-block:: none + + media-ctl -V "'ipu1_csi0':0[fmt:UYVY2X8/640x480@1/60]" + media-ctl -V "'ipu1_csi0':2[fmt:UYVY2X8/640x480@1/30]" + +Frame Interval Monitor in ipuX_csiY +----------------------------------- + +See ref:`imx_api_FIM`. + +ipuX_vdic +--------- + +The VDIC carries out motion compensated de-interlacing, with three +motion compensation modes: low, medium, and high motion. The mode is +specified with the menu control V4L2_CID_DEINTERLACING_MODE. The VDIC +has two sink pads and a single source pad. + +The direct sink pad receives from an ipuX_csiY direct pad. With this +link the VDIC can only operate in high motion mode. + +When the IDMAC sink pad is activated, it receives from an output +or mem2mem device node. With this pipeline, the VDIC can also operate +in low and medium modes, because these modes require receiving +frames from memory buffers. Note that an output or mem2mem device +is not implemented yet, so this sink pad currently has no links. + +The source pad routes to the IC pre-processing entity ipuX_ic_prp. + +ipuX_ic_prp +----------- + +This is the IC pre-processing entity. It acts as a router, routing +data from its sink pad to one or both of its source pads. + +This entity has a single sink pad. The sink pad can receive from the +ipuX_csiY direct pad, or from ipuX_vdic. + +This entity has two source pads. One source pad routes to the +pre-process encode task entity (ipuX_ic_prpenc), the other to the +pre-process viewfinder task entity (ipuX_ic_prpvf). Both source pads +can be activated at the same time if the sink pad is receiving from +ipuX_csiY. Only the source pad to the pre-process viewfinder task entity +can be activated if the sink pad is receiving from ipuX_vdic (frames +from the VDIC can only be processed by the pre-process viewfinder task). + +ipuX_ic_prpenc +-------------- + +This is the IC pre-processing encode entity. It has a single sink +pad from ipuX_ic_prp, and a single source pad. The source pad is +routed to a capture device node, with a node name of the format +"ipuX_ic_prpenc capture". + +This entity performs the IC pre-process encode task operations: +color-space conversion, resizing (downscaling and upscaling), +horizontal and vertical flip, and 90/270 degree rotation. Flip +and rotation are provided via standard V4L2 controls. + +Like the ipuX_csiY IDMAC source, this entity also supports simple +de-interlace without motion compensation, and pixel reordering. + +ipuX_ic_prpvf +------------- + +This is the IC pre-processing viewfinder entity. It has a single sink +pad from ipuX_ic_prp, and a single source pad. The source pad is routed +to a capture device node, with a node name of the format +"ipuX_ic_prpvf capture". + +This entity is identical in operation to ipuX_ic_prpenc, with the same +resizing and CSC operations and flip/rotation controls. It will receive +and process de-interlaced frames from the ipuX_vdic if ipuX_ic_prp is +receiving from ipuX_vdic. + +Like the ipuX_csiY IDMAC source, this entity supports simple +interweaving without motion compensation. However, note that if the +ipuX_vdic is included in the pipeline (ipuX_ic_prp is receiving from +ipuX_vdic), it's not possible to use interweave in ipuX_ic_prpvf, +since the ipuX_vdic has already carried out de-interlacing (with +motion compensation) and therefore the field type output from +ipuX_vdic can only be none (progressive). + +Capture Pipelines +----------------- + +The following describe the various use-cases supported by the pipelines. + +The links shown do not include the backend sensor, video mux, or mipi +csi-2 receiver links. This depends on the type of sensor interface +(parallel or mipi csi-2). So these pipelines begin with: + +sensor -> ipuX_csiY_mux -> ... + +for parallel sensors, or: + +sensor -> imx6-mipi-csi2 -> (ipuX_csiY_mux) -> ... + +for mipi csi-2 sensors. The imx6-mipi-csi2 receiver may need to route +to the video mux (ipuX_csiY_mux) before sending to the CSI, depending +on the mipi csi-2 virtual channel, hence ipuX_csiY_mux is shown in +parenthesis. + +Unprocessed Video Capture: +-------------------------- + +Send frames directly from sensor to camera device interface node, with +no conversions, via ipuX_csiY IDMAC source pad: + +-> ipuX_csiY:2 -> ipuX_csiY capture + +IC Direct Conversions: +---------------------- + +This pipeline uses the preprocess encode entity to route frames directly +from the CSI to the IC, to carry out scaling up to 1024x1024 resolution, +CSC, flipping, and image rotation: + +-> ipuX_csiY:1 -> 0:ipuX_ic_prp:1 -> 0:ipuX_ic_prpenc:1 -> ipuX_ic_prpenc capture + +Motion Compensated De-interlace: +-------------------------------- + +This pipeline routes frames from the CSI direct pad to the VDIC entity to +support motion-compensated de-interlacing (high motion mode only), +scaling up to 1024x1024, CSC, flip, and rotation: + +-> ipuX_csiY:1 -> 0:ipuX_vdic:2 -> 0:ipuX_ic_prp:2 -> 0:ipuX_ic_prpvf:1 -> ipuX_ic_prpvf capture + + +Usage Notes +----------- + +To aid in configuration and for backward compatibility with V4L2 +applications that access controls only from video device nodes, the +capture device interfaces inherit controls from the active entities +in the current pipeline, so controls can be accessed either directly +from the subdev or from the active capture device interface. For +example, the FIM controls are available either from the ipuX_csiY +subdevs or from the active capture device. + +The following are specific usage notes for the Sabre* reference +boards: + + +i.MX6Q SabreLite with OV5642 and OV5640 +--------------------------------------- + +This platform requires the OmniVision OV5642 module with a parallel +camera interface, and the OV5640 module with a MIPI CSI-2 +interface. Both modules are available from Boundary Devices: + +- https://boundarydevices.com/product/nit6x_5mp +- https://boundarydevices.com/product/nit6x_5mp_mipi + +Note that if only one camera module is available, the other sensor +node can be disabled in the device tree. + +The OV5642 module is connected to the parallel bus input on the i.MX +internal video mux to IPU1 CSI0. It's i2c bus connects to i2c bus 2. + +The MIPI CSI-2 OV5640 module is connected to the i.MX internal MIPI CSI-2 +receiver, and the four virtual channel outputs from the receiver are +routed as follows: vc0 to the IPU1 CSI0 mux, vc1 directly to IPU1 CSI1, +vc2 directly to IPU2 CSI0, and vc3 to the IPU2 CSI1 mux. The OV5640 is +also connected to i2c bus 2 on the SabreLite, therefore the OV5642 and +OV5640 must not share the same i2c slave address. + +The following basic example configures unprocessed video capture +pipelines for both sensors. The OV5642 is routed to ipu1_csi0, and +the OV5640, transmitting on MIPI CSI-2 virtual channel 1 (which is +imx6-mipi-csi2 pad 2), is routed to ipu1_csi1. Both sensors are +configured to output 640x480, and the OV5642 outputs YUYV2X8, the +OV5640 UYVY2X8: + +.. code-block:: none + + # Setup links for OV5642 + media-ctl -l "'ov5642 1-0042':0 -> 'ipu1_csi0_mux':1[1]" + media-ctl -l "'ipu1_csi0_mux':2 -> 'ipu1_csi0':0[1]" + media-ctl -l "'ipu1_csi0':2 -> 'ipu1_csi0 capture':0[1]" + # Setup links for OV5640 + media-ctl -l "'ov5640 1-0040':0 -> 'imx6-mipi-csi2':0[1]" + media-ctl -l "'imx6-mipi-csi2':2 -> 'ipu1_csi1':0[1]" + media-ctl -l "'ipu1_csi1':2 -> 'ipu1_csi1 capture':0[1]" + # Configure pads for OV5642 pipeline + media-ctl -V "'ov5642 1-0042':0 [fmt:YUYV2X8/640x480 field:none]" + media-ctl -V "'ipu1_csi0_mux':2 [fmt:YUYV2X8/640x480 field:none]" + media-ctl -V "'ipu1_csi0':2 [fmt:AYUV32/640x480 field:none]" + # Configure pads for OV5640 pipeline + media-ctl -V "'ov5640 1-0040':0 [fmt:UYVY2X8/640x480 field:none]" + media-ctl -V "'imx6-mipi-csi2':2 [fmt:UYVY2X8/640x480 field:none]" + media-ctl -V "'ipu1_csi1':2 [fmt:AYUV32/640x480 field:none]" + +Streaming can then begin independently on the capture device nodes +"ipu1_csi0 capture" and "ipu1_csi1 capture". The v4l2-ctl tool can +be used to select any supported YUV pixelformat on the capture device +nodes, including planar. + +i.MX6Q SabreAuto with ADV7180 decoder +------------------------------------- + +On the i.MX6Q SabreAuto, an on-board ADV7180 SD decoder is connected to the +parallel bus input on the internal video mux to IPU1 CSI0. + +The following example configures a pipeline to capture from the ADV7180 +video decoder, assuming NTSC 720x480 input signals, using simple +interweave (unconverted and without motion compensation). The adv7180 +must output sequential or alternating fields (field type 'seq-bt' for +NTSC, or 'alternate'): + +.. code-block:: none + + # Setup links + media-ctl -l "'adv7180 3-0021':0 -> 'ipu1_csi0_mux':1[1]" + media-ctl -l "'ipu1_csi0_mux':2 -> 'ipu1_csi0':0[1]" + media-ctl -l "'ipu1_csi0':2 -> 'ipu1_csi0 capture':0[1]" + # Configure pads + media-ctl -V "'adv7180 3-0021':0 [fmt:UYVY2X8/720x480 field:seq-bt]" + media-ctl -V "'ipu1_csi0_mux':2 [fmt:UYVY2X8/720x480]" + media-ctl -V "'ipu1_csi0':2 [fmt:AYUV32/720x480]" + # Configure "ipu1_csi0 capture" interface (assumed at /dev/video4) + v4l2-ctl -d4 --set-fmt-video=field=interlaced_bt + +Streaming can then begin on /dev/video4. The v4l2-ctl tool can also be +used to select any supported YUV pixelformat on /dev/video4. + +This example configures a pipeline to capture from the ADV7180 +video decoder, assuming PAL 720x576 input signals, with Motion +Compensated de-interlacing. The adv7180 must output sequential or +alternating fields (field type 'seq-tb' for PAL, or 'alternate'). + +.. code-block:: none + + # Setup links + media-ctl -l "'adv7180 3-0021':0 -> 'ipu1_csi0_mux':1[1]" + media-ctl -l "'ipu1_csi0_mux':2 -> 'ipu1_csi0':0[1]" + media-ctl -l "'ipu1_csi0':1 -> 'ipu1_vdic':0[1]" + media-ctl -l "'ipu1_vdic':2 -> 'ipu1_ic_prp':0[1]" + media-ctl -l "'ipu1_ic_prp':2 -> 'ipu1_ic_prpvf':0[1]" + media-ctl -l "'ipu1_ic_prpvf':1 -> 'ipu1_ic_prpvf capture':0[1]" + # Configure pads + media-ctl -V "'adv7180 3-0021':0 [fmt:UYVY2X8/720x576 field:seq-tb]" + media-ctl -V "'ipu1_csi0_mux':2 [fmt:UYVY2X8/720x576]" + media-ctl -V "'ipu1_csi0':1 [fmt:AYUV32/720x576]" + media-ctl -V "'ipu1_vdic':2 [fmt:AYUV32/720x576 field:none]" + media-ctl -V "'ipu1_ic_prp':2 [fmt:AYUV32/720x576 field:none]" + media-ctl -V "'ipu1_ic_prpvf':1 [fmt:AYUV32/720x576 field:none]" + # Configure "ipu1_ic_prpvf capture" interface (assumed at /dev/video2) + v4l2-ctl -d2 --set-fmt-video=field=none + +Streaming can then begin on /dev/video2. The v4l2-ctl tool can also be +used to select any supported YUV pixelformat on /dev/video2. + +This platform accepts Composite Video analog inputs to the ADV7180 on +Ain1 (connector J42). + +i.MX6DL SabreAuto with ADV7180 decoder +-------------------------------------- + +On the i.MX6DL SabreAuto, an on-board ADV7180 SD decoder is connected to the +parallel bus input on the internal video mux to IPU1 CSI0. + +The following example configures a pipeline to capture from the ADV7180 +video decoder, assuming NTSC 720x480 input signals, using simple +interweave (unconverted and without motion compensation). The adv7180 +must output sequential or alternating fields (field type 'seq-bt' for +NTSC, or 'alternate'): + +.. code-block:: none + + # Setup links + media-ctl -l "'adv7180 4-0021':0 -> 'ipu1_csi0_mux':4[1]" + media-ctl -l "'ipu1_csi0_mux':5 -> 'ipu1_csi0':0[1]" + media-ctl -l "'ipu1_csi0':2 -> 'ipu1_csi0 capture':0[1]" + # Configure pads + media-ctl -V "'adv7180 4-0021':0 [fmt:UYVY2X8/720x480 field:seq-bt]" + media-ctl -V "'ipu1_csi0_mux':5 [fmt:UYVY2X8/720x480]" + media-ctl -V "'ipu1_csi0':2 [fmt:AYUV32/720x480]" + # Configure "ipu1_csi0 capture" interface (assumed at /dev/video0) + v4l2-ctl -d0 --set-fmt-video=field=interlaced_bt + +Streaming can then begin on /dev/video0. The v4l2-ctl tool can also be +used to select any supported YUV pixelformat on /dev/video0. + +This example configures a pipeline to capture from the ADV7180 +video decoder, assuming PAL 720x576 input signals, with Motion +Compensated de-interlacing. The adv7180 must output sequential or +alternating fields (field type 'seq-tb' for PAL, or 'alternate'). + +.. code-block:: none + + # Setup links + media-ctl -l "'adv7180 4-0021':0 -> 'ipu1_csi0_mux':4[1]" + media-ctl -l "'ipu1_csi0_mux':5 -> 'ipu1_csi0':0[1]" + media-ctl -l "'ipu1_csi0':1 -> 'ipu1_vdic':0[1]" + media-ctl -l "'ipu1_vdic':2 -> 'ipu1_ic_prp':0[1]" + media-ctl -l "'ipu1_ic_prp':2 -> 'ipu1_ic_prpvf':0[1]" + media-ctl -l "'ipu1_ic_prpvf':1 -> 'ipu1_ic_prpvf capture':0[1]" + # Configure pads + media-ctl -V "'adv7180 4-0021':0 [fmt:UYVY2X8/720x576 field:seq-tb]" + media-ctl -V "'ipu1_csi0_mux':5 [fmt:UYVY2X8/720x576]" + media-ctl -V "'ipu1_csi0':1 [fmt:AYUV32/720x576]" + media-ctl -V "'ipu1_vdic':2 [fmt:AYUV32/720x576 field:none]" + media-ctl -V "'ipu1_ic_prp':2 [fmt:AYUV32/720x576 field:none]" + media-ctl -V "'ipu1_ic_prpvf':1 [fmt:AYUV32/720x576 field:none]" + # Configure "ipu1_ic_prpvf capture" interface (assumed at /dev/video2) + v4l2-ctl -d2 --set-fmt-video=field=none + +Streaming can then begin on /dev/video2. The v4l2-ctl tool can also be +used to select any supported YUV pixelformat on /dev/video2. + +This platform accepts Composite Video analog inputs to the ADV7180 on +Ain1 (connector J42). + +i.MX6Q SabreSD with MIPI CSI-2 OV5640 +------------------------------------- + +Similarly to i.MX6Q SabreLite, the i.MX6Q SabreSD supports a parallel +interface OV5642 module on IPU1 CSI0, and a MIPI CSI-2 OV5640 +module. The OV5642 connects to i2c bus 1 and the OV5640 to i2c bus 2. + +The device tree for SabreSD includes OF graphs for both the parallel +OV5642 and the MIPI CSI-2 OV5640, but as of this writing only the MIPI +CSI-2 OV5640 has been tested, so the OV5642 node is currently disabled. +The OV5640 module connects to MIPI connector J5. The NXP part number +for the OV5640 module that connects to the SabreSD board is H120729. + +The following example configures unprocessed video capture pipeline to +capture from the OV5640, transmitting on MIPI CSI-2 virtual channel 0: + +.. code-block:: none + + # Setup links + media-ctl -l "'ov5640 1-003c':0 -> 'imx6-mipi-csi2':0[1]" + media-ctl -l "'imx6-mipi-csi2':1 -> 'ipu1_csi0_mux':0[1]" + media-ctl -l "'ipu1_csi0_mux':2 -> 'ipu1_csi0':0[1]" + media-ctl -l "'ipu1_csi0':2 -> 'ipu1_csi0 capture':0[1]" + # Configure pads + media-ctl -V "'ov5640 1-003c':0 [fmt:UYVY2X8/640x480]" + media-ctl -V "'imx6-mipi-csi2':1 [fmt:UYVY2X8/640x480]" + media-ctl -V "'ipu1_csi0_mux':0 [fmt:UYVY2X8/640x480]" + media-ctl -V "'ipu1_csi0':0 [fmt:AYUV32/640x480]" + +Streaming can then begin on "ipu1_csi0 capture" node. The v4l2-ctl +tool can be used to select any supported pixelformat on the capture +device node. + +To determine what is the /dev/video node correspondent to +"ipu1_csi0 capture": + +.. code-block:: none + + media-ctl -e "ipu1_csi0 capture" + /dev/video0 + +/dev/video0 is the streaming element in this case. + +Starting the streaming via v4l2-ctl: + +.. code-block:: none + + v4l2-ctl --stream-mmap -d /dev/video0 + +Starting the streaming via Gstreamer and sending the content to the display: + +.. code-block:: none + + gst-launch-1.0 v4l2src device=/dev/video0 ! kmssink + +The following example configures a direct conversion pipeline to capture +from the OV5640, transmitting on MIPI CSI-2 virtual channel 0. It also +shows colorspace conversion and scaling at IC output. + +.. code-block:: none + + # Setup links + media-ctl -l "'ov5640 1-003c':0 -> 'imx6-mipi-csi2':0[1]" + media-ctl -l "'imx6-mipi-csi2':1 -> 'ipu1_csi0_mux':0[1]" + media-ctl -l "'ipu1_csi0_mux':2 -> 'ipu1_csi0':0[1]" + media-ctl -l "'ipu1_csi0':1 -> 'ipu1_ic_prp':0[1]" + media-ctl -l "'ipu1_ic_prp':1 -> 'ipu1_ic_prpenc':0[1]" + media-ctl -l "'ipu1_ic_prpenc':1 -> 'ipu1_ic_prpenc capture':0[1]" + # Configure pads + media-ctl -V "'ov5640 1-003c':0 [fmt:UYVY2X8/640x480]" + media-ctl -V "'imx6-mipi-csi2':1 [fmt:UYVY2X8/640x480]" + media-ctl -V "'ipu1_csi0_mux':2 [fmt:UYVY2X8/640x480]" + media-ctl -V "'ipu1_csi0':1 [fmt:AYUV32/640x480]" + media-ctl -V "'ipu1_ic_prp':1 [fmt:AYUV32/640x480]" + media-ctl -V "'ipu1_ic_prpenc':1 [fmt:ARGB8888_1X32/800x600]" + # Set a format at the capture interface + v4l2-ctl -d /dev/video1 --set-fmt-video=pixelformat=RGB3 + +Streaming can then begin on "ipu1_ic_prpenc capture" node. + +To determine what is the /dev/video node correspondent to +"ipu1_ic_prpenc capture": + +.. code-block:: none + + media-ctl -e "ipu1_ic_prpenc capture" + /dev/video1 + + +/dev/video1 is the streaming element in this case. + +Starting the streaming via v4l2-ctl: + +.. code-block:: none + + v4l2-ctl --stream-mmap -d /dev/video1 + +Starting the streaming via Gstreamer and sending the content to the display: + +.. code-block:: none + + gst-launch-1.0 v4l2src device=/dev/video1 ! kmssink + +Known Issues +------------ + +1. When using 90 or 270 degree rotation control at capture resolutions + near the IC resizer limit of 1024x1024, and combined with planar + pixel formats (YUV420, YUV422p), frame capture will often fail with + no end-of-frame interrupts from the IDMAC channel. To work around + this, use lower resolution and/or packed formats (YUYV, RGB3, etc.) + when 90 or 270 rotations are needed. + + +File list +--------- + +drivers/staging/media/imx/ +include/media/imx.h +include/linux/imx-media.h + +References +---------- + +.. [#f1] http://www.nxp.com/assets/documents/data/en/reference-manuals/IMX6DQRM.pdf +.. [#f2] http://www.nxp.com/assets/documents/data/en/reference-manuals/IMX6SDLRM.pdf + + +Authors +------- + +- Steve Longerbeam <steve_longerbeam@mentor.com> +- Philipp Zabel <kernel@pengutronix.de> +- Russell King <linux@armlinux.org.uk> + +Copyright (C) 2012-2017 Mentor Graphics Inc. diff --git a/Documentation/admin-guide/media/imx6q-sabreauto.dot b/Documentation/admin-guide/media/imx6q-sabreauto.dot new file mode 100644 index 000000000..bd6cf0b35 --- /dev/null +++ b/Documentation/admin-guide/media/imx6q-sabreauto.dot @@ -0,0 +1,51 @@ +digraph board { + rankdir=TB + n00000001 [label="{{<port0> 0} | ipu1_csi0\n/dev/v4l-subdev0 | {<port1> 1 | <port2> 2}}", shape=Mrecord, style=filled, fillcolor=green] + n00000001:port2 -> n00000005 [style=dashed] + n00000001:port1 -> n0000000f:port0 [style=dashed] + n00000001:port1 -> n0000000b:port0 [style=dashed] + n00000005 [label="ipu1_csi0 capture\n/dev/video0", shape=box, style=filled, fillcolor=yellow] + n0000000b [label="{{<port0> 0 | <port1> 1} 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+ n0000005b [label="ipu2_ic_prpvf capture\n/dev/video6", shape=box, style=filled, fillcolor=yellow] + n0000006b [label="{{<port0> 0} | ipu2_csi1\n/dev/v4l-subdev11 | {<port1> 1 | <port2> 2}}", shape=Mrecord, style=filled, fillcolor=green] + n0000006b:port2 -> n0000006f [style=dashed] + n0000006b:port1 -> n0000004b:port0 [style=dashed] + n0000006b:port1 -> n00000047:port0 [style=dashed] + n0000006f [label="ipu2_csi1 capture\n/dev/video7", shape=box, style=filled, fillcolor=yellow] + n00000079 [label="{{<port0> 0} | imx6-mipi-csi2\n/dev/v4l-subdev12 | {<port1> 1 | <port2> 2 | <port3> 3 | <port4> 4}}", shape=Mrecord, style=filled, fillcolor=green] + n00000079:port2 -> n0000002f:port0 [style=dashed] + n00000079:port3 -> n0000003d:port0 [style=dashed] + n00000079:port1 -> n0000007f:port0 [style=dashed] + n00000079:port4 -> n00000083:port0 [style=dashed] + n0000007f [label="{{<port0> 0 | <port1> 1} | ipu1_csi0_mux\n/dev/v4l-subdev13 | {<port2> 2}}", shape=Mrecord, style=filled, fillcolor=green] + n0000007f:port2 -> n00000001:port0 [style=dashed] + n00000083 [label="{{<port0> 0 | <port1> 1} | ipu2_csi1_mux\n/dev/v4l-subdev14 | {<port2> 2}}", shape=Mrecord, style=filled, fillcolor=green] + n00000083:port2 -> n0000006b:port0 [style=dashed] + n00000087 [label="{{} | ov5640 1-003c\n/dev/v4l-subdev15 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green] + n00000087:port0 -> n00000079:port0 [style=dashed] +} diff --git a/Documentation/admin-guide/media/imx7.rst b/Documentation/admin-guide/media/imx7.rst new file mode 100644 index 000000000..2fa27718f --- /dev/null +++ b/Documentation/admin-guide/media/imx7.rst @@ -0,0 +1,221 @@ +.. SPDX-License-Identifier: GPL-2.0 + +i.MX7 Video Capture Driver +========================== + +Introduction +------------ + +The i.MX7 contrary to the i.MX5/6 family does not contain an Image Processing +Unit (IPU); because of that the capabilities to perform operations or +manipulation of the capture frames are less feature rich. + +For image capture the i.MX7 has three units: +- CMOS Sensor Interface (CSI) +- Video Multiplexer +- MIPI CSI-2 Receiver + +.. code-block:: none + + MIPI Camera Input ---> MIPI CSI-2 --- > |\ + | \ + | \ + | M | + | U | ------> CSI ---> Capture + | X | + | / + Parallel Camera Input ----------------> | / + |/ + +For additional information, please refer to the latest versions of the i.MX7 +reference manual [#f1]_. + +Entities +-------- + +imx-mipi-csi2 +-------------- + +This is the MIPI CSI-2 receiver entity. It has one sink pad to receive the pixel +data from MIPI CSI-2 camera sensor. It has one source pad, corresponding to the +virtual channel 0. This module is compliant to previous version of Samsung +D-phy, and supports two D-PHY Rx Data lanes. + +csi-mux +------- + +This is the video multiplexer. It has two sink pads to select from either camera +sensor with a parallel interface or from MIPI CSI-2 virtual channel 0. It has +a single source pad that routes to the CSI. + +csi +--- + +The CSI enables the chip to connect directly to external CMOS image sensor. CSI +can interface directly with Parallel and MIPI CSI-2 buses. It has 256 x 64 FIFO +to store received image pixel data and embedded DMA controllers to transfer data +from the FIFO through AHB bus. + +This entity has one sink pad that receives from the csi-mux entity and a single +source pad that routes video frames directly to memory buffers. This pad is +routed to a capture device node. + +Usage Notes +----------- + +To aid in configuration and for backward compatibility with V4L2 applications +that access controls only from video device nodes, the capture device interfaces +inherit controls from the active entities in the current pipeline, so controls +can be accessed either directly from the subdev or from the active capture +device interface. For example, the sensor controls are available either from the +sensor subdevs or from the active capture device. + +Warp7 with OV2680 +----------------- + +On this platform an OV2680 MIPI CSI-2 module is connected to the internal MIPI +CSI-2 receiver. The following example configures a video capture pipeline with +an output of 800x600, and BGGR 10 bit bayer format: + +.. code-block:: none + + # Setup links + media-ctl -l "'ov2680 1-0036':0 -> 'imx7-mipi-csis.0':0[1]" + media-ctl -l "'imx7-mipi-csis.0':1 -> 'csi-mux':1[1]" + media-ctl -l "'csi-mux':2 -> 'csi':0[1]" + media-ctl -l "'csi':1 -> 'csi capture':0[1]" + + # Configure pads for pipeline + media-ctl -V "'ov2680 1-0036':0 [fmt:SBGGR10_1X10/800x600 field:none]" + media-ctl -V "'csi-mux':1 [fmt:SBGGR10_1X10/800x600 field:none]" + media-ctl -V "'csi-mux':2 [fmt:SBGGR10_1X10/800x600 field:none]" + media-ctl -V "'imx7-mipi-csis.0':0 [fmt:SBGGR10_1X10/800x600 field:none]" + media-ctl -V "'csi':0 [fmt:SBGGR10_1X10/800x600 field:none]" + +After this streaming can start. The v4l2-ctl tool can be used to select any of +the resolutions supported by the sensor. + +.. code-block:: none + + # media-ctl -p + Media controller API version 5.2.0 + + Media device information + ------------------------ + driver imx7-csi + model imx-media + serial + bus info + hw revision 0x0 + driver version 5.2.0 + + Device topology + - entity 1: csi (2 pads, 2 links) + type V4L2 subdev subtype Unknown flags 0 + device node name /dev/v4l-subdev0 + pad0: Sink + [fmt:SBGGR10_1X10/800x600 field:none colorspace:srgb xfer:srgb ycbcr:601 quantization:full-range] + <- "csi-mux":2 [ENABLED] + pad1: Source + [fmt:SBGGR10_1X10/800x600 field:none colorspace:srgb xfer:srgb ycbcr:601 quantization:full-range] + -> "csi capture":0 [ENABLED] + + - entity 4: csi capture (1 pad, 1 link) + type Node subtype V4L flags 0 + device node name /dev/video0 + pad0: Sink + <- "csi":1 [ENABLED] + + - entity 10: csi-mux (3 pads, 2 links) + type V4L2 subdev subtype Unknown flags 0 + device node name /dev/v4l-subdev1 + pad0: Sink + [fmt:Y8_1X8/1x1 field:none] + pad1: Sink + [fmt:SBGGR10_1X10/800x600 field:none] + <- "imx7-mipi-csis.0":1 [ENABLED] + pad2: Source + [fmt:SBGGR10_1X10/800x600 field:none] + -> "csi":0 [ENABLED] + + - entity 14: imx7-mipi-csis.0 (2 pads, 2 links) + type V4L2 subdev subtype Unknown flags 0 + device node name /dev/v4l-subdev2 + pad0: Sink + [fmt:SBGGR10_1X10/800x600 field:none] + <- "ov2680 1-0036":0 [ENABLED] + pad1: Source + [fmt:SBGGR10_1X10/800x600 field:none] + -> "csi-mux":1 [ENABLED] + + - entity 17: ov2680 1-0036 (1 pad, 1 link) + type V4L2 subdev subtype Sensor flags 0 + device node name /dev/v4l-subdev3 + pad0: Source + [fmt:SBGGR10_1X10/800x600@1/30 field:none colorspace:srgb] + -> "imx7-mipi-csis.0":0 [ENABLED] + +i.MX6ULL-EVK with OV5640 +------------------------ + +On this platform a parallel OV5640 sensor is connected to the CSI port. +The following example configures a video capture pipeline with an output +of 640x480 and UYVY8_2X8 format: + +.. code-block:: none + + # Setup links + media-ctl -l "'ov5640 1-003c':0 -> 'csi':0[1]" + media-ctl -l "'csi':1 -> 'csi capture':0[1]" + + # Configure pads for pipeline + media-ctl -v -V "'ov5640 1-003c':0 [fmt:UYVY8_2X8/640x480 field:none]" + +After this streaming can start: + +.. code-block:: none + + gst-launch-1.0 -v v4l2src device=/dev/video1 ! video/x-raw,format=UYVY,width=640,height=480 ! v4l2convert ! fbdevsink + +.. code-block:: none + + # media-ctl -p + Media controller API version 5.14.0 + + Media device information + ------------------------ + driver imx7-csi + model imx-media + serial + bus info + hw revision 0x0 + driver version 5.14.0 + + Device topology + - entity 1: csi (2 pads, 2 links) + type V4L2 subdev subtype Unknown flags 0 + device node name /dev/v4l-subdev0 + pad0: Sink + [fmt:UYVY8_2X8/640x480 field:none colorspace:srgb xfer:srgb ycbcr:601 quantization:full-range] + <- "ov5640 1-003c":0 [ENABLED,IMMUTABLE] + pad1: Source + [fmt:UYVY8_2X8/640x480 field:none colorspace:srgb xfer:srgb ycbcr:601 quantization:full-range] + -> "csi capture":0 [ENABLED,IMMUTABLE] + + - entity 4: csi capture (1 pad, 1 link) + type Node subtype V4L flags 0 + device node name /dev/video1 + pad0: Sink + <- "csi":1 [ENABLED,IMMUTABLE] + + - entity 10: ov5640 1-003c (1 pad, 1 link) + type V4L2 subdev subtype Sensor flags 0 + device node name /dev/v4l-subdev1 + pad0: Source + [fmt:UYVY8_2X8/640x480@1/30 field:none colorspace:srgb xfer:srgb ycbcr:601 quantization:full-range] + -> "csi":0 [ENABLED,IMMUTABLE] + +References +---------- + +.. [#f1] https://www.nxp.com/docs/en/reference-manual/IMX7SRM.pdf diff --git a/Documentation/admin-guide/media/index.rst b/Documentation/admin-guide/media/index.rst new file mode 100644 index 000000000..43f4a292b --- /dev/null +++ b/Documentation/admin-guide/media/index.rst @@ -0,0 +1,64 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. include:: <isonum.txt> + +==================================== +Media subsystem admin and user guide +==================================== + +This section contains usage information about media subsystem and +its supported drivers. + +Please see: + +Documentation/userspace-api/media/index.rst + + - for the userspace APIs used on media devices. + +Documentation/driver-api/media/index.rst + + - for driver development information and Kernel APIs used by + media devices; + +The media subsystem +=================== + +.. only:: html + + .. class:: toc-title + + Table of Contents + +.. toctree:: + :maxdepth: 2 + :numbered: + + intro + building + + remote-controller + + cec + + dvb + + cardlist + + v4l-drivers + dvb-drivers + +**Copyright** |copy| 1999-2020 : LinuxTV Developers + +:: + + This documentation is free software; you can redistribute it and/or modify it + under the terms of the GNU General Public License as published by the Free + Software Foundation; either version 2 of the License, or (at your option) any + later version. + + This program is distributed in the hope that it will be useful, but WITHOUT + ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for + more details. + + For more details see the file COPYING in the source distribution of Linux. diff --git a/Documentation/admin-guide/media/intro.rst b/Documentation/admin-guide/media/intro.rst new file mode 100644 index 000000000..fec8122f2 --- /dev/null +++ b/Documentation/admin-guide/media/intro.rst @@ -0,0 +1,27 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============ +Introduction +============ + +The media subsystem consists on Linux support for several different types +of devices: + +- Audio and video grabbers; +- PC and Laptop Cameras; +- Complex cameras found on Embedded hardware; +- Analog and digital TV; +- HDMI Customer Electronics Control (CEC); +- Multi-touch input devices; +- Remote Controllers; +- Media encoders and decoders. + +Due to the diversity of devices, the subsystem provides several different +APIs: + +- Remote Controller API; +- HDMI CEC API; +- Video4Linux API; +- Media controller API; +- Video4Linux Request API (experimental); +- Digital TV API (also known as DVB API). diff --git a/Documentation/admin-guide/media/ipu3.rst b/Documentation/admin-guide/media/ipu3.rst new file mode 100644 index 000000000..83b3cd03b --- /dev/null +++ b/Documentation/admin-guide/media/ipu3.rst @@ -0,0 +1,600 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. include:: <isonum.txt> + +=============================================================== +Intel Image Processing Unit 3 (IPU3) Imaging Unit (ImgU) driver +=============================================================== + +Copyright |copy| 2018 Intel Corporation + +Introduction +============ + +This file documents the Intel IPU3 (3rd generation Image Processing Unit) +Imaging Unit drivers located under drivers/media/pci/intel/ipu3 (CIO2) as well +as under drivers/staging/media/ipu3 (ImgU). + +The Intel IPU3 found in certain Kaby Lake (as well as certain Sky Lake) +platforms (U/Y processor lines) is made up of two parts namely the Imaging Unit +(ImgU) and the CIO2 device (MIPI CSI2 receiver). + +The CIO2 device receives the raw Bayer data from the sensors and outputs the +frames in a format that is specific to the IPU3 (for consumption by the IPU3 +ImgU). The CIO2 driver is available as drivers/media/pci/intel/ipu3/ipu3-cio2* +and is enabled through the CONFIG_VIDEO_IPU3_CIO2 config option. + +The Imaging Unit (ImgU) is responsible for processing images captured +by the IPU3 CIO2 device. The ImgU driver sources can be found under +drivers/staging/media/ipu3 directory. The driver is enabled through the +CONFIG_VIDEO_IPU3_IMGU config option. + +The two driver modules are named ipu3_csi2 and ipu3_imgu, respectively. + +The drivers has been tested on Kaby Lake platforms (U/Y processor lines). + +Both of the drivers implement V4L2, Media Controller and V4L2 sub-device +interfaces. The IPU3 CIO2 driver supports camera sensors connected to the CIO2 +MIPI CSI-2 interfaces through V4L2 sub-device sensor drivers. + +CIO2 +==== + +The CIO2 is represented as a single V4L2 subdev, which provides a V4L2 subdev +interface to the user space. There is a video node for each CSI-2 receiver, +with a single media controller interface for the entire device. + +The CIO2 contains four independent capture channel, each with its own MIPI CSI-2 +receiver and DMA engine. Each channel is modelled as a V4L2 sub-device exposed +to userspace as a V4L2 sub-device node and has two pads: + +.. tabularcolumns:: |p{0.8cm}|p{4.0cm}|p{4.0cm}| + +.. flat-table:: + :header-rows: 1 + + * - Pad + - Direction + - Purpose + + * - 0 + - sink + - MIPI CSI-2 input, connected to the sensor subdev + + * - 1 + - source + - Raw video capture, connected to the V4L2 video interface + +The V4L2 video interfaces model the DMA engines. They are exposed to userspace +as V4L2 video device nodes. + +Capturing frames in raw Bayer format +------------------------------------ + +CIO2 MIPI CSI2 receiver is used to capture frames (in packed raw Bayer format) +from the raw sensors connected to the CSI2 ports. The captured frames are used +as input to the ImgU driver. + +Image processing using IPU3 ImgU requires tools such as raw2pnm [#f1]_, and +yavta [#f2]_ due to the following unique requirements and / or features specific +to IPU3. + +-- The IPU3 CSI2 receiver outputs the captured frames from the sensor in packed +raw Bayer format that is specific to IPU3. + +-- Multiple video nodes have to be operated simultaneously. + +Let us take the example of ov5670 sensor connected to CSI2 port 0, for a +2592x1944 image capture. + +Using the media controller APIs, the ov5670 sensor is configured to send +frames in packed raw Bayer format to IPU3 CSI2 receiver. + +.. code-block:: none + + # This example assumes /dev/media0 as the CIO2 media device + export MDEV=/dev/media0 + + # and that ov5670 sensor is connected to i2c bus 10 with address 0x36 + export SDEV=$(media-ctl -d $MDEV -e "ov5670 10-0036") + + # Establish the link for the media devices using media-ctl [#f3]_ + media-ctl -d $MDEV -l "ov5670:0 -> ipu3-csi2 0:0[1]" + + # Set the format for the media devices + media-ctl -d $MDEV -V "ov5670:0 [fmt:SGRBG10/2592x1944]" + media-ctl -d $MDEV -V "ipu3-csi2 0:0 [fmt:SGRBG10/2592x1944]" + media-ctl -d $MDEV -V "ipu3-csi2 0:1 [fmt:SGRBG10/2592x1944]" + +Once the media pipeline is configured, desired sensor specific settings +(such as exposure and gain settings) can be set, using the yavta tool. + +e.g + +.. code-block:: none + + yavta -w 0x009e0903 444 $SDEV + yavta -w 0x009e0913 1024 $SDEV + yavta -w 0x009e0911 2046 $SDEV + +Once the desired sensor settings are set, frame captures can be done as below. + +e.g + +.. code-block:: none + + yavta --data-prefix -u -c10 -n5 -I -s2592x1944 --file=/tmp/frame-#.bin \ + -f IPU3_SGRBG10 $(media-ctl -d $MDEV -e "ipu3-cio2 0") + +With the above command, 10 frames are captured at 2592x1944 resolution, with +sGRBG10 format and output as IPU3_SGRBG10 format. + +The captured frames are available as /tmp/frame-#.bin files. + +ImgU +==== + +The ImgU is represented as two V4L2 subdevs, each of which provides a V4L2 +subdev interface to the user space. + +Each V4L2 subdev represents a pipe, which can support a maximum of 2 streams. +This helps to support advanced camera features like Continuous View Finder (CVF) +and Snapshot During Video(SDV). + +The ImgU contains two independent pipes, each modelled as a V4L2 sub-device +exposed to userspace as a V4L2 sub-device node. + +Each pipe has two sink pads and three source pads for the following purpose: + +.. tabularcolumns:: |p{0.8cm}|p{4.0cm}|p{4.0cm}| + +.. flat-table:: + :header-rows: 1 + + * - Pad + - Direction + - Purpose + + * - 0 + - sink + - Input raw video stream + + * - 1 + - sink + - Processing parameters + + * - 2 + - source + - Output processed video stream + + * - 3 + - source + - Output viewfinder video stream + + * - 4 + - source + - 3A statistics + +Each pad is connected to a corresponding V4L2 video interface, exposed to +userspace as a V4L2 video device node. + +Device operation +---------------- + +With ImgU, once the input video node ("ipu3-imgu 0/1":0, in +<entity>:<pad-number> format) is queued with buffer (in packed raw Bayer +format), ImgU starts processing the buffer and produces the video output in YUV +format and statistics output on respective output nodes. The driver is expected +to have buffers ready for all of parameter, output and statistics nodes, when +input video node is queued with buffer. + +At a minimum, all of input, main output, 3A statistics and viewfinder +video nodes should be enabled for IPU3 to start image processing. + +Each ImgU V4L2 subdev has the following set of video nodes. + +input, output and viewfinder video nodes +---------------------------------------- + +The frames (in packed raw Bayer format specific to the IPU3) received by the +input video node is processed by the IPU3 Imaging Unit and are output to 2 video +nodes, with each targeting a different purpose (main output and viewfinder +output). + +Details onand the Bayer format specific to the IPU3 can be found in +:ref:`v4l2-pix-fmt-ipu3-sbggr10`. + +The driver supports V4L2 Video Capture Interface as defined at :ref:`devices`. + +Only the multi-planar API is supported. More details can be found at +:ref:`planar-apis`. + +Parameters video node +--------------------- + +The parameters video node receives the ImgU algorithm parameters that are used +to configure how the ImgU algorithms process the image. + +Details on processing parameters specific to the IPU3 can be found in +:ref:`v4l2-meta-fmt-params`. + +3A statistics video node +------------------------ + +3A statistics video node is used by the ImgU driver to output the 3A (auto +focus, auto exposure and auto white balance) statistics for the frames that are +being processed by the ImgU to user space applications. User space applications +can use this statistics data to compute the desired algorithm parameters for +the ImgU. + +Configuring the Intel IPU3 +========================== + +The IPU3 ImgU pipelines can be configured using the Media Controller, defined at +:ref:`media_controller`. + +Running mode and firmware binary selection +------------------------------------------ + +ImgU works based on firmware, currently the ImgU firmware support run 2 pipes +in time-sharing with single input frame data. Each pipe can run at certain mode +- "VIDEO" or "STILL", "VIDEO" mode is commonly used for video frames capture, +and "STILL" is used for still frame capture. However, you can also select +"VIDEO" to capture still frames if you want to capture images with less system +load and power. For "STILL" mode, ImgU will try to use smaller BDS factor and +output larger bayer frame for further YUV processing than "VIDEO" mode to get +high quality images. Besides, "STILL" mode need XNR3 to do noise reduction, +hence "STILL" mode will need more power and memory bandwidth than "VIDEO" mode. +TNR will be enabled in "VIDEO" mode and bypassed by "STILL" mode. ImgU is +running at "VIDEO" mode by default, the user can use v4l2 control +V4L2_CID_INTEL_IPU3_MODE (currently defined in +drivers/staging/media/ipu3/include/uapi/intel-ipu3.h) to query and set the +running mode. For user, there is no difference for buffer queueing between the +"VIDEO" and "STILL" mode, mandatory input and main output node should be +enabled and buffers need be queued, the statistics and the view-finder queues +are optional. + +The firmware binary will be selected according to current running mode, such log +"using binary if_to_osys_striped " or "using binary if_to_osys_primary_striped" +could be observed if you enable the ImgU dynamic debug, the binary +if_to_osys_striped is selected for "VIDEO" and the binary +"if_to_osys_primary_striped" is selected for "STILL". + + +Processing the image in raw Bayer format +---------------------------------------- + +Configuring ImgU V4L2 subdev for image processing +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The ImgU V4L2 subdevs have to be configured with media controller APIs to have +all the video nodes setup correctly. + +Let us take "ipu3-imgu 0" subdev as an example. + +.. code-block:: none + + media-ctl -d $MDEV -r + media-ctl -d $MDEV -l "ipu3-imgu 0 input":0 -> "ipu3-imgu 0":0[1] + media-ctl -d $MDEV -l "ipu3-imgu 0":2 -> "ipu3-imgu 0 output":0[1] + media-ctl -d $MDEV -l "ipu3-imgu 0":3 -> "ipu3-imgu 0 viewfinder":0[1] + media-ctl -d $MDEV -l "ipu3-imgu 0":4 -> "ipu3-imgu 0 3a stat":0[1] + +Also the pipe mode of the corresponding V4L2 subdev should be set as desired +(e.g 0 for video mode or 1 for still mode) through the control id 0x009819a1 as +below. + +.. code-block:: none + + yavta -w "0x009819A1 1" /dev/v4l-subdev7 + +Certain hardware blocks in ImgU pipeline can change the frame resolution by +cropping or scaling, these hardware blocks include Input Feeder(IF), Bayer Down +Scaler (BDS) and Geometric Distortion Correction (GDC). +There is also a block which can change the frame resolution - YUV Scaler, it is +only applicable to the secondary output. + +RAW Bayer frames go through these ImgU pipeline hardware blocks and the final +processed image output to the DDR memory. + +.. kernel-figure:: ipu3_rcb.svg + :alt: ipu3 resolution blocks image + + IPU3 resolution change hardware blocks + +**Input Feeder** + +Input Feeder gets the Bayer frame data from the sensor, it can enable cropping +of lines and columns from the frame and then store pixels into device's internal +pixel buffer which are ready to readout by following blocks. + +**Bayer Down Scaler** + +Bayer Down Scaler is capable of performing image scaling in Bayer domain, the +downscale factor can be configured from 1X to 1/4X in each axis with +configuration steps of 0.03125 (1/32). + +**Geometric Distortion Correction** + +Geometric Distortion Correction is used to perform correction of distortions +and image filtering. It needs some extra filter and envelope padding pixels to +work, so the input resolution of GDC should be larger than the output +resolution. + +**YUV Scaler** + +YUV Scaler which similar with BDS, but it is mainly do image down scaling in +YUV domain, it can support up to 1/12X down scaling, but it can not be applied +to the main output. + +The ImgU V4L2 subdev has to be configured with the supported resolutions in all +the above hardware blocks, for a given input resolution. +For a given supported resolution for an input frame, the Input Feeder, Bayer +Down Scaler and GDC blocks should be configured with the supported resolutions +as each hardware block has its own alignment requirement. + +You must configure the output resolution of the hardware blocks smartly to meet +the hardware requirement along with keeping the maximum field of view. The +intermediate resolutions can be generated by specific tool - + +https://github.com/intel/intel-ipu3-pipecfg + +This tool can be used to generate intermediate resolutions. More information can +be obtained by looking at the following IPU3 ImgU configuration table. + +https://chromium.googlesource.com/chromiumos/overlays/board-overlays/+/master + +Under baseboard-poppy/media-libs/cros-camera-hal-configs-poppy/files/gcss +directory, graph_settings_ov5670.xml can be used as an example. + +The following steps prepare the ImgU pipeline for the image processing. + +1. The ImgU V4L2 subdev data format should be set by using the +VIDIOC_SUBDEV_S_FMT on pad 0, using the GDC width and height obtained above. + +2. The ImgU V4L2 subdev cropping should be set by using the +VIDIOC_SUBDEV_S_SELECTION on pad 0, with V4L2_SEL_TGT_CROP as the target, +using the input feeder height and width. + +3. The ImgU V4L2 subdev composing should be set by using the +VIDIOC_SUBDEV_S_SELECTION on pad 0, with V4L2_SEL_TGT_COMPOSE as the target, +using the BDS height and width. + +For the ov5670 example, for an input frame with a resolution of 2592x1944 +(which is input to the ImgU subdev pad 0), the corresponding resolutions +for input feeder, BDS and GDC are 2592x1944, 2592x1944 and 2560x1920 +respectively. + +Once this is done, the received raw Bayer frames can be input to the ImgU +V4L2 subdev as below, using the open source application v4l2n [#f1]_. + +For an image captured with 2592x1944 [#f4]_ resolution, with desired output +resolution as 2560x1920 and viewfinder resolution as 2560x1920, the following +v4l2n command can be used. This helps process the raw Bayer frames and produces +the desired results for the main output image and the viewfinder output, in NV12 +format. + +.. code-block:: none + + v4l2n --pipe=4 --load=/tmp/frame-#.bin --open=/dev/video4 + --fmt=type:VIDEO_OUTPUT_MPLANE,width=2592,height=1944,pixelformat=0X47337069 \ + --reqbufs=type:VIDEO_OUTPUT_MPLANE,count:1 --pipe=1 \ + --output=/tmp/frames.out --open=/dev/video5 \ + --fmt=type:VIDEO_CAPTURE_MPLANE,width=2560,height=1920,pixelformat=NV12 \ + --reqbufs=type:VIDEO_CAPTURE_MPLANE,count:1 --pipe=2 \ + --output=/tmp/frames.vf --open=/dev/video6 \ + --fmt=type:VIDEO_CAPTURE_MPLANE,width=2560,height=1920,pixelformat=NV12 \ + --reqbufs=type:VIDEO_CAPTURE_MPLANE,count:1 --pipe=3 --open=/dev/video7 \ + --output=/tmp/frames.3A --fmt=type:META_CAPTURE,? \ + --reqbufs=count:1,type:META_CAPTURE --pipe=1,2,3,4 --stream=5 + +You can also use yavta [#f2]_ command to do same thing as above: + +.. code-block:: none + + yavta --data-prefix -Bcapture-mplane -c10 -n5 -I -s2592x1944 \ + --file=frame-#.out-f NV12 /dev/video5 & \ + yavta --data-prefix -Bcapture-mplane -c10 -n5 -I -s2592x1944 \ + --file=frame-#.vf -f NV12 /dev/video6 & \ + yavta --data-prefix -Bmeta-capture -c10 -n5 -I \ + --file=frame-#.3a /dev/video7 & \ + yavta --data-prefix -Boutput-mplane -c10 -n5 -I -s2592x1944 \ + --file=/tmp/frame-in.cio2 -f IPU3_SGRBG10 /dev/video4 + +where /dev/video4, /dev/video5, /dev/video6 and /dev/video7 devices point to +input, output, viewfinder and 3A statistics video nodes respectively. + +Converting the raw Bayer image into YUV domain +---------------------------------------------- + +The processed images after the above step, can be converted to YUV domain +as below. + +Main output frames +~~~~~~~~~~~~~~~~~~ + +.. code-block:: none + + raw2pnm -x2560 -y1920 -fNV12 /tmp/frames.out /tmp/frames.out.ppm + +where 2560x1920 is output resolution, NV12 is the video format, followed +by input frame and output PNM file. + +Viewfinder output frames +~~~~~~~~~~~~~~~~~~~~~~~~ + +.. code-block:: none + + raw2pnm -x2560 -y1920 -fNV12 /tmp/frames.vf /tmp/frames.vf.ppm + +where 2560x1920 is output resolution, NV12 is the video format, followed +by input frame and output PNM file. + +Example user space code for IPU3 +================================ + +User space code that configures and uses IPU3 is available here. + +https://chromium.googlesource.com/chromiumos/platform/arc-camera/+/master/ + +The source can be located under hal/intel directory. + +Overview of IPU3 pipeline +========================= + +IPU3 pipeline has a number of image processing stages, each of which takes a +set of parameters as input. The major stages of pipelines are shown here: + +.. kernel-render:: DOT + :alt: IPU3 ImgU Pipeline + :caption: IPU3 ImgU Pipeline Diagram + + digraph "IPU3 ImgU" { + node [shape=box] + splines="ortho" + rankdir="LR" + + a [label="Raw pixels"] + b [label="Bayer Downscaling"] + c [label="Optical Black Correction"] + d [label="Linearization"] + e [label="Lens Shading Correction"] + f [label="White Balance / Exposure / Focus Apply"] + g [label="Bayer Noise Reduction"] + h [label="ANR"] + i [label="Demosaicing"] + j [label="Color Correction Matrix"] + k [label="Gamma correction"] + l [label="Color Space Conversion"] + m [label="Chroma Down Scaling"] + n [label="Chromatic Noise Reduction"] + o [label="Total Color Correction"] + p [label="XNR3"] + q [label="TNR"] + r [label="DDR", style=filled, fillcolor=yellow, shape=cylinder] + s [label="YUV Downscaling"] + t [label="DDR", style=filled, fillcolor=yellow, shape=cylinder] + + { rank=same; a -> b -> c -> d -> e -> f -> g -> h -> i } + { rank=same; j -> k -> l -> m -> n -> o -> p -> q -> s -> t} + + a -> j [style=invis, weight=10] + i -> j + q -> r + } + +The table below presents a description of the above algorithms. + +======================== ======================================================= +Name Description +======================== ======================================================= +Optical Black Correction Optical Black Correction block subtracts a pre-defined + value from the respective pixel values to obtain better + image quality. + Defined in struct ipu3_uapi_obgrid_param. +Linearization This algo block uses linearization parameters to + address non-linearity sensor effects. The Lookup table + table is defined in + struct ipu3_uapi_isp_lin_vmem_params. +SHD Lens shading correction is used to correct spatial + non-uniformity of the pixel response due to optical + lens shading. This is done by applying a different gain + for each pixel. The gain, black level etc are + configured in struct ipu3_uapi_shd_config_static. +BNR Bayer noise reduction block removes image noise by + applying a bilateral filter. + See struct ipu3_uapi_bnr_static_config for details. +ANR Advanced Noise Reduction is a block based algorithm + that performs noise reduction in the Bayer domain. The + convolution matrix etc can be found in + struct ipu3_uapi_anr_config. +DM Demosaicing converts raw sensor data in Bayer format + into RGB (Red, Green, Blue) presentation. Then add + outputs of estimation of Y channel for following stream + processing by Firmware. The struct is defined as + struct ipu3_uapi_dm_config. +Color Correction Color Correction algo transforms sensor specific color + space to the standard "sRGB" color space. This is done + by applying 3x3 matrix defined in + struct ipu3_uapi_ccm_mat_config. +Gamma correction Gamma correction struct ipu3_uapi_gamma_config is a + basic non-linear tone mapping correction that is + applied per pixel for each pixel component. +CSC Color space conversion transforms each pixel from the + RGB primary presentation to YUV (Y: brightness, + UV: Luminance) presentation. This is done by applying + a 3x3 matrix defined in + struct ipu3_uapi_csc_mat_config +CDS Chroma down sampling + After the CSC is performed, the Chroma Down Sampling + is applied for a UV plane down sampling by a factor + of 2 in each direction for YUV 4:2:0 using a 4x2 + configurable filter struct ipu3_uapi_cds_params. +CHNR Chroma noise reduction + This block processes only the chrominance pixels and + performs noise reduction by cleaning the high + frequency noise. + See struct struct ipu3_uapi_yuvp1_chnr_config. +TCC Total color correction as defined in struct + struct ipu3_uapi_yuvp2_tcc_static_config. +XNR3 eXtreme Noise Reduction V3 is the third revision of + noise reduction algorithm used to improve image + quality. This removes the low frequency noise in the + captured image. Two related structs are being defined, + struct ipu3_uapi_isp_xnr3_params for ISP data memory + and struct ipu3_uapi_isp_xnr3_vmem_params for vector + memory. +TNR Temporal Noise Reduction block compares successive + frames in time to remove anomalies / noise in pixel + values. struct ipu3_uapi_isp_tnr3_vmem_params and + struct ipu3_uapi_isp_tnr3_params are defined for ISP + vector and data memory respectively. +======================== ======================================================= + +Other often encountered acronyms not listed in above table: + + ACC + Accelerator cluster + AWB_FR + Auto white balance filter response statistics + BDS + Bayer downscaler parameters + CCM + Color correction matrix coefficients + IEFd + Image enhancement filter directed + Obgrid + Optical black level compensation + OSYS + Output system configuration + ROI + Region of interest + YDS + Y down sampling + YTM + Y-tone mapping + +A few stages of the pipeline will be executed by firmware running on the ISP +processor, while many others will use a set of fixed hardware blocks also +called accelerator cluster (ACC) to crunch pixel data and produce statistics. + +ACC parameters of individual algorithms, as defined by +struct ipu3_uapi_acc_param, can be chosen to be applied by the user +space through struct struct ipu3_uapi_flags embedded in +struct ipu3_uapi_params structure. For parameters that are configured as +not enabled by the user space, the corresponding structs are ignored by the +driver, in which case the existing configuration of the algorithm will be +preserved. + +References +========== + +.. [#f5] drivers/staging/media/ipu3/include/uapi/intel-ipu3.h + +.. [#f1] https://github.com/intel/nvt + +.. [#f2] http://git.ideasonboard.org/yavta.git + +.. [#f3] http://git.ideasonboard.org/?p=media-ctl.git;a=summary + +.. 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SPDX-License-Identifier: GPL-2.0 + +IVTV cards list +=============== + +.. tabularcolumns:: |p{1.4cm}|p{12.7cm}|p{3.4cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 2 19 18 + :stub-columns: 0 + + * - Card number + - Card name + - PCI subsystem IDs + + * - 0 + - Hauppauge WinTV PVR-250 + - IVTV16 104d:813d + + * - 1 + - Hauppauge WinTV PVR-350 + - IVTV16 104d:813d + + * - 2 + - Hauppauge WinTV PVR-150 + - IVTV16 104d:813d + + * - 3 + - AVerMedia M179 + - IVTV15 1461:a3cf, IVTV15 1461:a3ce + + * - 4 + - Yuan MPG600, Kuroutoshikou ITVC16-STVLP + - IVTV16 12ab:fff3, IVTV16 12ab:ffff + + * - 5 + - YUAN MPG160, Kuroutoshikou ITVC15-STVLP, I/O Data GV-M2TV/PCI + - IVTV15 10fc:40a0 + + * - 6 + - Yuan PG600, Diamond PVR-550 + - IVTV16 ff92:0070, IVTV16 ffab:0600 + + * - 7 + - Adaptec VideOh! AVC-2410 + - IVTV16 9005:0093 + + * - 8 + - Adaptec VideOh! AVC-2010 + - IVTV16 9005:0092 + + * - 9 + - Nagase Transgear 5000TV + - IVTV16 1461:bfff + + * - 10 + - AOpen VA2000MAX-SNT6 + - IVTV16 0000:ff5f + + * - 11 + - Yuan MPG600GR, Kuroutoshikou CX23416GYC-STVLP + - IVTV16 12ab:0600, IVTV16 fbab:0600, IVTV16 1154:0523 + + * - 12 + - I/O Data GV-MVP/RX, GV-MVP/RX2W (dual tuner) + - IVTV16 10fc:d01e, IVTV16 10fc:d038, IVTV16 10fc:d039 + + * - 13 + - I/O Data GV-MVP/RX2E + - IVTV16 10fc:d025 + + * - 14 + - GotView PCI DVD + - IVTV16 12ab:0600 + + * - 15 + - GotView PCI DVD2 Deluxe + - IVTV16 ffac:0600 + + * - 16 + - Yuan MPC622 + - IVTV16 ff01:d998 + + * - 17 + - Digital Cowboy DCT-MTVP1 + - IVTV16 1461:bfff + + * - 18 + - Yuan PG600-2, GotView PCI DVD Lite + - IVTV16 ffab:0600, IVTV16 ffad:0600 + + * - 19 + - Club3D ZAP-TV1x01 + - IVTV16 ffab:0600 + + * - 20 + - AVerTV MCE 116 Plus + - IVTV16 1461:c439 + + * - 21 + - ASUS Falcon2 + - IVTV16 1043:4b66, IVTV16 1043:462e, IVTV16 1043:4b2e + + * - 22 + - AVerMedia PVR-150 Plus / AVerTV M113 Partsnic (Daewoo) Tuner + - IVTV16 1461:c034, IVTV16 1461:c035 + + * - 23 + - AVerMedia EZMaker PCI Deluxe + - IVTV16 1461:c03f + + * - 24 + - AVerMedia M104 + - IVTV16 1461:c136 + + * - 25 + - Buffalo PC-MV5L/PCI + - IVTV16 1154:052b + + * - 26 + - AVerMedia UltraTV 1500 MCE / AVerTV M113 Philips Tuner + - IVTV16 1461:c019, IVTV16 1461:c01b + + * - 27 + - Sony VAIO Giga Pocket (ENX Kikyou) + - IVTV16 104d:813d + + * - 28 + - Hauppauge WinTV PVR-350 (V1) + - IVTV16 104d:813d + + * - 29 + - Yuan MPG600GR, Kuroutoshikou CX23416GYC-STVLP (no GR) + - IVTV16 104d:813d + + * - 30 + - Yuan MPG600GR, Kuroutoshikou CX23416GYC-STVLP (no GR/YCS) + - IVTV16 104d:813d diff --git a/Documentation/admin-guide/media/ivtv.rst b/Documentation/admin-guide/media/ivtv.rst new file mode 100644 index 000000000..101f16d02 --- /dev/null +++ b/Documentation/admin-guide/media/ivtv.rst @@ -0,0 +1,218 @@ +.. SPDX-License-Identifier: GPL-2.0 + +The ivtv driver +=============== + +Author: Hans Verkuil <hverkuil@xs4all.nl> + +This is a v4l2 device driver for the Conexant cx23415/6 MPEG encoder/decoder. +The cx23415 can do both encoding and decoding, the cx23416 can only do MPEG +encoding. Currently the only card featuring full decoding support is the +Hauppauge PVR-350. + +.. note:: + + #) This driver requires the latest encoder firmware (version 2.06.039, size + 376836 bytes). Get the firmware from here: + + https://linuxtv.org/downloads/firmware/#conexant + + #) 'normal' TV applications do not work with this driver, you need + an application that can handle MPEG input such as mplayer, xine, MythTV, + etc. + +The primary goal of the IVTV project is to provide a "clean room" Linux +Open Source driver implementation for video capture cards based on the +iCompression iTVC15 or Conexant CX23415/CX23416 MPEG Codec. + +Features +-------- + + * Hardware mpeg2 capture of broadcast video (and sound) via the tuner or + S-Video/Composite and audio line-in. + * Hardware mpeg2 capture of FM radio where hardware support exists + * Supports NTSC, PAL, SECAM with stereo sound + * Supports SAP and bilingual transmissions. + * Supports raw VBI (closed captions and teletext). + * Supports sliced VBI (closed captions and teletext) and is able to insert + this into the captured MPEG stream. + * Supports raw YUV and PCM input. + +Additional features for the PVR-350 (CX23415 based) +--------------------------------------------------- + + * Provides hardware mpeg2 playback + * Provides comprehensive OSD (On Screen Display: ie. graphics overlaying the + video signal) + * Provides a framebuffer (allowing X applications to appear on the video + device) + * Supports raw YUV output. + +IMPORTANT: In case of problems first read this page: + https://help.ubuntu.com/community/Install_IVTV_Troubleshooting + +See also +-------- + +https://linuxtv.org + +IRC +--- + +irc://irc.freenode.net/#v4l + +---------------------------------------------------------- + +Devices +------- + +A maximum of 12 ivtv boards are allowed at the moment. + +Cards that don't have a video output capability (i.e. non PVR350 cards) +lack the vbi8, vbi16, video16 and video48 devices. They also do not +support the framebuffer device /dev/fbx for OSD. + +The radio0 device may or may not be present, depending on whether the +card has a radio tuner or not. + +Here is a list of the base v4l devices: + +.. code-block:: none + + crw-rw---- 1 root video 81, 0 Jun 19 22:22 /dev/video0 + crw-rw---- 1 root video 81, 16 Jun 19 22:22 /dev/video16 + crw-rw---- 1 root video 81, 24 Jun 19 22:22 /dev/video24 + crw-rw---- 1 root video 81, 32 Jun 19 22:22 /dev/video32 + crw-rw---- 1 root video 81, 48 Jun 19 22:22 /dev/video48 + crw-rw---- 1 root video 81, 64 Jun 19 22:22 /dev/radio0 + crw-rw---- 1 root video 81, 224 Jun 19 22:22 /dev/vbi0 + crw-rw---- 1 root video 81, 228 Jun 19 22:22 /dev/vbi8 + crw-rw---- 1 root video 81, 232 Jun 19 22:22 /dev/vbi16 + +Base devices +------------ + +For every extra card you have the numbers increased by one. For example, +/dev/video0 is listed as the 'base' encoding capture device so we have: + +- /dev/video0 is the encoding capture device for the first card (card 0) +- /dev/video1 is the encoding capture device for the second card (card 1) +- /dev/video2 is the encoding capture device for the third card (card 2) + +Note that if the first card doesn't have a feature (eg no decoder, so no +video16, the second card will still use video17. The simple rule is 'add +the card number to the base device number'. If you have other capture +cards (e.g. WinTV PCI) that are detected first, then you have to tell +the ivtv module about it so that it will start counting at 1 (or 2, or +whatever). Otherwise the device numbers can get confusing. The ivtv +'ivtv_first_minor' module option can be used for that. + + +- /dev/video0 + + The encoding capture device(s). + + Read-only. + + Reading from this device gets you the MPEG1/2 program stream. + Example: + + .. code-block:: none + + cat /dev/video0 > my.mpg (you need to hit ctrl-c to exit) + + +- /dev/video16 + + The decoder output device(s) + + Write-only. Only present if the MPEG decoder (i.e. CX23415) exists. + + An mpeg2 stream sent to this device will appear on the selected video + display, audio will appear on the line-out/audio out. It is only + available for cards that support video out. Example: + + .. code-block:: none + + cat my.mpg >/dev/video16 + + +- /dev/video24 + + The raw audio capture device(s). + + Read-only + + The raw audio PCM stereo stream from the currently selected + tuner or audio line-in. Reading from this device results in a raw + (signed 16 bit Little Endian, 48000 Hz, stereo pcm) capture. + This device only captures audio. This should be replaced by an ALSA + device in the future. + Note that there is no corresponding raw audio output device, this is + not supported in the decoder firmware. + + +- /dev/video32 + + The raw video capture device(s) + + Read-only + + The raw YUV video output from the current video input. The YUV format + is a 16x16 linear tiled NV12 format (V4L2_PIX_FMT_NV12_16L16) + + Note that the YUV and PCM streams are not synchronized, so they are of + limited use. + + +- /dev/video48 + + The raw video display device(s) + + Write-only. Only present if the MPEG decoder (i.e. CX23415) exists. + + Writes a YUV stream to the decoder of the card. + + +- /dev/radio0 + + The radio tuner device(s) + + Cannot be read or written. + + Used to enable the radio tuner and tune to a frequency. You cannot + read or write audio streams with this device. Once you use this + device to tune the radio, use /dev/video24 to read the raw pcm stream + or /dev/video0 to get an mpeg2 stream with black video. + + +- /dev/vbi0 + + The 'vertical blank interval' (Teletext, CC, WSS etc) capture device(s) + + Read-only + + Captures the raw (or sliced) video data sent during the Vertical Blank + Interval. This data is used to encode teletext, closed captions, VPS, + widescreen signalling, electronic program guide information, and other + services. + + +- /dev/vbi8 + + Processed vbi feedback device(s) + + Read-only. Only present if the MPEG decoder (i.e. CX23415) exists. + + The sliced VBI data embedded in an MPEG stream is reproduced on this + device. So while playing back a recording on /dev/video16, you can + read the embedded VBI data from /dev/vbi8. + + +- /dev/vbi16 + + The vbi 'display' device(s) + + Write-only. Only present if the MPEG decoder (i.e. CX23415) exists. + + Can be used to send sliced VBI data to the video-out connector. diff --git a/Documentation/admin-guide/media/lmedm04.rst b/Documentation/admin-guide/media/lmedm04.rst new file mode 100644 index 000000000..a6ee33413 --- /dev/null +++ b/Documentation/admin-guide/media/lmedm04.rst @@ -0,0 +1,107 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Firmware files for lmedm04 cards +================================ + +To extract firmware for the DM04/QQBOX you need to copy the +following file(s) to this directory. + +For DM04+/QQBOX LME2510C (Sharp 7395 Tuner) +------------------------------------------- + +The Sharp 7395 driver can be found in windows/system32/drivers + +US2A0D.sys (dated 17 Mar 2009) + + +and run: + +.. code-block:: none + + scripts/get_dvb_firmware lme2510c_s7395 + +will produce dvb-usb-lme2510c-s7395.fw + +An alternative but older firmware can be found on the driver +disk DVB-S_EN_3.5A in BDADriver/driver + +LMEBDA_DVBS7395C.sys (dated 18 Jan 2008) + +and run: + +.. code-block:: none + + ./get_dvb_firmware lme2510c_s7395_old + +will produce dvb-usb-lme2510c-s7395.fw + +The LG firmware can be found on the driver +disk DM04+_5.1A[LG] in BDADriver/driver + +For DM04 LME2510 (LG Tuner) +--------------------------- + +LMEBDA_DVBS.sys (dated 13 Nov 2007) + +and run: + + +.. code-block:: none + + ./get_dvb_firmware lme2510_lg + +will produce dvb-usb-lme2510-lg.fw + + +Other LG firmware can be extracted manually from US280D.sys +only found in windows/system32/drivers + +dd if=US280D.sys ibs=1 skip=42360 count=3924 of=dvb-usb-lme2510-lg.fw + +For DM04 LME2510C (LG Tuner) +---------------------------- + +.. code-block:: none + + dd if=US280D.sys ibs=1 skip=35200 count=3850 of=dvb-usb-lme2510c-lg.fw + + +The Sharp 0194 tuner driver can be found in windows/system32/drivers + +US290D.sys (dated 09 Apr 2009) + +For LME2510 +----------- + +.. code-block:: none + + dd if=US290D.sys ibs=1 skip=36856 count=3976 of=dvb-usb-lme2510-s0194.fw + + +For LME2510C +------------ + + +.. code-block:: none + + dd if=US290D.sys ibs=1 skip=33152 count=3697 of=dvb-usb-lme2510c-s0194.fw + + +The m88rs2000 tuner driver can be found in windows/system32/drivers + +US2B0D.sys (dated 29 Jun 2010) + + +.. code-block:: none + + dd if=US2B0D.sys ibs=1 skip=34432 count=3871 of=dvb-usb-lme2510c-rs2000.fw + +We need to modify id of rs2000 firmware or it will warm boot id 3344:1120. + + +.. code-block:: none + + + echo -ne \\xF0\\x22 | dd conv=notrunc bs=1 count=2 seek=266 of=dvb-usb-lme2510c-rs2000.fw + +Copy the firmware file(s) to /lib/firmware diff --git a/Documentation/admin-guide/media/misc-cardlist.rst b/Documentation/admin-guide/media/misc-cardlist.rst new file mode 100644 index 000000000..4c26bcfcc --- /dev/null +++ b/Documentation/admin-guide/media/misc-cardlist.rst @@ -0,0 +1,28 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Firewire driver +=============== + +The media subsystem also provides a firewire driver for digital TV: + +======= ===================== +Driver Name +======= ===================== +firedtv FireDTV and FloppyDTV +======= ===================== + +Test drivers +============ + +In order to test userspace applications, there's a number of virtual +drivers, with provide test functionality, simulating real hardware +devices: + +======= ====================================== +Driver Name +======= ====================================== +vicodec Virtual Codec Driver +vim2m Virtual Memory-to-Memory Driver +vimc Virtual Media Controller Driver (VIMC) +vivid Virtual Video Test Driver +======= ====================================== diff --git a/Documentation/admin-guide/media/omap3isp.rst b/Documentation/admin-guide/media/omap3isp.rst new file mode 100644 index 000000000..f32e7375a --- /dev/null +++ b/Documentation/admin-guide/media/omap3isp.rst @@ -0,0 +1,92 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. include:: <isonum.txt> + +OMAP 3 Image Signal Processor (ISP) driver +========================================== + +Copyright |copy| 2010 Nokia Corporation + +Copyright |copy| 2009 Texas Instruments, Inc. + +Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>, +Sakari Ailus <sakari.ailus@iki.fi>, David Cohen <dacohen@gmail.com> + + +Introduction +------------ + +This file documents the Texas Instruments OMAP 3 Image Signal Processor (ISP) +driver located under drivers/media/platform/ti/omap3isp. The original driver was +written by Texas Instruments but since that it has been rewritten (twice) at +Nokia. + +The driver has been successfully used on the following versions of OMAP 3: + +- 3430 +- 3530 +- 3630 + +The driver implements V4L2, Media controller and v4l2_subdev interfaces. +Sensor, lens and flash drivers using the v4l2_subdev interface in the kernel +are supported. + + +Split to subdevs +---------------- + +The OMAP 3 ISP is split into V4L2 subdevs, each of the blocks inside the ISP +having one subdev to represent it. Each of the subdevs provide a V4L2 subdev +interface to userspace. + +- OMAP3 ISP CCP2 +- OMAP3 ISP CSI2a +- OMAP3 ISP CCDC +- OMAP3 ISP preview +- OMAP3 ISP resizer +- OMAP3 ISP AEWB +- OMAP3 ISP AF +- OMAP3 ISP histogram + +Each possible link in the ISP is modelled by a link in the Media controller +interface. For an example program see [#]_. + + +Controlling the OMAP 3 ISP +-------------------------- + +In general, the settings given to the OMAP 3 ISP take effect at the beginning +of the following frame. This is done when the module becomes idle during the +vertical blanking period on the sensor. In memory-to-memory operation the pipe +is run one frame at a time. Applying the settings is done between the frames. + +All the blocks in the ISP, excluding the CSI-2 and possibly the CCP2 receiver, +insist on receiving complete frames. Sensors must thus never send the ISP +partial frames. + +Autoidle does have issues with some ISP blocks on the 3430, at least. +Autoidle is only enabled on 3630 when the omap3isp module parameter autoidle +is non-zero. + +Technical reference manuals (TRMs) and other documentation +---------------------------------------------------------- + +OMAP 3430 TRM: +<URL:http://focus.ti.com/pdfs/wtbu/OMAP34xx_ES3.1.x_PUBLIC_TRM_vZM.zip> +Referenced 2011-03-05. + +OMAP 35xx TRM: +<URL:http://www.ti.com/litv/pdf/spruf98o> Referenced 2011-03-05. + +OMAP 3630 TRM: +<URL:http://focus.ti.com/pdfs/wtbu/OMAP36xx_ES1.x_PUBLIC_TRM_vQ.zip> +Referenced 2011-03-05. + +DM 3730 TRM: +<URL:http://www.ti.com/litv/pdf/sprugn4h> Referenced 2011-03-06. + + +References +---------- + +.. [#] http://git.ideasonboard.org/?p=media-ctl.git;a=summary diff --git a/Documentation/admin-guide/media/omap4_camera.rst b/Documentation/admin-guide/media/omap4_camera.rst new file mode 100644 index 000000000..2ada9b1e6 --- /dev/null +++ b/Documentation/admin-guide/media/omap4_camera.rst @@ -0,0 +1,62 @@ +.. SPDX-License-Identifier: GPL-2.0 + +OMAP4 ISS Driver +================ + +Author: Sergio Aguirre <sergio.a.aguirre@gmail.com> + +Copyright (C) 2012, Texas Instruments + +Introduction +------------ + +The OMAP44XX family of chips contains the Imaging SubSystem (a.k.a. ISS), +Which contains several components that can be categorized in 3 big groups: + +- Interfaces (2 Interfaces: CSI2-A & CSI2-B/CCP2) +- ISP (Image Signal Processor) +- SIMCOP (Still Image Coprocessor) + +For more information, please look in [#f1]_ for latest version of: +"OMAP4430 Multimedia Device Silicon Revision 2.x" + +As of Revision AB, the ISS is described in detail in section 8. + +This driver is supporting **only** the CSI2-A/B interfaces for now. + +It makes use of the Media Controller framework [#f2]_, and inherited most of the +code from OMAP3 ISP driver (found under drivers/media/platform/ti/omap3isp/\*), +except that it doesn't need an IOMMU now for ISS buffers memory mapping. + +Supports usage of MMAP buffers only (for now). + +Tested platforms +---------------- + +- OMAP4430SDP, w/ ES2.1 GP & SEVM4430-CAM-V1-0 (Contains IMX060 & OV5640, in + which only the last one is supported, outputting YUV422 frames). + +- TI Blaze MDP, w/ OMAP4430 ES2.2 EMU (Contains 1 IMX060 & 2 OV5650 sensors, in + which only the OV5650 are supported, outputting RAW10 frames). + +- PandaBoard, Rev. A2, w/ OMAP4430 ES2.1 GP & OV adapter board, tested with + following sensors: + * OV5640 + * OV5650 + +- Tested on mainline kernel: + + http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=summary + + Tag: v3.3 (commit c16fa4f2ad19908a47c63d8fa436a1178438c7e7) + +File list +--------- +drivers/staging/media/omap4iss/ +include/linux/platform_data/media/omap4iss.h + +References +---------- + +.. [#f1] http://focus.ti.com/general/docs/wtbu/wtbudocumentcenter.tsp?navigationId=12037&templateId=6123#62 +.. [#f2] http://lwn.net/Articles/420485/ diff --git a/Documentation/admin-guide/media/opera-firmware.rst b/Documentation/admin-guide/media/opera-firmware.rst new file mode 100644 index 000000000..fab358155 --- /dev/null +++ b/Documentation/admin-guide/media/opera-firmware.rst @@ -0,0 +1,33 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Opera firmware +============== + +Author: Marco Gittler <g.marco@freenet.de> + +To extract the firmware for the Opera DVB-S1 USB-Box +you need to copy the files: + +2830SCap2.sys +2830SLoad2.sys + +from the windriver disk into this directory. + +Then run: + +.. code-block:: none + + scripts/get_dvb_firmware opera1 + +and after that you have 2 files: + +dvb-usb-opera-01.fw +dvb-usb-opera1-fpga-01.fw + +in here. + +Copy them into /lib/firmware/ . + +After that the driver can load the firmware +(if you have enabled firmware loading +in kernel config and have hotplug running). diff --git a/Documentation/admin-guide/media/other-usb-cardlist.rst b/Documentation/admin-guide/media/other-usb-cardlist.rst new file mode 100644 index 000000000..fb88db50e --- /dev/null +++ b/Documentation/admin-guide/media/other-usb-cardlist.rst @@ -0,0 +1,78 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Other USB cards list +==================== + +================ ====================================== ===================== +Driver Card name USB IDs +================ ====================================== ===================== +airspy Airspy 1d50:60a1 +dvb-as102 Abilis Systems DVB-Titan 1BA6:0001 +dvb-as102 PCTV Systems picoStick (74e) 2013:0246 +dvb-as102 Elgato EyeTV DTT Deluxe 0fd9:002c +dvb-as102 nBox DVB-T Dongle 0b89:0007 +dvb-as102 Sky IT Digital Key (green led) 2137:0001 +b2c2-flexcop-usb Technisat/B2C2 FlexCop II/IIb/III 0af7:0101 + Digital TV +go7007 WIS GO7007 MPEG encoder 1943:a250, 093b:a002, + 093b:a004, 0eb1:6666, + 0eb1:6668 +hackrf HackRF Software Decoder Radio 1d50:6089 +hdpvr Hauppauge HD PVR 2040:4900, 2040:4901, + 2040:4902, 2040:4982, + 2040:4903 +msi2500 Mirics MSi3101 SDR Dongle 1df7:2500, 2040:d300 +pvrusb2 Hauppauge WinTV-PVR USB2 2040:2900, 2040:2950, + 2040:2400, 1164:0622, + 1164:0602, 11ba:1003, + 11ba:1001, 2040:7300, + 2040:7500, 2040:7501, + 0ccd:0039, 2040:7502, + 2040:7510 +pwc Creative Webcam 5 041E:400C +pwc Creative Webcam Pro Ex 041E:4011 +pwc Logitech QuickCam 3000 Pro 046D:08B0 +pwc Logitech QuickCam Notebook Pro 046D:08B1 +pwc Logitech QuickCam 4000 Pro 046D:08B2 +pwc Logitech QuickCam Zoom (old model) 046D:08B3 +pwc Logitech QuickCam Zoom (new model) 046D:08B4 +pwc Logitech QuickCam Orbit/Sphere 046D:08B5 +pwc Logitech/Cisco VT Camera 046D:08B6 +pwc Logitech ViewPort AV 100 046D:08B7 +pwc Logitech QuickCam 046D:08B8 +pwc Philips PCA645VC 0471:0302 +pwc Philips PCA646VC 0471:0303 +pwc Askey VC010 type 2 0471:0304 +pwc Philips PCVC675K (Vesta) 0471:0307 +pwc Philips PCVC680K (Vesta Pro) 0471:0308 +pwc Philips PCVC690K (Vesta Pro Scan) 0471:030C +pwc Philips PCVC730K (ToUCam Fun), 0471:0310 + PCVC830 (ToUCam II) +pwc Philips PCVC740K (ToUCam Pro), 0471:0311 + PCVC840 (ToUCam II) +pwc Philips PCVC750K (ToUCam Pro Scan) 0471:0312 +pwc Philips PCVC720K/40 (ToUCam XS) 0471:0313 +pwc Philips SPC 900NC 0471:0329 +pwc Philips SPC 880NC 0471:032C +pwc Sotec Afina Eye 04CC:8116 +pwc Samsung MPC-C10 055D:9000 +pwc Samsung MPC-C30 055D:9001 +pwc Samsung SNC-35E (Ver3.0) 055D:9002 +pwc Askey VC010 type 1 069A:0001 +pwc AME Co. Afina Eye 06BE:8116 +pwc Visionite VCS-UC300 0d81:1900 +pwc Visionite VCS-UM100 0d81:1910 +s2255drv Sensoray 2255 1943:2255, 1943:2257 +stk1160 STK1160 USB video capture dongle 05e1:0408 +dvb-ttusb-budget Technotrend/Hauppauge Nova-USB devices 0b48:1003, 0b48:1004, + 0b48:1005 +dvb-ttusb_dec Technotrend/Hauppauge MPEG decoder 0b48:1006 + DEC3000-s +dvb-ttusb_dec Technotrend/Hauppauge MPEG decoder 0b48:1007 +dvb-ttusb_dec Technotrend/Hauppauge MPEG decoder 0b48:1008 + DEC2000-t +dvb-ttusb_dec Technotrend/Hauppauge MPEG decoder + DEC2540-t 0b48:1009 +usbtv Fushicai USBTV007 Audio-Video Grabber 1b71:3002, 1f71:3301, + 1f71:3306 +================ ====================================== ===================== diff --git a/Documentation/admin-guide/media/pci-cardlist.rst b/Documentation/admin-guide/media/pci-cardlist.rst new file mode 100644 index 000000000..42528795d --- /dev/null +++ b/Documentation/admin-guide/media/pci-cardlist.rst @@ -0,0 +1,108 @@ +.. SPDX-License-Identifier: GPL-2.0 + +PCI drivers +=========== + +The PCI boards are identified by an identification called PCI ID. The PCI ID +is actually composed by two parts: + + - Vendor ID and device ID; + - Subsystem ID and Subsystem device ID; + +The ``lspci -nn`` command allows identifying the vendor/device PCI IDs: + +.. code-block:: none + :emphasize-lines: 3 + + $ lspci -nn + ... + 00:0a.0 Multimedia controller [0480]: Philips Semiconductors SAA7131/SAA7133/SAA7135 Video Broadcast Decoder [1131:7133] (rev d1) + 00:0b.0 Multimedia controller [0480]: Brooktree Corporation Bt878 Audio Capture [109e:0878] (rev 11) + 01:00.0 Multimedia video controller [0400]: Conexant Systems, Inc. CX23887/8 PCIe Broadcast Audio and Video Decoder with 3D Comb [14f1:8880] (rev 0f) + 02:01.0 Multimedia video controller [0400]: Internext Compression Inc iTVC15 (CX23415) Video Decoder [4444:0803] (rev 01) + 02:02.0 Multimedia video controller [0400]: Conexant Systems, Inc. CX23418 Single-Chip MPEG-2 Encoder with Integrated Analog Video/Broadcast Audio Decoder [14f1:5b7a] + 02:03.0 Multimedia video controller [0400]: Brooktree Corporation Bt878 Video Capture [109e:036e] (rev 11) + ... + +The subsystem IDs can be obtained using ``lspci -vn`` + +.. code-block:: none + :emphasize-lines: 4 + + $ lspci -vn + ... + 00:0a.0 0480: 1131:7133 (rev d1) + Subsystem: 1461:f01d + Flags: bus master, medium devsel, latency 32, IRQ 209 + Memory at e2002000 (32-bit, non-prefetchable) [size=2K] + Capabilities: [40] Power Management version 2 + ... + +At the above example, the first card uses the ``saa7134`` driver, and +has a vendor/device PCI ID equal to ``1131:7133`` and a PCI subsystem +ID equal to ``1461:f01d`` (see :doc:`Saa7134 card list<saa7134-cardlist>`). + +Unfortunately, sometimes the same PCI subsystem ID is used by different +products. So, several media drivers allow passing a ``card=`` parameter, +in order to setup a card number that would match the correct settings for +an specific board. + +The current supported PCI/PCIe cards (not including staging drivers) are +listed below\ [#]_. + +.. [#] some of the drivers have sub-drivers, not shown at this table + +================ ======================================================== +Driver Name +================ ======================================================== +altera-ci Altera FPGA based CI module +b2c2-flexcop-pci Technisat/B2C2 Air/Sky/Cable2PC PCI +bt878 DVB/ATSC Support for bt878 based TV cards +bttv BT8x8 Video For Linux +cobalt Cisco Cobalt +cx18 Conexant cx23418 MPEG encoder +cx23885 Conexant cx23885 (2388x successor) +cx25821 Conexant cx25821 +cx88xx Conexant 2388x (bt878 successor) +ddbridge Digital Devices bridge +dm1105 SDMC DM1105 based PCI cards +dt3155 DT3155 frame grabber +dvb-ttpci AV7110 cards +earth-pt1 PT1 cards +earth-pt3 Earthsoft PT3 cards +hexium_gemini Hexium Gemini frame grabber +hexium_orion Hexium HV-PCI6 and Orion frame grabber +hopper HOPPER based cards +ipu3-cio2 Intel ipu3-cio2 driver +ivtv Conexant cx23416/cx23415 MPEG encoder/decoder +ivtvfb Conexant cx23415 framebuffer +mantis MANTIS based cards +mxb Siemens-Nixdorf 'Multimedia eXtension Board' +netup-unidvb NetUP Universal DVB card +ngene Micronas nGene +pluto2 Pluto2 cards +saa7134 Philips SAA7134 +saa7164 NXP SAA7164 +smipcie SMI PCIe DVBSky cards +solo6x10 Bluecherry / Softlogic 6x10 capture cards (MPEG-4/H.264) +sta2x11_vip STA2X11 VIP Video For Linux +tw5864 Techwell TW5864 video/audio grabber and encoder +tw686x Intersil/Techwell TW686x +tw68 Techwell tw68x Video For Linux +zoran Zoran-36057/36067 JPEG codec +================ ======================================================== + +Some of those drivers support multiple devices, as shown at the card +lists below: + +.. toctree:: + :maxdepth: 1 + + bttv-cardlist + cx18-cardlist + cx23885-cardlist + cx88-cardlist + ivtv-cardlist + saa7134-cardlist + saa7164-cardlist + zoran-cardlist diff --git a/Documentation/admin-guide/media/philips.rst b/Documentation/admin-guide/media/philips.rst new file mode 100644 index 000000000..e2840be10 --- /dev/null +++ b/Documentation/admin-guide/media/philips.rst @@ -0,0 +1,247 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Philips webcams (pwc driver) +============================ + +This file contains some additional information for the Philips and OEM webcams. +E-mail: webcam@smcc.demon.nl Last updated: 2004-01-19 +Site: http://www.smcc.demon.nl/webcam/ + +As of this moment, the following cameras are supported: + + * Philips PCA645 + * Philips PCA646 + * Philips PCVC675 + * Philips PCVC680 + * Philips PCVC690 + * Philips PCVC720/40 + * Philips PCVC730 + * Philips PCVC740 + * Philips PCVC750 + * Askey VC010 + * Creative Labs Webcam 5 + * Creative Labs Webcam Pro Ex + * Logitech QuickCam 3000 Pro + * Logitech QuickCam 4000 Pro + * Logitech QuickCam Notebook Pro + * Logitech QuickCam Zoom + * Logitech QuickCam Orbit + * Logitech QuickCam Sphere + * Samsung MPC-C10 + * Samsung MPC-C30 + * Sotec Afina Eye + * AME CU-001 + * Visionite VCS-UM100 + * Visionite VCS-UC300 + +The main webpage for the Philips driver is at the address above. It contains +a lot of extra information, a FAQ, and the binary plugin 'PWCX'. This plugin +contains decompression routines that allow you to use higher image sizes and +framerates; in addition the webcam uses less bandwidth on the USB bus (handy +if you want to run more than 1 camera simultaneously). These routines fall +under a NDA, and may therefore not be distributed as source; however, its use +is completely optional. + +You can build this code either into your kernel, or as a module. I recommend +the latter, since it makes troubleshooting a lot easier. The built-in +microphone is supported through the USB Audio class. + +When you load the module you can set some default settings for the +camera; some programs depend on a particular image-size or -format and +don't know how to set it properly in the driver. The options are: + +size + Can be one of 'sqcif', 'qsif', 'qcif', 'sif', 'cif' or + 'vga', for an image size of resp. 128x96, 160x120, 176x144, + 320x240, 352x288 and 640x480 (of course, only for those cameras that + support these resolutions). + +fps + Specifies the desired framerate. Is an integer in the range of 4-30. + +fbufs + This parameter specifies the number of internal buffers to use for storing + frames from the cam. This will help if the process that reads images from + the cam is a bit slow or momentarily busy. However, on slow machines it + only introduces lag, so choose carefully. The default is 3, which is + reasonable. You can set it between 2 and 5. + +mbufs + This is an integer between 1 and 10. It will tell the module the number of + buffers to reserve for mmap(), VIDIOCCGMBUF, VIDIOCMCAPTURE and friends. + The default is 2, which is adequate for most applications (double + buffering). + + Should you experience a lot of 'Dumping frame...' messages during + grabbing with a tool that uses mmap(), you might want to increase if. + However, it doesn't really buffer images, it just gives you a bit more + slack when your program is behind. But you need a multi-threaded or + forked program to really take advantage of these buffers. + + The absolute maximum is 10, but don't set it too high! Every buffer takes + up 460 KB of RAM, so unless you have a lot of memory setting this to + something more than 4 is an absolute waste. This memory is only + allocated during open(), so nothing is wasted when the camera is not in + use. + +power_save + When power_save is enabled (set to 1), the module will try to shut down + the cam on close() and re-activate on open(). This will save power and + turn off the LED. Not all cameras support this though (the 645 and 646 + don't have power saving at all), and some models don't work either (they + will shut down, but never wake up). Consider this experimental. By + default this option is disabled. + +compression (only useful with the plugin) + With this option you can control the compression factor that the camera + uses to squeeze the image through the USB bus. You can set the + parameter between 0 and 3:: + + 0 = prefer uncompressed images; if the requested mode is not available + in an uncompressed format, the driver will silently switch to low + compression. + 1 = low compression. + 2 = medium compression. + 3 = high compression. + + High compression takes less bandwidth of course, but it could also + introduce some unwanted artefacts. The default is 2, medium compression. + See the FAQ on the website for an overview of which modes require + compression. + + The compression parameter does not apply to the 645 and 646 cameras + and OEM models derived from those (only a few). Most cams honour this + parameter. + +leds + This settings takes 2 integers, that define the on/off time for the LED + (in milliseconds). One of the interesting things that you can do with + this is let the LED blink while the camera is in use. This:: + + leds=500,500 + + will blink the LED once every second. But with:: + + leds=0,0 + + the LED never goes on, making it suitable for silent surveillance. + + By default the camera's LED is on solid while in use, and turned off + when the camera is not used anymore. + + This parameter works only with the ToUCam range of cameras (720, 730, 740, + 750) and OEMs. For other cameras this command is silently ignored, and + the LED cannot be controlled. + + Finally: this parameters does not take effect UNTIL the first time you + open the camera device. Until then, the LED remains on. + +dev_hint + A long standing problem with USB devices is their dynamic nature: you + never know what device a camera gets assigned; it depends on module load + order, the hub configuration, the order in which devices are plugged in, + and the phase of the moon (i.e. it can be random). With this option you + can give the driver a hint as to what video device node (/dev/videoX) it + should use with a specific camera. This is also handy if you have two + cameras of the same model. + + A camera is specified by its type (the number from the camera model, + like PCA645, PCVC750VC, etc) and optionally the serial number (visible + in /sys/kernel/debug/usb/devices). A hint consists of a string with the + following format:: + + [type[.serialnumber]:]node + + The square brackets mean that both the type and the serialnumber are + optional, but a serialnumber cannot be specified without a type (which + would be rather pointless). The serialnumber is separated from the type + by a '.'; the node number by a ':'. + + This somewhat cryptic syntax is best explained by a few examples:: + + dev_hint=3,5 The first detected cam gets assigned + /dev/video3, the second /dev/video5. Any + other cameras will get the first free + available slot (see below). + + dev_hint=645:1,680:2 The PCA645 camera will get /dev/video1, + and a PCVC680 /dev/video2. + + dev_hint=645.0123:3,645.4567:0 The PCA645 camera with serialnumber + 0123 goes to /dev/video3, the same + camera model with the 4567 serial + gets /dev/video0. + + dev_hint=750:1,4,5,6 The PCVC750 camera will get /dev/video1, the + next 3 Philips cams will use /dev/video4 + through /dev/video6. + + Some points worth knowing: + + - Serialnumbers are case sensitive and must be written full, including + leading zeroes (it's treated as a string). + - If a device node is already occupied, registration will fail and + the webcam is not available. + - You can have up to 64 video devices; be sure to make enough device + nodes in /dev if you want to spread the numbers. + After /dev/video9 comes /dev/video10 (not /dev/videoA). + - If a camera does not match any dev_hint, it will simply get assigned + the first available device node, just as it used to be. + +trace + In order to better detect problems, it is now possible to turn on a + 'trace' of some of the calls the module makes; it logs all items in your + kernel log at debug level. + + The trace variable is a bitmask; each bit represents a certain feature. + If you want to trace something, look up the bit value(s) in the table + below, add the values together and supply that to the trace variable. + + ====== ======= ================================================ ======= + Value Value Description Default + (dec) (hex) + ====== ======= ================================================ ======= + 1 0x1 Module initialization; this will log messages On + while loading and unloading the module + + 2 0x2 probe() and disconnect() traces On + + 4 0x4 Trace open() and close() calls Off + + 8 0x8 read(), mmap() and associated ioctl() calls Off + + 16 0x10 Memory allocation of buffers, etc. Off + + 32 0x20 Showing underflow, overflow and Dumping frame On + messages + + 64 0x40 Show viewport and image sizes Off + + 128 0x80 PWCX debugging Off + ====== ======= ================================================ ======= + + For example, to trace the open() & read() functions, sum 8 + 4 = 12, + so you would supply trace=12 during insmod or modprobe. If + you want to turn the initialization and probing tracing off, set trace=0. + The default value for trace is 35 (0x23). + + + +Example:: + + # modprobe pwc size=cif fps=15 power_save=1 + +The fbufs, mbufs and trace parameters are global and apply to all connected +cameras. Each camera has its own set of buffers. + +size and fps only specify defaults when you open() the device; this is to +accommodate some tools that don't set the size. You can change these +settings after open() with the Video4Linux ioctl() calls. The default of +defaults is QCIF size at 10 fps. + +The compression parameter is semiglobal; it sets the initial compression +preference for all camera's, but this parameter can be set per camera with +the VIDIOCPWCSCQUAL ioctl() call. + +All parameters are optional. + diff --git a/Documentation/admin-guide/media/platform-cardlist.rst b/Documentation/admin-guide/media/platform-cardlist.rst new file mode 100644 index 000000000..1230ae403 --- /dev/null +++ b/Documentation/admin-guide/media/platform-cardlist.rst @@ -0,0 +1,89 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Platform drivers +================ + +There are several drivers that are focused on providing support for +functionality that are already included at the main board, and don't +use neither USB nor PCI bus. Those drivers are called platform +drivers, and are very popular on embedded devices. + +The current supported of platform drivers (not including staging drivers) are +listed below + +================= ============================================================ +Driver Name +================= ============================================================ +am437x-vpfe TI AM437x VPFE +aspeed-video Aspeed AST2400 and AST2500 +atmel-isc ATMEL Image Sensor Controller (ISC) +atmel-isi ATMEL Image Sensor Interface (ISI) +c8sectpfe SDR platform devices +c8sectpfe SDR platform devices +cafe_ccic Marvell 88ALP01 (Cafe) CMOS Camera Controller +cdns-csi2rx Cadence MIPI-CSI2 RX Controller +cdns-csi2tx Cadence MIPI-CSI2 TX Controller +coda-vpu Chips&Media Coda multi-standard codec IP +dm355_ccdc TI DM355 CCDC video capture +dm644x_ccdc TI DM6446 CCDC video capture +exynos-fimc-is EXYNOS4x12 FIMC-IS (Imaging Subsystem) +exynos-fimc-lite EXYNOS FIMC-LITE camera interface +exynos-gsc Samsung Exynos G-Scaler +exy Samsung S5P/EXYNOS4 SoC series Camera Subsystem +imx-pxp i.MX Pixel Pipeline (PXP) +isdf TI DM365 ISIF video capture +mmp_camera Marvell Armada 610 integrated camera controller +mtk_jpeg Mediatek JPEG Codec +mtk-mdp Mediatek MDP +mtk-vcodec-dec Mediatek Video Codec +mtk-vpu Mediatek Video Processor Unit +mx2_emmaprp MX2 eMMa-PrP +omap3-isp OMAP 3 Camera +omap-vout OMAP2/OMAP3 V4L2-Display +pxa_camera PXA27x Quick Capture Interface +qcom-camss Qualcomm V4L2 Camera Subsystem +rcar-csi2 R-Car MIPI CSI-2 Receiver +rcar_drif Renesas Digital Radio Interface (DRIF) +rcar-fcp Renesas Frame Compression Processor +rcar_fdp1 Renesas Fine Display Processor +rcar_jpu Renesas JPEG Processing Unit +rcar-vin R-Car Video Input (VIN) +renesas-ceu Renesas Capture Engine Unit (CEU) +rockchip-rga Rockchip Raster 2d Graphic Acceleration Unit +s3c-camif Samsung S3C24XX/S3C64XX SoC Camera Interface +s5p-csis S5P/EXYNOS MIPI-CSI2 receiver (MIPI-CSIS) +s5p-fimc S5P/EXYNOS4 FIMC/CAMIF camera interface +s5p-g2d Samsung S5P and EXYNOS4 G2D 2d graphics accelerator +s5p-jpeg Samsung S5P/Exynos3250/Exynos4 JPEG codec +s5p-mfc Samsung S5P MFC Video Codec +sh_veu SuperH VEU mem2mem video processing +sh_vou SuperH VOU video output +stm32-dcmi STM32 Digital Camera Memory Interface (DCMI) +stm32-dma2d STM32 Chrom-Art Accelerator Unit +sun4i-csi Allwinner A10 CMOS Sensor Interface Support +sun6i-csi Allwinner V3s Camera Sensor Interface +sun8i-di Allwinner Deinterlace +sun8i-rotate Allwinner DE2 rotation +ti-cal TI Memory-to-memory multimedia devices +ti-csc TI DVB platform devices +ti-vpe TI VPE (Video Processing Engine) +venus-enc Qualcomm Venus V4L2 encoder/decoder +via-camera VIAFB camera controller +video-mux Video Multiplexer +vpif_display TI DaVinci VPIF V4L2-Display +vpif_capture TI DaVinci VPIF video capture +vsp1 Renesas VSP1 Video Processing Engine +xilinx-tpg Xilinx Video Test Pattern Generator +xilinx-video Xilinx Video IP (EXPERIMENTAL) +xilinx-vtc Xilinx Video Timing Controller +================= ============================================================ + +MMC/SDIO DVB adapters +--------------------- + +======= =========================================== +Driver Name +======= =========================================== +smssdio Siano SMS1xxx based MDTV via SDIO interface +======= =========================================== + diff --git a/Documentation/admin-guide/media/qcom_camss.rst b/Documentation/admin-guide/media/qcom_camss.rst new file mode 100644 index 000000000..8a8f3ff40 --- /dev/null +++ b/Documentation/admin-guide/media/qcom_camss.rst @@ -0,0 +1,185 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. include:: <isonum.txt> + +Qualcomm Camera Subsystem driver +================================ + +Introduction +------------ + +This file documents the Qualcomm Camera Subsystem driver located under +drivers/media/platform/qcom/camss. + +The current version of the driver supports the Camera Subsystem found on +Qualcomm MSM8916/APQ8016 and MSM8996/APQ8096 processors. + +The driver implements V4L2, Media controller and V4L2 subdev interfaces. +Camera sensor using V4L2 subdev interface in the kernel is supported. + +The driver is implemented using as a reference the Qualcomm Camera Subsystem +driver for Android as found in Code Linaro [#f1]_ [#f2]_. + + +Qualcomm Camera Subsystem hardware +---------------------------------- + +The Camera Subsystem hardware found on 8x16 / 8x96 processors and supported by +the driver consists of: + +- 2 / 3 CSIPHY modules. They handle the Physical layer of the CSI2 receivers. + A separate camera sensor can be connected to each of the CSIPHY module; +- 2 / 4 CSID (CSI Decoder) modules. They handle the Protocol and Application + layer of the CSI2 receivers. A CSID can decode data stream from any of the + CSIPHY. Each CSID also contains a TG (Test Generator) block which can generate + artificial input data for test purposes; +- ISPIF (ISP Interface) module. Handles the routing of the data streams from + the CSIDs to the inputs of the VFE; +- 1 / 2 VFE (Video Front End) module(s). Contain a pipeline of image processing + hardware blocks. The VFE has different input interfaces. The PIX (Pixel) input + interface feeds the input data to the image processing pipeline. The image + processing pipeline contains also a scale and crop module at the end. Three + RDI (Raw Dump Interface) input interfaces bypass the image processing + pipeline. The VFE also contains the AXI bus interface which writes the output + data to memory. + + +Supported functionality +----------------------- + +The current version of the driver supports: + +- Input from camera sensor via CSIPHY; +- Generation of test input data by the TG in CSID; +- RDI interface of VFE + + - Raw dump of the input data to memory. + + Supported formats: + + - YUYV/UYVY/YVYU/VYUY (packed YUV 4:2:2 - V4L2_PIX_FMT_YUYV / + V4L2_PIX_FMT_UYVY / V4L2_PIX_FMT_YVYU / V4L2_PIX_FMT_VYUY); + - MIPI RAW8 (8bit Bayer RAW - V4L2_PIX_FMT_SRGGB8 / + V4L2_PIX_FMT_SGRBG8 / V4L2_PIX_FMT_SGBRG8 / V4L2_PIX_FMT_SBGGR8); + - MIPI RAW10 (10bit packed Bayer RAW - V4L2_PIX_FMT_SBGGR10P / + V4L2_PIX_FMT_SGBRG10P / V4L2_PIX_FMT_SGRBG10P / V4L2_PIX_FMT_SRGGB10P / + V4L2_PIX_FMT_Y10P); + - MIPI RAW12 (12bit packed Bayer RAW - V4L2_PIX_FMT_SRGGB12P / + V4L2_PIX_FMT_SGBRG12P / V4L2_PIX_FMT_SGRBG12P / V4L2_PIX_FMT_SRGGB12P). + - (8x96 only) MIPI RAW14 (14bit packed Bayer RAW - V4L2_PIX_FMT_SRGGB14P / + V4L2_PIX_FMT_SGBRG14P / V4L2_PIX_FMT_SGRBG14P / V4L2_PIX_FMT_SRGGB14P). + + - (8x96 only) Format conversion of the input data. + + Supported input formats: + + - MIPI RAW10 (10bit packed Bayer RAW - V4L2_PIX_FMT_SBGGR10P / V4L2_PIX_FMT_Y10P). + + Supported output formats: + + - Plain16 RAW10 (10bit unpacked Bayer RAW - V4L2_PIX_FMT_SBGGR10 / V4L2_PIX_FMT_Y10). + +- PIX interface of VFE + + - Format conversion of the input data. + + Supported input formats: + + - YUYV/UYVY/YVYU/VYUY (packed YUV 4:2:2 - V4L2_PIX_FMT_YUYV / + V4L2_PIX_FMT_UYVY / V4L2_PIX_FMT_YVYU / V4L2_PIX_FMT_VYUY). + + Supported output formats: + + - NV12/NV21 (two plane YUV 4:2:0 - V4L2_PIX_FMT_NV12 / V4L2_PIX_FMT_NV21); + - NV16/NV61 (two plane YUV 4:2:2 - V4L2_PIX_FMT_NV16 / V4L2_PIX_FMT_NV61). + - (8x96 only) YUYV/UYVY/YVYU/VYUY (packed YUV 4:2:2 - V4L2_PIX_FMT_YUYV / + V4L2_PIX_FMT_UYVY / V4L2_PIX_FMT_YVYU / V4L2_PIX_FMT_VYUY). + + - Scaling support. Configuration of the VFE Encoder Scale module + for downscalling with ratio up to 16x. + + - Cropping support. Configuration of the VFE Encoder Crop module. + +- Concurrent and independent usage of two (8x96: three) data inputs - + could be camera sensors and/or TG. + + +Driver Architecture and Design +------------------------------ + +The driver implements the V4L2 subdev interface. With the goal to model the +hardware links between the modules and to expose a clean, logical and usable +interface, the driver is split into V4L2 sub-devices as follows (8x16 / 8x96): + +- 2 / 3 CSIPHY sub-devices - each CSIPHY is represented by a single sub-device; +- 2 / 4 CSID sub-devices - each CSID is represented by a single sub-device; +- 2 / 4 ISPIF sub-devices - ISPIF is represented by a number of sub-devices + equal to the number of CSID sub-devices; +- 4 / 8 VFE sub-devices - VFE is represented by a number of sub-devices equal to + the number of the input interfaces (3 RDI and 1 PIX for each VFE). + +The considerations to split the driver in this particular way are as follows: + +- representing CSIPHY and CSID modules by a separate sub-device for each module + allows to model the hardware links between these modules; +- representing VFE by a separate sub-devices for each input interface allows + to use the input interfaces concurrently and independently as this is + supported by the hardware; +- representing ISPIF by a number of sub-devices equal to the number of CSID + sub-devices allows to create linear media controller pipelines when using two + cameras simultaneously. This avoids branches in the pipelines which otherwise + will require a) userspace and b) media framework (e.g. power on/off + operations) to make assumptions about the data flow from a sink pad to a + source pad on a single media entity. + +Each VFE sub-device is linked to a separate video device node. + +The media controller pipeline graph is as follows (with connected two / three +OV5645 camera sensors): + +.. _qcom_camss_graph: + +.. kernel-figure:: qcom_camss_graph.dot + :alt: qcom_camss_graph.dot + :align: center + + Media pipeline graph 8x16 + +.. kernel-figure:: qcom_camss_8x96_graph.dot + :alt: qcom_camss_8x96_graph.dot + :align: center + + Media pipeline graph 8x96 + + +Implementation +-------------- + +Runtime configuration of the hardware (updating settings while streaming) is +not required to implement the currently supported functionality. The complete +configuration on each hardware module is applied on STREAMON ioctl based on +the current active media links, formats and controls set. + +The output size of the scaler module in the VFE is configured with the actual +compose selection rectangle on the sink pad of the 'msm_vfe0_pix' entity. + +The crop output area of the crop module in the VFE is configured with the actual +crop selection rectangle on the source pad of the 'msm_vfe0_pix' entity. + + +Documentation +------------- + +APQ8016 Specification: +https://developer.qualcomm.com/download/sd410/snapdragon-410-processor-device-specification.pdf +Referenced 2016-11-24. + +APQ8096 Specification: +https://developer.qualcomm.com/download/sd820e/qualcomm-snapdragon-820e-processor-apq8096sge-device-specification.pdf +Referenced 2018-06-22. + +References +---------- + +.. [#f1] https://git.codelinaro.org/clo/la/kernel/msm-3.10/ +.. [#f2] https://git.codelinaro.org/clo/la/kernel/msm-3.18/ diff --git a/Documentation/admin-guide/media/qcom_camss_8x96_graph.dot b/Documentation/admin-guide/media/qcom_camss_8x96_graph.dot new file mode 100644 index 000000000..7ed243b41 --- /dev/null +++ b/Documentation/admin-guide/media/qcom_camss_8x96_graph.dot @@ -0,0 +1,106 @@ +# SPDX-License-Identifier: GPL-2.0 + +digraph board { + rankdir=TB + n00000001 [label="{{<port0> 0} | msm_csiphy0\n/dev/v4l-subdev0 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green] + n00000001:port1 -> n0000000a:port0 [style=dashed] + n00000001:port1 -> n0000000d:port0 [style=dashed] + n00000001:port1 -> n00000010:port0 [style=dashed] + n00000001:port1 -> n00000013:port0 [style=dashed] + n00000004 [label="{{<port0> 0} | msm_csiphy1\n/dev/v4l-subdev1 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green] + n00000004:port1 -> n0000000a:port0 [style=dashed] + n00000004:port1 -> n0000000d:port0 [style=dashed] + n00000004:port1 -> 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msm_csiphy0\n/dev/v4l-subdev0 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green] + n00000001:port1 -> n00000007:port0 [style=dashed] + n00000001:port1 -> n0000000a:port0 [style=dashed] + n00000004 [label="{{<port0> 0} | msm_csiphy1\n/dev/v4l-subdev1 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green] + n00000004:port1 -> n00000007:port0 [style=dashed] + n00000004:port1 -> n0000000a:port0 [style=dashed] + n00000007 [label="{{<port0> 0} | msm_csid0\n/dev/v4l-subdev2 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green] + n00000007:port1 -> n0000000d:port0 [style=dashed] + n00000007:port1 -> n00000010:port0 [style=dashed] + n0000000a [label="{{<port0> 0} | msm_csid1\n/dev/v4l-subdev3 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green] + n0000000a:port1 -> n0000000d:port0 [style=dashed] + n0000000a:port1 -> n00000010:port0 [style=dashed] + n0000000d [label="{{<port0> 0} | msm_ispif0\n/dev/v4l-subdev4 | {<port1> 1}}", shape=Mrecord, style=filled, 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[style=bold] + n0000001f [label="msm_vfe0_video1\n/dev/video1", shape=box, style=filled, fillcolor=yellow] + n00000025 [label="{{<port0> 0} | msm_vfe0_rdi2\n/dev/v4l-subdev8 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green] + n00000025:port1 -> n00000028 [style=bold] + n00000028 [label="msm_vfe0_video2\n/dev/video2", shape=box, style=filled, fillcolor=yellow] + n0000002e [label="{{<port0> 0} | msm_vfe0_pix\n/dev/v4l-subdev9 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green] + n0000002e:port1 -> n00000031 [style=bold] + n00000031 [label="msm_vfe0_video3\n/dev/video3", shape=box, style=filled, fillcolor=yellow] + n00000057 [label="{{} | ov5645 1-0076\n/dev/v4l-subdev10 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green] + n00000057:port0 -> n00000001:port0 [style=bold] + n00000059 [label="{{} | ov5645 1-0074\n/dev/v4l-subdev11 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green] + n00000059:port0 -> n00000004:port0 [style=bold] +} diff --git a/Documentation/admin-guide/media/radio-cardlist.rst b/Documentation/admin-guide/media/radio-cardlist.rst new file mode 100644 index 000000000..a82a146bf --- /dev/null +++ b/Documentation/admin-guide/media/radio-cardlist.rst @@ -0,0 +1,44 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Radio drivers +============= + +There is also support for pure AM/FM radio, and even for some FM radio +transmitters: + +===================== ========================================================= +Driver Name +===================== ========================================================= +si4713 Silicon Labs Si4713 FM Radio Transmitter +radio-aztech Aztech/Packard Bell Radio +radio-cadet ADS Cadet AM/FM Tuner +radio-gemtek GemTek Radio card (or compatible) +radio-maxiradio Guillemot MAXI Radio FM 2000 radio +radio-miropcm20 miroSOUND PCM20 radio +radio-aimslab AIMSlab RadioTrack (aka RadioReveal) +radio-rtrack2 AIMSlab RadioTrack II +saa7706h SAA7706H Car Radio DSP +radio-sf16fmi SF16-FMI/SF16-FMP/SF16-FMD Radio +radio-sf16fmr2 SF16-FMR2/SF16-FMD2 Radio +radio-shark Griffin radioSHARK USB radio receiver +shark2 Griffin radioSHARK2 USB radio receiver +radio-si470x-common Silicon Labs Si470x FM Radio Receiver +radio-si476x Silicon Laboratories Si476x I2C FM Radio +radio-tea5764 TEA5764 I2C FM radio +tef6862 TEF6862 Car Radio Enhanced Selectivity Tuner +radio-terratec TerraTec ActiveRadio ISA Standalone +radio-timb Enable the Timberdale radio driver +radio-trust Trust FM radio card +radio-typhoon Typhoon Radio (a.k.a. EcoRadio) +radio-wl1273 Texas Instruments WL1273 I2C FM Radio +fm_drv ISA radio devices +fm_drv ISA radio devices +radio-zoltrix Zoltrix Radio +dsbr100 D-Link/GemTek USB FM radio +radio-keene Keene FM Transmitter USB +radio-ma901 Masterkit MA901 USB FM radio +radio-mr800 AverMedia MR 800 USB FM radio +radio-raremono Thanko's Raremono AM/FM/SW radio +radio-si470x-usb Silicon Labs Si470x FM Radio Receiver support with USB +radio-usb-si4713 Silicon Labs Si4713 FM Radio Transmitter support with USB +===================== ========================================================= diff --git a/Documentation/admin-guide/media/rcar-fdp1.rst b/Documentation/admin-guide/media/rcar-fdp1.rst new file mode 100644 index 000000000..88b0edcf9 --- /dev/null +++ b/Documentation/admin-guide/media/rcar-fdp1.rst @@ -0,0 +1,39 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Renesas R-Car Fine Display Processor (FDP1) Driver +================================================== + +The R-Car FDP1 driver implements driver-specific controls as follows. + +``V4L2_CID_DEINTERLACING_MODE (menu)`` + The video deinterlacing mode (such as Bob, Weave, ...). The R-Car FDP1 + driver implements the following modes. + +.. flat-table:: + :header-rows: 0 + :stub-columns: 0 + :widths: 1 4 + + * - ``"Progressive" (0)`` + - The input image video stream is progressive (not interlaced). No + deinterlacing is performed. Apart from (optional) format and encoding + conversion output frames are identical to the input frames. + * - ``"Adaptive 2D/3D" (1)`` + - Motion adaptive version of 2D and 3D deinterlacing. Use 3D deinterlacing + in the presence of fast motion and 2D deinterlacing with diagonal + interpolation otherwise. + * - ``"Fixed 2D" (2)`` + - The current field is scaled vertically by averaging adjacent lines to + recover missing lines. This method is also known as blending or Line + Averaging (LAV). + * - ``"Fixed 3D" (3)`` + - The previous and next fields are averaged to recover lines missing from + the current field. This method is also known as Field Averaging (FAV). + * - ``"Previous field" (4)`` + - The current field is weaved with the previous field, i.e. the previous + field is used to fill missing lines from the current field. This method + is also known as weave deinterlacing. + * - ``"Next field" (5)`` + - The current field is weaved with the next field, i.e. the next field is + used to fill missing lines from the current field. This method is also + known as weave deinterlacing. diff --git a/Documentation/admin-guide/media/remote-controller.rst b/Documentation/admin-guide/media/remote-controller.rst new file mode 100644 index 000000000..188944b00 --- /dev/null +++ b/Documentation/admin-guide/media/remote-controller.rst @@ -0,0 +1,76 @@ +.. SPDX-License-Identifier: GPL-2.0 + +====================================================== +Infrared remote control support in video4linux drivers +====================================================== + +Authors: Gerd Hoffmann, Mauro Carvalho Chehab + +Basics +====== + +Most analog and digital TV boards support remote controllers. Several of +them have a microprocessor that receives the IR carriers, convert into +pulse/space sequences and then to scan codes, returning such codes to +userspace ("scancode mode"). Other boards return just the pulse/space +sequences ("raw mode"). + +The support for remote controller in scancode mode is provided by the +standard Linux input layer. The support for raw mode is provided via LIRC. + +In order to check the support and test it, it is suggested to download +the `v4l-utils <https://git.linuxtv.org/v4l-utils.git/>`_. It provides +two tools to handle remote controllers: + +- ir-keytable: provides a way to query the remote controller, list the + protocols it supports, enable in-kernel support for IR decoder or + switch the protocol and to test the reception of scan codes; + +- ir-ctl: provide tools to handle remote controllers that support raw mode + via LIRC interface. + +Usually, the remote controller module is auto-loaded when the TV card is +detected. However, for a few devices, you need to manually load the +ir-kbd-i2c module. + +How it works +============ + +The modules register the remote as keyboard within the linux input +layer, i.e. you'll see the keys of the remote as normal key strokes +(if CONFIG_INPUT_KEYBOARD is enabled). + +Using the event devices (CONFIG_INPUT_EVDEV) it is possible for +applications to access the remote via /dev/input/event<n> devices. +The udev/systemd will automatically create the devices. If you install +the `v4l-utils <https://git.linuxtv.org/v4l-utils.git/>`_, it may also +automatically load a different keytable than the default one. Please see +`v4l-utils <https://git.linuxtv.org/v4l-utils.git/>`_ ir-keytable.1 +man page for details. + +The ir-keytable tool is nice for trouble shooting, i.e. to check +whenever the input device is really present, which of the devices it +is, check whenever pressing keys on the remote actually generates +events and the like. You can also use any other input utility that changes +the keymaps, like the input kbd utility. + + +Using with lircd +---------------- + +The latest versions of the lircd daemon supports reading events from the +linux input layer (via event device). It also supports receiving IR codes +in lirc mode. + + +Using without lircd +------------------- + +Xorg recognizes several IR keycodes that have its numerical value lower +than 247. With the advent of Wayland, the input driver got updated too, +and should now accept all keycodes. Yet, you may want to just reassign +the keycodes to something that your favorite media application likes. + +This can be done by setting +`v4l-utils <https://git.linuxtv.org/v4l-utils.git/>`_ to load your own +keytable in runtime. Please read ir-keytable.1 man page for details. diff --git a/Documentation/admin-guide/media/rkisp1.dot b/Documentation/admin-guide/media/rkisp1.dot new file mode 100644 index 000000000..54c1953a6 --- /dev/null +++ b/Documentation/admin-guide/media/rkisp1.dot @@ -0,0 +1,18 @@ +digraph board { + rankdir=TB + n00000001 [label="{{<port0> 0 | <port1> 1} | rkisp1_isp\n/dev/v4l-subdev0 | {<port2> 2 | <port3> 3}}", shape=Mrecord, style=filled, fillcolor=green] + n00000001:port2 -> n00000006:port0 + n00000001:port2 -> n00000009:port0 + n00000001:port3 -> n00000014 [style=bold] + n00000006 [label="{{<port0> 0} | rkisp1_resizer_mainpath\n/dev/v4l-subdev1 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green] + n00000006:port1 -> n0000000c [style=bold] + n00000009 [label="{{<port0> 0} | rkisp1_resizer_selfpath\n/dev/v4l-subdev2 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green] + n00000009:port1 -> n00000010 [style=bold] + n0000000c [label="rkisp1_mainpath\n/dev/video0", shape=box, style=filled, fillcolor=yellow] + n00000010 [label="rkisp1_selfpath\n/dev/video1", shape=box, style=filled, fillcolor=yellow] + n00000014 [label="rkisp1_stats\n/dev/video2", shape=box, style=filled, fillcolor=yellow] + n00000018 [label="rkisp1_params\n/dev/video3", shape=box, style=filled, fillcolor=yellow] + n00000018 -> n00000001:port1 [style=bold] + n0000001c [label="{{} | imx219 4-0010\n/dev/v4l-subdev3 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green] + n0000001c:port0 -> n00000001:port0 +} diff --git a/Documentation/admin-guide/media/rkisp1.rst b/Documentation/admin-guide/media/rkisp1.rst new file mode 100644 index 000000000..6f14d9561 --- /dev/null +++ b/Documentation/admin-guide/media/rkisp1.rst @@ -0,0 +1,197 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. include:: <isonum.txt> + +========================================= +Rockchip Image Signal Processor (rkisp1) +========================================= + +Introduction +============ + +This file documents the driver for the Rockchip ISP1 that is part of RK3288 +and RK3399 SoCs. The driver is located under drivers/media/platform/rockchip/ +rkisp1 and uses the Media-Controller API. + +Revisions +========= + +There exist multiple smaller revisions to this ISP that got introduced in +later SoCs. Revisions can be found in the enum :c:type:`rkisp1_cif_isp_version` +in the UAPI and the revision of the ISP inside the running SoC can be read +in the field hw_revision of struct media_device_info as returned by +ioctl MEDIA_IOC_DEVICE_INFO. + +Versions in use are: + +- RKISP1_V10: used at least in rk3288 and rk3399 +- RKISP1_V11: declared in the original vendor code, but not used +- RKISP1_V12: used at least in rk3326 and px30 +- RKISP1_V13: used at least in rk1808 + +Topology +======== +.. _rkisp1_topology_graph: + +.. kernel-figure:: rkisp1.dot + :alt: Diagram of the default media pipeline topology + :align: center + + +The driver has 4 video devices: + +- rkisp1_mainpath: capture device for retrieving images, usually in higher + resolution. +- rkisp1_selfpath: capture device for retrieving images. +- rkisp1_stats: a metadata capture device that sends statistics. +- rkisp1_params: a metadata output device that receives parameters + configurations from userspace. + +The driver has 3 subdevices: + +- rkisp1_resizer_mainpath: used to resize and downsample frames for the + mainpath capture device. +- rkisp1_resizer_selfpath: used to resize and downsample frames for the + selfpath capture device. +- rkisp1_isp: is connected to the sensor and is responsible for all the isp + operations. + + +rkisp1_mainpath, rkisp1_selfpath - Frames Capture Video Nodes +------------------------------------------------------------- +Those are the `mainpath` and `selfpath` capture devices to capture frames. +Those entities are the DMA engines that write the frames to memory. +The selfpath video device can capture YUV/RGB formats. Its input is YUV encoded +stream and it is able to convert it to RGB. The selfpath is not able to +capture bayer formats. +The mainpath can capture both bayer and YUV formats but it is not able to +capture RGB formats. +Both capture videos support +the ``V4L2_CAP_IO_MC`` :ref:`capability <device-capabilities>`. + + +rkisp1_resizer_mainpath, rkisp1_resizer_selfpath - Resizers Subdevices Nodes +---------------------------------------------------------------------------- +Those are resizer entities for the mainpath and the selfpath. Those entities +can scale the frames up and down and also change the YUV sampling (for example +YUV4:2:2 -> YUV4:2:0). They also have cropping capability on the sink pad. +The resizers entities can only operate on YUV:4:2:2 format +(MEDIA_BUS_FMT_YUYV8_2X8). +The mainpath capture device supports capturing video in bayer formats. In that +case the resizer of the mainpath is set to 'bypass' mode - it just forward the +frame without operating on it. + +rkisp1_isp - Image Signal Processing Subdevice Node +--------------------------------------------------- +This is the isp entity. It is connected to the sensor on sink pad 0 and +receives the frames using the CSI-2 protocol. It is responsible of configuring +the CSI-2 protocol. It has a cropping capability on sink pad 0 that is +connected to the sensor and on source pad 2 connected to the resizer entities. +Cropping on sink pad 0 defines the image region from the sensor. +Cropping on source pad 2 defines the region for the Image Stabilizer (IS). + +.. _rkisp1_stats: + +rkisp1_stats - Statistics Video Node +------------------------------------ +The statistics video node outputs the 3A (auto focus, auto exposure and auto +white balance) statistics, and also histogram statistics for the frames that +are being processed by the rkisp1 to userspace applications. +Using these data, applications can implement algorithms and re-parameterize +the driver through the rkisp_params node to improve image quality during a +video stream. +The buffer format is defined by struct :c:type:`rkisp1_stat_buffer`, and +userspace should set +:ref:`V4L2_META_FMT_RK_ISP1_STAT_3A <v4l2-meta-fmt-rk-isp1-stat-3a>` as the +dataformat. + +.. _rkisp1_params: + +rkisp1_params - Parameters Video Node +------------------------------------- +The rkisp1_params video node receives a set of parameters from userspace +to be applied to the hardware during a video stream, allowing userspace +to dynamically modify values such as black level, cross talk corrections +and others. + +The buffer format is defined by struct :c:type:`rkisp1_params_cfg`, and +userspace should set +:ref:`V4L2_META_FMT_RK_ISP1_PARAMS <v4l2-meta-fmt-rk-isp1-params>` as the +dataformat. + + +Capturing Video Frames Example +============================== + +In the following example, the sensor connected to pad 0 of 'rkisp1_isp' is +imx219. + +The following commands can be used to capture video from the selfpath video +node with dimension 900x800 planar format YUV 4:2:2. It uses all cropping +capabilities possible, (see explanation right below) + +.. code-block:: bash + + # set the links + "media-ctl" "-d" "platform:rkisp1" "-r" + "media-ctl" "-d" "platform:rkisp1" "-l" "'imx219 4-0010':0 -> 'rkisp1_isp':0 [1]" + "media-ctl" "-d" "platform:rkisp1" "-l" "'rkisp1_isp':2 -> 'rkisp1_resizer_selfpath':0 [1]" + "media-ctl" "-d" "platform:rkisp1" "-l" "'rkisp1_isp':2 -> 'rkisp1_resizer_mainpath':0 [0]" + + # set format for imx219 4-0010:0 + "media-ctl" "-d" "platform:rkisp1" "--set-v4l2" '"imx219 4-0010":0 [fmt:SRGGB10_1X10/1640x1232]' + + # set format for rkisp1_isp pads: + "media-ctl" "-d" "platform:rkisp1" "--set-v4l2" '"rkisp1_isp":0 [fmt:SRGGB10_1X10/1640x1232 crop: (0,0)/1600x1200]' + "media-ctl" "-d" "platform:rkisp1" "--set-v4l2" '"rkisp1_isp":2 [fmt:YUYV8_2X8/1600x1200 crop: (0,0)/1500x1100]' + + # set format for rkisp1_resizer_selfpath pads: + "media-ctl" "-d" "platform:rkisp1" "--set-v4l2" '"rkisp1_resizer_selfpath":0 [fmt:YUYV8_2X8/1500x1100 crop: (300,400)/1400x1000]' + "media-ctl" "-d" "platform:rkisp1" "--set-v4l2" '"rkisp1_resizer_selfpath":1 [fmt:YUYV8_2X8/900x800]' + + # set format for rkisp1_selfpath: + "v4l2-ctl" "-z" "platform:rkisp1" "-d" "rkisp1_selfpath" "-v" "width=900,height=800," + "v4l2-ctl" "-z" "platform:rkisp1" "-d" "rkisp1_selfpath" "-v" "pixelformat=422P" + + # start streaming: + v4l2-ctl "-z" "platform:rkisp1" "-d" "rkisp1_selfpath" "--stream-mmap" "--stream-count" "10" + + +In the above example the sensor is configured to bayer format: +`SRGGB10_1X10/1640x1232`. The rkisp1_isp:0 pad should be configured to the +same mbus format and dimensions as the sensor, otherwise streaming will fail +with 'EPIPE' error. So it is also configured to `SRGGB10_1X10/1640x1232`. +In addition, the rkisp1_isp:0 pad is configured to cropping `(0,0)/1600x1200`. + +The cropping dimensions are automatically propagated to be the format of the +isp source pad `rkisp1_isp:2`. Another cropping operation is configured on +the isp source pad: `(0,0)/1500x1100`. + +The resizer's sink pad `rkisp1_resizer_selfpath` should be configured to format +`YUYV8_2X8/1500x1100` in order to match the format on the other side of the +link. In addition a cropping `(300,400)/1400x1000` is configured on it. + +The source pad of the resizer, `rkisp1_resizer_selfpath:1` is configured to +format `YUYV8_2X8/900x800`. That means that the resizer first crop a window +of `(300,400)/1400x100` from the received frame and then scales this window +to dimension `900x800`. + +Note that the above example does not uses the stats-params control loop. +Therefore the capture frames will not go through the 3A algorithms and +probably won't have a good quality, and can even look dark and greenish. + +Configuring Quantization +======================== + +The driver supports limited and full range quantization on YUV formats, +where limited is the default. +To switch between one or the other, userspace should use the Colorspace +Conversion API (CSC) for subdevices on source pad 2 of the +isp (`rkisp1_isp:2`). The quantization configured on this pad is the +quantization of the captured video frames on the mainpath and selfpath +video nodes. +Note that the resizer and capture entities will always report +``V4L2_QUANTIZATION_DEFAULT`` even if the quantization is configured to full +range on `rkisp1_isp:2`. So in order to get the configured quantization, +application should get it from pad `rkisp1_isp:2`. + diff --git a/Documentation/admin-guide/media/saa7134-cardlist.rst b/Documentation/admin-guide/media/saa7134-cardlist.rst new file mode 100644 index 000000000..3ef8fab6b --- /dev/null +++ b/Documentation/admin-guide/media/saa7134-cardlist.rst @@ -0,0 +1,803 @@ +.. SPDX-License-Identifier: GPL-2.0 + +SAA7134 cards list +================== + +.. tabularcolumns:: |p{1.4cm}|p{11.1cm}|p{4.2cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 2 19 18 + :stub-columns: 0 + + * - Card number + - Card name + - PCI subsystem IDs + + * - 0 + - UNKNOWN/GENERIC + - + + * - 1 + - Proteus Pro [philips reference design] + - 1131:2001, 1131:2001 + + * - 2 + - LifeView FlyVIDEO3000 + - 5168:0138, 4e42:0138 + + * - 3 + - LifeView/Typhoon FlyVIDEO2000 + - 5168:0138, 4e42:0138 + + * - 4 + - EMPRESS + - 1131:6752 + + * - 5 + - SKNet Monster TV + - 1131:4e85 + + * - 6 + - Tevion MD 9717 + - + + * - 7 + - KNC One TV-Station RDS / Typhoon TV Tuner RDS + - 1131:fe01, 1894:fe01 + + * - 8 + - Terratec Cinergy 400 TV + - 153b:1142 + + * - 9 + - Medion 5044 + - + + * - 10 + - Kworld/KuroutoShikou SAA7130-TVPCI + - + + * - 11 + - Terratec Cinergy 600 TV + - 153b:1143 + + * - 12 + - Medion 7134 + - 16be:0003, 16be:5000 + + * - 13 + - Typhoon TV+Radio 90031 + - + + * - 14 + - ELSA EX-VISION 300TV + - 1048:226b + + * - 15 + - ELSA EX-VISION 500TV + - 1048:226a + + * - 16 + - ASUS TV-FM 7134 + - 1043:4842, 1043:4830, 1043:4840 + + * - 17 + - AOPEN VA1000 POWER + - 1131:7133 + + * - 18 + - BMK MPEX No Tuner + - + + * - 19 + - Compro VideoMate TV + - 185b:c100 + + * - 20 + - Matrox CronosPlus + - 102B:48d0 + + * - 21 + - 10MOONS PCI TV CAPTURE CARD + - 1131:2001 + + * - 22 + - AverMedia M156 / Medion 2819 + - 1461:a70b + + * - 23 + - BMK MPEX Tuner + - + + * - 24 + - KNC One TV-Station DVR + - 1894:a006 + + * - 25 + - ASUS TV-FM 7133 + - 1043:4843 + + * - 26 + - Pinnacle PCTV Stereo (saa7134) + - 11bd:002b + + * - 27 + - Manli MuchTV M-TV002 + - + + * - 28 + - Manli MuchTV M-TV001 + - + + * - 29 + - Nagase Sangyo TransGear 3000TV + - 1461:050c + + * - 30 + - Elitegroup ECS TVP3XP FM1216 Tuner Card(PAL-BG,FM) + - 1019:4cb4 + + * - 31 + - Elitegroup ECS TVP3XP FM1236 Tuner Card (NTSC,FM) + - 1019:4cb5 + + * - 32 + - AVACS SmartTV + - + + * - 33 + - AVerMedia DVD EZMaker + - 1461:10ff + + * - 34 + - Noval Prime TV 7133 + - + + * - 35 + - AverMedia AverTV Studio 305 + - 1461:2115 + + * - 36 + - UPMOST PURPLE TV + - 12ab:0800 + + * - 37 + - Items MuchTV Plus / IT-005 + - + + * - 38 + - Terratec Cinergy 200 TV + - 153b:1152 + + * - 39 + - LifeView FlyTV Platinum Mini + - 5168:0212, 4e42:0212, 5169:1502 + + * - 40 + - Compro VideoMate TV PVR/FM + - 185b:c100 + + * - 41 + - Compro VideoMate TV Gold+ + - 185b:c100 + + * - 42 + - Sabrent SBT-TVFM (saa7130) + - + + * - 43 + - :Zolid Xpert TV7134 + - + + * - 44 + - Empire PCI TV-Radio LE + - + + * - 45 + - Avermedia AVerTV Studio 307 + - 1461:9715 + + * - 46 + - AVerMedia Cardbus TV/Radio (E500) + - 1461:d6ee + + * - 47 + - Terratec Cinergy 400 mobile + - 153b:1162 + + * - 48 + - Terratec Cinergy 600 TV MK3 + - 153b:1158 + + * - 49 + - Compro VideoMate Gold+ Pal + - 185b:c200 + + * - 50 + - Pinnacle PCTV 300i DVB-T + PAL + - 11bd:002d + + * - 51 + - ProVideo PV952 + - 1540:9524 + + * - 52 + - AverMedia AverTV/305 + - 1461:2108 + + * - 53 + - ASUS TV-FM 7135 + - 1043:4845 + + * - 54 + - LifeView FlyTV Platinum FM / Gold + - 5168:0214, 5168:5214, 1489:0214, 5168:0304 + + * - 55 + - LifeView FlyDVB-T DUO / MSI TV@nywhere Duo + - 5168:0306, 4E42:0306 + + * - 56 + - Avermedia AVerTV 307 + - 1461:a70a + + * - 57 + - Avermedia AVerTV GO 007 FM + - 1461:f31f + + * - 58 + - ADS Tech Instant TV (saa7135) + - 1421:0350, 1421:0351, 1421:0370, 1421:1370 + + * - 59 + - Kworld/Tevion V-Stream Xpert TV PVR7134 + - + + * - 60 + - LifeView/Typhoon/Genius FlyDVB-T Duo Cardbus + - 5168:0502, 4e42:0502, 1489:0502 + + * - 61 + - Philips TOUGH DVB-T reference design + - 1131:2004 + + * - 62 + - Compro VideoMate TV Gold+II + - + + * - 63 + - Kworld Xpert TV PVR7134 + - + + * - 64 + - FlyTV mini Asus Digimatrix + - 1043:0210 + + * - 65 + - V-Stream Studio TV Terminator + - + + * - 66 + - Yuan TUN-900 (saa7135) + - + + * - 67 + - Beholder BeholdTV 409 FM + - 0000:4091 + + * - 68 + - GoTView 7135 PCI + - 5456:7135 + + * - 69 + - Philips EUROPA V3 reference design + - 1131:2004 + + * - 70 + - Compro Videomate DVB-T300 + - 185b:c900 + + * - 71 + - Compro Videomate DVB-T200 + - 185b:c901 + + * - 72 + - RTD Embedded Technologies VFG7350 + - 1435:7350 + + * - 73 + - RTD Embedded Technologies VFG7330 + - 1435:7330 + + * - 74 + - LifeView FlyTV Platinum Mini2 + - 14c0:1212 + + * - 75 + - AVerMedia AVerTVHD MCE A180 + - 1461:1044 + + * - 76 + - SKNet MonsterTV Mobile + - 1131:4ee9 + + * - 77 + - Pinnacle PCTV 40i/50i/110i (saa7133) + - 11bd:002e + + * - 78 + - ASUSTeK P7131 Dual + - 1043:4862 + + * - 79 + - Sedna/MuchTV PC TV Cardbus TV/Radio (ITO25 Rev:2B) + - + + * - 80 + - ASUS Digimatrix TV + - 1043:0210 + + * - 81 + - Philips Tiger reference design + - 1131:2018 + + * - 82 + - MSI TV@Anywhere plus + - 1462:6231, 1462:8624 + + * - 83 + - Terratec Cinergy 250 PCI TV + - 153b:1160 + + * - 84 + - LifeView FlyDVB Trio + - 5168:0319 + + * - 85 + - AverTV DVB-T 777 + - 1461:2c05, 1461:2c05 + + * - 86 + - LifeView FlyDVB-T / Genius VideoWonder DVB-T + - 5168:0301, 1489:0301 + + * - 87 + - ADS Instant TV Duo Cardbus PTV331 + - 0331:1421 + + * - 88 + - Tevion/KWorld DVB-T 220RF + - 17de:7201 + + * - 89 + - ELSA EX-VISION 700TV + - 1048:226c + + * - 90 + - Kworld ATSC110/115 + - 17de:7350, 17de:7352 + + * - 91 + - AVerMedia A169 B + - 1461:7360 + + * - 92 + - AVerMedia A169 B1 + - 1461:6360 + + * - 93 + - Medion 7134 Bridge #2 + - 16be:0005 + + * - 94 + - LifeView FlyDVB-T Hybrid Cardbus/MSI TV @nywhere A/D NB + - 5168:3306, 5168:3502, 5168:3307, 4e42:3502 + + * - 95 + - LifeView FlyVIDEO3000 (NTSC) + - 5169:0138 + + * - 96 + - Medion Md8800 Quadro + - 16be:0007, 16be:0008, 16be:000d + + * - 97 + - LifeView FlyDVB-S /Acorp TV134DS + - 5168:0300, 4e42:0300 + + * - 98 + - Proteus Pro 2309 + - 0919:2003 + + * - 99 + - AVerMedia TV Hybrid A16AR + - 1461:2c00 + + * - 100 + - Asus Europa2 OEM + - 1043:4860 + + * - 101 + - Pinnacle PCTV 310i + - 11bd:002f + + * - 102 + - Avermedia AVerTV Studio 507 + - 1461:9715 + + * - 103 + - Compro Videomate DVB-T200A + - + + * - 104 + - Hauppauge WinTV-HVR1110 DVB-T/Hybrid + - 0070:6700, 0070:6701, 0070:6702, 0070:6703, 0070:6704, 0070:6705 + + * - 105 + - Terratec Cinergy HT PCMCIA + - 153b:1172 + + * - 106 + - Encore ENLTV + - 1131:2342, 1131:2341, 3016:2344 + + * - 107 + - Encore ENLTV-FM + - 1131:230f + + * - 108 + - Terratec Cinergy HT PCI + - 153b:1175 + + * - 109 + - Philips Tiger - S Reference design + - + + * - 110 + - Avermedia M102 + - 1461:f31e + + * - 111 + - ASUS P7131 4871 + - 1043:4871 + + * - 112 + - ASUSTeK P7131 Hybrid + - 1043:4876 + + * - 113 + - Elitegroup ECS TVP3XP FM1246 Tuner Card (PAL,FM) + - 1019:4cb6 + + * - 114 + - KWorld DVB-T 210 + - 17de:7250 + + * - 115 + - Sabrent PCMCIA TV-PCB05 + - 0919:2003 + + * - 116 + - 10MOONS TM300 TV Card + - 1131:2304 + + * - 117 + - Avermedia Super 007 + - 1461:f01d + + * - 118 + - Beholder BeholdTV 401 + - 0000:4016 + + * - 119 + - Beholder BeholdTV 403 + - 0000:4036 + + * - 120 + - Beholder BeholdTV 403 FM + - 0000:4037 + + * - 121 + - Beholder BeholdTV 405 + - 0000:4050 + + * - 122 + - Beholder BeholdTV 405 FM + - 0000:4051 + + * - 123 + - Beholder BeholdTV 407 + - 0000:4070 + + * - 124 + - Beholder BeholdTV 407 FM + - 0000:4071 + + * - 125 + - Beholder BeholdTV 409 + - 0000:4090 + + * - 126 + - Beholder BeholdTV 505 FM + - 5ace:5050 + + * - 127 + - Beholder BeholdTV 507 FM / BeholdTV 509 FM + - 5ace:5070, 5ace:5090 + + * - 128 + - Beholder BeholdTV Columbus TV/FM + - 0000:5201 + + * - 129 + - Beholder BeholdTV 607 FM + - 5ace:6070 + + * - 130 + - Beholder BeholdTV M6 + - 5ace:6190 + + * - 131 + - Twinhan Hybrid DTV-DVB 3056 PCI + - 1822:0022 + + * - 132 + - Genius TVGO AM11MCE + - + + * - 133 + - NXP Snake DVB-S reference design + - + + * - 134 + - Medion/Creatix CTX953 Hybrid + - 16be:0010 + + * - 135 + - MSI TV@nywhere A/D v1.1 + - 1462:8625 + + * - 136 + - AVerMedia Cardbus TV/Radio (E506R) + - 1461:f436 + + * - 137 + - AVerMedia Hybrid TV/Radio (A16D) + - 1461:f936 + + * - 138 + - Avermedia M115 + - 1461:a836 + + * - 139 + - Compro VideoMate T750 + - 185b:c900 + + * - 140 + - Avermedia DVB-S Pro A700 + - 1461:a7a1 + + * - 141 + - Avermedia DVB-S Hybrid+FM A700 + - 1461:a7a2 + + * - 142 + - Beholder BeholdTV H6 + - 5ace:6290 + + * - 143 + - Beholder BeholdTV M63 + - 5ace:6191 + + * - 144 + - Beholder BeholdTV M6 Extra + - 5ace:6193 + + * - 145 + - AVerMedia MiniPCI DVB-T Hybrid M103 + - 1461:f636, 1461:f736 + + * - 146 + - ASUSTeK P7131 Analog + - + + * - 147 + - Asus Tiger 3in1 + - 1043:4878 + + * - 148 + - Encore ENLTV-FM v5.3 + - 1a7f:2008 + + * - 149 + - Avermedia PCI pure analog (M135A) + - 1461:f11d + + * - 150 + - Zogis Real Angel 220 + - + + * - 151 + - ADS Tech Instant HDTV + - 1421:0380 + + * - 152 + - Asus Tiger Rev:1.00 + - 1043:4857 + + * - 153 + - Kworld Plus TV Analog Lite PCI + - 17de:7128 + + * - 154 + - Avermedia AVerTV GO 007 FM Plus + - 1461:f31d + + * - 155 + - Hauppauge WinTV-HVR1150 ATSC/QAM-Hybrid + - 0070:6706, 0070:6708 + + * - 156 + - Hauppauge WinTV-HVR1120 DVB-T/Hybrid + - 0070:6707, 0070:6709, 0070:670a + + * - 157 + - Avermedia AVerTV Studio 507UA + - 1461:a11b + + * - 158 + - AVerMedia Cardbus TV/Radio (E501R) + - 1461:b7e9 + + * - 159 + - Beholder BeholdTV 505 RDS + - 0000:505B + + * - 160 + - Beholder BeholdTV 507 RDS + - 0000:5071 + + * - 161 + - Beholder BeholdTV 507 RDS + - 0000:507B + + * - 162 + - Beholder BeholdTV 607 FM + - 5ace:6071 + + * - 163 + - Beholder BeholdTV 609 FM + - 5ace:6090 + + * - 164 + - Beholder BeholdTV 609 FM + - 5ace:6091 + + * - 165 + - Beholder BeholdTV 607 RDS + - 5ace:6072 + + * - 166 + - Beholder BeholdTV 607 RDS + - 5ace:6073 + + * - 167 + - Beholder BeholdTV 609 RDS + - 5ace:6092 + + * - 168 + - Beholder BeholdTV 609 RDS + - 5ace:6093 + + * - 169 + - Compro VideoMate S350/S300 + - 185b:c900 + + * - 170 + - AverMedia AverTV Studio 505 + - 1461:a115 + + * - 171 + - Beholder BeholdTV X7 + - 5ace:7595 + + * - 172 + - RoverMedia TV Link Pro FM + - 19d1:0138 + + * - 173 + - Zolid Hybrid TV Tuner PCI + - 1131:2004 + + * - 174 + - Asus Europa Hybrid OEM + - 1043:4847 + + * - 175 + - Leadtek Winfast DTV1000S + - 107d:6655 + + * - 176 + - Beholder BeholdTV 505 RDS + - 0000:5051 + + * - 177 + - Hawell HW-404M7 + - + + * - 178 + - Beholder BeholdTV H7 + - 5ace:7190 + + * - 179 + - Beholder BeholdTV A7 + - 5ace:7090 + + * - 180 + - Avermedia PCI M733A + - 1461:4155, 1461:4255 + + * - 181 + - TechoTrend TT-budget T-3000 + - 13c2:2804 + + * - 182 + - Kworld PCI SBTVD/ISDB-T Full-Seg Hybrid + - 17de:b136 + + * - 183 + - Compro VideoMate Vista M1F + - 185b:c900 + + * - 184 + - Encore ENLTV-FM 3 + - 1a7f:2108 + + * - 185 + - MagicPro ProHDTV Pro2 DMB-TH/Hybrid + - 17de:d136 + + * - 186 + - Beholder BeholdTV 501 + - 5ace:5010 + + * - 187 + - Beholder BeholdTV 503 FM + - 5ace:5030 + + * - 188 + - Sensoray 811/911 + - 6000:0811, 6000:0911 + + * - 189 + - Kworld PC150-U + - 17de:a134 + + * - 190 + - Asus My Cinema PS3-100 + - 1043:48cd + + * - 191 + - Hawell HW-9004V1 + - + + * - 192 + - AverMedia AverTV Satellite Hybrid+FM A706 + - 1461:2055 + + * - 193 + - WIS Voyager or compatible + - 1905:7007 + + * - 194 + - AverMedia AverTV/505 + - 1461:a10a + + * - 195 + - Leadtek Winfast TV2100 FM + - 107d:6f3a + + * - 196 + - SnaZio* TVPVR PRO + - 1779:13cf diff --git a/Documentation/admin-guide/media/saa7134.rst b/Documentation/admin-guide/media/saa7134.rst new file mode 100644 index 000000000..51eae7eb5 --- /dev/null +++ b/Documentation/admin-guide/media/saa7134.rst @@ -0,0 +1,89 @@ +.. SPDX-License-Identifier: GPL-2.0 + +The saa7134 driver +================== + +Author Gerd Hoffmann + + +This is a v4l2/oss device driver for saa7130/33/34/35 based capture / TV +boards. + + +Status +------ + +Almost everything is working. video, sound, tuner, radio, mpeg ts, ... + +As with bttv, card-specific tweaks are needed. Check CARDLIST for a +list of known TV cards and saa7134-cards.c for the drivers card +configuration info. + + +Build +----- + +Once you pick up a Kernel source, you should configure, build, +install and boot the new kernel. You'll need at least +these config options:: + + ./scripts/config -e PCI + ./scripts/config -e INPUT + ./scripts/config -m I2C + ./scripts/config -m MEDIA_SUPPORT + ./scripts/config -e MEDIA_PCI_SUPPORT + ./scripts/config -e MEDIA_ANALOG_TV_SUPPORT + ./scripts/config -e MEDIA_DIGITAL_TV_SUPPORT + ./scripts/config -e MEDIA_RADIO_SUPPORT + ./scripts/config -e RC_CORE + ./scripts/config -e MEDIA_SUBDRV_AUTOSELECT + ./scripts/config -m VIDEO_SAA7134 + ./scripts/config -e SAA7134_ALSA + ./scripts/config -e VIDEO_SAA7134_RC + ./scripts/config -e VIDEO_SAA7134_DVB + ./scripts/config -e VIDEO_SAA7134_GO7007 + +To build and install, you should run:: + + make && make modules_install && make install + +Once the new Kernel is booted, saa7134 driver should be loaded automatically. + +Depending on the card you might have to pass ``card=<nr>`` as insmod option. +If so, please check Documentation/admin-guide/media/saa7134-cardlist.rst +for valid choices. + +Once you have your card type number, you can pass a modules configuration +via a file (usually, it is either ``/etc/modules.conf`` or some file at +``/etc/modules-load.d/``, but the actual place depends on your +distribution), with this content:: + + options saa7134 card=13 # Assuming that your card type is #13 + + +Changes / Fixes +--------------- + +Please mail to linux-media AT vger.kernel.org unified diffs against +the linux media git tree: + + https://git.linuxtv.org/media_tree.git/ + +This is done by committing a patch at a clone of the git tree and +submitting the patch using ``git send-email``. Don't forget to +describe at the lots what it changes / which problem it fixes / whatever +it is good for ... + + +Known Problems +-------------- + +* The tuner for the flyvideos isn't detected automatically and the + default might not work for you depending on which version you have. + There is a ``tuner=`` insmod option to override the driver's default. + +Credits +------- + +andrew.stevens@philips.com + werner.leeb@philips.com for providing +saa7134 hardware specs and sample board. diff --git a/Documentation/admin-guide/media/saa7164-cardlist.rst b/Documentation/admin-guide/media/saa7164-cardlist.rst new file mode 100644 index 000000000..7949c09aa --- /dev/null +++ b/Documentation/admin-guide/media/saa7164-cardlist.rst @@ -0,0 +1,71 @@ +.. SPDX-License-Identifier: GPL-2.0 + +SAA7164 cards list +================== + +.. tabularcolumns:: |p{1.4cm}|p{11.1cm}|p{4.2cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 2 19 18 + :stub-columns: 0 + + * - Card number + - Card name + - PCI subsystem IDs + + * - 0 + - Unknown + - + + * - 1 + - Generic Rev2 + - + + * - 2 + - Generic Rev3 + - + + * - 3 + - Hauppauge WinTV-HVR2250 + - 0070:8880, 0070:8810 + + * - 4 + - Hauppauge WinTV-HVR2200 + - 0070:8980 + + * - 5 + - Hauppauge WinTV-HVR2200 + - 0070:8900 + + * - 6 + - Hauppauge WinTV-HVR2200 + - 0070:8901 + + * - 7 + - Hauppauge WinTV-HVR2250 + - 0070:8891, 0070:8851 + + * - 8 + - Hauppauge WinTV-HVR2250 + - 0070:88A1 + + * - 9 + - Hauppauge WinTV-HVR2200 + - 0070:8940 + + * - 10 + - Hauppauge WinTV-HVR2200 + - 0070:8953 + + * - 11 + - Hauppauge WinTV-HVR2255(proto) + - 0070:f111 + + * - 12 + - Hauppauge WinTV-HVR2255 + - 0070:f111 + + * - 13 + - Hauppauge WinTV-HVR2205 + - 0070:f123, 0070:f120 diff --git a/Documentation/admin-guide/media/si470x.rst b/Documentation/admin-guide/media/si470x.rst new file mode 100644 index 000000000..d53bf5f95 --- /dev/null +++ b/Documentation/admin-guide/media/si470x.rst @@ -0,0 +1,167 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. include:: <isonum.txt> + +The Silicon Labs Si470x FM Radio Receivers driver +================================================= + +Copyright |copy| 2009 Tobias Lorenz <tobias.lorenz@gmx.net> + + +Information from Silicon Labs +----------------------------- + +Silicon Laboratories is the manufacturer of the radio ICs, that nowadays are the +most often used radio receivers in cell phones. Usually they are connected with +I2C. But SiLabs also provides a reference design, which integrates this IC, +together with a small microcontroller C8051F321, to form a USB radio. +Part of this reference design is also a radio application in binary and source +code. The software also contains an automatic firmware upgrade to the most +current version. Information on these can be downloaded here: +http://www.silabs.com/usbradio + + +Supported ICs +------------- + +The following ICs have a very similar register set, so that they are or will be +supported somewhen by the driver: + +- Si4700: FM radio receiver +- Si4701: FM radio receiver, RDS Support +- Si4702: FM radio receiver +- Si4703: FM radio receiver, RDS Support +- Si4704: FM radio receiver, no external antenna required +- Si4705: FM radio receiver, no external antenna required, RDS support, Dig I/O +- Si4706: Enhanced FM RDS/TMC radio receiver, no external antenna required, RDS + Support +- Si4707: Dedicated weather band radio receiver with SAME decoder, RDS Support +- Si4708: Smallest FM receivers +- Si4709: Smallest FM receivers, RDS Support + +More information on these can be downloaded here: +http://www.silabs.com/products/mcu/Pages/USBFMRadioRD.aspx + + +Supported USB devices +--------------------- + +Currently the following USB radios (vendor:product) with the Silicon Labs si470x +chips are known to work: + +- 10c4:818a: Silicon Labs USB FM Radio Reference Design +- 06e1:a155: ADS/Tech FM Radio Receiver (formerly Instant FM Music) (RDX-155-EF) +- 1b80:d700: KWorld USB FM Radio SnapMusic Mobile 700 (FM700) +- 10c5:819a: Sanei Electric, Inc. FM USB Radio (sold as DealExtreme.com PCear) + + +Software +-------- + +Testing is usually done with most application under Debian/testing: + +- fmtools - Utility for managing FM tuner cards +- gnomeradio - FM-radio tuner for the GNOME desktop +- gradio - GTK FM radio tuner +- kradio - Comfortable Radio Application for KDE +- radio - ncurses-based radio application +- mplayer - The Ultimate Movie Player For Linux +- v4l2-ctl - Collection of command line video4linux utilities + +For example, you can use: + +.. code-block:: none + + v4l2-ctl -d /dev/radio0 --set-ctrl=volume=10,mute=0 --set-freq=95.21 --all + +There is also a library libv4l, which can be used. It's going to have a function +for frequency seeking, either by using hardware functionality as in radio-si470x +or by implementing a function as we currently have in every of the mentioned +programs. Somewhen the radio programs should make use of libv4l. + +For processing RDS information, there is a project ongoing at: +http://rdsd.berlios.de/ + +There is currently no project for making TMC sentences human readable. + + +Audio Listing +------------- + +USB Audio is provided by the ALSA snd_usb_audio module. It is recommended to +also select SND_USB_AUDIO, as this is required to get sound from the radio. For +listing you have to redirect the sound, for example using one of the following +commands. Please adjust the audio devices to your needs (/dev/dsp* and hw:x,x). + +If you just want to test audio (very poor quality): + +.. code-block:: none + + cat /dev/dsp1 > /dev/dsp + +If you use sox + OSS try: + +.. code-block:: none + + sox -2 --endian little -r 96000 -t oss /dev/dsp1 -t oss /dev/dsp + +or using sox + alsa: + +.. code-block:: none + + sox --endian little -c 2 -S -r 96000 -t alsa hw:1 -t alsa -r 96000 hw:0 + +If you use arts try: + +.. code-block:: none + + arecord -D hw:1,0 -r96000 -c2 -f S16_LE | artsdsp aplay -B - + +If you use mplayer try: + +.. code-block:: none + + mplayer -radio adevice=hw=1.0:arate=96000 \ + -rawaudio rate=96000 \ + radio://<frequency>/capture + +Module Parameters +----------------- + +After loading the module, you still have access to some of them in the sysfs +mount under /sys/module/radio_si470x/parameters. The contents of read-only files +(0444) are not updated, even if space, band and de are changed using private +video controls. The others are runtime changeable. + + +Errors +------ + +Increase tune_timeout, if you often get -EIO errors. + +When timed out or band limit is reached, hw_freq_seek returns -EAGAIN. + +If you get any errors from snd_usb_audio, please report them to the ALSA people. + + +Open Issues +----------- + +V4L minor device allocation and parameter setting is not perfect. A solution is +currently under discussion. + +There is an USB interface for downloading/uploading new firmware images. Support +for it can be implemented using the request_firmware interface. + +There is a RDS interrupt mode. The driver is already using the same interface +for polling RDS information, but is currently not using the interrupt mode. + +There is a LED interface, which can be used to override the LED control +programmed in the firmware. This can be made available using the LED support +functions in the kernel. + + +Other useful information and links +---------------------------------- + +http://www.silabs.com/usbradio diff --git a/Documentation/admin-guide/media/si4713.rst b/Documentation/admin-guide/media/si4713.rst new file mode 100644 index 000000000..be8e6b49b --- /dev/null +++ b/Documentation/admin-guide/media/si4713.rst @@ -0,0 +1,192 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. include:: <isonum.txt> + +The Silicon Labs Si4713 FM Radio Transmitter Driver +=================================================== + +Copyright |copy| 2009 Nokia Corporation + +Contact: Eduardo Valentin <eduardo.valentin@nokia.com> + + +Information about the Device +---------------------------- + +This chip is a Silicon Labs product. It is a I2C device, currently on 0x63 address. +Basically, it has transmission and signal noise level measurement features. + +The Si4713 integrates transmit functions for FM broadcast stereo transmission. +The chip also allows integrated receive power scanning to identify low signal +power FM channels. + +The chip is programmed using commands and responses. There are also several +properties which can change the behavior of this chip. + +Users must comply with local regulations on radio frequency (RF) transmission. + +Device driver description +------------------------- + +There are two modules to handle this device. One is a I2C device driver +and the other is a platform driver. + +The I2C device driver exports a v4l2-subdev interface to the kernel. +All properties can also be accessed by v4l2 extended controls interface, by +using the v4l2-subdev calls (g_ext_ctrls, s_ext_ctrls). + +The platform device driver exports a v4l2 radio device interface to user land. +So, it uses the I2C device driver as a sub device in order to send the user +commands to the actual device. Basically it is a wrapper to the I2C device driver. + +Applications can use v4l2 radio API to specify frequency of operation, mute state, +etc. But mostly of its properties will be present in the extended controls. + +When the v4l2 mute property is set to 1 (true), the driver will turn the chip off. + +Properties description +---------------------- + +The properties can be accessed using v4l2 extended controls. +Here is an output from v4l2-ctl util: + +.. code-block:: none + + / # v4l2-ctl -d /dev/radio0 --all -L + Driver Info: + Driver name : radio-si4713 + Card type : Silicon Labs Si4713 Modulator + Bus info : + Driver version: 0 + Capabilities : 0x00080800 + RDS Output + Modulator + Audio output: 0 (FM Modulator Audio Out) + Frequency: 1408000 (88.000000 MHz) + Video Standard = 0x00000000 + Modulator: + Name : FM Modulator + Capabilities : 62.5 Hz stereo rds + Frequency range : 76.0 MHz - 108.0 MHz + Subchannel modulation: stereo+rds + + User Controls + + mute (bool) : default=1 value=0 + + FM Radio Modulator Controls + + rds_signal_deviation (int) : min=0 max=90000 step=10 default=200 value=200 flags=slider + rds_program_id (int) : min=0 max=65535 step=1 default=0 value=0 + rds_program_type (int) : min=0 max=31 step=1 default=0 value=0 + rds_ps_name (str) : min=0 max=96 step=8 value='si4713 ' + rds_radio_text (str) : min=0 max=384 step=32 value='' + audio_limiter_feature_enabled (bool) : default=1 value=1 + audio_limiter_release_time (int) : min=250 max=102390 step=50 default=5010 value=5010 flags=slider + audio_limiter_deviation (int) : min=0 max=90000 step=10 default=66250 value=66250 flags=slider + audio_compression_feature_enabl (bool) : default=1 value=1 + audio_compression_gain (int) : min=0 max=20 step=1 default=15 value=15 flags=slider + audio_compression_threshold (int) : min=-40 max=0 step=1 default=-40 value=-40 flags=slider + audio_compression_attack_time (int) : min=0 max=5000 step=500 default=0 value=0 flags=slider + audio_compression_release_time (int) : min=100000 max=1000000 step=100000 default=1000000 value=1000000 flags=slider + pilot_tone_feature_enabled (bool) : default=1 value=1 + pilot_tone_deviation (int) : min=0 max=90000 step=10 default=6750 value=6750 flags=slider + pilot_tone_frequency (int) : min=0 max=19000 step=1 default=19000 value=19000 flags=slider + pre_emphasis_settings (menu) : min=0 max=2 default=1 value=1 + tune_power_level (int) : min=0 max=120 step=1 default=88 value=88 flags=slider + tune_antenna_capacitor (int) : min=0 max=191 step=1 default=0 value=110 flags=slider + +Here is a summary of them: + +* Pilot is an audible tone sent by the device. + +- pilot_frequency - Configures the frequency of the stereo pilot tone. +- pilot_deviation - Configures pilot tone frequency deviation level. +- pilot_enabled - Enables or disables the pilot tone feature. + +* The si4713 device is capable of applying audio compression to the + transmitted signal. + +- acomp_enabled - Enables or disables the audio dynamic range control feature. +- acomp_gain - Sets the gain for audio dynamic range control. +- acomp_threshold - Sets the threshold level for audio dynamic range control. +- acomp_attack_time - Sets the attack time for audio dynamic range control. +- acomp_release_time - Sets the release time for audio dynamic range control. + +* Limiter setups audio deviation limiter feature. Once a over deviation occurs, + it is possible to adjust the front-end gain of the audio input and always + prevent over deviation. + +- limiter_enabled - Enables or disables the limiter feature. +- limiter_deviation - Configures audio frequency deviation level. +- limiter_release_time - Sets the limiter release time. + +* Tuning power + +- power_level - Sets the output power level for signal transmission. + antenna_capacitor - This selects the value of antenna tuning capacitor + manually or automatically if set to zero. + +* RDS related + +- rds_ps_name - Sets the RDS ps name field for transmission. +- rds_radio_text - Sets the RDS radio text for transmission. +- rds_pi - Sets the RDS PI field for transmission. +- rds_pty - Sets the RDS PTY field for transmission. + +* Region related + +- preemphasis - sets the preemphasis to be applied for transmission. + +RNL +--- + +This device also has an interface to measure received noise level. To do that, you should +ioctl the device node. Here is an code of example: + +.. code-block:: none + + int main (int argc, char *argv[]) + { + struct si4713_rnl rnl; + int fd = open("/dev/radio0", O_RDWR); + int rval; + + if (argc < 2) + return -EINVAL; + + if (fd < 0) + return fd; + + sscanf(argv[1], "%d", &rnl.frequency); + + rval = ioctl(fd, SI4713_IOC_MEASURE_RNL, &rnl); + if (rval < 0) + return rval; + + printf("received noise level: %d\n", rnl.rnl); + + close(fd); + } + +The struct si4713_rnl and SI4713_IOC_MEASURE_RNL are defined under +include/linux/platform_data/media/si4713.h. + +Stereo/Mono and RDS subchannels +------------------------------- + +The device can also be configured using the available sub channels for +transmission. To do that use S/G_MODULATOR ioctl and configure txsubchans properly. +Refer to the V4L2 API specification for proper use of this ioctl. + +Testing +------- +Testing is usually done with v4l2-ctl utility for managing FM tuner cards. +The tool can be found in v4l-dvb repository under v4l2-apps/util directory. + +Example for setting rds ps name: + +.. code-block:: none + + # v4l2-ctl -d /dev/radio0 --set-ctrl=rds_ps_name="Dummy" + diff --git a/Documentation/admin-guide/media/si476x.rst b/Documentation/admin-guide/media/si476x.rst new file mode 100644 index 000000000..c8882ee9f --- /dev/null +++ b/Documentation/admin-guide/media/si476x.rst @@ -0,0 +1,160 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. include:: <isonum.txt> + + +The SI476x Driver +================= + +Copyright |copy| 2013 Andrey Smirnov <andrew.smirnov@gmail.com> + +TODO for the driver +------------------- + +- According to the SiLabs' datasheet it is possible to update the + firmware of the radio chip in the run-time, thus bringing it to the + most recent version. Unfortunately I couldn't find any mentioning of + the said firmware update for the old chips that I tested the driver + against, so for chips like that the driver only exposes the old + functionality. + + +Parameters exposed over debugfs +------------------------------- +SI476x allow user to get multiple characteristics that can be very +useful for EoL testing/RF performance estimation, parameters that have +very little to do with V4L2 subsystem. Such parameters are exposed via +debugfs and can be accessed via regular file I/O operations. + +The drivers exposes following files: + +* /sys/kernel/debug/<device-name>/acf + This file contains ACF(Automatically Controlled Features) status + information. The contents of the file is binary data of the + following layout: + + .. tabularcolumns:: |p{7ex}|p{12ex}|L| + + ============= ============== ==================================== + Offset Name Description + ============= ============== ==================================== + 0x00 blend_int Flag, set when stereo separation has + crossed below the blend threshold + 0x01 hblend_int Flag, set when HiBlend cutoff + frequency is lower than threshold + 0x02 hicut_int Flag, set when HiCut cutoff + frequency is lower than threshold + 0x03 chbw_int Flag, set when channel filter + bandwidth is less than threshold + 0x04 softmute_int Flag indicating that softmute + attenuation has increased above + softmute threshold + 0x05 smute 0 - Audio is not soft muted + 1 - Audio is soft muted + 0x06 smattn Soft mute attenuation level in dB + 0x07 chbw Channel filter bandwidth in kHz + 0x08 hicut HiCut cutoff frequency in units of + 100Hz + 0x09 hiblend HiBlend cutoff frequency in units + of 100 Hz + 0x10 pilot 0 - Stereo pilot is not present + 1 - Stereo pilot is present + 0x11 stblend Stereo blend in % + ============= ============== ==================================== + + +* /sys/kernel/debug/<device-name>/rds_blckcnt + This file contains statistics about RDS receptions. It's binary data + has the following layout: + + .. tabularcolumns:: |p{7ex}|p{12ex}|L| + + ============= ============== ==================================== + Offset Name Description + ============= ============== ==================================== + 0x00 expected Number of expected RDS blocks + 0x02 received Number of received RDS blocks + 0x04 uncorrectable Number of uncorrectable RDS blocks + ============= ============== ==================================== + +* /sys/kernel/debug/<device-name>/agc + This file contains information about parameters pertaining to + AGC(Automatic Gain Control) + + The layout is: + + .. tabularcolumns:: |p{7ex}|p{12ex}|L| + + ============= ============== ==================================== + Offset Name Description + ============= ============== ==================================== + 0x00 mxhi 0 - FM Mixer PD high threshold is + not tripped + 1 - FM Mixer PD high threshold is + tripped + 0x01 mxlo ditto for FM Mixer PD low + 0x02 lnahi ditto for FM LNA PD high + 0x03 lnalo ditto for FM LNA PD low + 0x04 fmagc1 FMAGC1 attenuator resistance + (see datasheet for more detail) + 0x05 fmagc2 ditto for FMAGC2 + 0x06 pgagain PGA gain in dB + 0x07 fmwblang FM/WB LNA Gain in dB + ============= ============== ==================================== + +* /sys/kernel/debug/<device-name>/rsq + This file contains information about parameters pertaining to + RSQ(Received Signal Quality) + + The layout is: + + .. tabularcolumns:: |p{7ex}|p{12ex}|p{60ex}| + + ============= ============== ==================================== + Offset Name Description + ============= ============== ==================================== + 0x00 multhint 0 - multipath value has not crossed + the Multipath high threshold + 1 - multipath value has crossed + the Multipath high threshold + 0x01 multlint ditto for Multipath low threshold + 0x02 snrhint 0 - received signal's SNR has not + crossed high threshold + 1 - received signal's SNR has + crossed high threshold + 0x03 snrlint ditto for low threshold + 0x04 rssihint ditto for RSSI high threshold + 0x05 rssilint ditto for RSSI low threshold + 0x06 bltf Flag indicating if seek command + reached/wrapped seek band limit + 0x07 snr_ready Indicates that SNR metrics is ready + 0x08 rssiready ditto for RSSI metrics + 0x09 injside 0 - Low-side injection is being used + 1 - High-side injection is used + 0x10 afcrl Flag indicating if AFC rails + 0x11 valid Flag indicating if channel is valid + 0x12 readfreq Current tuned frequency + 0x14 freqoff Signed frequency offset in units of + 2ppm + 0x15 rssi Signed value of RSSI in dBuV + 0x16 snr Signed RF SNR in dB + 0x17 issi Signed Image Strength Signal + indicator + 0x18 lassi Signed Low side adjacent Channel + Strength indicator + 0x19 hassi ditto for High side + 0x20 mult Multipath indicator + 0x21 dev Frequency deviation + 0x24 assi Adjacent channel SSI + 0x25 usn Ultrasonic noise indicator + 0x26 pilotdev Pilot deviation in units of 100 Hz + 0x27 rdsdev ditto for RDS + 0x28 assidev ditto for ASSI + 0x29 strongdev Frequency deviation + 0x30 rdspi RDS PI code + ============= ============== ==================================== + +* /sys/kernel/debug/<device-name>/rsq_primary + This file contains information about parameters pertaining to + RSQ(Received Signal Quality) for primary tuner only. Layout is as + the one above. diff --git a/Documentation/admin-guide/media/siano-cardlist.rst b/Documentation/admin-guide/media/siano-cardlist.rst new file mode 100644 index 000000000..bb731a953 --- /dev/null +++ b/Documentation/admin-guide/media/siano-cardlist.rst @@ -0,0 +1,56 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Siano cards list +================ + +.. tabularcolumns:: p{13.3cm}|p{4.2cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 17 16 + :stub-columns: 0 + + * - Card name + - USB IDs + * - Hauppauge Catamount + - 2040:1700 + * - Hauppauge Okemo-A + - 2040:1800 + * - Hauppauge Okemo-B + - 2040:1801 + * - Hauppauge WinTV MiniCard + - 2040:2000, 2040:200a, 2040:2010, 2040:2011, 2040:2019 + * - Hauppauge WinTV MiniCard Rev 2 + - 2040:2009 + * - Hauppauge WinTV MiniStick + - 2040:5500, 2040:5510, 2040:5520, 2040:5530, 2040:5580, 2040:5590, 2040:b900, 2040:b910, 2040:b980, 2040:b990, 2040:c000, 2040:c010, 2040:c080, 2040:c090, 2040:c0a0, 2040:f5a0 + * - Hauppauge microStick 77e + - 2013:0257 + * - ONDA Data Card Digital Receiver + - 19D2:0078 + * - Siano Denver (ATSC-M/H) Digital Receiver + - 187f:0800 + * - Siano Denver (TDMB) Digital Receiver + - 187f:0700 + * - Siano Ming Digital Receiver + - 187f:0310 + * - Siano Nice Digital Receiver + - 187f:0202, 187f:0202 + * - Siano Nova A Digital Receiver + - 187f:0200 + * - Siano Nova B Digital Receiver + - 187f:0201 + * - Siano Pele Digital Receiver + - 187f:0500 + * - Siano Rio Digital Receiver + - 187f:0600, 3275:0080 + * - Siano Stellar Digital Receiver + - 187f:0100 + * - Siano Stellar Digital Receiver ROM + - 187f:0010 + * - Siano Vega Digital Receiver + - 187f:0300 + * - Siano Venice Digital Receiver + - 187f:0301, 187f:0301, 187f:0302 + * - ZTE Data Card Digital Receiver + - 19D2:0086 diff --git a/Documentation/admin-guide/media/technisat.rst b/Documentation/admin-guide/media/technisat.rst new file mode 100644 index 000000000..9eaa12366 --- /dev/null +++ b/Documentation/admin-guide/media/technisat.rst @@ -0,0 +1,100 @@ +.. SPDX-License-Identifier: GPL-2.0 + +How to set up the Technisat/B2C2 Flexcop devices +================================================ + +.. note:: + + This documentation is outdated. + +Author: Uwe Bugla <uwe.bugla@gmx.de> August 2009 + +Find out what device you have +----------------------------- + +Important Notice: The driver does NOT support Technisat USB 2 devices! + +First start your linux box with a shipped kernel: + +.. code-block:: none + + lspci -vvv for a PCI device (lsusb -vvv for an USB device) will show you for example: + 02:0b.0 Network controller: Techsan Electronics Co Ltd B2C2 FlexCopII DVB chip / + Technisat SkyStar2 DVB card (rev 02) + + dmesg | grep frontend may show you for example: + DVB: registering frontend 0 (Conexant CX24123/CX24109)... + +Kernel compilation: +------------------- + +If the Flexcop / Technisat is the only DVB / TV / Radio device in your box +get rid of unnecessary modules and check this one: + +``Multimedia support`` => ``Customise analog and hybrid tuner modules to build`` + +In this directory uncheck every driver which is activated there +(except ``Simple tuner support`` for ATSC 3rd generation only -> see case 9 please). + +Then please activate: + +- Main module part: + + ``Multimedia support`` => ``DVB/ATSC adapters`` => ``Technisat/B2C2 FlexcopII(b) and FlexCopIII adapters`` + + #) => ``Technisat/B2C2 Air/Sky/Cable2PC PCI`` (PCI card) or + #) => ``Technisat/B2C2 Air/Sky/Cable2PC USB`` (USB 1.1 adapter) + and for troubleshooting purposes: + #) => ``Enable debug for the B2C2 FlexCop drivers`` + +- Frontend / Tuner / Demodulator module part: + + ``Multimedia support`` => ``DVB/ATSC adapters`` + => ``Customise the frontend modules to build`` ``Customise DVB frontends`` => + + - SkyStar DVB-S Revision 2.3: + + #) => ``Zarlink VP310/MT312/ZL10313 based`` + #) => ``Generic I2C PLL based tuners`` + + - SkyStar DVB-S Revision 2.6: + + #) => ``ST STV0299 based`` + #) => ``Generic I2C PLL based tuners`` + + - SkyStar DVB-S Revision 2.7: + + #) => ``Samsung S5H1420 based`` + #) => ``Integrant ITD1000 Zero IF tuner for DVB-S/DSS`` + #) => ``ISL6421 SEC controller`` + + - SkyStar DVB-S Revision 2.8: + + #) => ``Conexant CX24123 based`` + #) => ``Conexant CX24113/CX24128 tuner for DVB-S/DSS`` + #) => ``ISL6421 SEC controller`` + + - AirStar DVB-T card: + + #) => ``Zarlink MT352 based`` + #) => ``Generic I2C PLL based tuners`` + + - CableStar DVB-C card: + + #) => ``ST STV0297 based`` + #) => ``Generic I2C PLL based tuners`` + + - AirStar ATSC card 1st generation: + + #) => ``Broadcom BCM3510`` + + - AirStar ATSC card 2nd generation: + + #) => ``NxtWave Communications NXT2002/NXT2004 based`` + #) => ``Generic I2C PLL based tuners`` + + - AirStar ATSC card 3rd generation: + + #) => ``LG Electronics LGDT3302/LGDT3303 based`` + #) ``Multimedia support`` => ``Customise analog and hybrid tuner modules to build`` => ``Simple tuner support`` + diff --git a/Documentation/admin-guide/media/ttusb-dec.rst b/Documentation/admin-guide/media/ttusb-dec.rst new file mode 100644 index 000000000..516bbab8a --- /dev/null +++ b/Documentation/admin-guide/media/ttusb-dec.rst @@ -0,0 +1,45 @@ +.. SPDX-License-Identifier: GPL-2.0 + +TechnoTrend/Hauppauge DEC USB Driver +==================================== + +Driver Status +------------- + +Supported: + + - DEC2000-t + - DEC2450-t + - DEC3000-s + - Video Streaming + - Audio Streaming + - Section Filters + - Channel Zapping + - Hotplug firmware loader + +To Do: + + - Tuner status information + - DVB network interface + - Streaming video PC->DEC + - Conax support for 2450-t + +Getting the Firmware +-------------------- +To download the firmware, use the following commands: + +.. code-block:: none + + scripts/get_dvb_firmware dec2000t + scripts/get_dvb_firmware dec2540t + scripts/get_dvb_firmware dec3000s + + +Hotplug Firmware Loading +------------------------ + +Since 2.6 kernels, the firmware is loaded at the point that the driver module +is loaded. + +Copy the three files downloaded above into the /usr/lib/hotplug/firmware or +/lib/firmware directory (depending on configuration of firmware hotplug). diff --git a/Documentation/admin-guide/media/tuner-cardlist.rst b/Documentation/admin-guide/media/tuner-cardlist.rst new file mode 100644 index 000000000..362617c59 --- /dev/null +++ b/Documentation/admin-guide/media/tuner-cardlist.rst @@ -0,0 +1,100 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Tuner cards list +================ + +============ ===================================================== +Tuner number Card name +============ ===================================================== +0 Temic PAL (4002 FH5) +1 Philips PAL_I (FI1246 and compatibles) +2 Philips NTSC (FI1236,FM1236 and compatibles) +3 Philips (SECAM+PAL_BG) (FI1216MF, FM1216MF, FR1216MF) +4 NoTuner +5 Philips PAL_BG (FI1216 and compatibles) +6 Temic NTSC (4032 FY5) +7 Temic PAL_I (4062 FY5) +8 Temic NTSC (4036 FY5) +9 Alps HSBH1 +10 Alps TSBE1 +11 Alps TSBB5 +12 Alps TSBE5 +13 Alps TSBC5 +14 Temic PAL_BG (4006FH5) +15 Alps TSCH6 +16 Temic PAL_DK (4016 FY5) +17 Philips NTSC_M (MK2) +18 Temic PAL_I (4066 FY5) +19 Temic PAL* auto (4006 FN5) +20 Temic PAL_BG (4009 FR5) or PAL_I (4069 FR5) +21 Temic NTSC (4039 FR5) +22 Temic PAL/SECAM multi (4046 FM5) +23 Philips PAL_DK (FI1256 and compatibles) +24 Philips PAL/SECAM multi (FQ1216ME) +25 LG PAL_I+FM (TAPC-I001D) +26 LG PAL_I (TAPC-I701D) +27 LG NTSC+FM (TPI8NSR01F) +28 LG PAL_BG+FM (TPI8PSB01D) +29 LG PAL_BG (TPI8PSB11D) +30 Temic PAL* auto + FM (4009 FN5) +31 SHARP NTSC_JP (2U5JF5540) +32 Samsung PAL TCPM9091PD27 +33 MT20xx universal +34 Temic PAL_BG (4106 FH5) +35 Temic PAL_DK/SECAM_L (4012 FY5) +36 Temic NTSC (4136 FY5) +37 LG PAL (newer TAPC series) +38 Philips PAL/SECAM multi (FM1216ME MK3) +39 LG NTSC (newer TAPC series) +40 HITACHI V7-J180AT +41 Philips PAL_MK (FI1216 MK) +42 Philips FCV1236D ATSC/NTSC dual in +43 Philips NTSC MK3 (FM1236MK3 or FM1236/F) +44 Philips 4 in 1 (ATI TV Wonder Pro/Conexant) +45 Microtune 4049 FM5 +46 Panasonic VP27s/ENGE4324D +47 LG NTSC (TAPE series) +48 Tenna TNF 8831 BGFF) +49 Microtune 4042 FI5 ATSC/NTSC dual in +50 TCL 2002N +51 Philips PAL/SECAM_D (FM 1256 I-H3) +52 Thomson DTT 7610 (ATSC/NTSC) +53 Philips FQ1286 +54 Philips/NXP TDA 8290/8295 + 8275/8275A/18271 +55 TCL 2002MB +56 Philips PAL/SECAM multi (FQ1216AME MK4) +57 Philips FQ1236A MK4 +58 Ymec TVision TVF-8531MF/8831MF/8731MF +59 Ymec TVision TVF-5533MF +60 Thomson DTT 761X (ATSC/NTSC) +61 Tena TNF9533-D/IF/TNF9533-B/DF +62 Philips TEA5767HN FM Radio +63 Philips FMD1216ME MK3 Hybrid Tuner +64 LG TDVS-H06xF +65 Ymec TVF66T5-B/DFF +66 LG TALN series +67 Philips TD1316 Hybrid Tuner +68 Philips TUV1236D ATSC/NTSC dual in +69 Tena TNF 5335 and similar models +70 Samsung TCPN 2121P30A +71 Xceive xc2028/xc3028 tuner +72 Thomson FE6600 +73 Samsung TCPG 6121P30A +75 Philips TEA5761 FM Radio +76 Xceive 5000 tuner +77 TCL tuner MF02GIP-5N-E +78 Philips FMD1216MEX MK3 Hybrid Tuner +79 Philips PAL/SECAM multi (FM1216 MK5) +80 Philips FQ1216LME MK3 PAL/SECAM w/active loopthrough +81 Partsnic (Daewoo) PTI-5NF05 +82 Philips CU1216L +83 NXP TDA18271 +84 Sony BTF-Pxn01Z +85 Philips FQ1236 MK5 +86 Tena TNF5337 MFD +87 Xceive 4000 tuner +88 Xceive 5000C tuner +89 Sony BTF-PG472Z PAL/SECAM +90 Sony BTF-PK467Z NTSC-M-JP +91 Sony BTF-PB463Z NTSC-M +============ ===================================================== diff --git a/Documentation/admin-guide/media/usb-cardlist.rst b/Documentation/admin-guide/media/usb-cardlist.rst new file mode 100644 index 000000000..5f5ab0723 --- /dev/null +++ b/Documentation/admin-guide/media/usb-cardlist.rst @@ -0,0 +1,149 @@ +.. SPDX-License-Identifier: GPL-2.0 + +USB drivers +=========== + +The USB boards are identified by an identification called USB ID. + +The ``lsusb`` command allows identifying the USB IDs:: + + $ lsusb + ... + Bus 001 Device 015: ID 046d:082d Logitech, Inc. HD Pro Webcam C920 + Bus 001 Device 074: ID 2040:b131 Hauppauge + Bus 001 Device 075: ID 2013:024f PCTV Systems nanoStick T2 290e + ... + +Newer camera devices use a standard way to expose themselves as such, +via USB Video Class. Those cameras are automatically supported by the +``uvc-driver``. + +Older cameras and TV USB devices uses USB Vendor Classes: each vendor +defines its own way to access the device. This section contains +card lists for such vendor-class devices. + +While this is not as common as on PCI, sometimes the same USB ID is used +by different products. So, several media drivers allow passing a ``card=`` +parameter, in order to setup a card number that would match the correct +settings for an specific product type. + +The current supported USB cards (not including staging drivers) are +listed below\ [#]_. + +.. [#] + + some of the drivers have sub-drivers, not shown at this table. + In particular, gspca driver has lots of sub-drivers, + for cameras not supported by the USB Video Class (UVC) driver, + as shown at :doc:`gspca card list <gspca-cardlist>`. + +====================== ========================================================= +Driver Name +====================== ========================================================= +airspy AirSpy +au0828 Auvitek AU0828 +b2c2-flexcop-usb Technisat/B2C2 Air/Sky/Cable2PC USB +cx231xx Conexant cx231xx USB video capture +dvb-as102 Abilis AS102 DVB receiver +dvb-ttusb-budget Technotrend/Hauppauge Nova - USB devices +dvb-usb-a800 AVerMedia AverTV DVB-T USB 2.0 (A800) +dvb-usb-af9005 Afatech AF9005 DVB-T USB1.1 +dvb-usb-af9015 Afatech AF9015 DVB-T USB2.0 +dvb-usb-af9035 Afatech AF9035 DVB-T USB2.0 +dvb-usb-anysee Anysee DVB-T/C USB2.0 +dvb-usb-au6610 Alcor Micro AU6610 USB2.0 +dvb-usb-az6007 AzureWave 6007 and clones DVB-T/C USB2.0 +dvb-usb-az6027 Azurewave DVB-S/S2 USB2.0 AZ6027 +dvb-usb-ce6230 Intel CE6230 DVB-T USB2.0 +dvb-usb-cinergyT2 Terratec CinergyT2/qanu USB 2.0 DVB-T +dvb-usb-cxusb Conexant USB2.0 hybrid +dvb-usb-dib0700 DiBcom DiB0700 +dvb-usb-dibusb-common DiBcom DiB3000M-B +dvb-usb-dibusb-mc DiBcom DiB3000M-C/P +dvb-usb-digitv Nebula Electronics uDigiTV DVB-T USB2.0 +dvb-usb-dtt200u WideView WT-200U and WT-220U (pen) DVB-T +dvb-usb-dtv5100 AME DTV-5100 USB2.0 DVB-T +dvb-usb-dvbsky DVBSky USB +dvb-usb-dw2102 DvbWorld & TeVii DVB-S/S2 USB2.0 +dvb-usb-ec168 E3C EC168 DVB-T USB2.0 +dvb-usb-gl861 Genesys Logic GL861 USB2.0 +dvb-usb-gp8psk GENPIX 8PSK->USB module +dvb-usb-lmedm04 LME DM04/QQBOX DVB-S USB2.0 +dvb-usb-m920x Uli m920x DVB-T USB2.0 +dvb-usb-nova-t-usb2 Hauppauge WinTV-NOVA-T usb2 DVB-T USB2.0 +dvb-usb-opera Opera1 DVB-S USB2.0 receiver +dvb-usb-pctv452e Pinnacle PCTV HDTV Pro USB device/TT Connect S2-3600 +dvb-usb-rtl28xxu Realtek RTL28xxU DVB USB +dvb-usb-technisat-usb2 Technisat DVB-S/S2 USB2.0 +dvb-usb-ttusb2 Pinnacle 400e DVB-S USB2.0 +dvb-usb-umt-010 HanfTek UMT-010 DVB-T USB2.0 +dvb_usb_v2 Support for various USB DVB devices v2 +dvb-usb-vp702x TwinhanDTV StarBox and clones DVB-S USB2.0 +dvb-usb-vp7045 TwinhanDTV Alpha/MagicBoxII, DNTV tinyUSB2, Beetle USB2.0 +em28xx Empia EM28xx USB devices +go7007 WIS GO7007 MPEG encoder +gspca Drivers for several USB Cameras +hackrf HackRF +hdpvr Hauppauge HD PVR +msi2500 Mirics MSi2500 +mxl111sf-tuner MxL111SF DTV USB2.0 +pvrusb2 Hauppauge WinTV-PVR USB2 +pwc USB Philips Cameras +s2250 Sensoray 2250/2251 +s2255drv USB Sensoray 2255 video capture device +smsusb Siano SMS1xxx based MDTV receiver +ttusb_dec Technotrend/Hauppauge USB DEC devices +usbtv USBTV007 video capture +uvcvideo USB Video Class (UVC) +zd1301 ZyDAS ZD1301 +====================== ========================================================= + +.. toctree:: + :maxdepth: 1 + + au0828-cardlist + cx231xx-cardlist + em28xx-cardlist + siano-cardlist + + gspca-cardlist + + dvb-usb-dib0700-cardlist + dvb-usb-dibusb-mb-cardlist + dvb-usb-dibusb-mc-cardlist + + dvb-usb-a800-cardlist + dvb-usb-af9005-cardlist + dvb-usb-az6027-cardlist + dvb-usb-cinergyT2-cardlist + dvb-usb-cxusb-cardlist + dvb-usb-digitv-cardlist + dvb-usb-dtt200u-cardlist + dvb-usb-dtv5100-cardlist + dvb-usb-dw2102-cardlist + dvb-usb-gp8psk-cardlist + dvb-usb-m920x-cardlist + dvb-usb-nova-t-usb2-cardlist + dvb-usb-opera1-cardlist + dvb-usb-pctv452e-cardlist + dvb-usb-technisat-usb2-cardlist + dvb-usb-ttusb2-cardlist + dvb-usb-umt-010-cardlist + dvb-usb-vp702x-cardlist + dvb-usb-vp7045-cardlist + + dvb-usb-af9015-cardlist + dvb-usb-af9035-cardlist + dvb-usb-anysee-cardlist + dvb-usb-au6610-cardlist + dvb-usb-az6007-cardlist + dvb-usb-ce6230-cardlist + dvb-usb-dvbsky-cardlist + dvb-usb-ec168-cardlist + dvb-usb-gl861-cardlist + dvb-usb-lmedm04-cardlist + dvb-usb-mxl111sf-cardlist + dvb-usb-rtl28xxu-cardlist + dvb-usb-zd1301-cardlist + + other-usb-cardlist diff --git a/Documentation/admin-guide/media/v4l-drivers.rst b/Documentation/admin-guide/media/v4l-drivers.rst new file mode 100644 index 000000000..1c41f87c3 --- /dev/null +++ b/Documentation/admin-guide/media/v4l-drivers.rst @@ -0,0 +1,32 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _uapi-v4l-drivers: + +=============================================== +Video4Linux (V4L) driver-specific documentation +=============================================== + +.. toctree:: + :maxdepth: 2 + + bttv + cafe_ccic + cx88 + fimc + imx + imx7 + ipu3 + ivtv + omap3isp + omap4_camera + philips + qcom_camss + rcar-fdp1 + rkisp1 + saa7134 + si470x + si4713 + si476x + vimc + visl + vivid diff --git a/Documentation/admin-guide/media/vimc.dot b/Documentation/admin-guide/media/vimc.dot new file mode 100644 index 000000000..92a5bb631 --- /dev/null +++ b/Documentation/admin-guide/media/vimc.dot @@ -0,0 +1,26 @@ +# SPDX-License-Identifier: GPL-2.0 + +digraph board { + rankdir=TB + n00000001 [label="{{} | Sensor A\n/dev/v4l-subdev0 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green] + n00000001:port0 -> n00000005:port0 [style=bold] + n00000001:port0 -> n0000000b [style=bold] + n00000001 -> n00000002 + n00000002 [label="{{} | Lens A\n/dev/v4l-subdev5 | {<port0>}}", shape=Mrecord, style=filled, fillcolor=green] + n00000003 [label="{{} | Sensor B\n/dev/v4l-subdev1 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green] + n00000003:port0 -> n00000008:port0 [style=bold] + n00000003:port0 -> n0000000f [style=bold] + n00000003 -> n00000004 + n00000004 [label="{{} | Lens B\n/dev/v4l-subdev6 | {<port0>}}", shape=Mrecord, style=filled, fillcolor=green] + n00000005 [label="{{<port0> 0} | Debayer A\n/dev/v4l-subdev2 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green] + n00000005:port1 -> n00000015:port0 + n00000008 [label="{{<port0> 0} | Debayer B\n/dev/v4l-subdev3 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green] + n00000008:port1 -> n00000015:port0 [style=dashed] + n0000000b [label="Raw Capture 0\n/dev/video0", shape=box, style=filled, fillcolor=yellow] + n0000000f [label="Raw Capture 1\n/dev/video1", shape=box, style=filled, fillcolor=yellow] + n00000013 [label="{{} | RGB/YUV Input\n/dev/v4l-subdev4 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green] + n00000013:port0 -> n00000015:port0 [style=dashed] + n00000015 [label="{{<port0> 0} | Scaler\n/dev/v4l-subdev5 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green] + n00000015:port1 -> n00000018 [style=bold] + n00000018 [label="RGB/YUV Capture\n/dev/video2", shape=box, style=filled, fillcolor=yellow] +} diff --git a/Documentation/admin-guide/media/vimc.rst b/Documentation/admin-guide/media/vimc.rst new file mode 100644 index 000000000..29d843a8d --- /dev/null +++ b/Documentation/admin-guide/media/vimc.rst @@ -0,0 +1,110 @@ +.. SPDX-License-Identifier: GPL-2.0 + +The Virtual Media Controller Driver (vimc) +========================================== + +The vimc driver emulates complex video hardware using the V4L2 API and the Media +API. It has a capture device and three subdevices: sensor, debayer and scaler. + +Topology +-------- + +The topology is hardcoded, although you could modify it in vimc-core and +recompile the driver to achieve your own topology. This is the default topology: + +.. _vimc_topology_graph: + +.. kernel-figure:: vimc.dot + :alt: Diagram of the default media pipeline topology + :align: center + + Media pipeline graph on vimc + +Configuring the topology +~~~~~~~~~~~~~~~~~~~~~~~~ + +Each subdevice will come with its default configuration (pixelformat, height, +width, ...). One needs to configure the topology in order to match the +configuration on each linked subdevice to stream frames through the pipeline. +If the configuration doesn't match, the stream will fail. The ``v4l-utils`` +package is a bundle of user-space applications, that comes with ``media-ctl`` and +``v4l2-ctl`` that can be used to configure the vimc configuration. This sequence +of commands fits for the default topology: + +.. code-block:: bash + + media-ctl -d platform:vimc -V '"Sensor A":0[fmt:SBGGR8_1X8/640x480]' + media-ctl -d platform:vimc -V '"Debayer A":0[fmt:SBGGR8_1X8/640x480]' + media-ctl -d platform:vimc -V '"Scaler":0[fmt:RGB888_1X24/640x480]' + media-ctl -d platform:vimc -V '"Scaler":0[crop:(100,50)/400x150]' + media-ctl -d platform:vimc -V '"Scaler":1[fmt:RGB888_1X24/300x700]' + v4l2-ctl -z platform:vimc -d "RGB/YUV Capture" -v width=300,height=700 + v4l2-ctl -z platform:vimc -d "Raw Capture 0" -v pixelformat=BA81 + +Subdevices +---------- + +Subdevices define the behavior of an entity in the topology. Depending on the +subdevice, the entity can have multiple pads of type source or sink. + +vimc-sensor: + Generates images in several formats using video test pattern generator. + Exposes: + + * 1 Pad source + +vimc-lens: + Ancillary lens for a sensor. Supports auto focus control. Linked to + a vimc-sensor using an ancillary link. The lens supports FOCUS_ABSOLUTE + control. + +.. code-block:: bash + + media-ctl -p + ... + - entity 28: Lens A (0 pad, 0 link) + type V4L2 subdev subtype Lens flags 0 + device node name /dev/v4l-subdev6 + - entity 29: Lens B (0 pad, 0 link) + type V4L2 subdev subtype Lens flags 0 + device node name /dev/v4l-subdev7 + v4l2-ctl -d /dev/v4l-subdev7 -C focus_absolute + focus_absolute: 0 + + +vimc-debayer: + Transforms images in bayer format into a non-bayer format. + Exposes: + + * 1 Pad sink + * 1 Pad source + +vimc-scaler: + Re-size the image to meet the source pad resolution. E.g.: if the sync + pad is configured to 360x480 and the source to 1280x720, the image will + be stretched to fit the source resolution. Works for any resolution + within the vimc limitations (even shrinking the image if necessary). + Exposes: + + * 1 Pad sink + * 1 Pad source + +vimc-capture: + Exposes node /dev/videoX to allow userspace to capture the stream. + Exposes: + + * 1 Pad sink + * 1 Pad source + +Module options +-------------- + +Vimc has a module parameter to configure the driver. + +* ``allocator=<unsigned int>`` + + memory allocator selection, default is 0. It specifies the way buffers + will be allocated. + + - 0: vmalloc + - 1: dma-contig diff --git a/Documentation/admin-guide/media/visl.rst b/Documentation/admin-guide/media/visl.rst new file mode 100644 index 000000000..7d2dc7834 --- /dev/null +++ b/Documentation/admin-guide/media/visl.rst @@ -0,0 +1,175 @@ +.. SPDX-License-Identifier: GPL-2.0 + +The Virtual Stateless Decoder Driver (visl) +=========================================== + +A virtual stateless decoder device for stateless uAPI development +purposes. + +This tool's objective is to help the development and testing of +userspace applications that use the V4L2 stateless API to decode media. + +A userspace implementation can use visl to run a decoding loop even when +no hardware is available or when the kernel uAPI for the codec has not +been upstreamed yet. This can reveal bugs at an early stage. + +This driver can also trace the contents of the V4L2 controls submitted +to it. It can also dump the contents of the vb2 buffers through a +debugfs interface. This is in many ways similar to the tracing +infrastructure available for other popular encode/decode APIs out there +and can help develop a userspace application by using another (working) +one as a reference. + +.. note:: + + No actual decoding of video frames is performed by visl. The + V4L2 test pattern generator is used to write various debug information + to the capture buffers instead. + +Module parameters +----------------- + +- visl_debug: Activates debug info, printing various debug messages through + dprintk. Also controls whether per-frame debug info is shown. Defaults to off. + Note that enabling this feature can result in slow performance through serial. + +- visl_transtime_ms: Simulated process time in milliseconds. Slowing down the + decoding speed can be useful for debugging. + +- visl_dprintk_frame_start, visl_dprintk_frame_nframes: Dictates a range of + frames where dprintk is activated. This only controls the dprintk tracing on a + per-frame basis. Note that printing a lot of data can be slow through serial. + +- keep_bitstream_buffers: Controls whether bitstream (i.e. OUTPUT) buffers are + kept after a decoding session. Defaults to false so as to reduce the amount of + clutter. keep_bitstream_buffers == false works well when live debugging the + client program with GDB. + +- bitstream_trace_frame_start, bitstream_trace_nframes: Similar to + visl_dprintk_frame_start, visl_dprintk_nframes, but controls the dumping of + buffer data through debugfs instead. + +What is the default use case for this driver? +--------------------------------------------- + +This driver can be used as a way to compare different userspace implementations. +This assumes that a working client is run against visl and that the ftrace and +OUTPUT buffer data is subsequently used to debug a work-in-progress +implementation. + +Information on reference frames, their timestamps, the status of the OUTPUT and +CAPTURE queues and more can be read directly from the CAPTURE buffers. + +Supported codecs +---------------- + +The following codecs are supported: + +- FWHT +- MPEG2 +- VP8 +- VP9 +- H.264 +- HEVC + +visl trace events +----------------- +The trace events are defined on a per-codec basis, e.g.: + +.. code-block:: bash + + $ ls /sys/kernel/debug/tracing/events/ | grep visl + visl_fwht_controls + visl_h264_controls + visl_hevc_controls + visl_mpeg2_controls + visl_vp8_controls + visl_vp9_controls + +For example, in order to dump HEVC SPS data: + +.. code-block:: bash + + $ echo 1 > /sys/kernel/debug/tracing/events/visl_hevc_controls/v4l2_ctrl_hevc_sps/enable + +The SPS data will be dumped to the trace buffer, i.e.: + +.. code-block:: bash + + $ cat /sys/kernel/debug/tracing/trace + video_parameter_set_id 0 + seq_parameter_set_id 0 + pic_width_in_luma_samples 1920 + pic_height_in_luma_samples 1080 + bit_depth_luma_minus8 0 + bit_depth_chroma_minus8 0 + log2_max_pic_order_cnt_lsb_minus4 4 + sps_max_dec_pic_buffering_minus1 6 + sps_max_num_reorder_pics 2 + sps_max_latency_increase_plus1 0 + log2_min_luma_coding_block_size_minus3 0 + log2_diff_max_min_luma_coding_block_size 3 + log2_min_luma_transform_block_size_minus2 0 + log2_diff_max_min_luma_transform_block_size 3 + max_transform_hierarchy_depth_inter 2 + max_transform_hierarchy_depth_intra 2 + pcm_sample_bit_depth_luma_minus1 0 + pcm_sample_bit_depth_chroma_minus1 0 + log2_min_pcm_luma_coding_block_size_minus3 0 + log2_diff_max_min_pcm_luma_coding_block_size 0 + num_short_term_ref_pic_sets 0 + num_long_term_ref_pics_sps 0 + chroma_format_idc 1 + sps_max_sub_layers_minus1 0 + flags AMP_ENABLED|SAMPLE_ADAPTIVE_OFFSET|TEMPORAL_MVP_ENABLED|STRONG_INTRA_SMOOTHING_ENABLED + + +Dumping OUTPUT buffer data through debugfs +------------------------------------------ + +If the **VISL_DEBUGFS** Kconfig is enabled, visl will populate +**/sys/kernel/debug/visl/bitstream** with OUTPUT buffer data according to the +values of bitstream_trace_frame_start and bitstream_trace_nframes. This can +highlight errors as broken clients may fail to fill the buffers properly. + +A single file is created for each processed OUTPUT buffer. Its name contains an +integer that denotes the buffer sequence, i.e.: + +.. code-block:: c + + snprintf(name, 32, "bitstream%d", run->src->sequence); + +Dumping the values is simply a matter of reading from the file, i.e.: + +For the buffer with sequence == 0: + +.. code-block:: bash + + $ xxd /sys/kernel/debug/visl/bitstream/bitstream0 + 00000000: 2601 af04 d088 bc25 a173 0e41 a4f2 3274 &......%.s.A..2t + 00000010: c668 cb28 e775 b4ac f53a ba60 f8fd 3aa1 .h.(.u...:.`..:. + 00000020: 46b4 bcfc 506c e227 2372 e5f5 d7ea 579f F...Pl.'#r....W. + 00000030: 6371 5eb5 0eb8 23b5 ca6a 5de5 983a 19e4 cq^...#..j]..:.. + 00000040: e8c3 4320 b4ba a226 cbc1 4138 3a12 32d6 ..C ...&..A8:.2. + 00000050: fef3 247b 3523 4e90 9682 ac8e eb0c a389 ..${5#N......... + 00000060: ddd0 6cfc 0187 0e20 7aae b15b 1812 3d33 ..l.... z..[..=3 + 00000070: e1c5 f425 a83a 00b7 4f18 8127 3c4c aefb ...%.:..O..'<L.. + +For the buffer with sequence == 1: + +.. code-block:: bash + + $ xxd /sys/kernel/debug/visl/bitstream/bitstream1 + 00000000: 0201 d021 49e1 0c40 aa11 1449 14a6 01dc ...!I..@...I.... + 00000010: 7023 889a c8cd 2cd0 13b4 dab0 e8ca 21fe p#....,.......!. + 00000020: c4c8 ab4c 486e 4e2f b0df 96cc c74e 8dde ...LHnN/.....N.. + 00000030: 8ce7 ee36 d880 4095 4d64 30a0 ff4f 0c5e ...6..@.Md0..O.^ + 00000040: f16b a6a1 d806 ca2a 0ece a673 7bea 1f37 .k.....*...s{..7 + 00000050: 370f 5bb9 1dc4 ba21 6434 bc53 0173 cba0 7.[....!d4.S.s.. + 00000060: dfe6 bc99 01ea b6e0 346b 92b5 c8de 9f5d ........4k.....] + 00000070: e7cc 3484 1769 fef2 a693 a945 2c8b 31da ..4..i.....E,.1. + +And so on. + +By default, the files are removed during STREAMOFF. This is to reduce the amount +of clutter. diff --git a/Documentation/admin-guide/media/vivid.rst b/Documentation/admin-guide/media/vivid.rst new file mode 100644 index 000000000..58ac25b2c --- /dev/null +++ b/Documentation/admin-guide/media/vivid.rst @@ -0,0 +1,1416 @@ +.. SPDX-License-Identifier: GPL-2.0 + +The Virtual Video Test Driver (vivid) +===================================== + +This driver emulates video4linux hardware of various types: video capture, video +output, vbi capture and output, metadata capture and output, radio receivers and +transmitters, touch capture and a software defined radio receiver. In addition a +simple framebuffer device is available for testing capture and output overlays. + +Up to 64 vivid instances can be created, each with up to 16 inputs and 16 outputs. + +Each input can be a webcam, TV capture device, S-Video capture device or an HDMI +capture device. Each output can be an S-Video output device or an HDMI output +device. + +These inputs and outputs act exactly as a real hardware device would behave. This +allows you to use this driver as a test input for application development, since +you can test the various features without requiring special hardware. + +This document describes the features implemented by this driver: + +- Support for read()/write(), MMAP, USERPTR and DMABUF streaming I/O. +- A large list of test patterns and variations thereof +- Working brightness, contrast, saturation and hue controls +- Support for the alpha color component +- Full colorspace support, including limited/full RGB range +- All possible control types are present +- Support for various pixel aspect ratios and video aspect ratios +- Error injection to test what happens if errors occur +- Supports crop/compose/scale in any combination for both input and output +- Can emulate up to 4K resolutions +- All Field settings are supported for testing interlaced capturing +- Supports all standard YUV and RGB formats, including two multiplanar YUV formats +- Raw and Sliced VBI capture and output support +- Radio receiver and transmitter support, including RDS support +- Software defined radio (SDR) support +- Capture and output overlay support +- Metadata capture and output support +- Touch capture support + +These features will be described in more detail below. + +Configuring the driver +---------------------- + +By default the driver will create a single instance that has a video capture +device with webcam, TV, S-Video and HDMI inputs, a video output device with +S-Video and HDMI outputs, one vbi capture device, one vbi output device, one +radio receiver device, one radio transmitter device and one SDR device. + +The number of instances, devices, video inputs and outputs and their types are +all configurable using the following module options: + +- n_devs: + + number of driver instances to create. By default set to 1. Up to 64 + instances can be created. + +- node_types: + + which devices should each driver instance create. An array of + hexadecimal values, one for each instance. The default is 0x1d3d. + Each value is a bitmask with the following meaning: + + - bit 0: Video Capture node + - bit 2-3: VBI Capture node: 0 = none, 1 = raw vbi, 2 = sliced vbi, 3 = both + - bit 4: Radio Receiver node + - bit 5: Software Defined Radio Receiver node + - bit 8: Video Output node + - bit 10-11: VBI Output node: 0 = none, 1 = raw vbi, 2 = sliced vbi, 3 = both + - bit 12: Radio Transmitter node + - bit 16: Framebuffer for testing overlays + - bit 17: Metadata Capture node + - bit 18: Metadata Output node + - bit 19: Touch Capture node + + So to create four instances, the first two with just one video capture + device, the second two with just one video output device you would pass + these module options to vivid: + + .. code-block:: none + + n_devs=4 node_types=0x1,0x1,0x100,0x100 + +- num_inputs: + + the number of inputs, one for each instance. By default 4 inputs + are created for each video capture device. At most 16 inputs can be created, + and there must be at least one. + +- input_types: + + the input types for each instance, the default is 0xe4. This defines + what the type of each input is when the inputs are created for each driver + instance. This is a hexadecimal value with up to 16 pairs of bits, each + pair gives the type and bits 0-1 map to input 0, bits 2-3 map to input 1, + 30-31 map to input 15. Each pair of bits has the following meaning: + + - 00: this is a webcam input + - 01: this is a TV tuner input + - 10: this is an S-Video input + - 11: this is an HDMI input + + So to create a video capture device with 8 inputs where input 0 is a TV + tuner, inputs 1-3 are S-Video inputs and inputs 4-7 are HDMI inputs you + would use the following module options: + + .. code-block:: none + + num_inputs=8 input_types=0xffa9 + +- num_outputs: + + the number of outputs, one for each instance. By default 2 outputs + are created for each video output device. At most 16 outputs can be + created, and there must be at least one. + +- output_types: + + the output types for each instance, the default is 0x02. This defines + what the type of each output is when the outputs are created for each + driver instance. This is a hexadecimal value with up to 16 bits, each bit + gives the type and bit 0 maps to output 0, bit 1 maps to output 1, bit + 15 maps to output 15. The meaning of each bit is as follows: + + - 0: this is an S-Video output + - 1: this is an HDMI output + + So to create a video output device with 8 outputs where outputs 0-3 are + S-Video outputs and outputs 4-7 are HDMI outputs you would use the + following module options: + + .. code-block:: none + + num_outputs=8 output_types=0xf0 + +- vid_cap_nr: + + give the desired videoX start number for each video capture device. + The default is -1 which will just take the first free number. This allows + you to map capture video nodes to specific videoX device nodes. Example: + + .. code-block:: none + + n_devs=4 vid_cap_nr=2,4,6,8 + + This will attempt to assign /dev/video2 for the video capture device of + the first vivid instance, video4 for the next up to video8 for the last + instance. If it can't succeed, then it will just take the next free + number. + +- vid_out_nr: + + give the desired videoX start number for each video output device. + The default is -1 which will just take the first free number. + +- vbi_cap_nr: + + give the desired vbiX start number for each vbi capture device. + The default is -1 which will just take the first free number. + +- vbi_out_nr: + + give the desired vbiX start number for each vbi output device. + The default is -1 which will just take the first free number. + +- radio_rx_nr: + + give the desired radioX start number for each radio receiver device. + The default is -1 which will just take the first free number. + +- radio_tx_nr: + + give the desired radioX start number for each radio transmitter + device. The default is -1 which will just take the first free number. + +- sdr_cap_nr: + + give the desired swradioX start number for each SDR capture device. + The default is -1 which will just take the first free number. + +- meta_cap_nr: + + give the desired videoX start number for each metadata capture device. + The default is -1 which will just take the first free number. + +- meta_out_nr: + + give the desired videoX start number for each metadata output device. + The default is -1 which will just take the first free number. + +- touch_cap_nr: + + give the desired v4l-touchX start number for each touch capture device. + The default is -1 which will just take the first free number. + +- ccs_cap_mode: + + specify the allowed video capture crop/compose/scaling combination + for each driver instance. Video capture devices can have any combination + of cropping, composing and scaling capabilities and this will tell the + vivid driver which of those is should emulate. By default the user can + select this through controls. + + The value is either -1 (controlled by the user) or a set of three bits, + each enabling (1) or disabling (0) one of the features: + + - bit 0: + + Enable crop support. Cropping will take only part of the + incoming picture. + - bit 1: + + Enable compose support. Composing will copy the incoming + picture into a larger buffer. + + - bit 2: + + Enable scaling support. Scaling can scale the incoming + picture. The scaler of the vivid driver can enlarge up + or down to four times the original size. The scaler is + very simple and low-quality. Simplicity and speed were + key, not quality. + + Note that this value is ignored by webcam inputs: those enumerate + discrete framesizes and that is incompatible with cropping, composing + or scaling. + +- ccs_out_mode: + + specify the allowed video output crop/compose/scaling combination + for each driver instance. Video output devices can have any combination + of cropping, composing and scaling capabilities and this will tell the + vivid driver which of those is should emulate. By default the user can + select this through controls. + + The value is either -1 (controlled by the user) or a set of three bits, + each enabling (1) or disabling (0) one of the features: + + - bit 0: + + Enable crop support. Cropping will take only part of the + outgoing buffer. + + - bit 1: + + Enable compose support. Composing will copy the incoming + buffer into a larger picture frame. + + - bit 2: + + Enable scaling support. Scaling can scale the incoming + buffer. The scaler of the vivid driver can enlarge up + or down to four times the original size. The scaler is + very simple and low-quality. Simplicity and speed were + key, not quality. + +- multiplanar: + + select whether each device instance supports multi-planar formats, + and thus the V4L2 multi-planar API. By default device instances are + single-planar. + + This module option can override that for each instance. Values are: + + - 1: this is a single-planar instance. + - 2: this is a multi-planar instance. + +- vivid_debug: + + enable driver debugging info + +- no_error_inj: + + if set disable the error injecting controls. This option is + needed in order to run a tool like v4l2-compliance. Tools like that + exercise all controls including a control like 'Disconnect' which + emulates a USB disconnect, making the device inaccessible and so + all tests that v4l2-compliance is doing will fail afterwards. + + There may be other situations as well where you want to disable the + error injection support of vivid. When this option is set, then the + controls that select crop, compose and scale behavior are also + removed. Unless overridden by ccs_cap_mode and/or ccs_out_mode the + will default to enabling crop, compose and scaling. + +- allocators: + + memory allocator selection, default is 0. It specifies the way buffers + will be allocated. + + - 0: vmalloc + - 1: dma-contig + +- cache_hints: + + specifies if the device should set queues' user-space cache and memory + consistency hint capability (V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS). + The hints are valid only when using MMAP streaming I/O. Default is 0. + + - 0: forbid hints + - 1: allow hints + +Taken together, all these module options allow you to precisely customize +the driver behavior and test your application with all sorts of permutations. +It is also very suitable to emulate hardware that is not yet available, e.g. +when developing software for a new upcoming device. + + +Video Capture +------------- + +This is probably the most frequently used feature. The video capture device +can be configured by using the module options num_inputs, input_types and +ccs_cap_mode (see section 1 for more detailed information), but by default +four inputs are configured: a webcam, a TV tuner, an S-Video and an HDMI +input, one input for each input type. Those are described in more detail +below. + +Special attention has been given to the rate at which new frames become +available. The jitter will be around 1 jiffie (that depends on the HZ +configuration of your kernel, so usually 1/100, 1/250 or 1/1000 of a second), +but the long-term behavior is exactly following the framerate. So a +framerate of 59.94 Hz is really different from 60 Hz. If the framerate +exceeds your kernel's HZ value, then you will get dropped frames, but the +frame/field sequence counting will keep track of that so the sequence +count will skip whenever frames are dropped. + + +Webcam Input +~~~~~~~~~~~~ + +The webcam input supports three framesizes: 320x180, 640x360 and 1280x720. It +supports frames per second settings of 10, 15, 25, 30, 50 and 60 fps. Which ones +are available depends on the chosen framesize: the larger the framesize, the +lower the maximum frames per second. + +The initially selected colorspace when you switch to the webcam input will be +sRGB. + + +TV and S-Video Inputs +~~~~~~~~~~~~~~~~~~~~~ + +The only difference between the TV and S-Video input is that the TV has a +tuner. Otherwise they behave identically. + +These inputs support audio inputs as well: one TV and one Line-In. They +both support all TV standards. If the standard is queried, then the Vivid +controls 'Standard Signal Mode' and 'Standard' determine what +the result will be. + +These inputs support all combinations of the field setting. Special care has +been taken to faithfully reproduce how fields are handled for the different +TV standards. This is particularly noticeable when generating a horizontally +moving image so the temporal effect of using interlaced formats becomes clearly +visible. For 50 Hz standards the top field is the oldest and the bottom field +is the newest in time. For 60 Hz standards that is reversed: the bottom field +is the oldest and the top field is the newest in time. + +When you start capturing in V4L2_FIELD_ALTERNATE mode the first buffer will +contain the top field for 50 Hz standards and the bottom field for 60 Hz +standards. This is what capture hardware does as well. + +Finally, for PAL/SECAM standards the first half of the top line contains noise. +This simulates the Wide Screen Signal that is commonly placed there. + +The initially selected colorspace when you switch to the TV or S-Video input +will be SMPTE-170M. + +The pixel aspect ratio will depend on the TV standard. The video aspect ratio +can be selected through the 'Standard Aspect Ratio' Vivid control. +Choices are '4x3', '16x9' which will give letterboxed widescreen video and +'16x9 Anamorphic' which will give full screen squashed anamorphic widescreen +video that will need to be scaled accordingly. + +The TV 'tuner' supports a frequency range of 44-958 MHz. Channels are available +every 6 MHz, starting from 49.25 MHz. For each channel the generated image +will be in color for the +/- 0.25 MHz around it, and in grayscale for ++/- 1 MHz around the channel. Beyond that it is just noise. The VIDIOC_G_TUNER +ioctl will return 100% signal strength for +/- 0.25 MHz and 50% for +/- 1 MHz. +It will also return correct afc values to show whether the frequency is too +low or too high. + +The audio subchannels that are returned are MONO for the +/- 1 MHz range around +a valid channel frequency. When the frequency is within +/- 0.25 MHz of the +channel it will return either MONO, STEREO, either MONO | SAP (for NTSC) or +LANG1 | LANG2 (for others), or STEREO | SAP. + +Which one is returned depends on the chosen channel, each next valid channel +will cycle through the possible audio subchannel combinations. This allows +you to test the various combinations by just switching channels.. + +Finally, for these inputs the v4l2_timecode struct is filled in the +dequeued v4l2_buffer struct. + + +HDMI Input +~~~~~~~~~~ + +The HDMI inputs supports all CEA-861 and DMT timings, both progressive and +interlaced, for pixelclock frequencies between 25 and 600 MHz. The field +mode for interlaced formats is always V4L2_FIELD_ALTERNATE. For HDMI the +field order is always top field first, and when you start capturing an +interlaced format you will receive the top field first. + +The initially selected colorspace when you switch to the HDMI input or +select an HDMI timing is based on the format resolution: for resolutions +less than or equal to 720x576 the colorspace is set to SMPTE-170M, for +others it is set to REC-709 (CEA-861 timings) or sRGB (VESA DMT timings). + +The pixel aspect ratio will depend on the HDMI timing: for 720x480 is it +set as for the NTSC TV standard, for 720x576 it is set as for the PAL TV +standard, and for all others a 1:1 pixel aspect ratio is returned. + +The video aspect ratio can be selected through the 'DV Timings Aspect Ratio' +Vivid control. Choices are 'Source Width x Height' (just use the +same ratio as the chosen format), '4x3' or '16x9', either of which can +result in pillarboxed or letterboxed video. + +For HDMI inputs it is possible to set the EDID. By default a simple EDID +is provided. You can only set the EDID for HDMI inputs. Internally, however, +the EDID is shared between all HDMI inputs. + +No interpretation is done of the EDID data with the exception of the +physical address. See the CEC section for more details. + +There is a maximum of 15 HDMI inputs (if there are more, then they will be +reduced to 15) since that's the limitation of the EDID physical address. + + +Video Output +------------ + +The video output device can be configured by using the module options +num_outputs, output_types and ccs_out_mode (see section 1 for more detailed +information), but by default two outputs are configured: an S-Video and an +HDMI input, one output for each output type. Those are described in more detail +below. + +Like with video capture the framerate is also exact in the long term. + + +S-Video Output +~~~~~~~~~~~~~~ + +This output supports audio outputs as well: "Line-Out 1" and "Line-Out 2". +The S-Video output supports all TV standards. + +This output supports all combinations of the field setting. + +The initially selected colorspace when you switch to the TV or S-Video input +will be SMPTE-170M. + + +HDMI Output +~~~~~~~~~~~ + +The HDMI output supports all CEA-861 and DMT timings, both progressive and +interlaced, for pixelclock frequencies between 25 and 600 MHz. The field +mode for interlaced formats is always V4L2_FIELD_ALTERNATE. + +The initially selected colorspace when you switch to the HDMI output or +select an HDMI timing is based on the format resolution: for resolutions +less than or equal to 720x576 the colorspace is set to SMPTE-170M, for +others it is set to REC-709 (CEA-861 timings) or sRGB (VESA DMT timings). + +The pixel aspect ratio will depend on the HDMI timing: for 720x480 is it +set as for the NTSC TV standard, for 720x576 it is set as for the PAL TV +standard, and for all others a 1:1 pixel aspect ratio is returned. + +An HDMI output has a valid EDID which can be obtained through VIDIOC_G_EDID. + +There is a maximum of 15 HDMI outputs (if there are more, then they will be +reduced to 15) since that's the limitation of the EDID physical address. See +also the CEC section for more details. + +VBI Capture +----------- + +There are three types of VBI capture devices: those that only support raw +(undecoded) VBI, those that only support sliced (decoded) VBI and those that +support both. This is determined by the node_types module option. In all +cases the driver will generate valid VBI data: for 60 Hz standards it will +generate Closed Caption and XDS data. The closed caption stream will +alternate between "Hello world!" and "Closed captions test" every second. +The XDS stream will give the current time once a minute. For 50 Hz standards +it will generate the Wide Screen Signal which is based on the actual Video +Aspect Ratio control setting and teletext pages 100-159, one page per frame. + +The VBI device will only work for the S-Video and TV inputs, it will give +back an error if the current input is a webcam or HDMI. + + +VBI Output +---------- + +There are three types of VBI output devices: those that only support raw +(undecoded) VBI, those that only support sliced (decoded) VBI and those that +support both. This is determined by the node_types module option. + +The sliced VBI output supports the Wide Screen Signal and the teletext signal +for 50 Hz standards and Closed Captioning + XDS for 60 Hz standards. + +The VBI device will only work for the S-Video output, it will give +back an error if the current output is HDMI. + + +Radio Receiver +-------------- + +The radio receiver emulates an FM/AM/SW receiver. The FM band also supports RDS. +The frequency ranges are: + + - FM: 64 MHz - 108 MHz + - AM: 520 kHz - 1710 kHz + - SW: 2300 kHz - 26.1 MHz + +Valid channels are emulated every 1 MHz for FM and every 100 kHz for AM and SW. +The signal strength decreases the further the frequency is from the valid +frequency until it becomes 0% at +/- 50 kHz (FM) or 5 kHz (AM/SW) from the +ideal frequency. The initial frequency when the driver is loaded is set to +95 MHz. + +The FM receiver supports RDS as well, both using 'Block I/O' and 'Controls' +modes. In the 'Controls' mode the RDS information is stored in read-only +controls. These controls are updated every time the frequency is changed, +or when the tuner status is requested. The Block I/O method uses the read() +interface to pass the RDS blocks on to the application for decoding. + +The RDS signal is 'detected' for +/- 12.5 kHz around the channel frequency, +and the further the frequency is away from the valid frequency the more RDS +errors are randomly introduced into the block I/O stream, up to 50% of all +blocks if you are +/- 12.5 kHz from the channel frequency. All four errors +can occur in equal proportions: blocks marked 'CORRECTED', blocks marked +'ERROR', blocks marked 'INVALID' and dropped blocks. + +The generated RDS stream contains all the standard fields contained in a +0B group, and also radio text and the current time. + +The receiver supports HW frequency seek, either in Bounded mode, Wrap Around +mode or both, which is configurable with the "Radio HW Seek Mode" control. + + +Radio Transmitter +----------------- + +The radio transmitter emulates an FM/AM/SW transmitter. The FM band also supports RDS. +The frequency ranges are: + + - FM: 64 MHz - 108 MHz + - AM: 520 kHz - 1710 kHz + - SW: 2300 kHz - 26.1 MHz + +The initial frequency when the driver is loaded is 95.5 MHz. + +The FM transmitter supports RDS as well, both using 'Block I/O' and 'Controls' +modes. In the 'Controls' mode the transmitted RDS information is configured +using controls, and in 'Block I/O' mode the blocks are passed to the driver +using write(). + + +Software Defined Radio Receiver +------------------------------- + +The SDR receiver has three frequency bands for the ADC tuner: + + - 300 kHz + - 900 kHz - 2800 kHz + - 3200 kHz + +The RF tuner supports 50 MHz - 2000 MHz. + +The generated data contains the In-phase and Quadrature components of a +1 kHz tone that has an amplitude of sqrt(2). + + +Metadata Capture +---------------- + +The Metadata capture generates UVC format metadata. The PTS and SCR are +transmitted based on the values set in vivid controls. + +The Metadata device will only work for the Webcam input, it will give +back an error for all other inputs. + + +Metadata Output +--------------- + +The Metadata output can be used to set brightness, contrast, saturation and hue. + +The Metadata device will only work for the Webcam output, it will give +back an error for all other outputs. + + +Touch Capture +------------- + +The Touch capture generates touch patterns simulating single tap, double tap, +triple tap, move from left to right, zoom in, zoom out, palm press (simulating +a large area being pressed on a touchpad), and simulating 16 simultaneous +touch points. + +Controls +-------- + +Different devices support different controls. The sections below will describe +each control and which devices support them. + + +User Controls - Test Controls +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The Button, Boolean, Integer 32 Bits, Integer 64 Bits, Menu, String, Bitmask and +Integer Menu are controls that represent all possible control types. The Menu +control and the Integer Menu control both have 'holes' in their menu list, +meaning that one or more menu items return EINVAL when VIDIOC_QUERYMENU is called. +Both menu controls also have a non-zero minimum control value. These features +allow you to check if your application can handle such things correctly. +These controls are supported for every device type. + + +User Controls - Video Capture +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The following controls are specific to video capture. + +The Brightness, Contrast, Saturation and Hue controls actually work and are +standard. There is one special feature with the Brightness control: each +video input has its own brightness value, so changing input will restore +the brightness for that input. In addition, each video input uses a different +brightness range (minimum and maximum control values). Switching inputs will +cause a control event to be sent with the V4L2_EVENT_CTRL_CH_RANGE flag set. +This allows you to test controls that can change their range. + +The 'Gain, Automatic' and Gain controls can be used to test volatile controls: +if 'Gain, Automatic' is set, then the Gain control is volatile and changes +constantly. If 'Gain, Automatic' is cleared, then the Gain control is a normal +control. + +The 'Horizontal Flip' and 'Vertical Flip' controls can be used to flip the +image. These combine with the 'Sensor Flipped Horizontally/Vertically' Vivid +controls. + +The 'Alpha Component' control can be used to set the alpha component for +formats containing an alpha channel. + + +User Controls - Audio +~~~~~~~~~~~~~~~~~~~~~ + +The following controls are specific to video capture and output and radio +receivers and transmitters. + +The 'Volume' and 'Mute' audio controls are typical for such devices to +control the volume and mute the audio. They don't actually do anything in +the vivid driver. + + +Vivid Controls +~~~~~~~~~~~~~~ + +These vivid custom controls control the image generation, error injection, etc. + + +Test Pattern Controls +^^^^^^^^^^^^^^^^^^^^^ + +The Test Pattern Controls are all specific to video capture. + +- Test Pattern: + + selects which test pattern to use. Use the CSC Colorbar for + testing colorspace conversions: the colors used in that test pattern + map to valid colors in all colorspaces. The colorspace conversion + is disabled for the other test patterns. + +- OSD Text Mode: + + selects whether the text superimposed on the + test pattern should be shown, and if so, whether only counters should + be displayed or the full text. + +- Horizontal Movement: + + selects whether the test pattern should + move to the left or right and at what speed. + +- Vertical Movement: + + does the same for the vertical direction. + +- Show Border: + + show a two-pixel wide border at the edge of the actual image, + excluding letter or pillarboxing. + +- Show Square: + + show a square in the middle of the image. If the image is + displayed with the correct pixel and image aspect ratio corrections, + then the width and height of the square on the monitor should be + the same. + +- Insert SAV Code in Image: + + adds a SAV (Start of Active Video) code to the image. + This can be used to check if such codes in the image are inadvertently + interpreted instead of being ignored. + +- Insert EAV Code in Image: + + does the same for the EAV (End of Active Video) code. + +- Insert Video Guard Band + + adds 4 columns of pixels with the HDMI Video Guard Band code at the + left hand side of the image. This only works with 3 or 4 byte RGB pixel + formats. The RGB pixel value 0xab/0x55/0xab turns out to be equivalent + to the HDMI Video Guard Band code that precedes each active video line + (see section 5.2.2.1 in the HDMI 1.3 Specification). To test if a video + receiver has correct HDMI Video Guard Band processing, enable this + control and then move the image to the left hand side of the screen. + That will result in video lines that start with multiple pixels that + have the same value as the Video Guard Band that precedes them. + Receivers that will just keep skipping Video Guard Band values will + now fail and either loose sync or these video lines will shift. + + +Capture Feature Selection Controls +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +These controls are all specific to video capture. + +- Sensor Flipped Horizontally: + + the image is flipped horizontally and the + V4L2_IN_ST_HFLIP input status flag is set. This emulates the case where + a sensor is for example mounted upside down. + +- Sensor Flipped Vertically: + + the image is flipped vertically and the + V4L2_IN_ST_VFLIP input status flag is set. This emulates the case where + a sensor is for example mounted upside down. + +- Standard Aspect Ratio: + + selects if the image aspect ratio as used for the TV or + S-Video input should be 4x3, 16x9 or anamorphic widescreen. This may + introduce letterboxing. + +- DV Timings Aspect Ratio: + + selects if the image aspect ratio as used for the HDMI + input should be the same as the source width and height ratio, or if + it should be 4x3 or 16x9. This may introduce letter or pillarboxing. + +- Timestamp Source: + + selects when the timestamp for each buffer is taken. + +- Colorspace: + + selects which colorspace should be used when generating the image. + This only applies if the CSC Colorbar test pattern is selected, + otherwise the test pattern will go through unconverted. + This behavior is also what you want, since a 75% Colorbar + should really have 75% signal intensity and should not be affected + by colorspace conversions. + + Changing the colorspace will result in the V4L2_EVENT_SOURCE_CHANGE + to be sent since it emulates a detected colorspace change. + +- Transfer Function: + + selects which colorspace transfer function should be used when + generating an image. This only applies if the CSC Colorbar test pattern is + selected, otherwise the test pattern will go through unconverted. + This behavior is also what you want, since a 75% Colorbar + should really have 75% signal intensity and should not be affected + by colorspace conversions. + + Changing the transfer function will result in the V4L2_EVENT_SOURCE_CHANGE + to be sent since it emulates a detected colorspace change. + +- Y'CbCr Encoding: + + selects which Y'CbCr encoding should be used when generating + a Y'CbCr image. This only applies if the format is set to a Y'CbCr format + as opposed to an RGB format. + + Changing the Y'CbCr encoding will result in the V4L2_EVENT_SOURCE_CHANGE + to be sent since it emulates a detected colorspace change. + +- Quantization: + + selects which quantization should be used for the RGB or Y'CbCr + encoding when generating the test pattern. + + Changing the quantization will result in the V4L2_EVENT_SOURCE_CHANGE + to be sent since it emulates a detected colorspace change. + +- Limited RGB Range (16-235): + + selects if the RGB range of the HDMI source should + be limited or full range. This combines with the Digital Video 'Rx RGB + Quantization Range' control and can be used to test what happens if + a source provides you with the wrong quantization range information. + See the description of that control for more details. + +- Apply Alpha To Red Only: + + apply the alpha channel as set by the 'Alpha Component' + user control to the red color of the test pattern only. + +- Enable Capture Cropping: + + enables crop support. This control is only present if + the ccs_cap_mode module option is set to the default value of -1 and if + the no_error_inj module option is set to 0 (the default). + +- Enable Capture Composing: + + enables composing support. This control is only + present if the ccs_cap_mode module option is set to the default value of + -1 and if the no_error_inj module option is set to 0 (the default). + +- Enable Capture Scaler: + + enables support for a scaler (maximum 4 times upscaling + and downscaling). This control is only present if the ccs_cap_mode + module option is set to the default value of -1 and if the no_error_inj + module option is set to 0 (the default). + +- Maximum EDID Blocks: + + determines how many EDID blocks the driver supports. + Note that the vivid driver does not actually interpret new EDID + data, it just stores it. It allows for up to 256 EDID blocks + which is the maximum supported by the standard. + +- Fill Percentage of Frame: + + can be used to draw only the top X percent + of the image. Since each frame has to be drawn by the driver, this + demands a lot of the CPU. For large resolutions this becomes + problematic. By drawing only part of the image this CPU load can + be reduced. + + +Output Feature Selection Controls +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +These controls are all specific to video output. + +- Enable Output Cropping: + + enables crop support. This control is only present if + the ccs_out_mode module option is set to the default value of -1 and if + the no_error_inj module option is set to 0 (the default). + +- Enable Output Composing: + + enables composing support. This control is only + present if the ccs_out_mode module option is set to the default value of + -1 and if the no_error_inj module option is set to 0 (the default). + +- Enable Output Scaler: + + enables support for a scaler (maximum 4 times upscaling + and downscaling). This control is only present if the ccs_out_mode + module option is set to the default value of -1 and if the no_error_inj + module option is set to 0 (the default). + + +Error Injection Controls +^^^^^^^^^^^^^^^^^^^^^^^^ + +The following two controls are only valid for video and vbi capture. + +- Standard Signal Mode: + + selects the behavior of VIDIOC_QUERYSTD: what should it return? + + Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE + to be sent since it emulates a changed input condition (e.g. a cable + was plugged in or out). + +- Standard: + + selects the standard that VIDIOC_QUERYSTD should return if the + previous control is set to "Selected Standard". + + Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE + to be sent since it emulates a changed input standard. + + +The following two controls are only valid for video capture. + +- DV Timings Signal Mode: + + selects the behavior of VIDIOC_QUERY_DV_TIMINGS: what + should it return? + + Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE + to be sent since it emulates a changed input condition (e.g. a cable + was plugged in or out). + +- DV Timings: + + selects the timings the VIDIOC_QUERY_DV_TIMINGS should return + if the previous control is set to "Selected DV Timings". + + Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE + to be sent since it emulates changed input timings. + + +The following controls are only present if the no_error_inj module option +is set to 0 (the default). These controls are valid for video and vbi +capture and output streams and for the SDR capture device except for the +Disconnect control which is valid for all devices. + +- Wrap Sequence Number: + + test what happens when you wrap the sequence number in + struct v4l2_buffer around. + +- Wrap Timestamp: + + test what happens when you wrap the timestamp in struct + v4l2_buffer around. + +- Percentage of Dropped Buffers: + + sets the percentage of buffers that + are never returned by the driver (i.e., they are dropped). + +- Disconnect: + + emulates a USB disconnect. The device will act as if it has + been disconnected. Only after all open filehandles to the device + node have been closed will the device become 'connected' again. + +- Inject V4L2_BUF_FLAG_ERROR: + + when pressed, the next frame returned by + the driver will have the error flag set (i.e. the frame is marked + corrupt). + +- Inject VIDIOC_REQBUFS Error: + + when pressed, the next REQBUFS or CREATE_BUFS + ioctl call will fail with an error. To be precise: the videobuf2 + queue_setup() op will return -EINVAL. + +- Inject VIDIOC_QBUF Error: + + when pressed, the next VIDIOC_QBUF or + VIDIOC_PREPARE_BUFFER ioctl call will fail with an error. To be + precise: the videobuf2 buf_prepare() op will return -EINVAL. + +- Inject VIDIOC_STREAMON Error: + + when pressed, the next VIDIOC_STREAMON ioctl + call will fail with an error. To be precise: the videobuf2 + start_streaming() op will return -EINVAL. + +- Inject Fatal Streaming Error: + + when pressed, the streaming core will be + marked as having suffered a fatal error, the only way to recover + from that is to stop streaming. To be precise: the videobuf2 + vb2_queue_error() function is called. + + +VBI Raw Capture Controls +^^^^^^^^^^^^^^^^^^^^^^^^ + +- Interlaced VBI Format: + + if set, then the raw VBI data will be interlaced instead + of providing it grouped by field. + + +Digital Video Controls +~~~~~~~~~~~~~~~~~~~~~~ + +- Rx RGB Quantization Range: + + sets the RGB quantization detection of the HDMI + input. This combines with the Vivid 'Limited RGB Range (16-235)' + control and can be used to test what happens if a source provides + you with the wrong quantization range information. This can be tested + by selecting an HDMI input, setting this control to Full or Limited + range and selecting the opposite in the 'Limited RGB Range (16-235)' + control. The effect is easy to see if the 'Gray Ramp' test pattern + is selected. + +- Tx RGB Quantization Range: + + sets the RGB quantization detection of the HDMI + output. It is currently not used for anything in vivid, but most HDMI + transmitters would typically have this control. + +- Transmit Mode: + + sets the transmit mode of the HDMI output to HDMI or DVI-D. This + affects the reported colorspace since DVI_D outputs will always use + sRGB. + +- Display Present: + + sets the presence of a "display" on the HDMI output. This affects + the tx_edid_present, tx_hotplug and tx_rxsense controls. + + +FM Radio Receiver Controls +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +- RDS Reception: + + set if the RDS receiver should be enabled. + +- RDS Program Type: + + +- RDS PS Name: + + +- RDS Radio Text: + + +- RDS Traffic Announcement: + + +- RDS Traffic Program: + + +- RDS Music: + + these are all read-only controls. If RDS Rx I/O Mode is set to + "Block I/O", then they are inactive as well. If RDS Rx I/O Mode is set + to "Controls", then these controls report the received RDS data. + +.. note:: + The vivid implementation of this is pretty basic: they are only + updated when you set a new frequency or when you get the tuner status + (VIDIOC_G_TUNER). + +- Radio HW Seek Mode: + + can be one of "Bounded", "Wrap Around" or "Both". This + determines if VIDIOC_S_HW_FREQ_SEEK will be bounded by the frequency + range or wrap-around or if it is selectable by the user. + +- Radio Programmable HW Seek: + + if set, then the user can provide the lower and + upper bound of the HW Seek. Otherwise the frequency range boundaries + will be used. + +- Generate RBDS Instead of RDS: + + if set, then generate RBDS (the US variant of + RDS) data instead of RDS (European-style RDS). This affects only the + PICODE and PTY codes. + +- RDS Rx I/O Mode: + + this can be "Block I/O" where the RDS blocks have to be read() + by the application, or "Controls" where the RDS data is provided by + the RDS controls mentioned above. + + +FM Radio Modulator Controls +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +- RDS Program ID: + + +- RDS Program Type: + + +- RDS PS Name: + + +- RDS Radio Text: + + +- RDS Stereo: + + +- RDS Artificial Head: + + +- RDS Compressed: + + +- RDS Dynamic PTY: + + +- RDS Traffic Announcement: + + +- RDS Traffic Program: + + +- RDS Music: + + these are all controls that set the RDS data that is transmitted by + the FM modulator. + +- RDS Tx I/O Mode: + + this can be "Block I/O" where the application has to use write() + to pass the RDS blocks to the driver, or "Controls" where the RDS data + is Provided by the RDS controls mentioned above. + +Metadata Capture Controls +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +- Generate PTS + + if set, then the generated metadata stream contains Presentation timestamp. + +- Generate SCR + + if set, then the generated metadata stream contains Source Clock information. + +Video, VBI and RDS Looping +-------------------------- + +The vivid driver supports looping of video output to video input, VBI output +to VBI input and RDS output to RDS input. For video/VBI looping this emulates +as if a cable was hooked up between the output and input connector. So video +and VBI looping is only supported between S-Video and HDMI inputs and outputs. +VBI is only valid for S-Video as it makes no sense for HDMI. + +Since radio is wireless this looping always happens if the radio receiver +frequency is close to the radio transmitter frequency. In that case the radio +transmitter will 'override' the emulated radio stations. + +Looping is currently supported only between devices created by the same +vivid driver instance. + + +Video and Sliced VBI looping +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The way to enable video/VBI looping is currently fairly crude. A 'Loop Video' +control is available in the "Vivid" control class of the video +capture and VBI capture devices. When checked the video looping will be enabled. +Once enabled any video S-Video or HDMI input will show a static test pattern +until the video output has started. At that time the video output will be +looped to the video input provided that: + +- the input type matches the output type. So the HDMI input cannot receive + video from the S-Video output. + +- the video resolution of the video input must match that of the video output. + So it is not possible to loop a 50 Hz (720x576) S-Video output to a 60 Hz + (720x480) S-Video input, or a 720p60 HDMI output to a 1080p30 input. + +- the pixel formats must be identical on both sides. Otherwise the driver would + have to do pixel format conversion as well, and that's taking things too far. + +- the field settings must be identical on both sides. Same reason as above: + requiring the driver to convert from one field format to another complicated + matters too much. This also prohibits capturing with 'Field Top' or 'Field + Bottom' when the output video is set to 'Field Alternate'. This combination, + while legal, became too complicated to support. Both sides have to be 'Field + Alternate' for this to work. Also note that for this specific case the + sequence and field counting in struct v4l2_buffer on the capture side may not + be 100% accurate. + +- field settings V4L2_FIELD_SEQ_TB/BT are not supported. While it is possible to + implement this, it would mean a lot of work to get this right. Since these + field values are rarely used the decision was made not to implement this for + now. + +- on the input side the "Standard Signal Mode" for the S-Video input or the + "DV Timings Signal Mode" for the HDMI input should be configured so that a + valid signal is passed to the video input. + +The framerates do not have to match, although this might change in the future. + +By default you will see the OSD text superimposed on top of the looped video. +This can be turned off by changing the "OSD Text Mode" control of the video +capture device. + +For VBI looping to work all of the above must be valid and in addition the vbi +output must be configured for sliced VBI. The VBI capture side can be configured +for either raw or sliced VBI. Note that at the moment only CC/XDS (60 Hz formats) +and WSS (50 Hz formats) VBI data is looped. Teletext VBI data is not looped. + + +Radio & RDS Looping +~~~~~~~~~~~~~~~~~~~ + +As mentioned in section 6 the radio receiver emulates stations are regular +frequency intervals. Depending on the frequency of the radio receiver a +signal strength value is calculated (this is returned by VIDIOC_G_TUNER). +However, it will also look at the frequency set by the radio transmitter and +if that results in a higher signal strength than the settings of the radio +transmitter will be used as if it was a valid station. This also includes +the RDS data (if any) that the transmitter 'transmits'. This is received +faithfully on the receiver side. Note that when the driver is loaded the +frequencies of the radio receiver and transmitter are not identical, so +initially no looping takes place. + + +Cropping, Composing, Scaling +---------------------------- + +This driver supports cropping, composing and scaling in any combination. Normally +which features are supported can be selected through the Vivid controls, +but it is also possible to hardcode it when the module is loaded through the +ccs_cap_mode and ccs_out_mode module options. See section 1 on the details of +these module options. + +This allows you to test your application for all these variations. + +Note that the webcam input never supports cropping, composing or scaling. That +only applies to the TV/S-Video/HDMI inputs and outputs. The reason is that +webcams, including this virtual implementation, normally use +VIDIOC_ENUM_FRAMESIZES to list a set of discrete framesizes that it supports. +And that does not combine with cropping, composing or scaling. This is +primarily a limitation of the V4L2 API which is carefully reproduced here. + +The minimum and maximum resolutions that the scaler can achieve are 16x16 and +(4096 * 4) x (2160 x 4), but it can only scale up or down by a factor of 4 or +less. So for a source resolution of 1280x720 the minimum the scaler can do is +320x180 and the maximum is 5120x2880. You can play around with this using the +qv4l2 test tool and you will see these dependencies. + +This driver also supports larger 'bytesperline' settings, something that +VIDIOC_S_FMT allows but that few drivers implement. + +The scaler is a simple scaler that uses the Coarse Bresenham algorithm. It's +designed for speed and simplicity, not quality. + +If the combination of crop, compose and scaling allows it, then it is possible +to change crop and compose rectangles on the fly. + + +Formats +------- + +The driver supports all the regular packed and planar 4:4:4, 4:2:2 and 4:2:0 +YUYV formats, 8, 16, 24 and 32 RGB packed formats and various multiplanar +formats. + +The alpha component can be set through the 'Alpha Component' User control +for those formats that support it. If the 'Apply Alpha To Red Only' control +is set, then the alpha component is only used for the color red and set to +0 otherwise. + +The driver has to be configured to support the multiplanar formats. By default +the driver instances are single-planar. This can be changed by setting the +multiplanar module option, see section 1 for more details on that option. + +If the driver instance is using the multiplanar formats/API, then the first +single planar format (YUYV) and the multiplanar NV16M and NV61M formats the +will have a plane that has a non-zero data_offset of 128 bytes. It is rare for +data_offset to be non-zero, so this is a useful feature for testing applications. + +Video output will also honor any data_offset that the application set. + + +Capture Overlay +--------------- + +Note: capture overlay support is implemented primarily to test the existing +V4L2 capture overlay API. In practice few if any GPUs support such overlays +anymore, and neither are they generally needed anymore since modern hardware +is so much more capable. By setting flag 0x10000 in the node_types module +option the vivid driver will create a simple framebuffer device that can be +used for testing this API. Whether this API should be used for new drivers is +questionable. + +This driver has support for a destructive capture overlay with bitmap clipping +and list clipping (up to 16 rectangles) capabilities. Overlays are not +supported for multiplanar formats. It also honors the struct v4l2_window field +setting: if it is set to FIELD_TOP or FIELD_BOTTOM and the capture setting is +FIELD_ALTERNATE, then only the top or bottom fields will be copied to the overlay. + +The overlay only works if you are also capturing at that same time. This is a +vivid limitation since it copies from a buffer to the overlay instead of +filling the overlay directly. And if you are not capturing, then no buffers +are available to fill. + +In addition, the pixelformat of the capture format and that of the framebuffer +must be the same for the overlay to work. Otherwise VIDIOC_OVERLAY will return +an error. + +In order to really see what it going on you will need to create two vivid +instances: the first with a framebuffer enabled. You configure the capture +overlay of the second instance to use the framebuffer of the first, then +you start capturing in the second instance. For the first instance you setup +the output overlay for the video output, turn on video looping and capture +to see the blended framebuffer overlay that's being written to by the second +instance. This setup would require the following commands: + +.. code-block:: none + + $ sudo modprobe vivid n_devs=2 node_types=0x10101,0x1 + $ v4l2-ctl -d1 --find-fb + /dev/fb1 is the framebuffer associated with base address 0x12800000 + $ sudo v4l2-ctl -d2 --set-fbuf fb=1 + $ v4l2-ctl -d1 --set-fbuf fb=1 + $ v4l2-ctl -d0 --set-fmt-video=pixelformat='AR15' + $ v4l2-ctl -d1 --set-fmt-video-out=pixelformat='AR15' + $ v4l2-ctl -d2 --set-fmt-video=pixelformat='AR15' + $ v4l2-ctl -d0 -i2 + $ v4l2-ctl -d2 -i2 + $ v4l2-ctl -d2 -c horizontal_movement=4 + $ v4l2-ctl -d1 --overlay=1 + $ v4l2-ctl -d0 -c loop_video=1 + $ v4l2-ctl -d2 --stream-mmap --overlay=1 + +And from another console: + +.. code-block:: none + + $ v4l2-ctl -d1 --stream-out-mmap + +And yet another console: + +.. code-block:: none + + $ qv4l2 + +and start streaming. + +As you can see, this is not for the faint of heart... + + +Output Overlay +-------------- + +Note: output overlays are primarily implemented in order to test the existing +V4L2 output overlay API. Whether this API should be used for new drivers is +questionable. + +This driver has support for an output overlay and is capable of: + + - bitmap clipping, + - list clipping (up to 16 rectangles) + - chromakey + - source chromakey + - global alpha + - local alpha + - local inverse alpha + +Output overlays are not supported for multiplanar formats. In addition, the +pixelformat of the capture format and that of the framebuffer must be the +same for the overlay to work. Otherwise VIDIOC_OVERLAY will return an error. + +Output overlays only work if the driver has been configured to create a +framebuffer by setting flag 0x10000 in the node_types module option. The +created framebuffer has a size of 720x576 and supports ARGB 1:5:5:5 and +RGB 5:6:5. + +In order to see the effects of the various clipping, chromakeying or alpha +processing capabilities you need to turn on video looping and see the results +on the capture side. The use of the clipping, chromakeying or alpha processing +capabilities will slow down the video loop considerably as a lot of checks have +to be done per pixel. + + +CEC (Consumer Electronics Control) +---------------------------------- + +If there are HDMI inputs then a CEC adapter will be created that has +the same number of input ports. This is the equivalent of e.g. a TV that +has that number of inputs. Each HDMI output will also create a +CEC adapter that is hooked up to the corresponding input port, or (if there +are more outputs than inputs) is not hooked up at all. In other words, +this is the equivalent of hooking up each output device to an input port of +the TV. Any remaining output devices remain unconnected. + +The EDID that each output reads reports a unique CEC physical address that is +based on the physical address of the EDID of the input. So if the EDID of the +receiver has physical address A.B.0.0, then each output will see an EDID +containing physical address A.B.C.0 where C is 1 to the number of inputs. If +there are more outputs than inputs then the remaining outputs have a CEC adapter +that is disabled and reports an invalid physical address. + + +Some Future Improvements +------------------------ + +Just as a reminder and in no particular order: + +- Add a virtual alsa driver to test audio +- Add virtual sub-devices and media controller support +- Some support for testing compressed video +- Add support to loop raw VBI output to raw VBI input +- Add support to loop teletext sliced VBI output to VBI input +- Fix sequence/field numbering when looping of video with alternate fields +- Add support for V4L2_CID_BG_COLOR for video outputs +- Add ARGB888 overlay support: better testing of the alpha channel +- Improve pixel aspect support in the tpg code by passing a real v4l2_fract +- Use per-queue locks and/or per-device locks to improve throughput +- Add support to loop from a specific output to a specific input across + vivid instances +- The SDR radio should use the same 'frequencies' for stations as the normal + radio receiver, and give back noise if the frequency doesn't match up with + a station frequency +- Make a thread for the RDS generation, that would help in particular for the + "Controls" RDS Rx I/O Mode as the read-only RDS controls could be updated + in real-time. +- Changing the EDID should cause hotplug detect emulation to happen. diff --git a/Documentation/admin-guide/media/zoran-cardlist.rst b/Documentation/admin-guide/media/zoran-cardlist.rst new file mode 100644 index 000000000..d7fc8bed6 --- /dev/null +++ b/Documentation/admin-guide/media/zoran-cardlist.rst @@ -0,0 +1,51 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Zoran cards list +================ + +.. tabularcolumns:: |p{1.4cm}|p{11.1cm}|p{4.2cm}| + +.. flat-table:: + :header-rows: 1 + :widths: 2 19 18 + :stub-columns: 0 + + * - Card number + - Card name + - PCI subsystem IDs + + * - 0 + - DC10(old) + - <any> + + * - 1 + - DC10(new) + - <any> + + * - 2 + - DC10_PLUS + - 1031:7efe + + * - 3 + - DC30 + - <any> + + * - 4 + - DC30_PLUS + - 1031:d801 + + * - 5 + - LML33 + - <any> + + * - 6 + - LML33R10 + - 12f8:8a02 + + * - 7 + - Buz + - 13ca:4231 + + * - 8 + - 6-Eyes + - <any> diff --git a/Documentation/admin-guide/mm/cma_debugfs.rst b/Documentation/admin-guide/mm/cma_debugfs.rst new file mode 100644 index 000000000..7367e6294 --- /dev/null +++ b/Documentation/admin-guide/mm/cma_debugfs.rst @@ -0,0 +1,25 @@ +===================== +CMA Debugfs Interface +===================== + +The CMA debugfs interface is useful to retrieve basic information out of the +different CMA areas and to test allocation/release in each of the areas. + +Each CMA area represents a directory under <debugfs>/cma/, represented by +its CMA name like below: + + <debugfs>/cma/<cma_name> + +The structure of the files created under that directory is as follows: + + - [RO] base_pfn: The base PFN (Page Frame Number) of the zone. + - [RO] count: Amount of memory in the CMA area. + - [RO] order_per_bit: Order of pages represented by one bit. + - [RO] bitmap: The bitmap of page states in the zone. + - [WO] alloc: Allocate N pages from that CMA area. For example:: + + echo 5 > <debugfs>/cma/<cma_name>/alloc + +would try to allocate 5 pages from the 'cma_name' area. + + - [WO] free: Free N pages from that CMA area, similar to the above. diff --git a/Documentation/admin-guide/mm/concepts.rst b/Documentation/admin-guide/mm/concepts.rst new file mode 100644 index 000000000..e796b0a7e --- /dev/null +++ b/Documentation/admin-guide/mm/concepts.rst @@ -0,0 +1,220 @@ +================= +Concepts overview +================= + +The memory management in Linux is a complex system that evolved over the +years and included more and more functionality to support a variety of +systems from MMU-less microcontrollers to supercomputers. The memory +management for systems without an MMU is called ``nommu`` and it +definitely deserves a dedicated document, which hopefully will be +eventually written. Yet, although some of the concepts are the same, +here we assume that an MMU is available and a CPU can translate a virtual +address to a physical address. + +.. contents:: :local: + +Virtual Memory Primer +===================== + +The physical memory in a computer system is a limited resource and +even for systems that support memory hotplug there is a hard limit on +the amount of memory that can be installed. The physical memory is not +necessarily contiguous; it might be accessible as a set of distinct +address ranges. Besides, different CPU architectures, and even +different implementations of the same architecture have different views +of how these address ranges are defined. + +All this makes dealing directly with physical memory quite complex and +to avoid this complexity a concept of virtual memory was developed. + +The virtual memory abstracts the details of physical memory from the +application software, allows to keep only needed information in the +physical memory (demand paging) and provides a mechanism for the +protection and controlled sharing of data between processes. + +With virtual memory, each and every memory access uses a virtual +address. When the CPU decodes an instruction that reads (or +writes) from (or to) the system memory, it translates the `virtual` +address encoded in that instruction to a `physical` address that the +memory controller can understand. + +The physical system memory is divided into page frames, or pages. The +size of each page is architecture specific. Some architectures allow +selection of the page size from several supported values; this +selection is performed at the kernel build time by setting an +appropriate kernel configuration option. + +Each physical memory page can be mapped as one or more virtual +pages. These mappings are described by page tables that allow +translation from a virtual address used by programs to the physical +memory address. The page tables are organized hierarchically. + +The tables at the lowest level of the hierarchy contain physical +addresses of actual pages used by the software. The tables at higher +levels contain physical addresses of the pages belonging to the lower +levels. The pointer to the top level page table resides in a +register. When the CPU performs the address translation, it uses this +register to access the top level page table. The high bits of the +virtual address are used to index an entry in the top level page +table. That entry is then used to access the next level in the +hierarchy with the next bits of the virtual address as the index to +that level page table. The lowest bits in the virtual address define +the offset inside the actual page. + +Huge Pages +========== + +The address translation requires several memory accesses and memory +accesses are slow relatively to CPU speed. To avoid spending precious +processor cycles on the address translation, CPUs maintain a cache of +such translations called Translation Lookaside Buffer (or +TLB). Usually TLB is pretty scarce resource and applications with +large memory working set will experience performance hit because of +TLB misses. + +Many modern CPU architectures allow mapping of the memory pages +directly by the higher levels in the page table. For instance, on x86, +it is possible to map 2M and even 1G pages using entries in the second +and the third level page tables. In Linux such pages are called +`huge`. Usage of huge pages significantly reduces pressure on TLB, +improves TLB hit-rate and thus improves overall system performance. + +There are two mechanisms in Linux that enable mapping of the physical +memory with the huge pages. The first one is `HugeTLB filesystem`, or +hugetlbfs. It is a pseudo filesystem that uses RAM as its backing +store. For the files created in this filesystem the data resides in +the memory and mapped using huge pages. The hugetlbfs is described at +Documentation/admin-guide/mm/hugetlbpage.rst. + +Another, more recent, mechanism that enables use of the huge pages is +called `Transparent HugePages`, or THP. Unlike the hugetlbfs that +requires users and/or system administrators to configure what parts of +the system memory should and can be mapped by the huge pages, THP +manages such mappings transparently to the user and hence the +name. See Documentation/admin-guide/mm/transhuge.rst for more details +about THP. + +Zones +===== + +Often hardware poses restrictions on how different physical memory +ranges can be accessed. In some cases, devices cannot perform DMA to +all the addressable memory. In other cases, the size of the physical +memory exceeds the maximal addressable size of virtual memory and +special actions are required to access portions of the memory. Linux +groups memory pages into `zones` according to their possible +usage. For example, ZONE_DMA will contain memory that can be used by +devices for DMA, ZONE_HIGHMEM will contain memory that is not +permanently mapped into kernel's address space and ZONE_NORMAL will +contain normally addressed pages. + +The actual layout of the memory zones is hardware dependent as not all +architectures define all zones, and requirements for DMA are different +for different platforms. + +Nodes +===== + +Many multi-processor machines are NUMA - Non-Uniform Memory Access - +systems. In such systems the memory is arranged into banks that have +different access latency depending on the "distance" from the +processor. Each bank is referred to as a `node` and for each node Linux +constructs an independent memory management subsystem. A node has its +own set of zones, lists of free and used pages and various statistics +counters. You can find more details about NUMA in +Documentation/mm/numa.rst` and in +Documentation/admin-guide/mm/numa_memory_policy.rst. + +Page cache +========== + +The physical memory is volatile and the common case for getting data +into the memory is to read it from files. Whenever a file is read, the +data is put into the `page cache` to avoid expensive disk access on +the subsequent reads. Similarly, when one writes to a file, the data +is placed in the page cache and eventually gets into the backing +storage device. The written pages are marked as `dirty` and when Linux +decides to reuse them for other purposes, it makes sure to synchronize +the file contents on the device with the updated data. + +Anonymous Memory +================ + +The `anonymous memory` or `anonymous mappings` represent memory that +is not backed by a filesystem. Such mappings are implicitly created +for program's stack and heap or by explicit calls to mmap(2) system +call. Usually, the anonymous mappings only define virtual memory areas +that the program is allowed to access. The read accesses will result +in creation of a page table entry that references a special physical +page filled with zeroes. When the program performs a write, a regular +physical page will be allocated to hold the written data. The page +will be marked dirty and if the kernel decides to repurpose it, +the dirty page will be swapped out. + +Reclaim +======= + +Throughout the system lifetime, a physical page can be used for storing +different types of data. It can be kernel internal data structures, +DMA'able buffers for device drivers use, data read from a filesystem, +memory allocated by user space processes etc. + +Depending on the page usage it is treated differently by the Linux +memory management. The pages that can be freed at any time, either +because they cache the data available elsewhere, for instance, on a +hard disk, or because they can be swapped out, again, to the hard +disk, are called `reclaimable`. The most notable categories of the +reclaimable pages are page cache and anonymous memory. + +In most cases, the pages holding internal kernel data and used as DMA +buffers cannot be repurposed, and they remain pinned until freed by +their user. Such pages are called `unreclaimable`. However, in certain +circumstances, even pages occupied with kernel data structures can be +reclaimed. For instance, in-memory caches of filesystem metadata can +be re-read from the storage device and therefore it is possible to +discard them from the main memory when system is under memory +pressure. + +The process of freeing the reclaimable physical memory pages and +repurposing them is called (surprise!) `reclaim`. Linux can reclaim +pages either asynchronously or synchronously, depending on the state +of the system. When the system is not loaded, most of the memory is free +and allocation requests will be satisfied immediately from the free +pages supply. As the load increases, the amount of the free pages goes +down and when it reaches a certain threshold (low watermark), an +allocation request will awaken the ``kswapd`` daemon. It will +asynchronously scan memory pages and either just free them if the data +they contain is available elsewhere, or evict to the backing storage +device (remember those dirty pages?). As memory usage increases even +more and reaches another threshold - min watermark - an allocation +will trigger `direct reclaim`. In this case allocation is stalled +until enough memory pages are reclaimed to satisfy the request. + +Compaction +========== + +As the system runs, tasks allocate and free the memory and it becomes +fragmented. Although with virtual memory it is possible to present +scattered physical pages as virtually contiguous range, sometimes it is +necessary to allocate large physically contiguous memory areas. Such +need may arise, for instance, when a device driver requires a large +buffer for DMA, or when THP allocates a huge page. Memory `compaction` +addresses the fragmentation issue. This mechanism moves occupied pages +from the lower part of a memory zone to free pages in the upper part +of the zone. When a compaction scan is finished free pages are grouped +together at the beginning of the zone and allocations of large +physically contiguous areas become possible. + +Like reclaim, the compaction may happen asynchronously in the ``kcompactd`` +daemon or synchronously as a result of a memory allocation request. + +OOM killer +========== + +It is possible that on a loaded machine memory will be exhausted and the +kernel will be unable to reclaim enough memory to continue to operate. In +order to save the rest of the system, it invokes the `OOM killer`. + +The `OOM killer` selects a task to sacrifice for the sake of the overall +system health. The selected task is killed in a hope that after it exits +enough memory will be freed to continue normal operation. diff --git a/Documentation/admin-guide/mm/damon/index.rst b/Documentation/admin-guide/mm/damon/index.rst new file mode 100644 index 000000000..33d37bb2f --- /dev/null +++ b/Documentation/admin-guide/mm/damon/index.rst @@ -0,0 +1,17 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========================== +DAMON: Data Access MONitor +========================== + +:doc:`DAMON </mm/damon/index>` allows light-weight data access monitoring. +Using DAMON, users can analyze the memory access patterns of their systems and +optimize those. + +.. toctree:: + :maxdepth: 2 + + start + usage + reclaim + lru_sort diff --git a/Documentation/admin-guide/mm/damon/lru_sort.rst b/Documentation/admin-guide/mm/damon/lru_sort.rst new file mode 100644 index 000000000..7b0775d28 --- /dev/null +++ b/Documentation/admin-guide/mm/damon/lru_sort.rst @@ -0,0 +1,294 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================= +DAMON-based LRU-lists Sorting +============================= + +DAMON-based LRU-lists Sorting (DAMON_LRU_SORT) is a static kernel module that +aimed to be used for proactive and lightweight data access pattern based +(de)prioritization of pages on their LRU-lists for making LRU-lists a more +trusworthy data access pattern source. + +Where Proactive LRU-lists Sorting is Required? +============================================== + +As page-granularity access checking overhead could be significant on huge +systems, LRU lists are normally not proactively sorted but partially and +reactively sorted for special events including specific user requests, system +calls and memory pressure. As a result, LRU lists are sometimes not so +perfectly prepared to be used as a trustworthy access pattern source for some +situations including reclamation target pages selection under sudden memory +pressure. + +Because DAMON can identify access patterns of best-effort accuracy while +inducing only user-specified range of overhead, proactively running +DAMON_LRU_SORT could be helpful for making LRU lists more trustworthy access +pattern source with low and controlled overhead. + +How It Works? +============= + +DAMON_LRU_SORT finds hot pages (pages of memory regions that showing access +rates that higher than a user-specified threshold) and cold pages (pages of +memory regions that showing no access for a time that longer than a +user-specified threshold) using DAMON, and prioritizes hot pages while +deprioritizing cold pages on their LRU-lists. To avoid it consuming too much +CPU for the prioritizations, a CPU time usage limit can be configured. Under +the limit, it prioritizes and deprioritizes more hot and cold pages first, +respectively. System administrators can also configure under what situation +this scheme should automatically activated and deactivated with three memory +pressure watermarks. + +Its default parameters for hotness/coldness thresholds and CPU quota limit are +conservatively chosen. That is, the module under its default parameters could +be widely used without harm for common situations while providing a level of +benefits for systems having clear hot/cold access patterns under memory +pressure while consuming only a limited small portion of CPU time. + +Interface: Module Parameters +============================ + +To use this feature, you should first ensure your system is running on a kernel +that is built with ``CONFIG_DAMON_LRU_SORT=y``. + +To let sysadmins enable or disable it and tune for the given system, +DAMON_LRU_SORT utilizes module parameters. That is, you can put +``damon_lru_sort.<parameter>=<value>`` on the kernel boot command line or write +proper values to ``/sys/module/damon_lru_sort/parameters/<parameter>`` files. + +Below are the description of each parameter. + +enabled +------- + +Enable or disable DAMON_LRU_SORT. + +You can enable DAMON_LRU_SORT by setting the value of this parameter as ``Y``. +Setting it as ``N`` disables DAMON_LRU_SORT. Note that DAMON_LRU_SORT could do +no real monitoring and LRU-lists sorting due to the watermarks-based activation +condition. Refer to below descriptions for the watermarks parameter for this. + +commit_inputs +------------- + +Make DAMON_LRU_SORT reads the input parameters again, except ``enabled``. + +Input parameters that updated while DAMON_LRU_SORT is running are not applied +by default. Once this parameter is set as ``Y``, DAMON_LRU_SORT reads values +of parametrs except ``enabled`` again. Once the re-reading is done, this +parameter is set as ``N``. If invalid parameters are found while the +re-reading, DAMON_LRU_SORT will be disabled. + +hot_thres_access_freq +--------------------- + +Access frequency threshold for hot memory regions identification in permil. + +If a memory region is accessed in frequency of this or higher, DAMON_LRU_SORT +identifies the region as hot, and mark it as accessed on the LRU list, so that +it could not be reclaimed under memory pressure. 50% by default. + +cold_min_age +------------ + +Time threshold for cold memory regions identification in microseconds. + +If a memory region is not accessed for this or longer time, DAMON_LRU_SORT +identifies the region as cold, and mark it as unaccessed on the LRU list, so +that it could be reclaimed first under memory pressure. 120 seconds by +default. + +quota_ms +-------- + +Limit of time for trying the LRU lists sorting in milliseconds. + +DAMON_LRU_SORT tries to use only up to this time within a time window +(quota_reset_interval_ms) for trying LRU lists sorting. This can be used +for limiting CPU consumption of DAMON_LRU_SORT. If the value is zero, the +limit is disabled. + +10 ms by default. + +quota_reset_interval_ms +----------------------- + +The time quota charge reset interval in milliseconds. + +The charge reset interval for the quota of time (quota_ms). That is, +DAMON_LRU_SORT does not try LRU-lists sorting for more than quota_ms +milliseconds or quota_sz bytes within quota_reset_interval_ms milliseconds. + +1 second by default. + +wmarks_interval +--------------- + +The watermarks check time interval in microseconds. + +Minimal time to wait before checking the watermarks, when DAMON_LRU_SORT is +enabled but inactive due to its watermarks rule. 5 seconds by default. + +wmarks_high +----------- + +Free memory rate (per thousand) for the high watermark. + +If free memory of the system in bytes per thousand bytes is higher than this, +DAMON_LRU_SORT becomes inactive, so it does nothing but periodically checks the +watermarks. 200 (20%) by default. + +wmarks_mid +---------- + +Free memory rate (per thousand) for the middle watermark. + +If free memory of the system in bytes per thousand bytes is between this and +the low watermark, DAMON_LRU_SORT becomes active, so starts the monitoring and +the LRU-lists sorting. 150 (15%) by default. + +wmarks_low +---------- + +Free memory rate (per thousand) for the low watermark. + +If free memory of the system in bytes per thousand bytes is lower than this, +DAMON_LRU_SORT becomes inactive, so it does nothing but periodically checks the +watermarks. 50 (5%) by default. + +sample_interval +--------------- + +Sampling interval for the monitoring in microseconds. + +The sampling interval of DAMON for the cold memory monitoring. Please refer to +the DAMON documentation (:doc:`usage`) for more detail. 5ms by default. + +aggr_interval +------------- + +Aggregation interval for the monitoring in microseconds. + +The aggregation interval of DAMON for the cold memory monitoring. Please +refer to the DAMON documentation (:doc:`usage`) for more detail. 100ms by +default. + +min_nr_regions +-------------- + +Minimum number of monitoring regions. + +The minimal number of monitoring regions of DAMON for the cold memory +monitoring. This can be used to set lower-bound of the monitoring quality. +But, setting this too high could result in increased monitoring overhead. +Please refer to the DAMON documentation (:doc:`usage`) for more detail. 10 by +default. + +max_nr_regions +-------------- + +Maximum number of monitoring regions. + +The maximum number of monitoring regions of DAMON for the cold memory +monitoring. This can be used to set upper-bound of the monitoring overhead. +However, setting this too low could result in bad monitoring quality. Please +refer to the DAMON documentation (:doc:`usage`) for more detail. 1000 by +defaults. + +monitor_region_start +-------------------- + +Start of target memory region in physical address. + +The start physical address of memory region that DAMON_LRU_SORT will do work +against. By default, biggest System RAM is used as the region. + +monitor_region_end +------------------ + +End of target memory region in physical address. + +The end physical address of memory region that DAMON_LRU_SORT will do work +against. By default, biggest System RAM is used as the region. + +kdamond_pid +----------- + +PID of the DAMON thread. + +If DAMON_LRU_SORT is enabled, this becomes the PID of the worker thread. Else, +-1. + +nr_lru_sort_tried_hot_regions +----------------------------- + +Number of hot memory regions that tried to be LRU-sorted. + +bytes_lru_sort_tried_hot_regions +-------------------------------- + +Total bytes of hot memory regions that tried to be LRU-sorted. + +nr_lru_sorted_hot_regions +------------------------- + +Number of hot memory regions that successfully be LRU-sorted. + +bytes_lru_sorted_hot_regions +---------------------------- + +Total bytes of hot memory regions that successfully be LRU-sorted. + +nr_hot_quota_exceeds +-------------------- + +Number of times that the time quota limit for hot regions have exceeded. + +nr_lru_sort_tried_cold_regions +------------------------------ + +Number of cold memory regions that tried to be LRU-sorted. + +bytes_lru_sort_tried_cold_regions +--------------------------------- + +Total bytes of cold memory regions that tried to be LRU-sorted. + +nr_lru_sorted_cold_regions +-------------------------- + +Number of cold memory regions that successfully be LRU-sorted. + +bytes_lru_sorted_cold_regions +----------------------------- + +Total bytes of cold memory regions that successfully be LRU-sorted. + +nr_cold_quota_exceeds +--------------------- + +Number of times that the time quota limit for cold regions have exceeded. + +Example +======= + +Below runtime example commands make DAMON_LRU_SORT to find memory regions +having >=50% access frequency and LRU-prioritize while LRU-deprioritizing +memory regions that not accessed for 120 seconds. The prioritization and +deprioritization is limited to be done using only up to 1% CPU time to avoid +DAMON_LRU_SORT consuming too much CPU time for the (de)prioritization. It also +asks DAMON_LRU_SORT to do nothing if the system's free memory rate is more than +50%, but start the real works if it becomes lower than 40%. If DAMON_RECLAIM +doesn't make progress and therefore the free memory rate becomes lower than +20%, it asks DAMON_LRU_SORT to do nothing again, so that we can fall back to +the LRU-list based page granularity reclamation. :: + + # cd /sys/module/damon_lru_sort/parameters + # echo 500 > hot_thres_access_freq + # echo 120000000 > cold_min_age + # echo 10 > quota_ms + # echo 1000 > quota_reset_interval_ms + # echo 500 > wmarks_high + # echo 400 > wmarks_mid + # echo 200 > wmarks_low + # echo Y > enabled diff --git a/Documentation/admin-guide/mm/damon/reclaim.rst b/Documentation/admin-guide/mm/damon/reclaim.rst new file mode 100644 index 000000000..343e25b25 --- /dev/null +++ b/Documentation/admin-guide/mm/damon/reclaim.rst @@ -0,0 +1,274 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================= +DAMON-based Reclamation +======================= + +DAMON-based Reclamation (DAMON_RECLAIM) is a static kernel module that aimed to +be used for proactive and lightweight reclamation under light memory pressure. +It doesn't aim to replace the LRU-list based page_granularity reclamation, but +to be selectively used for different level of memory pressure and requirements. + +Where Proactive Reclamation is Required? +======================================== + +On general memory over-committed systems, proactively reclaiming cold pages +helps saving memory and reducing latency spikes that incurred by the direct +reclaim of the process or CPU consumption of kswapd, while incurring only +minimal performance degradation [1]_ [2]_ . + +Free Pages Reporting [3]_ based memory over-commit virtualization systems are +good example of the cases. In such systems, the guest VMs reports their free +memory to host, and the host reallocates the reported memory to other guests. +As a result, the memory of the systems are fully utilized. However, the +guests could be not so memory-frugal, mainly because some kernel subsystems and +user-space applications are designed to use as much memory as available. Then, +guests could report only small amount of memory as free to host, results in +memory utilization drop of the systems. Running the proactive reclamation in +guests could mitigate this problem. + +How It Works? +============= + +DAMON_RECLAIM finds memory regions that didn't accessed for specific time +duration and page out. To avoid it consuming too much CPU for the paging out +operation, a speed limit can be configured. Under the speed limit, it pages +out memory regions that didn't accessed longer time first. System +administrators can also configure under what situation this scheme should +automatically activated and deactivated with three memory pressure watermarks. + +Interface: Module Parameters +============================ + +To use this feature, you should first ensure your system is running on a kernel +that is built with ``CONFIG_DAMON_RECLAIM=y``. + +To let sysadmins enable or disable it and tune for the given system, +DAMON_RECLAIM utilizes module parameters. That is, you can put +``damon_reclaim.<parameter>=<value>`` on the kernel boot command line or write +proper values to ``/sys/module/damon_reclaim/parameters/<parameter>`` files. + +Below are the description of each parameter. + +enabled +------- + +Enable or disable DAMON_RECLAIM. + +You can enable DAMON_RCLAIM by setting the value of this parameter as ``Y``. +Setting it as ``N`` disables DAMON_RECLAIM. Note that DAMON_RECLAIM could do +no real monitoring and reclamation due to the watermarks-based activation +condition. Refer to below descriptions for the watermarks parameter for this. + +commit_inputs +------------- + +Make DAMON_RECLAIM reads the input parameters again, except ``enabled``. + +Input parameters that updated while DAMON_RECLAIM is running are not applied +by default. Once this parameter is set as ``Y``, DAMON_RECLAIM reads values +of parametrs except ``enabled`` again. Once the re-reading is done, this +parameter is set as ``N``. If invalid parameters are found while the +re-reading, DAMON_RECLAIM will be disabled. + +min_age +------- + +Time threshold for cold memory regions identification in microseconds. + +If a memory region is not accessed for this or longer time, DAMON_RECLAIM +identifies the region as cold, and reclaims it. + +120 seconds by default. + +quota_ms +-------- + +Limit of time for the reclamation in milliseconds. + +DAMON_RECLAIM tries to use only up to this time within a time window +(quota_reset_interval_ms) for trying reclamation of cold pages. This can be +used for limiting CPU consumption of DAMON_RECLAIM. If the value is zero, the +limit is disabled. + +10 ms by default. + +quota_sz +-------- + +Limit of size of memory for the reclamation in bytes. + +DAMON_RECLAIM charges amount of memory which it tried to reclaim within a time +window (quota_reset_interval_ms) and makes no more than this limit is tried. +This can be used for limiting consumption of CPU and IO. If this value is +zero, the limit is disabled. + +128 MiB by default. + +quota_reset_interval_ms +----------------------- + +The time/size quota charge reset interval in milliseconds. + +The charget reset interval for the quota of time (quota_ms) and size +(quota_sz). That is, DAMON_RECLAIM does not try reclamation for more than +quota_ms milliseconds or quota_sz bytes within quota_reset_interval_ms +milliseconds. + +1 second by default. + +wmarks_interval +--------------- + +Minimal time to wait before checking the watermarks, when DAMON_RECLAIM is +enabled but inactive due to its watermarks rule. + +wmarks_high +----------- + +Free memory rate (per thousand) for the high watermark. + +If free memory of the system in bytes per thousand bytes is higher than this, +DAMON_RECLAIM becomes inactive, so it does nothing but only periodically checks +the watermarks. + +wmarks_mid +---------- + +Free memory rate (per thousand) for the middle watermark. + +If free memory of the system in bytes per thousand bytes is between this and +the low watermark, DAMON_RECLAIM becomes active, so starts the monitoring and +the reclaiming. + +wmarks_low +---------- + +Free memory rate (per thousand) for the low watermark. + +If free memory of the system in bytes per thousand bytes is lower than this, +DAMON_RECLAIM becomes inactive, so it does nothing but periodically checks the +watermarks. In the case, the system falls back to the LRU-list based page +granularity reclamation logic. + +sample_interval +--------------- + +Sampling interval for the monitoring in microseconds. + +The sampling interval of DAMON for the cold memory monitoring. Please refer to +the DAMON documentation (:doc:`usage`) for more detail. + +aggr_interval +------------- + +Aggregation interval for the monitoring in microseconds. + +The aggregation interval of DAMON for the cold memory monitoring. Please +refer to the DAMON documentation (:doc:`usage`) for more detail. + +min_nr_regions +-------------- + +Minimum number of monitoring regions. + +The minimal number of monitoring regions of DAMON for the cold memory +monitoring. This can be used to set lower-bound of the monitoring quality. +But, setting this too high could result in increased monitoring overhead. +Please refer to the DAMON documentation (:doc:`usage`) for more detail. + +max_nr_regions +-------------- + +Maximum number of monitoring regions. + +The maximum number of monitoring regions of DAMON for the cold memory +monitoring. This can be used to set upper-bound of the monitoring overhead. +However, setting this too low could result in bad monitoring quality. Please +refer to the DAMON documentation (:doc:`usage`) for more detail. + +monitor_region_start +-------------------- + +Start of target memory region in physical address. + +The start physical address of memory region that DAMON_RECLAIM will do work +against. That is, DAMON_RECLAIM will find cold memory regions in this region +and reclaims. By default, biggest System RAM is used as the region. + +monitor_region_end +------------------ + +End of target memory region in physical address. + +The end physical address of memory region that DAMON_RECLAIM will do work +against. That is, DAMON_RECLAIM will find cold memory regions in this region +and reclaims. By default, biggest System RAM is used as the region. + +skip_anon +--------- + +Skip anonymous pages reclamation. + +If this parameter is set as ``Y``, DAMON_RECLAIM does not reclaim anonymous +pages. By default, ``N``. + + +kdamond_pid +----------- + +PID of the DAMON thread. + +If DAMON_RECLAIM is enabled, this becomes the PID of the worker thread. Else, +-1. + +nr_reclaim_tried_regions +------------------------ + +Number of memory regions that tried to be reclaimed by DAMON_RECLAIM. + +bytes_reclaim_tried_regions +--------------------------- + +Total bytes of memory regions that tried to be reclaimed by DAMON_RECLAIM. + +nr_reclaimed_regions +-------------------- + +Number of memory regions that successfully be reclaimed by DAMON_RECLAIM. + +bytes_reclaimed_regions +----------------------- + +Total bytes of memory regions that successfully be reclaimed by DAMON_RECLAIM. + +nr_quota_exceeds +---------------- + +Number of times that the time/space quota limits have exceeded. + +Example +======= + +Below runtime example commands make DAMON_RECLAIM to find memory regions that +not accessed for 30 seconds or more and pages out. The reclamation is limited +to be done only up to 1 GiB per second to avoid DAMON_RECLAIM consuming too +much CPU time for the paging out operation. It also asks DAMON_RECLAIM to do +nothing if the system's free memory rate is more than 50%, but start the real +works if it becomes lower than 40%. If DAMON_RECLAIM doesn't make progress and +therefore the free memory rate becomes lower than 20%, it asks DAMON_RECLAIM to +do nothing again, so that we can fall back to the LRU-list based page +granularity reclamation. :: + + # cd /sys/module/damon_reclaim/parameters + # echo 30000000 > min_age + # echo $((1 * 1024 * 1024 * 1024)) > quota_sz + # echo 1000 > quota_reset_interval_ms + # echo 500 > wmarks_high + # echo 400 > wmarks_mid + # echo 200 > wmarks_low + # echo Y > enabled + +.. [1] https://research.google/pubs/pub48551/ +.. [2] https://lwn.net/Articles/787611/ +.. [3] https://www.kernel.org/doc/html/latest/mm/free_page_reporting.html diff --git a/Documentation/admin-guide/mm/damon/start.rst b/Documentation/admin-guide/mm/damon/start.rst new file mode 100644 index 000000000..7aa0071ff --- /dev/null +++ b/Documentation/admin-guide/mm/damon/start.rst @@ -0,0 +1,127 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============== +Getting Started +=============== + +This document briefly describes how you can use DAMON by demonstrating its +default user space tool. Please note that this document describes only a part +of its features for brevity. Please refer to the usage `doc +<https://github.com/awslabs/damo/blob/next/USAGE.md>`_ of the tool for more +details. + + +Prerequisites +============= + +Kernel +------ + +You should first ensure your system is running on a kernel built with +``CONFIG_DAMON_*=y``. + + +User Space Tool +--------------- + +For the demonstration, we will use the default user space tool for DAMON, +called DAMON Operator (DAMO). It is available at +https://github.com/awslabs/damo. The examples below assume that ``damo`` is on +your ``$PATH``. It's not mandatory, though. + +Because DAMO is using the sysfs interface (refer to :doc:`usage` for the +detail) of DAMON, you should ensure :doc:`sysfs </filesystems/sysfs>` is +mounted. + + +Recording Data Access Patterns +============================== + +The commands below record the memory access patterns of a program and save the +monitoring results to a file. :: + + $ git clone https://github.com/sjp38/masim + $ cd masim; make; ./masim ./configs/zigzag.cfg & + $ sudo damo record -o damon.data $(pidof masim) + +The first two lines of the commands download an artificial memory access +generator program and run it in the background. The generator will repeatedly +access two 100 MiB sized memory regions one by one. You can substitute this +with your real workload. The last line asks ``damo`` to record the access +pattern in the ``damon.data`` file. + + +Visualizing Recorded Patterns +============================= + +You can visualize the pattern in a heatmap, showing which memory region +(x-axis) got accessed when (y-axis) and how frequently (number).:: + + $ sudo damo report heats --heatmap stdout + 22222222222222222222222222222222222222211111111111111111111111111111111111111100 + 44444444444444444444444444444444444444434444444444444444444444444444444444443200 + 44444444444444444444444444444444444444433444444444444444444444444444444444444200 + 33333333333333333333333333333333333333344555555555555555555555555555555555555200 + 33333333333333333333333333333333333344444444444444444444444444444444444444444200 + 22222222222222222222222222222222222223355555555555555555555555555555555555555200 + 00000000000000000000000000000000000000288888888888888888888888888888888888888400 + 00000000000000000000000000000000000000288888888888888888888888888888888888888400 + 33333333333333333333333333333333333333355555555555555555555555555555555555555200 + 88888888888888888888888888888888888888600000000000000000000000000000000000000000 + 88888888888888888888888888888888888888600000000000000000000000000000000000000000 + 33333333333333333333333333333333333333444444444444444444444444444444444444443200 + 00000000000000000000000000000000000000288888888888888888888888888888888888888400 + [...] + # access_frequency: 0 1 2 3 4 5 6 7 8 9 + # x-axis: space (139728247021568-139728453431248: 196.848 MiB) + # y-axis: time (15256597248362-15326899978162: 1 m 10.303 s) + # resolution: 80x40 (2.461 MiB and 1.758 s for each character) + +You can also visualize the distribution of the working set size, sorted by the +size.:: + + $ sudo damo report wss --range 0 101 10 + # <percentile> <wss> + # target_id 18446632103789443072 + # avr: 107.708 MiB + 0 0 B | | + 10 95.328 MiB |**************************** | + 20 95.332 MiB |**************************** | + 30 95.340 MiB |**************************** | + 40 95.387 MiB |**************************** | + 50 95.387 MiB |**************************** | + 60 95.398 MiB |**************************** | + 70 95.398 MiB |**************************** | + 80 95.504 MiB |**************************** | + 90 190.703 MiB |********************************************************* | + 100 196.875 MiB |***********************************************************| + +Using ``--sortby`` option with the above command, you can show how the working +set size has chronologically changed.:: + + $ sudo damo report wss --range 0 101 10 --sortby time + # <percentile> <wss> + # target_id 18446632103789443072 + # avr: 107.708 MiB + 0 3.051 MiB | | + 10 190.703 MiB |***********************************************************| + 20 95.336 MiB |***************************** | + 30 95.328 MiB |***************************** | + 40 95.387 MiB |***************************** | + 50 95.332 MiB |***************************** | + 60 95.320 MiB |***************************** | + 70 95.398 MiB |***************************** | + 80 95.398 MiB |***************************** | + 90 95.340 MiB |***************************** | + 100 95.398 MiB |***************************** | + + +Data Access Pattern Aware Memory Management +=========================================== + +Below command makes every memory region of size >=4K that has not accessed for +>=60 seconds in your workload to be swapped out. :: + + $ sudo damo schemes --damos_access_rate 0 0 --damos_sz_region 4K max \ + --damos_age 60s max --damos_action pageout \ + <pid of your workload> diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst new file mode 100644 index 000000000..8da1b7281 --- /dev/null +++ b/Documentation/admin-guide/mm/damon/usage.rst @@ -0,0 +1,812 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============== +Detailed Usages +=============== + +DAMON provides below interfaces for different users. + +- *DAMON user space tool.* + `This <https://github.com/awslabs/damo>`_ is for privileged people such as + system administrators who want a just-working human-friendly interface. + Using this, users can use the DAMON’s major features in a human-friendly way. + It may not be highly tuned for special cases, though. For more detail, + please refer to its `usage document + <https://github.com/awslabs/damo/blob/next/USAGE.md>`_. +- *sysfs interface.* + :ref:`This <sysfs_interface>` is for privileged user space programmers who + want more optimized use of DAMON. Using this, users can use DAMON’s major + features by reading from and writing to special sysfs files. Therefore, + you can write and use your personalized DAMON sysfs wrapper programs that + reads/writes the sysfs files instead of you. The `DAMON user space tool + <https://github.com/awslabs/damo>`_ is one example of such programs. +- *debugfs interface. (DEPRECATED!)* + :ref:`This <debugfs_interface>` is almost identical to :ref:`sysfs interface + <sysfs_interface>`. This is deprecated, so users should move to the + :ref:`sysfs interface <sysfs_interface>`. If you depend on this and cannot + move, please report your usecase to damon@lists.linux.dev and + linux-mm@kvack.org. +- *Kernel Space Programming Interface.* + :doc:`This </mm/damon/api>` is for kernel space programmers. Using this, + users can utilize every feature of DAMON most flexibly and efficiently by + writing kernel space DAMON application programs for you. You can even extend + DAMON for various address spaces. For detail, please refer to the interface + :doc:`document </mm/damon/api>`. + +.. _sysfs_interface: + +sysfs Interface +=============== + +DAMON sysfs interface is built when ``CONFIG_DAMON_SYSFS`` is defined. It +creates multiple directories and files under its sysfs directory, +``<sysfs>/kernel/mm/damon/``. You can control DAMON by writing to and reading +from the files under the directory. + +For a short example, users can monitor the virtual address space of a given +workload as below. :: + + # cd /sys/kernel/mm/damon/admin/ + # echo 1 > kdamonds/nr_kdamonds && echo 1 > kdamonds/0/contexts/nr_contexts + # echo vaddr > kdamonds/0/contexts/0/operations + # echo 1 > kdamonds/0/contexts/0/targets/nr_targets + # echo $(pidof <workload>) > kdamonds/0/contexts/0/targets/0/pid_target + # echo on > kdamonds/0/state + +Files Hierarchy +--------------- + +The files hierarchy of DAMON sysfs interface is shown below. In the below +figure, parents-children relations are represented with indentations, each +directory is having ``/`` suffix, and files in each directory are separated by +comma (","). :: + + /sys/kernel/mm/damon/admin + │ kdamonds/nr_kdamonds + │ │ 0/state,pid + │ │ │ contexts/nr_contexts + │ │ │ │ 0/avail_operations,operations + │ │ │ │ │ monitoring_attrs/ + │ │ │ │ │ │ intervals/sample_us,aggr_us,update_us + │ │ │ │ │ │ nr_regions/min,max + │ │ │ │ │ targets/nr_targets + │ │ │ │ │ │ 0/pid_target + │ │ │ │ │ │ │ regions/nr_regions + │ │ │ │ │ │ │ │ 0/start,end + │ │ │ │ │ │ │ │ ... + │ │ │ │ │ │ ... + │ │ │ │ │ schemes/nr_schemes + │ │ │ │ │ │ 0/action + │ │ │ │ │ │ │ access_pattern/ + │ │ │ │ │ │ │ │ sz/min,max + │ │ │ │ │ │ │ │ nr_accesses/min,max + │ │ │ │ │ │ │ │ age/min,max + │ │ │ │ │ │ │ quotas/ms,bytes,reset_interval_ms + │ │ │ │ │ │ │ │ weights/sz_permil,nr_accesses_permil,age_permil + │ │ │ │ │ │ │ watermarks/metric,interval_us,high,mid,low + │ │ │ │ │ │ │ filters/nr_filters + │ │ │ │ │ │ │ │ 0/type,matching,memcg_id + │ │ │ │ │ │ │ stats/nr_tried,sz_tried,nr_applied,sz_applied,qt_exceeds + │ │ │ │ │ │ │ tried_regions/total_bytes + │ │ │ │ │ │ │ │ 0/start,end,nr_accesses,age + │ │ │ │ │ │ │ │ ... + │ │ │ │ │ │ ... + │ │ │ │ ... + │ │ ... + +Root +---- + +The root of the DAMON sysfs interface is ``<sysfs>/kernel/mm/damon/``, and it +has one directory named ``admin``. The directory contains the files for +privileged user space programs' control of DAMON. User space tools or daemons +having the root permission could use this directory. + +kdamonds/ +--------- + +The monitoring-related information including request specifications and results +are called DAMON context. DAMON executes each context with a kernel thread +called kdamond, and multiple kdamonds could run in parallel. + +Under the ``admin`` directory, one directory, ``kdamonds``, which has files for +controlling the kdamonds exist. In the beginning, this directory has only one +file, ``nr_kdamonds``. Writing a number (``N``) to the file creates the number +of child directories named ``0`` to ``N-1``. Each directory represents each +kdamond. + +kdamonds/<N>/ +------------- + +In each kdamond directory, two files (``state`` and ``pid``) and one directory +(``contexts``) exist. + +Reading ``state`` returns ``on`` if the kdamond is currently running, or +``off`` if it is not running. Writing ``on`` or ``off`` makes the kdamond be +in the state. Writing ``commit`` to the ``state`` file makes kdamond reads the +user inputs in the sysfs files except ``state`` file again. Writing +``update_schemes_stats`` to ``state`` file updates the contents of stats files +for each DAMON-based operation scheme of the kdamond. For details of the +stats, please refer to :ref:`stats section <sysfs_schemes_stats>`. + +Writing ``update_schemes_tried_regions`` to ``state`` file updates the +DAMON-based operation scheme action tried regions directory for each +DAMON-based operation scheme of the kdamond. Writing +``update_schemes_tried_bytes`` to ``state`` file updates only +``.../tried_regions/total_bytes`` files. Writing +``clear_schemes_tried_regions`` to ``state`` file clears the DAMON-based +operating scheme action tried regions directory for each DAMON-based operation +scheme of the kdamond. For details of the DAMON-based operation scheme action +tried regions directory, please refer to :ref:`tried_regions section +<sysfs_schemes_tried_regions>`. + +If the state is ``on``, reading ``pid`` shows the pid of the kdamond thread. + +``contexts`` directory contains files for controlling the monitoring contexts +that this kdamond will execute. + +kdamonds/<N>/contexts/ +---------------------- + +In the beginning, this directory has only one file, ``nr_contexts``. Writing a +number (``N``) to the file creates the number of child directories named as +``0`` to ``N-1``. Each directory represents each monitoring context. At the +moment, only one context per kdamond is supported, so only ``0`` or ``1`` can +be written to the file. + +.. _sysfs_contexts: + +contexts/<N>/ +------------- + +In each context directory, two files (``avail_operations`` and ``operations``) +and three directories (``monitoring_attrs``, ``targets``, and ``schemes``) +exist. + +DAMON supports multiple types of monitoring operations, including those for +virtual address space and the physical address space. You can get the list of +available monitoring operations set on the currently running kernel by reading +``avail_operations`` file. Based on the kernel configuration, the file will +list some or all of below keywords. + + - vaddr: Monitor virtual address spaces of specific processes + - fvaddr: Monitor fixed virtual address ranges + - paddr: Monitor the physical address space of the system + +Please refer to :ref:`regions sysfs directory <sysfs_regions>` for detailed +differences between the operations sets in terms of the monitoring target +regions. + +You can set and get what type of monitoring operations DAMON will use for the +context by writing one of the keywords listed in ``avail_operations`` file and +reading from the ``operations`` file. + +.. _sysfs_monitoring_attrs: + +contexts/<N>/monitoring_attrs/ +------------------------------ + +Files for specifying attributes of the monitoring including required quality +and efficiency of the monitoring are in ``monitoring_attrs`` directory. +Specifically, two directories, ``intervals`` and ``nr_regions`` exist in this +directory. + +Under ``intervals`` directory, three files for DAMON's sampling interval +(``sample_us``), aggregation interval (``aggr_us``), and update interval +(``update_us``) exist. You can set and get the values in micro-seconds by +writing to and reading from the files. + +Under ``nr_regions`` directory, two files for the lower-bound and upper-bound +of DAMON's monitoring regions (``min`` and ``max``, respectively), which +controls the monitoring overhead, exist. You can set and get the values by +writing to and rading from the files. + +For more details about the intervals and monitoring regions range, please refer +to the Design document (:doc:`/mm/damon/design`). + +contexts/<N>/targets/ +--------------------- + +In the beginning, this directory has only one file, ``nr_targets``. Writing a +number (``N``) to the file creates the number of child directories named ``0`` +to ``N-1``. Each directory represents each monitoring target. + +targets/<N>/ +------------ + +In each target directory, one file (``pid_target``) and one directory +(``regions``) exist. + +If you wrote ``vaddr`` to the ``contexts/<N>/operations``, each target should +be a process. You can specify the process to DAMON by writing the pid of the +process to the ``pid_target`` file. + +.. _sysfs_regions: + +targets/<N>/regions +------------------- + +When ``vaddr`` monitoring operations set is being used (``vaddr`` is written to +the ``contexts/<N>/operations`` file), DAMON automatically sets and updates the +monitoring target regions so that entire memory mappings of target processes +can be covered. However, users could want to set the initial monitoring region +to specific address ranges. + +In contrast, DAMON do not automatically sets and updates the monitoring target +regions when ``fvaddr`` or ``paddr`` monitoring operations sets are being used +(``fvaddr`` or ``paddr`` have written to the ``contexts/<N>/operations``). +Therefore, users should set the monitoring target regions by themselves in the +cases. + +For such cases, users can explicitly set the initial monitoring target regions +as they want, by writing proper values to the files under this directory. + +In the beginning, this directory has only one file, ``nr_regions``. Writing a +number (``N``) to the file creates the number of child directories named ``0`` +to ``N-1``. Each directory represents each initial monitoring target region. + +regions/<N>/ +------------ + +In each region directory, you will find two files (``start`` and ``end``). You +can set and get the start and end addresses of the initial monitoring target +region by writing to and reading from the files, respectively. + +Each region should not overlap with others. ``end`` of directory ``N`` should +be equal or smaller than ``start`` of directory ``N+1``. + +contexts/<N>/schemes/ +--------------------- + +The directory for DAMON-based Operation Schemes (:ref:`DAMOS +<damon_design_damos>`). Users can get and set the schemes by reading from and +writing to files under this directory. + +In the beginning, this directory has only one file, ``nr_schemes``. Writing a +number (``N``) to the file creates the number of child directories named ``0`` +to ``N-1``. Each directory represents each DAMON-based operation scheme. + +schemes/<N>/ +------------ + +In each scheme directory, five directories (``access_pattern``, ``quotas``, +``watermarks``, ``filters``, ``stats``, and ``tried_regions``) and one file +(``action``) exist. + +The ``action`` file is for setting and getting the scheme's :ref:`action +<damon_design_damos_action>`. The keywords that can be written to and read +from the file and their meaning are as below. + +Note that support of each action depends on the running DAMON operations set +:ref:`implementation <sysfs_contexts>`. + + - ``willneed``: Call ``madvise()`` for the region with ``MADV_WILLNEED``. + Supported by ``vaddr`` and ``fvaddr`` operations set. + - ``cold``: Call ``madvise()`` for the region with ``MADV_COLD``. + Supported by ``vaddr`` and ``fvaddr`` operations set. + - ``pageout``: Call ``madvise()`` for the region with ``MADV_PAGEOUT``. + Supported by ``vaddr``, ``fvaddr`` and ``paddr`` operations set. + - ``hugepage``: Call ``madvise()`` for the region with ``MADV_HUGEPAGE``. + Supported by ``vaddr`` and ``fvaddr`` operations set. + - ``nohugepage``: Call ``madvise()`` for the region with ``MADV_NOHUGEPAGE``. + Supported by ``vaddr`` and ``fvaddr`` operations set. + - ``lru_prio``: Prioritize the region on its LRU lists. + Supported by ``paddr`` operations set. + - ``lru_deprio``: Deprioritize the region on its LRU lists. + Supported by ``paddr`` operations set. + - ``stat``: Do nothing but count the statistics. + Supported by all operations sets. + +schemes/<N>/access_pattern/ +--------------------------- + +The directory for the target access :ref:`pattern +<damon_design_damos_access_pattern>` of the given DAMON-based operation scheme. + +Under the ``access_pattern`` directory, three directories (``sz``, +``nr_accesses``, and ``age``) each having two files (``min`` and ``max``) +exist. You can set and get the access pattern for the given scheme by writing +to and reading from the ``min`` and ``max`` files under ``sz``, +``nr_accesses``, and ``age`` directories, respectively. Note that the ``min`` +and the ``max`` form a closed interval. + +schemes/<N>/quotas/ +------------------- + +The directory for the :ref:`quotas <damon_design_damos_quotas>` of the given +DAMON-based operation scheme. + +Under ``quotas`` directory, three files (``ms``, ``bytes``, +``reset_interval_ms``) and one directory (``weights``) having three files +(``sz_permil``, ``nr_accesses_permil``, and ``age_permil``) in it exist. + +You can set the ``time quota`` in milliseconds, ``size quota`` in bytes, and +``reset interval`` in milliseconds by writing the values to the three files, +respectively. Then, DAMON tries to use only up to ``time quota`` milliseconds +for applying the ``action`` to memory regions of the ``access_pattern``, and to +apply the action to only up to ``bytes`` bytes of memory regions within the +``reset_interval_ms``. Setting both ``ms`` and ``bytes`` zero disables the +quota limits. + +You can also set the :ref:`prioritization weights +<damon_design_damos_quotas_prioritization>` for size, access frequency, and age +in per-thousand unit by writing the values to the three files under the +``weights`` directory. + +schemes/<N>/watermarks/ +----------------------- + +The directory for the :ref:`watermarks <damon_design_damos_watermarks>` of the +given DAMON-based operation scheme. + +Under the watermarks directory, five files (``metric``, ``interval_us``, +``high``, ``mid``, and ``low``) for setting the metric, the time interval +between check of the metric, and the three watermarks exist. You can set and +get the five values by writing to the files, respectively. + +Keywords and meanings of those that can be written to the ``metric`` file are +as below. + + - none: Ignore the watermarks + - free_mem_rate: System's free memory rate (per thousand) + +The ``interval`` should written in microseconds unit. + +schemes/<N>/filters/ +-------------------- + +The directory for the :ref:`filters <damon_design_damos_filters>` of the given +DAMON-based operation scheme. + +In the beginning, this directory has only one file, ``nr_filters``. Writing a +number (``N``) to the file creates the number of child directories named ``0`` +to ``N-1``. Each directory represents each filter. The filters are evaluated +in the numeric order. + +Each filter directory contains six files, namely ``type``, ``matcing``, +``memcg_path``, ``addr_start``, ``addr_end``, and ``target_idx``. To ``type`` +file, you can write one of four special keywords: ``anon`` for anonymous pages, +``memcg`` for specific memory cgroup, ``addr`` for specific address range (an +open-ended interval), or ``target`` for specific DAMON monitoring target +filtering. In case of the memory cgroup filtering, you can specify the memory +cgroup of the interest by writing the path of the memory cgroup from the +cgroups mount point to ``memcg_path`` file. In case of the address range +filtering, you can specify the start and end address of the range to +``addr_start`` and ``addr_end`` files, respectively. For the DAMON monitoring +target filtering, you can specify the index of the target between the list of +the DAMON context's monitoring targets list to ``target_idx`` file. You can +write ``Y`` or ``N`` to ``matching`` file to filter out pages that does or does +not match to the type, respectively. Then, the scheme's action will not be +applied to the pages that specified to be filtered out. + +For example, below restricts a DAMOS action to be applied to only non-anonymous +pages of all memory cgroups except ``/having_care_already``.:: + + # echo 2 > nr_filters + # # filter out anonymous pages + echo anon > 0/type + echo Y > 0/matching + # # further filter out all cgroups except one at '/having_care_already' + echo memcg > 1/type + echo /having_care_already > 1/memcg_path + echo N > 1/matching + +Note that ``anon`` and ``memcg`` filters are currently supported only when +``paddr`` `implementation <sysfs_contexts>` is being used. + +Also, memory regions that are filtered out by ``addr`` or ``target`` filters +are not counted as the scheme has tried to those, while regions that filtered +out by other type filters are counted as the scheme has tried to. The +difference is applied to :ref:`stats <damos_stats>` and +:ref:`tried regions <sysfs_schemes_tried_regions>`. + +.. _sysfs_schemes_stats: + +schemes/<N>/stats/ +------------------ + +DAMON counts the total number and bytes of regions that each scheme is tried to +be applied, the two numbers for the regions that each scheme is successfully +applied, and the total number of the quota limit exceeds. This statistics can +be used for online analysis or tuning of the schemes. + +The statistics can be retrieved by reading the files under ``stats`` directory +(``nr_tried``, ``sz_tried``, ``nr_applied``, ``sz_applied``, and +``qt_exceeds``), respectively. The files are not updated in real time, so you +should ask DAMON sysfs interface to update the content of the files for the +stats by writing a special keyword, ``update_schemes_stats`` to the relevant +``kdamonds/<N>/state`` file. + +.. _sysfs_schemes_tried_regions: + +schemes/<N>/tried_regions/ +-------------------------- + +This directory initially has one file, ``total_bytes``. + +When a special keyword, ``update_schemes_tried_regions``, is written to the +relevant ``kdamonds/<N>/state`` file, DAMON updates the ``total_bytes`` file so +that reading it returns the total size of the scheme tried regions, and creates +directories named integer starting from ``0`` under this directory. Each +directory contains files exposing detailed information about each of the memory +region that the corresponding scheme's ``action`` has tried to be applied under +this directory, during next :ref:`aggregation interval +<sysfs_monitoring_attrs>`. The information includes address range, +``nr_accesses``, and ``age`` of the region. + +Writing ``update_schemes_tried_bytes`` to the relevant ``kdamonds/<N>/state`` +file will only update the ``total_bytes`` file, and will not create the +subdirectories. + +The directories will be removed when another special keyword, +``clear_schemes_tried_regions``, is written to the relevant +``kdamonds/<N>/state`` file. + +The expected usage of this directory is investigations of schemes' behaviors, +and query-like efficient data access monitoring results retrievals. For the +latter use case, in particular, users can set the ``action`` as ``stat`` and +set the ``access pattern`` as their interested pattern that they want to query. + +tried_regions/<N>/ +------------------ + +In each region directory, you will find four files (``start``, ``end``, +``nr_accesses``, and ``age``). Reading the files will show the start and end +addresses, ``nr_accesses``, and ``age`` of the region that corresponding +DAMON-based operation scheme ``action`` has tried to be applied. + +Example +~~~~~~~ + +Below commands applies a scheme saying "If a memory region of size in [4KiB, +8KiB] is showing accesses per aggregate interval in [0, 5] for aggregate +interval in [10, 20], page out the region. For the paging out, use only up to +10ms per second, and also don't page out more than 1GiB per second. Under the +limitation, page out memory regions having longer age first. Also, check the +free memory rate of the system every 5 seconds, start the monitoring and paging +out when the free memory rate becomes lower than 50%, but stop it if the free +memory rate becomes larger than 60%, or lower than 30%". :: + + # cd <sysfs>/kernel/mm/damon/admin + # # populate directories + # echo 1 > kdamonds/nr_kdamonds; echo 1 > kdamonds/0/contexts/nr_contexts; + # echo 1 > kdamonds/0/contexts/0/schemes/nr_schemes + # cd kdamonds/0/contexts/0/schemes/0 + # # set the basic access pattern and the action + # echo 4096 > access_pattern/sz/min + # echo 8192 > access_pattern/sz/max + # echo 0 > access_pattern/nr_accesses/min + # echo 5 > access_pattern/nr_accesses/max + # echo 10 > access_pattern/age/min + # echo 20 > access_pattern/age/max + # echo pageout > action + # # set quotas + # echo 10 > quotas/ms + # echo $((1024*1024*1024)) > quotas/bytes + # echo 1000 > quotas/reset_interval_ms + # # set watermark + # echo free_mem_rate > watermarks/metric + # echo 5000000 > watermarks/interval_us + # echo 600 > watermarks/high + # echo 500 > watermarks/mid + # echo 300 > watermarks/low + +Please note that it's highly recommended to use user space tools like `damo +<https://github.com/awslabs/damo>`_ rather than manually reading and writing +the files as above. Above is only for an example. + +.. _debugfs_interface: + +debugfs Interface (DEPRECATED!) +=============================== + +.. note:: + + THIS IS DEPRECATED! + + DAMON debugfs interface is deprecated, so users should move to the + :ref:`sysfs interface <sysfs_interface>`. If you depend on this and cannot + move, please report your usecase to damon@lists.linux.dev and + linux-mm@kvack.org. + +DAMON exports eight files, ``attrs``, ``target_ids``, ``init_regions``, +``schemes``, ``monitor_on``, ``kdamond_pid``, ``mk_contexts`` and +``rm_contexts`` under its debugfs directory, ``<debugfs>/damon/``. + + +Attributes +---------- + +Users can get and set the ``sampling interval``, ``aggregation interval``, +``update interval``, and min/max number of monitoring target regions by +reading from and writing to the ``attrs`` file. To know about the monitoring +attributes in detail, please refer to the :doc:`/mm/damon/design`. For +example, below commands set those values to 5 ms, 100 ms, 1,000 ms, 10 and +1000, and then check it again:: + + # cd <debugfs>/damon + # echo 5000 100000 1000000 10 1000 > attrs + # cat attrs + 5000 100000 1000000 10 1000 + + +Target IDs +---------- + +Some types of address spaces supports multiple monitoring target. For example, +the virtual memory address spaces monitoring can have multiple processes as the +monitoring targets. Users can set the targets by writing relevant id values of +the targets to, and get the ids of the current targets by reading from the +``target_ids`` file. In case of the virtual address spaces monitoring, the +values should be pids of the monitoring target processes. For example, below +commands set processes having pids 42 and 4242 as the monitoring targets and +check it again:: + + # cd <debugfs>/damon + # echo 42 4242 > target_ids + # cat target_ids + 42 4242 + +Users can also monitor the physical memory address space of the system by +writing a special keyword, "``paddr\n``" to the file. Because physical address +space monitoring doesn't support multiple targets, reading the file will show a +fake value, ``42``, as below:: + + # cd <debugfs>/damon + # echo paddr > target_ids + # cat target_ids + 42 + +Note that setting the target ids doesn't start the monitoring. + + +Initial Monitoring Target Regions +--------------------------------- + +In case of the virtual address space monitoring, DAMON automatically sets and +updates the monitoring target regions so that entire memory mappings of target +processes can be covered. However, users can want to limit the monitoring +region to specific address ranges, such as the heap, the stack, or specific +file-mapped area. Or, some users can know the initial access pattern of their +workloads and therefore want to set optimal initial regions for the 'adaptive +regions adjustment'. + +In contrast, DAMON do not automatically sets and updates the monitoring target +regions in case of physical memory monitoring. Therefore, users should set the +monitoring target regions by themselves. + +In such cases, users can explicitly set the initial monitoring target regions +as they want, by writing proper values to the ``init_regions`` file. The input +should be a sequence of three integers separated by white spaces that represent +one region in below form.:: + + <target idx> <start address> <end address> + +The ``target idx`` should be the index of the target in ``target_ids`` file, +starting from ``0``, and the regions should be passed in address order. For +example, below commands will set a couple of address ranges, ``1-100`` and +``100-200`` as the initial monitoring target region of pid 42, which is the +first one (index ``0``) in ``target_ids``, and another couple of address +ranges, ``20-40`` and ``50-100`` as that of pid 4242, which is the second one +(index ``1``) in ``target_ids``.:: + + # cd <debugfs>/damon + # cat target_ids + 42 4242 + # echo "0 1 100 \ + 0 100 200 \ + 1 20 40 \ + 1 50 100" > init_regions + +Note that this sets the initial monitoring target regions only. In case of +virtual memory monitoring, DAMON will automatically updates the boundary of the +regions after one ``update interval``. Therefore, users should set the +``update interval`` large enough in this case, if they don't want the +update. + + +Schemes +------- + +Users can get and set the DAMON-based operation :ref:`schemes +<damon_design_damos>` by reading from and writing to ``schemes`` debugfs file. +Reading the file also shows the statistics of each scheme. To the file, each +of the schemes should be represented in each line in below form:: + + <target access pattern> <action> <quota> <watermarks> + +You can disable schemes by simply writing an empty string to the file. + +Target Access Pattern +~~~~~~~~~~~~~~~~~~~~~ + +The target access :ref:`pattern <damon_design_damos_access_pattern>` of the +scheme. The ``<target access pattern>`` is constructed with three ranges in +below form:: + + min-size max-size min-acc max-acc min-age max-age + +Specifically, bytes for the size of regions (``min-size`` and ``max-size``), +number of monitored accesses per aggregate interval for access frequency +(``min-acc`` and ``max-acc``), number of aggregate intervals for the age of +regions (``min-age`` and ``max-age``) are specified. Note that the ranges are +closed interval. + +Action +~~~~~~ + +The ``<action>`` is a predefined integer for memory management :ref:`actions +<damon_design_damos_action>`. The supported numbers and their meanings are as +below. + + - 0: Call ``madvise()`` for the region with ``MADV_WILLNEED``. Ignored if + ``target`` is ``paddr``. + - 1: Call ``madvise()`` for the region with ``MADV_COLD``. Ignored if + ``target`` is ``paddr``. + - 2: Call ``madvise()`` for the region with ``MADV_PAGEOUT``. + - 3: Call ``madvise()`` for the region with ``MADV_HUGEPAGE``. Ignored if + ``target`` is ``paddr``. + - 4: Call ``madvise()`` for the region with ``MADV_NOHUGEPAGE``. Ignored if + ``target`` is ``paddr``. + - 5: Do nothing but count the statistics + +Quota +~~~~~ + +Users can set the :ref:`quotas <damon_design_damos_quotas>` of the given scheme +via the ``<quota>`` in below form:: + + <ms> <sz> <reset interval> <priority weights> + +This makes DAMON to try to use only up to ``<ms>`` milliseconds for applying +the action to memory regions of the ``target access pattern`` within the +``<reset interval>`` milliseconds, and to apply the action to only up to +``<sz>`` bytes of memory regions within the ``<reset interval>``. Setting both +``<ms>`` and ``<sz>`` zero disables the quota limits. + +For the :ref:`prioritization <damon_design_damos_quotas_prioritization>`, users +can set the weights for the three properties in ``<priority weights>`` in below +form:: + + <size weight> <access frequency weight> <age weight> + +Watermarks +~~~~~~~~~~ + +Users can specify :ref:`watermarks <damon_design_damos_watermarks>` of the +given scheme via ``<watermarks>`` in below form:: + + <metric> <check interval> <high mark> <middle mark> <low mark> + +``<metric>`` is a predefined integer for the metric to be checked. The +supported numbers and their meanings are as below. + + - 0: Ignore the watermarks + - 1: System's free memory rate (per thousand) + +The value of the metric is checked every ``<check interval>`` microseconds. + +If the value is higher than ``<high mark>`` or lower than ``<low mark>``, the +scheme is deactivated. If the value is lower than ``<mid mark>``, the scheme +is activated. + +.. _damos_stats: + +Statistics +~~~~~~~~~~ + +It also counts the total number and bytes of regions that each scheme is tried +to be applied, the two numbers for the regions that each scheme is successfully +applied, and the total number of the quota limit exceeds. This statistics can +be used for online analysis or tuning of the schemes. + +The statistics can be shown by reading the ``schemes`` file. Reading the file +will show each scheme you entered in each line, and the five numbers for the +statistics will be added at the end of each line. + +Example +~~~~~~~ + +Below commands applies a scheme saying "If a memory region of size in [4KiB, +8KiB] is showing accesses per aggregate interval in [0, 5] for aggregate +interval in [10, 20], page out the region. For the paging out, use only up to +10ms per second, and also don't page out more than 1GiB per second. Under the +limitation, page out memory regions having longer age first. Also, check the +free memory rate of the system every 5 seconds, start the monitoring and paging +out when the free memory rate becomes lower than 50%, but stop it if the free +memory rate becomes larger than 60%, or lower than 30%".:: + + # cd <debugfs>/damon + # scheme="4096 8192 0 5 10 20 2" # target access pattern and action + # scheme+=" 10 $((1024*1024*1024)) 1000" # quotas + # scheme+=" 0 0 100" # prioritization weights + # scheme+=" 1 5000000 600 500 300" # watermarks + # echo "$scheme" > schemes + + +Turning On/Off +-------------- + +Setting the files as described above doesn't incur effect unless you explicitly +start the monitoring. You can start, stop, and check the current status of the +monitoring by writing to and reading from the ``monitor_on`` file. Writing +``on`` to the file starts the monitoring of the targets with the attributes. +Writing ``off`` to the file stops those. DAMON also stops if every target +process is terminated. Below example commands turn on, off, and check the +status of DAMON:: + + # cd <debugfs>/damon + # echo on > monitor_on + # echo off > monitor_on + # cat monitor_on + off + +Please note that you cannot write to the above-mentioned debugfs files while +the monitoring is turned on. If you write to the files while DAMON is running, +an error code such as ``-EBUSY`` will be returned. + + +Monitoring Thread PID +--------------------- + +DAMON does requested monitoring with a kernel thread called ``kdamond``. You +can get the pid of the thread by reading the ``kdamond_pid`` file. When the +monitoring is turned off, reading the file returns ``none``. :: + + # cd <debugfs>/damon + # cat monitor_on + off + # cat kdamond_pid + none + # echo on > monitor_on + # cat kdamond_pid + 18594 + + +Using Multiple Monitoring Threads +--------------------------------- + +One ``kdamond`` thread is created for each monitoring context. You can create +and remove monitoring contexts for multiple ``kdamond`` required use case using +the ``mk_contexts`` and ``rm_contexts`` files. + +Writing the name of the new context to the ``mk_contexts`` file creates a +directory of the name on the DAMON debugfs directory. The directory will have +DAMON debugfs files for the context. :: + + # cd <debugfs>/damon + # ls foo + # ls: cannot access 'foo': No such file or directory + # echo foo > mk_contexts + # ls foo + # attrs init_regions kdamond_pid schemes target_ids + +If the context is not needed anymore, you can remove it and the corresponding +directory by putting the name of the context to the ``rm_contexts`` file. :: + + # echo foo > rm_contexts + # ls foo + # ls: cannot access 'foo': No such file or directory + +Note that ``mk_contexts``, ``rm_contexts``, and ``monitor_on`` files are in the +root directory only. + + +.. _tracepoint: + +Tracepoint for Monitoring Results +================================= + +Users can get the monitoring results via the :ref:`tried_regions +<sysfs_schemes_tried_regions>` or a tracepoint, ``damon:damon_aggregated``. +While the tried regions directory is useful for getting a snapshot, the +tracepoint is useful for getting a full record of the results. While the +monitoring is turned on, you could record the tracepoint events and show +results using tracepoint supporting tools like ``perf``. For example:: + + # echo on > monitor_on + # perf record -e damon:damon_aggregated & + # sleep 5 + # kill 9 $(pidof perf) + # echo off > monitor_on + # perf script diff --git a/Documentation/admin-guide/mm/hugetlbpage.rst b/Documentation/admin-guide/mm/hugetlbpage.rst new file mode 100644 index 000000000..e4d4b4a8d --- /dev/null +++ b/Documentation/admin-guide/mm/hugetlbpage.rst @@ -0,0 +1,473 @@ +============= +HugeTLB Pages +============= + +Overview +======== + +The intent of this file is to give a brief summary of hugetlbpage support in +the Linux kernel. This support is built on top of multiple page size support +that is provided by most modern architectures. For example, x86 CPUs normally +support 4K and 2M (1G if architecturally supported) page sizes, ia64 +architecture supports multiple page sizes 4K, 8K, 64K, 256K, 1M, 4M, 16M, +256M and ppc64 supports 4K and 16M. A TLB is a cache of virtual-to-physical +translations. Typically this is a very scarce resource on processor. +Operating systems try to make best use of limited number of TLB resources. +This optimization is more critical now as bigger and bigger physical memories +(several GBs) are more readily available. + +Users can use the huge page support in Linux kernel by either using the mmap +system call or standard SYSV shared memory system calls (shmget, shmat). + +First the Linux kernel needs to be built with the CONFIG_HUGETLBFS +(present under "File systems") and CONFIG_HUGETLB_PAGE (selected +automatically when CONFIG_HUGETLBFS is selected) configuration +options. + +The ``/proc/meminfo`` file provides information about the total number of +persistent hugetlb pages in the kernel's huge page pool. It also displays +default huge page size and information about the number of free, reserved +and surplus huge pages in the pool of huge pages of default size. +The huge page size is needed for generating the proper alignment and +size of the arguments to system calls that map huge page regions. + +The output of ``cat /proc/meminfo`` will include lines like:: + + HugePages_Total: uuu + HugePages_Free: vvv + HugePages_Rsvd: www + HugePages_Surp: xxx + Hugepagesize: yyy kB + Hugetlb: zzz kB + +where: + +HugePages_Total + is the size of the pool of huge pages. +HugePages_Free + is the number of huge pages in the pool that are not yet + allocated. +HugePages_Rsvd + is short for "reserved," and is the number of huge pages for + which a commitment to allocate from the pool has been made, + but no allocation has yet been made. Reserved huge pages + guarantee that an application will be able to allocate a + huge page from the pool of huge pages at fault time. +HugePages_Surp + is short for "surplus," and is the number of huge pages in + the pool above the value in ``/proc/sys/vm/nr_hugepages``. The + maximum number of surplus huge pages is controlled by + ``/proc/sys/vm/nr_overcommit_hugepages``. + Note: When the feature of freeing unused vmemmap pages associated + with each hugetlb page is enabled, the number of surplus huge pages + may be temporarily larger than the maximum number of surplus huge + pages when the system is under memory pressure. +Hugepagesize + is the default hugepage size (in kB). +Hugetlb + is the total amount of memory (in kB), consumed by huge + pages of all sizes. + If huge pages of different sizes are in use, this number + will exceed HugePages_Total \* Hugepagesize. To get more + detailed information, please, refer to + ``/sys/kernel/mm/hugepages`` (described below). + + +``/proc/filesystems`` should also show a filesystem of type "hugetlbfs" +configured in the kernel. + +``/proc/sys/vm/nr_hugepages`` indicates the current number of "persistent" huge +pages in the kernel's huge page pool. "Persistent" huge pages will be +returned to the huge page pool when freed by a task. A user with root +privileges can dynamically allocate more or free some persistent huge pages +by increasing or decreasing the value of ``nr_hugepages``. + +Note: When the feature of freeing unused vmemmap pages associated with each +hugetlb page is enabled, we can fail to free the huge pages triggered by +the user when the system is under memory pressure. Please try again later. + +Pages that are used as huge pages are reserved inside the kernel and cannot +be used for other purposes. Huge pages cannot be swapped out under +memory pressure. + +Once a number of huge pages have been pre-allocated to the kernel huge page +pool, a user with appropriate privilege can use either the mmap system call +or shared memory system calls to use the huge pages. See the discussion of +:ref:`Using Huge Pages <using_huge_pages>`, below. + +The administrator can allocate persistent huge pages on the kernel boot +command line by specifying the "hugepages=N" parameter, where 'N' = the +number of huge pages requested. This is the most reliable method of +allocating huge pages as memory has not yet become fragmented. + +Some platforms support multiple huge page sizes. To allocate huge pages +of a specific size, one must precede the huge pages boot command parameters +with a huge page size selection parameter "hugepagesz=<size>". <size> must +be specified in bytes with optional scale suffix [kKmMgG]. The default huge +page size may be selected with the "default_hugepagesz=<size>" boot parameter. + +Hugetlb boot command line parameter semantics + +hugepagesz + Specify a huge page size. Used in conjunction with hugepages + parameter to preallocate a number of huge pages of the specified + size. Hence, hugepagesz and hugepages are typically specified in + pairs such as:: + + hugepagesz=2M hugepages=512 + + hugepagesz can only be specified once on the command line for a + specific huge page size. Valid huge page sizes are architecture + dependent. +hugepages + Specify the number of huge pages to preallocate. This typically + follows a valid hugepagesz or default_hugepagesz parameter. However, + if hugepages is the first or only hugetlb command line parameter it + implicitly specifies the number of huge pages of default size to + allocate. If the number of huge pages of default size is implicitly + specified, it can not be overwritten by a hugepagesz,hugepages + parameter pair for the default size. This parameter also has a + node format. The node format specifies the number of huge pages + to allocate on specific nodes. + + For example, on an architecture with 2M default huge page size:: + + hugepages=256 hugepagesz=2M hugepages=512 + + will result in 256 2M huge pages being allocated and a warning message + indicating that the hugepages=512 parameter is ignored. If a hugepages + parameter is preceded by an invalid hugepagesz parameter, it will + be ignored. + + Node format example:: + + hugepagesz=2M hugepages=0:1,1:2 + + It will allocate 1 2M hugepage on node0 and 2 2M hugepages on node1. + If the node number is invalid, the parameter will be ignored. + +default_hugepagesz + Specify the default huge page size. This parameter can + only be specified once on the command line. default_hugepagesz can + optionally be followed by the hugepages parameter to preallocate a + specific number of huge pages of default size. The number of default + sized huge pages to preallocate can also be implicitly specified as + mentioned in the hugepages section above. Therefore, on an + architecture with 2M default huge page size:: + + hugepages=256 + default_hugepagesz=2M hugepages=256 + hugepages=256 default_hugepagesz=2M + + will all result in 256 2M huge pages being allocated. Valid default + huge page size is architecture dependent. +hugetlb_free_vmemmap + When CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is set, this enables HugeTLB + Vmemmap Optimization (HVO). + +When multiple huge page sizes are supported, ``/proc/sys/vm/nr_hugepages`` +indicates the current number of pre-allocated huge pages of the default size. +Thus, one can use the following command to dynamically allocate/deallocate +default sized persistent huge pages:: + + echo 20 > /proc/sys/vm/nr_hugepages + +This command will try to adjust the number of default sized huge pages in the +huge page pool to 20, allocating or freeing huge pages, as required. + +On a NUMA platform, the kernel will attempt to distribute the huge page pool +over all the set of allowed nodes specified by the NUMA memory policy of the +task that modifies ``nr_hugepages``. The default for the allowed nodes--when the +task has default memory policy--is all on-line nodes with memory. Allowed +nodes with insufficient available, contiguous memory for a huge page will be +silently skipped when allocating persistent huge pages. See the +:ref:`discussion below <mem_policy_and_hp_alloc>` +of the interaction of task memory policy, cpusets and per node attributes +with the allocation and freeing of persistent huge pages. + +The success or failure of huge page allocation depends on the amount of +physically contiguous memory that is present in system at the time of the +allocation attempt. If the kernel is unable to allocate huge pages from +some nodes in a NUMA system, it will attempt to make up the difference by +allocating extra pages on other nodes with sufficient available contiguous +memory, if any. + +System administrators may want to put this command in one of the local rc +init files. This will enable the kernel to allocate huge pages early in +the boot process when the possibility of getting physical contiguous pages +is still very high. Administrators can verify the number of huge pages +actually allocated by checking the sysctl or meminfo. To check the per node +distribution of huge pages in a NUMA system, use:: + + cat /sys/devices/system/node/node*/meminfo | fgrep Huge + +``/proc/sys/vm/nr_overcommit_hugepages`` specifies how large the pool of +huge pages can grow, if more huge pages than ``/proc/sys/vm/nr_hugepages`` are +requested by applications. Writing any non-zero value into this file +indicates that the hugetlb subsystem is allowed to try to obtain that +number of "surplus" huge pages from the kernel's normal page pool, when the +persistent huge page pool is exhausted. As these surplus huge pages become +unused, they are freed back to the kernel's normal page pool. + +When increasing the huge page pool size via ``nr_hugepages``, any existing +surplus pages will first be promoted to persistent huge pages. Then, additional +huge pages will be allocated, if necessary and if possible, to fulfill +the new persistent huge page pool size. + +The administrator may shrink the pool of persistent huge pages for +the default huge page size by setting the ``nr_hugepages`` sysctl to a +smaller value. The kernel will attempt to balance the freeing of huge pages +across all nodes in the memory policy of the task modifying ``nr_hugepages``. +Any free huge pages on the selected nodes will be freed back to the kernel's +normal page pool. + +Caveat: Shrinking the persistent huge page pool via ``nr_hugepages`` such that +it becomes less than the number of huge pages in use will convert the balance +of the in-use huge pages to surplus huge pages. This will occur even if +the number of surplus pages would exceed the overcommit value. As long as +this condition holds--that is, until ``nr_hugepages+nr_overcommit_hugepages`` is +increased sufficiently, or the surplus huge pages go out of use and are freed-- +no more surplus huge pages will be allowed to be allocated. + +With support for multiple huge page pools at run-time available, much of +the huge page userspace interface in ``/proc/sys/vm`` has been duplicated in +sysfs. +The ``/proc`` interfaces discussed above have been retained for backwards +compatibility. The root huge page control directory in sysfs is:: + + /sys/kernel/mm/hugepages + +For each huge page size supported by the running kernel, a subdirectory +will exist, of the form:: + + hugepages-${size}kB + +Inside each of these directories, the set of files contained in ``/proc`` +will exist. In addition, two additional interfaces for demoting huge +pages may exist:: + + demote + demote_size + nr_hugepages + nr_hugepages_mempolicy + nr_overcommit_hugepages + free_hugepages + resv_hugepages + surplus_hugepages + +The demote interfaces provide the ability to split a huge page into +smaller huge pages. For example, the x86 architecture supports both +1GB and 2MB huge pages sizes. A 1GB huge page can be split into 512 +2MB huge pages. Demote interfaces are not available for the smallest +huge page size. The demote interfaces are: + +demote_size + is the size of demoted pages. When a page is demoted a corresponding + number of huge pages of demote_size will be created. By default, + demote_size is set to the next smaller huge page size. If there are + multiple smaller huge page sizes, demote_size can be set to any of + these smaller sizes. Only huge page sizes less than the current huge + pages size are allowed. + +demote + is used to demote a number of huge pages. A user with root privileges + can write to this file. It may not be possible to demote the + requested number of huge pages. To determine how many pages were + actually demoted, compare the value of nr_hugepages before and after + writing to the demote interface. demote is a write only interface. + +The interfaces which are the same as in ``/proc`` (all except demote and +demote_size) function as described above for the default huge page-sized case. + +.. _mem_policy_and_hp_alloc: + +Interaction of Task Memory Policy with Huge Page Allocation/Freeing +=================================================================== + +Whether huge pages are allocated and freed via the ``/proc`` interface or +the ``/sysfs`` interface using the ``nr_hugepages_mempolicy`` attribute, the +NUMA nodes from which huge pages are allocated or freed are controlled by the +NUMA memory policy of the task that modifies the ``nr_hugepages_mempolicy`` +sysctl or attribute. When the ``nr_hugepages`` attribute is used, mempolicy +is ignored. + +The recommended method to allocate or free huge pages to/from the kernel +huge page pool, using the ``nr_hugepages`` example above, is:: + + numactl --interleave <node-list> echo 20 \ + >/proc/sys/vm/nr_hugepages_mempolicy + +or, more succinctly:: + + numactl -m <node-list> echo 20 >/proc/sys/vm/nr_hugepages_mempolicy + +This will allocate or free ``abs(20 - nr_hugepages)`` to or from the nodes +specified in <node-list>, depending on whether number of persistent huge pages +is initially less than or greater than 20, respectively. No huge pages will be +allocated nor freed on any node not included in the specified <node-list>. + +When adjusting the persistent hugepage count via ``nr_hugepages_mempolicy``, any +memory policy mode--bind, preferred, local or interleave--may be used. The +resulting effect on persistent huge page allocation is as follows: + +#. Regardless of mempolicy mode [see + Documentation/admin-guide/mm/numa_memory_policy.rst], + persistent huge pages will be distributed across the node or nodes + specified in the mempolicy as if "interleave" had been specified. + However, if a node in the policy does not contain sufficient contiguous + memory for a huge page, the allocation will not "fallback" to the nearest + neighbor node with sufficient contiguous memory. To do this would cause + undesirable imbalance in the distribution of the huge page pool, or + possibly, allocation of persistent huge pages on nodes not allowed by + the task's memory policy. + +#. One or more nodes may be specified with the bind or interleave policy. + If more than one node is specified with the preferred policy, only the + lowest numeric id will be used. Local policy will select the node where + the task is running at the time the nodes_allowed mask is constructed. + For local policy to be deterministic, the task must be bound to a cpu or + cpus in a single node. Otherwise, the task could be migrated to some + other node at any time after launch and the resulting node will be + indeterminate. Thus, local policy is not very useful for this purpose. + Any of the other mempolicy modes may be used to specify a single node. + +#. The nodes allowed mask will be derived from any non-default task mempolicy, + whether this policy was set explicitly by the task itself or one of its + ancestors, such as numactl. This means that if the task is invoked from a + shell with non-default policy, that policy will be used. One can specify a + node list of "all" with numactl --interleave or --membind [-m] to achieve + interleaving over all nodes in the system or cpuset. + +#. Any task mempolicy specified--e.g., using numactl--will be constrained by + the resource limits of any cpuset in which the task runs. Thus, there will + be no way for a task with non-default policy running in a cpuset with a + subset of the system nodes to allocate huge pages outside the cpuset + without first moving to a cpuset that contains all of the desired nodes. + +#. Boot-time huge page allocation attempts to distribute the requested number + of huge pages over all on-lines nodes with memory. + +Per Node Hugepages Attributes +============================= + +A subset of the contents of the root huge page control directory in sysfs, +described above, will be replicated under each the system device of each +NUMA node with memory in:: + + /sys/devices/system/node/node[0-9]*/hugepages/ + +Under this directory, the subdirectory for each supported huge page size +contains the following attribute files:: + + nr_hugepages + free_hugepages + surplus_hugepages + +The free\_' and surplus\_' attribute files are read-only. They return the number +of free and surplus [overcommitted] huge pages, respectively, on the parent +node. + +The ``nr_hugepages`` attribute returns the total number of huge pages on the +specified node. When this attribute is written, the number of persistent huge +pages on the parent node will be adjusted to the specified value, if sufficient +resources exist, regardless of the task's mempolicy or cpuset constraints. + +Note that the number of overcommit and reserve pages remain global quantities, +as we don't know until fault time, when the faulting task's mempolicy is +applied, from which node the huge page allocation will be attempted. + +.. _using_huge_pages: + +Using Huge Pages +================ + +If the user applications are going to request huge pages using mmap system +call, then it is required that system administrator mount a file system of +type hugetlbfs:: + + mount -t hugetlbfs \ + -o uid=<value>,gid=<value>,mode=<value>,pagesize=<value>,size=<value>,\ + min_size=<value>,nr_inodes=<value> none /mnt/huge + +This command mounts a (pseudo) filesystem of type hugetlbfs on the directory +``/mnt/huge``. Any file created on ``/mnt/huge`` uses huge pages. + +The ``uid`` and ``gid`` options sets the owner and group of the root of the +file system. By default the ``uid`` and ``gid`` of the current process +are taken. + +The ``mode`` option sets the mode of root of file system to value & 01777. +This value is given in octal. By default the value 0755 is picked. + +If the platform supports multiple huge page sizes, the ``pagesize`` option can +be used to specify the huge page size and associated pool. ``pagesize`` +is specified in bytes. If ``pagesize`` is not specified the platform's +default huge page size and associated pool will be used. + +The ``size`` option sets the maximum value of memory (huge pages) allowed +for that filesystem (``/mnt/huge``). The ``size`` option can be specified +in bytes, or as a percentage of the specified huge page pool (``nr_hugepages``). +The size is rounded down to HPAGE_SIZE boundary. + +The ``min_size`` option sets the minimum value of memory (huge pages) allowed +for the filesystem. ``min_size`` can be specified in the same way as ``size``, +either bytes or a percentage of the huge page pool. +At mount time, the number of huge pages specified by ``min_size`` are reserved +for use by the filesystem. +If there are not enough free huge pages available, the mount will fail. +As huge pages are allocated to the filesystem and freed, the reserve count +is adjusted so that the sum of allocated and reserved huge pages is always +at least ``min_size``. + +The option ``nr_inodes`` sets the maximum number of inodes that ``/mnt/huge`` +can use. + +If the ``size``, ``min_size`` or ``nr_inodes`` option is not provided on +command line then no limits are set. + +For ``pagesize``, ``size``, ``min_size`` and ``nr_inodes`` options, you can +use [G|g]/[M|m]/[K|k] to represent giga/mega/kilo. +For example, size=2K has the same meaning as size=2048. + +While read system calls are supported on files that reside on hugetlb +file systems, write system calls are not. + +Regular chown, chgrp, and chmod commands (with right permissions) could be +used to change the file attributes on hugetlbfs. + +Also, it is important to note that no such mount command is required if +applications are going to use only shmat/shmget system calls or mmap with +MAP_HUGETLB. For an example of how to use mmap with MAP_HUGETLB see +:ref:`map_hugetlb <map_hugetlb>` below. + +Users who wish to use hugetlb memory via shared memory segment should be +members of a supplementary group and system admin needs to configure that gid +into ``/proc/sys/vm/hugetlb_shm_group``. It is possible for same or different +applications to use any combination of mmaps and shm* calls, though the mount of +filesystem will be required for using mmap calls without MAP_HUGETLB. + +Syscalls that operate on memory backed by hugetlb pages only have their lengths +aligned to the native page size of the processor; they will normally fail with +errno set to EINVAL or exclude hugetlb pages that extend beyond the length if +not hugepage aligned. For example, munmap(2) will fail if memory is backed by +a hugetlb page and the length is smaller than the hugepage size. + + +Examples +======== + +.. _map_hugetlb: + +``map_hugetlb`` + see tools/testing/selftests/mm/map_hugetlb.c + +``hugepage-shm`` + see tools/testing/selftests/mm/hugepage-shm.c + +``hugepage-mmap`` + see tools/testing/selftests/mm/hugepage-mmap.c + +The `libhugetlbfs`_ library provides a wide range of userspace tools +to help with huge page usability, environment setup, and control. + +.. _libhugetlbfs: https://github.com/libhugetlbfs/libhugetlbfs diff --git a/Documentation/admin-guide/mm/idle_page_tracking.rst b/Documentation/admin-guide/mm/idle_page_tracking.rst new file mode 100644 index 000000000..16fcf38da --- /dev/null +++ b/Documentation/admin-guide/mm/idle_page_tracking.rst @@ -0,0 +1,118 @@ +================== +Idle Page Tracking +================== + +Motivation +========== + +The idle page tracking feature allows to track which memory pages are being +accessed by a workload and which are idle. This information can be useful for +estimating the workload's working set size, which, in turn, can be taken into +account when configuring the workload parameters, setting memory cgroup limits, +or deciding where to place the workload within a compute cluster. + +It is enabled by CONFIG_IDLE_PAGE_TRACKING=y. + +.. _user_api: + +User API +======== + +The idle page tracking API is located at ``/sys/kernel/mm/page_idle``. +Currently, it consists of the only read-write file, +``/sys/kernel/mm/page_idle/bitmap``. + +The file implements a bitmap where each bit corresponds to a memory page. The +bitmap is represented by an array of 8-byte integers, and the page at PFN #i is +mapped to bit #i%64 of array element #i/64, byte order is native. When a bit is +set, the corresponding page is idle. + +A page is considered idle if it has not been accessed since it was marked idle +(for more details on what "accessed" actually means see the :ref:`Implementation +Details <impl_details>` section). +To mark a page idle one has to set the bit corresponding to +the page by writing to the file. A value written to the file is OR-ed with the +current bitmap value. + +Only accesses to user memory pages are tracked. These are pages mapped to a +process address space, page cache and buffer pages, swap cache pages. For other +page types (e.g. SLAB pages) an attempt to mark a page idle is silently ignored, +and hence such pages are never reported idle. + +For huge pages the idle flag is set only on the head page, so one has to read +``/proc/kpageflags`` in order to correctly count idle huge pages. + +Reading from or writing to ``/sys/kernel/mm/page_idle/bitmap`` will return +-EINVAL if you are not starting the read/write on an 8-byte boundary, or +if the size of the read/write is not a multiple of 8 bytes. Writing to +this file beyond max PFN will return -ENXIO. + +That said, in order to estimate the amount of pages that are not used by a +workload one should: + + 1. Mark all the workload's pages as idle by setting corresponding bits in + ``/sys/kernel/mm/page_idle/bitmap``. The pages can be found by reading + ``/proc/pid/pagemap`` if the workload is represented by a process, or by + filtering out alien pages using ``/proc/kpagecgroup`` in case the workload + is placed in a memory cgroup. + + 2. Wait until the workload accesses its working set. + + 3. Read ``/sys/kernel/mm/page_idle/bitmap`` and count the number of bits set. + If one wants to ignore certain types of pages, e.g. mlocked pages since they + are not reclaimable, he or she can filter them out using + ``/proc/kpageflags``. + +The page-types tool in the tools/mm directory can be used to assist in this. +If the tool is run initially with the appropriate option, it will mark all the +queried pages as idle. Subsequent runs of the tool can then show which pages have +their idle flag cleared in the interim. + +See Documentation/admin-guide/mm/pagemap.rst for more information about +``/proc/pid/pagemap``, ``/proc/kpageflags``, and ``/proc/kpagecgroup``. + +.. _impl_details: + +Implementation Details +====================== + +The kernel internally keeps track of accesses to user memory pages in order to +reclaim unreferenced pages first on memory shortage conditions. A page is +considered referenced if it has been recently accessed via a process address +space, in which case one or more PTEs it is mapped to will have the Accessed bit +set, or marked accessed explicitly by the kernel (see mark_page_accessed()). The +latter happens when: + + - a userspace process reads or writes a page using a system call (e.g. read(2) + or write(2)) + + - a page that is used for storing filesystem buffers is read or written, + because a process needs filesystem metadata stored in it (e.g. lists a + directory tree) + + - a page is accessed by a device driver using get_user_pages() + +When a dirty page is written to swap or disk as a result of memory reclaim or +exceeding the dirty memory limit, it is not marked referenced. + +The idle memory tracking feature adds a new page flag, the Idle flag. This flag +is set manually, by writing to ``/sys/kernel/mm/page_idle/bitmap`` (see the +:ref:`User API <user_api>` +section), and cleared automatically whenever a page is referenced as defined +above. + +When a page is marked idle, the Accessed bit must be cleared in all PTEs it is +mapped to, otherwise we will not be able to detect accesses to the page coming +from a process address space. To avoid interference with the reclaimer, which, +as noted above, uses the Accessed bit to promote actively referenced pages, one +more page flag is introduced, the Young flag. When the PTE Accessed bit is +cleared as a result of setting or updating a page's Idle flag, the Young flag +is set on the page. The reclaimer treats the Young flag as an extra PTE +Accessed bit and therefore will consider such a page as referenced. + +Since the idle memory tracking feature is based on the memory reclaimer logic, +it only works with pages that are on an LRU list, other pages are silently +ignored. That means it will ignore a user memory page if it is isolated, but +since there are usually not many of them, it should not affect the overall +result noticeably. In order not to stall scanning of the idle page bitmap, +locked pages may be skipped too. diff --git a/Documentation/admin-guide/mm/index.rst b/Documentation/admin-guide/mm/index.rst new file mode 100644 index 000000000..1f883abf3 --- /dev/null +++ b/Documentation/admin-guide/mm/index.rst @@ -0,0 +1,44 @@ +================= +Memory Management +================= + +Linux memory management subsystem is responsible, as the name implies, +for managing the memory in the system. This includes implementation of +virtual memory and demand paging, memory allocation both for kernel +internal structures and user space programs, mapping of files into +processes address space and many other cool things. + +Linux memory management is a complex system with many configurable +settings. Most of these settings are available via ``/proc`` +filesystem and can be quired and adjusted using ``sysctl``. These APIs +are described in Documentation/admin-guide/sysctl/vm.rst and in `man 5 proc`_. + +.. _man 5 proc: http://man7.org/linux/man-pages/man5/proc.5.html + +Linux memory management has its own jargon and if you are not yet +familiar with it, consider reading Documentation/admin-guide/mm/concepts.rst. + +Here we document in detail how to interact with various mechanisms in +the Linux memory management. + +.. toctree:: + :maxdepth: 1 + + concepts + cma_debugfs + damon/index + hugetlbpage + idle_page_tracking + ksm + memory-hotplug + multigen_lru + nommu-mmap + numa_memory_policy + numaperf + pagemap + shrinker_debugfs + soft-dirty + swap_numa + transhuge + userfaultfd + zswap diff --git a/Documentation/admin-guide/mm/ksm.rst b/Documentation/admin-guide/mm/ksm.rst new file mode 100644 index 000000000..776f244bd --- /dev/null +++ b/Documentation/admin-guide/mm/ksm.rst @@ -0,0 +1,257 @@ +======================= +Kernel Samepage Merging +======================= + +Overview +======== + +KSM is a memory-saving de-duplication feature, enabled by CONFIG_KSM=y, +added to the Linux kernel in 2.6.32. See ``mm/ksm.c`` for its implementation, +and http://lwn.net/Articles/306704/ and https://lwn.net/Articles/330589/ + +KSM was originally developed for use with KVM (where it was known as +Kernel Shared Memory), to fit more virtual machines into physical memory, +by sharing the data common between them. But it can be useful to any +application which generates many instances of the same data. + +The KSM daemon ksmd periodically scans those areas of user memory +which have been registered with it, looking for pages of identical +content which can be replaced by a single write-protected page (which +is automatically copied if a process later wants to update its +content). The amount of pages that KSM daemon scans in a single pass +and the time between the passes are configured using :ref:`sysfs +interface <ksm_sysfs>` + +KSM only merges anonymous (private) pages, never pagecache (file) pages. +KSM's merged pages were originally locked into kernel memory, but can now +be swapped out just like other user pages (but sharing is broken when they +are swapped back in: ksmd must rediscover their identity and merge again). + +Controlling KSM with madvise +============================ + +KSM only operates on those areas of address space which an application +has advised to be likely candidates for merging, by using the madvise(2) +system call:: + + int madvise(addr, length, MADV_MERGEABLE) + +The app may call + +:: + + int madvise(addr, length, MADV_UNMERGEABLE) + +to cancel that advice and restore unshared pages: whereupon KSM +unmerges whatever it merged in that range. Note: this unmerging call +may suddenly require more memory than is available - possibly failing +with EAGAIN, but more probably arousing the Out-Of-Memory killer. + +If KSM is not configured into the running kernel, madvise MADV_MERGEABLE +and MADV_UNMERGEABLE simply fail with EINVAL. If the running kernel was +built with CONFIG_KSM=y, those calls will normally succeed: even if the +KSM daemon is not currently running, MADV_MERGEABLE still registers +the range for whenever the KSM daemon is started; even if the range +cannot contain any pages which KSM could actually merge; even if +MADV_UNMERGEABLE is applied to a range which was never MADV_MERGEABLE. + +If a region of memory must be split into at least one new MADV_MERGEABLE +or MADV_UNMERGEABLE region, the madvise may return ENOMEM if the process +will exceed ``vm.max_map_count`` (see Documentation/admin-guide/sysctl/vm.rst). + +Like other madvise calls, they are intended for use on mapped areas of +the user address space: they will report ENOMEM if the specified range +includes unmapped gaps (though working on the intervening mapped areas), +and might fail with EAGAIN if not enough memory for internal structures. + +Applications should be considerate in their use of MADV_MERGEABLE, +restricting its use to areas likely to benefit. KSM's scans may use a lot +of processing power: some installations will disable KSM for that reason. + +.. _ksm_sysfs: + +KSM daemon sysfs interface +========================== + +The KSM daemon is controlled by sysfs files in ``/sys/kernel/mm/ksm/``, +readable by all but writable only by root: + +pages_to_scan + how many pages to scan before ksmd goes to sleep + e.g. ``echo 100 > /sys/kernel/mm/ksm/pages_to_scan``. + + Default: 100 (chosen for demonstration purposes) + +sleep_millisecs + how many milliseconds ksmd should sleep before next scan + e.g. ``echo 20 > /sys/kernel/mm/ksm/sleep_millisecs`` + + Default: 20 (chosen for demonstration purposes) + +merge_across_nodes + specifies if pages from different NUMA nodes can be merged. + When set to 0, ksm merges only pages which physically reside + in the memory area of same NUMA node. That brings lower + latency to access of shared pages. Systems with more nodes, at + significant NUMA distances, are likely to benefit from the + lower latency of setting 0. Smaller systems, which need to + minimize memory usage, are likely to benefit from the greater + sharing of setting 1 (default). You may wish to compare how + your system performs under each setting, before deciding on + which to use. ``merge_across_nodes`` setting can be changed only + when there are no ksm shared pages in the system: set run 2 to + unmerge pages first, then to 1 after changing + ``merge_across_nodes``, to remerge according to the new setting. + + Default: 1 (merging across nodes as in earlier releases) + +run + * set to 0 to stop ksmd from running but keep merged pages, + * set to 1 to run ksmd e.g. ``echo 1 > /sys/kernel/mm/ksm/run``, + * set to 2 to stop ksmd and unmerge all pages currently merged, but + leave mergeable areas registered for next run. + + Default: 0 (must be changed to 1 to activate KSM, except if + CONFIG_SYSFS is disabled) + +use_zero_pages + specifies whether empty pages (i.e. allocated pages that only + contain zeroes) should be treated specially. When set to 1, + empty pages are merged with the kernel zero page(s) instead of + with each other as it would happen normally. This can improve + the performance on architectures with coloured zero pages, + depending on the workload. Care should be taken when enabling + this setting, as it can potentially degrade the performance of + KSM for some workloads, for example if the checksums of pages + candidate for merging match the checksum of an empty + page. This setting can be changed at any time, it is only + effective for pages merged after the change. + + Default: 0 (normal KSM behaviour as in earlier releases) + +max_page_sharing + Maximum sharing allowed for each KSM page. This enforces a + deduplication limit to avoid high latency for virtual memory + operations that involve traversal of the virtual mappings that + share the KSM page. The minimum value is 2 as a newly created + KSM page will have at least two sharers. The higher this value + the faster KSM will merge the memory and the higher the + deduplication factor will be, but the slower the worst case + virtual mappings traversal could be for any given KSM + page. Slowing down this traversal means there will be higher + latency for certain virtual memory operations happening during + swapping, compaction, NUMA balancing and page migration, in + turn decreasing responsiveness for the caller of those virtual + memory operations. The scheduler latency of other tasks not + involved with the VM operations doing the virtual mappings + traversal is not affected by this parameter as these + traversals are always schedule friendly themselves. + +stable_node_chains_prune_millisecs + specifies how frequently KSM checks the metadata of the pages + that hit the deduplication limit for stale information. + Smaller milllisecs values will free up the KSM metadata with + lower latency, but they will make ksmd use more CPU during the + scan. It's a noop if not a single KSM page hit the + ``max_page_sharing`` yet. + +The effectiveness of KSM and MADV_MERGEABLE is shown in ``/sys/kernel/mm/ksm/``: + +general_profit + how effective is KSM. The calculation is explained below. +pages_scanned + how many pages are being scanned for ksm +pages_shared + how many shared pages are being used +pages_sharing + how many more sites are sharing them i.e. how much saved +pages_unshared + how many pages unique but repeatedly checked for merging +pages_volatile + how many pages changing too fast to be placed in a tree +full_scans + how many times all mergeable areas have been scanned +stable_node_chains + the number of KSM pages that hit the ``max_page_sharing`` limit +stable_node_dups + number of duplicated KSM pages +ksm_zero_pages + how many zero pages that are still mapped into processes were mapped by + KSM when deduplicating. + +When ``use_zero_pages`` is/was enabled, the sum of ``pages_sharing`` + +``ksm_zero_pages`` represents the actual number of pages saved by KSM. +if ``use_zero_pages`` has never been enabled, ``ksm_zero_pages`` is 0. + +A high ratio of ``pages_sharing`` to ``pages_shared`` indicates good +sharing, but a high ratio of ``pages_unshared`` to ``pages_sharing`` +indicates wasted effort. ``pages_volatile`` embraces several +different kinds of activity, but a high proportion there would also +indicate poor use of madvise MADV_MERGEABLE. + +The maximum possible ``pages_sharing/pages_shared`` ratio is limited by the +``max_page_sharing`` tunable. To increase the ratio ``max_page_sharing`` must +be increased accordingly. + +Monitoring KSM profit +===================== + +KSM can save memory by merging identical pages, but also can consume +additional memory, because it needs to generate a number of rmap_items to +save each scanned page's brief rmap information. Some of these pages may +be merged, but some may not be abled to be merged after being checked +several times, which are unprofitable memory consumed. + +1) How to determine whether KSM save memory or consume memory in system-wide + range? Here is a simple approximate calculation for reference:: + + general_profit =~ ksm_saved_pages * sizeof(page) - (all_rmap_items) * + sizeof(rmap_item); + + where ksm_saved_pages equals to the sum of ``pages_sharing`` + + ``ksm_zero_pages`` of the system, and all_rmap_items can be easily + obtained by summing ``pages_sharing``, ``pages_shared``, ``pages_unshared`` + and ``pages_volatile``. + +2) The KSM profit inner a single process can be similarly obtained by the + following approximate calculation:: + + process_profit =~ ksm_saved_pages * sizeof(page) - + ksm_rmap_items * sizeof(rmap_item). + + where ksm_saved_pages equals to the sum of ``ksm_merging_pages`` and + ``ksm_zero_pages``, both of which are shown under the directory + ``/proc/<pid>/ksm_stat``, and ksm_rmap_items is also shown in + ``/proc/<pid>/ksm_stat``. The process profit is also shown in + ``/proc/<pid>/ksm_stat`` as ksm_process_profit. + +From the perspective of application, a high ratio of ``ksm_rmap_items`` to +``ksm_merging_pages`` means a bad madvise-applied policy, so developers or +administrators have to rethink how to change madvise policy. Giving an example +for reference, a page's size is usually 4K, and the rmap_item's size is +separately 32B on 32-bit CPU architecture and 64B on 64-bit CPU architecture. +so if the ``ksm_rmap_items/ksm_merging_pages`` ratio exceeds 64 on 64-bit CPU +or exceeds 128 on 32-bit CPU, then the app's madvise policy should be dropped, +because the ksm profit is approximately zero or negative. + +Monitoring KSM events +===================== + +There are some counters in /proc/vmstat that may be used to monitor KSM events. +KSM might help save memory, it's a tradeoff by may suffering delay on KSM COW +or on swapping in copy. Those events could help users evaluate whether or how +to use KSM. For example, if cow_ksm increases too fast, user may decrease the +range of madvise(, , MADV_MERGEABLE). + +cow_ksm + is incremented every time a KSM page triggers copy on write (COW) + when users try to write to a KSM page, we have to make a copy. + +ksm_swpin_copy + is incremented every time a KSM page is copied when swapping in + note that KSM page might be copied when swapping in because do_swap_page() + cannot do all the locking needed to reconstitute a cross-anon_vma KSM page. + +-- +Izik Eidus, +Hugh Dickins, 17 Nov 2009 diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst new file mode 100644 index 000000000..cfe034cf1 --- /dev/null +++ b/Documentation/admin-guide/mm/memory-hotplug.rst @@ -0,0 +1,695 @@ +================== +Memory Hot(Un)Plug +================== + +This document describes generic Linux support for memory hot(un)plug with +a focus on System RAM, including ZONE_MOVABLE support. + +.. contents:: :local: + +Introduction +============ + +Memory hot(un)plug allows for increasing and decreasing the size of physical +memory available to a machine at runtime. In the simplest case, it consists of +physically plugging or unplugging a DIMM at runtime, coordinated with the +operating system. + +Memory hot(un)plug is used for various purposes: + +- The physical memory available to a machine can be adjusted at runtime, up- or + downgrading the memory capacity. This dynamic memory resizing, sometimes + referred to as "capacity on demand", is frequently used with virtual machines + and logical partitions. + +- Replacing hardware, such as DIMMs or whole NUMA nodes, without downtime. One + example is replacing failing memory modules. + +- Reducing energy consumption either by physically unplugging memory modules or + by logically unplugging (parts of) memory modules from Linux. + +Further, the basic memory hot(un)plug infrastructure in Linux is nowadays also +used to expose persistent memory, other performance-differentiated memory and +reserved memory regions as ordinary system RAM to Linux. + +Linux only supports memory hot(un)plug on selected 64 bit architectures, such as +x86_64, arm64, ppc64, s390x and ia64. + +Memory Hot(Un)Plug Granularity +------------------------------ + +Memory hot(un)plug in Linux uses the SPARSEMEM memory model, which divides the +physical memory address space into chunks of the same size: memory sections. The +size of a memory section is architecture dependent. For example, x86_64 uses +128 MiB and ppc64 uses 16 MiB. + +Memory sections are combined into chunks referred to as "memory blocks". The +size of a memory block is architecture dependent and corresponds to the smallest +granularity that can be hot(un)plugged. The default size of a memory block is +the same as memory section size, unless an architecture specifies otherwise. + +All memory blocks have the same size. + +Phases of Memory Hotplug +------------------------ + +Memory hotplug consists of two phases: + +(1) Adding the memory to Linux +(2) Onlining memory blocks + +In the first phase, metadata, such as the memory map ("memmap") and page tables +for the direct mapping, is allocated and initialized, and memory blocks are +created; the latter also creates sysfs files for managing newly created memory +blocks. + +In the second phase, added memory is exposed to the page allocator. After this +phase, the memory is visible in memory statistics, such as free and total +memory, of the system. + +Phases of Memory Hotunplug +-------------------------- + +Memory hotunplug consists of two phases: + +(1) Offlining memory blocks +(2) Removing the memory from Linux + +In the fist phase, memory is "hidden" from the page allocator again, for +example, by migrating busy memory to other memory locations and removing all +relevant free pages from the page allocator After this phase, the memory is no +longer visible in memory statistics of the system. + +In the second phase, the memory blocks are removed and metadata is freed. + +Memory Hotplug Notifications +============================ + +There are various ways how Linux is notified about memory hotplug events such +that it can start adding hotplugged memory. This description is limited to +systems that support ACPI; mechanisms specific to other firmware interfaces or +virtual machines are not described. + +ACPI Notifications +------------------ + +Platforms that support ACPI, such as x86_64, can support memory hotplug +notifications via ACPI. + +In general, a firmware supporting memory hotplug defines a memory class object +HID "PNP0C80". When notified about hotplug of a new memory device, the ACPI +driver will hotplug the memory to Linux. + +If the firmware supports hotplug of NUMA nodes, it defines an object _HID +"ACPI0004", "PNP0A05", or "PNP0A06". When notified about an hotplug event, all +assigned memory devices are added to Linux by the ACPI driver. + +Similarly, Linux can be notified about requests to hotunplug a memory device or +a NUMA node via ACPI. The ACPI driver will try offlining all relevant memory +blocks, and, if successful, hotunplug the memory from Linux. + +Manual Probing +-------------- + +On some architectures, the firmware may not be able to notify the operating +system about a memory hotplug event. Instead, the memory has to be manually +probed from user space. + +The probe interface is located at:: + + /sys/devices/system/memory/probe + +Only complete memory blocks can be probed. Individual memory blocks are probed +by providing the physical start address of the memory block:: + + % echo addr > /sys/devices/system/memory/probe + +Which results in a memory block for the range [addr, addr + memory_block_size) +being created. + +.. note:: + + Using the probe interface is discouraged as it is easy to crash the kernel, + because Linux cannot validate user input; this interface might be removed in + the future. + +Onlining and Offlining Memory Blocks +==================================== + +After a memory block has been created, Linux has to be instructed to actually +make use of that memory: the memory block has to be "online". + +Before a memory block can be removed, Linux has to stop using any memory part of +the memory block: the memory block has to be "offlined". + +The Linux kernel can be configured to automatically online added memory blocks +and drivers automatically trigger offlining of memory blocks when trying +hotunplug of memory. Memory blocks can only be removed once offlining succeeded +and drivers may trigger offlining of memory blocks when attempting hotunplug of +memory. + +Onlining Memory Blocks Manually +------------------------------- + +If auto-onlining of memory blocks isn't enabled, user-space has to manually +trigger onlining of memory blocks. Often, udev rules are used to automate this +task in user space. + +Onlining of a memory block can be triggered via:: + + % echo online > /sys/devices/system/memory/memoryXXX/state + +Or alternatively:: + + % echo 1 > /sys/devices/system/memory/memoryXXX/online + +The kernel will select the target zone automatically, depending on the +configured ``online_policy``. + +One can explicitly request to associate an offline memory block with +ZONE_MOVABLE by:: + + % echo online_movable > /sys/devices/system/memory/memoryXXX/state + +Or one can explicitly request a kernel zone (usually ZONE_NORMAL) by:: + + % echo online_kernel > /sys/devices/system/memory/memoryXXX/state + +In any case, if onlining succeeds, the state of the memory block is changed to +be "online". If it fails, the state of the memory block will remain unchanged +and the above commands will fail. + +Onlining Memory Blocks Automatically +------------------------------------ + +The kernel can be configured to try auto-onlining of newly added memory blocks. +If this feature is disabled, the memory blocks will stay offline until +explicitly onlined from user space. + +The configured auto-online behavior can be observed via:: + + % cat /sys/devices/system/memory/auto_online_blocks + +Auto-onlining can be enabled by writing ``online``, ``online_kernel`` or +``online_movable`` to that file, like:: + + % echo online > /sys/devices/system/memory/auto_online_blocks + +Similarly to manual onlining, with ``online`` the kernel will select the +target zone automatically, depending on the configured ``online_policy``. + +Modifying the auto-online behavior will only affect all subsequently added +memory blocks only. + +.. note:: + + In corner cases, auto-onlining can fail. The kernel won't retry. Note that + auto-onlining is not expected to fail in default configurations. + +.. note:: + + DLPAR on ppc64 ignores the ``offline`` setting and will still online added + memory blocks; if onlining fails, memory blocks are removed again. + +Offlining Memory Blocks +----------------------- + +In the current implementation, Linux's memory offlining will try migrating all +movable pages off the affected memory block. As most kernel allocations, such as +page tables, are unmovable, page migration can fail and, therefore, inhibit +memory offlining from succeeding. + +Having the memory provided by memory block managed by ZONE_MOVABLE significantly +increases memory offlining reliability; still, memory offlining can fail in +some corner cases. + +Further, memory offlining might retry for a long time (or even forever), until +aborted by the user. + +Offlining of a memory block can be triggered via:: + + % echo offline > /sys/devices/system/memory/memoryXXX/state + +Or alternatively:: + + % echo 0 > /sys/devices/system/memory/memoryXXX/online + +If offlining succeeds, the state of the memory block is changed to be "offline". +If it fails, the state of the memory block will remain unchanged and the above +commands will fail, for example, via:: + + bash: echo: write error: Device or resource busy + +or via:: + + bash: echo: write error: Invalid argument + +Observing the State of Memory Blocks +------------------------------------ + +The state (online/offline/going-offline) of a memory block can be observed +either via:: + + % cat /sys/device/system/memory/memoryXXX/state + +Or alternatively (1/0) via:: + + % cat /sys/device/system/memory/memoryXXX/online + +For an online memory block, the managing zone can be observed via:: + + % cat /sys/device/system/memory/memoryXXX/valid_zones + +Configuring Memory Hot(Un)Plug +============================== + +There are various ways how system administrators can configure memory +hot(un)plug and interact with memory blocks, especially, to online them. + +Memory Hot(Un)Plug Configuration via Sysfs +------------------------------------------ + +Some memory hot(un)plug properties can be configured or inspected via sysfs in:: + + /sys/devices/system/memory/ + +The following files are currently defined: + +====================== ========================================================= +``auto_online_blocks`` read-write: set or get the default state of new memory + blocks; configure auto-onlining. + + The default value depends on the + CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel configuration + option. + + See the ``state`` property of memory blocks for details. +``block_size_bytes`` read-only: the size in bytes of a memory block. +``probe`` write-only: add (probe) selected memory blocks manually + from user space by supplying the physical start address. + + Availability depends on the CONFIG_ARCH_MEMORY_PROBE + kernel configuration option. +``uevent`` read-write: generic udev file for device subsystems. +``crash_hotplug`` read-only: when changes to the system memory map + occur due to hot un/plug of memory, this file contains + '1' if the kernel updates the kdump capture kernel memory + map itself (via elfcorehdr), or '0' if userspace must update + the kdump capture kernel memory map. + + Availability depends on the CONFIG_MEMORY_HOTPLUG kernel + configuration option. +====================== ========================================================= + +.. note:: + + When the CONFIG_MEMORY_FAILURE kernel configuration option is enabled, two + additional files ``hard_offline_page`` and ``soft_offline_page`` are available + to trigger hwpoisoning of pages, for example, for testing purposes. Note that + this functionality is not really related to memory hot(un)plug or actual + offlining of memory blocks. + +Memory Block Configuration via Sysfs +------------------------------------ + +Each memory block is represented as a memory block device that can be +onlined or offlined. All memory blocks have their device information located in +sysfs. Each present memory block is listed under +``/sys/devices/system/memory`` as:: + + /sys/devices/system/memory/memoryXXX + +where XXX is the memory block id; the number of digits is variable. + +A present memory block indicates that some memory in the range is present; +however, a memory block might span memory holes. A memory block spanning memory +holes cannot be offlined. + +For example, assume 1 GiB memory block size. A device for a memory starting at +0x100000000 is ``/sys/device/system/memory/memory4``:: + + (0x100000000 / 1Gib = 4) + +This device covers address range [0x100000000 ... 0x140000000) + +The following files are currently defined: + +=================== ============================================================ +``online`` read-write: simplified interface to trigger onlining / + offlining and to observe the state of a memory block. + When onlining, the zone is selected automatically. +``phys_device`` read-only: legacy interface only ever used on s390x to + expose the covered storage increment. +``phys_index`` read-only: the memory block id (XXX). +``removable`` read-only: legacy interface that indicated whether a memory + block was likely to be offlineable or not. Nowadays, the + kernel return ``1`` if and only if it supports memory + offlining. +``state`` read-write: advanced interface to trigger onlining / + offlining and to observe the state of a memory block. + + When writing, ``online``, ``offline``, ``online_kernel`` and + ``online_movable`` are supported. + + ``online_movable`` specifies onlining to ZONE_MOVABLE. + ``online_kernel`` specifies onlining to the default kernel + zone for the memory block, such as ZONE_NORMAL. + ``online`` let's the kernel select the zone automatically. + + When reading, ``online``, ``offline`` and ``going-offline`` + may be returned. +``uevent`` read-write: generic uevent file for devices. +``valid_zones`` read-only: when a block is online, shows the zone it + belongs to; when a block is offline, shows what zone will + manage it when the block will be onlined. + + For online memory blocks, ``DMA``, ``DMA32``, ``Normal``, + ``Movable`` and ``none`` may be returned. ``none`` indicates + that memory provided by a memory block is managed by + multiple zones or spans multiple nodes; such memory blocks + cannot be offlined. ``Movable`` indicates ZONE_MOVABLE. + Other values indicate a kernel zone. + + For offline memory blocks, the first column shows the + zone the kernel would select when onlining the memory block + right now without further specifying a zone. + + Availability depends on the CONFIG_MEMORY_HOTREMOVE + kernel configuration option. +=================== ============================================================ + +.. note:: + + If the CONFIG_NUMA kernel configuration option is enabled, the memoryXXX/ + directories can also be accessed via symbolic links located in the + ``/sys/devices/system/node/node*`` directories. + + For example:: + + /sys/devices/system/node/node0/memory9 -> ../../memory/memory9 + + A backlink will also be created:: + + /sys/devices/system/memory/memory9/node0 -> ../../node/node0 + +Command Line Parameters +----------------------- + +Some command line parameters affect memory hot(un)plug handling. The following +command line parameters are relevant: + +======================== ======================================================= +``memhp_default_state`` configure auto-onlining by essentially setting + ``/sys/devices/system/memory/auto_online_blocks``. +``movable_node`` configure automatic zone selection in the kernel when + using the ``contig-zones`` online policy. When + set, the kernel will default to ZONE_MOVABLE when + onlining a memory block, unless other zones can be kept + contiguous. +======================== ======================================================= + +See Documentation/admin-guide/kernel-parameters.txt for a more generic +description of these command line parameters. + +Module Parameters +------------------ + +Instead of additional command line parameters or sysfs files, the +``memory_hotplug`` subsystem now provides a dedicated namespace for module +parameters. Module parameters can be set via the command line by predicating +them with ``memory_hotplug.`` such as:: + + memory_hotplug.memmap_on_memory=1 + +and they can be observed (and some even modified at runtime) via:: + + /sys/module/memory_hotplug/parameters/ + +The following module parameters are currently defined: + +================================ =============================================== +``memmap_on_memory`` read-write: Allocate memory for the memmap from + the added memory block itself. Even if enabled, + actual support depends on various other system + properties and should only be regarded as a + hint whether the behavior would be desired. + + While allocating the memmap from the memory + block itself makes memory hotplug less likely + to fail and keeps the memmap on the same NUMA + node in any case, it can fragment physical + memory in a way that huge pages in bigger + granularity cannot be formed on hotplugged + memory. + + With value "force" it could result in memory + wastage due to memmap size limitations. For + example, if the memmap for a memory block + requires 1 MiB, but the pageblock size is 2 + MiB, 1 MiB of hotplugged memory will be wasted. + Note that there are still cases where the + feature cannot be enforced: for example, if the + memmap is smaller than a single page, or if the + architecture does not support the forced mode + in all configurations. + +``online_policy`` read-write: Set the basic policy used for + automatic zone selection when onlining memory + blocks without specifying a target zone. + ``contig-zones`` has been the kernel default + before this parameter was added. After an + online policy was configured and memory was + online, the policy should not be changed + anymore. + + When set to ``contig-zones``, the kernel will + try keeping zones contiguous. If a memory block + intersects multiple zones or no zone, the + behavior depends on the ``movable_node`` kernel + command line parameter: default to ZONE_MOVABLE + if set, default to the applicable kernel zone + (usually ZONE_NORMAL) if not set. + + When set to ``auto-movable``, the kernel will + try onlining memory blocks to ZONE_MOVABLE if + possible according to the configuration and + memory device details. With this policy, one + can avoid zone imbalances when eventually + hotplugging a lot of memory later and still + wanting to be able to hotunplug as much as + possible reliably, very desirable in + virtualized environments. This policy ignores + the ``movable_node`` kernel command line + parameter and isn't really applicable in + environments that require it (e.g., bare metal + with hotunpluggable nodes) where hotplugged + memory might be exposed via the + firmware-provided memory map early during boot + to the system instead of getting detected, + added and onlined later during boot (such as + done by virtio-mem or by some hypervisors + implementing emulated DIMMs). As one example, a + hotplugged DIMM will be onlined either + completely to ZONE_MOVABLE or completely to + ZONE_NORMAL, not a mixture. + As another example, as many memory blocks + belonging to a virtio-mem device will be + onlined to ZONE_MOVABLE as possible, + special-casing units of memory blocks that can + only get hotunplugged together. *This policy + does not protect from setups that are + problematic with ZONE_MOVABLE and does not + change the zone of memory blocks dynamically + after they were onlined.* +``auto_movable_ratio`` read-write: Set the maximum MOVABLE:KERNEL + memory ratio in % for the ``auto-movable`` + online policy. Whether the ratio applies only + for the system across all NUMA nodes or also + per NUMA nodes depends on the + ``auto_movable_numa_aware`` configuration. + + All accounting is based on present memory pages + in the zones combined with accounting per + memory device. Memory dedicated to the CMA + allocator is accounted as MOVABLE, although + residing on one of the kernel zones. The + possible ratio depends on the actual workload. + The kernel default is "301" %, for example, + allowing for hotplugging 24 GiB to a 8 GiB VM + and automatically onlining all hotplugged + memory to ZONE_MOVABLE in many setups. The + additional 1% deals with some pages being not + present, for example, because of some firmware + allocations. + + Note that ZONE_NORMAL memory provided by one + memory device does not allow for more + ZONE_MOVABLE memory for a different memory + device. As one example, onlining memory of a + hotplugged DIMM to ZONE_NORMAL will not allow + for another hotplugged DIMM to get onlined to + ZONE_MOVABLE automatically. In contrast, memory + hotplugged by a virtio-mem device that got + onlined to ZONE_NORMAL will allow for more + ZONE_MOVABLE memory within *the same* + virtio-mem device. +``auto_movable_numa_aware`` read-write: Configure whether the + ``auto_movable_ratio`` in the ``auto-movable`` + online policy also applies per NUMA + node in addition to the whole system across all + NUMA nodes. The kernel default is "Y". + + Disabling NUMA awareness can be helpful when + dealing with NUMA nodes that should be + completely hotunpluggable, onlining the memory + completely to ZONE_MOVABLE automatically if + possible. + + Parameter availability depends on CONFIG_NUMA. +================================ =============================================== + +ZONE_MOVABLE +============ + +ZONE_MOVABLE is an important mechanism for more reliable memory offlining. +Further, having system RAM managed by ZONE_MOVABLE instead of one of the +kernel zones can increase the number of possible transparent huge pages and +dynamically allocated huge pages. + +Most kernel allocations are unmovable. Important examples include the memory +map (usually 1/64ths of memory), page tables, and kmalloc(). Such allocations +can only be served from the kernel zones. + +Most user space pages, such as anonymous memory, and page cache pages are +movable. Such allocations can be served from ZONE_MOVABLE and the kernel zones. + +Only movable allocations are served from ZONE_MOVABLE, resulting in unmovable +allocations being limited to the kernel zones. Without ZONE_MOVABLE, there is +absolutely no guarantee whether a memory block can be offlined successfully. + +Zone Imbalances +--------------- + +Having too much system RAM managed by ZONE_MOVABLE is called a zone imbalance, +which can harm the system or degrade performance. As one example, the kernel +might crash because it runs out of free memory for unmovable allocations, +although there is still plenty of free memory left in ZONE_MOVABLE. + +Usually, MOVABLE:KERNEL ratios of up to 3:1 or even 4:1 are fine. Ratios of 63:1 +are definitely impossible due to the overhead for the memory map. + +Actual safe zone ratios depend on the workload. Extreme cases, like excessive +long-term pinning of pages, might not be able to deal with ZONE_MOVABLE at all. + +.. note:: + + CMA memory part of a kernel zone essentially behaves like memory in + ZONE_MOVABLE and similar considerations apply, especially when combining + CMA with ZONE_MOVABLE. + +ZONE_MOVABLE Sizing Considerations +---------------------------------- + +We usually expect that a large portion of available system RAM will actually +be consumed by user space, either directly or indirectly via the page cache. In +the normal case, ZONE_MOVABLE can be used when allocating such pages just fine. + +With that in mind, it makes sense that we can have a big portion of system RAM +managed by ZONE_MOVABLE. However, there are some things to consider when using +ZONE_MOVABLE, especially when fine-tuning zone ratios: + +- Having a lot of offline memory blocks. Even offline memory blocks consume + memory for metadata and page tables in the direct map; having a lot of offline + memory blocks is not a typical case, though. + +- Memory ballooning without balloon compaction is incompatible with + ZONE_MOVABLE. Only some implementations, such as virtio-balloon and + pseries CMM, fully support balloon compaction. + + Further, the CONFIG_BALLOON_COMPACTION kernel configuration option might be + disabled. In that case, balloon inflation will only perform unmovable + allocations and silently create a zone imbalance, usually triggered by + inflation requests from the hypervisor. + +- Gigantic pages are unmovable, resulting in user space consuming a + lot of unmovable memory. + +- Huge pages are unmovable when an architectures does not support huge + page migration, resulting in a similar issue as with gigantic pages. + +- Page tables are unmovable. Excessive swapping, mapping extremely large + files or ZONE_DEVICE memory can be problematic, although only really relevant + in corner cases. When we manage a lot of user space memory that has been + swapped out or is served from a file/persistent memory/... we still need a lot + of page tables to manage that memory once user space accessed that memory. + +- In certain DAX configurations the memory map for the device memory will be + allocated from the kernel zones. + +- KASAN can have a significant memory overhead, for example, consuming 1/8th of + the total system memory size as (unmovable) tracking metadata. + +- Long-term pinning of pages. Techniques that rely on long-term pinnings + (especially, RDMA and vfio/mdev) are fundamentally problematic with + ZONE_MOVABLE, and therefore, memory offlining. Pinned pages cannot reside + on ZONE_MOVABLE as that would turn these pages unmovable. Therefore, they + have to be migrated off that zone while pinning. Pinning a page can fail + even if there is plenty of free memory in ZONE_MOVABLE. + + In addition, using ZONE_MOVABLE might make page pinning more expensive, + because of the page migration overhead. + +By default, all the memory configured at boot time is managed by the kernel +zones and ZONE_MOVABLE is not used. + +To enable ZONE_MOVABLE to include the memory present at boot and to control the +ratio between movable and kernel zones there are two command line options: +``kernelcore=`` and ``movablecore=``. See +Documentation/admin-guide/kernel-parameters.rst for their description. + +Memory Offlining and ZONE_MOVABLE +--------------------------------- + +Even with ZONE_MOVABLE, there are some corner cases where offlining a memory +block might fail: + +- Memory blocks with memory holes; this applies to memory blocks present during + boot and can apply to memory blocks hotplugged via the XEN balloon and the + Hyper-V balloon. + +- Mixed NUMA nodes and mixed zones within a single memory block prevent memory + offlining; this applies to memory blocks present during boot only. + +- Special memory blocks prevented by the system from getting offlined. Examples + include any memory available during boot on arm64 or memory blocks spanning + the crashkernel area on s390x; this usually applies to memory blocks present + during boot only. + +- Memory blocks overlapping with CMA areas cannot be offlined, this applies to + memory blocks present during boot only. + +- Concurrent activity that operates on the same physical memory area, such as + allocating gigantic pages, can result in temporary offlining failures. + +- Out of memory when dissolving huge pages, especially when HugeTLB Vmemmap + Optimization (HVO) is enabled. + + Offlining code may be able to migrate huge page contents, but may not be able + to dissolve the source huge page because it fails allocating (unmovable) pages + for the vmemmap, because the system might not have free memory in the kernel + zones left. + + Users that depend on memory offlining to succeed for movable zones should + carefully consider whether the memory savings gained from this feature are + worth the risk of possibly not being able to offline memory in certain + situations. + +Further, when running into out of memory situations while migrating pages, or +when still encountering permanently unmovable pages within ZONE_MOVABLE +(-> BUG), memory offlining will keep retrying until it eventually succeeds. + +When offlining is triggered from user space, the offlining context can be +terminated by sending a signal. A timeout based offlining can easily be +implemented via:: + + % timeout $TIMEOUT offline_block | failure_handling diff --git a/Documentation/admin-guide/mm/multigen_lru.rst b/Documentation/admin-guide/mm/multigen_lru.rst new file mode 100644 index 000000000..33e068830 --- /dev/null +++ b/Documentation/admin-guide/mm/multigen_lru.rst @@ -0,0 +1,162 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============= +Multi-Gen LRU +============= +The multi-gen LRU is an alternative LRU implementation that optimizes +page reclaim and improves performance under memory pressure. Page +reclaim decides the kernel's caching policy and ability to overcommit +memory. It directly impacts the kswapd CPU usage and RAM efficiency. + +Quick start +=========== +Build the kernel with the following configurations. + +* ``CONFIG_LRU_GEN=y`` +* ``CONFIG_LRU_GEN_ENABLED=y`` + +All set! + +Runtime options +=============== +``/sys/kernel/mm/lru_gen/`` contains stable ABIs described in the +following subsections. + +Kill switch +----------- +``enabled`` accepts different values to enable or disable the +following components. Its default value depends on +``CONFIG_LRU_GEN_ENABLED``. All the components should be enabled +unless some of them have unforeseen side effects. Writing to +``enabled`` has no effect when a component is not supported by the +hardware, and valid values will be accepted even when the main switch +is off. + +====== =============================================================== +Values Components +====== =============================================================== +0x0001 The main switch for the multi-gen LRU. +0x0002 Clearing the accessed bit in leaf page table entries in large + batches, when MMU sets it (e.g., on x86). This behavior can + theoretically worsen lock contention (mmap_lock). If it is + disabled, the multi-gen LRU will suffer a minor performance + degradation for workloads that contiguously map hot pages, + whose accessed bits can be otherwise cleared by fewer larger + batches. +0x0004 Clearing the accessed bit in non-leaf page table entries as + well, when MMU sets it (e.g., on x86). This behavior was not + verified on x86 varieties other than Intel and AMD. If it is + disabled, the multi-gen LRU will suffer a negligible + performance degradation. +[yYnN] Apply to all the components above. +====== =============================================================== + +E.g., +:: + + echo y >/sys/kernel/mm/lru_gen/enabled + cat /sys/kernel/mm/lru_gen/enabled + 0x0007 + echo 5 >/sys/kernel/mm/lru_gen/enabled + cat /sys/kernel/mm/lru_gen/enabled + 0x0005 + +Thrashing prevention +-------------------- +Personal computers are more sensitive to thrashing because it can +cause janks (lags when rendering UI) and negatively impact user +experience. The multi-gen LRU offers thrashing prevention to the +majority of laptop and desktop users who do not have ``oomd``. + +Users can write ``N`` to ``min_ttl_ms`` to prevent the working set of +``N`` milliseconds from getting evicted. The OOM killer is triggered +if this working set cannot be kept in memory. In other words, this +option works as an adjustable pressure relief valve, and when open, it +terminates applications that are hopefully not being used. + +Based on the average human detectable lag (~100ms), ``N=1000`` usually +eliminates intolerable janks due to thrashing. Larger values like +``N=3000`` make janks less noticeable at the risk of premature OOM +kills. + +The default value ``0`` means disabled. + +Experimental features +===================== +``/sys/kernel/debug/lru_gen`` accepts commands described in the +following subsections. Multiple command lines are supported, so does +concatenation with delimiters ``,`` and ``;``. + +``/sys/kernel/debug/lru_gen_full`` provides additional stats for +debugging. ``CONFIG_LRU_GEN_STATS=y`` keeps historical stats from +evicted generations in this file. + +Working set estimation +---------------------- +Working set estimation measures how much memory an application needs +in a given time interval, and it is usually done with little impact on +the performance of the application. E.g., data centers want to +optimize job scheduling (bin packing) to improve memory utilizations. +When a new job comes in, the job scheduler needs to find out whether +each server it manages can allocate a certain amount of memory for +this new job before it can pick a candidate. To do so, the job +scheduler needs to estimate the working sets of the existing jobs. + +When it is read, ``lru_gen`` returns a histogram of numbers of pages +accessed over different time intervals for each memcg and node. +``MAX_NR_GENS`` decides the number of bins for each histogram. The +histograms are noncumulative. +:: + + memcg memcg_id memcg_path + node node_id + min_gen_nr age_in_ms nr_anon_pages nr_file_pages + ... + max_gen_nr age_in_ms nr_anon_pages nr_file_pages + +Each bin contains an estimated number of pages that have been accessed +within ``age_in_ms``. E.g., ``min_gen_nr`` contains the coldest pages +and ``max_gen_nr`` contains the hottest pages, since ``age_in_ms`` of +the former is the largest and that of the latter is the smallest. + +Users can write the following command to ``lru_gen`` to create a new +generation ``max_gen_nr+1``: + + ``+ memcg_id node_id max_gen_nr [can_swap [force_scan]]`` + +``can_swap`` defaults to the swap setting and, if it is set to ``1``, +it forces the scan of anon pages when swap is off, and vice versa. +``force_scan`` defaults to ``1`` and, if it is set to ``0``, it +employs heuristics to reduce the overhead, which is likely to reduce +the coverage as well. + +A typical use case is that a job scheduler runs this command at a +certain time interval to create new generations, and it ranks the +servers it manages based on the sizes of their cold pages defined by +this time interval. + +Proactive reclaim +----------------- +Proactive reclaim induces page reclaim when there is no memory +pressure. It usually targets cold pages only. E.g., when a new job +comes in, the job scheduler wants to proactively reclaim cold pages on +the server it selected, to improve the chance of successfully landing +this new job. + +Users can write the following command to ``lru_gen`` to evict +generations less than or equal to ``min_gen_nr``. + + ``- memcg_id node_id min_gen_nr [swappiness [nr_to_reclaim]]`` + +``min_gen_nr`` should be less than ``max_gen_nr-1``, since +``max_gen_nr`` and ``max_gen_nr-1`` are not fully aged (equivalent to +the active list) and therefore cannot be evicted. ``swappiness`` +overrides the default value in ``/proc/sys/vm/swappiness``. +``nr_to_reclaim`` limits the number of pages to evict. + +A typical use case is that a job scheduler runs this command before it +tries to land a new job on a server. If it fails to materialize enough +cold pages because of the overestimation, it retries on the next +server according to the ranking result obtained from the working set +estimation step. This less forceful approach limits the impacts on the +existing jobs. diff --git a/Documentation/admin-guide/mm/nommu-mmap.rst b/Documentation/admin-guide/mm/nommu-mmap.rst new file mode 100644 index 000000000..530fed08d --- /dev/null +++ b/Documentation/admin-guide/mm/nommu-mmap.rst @@ -0,0 +1,283 @@ +============================= +No-MMU memory mapping support +============================= + +The kernel has limited support for memory mapping under no-MMU conditions, such +as are used in uClinux environments. From the userspace point of view, memory +mapping is made use of in conjunction with the mmap() system call, the shmat() +call and the execve() system call. From the kernel's point of view, execve() +mapping is actually performed by the binfmt drivers, which call back into the +mmap() routines to do the actual work. + +Memory mapping behaviour also involves the way fork(), vfork(), clone() and +ptrace() work. Under uClinux there is no fork(), and clone() must be supplied +the CLONE_VM flag. + +The behaviour is similar between the MMU and no-MMU cases, but not identical; +and it's also much more restricted in the latter case: + + (#) Anonymous mapping, MAP_PRIVATE + + In the MMU case: VM regions backed by arbitrary pages; copy-on-write + across fork. + + In the no-MMU case: VM regions backed by arbitrary contiguous runs of + pages. + + (#) Anonymous mapping, MAP_SHARED + + These behave very much like private mappings, except that they're + shared across fork() or clone() without CLONE_VM in the MMU case. Since + the no-MMU case doesn't support these, behaviour is identical to + MAP_PRIVATE there. + + (#) File, MAP_PRIVATE, PROT_READ / PROT_EXEC, !PROT_WRITE + + In the MMU case: VM regions backed by pages read from file; changes to + the underlying file are reflected in the mapping; copied across fork. + + In the no-MMU case: + + - If one exists, the kernel will re-use an existing mapping to the + same segment of the same file if that has compatible permissions, + even if this was created by another process. + + - If possible, the file mapping will be directly on the backing device + if the backing device has the NOMMU_MAP_DIRECT capability and + appropriate mapping protection capabilities. Ramfs, romfs, cramfs + and mtd might all permit this. + + - If the backing device can't or won't permit direct sharing, + but does have the NOMMU_MAP_COPY capability, then a copy of the + appropriate bit of the file will be read into a contiguous bit of + memory and any extraneous space beyond the EOF will be cleared + + - Writes to the file do not affect the mapping; writes to the mapping + are visible in other processes (no MMU protection), but should not + happen. + + (#) File, MAP_PRIVATE, PROT_READ / PROT_EXEC, PROT_WRITE + + In the MMU case: like the non-PROT_WRITE case, except that the pages in + question get copied before the write actually happens. From that point + on writes to the file underneath that page no longer get reflected into + the mapping's backing pages. The page is then backed by swap instead. + + In the no-MMU case: works much like the non-PROT_WRITE case, except + that a copy is always taken and never shared. + + (#) Regular file / blockdev, MAP_SHARED, PROT_READ / PROT_EXEC / PROT_WRITE + + In the MMU case: VM regions backed by pages read from file; changes to + pages written back to file; writes to file reflected into pages backing + mapping; shared across fork. + + In the no-MMU case: not supported. + + (#) Memory backed regular file, MAP_SHARED, PROT_READ / PROT_EXEC / PROT_WRITE + + In the MMU case: As for ordinary regular files. + + In the no-MMU case: The filesystem providing the memory-backed file + (such as ramfs or tmpfs) may choose to honour an open, truncate, mmap + sequence by providing a contiguous sequence of pages to map. In that + case, a shared-writable memory mapping will be possible. It will work + as for the MMU case. If the filesystem does not provide any such + support, then the mapping request will be denied. + + (#) Memory backed blockdev, MAP_SHARED, PROT_READ / PROT_EXEC / PROT_WRITE + + In the MMU case: As for ordinary regular files. + + In the no-MMU case: As for memory backed regular files, but the + blockdev must be able to provide a contiguous run of pages without + truncate being called. The ramdisk driver could do this if it allocated + all its memory as a contiguous array upfront. + + (#) Memory backed chardev, MAP_SHARED, PROT_READ / PROT_EXEC / PROT_WRITE + + In the MMU case: As for ordinary regular files. + + In the no-MMU case: The character device driver may choose to honour + the mmap() by providing direct access to the underlying device if it + provides memory or quasi-memory that can be accessed directly. Examples + of such are frame buffers and flash devices. If the driver does not + provide any such support, then the mapping request will be denied. + + +Further notes on no-MMU MMAP +============================ + + (#) A request for a private mapping of a file may return a buffer that is not + page-aligned. This is because XIP may take place, and the data may not be + paged aligned in the backing store. + + (#) A request for an anonymous mapping will always be page aligned. If + possible the size of the request should be a power of two otherwise some + of the space may be wasted as the kernel must allocate a power-of-2 + granule but will only discard the excess if appropriately configured as + this has an effect on fragmentation. + + (#) The memory allocated by a request for an anonymous mapping will normally + be cleared by the kernel before being returned in accordance with the + Linux man pages (ver 2.22 or later). + + In the MMU case this can be achieved with reasonable performance as + regions are backed by virtual pages, with the contents only being mapped + to cleared physical pages when a write happens on that specific page + (prior to which, the pages are effectively mapped to the global zero page + from which reads can take place). This spreads out the time it takes to + initialize the contents of a page - depending on the write-usage of the + mapping. + + In the no-MMU case, however, anonymous mappings are backed by physical + pages, and the entire map is cleared at allocation time. This can cause + significant delays during a userspace malloc() as the C library does an + anonymous mapping and the kernel then does a memset for the entire map. + + However, for memory that isn't required to be precleared - such as that + returned by malloc() - mmap() can take a MAP_UNINITIALIZED flag to + indicate to the kernel that it shouldn't bother clearing the memory before + returning it. Note that CONFIG_MMAP_ALLOW_UNINITIALIZED must be enabled + to permit this, otherwise the flag will be ignored. + + uClibc uses this to speed up malloc(), and the ELF-FDPIC binfmt uses this + to allocate the brk and stack region. + + (#) A list of all the private copy and anonymous mappings on the system is + visible through /proc/maps in no-MMU mode. + + (#) A list of all the mappings in use by a process is visible through + /proc/<pid>/maps in no-MMU mode. + + (#) Supplying MAP_FIXED or a requesting a particular mapping address will + result in an error. + + (#) Files mapped privately usually have to have a read method provided by the + driver or filesystem so that the contents can be read into the memory + allocated if mmap() chooses not to map the backing device directly. An + error will result if they don't. This is most likely to be encountered + with character device files, pipes, fifos and sockets. + + +Interprocess shared memory +========================== + +Both SYSV IPC SHM shared memory and POSIX shared memory is supported in NOMMU +mode. The former through the usual mechanism, the latter through files created +on ramfs or tmpfs mounts. + + +Futexes +======= + +Futexes are supported in NOMMU mode if the arch supports them. An error will +be given if an address passed to the futex system call lies outside the +mappings made by a process or if the mapping in which the address lies does not +support futexes (such as an I/O chardev mapping). + + +No-MMU mremap +============= + +The mremap() function is partially supported. It may change the size of a +mapping, and may move it [#]_ if MREMAP_MAYMOVE is specified and if the new size +of the mapping exceeds the size of the slab object currently occupied by the +memory to which the mapping refers, or if a smaller slab object could be used. + +MREMAP_FIXED is not supported, though it is ignored if there's no change of +address and the object does not need to be moved. + +Shared mappings may not be moved. Shareable mappings may not be moved either, +even if they are not currently shared. + +The mremap() function must be given an exact match for base address and size of +a previously mapped object. It may not be used to create holes in existing +mappings, move parts of existing mappings or resize parts of mappings. It must +act on a complete mapping. + +.. [#] Not currently supported. + + +Providing shareable character device support +============================================ + +To provide shareable character device support, a driver must provide a +file->f_op->get_unmapped_area() operation. The mmap() routines will call this +to get a proposed address for the mapping. This may return an error if it +doesn't wish to honour the mapping because it's too long, at a weird offset, +under some unsupported combination of flags or whatever. + +The driver should also provide backing device information with capabilities set +to indicate the permitted types of mapping on such devices. The default is +assumed to be readable and writable, not executable, and only shareable +directly (can't be copied). + +The file->f_op->mmap() operation will be called to actually inaugurate the +mapping. It can be rejected at that point. Returning the ENOSYS error will +cause the mapping to be copied instead if NOMMU_MAP_COPY is specified. + +The vm_ops->close() routine will be invoked when the last mapping on a chardev +is removed. An existing mapping will be shared, partially or not, if possible +without notifying the driver. + +It is permitted also for the file->f_op->get_unmapped_area() operation to +return -ENOSYS. This will be taken to mean that this operation just doesn't +want to handle it, despite the fact it's got an operation. For instance, it +might try directing the call to a secondary driver which turns out not to +implement it. Such is the case for the framebuffer driver which attempts to +direct the call to the device-specific driver. Under such circumstances, the +mapping request will be rejected if NOMMU_MAP_COPY is not specified, and a +copy mapped otherwise. + +.. important:: + + Some types of device may present a different appearance to anyone + looking at them in certain modes. Flash chips can be like this; for + instance if they're in programming or erase mode, you might see the + status reflected in the mapping, instead of the data. + + In such a case, care must be taken lest userspace see a shared or a + private mapping showing such information when the driver is busy + controlling the device. Remember especially: private executable + mappings may still be mapped directly off the device under some + circumstances! + + +Providing shareable memory-backed file support +============================================== + +Provision of shared mappings on memory backed files is similar to the provision +of support for shared mapped character devices. The main difference is that the +filesystem providing the service will probably allocate a contiguous collection +of pages and permit mappings to be made on that. + +It is recommended that a truncate operation applied to such a file that +increases the file size, if that file is empty, be taken as a request to gather +enough pages to honour a mapping. This is required to support POSIX shared +memory. + +Memory backed devices are indicated by the mapping's backing device info having +the memory_backed flag set. + + +Providing shareable block device support +======================================== + +Provision of shared mappings on block device files is exactly the same as for +character devices. If there isn't a real device underneath, then the driver +should allocate sufficient contiguous memory to honour any supported mapping. + + +Adjusting page trimming behaviour +================================= + +NOMMU mmap automatically rounds up to the nearest power-of-2 number of pages +when performing an allocation. This can have adverse effects on memory +fragmentation, and as such, is left configurable. The default behaviour is to +aggressively trim allocations and discard any excess pages back in to the page +allocator. In order to retain finer-grained control over fragmentation, this +behaviour can either be disabled completely, or bumped up to a higher page +watermark where trimming begins. + +Page trimming behaviour is configurable via the sysctl ``vm.nr_trim_pages``. diff --git a/Documentation/admin-guide/mm/numa_memory_policy.rst b/Documentation/admin-guide/mm/numa_memory_policy.rst new file mode 100644 index 000000000..eca38fa81 --- /dev/null +++ b/Documentation/admin-guide/mm/numa_memory_policy.rst @@ -0,0 +1,514 @@ +================== +NUMA Memory Policy +================== + +What is NUMA Memory Policy? +============================ + +In the Linux kernel, "memory policy" determines from which node the kernel will +allocate memory in a NUMA system or in an emulated NUMA system. Linux has +supported platforms with Non-Uniform Memory Access architectures since 2.4.?. +The current memory policy support was added to Linux 2.6 around May 2004. This +document attempts to describe the concepts and APIs of the 2.6 memory policy +support. + +Memory policies should not be confused with cpusets +(``Documentation/admin-guide/cgroup-v1/cpusets.rst``) +which is an administrative mechanism for restricting the nodes from which +memory may be allocated by a set of processes. Memory policies are a +programming interface that a NUMA-aware application can take advantage of. When +both cpusets and policies are applied to a task, the restrictions of the cpuset +takes priority. See :ref:`Memory Policies and cpusets <mem_pol_and_cpusets>` +below for more details. + +Memory Policy Concepts +====================== + +Scope of Memory Policies +------------------------ + +The Linux kernel supports _scopes_ of memory policy, described here from +most general to most specific: + +System Default Policy + this policy is "hard coded" into the kernel. It is the policy + that governs all page allocations that aren't controlled by + one of the more specific policy scopes discussed below. When + the system is "up and running", the system default policy will + use "local allocation" described below. However, during boot + up, the system default policy will be set to interleave + allocations across all nodes with "sufficient" memory, so as + not to overload the initial boot node with boot-time + allocations. + +Task/Process Policy + this is an optional, per-task policy. When defined for a + specific task, this policy controls all page allocations made + by or on behalf of the task that aren't controlled by a more + specific scope. If a task does not define a task policy, then + all page allocations that would have been controlled by the + task policy "fall back" to the System Default Policy. + + The task policy applies to the entire address space of a task. Thus, + it is inheritable, and indeed is inherited, across both fork() + [clone() w/o the CLONE_VM flag] and exec*(). This allows a parent task + to establish the task policy for a child task exec()'d from an + executable image that has no awareness of memory policy. See the + :ref:`Memory Policy APIs <memory_policy_apis>` section, + below, for an overview of the system call + that a task may use to set/change its task/process policy. + + In a multi-threaded task, task policies apply only to the thread + [Linux kernel task] that installs the policy and any threads + subsequently created by that thread. Any sibling threads existing + at the time a new task policy is installed retain their current + policy. + + A task policy applies only to pages allocated after the policy is + installed. Any pages already faulted in by the task when the task + changes its task policy remain where they were allocated based on + the policy at the time they were allocated. + +.. _vma_policy: + +VMA Policy + A "VMA" or "Virtual Memory Area" refers to a range of a task's + virtual address space. A task may define a specific policy for a range + of its virtual address space. See the + :ref:`Memory Policy APIs <memory_policy_apis>` section, + below, for an overview of the mbind() system call used to set a VMA + policy. + + A VMA policy will govern the allocation of pages that back + this region of the address space. Any regions of the task's + address space that don't have an explicit VMA policy will fall + back to the task policy, which may itself fall back to the + System Default Policy. + + VMA policies have a few complicating details: + + * VMA policy applies ONLY to anonymous pages. These include + pages allocated for anonymous segments, such as the task + stack and heap, and any regions of the address space + mmap()ed with the MAP_ANONYMOUS flag. If a VMA policy is + applied to a file mapping, it will be ignored if the mapping + used the MAP_SHARED flag. If the file mapping used the + MAP_PRIVATE flag, the VMA policy will only be applied when + an anonymous page is allocated on an attempt to write to the + mapping-- i.e., at Copy-On-Write. + + * VMA policies are shared between all tasks that share a + virtual address space--a.k.a. threads--independent of when + the policy is installed; and they are inherited across + fork(). However, because VMA policies refer to a specific + region of a task's address space, and because the address + space is discarded and recreated on exec*(), VMA policies + are NOT inheritable across exec(). Thus, only NUMA-aware + applications may use VMA policies. + + * A task may install a new VMA policy on a sub-range of a + previously mmap()ed region. When this happens, Linux splits + the existing virtual memory area into 2 or 3 VMAs, each with + its own policy. + + * By default, VMA policy applies only to pages allocated after + the policy is installed. Any pages already faulted into the + VMA range remain where they were allocated based on the + policy at the time they were allocated. However, since + 2.6.16, Linux supports page migration via the mbind() system + call, so that page contents can be moved to match a newly + installed policy. + +Shared Policy + Conceptually, shared policies apply to "memory objects" mapped + shared into one or more tasks' distinct address spaces. An + application installs shared policies the same way as VMA + policies--using the mbind() system call specifying a range of + virtual addresses that map the shared object. However, unlike + VMA policies, which can be considered to be an attribute of a + range of a task's address space, shared policies apply + directly to the shared object. Thus, all tasks that attach to + the object share the policy, and all pages allocated for the + shared object, by any task, will obey the shared policy. + + As of 2.6.22, only shared memory segments, created by shmget() or + mmap(MAP_ANONYMOUS|MAP_SHARED), support shared policy. When shared + policy support was added to Linux, the associated data structures were + added to hugetlbfs shmem segments. At the time, hugetlbfs did not + support allocation at fault time--a.k.a lazy allocation--so hugetlbfs + shmem segments were never "hooked up" to the shared policy support. + Although hugetlbfs segments now support lazy allocation, their support + for shared policy has not been completed. + + As mentioned above in :ref:`VMA policies <vma_policy>` section, + allocations of page cache pages for regular files mmap()ed + with MAP_SHARED ignore any VMA policy installed on the virtual + address range backed by the shared file mapping. Rather, + shared page cache pages, including pages backing private + mappings that have not yet been written by the task, follow + task policy, if any, else System Default Policy. + + The shared policy infrastructure supports different policies on subset + ranges of the shared object. However, Linux still splits the VMA of + the task that installs the policy for each range of distinct policy. + Thus, different tasks that attach to a shared memory segment can have + different VMA configurations mapping that one shared object. This + can be seen by examining the /proc/<pid>/numa_maps of tasks sharing + a shared memory region, when one task has installed shared policy on + one or more ranges of the region. + +Components of Memory Policies +----------------------------- + +A NUMA memory policy consists of a "mode", optional mode flags, and +an optional set of nodes. The mode determines the behavior of the +policy, the optional mode flags determine the behavior of the mode, +and the optional set of nodes can be viewed as the arguments to the +policy behavior. + +Internally, memory policies are implemented by a reference counted +structure, struct mempolicy. Details of this structure will be +discussed in context, below, as required to explain the behavior. + +NUMA memory policy supports the following 4 behavioral modes: + +Default Mode--MPOL_DEFAULT + This mode is only used in the memory policy APIs. Internally, + MPOL_DEFAULT is converted to the NULL memory policy in all + policy scopes. Any existing non-default policy will simply be + removed when MPOL_DEFAULT is specified. As a result, + MPOL_DEFAULT means "fall back to the next most specific policy + scope." + + For example, a NULL or default task policy will fall back to the + system default policy. A NULL or default vma policy will fall + back to the task policy. + + When specified in one of the memory policy APIs, the Default mode + does not use the optional set of nodes. + + It is an error for the set of nodes specified for this policy to + be non-empty. + +MPOL_BIND + This mode specifies that memory must come from the set of + nodes specified by the policy. Memory will be allocated from + the node in the set with sufficient free memory that is + closest to the node where the allocation takes place. + +MPOL_PREFERRED + This mode specifies that the allocation should be attempted + from the single node specified in the policy. If that + allocation fails, the kernel will search other nodes, in order + of increasing distance from the preferred node based on + information provided by the platform firmware. + + Internally, the Preferred policy uses a single node--the + preferred_node member of struct mempolicy. When the internal + mode flag MPOL_F_LOCAL is set, the preferred_node is ignored + and the policy is interpreted as local allocation. "Local" + allocation policy can be viewed as a Preferred policy that + starts at the node containing the cpu where the allocation + takes place. + + It is possible for the user to specify that local allocation + is always preferred by passing an empty nodemask with this + mode. If an empty nodemask is passed, the policy cannot use + the MPOL_F_STATIC_NODES or MPOL_F_RELATIVE_NODES flags + described below. + +MPOL_INTERLEAVED + This mode specifies that page allocations be interleaved, on a + page granularity, across the nodes specified in the policy. + This mode also behaves slightly differently, based on the + context where it is used: + + For allocation of anonymous pages and shared memory pages, + Interleave mode indexes the set of nodes specified by the + policy using the page offset of the faulting address into the + segment [VMA] containing the address modulo the number of + nodes specified by the policy. It then attempts to allocate a + page, starting at the selected node, as if the node had been + specified by a Preferred policy or had been selected by a + local allocation. That is, allocation will follow the per + node zonelist. + + For allocation of page cache pages, Interleave mode indexes + the set of nodes specified by the policy using a node counter + maintained per task. This counter wraps around to the lowest + specified node after it reaches the highest specified node. + This will tend to spread the pages out over the nodes + specified by the policy based on the order in which they are + allocated, rather than based on any page offset into an + address range or file. During system boot up, the temporary + interleaved system default policy works in this mode. + +MPOL_PREFERRED_MANY + This mode specifies that the allocation should be preferably + satisfied from the nodemask specified in the policy. If there is + a memory pressure on all nodes in the nodemask, the allocation + can fall back to all existing numa nodes. This is effectively + MPOL_PREFERRED allowed for a mask rather than a single node. + +NUMA memory policy supports the following optional mode flags: + +MPOL_F_STATIC_NODES + This flag specifies that the nodemask passed by + the user should not be remapped if the task or VMA's set of allowed + nodes changes after the memory policy has been defined. + + Without this flag, any time a mempolicy is rebound because of a + change in the set of allowed nodes, the preferred nodemask (Preferred + Many), preferred node (Preferred) or nodemask (Bind, Interleave) is + remapped to the new set of allowed nodes. This may result in nodes + being used that were previously undesired. + + With this flag, if the user-specified nodes overlap with the + nodes allowed by the task's cpuset, then the memory policy is + applied to their intersection. If the two sets of nodes do not + overlap, the Default policy is used. + + For example, consider a task that is attached to a cpuset with + mems 1-3 that sets an Interleave policy over the same set. If + the cpuset's mems change to 3-5, the Interleave will now occur + over nodes 3, 4, and 5. With this flag, however, since only node + 3 is allowed from the user's nodemask, the "interleave" only + occurs over that node. If no nodes from the user's nodemask are + now allowed, the Default behavior is used. + + MPOL_F_STATIC_NODES cannot be combined with the + MPOL_F_RELATIVE_NODES flag. It also cannot be used for + MPOL_PREFERRED policies that were created with an empty nodemask + (local allocation). + +MPOL_F_RELATIVE_NODES + This flag specifies that the nodemask passed + by the user will be mapped relative to the set of the task or VMA's + set of allowed nodes. The kernel stores the user-passed nodemask, + and if the allowed nodes changes, then that original nodemask will + be remapped relative to the new set of allowed nodes. + + Without this flag (and without MPOL_F_STATIC_NODES), anytime a + mempolicy is rebound because of a change in the set of allowed + nodes, the node (Preferred) or nodemask (Bind, Interleave) is + remapped to the new set of allowed nodes. That remap may not + preserve the relative nature of the user's passed nodemask to its + set of allowed nodes upon successive rebinds: a nodemask of + 1,3,5 may be remapped to 7-9 and then to 1-3 if the set of + allowed nodes is restored to its original state. + + With this flag, the remap is done so that the node numbers from + the user's passed nodemask are relative to the set of allowed + nodes. In other words, if nodes 0, 2, and 4 are set in the user's + nodemask, the policy will be effected over the first (and in the + Bind or Interleave case, the third and fifth) nodes in the set of + allowed nodes. The nodemask passed by the user represents nodes + relative to task or VMA's set of allowed nodes. + + If the user's nodemask includes nodes that are outside the range + of the new set of allowed nodes (for example, node 5 is set in + the user's nodemask when the set of allowed nodes is only 0-3), + then the remap wraps around to the beginning of the nodemask and, + if not already set, sets the node in the mempolicy nodemask. + + For example, consider a task that is attached to a cpuset with + mems 2-5 that sets an Interleave policy over the same set with + MPOL_F_RELATIVE_NODES. If the cpuset's mems change to 3-7, the + interleave now occurs over nodes 3,5-7. If the cpuset's mems + then change to 0,2-3,5, then the interleave occurs over nodes + 0,2-3,5. + + Thanks to the consistent remapping, applications preparing + nodemasks to specify memory policies using this flag should + disregard their current, actual cpuset imposed memory placement + and prepare the nodemask as if they were always located on + memory nodes 0 to N-1, where N is the number of memory nodes the + policy is intended to manage. Let the kernel then remap to the + set of memory nodes allowed by the task's cpuset, as that may + change over time. + + MPOL_F_RELATIVE_NODES cannot be combined with the + MPOL_F_STATIC_NODES flag. It also cannot be used for + MPOL_PREFERRED policies that were created with an empty nodemask + (local allocation). + +Memory Policy Reference Counting +================================ + +To resolve use/free races, struct mempolicy contains an atomic reference +count field. Internal interfaces, mpol_get()/mpol_put() increment and +decrement this reference count, respectively. mpol_put() will only free +the structure back to the mempolicy kmem cache when the reference count +goes to zero. + +When a new memory policy is allocated, its reference count is initialized +to '1', representing the reference held by the task that is installing the +new policy. When a pointer to a memory policy structure is stored in another +structure, another reference is added, as the task's reference will be dropped +on completion of the policy installation. + +During run-time "usage" of the policy, we attempt to minimize atomic operations +on the reference count, as this can lead to cache lines bouncing between cpus +and NUMA nodes. "Usage" here means one of the following: + +1) querying of the policy, either by the task itself [using the get_mempolicy() + API discussed below] or by another task using the /proc/<pid>/numa_maps + interface. + +2) examination of the policy to determine the policy mode and associated node + or node lists, if any, for page allocation. This is considered a "hot + path". Note that for MPOL_BIND, the "usage" extends across the entire + allocation process, which may sleep during page reclamation, because the + BIND policy nodemask is used, by reference, to filter ineligible nodes. + +We can avoid taking an extra reference during the usages listed above as +follows: + +1) we never need to get/free the system default policy as this is never + changed nor freed, once the system is up and running. + +2) for querying the policy, we do not need to take an extra reference on the + target task's task policy nor vma policies because we always acquire the + task's mm's mmap_lock for read during the query. The set_mempolicy() and + mbind() APIs [see below] always acquire the mmap_lock for write when + installing or replacing task or vma policies. Thus, there is no possibility + of a task or thread freeing a policy while another task or thread is + querying it. + +3) Page allocation usage of task or vma policy occurs in the fault path where + we hold them mmap_lock for read. Again, because replacing the task or vma + policy requires that the mmap_lock be held for write, the policy can't be + freed out from under us while we're using it for page allocation. + +4) Shared policies require special consideration. One task can replace a + shared memory policy while another task, with a distinct mmap_lock, is + querying or allocating a page based on the policy. To resolve this + potential race, the shared policy infrastructure adds an extra reference + to the shared policy during lookup while holding a spin lock on the shared + policy management structure. This requires that we drop this extra + reference when we're finished "using" the policy. We must drop the + extra reference on shared policies in the same query/allocation paths + used for non-shared policies. For this reason, shared policies are marked + as such, and the extra reference is dropped "conditionally"--i.e., only + for shared policies. + + Because of this extra reference counting, and because we must lookup + shared policies in a tree structure under spinlock, shared policies are + more expensive to use in the page allocation path. This is especially + true for shared policies on shared memory regions shared by tasks running + on different NUMA nodes. This extra overhead can be avoided by always + falling back to task or system default policy for shared memory regions, + or by prefaulting the entire shared memory region into memory and locking + it down. However, this might not be appropriate for all applications. + +.. _memory_policy_apis: + +Memory Policy APIs +================== + +Linux supports 4 system calls for controlling memory policy. These APIS +always affect only the calling task, the calling task's address space, or +some shared object mapped into the calling task's address space. + +.. note:: + the headers that define these APIs and the parameter data types for + user space applications reside in a package that is not part of the + Linux kernel. The kernel system call interfaces, with the 'sys\_' + prefix, are defined in <linux/syscalls.h>; the mode and flag + definitions are defined in <linux/mempolicy.h>. + +Set [Task] Memory Policy:: + + long set_mempolicy(int mode, const unsigned long *nmask, + unsigned long maxnode); + +Set's the calling task's "task/process memory policy" to mode +specified by the 'mode' argument and the set of nodes defined by +'nmask'. 'nmask' points to a bit mask of node ids containing at least +'maxnode' ids. Optional mode flags may be passed by combining the +'mode' argument with the flag (for example: MPOL_INTERLEAVE | +MPOL_F_STATIC_NODES). + +See the set_mempolicy(2) man page for more details + + +Get [Task] Memory Policy or Related Information:: + + long get_mempolicy(int *mode, + const unsigned long *nmask, unsigned long maxnode, + void *addr, int flags); + +Queries the "task/process memory policy" of the calling task, or the +policy or location of a specified virtual address, depending on the +'flags' argument. + +See the get_mempolicy(2) man page for more details + + +Install VMA/Shared Policy for a Range of Task's Address Space:: + + long mbind(void *start, unsigned long len, int mode, + const unsigned long *nmask, unsigned long maxnode, + unsigned flags); + +mbind() installs the policy specified by (mode, nmask, maxnodes) as a +VMA policy for the range of the calling task's address space specified +by the 'start' and 'len' arguments. Additional actions may be +requested via the 'flags' argument. + +See the mbind(2) man page for more details. + +Set home node for a Range of Task's Address Spacec:: + + long sys_set_mempolicy_home_node(unsigned long start, unsigned long len, + unsigned long home_node, + unsigned long flags); + +sys_set_mempolicy_home_node set the home node for a VMA policy present in the +task's address range. The system call updates the home node only for the existing +mempolicy range. Other address ranges are ignored. A home node is the NUMA node +closest to which page allocation will come from. Specifying the home node override +the default allocation policy to allocate memory close to the local node for an +executing CPU. + + +Memory Policy Command Line Interface +==================================== + +Although not strictly part of the Linux implementation of memory policy, +a command line tool, numactl(8), exists that allows one to: + ++ set the task policy for a specified program via set_mempolicy(2), fork(2) and + exec(2) + ++ set the shared policy for a shared memory segment via mbind(2) + +The numactl(8) tool is packaged with the run-time version of the library +containing the memory policy system call wrappers. Some distributions +package the headers and compile-time libraries in a separate development +package. + +.. _mem_pol_and_cpusets: + +Memory Policies and cpusets +=========================== + +Memory policies work within cpusets as described above. For memory policies +that require a node or set of nodes, the nodes are restricted to the set of +nodes whose memories are allowed by the cpuset constraints. If the nodemask +specified for the policy contains nodes that are not allowed by the cpuset and +MPOL_F_RELATIVE_NODES is not used, the intersection of the set of nodes +specified for the policy and the set of nodes with memory is used. If the +result is the empty set, the policy is considered invalid and cannot be +installed. If MPOL_F_RELATIVE_NODES is used, the policy's nodes are mapped +onto and folded into the task's set of allowed nodes as previously described. + +The interaction of memory policies and cpusets can be problematic when tasks +in two cpusets share access to a memory region, such as shared memory segments +created by shmget() of mmap() with the MAP_ANONYMOUS and MAP_SHARED flags, and +any of the tasks install shared policy on the region, only nodes whose +memories are allowed in both cpusets may be used in the policies. Obtaining +this information requires "stepping outside" the memory policy APIs to use the +cpuset information and requires that one know in what cpusets other task might +be attaching to the shared region. Furthermore, if the cpusets' allowed +memory sets are disjoint, "local" allocation is the only valid policy. diff --git a/Documentation/admin-guide/mm/numaperf.rst b/Documentation/admin-guide/mm/numaperf.rst new file mode 100644 index 000000000..90a12b6a8 --- /dev/null +++ b/Documentation/admin-guide/mm/numaperf.rst @@ -0,0 +1,176 @@ +======================= +NUMA Memory Performance +======================= + +NUMA Locality +============= + +Some platforms may have multiple types of memory attached to a compute +node. These disparate memory ranges may share some characteristics, such +as CPU cache coherence, but may have different performance. For example, +different media types and buses affect bandwidth and latency. + +A system supports such heterogeneous memory by grouping each memory type +under different domains, or "nodes", based on locality and performance +characteristics. Some memory may share the same node as a CPU, and others +are provided as memory only nodes. While memory only nodes do not provide +CPUs, they may still be local to one or more compute nodes relative to +other nodes. The following diagram shows one such example of two compute +nodes with local memory and a memory only node for each of compute node:: + + +------------------+ +------------------+ + | Compute Node 0 +-----+ Compute Node 1 | + | Local Node0 Mem | | Local Node1 Mem | + +--------+---------+ +--------+---------+ + | | + +--------+---------+ +--------+---------+ + | Slower Node2 Mem | | Slower Node3 Mem | + +------------------+ +--------+---------+ + +A "memory initiator" is a node containing one or more devices such as +CPUs or separate memory I/O devices that can initiate memory requests. +A "memory target" is a node containing one or more physical address +ranges accessible from one or more memory initiators. + +When multiple memory initiators exist, they may not all have the same +performance when accessing a given memory target. Each initiator-target +pair may be organized into different ranked access classes to represent +this relationship. The highest performing initiator to a given target +is considered to be one of that target's local initiators, and given +the highest access class, 0. Any given target may have one or more +local initiators, and any given initiator may have multiple local +memory targets. + +To aid applications matching memory targets with their initiators, the +kernel provides symlinks to each other. The following example lists the +relationship for the access class "0" memory initiators and targets:: + + # symlinks -v /sys/devices/system/node/nodeX/access0/targets/ + relative: /sys/devices/system/node/nodeX/access0/targets/nodeY -> ../../nodeY + + # symlinks -v /sys/devices/system/node/nodeY/access0/initiators/ + relative: /sys/devices/system/node/nodeY/access0/initiators/nodeX -> ../../nodeX + +A memory initiator may have multiple memory targets in the same access +class. The target memory's initiators in a given class indicate the +nodes' access characteristics share the same performance relative to other +linked initiator nodes. Each target within an initiator's access class, +though, do not necessarily perform the same as each other. + +The access class "1" is used to allow differentiation between initiators +that are CPUs and hence suitable for generic task scheduling, and +IO initiators such as GPUs and NICs. Unlike access class 0, only +nodes containing CPUs are considered. + +NUMA Performance +================ + +Applications may wish to consider which node they want their memory to +be allocated from based on the node's performance characteristics. If +the system provides these attributes, the kernel exports them under the +node sysfs hierarchy by appending the attributes directory under the +memory node's access class 0 initiators as follows:: + + /sys/devices/system/node/nodeY/access0/initiators/ + +These attributes apply only when accessed from nodes that have the +are linked under the this access's initiators. + +The performance characteristics the kernel provides for the local initiators +are exported are as follows:: + + # tree -P "read*|write*" /sys/devices/system/node/nodeY/access0/initiators/ + /sys/devices/system/node/nodeY/access0/initiators/ + |-- read_bandwidth + |-- read_latency + |-- write_bandwidth + `-- write_latency + +The bandwidth attributes are provided in MiB/second. + +The latency attributes are provided in nanoseconds. + +The values reported here correspond to the rated latency and bandwidth +for the platform. + +Access class 1 takes the same form but only includes values for CPU to +memory activity. + +NUMA Cache +========== + +System memory may be constructed in a hierarchy of elements with various +performance characteristics in order to provide large address space of +slower performing memory cached by a smaller higher performing memory. The +system physical addresses memory initiators are aware of are provided +by the last memory level in the hierarchy. The system meanwhile uses +higher performing memory to transparently cache access to progressively +slower levels. + +The term "far memory" is used to denote the last level memory in the +hierarchy. Each increasing cache level provides higher performing +initiator access, and the term "near memory" represents the fastest +cache provided by the system. + +This numbering is different than CPU caches where the cache level (ex: +L1, L2, L3) uses the CPU-side view where each increased level is lower +performing. In contrast, the memory cache level is centric to the last +level memory, so the higher numbered cache level corresponds to memory +nearer to the CPU, and further from far memory. + +The memory-side caches are not directly addressable by software. When +software accesses a system address, the system will return it from the +near memory cache if it is present. If it is not present, the system +accesses the next level of memory until there is either a hit in that +cache level, or it reaches far memory. + +An application does not need to know about caching attributes in order +to use the system. Software may optionally query the memory cache +attributes in order to maximize the performance out of such a setup. +If the system provides a way for the kernel to discover this information, +for example with ACPI HMAT (Heterogeneous Memory Attribute Table), +the kernel will append these attributes to the NUMA node memory target. + +When the kernel first registers a memory cache with a node, the kernel +will create the following directory:: + + /sys/devices/system/node/nodeX/memory_side_cache/ + +If that directory is not present, the system either does not provide +a memory-side cache, or that information is not accessible to the kernel. + +The attributes for each level of cache is provided under its cache +level index:: + + /sys/devices/system/node/nodeX/memory_side_cache/indexA/ + /sys/devices/system/node/nodeX/memory_side_cache/indexB/ + /sys/devices/system/node/nodeX/memory_side_cache/indexC/ + +Each cache level's directory provides its attributes. For example, the +following shows a single cache level and the attributes available for +software to query:: + + # tree /sys/devices/system/node/node0/memory_side_cache/ + /sys/devices/system/node/node0/memory_side_cache/ + |-- index1 + | |-- indexing + | |-- line_size + | |-- size + | `-- write_policy + +The "indexing" will be 0 if it is a direct-mapped cache, and non-zero +for any other indexed based, multi-way associativity. + +The "line_size" is the number of bytes accessed from the next cache +level on a miss. + +The "size" is the number of bytes provided by this cache level. + +The "write_policy" will be 0 for write-back, and non-zero for +write-through caching. + +See Also +======== + +[1] https://www.uefi.org/sites/default/files/resources/ACPI_6_2.pdf +- Section 5.2.27 diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst new file mode 100644 index 000000000..c8f380271 --- /dev/null +++ b/Documentation/admin-guide/mm/pagemap.rst @@ -0,0 +1,229 @@ +============================= +Examining Process Page Tables +============================= + +pagemap is a new (as of 2.6.25) set of interfaces in the kernel that allow +userspace programs to examine the page tables and related information by +reading files in ``/proc``. + +There are four components to pagemap: + + * ``/proc/pid/pagemap``. This file lets a userspace process find out which + physical frame each virtual page is mapped to. It contains one 64-bit + value for each virtual page, containing the following data (from + ``fs/proc/task_mmu.c``, above pagemap_read): + + * Bits 0-54 page frame number (PFN) if present + * Bits 0-4 swap type if swapped + * Bits 5-54 swap offset if swapped + * Bit 55 pte is soft-dirty (see + Documentation/admin-guide/mm/soft-dirty.rst) + * Bit 56 page exclusively mapped (since 4.2) + * Bit 57 pte is uffd-wp write-protected (since 5.13) (see + Documentation/admin-guide/mm/userfaultfd.rst) + * Bits 58-60 zero + * Bit 61 page is file-page or shared-anon (since 3.5) + * Bit 62 page swapped + * Bit 63 page present + + Since Linux 4.0 only users with the CAP_SYS_ADMIN capability can get PFNs. + In 4.0 and 4.1 opens by unprivileged fail with -EPERM. Starting from + 4.2 the PFN field is zeroed if the user does not have CAP_SYS_ADMIN. + Reason: information about PFNs helps in exploiting Rowhammer vulnerability. + + If the page is not present but in swap, then the PFN contains an + encoding of the swap file number and the page's offset into the + swap. Unmapped pages return a null PFN. This allows determining + precisely which pages are mapped (or in swap) and comparing mapped + pages between processes. + + Efficient users of this interface will use ``/proc/pid/maps`` to + determine which areas of memory are actually mapped and llseek to + skip over unmapped regions. + + * ``/proc/kpagecount``. This file contains a 64-bit count of the number of + times each page is mapped, indexed by PFN. + +The page-types tool in the tools/mm directory can be used to query the +number of times a page is mapped. + + * ``/proc/kpageflags``. This file contains a 64-bit set of flags for each + page, indexed by PFN. + + The flags are (from ``fs/proc/page.c``, above kpageflags_read): + + 0. LOCKED + 1. ERROR + 2. REFERENCED + 3. UPTODATE + 4. DIRTY + 5. LRU + 6. ACTIVE + 7. SLAB + 8. WRITEBACK + 9. RECLAIM + 10. BUDDY + 11. MMAP + 12. ANON + 13. SWAPCACHE + 14. SWAPBACKED + 15. COMPOUND_HEAD + 16. COMPOUND_TAIL + 17. HUGE + 18. UNEVICTABLE + 19. HWPOISON + 20. NOPAGE + 21. KSM + 22. THP + 23. OFFLINE + 24. ZERO_PAGE + 25. IDLE + 26. PGTABLE + + * ``/proc/kpagecgroup``. This file contains a 64-bit inode number of the + memory cgroup each page is charged to, indexed by PFN. Only available when + CONFIG_MEMCG is set. + +Short descriptions to the page flags +==================================== + +0 - LOCKED + The page is being locked for exclusive access, e.g. by undergoing read/write + IO. +7 - SLAB + The page is managed by the SLAB/SLUB kernel memory allocator. + When compound page is used, either will only set this flag on the head + page. +10 - BUDDY + A free memory block managed by the buddy system allocator. + The buddy system organizes free memory in blocks of various orders. + An order N block has 2^N physically contiguous pages, with the BUDDY flag + set for and _only_ for the first page. +15 - COMPOUND_HEAD + A compound page with order N consists of 2^N physically contiguous pages. + A compound page with order 2 takes the form of "HTTT", where H donates its + head page and T donates its tail page(s). The major consumers of compound + pages are hugeTLB pages (Documentation/admin-guide/mm/hugetlbpage.rst), + the SLUB etc. memory allocators and various device drivers. + However in this interface, only huge/giga pages are made visible + to end users. +16 - COMPOUND_TAIL + A compound page tail (see description above). +17 - HUGE + This is an integral part of a HugeTLB page. +19 - HWPOISON + Hardware detected memory corruption on this page: don't touch the data! +20 - NOPAGE + No page frame exists at the requested address. +21 - KSM + Identical memory pages dynamically shared between one or more processes. +22 - THP + Contiguous pages which construct transparent hugepages. +23 - OFFLINE + The page is logically offline. +24 - ZERO_PAGE + Zero page for pfn_zero or huge_zero page. +25 - IDLE + The page has not been accessed since it was marked idle (see + Documentation/admin-guide/mm/idle_page_tracking.rst). + Note that this flag may be stale in case the page was accessed via + a PTE. To make sure the flag is up-to-date one has to read + ``/sys/kernel/mm/page_idle/bitmap`` first. +26 - PGTABLE + The page is in use as a page table. + +IO related page flags +--------------------- + +1 - ERROR + IO error occurred. +3 - UPTODATE + The page has up-to-date data. + ie. for file backed page: (in-memory data revision >= on-disk one) +4 - DIRTY + The page has been written to, hence contains new data. + i.e. for file backed page: (in-memory data revision > on-disk one) +8 - WRITEBACK + The page is being synced to disk. + +LRU related page flags +---------------------- + +5 - LRU + The page is in one of the LRU lists. +6 - ACTIVE + The page is in the active LRU list. +18 - UNEVICTABLE + The page is in the unevictable (non-)LRU list It is somehow pinned and + not a candidate for LRU page reclaims, e.g. ramfs pages, + shmctl(SHM_LOCK) and mlock() memory segments. +2 - REFERENCED + The page has been referenced since last LRU list enqueue/requeue. +9 - RECLAIM + The page will be reclaimed soon after its pageout IO completed. +11 - MMAP + A memory mapped page. +12 - ANON + A memory mapped page that is not part of a file. +13 - SWAPCACHE + The page is mapped to swap space, i.e. has an associated swap entry. +14 - SWAPBACKED + The page is backed by swap/RAM. + +The page-types tool in the tools/mm directory can be used to query the +above flags. + +Using pagemap to do something useful +==================================== + +The general procedure for using pagemap to find out about a process' memory +usage goes like this: + + 1. Read ``/proc/pid/maps`` to determine which parts of the memory space are + mapped to what. + 2. Select the maps you are interested in -- all of them, or a particular + library, or the stack or the heap, etc. + 3. Open ``/proc/pid/pagemap`` and seek to the pages you would like to examine. + 4. Read a u64 for each page from pagemap. + 5. Open ``/proc/kpagecount`` and/or ``/proc/kpageflags``. For each PFN you + just read, seek to that entry in the file, and read the data you want. + +For example, to find the "unique set size" (USS), which is the amount of +memory that a process is using that is not shared with any other process, +you can go through every map in the process, find the PFNs, look those up +in kpagecount, and tally up the number of pages that are only referenced +once. + +Exceptions for Shared Memory +============================ + +Page table entries for shared pages are cleared when the pages are zapped or +swapped out. This makes swapped out pages indistinguishable from never-allocated +ones. + +In kernel space, the swap location can still be retrieved from the page cache. +However, values stored only on the normal PTE get lost irretrievably when the +page is swapped out (i.e. SOFT_DIRTY). + +In user space, whether the page is present, swapped or none can be deduced with +the help of lseek and/or mincore system calls. + +lseek() can differentiate between accessed pages (present or swapped out) and +holes (none/non-allocated) by specifying the SEEK_DATA flag on the file where +the pages are backed. For anonymous shared pages, the file can be found in +``/proc/pid/map_files/``. + +mincore() can differentiate between pages in memory (present, including swap +cache) and out of memory (swapped out or none/non-allocated). + +Other notes +=========== + +Reading from any of the files will return -EINVAL if you are not starting +the read on an 8-byte boundary (e.g., if you sought an odd number of bytes +into the file), or if the size of the read is not a multiple of 8 bytes. + +Before Linux 3.11 pagemap bits 55-60 were used for "page-shift" (which is +always 12 at most architectures). Since Linux 3.11 their meaning changes +after first clear of soft-dirty bits. Since Linux 4.2 they are used for +flags unconditionally. diff --git a/Documentation/admin-guide/mm/shrinker_debugfs.rst b/Documentation/admin-guide/mm/shrinker_debugfs.rst new file mode 100644 index 000000000..c582033bd --- /dev/null +++ b/Documentation/admin-guide/mm/shrinker_debugfs.rst @@ -0,0 +1,133 @@ +========================== +Shrinker Debugfs Interface +========================== + +Shrinker debugfs interface provides a visibility into the kernel memory +shrinkers subsystem and allows to get information about individual shrinkers +and interact with them. + +For each shrinker registered in the system a directory in **<debugfs>/shrinker/** +is created. The directory's name is composed from the shrinker's name and an +unique id: e.g. *kfree_rcu-0* or *sb-xfs:vda1-36*. + +Each shrinker directory contains **count** and **scan** files, which allow to +trigger *count_objects()* and *scan_objects()* callbacks for each memcg and +numa node (if applicable). + +Usage: +------ + +1. *List registered shrinkers* + + :: + + $ cd /sys/kernel/debug/shrinker/ + $ ls + dquota-cache-16 sb-devpts-28 sb-proc-47 sb-tmpfs-42 + mm-shadow-18 sb-devtmpfs-5 sb-proc-48 sb-tmpfs-43 + mm-zspool:zram0-34 sb-hugetlbfs-17 sb-pstore-31 sb-tmpfs-44 + rcu-kfree-0 sb-hugetlbfs-33 sb-rootfs-2 sb-tmpfs-49 + sb-aio-20 sb-iomem-12 sb-securityfs-6 sb-tracefs-13 + sb-anon_inodefs-15 sb-mqueue-21 sb-selinuxfs-22 sb-xfs:vda1-36 + sb-bdev-3 sb-nsfs-4 sb-sockfs-8 sb-zsmalloc-19 + sb-bpf-32 sb-pipefs-14 sb-sysfs-26 thp-deferred_split-10 + sb-btrfs:vda2-24 sb-proc-25 sb-tmpfs-1 thp-zero-9 + sb-cgroup2-30 sb-proc-39 sb-tmpfs-27 xfs-buf:vda1-37 + sb-configfs-23 sb-proc-41 sb-tmpfs-29 xfs-inodegc:vda1-38 + sb-dax-11 sb-proc-45 sb-tmpfs-35 + sb-debugfs-7 sb-proc-46 sb-tmpfs-40 + +2. *Get information about a specific shrinker* + + :: + + $ cd sb-btrfs\:vda2-24/ + $ ls + count scan + +3. *Count objects* + + Each line in the output has the following format:: + + <cgroup inode id> <nr of objects on node 0> <nr of objects on node 1> ... + <cgroup inode id> <nr of objects on node 0> <nr of objects on node 1> ... + ... + + If there are no objects on all numa nodes, a line is omitted. If there + are no objects at all, the output might be empty. + + If the shrinker is not memcg-aware or CONFIG_MEMCG is off, 0 is printed + as cgroup inode id. If the shrinker is not numa-aware, 0's are printed + for all nodes except the first one. + :: + + $ cat count + 1 224 2 + 21 98 0 + 55 818 10 + 2367 2 0 + 2401 30 0 + 225 13 0 + 599 35 0 + 939 124 0 + 1041 3 0 + 1075 1 0 + 1109 1 0 + 1279 60 0 + 1313 7 0 + 1347 39 0 + 1381 3 0 + 1449 14 0 + 1483 63 0 + 1517 53 0 + 1551 6 0 + 1585 1 0 + 1619 6 0 + 1653 40 0 + 1687 11 0 + 1721 8 0 + 1755 4 0 + 1789 52 0 + 1823 888 0 + 1857 1 0 + 1925 2 0 + 1959 32 0 + 2027 22 0 + 2061 9 0 + 2469 799 0 + 2537 861 0 + 2639 1 0 + 2707 70 0 + 2775 4 0 + 2877 84 0 + 293 1 0 + 735 8 0 + +4. *Scan objects* + + The expected input format:: + + <cgroup inode id> <numa id> <number of objects to scan> + + For a non-memcg-aware shrinker or on a system with no memory + cgrups **0** should be passed as cgroup id. + :: + + $ cd /sys/kernel/debug/shrinker/ + $ cd sb-btrfs\:vda2-24/ + + $ cat count | head -n 5 + 1 212 0 + 21 97 0 + 55 802 5 + 2367 2 0 + 225 13 0 + + $ echo "55 0 200" > scan + + $ cat count | head -n 5 + 1 212 0 + 21 96 0 + 55 752 5 + 2367 2 0 + 225 13 0 diff --git a/Documentation/admin-guide/mm/soft-dirty.rst b/Documentation/admin-guide/mm/soft-dirty.rst new file mode 100644 index 000000000..aeea936ca --- /dev/null +++ b/Documentation/admin-guide/mm/soft-dirty.rst @@ -0,0 +1,45 @@ +=============== +Soft-Dirty PTEs +=============== + +The soft-dirty is a bit on a PTE which helps to track which pages a task +writes to. In order to do this tracking one should + + 1. Clear soft-dirty bits from the task's PTEs. + + This is done by writing "4" into the ``/proc/PID/clear_refs`` file of the + task in question. + + 2. Wait some time. + + 3. Read soft-dirty bits from the PTEs. + + This is done by reading from the ``/proc/PID/pagemap``. The bit 55 of the + 64-bit qword is the soft-dirty one. If set, the respective PTE was + written to since step 1. + + +Internally, to do this tracking, the writable bit is cleared from PTEs +when the soft-dirty bit is cleared. So, after this, when the task tries to +modify a page at some virtual address the #PF occurs and the kernel sets +the soft-dirty bit on the respective PTE. + +Note, that although all the task's address space is marked as r/o after the +soft-dirty bits clear, the #PF-s that occur after that are processed fast. +This is so, since the pages are still mapped to physical memory, and thus all +the kernel does is finds this fact out and puts both writable and soft-dirty +bits on the PTE. + +While in most cases tracking memory changes by #PF-s is more than enough +there is still a scenario when we can lose soft dirty bits -- a task +unmaps a previously mapped memory region and then maps a new one at exactly +the same place. When unmap is called, the kernel internally clears PTE values +including soft dirty bits. To notify user space application about such +memory region renewal the kernel always marks new memory regions (and +expanded regions) as soft dirty. + +This feature is actively used by the checkpoint-restore project. You +can find more details about it on http://criu.org + + +-- Pavel Emelyanov, Apr 9, 2013 diff --git a/Documentation/admin-guide/mm/swap_numa.rst b/Documentation/admin-guide/mm/swap_numa.rst new file mode 100644 index 000000000..2e630627b --- /dev/null +++ b/Documentation/admin-guide/mm/swap_numa.rst @@ -0,0 +1,78 @@ +=========================================== +Automatically bind swap device to numa node +=========================================== + +If the system has more than one swap device and swap device has the node +information, we can make use of this information to decide which swap +device to use in get_swap_pages() to get better performance. + + +How to use this feature +======================= + +Swap device has priority and that decides the order of it to be used. To make +use of automatically binding, there is no need to manipulate priority settings +for swap devices. e.g. on a 2 node machine, assume 2 swap devices swapA and +swapB, with swapA attached to node 0 and swapB attached to node 1, are going +to be swapped on. Simply swapping them on by doing:: + + # swapon /dev/swapA + # swapon /dev/swapB + +Then node 0 will use the two swap devices in the order of swapA then swapB and +node 1 will use the two swap devices in the order of swapB then swapA. Note +that the order of them being swapped on doesn't matter. + +A more complex example on a 4 node machine. Assume 6 swap devices are going to +be swapped on: swapA and swapB are attached to node 0, swapC is attached to +node 1, swapD and swapE are attached to node 2 and swapF is attached to node3. +The way to swap them on is the same as above:: + + # swapon /dev/swapA + # swapon /dev/swapB + # swapon /dev/swapC + # swapon /dev/swapD + # swapon /dev/swapE + # swapon /dev/swapF + +Then node 0 will use them in the order of:: + + swapA/swapB -> swapC -> swapD -> swapE -> swapF + +swapA and swapB will be used in a round robin mode before any other swap device. + +node 1 will use them in the order of:: + + swapC -> swapA -> swapB -> swapD -> swapE -> swapF + +node 2 will use them in the order of:: + + swapD/swapE -> swapA -> swapB -> swapC -> swapF + +Similaly, swapD and swapE will be used in a round robin mode before any +other swap devices. + +node 3 will use them in the order of:: + + swapF -> swapA -> swapB -> swapC -> swapD -> swapE + + +Implementation details +====================== + +The current code uses a priority based list, swap_avail_list, to decide +which swap device to use and if multiple swap devices share the same +priority, they are used round robin. This change here replaces the single +global swap_avail_list with a per-numa-node list, i.e. for each numa node, +it sees its own priority based list of available swap devices. Swap +device's priority can be promoted on its matching node's swap_avail_list. + +The current swap device's priority is set as: user can set a >=0 value, +or the system will pick one starting from -1 then downwards. The priority +value in the swap_avail_list is the negated value of the swap device's +due to plist being sorted from low to high. The new policy doesn't change +the semantics for priority >=0 cases, the previous starting from -1 then +downwards now becomes starting from -2 then downwards and -1 is reserved +as the promoted value. So if multiple swap devices are attached to the same +node, they will all be promoted to priority -1 on that node's plist and will +be used round robin before any other swap devices. diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst new file mode 100644 index 000000000..b0cc8243e --- /dev/null +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -0,0 +1,427 @@ +============================ +Transparent Hugepage Support +============================ + +Objective +========= + +Performance critical computing applications dealing with large memory +working sets are already running on top of libhugetlbfs and in turn +hugetlbfs. Transparent HugePage Support (THP) is an alternative mean of +using huge pages for the backing of virtual memory with huge pages +that supports the automatic promotion and demotion of page sizes and +without the shortcomings of hugetlbfs. + +Currently THP only works for anonymous memory mappings and tmpfs/shmem. +But in the future it can expand to other filesystems. + +.. note:: + in the examples below we presume that the basic page size is 4K and + the huge page size is 2M, although the actual numbers may vary + depending on the CPU architecture. + +The reason applications are running faster is because of two +factors. The first factor is almost completely irrelevant and it's not +of significant interest because it'll also have the downside of +requiring larger clear-page copy-page in page faults which is a +potentially negative effect. The first factor consists in taking a +single page fault for each 2M virtual region touched by userland (so +reducing the enter/exit kernel frequency by a 512 times factor). This +only matters the first time the memory is accessed for the lifetime of +a memory mapping. The second long lasting and much more important +factor will affect all subsequent accesses to the memory for the whole +runtime of the application. The second factor consist of two +components: + +1) the TLB miss will run faster (especially with virtualization using + nested pagetables but almost always also on bare metal without + virtualization) + +2) a single TLB entry will be mapping a much larger amount of virtual + memory in turn reducing the number of TLB misses. With + virtualization and nested pagetables the TLB can be mapped of + larger size only if both KVM and the Linux guest are using + hugepages but a significant speedup already happens if only one of + the two is using hugepages just because of the fact the TLB miss is + going to run faster. + +THP can be enabled system wide or restricted to certain tasks or even +memory ranges inside task's address space. Unless THP is completely +disabled, there is ``khugepaged`` daemon that scans memory and +collapses sequences of basic pages into huge pages. + +The THP behaviour is controlled via :ref:`sysfs <thp_sysfs>` +interface and using madvise(2) and prctl(2) system calls. + +Transparent Hugepage Support maximizes the usefulness of free memory +if compared to the reservation approach of hugetlbfs by allowing all +unused memory to be used as cache or other movable (or even unmovable +entities). It doesn't require reservation to prevent hugepage +allocation failures to be noticeable from userland. It allows paging +and all other advanced VM features to be available on the +hugepages. It requires no modifications for applications to take +advantage of it. + +Applications however can be further optimized to take advantage of +this feature, like for example they've been optimized before to avoid +a flood of mmap system calls for every malloc(4k). Optimizing userland +is by far not mandatory and khugepaged already can take care of long +lived page allocations even for hugepage unaware applications that +deals with large amounts of memory. + +In certain cases when hugepages are enabled system wide, application +may end up allocating more memory resources. An application may mmap a +large region but only touch 1 byte of it, in that case a 2M page might +be allocated instead of a 4k page for no good. This is why it's +possible to disable hugepages system-wide and to only have them inside +MADV_HUGEPAGE madvise regions. + +Embedded systems should enable hugepages only inside madvise regions +to eliminate any risk of wasting any precious byte of memory and to +only run faster. + +Applications that gets a lot of benefit from hugepages and that don't +risk to lose memory by using hugepages, should use +madvise(MADV_HUGEPAGE) on their critical mmapped regions. + +.. _thp_sysfs: + +sysfs +===== + +Global THP controls +------------------- + +Transparent Hugepage Support for anonymous memory can be entirely disabled +(mostly for debugging purposes) or only enabled inside MADV_HUGEPAGE +regions (to avoid the risk of consuming more memory resources) or enabled +system wide. This can be achieved with one of:: + + echo always >/sys/kernel/mm/transparent_hugepage/enabled + echo madvise >/sys/kernel/mm/transparent_hugepage/enabled + echo never >/sys/kernel/mm/transparent_hugepage/enabled + +It's also possible to limit defrag efforts in the VM to generate +anonymous hugepages in case they're not immediately free to madvise +regions or to never try to defrag memory and simply fallback to regular +pages unless hugepages are immediately available. Clearly if we spend CPU +time to defrag memory, we would expect to gain even more by the fact we +use hugepages later instead of regular pages. This isn't always +guaranteed, but it may be more likely in case the allocation is for a +MADV_HUGEPAGE region. + +:: + + echo always >/sys/kernel/mm/transparent_hugepage/defrag + echo defer >/sys/kernel/mm/transparent_hugepage/defrag + echo defer+madvise >/sys/kernel/mm/transparent_hugepage/defrag + echo madvise >/sys/kernel/mm/transparent_hugepage/defrag + echo never >/sys/kernel/mm/transparent_hugepage/defrag + +always + means that an application requesting THP will stall on + allocation failure and directly reclaim pages and compact + memory in an effort to allocate a THP immediately. This may be + desirable for virtual machines that benefit heavily from THP + use and are willing to delay the VM start to utilise them. + +defer + means that an application will wake kswapd in the background + to reclaim pages and wake kcompactd to compact memory so that + THP is available in the near future. It's the responsibility + of khugepaged to then install the THP pages later. + +defer+madvise + will enter direct reclaim and compaction like ``always``, but + only for regions that have used madvise(MADV_HUGEPAGE); all + other regions will wake kswapd in the background to reclaim + pages and wake kcompactd to compact memory so that THP is + available in the near future. + +madvise + will enter direct reclaim like ``always`` but only for regions + that are have used madvise(MADV_HUGEPAGE). This is the default + behaviour. + +never + should be self-explanatory. + +By default kernel tries to use huge zero page on read page fault to +anonymous mapping. It's possible to disable huge zero page by writing 0 +or enable it back by writing 1:: + + echo 0 >/sys/kernel/mm/transparent_hugepage/use_zero_page + echo 1 >/sys/kernel/mm/transparent_hugepage/use_zero_page + +Some userspace (such as a test program, or an optimized memory allocation +library) may want to know the size (in bytes) of a transparent hugepage:: + + cat /sys/kernel/mm/transparent_hugepage/hpage_pmd_size + +khugepaged will be automatically started when +transparent_hugepage/enabled is set to "always" or "madvise, and it'll +be automatically shutdown if it's set to "never". + +Khugepaged controls +------------------- + +khugepaged runs usually at low frequency so while one may not want to +invoke defrag algorithms synchronously during the page faults, it +should be worth invoking defrag at least in khugepaged. However it's +also possible to disable defrag in khugepaged by writing 0 or enable +defrag in khugepaged by writing 1:: + + echo 0 >/sys/kernel/mm/transparent_hugepage/khugepaged/defrag + echo 1 >/sys/kernel/mm/transparent_hugepage/khugepaged/defrag + +You can also control how many pages khugepaged should scan at each +pass:: + + /sys/kernel/mm/transparent_hugepage/khugepaged/pages_to_scan + +and how many milliseconds to wait in khugepaged between each pass (you +can set this to 0 to run khugepaged at 100% utilization of one core):: + + /sys/kernel/mm/transparent_hugepage/khugepaged/scan_sleep_millisecs + +and how many milliseconds to wait in khugepaged if there's an hugepage +allocation failure to throttle the next allocation attempt:: + + /sys/kernel/mm/transparent_hugepage/khugepaged/alloc_sleep_millisecs + +The khugepaged progress can be seen in the number of pages collapsed (note +that this counter may not be an exact count of the number of pages +collapsed, since "collapsed" could mean multiple things: (1) A PTE mapping +being replaced by a PMD mapping, or (2) All 4K physical pages replaced by +one 2M hugepage. Each may happen independently, or together, depending on +the type of memory and the failures that occur. As such, this value should +be interpreted roughly as a sign of progress, and counters in /proc/vmstat +consulted for more accurate accounting):: + + /sys/kernel/mm/transparent_hugepage/khugepaged/pages_collapsed + +for each pass:: + + /sys/kernel/mm/transparent_hugepage/khugepaged/full_scans + +``max_ptes_none`` specifies how many extra small pages (that are +not already mapped) can be allocated when collapsing a group +of small pages into one large page:: + + /sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_none + +A higher value leads to use additional memory for programs. +A lower value leads to gain less thp performance. Value of +max_ptes_none can waste cpu time very little, you can +ignore it. + +``max_ptes_swap`` specifies how many pages can be brought in from +swap when collapsing a group of pages into a transparent huge page:: + + /sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_swap + +A higher value can cause excessive swap IO and waste +memory. A lower value can prevent THPs from being +collapsed, resulting fewer pages being collapsed into +THPs, and lower memory access performance. + +``max_ptes_shared`` specifies how many pages can be shared across multiple +processes. Exceeding the number would block the collapse:: + + /sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_shared + +A higher value may increase memory footprint for some workloads. + +Boot parameter +============== + +You can change the sysfs boot time defaults of Transparent Hugepage +Support by passing the parameter ``transparent_hugepage=always`` or +``transparent_hugepage=madvise`` or ``transparent_hugepage=never`` +to the kernel command line. + +Hugepages in tmpfs/shmem +======================== + +You can control hugepage allocation policy in tmpfs with mount option +``huge=``. It can have following values: + +always + Attempt to allocate huge pages every time we need a new page; + +never + Do not allocate huge pages; + +within_size + Only allocate huge page if it will be fully within i_size. + Also respect fadvise()/madvise() hints; + +advise + Only allocate huge pages if requested with fadvise()/madvise(); + +The default policy is ``never``. + +``mount -o remount,huge= /mountpoint`` works fine after mount: remounting +``huge=never`` will not attempt to break up huge pages at all, just stop more +from being allocated. + +There's also sysfs knob to control hugepage allocation policy for internal +shmem mount: /sys/kernel/mm/transparent_hugepage/shmem_enabled. The mount +is used for SysV SHM, memfds, shared anonymous mmaps (of /dev/zero or +MAP_ANONYMOUS), GPU drivers' DRM objects, Ashmem. + +In addition to policies listed above, shmem_enabled allows two further +values: + +deny + For use in emergencies, to force the huge option off from + all mounts; +force + Force the huge option on for all - very useful for testing; + +Need of application restart +=========================== + +The transparent_hugepage/enabled values and tmpfs mount option only affect +future behavior. So to make them effective you need to restart any +application that could have been using hugepages. This also applies to the +regions registered in khugepaged. + +Monitoring usage +================ + +The number of anonymous transparent huge pages currently used by the +system is available by reading the AnonHugePages field in ``/proc/meminfo``. +To identify what applications are using anonymous transparent huge pages, +it is necessary to read ``/proc/PID/smaps`` and count the AnonHugePages fields +for each mapping. + +The number of file transparent huge pages mapped to userspace is available +by reading ShmemPmdMapped and ShmemHugePages fields in ``/proc/meminfo``. +To identify what applications are mapping file transparent huge pages, it +is necessary to read ``/proc/PID/smaps`` and count the FileHugeMapped fields +for each mapping. + +Note that reading the smaps file is expensive and reading it +frequently will incur overhead. + +There are a number of counters in ``/proc/vmstat`` that may be used to +monitor how successfully the system is providing huge pages for use. + +thp_fault_alloc + is incremented every time a huge page is successfully + allocated to handle a page fault. + +thp_collapse_alloc + is incremented by khugepaged when it has found + a range of pages to collapse into one huge page and has + successfully allocated a new huge page to store the data. + +thp_fault_fallback + is incremented if a page fault fails to allocate + a huge page and instead falls back to using small pages. + +thp_fault_fallback_charge + is incremented if a page fault fails to charge a huge page and + instead falls back to using small pages even though the + allocation was successful. + +thp_collapse_alloc_failed + is incremented if khugepaged found a range + of pages that should be collapsed into one huge page but failed + the allocation. + +thp_file_alloc + is incremented every time a file huge page is successfully + allocated. + +thp_file_fallback + is incremented if a file huge page is attempted to be allocated + but fails and instead falls back to using small pages. + +thp_file_fallback_charge + is incremented if a file huge page cannot be charged and instead + falls back to using small pages even though the allocation was + successful. + +thp_file_mapped + is incremented every time a file huge page is mapped into + user address space. + +thp_split_page + is incremented every time a huge page is split into base + pages. This can happen for a variety of reasons but a common + reason is that a huge page is old and is being reclaimed. + This action implies splitting all PMD the page mapped with. + +thp_split_page_failed + is incremented if kernel fails to split huge + page. This can happen if the page was pinned by somebody. + +thp_deferred_split_page + is incremented when a huge page is put onto split + queue. This happens when a huge page is partially unmapped and + splitting it would free up some memory. Pages on split queue are + going to be split under memory pressure. + +thp_split_pmd + is incremented every time a PMD split into table of PTEs. + This can happen, for instance, when application calls mprotect() or + munmap() on part of huge page. It doesn't split huge page, only + page table entry. + +thp_zero_page_alloc + is incremented every time a huge zero page used for thp is + successfully allocated. Note, it doesn't count every map of + the huge zero page, only its allocation. + +thp_zero_page_alloc_failed + is incremented if kernel fails to allocate + huge zero page and falls back to using small pages. + +thp_swpout + is incremented every time a huge page is swapout in one + piece without splitting. + +thp_swpout_fallback + is incremented if a huge page has to be split before swapout. + Usually because failed to allocate some continuous swap space + for the huge page. + +As the system ages, allocating huge pages may be expensive as the +system uses memory compaction to copy data around memory to free a +huge page for use. There are some counters in ``/proc/vmstat`` to help +monitor this overhead. + +compact_stall + is incremented every time a process stalls to run + memory compaction so that a huge page is free for use. + +compact_success + is incremented if the system compacted memory and + freed a huge page for use. + +compact_fail + is incremented if the system tries to compact memory + but failed. + +It is possible to establish how long the stalls were using the function +tracer to record how long was spent in __alloc_pages() and +using the mm_page_alloc tracepoint to identify which allocations were +for huge pages. + +Optimizing the applications +=========================== + +To be guaranteed that the kernel will map a 2M page immediately in any +memory region, the mmap region has to be hugepage naturally +aligned. posix_memalign() can provide that guarantee. + +Hugetlbfs +========= + +You can use hugetlbfs on a kernel that has transparent hugepage +support enabled just fine as always. No difference can be noted in +hugetlbfs other than there will be less overall fragmentation. All +usual features belonging to hugetlbfs are preserved and +unaffected. libhugetlbfs will also work fine as usual. diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst new file mode 100644 index 000000000..4349a8c2b --- /dev/null +++ b/Documentation/admin-guide/mm/userfaultfd.rst @@ -0,0 +1,392 @@ +=========== +Userfaultfd +=========== + +Objective +========= + +Userfaults allow the implementation of on-demand paging from userland +and more generally they allow userland to take control of various +memory page faults, something otherwise only the kernel code could do. + +For example userfaults allows a proper and more optimal implementation +of the ``PROT_NONE+SIGSEGV`` trick. + +Design +====== + +Userspace creates a new userfaultfd, initializes it, and registers one or more +regions of virtual memory with it. Then, any page faults which occur within the +region(s) result in a message being delivered to the userfaultfd, notifying +userspace of the fault. + +The ``userfaultfd`` (aside from registering and unregistering virtual +memory ranges) provides two primary functionalities: + +1) ``read/POLLIN`` protocol to notify a userland thread of the faults + happening + +2) various ``UFFDIO_*`` ioctls that can manage the virtual memory regions + registered in the ``userfaultfd`` that allows userland to efficiently + resolve the userfaults it receives via 1) or to manage the virtual + memory in the background + +The real advantage of userfaults if compared to regular virtual memory +management of mremap/mprotect is that the userfaults in all their +operations never involve heavyweight structures like vmas (in fact the +``userfaultfd`` runtime load never takes the mmap_lock for writing). +Vmas are not suitable for page- (or hugepage) granular fault tracking +when dealing with virtual address spaces that could span +Terabytes. Too many vmas would be needed for that. + +The ``userfaultfd``, once created, can also be +passed using unix domain sockets to a manager process, so the same +manager process could handle the userfaults of a multitude of +different processes without them being aware about what is going on +(well of course unless they later try to use the ``userfaultfd`` +themselves on the same region the manager is already tracking, which +is a corner case that would currently return ``-EBUSY``). + +API +=== + +Creating a userfaultfd +---------------------- + +There are two ways to create a new userfaultfd, each of which provide ways to +restrict access to this functionality (since historically userfaultfds which +handle kernel page faults have been a useful tool for exploiting the kernel). + +The first way, supported since userfaultfd was introduced, is the +userfaultfd(2) syscall. Access to this is controlled in several ways: + +- Any user can always create a userfaultfd which traps userspace page faults + only. Such a userfaultfd can be created using the userfaultfd(2) syscall + with the flag UFFD_USER_MODE_ONLY. + +- In order to also trap kernel page faults for the address space, either the + process needs the CAP_SYS_PTRACE capability, or the system must have + vm.unprivileged_userfaultfd set to 1. By default, vm.unprivileged_userfaultfd + is set to 0. + +The second way, added to the kernel more recently, is by opening +/dev/userfaultfd and issuing a USERFAULTFD_IOC_NEW ioctl to it. This method +yields equivalent userfaultfds to the userfaultfd(2) syscall. + +Unlike userfaultfd(2), access to /dev/userfaultfd is controlled via normal +filesystem permissions (user/group/mode), which gives fine grained access to +userfaultfd specifically, without also granting other unrelated privileges at +the same time (as e.g. granting CAP_SYS_PTRACE would do). Users who have access +to /dev/userfaultfd can always create userfaultfds that trap kernel page faults; +vm.unprivileged_userfaultfd is not considered. + +Initializing a userfaultfd +-------------------------- + +When first opened the ``userfaultfd`` must be enabled invoking the +``UFFDIO_API`` ioctl specifying a ``uffdio_api.api`` value set to ``UFFD_API`` (or +a later API version) which will specify the ``read/POLLIN`` protocol +userland intends to speak on the ``UFFD`` and the ``uffdio_api.features`` +userland requires. The ``UFFDIO_API`` ioctl if successful (i.e. if the +requested ``uffdio_api.api`` is spoken also by the running kernel and the +requested features are going to be enabled) will return into +``uffdio_api.features`` and ``uffdio_api.ioctls`` two 64bit bitmasks of +respectively all the available features of the read(2) protocol and +the generic ioctl available. + +The ``uffdio_api.features`` bitmask returned by the ``UFFDIO_API`` ioctl +defines what memory types are supported by the ``userfaultfd`` and what +events, except page fault notifications, may be generated: + +- The ``UFFD_FEATURE_EVENT_*`` flags indicate that various other events + other than page faults are supported. These events are described in more + detail below in the `Non-cooperative userfaultfd`_ section. + +- ``UFFD_FEATURE_MISSING_HUGETLBFS`` and ``UFFD_FEATURE_MISSING_SHMEM`` + indicate that the kernel supports ``UFFDIO_REGISTER_MODE_MISSING`` + registrations for hugetlbfs and shared memory (covering all shmem APIs, + i.e. tmpfs, ``IPCSHM``, ``/dev/zero``, ``MAP_SHARED``, ``memfd_create``, + etc) virtual memory areas, respectively. + +- ``UFFD_FEATURE_MINOR_HUGETLBFS`` indicates that the kernel supports + ``UFFDIO_REGISTER_MODE_MINOR`` registration for hugetlbfs virtual memory + areas. ``UFFD_FEATURE_MINOR_SHMEM`` is the analogous feature indicating + support for shmem virtual memory areas. + +The userland application should set the feature flags it intends to use +when invoking the ``UFFDIO_API`` ioctl, to request that those features be +enabled if supported. + +Once the ``userfaultfd`` API has been enabled the ``UFFDIO_REGISTER`` +ioctl should be invoked (if present in the returned ``uffdio_api.ioctls`` +bitmask) to register a memory range in the ``userfaultfd`` by setting the +uffdio_register structure accordingly. The ``uffdio_register.mode`` +bitmask will specify to the kernel which kind of faults to track for +the range. The ``UFFDIO_REGISTER`` ioctl will return the +``uffdio_register.ioctls`` bitmask of ioctls that are suitable to resolve +userfaults on the range registered. Not all ioctls will necessarily be +supported for all memory types (e.g. anonymous memory vs. shmem vs. +hugetlbfs), or all types of intercepted faults. + +Userland can use the ``uffdio_register.ioctls`` to manage the virtual +address space in the background (to add or potentially also remove +memory from the ``userfaultfd`` registered range). This means a userfault +could be triggering just before userland maps in the background the +user-faulted page. + +Resolving Userfaults +-------------------- + +There are three basic ways to resolve userfaults: + +- ``UFFDIO_COPY`` atomically copies some existing page contents from + userspace. + +- ``UFFDIO_ZEROPAGE`` atomically zeros the new page. + +- ``UFFDIO_CONTINUE`` maps an existing, previously-populated page. + +These operations are atomic in the sense that they guarantee nothing can +see a half-populated page, since readers will keep userfaulting until the +operation has finished. + +By default, these wake up userfaults blocked on the range in question. +They support a ``UFFDIO_*_MODE_DONTWAKE`` ``mode`` flag, which indicates +that waking will be done separately at some later time. + +Which ioctl to choose depends on the kind of page fault, and what we'd +like to do to resolve it: + +- For ``UFFDIO_REGISTER_MODE_MISSING`` faults, the fault needs to be + resolved by either providing a new page (``UFFDIO_COPY``), or mapping + the zero page (``UFFDIO_ZEROPAGE``). By default, the kernel would map + the zero page for a missing fault. With userfaultfd, userspace can + decide what content to provide before the faulting thread continues. + +- For ``UFFDIO_REGISTER_MODE_MINOR`` faults, there is an existing page (in + the page cache). Userspace has the option of modifying the page's + contents before resolving the fault. Once the contents are correct + (modified or not), userspace asks the kernel to map the page and let the + faulting thread continue with ``UFFDIO_CONTINUE``. + +Notes: + +- You can tell which kind of fault occurred by examining + ``pagefault.flags`` within the ``uffd_msg``, checking for the + ``UFFD_PAGEFAULT_FLAG_*`` flags. + +- None of the page-delivering ioctls default to the range that you + registered with. You must fill in all fields for the appropriate + ioctl struct including the range. + +- You get the address of the access that triggered the missing page + event out of a struct uffd_msg that you read in the thread from the + uffd. You can supply as many pages as you want with these IOCTLs. + Keep in mind that unless you used DONTWAKE then the first of any of + those IOCTLs wakes up the faulting thread. + +- Be sure to test for all errors including + (``pollfd[0].revents & POLLERR``). This can happen, e.g. when ranges + supplied were incorrect. + +Write Protect Notifications +--------------------------- + +This is equivalent to (but faster than) using mprotect and a SIGSEGV +signal handler. + +Firstly you need to register a range with ``UFFDIO_REGISTER_MODE_WP``. +Instead of using mprotect(2) you use +``ioctl(uffd, UFFDIO_WRITEPROTECT, struct *uffdio_writeprotect)`` +while ``mode = UFFDIO_WRITEPROTECT_MODE_WP`` +in the struct passed in. The range does not default to and does not +have to be identical to the range you registered with. You can write +protect as many ranges as you like (inside the registered range). +Then, in the thread reading from uffd the struct will have +``msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WP`` set. Now you send +``ioctl(uffd, UFFDIO_WRITEPROTECT, struct *uffdio_writeprotect)`` +again while ``pagefault.mode`` does not have ``UFFDIO_WRITEPROTECT_MODE_WP`` +set. This wakes up the thread which will continue to run with writes. This +allows you to do the bookkeeping about the write in the uffd reading +thread before the ioctl. + +If you registered with both ``UFFDIO_REGISTER_MODE_MISSING`` and +``UFFDIO_REGISTER_MODE_WP`` then you need to think about the sequence in +which you supply a page and undo write protect. Note that there is a +difference between writes into a WP area and into a !WP area. The +former will have ``UFFD_PAGEFAULT_FLAG_WP`` set, the latter +``UFFD_PAGEFAULT_FLAG_WRITE``. The latter did not fail on protection but +you still need to supply a page when ``UFFDIO_REGISTER_MODE_MISSING`` was +used. + +Userfaultfd write-protect mode currently behave differently on none ptes +(when e.g. page is missing) over different types of memories. + +For anonymous memory, ``ioctl(UFFDIO_WRITEPROTECT)`` will ignore none ptes +(e.g. when pages are missing and not populated). For file-backed memories +like shmem and hugetlbfs, none ptes will be write protected just like a +present pte. In other words, there will be a userfaultfd write fault +message generated when writing to a missing page on file typed memories, +as long as the page range was write-protected before. Such a message will +not be generated on anonymous memories by default. + +If the application wants to be able to write protect none ptes on anonymous +memory, one can pre-populate the memory with e.g. MADV_POPULATE_READ. On +newer kernels, one can also detect the feature UFFD_FEATURE_WP_UNPOPULATED +and set the feature bit in advance to make sure none ptes will also be +write protected even upon anonymous memory. + +When using ``UFFDIO_REGISTER_MODE_WP`` in combination with either +``UFFDIO_REGISTER_MODE_MISSING`` or ``UFFDIO_REGISTER_MODE_MINOR``, when +resolving missing / minor faults with ``UFFDIO_COPY`` or ``UFFDIO_CONTINUE`` +respectively, it may be desirable for the new page / mapping to be +write-protected (so future writes will also result in a WP fault). These ioctls +support a mode flag (``UFFDIO_COPY_MODE_WP`` or ``UFFDIO_CONTINUE_MODE_WP`` +respectively) to configure the mapping this way. + +Memory Poisioning Emulation +--------------------------- + +In response to a fault (either missing or minor), an action userspace can +take to "resolve" it is to issue a ``UFFDIO_POISON``. This will cause any +future faulters to either get a SIGBUS, or in KVM's case the guest will +receive an MCE as if there were hardware memory poisoning. + +This is used to emulate hardware memory poisoning. Imagine a VM running on a +machine which experiences a real hardware memory error. Later, we live migrate +the VM to another physical machine. Since we want the migration to be +transparent to the guest, we want that same address range to act as if it was +still poisoned, even though it's on a new physical host which ostensibly +doesn't have a memory error in the exact same spot. + +QEMU/KVM +======== + +QEMU/KVM is using the ``userfaultfd`` syscall to implement postcopy live +migration. Postcopy live migration is one form of memory +externalization consisting of a virtual machine running with part or +all of its memory residing on a different node in the cloud. The +``userfaultfd`` abstraction is generic enough that not a single line of +KVM kernel code had to be modified in order to add postcopy live +migration to QEMU. + +Guest async page faults, ``FOLL_NOWAIT`` and all other ``GUP*`` features work +just fine in combination with userfaults. Userfaults trigger async +page faults in the guest scheduler so those guest processes that +aren't waiting for userfaults (i.e. network bound) can keep running in +the guest vcpus. + +It is generally beneficial to run one pass of precopy live migration +just before starting postcopy live migration, in order to avoid +generating userfaults for readonly guest regions. + +The implementation of postcopy live migration currently uses one +single bidirectional socket but in the future two different sockets +will be used (to reduce the latency of the userfaults to the minimum +possible without having to decrease ``/proc/sys/net/ipv4/tcp_wmem``). + +The QEMU in the source node writes all pages that it knows are missing +in the destination node, into the socket, and the migration thread of +the QEMU running in the destination node runs ``UFFDIO_COPY|ZEROPAGE`` +ioctls on the ``userfaultfd`` in order to map the received pages into the +guest (``UFFDIO_ZEROCOPY`` is used if the source page was a zero page). + +A different postcopy thread in the destination node listens with +poll() to the ``userfaultfd`` in parallel. When a ``POLLIN`` event is +generated after a userfault triggers, the postcopy thread read() from +the ``userfaultfd`` and receives the fault address (or ``-EAGAIN`` in case the +userfault was already resolved and waken by a ``UFFDIO_COPY|ZEROPAGE`` run +by the parallel QEMU migration thread). + +After the QEMU postcopy thread (running in the destination node) gets +the userfault address it writes the information about the missing page +into the socket. The QEMU source node receives the information and +roughly "seeks" to that page address and continues sending all +remaining missing pages from that new page offset. Soon after that +(just the time to flush the tcp_wmem queue through the network) the +migration thread in the QEMU running in the destination node will +receive the page that triggered the userfault and it'll map it as +usual with the ``UFFDIO_COPY|ZEROPAGE`` (without actually knowing if it +was spontaneously sent by the source or if it was an urgent page +requested through a userfault). + +By the time the userfaults start, the QEMU in the destination node +doesn't need to keep any per-page state bitmap relative to the live +migration around and a single per-page bitmap has to be maintained in +the QEMU running in the source node to know which pages are still +missing in the destination node. The bitmap in the source node is +checked to find which missing pages to send in round robin and we seek +over it when receiving incoming userfaults. After sending each page of +course the bitmap is updated accordingly. It's also useful to avoid +sending the same page twice (in case the userfault is read by the +postcopy thread just before ``UFFDIO_COPY|ZEROPAGE`` runs in the migration +thread). + +Non-cooperative userfaultfd +=========================== + +When the ``userfaultfd`` is monitored by an external manager, the manager +must be able to track changes in the process virtual memory +layout. Userfaultfd can notify the manager about such changes using +the same read(2) protocol as for the page fault notifications. The +manager has to explicitly enable these events by setting appropriate +bits in ``uffdio_api.features`` passed to ``UFFDIO_API`` ioctl: + +``UFFD_FEATURE_EVENT_FORK`` + enable ``userfaultfd`` hooks for fork(). When this feature is + enabled, the ``userfaultfd`` context of the parent process is + duplicated into the newly created process. The manager + receives ``UFFD_EVENT_FORK`` with file descriptor of the new + ``userfaultfd`` context in the ``uffd_msg.fork``. + +``UFFD_FEATURE_EVENT_REMAP`` + enable notifications about mremap() calls. When the + non-cooperative process moves a virtual memory area to a + different location, the manager will receive + ``UFFD_EVENT_REMAP``. The ``uffd_msg.remap`` will contain the old and + new addresses of the area and its original length. + +``UFFD_FEATURE_EVENT_REMOVE`` + enable notifications about madvise(MADV_REMOVE) and + madvise(MADV_DONTNEED) calls. The event ``UFFD_EVENT_REMOVE`` will + be generated upon these calls to madvise(). The ``uffd_msg.remove`` + will contain start and end addresses of the removed area. + +``UFFD_FEATURE_EVENT_UNMAP`` + enable notifications about memory unmapping. The manager will + get ``UFFD_EVENT_UNMAP`` with ``uffd_msg.remove`` containing start and + end addresses of the unmapped area. + +Although the ``UFFD_FEATURE_EVENT_REMOVE`` and ``UFFD_FEATURE_EVENT_UNMAP`` +are pretty similar, they quite differ in the action expected from the +``userfaultfd`` manager. In the former case, the virtual memory is +removed, but the area is not, the area remains monitored by the +``userfaultfd``, and if a page fault occurs in that area it will be +delivered to the manager. The proper resolution for such page fault is +to zeromap the faulting address. However, in the latter case, when an +area is unmapped, either explicitly (with munmap() system call), or +implicitly (e.g. during mremap()), the area is removed and in turn the +``userfaultfd`` context for such area disappears too and the manager will +not get further userland page faults from the removed area. Still, the +notification is required in order to prevent manager from using +``UFFDIO_COPY`` on the unmapped area. + +Unlike userland page faults which have to be synchronous and require +explicit or implicit wakeup, all the events are delivered +asynchronously and the non-cooperative process resumes execution as +soon as manager executes read(). The ``userfaultfd`` manager should +carefully synchronize calls to ``UFFDIO_COPY`` with the events +processing. To aid the synchronization, the ``UFFDIO_COPY`` ioctl will +return ``-ENOSPC`` when the monitored process exits at the time of +``UFFDIO_COPY``, and ``-ENOENT``, when the non-cooperative process has changed +its virtual memory layout simultaneously with outstanding ``UFFDIO_COPY`` +operation. + +The current asynchronous model of the event delivery is optimal for +single threaded non-cooperative ``userfaultfd`` manager implementations. A +synchronous event delivery model can be added later as a new +``userfaultfd`` feature to facilitate multithreading enhancements of the +non cooperative manager, for example to allow ``UFFDIO_COPY`` ioctls to +run in parallel to the event reception. Single threaded +implementations should continue to use the current async event +delivery model instead. diff --git a/Documentation/admin-guide/mm/zswap.rst b/Documentation/admin-guide/mm/zswap.rst new file mode 100644 index 000000000..45b98390e --- /dev/null +++ b/Documentation/admin-guide/mm/zswap.rst @@ -0,0 +1,158 @@ +===== +zswap +===== + +Overview +======== + +Zswap is a lightweight compressed cache for swap pages. It takes pages that are +in the process of being swapped out and attempts to compress them into a +dynamically allocated RAM-based memory pool. zswap basically trades CPU cycles +for potentially reduced swap I/O. This trade-off can also result in a +significant performance improvement if reads from the compressed cache are +faster than reads from a swap device. + +Some potential benefits: + +* Desktop/laptop users with limited RAM capacities can mitigate the + performance impact of swapping. +* Overcommitted guests that share a common I/O resource can + dramatically reduce their swap I/O pressure, avoiding heavy handed I/O + throttling by the hypervisor. This allows more work to get done with less + impact to the guest workload and guests sharing the I/O subsystem +* Users with SSDs as swap devices can extend the life of the device by + drastically reducing life-shortening writes. + +Zswap evicts pages from compressed cache on an LRU basis to the backing swap +device when the compressed pool reaches its size limit. This requirement had +been identified in prior community discussions. + +Whether Zswap is enabled at the boot time depends on whether +the ``CONFIG_ZSWAP_DEFAULT_ON`` Kconfig option is enabled or not. +This setting can then be overridden by providing the kernel command line +``zswap.enabled=`` option, for example ``zswap.enabled=0``. +Zswap can also be enabled and disabled at runtime using the sysfs interface. +An example command to enable zswap at runtime, assuming sysfs is mounted +at ``/sys``, is:: + + echo 1 > /sys/module/zswap/parameters/enabled + +When zswap is disabled at runtime it will stop storing pages that are +being swapped out. However, it will _not_ immediately write out or fault +back into memory all of the pages stored in the compressed pool. The +pages stored in zswap will remain in the compressed pool until they are +either invalidated or faulted back into memory. In order to force all +pages out of the compressed pool, a swapoff on the swap device(s) will +fault back into memory all swapped out pages, including those in the +compressed pool. + +Design +====== + +Zswap receives pages for compression from the swap subsystem and is able to +evict pages from its own compressed pool on an LRU basis and write them back to +the backing swap device in the case that the compressed pool is full. + +Zswap makes use of zpool for the managing the compressed memory pool. Each +allocation in zpool is not directly accessible by address. Rather, a handle is +returned by the allocation routine and that handle must be mapped before being +accessed. The compressed memory pool grows on demand and shrinks as compressed +pages are freed. The pool is not preallocated. By default, a zpool +of type selected in ``CONFIG_ZSWAP_ZPOOL_DEFAULT`` Kconfig option is created, +but it can be overridden at boot time by setting the ``zpool`` attribute, +e.g. ``zswap.zpool=zbud``. It can also be changed at runtime using the sysfs +``zpool`` attribute, e.g.:: + + echo zbud > /sys/module/zswap/parameters/zpool + +The zbud type zpool allocates exactly 1 page to store 2 compressed pages, which +means the compression ratio will always be 2:1 or worse (because of half-full +zbud pages). The zsmalloc type zpool has a more complex compressed page +storage method, and it can achieve greater storage densities. + +When a swap page is passed from swapout to zswap, zswap maintains a mapping +of the swap entry, a combination of the swap type and swap offset, to the zpool +handle that references that compressed swap page. This mapping is achieved +with a red-black tree per swap type. The swap offset is the search key for the +tree nodes. + +During a page fault on a PTE that is a swap entry, the swapin code calls the +zswap load function to decompress the page into the page allocated by the page +fault handler. + +Once there are no PTEs referencing a swap page stored in zswap (i.e. the count +in the swap_map goes to 0) the swap code calls the zswap invalidate function +to free the compressed entry. + +Zswap seeks to be simple in its policies. Sysfs attributes allow for one user +controlled policy: + +* max_pool_percent - The maximum percentage of memory that the compressed + pool can occupy. + +The default compressor is selected in ``CONFIG_ZSWAP_COMPRESSOR_DEFAULT`` +Kconfig option, but it can be overridden at boot time by setting the +``compressor`` attribute, e.g. ``zswap.compressor=lzo``. +It can also be changed at runtime using the sysfs "compressor" +attribute, e.g.:: + + echo lzo > /sys/module/zswap/parameters/compressor + +When the zpool and/or compressor parameter is changed at runtime, any existing +compressed pages are not modified; they are left in their own zpool. When a +request is made for a page in an old zpool, it is uncompressed using its +original compressor. Once all pages are removed from an old zpool, the zpool +and its compressor are freed. + +Some of the pages in zswap are same-value filled pages (i.e. contents of the +page have same value or repetitive pattern). These pages include zero-filled +pages and they are handled differently. During store operation, a page is +checked if it is a same-value filled page before compressing it. If true, the +compressed length of the page is set to zero and the pattern or same-filled +value is stored. + +Same-value filled pages identification feature is enabled by default and can be +disabled at boot time by setting the ``same_filled_pages_enabled`` attribute +to 0, e.g. ``zswap.same_filled_pages_enabled=0``. It can also be enabled and +disabled at runtime using the sysfs ``same_filled_pages_enabled`` +attribute, e.g.:: + + echo 1 > /sys/module/zswap/parameters/same_filled_pages_enabled + +When zswap same-filled page identification is disabled at runtime, it will stop +checking for the same-value filled pages during store operation. +In other words, every page will be then considered non-same-value filled. +However, the existing pages which are marked as same-value filled pages remain +stored unchanged in zswap until they are either loaded or invalidated. + +In some circumstances it might be advantageous to make use of just the zswap +ability to efficiently store same-filled pages without enabling the whole +compressed page storage. +In this case the handling of non-same-value pages by zswap (enabled by default) +can be disabled by setting the ``non_same_filled_pages_enabled`` attribute +to 0, e.g. ``zswap.non_same_filled_pages_enabled=0``. +It can also be enabled and disabled at runtime using the sysfs +``non_same_filled_pages_enabled`` attribute, e.g.:: + + echo 1 > /sys/module/zswap/parameters/non_same_filled_pages_enabled + +Disabling both ``zswap.same_filled_pages_enabled`` and +``zswap.non_same_filled_pages_enabled`` effectively disables accepting any new +pages by zswap. + +To prevent zswap from shrinking pool when zswap is full and there's a high +pressure on swap (this will result in flipping pages in and out zswap pool +without any real benefit but with a performance drop for the system), a +special parameter has been introduced to implement a sort of hysteresis to +refuse taking pages into zswap pool until it has sufficient space if the limit +has been hit. To set the threshold at which zswap would start accepting pages +again after it became full, use the sysfs ``accept_threshold_percent`` +attribute, e. g.:: + + echo 80 > /sys/module/zswap/parameters/accept_threshold_percent + +Setting this parameter to 100 will disable the hysteresis. + +A debugfs interface is provided for various statistic about pool size, number +of pages stored, same-value filled pages and various counters for the reasons +pages are rejected. diff --git a/Documentation/admin-guide/module-signing.rst b/Documentation/admin-guide/module-signing.rst new file mode 100644 index 000000000..2898b2703 --- /dev/null +++ b/Documentation/admin-guide/module-signing.rst @@ -0,0 +1,285 @@ +Kernel module signing facility +------------------------------ + +.. CONTENTS +.. +.. - Overview. +.. - Configuring module signing. +.. - Generating signing keys. +.. - Public keys in the kernel. +.. - Manually signing modules. +.. - Signed modules and stripping. +.. - Loading signed modules. +.. - Non-valid signatures and unsigned modules. +.. - Administering/protecting the private key. + + +======== +Overview +======== + +The kernel module signing facility cryptographically signs modules during +installation and then checks the signature upon loading the module. This +allows increased kernel security by disallowing the loading of unsigned modules +or modules signed with an invalid key. Module signing increases security by +making it harder to load a malicious module into the kernel. The module +signature checking is done by the kernel so that it is not necessary to have +trusted userspace bits. + +This facility uses X.509 ITU-T standard certificates to encode the public keys +involved. The signatures are not themselves encoded in any industrial standard +type. The facility currently only supports the RSA public key encryption +standard (though it is pluggable and permits others to be used). The possible +hash algorithms that can be used are SHA-1, SHA-224, SHA-256, SHA-384, and +SHA-512 (the algorithm is selected by data in the signature). + + +========================== +Configuring module signing +========================== + +The module signing facility is enabled by going to the +:menuselection:`Enable Loadable Module Support` section of +the kernel configuration and turning on:: + + CONFIG_MODULE_SIG "Module signature verification" + +This has a number of options available: + + (1) :menuselection:`Require modules to be validly signed` + (``CONFIG_MODULE_SIG_FORCE``) + + This specifies how the kernel should deal with a module that has a + signature for which the key is not known or a module that is unsigned. + + If this is off (ie. "permissive"), then modules for which the key is not + available and modules that are unsigned are permitted, but the kernel will + be marked as being tainted, and the concerned modules will be marked as + tainted, shown with the character 'E'. + + If this is on (ie. "restrictive"), only modules that have a valid + signature that can be verified by a public key in the kernel's possession + will be loaded. All other modules will generate an error. + + Irrespective of the setting here, if the module has a signature block that + cannot be parsed, it will be rejected out of hand. + + + (2) :menuselection:`Automatically sign all modules` + (``CONFIG_MODULE_SIG_ALL``) + + If this is on then modules will be automatically signed during the + modules_install phase of a build. If this is off, then the modules must + be signed manually using:: + + scripts/sign-file + + + (3) :menuselection:`Which hash algorithm should modules be signed with?` + + This presents a choice of which hash algorithm the installation phase will + sign the modules with: + + =============================== ========================================== + ``CONFIG_MODULE_SIG_SHA1`` :menuselection:`Sign modules with SHA-1` + ``CONFIG_MODULE_SIG_SHA224`` :menuselection:`Sign modules with SHA-224` + ``CONFIG_MODULE_SIG_SHA256`` :menuselection:`Sign modules with SHA-256` + ``CONFIG_MODULE_SIG_SHA384`` :menuselection:`Sign modules with SHA-384` + ``CONFIG_MODULE_SIG_SHA512`` :menuselection:`Sign modules with SHA-512` + =============================== ========================================== + + The algorithm selected here will also be built into the kernel (rather + than being a module) so that modules signed with that algorithm can have + their signatures checked without causing a dependency loop. + + + (4) :menuselection:`File name or PKCS#11 URI of module signing key` + (``CONFIG_MODULE_SIG_KEY``) + + Setting this option to something other than its default of + ``certs/signing_key.pem`` will disable the autogeneration of signing keys + and allow the kernel modules to be signed with a key of your choosing. + The string provided should identify a file containing both a private key + and its corresponding X.509 certificate in PEM form, or — on systems where + the OpenSSL ENGINE_pkcs11 is functional — a PKCS#11 URI as defined by + RFC7512. In the latter case, the PKCS#11 URI should reference both a + certificate and a private key. + + If the PEM file containing the private key is encrypted, or if the + PKCS#11 token requires a PIN, this can be provided at build time by + means of the ``KBUILD_SIGN_PIN`` variable. + + + (5) :menuselection:`Additional X.509 keys for default system keyring` + (``CONFIG_SYSTEM_TRUSTED_KEYS``) + + This option can be set to the filename of a PEM-encoded file containing + additional certificates which will be included in the system keyring by + default. + +Note that enabling module signing adds a dependency on the OpenSSL devel +packages to the kernel build processes for the tool that does the signing. + + +======================= +Generating signing keys +======================= + +Cryptographic keypairs are required to generate and check signatures. A +private key is used to generate a signature and the corresponding public key is +used to check it. The private key is only needed during the build, after which +it can be deleted or stored securely. The public key gets built into the +kernel so that it can be used to check the signatures as the modules are +loaded. + +Under normal conditions, when ``CONFIG_MODULE_SIG_KEY`` is unchanged from its +default, the kernel build will automatically generate a new keypair using +openssl if one does not exist in the file:: + + certs/signing_key.pem + +during the building of vmlinux (the public part of the key needs to be built +into vmlinux) using parameters in the:: + + certs/x509.genkey + +file (which is also generated if it does not already exist). + +It is strongly recommended that you provide your own x509.genkey file. + +Most notably, in the x509.genkey file, the req_distinguished_name section +should be altered from the default:: + + [ req_distinguished_name ] + #O = Unspecified company + CN = Build time autogenerated kernel key + #emailAddress = unspecified.user@unspecified.company + +The generated RSA key size can also be set with:: + + [ req ] + default_bits = 4096 + + +It is also possible to manually generate the key private/public files using the +x509.genkey key generation configuration file in the root node of the Linux +kernel sources tree and the openssl command. The following is an example to +generate the public/private key files:: + + openssl req -new -nodes -utf8 -sha256 -days 36500 -batch -x509 \ + -config x509.genkey -outform PEM -out kernel_key.pem \ + -keyout kernel_key.pem + +The full pathname for the resulting kernel_key.pem file can then be specified +in the ``CONFIG_MODULE_SIG_KEY`` option, and the certificate and key therein will +be used instead of an autogenerated keypair. + + +========================= +Public keys in the kernel +========================= + +The kernel contains a ring of public keys that can be viewed by root. They're +in a keyring called ".builtin_trusted_keys" that can be seen by:: + + [root@deneb ~]# cat /proc/keys + ... + 223c7853 I------ 1 perm 1f030000 0 0 keyring .builtin_trusted_keys: 1 + 302d2d52 I------ 1 perm 1f010000 0 0 asymmetri Fedora kernel signing key: d69a84e6bce3d216b979e9505b3e3ef9a7118079: X509.RSA a7118079 [] + ... + +Beyond the public key generated specifically for module signing, additional +trusted certificates can be provided in a PEM-encoded file referenced by the +``CONFIG_SYSTEM_TRUSTED_KEYS`` configuration option. + +Further, the architecture code may take public keys from a hardware store and +add those in also (e.g. from the UEFI key database). + +Finally, it is possible to add additional public keys by doing:: + + keyctl padd asymmetric "" [.builtin_trusted_keys-ID] <[key-file] + +e.g.:: + + keyctl padd asymmetric "" 0x223c7853 <my_public_key.x509 + +Note, however, that the kernel will only permit keys to be added to +``.builtin_trusted_keys`` **if** the new key's X.509 wrapper is validly signed by a key +that is already resident in the ``.builtin_trusted_keys`` at the time the key was added. + + +======================== +Manually signing modules +======================== + +To manually sign a module, use the scripts/sign-file tool available in +the Linux kernel source tree. The script requires 4 arguments: + + 1. The hash algorithm (e.g., sha256) + 2. The private key filename or PKCS#11 URI + 3. The public key filename + 4. The kernel module to be signed + +The following is an example to sign a kernel module:: + + scripts/sign-file sha512 kernel-signkey.priv \ + kernel-signkey.x509 module.ko + +The hash algorithm used does not have to match the one configured, but if it +doesn't, you should make sure that hash algorithm is either built into the +kernel or can be loaded without requiring itself. + +If the private key requires a passphrase or PIN, it can be provided in the +$KBUILD_SIGN_PIN environment variable. + + +============================ +Signed modules and stripping +============================ + +A signed module has a digital signature simply appended at the end. The string +``~Module signature appended~.`` at the end of the module's file confirms that a +signature is present but it does not confirm that the signature is valid! + +Signed modules are BRITTLE as the signature is outside of the defined ELF +container. Thus they MAY NOT be stripped once the signature is computed and +attached. Note the entire module is the signed payload, including any and all +debug information present at the time of signing. + + +====================== +Loading signed modules +====================== + +Modules are loaded with insmod, modprobe, ``init_module()`` or +``finit_module()``, exactly as for unsigned modules as no processing is +done in userspace. The signature checking is all done within the kernel. + + +========================================= +Non-valid signatures and unsigned modules +========================================= + +If ``CONFIG_MODULE_SIG_FORCE`` is enabled or module.sig_enforce=1 is supplied on +the kernel command line, the kernel will only load validly signed modules +for which it has a public key. Otherwise, it will also load modules that are +unsigned. Any module for which the kernel has a key, but which proves to have +a signature mismatch will not be permitted to load. + +Any module that has an unparsable signature will be rejected. + + +========================================= +Administering/protecting the private key +========================================= + +Since the private key is used to sign modules, viruses and malware could use +the private key to sign modules and compromise the operating system. The +private key must be either destroyed or moved to a secure location and not kept +in the root node of the kernel source tree. + +If you use the same private key to sign modules for multiple kernel +configurations, you must ensure that the module version information is +sufficient to prevent loading a module into a different kernel. Either +set ``CONFIG_MODVERSIONS=y`` or ensure that each configuration has a different +kernel release string by changing ``EXTRAVERSION`` or ``CONFIG_LOCALVERSION``. diff --git a/Documentation/admin-guide/mono.rst b/Documentation/admin-guide/mono.rst new file mode 100644 index 000000000..c6dab5680 --- /dev/null +++ b/Documentation/admin-guide/mono.rst @@ -0,0 +1,70 @@ +Mono(tm) Binary Kernel Support for Linux +----------------------------------------- + +To configure Linux to automatically execute Mono-based .NET binaries +(in the form of .exe files) without the need to use the mono CLR +wrapper, you can use the BINFMT_MISC kernel support. + +This will allow you to execute Mono-based .NET binaries just like any +other program after you have done the following: + +1) You MUST FIRST install the Mono CLR support, either by downloading + a binary package, a source tarball or by installing from Git. Binary + packages for several distributions can be found at: + + https://www.mono-project.com/download/ + + Instructions for compiling Mono can be found at: + + https://www.mono-project.com/docs/compiling-mono/linux/ + + Once the Mono CLR support has been installed, just check that + ``/usr/bin/mono`` (which could be located elsewhere, for example + ``/usr/local/bin/mono``) is working. + +2) You have to compile BINFMT_MISC either as a module or into + the kernel (``CONFIG_BINFMT_MISC``) and set it up properly. + If you choose to compile it as a module, you will have + to insert it manually with modprobe/insmod, as kmod + cannot be easily supported with binfmt_misc. + Read the file ``binfmt_misc.txt`` in this directory to know + more about the configuration process. + +3) Add the following entries to ``/etc/rc.local`` or similar script + to be run at system startup: + + .. code-block:: sh + + # Insert BINFMT_MISC module into the kernel + if [ ! -e /proc/sys/fs/binfmt_misc/register ]; then + /sbin/modprobe binfmt_misc + # Some distributions, like Fedora Core, perform + # the following command automatically when the + # binfmt_misc module is loaded into the kernel + # or during normal boot up (systemd-based systems). + # Thus, it is possible that the following line + # is not needed at all. + mount -t binfmt_misc none /proc/sys/fs/binfmt_misc + fi + + # Register support for .NET CLR binaries + if [ -e /proc/sys/fs/binfmt_misc/register ]; then + # Replace /usr/bin/mono with the correct pathname to + # the Mono CLR runtime (usually /usr/local/bin/mono + # when compiling from sources or CVS). + echo ':CLR:M::MZ::/usr/bin/mono:' > /proc/sys/fs/binfmt_misc/register + else + echo "No binfmt_misc support" + exit 1 + fi + +4) Check that ``.exe`` binaries can be ran without the need of a + wrapper script, simply by launching the ``.exe`` file directly + from a command prompt, for example:: + + /usr/bin/xsd.exe + + .. note:: + + If this fails with a permission denied error, check + that the ``.exe`` file has execute permissions. diff --git a/Documentation/admin-guide/namespaces/compatibility-list.rst b/Documentation/admin-guide/namespaces/compatibility-list.rst new file mode 100644 index 000000000..318800b2a --- /dev/null +++ b/Documentation/admin-guide/namespaces/compatibility-list.rst @@ -0,0 +1,43 @@ +============================= +Namespaces compatibility list +============================= + +This document contains the information about the problems user +may have when creating tasks living in different namespaces. + +Here's the summary. This matrix shows the known problems, that +occur when tasks share some namespace (the columns) while living +in different other namespaces (the rows): + +==== === === === === ==== === +- UTS IPC VFS PID User Net +==== === === === === ==== === +UTS X +IPC X 1 +VFS X +PID 1 1 X +User 2 2 X +Net X +==== === === === === ==== === + +1. Both the IPC and the PID namespaces provide IDs to address + object inside the kernel. E.g. semaphore with IPCID or + process group with pid. + + In both cases, tasks shouldn't try exposing this ID to some + other task living in a different namespace via a shared filesystem + or IPC shmem/message. The fact is that this ID is only valid + within the namespace it was obtained in and may refer to some + other object in another namespace. + +2. Intentionally, two equal user IDs in different user namespaces + should not be equal from the VFS point of view. In other + words, user 10 in one user namespace shouldn't have the same + access permissions to files, belonging to user 10 in another + namespace. + + The same is true for the IPC namespaces being shared - two users + from different user namespaces should not access the same IPC objects + even having equal UIDs. + + But currently this is not so. diff --git a/Documentation/admin-guide/namespaces/index.rst b/Documentation/admin-guide/namespaces/index.rst new file mode 100644 index 000000000..384f2e0f3 --- /dev/null +++ b/Documentation/admin-guide/namespaces/index.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========== +Namespaces +========== + +.. toctree:: + :maxdepth: 1 + + compatibility-list + resource-control diff --git a/Documentation/admin-guide/namespaces/resource-control.rst b/Documentation/admin-guide/namespaces/resource-control.rst new file mode 100644 index 000000000..369556e00 --- /dev/null +++ b/Documentation/admin-guide/namespaces/resource-control.rst @@ -0,0 +1,18 @@ +=========================== +Namespaces research control +=========================== + +There are a lot of kinds of objects in the kernel that don't have +individual limits or that have limits that are ineffective when a set +of processes is allowed to switch user ids. With user namespaces +enabled in a kernel for people who don't trust their users or their +users programs to play nice this problems becomes more acute. + +Therefore it is recommended that memory control groups be enabled in +kernels that enable user namespaces, and it is further recommended +that userspace configure memory control groups to limit how much +memory user's they don't trust to play nice can use. + +Memory control groups can be configured by installing the libcgroup +package present on most distros editing /etc/cgrules.conf, +/etc/cgconfig.conf and setting up libpam-cgroup. diff --git a/Documentation/admin-guide/nfs/index.rst b/Documentation/admin-guide/nfs/index.rst new file mode 100644 index 000000000..3601a708f --- /dev/null +++ b/Documentation/admin-guide/nfs/index.rst @@ -0,0 +1,14 @@ +============= +NFS +============= + +.. toctree:: + :maxdepth: 1 + + nfs-client + nfsroot + nfs-rdma + nfsd-admin-interfaces + nfs-idmapper + pnfs-block-server + pnfs-scsi-server diff --git a/Documentation/admin-guide/nfs/nfs-client.rst b/Documentation/admin-guide/nfs/nfs-client.rst new file mode 100644 index 000000000..36760685d --- /dev/null +++ b/Documentation/admin-guide/nfs/nfs-client.rst @@ -0,0 +1,144 @@ +========== +NFS Client +========== + +The NFS client +============== + +The NFS version 2 protocol was first documented in RFC1094 (March 1989). +Since then two more major releases of NFS have been published, with NFSv3 +being documented in RFC1813 (June 1995), and NFSv4 in RFC3530 (April +2003). + +The Linux NFS client currently supports all the above published versions, +and work is in progress on adding support for minor version 1 of the NFSv4 +protocol. + +The purpose of this document is to provide information on some of the +special features of the NFS client that can be configured by system +administrators. + + +The nfs4_unique_id parameter +============================ + +NFSv4 requires clients to identify themselves to servers with a unique +string. File open and lock state shared between one client and one server +is associated with this identity. To support robust NFSv4 state recovery +and transparent state migration, this identity string must not change +across client reboots. + +Without any other intervention, the Linux client uses a string that contains +the local system's node name. System administrators, however, often do not +take care to ensure that node names are fully qualified and do not change +over the lifetime of a client system. Node names can have other +administrative requirements that require particular behavior that does not +work well as part of an nfs_client_id4 string. + +The nfs.nfs4_unique_id boot parameter specifies a unique string that can be +used together with a system's node name when an NFS client identifies itself to +a server. Thus, if the system's node name is not unique, its +nfs.nfs4_unique_id can help prevent collisions with other clients. + +The nfs.nfs4_unique_id string is typically a UUID, though it can contain +anything that is believed to be unique across all NFS clients. An +nfs4_unique_id string should be chosen when a client system is installed, +just as a system's root file system gets a fresh UUID in its label at +install time. + +The string should remain fixed for the lifetime of the client. It can be +changed safely if care is taken that the client shuts down cleanly and all +outstanding NFSv4 state has expired, to prevent loss of NFSv4 state. + +This string can be stored in an NFS client's grub.conf, or it can be provided +via a net boot facility such as PXE. It may also be specified as an nfs.ko +module parameter. + +This uniquifier string will be the same for all NFS clients running in +containers unless it is overridden by a value written to +/sys/fs/nfs/net/nfs_client/identifier which will be local to the network +namespace of the process which writes. + + +The DNS resolver +================ + +NFSv4 allows for one server to refer the NFS client to data that has been +migrated onto another server by means of the special "fs_locations" +attribute. See `RFC3530 Section 6: Filesystem Migration and Replication`_ and +`Implementation Guide for Referrals in NFSv4`_. + +.. _RFC3530 Section 6\: Filesystem Migration and Replication: https://tools.ietf.org/html/rfc3530#section-6 +.. _Implementation Guide for Referrals in NFSv4: https://tools.ietf.org/html/draft-ietf-nfsv4-referrals-00 + +The fs_locations information can take the form of either an ip address and +a path, or a DNS hostname and a path. The latter requires the NFS client to +do a DNS lookup in order to mount the new volume, and hence the need for an +upcall to allow userland to provide this service. + +Assuming that the user has the 'rpc_pipefs' filesystem mounted in the usual +/var/lib/nfs/rpc_pipefs, the upcall consists of the following steps: + + (1) The process checks the dns_resolve cache to see if it contains a + valid entry. If so, it returns that entry and exits. + + (2) If no valid entry exists, the helper script '/sbin/nfs_cache_getent' + (may be changed using the 'nfs.cache_getent' kernel boot parameter) + is run, with two arguments: + - the cache name, "dns_resolve" + - the hostname to resolve + + (3) After looking up the corresponding ip address, the helper script + writes the result into the rpc_pipefs pseudo-file + '/var/lib/nfs/rpc_pipefs/cache/dns_resolve/channel' + in the following (text) format: + + "<ip address> <hostname> <ttl>\n" + + Where <ip address> is in the usual IPv4 (123.456.78.90) or IPv6 + (ffee:ddcc:bbaa:9988:7766:5544:3322:1100, ffee::1100, ...) format. + <hostname> is identical to the second argument of the helper + script, and <ttl> is the 'time to live' of this cache entry (in + units of seconds). + + .. note:: + If <ip address> is invalid, say the string "0", then a negative + entry is created, which will cause the kernel to treat the hostname + as having no valid DNS translation. + + + + +A basic sample /sbin/nfs_cache_getent +===================================== +.. code-block:: sh + + #!/bin/bash + # + ttl=600 + # + cut=/usr/bin/cut + getent=/usr/bin/getent + rpc_pipefs=/var/lib/nfs/rpc_pipefs + # + die() + { + echo "Usage: $0 cache_name entry_name" + exit 1 + } + + [ $# -lt 2 ] && die + cachename="$1" + cache_path=${rpc_pipefs}/cache/${cachename}/channel + + case "${cachename}" in + dns_resolve) + name="$2" + result="$(${getent} hosts ${name} | ${cut} -f1 -d\ )" + [ -z "${result}" ] && result="0" + ;; + *) + die + ;; + esac + echo "${result} ${name} ${ttl}" >${cache_path} diff --git a/Documentation/admin-guide/nfs/nfs-idmapper.rst b/Documentation/admin-guide/nfs/nfs-idmapper.rst new file mode 100644 index 000000000..58b8e6341 --- /dev/null +++ b/Documentation/admin-guide/nfs/nfs-idmapper.rst @@ -0,0 +1,78 @@ +============= +NFS ID Mapper +============= + +Id mapper is used by NFS to translate user and group ids into names, and to +translate user and group names into ids. Part of this translation involves +performing an upcall to userspace to request the information. There are two +ways NFS could obtain this information: placing a call to /sbin/request-key +or by placing a call to the rpc.idmap daemon. + +NFS will attempt to call /sbin/request-key first. If this succeeds, the +result will be cached using the generic request-key cache. This call should +only fail if /etc/request-key.conf is not configured for the id_resolver key +type, see the "Configuring" section below if you wish to use the request-key +method. + +If the call to /sbin/request-key fails (if /etc/request-key.conf is not +configured with the id_resolver key type), then the idmapper will ask the +legacy rpc.idmap daemon for the id mapping. This result will be stored +in a custom NFS idmap cache. + + +Configuring +=========== + +The file /etc/request-key.conf will need to be modified so /sbin/request-key can +direct the upcall. The following line should be added: + +``#OP TYPE DESCRIPTION CALLOUT INFO PROGRAM ARG1 ARG2 ARG3 ...`` +``#====== ======= =============== =============== ===============================`` +``create id_resolver * * /usr/sbin/nfs.idmap %k %d 600`` + + +This will direct all id_resolver requests to the program /usr/sbin/nfs.idmap. +The last parameter, 600, defines how many seconds into the future the key will +expire. This parameter is optional for /usr/sbin/nfs.idmap. When the timeout +is not specified, nfs.idmap will default to 600 seconds. + +id mapper uses for key descriptions:: + + uid: Find the UID for the given user + gid: Find the GID for the given group + user: Find the user name for the given UID + group: Find the group name for the given GID + +You can handle any of these individually, rather than using the generic upcall +program. If you would like to use your own program for a uid lookup then you +would edit your request-key.conf so it look similar to this: + +``#OP TYPE DESCRIPTION CALLOUT INFO PROGRAM ARG1 ARG2 ARG3 ...`` +``#====== ======= =============== =============== ===============================`` +``create id_resolver uid:* * /some/other/program %k %d 600`` +``create id_resolver * * /usr/sbin/nfs.idmap %k %d 600`` + + +Notice that the new line was added above the line for the generic program. +request-key will find the first matching line and corresponding program. In +this case, /some/other/program will handle all uid lookups and +/usr/sbin/nfs.idmap will handle gid, user, and group lookups. + +See Documentation/security/keys/request-key.rst for more information +about the request-key function. + + +nfs.idmap +========= + +nfs.idmap is designed to be called by request-key, and should not be run "by +hand". This program takes two arguments, a serialized key and a key +description. The serialized key is first converted into a key_serial_t, and +then passed as an argument to keyctl_instantiate (both are part of keyutils.h). + +The actual lookups are performed by functions found in nfsidmap.h. nfs.idmap +determines the correct function to call by looking at the first part of the +description string. For example, a uid lookup description will appear as +"uid:user@domain". + +nfs.idmap will return 0 if the key was instantiated, and non-zero otherwise. diff --git a/Documentation/admin-guide/nfs/nfs-rdma.rst b/Documentation/admin-guide/nfs/nfs-rdma.rst new file mode 100644 index 000000000..f137485f8 --- /dev/null +++ b/Documentation/admin-guide/nfs/nfs-rdma.rst @@ -0,0 +1,292 @@ +=================== +Setting up NFS/RDMA +=================== + +:Author: + NetApp and Open Grid Computing (May 29, 2008) + +.. warning:: + This document is probably obsolete. + +Overview +======== + +This document describes how to install and setup the Linux NFS/RDMA client +and server software. + +The NFS/RDMA client was first included in Linux 2.6.24. The NFS/RDMA server +was first included in the following release, Linux 2.6.25. + +In our testing, we have obtained excellent performance results (full 10Gbit +wire bandwidth at minimal client CPU) under many workloads. The code passes +the full Connectathon test suite and operates over both Infiniband and iWARP +RDMA adapters. + +Getting Help +============ + +If you get stuck, you can ask questions on the +nfs-rdma-devel@lists.sourceforge.net mailing list. + +Installation +============ + +These instructions are a step by step guide to building a machine for +use with NFS/RDMA. + +- Install an RDMA device + + Any device supported by the drivers in drivers/infiniband/hw is acceptable. + + Testing has been performed using several Mellanox-based IB cards, the + Ammasso AMS1100 iWARP adapter, and the Chelsio cxgb3 iWARP adapter. + +- Install a Linux distribution and tools + + The first kernel release to contain both the NFS/RDMA client and server was + Linux 2.6.25 Therefore, a distribution compatible with this and subsequent + Linux kernel release should be installed. + + The procedures described in this document have been tested with + distributions from Red Hat's Fedora Project (http://fedora.redhat.com/). + +- Install nfs-utils-1.1.2 or greater on the client + + An NFS/RDMA mount point can be obtained by using the mount.nfs command in + nfs-utils-1.1.2 or greater (nfs-utils-1.1.1 was the first nfs-utils + version with support for NFS/RDMA mounts, but for various reasons we + recommend using nfs-utils-1.1.2 or greater). To see which version of + mount.nfs you are using, type: + + .. code-block:: sh + + $ /sbin/mount.nfs -V + + If the version is less than 1.1.2 or the command does not exist, + you should install the latest version of nfs-utils. + + Download the latest package from: https://www.kernel.org/pub/linux/utils/nfs + + Uncompress the package and follow the installation instructions. + + If you will not need the idmapper and gssd executables (you do not need + these to create an NFS/RDMA enabled mount command), the installation + process can be simplified by disabling these features when running + configure: + + .. code-block:: sh + + $ ./configure --disable-gss --disable-nfsv4 + + To build nfs-utils you will need the tcp_wrappers package installed. For + more information on this see the package's README and INSTALL files. + + After building the nfs-utils package, there will be a mount.nfs binary in + the utils/mount directory. This binary can be used to initiate NFS v2, v3, + or v4 mounts. To initiate a v4 mount, the binary must be called + mount.nfs4. The standard technique is to create a symlink called + mount.nfs4 to mount.nfs. + + This mount.nfs binary should be installed at /sbin/mount.nfs as follows: + + .. code-block:: sh + + $ sudo cp utils/mount/mount.nfs /sbin/mount.nfs + + In this location, mount.nfs will be invoked automatically for NFS mounts + by the system mount command. + + .. note:: + mount.nfs and therefore nfs-utils-1.1.2 or greater is only needed + on the NFS client machine. You do not need this specific version of + nfs-utils on the server. Furthermore, only the mount.nfs command from + nfs-utils-1.1.2 is needed on the client. + +- Install a Linux kernel with NFS/RDMA + + The NFS/RDMA client and server are both included in the mainline Linux + kernel version 2.6.25 and later. This and other versions of the Linux + kernel can be found at: https://www.kernel.org/pub/linux/kernel/ + + Download the sources and place them in an appropriate location. + +- Configure the RDMA stack + + Make sure your kernel configuration has RDMA support enabled. Under + Device Drivers -> InfiniBand support, update the kernel configuration + to enable InfiniBand support [NOTE: the option name is misleading. Enabling + InfiniBand support is required for all RDMA devices (IB, iWARP, etc.)]. + + Enable the appropriate IB HCA support (mlx4, mthca, ehca, ipath, etc.) or + iWARP adapter support (amso, cxgb3, etc.). + + If you are using InfiniBand, be sure to enable IP-over-InfiniBand support. + +- Configure the NFS client and server + + Your kernel configuration must also have NFS file system support and/or + NFS server support enabled. These and other NFS related configuration + options can be found under File Systems -> Network File Systems. + +- Build, install, reboot + + The NFS/RDMA code will be enabled automatically if NFS and RDMA + are turned on. The NFS/RDMA client and server are configured via the hidden + SUNRPC_XPRT_RDMA config option that depends on SUNRPC and INFINIBAND. The + value of SUNRPC_XPRT_RDMA will be: + + #. N if either SUNRPC or INFINIBAND are N, in this case the NFS/RDMA client + and server will not be built + + #. M if both SUNRPC and INFINIBAND are on (M or Y) and at least one is M, + in this case the NFS/RDMA client and server will be built as modules + + #. Y if both SUNRPC and INFINIBAND are Y, in this case the NFS/RDMA client + and server will be built into the kernel + + Therefore, if you have followed the steps above and turned no NFS and RDMA, + the NFS/RDMA client and server will be built. + + Build a new kernel, install it, boot it. + +Check RDMA and NFS Setup +======================== + +Before configuring the NFS/RDMA software, it is a good idea to test +your new kernel to ensure that the kernel is working correctly. +In particular, it is a good idea to verify that the RDMA stack +is functioning as expected and standard NFS over TCP/IP and/or UDP/IP +is working properly. + +- Check RDMA Setup + + If you built the RDMA components as modules, load them at + this time. For example, if you are using a Mellanox Tavor/Sinai/Arbel + card: + + .. code-block:: sh + + $ modprobe ib_mthca + $ modprobe ib_ipoib + + If you are using InfiniBand, make sure there is a Subnet Manager (SM) + running on the network. If your IB switch has an embedded SM, you can + use it. Otherwise, you will need to run an SM, such as OpenSM, on one + of your end nodes. + + If an SM is running on your network, you should see the following: + + .. code-block:: sh + + $ cat /sys/class/infiniband/driverX/ports/1/state + 4: ACTIVE + + where driverX is mthca0, ipath5, ehca3, etc. + + To further test the InfiniBand software stack, use IPoIB (this + assumes you have two IB hosts named host1 and host2): + + .. code-block:: sh + + host1$ ip link set dev ib0 up + host1$ ip address add dev ib0 a.b.c.x + host2$ ip link set dev ib0 up + host2$ ip address add dev ib0 a.b.c.y + host1$ ping a.b.c.y + host2$ ping a.b.c.x + + For other device types, follow the appropriate procedures. + +- Check NFS Setup + + For the NFS components enabled above (client and/or server), + test their functionality over standard Ethernet using TCP/IP or UDP/IP. + +NFS/RDMA Setup +============== + +We recommend that you use two machines, one to act as the client and +one to act as the server. + +One time configuration: +----------------------- + +- On the server system, configure the /etc/exports file and start the NFS/RDMA server. + + Exports entries with the following formats have been tested:: + + /vol0 192.168.0.47(fsid=0,rw,async,insecure,no_root_squash) + /vol0 192.168.0.0/255.255.255.0(fsid=0,rw,async,insecure,no_root_squash) + + The IP address(es) is(are) the client's IPoIB address for an InfiniBand + HCA or the client's iWARP address(es) for an RNIC. + + .. note:: + The "insecure" option must be used because the NFS/RDMA client does + not use a reserved port. + +Each time a machine boots: +-------------------------- + +- Load and configure the RDMA drivers + + For InfiniBand using a Mellanox adapter: + + .. code-block:: sh + + $ modprobe ib_mthca + $ modprobe ib_ipoib + $ ip li set dev ib0 up + $ ip addr add dev ib0 a.b.c.d + + .. note:: + Please use unique addresses for the client and server! + +- Start the NFS server + + If the NFS/RDMA server was built as a module (CONFIG_SUNRPC_XPRT_RDMA=m in + kernel config), load the RDMA transport module: + + .. code-block:: sh + + $ modprobe svcrdma + + Regardless of how the server was built (module or built-in), start the + server: + + .. code-block:: sh + + $ /etc/init.d/nfs start + + or + + .. code-block:: sh + + $ service nfs start + + Instruct the server to listen on the RDMA transport: + + .. code-block:: sh + + $ echo rdma 20049 > /proc/fs/nfsd/portlist + +- On the client system + + If the NFS/RDMA client was built as a module (CONFIG_SUNRPC_XPRT_RDMA=m in + kernel config), load the RDMA client module: + + .. code-block:: sh + + $ modprobe xprtrdma.ko + + Regardless of how the client was built (module or built-in), use this + command to mount the NFS/RDMA server: + + .. code-block:: sh + + $ mount -o rdma,port=20049 <IPoIB-server-name-or-address>:/<export> /mnt + + To verify that the mount is using RDMA, run "cat /proc/mounts" and check + the "proto" field for the given mount. + + Congratulations! You're using NFS/RDMA! diff --git a/Documentation/admin-guide/nfs/nfsd-admin-interfaces.rst b/Documentation/admin-guide/nfs/nfsd-admin-interfaces.rst new file mode 100644 index 000000000..c05926f79 --- /dev/null +++ b/Documentation/admin-guide/nfs/nfsd-admin-interfaces.rst @@ -0,0 +1,40 @@ +================================== +Administrative interfaces for nfsd +================================== + +Note that normally these interfaces are used only by the utilities in +nfs-utils. + +nfsd is controlled mainly by pseudofiles under the "nfsd" filesystem, +which is normally mounted at /proc/fs/nfsd/. + +The server is always started by the first write of a nonzero value to +nfsd/threads. + +Before doing that, NFSD can be told which sockets to listen on by +writing to nfsd/portlist; that write may be: + + - an ascii-encoded file descriptor, which should refer to a + bound (and listening, for tcp) socket, or + - "transportname port", where transportname is currently either + "udp", "tcp", or "rdma". + +If nfsd is started without doing any of these, then it will create one +udp and one tcp listener at port 2049 (see nfsd_init_socks). + +On startup, nfsd and lockd grace periods start. nfsd is shut down by a write of +0 to nfsd/threads. All locks and state are thrown away at that point. + +Between startup and shutdown, the number of threads may be adjusted up +or down by additional writes to nfsd/threads or by writes to +nfsd/pool_threads. + +For more detail about files under nfsd/ and what they control, see +fs/nfsd/nfsctl.c; most of them have detailed comments. + +Implementation notes +==================== + +Note that the rpc server requires the caller to serialize addition and +removal of listening sockets, and startup and shutdown of the server. +For nfsd this is done using nfsd_mutex. diff --git a/Documentation/admin-guide/nfs/nfsroot.rst b/Documentation/admin-guide/nfs/nfsroot.rst new file mode 100644 index 000000000..135218f33 --- /dev/null +++ b/Documentation/admin-guide/nfs/nfsroot.rst @@ -0,0 +1,364 @@ +=============================================== +Mounting the root filesystem via NFS (nfsroot) +=============================================== + +:Authors: + Written 1996 by Gero Kuhlmann <gero@gkminix.han.de> + + Updated 1997 by Martin Mares <mj@atrey.karlin.mff.cuni.cz> + + Updated 2006 by Nico Schottelius <nico-kernel-nfsroot@schottelius.org> + + Updated 2006 by Horms <horms@verge.net.au> + + Updated 2018 by Chris Novakovic <chris@chrisn.me.uk> + + + +In order to use a diskless system, such as an X-terminal or printer server for +example, it is necessary for the root filesystem to be present on a non-disk +device. This may be an initramfs (see +Documentation/filesystems/ramfs-rootfs-initramfs.rst), a ramdisk (see +Documentation/admin-guide/initrd.rst) or a filesystem mounted via NFS. The +following text describes on how to use NFS for the root filesystem. For the rest +of this text 'client' means the diskless system, and 'server' means the NFS +server. + + + + +Enabling nfsroot capabilities +============================= + +In order to use nfsroot, NFS client support needs to be selected as +built-in during configuration. Once this has been selected, the nfsroot +option will become available, which should also be selected. + +In the networking options, kernel level autoconfiguration can be selected, +along with the types of autoconfiguration to support. Selecting all of +DHCP, BOOTP and RARP is safe. + + + + +Kernel command line +=================== + +When the kernel has been loaded by a boot loader (see below) it needs to be +told what root fs device to use. And in the case of nfsroot, where to find +both the server and the name of the directory on the server to mount as root. +This can be established using the following kernel command line parameters: + + +root=/dev/nfs + This is necessary to enable the pseudo-NFS-device. Note that it's not a + real device but just a synonym to tell the kernel to use NFS instead of + a real device. + + +nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>] + If the `nfsroot' parameter is NOT given on the command line, + the default ``"/tftpboot/%s"`` will be used. + + <server-ip> Specifies the IP address of the NFS server. + The default address is determined by the ip parameter + (see below). This parameter allows the use of different + servers for IP autoconfiguration and NFS. + + <root-dir> Name of the directory on the server to mount as root. + If there is a "%s" token in the string, it will be + replaced by the ASCII-representation of the client's + IP address. + + <nfs-options> Standard NFS options. All options are separated by commas. + The following defaults are used:: + + port = as given by server portmap daemon + rsize = 4096 + wsize = 4096 + timeo = 7 + retrans = 3 + acregmin = 3 + acregmax = 60 + acdirmin = 30 + acdirmax = 60 + flags = hard, nointr, noposix, cto, ac + + +ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>:<dns0-ip>:<dns1-ip>:<ntp0-ip> + This parameter tells the kernel how to configure IP addresses of devices + and also how to set up the IP routing table. It was originally called + nfsaddrs, but now the boot-time IP configuration works independently of + NFS, so it was renamed to ip and the old name remained as an alias for + compatibility reasons. + + If this parameter is missing from the kernel command line, all fields are + assumed to be empty, and the defaults mentioned below apply. In general + this means that the kernel tries to configure everything using + autoconfiguration. + + The <autoconf> parameter can appear alone as the value to the ip + parameter (without all the ':' characters before). If the value is + "ip=off" or "ip=none", no autoconfiguration will take place, otherwise + autoconfiguration will take place. The most common way to use this + is "ip=dhcp". + + <client-ip> IP address of the client. + Default: Determined using autoconfiguration. + + <server-ip> IP address of the NFS server. + If RARP is used to determine + the client address and this parameter is NOT empty only + replies from the specified server are accepted. + + Only required for NFS root. That is autoconfiguration + will not be triggered if it is missing and NFS root is not + in operation. + + Value is exported to /proc/net/pnp with the prefix "bootserver " + (see below). + + Default: Determined using autoconfiguration. + The address of the autoconfiguration server is used. + + <gw-ip> IP address of a gateway if the server is on a different subnet. + Default: Determined using autoconfiguration. + + <netmask> Netmask for local network interface. + If unspecified the netmask is derived from the client IP address + assuming classful addressing. + + Default: Determined using autoconfiguration. + + <hostname> Name of the client. + If a '.' character is present, anything + before the first '.' is used as the client's hostname, and anything + after it is used as its NIS domain name. May be supplied by + autoconfiguration, but its absence will not trigger autoconfiguration. + If specified and DHCP is used, the user-provided hostname (and NIS + domain name, if present) will be carried in the DHCP request; this + may cause a DNS record to be created or updated for the client. + + Default: Client IP address is used in ASCII notation. + + <device> Name of network device to use. + Default: If the host only has one device, it is used. + Otherwise the device is determined using + autoconfiguration. This is done by sending + autoconfiguration requests out of all devices, + and using the device that received the first reply. + + <autoconf> Method to use for autoconfiguration. + In the case of options + which specify multiple autoconfiguration protocols, + requests are sent using all protocols, and the first one + to reply is used. + + Only autoconfiguration protocols that have been compiled + into the kernel will be used, regardless of the value of + this option:: + + off or none: don't use autoconfiguration + (do static IP assignment instead) + on or any: use any protocol available in the kernel + (default) + dhcp: use DHCP + bootp: use BOOTP + rarp: use RARP + both: use both BOOTP and RARP but not DHCP + (old option kept for backwards compatibility) + + if dhcp is used, the client identifier can be used by following + format "ip=dhcp,client-id-type,client-id-value" + + Default: any + + <dns0-ip> IP address of primary nameserver. + Value is exported to /proc/net/pnp with the prefix "nameserver " + (see below). + + Default: None if not using autoconfiguration; determined + automatically if using autoconfiguration. + + <dns1-ip> IP address of secondary nameserver. + See <dns0-ip>. + + <ntp0-ip> IP address of a Network Time Protocol (NTP) server. + Value is exported to /proc/net/ipconfig/ntp_servers, but is + otherwise unused (see below). + + Default: None if not using autoconfiguration; determined + automatically if using autoconfiguration. + + After configuration (whether manual or automatic) is complete, two files + are created in the following format; lines are omitted if their respective + value is empty following configuration: + + - /proc/net/pnp: + + #PROTO: <DHCP|BOOTP|RARP|MANUAL> (depending on configuration method) + domain <dns-domain> (if autoconfigured, the DNS domain) + nameserver <dns0-ip> (primary name server IP) + nameserver <dns1-ip> (secondary name server IP) + nameserver <dns2-ip> (tertiary name server IP) + bootserver <server-ip> (NFS server IP) + + - /proc/net/ipconfig/ntp_servers: + + <ntp0-ip> (NTP server IP) + <ntp1-ip> (NTP server IP) + <ntp2-ip> (NTP server IP) + + <dns-domain> and <dns2-ip> (in /proc/net/pnp) and <ntp1-ip> and <ntp2-ip> + (in /proc/net/ipconfig/ntp_servers) are requested during autoconfiguration; + they cannot be specified as part of the "ip=" kernel command line parameter. + + Because the "domain" and "nameserver" options are recognised by DNS + resolvers, /etc/resolv.conf is often linked to /proc/net/pnp on systems + that use an NFS root filesystem. + + Note that the kernel will not synchronise the system time with any NTP + servers it discovers; this is the responsibility of a user space process + (e.g. an initrd/initramfs script that passes the IP addresses listed in + /proc/net/ipconfig/ntp_servers to an NTP client before mounting the real + root filesystem if it is on NFS). + + +nfsrootdebug + This parameter enables debugging messages to appear in the kernel + log at boot time so that administrators can verify that the correct + NFS mount options, server address, and root path are passed to the + NFS client. + + +rdinit=<executable file> + To specify which file contains the program that starts system + initialization, administrators can use this command line parameter. + The default value of this parameter is "/init". If the specified + file exists and the kernel can execute it, root filesystem related + kernel command line parameters, including 'nfsroot=', are ignored. + + A description of the process of mounting the root file system can be + found in Documentation/driver-api/early-userspace/early_userspace_support.rst + + +Boot Loader +=========== + +To get the kernel into memory different approaches can be used. +They depend on various facilities being available: + + +- Booting from a floppy using syslinux + + When building kernels, an easy way to create a boot floppy that uses + syslinux is to use the zdisk or bzdisk make targets which use zimage + and bzimage images respectively. Both targets accept the + FDARGS parameter which can be used to set the kernel command line. + + e.g:: + + make bzdisk FDARGS="root=/dev/nfs" + + Note that the user running this command will need to have + access to the floppy drive device, /dev/fd0 + + For more information on syslinux, including how to create bootdisks + for prebuilt kernels, see https://syslinux.zytor.com/ + + .. note:: + Previously it was possible to write a kernel directly to + a floppy using dd, configure the boot device using rdev, and + boot using the resulting floppy. Linux no longer supports this + method of booting. + +- Booting from a cdrom using isolinux + + When building kernels, an easy way to create a bootable cdrom that + uses isolinux is to use the isoimage target which uses a bzimage + image. Like zdisk and bzdisk, this target accepts the FDARGS + parameter which can be used to set the kernel command line. + + e.g:: + + make isoimage FDARGS="root=/dev/nfs" + + The resulting iso image will be arch/<ARCH>/boot/image.iso + This can be written to a cdrom using a variety of tools including + cdrecord. + + e.g:: + + cdrecord dev=ATAPI:1,0,0 arch/x86/boot/image.iso + + For more information on isolinux, including how to create bootdisks + for prebuilt kernels, see https://syslinux.zytor.com/ + +- Using LILO + + When using LILO all the necessary command line parameters may be + specified using the 'append=' directive in the LILO configuration + file. + + However, to use the 'root=' directive you also need to create + a dummy root device, which may be removed after LILO is run. + + e.g:: + + mknod /dev/boot255 c 0 255 + + For information on configuring LILO, please refer to its documentation. + +- Using GRUB + + When using GRUB, kernel parameter are simply appended after the kernel + specification: kernel <kernel> <parameters> + +- Using loadlin + + loadlin may be used to boot Linux from a DOS command prompt without + requiring a local hard disk to mount as root. This has not been + thoroughly tested by the authors of this document, but in general + it should be possible configure the kernel command line similarly + to the configuration of LILO. + + Please refer to the loadlin documentation for further information. + +- Using a boot ROM + + This is probably the most elegant way of booting a diskless client. + With a boot ROM the kernel is loaded using the TFTP protocol. The + authors of this document are not aware of any no commercial boot + ROMs that support booting Linux over the network. However, there + are two free implementations of a boot ROM, netboot-nfs and + etherboot, both of which are available on sunsite.unc.edu, and both + of which contain everything you need to boot a diskless Linux client. + +- Using pxelinux + + Pxelinux may be used to boot linux using the PXE boot loader + which is present on many modern network cards. + + When using pxelinux, the kernel image is specified using + "kernel <relative-path-below /tftpboot>". The nfsroot parameters + are passed to the kernel by adding them to the "append" line. + It is common to use serial console in conjunction with pxeliunx, + see Documentation/admin-guide/serial-console.rst for more information. + + For more information on isolinux, including how to create bootdisks + for prebuilt kernels, see https://syslinux.zytor.com/ + + + + +Credits +======= + + The nfsroot code in the kernel and the RARP support have been written + by Gero Kuhlmann <gero@gkminix.han.de>. + + The rest of the IP layer autoconfiguration code has been written + by Martin Mares <mj@atrey.karlin.mff.cuni.cz>. + + In order to write the initial version of nfsroot I would like to thank + Jens-Uwe Mager <jum@anubis.han.de> for his help. diff --git a/Documentation/admin-guide/nfs/pnfs-block-server.rst b/Documentation/admin-guide/nfs/pnfs-block-server.rst new file mode 100644 index 000000000..20fe9f511 --- /dev/null +++ b/Documentation/admin-guide/nfs/pnfs-block-server.rst @@ -0,0 +1,42 @@ +=================================== +pNFS block layout server user guide +=================================== + +The Linux NFS server now supports the pNFS block layout extension. In this +case the NFS server acts as Metadata Server (MDS) for pNFS, which in addition +to handling all the metadata access to the NFS export also hands out layouts +to the clients to directly access the underlying block devices that are +shared with the client. + +To use pNFS block layouts with the Linux NFS server the exported file +system needs to support the pNFS block layouts (currently just XFS), and the +file system must sit on shared storage (typically iSCSI) that is accessible +to the clients in addition to the MDS. As of now the file system needs to +sit directly on the exported volume, striping or concatenation of +volumes on the MDS and clients is not supported yet. + +On the server, pNFS block volume support is automatically if the file system +support it. On the client make sure the kernel has the CONFIG_PNFS_BLOCK +option enabled, the blkmapd daemon from nfs-utils is running, and the +file system is mounted using the NFSv4.1 protocol version (mount -o vers=4.1). + +If the nfsd server needs to fence a non-responding client it calls +/sbin/nfsd-recall-failed with the first argument set to the IP address of +the client, and the second argument set to the device node without the /dev +prefix for the file system to be fenced. Below is an example file that shows +how to translate the device into a serial number from SCSI EVPD 0x80:: + + cat > /sbin/nfsd-recall-failed << EOF + +.. code-block:: sh + + #!/bin/sh + + CLIENT="$1" + DEV="/dev/$2" + EVPD=`sg_inq --page=0x80 ${DEV} | \ + grep "Unit serial number:" | \ + awk -F ': ' '{print $2}'` + + echo "fencing client ${CLIENT} serial ${EVPD}" >> /var/log/pnfsd-fence.log + EOF diff --git a/Documentation/admin-guide/nfs/pnfs-scsi-server.rst b/Documentation/admin-guide/nfs/pnfs-scsi-server.rst new file mode 100644 index 000000000..b2eec2288 --- /dev/null +++ b/Documentation/admin-guide/nfs/pnfs-scsi-server.rst @@ -0,0 +1,24 @@ + +================================== +pNFS SCSI layout server user guide +================================== + +This document describes support for pNFS SCSI layouts in the Linux NFS server. +With pNFS SCSI layouts, the NFS server acts as Metadata Server (MDS) for pNFS, +which in addition to handling all the metadata access to the NFS export, +also hands out layouts to the clients so that they can directly access the +underlying SCSI LUNs that are shared with the client. + +To use pNFS SCSI layouts with the Linux NFS server, the exported file +system needs to support the pNFS SCSI layouts (currently just XFS), and the +file system must sit on a SCSI LUN that is accessible to the clients in +addition to the MDS. As of now the file system needs to sit directly on the +exported LUN, striping or concatenation of LUNs on the MDS and clients +is not supported yet. + +On a server built with CONFIG_NFSD_SCSI, the pNFS SCSI volume support is +automatically enabled if the file system is exported using the "pnfs" +option and the underlying SCSI device support persistent reservations. +On the client make sure the kernel has the CONFIG_PNFS_BLOCK option +enabled, and the file system is mounted using the NFSv4.1 protocol +version (mount -o vers=4.1). diff --git a/Documentation/admin-guide/numastat.rst b/Documentation/admin-guide/numastat.rst new file mode 100644 index 000000000..08ec2c2bd --- /dev/null +++ b/Documentation/admin-guide/numastat.rst @@ -0,0 +1,55 @@ +=============================== +Numa policy hit/miss statistics +=============================== + +/sys/devices/system/node/node*/numastat + +All units are pages. Hugepages have separate counters. + +The numa_hit, numa_miss and numa_foreign counters reflect how well processes +are able to allocate memory from nodes they prefer. If they succeed, numa_hit +is incremented on the preferred node, otherwise numa_foreign is incremented on +the preferred node and numa_miss on the node where allocation succeeded. + +Usually preferred node is the one local to the CPU where the process executes, +but restrictions such as mempolicies can change that, so there are also two +counters based on CPU local node. local_node is similar to numa_hit and is +incremented on allocation from a node by CPU on the same node. other_node is +similar to numa_miss and is incremented on the node where allocation succeeds +from a CPU from a different node. Note there is no counter analogical to +numa_foreign. + +In more detail: + +=============== ============================================================ +numa_hit A process wanted to allocate memory from this node, + and succeeded. + +numa_miss A process wanted to allocate memory from another node, + but ended up with memory from this node. + +numa_foreign A process wanted to allocate on this node, + but ended up with memory from another node. + +local_node A process ran on this node's CPU, + and got memory from this node. + +other_node A process ran on a different node's CPU + and got memory from this node. + +interleave_hit Interleaving wanted to allocate from this node + and succeeded. +=============== ============================================================ + +For easier reading you can use the numastat utility from the numactl package +(http://oss.sgi.com/projects/libnuma/). Note that it only works +well right now on machines with a small number of CPUs. + +Note that on systems with memoryless nodes (where a node has CPUs but no +memory) the numa_hit, numa_miss and numa_foreign statistics can be skewed +heavily. In the current kernel implementation, if a process prefers a +memoryless node (i.e. because it is running on one of its local CPU), the +implementation actually treats one of the nearest nodes with memory as the +preferred node. As a result, such allocation will not increase the numa_foreign +counter on the memoryless node, and will skew the numa_hit, numa_miss and +numa_foreign statistics of the nearest node. diff --git a/Documentation/admin-guide/parport.rst b/Documentation/admin-guide/parport.rst new file mode 100644 index 000000000..ad3f9b8a1 --- /dev/null +++ b/Documentation/admin-guide/parport.rst @@ -0,0 +1,286 @@ +Parport ++++++++ + +The ``parport`` code provides parallel-port support under Linux. This +includes the ability to share one port between multiple device +drivers. + +You can pass parameters to the ``parport`` code to override its automatic +detection of your hardware. This is particularly useful if you want +to use IRQs, since in general these can't be autoprobed successfully. +By default IRQs are not used even if they **can** be probed. This is +because there are a lot of people using the same IRQ for their +parallel port and a sound card or network card. + +The ``parport`` code is split into two parts: generic (which deals with +port-sharing) and architecture-dependent (which deals with actually +using the port). + + +Parport as modules +================== + +If you load the `parport`` code as a module, say:: + + # insmod parport + +to load the generic ``parport`` code. You then must load the +architecture-dependent code with (for example):: + + # insmod parport_pc io=0x3bc,0x378,0x278 irq=none,7,auto + +to tell the ``parport`` code that you want three PC-style ports, one at +0x3bc with no IRQ, one at 0x378 using IRQ 7, and one at 0x278 with an +auto-detected IRQ. Currently, PC-style (``parport_pc``), Sun ``bpp``, +Amiga, Atari, and MFC3 hardware is supported. + +PCI parallel I/O card support comes from ``parport_pc``. Base I/O +addresses should not be specified for supported PCI cards since they +are automatically detected. + + +modprobe +-------- + +If you use modprobe , you will find it useful to add lines as below to a +configuration file in /etc/modprobe.d/ directory:: + + alias parport_lowlevel parport_pc + options parport_pc io=0x378,0x278 irq=7,auto + +modprobe will load ``parport_pc`` (with the options ``io=0x378,0x278 irq=7,auto``) +whenever a parallel port device driver (such as ``lp``) is loaded. + +Note that these are example lines only! You shouldn't in general need +to specify any options to ``parport_pc`` in order to be able to use a +parallel port. + + +Parport probe [optional] +------------------------ + +In 2.2 kernels there was a module called ``parport_probe``, which was used +for collecting IEEE 1284 device ID information. This has now been +enhanced and now lives with the IEEE 1284 support. When a parallel +port is detected, the devices that are connected to it are analysed, +and information is logged like this:: + + parport0: Printer, BJC-210 (Canon) + +The probe information is available from files in ``/proc/sys/dev/parport/``. + + +Parport linked into the kernel statically +========================================= + +If you compile the ``parport`` code into the kernel, then you can use +kernel boot parameters to get the same effect. Add something like the +following to your LILO command line:: + + parport=0x3bc parport=0x378,7 parport=0x278,auto,nofifo + +You can have many ``parport=...`` statements, one for each port you want +to add. Adding ``parport=0`` to the kernel command-line will disable +parport support entirely. Adding ``parport=auto`` to the kernel +command-line will make ``parport`` use any IRQ lines or DMA channels that +it auto-detects. + + +Files in /proc +============== + +If you have configured the ``/proc`` filesystem into your kernel, you will +see a new directory entry: ``/proc/sys/dev/parport``. In there will be a +directory entry for each parallel port for which parport is +configured. In each of those directories are a collection of files +describing that parallel port. + +The ``/proc/sys/dev/parport`` directory tree looks like:: + + parport + |-- default + | |-- spintime + | `-- timeslice + |-- parport0 + | |-- autoprobe + | |-- autoprobe0 + | |-- autoprobe1 + | |-- autoprobe2 + | |-- autoprobe3 + | |-- devices + | | |-- active + | | `-- lp + | | `-- timeslice + | |-- base-addr + | |-- irq + | |-- dma + | |-- modes + | `-- spintime + `-- parport1 + |-- autoprobe + |-- autoprobe0 + |-- autoprobe1 + |-- autoprobe2 + |-- autoprobe3 + |-- devices + | |-- active + | `-- ppa + | `-- timeslice + |-- base-addr + |-- irq + |-- dma + |-- modes + `-- spintime + +.. tabularcolumns:: |p{4.0cm}|p{13.5cm}| + +======================= ======================================================= +File Contents +======================= ======================================================= +``devices/active`` A list of the device drivers using that port. A "+" + will appear by the name of the device currently using + the port (it might not appear against any). The + string "none" means that there are no device drivers + using that port. + +``base-addr`` Parallel port's base address, or addresses if the port + has more than one in which case they are separated + with tabs. These values might not have any sensible + meaning for some ports. + +``irq`` Parallel port's IRQ, or -1 if none is being used. + +``dma`` Parallel port's DMA channel, or -1 if none is being + used. + +``modes`` Parallel port's hardware modes, comma-separated, + meaning: + + - PCSPP + PC-style SPP registers are available. + + - TRISTATE + Port is bidirectional. + + - COMPAT + Hardware acceleration for printers is + available and will be used. + + - EPP + Hardware acceleration for EPP protocol + is available and will be used. + + - ECP + Hardware acceleration for ECP protocol + is available and will be used. + + - DMA + DMA is available and will be used. + + Note that the current implementation will only take + advantage of COMPAT and ECP modes if it has an IRQ + line to use. + +``autoprobe`` Any IEEE-1284 device ID information that has been + acquired from the (non-IEEE 1284.3) device. + +``autoprobe[0-3]`` IEEE 1284 device ID information retrieved from + daisy-chain devices that conform to IEEE 1284.3. + +``spintime`` The number of microseconds to busy-loop while waiting + for the peripheral to respond. You might find that + adjusting this improves performance, depending on your + peripherals. This is a port-wide setting, i.e. it + applies to all devices on a particular port. + +``timeslice`` The number of milliseconds that a device driver is + allowed to keep a port claimed for. This is advisory, + and driver can ignore it if it must. + +``default/*`` The defaults for spintime and timeslice. When a new + port is registered, it picks up the default spintime. + When a new device is registered, it picks up the + default timeslice. +======================= ======================================================= + +Device drivers +============== + +Once the parport code is initialised, you can attach device drivers to +specific ports. Normally this happens automatically; if the lp driver +is loaded it will create one lp device for each port found. You can +override this, though, by using parameters either when you load the lp +driver:: + + # insmod lp parport=0,2 + +or on the LILO command line:: + + lp=parport0 lp=parport2 + +Both the above examples would inform lp that you want ``/dev/lp0`` to be +the first parallel port, and /dev/lp1 to be the **third** parallel port, +with no lp device associated with the second port (parport1). Note +that this is different to the way older kernels worked; there used to +be a static association between the I/O port address and the device +name, so ``/dev/lp0`` was always the port at 0x3bc. This is no longer the +case - if you only have one port, it will default to being ``/dev/lp0``, +regardless of base address. + +Also: + + * If you selected the IEEE 1284 support at compile time, you can say + ``lp=auto`` on the kernel command line, and lp will create devices + only for those ports that seem to have printers attached. + + * If you give PLIP the ``timid`` parameter, either with ``plip=timid`` on + the command line, or with ``insmod plip timid=1`` when using modules, + it will avoid any ports that seem to be in use by other devices. + + * IRQ autoprobing works only for a few port types at the moment. + +Reporting printer problems with parport +======================================= + +If you are having problems printing, please go through these steps to +try to narrow down where the problem area is. + +When reporting problems with parport, really you need to give all of +the messages that ``parport_pc`` spits out when it initialises. There are +several code paths: + +- polling +- interrupt-driven, protocol in software +- interrupt-driven, protocol in hardware using PIO +- interrupt-driven, protocol in hardware using DMA + +The kernel messages that ``parport_pc`` logs give an indication of which +code path is being used. (They could be a lot better actually..) + +For normal printer protocol, having IEEE 1284 modes enabled or not +should not make a difference. + +To turn off the 'protocol in hardware' code paths, disable +``CONFIG_PARPORT_PC_FIFO``. Note that when they are enabled they are not +necessarily **used**; it depends on whether the hardware is available, +enabled by the BIOS, and detected by the driver. + +So, to start with, disable ``CONFIG_PARPORT_PC_FIFO``, and load ``parport_pc`` +with ``irq=none``. See if printing works then. It really should, +because this is the simplest code path. + +If that works fine, try with ``io=0x378 irq=7`` (adjust for your +hardware), to make it use interrupt-driven in-software protocol. + +If **that** works fine, then one of the hardware modes isn't working +right. Enable ``CONFIG_FIFO`` (no, it isn't a module option, +and yes, it should be), set the port to ECP mode in the BIOS and note +the DMA channel, and try with:: + + io=0x378 irq=7 dma=none (for PIO) + io=0x378 irq=7 dma=3 (for DMA) + +---------- + +philb@gnu.org +tim@cyberelk.net diff --git a/Documentation/admin-guide/perf-security.rst b/Documentation/admin-guide/perf-security.rst new file mode 100644 index 000000000..34aa33432 --- /dev/null +++ b/Documentation/admin-guide/perf-security.rst @@ -0,0 +1,325 @@ +.. _perf_security: + +Perf events and tool security +============================= + +Overview +-------- + +Usage of Performance Counters for Linux (perf_events) [1]_ , [2]_ , [3]_ +can impose a considerable risk of leaking sensitive data accessed by +monitored processes. The data leakage is possible both in scenarios of +direct usage of perf_events system call API [2]_ and over data files +generated by Perf tool user mode utility (Perf) [3]_ , [4]_ . The risk +depends on the nature of data that perf_events performance monitoring +units (PMU) [2]_ and Perf collect and expose for performance analysis. +Collected system and performance data may be split into several +categories: + +1. System hardware and software configuration data, for example: a CPU + model and its cache configuration, an amount of available memory and + its topology, used kernel and Perf versions, performance monitoring + setup including experiment time, events configuration, Perf command + line parameters, etc. + +2. User and kernel module paths and their load addresses with sizes, + process and thread names with their PIDs and TIDs, timestamps for + captured hardware and software events. + +3. Content of kernel software counters (e.g., for context switches, page + faults, CPU migrations), architectural hardware performance counters + (PMC) [8]_ and machine specific registers (MSR) [9]_ that provide + execution metrics for various monitored parts of the system (e.g., + memory controller (IMC), interconnect (QPI/UPI) or peripheral (PCIe) + uncore counters) without direct attribution to any execution context + state. + +4. Content of architectural execution context registers (e.g., RIP, RSP, + RBP on x86_64), process user and kernel space memory addresses and + data, content of various architectural MSRs that capture data from + this category. + +Data that belong to the fourth category can potentially contain +sensitive process data. If PMUs in some monitoring modes capture values +of execution context registers or data from process memory then access +to such monitoring modes requires to be ordered and secured properly. +So, perf_events performance monitoring and observability operations are +the subject for security access control management [5]_ . + +perf_events access control +------------------------------- + +To perform security checks, the Linux implementation splits processes +into two categories [6]_ : a) privileged processes (whose effective user +ID is 0, referred to as superuser or root), and b) unprivileged +processes (whose effective UID is nonzero). Privileged processes bypass +all kernel security permission checks so perf_events performance +monitoring is fully available to privileged processes without access, +scope and resource restrictions. + +Unprivileged processes are subject to a full security permission check +based on the process's credentials [5]_ (usually: effective UID, +effective GID, and supplementary group list). + +Linux divides the privileges traditionally associated with superuser +into distinct units, known as capabilities [6]_ , which can be +independently enabled and disabled on per-thread basis for processes and +files of unprivileged users. + +Unprivileged processes with enabled CAP_PERFMON capability are treated +as privileged processes with respect to perf_events performance +monitoring and observability operations, thus, bypass *scope* permissions +checks in the kernel. CAP_PERFMON implements the principle of least +privilege [13]_ (POSIX 1003.1e: 2.2.2.39) for performance monitoring and +observability operations in the kernel and provides a secure approach to +performance monitoring and observability in the system. + +For backward compatibility reasons the access to perf_events monitoring and +observability operations is also open for CAP_SYS_ADMIN privileged +processes but CAP_SYS_ADMIN usage for secure monitoring and observability +use cases is discouraged with respect to the CAP_PERFMON capability. +If system audit records [14]_ for a process using perf_events system call +API contain denial records of acquiring both CAP_PERFMON and CAP_SYS_ADMIN +capabilities then providing the process with CAP_PERFMON capability singly +is recommended as the preferred secure approach to resolve double access +denial logging related to usage of performance monitoring and observability. + +Prior Linux v5.9 unprivileged processes using perf_events system call +are also subject for PTRACE_MODE_READ_REALCREDS ptrace access mode check +[7]_ , whose outcome determines whether monitoring is permitted. +So unprivileged processes provided with CAP_SYS_PTRACE capability are +effectively permitted to pass the check. Starting from Linux v5.9 +CAP_SYS_PTRACE capability is not required and CAP_PERFMON is enough to +be provided for processes to make performance monitoring and observability +operations. + +Other capabilities being granted to unprivileged processes can +effectively enable capturing of additional data required for later +performance analysis of monitored processes or a system. For example, +CAP_SYSLOG capability permits reading kernel space memory addresses from +/proc/kallsyms file. + +Privileged Perf users groups +--------------------------------- + +Mechanisms of capabilities, privileged capability-dumb files [6]_, +file system ACLs [10]_ and sudo [15]_ utility can be used to create +dedicated groups of privileged Perf users who are permitted to execute +performance monitoring and observability without limits. The following +steps can be taken to create such groups of privileged Perf users. + +1. Create perf_users group of privileged Perf users, assign perf_users + group to Perf tool executable and limit access to the executable for + other users in the system who are not in the perf_users group: + +:: + + # groupadd perf_users + # ls -alhF + -rwxr-xr-x 2 root root 11M Oct 19 15:12 perf + # chgrp perf_users perf + # ls -alhF + -rwxr-xr-x 2 root perf_users 11M Oct 19 15:12 perf + # chmod o-rwx perf + # ls -alhF + -rwxr-x--- 2 root perf_users 11M Oct 19 15:12 perf + +2. Assign the required capabilities to the Perf tool executable file and + enable members of perf_users group with monitoring and observability + privileges [6]_ : + +:: + + # setcap "cap_perfmon,cap_sys_ptrace,cap_syslog=ep" perf + # setcap -v "cap_perfmon,cap_sys_ptrace,cap_syslog=ep" perf + perf: OK + # getcap perf + perf = cap_sys_ptrace,cap_syslog,cap_perfmon+ep + +If the libcap [16]_ installed doesn't yet support "cap_perfmon", use "38" instead, +i.e.: + +:: + + # setcap "38,cap_ipc_lock,cap_sys_ptrace,cap_syslog=ep" perf + +Note that you may need to have 'cap_ipc_lock' in the mix for tools such as +'perf top', alternatively use 'perf top -m N', to reduce the memory that +it uses for the perf ring buffer, see the memory allocation section below. + +Using a libcap without support for CAP_PERFMON will make cap_get_flag(caps, 38, +CAP_EFFECTIVE, &val) fail, which will lead the default event to be 'cycles:u', +so as a workaround explicitly ask for the 'cycles' event, i.e.: + +:: + + # perf top -e cycles + +To get kernel and user samples with a perf binary with just CAP_PERFMON. + +As a result, members of perf_users group are capable of conducting +performance monitoring and observability by using functionality of the +configured Perf tool executable that, when executes, passes perf_events +subsystem scope checks. + +In case Perf tool executable can't be assigned required capabilities (e.g. +file system is mounted with nosuid option or extended attributes are +not supported by the file system) then creation of the capabilities +privileged environment, naturally shell, is possible. The shell provides +inherent processes with CAP_PERFMON and other required capabilities so that +performance monitoring and observability operations are available in the +environment without limits. Access to the environment can be open via sudo +utility for members of perf_users group only. In order to create such +environment: + +1. Create shell script that uses capsh utility [16]_ to assign CAP_PERFMON + and other required capabilities into ambient capability set of the shell + process, lock the process security bits after enabling SECBIT_NO_SETUID_FIXUP, + SECBIT_NOROOT and SECBIT_NO_CAP_AMBIENT_RAISE bits and then change + the process identity to sudo caller of the script who should essentially + be a member of perf_users group: + +:: + + # ls -alh /usr/local/bin/perf.shell + -rwxr-xr-x. 1 root root 83 Oct 13 23:57 /usr/local/bin/perf.shell + # cat /usr/local/bin/perf.shell + exec /usr/sbin/capsh --iab=^cap_perfmon --secbits=239 --user=$SUDO_USER -- -l + +2. Extend sudo policy at /etc/sudoers file with a rule for perf_users group: + +:: + + # grep perf_users /etc/sudoers + %perf_users ALL=/usr/local/bin/perf.shell + +3. Check that members of perf_users group have access to the privileged + shell and have CAP_PERFMON and other required capabilities enabled + in permitted, effective and ambient capability sets of an inherent process: + +:: + + $ id + uid=1003(capsh_test) gid=1004(capsh_test) groups=1004(capsh_test),1000(perf_users) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 + $ sudo perf.shell + [sudo] password for capsh_test: + $ grep Cap /proc/self/status + CapInh: 0000004000000000 + CapPrm: 0000004000000000 + CapEff: 0000004000000000 + CapBnd: 000000ffffffffff + CapAmb: 0000004000000000 + $ capsh --decode=0000004000000000 + 0x0000004000000000=cap_perfmon + +As a result, members of perf_users group have access to the privileged +environment where they can use tools employing performance monitoring APIs +governed by CAP_PERFMON Linux capability. + +This specific access control management is only available to superuser +or root running processes with CAP_SETPCAP, CAP_SETFCAP [6]_ +capabilities. + +Unprivileged users +----------------------------------- + +perf_events *scope* and *access* control for unprivileged processes +is governed by perf_event_paranoid [2]_ setting: + +-1: + Impose no *scope* and *access* restrictions on using perf_events + performance monitoring. Per-user per-cpu perf_event_mlock_kb [2]_ + locking limit is ignored when allocating memory buffers for storing + performance data. This is the least secure mode since allowed + monitored *scope* is maximized and no perf_events specific limits + are imposed on *resources* allocated for performance monitoring. + +>=0: + *scope* includes per-process and system wide performance monitoring + but excludes raw tracepoints and ftrace function tracepoints + monitoring. CPU and system events happened when executing either in + user or in kernel space can be monitored and captured for later + analysis. Per-user per-cpu perf_event_mlock_kb locking limit is + imposed but ignored for unprivileged processes with CAP_IPC_LOCK + [6]_ capability. + +>=1: + *scope* includes per-process performance monitoring only and + excludes system wide performance monitoring. CPU and system events + happened when executing either in user or in kernel space can be + monitored and captured for later analysis. Per-user per-cpu + perf_event_mlock_kb locking limit is imposed but ignored for + unprivileged processes with CAP_IPC_LOCK capability. + +>=2: + *scope* includes per-process performance monitoring only. CPU and + system events happened when executing in user space only can be + monitored and captured for later analysis. Per-user per-cpu + perf_event_mlock_kb locking limit is imposed but ignored for + unprivileged processes with CAP_IPC_LOCK capability. + +Resource control +--------------------------------- + +Open file descriptors ++++++++++++++++++++++ + +The perf_events system call API [2]_ allocates file descriptors for +every configured PMU event. Open file descriptors are a per-process +accountable resource governed by the RLIMIT_NOFILE [11]_ limit +(ulimit -n), which is usually derived from the login shell process. When +configuring Perf collection for a long list of events on a large server +system, this limit can be easily hit preventing required monitoring +configuration. RLIMIT_NOFILE limit can be increased on per-user basis +modifying content of the limits.conf file [12]_ . Ordinarily, a Perf +sampling session (perf record) requires an amount of open perf_event +file descriptors that is not less than the number of monitored events +multiplied by the number of monitored CPUs. + +Memory allocation ++++++++++++++++++ + +The amount of memory available to user processes for capturing +performance monitoring data is governed by the perf_event_mlock_kb [2]_ +setting. This perf_event specific resource setting defines overall +per-cpu limits of memory allowed for mapping by the user processes to +execute performance monitoring. The setting essentially extends the +RLIMIT_MEMLOCK [11]_ limit, but only for memory regions mapped +specifically for capturing monitored performance events and related data. + +For example, if a machine has eight cores and perf_event_mlock_kb limit +is set to 516 KiB, then a user process is provided with 516 KiB * 8 = +4128 KiB of memory above the RLIMIT_MEMLOCK limit (ulimit -l) for +perf_event mmap buffers. In particular, this means that, if the user +wants to start two or more performance monitoring processes, the user is +required to manually distribute the available 4128 KiB between the +monitoring processes, for example, using the --mmap-pages Perf record +mode option. Otherwise, the first started performance monitoring process +allocates all available 4128 KiB and the other processes will fail to +proceed due to the lack of memory. + +RLIMIT_MEMLOCK and perf_event_mlock_kb resource constraints are ignored +for processes with the CAP_IPC_LOCK capability. Thus, perf_events/Perf +privileged users can be provided with memory above the constraints for +perf_events/Perf performance monitoring purpose by providing the Perf +executable with CAP_IPC_LOCK capability. + +Bibliography +------------ + +.. [1] `<https://lwn.net/Articles/337493/>`_ +.. [2] `<http://man7.org/linux/man-pages/man2/perf_event_open.2.html>`_ +.. [3] `<http://web.eece.maine.edu/~vweaver/projects/perf_events/>`_ +.. [4] `<https://perf.wiki.kernel.org/index.php/Main_Page>`_ +.. [5] `<https://www.kernel.org/doc/html/latest/security/credentials.html>`_ +.. [6] `<http://man7.org/linux/man-pages/man7/capabilities.7.html>`_ +.. [7] `<http://man7.org/linux/man-pages/man2/ptrace.2.html>`_ +.. [8] `<https://en.wikipedia.org/wiki/Hardware_performance_counter>`_ +.. [9] `<https://en.wikipedia.org/wiki/Model-specific_register>`_ +.. [10] `<http://man7.org/linux/man-pages/man5/acl.5.html>`_ +.. [11] `<http://man7.org/linux/man-pages/man2/getrlimit.2.html>`_ +.. [12] `<http://man7.org/linux/man-pages/man5/limits.conf.5.html>`_ +.. [13] `<https://sites.google.com/site/fullycapable>`_ +.. [14] `<http://man7.org/linux/man-pages/man8/auditd.8.html>`_ +.. [15] `<https://man7.org/linux/man-pages/man8/sudo.8.html>`_ +.. [16] `<https://git.kernel.org/pub/scm/libs/libcap/libcap.git/>`_ diff --git a/Documentation/admin-guide/perf/alibaba_pmu.rst b/Documentation/admin-guide/perf/alibaba_pmu.rst new file mode 100644 index 000000000..7d8400239 --- /dev/null +++ b/Documentation/admin-guide/perf/alibaba_pmu.rst @@ -0,0 +1,105 @@ +============================================================= +Alibaba's T-Head SoC Uncore Performance Monitoring Unit (PMU) +============================================================= + +The Yitian 710, custom-built by Alibaba Group's chip development business, +T-Head, implements uncore PMU for performance and functional debugging to +facilitate system maintenance. + +DDR Sub-System Driveway (DRW) PMU Driver +========================================= + +Yitian 710 employs eight DDR5/4 channels, four on each die. Each DDR5 channel +is independent of others to service system memory requests. And one DDR5 +channel is split into two independent sub-channels. The DDR Sub-System Driveway +implements separate PMUs for each sub-channel to monitor various performance +metrics. + +The Driveway PMU devices are named as ali_drw_<sys_base_addr> with perf. +For example, ali_drw_21000 and ali_drw_21080 are two PMU devices for two +sub-channels of the same channel in die 0. And the PMU device of die 1 is +prefixed with ali_drw_400XXXXX, e.g. ali_drw_40021000. + +Each sub-channel has 36 PMU counters in total, which is classified into +four groups: + +- Group 0: PMU Cycle Counter. This group has one pair of counters + pmu_cycle_cnt_low and pmu_cycle_cnt_high, that is used as the cycle count + based on DDRC core clock. + +- Group 1: PMU Bandwidth Counters. This group has 8 counters that are used + to count the total access number of either the eight bank groups in a + selected rank, or four ranks separately in the first 4 counters. The base + transfer unit is 64B. + +- Group 2: PMU Retry Counters. This group has 10 counters, that intend to + count the total retry number of each type of uncorrectable error. + +- Group 3: PMU Common Counters. This group has 16 counters, that are used + to count the common events. + +For now, the Driveway PMU driver only uses counters in group 0 and group 3. + +The DDR Controller (DDRCTL) and DDR PHY combine to create a complete solution +for connecting an SoC application bus to DDR memory devices. The DDRCTL +receives transactions Host Interface (HIF) which is custom-defined by Synopsys. +These transactions are queued internally and scheduled for access while +satisfying the SDRAM protocol timing requirements, transaction priorities, and +dependencies between the transactions. The DDRCTL in turn issues commands on +the DDR PHY Interface (DFI) to the PHY module, which launches and captures data +to and from the SDRAM. The driveway PMUs have hardware logic to gather +statistics and performance logging signals on HIF, DFI, etc. + +By counting the READ, WRITE and RMW commands sent to the DDRC through the HIF +interface, we could calculate the bandwidth. Example usage of counting memory +data bandwidth:: + + perf stat \ + -e ali_drw_21000/hif_wr/ \ + -e ali_drw_21000/hif_rd/ \ + -e ali_drw_21000/hif_rmw/ \ + -e ali_drw_21000/cycle/ \ + -e ali_drw_21080/hif_wr/ \ + -e ali_drw_21080/hif_rd/ \ + -e ali_drw_21080/hif_rmw/ \ + -e ali_drw_21080/cycle/ \ + -e ali_drw_23000/hif_wr/ \ + -e ali_drw_23000/hif_rd/ \ + -e ali_drw_23000/hif_rmw/ \ + -e ali_drw_23000/cycle/ \ + -e ali_drw_23080/hif_wr/ \ + -e ali_drw_23080/hif_rd/ \ + -e ali_drw_23080/hif_rmw/ \ + -e ali_drw_23080/cycle/ \ + -e ali_drw_25000/hif_wr/ \ + -e ali_drw_25000/hif_rd/ \ + -e ali_drw_25000/hif_rmw/ \ + -e ali_drw_25000/cycle/ \ + -e ali_drw_25080/hif_wr/ \ + -e ali_drw_25080/hif_rd/ \ + -e ali_drw_25080/hif_rmw/ \ + -e ali_drw_25080/cycle/ \ + -e ali_drw_27000/hif_wr/ \ + -e ali_drw_27000/hif_rd/ \ + -e ali_drw_27000/hif_rmw/ \ + -e ali_drw_27000/cycle/ \ + -e ali_drw_27080/hif_wr/ \ + -e ali_drw_27080/hif_rd/ \ + -e ali_drw_27080/hif_rmw/ \ + -e ali_drw_27080/cycle/ -- sleep 10 + +Example usage of counting all memory read/write bandwidth by metric:: + + perf stat -M ddr_read_bandwidth.all -- sleep 10 + perf stat -M ddr_write_bandwidth.all -- sleep 10 + +The average DRAM bandwidth can be calculated as follows: + +- Read Bandwidth = perf_hif_rd * DDRC_WIDTH * DDRC_Freq / DDRC_Cycle +- Write Bandwidth = (perf_hif_wr + perf_hif_rmw) * DDRC_WIDTH * DDRC_Freq / DDRC_Cycle + +Here, DDRC_WIDTH = 64 bytes. + +The current driver does not support sampling. So "perf record" is +unsupported. Also attach to a task is unsupported as the events are all +uncore. diff --git a/Documentation/admin-guide/perf/arm-ccn.rst b/Documentation/admin-guide/perf/arm-ccn.rst new file mode 100644 index 000000000..f62f7fe50 --- /dev/null +++ b/Documentation/admin-guide/perf/arm-ccn.rst @@ -0,0 +1,61 @@ +========================== +ARM Cache Coherent Network +========================== + +CCN-504 is a ring-bus interconnect consisting of 11 crosspoints +(XPs), with each crosspoint supporting up to two device ports, +so nodes (devices) 0 and 1 are connected to crosspoint 0, +nodes 2 and 3 to crosspoint 1 etc. + +PMU (perf) driver +----------------- + +The CCN driver registers a perf PMU driver, which provides +description of available events and configuration options +in sysfs, see /sys/bus/event_source/devices/ccn*. + +The "format" directory describes format of the config, config1 +and config2 fields of the perf_event_attr structure. The "events" +directory provides configuration templates for all documented +events, that can be used with perf tool. For example "xp_valid_flit" +is an equivalent of "type=0x8,event=0x4". Other parameters must be +explicitly specified. + +For events originating from device, "node" defines its index. + +Crosspoint PMU events require "xp" (index), "bus" (bus number) +and "vc" (virtual channel ID). + +Crosspoint watchpoint-based events (special "event" value 0xfe) +require "xp" and "vc" as above plus "port" (device port index), +"dir" (transmit/receive direction), comparator values ("cmp_l" +and "cmp_h") and "mask", being index of the comparator mask. + +Masks are defined separately from the event description +(due to limited number of the config values) in the "cmp_mask" +directory, with first 8 configurable by user and additional +4 hardcoded for the most frequent use cases. + +Cycle counter is described by a "type" value 0xff and does +not require any other settings. + +The driver also provides a "cpumask" sysfs attribute, which contains +a single CPU ID, of the processor which will be used to handle all +the CCN PMU events. It is recommended that the user space tools +request the events on this processor (if not, the perf_event->cpu value +will be overwritten anyway). In case of this processor being offlined, +the events are migrated to another one and the attribute is updated. + +Example of perf tool use:: + + / # perf list | grep ccn + ccn/cycles/ [Kernel PMU event] + <...> + ccn/xp_valid_flit,xp=?,port=?,vc=?,dir=?/ [Kernel PMU event] + <...> + + / # perf stat -a -e ccn/cycles/,ccn/xp_valid_flit,xp=1,port=0,vc=1,dir=1/ \ + sleep 1 + +The driver does not support sampling, therefore "perf record" will +not work. Per-task (without "-a") perf sessions are not supported. diff --git a/Documentation/admin-guide/perf/arm-cmn.rst b/Documentation/admin-guide/perf/arm-cmn.rst new file mode 100644 index 000000000..796e25b70 --- /dev/null +++ b/Documentation/admin-guide/perf/arm-cmn.rst @@ -0,0 +1,65 @@ +============================= +Arm Coherent Mesh Network PMU +============================= + +CMN-600 is a configurable mesh interconnect consisting of a rectangular +grid of crosspoints (XPs), with each crosspoint supporting up to two +device ports to which various AMBA CHI agents are attached. + +CMN implements a distributed PMU design as part of its debug and trace +functionality. This consists of a local monitor (DTM) at every XP, which +counts up to 4 event signals from the connected device nodes and/or the +XP itself. Overflow from these local counters is accumulated in up to 8 +global counters implemented by the main controller (DTC), which provides +overall PMU control and interrupts for global counter overflow. + +PMU events +---------- + +The PMU driver registers a single PMU device for the whole interconnect, +see /sys/bus/event_source/devices/arm_cmn_0. Multi-chip systems may link +more than one CMN together via external CCIX links - in this situation, +each mesh counts its own events entirely independently, and additional +PMU devices will be named arm_cmn_{1..n}. + +Most events are specified in a format based directly on the TRM +definitions - "type" selects the respective node type, and "eventid" the +event number. Some events require an additional occupancy ID, which is +specified by "occupid". + +* Since RN-D nodes do not have any distinct events from RN-I nodes, they + are treated as the same type (0xa), and the common event templates are + named "rnid_*". + +* The cycle counter is treated as a synthetic event belonging to the DTC + node ("type" == 0x3, "eventid" is ignored). + +* XP events also encode the port and channel in the "eventid" field, to + match the underlying pmu_event0_id encoding for the pmu_event_sel + register. The event templates are named with prefixes to cover all + permutations. + +By default each event provides an aggregate count over all nodes of the +given type. To target a specific node, "bynodeid" must be set to 1 and +"nodeid" to the appropriate value derived from the CMN configuration +(as defined in the "Node ID Mapping" section of the TRM). + +Watchpoints +----------- + +The PMU can also count watchpoint events to monitor specific flit +traffic. Watchpoints are treated as a synthetic event type, and like PMU +events can be global or targeted with a particular XP's "nodeid" value. +Since the watchpoint direction is otherwise implicit in the underlying +register selection, separate events are provided for flit uploads and +downloads. + +The flit match value and mask are passed in config1 and config2 ("val" +and "mask" respectively). "wp_dev_sel", "wp_chn_sel", "wp_grp" and +"wp_exclusive" are specified per the TRM definitions for dtm_wp_config0. +Where a watchpoint needs to match fields from both match groups on the +REQ or SNP channel, it can be specified as two events - one for each +group - with the same nonzero "combine" value. The count for such a +pair of combined events will be attributed to the primary match. +Watchpoint events with a "combine" value of 0 are considered independent +and will count individually. diff --git a/Documentation/admin-guide/perf/arm_dsu_pmu.rst b/Documentation/admin-guide/perf/arm_dsu_pmu.rst new file mode 100644 index 000000000..7fd34db75 --- /dev/null +++ b/Documentation/admin-guide/perf/arm_dsu_pmu.rst @@ -0,0 +1,29 @@ +================================== +ARM DynamIQ Shared Unit (DSU) PMU +================================== + +ARM DynamIQ Shared Unit integrates one or more cores with an L3 memory system, +control logic and external interfaces to form a multicore cluster. The PMU +allows counting the various events related to the L3 cache, Snoop Control Unit +etc, using 32bit independent counters. It also provides a 64bit cycle counter. + +The PMU can only be accessed via CPU system registers and are common to the +cores connected to the same DSU. Like most of the other uncore PMUs, DSU +PMU doesn't support process specific events and cannot be used in sampling mode. + +The DSU provides a bitmap for a subset of implemented events via hardware +registers. There is no way for the driver to determine if the other events +are available or not. Hence the driver exposes only those events advertised +by the DSU, in "events" directory under:: + + /sys/bus/event_sources/devices/arm_dsu_<N>/ + +The user should refer to the TRM of the product to figure out the supported events +and use the raw event code for the unlisted events. + +The driver also exposes the CPUs connected to the DSU instance in "associated_cpus". + + +e.g usage:: + + perf stat -a -e arm_dsu_0/cycles/ diff --git a/Documentation/admin-guide/perf/cxl.rst b/Documentation/admin-guide/perf/cxl.rst new file mode 100644 index 000000000..9233ea0d0 --- /dev/null +++ b/Documentation/admin-guide/perf/cxl.rst @@ -0,0 +1,68 @@ +.. SPDX-License-Identifier: GPL-2.0 + +====================================== +CXL Performance Monitoring Unit (CPMU) +====================================== + +The CXL rev 3.0 specification provides a definition of CXL Performance +Monitoring Unit in section 13.2: Performance Monitoring. + +CXL components (e.g. Root Port, Switch Upstream Port, End Point) may have +any number of CPMU instances. CPMU capabilities are fully discoverable from +the devices. The specification provides event definitions for all CXL protocol +message types and a set of additional events for things commonly counted on +CXL devices (e.g. DRAM events). + +CPMU driver +=========== + +The CPMU driver registers a perf PMU with the name pmu_mem<X>.<Y> on the CXL bus +representing the Yth CPMU for memX. + + /sys/bus/cxl/device/pmu_mem<X>.<Y> + +The associated PMU is registered as + + /sys/bus/event_sources/devices/cxl_pmu_mem<X>.<Y> + +In common with other CXL bus devices, the id has no specific meaning and the +relationship to specific CXL device should be established via the device parent +of the device on the CXL bus. + +PMU driver provides description of available events and filter options in sysfs. + +The "format" directory describes all formats of the config (event vendor id, +group id and mask) config1 (threshold, filter enables) and config2 (filter +parameters) fields of the perf_event_attr structure. The "events" directory +describes all documented events show in perf list. + +The events shown in perf list are the most fine grained events with a single +bit of the event mask set. More general events may be enable by setting +multiple mask bits in config. For example, all Device to Host Read Requests +may be captured on a single counter by setting the bits for all of + +* d2h_req_rdcurr +* d2h_req_rdown +* d2h_req_rdshared +* d2h_req_rdany +* d2h_req_rdownnodata + +Example of usage:: + + $#perf list + cxl_pmu_mem0.0/clock_ticks/ [Kernel PMU event] + cxl_pmu_mem0.0/d2h_req_rdshared/ [Kernel PMU event] + cxl_pmu_mem0.0/h2d_req_snpcur/ [Kernel PMU event] + cxl_pmu_mem0.0/h2d_req_snpdata/ [Kernel PMU event] + cxl_pmu_mem0.0/h2d_req_snpinv/ [Kernel PMU event] + ----------------------------------------------------------- + + $# perf stat -a -e cxl_pmu_mem0.0/clock_ticks/ -e cxl_pmu_mem0.0/d2h_req_rdshared/ + +Vendor specific events may also be available and if so can be used via + + $# perf stat -a -e cxl_pmu_mem0.0/vid=VID,gid=GID,mask=MASK/ + +The driver does not support sampling so "perf record" is unsupported. +It only supports system-wide counting so attaching to a task is +unsupported. diff --git a/Documentation/admin-guide/perf/hisi-pcie-pmu.rst b/Documentation/admin-guide/perf/hisi-pcie-pmu.rst new file mode 100644 index 000000000..7e863662e --- /dev/null +++ b/Documentation/admin-guide/perf/hisi-pcie-pmu.rst @@ -0,0 +1,130 @@ +================================================ +HiSilicon PCIe Performance Monitoring Unit (PMU) +================================================ + +On Hip09, HiSilicon PCIe Performance Monitoring Unit (PMU) could monitor +bandwidth, latency, bus utilization and buffer occupancy data of PCIe. + +Each PCIe Core has a PMU to monitor multi Root Ports of this PCIe Core and +all Endpoints downstream these Root Ports. + + +HiSilicon PCIe PMU driver +========================= + +The PCIe PMU driver registers a perf PMU with the name of its sicl-id and PCIe +Core id.:: + + /sys/bus/event_source/hisi_pcie<sicl>_core<core> + +PMU driver provides description of available events and filter options in sysfs, +see /sys/bus/event_source/devices/hisi_pcie<sicl>_core<core>. + +The "format" directory describes all formats of the config (events) and config1 +(filter options) fields of the perf_event_attr structure. The "events" directory +describes all documented events shown in perf list. + +The "identifier" sysfs file allows users to identify the version of the +PMU hardware device. + +The "bus" sysfs file allows users to get the bus number of Root Ports +monitored by PMU. + +Example usage of perf:: + + $# perf list + hisi_pcie0_core0/rx_mwr_latency/ [kernel PMU event] + hisi_pcie0_core0/rx_mwr_cnt/ [kernel PMU event] + ------------------------------------------ + + $# perf stat -e hisi_pcie0_core0/rx_mwr_latency/ + $# perf stat -e hisi_pcie0_core0/rx_mwr_cnt/ + $# perf stat -g -e hisi_pcie0_core0/rx_mwr_latency/ -e hisi_pcie0_core0/rx_mwr_cnt/ + +The current driver does not support sampling. So "perf record" is unsupported. +Also attach to a task is unsupported for PCIe PMU. + +Filter options +-------------- + +1. Target filter + + PMU could only monitor the performance of traffic downstream target Root + Ports or downstream target Endpoint. PCIe PMU driver support "port" and + "bdf" interfaces for users, and these two interfaces aren't supported at the + same time. + + - port + + "port" filter can be used in all PCIe PMU events, target Root Port can be + selected by configuring the 16-bits-bitmap "port". Multi ports can be + selected for AP-layer-events, and only one port can be selected for + TL/DL-layer-events. + + For example, if target Root Port is 0000:00:00.0 (x8 lanes), bit0 of + bitmap should be set, port=0x1; if target Root Port is 0000:00:04.0 (x4 + lanes), bit8 is set, port=0x100; if these two Root Ports are both + monitored, port=0x101. + + Example usage of perf:: + + $# perf stat -e hisi_pcie0_core0/rx_mwr_latency,port=0x1/ sleep 5 + + - bdf + + "bdf" filter can only be used in bandwidth events, target Endpoint is + selected by configuring BDF to "bdf". Counter only counts the bandwidth of + message requested by target Endpoint. + + For example, "bdf=0x3900" means BDF of target Endpoint is 0000:39:00.0. + + Example usage of perf:: + + $# perf stat -e hisi_pcie0_core0/rx_mrd_flux,bdf=0x3900/ sleep 5 + +2. Trigger filter + + Event statistics start when the first time TLP length is greater/smaller + than trigger condition. You can set the trigger condition by writing + "trig_len", and set the trigger mode by writing "trig_mode". This filter can + only be used in bandwidth events. + + For example, "trig_len=4" means trigger condition is 2^4 DW, "trig_mode=0" + means statistics start when TLP length > trigger condition, "trig_mode=1" + means start when TLP length < condition. + + Example usage of perf:: + + $# perf stat -e hisi_pcie0_core0/rx_mrd_flux,trig_len=0x4,trig_mode=1/ sleep 5 + +3. Threshold filter + + Counter counts when TLP length within the specified range. You can set the + threshold by writing "thr_len", and set the threshold mode by writing + "thr_mode". This filter can only be used in bandwidth events. + + For example, "thr_len=4" means threshold is 2^4 DW, "thr_mode=0" means + counter counts when TLP length >= threshold, and "thr_mode=1" means counts + when TLP length < threshold. + + Example usage of perf:: + + $# perf stat -e hisi_pcie0_core0/rx_mrd_flux,thr_len=0x4,thr_mode=1/ sleep 5 + +4. TLP Length filter + + When counting bandwidth, the data can be composed of certain parts of TLP + packets. You can specify it through "len_mode": + + - 2'b00: Reserved (Do not use this since the behaviour is undefined) + - 2'b01: Bandwidth of TLP payloads + - 2'b10: Bandwidth of TLP headers + - 2'b11: Bandwidth of both TLP payloads and headers + + For example, "len_mode=2" means only counting the bandwidth of TLP headers + and "len_mode=3" means the final bandwidth data is composed of both TLP + headers and payloads. Default value if not specified is 2'b11. + + Example usage of perf:: + + $# perf stat -e hisi_pcie0_core0/rx_mrd_flux,len_mode=0x1/ sleep 5 diff --git a/Documentation/admin-guide/perf/hisi-pmu.rst b/Documentation/admin-guide/perf/hisi-pmu.rst new file mode 100644 index 000000000..e0174d208 --- /dev/null +++ b/Documentation/admin-guide/perf/hisi-pmu.rst @@ -0,0 +1,126 @@ +====================================================== +HiSilicon SoC uncore Performance Monitoring Unit (PMU) +====================================================== + +The HiSilicon SoC chip includes various independent system device PMUs +such as L3 cache (L3C), Hydra Home Agent (HHA) and DDRC. These PMUs are +independent and have hardware logic to gather statistics and performance +information. + +The HiSilicon SoC encapsulates multiple CPU and IO dies. Each CPU cluster +(CCL) is made up of 4 cpu cores sharing one L3 cache; each CPU die is +called Super CPU cluster (SCCL) and is made up of 6 CCLs. Each SCCL has +two HHAs (0 - 1) and four DDRCs (0 - 3), respectively. + +HiSilicon SoC uncore PMU driver +------------------------------- + +Each device PMU has separate registers for event counting, control and +interrupt, and the PMU driver shall register perf PMU drivers like L3C, +HHA and DDRC etc. The available events and configuration options shall +be described in the sysfs, see: + +/sys/devices/hisi_sccl{X}_<l3c{Y}/hha{Y}/ddrc{Y}>/, or +/sys/bus/event_source/devices/hisi_sccl{X}_<l3c{Y}/hha{Y}/ddrc{Y}>. +The "perf list" command shall list the available events from sysfs. + +Each L3C, HHA and DDRC is registered as a separate PMU with perf. The PMU +name will appear in event listing as hisi_sccl<sccl-id>_module<index-id>. +where "sccl-id" is the identifier of the SCCL and "index-id" is the index of +module. + +e.g. hisi_sccl3_l3c0/rd_hit_cpipe is READ_HIT_CPIPE event of L3C index #0 in +SCCL ID #3. + +e.g. hisi_sccl1_hha0/rx_operations is RX_OPERATIONS event of HHA index #0 in +SCCL ID #1. + +The driver also provides a "cpumask" sysfs attribute, which shows the CPU core +ID used to count the uncore PMU event. + +Example usage of perf:: + + $# perf list + hisi_sccl3_l3c0/rd_hit_cpipe/ [kernel PMU event] + ------------------------------------------ + hisi_sccl3_l3c0/wr_hit_cpipe/ [kernel PMU event] + ------------------------------------------ + hisi_sccl1_l3c0/rd_hit_cpipe/ [kernel PMU event] + ------------------------------------------ + hisi_sccl1_l3c0/wr_hit_cpipe/ [kernel PMU event] + ------------------------------------------ + + $# perf stat -a -e hisi_sccl3_l3c0/rd_hit_cpipe/ sleep 5 + $# perf stat -a -e hisi_sccl3_l3c0/config=0x02/ sleep 5 + +For HiSilicon uncore PMU v2 whose identifier is 0x30, the topology is the same +as PMU v1, but some new functions are added to the hardware. + +1. L3C PMU supports filtering by core/thread within the cluster which can be +specified as a bitmap:: + + $# perf stat -a -e hisi_sccl3_l3c0/config=0x02,tt_core=0x3/ sleep 5 + +This will only count the operations from core/thread 0 and 1 in this cluster. + +2. Tracetag allow the user to chose to count only read, write or atomic +operations via the tt_req parameeter in perf. The default value counts all +operations. tt_req is 3bits, 3'b100 represents read operations, 3'b101 +represents write operations, 3'b110 represents atomic store operations and +3'b111 represents atomic non-store operations, other values are reserved:: + + $# perf stat -a -e hisi_sccl3_l3c0/config=0x02,tt_req=0x4/ sleep 5 + +This will only count the read operations in this cluster. + +3. Datasrc allows the user to check where the data comes from. It is 5 bits. +Some important codes are as follows: + +- 5'b00001: comes from L3C in this die; +- 5'b01000: comes from L3C in the cross-die; +- 5'b01001: comes from L3C which is in another socket; +- 5'b01110: comes from the local DDR; +- 5'b01111: comes from the cross-die DDR; +- 5'b10000: comes from cross-socket DDR; + +etc, it is mainly helpful to find that the data source is nearest from the CPU +cores. If datasrc_cfg is used in the multi-chips, the datasrc_skt shall be +configured in perf command:: + + $# perf stat -a -e hisi_sccl3_l3c0/config=0xb9,datasrc_cfg=0xE/, + hisi_sccl3_l3c0/config=0xb9,datasrc_cfg=0xF/ sleep 5 + +4. Some HiSilicon SoCs encapsulate multiple CPU and IO dies. Each CPU die +contains several Compute Clusters (CCLs). The I/O dies are called Super I/O +clusters (SICL) containing multiple I/O clusters (ICLs). Each CCL/ICL in the +SoC has a unique ID. Each ID is 11bits, include a 6-bit SCCL-ID and 5-bit +CCL/ICL-ID. For I/O die, the ICL-ID is followed by: + +- 5'b00000: I/O_MGMT_ICL; +- 5'b00001: Network_ICL; +- 5'b00011: HAC_ICL; +- 5'b10000: PCIe_ICL; + +5. uring_channel: UC PMU events 0x47~0x59 supports filtering by tx request +uring channel. It is 2 bits. Some important codes are as follows: + +- 2'b11: count the events which sent to the uring_ext (MATA) channel; +- 2'b01: is the same as 2'b11; +- 2'b10: count the events which sent to the uring (non-MATA) channel; +- 2'b00: default value, count the events which sent to the both uring and + uring_ext channel; + +Users could configure IDs to count data come from specific CCL/ICL, by setting +srcid_cmd & srcid_msk, and data desitined for specific CCL/ICL by setting +tgtid_cmd & tgtid_msk. A set bit in srcid_msk/tgtid_msk means the PMU will not +check the bit when matching against the srcid_cmd/tgtid_cmd. + +If all of these options are disabled, it can works by the default value that +doesn't distinguish the filter condition and ID information and will return +the total counter values in the PMU counters. + +The current driver does not support sampling. So "perf record" is unsupported. +Also attach to a task is unsupported as the events are all uncore. + +Note: Please contact the maintainer for a complete list of events supported for +the PMU devices in the SoC and its information if needed. diff --git a/Documentation/admin-guide/perf/hns3-pmu.rst b/Documentation/admin-guide/perf/hns3-pmu.rst new file mode 100644 index 000000000..75a40846d --- /dev/null +++ b/Documentation/admin-guide/perf/hns3-pmu.rst @@ -0,0 +1,136 @@ +====================================== +HNS3 Performance Monitoring Unit (PMU) +====================================== + +HNS3(HiSilicon network system 3) Performance Monitoring Unit (PMU) is an +End Point device to collect performance statistics of HiSilicon SoC NIC. +On Hip09, each SICL(Super I/O cluster) has one PMU device. + +HNS3 PMU supports collection of performance statistics such as bandwidth, +latency, packet rate and interrupt rate. + +Each HNS3 PMU supports 8 hardware events. + +HNS3 PMU driver +=============== + +The HNS3 PMU driver registers a perf PMU with the name of its sicl id.:: + + /sys/devices/hns3_pmu_sicl_<sicl_id> + +PMU driver provides description of available events, filter modes, format, +identifier and cpumask in sysfs. + +The "events" directory describes the event code of all supported events +shown in perf list. + +The "filtermode" directory describes the supported filter modes of each +event. + +The "format" directory describes all formats of the config (events) and +config1 (filter options) fields of the perf_event_attr structure. + +The "identifier" file shows version of PMU hardware device. + +The "bdf_min" and "bdf_max" files show the supported bdf range of each +pmu device. + +The "hw_clk_freq" file shows the hardware clock frequency of each pmu +device. + +Example usage of checking event code and subevent code:: + + $# cat /sys/devices/hns3_pmu_sicl_0/events/dly_tx_normal_to_mac_time + config=0x00204 + $# cat /sys/devices/hns3_pmu_sicl_0/events/dly_tx_normal_to_mac_packet_num + config=0x10204 + +Each performance statistic has a pair of events to get two values to +calculate real performance data in userspace. + +The bits 0~15 of config (here 0x0204) are the true hardware event code. If +two events have same value of bits 0~15 of config, that means they are +event pair. And the bit 16 of config indicates getting counter 0 or +counter 1 of hardware event. + +After getting two values of event pair in userspace, the formula of +computation to calculate real performance data is::: + + counter 0 / counter 1 + +Example usage of checking supported filter mode:: + + $# cat /sys/devices/hns3_pmu_sicl_0/filtermode/bw_ssu_rpu_byte_num + filter mode supported: global/port/port-tc/func/func-queue/ + +Example usage of perf:: + + $# perf list + hns3_pmu_sicl_0/bw_ssu_rpu_byte_num/ [kernel PMU event] + hns3_pmu_sicl_0/bw_ssu_rpu_time/ [kernel PMU event] + ------------------------------------------ + + $# perf stat -g -e hns3_pmu_sicl_0/bw_ssu_rpu_byte_num,global=1/ -e hns3_pmu_sicl_0/bw_ssu_rpu_time,global=1/ -I 1000 + or + $# perf stat -g -e hns3_pmu_sicl_0/config=0x00002,global=1/ -e hns3_pmu_sicl_0/config=0x10002,global=1/ -I 1000 + + +Filter modes +-------------- + +1. global mode +PMU collect performance statistics for all HNS3 PCIe functions of IO DIE. +Set the "global" filter option to 1 will enable this mode. +Example usage of perf:: + + $# perf stat -a -e hns3_pmu_sicl_0/config=0x1020F,global=1/ -I 1000 + +2. port mode +PMU collect performance statistic of one whole physical port. The port id +is same as mac id. The "tc" filter option must be set to 0xF in this mode, +here tc stands for traffic class. + +Example usage of perf:: + + $# perf stat -a -e hns3_pmu_sicl_0/config=0x1020F,port=0,tc=0xF/ -I 1000 + +3. port-tc mode +PMU collect performance statistic of one tc of physical port. The port id +is same as mac id. The "tc" filter option must be set to 0 ~ 7 in this +mode. +Example usage of perf:: + + $# perf stat -a -e hns3_pmu_sicl_0/config=0x1020F,port=0,tc=0/ -I 1000 + +4. func mode +PMU collect performance statistic of one PF/VF. The function id is BDF of +PF/VF, its conversion formula:: + + func = (bus << 8) + (device << 3) + (function) + +for example: + BDF func + 35:00.0 0x3500 + 35:00.1 0x3501 + 35:01.0 0x3508 + +In this mode, the "queue" filter option must be set to 0xFFFF. +Example usage of perf:: + + $# perf stat -a -e hns3_pmu_sicl_0/config=0x1020F,bdf=0x3500,queue=0xFFFF/ -I 1000 + +5. func-queue mode +PMU collect performance statistic of one queue of PF/VF. The function id +is BDF of PF/VF, the "queue" filter option must be set to the exact queue +id of function. +Example usage of perf:: + + $# perf stat -a -e hns3_pmu_sicl_0/config=0x1020F,bdf=0x3500,queue=0/ -I 1000 + +6. func-intr mode +PMU collect performance statistic of one interrupt of PF/VF. The function +id is BDF of PF/VF, the "intr" filter option must be set to the exact +interrupt id of function. +Example usage of perf:: + + $# perf stat -a -e hns3_pmu_sicl_0/config=0x00301,bdf=0x3500,intr=0/ -I 1000 diff --git a/Documentation/admin-guide/perf/imx-ddr.rst b/Documentation/admin-guide/perf/imx-ddr.rst new file mode 100644 index 000000000..90926d0fb --- /dev/null +++ b/Documentation/admin-guide/perf/imx-ddr.rst @@ -0,0 +1,71 @@ +===================================================== +Freescale i.MX8 DDR Performance Monitoring Unit (PMU) +===================================================== + +There are no performance counters inside the DRAM controller, so performance +signals are brought out to the edge of the controller where a set of 4 x 32 bit +counters is implemented. This is controlled by the CSV modes programmed in counter +control register which causes a large number of PERF signals to be generated. + +Selection of the value for each counter is done via the config registers. There +is one register for each counter. Counter 0 is special in that it always counts +“time” and when expired causes a lock on itself and the other counters and an +interrupt is raised. If any other counter overflows, it continues counting, and +no interrupt is raised. + +The "format" directory describes format of the config (event ID) and config1 +(AXI filtering) fields of the perf_event_attr structure, see /sys/bus/event_source/ +devices/imx8_ddr0/format/. The "events" directory describes the events types +hardware supported that can be used with perf tool, see /sys/bus/event_source/ +devices/imx8_ddr0/events/. The "caps" directory describes filter features implemented +in DDR PMU, see /sys/bus/events_source/devices/imx8_ddr0/caps/. + + .. code-block:: bash + + perf stat -a -e imx8_ddr0/cycles/ cmd + perf stat -a -e imx8_ddr0/read/,imx8_ddr0/write/ cmd + +AXI filtering is only used by CSV modes 0x41 (axid-read) and 0x42 (axid-write) +to count reading or writing matches filter setting. Filter setting is various +from different DRAM controller implementations, which is distinguished by quirks +in the driver. You also can dump info from userspace, filter in "caps" directory +indicates whether PMU supports AXI ID filter or not; enhanced_filter indicates +whether PMU supports enhanced AXI ID filter or not. Value 0 for un-supported, and +value 1 for supported. + +* With DDR_CAP_AXI_ID_FILTER quirk(filter: 1, enhanced_filter: 0). + Filter is defined with two configuration parts: + --AXI_ID defines AxID matching value. + --AXI_MASKING defines which bits of AxID are meaningful for the matching. + + - 0: corresponding bit is masked. + - 1: corresponding bit is not masked, i.e. used to do the matching. + + AXI_ID and AXI_MASKING are mapped on DPCR1 register in performance counter. + When non-masked bits are matching corresponding AXI_ID bits then counter is + incremented. Perf counter is incremented if:: + + AxID && AXI_MASKING == AXI_ID && AXI_MASKING + + This filter doesn't support filter different AXI ID for axid-read and axid-write + event at the same time as this filter is shared between counters. + + .. code-block:: bash + + perf stat -a -e imx8_ddr0/axid-read,axi_mask=0xMMMM,axi_id=0xDDDD/ cmd + perf stat -a -e imx8_ddr0/axid-write,axi_mask=0xMMMM,axi_id=0xDDDD/ cmd + + .. note:: + + axi_mask is inverted in userspace(i.e. set bits are bits to mask), and + it will be reverted in driver automatically. so that the user can just specify + axi_id to monitor a specific id, rather than having to specify axi_mask. + + .. code-block:: bash + + perf stat -a -e imx8_ddr0/axid-read,axi_id=0x12/ cmd, which will monitor ARID=0x12 + +* With DDR_CAP_AXI_ID_FILTER_ENHANCED quirk(filter: 1, enhanced_filter: 1). + This is an extension to the DDR_CAP_AXI_ID_FILTER quirk which permits + counting the number of bytes (as opposed to the number of bursts) from DDR + read and write transactions concurrently with another set of data counters. diff --git a/Documentation/admin-guide/perf/index.rst b/Documentation/admin-guide/perf/index.rst new file mode 100644 index 000000000..f60be04e4 --- /dev/null +++ b/Documentation/admin-guide/perf/index.rst @@ -0,0 +1,24 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=========================== +Performance monitor support +=========================== + +.. toctree:: + :maxdepth: 1 + + hisi-pmu + hisi-pcie-pmu + hns3-pmu + imx-ddr + qcom_l2_pmu + qcom_l3_pmu + arm-ccn + arm-cmn + xgene-pmu + arm_dsu_pmu + thunderx2-pmu + alibaba_pmu + nvidia-pmu + meson-ddr-pmu + cxl diff --git a/Documentation/admin-guide/perf/meson-ddr-pmu.rst b/Documentation/admin-guide/perf/meson-ddr-pmu.rst new file mode 100644 index 000000000..8e71be1d6 --- /dev/null +++ b/Documentation/admin-guide/perf/meson-ddr-pmu.rst @@ -0,0 +1,70 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=========================================================== +Amlogic SoC DDR Bandwidth Performance Monitoring Unit (PMU) +=========================================================== + +The Amlogic Meson G12 SoC contains a bandwidth monitor inside DRAM controller. +The monitor includes 4 channels. Each channel can count the request accessing +DRAM. The channel can count up to 3 AXI port simultaneously. It can be helpful +to show if the performance bottleneck is on DDR bandwidth. + +Currently, this driver supports the following 5 perf events: + ++ meson_ddr_bw/total_rw_bytes/ ++ meson_ddr_bw/chan_1_rw_bytes/ ++ meson_ddr_bw/chan_2_rw_bytes/ ++ meson_ddr_bw/chan_3_rw_bytes/ ++ meson_ddr_bw/chan_4_rw_bytes/ + +meson_ddr_bw/chan_{1,2,3,4}_rw_bytes/ events are channel-specific events. +Each channel support filtering, which can let the channel to monitor +individual IP module in SoC. + +Below are DDR access request event filter keywords: + ++ arm - from CPU ++ vpu_read1 - from OSD + VPP read ++ gpu - from 3D GPU ++ pcie - from PCIe controller ++ hdcp - from HDCP controller ++ hevc_front - from HEVC codec front end ++ usb3_0 - from USB3.0 controller ++ hevc_back - from HEVC codec back end ++ h265enc - from HEVC encoder ++ vpu_read2 - from DI read ++ vpu_write1 - from VDIN write ++ vpu_write2 - from di write ++ vdec - from legacy codec video decoder ++ hcodec - from H264 encoder ++ ge2d - from ge2d ++ spicc1 - from SPI controller 1 ++ usb0 - from USB2.0 controller 0 ++ dma - from system DMA controller 1 ++ arb0 - from arb0 ++ sd_emmc_b - from SD eMMC b controller ++ usb1 - from USB2.0 controller 1 ++ audio - from Audio module ++ sd_emmc_c - from SD eMMC c controller ++ spicc2 - from SPI controller 2 ++ ethernet - from Ethernet controller + + +Examples: + + + Show the total DDR bandwidth per seconds: + + .. code-block:: bash + + perf stat -a -e meson_ddr_bw/total_rw_bytes/ -I 1000 sleep 10 + + + + Show individual DDR bandwidth from CPU and GPU respectively, as well as + sum of them: + + .. code-block:: bash + + perf stat -a -e meson_ddr_bw/chan_1_rw_bytes,arm=1/ -I 1000 sleep 10 + perf stat -a -e meson_ddr_bw/chan_2_rw_bytes,gpu=1/ -I 1000 sleep 10 + perf stat -a -e meson_ddr_bw/chan_3_rw_bytes,arm=1,gpu=1/ -I 1000 sleep 10 + diff --git a/Documentation/admin-guide/perf/nvidia-pmu.rst b/Documentation/admin-guide/perf/nvidia-pmu.rst new file mode 100644 index 000000000..2e0d47cfe --- /dev/null +++ b/Documentation/admin-guide/perf/nvidia-pmu.rst @@ -0,0 +1,299 @@ +========================================================= +NVIDIA Tegra SoC Uncore Performance Monitoring Unit (PMU) +========================================================= + +The NVIDIA Tegra SoC includes various system PMUs to measure key performance +metrics like memory bandwidth, latency, and utilization: + +* Scalable Coherency Fabric (SCF) +* NVLink-C2C0 +* NVLink-C2C1 +* CNVLink +* PCIE + +PMU Driver +---------- + +The PMUs in this document are based on ARM CoreSight PMU Architecture as +described in document: ARM IHI 0091. Since this is a standard architecture, the +PMUs are managed by a common driver "arm-cs-arch-pmu". This driver describes +the available events and configuration of each PMU in sysfs. Please see the +sections below to get the sysfs path of each PMU. Like other uncore PMU drivers, +the driver provides "cpumask" sysfs attribute to show the CPU id used to handle +the PMU event. There is also "associated_cpus" sysfs attribute, which contains a +list of CPUs associated with the PMU instance. + +.. _SCF_PMU_Section: + +SCF PMU +------- + +The SCF PMU monitors system level cache events, CPU traffic, and +strongly-ordered (SO) PCIE write traffic to local/remote memory. Please see +:ref:`NVIDIA_Uncore_PMU_Traffic_Coverage_Section` for more info about the PMU +traffic coverage. + +The events and configuration options of this PMU device are described in sysfs, +see /sys/bus/event_sources/devices/nvidia_scf_pmu_<socket-id>. + +Example usage: + +* Count event id 0x0 in socket 0:: + + perf stat -a -e nvidia_scf_pmu_0/event=0x0/ + +* Count event id 0x0 in socket 1:: + + perf stat -a -e nvidia_scf_pmu_1/event=0x0/ + +NVLink-C2C0 PMU +-------------------- + +The NVLink-C2C0 PMU monitors incoming traffic from a GPU/CPU connected with +NVLink-C2C (Chip-2-Chip) interconnect. The type of traffic captured by this PMU +varies dependent on the chip configuration: + +* NVIDIA Grace Hopper Superchip: Hopper GPU is connected with Grace SoC. + + In this config, the PMU captures GPU ATS translated or EGM traffic from the GPU. + +* NVIDIA Grace CPU Superchip: two Grace CPU SoCs are connected. + + In this config, the PMU captures read and relaxed ordered (RO) writes from + PCIE device of the remote SoC. + +Please see :ref:`NVIDIA_Uncore_PMU_Traffic_Coverage_Section` for more info about +the PMU traffic coverage. + +The events and configuration options of this PMU device are described in sysfs, +see /sys/bus/event_sources/devices/nvidia_nvlink_c2c0_pmu_<socket-id>. + +Example usage: + +* Count event id 0x0 from the GPU/CPU connected with socket 0:: + + perf stat -a -e nvidia_nvlink_c2c0_pmu_0/event=0x0/ + +* Count event id 0x0 from the GPU/CPU connected with socket 1:: + + perf stat -a -e nvidia_nvlink_c2c0_pmu_1/event=0x0/ + +* Count event id 0x0 from the GPU/CPU connected with socket 2:: + + perf stat -a -e nvidia_nvlink_c2c0_pmu_2/event=0x0/ + +* Count event id 0x0 from the GPU/CPU connected with socket 3:: + + perf stat -a -e nvidia_nvlink_c2c0_pmu_3/event=0x0/ + +NVLink-C2C1 PMU +------------------- + +The NVLink-C2C1 PMU monitors incoming traffic from a GPU connected with +NVLink-C2C (Chip-2-Chip) interconnect. This PMU captures untranslated GPU +traffic, in contrast with NvLink-C2C0 PMU that captures ATS translated traffic. +Please see :ref:`NVIDIA_Uncore_PMU_Traffic_Coverage_Section` for more info about +the PMU traffic coverage. + +The events and configuration options of this PMU device are described in sysfs, +see /sys/bus/event_sources/devices/nvidia_nvlink_c2c1_pmu_<socket-id>. + +Example usage: + +* Count event id 0x0 from the GPU connected with socket 0:: + + perf stat -a -e nvidia_nvlink_c2c1_pmu_0/event=0x0/ + +* Count event id 0x0 from the GPU connected with socket 1:: + + perf stat -a -e nvidia_nvlink_c2c1_pmu_1/event=0x0/ + +* Count event id 0x0 from the GPU connected with socket 2:: + + perf stat -a -e nvidia_nvlink_c2c1_pmu_2/event=0x0/ + +* Count event id 0x0 from the GPU connected with socket 3:: + + perf stat -a -e nvidia_nvlink_c2c1_pmu_3/event=0x0/ + +CNVLink PMU +--------------- + +The CNVLink PMU monitors traffic from GPU and PCIE device on remote sockets +to local memory. For PCIE traffic, this PMU captures read and relaxed ordered +(RO) write traffic. Please see :ref:`NVIDIA_Uncore_PMU_Traffic_Coverage_Section` +for more info about the PMU traffic coverage. + +The events and configuration options of this PMU device are described in sysfs, +see /sys/bus/event_sources/devices/nvidia_cnvlink_pmu_<socket-id>. + +Each SoC socket can be connected to one or more sockets via CNVLink. The user can +use "rem_socket" bitmap parameter to select the remote socket(s) to monitor. +Each bit represents the socket number, e.g. "rem_socket=0xE" corresponds to +socket 1 to 3. +/sys/bus/event_sources/devices/nvidia_cnvlink_pmu_<socket-id>/format/rem_socket +shows the valid bits that can be set in the "rem_socket" parameter. + +The PMU can not distinguish the remote traffic initiator, therefore it does not +provide filter to select the traffic source to monitor. It reports combined +traffic from remote GPU and PCIE devices. + +Example usage: + +* Count event id 0x0 for the traffic from remote socket 1, 2, and 3 to socket 0:: + + perf stat -a -e nvidia_cnvlink_pmu_0/event=0x0,rem_socket=0xE/ + +* Count event id 0x0 for the traffic from remote socket 0, 2, and 3 to socket 1:: + + perf stat -a -e nvidia_cnvlink_pmu_1/event=0x0,rem_socket=0xD/ + +* Count event id 0x0 for the traffic from remote socket 0, 1, and 3 to socket 2:: + + perf stat -a -e nvidia_cnvlink_pmu_2/event=0x0,rem_socket=0xB/ + +* Count event id 0x0 for the traffic from remote socket 0, 1, and 2 to socket 3:: + + perf stat -a -e nvidia_cnvlink_pmu_3/event=0x0,rem_socket=0x7/ + + +PCIE PMU +------------ + +The PCIE PMU monitors all read/write traffic from PCIE root ports to +local/remote memory. Please see :ref:`NVIDIA_Uncore_PMU_Traffic_Coverage_Section` +for more info about the PMU traffic coverage. + +The events and configuration options of this PMU device are described in sysfs, +see /sys/bus/event_sources/devices/nvidia_pcie_pmu_<socket-id>. + +Each SoC socket can support multiple root ports. The user can use +"root_port" bitmap parameter to select the port(s) to monitor, i.e. +"root_port=0xF" corresponds to root port 0 to 3. +/sys/bus/event_sources/devices/nvidia_pcie_pmu_<socket-id>/format/root_port +shows the valid bits that can be set in the "root_port" parameter. + +Example usage: + +* Count event id 0x0 from root port 0 and 1 of socket 0:: + + perf stat -a -e nvidia_pcie_pmu_0/event=0x0,root_port=0x3/ + +* Count event id 0x0 from root port 0 and 1 of socket 1:: + + perf stat -a -e nvidia_pcie_pmu_1/event=0x0,root_port=0x3/ + +.. _NVIDIA_Uncore_PMU_Traffic_Coverage_Section: + +Traffic Coverage +---------------- + +The PMU traffic coverage may vary dependent on the chip configuration: + +* **NVIDIA Grace Hopper Superchip**: Hopper GPU is connected with Grace SoC. + + Example configuration with two Grace SoCs:: + + ********************************* ********************************* + * SOCKET-A * * SOCKET-B * + * * * * + * :::::::: * * :::::::: * + * : PCIE : * * : PCIE : * + * :::::::: * * :::::::: * + * | * * | * + * | * * | * + * ::::::: ::::::::: * * ::::::::: ::::::: * + * : : : : * * : : : : * + * : GPU :<--NVLink-->: Grace :<---CNVLink--->: Grace :<--NVLink-->: GPU : * + * : : C2C : SoC : * * : SoC : C2C : : * + * ::::::: ::::::::: * * ::::::::: ::::::: * + * | | * * | | * + * | | * * | | * + * &&&&&&&& &&&&&&&& * * &&&&&&&& &&&&&&&& * + * & GMEM & & CMEM & * * & CMEM & & GMEM & * + * &&&&&&&& &&&&&&&& * * &&&&&&&& &&&&&&&& * + * * * * + ********************************* ********************************* + + GMEM = GPU Memory (e.g. HBM) + CMEM = CPU Memory (e.g. LPDDR5X) + + | + | Following table contains traffic coverage of Grace SoC PMU in socket-A: + + :: + + +--------------+-------+-----------+-----------+-----+----------+----------+ + | | Source | + + +-------+-----------+-----------+-----+----------+----------+ + | Destination | |GPU ATS |GPU Not-ATS| | Socket-B | Socket-B | + | |PCI R/W|Translated,|Translated | CPU | CPU/PCIE1| GPU/PCIE2| + | | |EGM | | | | | + +==============+=======+===========+===========+=====+==========+==========+ + | Local | PCIE |NVLink-C2C0|NVLink-C2C1| SCF | SCF PMU | CNVLink | + | SYSRAM/CMEM | PMU |PMU |PMU | PMU | | PMU | + +--------------+-------+-----------+-----------+-----+----------+----------+ + | Local GMEM | PCIE | N/A |NVLink-C2C1| SCF | SCF PMU | CNVLink | + | | PMU | |PMU | PMU | | PMU | + +--------------+-------+-----------+-----------+-----+----------+----------+ + | Remote | PCIE |NVLink-C2C0|NVLink-C2C1| SCF | | | + | SYSRAM/CMEM | PMU |PMU |PMU | PMU | N/A | N/A | + | over CNVLink | | | | | | | + +--------------+-------+-----------+-----------+-----+----------+----------+ + | Remote GMEM | PCIE |NVLink-C2C0|NVLink-C2C1| SCF | | | + | over CNVLink | PMU |PMU |PMU | PMU | N/A | N/A | + +--------------+-------+-----------+-----------+-----+----------+----------+ + + PCIE1 traffic represents strongly ordered (SO) writes. + PCIE2 traffic represents reads and relaxed ordered (RO) writes. + +* **NVIDIA Grace CPU Superchip**: two Grace CPU SoCs are connected. + + Example configuration with two Grace SoCs:: + + ******************* ******************* + * SOCKET-A * * SOCKET-B * + * * * * + * :::::::: * * :::::::: * + * : PCIE : * * : PCIE : * + * :::::::: * * :::::::: * + * | * * | * + * | * * | * + * ::::::::: * * ::::::::: * + * : : * * : : * + * : Grace :<--------NVLink------->: Grace : * + * : SoC : * C2C * : SoC : * + * ::::::::: * * ::::::::: * + * | * * | * + * | * * | * + * &&&&&&&& * * &&&&&&&& * + * & CMEM & * * & CMEM & * + * &&&&&&&& * * &&&&&&&& * + * * * * + ******************* ******************* + + GMEM = GPU Memory (e.g. HBM) + CMEM = CPU Memory (e.g. LPDDR5X) + + | + | Following table contains traffic coverage of Grace SoC PMU in socket-A: + + :: + + +-----------------+-----------+---------+----------+-------------+ + | | Source | + + +-----------+---------+----------+-------------+ + | Destination | | | Socket-B | Socket-B | + | | PCI R/W | CPU | CPU/PCIE1| PCIE2 | + | | | | | | + +=================+===========+=========+==========+=============+ + | Local | PCIE PMU | SCF PMU | SCF PMU | NVLink-C2C0 | + | SYSRAM/CMEM | | | | PMU | + +-----------------+-----------+---------+----------+-------------+ + | Remote | | | | | + | SYSRAM/CMEM | PCIE PMU | SCF PMU | N/A | N/A | + | over NVLink-C2C | | | | | + +-----------------+-----------+---------+----------+-------------+ + + PCIE1 traffic represents strongly ordered (SO) writes. + PCIE2 traffic represents reads and relaxed ordered (RO) writes. diff --git a/Documentation/admin-guide/perf/qcom_l2_pmu.rst b/Documentation/admin-guide/perf/qcom_l2_pmu.rst new file mode 100644 index 000000000..c130178a4 --- /dev/null +++ b/Documentation/admin-guide/perf/qcom_l2_pmu.rst @@ -0,0 +1,39 @@ +===================================================================== +Qualcomm Technologies Level-2 Cache Performance Monitoring Unit (PMU) +===================================================================== + +This driver supports the L2 cache clusters found in Qualcomm Technologies +Centriq SoCs. There are multiple physical L2 cache clusters, each with their +own PMU. Each cluster has one or more CPUs associated with it. + +There is one logical L2 PMU exposed, which aggregates the results from +the physical PMUs. + +The driver provides a description of its available events and configuration +options in sysfs, see /sys/devices/l2cache_0. + +The "format" directory describes the format of the events. + +Events can be envisioned as a 2-dimensional array. Each column represents +a group of events. There are 8 groups. Only one entry from each +group can be in use at a time. If multiple events from the same group +are specified, the conflicting events cannot be counted at the same time. + +Events are specified as 0xCCG, where CC is 2 hex digits specifying +the code (array row) and G specifies the group (column) 0-7. + +In addition there is a cycle counter event specified by the value 0xFE +which is outside the above scheme. + +The driver provides a "cpumask" sysfs attribute which contains a mask +consisting of one CPU per cluster which will be used to handle all the PMU +events on that cluster. + +Examples for use with perf:: + + perf stat -e l2cache_0/config=0x001/,l2cache_0/config=0x042/ -a sleep 1 + + perf stat -e l2cache_0/config=0xfe/ -C 2 sleep 1 + +The driver does not support sampling, therefore "perf record" will +not work. Per-task perf sessions are not supported. diff --git a/Documentation/admin-guide/perf/qcom_l3_pmu.rst b/Documentation/admin-guide/perf/qcom_l3_pmu.rst new file mode 100644 index 000000000..a3d014a46 --- /dev/null +++ b/Documentation/admin-guide/perf/qcom_l3_pmu.rst @@ -0,0 +1,26 @@ +=========================================================================== +Qualcomm Datacenter Technologies L3 Cache Performance Monitoring Unit (PMU) +=========================================================================== + +This driver supports the L3 cache PMUs found in Qualcomm Datacenter Technologies +Centriq SoCs. The L3 cache on these SOCs is composed of multiple slices, shared +by all cores within a socket. Each slice is exposed as a separate uncore perf +PMU with device name l3cache_<socket>_<instance>. User space is responsible +for aggregating across slices. + +The driver provides a description of its available events and configuration +options in sysfs, see /sys/devices/l3cache*. Given that these are uncore PMUs +the driver also exposes a "cpumask" sysfs attribute which contains a mask +consisting of one CPU per socket which will be used to handle all the PMU +events on that socket. + +The hardware implements 32bit event counters and has a flat 8bit event space +exposed via the "event" format attribute. In addition to the 32bit physical +counters the driver supports virtual 64bit hardware counters by using hardware +counter chaining. This feature is exposed via the "lc" (long counter) format +flag. E.g.:: + + perf stat -e l3cache_0_0/read-miss,lc/ + +Given that these are uncore PMUs the driver does not support sampling, therefore +"perf record" will not work. Per-task perf sessions are not supported. diff --git a/Documentation/admin-guide/perf/thunderx2-pmu.rst b/Documentation/admin-guide/perf/thunderx2-pmu.rst new file mode 100644 index 000000000..01f158238 --- /dev/null +++ b/Documentation/admin-guide/perf/thunderx2-pmu.rst @@ -0,0 +1,44 @@ +============================================================= +Cavium ThunderX2 SoC Performance Monitoring Unit (PMU UNCORE) +============================================================= + +The ThunderX2 SoC PMU consists of independent, system-wide, per-socket +PMUs such as the Level 3 Cache (L3C), DDR4 Memory Controller (DMC) and +Cavium Coherent Processor Interconnect (CCPI2). + +The DMC has 8 interleaved channels and the L3C has 16 interleaved tiles. +Events are counted for the default channel (i.e. channel 0) and prorated +to the total number of channels/tiles. + +The DMC and L3C support up to 4 counters, while the CCPI2 supports up to 8 +counters. Counters are independently programmable to different events and +can be started and stopped individually. None of the counters support an +overflow interrupt. DMC and L3C counters are 32-bit and read every 2 seconds. +The CCPI2 counters are 64-bit and assumed not to overflow in normal operation. + +PMU UNCORE (perf) driver: + +The thunderx2_pmu driver registers per-socket perf PMUs for the DMC and +L3C devices. Each PMU can be used to count up to 4 (DMC/L3C) or up to 8 +(CCPI2) events simultaneously. The PMUs provide a description of their +available events and configuration options under sysfs, see +/sys/devices/uncore_<l3c_S/dmc_S/ccpi2_S/>; S is the socket id. + +The driver does not support sampling, therefore "perf record" will not +work. Per-task perf sessions are also not supported. + +Examples:: + + # perf stat -a -e uncore_dmc_0/cnt_cycles/ sleep 1 + + # perf stat -a -e \ + uncore_dmc_0/cnt_cycles/,\ + uncore_dmc_0/data_transfers/,\ + uncore_dmc_0/read_txns/,\ + uncore_dmc_0/write_txns/ sleep 1 + + # perf stat -a -e \ + uncore_l3c_0/read_request/,\ + uncore_l3c_0/read_hit/,\ + uncore_l3c_0/inv_request/,\ + uncore_l3c_0/inv_hit/ sleep 1 diff --git a/Documentation/admin-guide/perf/xgene-pmu.rst b/Documentation/admin-guide/perf/xgene-pmu.rst new file mode 100644 index 000000000..644f8ed89 --- /dev/null +++ b/Documentation/admin-guide/perf/xgene-pmu.rst @@ -0,0 +1,49 @@ +================================================ +APM X-Gene SoC Performance Monitoring Unit (PMU) +================================================ + +X-Gene SoC PMU consists of various independent system device PMUs such as +L3 cache(s), I/O bridge(s), memory controller bridge(s) and memory +controller(s). These PMU devices are loosely architected to follow the +same model as the PMU for ARM cores. The PMUs share the same top level +interrupt and status CSR region. + +PMU (perf) driver +----------------- + +The xgene-pmu driver registers several perf PMU drivers. Each of the perf +driver provides description of its available events and configuration options +in sysfs, see /sys/devices/<l3cX/iobX/mcbX/mcX>/. + +The "format" directory describes format of the config (event ID), +config1 (agent ID) fields of the perf_event_attr structure. The "events" +directory provides configuration templates for all supported event types that +can be used with perf tool. For example, "l3c0/bank-fifo-full/" is an +equivalent of "l3c0/config=0x0b/". + +Most of the SoC PMU has a specific list of agent ID used for monitoring +performance of a specific datapath. For example, agents of a L3 cache can be +a specific CPU or an I/O bridge. Each PMU has a set of 2 registers capable of +masking the agents from which the request come from. If the bit with +the bit number corresponding to the agent is set, the event is counted only if +it is caused by a request from that agent. Each agent ID bit is inversely mapped +to a corresponding bit in "config1" field. By default, the event will be +counted for all agent requests (config1 = 0x0). For all the supported agents of +each PMU, please refer to APM X-Gene User Manual. + +Each perf driver also provides a "cpumask" sysfs attribute, which contains a +single CPU ID of the processor which will be used to handle all the PMU events. + +Example for perf tool use:: + + / # perf list | grep -e l3c -e iob -e mcb -e mc + l3c0/ackq-full/ [Kernel PMU event] + <...> + mcb1/mcb-csw-stall/ [Kernel PMU event] + + / # perf stat -a -e l3c0/read-miss/,mcb1/csw-write-request/ sleep 1 + + / # perf stat -a -e l3c0/read-miss,config1=0xfffffffffffffffe/ sleep 1 + +The driver does not support sampling, therefore "perf record" will +not work. Per-task (without "-a") perf sessions are not supported. diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst new file mode 100644 index 000000000..1cf40f692 --- /dev/null +++ b/Documentation/admin-guide/pm/amd-pstate.rst @@ -0,0 +1,720 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + +=============================================== +``amd-pstate`` CPU Performance Scaling Driver +=============================================== + +:Copyright: |copy| 2021 Advanced Micro Devices, Inc. + +:Author: Huang Rui <ray.huang@amd.com> + + +Introduction +=================== + +``amd-pstate`` is the AMD CPU performance scaling driver that introduces a +new CPU frequency control mechanism on modern AMD APU and CPU series in +Linux kernel. The new mechanism is based on Collaborative Processor +Performance Control (CPPC) which provides finer grain frequency management +than legacy ACPI hardware P-States. Current AMD CPU/APU platforms are using +the ACPI P-states driver to manage CPU frequency and clocks with switching +only in 3 P-states. CPPC replaces the ACPI P-states controls and allows a +flexible, low-latency interface for the Linux kernel to directly +communicate the performance hints to hardware. + +``amd-pstate`` leverages the Linux kernel governors such as ``schedutil``, +``ondemand``, etc. to manage the performance hints which are provided by +CPPC hardware functionality that internally follows the hardware +specification (for details refer to AMD64 Architecture Programmer's Manual +Volume 2: System Programming [1]_). Currently, ``amd-pstate`` supports basic +frequency control function according to kernel governors on some of the +Zen2 and Zen3 processors, and we will implement more AMD specific functions +in future after we verify them on the hardware and SBIOS. + + +AMD CPPC Overview +======================= + +Collaborative Processor Performance Control (CPPC) interface enumerates a +continuous, abstract, and unit-less performance value in a scale that is +not tied to a specific performance state / frequency. This is an ACPI +standard [2]_ which software can specify application performance goals and +hints as a relative target to the infrastructure limits. AMD processors +provide the low latency register model (MSR) instead of an AML code +interpreter for performance adjustments. ``amd-pstate`` will initialize a +``struct cpufreq_driver`` instance, ``amd_pstate_driver``, with the callbacks +to manage each performance update behavior. :: + + Highest Perf ------>+-----------------------+ +-----------------------+ + | | | | + | | | | + | | Max Perf ---->| | + | | | | + | | | | + Nominal Perf ------>+-----------------------+ +-----------------------+ + | | | | + | | | | + | | | | + | | | | + | | | | + | | | | + | | Desired Perf ---->| | + | | | | + | | | | + | | | | + | | | | + | | | | + | | | | + | | | | + | | | | + | | | | + Lowest non- | | | | + linear perf ------>+-----------------------+ +-----------------------+ + | | | | + | | Lowest perf ---->| | + | | | | + Lowest perf ------>+-----------------------+ +-----------------------+ + | | | | + | | | | + | | | | + 0 ------>+-----------------------+ +-----------------------+ + + AMD P-States Performance Scale + + +.. _perf_cap: + +AMD CPPC Performance Capability +-------------------------------- + +Highest Performance (RO) +......................... + +This is the absolute maximum performance an individual processor may reach, +assuming ideal conditions. This performance level may not be sustainable +for long durations and may only be achievable if other platform components +are in a specific state; for example, it may require other processors to be in +an idle state. This would be equivalent to the highest frequencies +supported by the processor. + +Nominal (Guaranteed) Performance (RO) +...................................... + +This is the maximum sustained performance level of the processor, assuming +ideal operating conditions. In the absence of an external constraint (power, +thermal, etc.), this is the performance level the processor is expected to +be able to maintain continuously. All cores/processors are expected to be +able to sustain their nominal performance state simultaneously. + +Lowest non-linear Performance (RO) +................................... + +This is the lowest performance level at which nonlinear power savings are +achieved, for example, due to the combined effects of voltage and frequency +scaling. Above this threshold, lower performance levels should be generally +more energy efficient than higher performance levels. This register +effectively conveys the most efficient performance level to ``amd-pstate``. + +Lowest Performance (RO) +........................ + +This is the absolute lowest performance level of the processor. Selecting a +performance level lower than the lowest nonlinear performance level may +cause an efficiency penalty but should reduce the instantaneous power +consumption of the processor. + +AMD CPPC Performance Control +------------------------------ + +``amd-pstate`` passes performance goals through these registers. The +register drives the behavior of the desired performance target. + +Minimum requested performance (RW) +................................... + +``amd-pstate`` specifies the minimum allowed performance level. + +Maximum requested performance (RW) +................................... + +``amd-pstate`` specifies a limit the maximum performance that is expected +to be supplied by the hardware. + +Desired performance target (RW) +................................... + +``amd-pstate`` specifies a desired target in the CPPC performance scale as +a relative number. This can be expressed as percentage of nominal +performance (infrastructure max). Below the nominal sustained performance +level, desired performance expresses the average performance level of the +processor subject to hardware. Above the nominal performance level, +the processor must provide at least nominal performance requested and go higher +if current operating conditions allow. + +Energy Performance Preference (EPP) (RW) +......................................... + +This attribute provides a hint to the hardware if software wants to bias +toward performance (0x0) or energy efficiency (0xff). + + +Key Governors Support +======================= + +``amd-pstate`` can be used with all the (generic) scaling governors listed +by the ``scaling_available_governors`` policy attribute in ``sysfs``. Then, +it is responsible for the configuration of policy objects corresponding to +CPUs and provides the ``CPUFreq`` core (and the scaling governors attached +to the policy objects) with accurate information on the maximum and minimum +operating frequencies supported by the hardware. Users can check the +``scaling_cur_freq`` information comes from the ``CPUFreq`` core. + +``amd-pstate`` mainly supports ``schedutil`` and ``ondemand`` for dynamic +frequency control. It is to fine tune the processor configuration on +``amd-pstate`` to the ``schedutil`` with CPU CFS scheduler. ``amd-pstate`` +registers the adjust_perf callback to implement performance update behavior +similar to CPPC. It is initialized by ``sugov_start`` and then populates the +CPU's update_util_data pointer to assign ``sugov_update_single_perf`` as the +utilization update callback function in the CPU scheduler. The CPU scheduler +will call ``cpufreq_update_util`` and assigns the target performance according +to the ``struct sugov_cpu`` that the utilization update belongs to. +Then, ``amd-pstate`` updates the desired performance according to the CPU +scheduler assigned. + +.. _processor_support: + +Processor Support +======================= + +The ``amd-pstate`` initialization will fail if the ``_CPC`` entry in the ACPI +SBIOS does not exist in the detected processor. It uses ``acpi_cpc_valid`` +to check the existence of ``_CPC``. All Zen based processors support the legacy +ACPI hardware P-States function, so when ``amd-pstate`` fails initialization, +the kernel will fall back to initialize the ``acpi-cpufreq`` driver. + +There are two types of hardware implementations for ``amd-pstate``: one is +`Full MSR Support <perf_cap_>`_ and another is `Shared Memory Support +<perf_cap_>`_. It can use the :c:macro:`X86_FEATURE_CPPC` feature flag to +indicate the different types. (For details, refer to the Processor Programming +Reference (PPR) for AMD Family 19h Model 51h, Revision A1 Processors [3]_.) +``amd-pstate`` is to register different ``static_call`` instances for different +hardware implementations. + +Currently, some of the Zen2 and Zen3 processors support ``amd-pstate``. In the +future, it will be supported on more and more AMD processors. + +Full MSR Support +----------------- + +Some new Zen3 processors such as Cezanne provide the MSR registers directly +while the :c:macro:`X86_FEATURE_CPPC` CPU feature flag is set. +``amd-pstate`` can handle the MSR register to implement the fast switch +function in ``CPUFreq`` that can reduce the latency of frequency control in +interrupt context. The functions with a ``pstate_xxx`` prefix represent the +operations on MSR registers. + +Shared Memory Support +---------------------- + +If the :c:macro:`X86_FEATURE_CPPC` CPU feature flag is not set, the +processor supports the shared memory solution. In this case, ``amd-pstate`` +uses the ``cppc_acpi`` helper methods to implement the callback functions +that are defined on ``static_call``. The functions with the ``cppc_xxx`` prefix +represent the operations of ACPI CPPC helpers for the shared memory solution. + + +AMD P-States and ACPI hardware P-States always can be supported in one +processor. But AMD P-States has the higher priority and if it is enabled +with :c:macro:`MSR_AMD_CPPC_ENABLE` or ``cppc_set_enable``, it will respond +to the request from AMD P-States. + + +User Space Interface in ``sysfs`` - Per-policy control +====================================================== + +``amd-pstate`` exposes several global attributes (files) in ``sysfs`` to +control its functionality at the system level. They are located in the +``/sys/devices/system/cpu/cpufreq/policyX/`` directory and affect all CPUs. :: + + root@hr-test1:/home/ray# ls /sys/devices/system/cpu/cpufreq/policy0/*amd* + /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_highest_perf + /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_lowest_nonlinear_freq + /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_max_freq + + +``amd_pstate_highest_perf / amd_pstate_max_freq`` + +Maximum CPPC performance and CPU frequency that the driver is allowed to +set, in percent of the maximum supported CPPC performance level (the highest +performance supported in `AMD CPPC Performance Capability <perf_cap_>`_). +In some ASICs, the highest CPPC performance is not the one in the ``_CPC`` +table, so we need to expose it to sysfs. If boost is not active, but +still supported, this maximum frequency will be larger than the one in +``cpuinfo``. +This attribute is read-only. + +``amd_pstate_lowest_nonlinear_freq`` + +The lowest non-linear CPPC CPU frequency that the driver is allowed to set, +in percent of the maximum supported CPPC performance level. (Please see the +lowest non-linear performance in `AMD CPPC Performance Capability +<perf_cap_>`_.) +This attribute is read-only. + +``energy_performance_available_preferences`` + +A list of all the supported EPP preferences that could be used for +``energy_performance_preference`` on this system. +These profiles represent different hints that are provided +to the low-level firmware about the user's desired energy vs efficiency +tradeoff. ``default`` represents the epp value is set by platform +firmware. This attribute is read-only. + +``energy_performance_preference`` + +The current energy performance preference can be read from this attribute. +and user can change current preference according to energy or performance needs +Please get all support profiles list from +``energy_performance_available_preferences`` attribute, all the profiles are +integer values defined between 0 to 255 when EPP feature is enabled by platform +firmware, if EPP feature is disabled, driver will ignore the written value +This attribute is read-write. + +Other performance and frequency values can be read back from +``/sys/devices/system/cpu/cpuX/acpi_cppc/``, see :ref:`cppc_sysfs`. + + +``amd-pstate`` vs ``acpi-cpufreq`` +====================================== + +On the majority of AMD platforms supported by ``acpi-cpufreq``, the ACPI tables +provided by the platform firmware are used for CPU performance scaling, but +only provide 3 P-states on AMD processors. +However, on modern AMD APU and CPU series, hardware provides the Collaborative +Processor Performance Control according to the ACPI protocol and customizes this +for AMD platforms. That is, fine-grained and continuous frequency ranges +instead of the legacy hardware P-states. ``amd-pstate`` is the kernel +module which supports the new AMD P-States mechanism on most of the future AMD +platforms. The AMD P-States mechanism is the more performance and energy +efficiency frequency management method on AMD processors. + + +AMD Pstate Driver Operation Modes +================================= + +``amd_pstate`` CPPC has 3 operation modes: autonomous (active) mode, +non-autonomous (passive) mode and guided autonomous (guided) mode. +Active/passive/guided mode can be chosen by different kernel parameters. + +- In autonomous mode, platform ignores the desired performance level request + and takes into account only the values set to the minimum, maximum and energy + performance preference registers. +- In non-autonomous mode, platform gets desired performance level + from OS directly through Desired Performance Register. +- In guided-autonomous mode, platform sets operating performance level + autonomously according to the current workload and within the limits set by + OS through min and max performance registers. + +Active Mode +------------ + +``amd_pstate=active`` + +This is the low-level firmware control mode which is implemented by ``amd_pstate_epp`` +driver with ``amd_pstate=active`` passed to the kernel in the command line. +In this mode, ``amd_pstate_epp`` driver provides a hint to the hardware if software +wants to bias toward performance (0x0) or energy efficiency (0xff) to the CPPC firmware. +then CPPC power algorithm will calculate the runtime workload and adjust the realtime +cores frequency according to the power supply and thermal, core voltage and some other +hardware conditions. + +Passive Mode +------------ + +``amd_pstate=passive`` + +It will be enabled if the ``amd_pstate=passive`` is passed to the kernel in the command line. +In this mode, ``amd_pstate`` driver software specifies a desired QoS target in the CPPC +performance scale as a relative number. This can be expressed as percentage of nominal +performance (infrastructure max). Below the nominal sustained performance level, +desired performance expresses the average performance level of the processor subject +to the Performance Reduction Tolerance register. Above the nominal performance level, +processor must provide at least nominal performance requested and go higher if current +operating conditions allow. + +Guided Mode +----------- + +``amd_pstate=guided`` + +If ``amd_pstate=guided`` is passed to kernel command line option then this mode +is activated. In this mode, driver requests minimum and maximum performance +level and the platform autonomously selects a performance level in this range +and appropriate to the current workload. + +User Space Interface in ``sysfs`` - General +=========================================== + +Global Attributes +----------------- + +``amd-pstate`` exposes several global attributes (files) in ``sysfs`` to +control its functionality at the system level. They are located in the +``/sys/devices/system/cpu/amd-pstate/`` directory and affect all CPUs. + +``status`` + Operation mode of the driver: "active", "passive" or "disable". + + "active" + The driver is functional and in the ``active mode`` + + "passive" + The driver is functional and in the ``passive mode`` + + "guided" + The driver is functional and in the ``guided mode`` + + "disable" + The driver is unregistered and not functional now. + + This attribute can be written to in order to change the driver's + operation mode or to unregister it. The string written to it must be + one of the possible values of it and, if successful, writing one of + these values to the sysfs file will cause the driver to switch over + to the operation mode represented by that string - or to be + unregistered in the "disable" case. + +``cpupower`` tool support for ``amd-pstate`` +=============================================== + +``amd-pstate`` is supported by the ``cpupower`` tool, which can be used to dump +frequency information. Development is in progress to support more and more +operations for the new ``amd-pstate`` module with this tool. :: + + root@hr-test1:/home/ray# cpupower frequency-info + analyzing CPU 0: + driver: amd-pstate + CPUs which run at the same hardware frequency: 0 + CPUs which need to have their frequency coordinated by software: 0 + maximum transition latency: 131 us + hardware limits: 400 MHz - 4.68 GHz + available cpufreq governors: ondemand conservative powersave userspace performance schedutil + current policy: frequency should be within 400 MHz and 4.68 GHz. + The governor "schedutil" may decide which speed to use + within this range. + current CPU frequency: Unable to call hardware + current CPU frequency: 4.02 GHz (asserted by call to kernel) + boost state support: + Supported: yes + Active: yes + AMD PSTATE Highest Performance: 166. Maximum Frequency: 4.68 GHz. + AMD PSTATE Nominal Performance: 117. Nominal Frequency: 3.30 GHz. + AMD PSTATE Lowest Non-linear Performance: 39. Lowest Non-linear Frequency: 1.10 GHz. + AMD PSTATE Lowest Performance: 15. Lowest Frequency: 400 MHz. + + +Diagnostics and Tuning +======================= + +Trace Events +-------------- + +There are two static trace events that can be used for ``amd-pstate`` +diagnostics. One of them is the ``cpu_frequency`` trace event generally used +by ``CPUFreq``, and the other one is the ``amd_pstate_perf`` trace event +specific to ``amd-pstate``. The following sequence of shell commands can +be used to enable them and see their output (if the kernel is +configured to support event tracing). :: + + root@hr-test1:/home/ray# cd /sys/kernel/tracing/ + root@hr-test1:/sys/kernel/tracing# echo 1 > events/amd_cpu/enable + root@hr-test1:/sys/kernel/tracing# cat trace + # tracer: nop + # + # entries-in-buffer/entries-written: 47827/42233061 #P:2 + # + # _-----=> irqs-off + # / _----=> need-resched + # | / _---=> hardirq/softirq + # || / _--=> preempt-depth + # ||| / delay + # TASK-PID CPU# |||| TIMESTAMP FUNCTION + # | | | |||| | | + <idle>-0 [015] dN... 4995.979886: amd_pstate_perf: amd_min_perf=85 amd_des_perf=85 amd_max_perf=166 cpu_id=15 changed=false fast_switch=true + <idle>-0 [007] d.h.. 4995.979893: amd_pstate_perf: amd_min_perf=85 amd_des_perf=85 amd_max_perf=166 cpu_id=7 changed=false fast_switch=true + cat-2161 [000] d.... 4995.980841: amd_pstate_perf: amd_min_perf=85 amd_des_perf=85 amd_max_perf=166 cpu_id=0 changed=false fast_switch=true + sshd-2125 [004] d.s.. 4995.980968: amd_pstate_perf: amd_min_perf=85 amd_des_perf=85 amd_max_perf=166 cpu_id=4 changed=false fast_switch=true + <idle>-0 [007] d.s.. 4995.980968: amd_pstate_perf: amd_min_perf=85 amd_des_perf=85 amd_max_perf=166 cpu_id=7 changed=false fast_switch=true + <idle>-0 [003] d.s.. 4995.980971: amd_pstate_perf: amd_min_perf=85 amd_des_perf=85 amd_max_perf=166 cpu_id=3 changed=false fast_switch=true + <idle>-0 [011] d.s.. 4995.980996: amd_pstate_perf: amd_min_perf=85 amd_des_perf=85 amd_max_perf=166 cpu_id=11 changed=false fast_switch=true + +The ``cpu_frequency`` trace event will be triggered either by the ``schedutil`` scaling +governor (for the policies it is attached to), or by the ``CPUFreq`` core (for the +policies with other scaling governors). + + +Tracer Tool +------------- + +``amd_pstate_tracer.py`` can record and parse ``amd-pstate`` trace log, then +generate performance plots. This utility can be used to debug and tune the +performance of ``amd-pstate`` driver. The tracer tool needs to import intel +pstate tracer. + +Tracer tool located in ``linux/tools/power/x86/amd_pstate_tracer``. It can be +used in two ways. If trace file is available, then directly parse the file +with command :: + + ./amd_pstate_trace.py [-c cpus] -t <trace_file> -n <test_name> + +Or generate trace file with root privilege, then parse and plot with command :: + + sudo ./amd_pstate_trace.py [-c cpus] -n <test_name> -i <interval> [-m kbytes] + +The test result can be found in ``results/test_name``. Following is the example +about part of the output. :: + + common_cpu common_secs common_usecs min_perf des_perf max_perf freq mperf apef tsc load duration_ms sample_num elapsed_time common_comm + CPU_005 712 116384 39 49 166 0.7565 9645075 2214891 38431470 25.1 11.646 469 2.496 kworker/5:0-40 + CPU_006 712 116408 39 49 166 0.6769 8950227 1839034 37192089 24.06 11.272 470 2.496 kworker/6:0-1264 + +Unit Tests for amd-pstate +------------------------- + +``amd-pstate-ut`` is a test module for testing the ``amd-pstate`` driver. + + * It can help all users to verify their processor support (SBIOS/Firmware or Hardware). + + * Kernel can have a basic function test to avoid the kernel regression during the update. + + * We can introduce more functional or performance tests to align the result together, it will benefit power and performance scale optimization. + +1. Test case descriptions + + 1). Basic tests + + Test prerequisite and basic functions for the ``amd-pstate`` driver. + + +---------+--------------------------------+------------------------------------------------------------------------------------+ + | Index | Functions | Description | + +=========+================================+====================================================================================+ + | 1 | amd_pstate_ut_acpi_cpc_valid || Check whether the _CPC object is present in SBIOS. | + | | || | + | | || The detail refer to `Processor Support <processor_support_>`_. | + +---------+--------------------------------+------------------------------------------------------------------------------------+ + | 2 | amd_pstate_ut_check_enabled || Check whether AMD P-State is enabled. | + | | || | + | | || AMD P-States and ACPI hardware P-States always can be supported in one processor. | + | | | But AMD P-States has the higher priority and if it is enabled with | + | | | :c:macro:`MSR_AMD_CPPC_ENABLE` or ``cppc_set_enable``, it will respond to the | + | | | request from AMD P-States. | + +---------+--------------------------------+------------------------------------------------------------------------------------+ + | 3 | amd_pstate_ut_check_perf || Check if the each performance values are reasonable. | + | | || highest_perf >= nominal_perf > lowest_nonlinear_perf > lowest_perf > 0. | + +---------+--------------------------------+------------------------------------------------------------------------------------+ + | 4 | amd_pstate_ut_check_freq || Check if the each frequency values and max freq when set support boost mode | + | | | are reasonable. | + | | || max_freq >= nominal_freq > lowest_nonlinear_freq > min_freq > 0 | + | | || If boost is not active but supported, this maximum frequency will be larger than | + | | | the one in ``cpuinfo``. | + +---------+--------------------------------+------------------------------------------------------------------------------------+ + + 2). Tbench test + + Test and monitor the cpu changes when running tbench benchmark under the specified governor. + These changes include desire performance, frequency, load, performance, energy etc. + The specified governor is ondemand or schedutil. + Tbench can also be tested on the ``acpi-cpufreq`` kernel driver for comparison. + + 3). Gitsource test + + Test and monitor the cpu changes when running gitsource benchmark under the specified governor. + These changes include desire performance, frequency, load, time, energy etc. + The specified governor is ondemand or schedutil. + Gitsource can also be tested on the ``acpi-cpufreq`` kernel driver for comparison. + +#. How to execute the tests + + We use test module in the kselftest frameworks to implement it. + We create ``amd-pstate-ut`` module and tie it into kselftest.(for + details refer to Linux Kernel Selftests [4]_). + + 1). Build + + + open the :c:macro:`CONFIG_X86_AMD_PSTATE` configuration option. + + set the :c:macro:`CONFIG_X86_AMD_PSTATE_UT` configuration option to M. + + make project + + make selftest :: + + $ cd linux + $ make -C tools/testing/selftests + + + make perf :: + + $ cd tools/perf/ + $ make + + + 2). Installation & Steps :: + + $ make -C tools/testing/selftests install INSTALL_PATH=~/kselftest + $ cp tools/perf/perf /usr/bin/perf + $ sudo ./kselftest/run_kselftest.sh -c amd-pstate + + 3). Specified test case :: + + $ cd ~/kselftest/amd-pstate + $ sudo ./run.sh -t basic + $ sudo ./run.sh -t tbench + $ sudo ./run.sh -t tbench -m acpi-cpufreq + $ sudo ./run.sh -t gitsource + $ sudo ./run.sh -t gitsource -m acpi-cpufreq + $ ./run.sh --help + ./run.sh: illegal option -- - + Usage: ./run.sh [OPTION...] + [-h <help>] + [-o <output-file-for-dump>] + [-c <all: All testing, + basic: Basic testing, + tbench: Tbench testing, + gitsource: Gitsource testing.>] + [-t <tbench time limit>] + [-p <tbench process number>] + [-l <loop times for tbench>] + [-i <amd tracer interval>] + [-m <comparative test: acpi-cpufreq>] + + + 4). Results + + + basic + + When you finish test, you will get the following log info :: + + $ dmesg | grep "amd_pstate_ut" | tee log.txt + [12977.570663] amd_pstate_ut: 1 amd_pstate_ut_acpi_cpc_valid success! + [12977.570673] amd_pstate_ut: 2 amd_pstate_ut_check_enabled success! + [12977.571207] amd_pstate_ut: 3 amd_pstate_ut_check_perf success! + [12977.571212] amd_pstate_ut: 4 amd_pstate_ut_check_freq success! + + + tbench + + When you finish test, you will get selftest.tbench.csv and png images. + The selftest.tbench.csv file contains the raw data and the drop of the comparative test. + The png images shows the performance, energy and performan per watt of each test. + Open selftest.tbench.csv : + + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + Governor | Round | Des-perf | Freq | Load | Performance | Energy | Performance Per Watt | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + Unit | | | GHz | | MB/s | J | MB/J | + +=================================================+==============+==========+=========+==========+=============+=========+======================+ + + amd-pstate-ondemand | 1 | | | | 2504.05 | 1563.67 | 158.5378 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + amd-pstate-ondemand | 2 | | | | 2243.64 | 1430.32 | 155.2941 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + amd-pstate-ondemand | 3 | | | | 2183.88 | 1401.32 | 154.2860 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + amd-pstate-ondemand | Average | | | | 2310.52 | 1465.1 | 156.1268 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + amd-pstate-schedutil | 1 | 165.329 | 1.62257 | 99.798 | 2136.54 | 1395.26 | 151.5971 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + amd-pstate-schedutil | 2 | 166 | 1.49761 | 99.9993 | 2100.56 | 1380.5 | 150.6377 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + amd-pstate-schedutil | 3 | 166 | 1.47806 | 99.9993 | 2084.12 | 1375.76 | 149.9737 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + amd-pstate-schedutil | Average | 165.776 | 1.53275 | 99.9322 | 2107.07 | 1383.84 | 150.7399 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-ondemand | 1 | | | | 2529.9 | 1564.4 | 160.0997 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-ondemand | 2 | | | | 2249.76 | 1432.97 | 155.4297 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-ondemand | 3 | | | | 2181.46 | 1406.88 | 153.5060 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-ondemand | Average | | | | 2320.37 | 1468.08 | 156.4741 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-schedutil | 1 | | | | 2137.64 | 1385.24 | 152.7723 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-schedutil | 2 | | | | 2107.05 | 1372.23 | 152.0138 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-schedutil | 3 | | | | 2085.86 | 1365.35 | 151.2433 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-schedutil | Average | | | | 2110.18 | 1374.27 | 152.0136 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-ondemand VS acpi-cpufreq-schedutil | Comprison(%) | | | | -9.0584 | -6.3899 | -2.8506 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + amd-pstate-ondemand VS amd-pstate-schedutil | Comprison(%) | | | | 8.8053 | -5.5463 | -3.4503 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-ondemand VS amd-pstate-ondemand | Comprison(%) | | | | -0.4245 | -0.2029 | -0.2219 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-schedutil VS amd-pstate-schedutil | Comprison(%) | | | | -0.1473 | 0.6963 | -0.8378 | + +-------------------------------------------------+--------------+----------+---------+----------+-------------+---------+----------------------+ + + + gitsource + + When you finish test, you will get selftest.gitsource.csv and png images. + The selftest.gitsource.csv file contains the raw data and the drop of the comparative test. + The png images shows the performance, energy and performan per watt of each test. + Open selftest.gitsource.csv : + + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + Governor | Round | Des-perf | Freq | Load | Time | Energy | Performance Per Watt | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + Unit | | | GHz | | s | J | 1/J | + +=================================================+==============+==========+==========+==========+=============+=========+======================+ + + amd-pstate-ondemand | 1 | 50.119 | 2.10509 | 23.3076 | 475.69 | 865.78 | 0.001155027 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + amd-pstate-ondemand | 2 | 94.8006 | 1.98771 | 56.6533 | 467.1 | 839.67 | 0.001190944 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + amd-pstate-ondemand | 3 | 76.6091 | 2.53251 | 43.7791 | 467.69 | 855.85 | 0.001168429 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + amd-pstate-ondemand | Average | 73.8429 | 2.20844 | 41.2467 | 470.16 | 853.767 | 0.001171279 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + amd-pstate-schedutil | 1 | 165.919 | 1.62319 | 98.3868 | 464.17 | 866.8 | 0.001153668 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + amd-pstate-schedutil | 2 | 165.97 | 1.31309 | 99.5712 | 480.15 | 880.4 | 0.001135847 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + amd-pstate-schedutil | 3 | 165.973 | 1.28448 | 99.9252 | 481.79 | 867.02 | 0.001153375 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + amd-pstate-schedutil | Average | 165.954 | 1.40692 | 99.2944 | 475.37 | 871.407 | 0.001147569 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-ondemand | 1 | | | | 2379.62 | 742.96 | 0.001345967 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-ondemand | 2 | | | | 441.74 | 817.49 | 0.001223256 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-ondemand | 3 | | | | 455.48 | 820.01 | 0.001219497 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-ondemand | Average | | | | 425.613 | 793.487 | 0.001260260 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-schedutil | 1 | | | | 459.69 | 838.54 | 0.001192548 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-schedutil | 2 | | | | 466.55 | 830.89 | 0.001203528 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-schedutil | 3 | | | | 470.38 | 837.32 | 0.001194286 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-schedutil | Average | | | | 465.54 | 835.583 | 0.001196769 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-ondemand VS acpi-cpufreq-schedutil | Comprison(%) | | | | 9.3810 | 5.3051 | -5.0379 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + amd-pstate-ondemand VS amd-pstate-schedutil | Comprison(%) | 124.7392 | -36.2934 | 140.7329 | 1.1081 | 2.0661 | -2.0242 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-ondemand VS amd-pstate-ondemand | Comprison(%) | | | | 10.4665 | 7.5968 | -7.0605 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + + acpi-cpufreq-schedutil VS amd-pstate-schedutil | Comprison(%) | | | | 2.1115 | 4.2873 | -4.1110 | + +-------------------------------------------------+--------------+----------+----------+----------+-------------+---------+----------------------+ + +Reference +=========== + +.. [1] AMD64 Architecture Programmer's Manual Volume 2: System Programming, + https://www.amd.com/system/files/TechDocs/24593.pdf + +.. [2] Advanced Configuration and Power Interface Specification, + https://uefi.org/sites/default/files/resources/ACPI_Spec_6_4_Jan22.pdf + +.. [3] Processor Programming Reference (PPR) for AMD Family 19h Model 51h, Revision A1 Processors + https://www.amd.com/system/files/TechDocs/56569-A1-PUB.zip + +.. [4] Linux Kernel Selftests, + https://www.kernel.org/doc/html/latest/dev-tools/kselftest.html diff --git a/Documentation/admin-guide/pm/cpufreq.rst b/Documentation/admin-guide/pm/cpufreq.rst new file mode 100644 index 000000000..6adb7988e --- /dev/null +++ b/Documentation/admin-guide/pm/cpufreq.rst @@ -0,0 +1,708 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + +.. |intel_pstate| replace:: :doc:`intel_pstate <intel_pstate>` + +======================= +CPU Performance Scaling +======================= + +:Copyright: |copy| 2017 Intel Corporation + +:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> + + +The Concept of CPU Performance Scaling +====================================== + +The majority of modern processors are capable of operating in a number of +different clock frequency and voltage configurations, often referred to as +Operating Performance Points or P-states (in ACPI terminology). As a rule, +the higher the clock frequency and the higher the voltage, the more instructions +can be retired by the CPU over a unit of time, but also the higher the clock +frequency and the higher the voltage, the more energy is consumed over a unit of +time (or the more power is drawn) by the CPU in the given P-state. Therefore +there is a natural tradeoff between the CPU capacity (the number of instructions +that can be executed over a unit of time) and the power drawn by the CPU. + +In some situations it is desirable or even necessary to run the program as fast +as possible and then there is no reason to use any P-states different from the +highest one (i.e. the highest-performance frequency/voltage configuration +available). In some other cases, however, it may not be necessary to execute +instructions so quickly and maintaining the highest available CPU capacity for a +relatively long time without utilizing it entirely may be regarded as wasteful. +It also may not be physically possible to maintain maximum CPU capacity for too +long for thermal or power supply capacity reasons or similar. To cover those +cases, there are hardware interfaces allowing CPUs to be switched between +different frequency/voltage configurations or (in the ACPI terminology) to be +put into different P-states. + +Typically, they are used along with algorithms to estimate the required CPU +capacity, so as to decide which P-states to put the CPUs into. Of course, since +the utilization of the system generally changes over time, that has to be done +repeatedly on a regular basis. The activity by which this happens is referred +to as CPU performance scaling or CPU frequency scaling (because it involves +adjusting the CPU clock frequency). + + +CPU Performance Scaling in Linux +================================ + +The Linux kernel supports CPU performance scaling by means of the ``CPUFreq`` +(CPU Frequency scaling) subsystem that consists of three layers of code: the +core, scaling governors and scaling drivers. + +The ``CPUFreq`` core provides the common code infrastructure and user space +interfaces for all platforms that support CPU performance scaling. It defines +the basic framework in which the other components operate. + +Scaling governors implement algorithms to estimate the required CPU capacity. +As a rule, each governor implements one, possibly parametrized, scaling +algorithm. + +Scaling drivers talk to the hardware. They provide scaling governors with +information on the available P-states (or P-state ranges in some cases) and +access platform-specific hardware interfaces to change CPU P-states as requested +by scaling governors. + +In principle, all available scaling governors can be used with every scaling +driver. That design is based on the observation that the information used by +performance scaling algorithms for P-state selection can be represented in a +platform-independent form in the majority of cases, so it should be possible +to use the same performance scaling algorithm implemented in exactly the same +way regardless of which scaling driver is used. Consequently, the same set of +scaling governors should be suitable for every supported platform. + +However, that observation may not hold for performance scaling algorithms +based on information provided by the hardware itself, for example through +feedback registers, as that information is typically specific to the hardware +interface it comes from and may not be easily represented in an abstract, +platform-independent way. For this reason, ``CPUFreq`` allows scaling drivers +to bypass the governor layer and implement their own performance scaling +algorithms. That is done by the |intel_pstate| scaling driver. + + +``CPUFreq`` Policy Objects +========================== + +In some cases the hardware interface for P-state control is shared by multiple +CPUs. That is, for example, the same register (or set of registers) is used to +control the P-state of multiple CPUs at the same time and writing to it affects +all of those CPUs simultaneously. + +Sets of CPUs sharing hardware P-state control interfaces are represented by +``CPUFreq`` as struct cpufreq_policy objects. For consistency, +struct cpufreq_policy is also used when there is only one CPU in the given +set. + +The ``CPUFreq`` core maintains a pointer to a struct cpufreq_policy object for +every CPU in the system, including CPUs that are currently offline. If multiple +CPUs share the same hardware P-state control interface, all of the pointers +corresponding to them point to the same struct cpufreq_policy object. + +``CPUFreq`` uses struct cpufreq_policy as its basic data type and the design +of its user space interface is based on the policy concept. + + +CPU Initialization +================== + +First of all, a scaling driver has to be registered for ``CPUFreq`` to work. +It is only possible to register one scaling driver at a time, so the scaling +driver is expected to be able to handle all CPUs in the system. + +The scaling driver may be registered before or after CPU registration. If +CPUs are registered earlier, the driver core invokes the ``CPUFreq`` core to +take a note of all of the already registered CPUs during the registration of the +scaling driver. In turn, if any CPUs are registered after the registration of +the scaling driver, the ``CPUFreq`` core will be invoked to take note of them +at their registration time. + +In any case, the ``CPUFreq`` core is invoked to take note of any logical CPU it +has not seen so far as soon as it is ready to handle that CPU. [Note that the +logical CPU may be a physical single-core processor, or a single core in a +multicore processor, or a hardware thread in a physical processor or processor +core. In what follows "CPU" always means "logical CPU" unless explicitly stated +otherwise and the word "processor" is used to refer to the physical part +possibly including multiple logical CPUs.] + +Once invoked, the ``CPUFreq`` core checks if the policy pointer is already set +for the given CPU and if so, it skips the policy object creation. Otherwise, +a new policy object is created and initialized, which involves the creation of +a new policy directory in ``sysfs``, and the policy pointer corresponding to +the given CPU is set to the new policy object's address in memory. + +Next, the scaling driver's ``->init()`` callback is invoked with the policy +pointer of the new CPU passed to it as the argument. That callback is expected +to initialize the performance scaling hardware interface for the given CPU (or, +more precisely, for the set of CPUs sharing the hardware interface it belongs +to, represented by its policy object) and, if the policy object it has been +called for is new, to set parameters of the policy, like the minimum and maximum +frequencies supported by the hardware, the table of available frequencies (if +the set of supported P-states is not a continuous range), and the mask of CPUs +that belong to the same policy (including both online and offline CPUs). That +mask is then used by the core to populate the policy pointers for all of the +CPUs in it. + +The next major initialization step for a new policy object is to attach a +scaling governor to it (to begin with, that is the default scaling governor +determined by the kernel command line or configuration, but it may be changed +later via ``sysfs``). First, a pointer to the new policy object is passed to +the governor's ``->init()`` callback which is expected to initialize all of the +data structures necessary to handle the given policy and, possibly, to add +a governor ``sysfs`` interface to it. Next, the governor is started by +invoking its ``->start()`` callback. + +That callback is expected to register per-CPU utilization update callbacks for +all of the online CPUs belonging to the given policy with the CPU scheduler. +The utilization update callbacks will be invoked by the CPU scheduler on +important events, like task enqueue and dequeue, on every iteration of the +scheduler tick or generally whenever the CPU utilization may change (from the +scheduler's perspective). They are expected to carry out computations needed +to determine the P-state to use for the given policy going forward and to +invoke the scaling driver to make changes to the hardware in accordance with +the P-state selection. The scaling driver may be invoked directly from +scheduler context or asynchronously, via a kernel thread or workqueue, depending +on the configuration and capabilities of the scaling driver and the governor. + +Similar steps are taken for policy objects that are not new, but were "inactive" +previously, meaning that all of the CPUs belonging to them were offline. The +only practical difference in that case is that the ``CPUFreq`` core will attempt +to use the scaling governor previously used with the policy that became +"inactive" (and is re-initialized now) instead of the default governor. + +In turn, if a previously offline CPU is being brought back online, but some +other CPUs sharing the policy object with it are online already, there is no +need to re-initialize the policy object at all. In that case, it only is +necessary to restart the scaling governor so that it can take the new online CPU +into account. That is achieved by invoking the governor's ``->stop`` and +``->start()`` callbacks, in this order, for the entire policy. + +As mentioned before, the |intel_pstate| scaling driver bypasses the scaling +governor layer of ``CPUFreq`` and provides its own P-state selection algorithms. +Consequently, if |intel_pstate| is used, scaling governors are not attached to +new policy objects. Instead, the driver's ``->setpolicy()`` callback is invoked +to register per-CPU utilization update callbacks for each policy. These +callbacks are invoked by the CPU scheduler in the same way as for scaling +governors, but in the |intel_pstate| case they both determine the P-state to +use and change the hardware configuration accordingly in one go from scheduler +context. + +The policy objects created during CPU initialization and other data structures +associated with them are torn down when the scaling driver is unregistered +(which happens when the kernel module containing it is unloaded, for example) or +when the last CPU belonging to the given policy in unregistered. + + +Policy Interface in ``sysfs`` +============================= + +During the initialization of the kernel, the ``CPUFreq`` core creates a +``sysfs`` directory (kobject) called ``cpufreq`` under +:file:`/sys/devices/system/cpu/`. + +That directory contains a ``policyX`` subdirectory (where ``X`` represents an +integer number) for every policy object maintained by the ``CPUFreq`` core. +Each ``policyX`` directory is pointed to by ``cpufreq`` symbolic links +under :file:`/sys/devices/system/cpu/cpuY/` (where ``Y`` represents an integer +that may be different from the one represented by ``X``) for all of the CPUs +associated with (or belonging to) the given policy. The ``policyX`` directories +in :file:`/sys/devices/system/cpu/cpufreq` each contain policy-specific +attributes (files) to control ``CPUFreq`` behavior for the corresponding policy +objects (that is, for all of the CPUs associated with them). + +Some of those attributes are generic. They are created by the ``CPUFreq`` core +and their behavior generally does not depend on what scaling driver is in use +and what scaling governor is attached to the given policy. Some scaling drivers +also add driver-specific attributes to the policy directories in ``sysfs`` to +control policy-specific aspects of driver behavior. + +The generic attributes under :file:`/sys/devices/system/cpu/cpufreq/policyX/` +are the following: + +``affected_cpus`` + List of online CPUs belonging to this policy (i.e. sharing the hardware + performance scaling interface represented by the ``policyX`` policy + object). + +``bios_limit`` + If the platform firmware (BIOS) tells the OS to apply an upper limit to + CPU frequencies, that limit will be reported through this attribute (if + present). + + The existence of the limit may be a result of some (often unintentional) + BIOS settings, restrictions coming from a service processor or another + BIOS/HW-based mechanisms. + + This does not cover ACPI thermal limitations which can be discovered + through a generic thermal driver. + + This attribute is not present if the scaling driver in use does not + support it. + +``cpuinfo_cur_freq`` + Current frequency of the CPUs belonging to this policy as obtained from + the hardware (in KHz). + + This is expected to be the frequency the hardware actually runs at. + If that frequency cannot be determined, this attribute should not + be present. + +``cpuinfo_max_freq`` + Maximum possible operating frequency the CPUs belonging to this policy + can run at (in kHz). + +``cpuinfo_min_freq`` + Minimum possible operating frequency the CPUs belonging to this policy + can run at (in kHz). + +``cpuinfo_transition_latency`` + The time it takes to switch the CPUs belonging to this policy from one + P-state to another, in nanoseconds. + + If unknown or if known to be so high that the scaling driver does not + work with the `ondemand`_ governor, -1 (:c:macro:`CPUFREQ_ETERNAL`) + will be returned by reads from this attribute. + +``related_cpus`` + List of all (online and offline) CPUs belonging to this policy. + +``scaling_available_governors`` + List of ``CPUFreq`` scaling governors present in the kernel that can + be attached to this policy or (if the |intel_pstate| scaling driver is + in use) list of scaling algorithms provided by the driver that can be + applied to this policy. + + [Note that some governors are modular and it may be necessary to load a + kernel module for the governor held by it to become available and be + listed by this attribute.] + +``scaling_cur_freq`` + Current frequency of all of the CPUs belonging to this policy (in kHz). + + In the majority of cases, this is the frequency of the last P-state + requested by the scaling driver from the hardware using the scaling + interface provided by it, which may or may not reflect the frequency + the CPU is actually running at (due to hardware design and other + limitations). + + Some architectures (e.g. ``x86``) may attempt to provide information + more precisely reflecting the current CPU frequency through this + attribute, but that still may not be the exact current CPU frequency as + seen by the hardware at the moment. + +``scaling_driver`` + The scaling driver currently in use. + +``scaling_governor`` + The scaling governor currently attached to this policy or (if the + |intel_pstate| scaling driver is in use) the scaling algorithm + provided by the driver that is currently applied to this policy. + + This attribute is read-write and writing to it will cause a new scaling + governor to be attached to this policy or a new scaling algorithm + provided by the scaling driver to be applied to it (in the + |intel_pstate| case), as indicated by the string written to this + attribute (which must be one of the names listed by the + ``scaling_available_governors`` attribute described above). + +``scaling_max_freq`` + Maximum frequency the CPUs belonging to this policy are allowed to be + running at (in kHz). + + This attribute is read-write and writing a string representing an + integer to it will cause a new limit to be set (it must not be lower + than the value of the ``scaling_min_freq`` attribute). + +``scaling_min_freq`` + Minimum frequency the CPUs belonging to this policy are allowed to be + running at (in kHz). + + This attribute is read-write and writing a string representing a + non-negative integer to it will cause a new limit to be set (it must not + be higher than the value of the ``scaling_max_freq`` attribute). + +``scaling_setspeed`` + This attribute is functional only if the `userspace`_ scaling governor + is attached to the given policy. + + It returns the last frequency requested by the governor (in kHz) or can + be written to in order to set a new frequency for the policy. + + +Generic Scaling Governors +========================= + +``CPUFreq`` provides generic scaling governors that can be used with all +scaling drivers. As stated before, each of them implements a single, possibly +parametrized, performance scaling algorithm. + +Scaling governors are attached to policy objects and different policy objects +can be handled by different scaling governors at the same time (although that +may lead to suboptimal results in some cases). + +The scaling governor for a given policy object can be changed at any time with +the help of the ``scaling_governor`` policy attribute in ``sysfs``. + +Some governors expose ``sysfs`` attributes to control or fine-tune the scaling +algorithms implemented by them. Those attributes, referred to as governor +tunables, can be either global (system-wide) or per-policy, depending on the +scaling driver in use. If the driver requires governor tunables to be +per-policy, they are located in a subdirectory of each policy directory. +Otherwise, they are located in a subdirectory under +:file:`/sys/devices/system/cpu/cpufreq/`. In either case the name of the +subdirectory containing the governor tunables is the name of the governor +providing them. + +``performance`` +--------------- + +When attached to a policy object, this governor causes the highest frequency, +within the ``scaling_max_freq`` policy limit, to be requested for that policy. + +The request is made once at that time the governor for the policy is set to +``performance`` and whenever the ``scaling_max_freq`` or ``scaling_min_freq`` +policy limits change after that. + +``powersave`` +------------- + +When attached to a policy object, this governor causes the lowest frequency, +within the ``scaling_min_freq`` policy limit, to be requested for that policy. + +The request is made once at that time the governor for the policy is set to +``powersave`` and whenever the ``scaling_max_freq`` or ``scaling_min_freq`` +policy limits change after that. + +``userspace`` +------------- + +This governor does not do anything by itself. Instead, it allows user space +to set the CPU frequency for the policy it is attached to by writing to the +``scaling_setspeed`` attribute of that policy. + +``schedutil`` +------------- + +This governor uses CPU utilization data available from the CPU scheduler. It +generally is regarded as a part of the CPU scheduler, so it can access the +scheduler's internal data structures directly. + +It runs entirely in scheduler context, although in some cases it may need to +invoke the scaling driver asynchronously when it decides that the CPU frequency +should be changed for a given policy (that depends on whether or not the driver +is capable of changing the CPU frequency from scheduler context). + +The actions of this governor for a particular CPU depend on the scheduling class +invoking its utilization update callback for that CPU. If it is invoked by the +RT or deadline scheduling classes, the governor will increase the frequency to +the allowed maximum (that is, the ``scaling_max_freq`` policy limit). In turn, +if it is invoked by the CFS scheduling class, the governor will use the +Per-Entity Load Tracking (PELT) metric for the root control group of the +given CPU as the CPU utilization estimate (see the *Per-entity load tracking* +LWN.net article [1]_ for a description of the PELT mechanism). Then, the new +CPU frequency to apply is computed in accordance with the formula + + f = 1.25 * ``f_0`` * ``util`` / ``max`` + +where ``util`` is the PELT number, ``max`` is the theoretical maximum of +``util``, and ``f_0`` is either the maximum possible CPU frequency for the given +policy (if the PELT number is frequency-invariant), or the current CPU frequency +(otherwise). + +This governor also employs a mechanism allowing it to temporarily bump up the +CPU frequency for tasks that have been waiting on I/O most recently, called +"IO-wait boosting". That happens when the :c:macro:`SCHED_CPUFREQ_IOWAIT` flag +is passed by the scheduler to the governor callback which causes the frequency +to go up to the allowed maximum immediately and then draw back to the value +returned by the above formula over time. + +This governor exposes only one tunable: + +``rate_limit_us`` + Minimum time (in microseconds) that has to pass between two consecutive + runs of governor computations (default: 1000 times the scaling driver's + transition latency). + + The purpose of this tunable is to reduce the scheduler context overhead + of the governor which might be excessive without it. + +This governor generally is regarded as a replacement for the older `ondemand`_ +and `conservative`_ governors (described below), as it is simpler and more +tightly integrated with the CPU scheduler, its overhead in terms of CPU context +switches and similar is less significant, and it uses the scheduler's own CPU +utilization metric, so in principle its decisions should not contradict the +decisions made by the other parts of the scheduler. + +``ondemand`` +------------ + +This governor uses CPU load as a CPU frequency selection metric. + +In order to estimate the current CPU load, it measures the time elapsed between +consecutive invocations of its worker routine and computes the fraction of that +time in which the given CPU was not idle. The ratio of the non-idle (active) +time to the total CPU time is taken as an estimate of the load. + +If this governor is attached to a policy shared by multiple CPUs, the load is +estimated for all of them and the greatest result is taken as the load estimate +for the entire policy. + +The worker routine of this governor has to run in process context, so it is +invoked asynchronously (via a workqueue) and CPU P-states are updated from +there if necessary. As a result, the scheduler context overhead from this +governor is minimum, but it causes additional CPU context switches to happen +relatively often and the CPU P-state updates triggered by it can be relatively +irregular. Also, it affects its own CPU load metric by running code that +reduces the CPU idle time (even though the CPU idle time is only reduced very +slightly by it). + +It generally selects CPU frequencies proportional to the estimated load, so that +the value of the ``cpuinfo_max_freq`` policy attribute corresponds to the load of +1 (or 100%), and the value of the ``cpuinfo_min_freq`` policy attribute +corresponds to the load of 0, unless when the load exceeds a (configurable) +speedup threshold, in which case it will go straight for the highest frequency +it is allowed to use (the ``scaling_max_freq`` policy limit). + +This governor exposes the following tunables: + +``sampling_rate`` + This is how often the governor's worker routine should run, in + microseconds. + + Typically, it is set to values of the order of 10000 (10 ms). Its + default value is equal to the value of ``cpuinfo_transition_latency`` + for each policy this governor is attached to (but since the unit here + is greater by 1000, this means that the time represented by + ``sampling_rate`` is 1000 times greater than the transition latency by + default). + + If this tunable is per-policy, the following shell command sets the time + represented by it to be 750 times as high as the transition latency:: + + # echo `$(($(cat cpuinfo_transition_latency) * 750 / 1000)) > ondemand/sampling_rate + +``up_threshold`` + If the estimated CPU load is above this value (in percent), the governor + will set the frequency to the maximum value allowed for the policy. + Otherwise, the selected frequency will be proportional to the estimated + CPU load. + +``ignore_nice_load`` + If set to 1 (default 0), it will cause the CPU load estimation code to + treat the CPU time spent on executing tasks with "nice" levels greater + than 0 as CPU idle time. + + This may be useful if there are tasks in the system that should not be + taken into account when deciding what frequency to run the CPUs at. + Then, to make that happen it is sufficient to increase the "nice" level + of those tasks above 0 and set this attribute to 1. + +``sampling_down_factor`` + Temporary multiplier, between 1 (default) and 100 inclusive, to apply to + the ``sampling_rate`` value if the CPU load goes above ``up_threshold``. + + This causes the next execution of the governor's worker routine (after + setting the frequency to the allowed maximum) to be delayed, so the + frequency stays at the maximum level for a longer time. + + Frequency fluctuations in some bursty workloads may be avoided this way + at the cost of additional energy spent on maintaining the maximum CPU + capacity. + +``powersave_bias`` + Reduction factor to apply to the original frequency target of the + governor (including the maximum value used when the ``up_threshold`` + value is exceeded by the estimated CPU load) or sensitivity threshold + for the AMD frequency sensitivity powersave bias driver + (:file:`drivers/cpufreq/amd_freq_sensitivity.c`), between 0 and 1000 + inclusive. + + If the AMD frequency sensitivity powersave bias driver is not loaded, + the effective frequency to apply is given by + + f * (1 - ``powersave_bias`` / 1000) + + where f is the governor's original frequency target. The default value + of this attribute is 0 in that case. + + If the AMD frequency sensitivity powersave bias driver is loaded, the + value of this attribute is 400 by default and it is used in a different + way. + + On Family 16h (and later) AMD processors there is a mechanism to get a + measured workload sensitivity, between 0 and 100% inclusive, from the + hardware. That value can be used to estimate how the performance of the + workload running on a CPU will change in response to frequency changes. + + The performance of a workload with the sensitivity of 0 (memory-bound or + IO-bound) is not expected to increase at all as a result of increasing + the CPU frequency, whereas workloads with the sensitivity of 100% + (CPU-bound) are expected to perform much better if the CPU frequency is + increased. + + If the workload sensitivity is less than the threshold represented by + the ``powersave_bias`` value, the sensitivity powersave bias driver + will cause the governor to select a frequency lower than its original + target, so as to avoid over-provisioning workloads that will not benefit + from running at higher CPU frequencies. + +``conservative`` +---------------- + +This governor uses CPU load as a CPU frequency selection metric. + +It estimates the CPU load in the same way as the `ondemand`_ governor described +above, but the CPU frequency selection algorithm implemented by it is different. + +Namely, it avoids changing the frequency significantly over short time intervals +which may not be suitable for systems with limited power supply capacity (e.g. +battery-powered). To achieve that, it changes the frequency in relatively +small steps, one step at a time, up or down - depending on whether or not a +(configurable) threshold has been exceeded by the estimated CPU load. + +This governor exposes the following tunables: + +``freq_step`` + Frequency step in percent of the maximum frequency the governor is + allowed to set (the ``scaling_max_freq`` policy limit), between 0 and + 100 (5 by default). + + This is how much the frequency is allowed to change in one go. Setting + it to 0 will cause the default frequency step (5 percent) to be used + and setting it to 100 effectively causes the governor to periodically + switch the frequency between the ``scaling_min_freq`` and + ``scaling_max_freq`` policy limits. + +``down_threshold`` + Threshold value (in percent, 20 by default) used to determine the + frequency change direction. + + If the estimated CPU load is greater than this value, the frequency will + go up (by ``freq_step``). If the load is less than this value (and the + ``sampling_down_factor`` mechanism is not in effect), the frequency will + go down. Otherwise, the frequency will not be changed. + +``sampling_down_factor`` + Frequency decrease deferral factor, between 1 (default) and 10 + inclusive. + + It effectively causes the frequency to go down ``sampling_down_factor`` + times slower than it ramps up. + + +Frequency Boost Support +======================= + +Background +---------- + +Some processors support a mechanism to raise the operating frequency of some +cores in a multicore package temporarily (and above the sustainable frequency +threshold for the whole package) under certain conditions, for example if the +whole chip is not fully utilized and below its intended thermal or power budget. + +Different names are used by different vendors to refer to this functionality. +For Intel processors it is referred to as "Turbo Boost", AMD calls it +"Turbo-Core" or (in technical documentation) "Core Performance Boost" and so on. +As a rule, it also is implemented differently by different vendors. The simple +term "frequency boost" is used here for brevity to refer to all of those +implementations. + +The frequency boost mechanism may be either hardware-based or software-based. +If it is hardware-based (e.g. on x86), the decision to trigger the boosting is +made by the hardware (although in general it requires the hardware to be put +into a special state in which it can control the CPU frequency within certain +limits). If it is software-based (e.g. on ARM), the scaling driver decides +whether or not to trigger boosting and when to do that. + +The ``boost`` File in ``sysfs`` +------------------------------- + +This file is located under :file:`/sys/devices/system/cpu/cpufreq/` and controls +the "boost" setting for the whole system. It is not present if the underlying +scaling driver does not support the frequency boost mechanism (or supports it, +but provides a driver-specific interface for controlling it, like +|intel_pstate|). + +If the value in this file is 1, the frequency boost mechanism is enabled. This +means that either the hardware can be put into states in which it is able to +trigger boosting (in the hardware-based case), or the software is allowed to +trigger boosting (in the software-based case). It does not mean that boosting +is actually in use at the moment on any CPUs in the system. It only means a +permission to use the frequency boost mechanism (which still may never be used +for other reasons). + +If the value in this file is 0, the frequency boost mechanism is disabled and +cannot be used at all. + +The only values that can be written to this file are 0 and 1. + +Rationale for Boost Control Knob +-------------------------------- + +The frequency boost mechanism is generally intended to help to achieve optimum +CPU performance on time scales below software resolution (e.g. below the +scheduler tick interval) and it is demonstrably suitable for many workloads, but +it may lead to problems in certain situations. + +For this reason, many systems make it possible to disable the frequency boost +mechanism in the platform firmware (BIOS) setup, but that requires the system to +be restarted for the setting to be adjusted as desired, which may not be +practical at least in some cases. For example: + + 1. Boosting means overclocking the processor, although under controlled + conditions. Generally, the processor's energy consumption increases + as a result of increasing its frequency and voltage, even temporarily. + That may not be desirable on systems that switch to power sources of + limited capacity, such as batteries, so the ability to disable the boost + mechanism while the system is running may help there (but that depends on + the workload too). + + 2. In some situations deterministic behavior is more important than + performance or energy consumption (or both) and the ability to disable + boosting while the system is running may be useful then. + + 3. To examine the impact of the frequency boost mechanism itself, it is useful + to be able to run tests with and without boosting, preferably without + restarting the system in the meantime. + + 4. Reproducible results are important when running benchmarks. Since + the boosting functionality depends on the load of the whole package, + single-thread performance may vary because of it which may lead to + unreproducible results sometimes. That can be avoided by disabling the + frequency boost mechanism before running benchmarks sensitive to that + issue. + +Legacy AMD ``cpb`` Knob +----------------------- + +The AMD powernow-k8 scaling driver supports a ``sysfs`` knob very similar to +the global ``boost`` one. It is used for disabling/enabling the "Core +Performance Boost" feature of some AMD processors. + +If present, that knob is located in every ``CPUFreq`` policy directory in +``sysfs`` (:file:`/sys/devices/system/cpu/cpufreq/policyX/`) and is called +``cpb``, which indicates a more fine grained control interface. The actual +implementation, however, works on the system-wide basis and setting that knob +for one policy causes the same value of it to be set for all of the other +policies at the same time. + +That knob is still supported on AMD processors that support its underlying +hardware feature, but it may be configured out of the kernel (via the +:c:macro:`CONFIG_X86_ACPI_CPUFREQ_CPB` configuration option) and the global +``boost`` knob is present regardless. Thus it is always possible use the +``boost`` knob instead of the ``cpb`` one which is highly recommended, as that +is more consistent with what all of the other systems do (and the ``cpb`` knob +may not be supported any more in the future). + +The ``cpb`` knob is never present for any processors without the underlying +hardware feature (e.g. all Intel ones), even if the +:c:macro:`CONFIG_X86_ACPI_CPUFREQ_CPB` configuration option is set. + + +References +========== + +.. [1] Jonathan Corbet, *Per-entity load tracking*, + https://lwn.net/Articles/531853/ diff --git a/Documentation/admin-guide/pm/cpufreq_drivers.rst b/Documentation/admin-guide/pm/cpufreq_drivers.rst new file mode 100644 index 000000000..9a134ae65 --- /dev/null +++ b/Documentation/admin-guide/pm/cpufreq_drivers.rst @@ -0,0 +1,274 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================================================= +Legacy Documentation of CPU Performance Scaling Drivers +======================================================= + +Included below are historic documents describing assorted +:doc:`CPU performance scaling <cpufreq>` drivers. They are reproduced verbatim, +with the original white space formatting and indentation preserved, except for +the added leading space character in every line of text. + + +AMD PowerNow! Drivers +===================== + +:: + + PowerNow! and Cool'n'Quiet are AMD names for frequency + management capabilities in AMD processors. As the hardware + implementation changes in new generations of the processors, + there is a different cpu-freq driver for each generation. + + Note that the driver's will not load on the "wrong" hardware, + so it is safe to try each driver in turn when in doubt as to + which is the correct driver. + + Note that the functionality to change frequency (and voltage) + is not available in all processors. The drivers will refuse + to load on processors without this capability. The capability + is detected with the cpuid instruction. + + The drivers use BIOS supplied tables to obtain frequency and + voltage information appropriate for a particular platform. + Frequency transitions will be unavailable if the BIOS does + not supply these tables. + + 6th Generation: powernow-k6 + + 7th Generation: powernow-k7: Athlon, Duron, Geode. + + 8th Generation: powernow-k8: Athlon, Athlon 64, Opteron, Sempron. + Documentation on this functionality in 8th generation processors + is available in the "BIOS and Kernel Developer's Guide", publication + 26094, in chapter 9, available for download from www.amd.com. + + BIOS supplied data, for powernow-k7 and for powernow-k8, may be + from either the PSB table or from ACPI objects. The ACPI support + is only available if the kernel config sets CONFIG_ACPI_PROCESSOR. + The powernow-k8 driver will attempt to use ACPI if so configured, + and fall back to PST if that fails. + The powernow-k7 driver will try to use the PSB support first, and + fall back to ACPI if the PSB support fails. A module parameter, + acpi_force, is provided to force ACPI support to be used instead + of PSB support. + + +``cpufreq-nforce2`` +=================== + +:: + + The cpufreq-nforce2 driver changes the FSB on nVidia nForce2 platforms. + + This works better than on other platforms, because the FSB of the CPU + can be controlled independently from the PCI/AGP clock. + + The module has two options: + + fid: multiplier * 10 (for example 8.5 = 85) + min_fsb: minimum FSB + + If not set, fid is calculated from the current CPU speed and the FSB. + min_fsb defaults to FSB at boot time - 50 MHz. + + IMPORTANT: The available range is limited downwards! + Also the minimum available FSB can differ, for systems + booting with 200 MHz, 150 should always work. + + +``pcc-cpufreq`` +=============== + +:: + + /* + * pcc-cpufreq.txt - PCC interface documentation + * + * Copyright (C) 2009 Red Hat, Matthew Garrett <mjg@redhat.com> + * Copyright (C) 2009 Hewlett-Packard Development Company, L.P. + * Nagananda Chumbalkar <nagananda.chumbalkar@hp.com> + */ + + + Processor Clocking Control Driver + --------------------------------- + + Contents: + --------- + 1. Introduction + 1.1 PCC interface + 1.1.1 Get Average Frequency + 1.1.2 Set Desired Frequency + 1.2 Platforms affected + 2. Driver and /sys details + 2.1 scaling_available_frequencies + 2.2 cpuinfo_transition_latency + 2.3 cpuinfo_cur_freq + 2.4 related_cpus + 3. Caveats + + 1. Introduction: + ---------------- + Processor Clocking Control (PCC) is an interface between the platform + firmware and OSPM. It is a mechanism for coordinating processor + performance (ie: frequency) between the platform firmware and the OS. + + The PCC driver (pcc-cpufreq) allows OSPM to take advantage of the PCC + interface. + + OS utilizes the PCC interface to inform platform firmware what frequency the + OS wants for a logical processor. The platform firmware attempts to achieve + the requested frequency. If the request for the target frequency could not be + satisfied by platform firmware, then it usually means that power budget + conditions are in place, and "power capping" is taking place. + + 1.1 PCC interface: + ------------------ + The complete PCC specification is available here: + https://acpica.org/sites/acpica/files/Processor-Clocking-Control-v1p0.pdf + + PCC relies on a shared memory region that provides a channel for communication + between the OS and platform firmware. PCC also implements a "doorbell" that + is used by the OS to inform the platform firmware that a command has been + sent. + + The ACPI PCCH() method is used to discover the location of the PCC shared + memory region. The shared memory region header contains the "command" and + "status" interface. PCCH() also contains details on how to access the platform + doorbell. + + The following commands are supported by the PCC interface: + * Get Average Frequency + * Set Desired Frequency + + The ACPI PCCP() method is implemented for each logical processor and is + used to discover the offsets for the input and output buffers in the shared + memory region. + + When PCC mode is enabled, the platform will not expose processor performance + or throttle states (_PSS, _TSS and related ACPI objects) to OSPM. Therefore, + the native P-state driver (such as acpi-cpufreq for Intel, powernow-k8 for + AMD) will not load. + + However, OSPM remains in control of policy. The governor (eg: "ondemand") + computes the required performance for each processor based on server workload. + The PCC driver fills in the command interface, and the input buffer and + communicates the request to the platform firmware. The platform firmware is + responsible for delivering the requested performance. + + Each PCC command is "global" in scope and can affect all the logical CPUs in + the system. Therefore, PCC is capable of performing "group" updates. With PCC + the OS is capable of getting/setting the frequency of all the logical CPUs in + the system with a single call to the BIOS. + + 1.1.1 Get Average Frequency: + ---------------------------- + This command is used by the OSPM to query the running frequency of the + processor since the last time this command was completed. The output buffer + indicates the average unhalted frequency of the logical processor expressed as + a percentage of the nominal (ie: maximum) CPU frequency. The output buffer + also signifies if the CPU frequency is limited by a power budget condition. + + 1.1.2 Set Desired Frequency: + ---------------------------- + This command is used by the OSPM to communicate to the platform firmware the + desired frequency for a logical processor. The output buffer is currently + ignored by OSPM. The next invocation of "Get Average Frequency" will inform + OSPM if the desired frequency was achieved or not. + + 1.2 Platforms affected: + ----------------------- + The PCC driver will load on any system where the platform firmware: + * supports the PCC interface, and the associated PCCH() and PCCP() methods + * assumes responsibility for managing the hardware clocking controls in order + to deliver the requested processor performance + + Currently, certain HP ProLiant platforms implement the PCC interface. On those + platforms PCC is the "default" choice. + + However, it is possible to disable this interface via a BIOS setting. In + such an instance, as is also the case on platforms where the PCC interface + is not implemented, the PCC driver will fail to load silently. + + 2. Driver and /sys details: + --------------------------- + When the driver loads, it merely prints the lowest and the highest CPU + frequencies supported by the platform firmware. + + The PCC driver loads with a message such as: + pcc-cpufreq: (v1.00.00) driver loaded with frequency limits: 1600 MHz, 2933 + MHz + + This means that the OPSM can request the CPU to run at any frequency in + between the limits (1600 MHz, and 2933 MHz) specified in the message. + + Internally, there is no need for the driver to convert the "target" frequency + to a corresponding P-state. + + The VERSION number for the driver will be of the format v.xy.ab. + eg: 1.00.02 + ----- -- + | | + | -- this will increase with bug fixes/enhancements to the driver + |-- this is the version of the PCC specification the driver adheres to + + + The following is a brief discussion on some of the fields exported via the + /sys filesystem and how their values are affected by the PCC driver: + + 2.1 scaling_available_frequencies: + ---------------------------------- + scaling_available_frequencies is not created in /sys. No intermediate + frequencies need to be listed because the BIOS will try to achieve any + frequency, within limits, requested by the governor. A frequency does not have + to be strictly associated with a P-state. + + 2.2 cpuinfo_transition_latency: + ------------------------------- + The cpuinfo_transition_latency field is 0. The PCC specification does + not include a field to expose this value currently. + + 2.3 cpuinfo_cur_freq: + --------------------- + A) Often cpuinfo_cur_freq will show a value different than what is declared + in the scaling_available_frequencies or scaling_cur_freq, or scaling_max_freq. + This is due to "turbo boost" available on recent Intel processors. If certain + conditions are met the BIOS can achieve a slightly higher speed than requested + by OSPM. An example: + + scaling_cur_freq : 2933000 + cpuinfo_cur_freq : 3196000 + + B) There is a round-off error associated with the cpuinfo_cur_freq value. + Since the driver obtains the current frequency as a "percentage" (%) of the + nominal frequency from the BIOS, sometimes, the values displayed by + scaling_cur_freq and cpuinfo_cur_freq may not match. An example: + + scaling_cur_freq : 1600000 + cpuinfo_cur_freq : 1583000 + + In this example, the nominal frequency is 2933 MHz. The driver obtains the + current frequency, cpuinfo_cur_freq, as 54% of the nominal frequency: + + 54% of 2933 MHz = 1583 MHz + + Nominal frequency is the maximum frequency of the processor, and it usually + corresponds to the frequency of the P0 P-state. + + 2.4 related_cpus: + ----------------- + The related_cpus field is identical to affected_cpus. + + affected_cpus : 4 + related_cpus : 4 + + Currently, the PCC driver does not evaluate _PSD. The platforms that support + PCC do not implement SW_ALL. So OSPM doesn't need to perform any coordination + to ensure that the same frequency is requested of all dependent CPUs. + + 3. Caveats: + ----------- + The "cpufreq_stats" module in its present form cannot be loaded and + expected to work with the PCC driver. Since the "cpufreq_stats" module + provides information wrt each P-state, it is not applicable to the PCC driver. diff --git a/Documentation/admin-guide/pm/cpuidle.rst b/Documentation/admin-guide/pm/cpuidle.rst new file mode 100644 index 000000000..19754beb5 --- /dev/null +++ b/Documentation/admin-guide/pm/cpuidle.rst @@ -0,0 +1,662 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + +.. |struct cpuidle_state| replace:: :c:type:`struct cpuidle_state <cpuidle_state>` +.. |cpufreq| replace:: :doc:`CPU Performance Scaling <cpufreq>` + +======================== +CPU Idle Time Management +======================== + +:Copyright: |copy| 2018 Intel Corporation + +:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> + + +Concepts +======== + +Modern processors are generally able to enter states in which the execution of +a program is suspended and instructions belonging to it are not fetched from +memory or executed. Those states are the *idle* states of the processor. + +Since part of the processor hardware is not used in idle states, entering them +generally allows power drawn by the processor to be reduced and, in consequence, +it is an opportunity to save energy. + +CPU idle time management is an energy-efficiency feature concerned about using +the idle states of processors for this purpose. + +Logical CPUs +------------ + +CPU idle time management operates on CPUs as seen by the *CPU scheduler* (that +is the part of the kernel responsible for the distribution of computational +work in the system). In its view, CPUs are *logical* units. That is, they need +not be separate physical entities and may just be interfaces appearing to +software as individual single-core processors. In other words, a CPU is an +entity which appears to be fetching instructions that belong to one sequence +(program) from memory and executing them, but it need not work this way +physically. Generally, three different cases can be consider here. + +First, if the whole processor can only follow one sequence of instructions (one +program) at a time, it is a CPU. In that case, if the hardware is asked to +enter an idle state, that applies to the processor as a whole. + +Second, if the processor is multi-core, each core in it is able to follow at +least one program at a time. The cores need not be entirely independent of each +other (for example, they may share caches), but still most of the time they +work physically in parallel with each other, so if each of them executes only +one program, those programs run mostly independently of each other at the same +time. The entire cores are CPUs in that case and if the hardware is asked to +enter an idle state, that applies to the core that asked for it in the first +place, but it also may apply to a larger unit (say a "package" or a "cluster") +that the core belongs to (in fact, it may apply to an entire hierarchy of larger +units containing the core). Namely, if all of the cores in the larger unit +except for one have been put into idle states at the "core level" and the +remaining core asks the processor to enter an idle state, that may trigger it +to put the whole larger unit into an idle state which also will affect the +other cores in that unit. + +Finally, each core in a multi-core processor may be able to follow more than one +program in the same time frame (that is, each core may be able to fetch +instructions from multiple locations in memory and execute them in the same time +frame, but not necessarily entirely in parallel with each other). In that case +the cores present themselves to software as "bundles" each consisting of +multiple individual single-core "processors", referred to as *hardware threads* +(or hyper-threads specifically on Intel hardware), that each can follow one +sequence of instructions. Then, the hardware threads are CPUs from the CPU idle +time management perspective and if the processor is asked to enter an idle state +by one of them, the hardware thread (or CPU) that asked for it is stopped, but +nothing more happens, unless all of the other hardware threads within the same +core also have asked the processor to enter an idle state. In that situation, +the core may be put into an idle state individually or a larger unit containing +it may be put into an idle state as a whole (if the other cores within the +larger unit are in idle states already). + +Idle CPUs +--------- + +Logical CPUs, simply referred to as "CPUs" in what follows, are regarded as +*idle* by the Linux kernel when there are no tasks to run on them except for the +special "idle" task. + +Tasks are the CPU scheduler's representation of work. Each task consists of a +sequence of instructions to execute, or code, data to be manipulated while +running that code, and some context information that needs to be loaded into the +processor every time the task's code is run by a CPU. The CPU scheduler +distributes work by assigning tasks to run to the CPUs present in the system. + +Tasks can be in various states. In particular, they are *runnable* if there are +no specific conditions preventing their code from being run by a CPU as long as +there is a CPU available for that (for example, they are not waiting for any +events to occur or similar). When a task becomes runnable, the CPU scheduler +assigns it to one of the available CPUs to run and if there are no more runnable +tasks assigned to it, the CPU will load the given task's context and run its +code (from the instruction following the last one executed so far, possibly by +another CPU). [If there are multiple runnable tasks assigned to one CPU +simultaneously, they will be subject to prioritization and time sharing in order +to allow them to make some progress over time.] + +The special "idle" task becomes runnable if there are no other runnable tasks +assigned to the given CPU and the CPU is then regarded as idle. In other words, +in Linux idle CPUs run the code of the "idle" task called *the idle loop*. That +code may cause the processor to be put into one of its idle states, if they are +supported, in order to save energy, but if the processor does not support any +idle states, or there is not enough time to spend in an idle state before the +next wakeup event, or there are strict latency constraints preventing any of the +available idle states from being used, the CPU will simply execute more or less +useless instructions in a loop until it is assigned a new task to run. + + +.. _idle-loop: + +The Idle Loop +============= + +The idle loop code takes two major steps in every iteration of it. First, it +calls into a code module referred to as the *governor* that belongs to the CPU +idle time management subsystem called ``CPUIdle`` to select an idle state for +the CPU to ask the hardware to enter. Second, it invokes another code module +from the ``CPUIdle`` subsystem, called the *driver*, to actually ask the +processor hardware to enter the idle state selected by the governor. + +The role of the governor is to find an idle state most suitable for the +conditions at hand. For this purpose, idle states that the hardware can be +asked to enter by logical CPUs are represented in an abstract way independent of +the platform or the processor architecture and organized in a one-dimensional +(linear) array. That array has to be prepared and supplied by the ``CPUIdle`` +driver matching the platform the kernel is running on at the initialization +time. This allows ``CPUIdle`` governors to be independent of the underlying +hardware and to work with any platforms that the Linux kernel can run on. + +Each idle state present in that array is characterized by two parameters to be +taken into account by the governor, the *target residency* and the (worst-case) +*exit latency*. The target residency is the minimum time the hardware must +spend in the given state, including the time needed to enter it (which may be +substantial), in order to save more energy than it would save by entering one of +the shallower idle states instead. [The "depth" of an idle state roughly +corresponds to the power drawn by the processor in that state.] The exit +latency, in turn, is the maximum time it will take a CPU asking the processor +hardware to enter an idle state to start executing the first instruction after a +wakeup from that state. Note that in general the exit latency also must cover +the time needed to enter the given state in case the wakeup occurs when the +hardware is entering it and it must be entered completely to be exited in an +ordered manner. + +There are two types of information that can influence the governor's decisions. +First of all, the governor knows the time until the closest timer event. That +time is known exactly, because the kernel programs timers and it knows exactly +when they will trigger, and it is the maximum time the hardware that the given +CPU depends on can spend in an idle state, including the time necessary to enter +and exit it. However, the CPU may be woken up by a non-timer event at any time +(in particular, before the closest timer triggers) and it generally is not known +when that may happen. The governor can only see how much time the CPU actually +was idle after it has been woken up (that time will be referred to as the *idle +duration* from now on) and it can use that information somehow along with the +time until the closest timer to estimate the idle duration in future. How the +governor uses that information depends on what algorithm is implemented by it +and that is the primary reason for having more than one governor in the +``CPUIdle`` subsystem. + +There are four ``CPUIdle`` governors available, ``menu``, `TEO <teo-gov_>`_, +``ladder`` and ``haltpoll``. Which of them is used by default depends on the +configuration of the kernel and in particular on whether or not the scheduler +tick can be `stopped by the idle loop <idle-cpus-and-tick_>`_. Available +governors can be read from the :file:`available_governors`, and the governor +can be changed at runtime. The name of the ``CPUIdle`` governor currently +used by the kernel can be read from the :file:`current_governor_ro` or +:file:`current_governor` file under :file:`/sys/devices/system/cpu/cpuidle/` +in ``sysfs``. + +Which ``CPUIdle`` driver is used, on the other hand, usually depends on the +platform the kernel is running on, but there are platforms with more than one +matching driver. For example, there are two drivers that can work with the +majority of Intel platforms, ``intel_idle`` and ``acpi_idle``, one with +hardcoded idle states information and the other able to read that information +from the system's ACPI tables, respectively. Still, even in those cases, the +driver chosen at the system initialization time cannot be replaced later, so the +decision on which one of them to use has to be made early (on Intel platforms +the ``acpi_idle`` driver will be used if ``intel_idle`` is disabled for some +reason or if it does not recognize the processor). The name of the ``CPUIdle`` +driver currently used by the kernel can be read from the :file:`current_driver` +file under :file:`/sys/devices/system/cpu/cpuidle/` in ``sysfs``. + + +.. _idle-cpus-and-tick: + +Idle CPUs and The Scheduler Tick +================================ + +The scheduler tick is a timer that triggers periodically in order to implement +the time sharing strategy of the CPU scheduler. Of course, if there are +multiple runnable tasks assigned to one CPU at the same time, the only way to +allow them to make reasonable progress in a given time frame is to make them +share the available CPU time. Namely, in rough approximation, each task is +given a slice of the CPU time to run its code, subject to the scheduling class, +prioritization and so on and when that time slice is used up, the CPU should be +switched over to running (the code of) another task. The currently running task +may not want to give the CPU away voluntarily, however, and the scheduler tick +is there to make the switch happen regardless. That is not the only role of the +tick, but it is the primary reason for using it. + +The scheduler tick is problematic from the CPU idle time management perspective, +because it triggers periodically and relatively often (depending on the kernel +configuration, the length of the tick period is between 1 ms and 10 ms). +Thus, if the tick is allowed to trigger on idle CPUs, it will not make sense +for them to ask the hardware to enter idle states with target residencies above +the tick period length. Moreover, in that case the idle duration of any CPU +will never exceed the tick period length and the energy used for entering and +exiting idle states due to the tick wakeups on idle CPUs will be wasted. + +Fortunately, it is not really necessary to allow the tick to trigger on idle +CPUs, because (by definition) they have no tasks to run except for the special +"idle" one. In other words, from the CPU scheduler perspective, the only user +of the CPU time on them is the idle loop. Since the time of an idle CPU need +not be shared between multiple runnable tasks, the primary reason for using the +tick goes away if the given CPU is idle. Consequently, it is possible to stop +the scheduler tick entirely on idle CPUs in principle, even though that may not +always be worth the effort. + +Whether or not it makes sense to stop the scheduler tick in the idle loop +depends on what is expected by the governor. First, if there is another +(non-tick) timer due to trigger within the tick range, stopping the tick clearly +would be a waste of time, even though the timer hardware may not need to be +reprogrammed in that case. Second, if the governor is expecting a non-timer +wakeup within the tick range, stopping the tick is not necessary and it may even +be harmful. Namely, in that case the governor will select an idle state with +the target residency within the time until the expected wakeup, so that state is +going to be relatively shallow. The governor really cannot select a deep idle +state then, as that would contradict its own expectation of a wakeup in short +order. Now, if the wakeup really occurs shortly, stopping the tick would be a +waste of time and in this case the timer hardware would need to be reprogrammed, +which is expensive. On the other hand, if the tick is stopped and the wakeup +does not occur any time soon, the hardware may spend indefinite amount of time +in the shallow idle state selected by the governor, which will be a waste of +energy. Hence, if the governor is expecting a wakeup of any kind within the +tick range, it is better to allow the tick trigger. Otherwise, however, the +governor will select a relatively deep idle state, so the tick should be stopped +so that it does not wake up the CPU too early. + +In any case, the governor knows what it is expecting and the decision on whether +or not to stop the scheduler tick belongs to it. Still, if the tick has been +stopped already (in one of the previous iterations of the loop), it is better +to leave it as is and the governor needs to take that into account. + +The kernel can be configured to disable stopping the scheduler tick in the idle +loop altogether. That can be done through the build-time configuration of it +(by unsetting the ``CONFIG_NO_HZ_IDLE`` configuration option) or by passing +``nohz=off`` to it in the command line. In both cases, as the stopping of the +scheduler tick is disabled, the governor's decisions regarding it are simply +ignored by the idle loop code and the tick is never stopped. + +The systems that run kernels configured to allow the scheduler tick to be +stopped on idle CPUs are referred to as *tickless* systems and they are +generally regarded as more energy-efficient than the systems running kernels in +which the tick cannot be stopped. If the given system is tickless, it will use +the ``menu`` governor by default and if it is not tickless, the default +``CPUIdle`` governor on it will be ``ladder``. + + +.. _menu-gov: + +The ``menu`` Governor +===================== + +The ``menu`` governor is the default ``CPUIdle`` governor for tickless systems. +It is quite complex, but the basic principle of its design is straightforward. +Namely, when invoked to select an idle state for a CPU (i.e. an idle state that +the CPU will ask the processor hardware to enter), it attempts to predict the +idle duration and uses the predicted value for idle state selection. + +It first obtains the time until the closest timer event with the assumption +that the scheduler tick will be stopped. That time, referred to as the *sleep +length* in what follows, is the upper bound on the time before the next CPU +wakeup. It is used to determine the sleep length range, which in turn is needed +to get the sleep length correction factor. + +The ``menu`` governor maintains two arrays of sleep length correction factors. +One of them is used when tasks previously running on the given CPU are waiting +for some I/O operations to complete and the other one is used when that is not +the case. Each array contains several correction factor values that correspond +to different sleep length ranges organized so that each range represented in the +array is approximately 10 times wider than the previous one. + +The correction factor for the given sleep length range (determined before +selecting the idle state for the CPU) is updated after the CPU has been woken +up and the closer the sleep length is to the observed idle duration, the closer +to 1 the correction factor becomes (it must fall between 0 and 1 inclusive). +The sleep length is multiplied by the correction factor for the range that it +falls into to obtain the first approximation of the predicted idle duration. + +Next, the governor uses a simple pattern recognition algorithm to refine its +idle duration prediction. Namely, it saves the last 8 observed idle duration +values and, when predicting the idle duration next time, it computes the average +and variance of them. If the variance is small (smaller than 400 square +milliseconds) or it is small relative to the average (the average is greater +that 6 times the standard deviation), the average is regarded as the "typical +interval" value. Otherwise, the longest of the saved observed idle duration +values is discarded and the computation is repeated for the remaining ones. +Again, if the variance of them is small (in the above sense), the average is +taken as the "typical interval" value and so on, until either the "typical +interval" is determined or too many data points are disregarded, in which case +the "typical interval" is assumed to equal "infinity" (the maximum unsigned +integer value). The "typical interval" computed this way is compared with the +sleep length multiplied by the correction factor and the minimum of the two is +taken as the predicted idle duration. + +Then, the governor computes an extra latency limit to help "interactive" +workloads. It uses the observation that if the exit latency of the selected +idle state is comparable with the predicted idle duration, the total time spent +in that state probably will be very short and the amount of energy to save by +entering it will be relatively small, so likely it is better to avoid the +overhead related to entering that state and exiting it. Thus selecting a +shallower state is likely to be a better option then. The first approximation +of the extra latency limit is the predicted idle duration itself which +additionally is divided by a value depending on the number of tasks that +previously ran on the given CPU and now they are waiting for I/O operations to +complete. The result of that division is compared with the latency limit coming +from the power management quality of service, or `PM QoS <cpu-pm-qos_>`_, +framework and the minimum of the two is taken as the limit for the idle states' +exit latency. + +Now, the governor is ready to walk the list of idle states and choose one of +them. For this purpose, it compares the target residency of each state with +the predicted idle duration and the exit latency of it with the computed latency +limit. It selects the state with the target residency closest to the predicted +idle duration, but still below it, and exit latency that does not exceed the +limit. + +In the final step the governor may still need to refine the idle state selection +if it has not decided to `stop the scheduler tick <idle-cpus-and-tick_>`_. That +happens if the idle duration predicted by it is less than the tick period and +the tick has not been stopped already (in a previous iteration of the idle +loop). Then, the sleep length used in the previous computations may not reflect +the real time until the closest timer event and if it really is greater than +that time, the governor may need to select a shallower state with a suitable +target residency. + + +.. _teo-gov: + +The Timer Events Oriented (TEO) Governor +======================================== + +The timer events oriented (TEO) governor is an alternative ``CPUIdle`` governor +for tickless systems. It follows the same basic strategy as the ``menu`` `one +<menu-gov_>`_: it always tries to find the deepest idle state suitable for the +given conditions. However, it applies a different approach to that problem. + +.. kernel-doc:: drivers/cpuidle/governors/teo.c + :doc: teo-description + +.. _idle-states-representation: + +Representation of Idle States +============================= + +For the CPU idle time management purposes all of the physical idle states +supported by the processor have to be represented as a one-dimensional array of +|struct cpuidle_state| objects each allowing an individual (logical) CPU to ask +the processor hardware to enter an idle state of certain properties. If there +is a hierarchy of units in the processor, one |struct cpuidle_state| object can +cover a combination of idle states supported by the units at different levels of +the hierarchy. In that case, the `target residency and exit latency parameters +of it <idle-loop_>`_, must reflect the properties of the idle state at the +deepest level (i.e. the idle state of the unit containing all of the other +units). + +For example, take a processor with two cores in a larger unit referred to as +a "module" and suppose that asking the hardware to enter a specific idle state +(say "X") at the "core" level by one core will trigger the module to try to +enter a specific idle state of its own (say "MX") if the other core is in idle +state "X" already. In other words, asking for idle state "X" at the "core" +level gives the hardware a license to go as deep as to idle state "MX" at the +"module" level, but there is no guarantee that this is going to happen (the core +asking for idle state "X" may just end up in that state by itself instead). +Then, the target residency of the |struct cpuidle_state| object representing +idle state "X" must reflect the minimum time to spend in idle state "MX" of +the module (including the time needed to enter it), because that is the minimum +time the CPU needs to be idle to save any energy in case the hardware enters +that state. Analogously, the exit latency parameter of that object must cover +the exit time of idle state "MX" of the module (and usually its entry time too), +because that is the maximum delay between a wakeup signal and the time the CPU +will start to execute the first new instruction (assuming that both cores in the +module will always be ready to execute instructions as soon as the module +becomes operational as a whole). + +There are processors without direct coordination between different levels of the +hierarchy of units inside them, however. In those cases asking for an idle +state at the "core" level does not automatically affect the "module" level, for +example, in any way and the ``CPUIdle`` driver is responsible for the entire +handling of the hierarchy. Then, the definition of the idle state objects is +entirely up to the driver, but still the physical properties of the idle state +that the processor hardware finally goes into must always follow the parameters +used by the governor for idle state selection (for instance, the actual exit +latency of that idle state must not exceed the exit latency parameter of the +idle state object selected by the governor). + +In addition to the target residency and exit latency idle state parameters +discussed above, the objects representing idle states each contain a few other +parameters describing the idle state and a pointer to the function to run in +order to ask the hardware to enter that state. Also, for each +|struct cpuidle_state| object, there is a corresponding +:c:type:`struct cpuidle_state_usage <cpuidle_state_usage>` one containing usage +statistics of the given idle state. That information is exposed by the kernel +via ``sysfs``. + +For each CPU in the system, there is a :file:`/sys/devices/system/cpu/cpu<N>/cpuidle/` +directory in ``sysfs``, where the number ``<N>`` is assigned to the given +CPU at the initialization time. That directory contains a set of subdirectories +called :file:`state0`, :file:`state1` and so on, up to the number of idle state +objects defined for the given CPU minus one. Each of these directories +corresponds to one idle state object and the larger the number in its name, the +deeper the (effective) idle state represented by it. Each of them contains +a number of files (attributes) representing the properties of the idle state +object corresponding to it, as follows: + +``above`` + Total number of times this idle state had been asked for, but the + observed idle duration was certainly too short to match its target + residency. + +``below`` + Total number of times this idle state had been asked for, but certainly + a deeper idle state would have been a better match for the observed idle + duration. + +``desc`` + Description of the idle state. + +``disable`` + Whether or not this idle state is disabled. + +``default_status`` + The default status of this state, "enabled" or "disabled". + +``latency`` + Exit latency of the idle state in microseconds. + +``name`` + Name of the idle state. + +``power`` + Power drawn by hardware in this idle state in milliwatts (if specified, + 0 otherwise). + +``residency`` + Target residency of the idle state in microseconds. + +``time`` + Total time spent in this idle state by the given CPU (as measured by the + kernel) in microseconds. + +``usage`` + Total number of times the hardware has been asked by the given CPU to + enter this idle state. + +``rejected`` + Total number of times a request to enter this idle state on the given + CPU was rejected. + +The :file:`desc` and :file:`name` files both contain strings. The difference +between them is that the name is expected to be more concise, while the +description may be longer and it may contain white space or special characters. +The other files listed above contain integer numbers. + +The :file:`disable` attribute is the only writeable one. If it contains 1, the +given idle state is disabled for this particular CPU, which means that the +governor will never select it for this particular CPU and the ``CPUIdle`` +driver will never ask the hardware to enter it for that CPU as a result. +However, disabling an idle state for one CPU does not prevent it from being +asked for by the other CPUs, so it must be disabled for all of them in order to +never be asked for by any of them. [Note that, due to the way the ``ladder`` +governor is implemented, disabling an idle state prevents that governor from +selecting any idle states deeper than the disabled one too.] + +If the :file:`disable` attribute contains 0, the given idle state is enabled for +this particular CPU, but it still may be disabled for some or all of the other +CPUs in the system at the same time. Writing 1 to it causes the idle state to +be disabled for this particular CPU and writing 0 to it allows the governor to +take it into consideration for the given CPU and the driver to ask for it, +unless that state was disabled globally in the driver (in which case it cannot +be used at all). + +The :file:`power` attribute is not defined very well, especially for idle state +objects representing combinations of idle states at different levels of the +hierarchy of units in the processor, and it generally is hard to obtain idle +state power numbers for complex hardware, so :file:`power` often contains 0 (not +available) and if it contains a nonzero number, that number may not be very +accurate and it should not be relied on for anything meaningful. + +The number in the :file:`time` file generally may be greater than the total time +really spent by the given CPU in the given idle state, because it is measured by +the kernel and it may not cover the cases in which the hardware refused to enter +this idle state and entered a shallower one instead of it (or even it did not +enter any idle state at all). The kernel can only measure the time span between +asking the hardware to enter an idle state and the subsequent wakeup of the CPU +and it cannot say what really happened in the meantime at the hardware level. +Moreover, if the idle state object in question represents a combination of idle +states at different levels of the hierarchy of units in the processor, +the kernel can never say how deep the hardware went down the hierarchy in any +particular case. For these reasons, the only reliable way to find out how +much time has been spent by the hardware in different idle states supported by +it is to use idle state residency counters in the hardware, if available. + +Generally, an interrupt received when trying to enter an idle state causes the +idle state entry request to be rejected, in which case the ``CPUIdle`` driver +may return an error code to indicate that this was the case. The :file:`usage` +and :file:`rejected` files report the number of times the given idle state +was entered successfully or rejected, respectively. + +.. _cpu-pm-qos: + +Power Management Quality of Service for CPUs +============================================ + +The power management quality of service (PM QoS) framework in the Linux kernel +allows kernel code and user space processes to set constraints on various +energy-efficiency features of the kernel to prevent performance from dropping +below a required level. + +CPU idle time management can be affected by PM QoS in two ways, through the +global CPU latency limit and through the resume latency constraints for +individual CPUs. Kernel code (e.g. device drivers) can set both of them with +the help of special internal interfaces provided by the PM QoS framework. User +space can modify the former by opening the :file:`cpu_dma_latency` special +device file under :file:`/dev/` and writing a binary value (interpreted as a +signed 32-bit integer) to it. In turn, the resume latency constraint for a CPU +can be modified from user space by writing a string (representing a signed +32-bit integer) to the :file:`power/pm_qos_resume_latency_us` file under +:file:`/sys/devices/system/cpu/cpu<N>/` in ``sysfs``, where the CPU number +``<N>`` is allocated at the system initialization time. Negative values +will be rejected in both cases and, also in both cases, the written integer +number will be interpreted as a requested PM QoS constraint in microseconds. + +The requested value is not automatically applied as a new constraint, however, +as it may be less restrictive (greater in this particular case) than another +constraint previously requested by someone else. For this reason, the PM QoS +framework maintains a list of requests that have been made so far for the +global CPU latency limit and for each individual CPU, aggregates them and +applies the effective (minimum in this particular case) value as the new +constraint. + +In fact, opening the :file:`cpu_dma_latency` special device file causes a new +PM QoS request to be created and added to a global priority list of CPU latency +limit requests and the file descriptor coming from the "open" operation +represents that request. If that file descriptor is then used for writing, the +number written to it will be associated with the PM QoS request represented by +it as a new requested limit value. Next, the priority list mechanism will be +used to determine the new effective value of the entire list of requests and +that effective value will be set as a new CPU latency limit. Thus requesting a +new limit value will only change the real limit if the effective "list" value is +affected by it, which is the case if it is the minimum of the requested values +in the list. + +The process holding a file descriptor obtained by opening the +:file:`cpu_dma_latency` special device file controls the PM QoS request +associated with that file descriptor, but it controls this particular PM QoS +request only. + +Closing the :file:`cpu_dma_latency` special device file or, more precisely, the +file descriptor obtained while opening it, causes the PM QoS request associated +with that file descriptor to be removed from the global priority list of CPU +latency limit requests and destroyed. If that happens, the priority list +mechanism will be used again, to determine the new effective value for the whole +list and that value will become the new limit. + +In turn, for each CPU there is one resume latency PM QoS request associated with +the :file:`power/pm_qos_resume_latency_us` file under +:file:`/sys/devices/system/cpu/cpu<N>/` in ``sysfs`` and writing to it causes +this single PM QoS request to be updated regardless of which user space +process does that. In other words, this PM QoS request is shared by the entire +user space, so access to the file associated with it needs to be arbitrated +to avoid confusion. [Arguably, the only legitimate use of this mechanism in +practice is to pin a process to the CPU in question and let it use the +``sysfs`` interface to control the resume latency constraint for it.] It is +still only a request, however. It is an entry in a priority list used to +determine the effective value to be set as the resume latency constraint for the +CPU in question every time the list of requests is updated this way or another +(there may be other requests coming from kernel code in that list). + +CPU idle time governors are expected to regard the minimum of the global +(effective) CPU latency limit and the effective resume latency constraint for +the given CPU as the upper limit for the exit latency of the idle states that +they are allowed to select for that CPU. They should never select any idle +states with exit latency beyond that limit. + + +Idle States Control Via Kernel Command Line +=========================================== + +In addition to the ``sysfs`` interface allowing individual idle states to be +`disabled for individual CPUs <idle-states-representation_>`_, there are kernel +command line parameters affecting CPU idle time management. + +The ``cpuidle.off=1`` kernel command line option can be used to disable the +CPU idle time management entirely. It does not prevent the idle loop from +running on idle CPUs, but it prevents the CPU idle time governors and drivers +from being invoked. If it is added to the kernel command line, the idle loop +will ask the hardware to enter idle states on idle CPUs via the CPU architecture +support code that is expected to provide a default mechanism for this purpose. +That default mechanism usually is the least common denominator for all of the +processors implementing the architecture (i.e. CPU instruction set) in question, +however, so it is rather crude and not very energy-efficient. For this reason, +it is not recommended for production use. + +The ``cpuidle.governor=`` kernel command line switch allows the ``CPUIdle`` +governor to use to be specified. It has to be appended with a string matching +the name of an available governor (e.g. ``cpuidle.governor=menu``) and that +governor will be used instead of the default one. It is possible to force +the ``menu`` governor to be used on the systems that use the ``ladder`` governor +by default this way, for example. + +The other kernel command line parameters controlling CPU idle time management +described below are only relevant for the *x86* architecture and references +to ``intel_idle`` affect Intel processors only. + +The *x86* architecture support code recognizes three kernel command line +options related to CPU idle time management: ``idle=poll``, ``idle=halt``, +and ``idle=nomwait``. The first two of them disable the ``acpi_idle`` and +``intel_idle`` drivers altogether, which effectively causes the entire +``CPUIdle`` subsystem to be disabled and makes the idle loop invoke the +architecture support code to deal with idle CPUs. How it does that depends on +which of the two parameters is added to the kernel command line. In the +``idle=halt`` case, the architecture support code will use the ``HLT`` +instruction of the CPUs (which, as a rule, suspends the execution of the program +and causes the hardware to attempt to enter the shallowest available idle state) +for this purpose, and if ``idle=poll`` is used, idle CPUs will execute a +more or less "lightweight" sequence of instructions in a tight loop. [Note +that using ``idle=poll`` is somewhat drastic in many cases, as preventing idle +CPUs from saving almost any energy at all may not be the only effect of it. +For example, on Intel hardware it effectively prevents CPUs from using +P-states (see |cpufreq|) that require any number of CPUs in a package to be +idle, so it very well may hurt single-thread computations performance as well as +energy-efficiency. Thus using it for performance reasons may not be a good idea +at all.] + +The ``idle=nomwait`` option prevents the use of ``MWAIT`` instruction of +the CPU to enter idle states. When this option is used, the ``acpi_idle`` +driver will use the ``HLT`` instruction instead of ``MWAIT``. On systems +running Intel processors, this option disables the ``intel_idle`` driver +and forces the use of the ``acpi_idle`` driver instead. Note that in either +case, ``acpi_idle`` driver will function only if all the information needed +by it is in the system's ACPI tables. + +In addition to the architecture-level kernel command line options affecting CPU +idle time management, there are parameters affecting individual ``CPUIdle`` +drivers that can be passed to them via the kernel command line. Specifically, +the ``intel_idle.max_cstate=<n>`` and ``processor.max_cstate=<n>`` parameters, +where ``<n>`` is an idle state index also used in the name of the given +state's directory in ``sysfs`` (see +`Representation of Idle States <idle-states-representation_>`_), causes the +``intel_idle`` and ``acpi_idle`` drivers, respectively, to discard all of the +idle states deeper than idle state ``<n>``. In that case, they will never ask +for any of those idle states or expose them to the governor. [The behavior of +the two drivers is different for ``<n>`` equal to ``0``. Adding +``intel_idle.max_cstate=0`` to the kernel command line disables the +``intel_idle`` driver and allows ``acpi_idle`` to be used, whereas +``processor.max_cstate=0`` is equivalent to ``processor.max_cstate=1``. +Also, the ``acpi_idle`` driver is part of the ``processor`` kernel module that +can be loaded separately and ``max_cstate=<n>`` can be passed to it as a module +parameter when it is loaded.] diff --git a/Documentation/admin-guide/pm/index.rst b/Documentation/admin-guide/pm/index.rst new file mode 100644 index 000000000..39f8f9f81 --- /dev/null +++ b/Documentation/admin-guide/pm/index.rst @@ -0,0 +1,12 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================ +Power Management +================ + +.. toctree:: + :maxdepth: 2 + + strategies + system-wide + working-state diff --git a/Documentation/admin-guide/pm/intel-speed-select.rst b/Documentation/admin-guide/pm/intel-speed-select.rst new file mode 100644 index 000000000..a2bfb9716 --- /dev/null +++ b/Documentation/admin-guide/pm/intel-speed-select.rst @@ -0,0 +1,939 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================================================ +Intel(R) Speed Select Technology User Guide +============================================================ + +The Intel(R) Speed Select Technology (Intel(R) SST) provides a powerful new +collection of features that give more granular control over CPU performance. +With Intel(R) SST, one server can be configured for power and performance for a +variety of diverse workload requirements. + +Refer to the links below for an overview of the technology: + +- https://www.intel.com/content/www/us/en/architecture-and-technology/speed-select-technology-article.html +- https://builders.intel.com/docs/networkbuilders/intel-speed-select-technology-base-frequency-enhancing-performance.pdf + +These capabilities are further enhanced in some of the newer generations of +server platforms where these features can be enumerated and controlled +dynamically without pre-configuring via BIOS setup options. This dynamic +configuration is done via mailbox commands to the hardware. One way to enumerate +and configure these features is by using the Intel Speed Select utility. + +This document explains how to use the Intel Speed Select tool to enumerate and +control Intel(R) SST features. This document gives example commands and explains +how these commands change the power and performance profile of the system under +test. Using this tool as an example, customers can replicate the messaging +implemented in the tool in their production software. + +intel-speed-select configuration tool +====================================== + +Most Linux distribution packages may include the "intel-speed-select" tool. If not, +it can be built by downloading the Linux kernel tree from kernel.org. Once +downloaded, the tool can be built without building the full kernel. + +From the kernel tree, run the following commands:: + +# cd tools/power/x86/intel-speed-select/ +# make +# make install + +Getting Help +------------ + +To get help with the tool, execute the command below:: + +# intel-speed-select --help + +The top-level help describes arguments and features. Notice that there is a +multi-level help structure in the tool. For example, to get help for the feature "perf-profile":: + +# intel-speed-select perf-profile --help + +To get help on a command, another level of help is provided. For example for the command info "info":: + +# intel-speed-select perf-profile info --help + +Summary of platform capability +------------------------------ +To check the current platform and driver capabilities, execute:: + +#intel-speed-select --info + +For example on a test system:: + + # intel-speed-select --info + Intel(R) Speed Select Technology + Executing on CPU model: X + Platform: API version : 1 + Platform: Driver version : 1 + Platform: mbox supported : 1 + Platform: mmio supported : 1 + Intel(R) SST-PP (feature perf-profile) is supported + TDP level change control is unlocked, max level: 4 + Intel(R) SST-TF (feature turbo-freq) is supported + Intel(R) SST-BF (feature base-freq) is not supported + Intel(R) SST-CP (feature core-power) is supported + +Intel(R) Speed Select Technology - Performance Profile (Intel(R) SST-PP) +------------------------------------------------------------------------ + +This feature allows configuration of a server dynamically based on workload +performance requirements. This helps users during deployment as they do not have +to choose a specific server configuration statically. This Intel(R) Speed Select +Technology - Performance Profile (Intel(R) SST-PP) feature introduces a mechanism +that allows multiple optimized performance profiles per system. Each profile +defines a set of CPUs that need to be online and rest offline to sustain a +guaranteed base frequency. Once the user issues a command to use a specific +performance profile and meet CPU online/offline requirement, the user can expect +a change in the base frequency dynamically. This feature is called +"perf-profile" when using the Intel Speed Select tool. + +Number or performance levels +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +There can be multiple performance profiles on a system. To get the number of +profiles, execute the command below:: + + # intel-speed-select perf-profile get-config-levels + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + get-config-levels:4 + package-1 + die-0 + cpu-14 + get-config-levels:4 + +On this system under test, there are 4 performance profiles in addition to the +base performance profile (which is performance level 0). + +Lock/Unlock status +~~~~~~~~~~~~~~~~~~ + +Even if there are multiple performance profiles, it is possible that they +are locked. If they are locked, users cannot issue a command to change the +performance state. It is possible that there is a BIOS setup to unlock or check +with your system vendor. + +To check if the system is locked, execute the following command:: + + # intel-speed-select perf-profile get-lock-status + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + get-lock-status:0 + package-1 + die-0 + cpu-14 + get-lock-status:0 + +In this case, lock status is 0, which means that the system is unlocked. + +Properties of a performance level +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To get properties of a specific performance level (For example for the level 0, below), execute the command below:: + + # intel-speed-select perf-profile info -l 0 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + perf-profile-level-0 + cpu-count:28 + enable-cpu-mask:000003ff,f0003fff + enable-cpu-list:0,1,2,3,4,5,6,7,8,9,10,11,12,13,28,29,30,31,32,33,34,35,36,37,38,39,40,41 + thermal-design-power-ratio:26 + base-frequency(MHz):2600 + speed-select-turbo-freq:disabled + speed-select-base-freq:disabled + ... + ... + +Here -l option is used to specify a performance level. + +If the option -l is omitted, then this command will print information about all +the performance levels. The above command is printing properties of the +performance level 0. + +For this performance profile, the list of CPUs displayed by the +"enable-cpu-mask/enable-cpu-list" at the max can be "online." When that +condition is met, then base frequency of 2600 MHz can be maintained. To +understand more, execute "intel-speed-select perf-profile info" for performance +level 4:: + + # intel-speed-select perf-profile info -l 4 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + perf-profile-level-4 + cpu-count:28 + enable-cpu-mask:000000fa,f0000faf + enable-cpu-list:0,1,2,3,5,7,8,9,10,11,28,29,30,31,33,35,36,37,38,39 + thermal-design-power-ratio:28 + base-frequency(MHz):2800 + speed-select-turbo-freq:disabled + speed-select-base-freq:unsupported + ... + ... + +There are fewer CPUs in the "enable-cpu-mask/enable-cpu-list". Consequently, if +the user only keeps these CPUs online and the rest "offline," then the base +frequency is increased to 2.8 GHz compared to 2.6 GHz at performance level 0. + +Get current performance level +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To get the current performance level, execute:: + + # intel-speed-select perf-profile get-config-current-level + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + get-config-current_level:0 + +First verify that the base_frequency displayed by the cpufreq sysfs is correct:: + + # cat /sys/devices/system/cpu/cpu0/cpufreq/base_frequency + 2600000 + +This matches the base-frequency (MHz) field value displayed from the +"perf-profile info" command for performance level 0(cpufreq frequency is in +KHz). + +To check if the average frequency is equal to the base frequency for a 100% busy +workload, disable turbo:: + +# echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo + +Then runs a busy workload on all CPUs, for example:: + +#stress -c 64 + +To verify the base frequency, run turbostat:: + + #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1 + + Package Core CPU Bzy_MHz + - - 2600 + 0 0 0 2600 + 0 1 1 2600 + 0 2 2 2600 + 0 3 3 2600 + 0 4 4 2600 + . . . . + + +Changing performance level +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To the change the performance level to 4, execute:: + + # intel-speed-select -d perf-profile set-config-level -l 4 -o + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + perf-profile + set_tdp_level:success + +In the command above, "-o" is optional. If it is specified, then it will also +offline CPUs which are not present in the enable_cpu_mask for this performance +level. + +Now if the base_frequency is checked:: + + #cat /sys/devices/system/cpu/cpu0/cpufreq/base_frequency + 2800000 + +Which shows that the base frequency now increased from 2600 MHz at performance +level 0 to 2800 MHz at performance level 4. As a result, any workload, which can +use fewer CPUs, can see a boost of 200 MHz compared to performance level 0. + +Changing performance level via BMC Interface +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +It is possible to change SST-PP level using out of band (OOB) agent (Via some +remote management console, through BMC "Baseboard Management Controller" +interface). This mode is supported from the Sapphire Rapids processor +generation. The kernel and tool change to support this mode is added to Linux +kernel version 5.18. To enable this feature, kernel config +"CONFIG_INTEL_HFI_THERMAL" is required. The minimum version of the tool +is "v1.12" to support this feature, which is part of Linux kernel version 5.18. + +To support such configuration, this tool can be used as a daemon. Add +a command line option --oob:: + + # intel-speed-select --oob + Intel(R) Speed Select Technology + Executing on CPU model:143[0x8f] + OOB mode is enabled and will run as daemon + +In this mode the tool will online/offline CPUs based on the new performance +level. + +Check presence of other Intel(R) SST features +--------------------------------------------- + +Each of the performance profiles also specifies weather there is support of +other two Intel(R) SST features (Intel(R) Speed Select Technology - Base Frequency +(Intel(R) SST-BF) and Intel(R) Speed Select Technology - Turbo Frequency (Intel +SST-TF)). + +For example, from the output of "perf-profile info" above, for level 0 and level +4: + +For level 0:: + speed-select-turbo-freq:disabled + speed-select-base-freq:disabled + +For level 4:: + speed-select-turbo-freq:disabled + speed-select-base-freq:unsupported + +Given these results, the "speed-select-base-freq" (Intel(R) SST-BF) in level 4 +changed from "disabled" to "unsupported" compared to performance level 0. + +This means that at performance level 4, the "speed-select-base-freq" feature is +not supported. However, at performance level 0, this feature is "supported", but +currently "disabled", meaning the user has not activated this feature. Whereas +"speed-select-turbo-freq" (Intel(R) SST-TF) is supported at both performance +levels, but currently not activated by the user. + +The Intel(R) SST-BF and the Intel(R) SST-TF features are built on a foundation +technology called Intel(R) Speed Select Technology - Core Power (Intel(R) SST-CP). +The platform firmware enables this feature when Intel(R) SST-BF or Intel(R) SST-TF +is supported on a platform. + +Intel(R) Speed Select Technology Core Power (Intel(R) SST-CP) +--------------------------------------------------------------- + +Intel(R) Speed Select Technology Core Power (Intel(R) SST-CP) is an interface that +allows users to define per core priority. This defines a mechanism to distribute +power among cores when there is a power constrained scenario. This defines a +class of service (CLOS) configuration. + +The user can configure up to 4 class of service configurations. Each CLOS group +configuration allows definitions of parameters, which affects how the frequency +can be limited and power is distributed. Each CPU core can be tied to a class of +service and hence an associated priority. The granularity is at core level not +at per CPU level. + +Enable CLOS based prioritization +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To use CLOS based prioritization feature, firmware must be informed to enable +and use a priority type. There is a default per platform priority type, which +can be changed with optional command line parameter. + +To enable and check the options, execute:: + + # intel-speed-select core-power enable --help + Intel(R) Speed Select Technology + Executing on CPU model: X + Enable core-power for a package/die + Clos Enable: Specify priority type with [--priority|-p] + 0: Proportional, 1: Ordered + +There are two types of priority types: + +- Ordered + +Priority for ordered throttling is defined based on the index of the assigned +CLOS group. Where CLOS0 gets highest priority (throttled last). + +Priority order is: +CLOS0 > CLOS1 > CLOS2 > CLOS3. + +- Proportional + +When proportional priority is used, there is an additional parameter called +frequency_weight, which can be specified per CLOS group. The goal of +proportional priority is to provide each core with the requested min., then +distribute all remaining (excess/deficit) budgets in proportion to a defined +weight. This proportional priority can be configured using "core-power config" +command. + +To enable with the platform default priority type, execute:: + + # intel-speed-select core-power enable + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + core-power + enable:success + package-1 + die-0 + cpu-6 + core-power + enable:success + +The scope of this enable is per package or die scoped when a package contains +multiple dies. To check if CLOS is enabled and get priority type, "core-power +info" command can be used. For example to check the status of core-power feature +on CPU 0, execute:: + + # intel-speed-select -c 0 core-power info + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + core-power + support-status:supported + enable-status:enabled + clos-enable-status:enabled + priority-type:proportional + package-1 + die-0 + cpu-24 + core-power + support-status:supported + enable-status:enabled + clos-enable-status:enabled + priority-type:proportional + +Configuring CLOS groups +~~~~~~~~~~~~~~~~~~~~~~~ + +Each CLOS group has its own attributes including min, max, freq_weight and +desired. These parameters can be configured with "core-power config" command. +Defaults will be used if user skips setting a parameter except clos id, which is +mandatory. To check core-power config options, execute:: + + # intel-speed-select core-power config --help + Intel(R) Speed Select Technology + Executing on CPU model: X + Set core-power configuration for one of the four clos ids + Specify targeted clos id with [--clos|-c] + Specify clos Proportional Priority [--weight|-w] + Specify clos min in MHz with [--min|-n] + Specify clos max in MHz with [--max|-m] + +For example:: + + # intel-speed-select core-power config -c 0 + Intel(R) Speed Select Technology + Executing on CPU model: X + clos epp is not specified, default: 0 + clos frequency weight is not specified, default: 0 + clos min is not specified, default: 0 MHz + clos max is not specified, default: 25500 MHz + clos desired is not specified, default: 0 + package-0 + die-0 + cpu-0 + core-power + config:success + package-1 + die-0 + cpu-6 + core-power + config:success + +The user has the option to change defaults. For example, the user can change the +"min" and set the base frequency to always get guaranteed base frequency. + +Get the current CLOS configuration +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To check the current configuration, "core-power get-config" can be used. For +example, to get the configuration of CLOS 0:: + + # intel-speed-select core-power get-config -c 0 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + core-power + clos:0 + epp:0 + clos-proportional-priority:0 + clos-min:0 MHz + clos-max:Max Turbo frequency + clos-desired:0 MHz + package-1 + die-0 + cpu-24 + core-power + clos:0 + epp:0 + clos-proportional-priority:0 + clos-min:0 MHz + clos-max:Max Turbo frequency + clos-desired:0 MHz + +Associating a CPU with a CLOS group +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To associate a CPU to a CLOS group "core-power assoc" command can be used:: + + # intel-speed-select core-power assoc --help + Intel(R) Speed Select Technology + Executing on CPU model: X + Associate a clos id to a CPU + Specify targeted clos id with [--clos|-c] + + +For example to associate CPU 10 to CLOS group 3, execute:: + + # intel-speed-select -c 10 core-power assoc -c 3 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-10 + core-power + assoc:success + +Once a CPU is associated, its sibling CPUs are also associated to a CLOS group. +Once associated, avoid changing Linux "cpufreq" subsystem scaling frequency +limits. + +To check the existing association for a CPU, "core-power get-assoc" command can +be used. For example, to get association of CPU 10, execute:: + + # intel-speed-select -c 10 core-power get-assoc + Intel(R) Speed Select Technology + Executing on CPU model: X + package-1 + die-0 + cpu-10 + get-assoc + clos:3 + +This shows that CPU 10 is part of a CLOS group 3. + + +Disable CLOS based prioritization +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To disable, execute:: + +# intel-speed-select core-power disable + +Some features like Intel(R) SST-TF can only be enabled when CLOS based prioritization +is enabled. For this reason, disabling while Intel(R) SST-TF is enabled can cause +Intel(R) SST-TF to fail. This will cause the "disable" command to display an error +if Intel(R) SST-TF is already enabled. In turn, to disable, the Intel(R) SST-TF +feature must be disabled first. + +Intel(R) Speed Select Technology - Base Frequency (Intel(R) SST-BF) +------------------------------------------------------------------- + +The Intel(R) Speed Select Technology - Base Frequency (Intel(R) SST-BF) feature lets +the user control base frequency. If some critical workload threads demand +constant high guaranteed performance, then this feature can be used to execute +the thread at higher base frequency on specific sets of CPUs (high priority +CPUs) at the cost of lower base frequency (low priority CPUs) on other CPUs. +This feature does not require offline of the low priority CPUs. + +The support of Intel(R) SST-BF depends on the Intel(R) Speed Select Technology - +Performance Profile (Intel(R) SST-PP) performance level configuration. It is +possible that only certain performance levels support Intel(R) SST-BF. It is also +possible that only base performance level (level = 0) has support of Intel +SST-BF. Consequently, first select the desired performance level to enable this +feature. + +In the system under test here, Intel(R) SST-BF is supported at the base +performance level 0, but currently disabled. For example for the level 0:: + + # intel-speed-select -c 0 perf-profile info -l 0 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + perf-profile-level-0 + ... + + speed-select-base-freq:disabled + ... + +Before enabling Intel(R) SST-BF and measuring its impact on a workload +performance, execute some workload and measure performance and get a baseline +performance to compare against. + +Here the user wants more guaranteed performance. For this reason, it is likely +that turbo is disabled. To disable turbo, execute:: + +#echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo + +Based on the output of the "intel-speed-select perf-profile info -l 0" base +frequency of guaranteed frequency 2600 MHz. + + +Measure baseline performance for comparison +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To compare, pick a multi-threaded workload where each thread can be scheduled on +separate CPUs. "Hackbench pipe" test is a good example on how to improve +performance using Intel(R) SST-BF. + +Below, the workload is measuring average scheduler wakeup latency, so a lower +number means better performance:: + + # taskset -c 3,4 perf bench -r 100 sched pipe + # Running 'sched/pipe' benchmark: + # Executed 1000000 pipe operations between two processes + Total time: 6.102 [sec] + 6.102445 usecs/op + 163868 ops/sec + +While running the above test, if we take turbostat output, it will show us that +2 of the CPUs are busy and reaching max. frequency (which would be the base +frequency as the turbo is disabled). The turbostat output:: + + #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1 + Package Core CPU Bzy_MHz + 0 0 0 1000 + 0 1 1 1005 + 0 2 2 1000 + 0 3 3 2600 + 0 4 4 2600 + 0 5 5 1000 + 0 6 6 1000 + 0 7 7 1005 + 0 8 8 1005 + 0 9 9 1000 + 0 10 10 1000 + 0 11 11 995 + 0 12 12 1000 + 0 13 13 1000 + +From the above turbostat output, both CPU 3 and 4 are very busy and reaching +full guaranteed frequency of 2600 MHz. + +Intel(R) SST-BF Capabilities +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To get capabilities of Intel(R) SST-BF for the current performance level 0, +execute:: + + # intel-speed-select base-freq info -l 0 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + speed-select-base-freq + high-priority-base-frequency(MHz):3000 + high-priority-cpu-mask:00000216,00002160 + high-priority-cpu-list:5,6,8,13,33,34,36,41 + low-priority-base-frequency(MHz):2400 + tjunction-temperature(C):125 + thermal-design-power(W):205 + +The above capabilities show that there are some CPUs on this system that can +offer base frequency of 3000 MHz compared to the standard base frequency at this +performance levels. Nevertheless, these CPUs are fixed, and they are presented +via high-priority-cpu-list/high-priority-cpu-mask. But if this Intel(R) SST-BF +feature is selected, the low priorities CPUs (which are not in +high-priority-cpu-list) can only offer up to 2400 MHz. As a result, if this +clipping of low priority CPUs is acceptable, then the user can enable Intel +SST-BF feature particularly for the above "sched pipe" workload since only two +CPUs are used, they can be scheduled on high priority CPUs and can get boost of +400 MHz. + +Enable Intel(R) SST-BF +~~~~~~~~~~~~~~~~~~~~~~ + +To enable Intel(R) SST-BF feature, execute:: + + # intel-speed-select base-freq enable -a + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + base-freq + enable:success + package-1 + die-0 + cpu-14 + base-freq + enable:success + +In this case, -a option is optional. This not only enables Intel(R) SST-BF, but it +also adjusts the priority of cores using Intel(R) Speed Select Technology Core +Power (Intel(R) SST-CP) features. This option sets the minimum performance of each +Intel(R) Speed Select Technology - Performance Profile (Intel(R) SST-PP) class to +maximum performance so that the hardware will give maximum performance possible +for each CPU. + +If -a option is not used, then the following steps are required before enabling +Intel(R) SST-BF: + +- Discover Intel(R) SST-BF and note low and high priority base frequency +- Note the high priority CPU list +- Enable CLOS using core-power feature set +- Configure CLOS parameters. Use CLOS.min to set to minimum performance +- Subscribe desired CPUs to CLOS groups + +With this configuration, if the same workload is executed by pinning the +workload to high priority CPUs (CPU 5 and 6 in this case):: + + #taskset -c 5,6 perf bench -r 100 sched pipe + # Running 'sched/pipe' benchmark: + # Executed 1000000 pipe operations between two processes + Total time: 5.627 [sec] + 5.627922 usecs/op + 177685 ops/sec + +This way, by enabling Intel(R) SST-BF, the performance of this benchmark is +improved (latency reduced) by 7.79%. From the turbostat output, it can be +observed that the high priority CPUs reached 3000 MHz compared to 2600 MHz. +The turbostat output:: + + #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1 + Package Core CPU Bzy_MHz + 0 0 0 2151 + 0 1 1 2166 + 0 2 2 2175 + 0 3 3 2175 + 0 4 4 2175 + 0 5 5 3000 + 0 6 6 3000 + 0 7 7 2180 + 0 8 8 2662 + 0 9 9 2176 + 0 10 10 2175 + 0 11 11 2176 + 0 12 12 2176 + 0 13 13 2661 + +Disable Intel(R) SST-BF +~~~~~~~~~~~~~~~~~~~~~~~ + +To disable the Intel(R) SST-BF feature, execute:: + +# intel-speed-select base-freq disable -a + + +Intel(R) Speed Select Technology - Turbo Frequency (Intel(R) SST-TF) +-------------------------------------------------------------------- + +This feature enables the ability to set different "All core turbo ratio limits" +to cores based on the priority. By using this feature, some cores can be +configured to get higher turbo frequency by designating them as high priority at +the cost of lower or no turbo frequency on the low priority cores. + +For this reason, this feature is only useful when system is busy utilizing all +CPUs, but the user wants some configurable option to get high performance on +some CPUs. + +The support of Intel(R) Speed Select Technology - Turbo Frequency (Intel(R) SST-TF) +depends on the Intel(R) Speed Select Technology - Performance Profile (Intel +SST-PP) performance level configuration. It is possible that only a certain +performance level supports Intel(R) SST-TF. It is also possible that only the base +performance level (level = 0) has the support of Intel(R) SST-TF. Hence, first +select the desired performance level to enable this feature. + +In the system under test here, Intel(R) SST-TF is supported at the base +performance level 0, but currently disabled:: + + # intel-speed-select -c 0 perf-profile info -l 0 + Intel(R) Speed Select Technology + package-0 + die-0 + cpu-0 + perf-profile-level-0 + ... + ... + speed-select-turbo-freq:disabled + ... + ... + + +To check if performance can be improved using Intel(R) SST-TF feature, get the turbo +frequency properties with Intel(R) SST-TF enabled and compare to the base turbo +capability of this system. + +Get Base turbo capability +~~~~~~~~~~~~~~~~~~~~~~~~~ + +To get the base turbo capability of performance level 0, execute:: + + # intel-speed-select perf-profile info -l 0 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + perf-profile-level-0 + ... + ... + turbo-ratio-limits-sse + bucket-0 + core-count:2 + max-turbo-frequency(MHz):3200 + bucket-1 + core-count:4 + max-turbo-frequency(MHz):3100 + bucket-2 + core-count:6 + max-turbo-frequency(MHz):3100 + bucket-3 + core-count:8 + max-turbo-frequency(MHz):3100 + bucket-4 + core-count:10 + max-turbo-frequency(MHz):3100 + bucket-5 + core-count:12 + max-turbo-frequency(MHz):3100 + bucket-6 + core-count:14 + max-turbo-frequency(MHz):3100 + bucket-7 + core-count:16 + max-turbo-frequency(MHz):3100 + +Based on the data above, when all the CPUS are busy, the max. frequency of 3100 +MHz can be achieved. If there is some busy workload on cpu 0 - 11 (e.g. stress) +and on CPU 12 and 13, execute "hackbench pipe" workload:: + + # taskset -c 12,13 perf bench -r 100 sched pipe + # Running 'sched/pipe' benchmark: + # Executed 1000000 pipe operations between two processes + Total time: 5.705 [sec] + 5.705488 usecs/op + 175269 ops/sec + +The turbostat output:: + + #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1 + Package Core CPU Bzy_MHz + 0 0 0 3000 + 0 1 1 3000 + 0 2 2 3000 + 0 3 3 3000 + 0 4 4 3000 + 0 5 5 3100 + 0 6 6 3100 + 0 7 7 3000 + 0 8 8 3100 + 0 9 9 3000 + 0 10 10 3000 + 0 11 11 3000 + 0 12 12 3100 + 0 13 13 3100 + +Based on turbostat output, the performance is limited by frequency cap of 3100 +MHz. To check if the hackbench performance can be improved for CPU 12 and CPU +13, first check the capability of the Intel(R) SST-TF feature for this performance +level. + +Get Intel(R) SST-TF Capability +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To get the capability, the "turbo-freq info" command can be used:: + + # intel-speed-select turbo-freq info -l 0 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + speed-select-turbo-freq + bucket-0 + high-priority-cores-count:2 + high-priority-max-frequency(MHz):3200 + high-priority-max-avx2-frequency(MHz):3200 + high-priority-max-avx512-frequency(MHz):3100 + bucket-1 + high-priority-cores-count:4 + high-priority-max-frequency(MHz):3100 + high-priority-max-avx2-frequency(MHz):3000 + high-priority-max-avx512-frequency(MHz):2900 + bucket-2 + high-priority-cores-count:6 + high-priority-max-frequency(MHz):3100 + high-priority-max-avx2-frequency(MHz):3000 + high-priority-max-avx512-frequency(MHz):2900 + speed-select-turbo-freq-clip-frequencies + low-priority-max-frequency(MHz):2600 + low-priority-max-avx2-frequency(MHz):2400 + low-priority-max-avx512-frequency(MHz):2100 + +Based on the output above, there is an Intel(R) SST-TF bucket for which there are +two high priority cores. If only two high priority cores are set, then max. +turbo frequency on those cores can be increased to 3200 MHz. This is 100 MHz +more than the base turbo capability for all cores. + +In turn, for the hackbench workload, two CPUs can be set as high priority and +rest as low priority. One side effect is that once enabled, the low priority +cores will be clipped to a lower frequency of 2600 MHz. + +Enable Intel(R) SST-TF +~~~~~~~~~~~~~~~~~~~~~~ + +To enable Intel(R) SST-TF, execute:: + + # intel-speed-select -c 12,13 turbo-freq enable -a + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-12 + turbo-freq + enable:success + package-0 + die-0 + cpu-13 + turbo-freq + enable:success + package--1 + die-0 + cpu-63 + turbo-freq --auto + enable:success + +In this case, the option "-a" is optional. If set, it enables Intel(R) SST-TF +feature and also sets the CPUs to high and low priority using Intel Speed +Select Technology Core Power (Intel(R) SST-CP) features. The CPU numbers passed +with "-c" arguments are marked as high priority, including its siblings. + +If -a option is not used, then the following steps are required before enabling +Intel(R) SST-TF: + +- Discover Intel(R) SST-TF and note buckets of high priority cores and maximum frequency + +- Enable CLOS using core-power feature set - Configure CLOS parameters + +- Subscribe desired CPUs to CLOS groups making sure that high priority cores are set to the maximum frequency + +If the same hackbench workload is executed, schedule hackbench threads on high +priority CPUs:: + + #taskset -c 12,13 perf bench -r 100 sched pipe + # Running 'sched/pipe' benchmark: + # Executed 1000000 pipe operations between two processes + Total time: 5.510 [sec] + 5.510165 usecs/op + 180826 ops/sec + +This improved performance by around 3.3% improvement on a busy system. Here the +turbostat output will show that the CPU 12 and CPU 13 are getting 100 MHz boost. +The turbostat output:: + + #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1 + Package Core CPU Bzy_MHz + ... + 0 12 12 3200 + 0 13 13 3200 diff --git a/Documentation/admin-guide/pm/intel_epb.rst b/Documentation/admin-guide/pm/intel_epb.rst new file mode 100644 index 000000000..005121167 --- /dev/null +++ b/Documentation/admin-guide/pm/intel_epb.rst @@ -0,0 +1,41 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + +====================================== +Intel Performance and Energy Bias Hint +====================================== + +:Copyright: |copy| 2019 Intel Corporation + +:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> + + +.. kernel-doc:: arch/x86/kernel/cpu/intel_epb.c + :doc: overview + +Intel Performance and Energy Bias Attribute in ``sysfs`` +======================================================== + +The Intel Performance and Energy Bias Hint (EPB) value for a given (logical) CPU +can be checked or updated through a ``sysfs`` attribute (file) under +:file:`/sys/devices/system/cpu/cpu<N>/power/`, where the CPU number ``<N>`` +is allocated at the system initialization time: + +``energy_perf_bias`` + Shows the current EPB value for the CPU in a sliding scale 0 - 15, where + a value of 0 corresponds to a hint preference for highest performance + and a value of 15 corresponds to the maximum energy savings. + + In order to update the EPB value for the CPU, this attribute can be + written to, either with a number in the 0 - 15 sliding scale above, or + with one of the strings: "performance", "balance-performance", "normal", + "balance-power", "power" that represent values reflected by their + meaning. + + This attribute is present for all online CPUs supporting the EPB + feature. + +Note that while the EPB interface to the processor is defined at the logical CPU +level, the physical register backing it may be shared by multiple CPUs (for +example, SMT siblings or cores in one package). For this reason, updating the +EPB value for one CPU may cause the EPB values for other CPUs to change. diff --git a/Documentation/admin-guide/pm/intel_idle.rst b/Documentation/admin-guide/pm/intel_idle.rst new file mode 100644 index 000000000..b799a43da --- /dev/null +++ b/Documentation/admin-guide/pm/intel_idle.rst @@ -0,0 +1,272 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + +============================================== +``intel_idle`` CPU Idle Time Management Driver +============================================== + +:Copyright: |copy| 2020 Intel Corporation + +:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> + + +General Information +=================== + +``intel_idle`` is a part of the +:doc:`CPU idle time management subsystem <cpuidle>` in the Linux kernel +(``CPUIdle``). It is the default CPU idle time management driver for the +Nehalem and later generations of Intel processors, but the level of support for +a particular processor model in it depends on whether or not it recognizes that +processor model and may also depend on information coming from the platform +firmware. [To understand ``intel_idle`` it is necessary to know how ``CPUIdle`` +works in general, so this is the time to get familiar with +Documentation/admin-guide/pm/cpuidle.rst if you have not done that yet.] + +``intel_idle`` uses the ``MWAIT`` instruction to inform the processor that the +logical CPU executing it is idle and so it may be possible to put some of the +processor's functional blocks into low-power states. That instruction takes two +arguments (passed in the ``EAX`` and ``ECX`` registers of the target CPU), the +first of which, referred to as a *hint*, can be used by the processor to +determine what can be done (for details refer to Intel Software Developer’s +Manual [1]_). Accordingly, ``intel_idle`` refuses to work with processors in +which the support for the ``MWAIT`` instruction has been disabled (for example, +via the platform firmware configuration menu) or which do not support that +instruction at all. + +``intel_idle`` is not modular, so it cannot be unloaded, which means that the +only way to pass early-configuration-time parameters to it is via the kernel +command line. + + +.. _intel-idle-enumeration-of-states: + +Enumeration of Idle States +========================== + +Each ``MWAIT`` hint value is interpreted by the processor as a license to +reconfigure itself in a certain way in order to save energy. The processor +configurations (with reduced power draw) resulting from that are referred to +as C-states (in the ACPI terminology) or idle states. The list of meaningful +``MWAIT`` hint values and idle states (i.e. low-power configurations of the +processor) corresponding to them depends on the processor model and it may also +depend on the configuration of the platform. + +In order to create a list of available idle states required by the ``CPUIdle`` +subsystem (see :ref:`idle-states-representation` in +Documentation/admin-guide/pm/cpuidle.rst), +``intel_idle`` can use two sources of information: static tables of idle states +for different processor models included in the driver itself and the ACPI tables +of the system. The former are always used if the processor model at hand is +recognized by ``intel_idle`` and the latter are used if that is required for +the given processor model (which is the case for all server processor models +recognized by ``intel_idle``) or if the processor model is not recognized. +[There is a module parameter that can be used to make the driver use the ACPI +tables with any processor model recognized by it; see +`below <intel-idle-parameters_>`_.] + +If the ACPI tables are going to be used for building the list of available idle +states, ``intel_idle`` first looks for a ``_CST`` object under one of the ACPI +objects corresponding to the CPUs in the system (refer to the ACPI specification +[2]_ for the description of ``_CST`` and its output package). Because the +``CPUIdle`` subsystem expects that the list of idle states supplied by the +driver will be suitable for all of the CPUs handled by it and ``intel_idle`` is +registered as the ``CPUIdle`` driver for all of the CPUs in the system, the +driver looks for the first ``_CST`` object returning at least one valid idle +state description and such that all of the idle states included in its return +package are of the FFH (Functional Fixed Hardware) type, which means that the +``MWAIT`` instruction is expected to be used to tell the processor that it can +enter one of them. The return package of that ``_CST`` is then assumed to be +applicable to all of the other CPUs in the system and the idle state +descriptions extracted from it are stored in a preliminary list of idle states +coming from the ACPI tables. [This step is skipped if ``intel_idle`` is +configured to ignore the ACPI tables; see `below <intel-idle-parameters_>`_.] + +Next, the first (index 0) entry in the list of available idle states is +initialized to represent a "polling idle state" (a pseudo-idle state in which +the target CPU continuously fetches and executes instructions), and the +subsequent (real) idle state entries are populated as follows. + +If the processor model at hand is recognized by ``intel_idle``, there is a +(static) table of idle state descriptions for it in the driver. In that case, +the "internal" table is the primary source of information on idle states and the +information from it is copied to the final list of available idle states. If +using the ACPI tables for the enumeration of idle states is not required +(depending on the processor model), all of the listed idle state are enabled by +default (so all of them will be taken into consideration by ``CPUIdle`` +governors during CPU idle state selection). Otherwise, some of the listed idle +states may not be enabled by default if there are no matching entries in the +preliminary list of idle states coming from the ACPI tables. In that case user +space still can enable them later (on a per-CPU basis) with the help of +the ``disable`` idle state attribute in ``sysfs`` (see +:ref:`idle-states-representation` in +Documentation/admin-guide/pm/cpuidle.rst). This basically means that +the idle states "known" to the driver may not be enabled by default if they have +not been exposed by the platform firmware (through the ACPI tables). + +If the given processor model is not recognized by ``intel_idle``, but it +supports ``MWAIT``, the preliminary list of idle states coming from the ACPI +tables is used for building the final list that will be supplied to the +``CPUIdle`` core during driver registration. For each idle state in that list, +the description, ``MWAIT`` hint and exit latency are copied to the corresponding +entry in the final list of idle states. The name of the idle state represented +by it (to be returned by the ``name`` idle state attribute in ``sysfs``) is +"CX_ACPI", where X is the index of that idle state in the final list (note that +the minimum value of X is 1, because 0 is reserved for the "polling" state), and +its target residency is based on the exit latency value. Specifically, for +C1-type idle states the exit latency value is also used as the target residency +(for compatibility with the majority of the "internal" tables of idle states for +various processor models recognized by ``intel_idle``) and for the other idle +state types (C2 and C3) the target residency value is 3 times the exit latency +(again, that is because it reflects the target residency to exit latency ratio +in the majority of cases for the processor models recognized by ``intel_idle``). +All of the idle states in the final list are enabled by default in this case. + + +.. _intel-idle-initialization: + +Initialization +============== + +The initialization of ``intel_idle`` starts with checking if the kernel command +line options forbid the use of the ``MWAIT`` instruction. If that is the case, +an error code is returned right away. + +The next step is to check whether or not the processor model is known to the +driver, which determines the idle states enumeration method (see +`above <intel-idle-enumeration-of-states_>`_), and whether or not the processor +supports ``MWAIT`` (the initialization fails if that is not the case). Then, +the ``MWAIT`` support in the processor is enumerated through ``CPUID`` and the +driver initialization fails if the level of support is not as expected (for +example, if the total number of ``MWAIT`` substates returned is 0). + +Next, if the driver is not configured to ignore the ACPI tables (see +`below <intel-idle-parameters_>`_), the idle states information provided by the +platform firmware is extracted from them. + +Then, ``CPUIdle`` device objects are allocated for all CPUs and the list of +available idle states is created as explained +`above <intel-idle-enumeration-of-states_>`_. + +Finally, ``intel_idle`` is registered with the help of cpuidle_register_driver() +as the ``CPUIdle`` driver for all CPUs in the system and a CPU online callback +for configuring individual CPUs is registered via cpuhp_setup_state(), which +(among other things) causes the callback routine to be invoked for all of the +CPUs present in the system at that time (each CPU executes its own instance of +the callback routine). That routine registers a ``CPUIdle`` device for the CPU +running it (which enables the ``CPUIdle`` subsystem to operate that CPU) and +optionally performs some CPU-specific initialization actions that may be +required for the given processor model. + + +.. _intel-idle-parameters: + +Kernel Command Line Options and Module Parameters +================================================= + +The *x86* architecture support code recognizes three kernel command line +options related to CPU idle time management: ``idle=poll``, ``idle=halt``, +and ``idle=nomwait``. If any of them is present in the kernel command line, the +``MWAIT`` instruction is not allowed to be used, so the initialization of +``intel_idle`` will fail. + +Apart from that there are four module parameters recognized by ``intel_idle`` +itself that can be set via the kernel command line (they cannot be updated via +sysfs, so that is the only way to change their values). + +The ``max_cstate`` parameter value is the maximum idle state index in the list +of idle states supplied to the ``CPUIdle`` core during the registration of the +driver. It is also the maximum number of regular (non-polling) idle states that +can be used by ``intel_idle``, so the enumeration of idle states is terminated +after finding that number of usable idle states (the other idle states that +potentially might have been used if ``max_cstate`` had been greater are not +taken into consideration at all). Setting ``max_cstate`` can prevent +``intel_idle`` from exposing idle states that are regarded as "too deep" for +some reason to the ``CPUIdle`` core, but it does so by making them effectively +invisible until the system is shut down and started again which may not always +be desirable. In practice, it is only really necessary to do that if the idle +states in question cannot be enabled during system startup, because in the +working state of the system the CPU power management quality of service (PM +QoS) feature can be used to prevent ``CPUIdle`` from touching those idle states +even if they have been enumerated (see :ref:`cpu-pm-qos` in +Documentation/admin-guide/pm/cpuidle.rst). +Setting ``max_cstate`` to 0 causes the ``intel_idle`` initialization to fail. + +The ``no_acpi`` and ``use_acpi`` module parameters (recognized by ``intel_idle`` +if the kernel has been configured with ACPI support) can be set to make the +driver ignore the system's ACPI tables entirely or use them for all of the +recognized processor models, respectively (they both are unset by default and +``use_acpi`` has no effect if ``no_acpi`` is set). + +The value of the ``states_off`` module parameter (0 by default) represents a +list of idle states to be disabled by default in the form of a bitmask. + +Namely, the positions of the bits that are set in the ``states_off`` value are +the indices of idle states to be disabled by default (as reflected by the names +of the corresponding idle state directories in ``sysfs``, :file:`state0`, +:file:`state1` ... :file:`state<i>` ..., where ``<i>`` is the index of the given +idle state; see :ref:`idle-states-representation` in +Documentation/admin-guide/pm/cpuidle.rst). + +For example, if ``states_off`` is equal to 3, the driver will disable idle +states 0 and 1 by default, and if it is equal to 8, idle state 3 will be +disabled by default and so on (bit positions beyond the maximum idle state index +are ignored). + +The idle states disabled this way can be enabled (on a per-CPU basis) from user +space via ``sysfs``. + + +.. _intel-idle-core-and-package-idle-states: + +Core and Package Levels of Idle States +====================================== + +Typically, in a processor supporting the ``MWAIT`` instruction there are (at +least) two levels of idle states (or C-states). One level, referred to as +"core C-states", covers individual cores in the processor, whereas the other +level, referred to as "package C-states", covers the entire processor package +and it may also involve other components of the system (GPUs, memory +controllers, I/O hubs etc.). + +Some of the ``MWAIT`` hint values allow the processor to use core C-states only +(most importantly, that is the case for the ``MWAIT`` hint value corresponding +to the ``C1`` idle state), but the majority of them give it a license to put +the target core (i.e. the core containing the logical CPU executing ``MWAIT`` +with the given hint value) into a specific core C-state and then (if possible) +to enter a specific package C-state at the deeper level. For example, the +``MWAIT`` hint value representing the ``C3`` idle state allows the processor to +put the target core into the low-power state referred to as "core ``C3``" (or +``CC3``), which happens if all of the logical CPUs (SMT siblings) in that core +have executed ``MWAIT`` with the ``C3`` hint value (or with a hint value +representing a deeper idle state), and in addition to that (in the majority of +cases) it gives the processor a license to put the entire package (possibly +including some non-CPU components such as a GPU or a memory controller) into the +low-power state referred to as "package ``C3``" (or ``PC3``), which happens if +all of the cores have gone into the ``CC3`` state and (possibly) some additional +conditions are satisfied (for instance, if the GPU is covered by ``PC3``, it may +be required to be in a certain GPU-specific low-power state for ``PC3`` to be +reachable). + +As a rule, there is no simple way to make the processor use core C-states only +if the conditions for entering the corresponding package C-states are met, so +the logical CPU executing ``MWAIT`` with a hint value that is not core-level +only (like for ``C1``) must always assume that this may cause the processor to +enter a package C-state. [That is why the exit latency and target residency +values corresponding to the majority of ``MWAIT`` hint values in the "internal" +tables of idle states in ``intel_idle`` reflect the properties of package +C-states.] If using package C-states is not desirable at all, either +:ref:`PM QoS <cpu-pm-qos>` or the ``max_cstate`` module parameter of +``intel_idle`` described `above <intel-idle-parameters_>`_ must be used to +restrict the range of permissible idle states to the ones with core-level only +``MWAIT`` hint values (like ``C1``). + + +References +========== + +.. [1] *Intel® 64 and IA-32 Architectures Software Developer’s Manual Volume 2B*, + https://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-vol-2b-manual.html + +.. [2] *Advanced Configuration and Power Interface (ACPI) Specification*, + https://uefi.org/specifications diff --git a/Documentation/admin-guide/pm/intel_pstate.rst b/Documentation/admin-guide/pm/intel_pstate.rst new file mode 100644 index 000000000..bf13ad25a --- /dev/null +++ b/Documentation/admin-guide/pm/intel_pstate.rst @@ -0,0 +1,770 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + +=============================================== +``intel_pstate`` CPU Performance Scaling Driver +=============================================== + +:Copyright: |copy| 2017 Intel Corporation + +:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> + + +General Information +=================== + +``intel_pstate`` is a part of the +:doc:`CPU performance scaling subsystem <cpufreq>` in the Linux kernel +(``CPUFreq``). It is a scaling driver for the Sandy Bridge and later +generations of Intel processors. Note, however, that some of those processors +may not be supported. [To understand ``intel_pstate`` it is necessary to know +how ``CPUFreq`` works in general, so this is the time to read +Documentation/admin-guide/pm/cpufreq.rst if you have not done that yet.] + +For the processors supported by ``intel_pstate``, the P-state concept is broader +than just an operating frequency or an operating performance point (see the +LinuxCon Europe 2015 presentation by Kristen Accardi [1]_ for more +information about that). For this reason, the representation of P-states used +by ``intel_pstate`` internally follows the hardware specification (for details +refer to Intel Software Developer’s Manual [2]_). However, the ``CPUFreq`` core +uses frequencies for identifying operating performance points of CPUs and +frequencies are involved in the user space interface exposed by it, so +``intel_pstate`` maps its internal representation of P-states to frequencies too +(fortunately, that mapping is unambiguous). At the same time, it would not be +practical for ``intel_pstate`` to supply the ``CPUFreq`` core with a table of +available frequencies due to the possible size of it, so the driver does not do +that. Some functionality of the core is limited by that. + +Since the hardware P-state selection interface used by ``intel_pstate`` is +available at the logical CPU level, the driver always works with individual +CPUs. Consequently, if ``intel_pstate`` is in use, every ``CPUFreq`` policy +object corresponds to one logical CPU and ``CPUFreq`` policies are effectively +equivalent to CPUs. In particular, this means that they become "inactive" every +time the corresponding CPU is taken offline and need to be re-initialized when +it goes back online. + +``intel_pstate`` is not modular, so it cannot be unloaded, which means that the +only way to pass early-configuration-time parameters to it is via the kernel +command line. However, its configuration can be adjusted via ``sysfs`` to a +great extent. In some configurations it even is possible to unregister it via +``sysfs`` which allows another ``CPUFreq`` scaling driver to be loaded and +registered (see `below <status_attr_>`_). + + +Operation Modes +=============== + +``intel_pstate`` can operate in two different modes, active or passive. In the +active mode, it uses its own internal performance scaling governor algorithm or +allows the hardware to do performance scaling by itself, while in the passive +mode it responds to requests made by a generic ``CPUFreq`` governor implementing +a certain performance scaling algorithm. Which of them will be in effect +depends on what kernel command line options are used and on the capabilities of +the processor. + +Active Mode +----------- + +This is the default operation mode of ``intel_pstate`` for processors with +hardware-managed P-states (HWP) support. If it works in this mode, the +``scaling_driver`` policy attribute in ``sysfs`` for all ``CPUFreq`` policies +contains the string "intel_pstate". + +In this mode the driver bypasses the scaling governors layer of ``CPUFreq`` and +provides its own scaling algorithms for P-state selection. Those algorithms +can be applied to ``CPUFreq`` policies in the same way as generic scaling +governors (that is, through the ``scaling_governor`` policy attribute in +``sysfs``). [Note that different P-state selection algorithms may be chosen for +different policies, but that is not recommended.] + +They are not generic scaling governors, but their names are the same as the +names of some of those governors. Moreover, confusingly enough, they generally +do not work in the same way as the generic governors they share the names with. +For example, the ``powersave`` P-state selection algorithm provided by +``intel_pstate`` is not a counterpart of the generic ``powersave`` governor +(roughly, it corresponds to the ``schedutil`` and ``ondemand`` governors). + +There are two P-state selection algorithms provided by ``intel_pstate`` in the +active mode: ``powersave`` and ``performance``. The way they both operate +depends on whether or not the hardware-managed P-states (HWP) feature has been +enabled in the processor and possibly on the processor model. + +Which of the P-state selection algorithms is used by default depends on the +:c:macro:`CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE` kernel configuration option. +Namely, if that option is set, the ``performance`` algorithm will be used by +default, and the other one will be used by default if it is not set. + +Active Mode With HWP +~~~~~~~~~~~~~~~~~~~~ + +If the processor supports the HWP feature, it will be enabled during the +processor initialization and cannot be disabled after that. It is possible +to avoid enabling it by passing the ``intel_pstate=no_hwp`` argument to the +kernel in the command line. + +If the HWP feature has been enabled, ``intel_pstate`` relies on the processor to +select P-states by itself, but still it can give hints to the processor's +internal P-state selection logic. What those hints are depends on which P-state +selection algorithm has been applied to the given policy (or to the CPU it +corresponds to). + +Even though the P-state selection is carried out by the processor automatically, +``intel_pstate`` registers utilization update callbacks with the CPU scheduler +in this mode. However, they are not used for running a P-state selection +algorithm, but for periodic updates of the current CPU frequency information to +be made available from the ``scaling_cur_freq`` policy attribute in ``sysfs``. + +HWP + ``performance`` +..................... + +In this configuration ``intel_pstate`` will write 0 to the processor's +Energy-Performance Preference (EPP) knob (if supported) or its +Energy-Performance Bias (EPB) knob (otherwise), which means that the processor's +internal P-state selection logic is expected to focus entirely on performance. + +This will override the EPP/EPB setting coming from the ``sysfs`` interface +(see `Energy vs Performance Hints`_ below). Moreover, any attempts to change +the EPP/EPB to a value different from 0 ("performance") via ``sysfs`` in this +configuration will be rejected. + +Also, in this configuration the range of P-states available to the processor's +internal P-state selection logic is always restricted to the upper boundary +(that is, the maximum P-state that the driver is allowed to use). + +HWP + ``powersave`` +................... + +In this configuration ``intel_pstate`` will set the processor's +Energy-Performance Preference (EPP) knob (if supported) or its +Energy-Performance Bias (EPB) knob (otherwise) to whatever value it was +previously set to via ``sysfs`` (or whatever default value it was +set to by the platform firmware). This usually causes the processor's +internal P-state selection logic to be less performance-focused. + +Active Mode Without HWP +~~~~~~~~~~~~~~~~~~~~~~~ + +This operation mode is optional for processors that do not support the HWP +feature or when the ``intel_pstate=no_hwp`` argument is passed to the kernel in +the command line. The active mode is used in those cases if the +``intel_pstate=active`` argument is passed to the kernel in the command line. +In this mode ``intel_pstate`` may refuse to work with processors that are not +recognized by it. [Note that ``intel_pstate`` will never refuse to work with +any processor with the HWP feature enabled.] + +In this mode ``intel_pstate`` registers utilization update callbacks with the +CPU scheduler in order to run a P-state selection algorithm, either +``powersave`` or ``performance``, depending on the ``scaling_governor`` policy +setting in ``sysfs``. The current CPU frequency information to be made +available from the ``scaling_cur_freq`` policy attribute in ``sysfs`` is +periodically updated by those utilization update callbacks too. + +``performance`` +............... + +Without HWP, this P-state selection algorithm is always the same regardless of +the processor model and platform configuration. + +It selects the maximum P-state it is allowed to use, subject to limits set via +``sysfs``, every time the driver configuration for the given CPU is updated +(e.g. via ``sysfs``). + +This is the default P-state selection algorithm if the +:c:macro:`CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE` kernel configuration option +is set. + +``powersave`` +............. + +Without HWP, this P-state selection algorithm is similar to the algorithm +implemented by the generic ``schedutil`` scaling governor except that the +utilization metric used by it is based on numbers coming from feedback +registers of the CPU. It generally selects P-states proportional to the +current CPU utilization. + +This algorithm is run by the driver's utilization update callback for the +given CPU when it is invoked by the CPU scheduler, but not more often than +every 10 ms. Like in the ``performance`` case, the hardware configuration +is not touched if the new P-state turns out to be the same as the current +one. + +This is the default P-state selection algorithm if the +:c:macro:`CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE` kernel configuration option +is not set. + +Passive Mode +------------ + +This is the default operation mode of ``intel_pstate`` for processors without +hardware-managed P-states (HWP) support. It is always used if the +``intel_pstate=passive`` argument is passed to the kernel in the command line +regardless of whether or not the given processor supports HWP. [Note that the +``intel_pstate=no_hwp`` setting causes the driver to start in the passive mode +if it is not combined with ``intel_pstate=active``.] Like in the active mode +without HWP support, in this mode ``intel_pstate`` may refuse to work with +processors that are not recognized by it if HWP is prevented from being enabled +through the kernel command line. + +If the driver works in this mode, the ``scaling_driver`` policy attribute in +``sysfs`` for all ``CPUFreq`` policies contains the string "intel_cpufreq". +Then, the driver behaves like a regular ``CPUFreq`` scaling driver. That is, +it is invoked by generic scaling governors when necessary to talk to the +hardware in order to change the P-state of a CPU (in particular, the +``schedutil`` governor can invoke it directly from scheduler context). + +While in this mode, ``intel_pstate`` can be used with all of the (generic) +scaling governors listed by the ``scaling_available_governors`` policy attribute +in ``sysfs`` (and the P-state selection algorithms described above are not +used). Then, it is responsible for the configuration of policy objects +corresponding to CPUs and provides the ``CPUFreq`` core (and the scaling +governors attached to the policy objects) with accurate information on the +maximum and minimum operating frequencies supported by the hardware (including +the so-called "turbo" frequency ranges). In other words, in the passive mode +the entire range of available P-states is exposed by ``intel_pstate`` to the +``CPUFreq`` core. However, in this mode the driver does not register +utilization update callbacks with the CPU scheduler and the ``scaling_cur_freq`` +information comes from the ``CPUFreq`` core (and is the last frequency selected +by the current scaling governor for the given policy). + + +.. _turbo: + +Turbo P-states Support +====================== + +In the majority of cases, the entire range of P-states available to +``intel_pstate`` can be divided into two sub-ranges that correspond to +different types of processor behavior, above and below a boundary that +will be referred to as the "turbo threshold" in what follows. + +The P-states above the turbo threshold are referred to as "turbo P-states" and +the whole sub-range of P-states they belong to is referred to as the "turbo +range". These names are related to the Turbo Boost technology allowing a +multicore processor to opportunistically increase the P-state of one or more +cores if there is enough power to do that and if that is not going to cause the +thermal envelope of the processor package to be exceeded. + +Specifically, if software sets the P-state of a CPU core within the turbo range +(that is, above the turbo threshold), the processor is permitted to take over +performance scaling control for that core and put it into turbo P-states of its +choice going forward. However, that permission is interpreted differently by +different processor generations. Namely, the Sandy Bridge generation of +processors will never use any P-states above the last one set by software for +the given core, even if it is within the turbo range, whereas all of the later +processor generations will take it as a license to use any P-states from the +turbo range, even above the one set by software. In other words, on those +processors setting any P-state from the turbo range will enable the processor +to put the given core into all turbo P-states up to and including the maximum +supported one as it sees fit. + +One important property of turbo P-states is that they are not sustainable. More +precisely, there is no guarantee that any CPUs will be able to stay in any of +those states indefinitely, because the power distribution within the processor +package may change over time or the thermal envelope it was designed for might +be exceeded if a turbo P-state was used for too long. + +In turn, the P-states below the turbo threshold generally are sustainable. In +fact, if one of them is set by software, the processor is not expected to change +it to a lower one unless in a thermal stress or a power limit violation +situation (a higher P-state may still be used if it is set for another CPU in +the same package at the same time, for example). + +Some processors allow multiple cores to be in turbo P-states at the same time, +but the maximum P-state that can be set for them generally depends on the number +of cores running concurrently. The maximum turbo P-state that can be set for 3 +cores at the same time usually is lower than the analogous maximum P-state for +2 cores, which in turn usually is lower than the maximum turbo P-state that can +be set for 1 core. The one-core maximum turbo P-state is thus the maximum +supported one overall. + +The maximum supported turbo P-state, the turbo threshold (the maximum supported +non-turbo P-state) and the minimum supported P-state are specific to the +processor model and can be determined by reading the processor's model-specific +registers (MSRs). Moreover, some processors support the Configurable TDP +(Thermal Design Power) feature and, when that feature is enabled, the turbo +threshold effectively becomes a configurable value that can be set by the +platform firmware. + +Unlike ``_PSS`` objects in the ACPI tables, ``intel_pstate`` always exposes +the entire range of available P-states, including the whole turbo range, to the +``CPUFreq`` core and (in the passive mode) to generic scaling governors. This +generally causes turbo P-states to be set more often when ``intel_pstate`` is +used relative to ACPI-based CPU performance scaling (see `below <acpi-cpufreq_>`_ +for more information). + +Moreover, since ``intel_pstate`` always knows what the real turbo threshold is +(even if the Configurable TDP feature is enabled in the processor), its +``no_turbo`` attribute in ``sysfs`` (described `below <no_turbo_attr_>`_) should +work as expected in all cases (that is, if set to disable turbo P-states, it +always should prevent ``intel_pstate`` from using them). + + +Processor Support +================= + +To handle a given processor ``intel_pstate`` requires a number of different +pieces of information on it to be known, including: + + * The minimum supported P-state. + + * The maximum supported `non-turbo P-state <turbo_>`_. + + * Whether or not turbo P-states are supported at all. + + * The maximum supported `one-core turbo P-state <turbo_>`_ (if turbo P-states + are supported). + + * The scaling formula to translate the driver's internal representation + of P-states into frequencies and the other way around. + +Generally, ways to obtain that information are specific to the processor model +or family. Although it often is possible to obtain all of it from the processor +itself (using model-specific registers), there are cases in which hardware +manuals need to be consulted to get to it too. + +For this reason, there is a list of supported processors in ``intel_pstate`` and +the driver initialization will fail if the detected processor is not in that +list, unless it supports the HWP feature. [The interface to obtain all of the +information listed above is the same for all of the processors supporting the +HWP feature, which is why ``intel_pstate`` works with all of them.] + + +User Space Interface in ``sysfs`` +================================= + +Global Attributes +----------------- + +``intel_pstate`` exposes several global attributes (files) in ``sysfs`` to +control its functionality at the system level. They are located in the +``/sys/devices/system/cpu/intel_pstate/`` directory and affect all CPUs. + +Some of them are not present if the ``intel_pstate=per_cpu_perf_limits`` +argument is passed to the kernel in the command line. + +``max_perf_pct`` + Maximum P-state the driver is allowed to set in percent of the + maximum supported performance level (the highest supported `turbo + P-state <turbo_>`_). + + This attribute will not be exposed if the + ``intel_pstate=per_cpu_perf_limits`` argument is present in the kernel + command line. + +``min_perf_pct`` + Minimum P-state the driver is allowed to set in percent of the + maximum supported performance level (the highest supported `turbo + P-state <turbo_>`_). + + This attribute will not be exposed if the + ``intel_pstate=per_cpu_perf_limits`` argument is present in the kernel + command line. + +``num_pstates`` + Number of P-states supported by the processor (between 0 and 255 + inclusive) including both turbo and non-turbo P-states (see + `Turbo P-states Support`_). + + This attribute is present only if the value exposed by it is the same + for all of the CPUs in the system. + + The value of this attribute is not affected by the ``no_turbo`` + setting described `below <no_turbo_attr_>`_. + + This attribute is read-only. + +``turbo_pct`` + Ratio of the `turbo range <turbo_>`_ size to the size of the entire + range of supported P-states, in percent. + + This attribute is present only if the value exposed by it is the same + for all of the CPUs in the system. + + This attribute is read-only. + +.. _no_turbo_attr: + +``no_turbo`` + If set (equal to 1), the driver is not allowed to set any turbo P-states + (see `Turbo P-states Support`_). If unset (equal to 0, which is the + default), turbo P-states can be set by the driver. + [Note that ``intel_pstate`` does not support the general ``boost`` + attribute (supported by some other scaling drivers) which is replaced + by this one.] + + This attribute does not affect the maximum supported frequency value + supplied to the ``CPUFreq`` core and exposed via the policy interface, + but it affects the maximum possible value of per-policy P-state limits + (see `Interpretation of Policy Attributes`_ below for details). + +``hwp_dynamic_boost`` + This attribute is only present if ``intel_pstate`` works in the + `active mode with the HWP feature enabled <Active Mode With HWP_>`_ in + the processor. If set (equal to 1), it causes the minimum P-state limit + to be increased dynamically for a short time whenever a task previously + waiting on I/O is selected to run on a given logical CPU (the purpose + of this mechanism is to improve performance). + + This setting has no effect on logical CPUs whose minimum P-state limit + is directly set to the highest non-turbo P-state or above it. + +.. _status_attr: + +``status`` + Operation mode of the driver: "active", "passive" or "off". + + "active" + The driver is functional and in the `active mode + <Active Mode_>`_. + + "passive" + The driver is functional and in the `passive mode + <Passive Mode_>`_. + + "off" + The driver is not functional (it is not registered as a scaling + driver with the ``CPUFreq`` core). + + This attribute can be written to in order to change the driver's + operation mode or to unregister it. The string written to it must be + one of the possible values of it and, if successful, the write will + cause the driver to switch over to the operation mode represented by + that string - or to be unregistered in the "off" case. [Actually, + switching over from the active mode to the passive mode or the other + way around causes the driver to be unregistered and registered again + with a different set of callbacks, so all of its settings (the global + as well as the per-policy ones) are then reset to their default + values, possibly depending on the target operation mode.] + +``energy_efficiency`` + This attribute is only present on platforms with CPUs matching the Kaby + Lake or Coffee Lake desktop CPU model. By default, energy-efficiency + optimizations are disabled on these CPU models if HWP is enabled. + Enabling energy-efficiency optimizations may limit maximum operating + frequency with or without the HWP feature. With HWP enabled, the + optimizations are done only in the turbo frequency range. Without it, + they are done in the entire available frequency range. Setting this + attribute to "1" enables the energy-efficiency optimizations and setting + to "0" disables them. + +Interpretation of Policy Attributes +----------------------------------- + +The interpretation of some ``CPUFreq`` policy attributes described in +Documentation/admin-guide/pm/cpufreq.rst is special with ``intel_pstate`` +as the current scaling driver and it generally depends on the driver's +`operation mode <Operation Modes_>`_. + +First of all, the values of the ``cpuinfo_max_freq``, ``cpuinfo_min_freq`` and +``scaling_cur_freq`` attributes are produced by applying a processor-specific +multiplier to the internal P-state representation used by ``intel_pstate``. +Also, the values of the ``scaling_max_freq`` and ``scaling_min_freq`` +attributes are capped by the frequency corresponding to the maximum P-state that +the driver is allowed to set. + +If the ``no_turbo`` `global attribute <no_turbo_attr_>`_ is set, the driver is +not allowed to use turbo P-states, so the maximum value of ``scaling_max_freq`` +and ``scaling_min_freq`` is limited to the maximum non-turbo P-state frequency. +Accordingly, setting ``no_turbo`` causes ``scaling_max_freq`` and +``scaling_min_freq`` to go down to that value if they were above it before. +However, the old values of ``scaling_max_freq`` and ``scaling_min_freq`` will be +restored after unsetting ``no_turbo``, unless these attributes have been written +to after ``no_turbo`` was set. + +If ``no_turbo`` is not set, the maximum possible value of ``scaling_max_freq`` +and ``scaling_min_freq`` corresponds to the maximum supported turbo P-state, +which also is the value of ``cpuinfo_max_freq`` in either case. + +Next, the following policy attributes have special meaning if +``intel_pstate`` works in the `active mode <Active Mode_>`_: + +``scaling_available_governors`` + List of P-state selection algorithms provided by ``intel_pstate``. + +``scaling_governor`` + P-state selection algorithm provided by ``intel_pstate`` currently in + use with the given policy. + +``scaling_cur_freq`` + Frequency of the average P-state of the CPU represented by the given + policy for the time interval between the last two invocations of the + driver's utilization update callback by the CPU scheduler for that CPU. + +One more policy attribute is present if the HWP feature is enabled in the +processor: + +``base_frequency`` + Shows the base frequency of the CPU. Any frequency above this will be + in the turbo frequency range. + +The meaning of these attributes in the `passive mode <Passive Mode_>`_ is the +same as for other scaling drivers. + +Additionally, the value of the ``scaling_driver`` attribute for ``intel_pstate`` +depends on the operation mode of the driver. Namely, it is either +"intel_pstate" (in the `active mode <Active Mode_>`_) or "intel_cpufreq" (in the +`passive mode <Passive Mode_>`_). + +Coordination of P-State Limits +------------------------------ + +``intel_pstate`` allows P-state limits to be set in two ways: with the help of +the ``max_perf_pct`` and ``min_perf_pct`` `global attributes +<Global Attributes_>`_ or via the ``scaling_max_freq`` and ``scaling_min_freq`` +``CPUFreq`` policy attributes. The coordination between those limits is based +on the following rules, regardless of the current operation mode of the driver: + + 1. All CPUs are affected by the global limits (that is, none of them can be + requested to run faster than the global maximum and none of them can be + requested to run slower than the global minimum). + + 2. Each individual CPU is affected by its own per-policy limits (that is, it + cannot be requested to run faster than its own per-policy maximum and it + cannot be requested to run slower than its own per-policy minimum). The + effective performance depends on whether the platform supports per core + P-states, hyper-threading is enabled and on current performance requests + from other CPUs. When platform doesn't support per core P-states, the + effective performance can be more than the policy limits set on a CPU, if + other CPUs are requesting higher performance at that moment. Even with per + core P-states support, when hyper-threading is enabled, if the sibling CPU + is requesting higher performance, the other siblings will get higher + performance than their policy limits. + + 3. The global and per-policy limits can be set independently. + +In the `active mode with the HWP feature enabled <Active Mode With HWP_>`_, the +resulting effective values are written into hardware registers whenever the +limits change in order to request its internal P-state selection logic to always +set P-states within these limits. Otherwise, the limits are taken into account +by scaling governors (in the `passive mode <Passive Mode_>`_) and by the driver +every time before setting a new P-state for a CPU. + +Additionally, if the ``intel_pstate=per_cpu_perf_limits`` command line argument +is passed to the kernel, ``max_perf_pct`` and ``min_perf_pct`` are not exposed +at all and the only way to set the limits is by using the policy attributes. + + +Energy vs Performance Hints +--------------------------- + +If the hardware-managed P-states (HWP) is enabled in the processor, additional +attributes, intended to allow user space to help ``intel_pstate`` to adjust the +processor's internal P-state selection logic by focusing it on performance or on +energy-efficiency, or somewhere between the two extremes, are present in every +``CPUFreq`` policy directory in ``sysfs``. They are : + +``energy_performance_preference`` + Current value of the energy vs performance hint for the given policy + (or the CPU represented by it). + + The hint can be changed by writing to this attribute. + +``energy_performance_available_preferences`` + List of strings that can be written to the + ``energy_performance_preference`` attribute. + + They represent different energy vs performance hints and should be + self-explanatory, except that ``default`` represents whatever hint + value was set by the platform firmware. + +Strings written to the ``energy_performance_preference`` attribute are +internally translated to integer values written to the processor's +Energy-Performance Preference (EPP) knob (if supported) or its +Energy-Performance Bias (EPB) knob. It is also possible to write a positive +integer value between 0 to 255, if the EPP feature is present. If the EPP +feature is not present, writing integer value to this attribute is not +supported. In this case, user can use the +"/sys/devices/system/cpu/cpu*/power/energy_perf_bias" interface. + +[Note that tasks may by migrated from one CPU to another by the scheduler's +load-balancing algorithm and if different energy vs performance hints are +set for those CPUs, that may lead to undesirable outcomes. To avoid such +issues it is better to set the same energy vs performance hint for all CPUs +or to pin every task potentially sensitive to them to a specific CPU.] + +.. _acpi-cpufreq: + +``intel_pstate`` vs ``acpi-cpufreq`` +==================================== + +On the majority of systems supported by ``intel_pstate``, the ACPI tables +provided by the platform firmware contain ``_PSS`` objects returning information +that can be used for CPU performance scaling (refer to the ACPI specification +[3]_ for details on the ``_PSS`` objects and the format of the information +returned by them). + +The information returned by the ACPI ``_PSS`` objects is used by the +``acpi-cpufreq`` scaling driver. On systems supported by ``intel_pstate`` +the ``acpi-cpufreq`` driver uses the same hardware CPU performance scaling +interface, but the set of P-states it can use is limited by the ``_PSS`` +output. + +On those systems each ``_PSS`` object returns a list of P-states supported by +the corresponding CPU which basically is a subset of the P-states range that can +be used by ``intel_pstate`` on the same system, with one exception: the whole +`turbo range <turbo_>`_ is represented by one item in it (the topmost one). By +convention, the frequency returned by ``_PSS`` for that item is greater by 1 MHz +than the frequency of the highest non-turbo P-state listed by it, but the +corresponding P-state representation (following the hardware specification) +returned for it matches the maximum supported turbo P-state (or is the +special value 255 meaning essentially "go as high as you can get"). + +The list of P-states returned by ``_PSS`` is reflected by the table of +available frequencies supplied by ``acpi-cpufreq`` to the ``CPUFreq`` core and +scaling governors and the minimum and maximum supported frequencies reported by +it come from that list as well. In particular, given the special representation +of the turbo range described above, this means that the maximum supported +frequency reported by ``acpi-cpufreq`` is higher by 1 MHz than the frequency +of the highest supported non-turbo P-state listed by ``_PSS`` which, of course, +affects decisions made by the scaling governors, except for ``powersave`` and +``performance``. + +For example, if a given governor attempts to select a frequency proportional to +estimated CPU load and maps the load of 100% to the maximum supported frequency +(possibly multiplied by a constant), then it will tend to choose P-states below +the turbo threshold if ``acpi-cpufreq`` is used as the scaling driver, because +in that case the turbo range corresponds to a small fraction of the frequency +band it can use (1 MHz vs 1 GHz or more). In consequence, it will only go to +the turbo range for the highest loads and the other loads above 50% that might +benefit from running at turbo frequencies will be given non-turbo P-states +instead. + +One more issue related to that may appear on systems supporting the +`Configurable TDP feature <turbo_>`_ allowing the platform firmware to set the +turbo threshold. Namely, if that is not coordinated with the lists of P-states +returned by ``_PSS`` properly, there may be more than one item corresponding to +a turbo P-state in those lists and there may be a problem with avoiding the +turbo range (if desirable or necessary). Usually, to avoid using turbo +P-states overall, ``acpi-cpufreq`` simply avoids using the topmost state listed +by ``_PSS``, but that is not sufficient when there are other turbo P-states in +the list returned by it. + +Apart from the above, ``acpi-cpufreq`` works like ``intel_pstate`` in the +`passive mode <Passive Mode_>`_, except that the number of P-states it can set +is limited to the ones listed by the ACPI ``_PSS`` objects. + + +Kernel Command Line Options for ``intel_pstate`` +================================================ + +Several kernel command line options can be used to pass early-configuration-time +parameters to ``intel_pstate`` in order to enforce specific behavior of it. All +of them have to be prepended with the ``intel_pstate=`` prefix. + +``disable`` + Do not register ``intel_pstate`` as the scaling driver even if the + processor is supported by it. + +``active`` + Register ``intel_pstate`` in the `active mode <Active Mode_>`_ to start + with. + +``passive`` + Register ``intel_pstate`` in the `passive mode <Passive Mode_>`_ to + start with. + +``force`` + Register ``intel_pstate`` as the scaling driver instead of + ``acpi-cpufreq`` even if the latter is preferred on the given system. + + This may prevent some platform features (such as thermal controls and + power capping) that rely on the availability of ACPI P-states + information from functioning as expected, so it should be used with + caution. + + This option does not work with processors that are not supported by + ``intel_pstate`` and on platforms where the ``pcc-cpufreq`` scaling + driver is used instead of ``acpi-cpufreq``. + +``no_hwp`` + Do not enable the hardware-managed P-states (HWP) feature even if it is + supported by the processor. + +``hwp_only`` + Register ``intel_pstate`` as the scaling driver only if the + hardware-managed P-states (HWP) feature is supported by the processor. + +``support_acpi_ppc`` + Take ACPI ``_PPC`` performance limits into account. + + If the preferred power management profile in the FADT (Fixed ACPI + Description Table) is set to "Enterprise Server" or "Performance + Server", the ACPI ``_PPC`` limits are taken into account by default + and this option has no effect. + +``per_cpu_perf_limits`` + Use per-logical-CPU P-State limits (see `Coordination of P-state + Limits`_ for details). + + +Diagnostics and Tuning +====================== + +Trace Events +------------ + +There are two static trace events that can be used for ``intel_pstate`` +diagnostics. One of them is the ``cpu_frequency`` trace event generally used +by ``CPUFreq``, and the other one is the ``pstate_sample`` trace event specific +to ``intel_pstate``. Both of them are triggered by ``intel_pstate`` only if +it works in the `active mode <Active Mode_>`_. + +The following sequence of shell commands can be used to enable them and see +their output (if the kernel is generally configured to support event tracing):: + + # cd /sys/kernel/tracing/ + # echo 1 > events/power/pstate_sample/enable + # echo 1 > events/power/cpu_frequency/enable + # cat trace + gnome-terminal--4510 [001] ..s. 1177.680733: pstate_sample: core_busy=107 scaled=94 from=26 to=26 mperf=1143818 aperf=1230607 tsc=29838618 freq=2474476 + cat-5235 [002] ..s. 1177.681723: cpu_frequency: state=2900000 cpu_id=2 + +If ``intel_pstate`` works in the `passive mode <Passive Mode_>`_, the +``cpu_frequency`` trace event will be triggered either by the ``schedutil`` +scaling governor (for the policies it is attached to), or by the ``CPUFreq`` +core (for the policies with other scaling governors). + +``ftrace`` +---------- + +The ``ftrace`` interface can be used for low-level diagnostics of +``intel_pstate``. For example, to check how often the function to set a +P-state is called, the ``ftrace`` filter can be set to +:c:func:`intel_pstate_set_pstate`:: + + # cd /sys/kernel/tracing/ + # cat available_filter_functions | grep -i pstate + intel_pstate_set_pstate + intel_pstate_cpu_init + ... + # echo intel_pstate_set_pstate > set_ftrace_filter + # echo function > current_tracer + # cat trace | head -15 + # tracer: function + # + # entries-in-buffer/entries-written: 80/80 #P:4 + # + # _-----=> irqs-off + # / _----=> need-resched + # | / _---=> hardirq/softirq + # || / _--=> preempt-depth + # ||| / delay + # TASK-PID CPU# |||| TIMESTAMP FUNCTION + # | | | |||| | | + Xorg-3129 [000] ..s. 2537.644844: intel_pstate_set_pstate <-intel_pstate_timer_func + gnome-terminal--4510 [002] ..s. 2537.649844: intel_pstate_set_pstate <-intel_pstate_timer_func + gnome-shell-3409 [001] ..s. 2537.650850: intel_pstate_set_pstate <-intel_pstate_timer_func + <idle>-0 [000] ..s. 2537.654843: intel_pstate_set_pstate <-intel_pstate_timer_func + + +References +========== + +.. [1] Kristen Accardi, *Balancing Power and Performance in the Linux Kernel*, + https://events.static.linuxfound.org/sites/events/files/slides/LinuxConEurope_2015.pdf + +.. [2] *Intel® 64 and IA-32 Architectures Software Developer’s Manual Volume 3: System Programming Guide*, + https://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-system-programming-manual-325384.html + +.. [3] *Advanced Configuration and Power Interface Specification*, + https://uefi.org/sites/default/files/resources/ACPI_6_3_final_Jan30.pdf diff --git a/Documentation/admin-guide/pm/intel_uncore_frequency_scaling.rst b/Documentation/admin-guide/pm/intel_uncore_frequency_scaling.rst new file mode 100644 index 000000000..5ab3440e6 --- /dev/null +++ b/Documentation/admin-guide/pm/intel_uncore_frequency_scaling.rst @@ -0,0 +1,115 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + +============================== +Intel Uncore Frequency Scaling +============================== + +:Copyright: |copy| 2022-2023 Intel Corporation + +:Author: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> + +Introduction +------------ + +The uncore can consume significant amount of power in Intel's Xeon servers based +on the workload characteristics. To optimize the total power and improve overall +performance, SoCs have internal algorithms for scaling uncore frequency. These +algorithms monitor workload usage of uncore and set a desirable frequency. + +It is possible that users have different expectations of uncore performance and +want to have control over it. The objective is similar to allowing users to set +the scaling min/max frequencies via cpufreq sysfs to improve CPU performance. +Users may have some latency sensitive workloads where they do not want any +change to uncore frequency. Also, users may have workloads which require +different core and uncore performance at distinct phases and they may want to +use both cpufreq and the uncore scaling interface to distribute power and +improve overall performance. + +Sysfs Interface +--------------- + +To control uncore frequency, a sysfs interface is provided in the directory: +`/sys/devices/system/cpu/intel_uncore_frequency/`. + +There is one directory for each package and die combination as the scope of +uncore scaling control is per die in multiple die/package SoCs or per +package for single die per package SoCs. The name represents the +scope of control. For example: 'package_00_die_00' is for package id 0 and +die 0. + +Each package_*_die_* contains the following attributes: + +``initial_max_freq_khz`` + Out of reset, this attribute represent the maximum possible frequency. + This is a read-only attribute. If users adjust max_freq_khz, + they can always go back to maximum using the value from this attribute. + +``initial_min_freq_khz`` + Out of reset, this attribute represent the minimum possible frequency. + This is a read-only attribute. If users adjust min_freq_khz, + they can always go back to minimum using the value from this attribute. + +``max_freq_khz`` + This attribute is used to set the maximum uncore frequency. + +``min_freq_khz`` + This attribute is used to set the minimum uncore frequency. + +``current_freq_khz`` + This attribute is used to get the current uncore frequency. + +SoCs with TPMI (Topology Aware Register and PM Capsule Interface) +----------------------------------------------------------------- + +An SoC can contain multiple power domains with individual or collection +of mesh partitions. This partition is called fabric cluster. + +Certain type of meshes will need to run at the same frequency, they will +be placed in the same fabric cluster. Benefit of fabric cluster is that it +offers a scalable mechanism to deal with partitioned fabrics in a SoC. + +The current sysfs interface supports controls at package and die level. +This interface is not enough to support more granular control at +fabric cluster level. + +SoCs with the support of TPMI (Topology Aware Register and PM Capsule +Interface), can have multiple power domains. Each power domain can +contain one or more fabric clusters. + +To represent controls at fabric cluster level in addition to the +controls at package and die level (like systems without TPMI +support), sysfs is enhanced. This granular interface is presented in the +sysfs with directories names prefixed with "uncore". For example: +uncore00, uncore01 etc. + +The scope of control is specified by attributes "package_id", "domain_id" +and "fabric_cluster_id" in the directory. + +Attributes in each directory: + +``domain_id`` + This attribute is used to get the power domain id of this instance. + +``fabric_cluster_id`` + This attribute is used to get the fabric cluster id of this instance. + +``package_id`` + This attribute is used to get the package id of this instance. + +The other attributes are same as presented at package_*_die_* level. + +In most of current use cases, the "max_freq_khz" and "min_freq_khz" +is updated at "package_*_die_*" level. This model will be still supported +with the following approach: + +When user uses controls at "package_*_die_*" level, then every fabric +cluster is affected in that package and die. For example: user changes +"max_freq_khz" in the package_00_die_00, then "max_freq_khz" for uncore* +directory with the same package id will be updated. In this case user can +still update "max_freq_khz" at each uncore* level, which is more restrictive. +Similarly, user can update "min_freq_khz" at "package_*_die_*" level +to apply at each uncore* level. + +Support for "current_freq_khz" is available only at each fabric cluster +level (i.e., in uncore* directory). diff --git a/Documentation/admin-guide/pm/sleep-states.rst b/Documentation/admin-guide/pm/sleep-states.rst new file mode 100644 index 000000000..ee55a460c --- /dev/null +++ b/Documentation/admin-guide/pm/sleep-states.rst @@ -0,0 +1,291 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + +=================== +System Sleep States +=================== + +:Copyright: |copy| 2017 Intel Corporation + +:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> + + +Sleep states are global low-power states of the entire system in which user +space code cannot be executed and the overall system activity is significantly +reduced. + + +Sleep States That Can Be Supported +================================== + +Depending on its configuration and the capabilities of the platform it runs on, +the Linux kernel can support up to four system sleep states, including +hibernation and up to three variants of system suspend. The sleep states that +can be supported by the kernel are listed below. + +.. _s2idle: + +Suspend-to-Idle +--------------- + +This is a generic, pure software, light-weight variant of system suspend (also +referred to as S2I or S2Idle). It allows more energy to be saved relative to +runtime idle by freezing user space, suspending the timekeeping and putting all +I/O devices into low-power states (possibly lower-power than available in the +working state), such that the processors can spend time in their deepest idle +states while the system is suspended. + +The system is woken up from this state by in-band interrupts, so theoretically +any devices that can cause interrupts to be generated in the working state can +also be set up as wakeup devices for S2Idle. + +This state can be used on platforms without support for :ref:`standby <standby>` +or :ref:`suspend-to-RAM <s2ram>`, or it can be used in addition to any of the +deeper system suspend variants to provide reduced resume latency. It is always +supported if the :c:macro:`CONFIG_SUSPEND` kernel configuration option is set. + +.. _standby: + +Standby +------- + +This state, if supported, offers moderate, but real, energy savings, while +providing a relatively straightforward transition back to the working state. No +operating state is lost (the system core logic retains power), so the system can +go back to where it left off easily enough. + +In addition to freezing user space, suspending the timekeeping and putting all +I/O devices into low-power states, which is done for :ref:`suspend-to-idle +<s2idle>` too, nonboot CPUs are taken offline and all low-level system functions +are suspended during transitions into this state. For this reason, it should +allow more energy to be saved relative to :ref:`suspend-to-idle <s2idle>`, but +the resume latency will generally be greater than for that state. + +The set of devices that can wake up the system from this state usually is +reduced relative to :ref:`suspend-to-idle <s2idle>` and it may be necessary to +rely on the platform for setting up the wakeup functionality as appropriate. + +This state is supported if the :c:macro:`CONFIG_SUSPEND` kernel configuration +option is set and the support for it is registered by the platform with the +core system suspend subsystem. On ACPI-based systems this state is mapped to +the S1 system state defined by ACPI. + +.. _s2ram: + +Suspend-to-RAM +-------------- + +This state (also referred to as STR or S2RAM), if supported, offers significant +energy savings as everything in the system is put into a low-power state, except +for memory, which should be placed into the self-refresh mode to retain its +contents. All of the steps carried out when entering :ref:`standby <standby>` +are also carried out during transitions to S2RAM. Additional operations may +take place depending on the platform capabilities. In particular, on ACPI-based +systems the kernel passes control to the platform firmware (BIOS) as the last +step during S2RAM transitions and that usually results in powering down some +more low-level components that are not directly controlled by the kernel. + +The state of devices and CPUs is saved and held in memory. All devices are +suspended and put into low-power states. In many cases, all peripheral buses +lose power when entering S2RAM, so devices must be able to handle the transition +back to the "on" state. + +On ACPI-based systems S2RAM requires some minimal boot-strapping code in the +platform firmware to resume the system from it. This may be the case on other +platforms too. + +The set of devices that can wake up the system from S2RAM usually is reduced +relative to :ref:`suspend-to-idle <s2idle>` and :ref:`standby <standby>` and it +may be necessary to rely on the platform for setting up the wakeup functionality +as appropriate. + +S2RAM is supported if the :c:macro:`CONFIG_SUSPEND` kernel configuration option +is set and the support for it is registered by the platform with the core system +suspend subsystem. On ACPI-based systems it is mapped to the S3 system state +defined by ACPI. + +.. _hibernation: + +Hibernation +----------- + +This state (also referred to as Suspend-to-Disk or STD) offers the greatest +energy savings and can be used even in the absence of low-level platform support +for system suspend. However, it requires some low-level code for resuming the +system to be present for the underlying CPU architecture. + +Hibernation is significantly different from any of the system suspend variants. +It takes three system state changes to put it into hibernation and two system +state changes to resume it. + +First, when hibernation is triggered, the kernel stops all system activity and +creates a snapshot image of memory to be written into persistent storage. Next, +the system goes into a state in which the snapshot image can be saved, the image +is written out and finally the system goes into the target low-power state in +which power is cut from almost all of its hardware components, including memory, +except for a limited set of wakeup devices. + +Once the snapshot image has been written out, the system may either enter a +special low-power state (like ACPI S4), or it may simply power down itself. +Powering down means minimum power draw and it allows this mechanism to work on +any system. However, entering a special low-power state may allow additional +means of system wakeup to be used (e.g. pressing a key on the keyboard or +opening a laptop lid). + +After wakeup, control goes to the platform firmware that runs a boot loader +which boots a fresh instance of the kernel (control may also go directly to +the boot loader, depending on the system configuration, but anyway it causes +a fresh instance of the kernel to be booted). That new instance of the kernel +(referred to as the ``restore kernel``) looks for a hibernation image in +persistent storage and if one is found, it is loaded into memory. Next, all +activity in the system is stopped and the restore kernel overwrites itself with +the image contents and jumps into a special trampoline area in the original +kernel stored in the image (referred to as the ``image kernel``), which is where +the special architecture-specific low-level code is needed. Finally, the +image kernel restores the system to the pre-hibernation state and allows user +space to run again. + +Hibernation is supported if the :c:macro:`CONFIG_HIBERNATION` kernel +configuration option is set. However, this option can only be set if support +for the given CPU architecture includes the low-level code for system resume. + + +Basic ``sysfs`` Interfaces for System Suspend and Hibernation +============================================================= + +The power management subsystem provides userspace with a unified ``sysfs`` +interface for system sleep regardless of the underlying system architecture or +platform. That interface is located in the :file:`/sys/power/` directory +(assuming that ``sysfs`` is mounted at :file:`/sys`) and it consists of the +following attributes (files): + +``state`` + This file contains a list of strings representing sleep states supported + by the kernel. Writing one of these strings into it causes the kernel + to start a transition of the system into the sleep state represented by + that string. + + In particular, the "disk", "freeze" and "standby" strings represent the + :ref:`hibernation <hibernation>`, :ref:`suspend-to-idle <s2idle>` and + :ref:`standby <standby>` sleep states, respectively. The "mem" string + is interpreted in accordance with the contents of the ``mem_sleep`` file + described below. + + If the kernel does not support any system sleep states, this file is + not present. + +``mem_sleep`` + This file contains a list of strings representing supported system + suspend variants and allows user space to select the variant to be + associated with the "mem" string in the ``state`` file described above. + + The strings that may be present in this file are "s2idle", "shallow" + and "deep". The "s2idle" string always represents :ref:`suspend-to-idle + <s2idle>` and, by convention, "shallow" and "deep" represent + :ref:`standby <standby>` and :ref:`suspend-to-RAM <s2ram>`, + respectively. + + Writing one of the listed strings into this file causes the system + suspend variant represented by it to be associated with the "mem" string + in the ``state`` file. The string representing the suspend variant + currently associated with the "mem" string in the ``state`` file is + shown in square brackets. + + If the kernel does not support system suspend, this file is not present. + +``disk`` + This file controls the operating mode of hibernation (Suspend-to-Disk). + Specifically, it tells the kernel what to do after creating a + hibernation image. + + Reading from it returns a list of supported options encoded as: + + ``platform`` + Put the system into a special low-power state (e.g. ACPI S4) to + make additional wakeup options available and possibly allow the + platform firmware to take a simplified initialization path after + wakeup. + + It is only available if the platform provides a special + mechanism to put the system to sleep after creating a + hibernation image (platforms with ACPI do that as a rule, for + example). + + ``shutdown`` + Power off the system. + + ``reboot`` + Reboot the system (useful for diagnostics mostly). + + ``suspend`` + Hybrid system suspend. Put the system into the suspend sleep + state selected through the ``mem_sleep`` file described above. + If the system is successfully woken up from that state, discard + the hibernation image and continue. Otherwise, use the image + to restore the previous state of the system. + + It is available if system suspend is supported. + + ``test_resume`` + Diagnostic operation. Load the image as though the system had + just woken up from hibernation and the currently running kernel + instance was a restore kernel and follow up with full system + resume. + + Writing one of the strings listed above into this file causes the option + represented by it to be selected. + + The currently selected option is shown in square brackets, which means + that the operation represented by it will be carried out after creating + and saving the image when hibernation is triggered by writing ``disk`` + to :file:`/sys/power/state`. + + If the kernel does not support hibernation, this file is not present. + +``image_size`` + This file controls the size of hibernation images. + + It can be written a string representing a non-negative integer that will + be used as a best-effort upper limit of the image size, in bytes. The + hibernation core will do its best to ensure that the image size will not + exceed that number, but if that turns out to be impossible to achieve, a + hibernation image will still be created and its size will be as small as + possible. In particular, writing '0' to this file causes the size of + hibernation images to be minimum. + + Reading from it returns the current image size limit, which is set to + around 2/5 of the available RAM size by default. + +``pm_trace`` + This file controls the "PM trace" mechanism saving the last suspend + or resume event point in the RTC memory across reboots. It helps to + debug hard lockups or reboots due to device driver failures that occur + during system suspend or resume (which is more common) more effectively. + + If it contains "1", the fingerprint of each suspend/resume event point + in turn will be stored in the RTC memory (overwriting the actual RTC + information), so it will survive a system crash if one occurs right + after storing it and it can be used later to identify the driver that + caused the crash to happen. + + It contains "0" by default, which may be changed to "1" by writing a + string representing a nonzero integer into it. + +According to the above, there are two ways to make the system go into the +:ref:`suspend-to-idle <s2idle>` state. The first one is to write "freeze" +directly to :file:`/sys/power/state`. The second one is to write "s2idle" to +:file:`/sys/power/mem_sleep` and then to write "mem" to +:file:`/sys/power/state`. Likewise, there are two ways to make the system go +into the :ref:`standby <standby>` state (the strings to write to the control +files in that case are "standby" or "shallow" and "mem", respectively) if that +state is supported by the platform. However, there is only one way to make the +system go into the :ref:`suspend-to-RAM <s2ram>` state (write "deep" into +:file:`/sys/power/mem_sleep` and "mem" into :file:`/sys/power/state`). + +The default suspend variant (ie. the one to be used without writing anything +into :file:`/sys/power/mem_sleep`) is either "deep" (on the majority of systems +supporting :ref:`suspend-to-RAM <s2ram>`) or "s2idle", but it can be overridden +by the value of the ``mem_sleep_default`` parameter in the kernel command line. +On some systems with ACPI, depending on the information in the ACPI tables, the +default may be "s2idle" even if :ref:`suspend-to-RAM <s2ram>` is supported in +principle. diff --git a/Documentation/admin-guide/pm/strategies.rst b/Documentation/admin-guide/pm/strategies.rst new file mode 100644 index 000000000..dd0362e32 --- /dev/null +++ b/Documentation/admin-guide/pm/strategies.rst @@ -0,0 +1,56 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + +=========================== +Power Management Strategies +=========================== + +:Copyright: |copy| 2017 Intel Corporation + +:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> + + +The Linux kernel supports two major high-level power management strategies. + +One of them is based on using global low-power states of the whole system in +which user space code cannot be executed and the overall system activity is +significantly reduced, referred to as :doc:`sleep states <sleep-states>`. The +kernel puts the system into one of these states when requested by user space +and the system stays in it until a special signal is received from one of +designated devices, triggering a transition to the ``working state`` in which +user space code can run. Because sleep states are global and the whole system +is affected by the state changes, this strategy is referred to as the +:doc:`system-wide power management <system-wide>`. + +The other strategy, referred to as the :doc:`working-state power management +<working-state>`, is based on adjusting the power states of individual hardware +components of the system, as needed, in the working state. In consequence, if +this strategy is in use, the working state of the system usually does not +correspond to any particular physical configuration of it, but can be treated as +a metastate covering a range of different power states of the system in which +the individual components of it can be either ``active`` (in use) or +``inactive`` (idle). If they are active, they have to be in power states +allowing them to process data and to be accessed by software. In turn, if they +are inactive, ideally, they should be in low-power states in which they may not +be accessible. + +If all of the system components are active, the system as a whole is regarded as +"runtime active" and that situation typically corresponds to the maximum power +draw (or maximum energy usage) of it. If all of them are inactive, the system +as a whole is regarded as "runtime idle" which may be very close to a sleep +state from the physical system configuration and power draw perspective, but +then it takes much less time and effort to start executing user space code than +for the same system in a sleep state. However, transitions from sleep states +back to the working state can only be started by a limited set of devices, so +typically the system can spend much more time in a sleep state than it can be +runtime idle in one go. For this reason, systems usually use less energy in +sleep states than when they are runtime idle most of the time. + +Moreover, the two power management strategies address different usage scenarios. +Namely, if the user indicates that the system will not be in use going forward, +for example by closing its lid (if the system is a laptop), it probably should +go into a sleep state at that point. On the other hand, if the user simply goes +away from the laptop keyboard, it probably should stay in the working state and +use the working-state power management in case it becomes idle, because the user +may come back to it at any time and then may want the system to be immediately +accessible. diff --git a/Documentation/admin-guide/pm/suspend-flows.rst b/Documentation/admin-guide/pm/suspend-flows.rst new file mode 100644 index 000000000..c479d7462 --- /dev/null +++ b/Documentation/admin-guide/pm/suspend-flows.rst @@ -0,0 +1,270 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + +========================= +System Suspend Code Flows +========================= + +:Copyright: |copy| 2020 Intel Corporation + +:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> + +At least one global system-wide transition needs to be carried out for the +system to get from the working state into one of the supported +:doc:`sleep states <sleep-states>`. Hibernation requires more than one +transition to occur for this purpose, but the other sleep states, commonly +referred to as *system-wide suspend* (or simply *system suspend*) states, need +only one. + +For those sleep states, the transition from the working state of the system into +the target sleep state is referred to as *system suspend* too (in the majority +of cases, whether this means a transition or a sleep state of the system should +be clear from the context) and the transition back from the sleep state into the +working state is referred to as *system resume*. + +The kernel code flows associated with the suspend and resume transitions for +different sleep states of the system are quite similar, but there are some +significant differences between the :ref:`suspend-to-idle <s2idle>` code flows +and the code flows related to the :ref:`suspend-to-RAM <s2ram>` and +:ref:`standby <standby>` sleep states. + +The :ref:`suspend-to-RAM <s2ram>` and :ref:`standby <standby>` sleep states +cannot be implemented without platform support and the difference between them +boils down to the platform-specific actions carried out by the suspend and +resume hooks that need to be provided by the platform driver to make them +available. Apart from that, the suspend and resume code flows for these sleep +states are mostly identical, so they both together will be referred to as +*platform-dependent suspend* states in what follows. + + +.. _s2idle_suspend: + +Suspend-to-idle Suspend Code Flow +================================= + +The following steps are taken in order to transition the system from the working +state to the :ref:`suspend-to-idle <s2idle>` sleep state: + + 1. Invoking system-wide suspend notifiers. + + Kernel subsystems can register callbacks to be invoked when the suspend + transition is about to occur and when the resume transition has finished. + + That allows them to prepare for the change of the system state and to clean + up after getting back to the working state. + + 2. Freezing tasks. + + Tasks are frozen primarily in order to avoid unchecked hardware accesses + from user space through MMIO regions or I/O registers exposed directly to + it and to prevent user space from entering the kernel while the next step + of the transition is in progress (which might have been problematic for + various reasons). + + All user space tasks are intercepted as though they were sent a signal and + put into uninterruptible sleep until the end of the subsequent system resume + transition. + + The kernel threads that choose to be frozen during system suspend for + specific reasons are frozen subsequently, but they are not intercepted. + Instead, they are expected to periodically check whether or not they need + to be frozen and to put themselves into uninterruptible sleep if so. [Note, + however, that kernel threads can use locking and other concurrency controls + available in kernel space to synchronize themselves with system suspend and + resume, which can be much more precise than the freezing, so the latter is + not a recommended option for kernel threads.] + + 3. Suspending devices and reconfiguring IRQs. + + Devices are suspended in four phases called *prepare*, *suspend*, + *late suspend* and *noirq suspend* (see :ref:`driverapi_pm_devices` for more + information on what exactly happens in each phase). + + Every device is visited in each phase, but typically it is not physically + accessed in more than two of them. + + The runtime PM API is disabled for every device during the *late* suspend + phase and high-level ("action") interrupt handlers are prevented from being + invoked before the *noirq* suspend phase. + + Interrupts are still handled after that, but they are only acknowledged to + interrupt controllers without performing any device-specific actions that + would be triggered in the working state of the system (those actions are + deferred till the subsequent system resume transition as described + `below <s2idle_resume_>`_). + + IRQs associated with system wakeup devices are "armed" so that the resume + transition of the system is started when one of them signals an event. + + 4. Freezing the scheduler tick and suspending timekeeping. + + When all devices have been suspended, CPUs enter the idle loop and are put + into the deepest available idle state. While doing that, each of them + "freezes" its own scheduler tick so that the timer events associated with + the tick do not occur until the CPU is woken up by another interrupt source. + + The last CPU to enter the idle state also stops the timekeeping which + (among other things) prevents high resolution timers from triggering going + forward until the first CPU that is woken up restarts the timekeeping. + That allows the CPUs to stay in the deep idle state relatively long in one + go. + + From this point on, the CPUs can only be woken up by non-timer hardware + interrupts. If that happens, they go back to the idle state unless the + interrupt that woke up one of them comes from an IRQ that has been armed for + system wakeup, in which case the system resume transition is started. + + +.. _s2idle_resume: + +Suspend-to-idle Resume Code Flow +================================ + +The following steps are taken in order to transition the system from the +:ref:`suspend-to-idle <s2idle>` sleep state into the working state: + + 1. Resuming timekeeping and unfreezing the scheduler tick. + + When one of the CPUs is woken up (by a non-timer hardware interrupt), it + leaves the idle state entered in the last step of the preceding suspend + transition, restarts the timekeeping (unless it has been restarted already + by another CPU that woke up earlier) and the scheduler tick on that CPU is + unfrozen. + + If the interrupt that has woken up the CPU was armed for system wakeup, + the system resume transition begins. + + 2. Resuming devices and restoring the working-state configuration of IRQs. + + Devices are resumed in four phases called *noirq resume*, *early resume*, + *resume* and *complete* (see :ref:`driverapi_pm_devices` for more + information on what exactly happens in each phase). + + Every device is visited in each phase, but typically it is not physically + accessed in more than two of them. + + The working-state configuration of IRQs is restored after the *noirq* resume + phase and the runtime PM API is re-enabled for every device whose driver + supports it during the *early* resume phase. + + 3. Thawing tasks. + + Tasks frozen in step 2 of the preceding `suspend <s2idle_suspend_>`_ + transition are "thawed", which means that they are woken up from the + uninterruptible sleep that they went into at that time and user space tasks + are allowed to exit the kernel. + + 4. Invoking system-wide resume notifiers. + + This is analogous to step 1 of the `suspend <s2idle_suspend_>`_ transition + and the same set of callbacks is invoked at this point, but a different + "notification type" parameter value is passed to them. + + +Platform-dependent Suspend Code Flow +==================================== + +The following steps are taken in order to transition the system from the working +state to platform-dependent suspend state: + + 1. Invoking system-wide suspend notifiers. + + This step is the same as step 1 of the suspend-to-idle suspend transition + described `above <s2idle_suspend_>`_. + + 2. Freezing tasks. + + This step is the same as step 2 of the suspend-to-idle suspend transition + described `above <s2idle_suspend_>`_. + + 3. Suspending devices and reconfiguring IRQs. + + This step is analogous to step 3 of the suspend-to-idle suspend transition + described `above <s2idle_suspend_>`_, but the arming of IRQs for system + wakeup generally does not have any effect on the platform. + + There are platforms that can go into a very deep low-power state internally + when all CPUs in them are in sufficiently deep idle states and all I/O + devices have been put into low-power states. On those platforms, + suspend-to-idle can reduce system power very effectively. + + On the other platforms, however, low-level components (like interrupt + controllers) need to be turned off in a platform-specific way (implemented + in the hooks provided by the platform driver) to achieve comparable power + reduction. + + That usually prevents in-band hardware interrupts from waking up the system, + which must be done in a special platform-dependent way. Then, the + configuration of system wakeup sources usually starts when system wakeup + devices are suspended and is finalized by the platform suspend hooks later + on. + + 4. Disabling non-boot CPUs. + + On some platforms the suspend hooks mentioned above must run in a one-CPU + configuration of the system (in particular, the hardware cannot be accessed + by any code running in parallel with the platform suspend hooks that may, + and often do, trap into the platform firmware in order to finalize the + suspend transition). + + For this reason, the CPU offline/online (CPU hotplug) framework is used + to take all of the CPUs in the system, except for one (the boot CPU), + offline (typically, the CPUs that have been taken offline go into deep idle + states). + + This means that all tasks are migrated away from those CPUs and all IRQs are + rerouted to the only CPU that remains online. + + 5. Suspending core system components. + + This prepares the core system components for (possibly) losing power going + forward and suspends the timekeeping. + + 6. Platform-specific power removal. + + This is expected to remove power from all of the system components except + for the memory controller and RAM (in order to preserve the contents of the + latter) and some devices designated for system wakeup. + + In many cases control is passed to the platform firmware which is expected + to finalize the suspend transition as needed. + + +Platform-dependent Resume Code Flow +=================================== + +The following steps are taken in order to transition the system from a +platform-dependent suspend state into the working state: + + 1. Platform-specific system wakeup. + + The platform is woken up by a signal from one of the designated system + wakeup devices (which need not be an in-band hardware interrupt) and + control is passed back to the kernel (the working configuration of the + platform may need to be restored by the platform firmware before the + kernel gets control again). + + 2. Resuming core system components. + + The suspend-time configuration of the core system components is restored and + the timekeeping is resumed. + + 3. Re-enabling non-boot CPUs. + + The CPUs disabled in step 4 of the preceding suspend transition are taken + back online and their suspend-time configuration is restored. + + 4. Resuming devices and restoring the working-state configuration of IRQs. + + This step is the same as step 2 of the suspend-to-idle suspend transition + described `above <s2idle_resume_>`_. + + 5. Thawing tasks. + + This step is the same as step 3 of the suspend-to-idle suspend transition + described `above <s2idle_resume_>`_. + + 6. Invoking system-wide resume notifiers. + + This step is the same as step 4 of the suspend-to-idle suspend transition + described `above <s2idle_resume_>`_. diff --git a/Documentation/admin-guide/pm/system-wide.rst b/Documentation/admin-guide/pm/system-wide.rst new file mode 100644 index 000000000..1a1924d71 --- /dev/null +++ b/Documentation/admin-guide/pm/system-wide.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================ +System-Wide Power Management +============================ + +.. toctree:: + :maxdepth: 2 + + sleep-states + suspend-flows diff --git a/Documentation/admin-guide/pm/working-state.rst b/Documentation/admin-guide/pm/working-state.rst new file mode 100644 index 000000000..ee4588781 --- /dev/null +++ b/Documentation/admin-guide/pm/working-state.rst @@ -0,0 +1,18 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================== +Working-State Power Management +============================== + +.. toctree:: + :maxdepth: 2 + + cpuidle + intel_idle + cpufreq + intel_pstate + amd-pstate + cpufreq_drivers + intel_epb + intel-speed-select + intel_uncore_frequency_scaling diff --git a/Documentation/admin-guide/pnp.rst b/Documentation/admin-guide/pnp.rst new file mode 100644 index 000000000..3eda08191 --- /dev/null +++ b/Documentation/admin-guide/pnp.rst @@ -0,0 +1,288 @@ +================================= +Linux Plug and Play Documentation +================================= + +:Author: Adam Belay <ambx1@neo.rr.com> +:Last updated: Oct. 16, 2002 + + +Overview +-------- + +Plug and Play provides a means of detecting and setting resources for legacy or +otherwise unconfigurable devices. The Linux Plug and Play Layer provides these +services to compatible drivers. + + +The User Interface +------------------ + +The Linux Plug and Play user interface provides a means to activate PnP devices +for legacy and user level drivers that do not support Linux Plug and Play. The +user interface is integrated into sysfs. + +In addition to the standard sysfs file the following are created in each +device's directory: +- id - displays a list of support EISA IDs +- options - displays possible resource configurations +- resources - displays currently allocated resources and allows resource changes + +activating a device +^^^^^^^^^^^^^^^^^^^ + +:: + + # echo "auto" > resources + +this will invoke the automatic resource config system to activate the device + +manually activating a device +^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +:: + + # echo "manual <depnum> <mode>" > resources + + <depnum> - the configuration number + <mode> - static or dynamic + static = for next boot + dynamic = now + +disabling a device +^^^^^^^^^^^^^^^^^^ + +:: + + # echo "disable" > resources + + +EXAMPLE: + +Suppose you need to activate the floppy disk controller. + +1. change to the proper directory, in my case it is + /driver/bus/pnp/devices/00:0f:: + + # cd /driver/bus/pnp/devices/00:0f + # cat name + PC standard floppy disk controller + +2. check if the device is already active:: + + # cat resources + DISABLED + + - Notice the string "DISABLED". This means the device is not active. + +3. check the device's possible configurations (optional):: + + # cat options + Dependent: 01 - Priority acceptable + port 0x3f0-0x3f0, align 0x7, size 0x6, 16-bit address decoding + port 0x3f7-0x3f7, align 0x0, size 0x1, 16-bit address decoding + irq 6 + dma 2 8-bit compatible + Dependent: 02 - Priority acceptable + port 0x370-0x370, align 0x7, size 0x6, 16-bit address decoding + port 0x377-0x377, align 0x0, size 0x1, 16-bit address decoding + irq 6 + dma 2 8-bit compatible + +4. now activate the device:: + + # echo "auto" > resources + +5. finally check if the device is active:: + + # cat resources + io 0x3f0-0x3f5 + io 0x3f7-0x3f7 + irq 6 + dma 2 + +also there are a series of kernel parameters:: + + pnp_reserve_irq=irq1[,irq2] .... + pnp_reserve_dma=dma1[,dma2] .... + pnp_reserve_io=io1,size1[,io2,size2] .... + pnp_reserve_mem=mem1,size1[,mem2,size2] .... + + + +The Unified Plug and Play Layer +------------------------------- + +All Plug and Play drivers, protocols, and services meet at a central location +called the Plug and Play Layer. This layer is responsible for the exchange of +information between PnP drivers and PnP protocols. Thus it automatically +forwards commands to the proper protocol. This makes writing PnP drivers +significantly easier. + +The following functions are available from the Plug and Play Layer: + +pnp_get_protocol + increments the number of uses by one + +pnp_put_protocol + deincrements the number of uses by one + +pnp_register_protocol + use this to register a new PnP protocol + +pnp_unregister_protocol + use this function to remove a PnP protocol from the Plug and Play Layer + +pnp_register_driver + adds a PnP driver to the Plug and Play Layer + + this includes driver model integration + returns zero for success or a negative error number for failure; count + calls to the .add() method if you need to know how many devices bind to + the driver + +pnp_unregister_driver + removes a PnP driver from the Plug and Play Layer + + + +Plug and Play Protocols +----------------------- + +This section contains information for PnP protocol developers. + +The following Protocols are currently available in the computing world: + +- PNPBIOS: + used for system devices such as serial and parallel ports. +- ISAPNP: + provides PnP support for the ISA bus +- ACPI: + among its many uses, ACPI provides information about system level + devices. + +It is meant to replace the PNPBIOS. It is not currently supported by Linux +Plug and Play but it is planned to be in the near future. + + +Requirements for a Linux PnP protocol: +1. the protocol must use EISA IDs +2. the protocol must inform the PnP Layer of a device's current configuration + +- the ability to set resources is optional but preferred. + +The following are PnP protocol related functions: + +pnp_add_device + use this function to add a PnP device to the PnP layer + + only call this function when all wanted values are set in the pnp_dev + structure + +pnp_init_device + call this to initialize the PnP structure + +pnp_remove_device + call this to remove a device from the Plug and Play Layer. + it will fail if the device is still in use. + automatically will free mem used by the device and related structures + +pnp_add_id + adds an EISA ID to the list of supported IDs for the specified device + +For more information consult the source of a protocol such as +/drivers/pnp/pnpbios/core.c. + + + +Linux Plug and Play Drivers +--------------------------- + +This section contains information for Linux PnP driver developers. + +The New Way +^^^^^^^^^^^ + +1. first make a list of supported EISA IDS + + ex:: + + static const struct pnp_id pnp_dev_table[] = { + /* Standard LPT Printer Port */ + {.id = "PNP0400", .driver_data = 0}, + /* ECP Printer Port */ + {.id = "PNP0401", .driver_data = 0}, + {.id = ""} + }; + + Please note that the character 'X' can be used as a wild card in the function + portion (last four characters). + + ex:: + + /* Unknown PnP modems */ + { "PNPCXXX", UNKNOWN_DEV }, + + Supported PnP card IDs can optionally be defined. + ex:: + + static const struct pnp_id pnp_card_table[] = { + { "ANYDEVS", 0 }, + { "", 0 } + }; + +2. Optionally define probe and remove functions. It may make sense not to + define these functions if the driver already has a reliable method of detecting + the resources, such as the parport_pc driver. + + ex:: + + static int + serial_pnp_probe(struct pnp_dev * dev, const struct pnp_id *card_id, const + struct pnp_id *dev_id) + { + . . . + + ex:: + + static void serial_pnp_remove(struct pnp_dev * dev) + { + . . . + + consult /drivers/serial/8250_pnp.c for more information. + +3. create a driver structure + + ex:: + + static struct pnp_driver serial_pnp_driver = { + .name = "serial", + .card_id_table = pnp_card_table, + .id_table = pnp_dev_table, + .probe = serial_pnp_probe, + .remove = serial_pnp_remove, + }; + + * name and id_table cannot be NULL. + +4. register the driver + + ex:: + + static int __init serial8250_pnp_init(void) + { + return pnp_register_driver(&serial_pnp_driver); + } + +The Old Way +^^^^^^^^^^^ + +A series of compatibility functions have been created to make it easy to convert +ISAPNP drivers. They should serve as a temporary solution only. + +They are as follows:: + + struct pnp_dev *pnp_find_dev(struct pnp_card *card, + unsigned short vendor, + unsigned short function, + struct pnp_dev *from) + diff --git a/Documentation/admin-guide/pstore-blk.rst b/Documentation/admin-guide/pstore-blk.rst new file mode 100644 index 000000000..2d22ead95 --- /dev/null +++ b/Documentation/admin-guide/pstore-blk.rst @@ -0,0 +1,234 @@ +.. SPDX-License-Identifier: GPL-2.0 + +pstore block oops/panic logger +============================== + +Introduction +------------ + +pstore block (pstore/blk) is an oops/panic logger that writes its logs to a +block device and non-block device before the system crashes. You can get +these log files by mounting pstore filesystem like:: + + mount -t pstore pstore /sys/fs/pstore + + +pstore block concepts +--------------------- + +pstore/blk provides efficient configuration method for pstore/blk, which +divides all configurations into two parts, configurations for user and +configurations for driver. + +Configurations for user determine how pstore/blk works, such as pmsg_size, +kmsg_size and so on. All of them support both Kconfig and module parameters, +but module parameters have priority over Kconfig. + +Configurations for driver are all about block device and non-block device, +such as total_size of block device and read/write operations. + +Configurations for user +----------------------- + +All of these configurations support both Kconfig and module parameters, but +module parameters have priority over Kconfig. + +Here is an example for module parameters:: + + pstore_blk.blkdev=/dev/mmcblk0p7 pstore_blk.kmsg_size=64 best_effort=y + +The detail of each configurations may be of interest to you. + +blkdev +~~~~~~ + +The block device to use. Most of the time, it is a partition of block device. +It's required for pstore/blk. It is also used for MTD device. + +When pstore/blk is built as a module, "blkdev" accepts the following variants: + +1. /dev/<disk_name> represents the device number of disk +#. /dev/<disk_name><decimal> represents the device number of partition - device + number of disk plus the partition number +#. /dev/<disk_name>p<decimal> - same as the above; this form is used when disk + name of partitioned disk ends with a digit. + +When pstore/blk is built into the kernel, "blkdev" accepts the following variants: + +#. <hex_major><hex_minor> device number in hexadecimal representation, + with no leading 0x, for example b302. +#. PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF represents the unique id of + a partition if the partition table provides it. The UUID may be either an + EFI/GPT UUID, or refer to an MSDOS partition using the format SSSSSSSS-PP, + where SSSSSSSS is a zero-filled hex representation of the 32-bit + "NT disk signature", and PP is a zero-filled hex representation of the + 1-based partition number. +#. PARTUUID=<UUID>/PARTNROFF=<int> to select a partition in relation to a + partition with a known unique id. +#. <major>:<minor> major and minor number of the device separated by a colon. + +It accepts the following variants for MTD device: + +1. <device name> MTD device name. "pstore" is recommended. +#. <device number> MTD device number. + +kmsg_size +~~~~~~~~~ + +The chunk size in KB for oops/panic front-end. It **MUST** be a multiple of 4. +It's optional if you do not care oops/panic log. + +There are multiple chunks for oops/panic front-end depending on the remaining +space except other pstore front-ends. + +pstore/blk will log to oops/panic chunks one by one, and always overwrite the +oldest chunk if there is no more free chunk. + +pmsg_size +~~~~~~~~~ + +The chunk size in KB for pmsg front-end. It **MUST** be a multiple of 4. +It's optional if you do not care pmsg log. + +Unlike oops/panic front-end, there is only one chunk for pmsg front-end. + +Pmsg is a user space accessible pstore object. Writes to */dev/pmsg0* are +appended to the chunk. On reboot the contents are available in +*/sys/fs/pstore/pmsg-pstore-blk-0*. + +console_size +~~~~~~~~~~~~ + +The chunk size in KB for console front-end. It **MUST** be a multiple of 4. +It's optional if you do not care console log. + +Similar to pmsg front-end, there is only one chunk for console front-end. + +All log of console will be appended to the chunk. On reboot the contents are +available in */sys/fs/pstore/console-pstore-blk-0*. + +ftrace_size +~~~~~~~~~~~ + +The chunk size in KB for ftrace front-end. It **MUST** be a multiple of 4. +It's optional if you do not care console log. + +Similar to oops front-end, there are multiple chunks for ftrace front-end +depending on the count of cpu processors. Each chunk size is equal to +ftrace_size / processors_count. + +All log of ftrace will be appended to the chunk. On reboot the contents are +combined and available in */sys/fs/pstore/ftrace-pstore-blk-0*. + +Persistent function tracing might be useful for debugging software or hardware +related hangs. Here is an example of usage:: + + # mount -t pstore pstore /sys/fs/pstore + # mount -t debugfs debugfs /sys/kernel/debug/ + # echo 1 > /sys/kernel/debug/pstore/record_ftrace + # reboot -f + [...] + # mount -t pstore pstore /sys/fs/pstore + # tail /sys/fs/pstore/ftrace-pstore-blk-0 + CPU:0 ts:5914676 c0063828 c0063b94 call_cpuidle <- cpu_startup_entry+0x1b8/0x1e0 + CPU:0 ts:5914678 c039ecdc c006385c cpuidle_enter_state <- call_cpuidle+0x44/0x48 + CPU:0 ts:5914680 c039e9a0 c039ecf0 cpuidle_enter_freeze <- cpuidle_enter_state+0x304/0x314 + CPU:0 ts:5914681 c0063870 c039ea30 sched_idle_set_state <- cpuidle_enter_state+0x44/0x314 + CPU:1 ts:5916720 c0160f59 c015ee04 kernfs_unmap_bin_file <- __kernfs_remove+0x140/0x204 + CPU:1 ts:5916721 c05ca625 c015ee0c __mutex_lock_slowpath <- __kernfs_remove+0x148/0x204 + CPU:1 ts:5916723 c05c813d c05ca630 yield_to <- __mutex_lock_slowpath+0x314/0x358 + CPU:1 ts:5916724 c05ca2d1 c05ca638 __ww_mutex_lock <- __mutex_lock_slowpath+0x31c/0x358 + +max_reason +~~~~~~~~~~ + +Limiting which kinds of kmsg dumps are stored can be controlled via +the ``max_reason`` value, as defined in include/linux/kmsg_dump.h's +``enum kmsg_dump_reason``. For example, to store both Oopses and Panics, +``max_reason`` should be set to 2 (KMSG_DUMP_OOPS), to store only Panics +``max_reason`` should be set to 1 (KMSG_DUMP_PANIC). Setting this to 0 +(KMSG_DUMP_UNDEF), means the reason filtering will be controlled by the +``printk.always_kmsg_dump`` boot param: if unset, it'll be KMSG_DUMP_OOPS, +otherwise KMSG_DUMP_MAX. + +Configurations for driver +------------------------- + +A device driver uses ``register_pstore_device`` with +``struct pstore_device_info`` to register to pstore/blk. + +.. kernel-doc:: fs/pstore/blk.c + :export: + +Compression and header +---------------------- + +Block device is large enough for uncompressed oops data. Actually we do not +recommend data compression because pstore/blk will insert some information into +the first line of oops/panic data. For example:: + + Panic: Total 16 times + +It means that it's OOPS|Panic for the 16th time since the first booting. +Sometimes the number of occurrences of oops|panic since the first booting is +important to judge whether the system is stable. + +The following line is inserted by pstore filesystem. For example:: + + Oops#2 Part1 + +It means that it's OOPS for the 2nd time on the last boot. + +Reading the data +---------------- + +The dump data can be read from the pstore filesystem. The format for these +files is ``dmesg-pstore-blk-[N]`` for oops/panic front-end, +``pmsg-pstore-blk-0`` for pmsg front-end and so on. The timestamp of the +dump file records the trigger time. To delete a stored record from block +device, simply unlink the respective pstore file. + +Attentions in panic read/write APIs +----------------------------------- + +If on panic, the kernel is not going to run for much longer, the tasks will not +be scheduled and most kernel resources will be out of service. It +looks like a single-threaded program running on a single-core computer. + +The following points require special attention for panic read/write APIs: + +1. Can **NOT** allocate any memory. + If you need memory, just allocate while the block driver is initializing + rather than waiting until the panic. +#. Must be polled, **NOT** interrupt driven. + No task schedule any more. The block driver should delay to ensure the write + succeeds, but NOT sleep. +#. Can **NOT** take any lock. + There is no other task, nor any shared resource; you are safe to break all + locks. +#. Just use CPU to transfer. + Do not use DMA to transfer unless you are sure that DMA will not keep lock. +#. Control registers directly. + Please control registers directly rather than use Linux kernel resources. + Do I/O map while initializing rather than wait until a panic occurs. +#. Reset your block device and controller if necessary. + If you are not sure of the state of your block device and controller when + a panic occurs, you are safe to stop and reset them. + +pstore/blk supports psblk_blkdev_info(), which is defined in +*linux/pstore_blk.h*, to get information of using block device, such as the +device number, sector count and start sector of the whole disk. + +pstore block internals +---------------------- + +For developer reference, here are all the important structures and APIs: + +.. kernel-doc:: fs/pstore/zone.c + :internal: + +.. kernel-doc:: include/linux/pstore_zone.h + :internal: + +.. kernel-doc:: include/linux/pstore_blk.h + :internal: diff --git a/Documentation/admin-guide/quickly-build-trimmed-linux.rst b/Documentation/admin-guide/quickly-build-trimmed-linux.rst new file mode 100644 index 000000000..f08149bc5 --- /dev/null +++ b/Documentation/admin-guide/quickly-build-trimmed-linux.rst @@ -0,0 +1,1097 @@ +.. SPDX-License-Identifier: (GPL-2.0+ OR CC-BY-4.0) +.. [see the bottom of this file for redistribution information] + +=========================================== +How to quickly build a trimmed Linux kernel +=========================================== + +This guide explains how to swiftly build Linux kernels that are ideal for +testing purposes, but perfectly fine for day-to-day use, too. + +The essence of the process (aka 'TL;DR') +======================================== + +*[If you are new to compiling Linux, ignore this TLDR and head over to the next +section below: it contains a step-by-step guide, which is more detailed, but +still brief and easy to follow; that guide and its accompanying reference +section also mention alternatives, pitfalls, and additional aspects, all of +which might be relevant for you.]* + +If your system uses techniques like Secure Boot, prepare it to permit starting +self-compiled Linux kernels; install compilers and everything else needed for +building Linux; make sure to have 12 Gigabyte free space in your home directory. +Now run the following commands to download fresh Linux mainline sources, which +you then use to configure, build and install your own kernel:: + + git clone --depth 1 -b master \ + https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git ~/linux/ + cd ~/linux/ + # Hint: if you want to apply patches, do it at this point. See below for details. + # Hint: it's recommended to tag your build at this point. See below for details. + yes "" | make localmodconfig + # Hint: at this point you might want to adjust the build configuration; you'll + # have to, if you are running Debian. See below for details. + make -j $(nproc --all) + # Note: on many commodity distributions the next command suffices, but on Arch + # Linux, its derivatives, and some others it does not. See below for details. + command -v installkernel && sudo make modules_install install + reboot + +If you later want to build a newer mainline snapshot, use these commands:: + + cd ~/linux/ + git fetch --depth 1 origin + # Note: the next command will discard any changes you did to the code: + git checkout --force --detach origin/master + # Reminder: if you want to (re)apply patches, do it at this point. + # Reminder: you might want to add or modify a build tag at this point. + make olddefconfig + make -j $(nproc --all) + # Reminder: the next command on some distributions does not suffice. + command -v installkernel && sudo make modules_install install + reboot + +Step-by-step guide +================== + +Compiling your own Linux kernel is easy in principle. There are various ways to +do it. Which of them actually work and is the best depends on the circumstances. + +This guide describes a way perfectly suited for those who want to quickly +install Linux from sources without being bothered by complicated details; the +goal is to cover everything typically needed on mainstream Linux distributions +running on commodity PC or server hardware. + +The described approach is great for testing purposes, for example to try a +proposed fix or to check if a problem was already fixed in the latest codebase. +Nonetheless, kernels built this way are also totally fine for day-to-day use +while at the same time being easy to keep up to date. + +The following steps describe the important aspects of the process; a +comprehensive reference section later explains each of them in more detail. It +sometimes also describes alternative approaches, pitfalls, as well as errors +that might occur at a particular point -- and how to then get things rolling +again. + +.. + Note: if you see this note, you are reading the text's source file. You + might want to switch to a rendered version, as it makes it a lot easier to + quickly look something up in the reference section and afterwards jump back + to where you left off. Find a the latest rendered version here: + https://docs.kernel.org/admin-guide/quickly-build-trimmed-linux.html + +.. _backup_sbs: + + * Create a fresh backup and put system repair and restore tools at hand, just + to be prepared for the unlikely case of something going sideways. + + [:ref:`details<backup>`] + +.. _secureboot_sbs: + + * On platforms with 'Secure Boot' or similar techniques, prepare everything to + ensure the system will permit your self-compiled kernel to boot later. The + quickest and easiest way to achieve this on commodity x86 systems is to + disable such techniques in the BIOS setup utility; alternatively, remove + their restrictions through a process initiated by + ``mokutil --disable-validation``. + + [:ref:`details<secureboot>`] + +.. _buildrequires_sbs: + + * Install all software required to build a Linux kernel. Often you will need: + 'bc', 'binutils' ('ld' et al.), 'bison', 'flex', 'gcc', 'git', 'openssl', + 'pahole', 'perl', and the development headers for 'libelf' and 'openssl'. The + reference section shows how to quickly install those on various popular Linux + distributions. + + [:ref:`details<buildrequires>`] + +.. _diskspace_sbs: + + * Ensure to have enough free space for building and installing Linux. For the + latter 150 Megabyte in /lib/ and 100 in /boot/ are a safe bet. For storing + sources and build artifacts 12 Gigabyte in your home directory should + typically suffice. If you have less available, be sure to check the reference + section for the step that explains adjusting your kernels build + configuration: it mentions a trick that reduce the amount of required space + in /home/ to around 4 Gigabyte. + + [:ref:`details<diskspace>`] + +.. _sources_sbs: + + * Retrieve the sources of the Linux version you intend to build; then change + into the directory holding them, as all further commands in this guide are + meant to be executed from there. + + *[Note: the following paragraphs describe how to retrieve the sources by + partially cloning the Linux stable git repository. This is called a shallow + clone. The reference section explains two alternatives:* :ref:`packaged + archives<sources_archive>` *and* :ref:`a full git clone<sources_full>` *; + prefer the latter, if downloading a lot of data does not bother you, as that + will avoid some* :ref:`peculiar characteristics of shallow clones the + reference section explains<sources_shallow>` *.]* + + First, execute the following command to retrieve a fresh mainline codebase:: + + git clone --no-checkout --depth 1 -b master \ + https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git ~/linux/ + cd ~/linux/ + + If you want to access recent mainline releases and pre-releases, deepen you + clone's history to the oldest mainline version you are interested in:: + + git fetch --shallow-exclude=v6.0 origin + + In case you want to access a stable/longterm release (say v6.1.5), simply add + the branch holding that series; afterwards fetch the history at least up to + the mainline version that started the series (v6.1):: + + git remote set-branches --add origin linux-6.1.y + git fetch --shallow-exclude=v6.0 origin + + Now checkout the code you are interested in. If you just performed the + initial clone, you will be able to check out a fresh mainline codebase, which + is ideal for checking whether developers already fixed an issue:: + + git checkout --detach origin/master + + If you deepened your clone, you instead of ``origin/master`` can specify the + version you deepened to (``v6.0`` above); later releases like ``v6.1`` and + pre-release like ``v6.2-rc1`` will work, too. Stable or longterm versions + like ``v6.1.5`` work just the same, if you added the appropriate + stable/longterm branch as described. + + [:ref:`details<sources>`] + +.. _patching_sbs: + + * In case you want to apply a kernel patch, do so now. Often a command like + this will do the trick:: + + patch -p1 < ../proposed-fix.patch + + If the ``-p1`` is actually needed, depends on how the patch was created; in + case it does not apply thus try without it. + + If you cloned the sources with git and anything goes sideways, run ``git + reset --hard`` to undo any changes to the sources. + + [:ref:`details<patching>`] + +.. _tagging_sbs: + + * If you patched your kernel or have one of the same version installed already, + better add a unique tag to the one you are about to build:: + + echo "-proposed_fix" > localversion + + Running ``uname -r`` under your kernel later will then print something like + '6.1-rc4-proposed_fix'. + + [:ref:`details<tagging>`] + + .. _configuration_sbs: + + * Create the build configuration for your kernel based on an existing + configuration. + + If you already prepared such a '.config' file yourself, copy it to + ~/linux/ and run ``make olddefconfig``. + + Use the same command, if your distribution or somebody else already tailored + your running kernel to your or your hardware's needs: the make target + 'olddefconfig' will then try to use that kernel's .config as base. + + Using this make target is fine for everybody else, too -- but you often can + save a lot of time by using this command instead:: + + yes "" | make localmodconfig + + This will try to pick your distribution's kernel as base, but then disable + modules for any features apparently superfluous for your setup. This will + reduce the compile time enormously, especially if you are running an + universal kernel from a commodity Linux distribution. + + There is a catch: 'localmodconfig' is likely to disable kernel features you + did not use since you booted your Linux -- like drivers for currently + disconnected peripherals or a virtualization software not haven't used yet. + You can reduce or nearly eliminate that risk with tricks the reference + section outlines; but when building a kernel just for quick testing purposes + it is often negligible if such features are missing. But you should keep that + aspect in mind when using a kernel built with this make target, as it might + be the reason why something you only use occasionally stopped working. + + [:ref:`details<configuration>`] + +.. _configmods_sbs: + + * Check if you might want to or have to adjust some kernel configuration + options: + + * Evaluate how you want to handle debug symbols. Enable them, if you later + might need to decode a stack trace found for example in a 'panic', 'Oops', + 'warning', or 'BUG'; on the other hand disable them, if you are short on + storage space or prefer a smaller kernel binary. See the reference section + for details on how to do either. If neither applies, it will likely be fine + to simply not bother with this. [:ref:`details<configmods_debugsymbols>`] + + * Are you running Debian? Then to avoid known problems by performing + additional adjustments explained in the reference section. + [:ref:`details<configmods_distros>`]. + + * If you want to influence the other aspects of the configuration, do so now + by using make targets like 'menuconfig' or 'xconfig'. + [:ref:`details<configmods_individual>`]. + +.. _build_sbs: + + * Build the image and the modules of your kernel:: + + make -j $(nproc --all) + + If you want your kernel packaged up as deb, rpm, or tar file, see the + reference section for alternatives. + + [:ref:`details<build>`] + +.. _install_sbs: + + * Now install your kernel:: + + command -v installkernel && sudo make modules_install install + + Often all left for you to do afterwards is a ``reboot``, as many commodity + Linux distributions will then create an initramfs (also known as initrd) and + an entry for your kernel in your bootloader's configuration; but on some + distributions you have to take care of these two steps manually for reasons + the reference section explains. + + On a few distributions like Arch Linux and its derivatives the above command + does nothing at all; in that case you have to manually install your kernel, + as outlined in the reference section. + + If you are running a immutable Linux distribution, check its documentation + and the web to find out how to install your own kernel there. + + [:ref:`details<install>`] + +.. _another_sbs: + + * To later build another kernel you need similar steps, but sometimes slightly + different commands. + + First, switch back into the sources tree:: + + cd ~/linux/ + + In case you want to build a version from a stable/longterm series you have + not used yet (say 6.2.y), tell git to track it:: + + git remote set-branches --add origin linux-6.2.y + + Now fetch the latest upstream changes; you again need to specify the earliest + version you care about, as git otherwise might retrieve the entire commit + history:: + + git fetch --shallow-exclude=v6.0 origin + + Now switch to the version you are interested in -- but be aware the command + used here will discard any modifications you performed, as they would + conflict with the sources you want to checkout:: + + git checkout --force --detach origin/master + + At this point you might want to patch the sources again or set/modify a build + tag, as explained earlier. Afterwards adjust the build configuration to the + new codebase using olddefconfig, which will now adjust the configuration file + you prepared earlier using localmodconfig (~/linux/.config) for your next + kernel:: + + # reminder: if you want to apply patches, do it at this point + # reminder: you might want to update your build tag at this point + make olddefconfig + + Now build your kernel:: + + make -j $(nproc --all) + + Afterwards install the kernel as outlined above:: + + command -v installkernel && sudo make modules_install install + + [:ref:`details<another>`] + +.. _uninstall_sbs: + + * Your kernel is easy to remove later, as its parts are only stored in two + places and clearly identifiable by the kernel's release name. Just ensure to + not delete the kernel you are running, as that might render your system + unbootable. + + Start by deleting the directory holding your kernel's modules, which is named + after its release name -- '6.0.1-foobar' in the following example:: + + sudo rm -rf /lib/modules/6.0.1-foobar + + Now try the following command, which on some distributions will delete all + other kernel files installed while also removing the kernel's entry from the + bootloader configuration:: + + command -v kernel-install && sudo kernel-install -v remove 6.0.1-foobar + + If that command does not output anything or fails, see the reference section; + do the same if any files named '*6.0.1-foobar*' remain in /boot/. + + [:ref:`details<uninstall>`] + +.. _submit_improvements: + +Did you run into trouble following any of the above steps that is not cleared up +by the reference section below? Or do you have ideas how to improve the text? +Then please take a moment of your time and let the maintainer of this document +know by email (Thorsten Leemhuis <linux@leemhuis.info>), ideally while CCing the +Linux docs mailing list (linux-doc@vger.kernel.org). Such feedback is vital to +improve this document further, which is in everybody's interest, as it will +enable more people to master the task described here. + +Reference section for the step-by-step guide +============================================ + +This section holds additional information for each of the steps in the above +guide. + +.. _backup: + +Prepare for emergencies +----------------------- + + *Create a fresh backup and put system repair and restore tools at hand* + [:ref:`... <backup_sbs>`] + +Remember, you are dealing with computers, which sometimes do unexpected things +-- especially if you fiddle with crucial parts like the kernel of an operating +system. That's what you are about to do in this process. Hence, better prepare +for something going sideways, even if that should not happen. + +[:ref:`back to step-by-step guide <backup_sbs>`] + +.. _secureboot: + +Dealing with techniques like Secure Boot +---------------------------------------- + + *On platforms with 'Secure Boot' or similar techniques, prepare everything to + ensure the system will permit your self-compiled kernel to boot later.* + [:ref:`... <secureboot_sbs>`] + +Many modern systems allow only certain operating systems to start; they thus by +default will reject booting self-compiled kernels. + +You ideally deal with this by making your platform trust your self-built kernels +with the help of a certificate and signing. How to do that is not described +here, as it requires various steps that would take the text too far away from +its purpose; 'Documentation/admin-guide/module-signing.rst' and various web +sides already explain this in more detail. + +Temporarily disabling solutions like Secure Boot is another way to make your own +Linux boot. On commodity x86 systems it is possible to do this in the BIOS Setup +utility; the steps to do so are not described here, as they greatly vary between +machines. + +On mainstream x86 Linux distributions there is a third and universal option: +disable all Secure Boot restrictions for your Linux environment. You can +initiate this process by running ``mokutil --disable-validation``; this will +tell you to create a one-time password, which is safe to write down. Now +restart; right after your BIOS performed all self-tests the bootloader Shim will +show a blue box with a message 'Press any key to perform MOK management'. Hit +some key before the countdown exposes. This will open a menu and choose 'Change +Secure Boot state' there. Shim's 'MokManager' will now ask you to enter three +randomly chosen characters from the one-time password specified earlier. Once +you provided them, confirm that you really want to disable the validation. +Afterwards, permit MokManager to reboot the machine. + +[:ref:`back to step-by-step guide <secureboot_sbs>`] + +.. _buildrequires: + +Install build requirements +-------------------------- + + *Install all software required to build a Linux kernel.* + [:ref:`...<buildrequires_sbs>`] + +The kernel is pretty stand-alone, but besides tools like the compiler you will +sometimes need a few libraries to build one. How to install everything needed +depends on your Linux distribution and the configuration of the kernel you are +about to build. + +Here are a few examples what you typically need on some mainstream +distributions: + + * Debian, Ubuntu, and derivatives:: + + sudo apt install bc binutils bison dwarves flex gcc git make openssl \ + pahole perl-base libssl-dev libelf-dev + + * Fedora and derivatives:: + + sudo dnf install binutils /usr/include/{libelf.h,openssl/pkcs7.h} \ + /usr/bin/{bc,bison,flex,gcc,git,openssl,make,perl,pahole} + + * openSUSE and derivatives:: + + sudo zypper install bc binutils bison dwarves flex gcc git make perl-base \ + openssl openssl-devel libelf-dev + +In case you wonder why these lists include openssl and its development headers: +they are needed for the Secure Boot support, which many distributions enable in +their kernel configuration for x86 machines. + +Sometimes you will need tools for compression formats like bzip2, gzip, lz4, +lzma, lzo, xz, or zstd as well. + +You might need additional libraries and their development headers in case you +perform tasks not covered in this guide. For example, zlib will be needed when +building kernel tools from the tools/ directory; adjusting the build +configuration with make targets like 'menuconfig' or 'xconfig' will require +development headers for ncurses or Qt5. + +[:ref:`back to step-by-step guide <buildrequires_sbs>`] + +.. _diskspace: + +Space requirements +------------------ + + *Ensure to have enough free space for building and installing Linux.* + [:ref:`... <diskspace_sbs>`] + +The numbers mentioned are rough estimates with a big extra charge to be on the +safe side, so often you will need less. + +If you have space constraints, remember to read the reference section when you +reach the :ref:`section about configuration adjustments' <configmods>`, as +ensuring debug symbols are disabled will reduce the consumed disk space by quite +a few gigabytes. + +[:ref:`back to step-by-step guide <diskspace_sbs>`] + + +.. _sources: + +Download the sources +-------------------- + + *Retrieve the sources of the Linux version you intend to build.* + [:ref:`...<sources_sbs>`] + +The step-by-step guide outlines how to retrieve Linux' sources using a shallow +git clone. There is :ref:`more to tell about this method<sources_shallow>` and +two alternate ways worth describing: :ref:`packaged archives<sources_archive>` +and :ref:`a full git clone<sources_full>`. And the aspects ':ref:`wouldn't it +be wiser to use a proper pre-release than the latest mainline code +<sources_snapshot>`' and ':ref:`how to get an even fresher mainline codebase +<sources_fresher>`' need elaboration, too. + +Note, to keep things simple the commands used in this guide store the build +artifacts in the source tree. If you prefer to separate them, simply add +something like ``O=~/linux-builddir/`` to all make calls; also adjust the path +in all commands that add files or modify any generated (like your '.config'). + +[:ref:`back to step-by-step guide <sources_sbs>`] + +.. _sources_shallow: + +Noteworthy characteristics of shallow clones +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The step-by-step guide uses a shallow clone, as it is the best solution for most +of this document's target audience. There are a few aspects of this approach +worth mentioning: + + * This document in most places uses ``git fetch`` with ``--shallow-exclude=`` + to specify the earliest version you care about (or to be precise: its git + tag). You alternatively can use the parameter ``--shallow-since=`` to specify + an absolute (say ``'2023-07-15'``) or relative (``'12 months'``) date to + define the depth of the history you want to download. As a second + alternative, you can also specify a certain depth explicitly with a parameter + like ``--depth=1``, unless you add branches for stable/longterm kernels. + + * When running ``git fetch``, remember to always specify the oldest version, + the time you care about, or an explicit depth as shown in the step-by-step + guide. Otherwise you will risk downloading nearly the entire git history, + which will consume quite a bit of time and bandwidth while also stressing the + servers. + + Note, you do not have to use the same version or date all the time. But when + you change it over time, git will deepen or flatten the history to the + specified point. That allows you to retrieve versions you initially thought + you did not need -- or it will discard the sources of older versions, for + example in case you want to free up some disk space. The latter will happen + automatically when using ``--shallow-since=`` or + ``--depth=``. + + * Be warned, when deepening your clone you might encounter an error like + 'fatal: error in object: unshallow cafecaca0c0dacafecaca0c0dacafecaca0c0da'. + In that case run ``git repack -d`` and try again`` + + * In case you want to revert changes from a certain version (say Linux 6.3) or + perform a bisection (v6.2..v6.3), better tell ``git fetch`` to retrieve + objects up to three versions earlier (e.g. 6.0): ``git describe`` will then + be able to describe most commits just like it would in a full git clone. + +[:ref:`back to step-by-step guide <sources_sbs>`] [:ref:`back to section intro <sources>`] + +.. _sources_archive: + +Downloading the sources using a packages archive +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +People new to compiling Linux often assume downloading an archive via the +front-page of https://kernel.org is the best approach to retrieve Linux' +sources. It actually can be, if you are certain to build just one particular +kernel version without changing any code. Thing is: you might be sure this will +be the case, but in practice it often will turn out to be a wrong assumption. + +That's because when reporting or debugging an issue developers will often ask to +give another version a try. They also might suggest temporarily undoing a commit +with ``git revert`` or might provide various patches to try. Sometimes reporters +will also be asked to use ``git bisect`` to find the change causing a problem. +These things rely on git or are a lot easier and quicker to handle with it. + +A shallow clone also does not add any significant overhead. For example, when +you use ``git clone --depth=1`` to create a shallow clone of the latest mainline +codebase git will only retrieve a little more data than downloading the latest +mainline pre-release (aka 'rc') via the front-page of kernel.org would. + +A shallow clone therefore is often the better choice. If you nevertheless want +to use a packaged source archive, download one via kernel.org; afterwards +extract its content to some directory and change to the subdirectory created +during extraction. The rest of the step-by-step guide will work just fine, apart +from things that rely on git -- but this mainly concerns the section on +successive builds of other versions. + +[:ref:`back to step-by-step guide <sources_sbs>`] [:ref:`back to section intro <sources>`] + +.. _sources_full: + +Downloading the sources using a full git clone +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +If downloading and storing a lot of data (~4,4 Gigabyte as of early 2023) is +nothing that bothers you, instead of a shallow clone perform a full git clone +instead. You then will avoid the specialties mentioned above and will have all +versions and individual commits at hand at any time:: + + curl -L \ + https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/clone.bundle \ + -o linux-stable.git.bundle + git clone linux-stable.git.bundle ~/linux/ + rm linux-stable.git.bundle + cd ~/linux/ + git remote set-url origin \ + https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git + git fetch origin + git checkout --detach origin/master + +[:ref:`back to step-by-step guide <sources_sbs>`] [:ref:`back to section intro <sources>`] + +.. _sources_snapshot: + +Proper pre-releases (RCs) vs. latest mainline +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +When cloning the sources using git and checking out origin/master, you often +will retrieve a codebase that is somewhere between the latest and the next +release or pre-release. This almost always is the code you want when giving +mainline a shot: pre-releases like v6.1-rc5 are in no way special, as they do +not get any significant extra testing before being published. + +There is one exception: you might want to stick to the latest mainline release +(say v6.1) before its successor's first pre-release (v6.2-rc1) is out. That is +because compiler errors and other problems are more likely to occur during this +time, as mainline then is in its 'merge window': a usually two week long phase, +in which the bulk of the changes for the next release is merged. + +[:ref:`back to step-by-step guide <sources_sbs>`] [:ref:`back to section intro <sources>`] + +.. _sources_fresher: + +Avoiding the mainline lag +~~~~~~~~~~~~~~~~~~~~~~~~~ + +The explanations for both the shallow clone and the full clone both retrieve the +code from the Linux stable git repository. That makes things simpler for this +document's audience, as it allows easy access to both mainline and +stable/longterm releases. This approach has just one downside: + +Changes merged into the mainline repository are only synced to the master branch +of the Linux stable repository every few hours. This lag most of the time is +not something to worry about; but in case you really need the latest code, just +add the mainline repo as additional remote and checkout the code from there:: + + git remote add mainline \ + https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git + git fetch mainline + git checkout --detach mainline/master + +When doing this with a shallow clone, remember to call ``git fetch`` with one +of the parameters described earlier to limit the depth. + +[:ref:`back to step-by-step guide <sources_sbs>`] [:ref:`back to section intro <sources>`] + +.. _patching: + +Patch the sources (optional) +---------------------------- + + *In case you want to apply a kernel patch, do so now.* + [:ref:`...<patching_sbs>`] + +This is the point where you might want to patch your kernel -- for example when +a developer proposed a fix and asked you to check if it helps. The step-by-step +guide already explains everything crucial here. + +[:ref:`back to step-by-step guide <patching_sbs>`] + +.. _tagging: + +Tagging this kernel build (optional, often wise) +------------------------------------------------ + + *If you patched your kernel or already have that kernel version installed, + better tag your kernel by extending its release name:* + [:ref:`...<tagging_sbs>`] + +Tagging your kernel will help avoid confusion later, especially when you patched +your kernel. Adding an individual tag will also ensure the kernel's image and +its modules are installed in parallel to any existing kernels. + +There are various ways to add such a tag. The step-by-step guide realizes one by +creating a 'localversion' file in your build directory from which the kernel +build scripts will automatically pick up the tag. You can later change that file +to use a different tag in subsequent builds or simply remove that file to dump +the tag. + +[:ref:`back to step-by-step guide <tagging_sbs>`] + +.. _configuration: + +Define the build configuration for your kernel +---------------------------------------------- + + *Create the build configuration for your kernel based on an existing + configuration.* [:ref:`... <configuration_sbs>`] + +There are various aspects for this steps that require a more careful +explanation: + +Pitfalls when using another configuration file as base +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Make targets like localmodconfig and olddefconfig share a few common snares you +want to be aware of: + + * These targets will reuse a kernel build configuration in your build directory + (e.g. '~/linux/.config'), if one exists. In case you want to start from + scratch you thus need to delete it. + + * The make targets try to find the configuration for your running kernel + automatically, but might choose poorly. A line like '# using defaults found + in /boot/config-6.0.7-250.fc36.x86_64' or 'using config: + '/boot/config-6.0.7-250.fc36.x86_64' tells you which file they picked. If + that is not the intended one, simply store it as '~/linux/.config' + before using these make targets. + + * Unexpected things might happen if you try to use a config file prepared for + one kernel (say v6.0) on an older generation (say v5.15). In that case you + might want to use a configuration as base which your distribution utilized + when they used that or an slightly older kernel version. + +Influencing the configuration +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The make target olddefconfig and the ``yes "" |`` used when utilizing +localmodconfig will set any undefined build options to their default value. This +among others will disable many kernel features that were introduced after your +base kernel was released. + +If you want to set these configurations options manually, use ``oldconfig`` +instead of ``olddefconfig`` or omit the ``yes "" |`` when utilizing +localmodconfig. Then for each undefined configuration option you will be asked +how to proceed. In case you are unsure what to answer, simply hit 'enter' to +apply the default value. + +Big pitfall when using localmodconfig +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +As explained briefly in the step-by-step guide already: with localmodconfig it +can easily happen that your self-built kernel will lack modules for tasks you +did not perform before utilizing this make target. That's because those tasks +require kernel modules that are normally autoloaded when you perform that task +for the first time; if you didn't perform that task at least once before using +localmodonfig, the latter will thus assume these modules are superfluous and +disable them. + +You can try to avoid this by performing typical tasks that often will autoload +additional kernel modules: start a VM, establish VPN connections, loop-mount a +CD/DVD ISO, mount network shares (CIFS, NFS, ...), and connect all external +devices (2FA keys, headsets, webcams, ...) as well as storage devices with file +systems you otherwise do not utilize (btrfs, ext4, FAT, NTFS, XFS, ...). But it +is hard to think of everything that might be needed -- even kernel developers +often forget one thing or another at this point. + +Do not let that risk bother you, especially when compiling a kernel only for +testing purposes: everything typically crucial will be there. And if you forget +something important you can turn on a missing feature later and quickly run the +commands to compile and install a better kernel. + +But if you plan to build and use self-built kernels regularly, you might want to +reduce the risk by recording which modules your system loads over the course of +a few weeks. You can automate this with `modprobed-db +<https://github.com/graysky2/modprobed-db>`_. Afterwards use ``LSMOD=<path>`` to +point localmodconfig to the list of modules modprobed-db noticed being used:: + + yes "" | make LSMOD="${HOME}"/.config/modprobed.db localmodconfig + +Remote building with localmodconfig +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +If you want to use localmodconfig to build a kernel for another machine, run +``lsmod > lsmod_foo-machine`` on it and transfer that file to your build host. +Now point the build scripts to the file like this: ``yes "" | make +LSMOD=~/lsmod_foo-machine localmodconfig``. Note, in this case +you likely want to copy a base kernel configuration from the other machine over +as well and place it as .config in your build directory. + +[:ref:`back to step-by-step guide <configuration_sbs>`] + +.. _configmods: + +Adjust build configuration +-------------------------- + + *Check if you might want to or have to adjust some kernel configuration + options:* + +Depending on your needs you at this point might want or have to adjust some +kernel configuration options. + +.. _configmods_debugsymbols: + +Debug symbols +~~~~~~~~~~~~~ + + *Evaluate how you want to handle debug symbols.* + [:ref:`...<configmods_sbs>`] + +Most users do not need to care about this, it's often fine to leave everything +as it is; but you should take a closer look at this, if you might need to decode +a stack trace or want to reduce space consumption. + +Having debug symbols available can be important when your kernel throws a +'panic', 'Oops', 'warning', or 'BUG' later when running, as then you will be +able to find the exact place where the problem occurred in the code. But +collecting and embedding the needed debug information takes time and consumes +quite a bit of space: in late 2022 the build artifacts for a typical x86 kernel +configured with localmodconfig consumed around 5 Gigabyte of space with debug +symbols, but less than 1 when they were disabled. The resulting kernel image and +the modules are bigger as well, which increases load times. + +Hence, if you want a small kernel and are unlikely to decode a stack trace +later, you might want to disable debug symbols to avoid above downsides:: + + ./scripts/config --file .config -d DEBUG_INFO \ + -d DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT -d DEBUG_INFO_DWARF4 \ + -d DEBUG_INFO_DWARF5 -e CONFIG_DEBUG_INFO_NONE + make olddefconfig + +You on the other hand definitely want to enable them, if there is a decent +chance that you need to decode a stack trace later (as explained by 'Decode +failure messages' in Documentation/admin-guide/tainted-kernels.rst in more +detail):: + + ./scripts/config --file .config -d DEBUG_INFO_NONE -e DEBUG_KERNEL + -e DEBUG_INFO -e DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT -e KALLSYMS -e KALLSYMS_ALL + make olddefconfig + +Note, many mainstream distributions enable debug symbols in their kernel +configurations -- make targets like localmodconfig and olddefconfig thus will +often pick that setting up. + +[:ref:`back to step-by-step guide <configmods_sbs>`] + +.. _configmods_distros: + +Distro specific adjustments +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + + *Are you running* [:ref:`... <configmods_sbs>`] + +The following sections help you to avoid build problems that are known to occur +when following this guide on a few commodity distributions. + +**Debian:** + + * Remove a stale reference to a certificate file that would cause your build to + fail:: + + ./scripts/config --file .config --set-str SYSTEM_TRUSTED_KEYS '' + + Alternatively, download the needed certificate and make that configuration + option point to it, as `the Debian handbook explains in more detail + <https://debian-handbook.info/browse/stable/sect.kernel-compilation.html>`_ + -- or generate your own, as explained in + Documentation/admin-guide/module-signing.rst. + +[:ref:`back to step-by-step guide <configmods_sbs>`] + +.. _configmods_individual: + +Individual adjustments +~~~~~~~~~~~~~~~~~~~~~~ + + *If you want to influence the other aspects of the configuration, do so + now* [:ref:`... <configmods_sbs>`] + +You at this point can use a command like ``make menuconfig`` to enable or +disable certain features using a text-based user interface; to use a graphical +configuration utilize, use the make target ``xconfig`` or ``gconfig`` instead. +All of them require development libraries from toolkits they are based on +(ncurses, Qt5, Gtk2); an error message will tell you if something required is +missing. + +[:ref:`back to step-by-step guide <configmods_sbs>`] + +.. _build: + +Build your kernel +----------------- + + *Build the image and the modules of your kernel* [:ref:`... <build_sbs>`] + +A lot can go wrong at this stage, but the instructions below will help you help +yourself. Another subsection explains how to directly package your kernel up as +deb, rpm or tar file. + +Dealing with build errors +~~~~~~~~~~~~~~~~~~~~~~~~~ + +When a build error occurs, it might be caused by some aspect of your machine's +setup that often can be fixed quickly; other times though the problem lies in +the code and can only be fixed by a developer. A close examination of the +failure messages coupled with some research on the internet will often tell you +which of the two it is. To perform such a investigation, restart the build +process like this:: + + make V=1 + +The ``V=1`` activates verbose output, which might be needed to see the actual +error. To make it easier to spot, this command also omits the ``-j $(nproc +--all)`` used earlier to utilize every CPU core in the system for the job -- but +this parallelism also results in some clutter when failures occur. + +After a few seconds the build process should run into the error again. Now try +to find the most crucial line describing the problem. Then search the internet +for the most important and non-generic section of that line (say 4 to 8 words); +avoid or remove anything that looks remotely system-specific, like your username +or local path names like ``/home/username/linux/``. First try your regular +internet search engine with that string, afterwards search Linux kernel mailing +lists via `lore.kernel.org/all/ <https://lore.kernel.org/all/>`_. + +This most of the time will find something that will explain what is wrong; quite +often one of the hits will provide a solution for your problem, too. If you +do not find anything that matches your problem, try again from a different angle +by modifying your search terms or using another line from the error messages. + +In the end, most trouble you are to run into has likely been encountered and +reported by others already. That includes issues where the cause is not your +system, but lies the code. If you run into one of those, you might thus find a +solution (e.g. a patch) or workaround for your problem, too. + +Package your kernel up +~~~~~~~~~~~~~~~~~~~~~~ + +The step-by-step guide uses the default make targets (e.g. 'bzImage' and +'modules' on x86) to build the image and the modules of your kernel, which later +steps of the guide then install. You instead can also directly build everything +and directly package it up by using one of the following targets: + + * ``make -j $(nproc --all) bindeb-pkg`` to generate a deb package + + * ``make -j $(nproc --all) binrpm-pkg`` to generate a rpm package + + * ``make -j $(nproc --all) tarbz2-pkg`` to generate a bz2 compressed tarball + +This is just a selection of available make targets for this purpose, see +``make help`` for others. You can also use these targets after running +``make -j $(nproc --all)``, as they will pick up everything already built. + +If you employ the targets to generate deb or rpm packages, ignore the +step-by-step guide's instructions on installing and removing your kernel; +instead install and remove the packages using the package utility for the format +(e.g. dpkg and rpm) or a package management utility build on top of them (apt, +aptitude, dnf/yum, zypper, ...). Be aware that the packages generated using +these two make targets are designed to work on various distributions utilizing +those formats, they thus will sometimes behave differently than your +distribution's kernel packages. + +[:ref:`back to step-by-step guide <build_sbs>`] + +.. _install: + +Install your kernel +------------------- + + *Now install your kernel* [:ref:`... <install_sbs>`] + +What you need to do after executing the command in the step-by-step guide +depends on the existence and the implementation of an ``installkernel`` +executable. Many commodity Linux distributions ship such a kernel installer in +``/sbin/`` that does everything needed, hence there is nothing left for you +except rebooting. But some distributions contain an installkernel that does +only part of the job -- and a few lack it completely and leave all the work to +you. + +If ``installkernel`` is found, the kernel's build system will delegate the +actual installation of your kernel's image and related files to this executable. +On almost all Linux distributions it will store the image as '/boot/vmlinuz- +<your kernel's release name>' and put a 'System.map-<your kernel's release +name>' alongside it. Your kernel will thus be installed in parallel to any +existing ones, unless you already have one with exactly the same release name. + +Installkernel on many distributions will afterwards generate an 'initramfs' +(often also called 'initrd'), which commodity distributions rely on for booting; +hence be sure to keep the order of the two make targets used in the step-by-step +guide, as things will go sideways if you install your kernel's image before its +modules. Often installkernel will then add your kernel to the bootloader +configuration, too. You have to take care of one or both of these tasks +yourself, if your distributions installkernel doesn't handle them. + +A few distributions like Arch Linux and its derivatives totally lack an +installkernel executable. On those just install the modules using the kernel's +build system and then install the image and the System.map file manually:: + + sudo make modules_install + sudo install -m 0600 $(make -s image_name) /boot/vmlinuz-$(make -s kernelrelease) + sudo install -m 0600 System.map /boot/System.map-$(make -s kernelrelease) + +If your distribution boots with the help of an initramfs, now generate one for +your kernel using the tools your distribution provides for this process. +Afterwards add your kernel to your bootloader configuration and reboot. + +[:ref:`back to step-by-step guide <install_sbs>`] + +.. _another: + +Another round later +------------------- + + *To later build another kernel you need similar, but sometimes slightly + different commands* [:ref:`... <another_sbs>`] + +The process to build later kernels is similar, but at some points slightly +different. You for example do not want to use 'localmodconfig' for succeeding +kernel builds, as you already created a trimmed down configuration you want to +use from now on. Hence instead just use ``oldconfig`` or ``olddefconfig`` to +adjust your build configurations to the needs of the kernel version you are +about to build. + +If you created a shallow-clone with git, remember what the :ref:`section that +explained the setup described in more detail <sources>`: you need to use a +slightly different ``git fetch`` command and when switching to another series +need to add an additional remote branch. + +[:ref:`back to step-by-step guide <another_sbs>`] + +.. _uninstall: + +Uninstall the kernel later +-------------------------- + + *All parts of your installed kernel are identifiable by its release name and + thus easy to remove later.* [:ref:`... <uninstall_sbs>`] + +Do not worry installing your kernel manually and thus bypassing your +distribution's packaging system will totally mess up your machine: all parts of +your kernel are easy to remove later, as files are stored in two places only and +normally identifiable by the kernel's release name. + +One of the two places is a directory in /lib/modules/, which holds the modules +for each installed kernel. This directory is named after the kernel's release +name; hence, to remove all modules for one of your kernels, simply remove its +modules directory in /lib/modules/. + +The other place is /boot/, where typically one to five files will be placed +during installation of a kernel. All of them usually contain the release name in +their file name, but how many files and their name depends somewhat on your +distribution's installkernel executable (:ref:`see above <install>`) and its +initramfs generator. On some distributions the ``kernel-install`` command +mentioned in the step-by-step guide will remove all of these files for you -- +and the entry for your kernel in the bootloader configuration at the same time, +too. On others you have to take care of these steps yourself. The following +command should interactively remove the two main files of a kernel with the +release name '6.0.1-foobar':: + + rm -i /boot/{System.map,vmlinuz}-6.0.1-foobar + +Now remove the belonging initramfs, which often will be called something like +``/boot/initramfs-6.0.1-foobar.img`` or ``/boot/initrd.img-6.0.1-foobar``. +Afterwards check for other files in /boot/ that have '6.0.1-foobar' in their +name and delete them as well. Now remove the kernel from your bootloader's +configuration. + +Note, be very careful with wildcards like '*' when deleting files or directories +for kernels manually: you might accidentally remove files of a 6.0.11 kernel +when all you want is to remove 6.0 or 6.0.1. + +[:ref:`back to step-by-step guide <uninstall_sbs>`] + +.. _faq: + +FAQ +=== + +Why does this 'how-to' not work on my system? +--------------------------------------------- + +As initially stated, this guide is 'designed to cover everything typically +needed [to build a kernel] on mainstream Linux distributions running on +commodity PC or server hardware'. The outlined approach despite this should work +on many other setups as well. But trying to cover every possible use-case in one +guide would defeat its purpose, as without such a focus you would need dozens or +hundreds of constructs along the lines of 'in case you are having <insert +machine or distro>, you at this point have to do <this and that> +<instead|additionally>'. Each of which would make the text longer, more +complicated, and harder to follow. + +That being said: this of course is a balancing act. Hence, if you think an +additional use-case is worth describing, suggest it to the maintainers of this +document, as :ref:`described above <submit_improvements>`. + + +.. + end-of-content +.. + This document is maintained by Thorsten Leemhuis <linux@leemhuis.info>. If + you spot a typo or small mistake, feel free to let him know directly and + he'll fix it. You are free to do the same in a mostly informal way if you + want to contribute changes to the text -- but for copyright reasons please CC + linux-doc@vger.kernel.org and 'sign-off' your contribution as + Documentation/process/submitting-patches.rst explains in the section 'Sign + your work - the Developer's Certificate of Origin'. +.. + This text is available under GPL-2.0+ or CC-BY-4.0, as stated at the top + of the file. If you want to distribute this text under CC-BY-4.0 only, + please use 'The Linux kernel development community' for author attribution + and link this as source: + https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/Documentation/admin-guide/quickly-build-trimmed-linux.rst +.. + Note: Only the content of this RST file as found in the Linux kernel sources + is available under CC-BY-4.0, as versions of this text that were processed + (for example by the kernel's build system) might contain content taken from + files which use a more restrictive license. + diff --git a/Documentation/admin-guide/ramoops.rst b/Documentation/admin-guide/ramoops.rst new file mode 100644 index 000000000..e9f851421 --- /dev/null +++ b/Documentation/admin-guide/ramoops.rst @@ -0,0 +1,164 @@ +Ramoops oops/panic logger +========================= + +Sergiu Iordache <sergiu@chromium.org> + +Updated: 10 Feb 2021 + +Introduction +------------ + +Ramoops is an oops/panic logger that writes its logs to RAM before the system +crashes. It works by logging oopses and panics in a circular buffer. Ramoops +needs a system with persistent RAM so that the content of that area can +survive after a restart. + +Ramoops concepts +---------------- + +Ramoops uses a predefined memory area to store the dump. The start and size +and type of the memory area are set using three variables: + + * ``mem_address`` for the start + * ``mem_size`` for the size. The memory size will be rounded down to a + power of two. + * ``mem_type`` to specify if the memory type (default is pgprot_writecombine). + +Typically the default value of ``mem_type=0`` should be used as that sets the pstore +mapping to pgprot_writecombine. Setting ``mem_type=1`` attempts to use +``pgprot_noncached``, which only works on some platforms. This is because pstore +depends on atomic operations. At least on ARM, pgprot_noncached causes the +memory to be mapped strongly ordered, and atomic operations on strongly ordered +memory are implementation defined, and won't work on many ARMs such as omaps. +Setting ``mem_type=2`` attempts to treat the memory region as normal memory, +which enables full cache on it. This can improve the performance. + +The memory area is divided into ``record_size`` chunks (also rounded down to +power of two) and each kmesg dump writes a ``record_size`` chunk of +information. + +Limiting which kinds of kmsg dumps are stored can be controlled via +the ``max_reason`` value, as defined in include/linux/kmsg_dump.h's +``enum kmsg_dump_reason``. For example, to store both Oopses and Panics, +``max_reason`` should be set to 2 (KMSG_DUMP_OOPS), to store only Panics +``max_reason`` should be set to 1 (KMSG_DUMP_PANIC). Setting this to 0 +(KMSG_DUMP_UNDEF), means the reason filtering will be controlled by the +``printk.always_kmsg_dump`` boot param: if unset, it'll be KMSG_DUMP_OOPS, +otherwise KMSG_DUMP_MAX. + +The module uses a counter to record multiple dumps but the counter gets reset +on restart (i.e. new dumps after the restart will overwrite old ones). + +Ramoops also supports software ECC protection of persistent memory regions. +This might be useful when a hardware reset was used to bring the machine back +to life (i.e. a watchdog triggered). In such cases, RAM may be somewhat +corrupt, but usually it is restorable. + +Setting the parameters +---------------------- + +Setting the ramoops parameters can be done in several different manners: + + A. Use the module parameters (which have the names of the variables described + as before). For quick debugging, you can also reserve parts of memory during + boot and then use the reserved memory for ramoops. For example, assuming a + machine with > 128 MB of memory, the following kernel command line will tell + the kernel to use only the first 128 MB of memory, and place ECC-protected + ramoops region at 128 MB boundary:: + + mem=128M ramoops.mem_address=0x8000000 ramoops.ecc=1 + + B. Use Device Tree bindings, as described in + ``Documentation/devicetree/bindings/reserved-memory/ramoops.yaml``. + For example:: + + reserved-memory { + #address-cells = <2>; + #size-cells = <2>; + ranges; + + ramoops@8f000000 { + compatible = "ramoops"; + reg = <0 0x8f000000 0 0x100000>; + record-size = <0x4000>; + console-size = <0x4000>; + }; + }; + + C. Use a platform device and set the platform data. The parameters can then + be set through that platform data. An example of doing that is: + + .. code-block:: c + + #include <linux/pstore_ram.h> + [...] + + static struct ramoops_platform_data ramoops_data = { + .mem_size = <...>, + .mem_address = <...>, + .mem_type = <...>, + .record_size = <...>, + .max_reason = <...>, + .ecc = <...>, + }; + + static struct platform_device ramoops_dev = { + .name = "ramoops", + .dev = { + .platform_data = &ramoops_data, + }, + }; + + [... inside a function ...] + int ret; + + ret = platform_device_register(&ramoops_dev); + if (ret) { + printk(KERN_ERR "unable to register platform device\n"); + return ret; + } + +You can specify either RAM memory or peripheral devices' memory. However, when +specifying RAM, be sure to reserve the memory by issuing memblock_reserve() +very early in the architecture code, e.g.:: + + #include <linux/memblock.h> + + memblock_reserve(ramoops_data.mem_address, ramoops_data.mem_size); + +Dump format +----------- + +The data dump begins with a header, currently defined as ``====`` followed by a +timestamp and a new line. The dump then continues with the actual data. + +Reading the data +---------------- + +The dump data can be read from the pstore filesystem. The format for these +files is ``dmesg-ramoops-N``, where N is the record number in memory. To delete +a stored record from RAM, simply unlink the respective pstore file. + +Persistent function tracing +--------------------------- + +Persistent function tracing might be useful for debugging software or hardware +related hangs. The functions call chain log is stored in a ``ftrace-ramoops`` +file. Here is an example of usage:: + + # mount -t debugfs debugfs /sys/kernel/debug/ + # echo 1 > /sys/kernel/debug/pstore/record_ftrace + # reboot -f + [...] + # mount -t pstore pstore /mnt/ + # tail /mnt/ftrace-ramoops + 0 ffffffff8101ea64 ffffffff8101bcda native_apic_mem_read <- disconnect_bsp_APIC+0x6a/0xc0 + 0 ffffffff8101ea44 ffffffff8101bcf6 native_apic_mem_write <- disconnect_bsp_APIC+0x86/0xc0 + 0 ffffffff81020084 ffffffff8101a4b5 hpet_disable <- native_machine_shutdown+0x75/0x90 + 0 ffffffff81005f94 ffffffff8101a4bb iommu_shutdown_noop <- native_machine_shutdown+0x7b/0x90 + 0 ffffffff8101a6a1 ffffffff8101a437 native_machine_emergency_restart <- native_machine_restart+0x37/0x40 + 0 ffffffff811f9876 ffffffff8101a73a acpi_reboot <- native_machine_emergency_restart+0xaa/0x1e0 + 0 ffffffff8101a514 ffffffff8101a772 mach_reboot_fixups <- native_machine_emergency_restart+0xe2/0x1e0 + 0 ffffffff811d9c54 ffffffff8101a7a0 __const_udelay <- native_machine_emergency_restart+0x110/0x1e0 + 0 ffffffff811d9c34 ffffffff811d9c80 __delay <- __const_udelay+0x30/0x40 + 0 ffffffff811d9d14 ffffffff811d9c3f delay_tsc <- __delay+0xf/0x20 diff --git a/Documentation/admin-guide/rapidio.rst b/Documentation/admin-guide/rapidio.rst new file mode 100644 index 000000000..71ff658ab --- /dev/null +++ b/Documentation/admin-guide/rapidio.rst @@ -0,0 +1,107 @@ +======================= +RapidIO Subsystem Guide +======================= + +:Author: Matt Porter + +Introduction +============ + +RapidIO is a high speed switched fabric interconnect with features aimed +at the embedded market. RapidIO provides support for memory-mapped I/O +as well as message-based transactions over the switched fabric network. +RapidIO has a standardized discovery mechanism not unlike the PCI bus +standard that allows simple detection of devices in a network. + +This documentation is provided for developers intending to support +RapidIO on new architectures, write new drivers, or to understand the +subsystem internals. + +Known Bugs and Limitations +========================== + +Bugs +---- + +None. ;) + +Limitations +----------- + +1. Access/management of RapidIO memory regions is not supported + +2. Multiple host enumeration is not supported + +RapidIO driver interface +======================== + +Drivers are provided a set of calls in order to interface with the +subsystem to gather info on devices, request/map memory region +resources, and manage mailboxes/doorbells. + +Functions +--------- + +.. kernel-doc:: include/linux/rio_drv.h + :internal: + +.. kernel-doc:: drivers/rapidio/rio-driver.c + :export: + +.. kernel-doc:: drivers/rapidio/rio.c + :export: + +Internals +========= + +This chapter contains the autogenerated documentation of the RapidIO +subsystem. + +Structures +---------- + +.. kernel-doc:: include/linux/rio.h + :internal: + +Enumeration and Discovery +------------------------- + +.. kernel-doc:: drivers/rapidio/rio-scan.c + :internal: + +Driver functionality +-------------------- + +.. kernel-doc:: drivers/rapidio/rio.c + :internal: + +.. kernel-doc:: drivers/rapidio/rio-access.c + :internal: + +Device model support +-------------------- + +.. kernel-doc:: drivers/rapidio/rio-driver.c + :internal: + +PPC32 support +------------- + +.. kernel-doc:: arch/powerpc/sysdev/fsl_rio.c + :internal: + +Credits +======= + +The following people have contributed to the RapidIO subsystem directly +or indirectly: + +1. Matt Porter\ mporter@kernel.crashing.org + +2. Randy Vinson\ rvinson@mvista.com + +3. Dan Malek\ dan@embeddedalley.com + +The following people have contributed to this document: + +1. Matt Porter\ mporter@kernel.crashing.org diff --git a/Documentation/admin-guide/ras.rst b/Documentation/admin-guide/ras.rst new file mode 100644 index 000000000..8e03751d1 --- /dev/null +++ b/Documentation/admin-guide/ras.rst @@ -0,0 +1,1219 @@ +.. include:: <isonum.txt> + +============================================ +Reliability, Availability and Serviceability +============================================ + +RAS concepts +************ + +Reliability, Availability and Serviceability (RAS) is a concept used on +servers meant to measure their robustness. + +Reliability + is the probability that a system will produce correct outputs. + + * Generally measured as Mean Time Between Failures (MTBF) + * Enhanced by features that help to avoid, detect and repair hardware faults + +Availability + is the probability that a system is operational at a given time + + * Generally measured as a percentage of downtime per a period of time + * Often uses mechanisms to detect and correct hardware faults in + runtime; + +Serviceability (or maintainability) + is the simplicity and speed with which a system can be repaired or + maintained + + * Generally measured on Mean Time Between Repair (MTBR) + +Improving RAS +------------- + +In order to reduce systems downtime, a system should be capable of detecting +hardware errors, and, when possible correcting them in runtime. It should +also provide mechanisms to detect hardware degradation, in order to warn +the system administrator to take the action of replacing a component before +it causes data loss or system downtime. + +Among the monitoring measures, the most usual ones include: + +* CPU – detect errors at instruction execution and at L1/L2/L3 caches; +* Memory – add error correction logic (ECC) to detect and correct errors; +* I/O – add CRC checksums for transferred data; +* Storage – RAID, journal file systems, checksums, + Self-Monitoring, Analysis and Reporting Technology (SMART). + +By monitoring the number of occurrences of error detections, it is possible +to identify if the probability of hardware errors is increasing, and, on such +case, do a preventive maintenance to replace a degraded component while +those errors are correctable. + +Types of errors +--------------- + +Most mechanisms used on modern systems use technologies like Hamming +Codes that allow error correction when the number of errors on a bit packet +is below a threshold. If the number of errors is above, those mechanisms +can indicate with a high degree of confidence that an error happened, but +they can't correct. + +Also, sometimes an error occur on a component that it is not used. For +example, a part of the memory that it is not currently allocated. + +That defines some categories of errors: + +* **Correctable Error (CE)** - the error detection mechanism detected and + corrected the error. Such errors are usually not fatal, although some + Kernel mechanisms allow the system administrator to consider them as fatal. + +* **Uncorrected Error (UE)** - the amount of errors happened above the error + correction threshold, and the system was unable to auto-correct. + +* **Fatal Error** - when an UE error happens on a critical component of the + system (for example, a piece of the Kernel got corrupted by an UE), the + only reliable way to avoid data corruption is to hang or reboot the machine. + +* **Non-fatal Error** - when an UE error happens on an unused component, + like a CPU in power down state or an unused memory bank, the system may + still run, eventually replacing the affected hardware by a hot spare, + if available. + + Also, when an error happens on a userspace process, it is also possible to + kill such process and let userspace restart it. + +The mechanism for handling non-fatal errors is usually complex and may +require the help of some userspace application, in order to apply the +policy desired by the system administrator. + +Identifying a bad hardware component +------------------------------------ + +Just detecting a hardware flaw is usually not enough, as the system needs +to pinpoint to the minimal replaceable unit (MRU) that should be exchanged +to make the hardware reliable again. + +So, it requires not only error logging facilities, but also mechanisms that +will translate the error message to the silkscreen or component label for +the MRU. + +Typically, it is very complex for memory, as modern CPUs interlace memory +from different memory modules, in order to provide a better performance. The +DMI BIOS usually have a list of memory module labels, with can be obtained +using the ``dmidecode`` tool. For example, on a desktop machine, it shows:: + + Memory Device + Total Width: 64 bits + Data Width: 64 bits + Size: 16384 MB + Form Factor: SODIMM + Set: None + Locator: ChannelA-DIMM0 + Bank Locator: BANK 0 + Type: DDR4 + Type Detail: Synchronous + Speed: 2133 MHz + Rank: 2 + Configured Clock Speed: 2133 MHz + +On the above example, a DDR4 SO-DIMM memory module is located at the +system's memory labeled as "BANK 0", as given by the *bank locator* field. +Please notice that, on such system, the *total width* is equal to the +*data width*. It means that such memory module doesn't have error +detection/correction mechanisms. + +Unfortunately, not all systems use the same field to specify the memory +bank. On this example, from an older server, ``dmidecode`` shows:: + + Memory Device + Array Handle: 0x1000 + Error Information Handle: Not Provided + Total Width: 72 bits + Data Width: 64 bits + Size: 8192 MB + Form Factor: DIMM + Set: 1 + Locator: DIMM_A1 + Bank Locator: Not Specified + Type: DDR3 + Type Detail: Synchronous Registered (Buffered) + Speed: 1600 MHz + Rank: 2 + Configured Clock Speed: 1600 MHz + +There, the DDR3 RDIMM memory module is located at the system's memory labeled +as "DIMM_A1", as given by the *locator* field. Please notice that this +memory module has 64 bits of *data width* and 72 bits of *total width*. So, +it has 8 extra bits to be used by error detection and correction mechanisms. +Such kind of memory is called Error-correcting code memory (ECC memory). + +To make things even worse, it is not uncommon that systems with different +labels on their system's board to use exactly the same BIOS, meaning that +the labels provided by the BIOS won't match the real ones. + +ECC memory +---------- + +As mentioned in the previous section, ECC memory has extra bits to be +used for error correction. In the above example, a memory module has +64 bits of *data width*, and 72 bits of *total width*. The extra 8 +bits which are used for the error detection and correction mechanisms +are referred to as the *syndrome*\ [#f1]_\ [#f2]_. + +So, when the cpu requests the memory controller to write a word with +*data width*, the memory controller calculates the *syndrome* in real time, +using Hamming code, or some other error correction code, like SECDED+, +producing a code with *total width* size. Such code is then written +on the memory modules. + +At read, the *total width* bits code is converted back, using the same +ECC code used on write, producing a word with *data width* and a *syndrome*. +The word with *data width* is sent to the CPU, even when errors happen. + +The memory controller also looks at the *syndrome* in order to check if +there was an error, and if the ECC code was able to fix such error. +If the error was corrected, a Corrected Error (CE) happened. If not, an +Uncorrected Error (UE) happened. + +The information about the CE/UE errors is stored on some special registers +at the memory controller and can be accessed by reading such registers, +either by BIOS, by some special CPUs or by Linux EDAC driver. On x86 64 +bit CPUs, such errors can also be retrieved via the Machine Check +Architecture (MCA)\ [#f3]_. + +.. [#f1] Please notice that several memory controllers allow operation on a + mode called "Lock-Step", where it groups two memory modules together, + doing 128-bit reads/writes. That gives 16 bits for error correction, with + significantly improves the error correction mechanism, at the expense + that, when an error happens, there's no way to know what memory module is + to blame. So, it has to blame both memory modules. + +.. [#f2] Some memory controllers also allow using memory in mirror mode. + On such mode, the same data is written to two memory modules. At read, + the system checks both memory modules, in order to check if both provide + identical data. On such configuration, when an error happens, there's no + way to know what memory module is to blame. So, it has to blame both + memory modules (or 4 memory modules, if the system is also on Lock-step + mode). + +.. [#f3] For more details about the Machine Check Architecture (MCA), + please read Documentation/arch/x86/x86_64/machinecheck.rst at the Kernel tree. + +EDAC - Error Detection And Correction +************************************* + +.. note:: + + "bluesmoke" was the name for this device driver subsystem when it + was "out-of-tree" and maintained at http://bluesmoke.sourceforge.net. + That site is mostly archaic now and can be used only for historical + purposes. + + When the subsystem was pushed upstream for the first time, on + Kernel 2.6.16, it was renamed to ``EDAC``. + +Purpose +------- + +The ``edac`` kernel module's goal is to detect and report hardware errors +that occur within the computer system running under linux. + +Memory +------ + +Memory Correctable Errors (CE) and Uncorrectable Errors (UE) are the +primary errors being harvested. These types of errors are harvested by +the ``edac_mc`` device. + +Detecting CE events, then harvesting those events and reporting them, +**can** but must not necessarily be a predictor of future UE events. With +CE events only, the system can and will continue to operate as no data +has been damaged yet. + +However, preventive maintenance and proactive part replacement of memory +modules exhibiting CEs can reduce the likelihood of the dreaded UE events +and system panics. + +Other hardware elements +----------------------- + +A new feature for EDAC, the ``edac_device`` class of device, was added in +the 2.6.23 version of the kernel. + +This new device type allows for non-memory type of ECC hardware detectors +to have their states harvested and presented to userspace via the sysfs +interface. + +Some architectures have ECC detectors for L1, L2 and L3 caches, +along with DMA engines, fabric switches, main data path switches, +interconnections, and various other hardware data paths. If the hardware +reports it, then a edac_device device probably can be constructed to +harvest and present that to userspace. + + +PCI bus scanning +---------------- + +In addition, PCI devices are scanned for PCI Bus Parity and SERR Errors +in order to determine if errors are occurring during data transfers. + +The presence of PCI Parity errors must be examined with a grain of salt. +There are several add-in adapters that do **not** follow the PCI specification +with regards to Parity generation and reporting. The specification says +the vendor should tie the parity status bits to 0 if they do not intend +to generate parity. Some vendors do not do this, and thus the parity bit +can "float" giving false positives. + +There is a PCI device attribute located in sysfs that is checked by +the EDAC PCI scanning code. If that attribute is set, PCI parity/error +scanning is skipped for that device. The attribute is:: + + broken_parity_status + +and is located in ``/sys/devices/pci<XXX>/0000:XX:YY.Z`` directories for +PCI devices. + + +Versioning +---------- + +EDAC is composed of a "core" module (``edac_core.ko``) and several Memory +Controller (MC) driver modules. On a given system, the CORE is loaded +and one MC driver will be loaded. Both the CORE and the MC driver (or +``edac_device`` driver) have individual versions that reflect current +release level of their respective modules. + +Thus, to "report" on what version a system is running, one must report +both the CORE's and the MC driver's versions. + + +Loading +------- + +If ``edac`` was statically linked with the kernel then no loading +is necessary. If ``edac`` was built as modules then simply modprobe +the ``edac`` pieces that you need. You should be able to modprobe +hardware-specific modules and have the dependencies load the necessary +core modules. + +Example:: + + $ modprobe amd76x_edac + +loads both the ``amd76x_edac.ko`` memory controller module and the +``edac_mc.ko`` core module. + + +Sysfs interface +--------------- + +EDAC presents a ``sysfs`` interface for control and reporting purposes. It +lives in the /sys/devices/system/edac directory. + +Within this directory there currently reside 2 components: + + ======= ============================== + mc memory controller(s) system + pci PCI control and status system + ======= ============================== + + + +Memory Controller (mc) Model +---------------------------- + +Each ``mc`` device controls a set of memory modules [#f4]_. These modules +are laid out in a Chip-Select Row (``csrowX``) and Channel table (``chX``). +There can be multiple csrows and multiple channels. + +.. [#f4] Nowadays, the term DIMM (Dual In-line Memory Module) is widely + used to refer to a memory module, although there are other memory + packaging alternatives, like SO-DIMM, SIMM, etc. The UEFI + specification (Version 2.7) defines a memory module in the Common + Platform Error Record (CPER) section to be an SMBIOS Memory Device + (Type 17). Along this document, and inside the EDAC subsystem, the term + "dimm" is used for all memory modules, even when they use a + different kind of packaging. + +Memory controllers allow for several csrows, with 8 csrows being a +typical value. Yet, the actual number of csrows depends on the layout of +a given motherboard, memory controller and memory module characteristics. + +Dual channels allow for dual data length (e. g. 128 bits, on 64 bit systems) +data transfers to/from the CPU from/to memory. Some newer chipsets allow +for more than 2 channels, like Fully Buffered DIMMs (FB-DIMMs) memory +controllers. The following example will assume 2 channels: + + +------------+-----------------------+ + | CS Rows | Channels | + +------------+-----------+-----------+ + | | ``ch0`` | ``ch1`` | + +============+===========+===========+ + | |**DIMM_A0**|**DIMM_B0**| + +------------+-----------+-----------+ + | ``csrow0`` | rank0 | rank0 | + +------------+-----------+-----------+ + | ``csrow1`` | rank1 | rank1 | + +------------+-----------+-----------+ + | |**DIMM_A1**|**DIMM_B1**| + +------------+-----------+-----------+ + | ``csrow2`` | rank0 | rank0 | + +------------+-----------+-----------+ + | ``csrow3`` | rank1 | rank1 | + +------------+-----------+-----------+ + +In the above example, there are 4 physical slots on the motherboard +for memory DIMMs: + + +---------+---------+ + | DIMM_A0 | DIMM_B0 | + +---------+---------+ + | DIMM_A1 | DIMM_B1 | + +---------+---------+ + +Labels for these slots are usually silk-screened on the motherboard. +Slots labeled ``A`` are channel 0 in this example. Slots labeled ``B`` are +channel 1. Notice that there are two csrows possible on a physical DIMM. +These csrows are allocated their csrow assignment based on the slot into +which the memory DIMM is placed. Thus, when 1 DIMM is placed in each +Channel, the csrows cross both DIMMs. + +Memory DIMMs come single or dual "ranked". A rank is a populated csrow. +In the example above 2 dual ranked DIMMs are similarly placed. Thus, +both csrow0 and csrow1 are populated. On the other hand, when 2 single +ranked DIMMs are placed in slots DIMM_A0 and DIMM_B0, then they will +have just one csrow (csrow0) and csrow1 will be empty. The pattern +repeats itself for csrow2 and csrow3. Also note that some memory +controllers don't have any logic to identify the memory module, see +``rankX`` directories below. + +The representation of the above is reflected in the directory +tree in EDAC's sysfs interface. Starting in directory +``/sys/devices/system/edac/mc``, each memory controller will be +represented by its own ``mcX`` directory, where ``X`` is the +index of the MC:: + + ..../edac/mc/ + | + |->mc0 + |->mc1 + |->mc2 + .... + +Under each ``mcX`` directory each ``csrowX`` is again represented by a +``csrowX``, where ``X`` is the csrow index:: + + .../mc/mc0/ + | + |->csrow0 + |->csrow2 + |->csrow3 + .... + +Notice that there is no csrow1, which indicates that csrow0 is composed +of a single ranked DIMMs. This should also apply in both Channels, in +order to have dual-channel mode be operational. Since both csrow2 and +csrow3 are populated, this indicates a dual ranked set of DIMMs for +channels 0 and 1. + +Within each of the ``mcX`` and ``csrowX`` directories are several EDAC +control and attribute files. + +``mcX`` directories +------------------- + +In ``mcX`` directories are EDAC control and attribute files for +this ``X`` instance of the memory controllers. + +For a description of the sysfs API, please see: + + Documentation/ABI/testing/sysfs-devices-edac + + +``dimmX`` or ``rankX`` directories +---------------------------------- + +The recommended way to use the EDAC subsystem is to look at the information +provided by the ``dimmX`` or ``rankX`` directories [#f5]_. + +A typical EDAC system has the following structure under +``/sys/devices/system/edac/``\ [#f6]_:: + + /sys/devices/system/edac/ + ├── mc + │ ├── mc0 + │ │ ├── ce_count + │ │ ├── ce_noinfo_count + │ │ ├── dimm0 + │ │ │ ├── dimm_ce_count + │ │ │ ├── dimm_dev_type + │ │ │ ├── dimm_edac_mode + │ │ │ ├── dimm_label + │ │ │ ├── dimm_location + │ │ │ ├── dimm_mem_type + │ │ │ ├── dimm_ue_count + │ │ │ ├── size + │ │ │ └── uevent + │ │ ├── max_location + │ │ ├── mc_name + │ │ ├── reset_counters + │ │ ├── seconds_since_reset + │ │ ├── size_mb + │ │ ├── ue_count + │ │ ├── ue_noinfo_count + │ │ └── uevent + │ ├── mc1 + │ │ ├── ce_count + │ │ ├── ce_noinfo_count + │ │ ├── dimm0 + │ │ │ ├── dimm_ce_count + │ │ │ ├── dimm_dev_type + │ │ │ ├── dimm_edac_mode + │ │ │ ├── dimm_label + │ │ │ ├── dimm_location + │ │ │ ├── dimm_mem_type + │ │ │ ├── dimm_ue_count + │ │ │ ├── size + │ │ │ └── uevent + │ │ ├── max_location + │ │ ├── mc_name + │ │ ├── reset_counters + │ │ ├── seconds_since_reset + │ │ ├── size_mb + │ │ ├── ue_count + │ │ ├── ue_noinfo_count + │ │ └── uevent + │ └── uevent + └── uevent + +In the ``dimmX`` directories are EDAC control and attribute files for +this ``X`` memory module: + +- ``size`` - Total memory managed by this csrow attribute file + + This attribute file displays, in count of megabytes, the memory + that this csrow contains. + +- ``dimm_ue_count`` - Uncorrectable Errors count attribute file + + This attribute file displays the total count of uncorrectable + errors that have occurred on this DIMM. If panic_on_ue is set + this counter will not have a chance to increment, since EDAC + will panic the system. + +- ``dimm_ce_count`` - Correctable Errors count attribute file + + This attribute file displays the total count of correctable + errors that have occurred on this DIMM. This count is very + important to examine. CEs provide early indications that a + DIMM is beginning to fail. This count field should be + monitored for non-zero values and report such information + to the system administrator. + +- ``dimm_dev_type`` - Device type attribute file + + This attribute file will display what type of DRAM device is + being utilized on this DIMM. + Examples: + + - x1 + - x2 + - x4 + - x8 + +- ``dimm_edac_mode`` - EDAC Mode of operation attribute file + + This attribute file will display what type of Error detection + and correction is being utilized. + +- ``dimm_label`` - memory module label control file + + This control file allows this DIMM to have a label assigned + to it. With this label in the module, when errors occur + the output can provide the DIMM label in the system log. + This becomes vital for panic events to isolate the + cause of the UE event. + + DIMM Labels must be assigned after booting, with information + that correctly identifies the physical slot with its + silk screen label. This information is currently very + motherboard specific and determination of this information + must occur in userland at this time. + +- ``dimm_location`` - location of the memory module + + The location can have up to 3 levels, and describe how the + memory controller identifies the location of a memory module. + Depending on the type of memory and memory controller, it + can be: + + - *csrow* and *channel* - used when the memory controller + doesn't identify a single DIMM - e. g. in ``rankX`` dir; + - *branch*, *channel*, *slot* - typically used on FB-DIMM memory + controllers; + - *channel*, *slot* - used on Nehalem and newer Intel drivers. + +- ``dimm_mem_type`` - Memory Type attribute file + + This attribute file will display what type of memory is currently + on this csrow. Normally, either buffered or unbuffered memory. + Examples: + + - Registered-DDR + - Unbuffered-DDR + +.. [#f5] On some systems, the memory controller doesn't have any logic + to identify the memory module. On such systems, the directory is called ``rankX`` and works on a similar way as the ``csrowX`` directories. + On modern Intel memory controllers, the memory controller identifies the + memory modules directly. On such systems, the directory is called ``dimmX``. + +.. [#f6] There are also some ``power`` directories and ``subsystem`` + symlinks inside the sysfs mapping that are automatically created by + the sysfs subsystem. Currently, they serve no purpose. + +``csrowX`` directories +---------------------- + +When CONFIG_EDAC_LEGACY_SYSFS is enabled, sysfs will contain the ``csrowX`` +directories. As this API doesn't work properly for Rambus, FB-DIMMs and +modern Intel Memory Controllers, this is being deprecated in favor of +``dimmX`` directories. + +In the ``csrowX`` directories are EDAC control and attribute files for +this ``X`` instance of csrow: + + +- ``ue_count`` - Total Uncorrectable Errors count attribute file + + This attribute file displays the total count of uncorrectable + errors that have occurred on this csrow. If panic_on_ue is set + this counter will not have a chance to increment, since EDAC + will panic the system. + + +- ``ce_count`` - Total Correctable Errors count attribute file + + This attribute file displays the total count of correctable + errors that have occurred on this csrow. This count is very + important to examine. CEs provide early indications that a + DIMM is beginning to fail. This count field should be + monitored for non-zero values and report such information + to the system administrator. + + +- ``size_mb`` - Total memory managed by this csrow attribute file + + This attribute file displays, in count of megabytes, the memory + that this csrow contains. + + +- ``mem_type`` - Memory Type attribute file + + This attribute file will display what type of memory is currently + on this csrow. Normally, either buffered or unbuffered memory. + Examples: + + - Registered-DDR + - Unbuffered-DDR + + +- ``edac_mode`` - EDAC Mode of operation attribute file + + This attribute file will display what type of Error detection + and correction is being utilized. + + +- ``dev_type`` - Device type attribute file + + This attribute file will display what type of DRAM device is + being utilized on this DIMM. + Examples: + + - x1 + - x2 + - x4 + - x8 + + +- ``ch0_ce_count`` - Channel 0 CE Count attribute file + + This attribute file will display the count of CEs on this + DIMM located in channel 0. + + +- ``ch0_ue_count`` - Channel 0 UE Count attribute file + + This attribute file will display the count of UEs on this + DIMM located in channel 0. + + +- ``ch0_dimm_label`` - Channel 0 DIMM Label control file + + + This control file allows this DIMM to have a label assigned + to it. With this label in the module, when errors occur + the output can provide the DIMM label in the system log. + This becomes vital for panic events to isolate the + cause of the UE event. + + DIMM Labels must be assigned after booting, with information + that correctly identifies the physical slot with its + silk screen label. This information is currently very + motherboard specific and determination of this information + must occur in userland at this time. + + +- ``ch1_ce_count`` - Channel 1 CE Count attribute file + + + This attribute file will display the count of CEs on this + DIMM located in channel 1. + + +- ``ch1_ue_count`` - Channel 1 UE Count attribute file + + + This attribute file will display the count of UEs on this + DIMM located in channel 0. + + +- ``ch1_dimm_label`` - Channel 1 DIMM Label control file + + This control file allows this DIMM to have a label assigned + to it. With this label in the module, when errors occur + the output can provide the DIMM label in the system log. + This becomes vital for panic events to isolate the + cause of the UE event. + + DIMM Labels must be assigned after booting, with information + that correctly identifies the physical slot with its + silk screen label. This information is currently very + motherboard specific and determination of this information + must occur in userland at this time. + + +System Logging +-------------- + +If logging for UEs and CEs is enabled, then system logs will contain +information indicating that errors have been detected:: + + EDAC MC0: CE page 0x283, offset 0xce0, grain 8, syndrome 0x6ec3, row 0, channel 1 "DIMM_B1": amd76x_edac + EDAC MC0: CE page 0x1e5, offset 0xfb0, grain 8, syndrome 0xb741, row 0, channel 1 "DIMM_B1": amd76x_edac + + +The structure of the message is: + + +---------------------------------------+-------------+ + | Content | Example | + +=======================================+=============+ + | The memory controller | MC0 | + +---------------------------------------+-------------+ + | Error type | CE | + +---------------------------------------+-------------+ + | Memory page | 0x283 | + +---------------------------------------+-------------+ + | Offset in the page | 0xce0 | + +---------------------------------------+-------------+ + | The byte granularity | grain 8 | + | or resolution of the error | | + +---------------------------------------+-------------+ + | The error syndrome | 0xb741 | + +---------------------------------------+-------------+ + | Memory row | row 0 | + +---------------------------------------+-------------+ + | Memory channel | channel 1 | + +---------------------------------------+-------------+ + | DIMM label, if set prior | DIMM B1 | + +---------------------------------------+-------------+ + | And then an optional, driver-specific | | + | message that may have additional | | + | information. | | + +---------------------------------------+-------------+ + +Both UEs and CEs with no info will lack all but memory controller, error +type, a notice of "no info" and then an optional, driver-specific error +message. + + +PCI Bus Parity Detection +------------------------ + +On Header Type 00 devices, the primary status is looked at for any +parity error regardless of whether parity is enabled on the device or +not. (The spec indicates parity is generated in some cases). On Header +Type 01 bridges, the secondary status register is also looked at to see +if parity occurred on the bus on the other side of the bridge. + + +Sysfs configuration +------------------- + +Under ``/sys/devices/system/edac/pci`` are control and attribute files as +follows: + + +- ``check_pci_parity`` - Enable/Disable PCI Parity checking control file + + This control file enables or disables the PCI Bus Parity scanning + operation. Writing a 1 to this file enables the scanning. Writing + a 0 to this file disables the scanning. + + Enable:: + + echo "1" >/sys/devices/system/edac/pci/check_pci_parity + + Disable:: + + echo "0" >/sys/devices/system/edac/pci/check_pci_parity + + +- ``pci_parity_count`` - Parity Count + + This attribute file will display the number of parity errors that + have been detected. + + +Module parameters +----------------- + +- ``edac_mc_panic_on_ue`` - Panic on UE control file + + An uncorrectable error will cause a machine panic. This is usually + desirable. It is a bad idea to continue when an uncorrectable error + occurs - it is indeterminate what was uncorrected and the operating + system context might be so mangled that continuing will lead to further + corruption. If the kernel has MCE configured, then EDAC will never + notice the UE. + + LOAD TIME:: + + module/kernel parameter: edac_mc_panic_on_ue=[0|1] + + RUN TIME:: + + echo "1" > /sys/module/edac_core/parameters/edac_mc_panic_on_ue + + +- ``edac_mc_log_ue`` - Log UE control file + + + Generate kernel messages describing uncorrectable errors. These errors + are reported through the system message log system. UE statistics + will be accumulated even when UE logging is disabled. + + LOAD TIME:: + + module/kernel parameter: edac_mc_log_ue=[0|1] + + RUN TIME:: + + echo "1" > /sys/module/edac_core/parameters/edac_mc_log_ue + + +- ``edac_mc_log_ce`` - Log CE control file + + + Generate kernel messages describing correctable errors. These + errors are reported through the system message log system. + CE statistics will be accumulated even when CE logging is disabled. + + LOAD TIME:: + + module/kernel parameter: edac_mc_log_ce=[0|1] + + RUN TIME:: + + echo "1" > /sys/module/edac_core/parameters/edac_mc_log_ce + + +- ``edac_mc_poll_msec`` - Polling period control file + + + The time period, in milliseconds, for polling for error information. + Too small a value wastes resources. Too large a value might delay + necessary handling of errors and might loose valuable information for + locating the error. 1000 milliseconds (once each second) is the current + default. Systems which require all the bandwidth they can get, may + increase this. + + LOAD TIME:: + + module/kernel parameter: edac_mc_poll_msec=[0|1] + + RUN TIME:: + + echo "1000" > /sys/module/edac_core/parameters/edac_mc_poll_msec + + +- ``panic_on_pci_parity`` - Panic on PCI PARITY Error + + + This control file enables or disables panicking when a parity + error has been detected. + + + module/kernel parameter:: + + edac_panic_on_pci_pe=[0|1] + + Enable:: + + echo "1" > /sys/module/edac_core/parameters/edac_panic_on_pci_pe + + Disable:: + + echo "0" > /sys/module/edac_core/parameters/edac_panic_on_pci_pe + + + +EDAC device type +---------------- + +In the header file, edac_pci.h, there is a series of edac_device structures +and APIs for the EDAC_DEVICE. + +User space access to an edac_device is through the sysfs interface. + +At the location ``/sys/devices/system/edac`` (sysfs) new edac_device devices +will appear. + +There is a three level tree beneath the above ``edac`` directory. For example, +the ``test_device_edac`` device (found at the http://bluesmoke.sourceforget.net +website) installs itself as:: + + /sys/devices/system/edac/test-instance + +in this directory are various controls, a symlink and one or more ``instance`` +directories. + +The standard default controls are: + + ============== ======================================================= + log_ce boolean to log CE events + log_ue boolean to log UE events + panic_on_ue boolean to ``panic`` the system if an UE is encountered + (default off, can be set true via startup script) + poll_msec time period between POLL cycles for events + ============== ======================================================= + +The test_device_edac device adds at least one of its own custom control: + + ============== ================================================== + test_bits which in the current test driver does nothing but + show how it is installed. A ported driver can + add one or more such controls and/or attributes + for specific uses. + One out-of-tree driver uses controls here to allow + for ERROR INJECTION operations to hardware + injection registers + ============== ================================================== + +The symlink points to the 'struct dev' that is registered for this edac_device. + +Instances +--------- + +One or more instance directories are present. For the ``test_device_edac`` +case: + + +----------------+ + | test-instance0 | + +----------------+ + + +In this directory there are two default counter attributes, which are totals of +counter in deeper subdirectories. + + ============== ==================================== + ce_count total of CE events of subdirectories + ue_count total of UE events of subdirectories + ============== ==================================== + +Blocks +------ + +At the lowest directory level is the ``block`` directory. There can be 0, 1 +or more blocks specified in each instance: + + +-------------+ + | test-block0 | + +-------------+ + +In this directory the default attributes are: + + ============== ================================================ + ce_count which is counter of CE events for this ``block`` + of hardware being monitored + ue_count which is counter of UE events for this ``block`` + of hardware being monitored + ============== ================================================ + + +The ``test_device_edac`` device adds 4 attributes and 1 control: + + ================== ==================================================== + test-block-bits-0 for every POLL cycle this counter + is incremented + test-block-bits-1 every 10 cycles, this counter is bumped once, + and test-block-bits-0 is set to 0 + test-block-bits-2 every 100 cycles, this counter is bumped once, + and test-block-bits-1 is set to 0 + test-block-bits-3 every 1000 cycles, this counter is bumped once, + and test-block-bits-2 is set to 0 + ================== ==================================================== + + + ================== ==================================================== + reset-counters writing ANY thing to this control will + reset all the above counters. + ================== ==================================================== + + +Use of the ``test_device_edac`` driver should enable any others to create their own +unique drivers for their hardware systems. + +The ``test_device_edac`` sample driver is located at the +http://bluesmoke.sourceforge.net project site for EDAC. + + +Usage of EDAC APIs on Nehalem and newer Intel CPUs +-------------------------------------------------- + +On older Intel architectures, the memory controller was part of the North +Bridge chipset. Nehalem, Sandy Bridge, Ivy Bridge, Haswell, Sky Lake and +newer Intel architectures integrated an enhanced version of the memory +controller (MC) inside the CPUs. + +This chapter will cover the differences of the enhanced memory controllers +found on newer Intel CPUs, such as ``i7core_edac``, ``sb_edac`` and +``sbx_edac`` drivers. + +.. note:: + + The Xeon E7 processor families use a separate chip for the memory + controller, called Intel Scalable Memory Buffer. This section doesn't + apply for such families. + +1) There is one Memory Controller per Quick Patch Interconnect + (QPI). At the driver, the term "socket" means one QPI. This is + associated with a physical CPU socket. + + Each MC have 3 physical read channels, 3 physical write channels and + 3 logic channels. The driver currently sees it as just 3 channels. + Each channel can have up to 3 DIMMs. + + The minimum known unity is DIMMs. There are no information about csrows. + As EDAC API maps the minimum unity is csrows, the driver sequentially + maps channel/DIMM into different csrows. + + For example, supposing the following layout:: + + Ch0 phy rd0, wr0 (0x063f4031): 2 ranks, UDIMMs + dimm 0 1024 Mb offset: 0, bank: 8, rank: 1, row: 0x4000, col: 0x400 + dimm 1 1024 Mb offset: 4, bank: 8, rank: 1, row: 0x4000, col: 0x400 + Ch1 phy rd1, wr1 (0x063f4031): 2 ranks, UDIMMs + dimm 0 1024 Mb offset: 0, bank: 8, rank: 1, row: 0x4000, col: 0x400 + Ch2 phy rd3, wr3 (0x063f4031): 2 ranks, UDIMMs + dimm 0 1024 Mb offset: 0, bank: 8, rank: 1, row: 0x4000, col: 0x400 + + The driver will map it as:: + + csrow0: channel 0, dimm0 + csrow1: channel 0, dimm1 + csrow2: channel 1, dimm0 + csrow3: channel 2, dimm0 + + exports one DIMM per csrow. + + Each QPI is exported as a different memory controller. + +2) The MC has the ability to inject errors to test drivers. The drivers + implement this functionality via some error injection nodes: + + For injecting a memory error, there are some sysfs nodes, under + ``/sys/devices/system/edac/mc/mc?/``: + + - ``inject_addrmatch/*``: + Controls the error injection mask register. It is possible to specify + several characteristics of the address to match an error code:: + + dimm = the affected dimm. Numbers are relative to a channel; + rank = the memory rank; + channel = the channel that will generate an error; + bank = the affected bank; + page = the page address; + column (or col) = the address column. + + each of the above values can be set to "any" to match any valid value. + + At driver init, all values are set to any. + + For example, to generate an error at rank 1 of dimm 2, for any channel, + any bank, any page, any column:: + + echo 2 >/sys/devices/system/edac/mc/mc0/inject_addrmatch/dimm + echo 1 >/sys/devices/system/edac/mc/mc0/inject_addrmatch/rank + + To return to the default behaviour of matching any, you can do:: + + echo any >/sys/devices/system/edac/mc/mc0/inject_addrmatch/dimm + echo any >/sys/devices/system/edac/mc/mc0/inject_addrmatch/rank + + - ``inject_eccmask``: + specifies what bits will have troubles, + + - ``inject_section``: + specifies what ECC cache section will get the error:: + + 3 for both + 2 for the highest + 1 for the lowest + + - ``inject_type``: + specifies the type of error, being a combination of the following bits:: + + bit 0 - repeat + bit 1 - ecc + bit 2 - parity + + - ``inject_enable``: + starts the error generation when something different than 0 is written. + + All inject vars can be read. root permission is needed for write. + + Datasheet states that the error will only be generated after a write on an + address that matches inject_addrmatch. It seems, however, that reading will + also produce an error. + + For example, the following code will generate an error for any write access + at socket 0, on any DIMM/address on channel 2:: + + echo 2 >/sys/devices/system/edac/mc/mc0/inject_addrmatch/channel + echo 2 >/sys/devices/system/edac/mc/mc0/inject_type + echo 64 >/sys/devices/system/edac/mc/mc0/inject_eccmask + echo 3 >/sys/devices/system/edac/mc/mc0/inject_section + echo 1 >/sys/devices/system/edac/mc/mc0/inject_enable + dd if=/dev/mem of=/dev/null seek=16k bs=4k count=1 >& /dev/null + + For socket 1, it is needed to replace "mc0" by "mc1" at the above + commands. + + The generated error message will look like:: + + EDAC MC0: UE row 0, channel-a= 0 channel-b= 0 labels "-": NON_FATAL (addr = 0x0075b980, socket=0, Dimm=0, Channel=2, syndrome=0x00000040, count=1, Err=8c0000400001009f:4000080482 (read error: read ECC error)) + +3) Corrected Error memory register counters + + Those newer MCs have some registers to count memory errors. The driver + uses those registers to report Corrected Errors on devices with Registered + DIMMs. + + However, those counters don't work with Unregistered DIMM. As the chipset + offers some counters that also work with UDIMMs (but with a worse level of + granularity than the default ones), the driver exposes those registers for + UDIMM memories. + + They can be read by looking at the contents of ``all_channel_counts/``:: + + $ for i in /sys/devices/system/edac/mc/mc0/all_channel_counts/*; do echo $i; cat $i; done + /sys/devices/system/edac/mc/mc0/all_channel_counts/udimm0 + 0 + /sys/devices/system/edac/mc/mc0/all_channel_counts/udimm1 + 0 + /sys/devices/system/edac/mc/mc0/all_channel_counts/udimm2 + 0 + + What happens here is that errors on different csrows, but at the same + dimm number will increment the same counter. + So, in this memory mapping:: + + csrow0: channel 0, dimm0 + csrow1: channel 0, dimm1 + csrow2: channel 1, dimm0 + csrow3: channel 2, dimm0 + + The hardware will increment udimm0 for an error at the first dimm at either + csrow0, csrow2 or csrow3; + + The hardware will increment udimm1 for an error at the second dimm at either + csrow0, csrow2 or csrow3; + + The hardware will increment udimm2 for an error at the third dimm at either + csrow0, csrow2 or csrow3; + +4) Standard error counters + + The standard error counters are generated when an mcelog error is received + by the driver. Since, with UDIMM, this is counted by software, it is + possible that some errors could be lost. With RDIMM's, they display the + contents of the registers + +Reference documents used on ``amd64_edac`` +------------------------------------------ + +``amd64_edac`` module is based on the following documents +(available from http://support.amd.com/en-us/search/tech-docs): + +1. :Title: BIOS and Kernel Developer's Guide for AMD Athlon 64 and AMD + Opteron Processors + :AMD publication #: 26094 + :Revision: 3.26 + :Link: http://support.amd.com/TechDocs/26094.PDF + +2. :Title: BIOS and Kernel Developer's Guide for AMD NPT Family 0Fh + Processors + :AMD publication #: 32559 + :Revision: 3.00 + :Issue Date: May 2006 + :Link: http://support.amd.com/TechDocs/32559.pdf + +3. :Title: BIOS and Kernel Developer's Guide (BKDG) For AMD Family 10h + Processors + :AMD publication #: 31116 + :Revision: 3.00 + :Issue Date: September 07, 2007 + :Link: http://support.amd.com/TechDocs/31116.pdf + +4. :Title: BIOS and Kernel Developer's Guide (BKDG) for AMD Family 15h + Models 30h-3Fh Processors + :AMD publication #: 49125 + :Revision: 3.06 + :Issue Date: 2/12/2015 (latest release) + :Link: http://support.amd.com/TechDocs/49125_15h_Models_30h-3Fh_BKDG.pdf + +5. :Title: BIOS and Kernel Developer's Guide (BKDG) for AMD Family 15h + Models 60h-6Fh Processors + :AMD publication #: 50742 + :Revision: 3.01 + :Issue Date: 7/23/2015 (latest release) + :Link: http://support.amd.com/TechDocs/50742_15h_Models_60h-6Fh_BKDG.pdf + +6. :Title: BIOS and Kernel Developer's Guide (BKDG) for AMD Family 16h + Models 00h-0Fh Processors + :AMD publication #: 48751 + :Revision: 3.03 + :Issue Date: 2/23/2015 (latest release) + :Link: http://support.amd.com/TechDocs/48751_16h_bkdg.pdf + +Credits +======= + +* Written by Doug Thompson <dougthompson@xmission.com> + + - 7 Dec 2005 + - 17 Jul 2007 Updated + +* |copy| Mauro Carvalho Chehab + + - 05 Aug 2009 Nehalem interface + - 26 Oct 2016 Converted to ReST and cleanups at the Nehalem section + +* EDAC authors/maintainers: + + - Doug Thompson, Dave Jiang, Dave Peterson et al, + - Mauro Carvalho Chehab + - Borislav Petkov + - original author: Thayne Harbaugh diff --git a/Documentation/admin-guide/reporting-issues.rst b/Documentation/admin-guide/reporting-issues.rst new file mode 100644 index 000000000..2fd5a0302 --- /dev/null +++ b/Documentation/admin-guide/reporting-issues.rst @@ -0,0 +1,1764 @@ +.. SPDX-License-Identifier: (GPL-2.0+ OR CC-BY-4.0) +.. See the bottom of this file for additional redistribution information. + +Reporting issues +++++++++++++++++ + + +The short guide (aka TL;DR) +=========================== + +Are you facing a regression with vanilla kernels from the same stable or +longterm series? One still supported? Then search the `LKML +<https://lore.kernel.org/lkml/>`_ and the `Linux stable mailing list +<https://lore.kernel.org/stable/>`_ archives for matching reports to join. If +you don't find any, install `the latest release from that series +<https://kernel.org/>`_. If it still shows the issue, report it to the stable +mailing list (stable@vger.kernel.org) and CC the regressions list +(regressions@lists.linux.dev); ideally also CC the maintainer and the mailing +list for the subsystem in question. + +In all other cases try your best guess which kernel part might be causing the +issue. Check the :ref:`MAINTAINERS <maintainers>` file for how its developers +expect to be told about problems, which most of the time will be by email with a +mailing list in CC. Check the destination's archives for matching reports; +search the `LKML <https://lore.kernel.org/lkml/>`_ and the web, too. If you +don't find any to join, install `the latest mainline kernel +<https://kernel.org/>`_. If the issue is present there, send a report. + +The issue was fixed there, but you would like to see it resolved in a still +supported stable or longterm series as well? Then install its latest release. +If it shows the problem, search for the change that fixed it in mainline and +check if backporting is in the works or was discarded; if it's neither, ask +those who handled the change for it. + +**General remarks**: When installing and testing a kernel as outlined above, +ensure it's vanilla (IOW: not patched and not using add-on modules). Also make +sure it's built and running in a healthy environment and not already tainted +before the issue occurs. + +If you are facing multiple issues with the Linux kernel at once, report each +separately. While writing your report, include all information relevant to the +issue, like the kernel and the distro used. In case of a regression, CC the +regressions mailing list (regressions@lists.linux.dev) to your report. Also try +to pin-point the culprit with a bisection; if you succeed, include its +commit-id and CC everyone in the sign-off-by chain. + +Once the report is out, answer any questions that come up and help where you +can. That includes keeping the ball rolling by occasionally retesting with newer +releases and sending a status update afterwards. + +Step-by-step guide how to report issues to the kernel maintainers +================================================================= + +The above TL;DR outlines roughly how to report issues to the Linux kernel +developers. It might be all that's needed for people already familiar with +reporting issues to Free/Libre & Open Source Software (FLOSS) projects. For +everyone else there is this section. It is more detailed and uses a +step-by-step approach. It still tries to be brief for readability and leaves +out a lot of details; those are described below the step-by-step guide in a +reference section, which explains each of the steps in more detail. + +Note: this section covers a few more aspects than the TL;DR and does things in +a slightly different order. That's in your interest, to make sure you notice +early if an issue that looks like a Linux kernel problem is actually caused by +something else. These steps thus help to ensure the time you invest in this +process won't feel wasted in the end: + + * Are you facing an issue with a Linux kernel a hardware or software vendor + provided? Then in almost all cases you are better off to stop reading this + document and reporting the issue to your vendor instead, unless you are + willing to install the latest Linux version yourself. Be aware the latter + will often be needed anyway to hunt down and fix issues. + + * Perform a rough search for existing reports with your favorite internet + search engine; additionally, check the archives of the `Linux Kernel Mailing + List (LKML) <https://lore.kernel.org/lkml/>`_. If you find matching reports, + join the discussion instead of sending a new one. + + * See if the issue you are dealing with qualifies as regression, security + issue, or a really severe problem: those are 'issues of high priority' that + need special handling in some steps that are about to follow. + + * Make sure it's not the kernel's surroundings that are causing the issue + you face. + + * Create a fresh backup and put system repair and restore tools at hand. + + * Ensure your system does not enhance its kernels by building additional + kernel modules on-the-fly, which solutions like DKMS might be doing locally + without your knowledge. + + * Check if your kernel was 'tainted' when the issue occurred, as the event + that made the kernel set this flag might be causing the issue you face. + + * Write down coarsely how to reproduce the issue. If you deal with multiple + issues at once, create separate notes for each of them and make sure they + work independently on a freshly booted system. That's needed, as each issue + needs to get reported to the kernel developers separately, unless they are + strongly entangled. + + * If you are facing a regression within a stable or longterm version line + (say something broke when updating from 5.10.4 to 5.10.5), scroll down to + 'Dealing with regressions within a stable and longterm kernel line'. + + * Locate the driver or kernel subsystem that seems to be causing the issue. + Find out how and where its developers expect reports. Note: most of the + time this won't be bugzilla.kernel.org, as issues typically need to be sent + by mail to a maintainer and a public mailing list. + + * Search the archives of the bug tracker or mailing list in question + thoroughly for reports that might match your issue. If you find anything, + join the discussion instead of sending a new report. + +After these preparations you'll now enter the main part: + + * Unless you are already running the latest 'mainline' Linux kernel, better + go and install it for the reporting process. Testing and reporting with + the latest 'stable' Linux can be an acceptable alternative in some + situations; during the merge window that actually might be even the best + approach, but in that development phase it can be an even better idea to + suspend your efforts for a few days anyway. Whatever version you choose, + ideally use a 'vanilla' build. Ignoring these advices will dramatically + increase the risk your report will be rejected or ignored. + + * Ensure the kernel you just installed does not 'taint' itself when + running. + + * Reproduce the issue with the kernel you just installed. If it doesn't show + up there, scroll down to the instructions for issues only happening with + stable and longterm kernels. + + * Optimize your notes: try to find and write the most straightforward way to + reproduce your issue. Make sure the end result has all the important + details, and at the same time is easy to read and understand for others + that hear about it for the first time. And if you learned something in this + process, consider searching again for existing reports about the issue. + + * If your failure involves a 'panic', 'Oops', 'warning', or 'BUG', consider + decoding the kernel log to find the line of code that triggered the error. + + * If your problem is a regression, try to narrow down when the issue was + introduced as much as possible. + + * Start to compile the report by writing a detailed description about the + issue. Always mention a few things: the latest kernel version you installed + for reproducing, the Linux Distribution used, and your notes on how to + reproduce the issue. Ideally, make the kernel's build configuration + (.config) and the output from ``dmesg`` available somewhere on the net and + link to it. Include or upload all other information that might be relevant, + like the output/screenshot of an Oops or the output from ``lspci``. Once + you wrote this main part, insert a normal length paragraph on top of it + outlining the issue and the impact quickly. On top of this add one sentence + that briefly describes the problem and gets people to read on. Now give the + thing a descriptive title or subject that yet again is shorter. Then you're + ready to send or file the report like the MAINTAINERS file told you, unless + you are dealing with one of those 'issues of high priority': they need + special care which is explained in 'Special handling for high priority + issues' below. + + * Wait for reactions and keep the thing rolling until you can accept the + outcome in one way or the other. Thus react publicly and in a timely manner + to any inquiries. Test proposed fixes. Do proactive testing: retest with at + least every first release candidate (RC) of a new mainline version and + report your results. Send friendly reminders if things stall. And try to + help yourself, if you don't get any help or if it's unsatisfying. + + +Reporting regressions within a stable and longterm kernel line +-------------------------------------------------------------- + +This subsection is for you, if you followed above process and got sent here at +the point about regression within a stable or longterm kernel version line. You +face one of those if something breaks when updating from 5.10.4 to 5.10.5 (a +switch from 5.9.15 to 5.10.5 does not qualify). The developers want to fix such +regressions as quickly as possible, hence there is a streamlined process to +report them: + + * Check if the kernel developers still maintain the Linux kernel version + line you care about: go to the `front page of kernel.org + <https://kernel.org/>`_ and make sure it mentions + the latest release of the particular version line without an '[EOL]' tag. + + * Check the archives of the `Linux stable mailing list + <https://lore.kernel.org/stable/>`_ for existing reports. + + * Install the latest release from the particular version line as a vanilla + kernel. Ensure this kernel is not tainted and still shows the problem, as + the issue might have already been fixed there. If you first noticed the + problem with a vendor kernel, check a vanilla build of the last version + known to work performs fine as well. + + * Send a short problem report to the Linux stable mailing list + (stable@vger.kernel.org) and CC the Linux regressions mailing list + (regressions@lists.linux.dev); if you suspect the cause in a particular + subsystem, CC its maintainer and its mailing list. Roughly describe the + issue and ideally explain how to reproduce it. Mention the first version + that shows the problem and the last version that's working fine. Then + wait for further instructions. + +The reference section below explains each of these steps in more detail. + + +Reporting issues only occurring in older kernel version lines +------------------------------------------------------------- + +This subsection is for you, if you tried the latest mainline kernel as outlined +above, but failed to reproduce your issue there; at the same time you want to +see the issue fixed in a still supported stable or longterm series or vendor +kernels regularly rebased on those. If that the case, follow these steps: + + * Prepare yourself for the possibility that going through the next few steps + might not get the issue solved in older releases: the fix might be too big + or risky to get backported there. + + * Perform the first three steps in the section "Dealing with regressions + within a stable and longterm kernel line" above. + + * Search the Linux kernel version control system for the change that fixed + the issue in mainline, as its commit message might tell you if the fix is + scheduled for backporting already. If you don't find anything that way, + search the appropriate mailing lists for posts that discuss such an issue + or peer-review possible fixes; then check the discussions if the fix was + deemed unsuitable for backporting. If backporting was not considered at + all, join the newest discussion, asking if it's in the cards. + + * One of the former steps should lead to a solution. If that doesn't work + out, ask the maintainers for the subsystem that seems to be causing the + issue for advice; CC the mailing list for the particular subsystem as well + as the stable mailing list. + +The reference section below explains each of these steps in more detail. + + +Reference section: Reporting issues to the kernel maintainers +============================================================= + +The detailed guides above outline all the major steps in brief fashion, which +should be enough for most people. But sometimes there are situations where even +experienced users might wonder how to actually do one of those steps. That's +what this section is for, as it will provide a lot more details on each of the +above steps. Consider this as reference documentation: it's possible to read it +from top to bottom. But it's mainly meant to skim over and a place to look up +details how to actually perform those steps. + +A few words of general advice before digging into the details: + + * The Linux kernel developers are well aware this process is complicated and + demands more than other FLOSS projects. We'd love to make it simpler. But + that would require work in various places as well as some infrastructure, + which would need constant maintenance; nobody has stepped up to do that + work, so that's just how things are for now. + + * A warranty or support contract with some vendor doesn't entitle you to + request fixes from developers in the upstream Linux kernel community: such + contracts are completely outside the scope of the Linux kernel, its + development community, and this document. That's why you can't demand + anything such a contract guarantees in this context, not even if the + developer handling the issue works for the vendor in question. If you want + to claim your rights, use the vendor's support channel instead. When doing + so, you might want to mention you'd like to see the issue fixed in the + upstream Linux kernel; motivate them by saying it's the only way to ensure + the fix in the end will get incorporated in all Linux distributions. + + * If you never reported an issue to a FLOSS project before you should consider + reading `How to Report Bugs Effectively + <https://www.chiark.greenend.org.uk/~sgtatham/bugs.html>`_, `How To Ask + Questions The Smart Way + <http://www.catb.org/esr/faqs/smart-questions.html>`_, and `How to ask good + questions <https://jvns.ca/blog/good-questions/>`_. + +With that off the table, find below the details on how to properly report +issues to the Linux kernel developers. + + +Make sure you're using the upstream Linux kernel +------------------------------------------------ + + *Are you facing an issue with a Linux kernel a hardware or software vendor + provided? Then in almost all cases you are better off to stop reading this + document and reporting the issue to your vendor instead, unless you are + willing to install the latest Linux version yourself. Be aware the latter + will often be needed anyway to hunt down and fix issues.* + +Like most programmers, Linux kernel developers don't like to spend time dealing +with reports for issues that don't even happen with their current code. It's +just a waste everybody's time, especially yours. Unfortunately such situations +easily happen when it comes to the kernel and often leads to frustration on both +sides. That's because almost all Linux-based kernels pre-installed on devices +(Computers, Laptops, Smartphones, Routers, …) and most shipped by Linux +distributors are quite distant from the official Linux kernel as distributed by +kernel.org: these kernels from these vendors are often ancient from the point of +Linux development or heavily modified, often both. + +Most of these vendor kernels are quite unsuitable for reporting issues to the +Linux kernel developers: an issue you face with one of them might have been +fixed by the Linux kernel developers months or years ago already; additionally, +the modifications and enhancements by the vendor might be causing the issue you +face, even if they look small or totally unrelated. That's why you should report +issues with these kernels to the vendor. Its developers should look into the +report and, in case it turns out to be an upstream issue, fix it directly +upstream or forward the report there. In practice that often does not work out +or might not what you want. You thus might want to consider circumventing the +vendor by installing the very latest Linux kernel core yourself. If that's an +option for you move ahead in this process, as a later step in this guide will +explain how to do that once it rules out other potential causes for your issue. + +Note, the previous paragraph is starting with the word 'most', as sometimes +developers in fact are willing to handle reports about issues occurring with +vendor kernels. If they do in the end highly depends on the developers and the +issue in question. Your chances are quite good if the distributor applied only +small modifications to a kernel based on a recent Linux version; that for +example often holds true for the mainline kernels shipped by Debian GNU/Linux +Sid or Fedora Rawhide. Some developers will also accept reports about issues +with kernels from distributions shipping the latest stable kernel, as long as +its only slightly modified; that for example is often the case for Arch Linux, +regular Fedora releases, and openSUSE Tumbleweed. But keep in mind, you better +want to use a mainline Linux and avoid using a stable kernel for this +process, as outlined in the section 'Install a fresh kernel for testing' in more +detail. + +Obviously you are free to ignore all this advice and report problems with an old +or heavily modified vendor kernel to the upstream Linux developers. But note, +those often get rejected or ignored, so consider yourself warned. But it's still +better than not reporting the issue at all: sometimes such reports directly or +indirectly will help to get the issue fixed over time. + + +Search for existing reports, first run +-------------------------------------- + + *Perform a rough search for existing reports with your favorite internet + search engine; additionally, check the archives of the Linux Kernel Mailing + List (LKML). If you find matching reports, join the discussion instead of + sending a new one.* + +Reporting an issue that someone else already brought forward is often a waste of +time for everyone involved, especially you as the reporter. So it's in your own +interest to thoroughly check if somebody reported the issue already. At this +step of the process it's okay to just perform a rough search: a later step will +tell you to perform a more detailed search once you know where your issue needs +to be reported to. Nevertheless, do not hurry with this step of the reporting +process, it can save you time and trouble. + +Simply search the internet with your favorite search engine first. Afterwards, +search the `Linux Kernel Mailing List (LKML) archives +<https://lore.kernel.org/lkml/>`_. + +If you get flooded with results consider telling your search engine to limit +search timeframe to the past month or year. And wherever you search, make sure +to use good search terms; vary them a few times, too. While doing so try to +look at the issue from the perspective of someone else: that will help you to +come up with other words to use as search terms. Also make sure not to use too +many search terms at once. Remember to search with and without information like +the name of the kernel driver or the name of the affected hardware component. +But its exact brand name (say 'ASUS Red Devil Radeon RX 5700 XT Gaming OC') +often is not much helpful, as it is too specific. Instead try search terms like +the model line (Radeon 5700 or Radeon 5000) and the code name of the main chip +('Navi' or 'Navi10') with and without its manufacturer ('AMD'). + +In case you find an existing report about your issue, join the discussion, as +you might be able to provide valuable additional information. That can be +important even when a fix is prepared or in its final stages already, as +developers might look for people that can provide additional information or +test a proposed fix. Jump to the section 'Duties after the report went out' for +details on how to get properly involved. + +Note, searching `bugzilla.kernel.org <https://bugzilla.kernel.org/>`_ might also +be a good idea, as that might provide valuable insights or turn up matching +reports. If you find the latter, just keep in mind: most subsystems expect +reports in different places, as described below in the section "Check where you +need to report your issue". The developers that should take care of the issue +thus might not even be aware of the bugzilla ticket. Hence, check the ticket if +the issue already got reported as outlined in this document and if not consider +doing so. + + +Issue of high priority? +----------------------- + + *See if the issue you are dealing with qualifies as regression, security + issue, or a really severe problem: those are 'issues of high priority' that + need special handling in some steps that are about to follow.* + +Linus Torvalds and the leading Linux kernel developers want to see some issues +fixed as soon as possible, hence there are 'issues of high priority' that get +handled slightly differently in the reporting process. Three type of cases +qualify: regressions, security issues, and really severe problems. + +You deal with a regression if some application or practical use case running +fine with one Linux kernel works worse or not at all with a newer version +compiled using a similar configuration. The document +Documentation/admin-guide/reporting-regressions.rst explains this in more +detail. It also provides a good deal of other information about regressions you +might want to be aware of; it for example explains how to add your issue to the +list of tracked regressions, to ensure it won't fall through the cracks. + +What qualifies as security issue is left to your judgment. Consider reading +Documentation/process/security-bugs.rst before proceeding, as it +provides additional details how to best handle security issues. + +An issue is a 'really severe problem' when something totally unacceptably bad +happens. That's for example the case when a Linux kernel corrupts the data it's +handling or damages hardware it's running on. You're also dealing with a severe +issue when the kernel suddenly stops working with an error message ('kernel +panic') or without any farewell note at all. Note: do not confuse a 'panic' (a +fatal error where the kernel stop itself) with a 'Oops' (a recoverable error), +as the kernel remains running after the latter. + + +Ensure a healthy environment +---------------------------- + + *Make sure it's not the kernel's surroundings that are causing the issue + you face.* + +Problems that look a lot like a kernel issue are sometimes caused by build or +runtime environment. It's hard to rule out that problem completely, but you +should minimize it: + + * Use proven tools when building your kernel, as bugs in the compiler or the + binutils can cause the resulting kernel to misbehave. + + * Ensure your computer components run within their design specifications; + that's especially important for the main processor, the main memory, and the + motherboard. Therefore, stop undervolting or overclocking when facing a + potential kernel issue. + + * Try to make sure it's not faulty hardware that is causing your issue. Bad + main memory for example can result in a multitude of issues that will + manifest itself in problems looking like kernel issues. + + * If you're dealing with a filesystem issue, you might want to check the file + system in question with ``fsck``, as it might be damaged in a way that leads + to unexpected kernel behavior. + + * When dealing with a regression, make sure it's not something else that + changed in parallel to updating the kernel. The problem for example might be + caused by other software that was updated at the same time. It can also + happen that a hardware component coincidentally just broke when you rebooted + into a new kernel for the first time. Updating the systems BIOS or changing + something in the BIOS Setup can also lead to problems that on look a lot + like a kernel regression. + + +Prepare for emergencies +----------------------- + + *Create a fresh backup and put system repair and restore tools at hand.* + +Reminder, you are dealing with computers, which sometimes do unexpected things, +especially if you fiddle with crucial parts like the kernel of its operating +system. That's what you are about to do in this process. Thus, make sure to +create a fresh backup; also ensure you have all tools at hand to repair or +reinstall the operating system as well as everything you need to restore the +backup. + + +Make sure your kernel doesn't get enhanced +------------------------------------------ + + *Ensure your system does not enhance its kernels by building additional + kernel modules on-the-fly, which solutions like DKMS might be doing locally + without your knowledge.* + +The risk your issue report gets ignored or rejected dramatically increases if +your kernel gets enhanced in any way. That's why you should remove or disable +mechanisms like akmods and DKMS: those build add-on kernel modules +automatically, for example when you install a new Linux kernel or boot it for +the first time. Also remove any modules they might have installed. Then reboot +before proceeding. + +Note, you might not be aware that your system is using one of these solutions: +they often get set up silently when you install Nvidia's proprietary graphics +driver, VirtualBox, or other software that requires a some support from a +module not part of the Linux kernel. That why your might need to uninstall the +packages with such software to get rid of any 3rd party kernel module. + + +Check 'taint' flag +------------------ + + *Check if your kernel was 'tainted' when the issue occurred, as the event + that made the kernel set this flag might be causing the issue you face.* + +The kernel marks itself with a 'taint' flag when something happens that might +lead to follow-up errors that look totally unrelated. The issue you face might +be such an error if your kernel is tainted. That's why it's in your interest to +rule this out early before investing more time into this process. This is the +only reason why this step is here, as this process later will tell you to +install the latest mainline kernel; you will need to check the taint flag again +then, as that's when it matters because it's the kernel the report will focus +on. + +On a running system is easy to check if the kernel tainted itself: if ``cat +/proc/sys/kernel/tainted`` returns '0' then the kernel is not tainted and +everything is fine. Checking that file is impossible in some situations; that's +why the kernel also mentions the taint status when it reports an internal +problem (a 'kernel bug'), a recoverable error (a 'kernel Oops') or a +non-recoverable error before halting operation (a 'kernel panic'). Look near +the top of the error messages printed when one of these occurs and search for a +line starting with 'CPU:'. It should end with 'Not tainted' if the kernel was +not tainted when it noticed the problem; it was tainted if you see 'Tainted:' +followed by a few spaces and some letters. + +If your kernel is tainted, study Documentation/admin-guide/tainted-kernels.rst +to find out why. Try to eliminate the reason. Often it's caused by one these +three things: + + 1. A recoverable error (a 'kernel Oops') occurred and the kernel tainted + itself, as the kernel knows it might misbehave in strange ways after that + point. In that case check your kernel or system log and look for a section + that starts with this:: + + Oops: 0000 [#1] SMP + + That's the first Oops since boot-up, as the '#1' between the brackets shows. + Every Oops and any other problem that happens after that point might be a + follow-up problem to that first Oops, even if both look totally unrelated. + Rule this out by getting rid of the cause for the first Oops and reproducing + the issue afterwards. Sometimes simply restarting will be enough, sometimes + a change to the configuration followed by a reboot can eliminate the Oops. + But don't invest too much time into this at this point of the process, as + the cause for the Oops might already be fixed in the newer Linux kernel + version you are going to install later in this process. + + 2. Your system uses a software that installs its own kernel modules, for + example Nvidia's proprietary graphics driver or VirtualBox. The kernel + taints itself when it loads such module from external sources (even if + they are Open Source): they sometimes cause errors in unrelated kernel + areas and thus might be causing the issue you face. You therefore have to + prevent those modules from loading when you want to report an issue to the + Linux kernel developers. Most of the time the easiest way to do that is: + temporarily uninstall such software including any modules they might have + installed. Afterwards reboot. + + 3. The kernel also taints itself when it's loading a module that resides in + the staging tree of the Linux kernel source. That's a special area for + code (mostly drivers) that does not yet fulfill the normal Linux kernel + quality standards. When you report an issue with such a module it's + obviously okay if the kernel is tainted; just make sure the module in + question is the only reason for the taint. If the issue happens in an + unrelated area reboot and temporarily block the module from being loaded + by specifying ``foo.blacklist=1`` as kernel parameter (replace 'foo' with + the name of the module in question). + + +Document how to reproduce issue +------------------------------- + + *Write down coarsely how to reproduce the issue. If you deal with multiple + issues at once, create separate notes for each of them and make sure they + work independently on a freshly booted system. That's needed, as each issue + needs to get reported to the kernel developers separately, unless they are + strongly entangled.* + +If you deal with multiple issues at once, you'll have to report each of them +separately, as they might be handled by different developers. Describing +various issues in one report also makes it quite difficult for others to tear +it apart. Hence, only combine issues in one report if they are very strongly +entangled. + +Additionally, during the reporting process you will have to test if the issue +happens with other kernel versions. Therefore, it will make your work easier if +you know exactly how to reproduce an issue quickly on a freshly booted system. + +Note: it's often fruitless to report issues that only happened once, as they +might be caused by a bit flip due to cosmic radiation. That's why you should +try to rule that out by reproducing the issue before going further. Feel free +to ignore this advice if you are experienced enough to tell a one-time error +due to faulty hardware apart from a kernel issue that rarely happens and thus +is hard to reproduce. + + +Regression in stable or longterm kernel? +---------------------------------------- + + *If you are facing a regression within a stable or longterm version line + (say something broke when updating from 5.10.4 to 5.10.5), scroll down to + 'Dealing with regressions within a stable and longterm kernel line'.* + +Regression within a stable and longterm kernel version line are something the +Linux developers want to fix badly, as such issues are even more unwanted than +regression in the main development branch, as they can quickly affect a lot of +people. The developers thus want to learn about such issues as quickly as +possible, hence there is a streamlined process to report them. Note, +regressions with newer kernel version line (say something broke when switching +from 5.9.15 to 5.10.5) do not qualify. + + +Check where you need to report your issue +----------------------------------------- + + *Locate the driver or kernel subsystem that seems to be causing the issue. + Find out how and where its developers expect reports. Note: most of the + time this won't be bugzilla.kernel.org, as issues typically need to be sent + by mail to a maintainer and a public mailing list.* + +It's crucial to send your report to the right people, as the Linux kernel is a +big project and most of its developers are only familiar with a small subset of +it. Quite a few programmers for example only care for just one driver, for +example one for a WiFi chip; its developer likely will only have small or no +knowledge about the internals of remote or unrelated "subsystems", like the TCP +stack, the PCIe/PCI subsystem, memory management or file systems. + +Problem is: the Linux kernel lacks a central bug tracker where you can simply +file your issue and make it reach the developers that need to know about it. +That's why you have to find the right place and way to report issues yourself. +You can do that with the help of a script (see below), but it mainly targets +kernel developers and experts. For everybody else the MAINTAINERS file is the +better place. + +How to read the MAINTAINERS file +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +To illustrate how to use the :ref:`MAINTAINERS <maintainers>` file, lets assume +the WiFi in your Laptop suddenly misbehaves after updating the kernel. In that +case it's likely an issue in the WiFi driver. Obviously it could also be some +code it builds upon, but unless you suspect something like that stick to the +driver. If it's really something else, the driver's developers will get the +right people involved. + +Sadly, there is no way to check which code is driving a particular hardware +component that is both universal and easy. + +In case of a problem with the WiFi driver you for example might want to look at +the output of ``lspci -k``, as it lists devices on the PCI/PCIe bus and the +kernel module driving it:: + + [user@something ~]$ lspci -k + [...] + 3a:00.0 Network controller: Qualcomm Atheros QCA6174 802.11ac Wireless Network Adapter (rev 32) + Subsystem: Bigfoot Networks, Inc. Device 1535 + Kernel driver in use: ath10k_pci + Kernel modules: ath10k_pci + [...] + +But this approach won't work if your WiFi chip is connected over USB or some +other internal bus. In those cases you might want to check your WiFi manager or +the output of ``ip link``. Look for the name of the problematic network +interface, which might be something like 'wlp58s0'. This name can be used like +this to find the module driving it:: + + [user@something ~]$ realpath --relative-to=/sys/module/ /sys/class/net/wlp58s0/device/driver/module + ath10k_pci + +In case tricks like these don't bring you any further, try to search the +internet on how to narrow down the driver or subsystem in question. And if you +are unsure which it is: just try your best guess, somebody will help you if you +guessed poorly. + +Once you know the driver or subsystem, you want to search for it in the +MAINTAINERS file. In the case of 'ath10k_pci' you won't find anything, as the +name is too specific. Sometimes you will need to search on the net for help; +but before doing so, try a somewhat shorted or modified name when searching the +MAINTAINERS file, as then you might find something like this:: + + QUALCOMM ATHEROS ATH10K WIRELESS DRIVER + Mail: A. Some Human <shuman@example.com> + Mailing list: ath10k@lists.infradead.org + Status: Supported + Web-page: https://wireless.wiki.kernel.org/en/users/Drivers/ath10k + SCM: git git://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git + Files: drivers/net/wireless/ath/ath10k/ + +Note: the line description will be abbreviations, if you read the plain +MAINTAINERS file found in the root of the Linux source tree. 'Mail:' for +example will be 'M:', 'Mailing list:' will be 'L', and 'Status:' will be 'S:'. +A section near the top of the file explains these and other abbreviations. + +First look at the line 'Status'. Ideally it should be 'Supported' or +'Maintained'. If it states 'Obsolete' then you are using some outdated approach +that was replaced by a newer solution you need to switch to. Sometimes the code +only has someone who provides 'Odd Fixes' when feeling motivated. And with +'Orphan' you are totally out of luck, as nobody takes care of the code anymore. +That only leaves these options: arrange yourself to live with the issue, fix it +yourself, or find a programmer somewhere willing to fix it. + +After checking the status, look for a line starting with 'bugs:': it will tell +you where to find a subsystem specific bug tracker to file your issue. The +example above does not have such a line. That is the case for most sections, as +Linux kernel development is completely driven by mail. Very few subsystems use +a bug tracker, and only some of those rely on bugzilla.kernel.org. + +In this and many other cases you thus have to look for lines starting with +'Mail:' instead. Those mention the name and the email addresses for the +maintainers of the particular code. Also look for a line starting with 'Mailing +list:', which tells you the public mailing list where the code is developed. +Your report later needs to go by mail to those addresses. Additionally, for all +issue reports sent by email, make sure to add the Linux Kernel Mailing List +(LKML) <linux-kernel@vger.kernel.org> to CC. Don't omit either of the mailing +lists when sending your issue report by mail later! Maintainers are busy people +and might leave some work for other developers on the subsystem specific list; +and LKML is important to have one place where all issue reports can be found. + + +Finding the maintainers with the help of a script +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +For people that have the Linux sources at hand there is a second option to find +the proper place to report: the script 'scripts/get_maintainer.pl' which tries +to find all people to contact. It queries the MAINTAINERS file and needs to be +called with a path to the source code in question. For drivers compiled as +module if often can be found with a command like this:: + + $ modinfo ath10k_pci | grep filename | sed 's!/lib/modules/.*/kernel/!!; s!filename:!!; s!\.ko\(\|\.xz\)!!' + drivers/net/wireless/ath/ath10k/ath10k_pci.ko + +Pass parts of this to the script:: + + $ ./scripts/get_maintainer.pl -f drivers/net/wireless/ath/ath10k* + Some Human <shuman@example.com> (supporter:QUALCOMM ATHEROS ATH10K WIRELESS DRIVER) + Another S. Human <asomehuman@example.com> (maintainer:NETWORKING DRIVERS) + ath10k@lists.infradead.org (open list:QUALCOMM ATHEROS ATH10K WIRELESS DRIVER) + linux-wireless@vger.kernel.org (open list:NETWORKING DRIVERS (WIRELESS)) + netdev@vger.kernel.org (open list:NETWORKING DRIVERS) + linux-kernel@vger.kernel.org (open list) + +Don't sent your report to all of them. Send it to the maintainers, which the +script calls "supporter:"; additionally CC the most specific mailing list for +the code as well as the Linux Kernel Mailing List (LKML). In this case you thus +would need to send the report to 'Some Human <shuman@example.com>' with +'ath10k@lists.infradead.org' and 'linux-kernel@vger.kernel.org' in CC. + +Note: in case you cloned the Linux sources with git you might want to call +``get_maintainer.pl`` a second time with ``--git``. The script then will look +at the commit history to find which people recently worked on the code in +question, as they might be able to help. But use these results with care, as it +can easily send you in a wrong direction. That for example happens quickly in +areas rarely changed (like old or unmaintained drivers): sometimes such code is +modified during tree-wide cleanups by developers that do not care about the +particular driver at all. + + +Search for existing reports, second run +--------------------------------------- + + *Search the archives of the bug tracker or mailing list in question + thoroughly for reports that might match your issue. If you find anything, + join the discussion instead of sending a new report.* + +As mentioned earlier already: reporting an issue that someone else already +brought forward is often a waste of time for everyone involved, especially you +as the reporter. That's why you should search for existing report again, now +that you know where they need to be reported to. If it's mailing list, you will +often find its archives on `lore.kernel.org <https://lore.kernel.org/>`_. + +But some list are hosted in different places. That for example is the case for +the ath10k WiFi driver used as example in the previous step. But you'll often +find the archives for these lists easily on the net. Searching for 'archive +ath10k@lists.infradead.org' for example will lead you to the `Info page for the +ath10k mailing list <https://lists.infradead.org/mailman/listinfo/ath10k>`_, +which at the top links to its +`list archives <https://lists.infradead.org/pipermail/ath10k/>`_. Sadly this and +quite a few other lists miss a way to search the archives. In those cases use a +regular internet search engine and add something like +'site:lists.infradead.org/pipermail/ath10k/' to your search terms, which limits +the results to the archives at that URL. + +It's also wise to check the internet, LKML and maybe bugzilla.kernel.org again +at this point. If your report needs to be filed in a bug tracker, you may want +to check the mailing list archives for the subsystem as well, as someone might +have reported it only there. + +For details how to search and what to do if you find matching reports see +"Search for existing reports, first run" above. + +Do not hurry with this step of the reporting process: spending 30 to 60 minutes +or even more time can save you and others quite a lot of time and trouble. + + +Install a fresh kernel for testing +---------------------------------- + + *Unless you are already running the latest 'mainline' Linux kernel, better + go and install it for the reporting process. Testing and reporting with + the latest 'stable' Linux can be an acceptable alternative in some + situations; during the merge window that actually might be even the best + approach, but in that development phase it can be an even better idea to + suspend your efforts for a few days anyway. Whatever version you choose, + ideally use a 'vanilla' built. Ignoring these advices will dramatically + increase the risk your report will be rejected or ignored.* + +As mentioned in the detailed explanation for the first step already: Like most +programmers, Linux kernel developers don't like to spend time dealing with +reports for issues that don't even happen with the current code. It's just a +waste everybody's time, especially yours. That's why it's in everybody's +interest that you confirm the issue still exists with the latest upstream code +before reporting it. You are free to ignore this advice, but as outlined +earlier: doing so dramatically increases the risk that your issue report might +get rejected or simply ignored. + +In the scope of the kernel "latest upstream" normally means: + + * Install a mainline kernel; the latest stable kernel can be an option, but + most of the time is better avoided. Longterm kernels (sometimes called 'LTS + kernels') are unsuitable at this point of the process. The next subsection + explains all of this in more detail. + + * The over next subsection describes way to obtain and install such a kernel. + It also outlines that using a pre-compiled kernel are fine, but better are + vanilla, which means: it was built using Linux sources taken straight `from + kernel.org <https://kernel.org/>`_ and not modified or enhanced in any way. + +Choosing the right version for testing +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Head over to `kernel.org <https://kernel.org/>`_ to find out which version you +want to use for testing. Ignore the big yellow button that says 'Latest release' +and look a little lower at the table. At its top you'll see a line starting with +mainline, which most of the time will point to a pre-release with a version +number like '5.8-rc2'. If that's the case, you'll want to use this mainline +kernel for testing, as that where all fixes have to be applied first. Do not let +that 'rc' scare you, these 'development kernels' are pretty reliable — and you +made a backup, as you were instructed above, didn't you? + +In about two out of every nine to ten weeks, mainline might point you to a +proper release with a version number like '5.7'. If that happens, consider +suspending the reporting process until the first pre-release of the next +version (5.8-rc1) shows up on kernel.org. That's because the Linux development +cycle then is in its two-week long 'merge window'. The bulk of the changes and +all intrusive ones get merged for the next release during this time. It's a bit +more risky to use mainline during this period. Kernel developers are also often +quite busy then and might have no spare time to deal with issue reports. It's +also quite possible that one of the many changes applied during the merge +window fixes the issue you face; that's why you soon would have to retest with +a newer kernel version anyway, as outlined below in the section 'Duties after +the report went out'. + +That's why it might make sense to wait till the merge window is over. But don't +to that if you're dealing with something that shouldn't wait. In that case +consider obtaining the latest mainline kernel via git (see below) or use the +latest stable version offered on kernel.org. Using that is also acceptable in +case mainline for some reason does currently not work for you. An in general: +using it for reproducing the issue is also better than not reporting it issue +at all. + +Better avoid using the latest stable kernel outside merge windows, as all fixes +must be applied to mainline first. That's why checking the latest mainline +kernel is so important: any issue you want to see fixed in older version lines +needs to be fixed in mainline first before it can get backported, which can +take a few days or weeks. Another reason: the fix you hope for might be too +hard or risky for backporting; reporting the issue again hence is unlikely to +change anything. + +These aspects are also why longterm kernels (sometimes called "LTS kernels") +are unsuitable for this part of the reporting process: they are to distant from +the current code. Hence go and test mainline first and follow the process +further: if the issue doesn't occur with mainline it will guide you how to get +it fixed in older version lines, if that's in the cards for the fix in question. + +How to obtain a fresh Linux kernel +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +**Using a pre-compiled kernel**: This is often the quickest, easiest, and safest +way for testing — especially is you are unfamiliar with the Linux kernel. The +problem: most of those shipped by distributors or add-on repositories are build +from modified Linux sources. They are thus not vanilla and therefore often +unsuitable for testing and issue reporting: the changes might cause the issue +you face or influence it somehow. + +But you are in luck if you are using a popular Linux distribution: for quite a +few of them you'll find repositories on the net that contain packages with the +latest mainline or stable Linux built as vanilla kernel. It's totally okay to +use these, just make sure from the repository's description they are vanilla or +at least close to it. Additionally ensure the packages contain the latest +versions as offered on kernel.org. The packages are likely unsuitable if they +are older than a week, as new mainline and stable kernels typically get released +at least once a week. + +Please note that you might need to build your own kernel manually later: that's +sometimes needed for debugging or testing fixes, as described later in this +document. Also be aware that pre-compiled kernels might lack debug symbols that +are needed to decode messages the kernel prints when a panic, Oops, warning, or +BUG occurs; if you plan to decode those, you might be better off compiling a +kernel yourself (see the end of this subsection and the section titled 'Decode +failure messages' for details). + +**Using git**: Developers and experienced Linux users familiar with git are +often best served by obtaining the latest Linux kernel sources straight from the +`official development repository on kernel.org +<https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/>`_. +Those are likely a bit ahead of the latest mainline pre-release. Don't worry +about it: they are as reliable as a proper pre-release, unless the kernel's +development cycle is currently in the middle of a merge window. But even then +they are quite reliable. + +**Conventional**: People unfamiliar with git are often best served by +downloading the sources as tarball from `kernel.org <https://kernel.org/>`_. + +How to actually build a kernel is not described here, as many websites explain +the necessary steps already. If you are new to it, consider following one of +those how-to's that suggest to use ``make localmodconfig``, as that tries to +pick up the configuration of your current kernel and then tries to adjust it +somewhat for your system. That does not make the resulting kernel any better, +but quicker to compile. + +Note: If you are dealing with a panic, Oops, warning, or BUG from the kernel, +please try to enable CONFIG_KALLSYMS when configuring your kernel. +Additionally, enable CONFIG_DEBUG_KERNEL and CONFIG_DEBUG_INFO, too; the +latter is the relevant one of those two, but can only be reached if you enable +the former. Be aware CONFIG_DEBUG_INFO increases the storage space required to +build a kernel by quite a bit. But that's worth it, as these options will allow +you later to pinpoint the exact line of code that triggers your issue. The +section 'Decode failure messages' below explains this in more detail. + +But keep in mind: Always keep a record of the issue encountered in case it is +hard to reproduce. Sending an undecoded report is better than not reporting +the issue at all. + + +Check 'taint' flag +------------------ + + *Ensure the kernel you just installed does not 'taint' itself when + running.* + +As outlined above in more detail already: the kernel sets a 'taint' flag when +something happens that can lead to follow-up errors that look totally +unrelated. That's why you need to check if the kernel you just installed does +not set this flag. And if it does, you in almost all the cases needs to +eliminate the reason for it before you reporting issues that occur with it. See +the section above for details how to do that. + + +Reproduce issue with the fresh kernel +------------------------------------- + + *Reproduce the issue with the kernel you just installed. If it doesn't show + up there, scroll down to the instructions for issues only happening with + stable and longterm kernels.* + +Check if the issue occurs with the fresh Linux kernel version you just +installed. If it was fixed there already, consider sticking with this version +line and abandoning your plan to report the issue. But keep in mind that other +users might still be plagued by it, as long as it's not fixed in either stable +and longterm version from kernel.org (and thus vendor kernels derived from +those). If you prefer to use one of those or just want to help their users, +head over to the section "Details about reporting issues only occurring in +older kernel version lines" below. + + +Optimize description to reproduce issue +--------------------------------------- + + *Optimize your notes: try to find and write the most straightforward way to + reproduce your issue. Make sure the end result has all the important + details, and at the same time is easy to read and understand for others + that hear about it for the first time. And if you learned something in this + process, consider searching again for existing reports about the issue.* + +An unnecessarily complex report will make it hard for others to understand your +report. Thus try to find a reproducer that's straight forward to describe and +thus easy to understand in written form. Include all important details, but at +the same time try to keep it as short as possible. + +In this in the previous steps you likely have learned a thing or two about the +issue you face. Use this knowledge and search again for existing reports +instead you can join. + + +Decode failure messages +----------------------- + + *If your failure involves a 'panic', 'Oops', 'warning', or 'BUG', consider + decoding the kernel log to find the line of code that triggered the error.* + +When the kernel detects an internal problem, it will log some information about +the executed code. This makes it possible to pinpoint the exact line in the +source code that triggered the issue and shows how it was called. But that only +works if you enabled CONFIG_DEBUG_INFO and CONFIG_KALLSYMS when configuring +your kernel. If you did so, consider to decode the information from the +kernel's log. That will make it a lot easier to understand what lead to the +'panic', 'Oops', 'warning', or 'BUG', which increases the chances that someone +can provide a fix. + +Decoding can be done with a script you find in the Linux source tree. If you +are running a kernel you compiled yourself earlier, call it like this:: + + [user@something ~]$ sudo dmesg | ./linux-5.10.5/scripts/decode_stacktrace.sh ./linux-5.10.5/vmlinux + +If you are running a packaged vanilla kernel, you will likely have to install +the corresponding packages with debug symbols. Then call the script (which you +might need to get from the Linux sources if your distro does not package it) +like this:: + + [user@something ~]$ sudo dmesg | ./linux-5.10.5/scripts/decode_stacktrace.sh \ + /usr/lib/debug/lib/modules/5.10.10-4.1.x86_64/vmlinux /usr/src/kernels/5.10.10-4.1.x86_64/ + +The script will work on log lines like the following, which show the address of +the code the kernel was executing when the error occurred:: + + [ 68.387301] RIP: 0010:test_module_init+0x5/0xffa [test_module] + +Once decoded, these lines will look like this:: + + [ 68.387301] RIP: 0010:test_module_init (/home/username/linux-5.10.5/test-module/test-module.c:16) test_module + +In this case the executed code was built from the file +'~/linux-5.10.5/test-module/test-module.c' and the error occurred by the +instructions found in line '16'. + +The script will similarly decode the addresses mentioned in the section +starting with 'Call trace', which show the path to the function where the +problem occurred. Additionally, the script will show the assembler output for +the code section the kernel was executing. + +Note, if you can't get this to work, simply skip this step and mention the +reason for it in the report. If you're lucky, it might not be needed. And if it +is, someone might help you to get things going. Also be aware this is just one +of several ways to decode kernel stack traces. Sometimes different steps will +be required to retrieve the relevant details. Don't worry about that, if that's +needed in your case, developers will tell you what to do. + + +Special care for regressions +---------------------------- + + *If your problem is a regression, try to narrow down when the issue was + introduced as much as possible.* + +Linux lead developer Linus Torvalds insists that the Linux kernel never +worsens, that's why he deems regressions as unacceptable and wants to see them +fixed quickly. That's why changes that introduced a regression are often +promptly reverted if the issue they cause can't get solved quickly any other +way. Reporting a regression is thus a bit like playing a kind of trump card to +get something quickly fixed. But for that to happen the change that's causing +the regression needs to be known. Normally it's up to the reporter to track +down the culprit, as maintainers often won't have the time or setup at hand to +reproduce it themselves. + +To find the change there is a process called 'bisection' which the document +Documentation/admin-guide/bug-bisect.rst describes in detail. That process +will often require you to build about ten to twenty kernel images, trying to +reproduce the issue with each of them before building the next. Yes, that takes +some time, but don't worry, it works a lot quicker than most people assume. +Thanks to a 'binary search' this will lead you to the one commit in the source +code management system that's causing the regression. Once you find it, search +the net for the subject of the change, its commit id and the shortened commit id +(the first 12 characters of the commit id). This will lead you to existing +reports about it, if there are any. + +Note, a bisection needs a bit of know-how, which not everyone has, and quite a +bit of effort, which not everyone is willing to invest. Nevertheless, it's +highly recommended performing a bisection yourself. If you really can't or +don't want to go down that route at least find out which mainline kernel +introduced the regression. If something for example breaks when switching from +5.5.15 to 5.8.4, then try at least all the mainline releases in that area (5.6, +5.7 and 5.8) to check when it first showed up. Unless you're trying to find a +regression in a stable or longterm kernel, avoid testing versions which number +has three sections (5.6.12, 5.7.8), as that makes the outcome hard to +interpret, which might render your testing useless. Once you found the major +version which introduced the regression, feel free to move on in the reporting +process. But keep in mind: it depends on the issue at hand if the developers +will be able to help without knowing the culprit. Sometimes they might +recognize from the report want went wrong and can fix it; other times they will +be unable to help unless you perform a bisection. + +When dealing with regressions make sure the issue you face is really caused by +the kernel and not by something else, as outlined above already. + +In the whole process keep in mind: an issue only qualifies as regression if the +older and the newer kernel got built with a similar configuration. This can be +achieved by using ``make olddefconfig``, as explained in more detail by +Documentation/admin-guide/reporting-regressions.rst; that document also +provides a good deal of other information about regressions you might want to be +aware of. + + +Write and send the report +------------------------- + + *Start to compile the report by writing a detailed description about the + issue. Always mention a few things: the latest kernel version you installed + for reproducing, the Linux Distribution used, and your notes on how to + reproduce the issue. Ideally, make the kernel's build configuration + (.config) and the output from ``dmesg`` available somewhere on the net and + link to it. Include or upload all other information that might be relevant, + like the output/screenshot of an Oops or the output from ``lspci``. Once + you wrote this main part, insert a normal length paragraph on top of it + outlining the issue and the impact quickly. On top of this add one sentence + that briefly describes the problem and gets people to read on. Now give the + thing a descriptive title or subject that yet again is shorter. Then you're + ready to send or file the report like the MAINTAINERS file told you, unless + you are dealing with one of those 'issues of high priority': they need + special care which is explained in 'Special handling for high priority + issues' below.* + +Now that you have prepared everything it's time to write your report. How to do +that is partly explained by the three documents linked to in the preface above. +That's why this text will only mention a few of the essentials as well as +things specific to the Linux kernel. + +There is one thing that fits both categories: the most crucial parts of your +report are the title/subject, the first sentence, and the first paragraph. +Developers often get quite a lot of mail. They thus often just take a few +seconds to skim a mail before deciding to move on or look closer. Thus: the +better the top section of your report, the higher are the chances that someone +will look into it and help you. And that is why you should ignore them for now +and write the detailed report first. ;-) + +Things each report should mention +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Describe in detail how your issue happens with the fresh vanilla kernel you +installed. Try to include the step-by-step instructions you wrote and optimized +earlier that outline how you and ideally others can reproduce the issue; in +those rare cases where that's impossible try to describe what you did to +trigger it. + +Also include all the relevant information others might need to understand the +issue and its environment. What's actually needed depends a lot on the issue, +but there are some things you should include always: + + * the output from ``cat /proc/version``, which contains the Linux kernel + version number and the compiler it was built with. + + * the Linux distribution the machine is running (``hostnamectl | grep + "Operating System"``) + + * the architecture of the CPU and the operating system (``uname -mi``) + + * if you are dealing with a regression and performed a bisection, mention the + subject and the commit-id of the change that is causing it. + +In a lot of cases it's also wise to make two more things available to those +that read your report: + + * the configuration used for building your Linux kernel (the '.config' file) + + * the kernel's messages that you get from ``dmesg`` written to a file. Make + sure that it starts with a line like 'Linux version 5.8-1 + (foobar@example.com) (gcc (GCC) 10.2.1, GNU ld version 2.34) #1 SMP Mon Aug + 3 14:54:37 UTC 2020' If it's missing, then important messages from the first + boot phase already got discarded. In this case instead consider using + ``journalctl -b 0 -k``; alternatively you can also reboot, reproduce the + issue and call ``dmesg`` right afterwards. + +These two files are big, that's why it's a bad idea to put them directly into +your report. If you are filing the issue in a bug tracker then attach them to +the ticket. If you report the issue by mail do not attach them, as that makes +the mail too large; instead do one of these things: + + * Upload the files somewhere public (your website, a public file paste + service, a ticket created just for this purpose on `bugzilla.kernel.org + <https://bugzilla.kernel.org/>`_, ...) and include a link to them in your + report. Ideally use something where the files stay available for years, as + they could be useful to someone many years from now; this for example can + happen if five or ten years from now a developer works on some code that was + changed just to fix your issue. + + * Put the files aside and mention you will send them later in individual + replies to your own mail. Just remember to actually do that once the report + went out. ;-) + +Things that might be wise to provide +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Depending on the issue you might need to add more background data. Here are a +few suggestions what often is good to provide: + + * If you are dealing with a 'warning', an 'OOPS' or a 'panic' from the kernel, + include it. If you can't copy'n'paste it, try to capture a netconsole trace + or at least take a picture of the screen. + + * If the issue might be related to your computer hardware, mention what kind + of system you use. If you for example have problems with your graphics card, + mention its manufacturer, the card's model, and what chip is uses. If it's a + laptop mention its name, but try to make sure it's meaningful. 'Dell XPS 13' + for example is not, because it might be the one from 2012; that one looks + not that different from the one sold today, but apart from that the two have + nothing in common. Hence, in such cases add the exact model number, which + for example are '9380' or '7390' for XPS 13 models introduced during 2019. + Names like 'Lenovo Thinkpad T590' are also somewhat ambiguous: there are + variants of this laptop with and without a dedicated graphics chip, so try + to find the exact model name or specify the main components. + + * Mention the relevant software in use. If you have problems with loading + modules, you want to mention the versions of kmod, systemd, and udev in use. + If one of the DRM drivers misbehaves, you want to state the versions of + libdrm and Mesa; also specify your Wayland compositor or the X-Server and + its driver. If you have a filesystem issue, mention the version of + corresponding filesystem utilities (e2fsprogs, btrfs-progs, xfsprogs, ...). + + * Gather additional information from the kernel that might be of interest. The + output from ``lspci -nn`` will for example help others to identify what + hardware you use. If you have a problem with hardware you even might want to + make the output from ``sudo lspci -vvv`` available, as that provides + insights how the components were configured. For some issues it might be + good to include the contents of files like ``/proc/cpuinfo``, + ``/proc/ioports``, ``/proc/iomem``, ``/proc/modules``, or + ``/proc/scsi/scsi``. Some subsystem also offer tools to collect relevant + information. One such tool is ``alsa-info.sh`` `which the audio/sound + subsystem developers provide <https://www.alsa-project.org/wiki/AlsaInfo>`_. + +Those examples should give your some ideas of what data might be wise to +attach, but you have to think yourself what will be helpful for others to know. +Don't worry too much about forgetting something, as developers will ask for +additional details they need. But making everything important available from +the start increases the chance someone will take a closer look. + + +The important part: the head of your report +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Now that you have the detailed part of the report prepared let's get to the +most important section: the first few sentences. Thus go to the top, add +something like 'The detailed description:' before the part you just wrote and +insert two newlines at the top. Now write one normal length paragraph that +describes the issue roughly. Leave out all boring details and focus on the +crucial parts readers need to know to understand what this is all about; if you +think this bug affects a lot of users, mention this to get people interested. + +Once you did that insert two more lines at the top and write a one sentence +summary that explains quickly what the report is about. After that you have to +get even more abstract and write an even shorter subject/title for the report. + +Now that you have written this part take some time to optimize it, as it is the +most important parts of your report: a lot of people will only read this before +they decide if reading the rest is time well spent. + +Now send or file the report like the :ref:`MAINTAINERS <maintainers>` file told +you, unless it's one of those 'issues of high priority' outlined earlier: in +that case please read the next subsection first before sending the report on +its way. + +Special handling for high priority issues +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Reports for high priority issues need special handling. + +**Severe issues**: make sure the subject or ticket title as well as the first +paragraph makes the severeness obvious. + +**Regressions**: make the report's subject start with '[REGRESSION]'. + +In case you performed a successful bisection, use the title of the change that +introduced the regression as the second part of your subject. Make the report +also mention the commit id of the culprit. In case of an unsuccessful bisection, +make your report mention the latest tested version that's working fine (say 5.7) +and the oldest where the issue occurs (say 5.8-rc1). + +When sending the report by mail, CC the Linux regressions mailing list +(regressions@lists.linux.dev). In case the report needs to be filed to some web +tracker, proceed to do so. Once filed, forward the report by mail to the +regressions list; CC the maintainer and the mailing list for the subsystem in +question. Make sure to inline the forwarded report, hence do not attach it. +Also add a short note at the top where you mention the URL to the ticket. + +When mailing or forwarding the report, in case of a successful bisection add the +author of the culprit to the recipients; also CC everyone in the signed-off-by +chain, which you find at the end of its commit message. + +**Security issues**: for these issues your will have to evaluate if a +short-term risk to other users would arise if details were publicly disclosed. +If that's not the case simply proceed with reporting the issue as described. +For issues that bear such a risk you will need to adjust the reporting process +slightly: + + * If the MAINTAINERS file instructed you to report the issue by mail, do not + CC any public mailing lists. + + * If you were supposed to file the issue in a bug tracker make sure to mark + the ticket as 'private' or 'security issue'. If the bug tracker does not + offer a way to keep reports private, forget about it and send your report as + a private mail to the maintainers instead. + +In both cases make sure to also mail your report to the addresses the +MAINTAINERS file lists in the section 'security contact'. Ideally directly CC +them when sending the report by mail. If you filed it in a bug tracker, forward +the report's text to these addresses; but on top of it put a small note where +you mention that you filed it with a link to the ticket. + +See Documentation/process/security-bugs.rst for more information. + + +Duties after the report went out +-------------------------------- + + *Wait for reactions and keep the thing rolling until you can accept the + outcome in one way or the other. Thus react publicly and in a timely manner + to any inquiries. Test proposed fixes. Do proactive testing: retest with at + least every first release candidate (RC) of a new mainline version and + report your results. Send friendly reminders if things stall. And try to + help yourself, if you don't get any help or if it's unsatisfying.* + +If your report was good and you are really lucky then one of the developers +might immediately spot what's causing the issue; they then might write a patch +to fix it, test it, and send it straight for integration in mainline while +tagging it for later backport to stable and longterm kernels that need it. Then +all you need to do is reply with a 'Thank you very much' and switch to a version +with the fix once it gets released. + +But this ideal scenario rarely happens. That's why the job is only starting +once you got the report out. What you'll have to do depends on the situations, +but often it will be the things listed below. But before digging into the +details, here are a few important things you need to keep in mind for this part +of the process. + + +General advice for further interactions +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +**Always reply in public**: When you filed the issue in a bug tracker, always +reply there and do not contact any of the developers privately about it. For +mailed reports always use the 'Reply-all' function when replying to any mails +you receive. That includes mails with any additional data you might want to add +to your report: go to your mail applications 'Sent' folder and use 'reply-all' +on your mail with the report. This approach will make sure the public mailing +list(s) and everyone else that gets involved over time stays in the loop; it +also keeps the mail thread intact, which among others is really important for +mailing lists to group all related mails together. + +There are just two situations where a comment in a bug tracker or a 'Reply-all' +is unsuitable: + + * Someone tells you to send something privately. + + * You were told to send something, but noticed it contains sensitive + information that needs to be kept private. In that case it's okay to send it + in private to the developer that asked for it. But note in the ticket or a + mail that you did that, so everyone else knows you honored the request. + +**Do research before asking for clarifications or help**: In this part of the +process someone might tell you to do something that requires a skill you might +not have mastered yet. For example, you might be asked to use some test tools +you never have heard of yet; or you might be asked to apply a patch to the +Linux kernel sources to test if it helps. In some cases it will be fine sending +a reply asking for instructions how to do that. But before going that route try +to find the answer own your own by searching the internet; alternatively +consider asking in other places for advice. For example ask a friend or post +about it to a chatroom or forum you normally hang out. + +**Be patient**: If you are really lucky you might get a reply to your report +within a few hours. But most of the time it will take longer, as maintainers +are scattered around the globe and thus might be in a different time zone – one +where they already enjoy their night away from keyboard. + +In general, kernel developers will take one to five business days to respond to +reports. Sometimes it will take longer, as they might be busy with the merge +windows, other work, visiting developer conferences, or simply enjoying a long +summer holiday. + +The 'issues of high priority' (see above for an explanation) are an exception +here: maintainers should address them as soon as possible; that's why you +should wait a week at maximum (or just two days if it's something urgent) +before sending a friendly reminder. + +Sometimes the maintainer might not be responding in a timely manner; other +times there might be disagreements, for example if an issue qualifies as +regression or not. In such cases raise your concerns on the mailing list and +ask others for public or private replies how to move on. If that fails, it +might be appropriate to get a higher authority involved. In case of a WiFi +driver that would be the wireless maintainers; if there are no higher level +maintainers or all else fails, it might be one of those rare situations where +it's okay to get Linus Torvalds involved. + +**Proactive testing**: Every time the first pre-release (the 'rc1') of a new +mainline kernel version gets released, go and check if the issue is fixed there +or if anything of importance changed. Mention the outcome in the ticket or in a +mail you sent as reply to your report (make sure it has all those in the CC +that up to that point participated in the discussion). This will show your +commitment and that you are willing to help. It also tells developers if the +issue persists and makes sure they do not forget about it. A few other +occasional retests (for example with rc3, rc5 and the final) are also a good +idea, but only report your results if something relevant changed or if you are +writing something anyway. + +With all these general things off the table let's get into the details of how +to help to get issues resolved once they were reported. + +Inquires and testing request +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Here are your duties in case you got replies to your report: + +**Check who you deal with**: Most of the time it will be the maintainer or a +developer of the particular code area that will respond to your report. But as +issues are normally reported in public it could be anyone that's replying — +including people that want to help, but in the end might guide you totally off +track with their questions or requests. That rarely happens, but it's one of +many reasons why it's wise to quickly run an internet search to see who you're +interacting with. By doing this you also get aware if your report was heard by +the right people, as a reminder to the maintainer (see below) might be in order +later if discussion fades out without leading to a satisfying solution for the +issue. + +**Inquiries for data**: Often you will be asked to test something or provide +additional details. Try to provide the requested information soon, as you have +the attention of someone that might help and risk losing it the longer you +wait; that outcome is even likely if you do not provide the information within +a few business days. + +**Requests for testing**: When you are asked to test a diagnostic patch or a +possible fix, try to test it in timely manner, too. But do it properly and make +sure to not rush it: mixing things up can happen easily and can lead to a lot +of confusion for everyone involved. A common mistake for example is thinking a +proposed patch with a fix was applied, but in fact wasn't. Things like that +happen even to experienced testers occasionally, but they most of the time will +notice when the kernel with the fix behaves just as one without it. + +What to do when nothing of substance happens +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Some reports will not get any reaction from the responsible Linux kernel +developers; or a discussion around the issue evolved, but faded out with +nothing of substance coming out of it. + +In these cases wait two (better: three) weeks before sending a friendly +reminder: maybe the maintainer was just away from keyboard for a while when +your report arrived or had something more important to take care of. When +writing the reminder, kindly ask if anything else from your side is needed to +get the ball running somehow. If the report got out by mail, do that in the +first lines of a mail that is a reply to your initial mail (see above) which +includes a full quote of the original report below: that's on of those few +situations where such a 'TOFU' (Text Over, Fullquote Under) is the right +approach, as then all the recipients will have the details at hand immediately +in the proper order. + +After the reminder wait three more weeks for replies. If you still don't get a +proper reaction, you first should reconsider your approach. Did you maybe try +to reach out to the wrong people? Was the report maybe offensive or so +confusing that people decided to completely stay away from it? The best way to +rule out such factors: show the report to one or two people familiar with FLOSS +issue reporting and ask for their opinion. Also ask them for their advice how +to move forward. That might mean: prepare a better report and make those people +review it before you send it out. Such an approach is totally fine; just +mention that this is the second and improved report on the issue and include a +link to the first report. + +If the report was proper you can send a second reminder; in it ask for advice +why the report did not get any replies. A good moment for this second reminder +mail is shortly after the first pre-release (the 'rc1') of a new Linux kernel +version got published, as you should retest and provide a status update at that +point anyway (see above). + +If the second reminder again results in no reaction within a week, try to +contact a higher-level maintainer asking for advice: even busy maintainers by +then should at least have sent some kind of acknowledgment. + +Remember to prepare yourself for a disappointment: maintainers ideally should +react somehow to every issue report, but they are only obliged to fix those +'issues of high priority' outlined earlier. So don't be too devastating if you +get a reply along the lines of 'thanks for the report, I have more important +issues to deal with currently and won't have time to look into this for the +foreseeable future'. + +It's also possible that after some discussion in the bug tracker or on a list +nothing happens anymore and reminders don't help to motivate anyone to work out +a fix. Such situations can be devastating, but is within the cards when it +comes to Linux kernel development. This and several other reasons for not +getting help are explained in 'Why some issues won't get any reaction or remain +unfixed after being reported' near the end of this document. + +Don't get devastated if you don't find any help or if the issue in the end does +not get solved: the Linux kernel is FLOSS and thus you can still help yourself. +You for example could try to find others that are affected and team up with +them to get the issue resolved. Such a team could prepare a fresh report +together that mentions how many you are and why this is something that in your +option should get fixed. Maybe together you can also narrow down the root cause +or the change that introduced a regression, which often makes developing a fix +easier. And with a bit of luck there might be someone in the team that knows a +bit about programming and might be able to write a fix. + + +Reference for "Reporting regressions within a stable and longterm kernel line" +------------------------------------------------------------------------------ + +This subsection provides details for the steps you need to perform if you face +a regression within a stable and longterm kernel line. + +Make sure the particular version line still gets support +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + + *Check if the kernel developers still maintain the Linux kernel version + line you care about: go to the front page of kernel.org and make sure it + mentions the latest release of the particular version line without an + '[EOL]' tag.* + +Most kernel version lines only get supported for about three months, as +maintaining them longer is quite a lot of work. Hence, only one per year is +chosen and gets supported for at least two years (often six). That's why you +need to check if the kernel developers still support the version line you care +for. + +Note, if kernel.org lists two stable version lines on the front page, you +should consider switching to the newer one and forget about the older one: +support for it is likely to be abandoned soon. Then it will get a "end-of-life" +(EOL) stamp. Version lines that reached that point still get mentioned on the +kernel.org front page for a week or two, but are unsuitable for testing and +reporting. + +Search stable mailing list +~~~~~~~~~~~~~~~~~~~~~~~~~~ + + *Check the archives of the Linux stable mailing list for existing reports.* + +Maybe the issue you face is already known and was fixed or is about to. Hence, +`search the archives of the Linux stable mailing list +<https://lore.kernel.org/stable/>`_ for reports about an issue like yours. If +you find any matches, consider joining the discussion, unless the fix is +already finished and scheduled to get applied soon. + +Reproduce issue with the newest release +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + + *Install the latest release from the particular version line as a vanilla + kernel. Ensure this kernel is not tainted and still shows the problem, as + the issue might have already been fixed there. If you first noticed the + problem with a vendor kernel, check a vanilla build of the last version + known to work performs fine as well.* + +Before investing any more time in this process you want to check if the issue +was already fixed in the latest release of version line you're interested in. +This kernel needs to be vanilla and shouldn't be tainted before the issue +happens, as detailed outlined already above in the section "Install a fresh +kernel for testing". + +Did you first notice the regression with a vendor kernel? Then changes the +vendor applied might be interfering. You need to rule that out by performing +a recheck. Say something broke when you updated from 5.10.4-vendor.42 to +5.10.5-vendor.43. Then after testing the latest 5.10 release as outlined in +the previous paragraph check if a vanilla build of Linux 5.10.4 works fine as +well. If things are broken there, the issue does not qualify as upstream +regression and you need switch back to the main step-by-step guide to report +the issue. + +Report the regression +~~~~~~~~~~~~~~~~~~~~~ + + *Send a short problem report to the Linux stable mailing list + (stable@vger.kernel.org) and CC the Linux regressions mailing list + (regressions@lists.linux.dev); if you suspect the cause in a particular + subsystem, CC its maintainer and its mailing list. Roughly describe the + issue and ideally explain how to reproduce it. Mention the first version + that shows the problem and the last version that's working fine. Then + wait for further instructions.* + +When reporting a regression that happens within a stable or longterm kernel +line (say when updating from 5.10.4 to 5.10.5) a brief report is enough for +the start to get the issue reported quickly. Hence a rough description to the +stable and regressions mailing list is all it takes; but in case you suspect +the cause in a particular subsystem, CC its maintainers and its mailing list +as well, because that will speed things up. + +And note, it helps developers a great deal if you can specify the exact version +that introduced the problem. Hence if possible within a reasonable time frame, +try to find that version using vanilla kernels. Lets assume something broke when +your distributor released a update from Linux kernel 5.10.5 to 5.10.8. Then as +instructed above go and check the latest kernel from that version line, say +5.10.9. If it shows the problem, try a vanilla 5.10.5 to ensure that no patches +the distributor applied interfere. If the issue doesn't manifest itself there, +try 5.10.7 and then (depending on the outcome) 5.10.8 or 5.10.6 to find the +first version where things broke. Mention it in the report and state that 5.10.9 +is still broken. + +What the previous paragraph outlines is basically a rough manual 'bisection'. +Once your report is out your might get asked to do a proper one, as it allows to +pinpoint the exact change that causes the issue (which then can easily get +reverted to fix the issue quickly). Hence consider to do a proper bisection +right away if time permits. See the section 'Special care for regressions' and +the document Documentation/admin-guide/bug-bisect.rst for details how to +perform one. In case of a successful bisection add the author of the culprit to +the recipients; also CC everyone in the signed-off-by chain, which you find at +the end of its commit message. + + +Reference for "Reporting issues only occurring in older kernel version lines" +----------------------------------------------------------------------------- + +This section provides details for the steps you need to take if you could not +reproduce your issue with a mainline kernel, but want to see it fixed in older +version lines (aka stable and longterm kernels). + +Some fixes are too complex +~~~~~~~~~~~~~~~~~~~~~~~~~~ + + *Prepare yourself for the possibility that going through the next few steps + might not get the issue solved in older releases: the fix might be too big + or risky to get backported there.* + +Even small and seemingly obvious code-changes sometimes introduce new and +totally unexpected problems. The maintainers of the stable and longterm kernels +are very aware of that and thus only apply changes to these kernels that are +within rules outlined in Documentation/process/stable-kernel-rules.rst. + +Complex or risky changes for example do not qualify and thus only get applied +to mainline. Other fixes are easy to get backported to the newest stable and +longterm kernels, but too risky to integrate into older ones. So be aware the +fix you are hoping for might be one of those that won't be backported to the +version line your care about. In that case you'll have no other choice then to +live with the issue or switch to a newer Linux version, unless you want to +patch the fix into your kernels yourself. + +Common preparations +~~~~~~~~~~~~~~~~~~~ + + *Perform the first three steps in the section "Reporting issues only + occurring in older kernel version lines" above.* + +You need to carry out a few steps already described in another section of this +guide. Those steps will let you: + + * Check if the kernel developers still maintain the Linux kernel version line + you care about. + + * Search the Linux stable mailing list for exiting reports. + + * Check with the latest release. + + +Check code history and search for existing discussions +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + + *Search the Linux kernel version control system for the change that fixed + the issue in mainline, as its commit message might tell you if the fix is + scheduled for backporting already. If you don't find anything that way, + search the appropriate mailing lists for posts that discuss such an issue + or peer-review possible fixes; then check the discussions if the fix was + deemed unsuitable for backporting. If backporting was not considered at + all, join the newest discussion, asking if it's in the cards.* + +In a lot of cases the issue you deal with will have happened with mainline, but +got fixed there. The commit that fixed it would need to get backported as well +to get the issue solved. That's why you want to search for it or any +discussions abound it. + + * First try to find the fix in the Git repository that holds the Linux kernel + sources. You can do this with the web interfaces `on kernel.org + <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/>`_ + or its mirror `on GitHub <https://github.com/torvalds/linux>`_; if you have + a local clone you alternatively can search on the command line with ``git + log --grep=<pattern>``. + + If you find the fix, look if the commit message near the end contains a + 'stable tag' that looks like this: + + Cc: <stable@vger.kernel.org> # 5.4+ + + If that's case the developer marked the fix safe for backporting to version + line 5.4 and later. Most of the time it's getting applied there within two + weeks, but sometimes it takes a bit longer. + + * If the commit doesn't tell you anything or if you can't find the fix, look + again for discussions about the issue. Search the net with your favorite + internet search engine as well as the archives for the `Linux kernel + developers mailing list <https://lore.kernel.org/lkml/>`_. Also read the + section `Locate kernel area that causes the issue` above and follow the + instructions to find the subsystem in question: its bug tracker or mailing + list archive might have the answer you are looking for. + + * If you see a proposed fix, search for it in the version control system as + outlined above, as the commit might tell you if a backport can be expected. + + * Check the discussions for any indicators the fix might be too risky to get + backported to the version line you care about. If that's the case you have + to live with the issue or switch to the kernel version line where the fix + got applied. + + * If the fix doesn't contain a stable tag and backporting was not discussed, + join the discussion: mention the version where you face the issue and that + you would like to see it fixed, if suitable. + + +Ask for advice +~~~~~~~~~~~~~~ + + *One of the former steps should lead to a solution. If that doesn't work + out, ask the maintainers for the subsystem that seems to be causing the + issue for advice; CC the mailing list for the particular subsystem as well + as the stable mailing list.* + +If the previous three steps didn't get you closer to a solution there is only +one option left: ask for advice. Do that in a mail you sent to the maintainers +for the subsystem where the issue seems to have its roots; CC the mailing list +for the subsystem as well as the stable mailing list (stable@vger.kernel.org). + + +Why some issues won't get any reaction or remain unfixed after being reported +============================================================================= + +When reporting a problem to the Linux developers, be aware only 'issues of high +priority' (regressions, security issues, severe problems) are definitely going +to get resolved. The maintainers or if all else fails Linus Torvalds himself +will make sure of that. They and the other kernel developers will fix a lot of +other issues as well. But be aware that sometimes they can't or won't help; and +sometimes there isn't even anyone to send a report to. + +This is best explained with kernel developers that contribute to the Linux +kernel in their spare time. Quite a few of the drivers in the kernel were +written by such programmers, often because they simply wanted to make their +hardware usable on their favorite operating system. + +These programmers most of the time will happily fix problems other people +report. But nobody can force them to do, as they are contributing voluntarily. + +Then there are situations where such developers really want to fix an issue, +but can't: sometimes they lack hardware programming documentation to do so. +This often happens when the publicly available docs are superficial or the +driver was written with the help of reverse engineering. + +Sooner or later spare time developers will also stop caring for the driver. +Maybe their test hardware broke, got replaced by something more fancy, or is so +old that it's something you don't find much outside of computer museums +anymore. Sometimes developer stops caring for their code and Linux at all, as +something different in their life became way more important. In some cases +nobody is willing to take over the job as maintainer – and nobody can be forced +to, as contributing to the Linux kernel is done on a voluntary basis. Abandoned +drivers nevertheless remain in the kernel: they are still useful for people and +removing would be a regression. + +The situation is not that different with developers that are paid for their +work on the Linux kernel. Those contribute most changes these days. But their +employers sooner or later also stop caring for their code or make its +programmer focus on other things. Hardware vendors for example earn their money +mainly by selling new hardware; quite a few of them hence are not investing +much time and energy in maintaining a Linux kernel driver for something they +stopped selling years ago. Enterprise Linux distributors often care for a +longer time period, but in new versions often leave support for old and rare +hardware aside to limit the scope. Often spare time contributors take over once +a company orphans some code, but as mentioned above: sooner or later they will +leave the code behind, too. + +Priorities are another reason why some issues are not fixed, as maintainers +quite often are forced to set those, as time to work on Linux is limited. +That's true for spare time or the time employers grant their developers to +spend on maintenance work on the upstream kernel. Sometimes maintainers also +get overwhelmed with reports, even if a driver is working nearly perfectly. To +not get completely stuck, the programmer thus might have no other choice than +to prioritize issue reports and reject some of them. + +But don't worry too much about all of this, a lot of drivers have active +maintainers who are quite interested in fixing as many issues as possible. + + +Closing words +============= + +Compared with other Free/Libre & Open Source Software it's hard to report +issues to the Linux kernel developers: the length and complexity of this +document and the implications between the lines illustrate that. But that's how +it is for now. The main author of this text hopes documenting the state of the +art will lay some groundwork to improve the situation over time. + + +.. + end-of-content +.. + This document is maintained by Thorsten Leemhuis <linux@leemhuis.info>. If + you spot a typo or small mistake, feel free to let him know directly and + he'll fix it. You are free to do the same in a mostly informal way if you + want to contribute changes to the text, but for copyright reasons please CC + linux-doc@vger.kernel.org and "sign-off" your contribution as + Documentation/process/submitting-patches.rst outlines in the section "Sign + your work - the Developer's Certificate of Origin". +.. + This text is available under GPL-2.0+ or CC-BY-4.0, as stated at the top + of the file. If you want to distribute this text under CC-BY-4.0 only, + please use "The Linux kernel developers" for author attribution and link + this as source: + https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/Documentation/admin-guide/reporting-issues.rst +.. + Note: Only the content of this RST file as found in the Linux kernel sources + is available under CC-BY-4.0, as versions of this text that were processed + (for example by the kernel's build system) might contain content taken from + files which use a more restrictive license. diff --git a/Documentation/admin-guide/reporting-regressions.rst b/Documentation/admin-guide/reporting-regressions.rst new file mode 100644 index 000000000..d8adccdae --- /dev/null +++ b/Documentation/admin-guide/reporting-regressions.rst @@ -0,0 +1,451 @@ +.. SPDX-License-Identifier: (GPL-2.0+ OR CC-BY-4.0) +.. [see the bottom of this file for redistribution information] + +Reporting regressions ++++++++++++++++++++++ + +"*We don't cause regressions*" is the first rule of Linux kernel development; +Linux founder and lead developer Linus Torvalds established it himself and +ensures it's obeyed. + +This document describes what the rule means for users and how the Linux kernel's +development model ensures to address all reported regressions; aspects relevant +for kernel developers are left to Documentation/process/handling-regressions.rst. + + +The important bits (aka "TL;DR") +================================ + +#. It's a regression if something running fine with one Linux kernel works worse + or not at all with a newer version. Note, the newer kernel has to be compiled + using a similar configuration; the detailed explanations below describes this + and other fine print in more detail. + +#. Report your issue as outlined in Documentation/admin-guide/reporting-issues.rst, + it already covers all aspects important for regressions and repeated + below for convenience. Two of them are important: start your report's subject + with "[REGRESSION]" and CC or forward it to `the regression mailing list + <https://lore.kernel.org/regressions/>`_ (regressions@lists.linux.dev). + +#. Optional, but recommended: when sending or forwarding your report, make the + Linux kernel regression tracking bot "regzbot" track the issue by specifying + when the regression started like this:: + + #regzbot introduced v5.13..v5.14-rc1 + + +All the details on Linux kernel regressions relevant for users +============================================================== + + +The important basics +-------------------- + + +What is a "regression" and what is the "no regressions rule"? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +It's a regression if some application or practical use case running fine with +one Linux kernel works worse or not at all with a newer version compiled using a +similar configuration. The "no regressions rule" forbids this to take place; if +it happens by accident, developers that caused it are expected to quickly fix +the issue. + +It thus is a regression when a WiFi driver from Linux 5.13 works fine, but with +5.14 doesn't work at all, works significantly slower, or misbehaves somehow. +It's also a regression if a perfectly working application suddenly shows erratic +behavior with a newer kernel version; such issues can be caused by changes in +procfs, sysfs, or one of the many other interfaces Linux provides to userland +software. But keep in mind, as mentioned earlier: 5.14 in this example needs to +be built from a configuration similar to the one from 5.13. This can be achieved +using ``make olddefconfig``, as explained in more detail below. + +Note the "practical use case" in the first sentence of this section: developers +despite the "no regressions" rule are free to change any aspect of the kernel +and even APIs or ABIs to userland, as long as no existing application or use +case breaks. + +Also be aware the "no regressions" rule covers only interfaces the kernel +provides to the userland. It thus does not apply to kernel-internal interfaces +like the module API, which some externally developed drivers use to hook into +the kernel. + +How do I report a regression? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Just report the issue as outlined in +Documentation/admin-guide/reporting-issues.rst, it already describes the +important points. The following aspects outlined there are especially relevant +for regressions: + + * When checking for existing reports to join, also search the `archives of the + Linux regressions mailing list <https://lore.kernel.org/regressions/>`_ and + `regzbot's web-interface <https://linux-regtracking.leemhuis.info/regzbot/>`_. + + * Start your report's subject with "[REGRESSION]". + + * In your report, clearly mention the last kernel version that worked fine and + the first broken one. Ideally try to find the exact change causing the + regression using a bisection, as explained below in more detail. + + * Remember to let the Linux regressions mailing list + (regressions@lists.linux.dev) know about your report: + + * If you report the regression by mail, CC the regressions list. + + * If you report your regression to some bug tracker, forward the submitted + report by mail to the regressions list while CCing the maintainer and the + mailing list for the subsystem in question. + + If it's a regression within a stable or longterm series (e.g. + v5.15.3..v5.15.5), remember to CC the `Linux stable mailing list + <https://lore.kernel.org/stable/>`_ (stable@vger.kernel.org). + + In case you performed a successful bisection, add everyone to the CC the + culprit's commit message mentions in lines starting with "Signed-off-by:". + +When CCing for forwarding your report to the list, consider directly telling the +aforementioned Linux kernel regression tracking bot about your report. To do +that, include a paragraph like this in your mail:: + + #regzbot introduced: v5.13..v5.14-rc1 + +Regzbot will then consider your mail a report for a regression introduced in the +specified version range. In above case Linux v5.13 still worked fine and Linux +v5.14-rc1 was the first version where you encountered the issue. If you +performed a bisection to find the commit that caused the regression, specify the +culprit's commit-id instead:: + + #regzbot introduced: 1f2e3d4c5d + +Placing such a "regzbot command" is in your interest, as it will ensure the +report won't fall through the cracks unnoticed. If you omit this, the Linux +kernel's regressions tracker will take care of telling regzbot about your +regression, as long as you send a copy to the regressions mailing lists. But the +regression tracker is just one human which sometimes has to rest or occasionally +might even enjoy some time away from computers (as crazy as that might sound). +Relying on this person thus will result in an unnecessary delay before the +regressions becomes mentioned `on the list of tracked and unresolved Linux +kernel regressions <https://linux-regtracking.leemhuis.info/regzbot/>`_ and the +weekly regression reports sent by regzbot. Such delays can result in Linus +Torvalds being unaware of important regressions when deciding between "continue +development or call this finished and release the final?". + +Are really all regressions fixed? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Nearly all of them are, as long as the change causing the regression (the +"culprit commit") is reliably identified. Some regressions can be fixed without +this, but often it's required. + +Who needs to find the root cause of a regression? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Developers of the affected code area should try to locate the culprit on their +own. But for them that's often impossible to do with reasonable effort, as quite +a lot of issues only occur in a particular environment outside the developer's +reach -- for example, a specific hardware platform, firmware, Linux distro, +system's configuration, or application. That's why in the end it's often up to +the reporter to locate the culprit commit; sometimes users might even need to +run additional tests afterwards to pinpoint the exact root cause. Developers +should offer advice and reasonably help where they can, to make this process +relatively easy and achievable for typical users. + +How can I find the culprit? +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Perform a bisection, as roughly outlined in +Documentation/admin-guide/reporting-issues.rst and described in more detail by +Documentation/admin-guide/bug-bisect.rst. It might sound like a lot of work, but +in many cases finds the culprit relatively quickly. If it's hard or +time-consuming to reliably reproduce the issue, consider teaming up with other +affected users to narrow down the search range together. + +Who can I ask for advice when it comes to regressions? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Send a mail to the regressions mailing list (regressions@lists.linux.dev) while +CCing the Linux kernel's regression tracker (regressions@leemhuis.info); if the +issue might better be dealt with in private, feel free to omit the list. + + +Additional details about regressions +------------------------------------ + + +What is the goal of the "no regressions rule"? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Users should feel safe when updating kernel versions and not have to worry +something might break. This is in the interest of the kernel developers to make +updating attractive: they don't want users to stay on stable or longterm Linux +series that are either abandoned or more than one and a half years old. That's +in everybody's interest, as `those series might have known bugs, security +issues, or other problematic aspects already fixed in later versions +<http://www.kroah.com/log/blog/2018/08/24/what-stable-kernel-should-i-use/>`_. +Additionally, the kernel developers want to make it simple and appealing for +users to test the latest pre-release or regular release. That's also in +everybody's interest, as it's a lot easier to track down and fix problems, if +they are reported shortly after being introduced. + +Is the "no regressions" rule really adhered in practice? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +It's taken really seriously, as can be seen by many mailing list posts from +Linux creator and lead developer Linus Torvalds, some of which are quoted in +Documentation/process/handling-regressions.rst. + +Exceptions to this rule are extremely rare; in the past developers almost always +turned out to be wrong when they assumed a particular situation was warranting +an exception. + +Who ensures the "no regressions" is actually followed? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The subsystem maintainers should take care of that, which are watched and +supported by the tree maintainers -- e.g. Linus Torvalds for mainline and +Greg Kroah-Hartman et al. for various stable/longterm series. + +All of them are helped by people trying to ensure no regression report falls +through the cracks. One of them is Thorsten Leemhuis, who's currently acting as +the Linux kernel's "regressions tracker"; to facilitate this work he relies on +regzbot, the Linux kernel regression tracking bot. That's why you want to bring +your report on the radar of these people by CCing or forwarding each report to +the regressions mailing list, ideally with a "regzbot command" in your mail to +get it tracked immediately. + +How quickly are regressions normally fixed? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Developers should fix any reported regression as quickly as possible, to provide +affected users with a solution in a timely manner and prevent more users from +running into the issue; nevertheless developers need to take enough time and +care to ensure regression fixes do not cause additional damage. + +The answer thus depends on various factors like the impact of a regression, its +age, or the Linux series in which it occurs. In the end though, most regressions +should be fixed within two weeks. + +Is it a regression, if the issue can be avoided by updating some software? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Almost always: yes. If a developer tells you otherwise, ask the regression +tracker for advice as outlined above. + +Is it a regression, if a newer kernel works slower or consumes more energy? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Yes, but the difference has to be significant. A five percent slow-down in a +micro-benchmark thus is unlikely to qualify as regression, unless it also +influences the results of a broad benchmark by more than one percent. If in +doubt, ask for advice. + +Is it a regression, if an external kernel module breaks when updating Linux? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +No, as the "no regression" rule is about interfaces and services the Linux +kernel provides to the userland. It thus does not cover building or running +externally developed kernel modules, as they run in kernel-space and hook into +the kernel using internal interfaces occasionally changed. + +How are regressions handled that are caused by security fixes? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +In extremely rare situations security issues can't be fixed without causing +regressions; those fixes are given way, as they are the lesser evil in the end. +Luckily this middling almost always can be avoided, as key developers for the +affected area and often Linus Torvalds himself try very hard to fix security +issues without causing regressions. + +If you nevertheless face such a case, check the mailing list archives if people +tried their best to avoid the regression. If not, report it; if in doubt, ask +for advice as outlined above. + +What happens if fixing a regression is impossible without causing another? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Sadly these things happen, but luckily not very often; if they occur, expert +developers of the affected code area should look into the issue to find a fix +that avoids regressions or at least their impact. If you run into such a +situation, do what was outlined already for regressions caused by security +fixes: check earlier discussions if people already tried their best and ask for +advice if in doubt. + +A quick note while at it: these situations could be avoided, if people would +regularly give mainline pre-releases (say v5.15-rc1 or -rc3) from each +development cycle a test run. This is best explained by imagining a change +integrated between Linux v5.14 and v5.15-rc1 which causes a regression, but at +the same time is a hard requirement for some other improvement applied for +5.15-rc1. All these changes often can simply be reverted and the regression thus +solved, if someone finds and reports it before 5.15 is released. A few days or +weeks later this solution can become impossible, as some software might have +started to rely on aspects introduced by one of the follow-up changes: reverting +all changes would then cause a regression for users of said software and thus is +out of the question. + +Is it a regression, if some feature I relied on was removed months ago? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +It is, but often it's hard to fix such regressions due to the aspects outlined +in the previous section. It hence needs to be dealt with on a case-by-case +basis. This is another reason why it's in everybody's interest to regularly test +mainline pre-releases. + +Does the "no regression" rule apply if I seem to be the only affected person? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +It does, but only for practical usage: the Linux developers want to be free to +remove support for hardware only to be found in attics and museums anymore. + +Note, sometimes regressions can't be avoided to make progress -- and the latter +is needed to prevent Linux from stagnation. Hence, if only very few users seem +to be affected by a regression, it for the greater good might be in their and +everyone else's interest to lettings things pass. Especially if there is an +easy way to circumvent the regression somehow, for example by updating some +software or using a kernel parameter created just for this purpose. + +Does the regression rule apply for code in the staging tree as well? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Not according to the `help text for the configuration option covering all +staging code <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/staging/Kconfig>`_, +which since its early days states:: + + Please note that these drivers are under heavy development, may or + may not work, and may contain userspace interfaces that most likely + will be changed in the near future. + +The staging developers nevertheless often adhere to the "no regressions" rule, +but sometimes bend it to make progress. That's for example why some users had to +deal with (often negligible) regressions when a WiFi driver from the staging +tree was replaced by a totally different one written from scratch. + +Why do later versions have to be "compiled with a similar configuration"? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Because the Linux kernel developers sometimes integrate changes known to cause +regressions, but make them optional and disable them in the kernel's default +configuration. This trick allows progress, as the "no regressions" rule +otherwise would lead to stagnation. + +Consider for example a new security feature blocking access to some kernel +interfaces often abused by malware, which at the same time are required to run a +few rarely used applications. The outlined approach makes both camps happy: +people using these applications can leave the new security feature off, while +everyone else can enable it without running into trouble. + +How to create a configuration similar to the one of an older kernel? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Start your machine with a known-good kernel and configure the newer Linux +version with ``make olddefconfig``. This makes the kernel's build scripts pick +up the configuration file (the ".config" file) from the running kernel as base +for the new one you are about to compile; afterwards they set all new +configuration options to their default value, which should disable new features +that might cause regressions. + +Can I report a regression I found with pre-compiled vanilla kernels? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +You need to ensure the newer kernel was compiled with a similar configuration +file as the older one (see above), as those that built them might have enabled +some known-to-be incompatible feature for the newer kernel. If in doubt, report +the matter to the kernel's provider and ask for advice. + + +More about regression tracking with "regzbot" +--------------------------------------------- + +What is regression tracking and why should I care about it? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Rules like "no regressions" need someone to ensure they are followed, otherwise +they are broken either accidentally or on purpose. History has shown this to be +true for Linux kernel development as well. That's why Thorsten Leemhuis, the +Linux Kernel's regression tracker, and some people try to ensure all regression +are fixed by keeping an eye on them until they are resolved. Neither of them are +paid for this, that's why the work is done on a best effort basis. + +Why and how are Linux kernel regressions tracked using a bot? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Tracking regressions completely manually has proven to be quite hard due to the +distributed and loosely structured nature of Linux kernel development process. +That's why the Linux kernel's regression tracker developed regzbot to facilitate +the work, with the long term goal to automate regression tracking as much as +possible for everyone involved. + +Regzbot works by watching for replies to reports of tracked regressions. +Additionally, it's looking out for posted or committed patches referencing such +reports with "Link:" tags; replies to such patch postings are tracked as well. +Combined this data provides good insights into the current state of the fixing +process. + +How to see which regressions regzbot tracks currently? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Check out `regzbot's web-interface <https://linux-regtracking.leemhuis.info/regzbot/>`_. + +What kind of issues are supposed to be tracked by regzbot? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The bot is meant to track regressions, hence please don't involve regzbot for +regular issues. But it's okay for the Linux kernel's regression tracker if you +involve regzbot to track severe issues, like reports about hangs, corrupted +data, or internal errors (Panic, Oops, BUG(), warning, ...). + +How to change aspects of a tracked regression? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +By using a 'regzbot command' in a direct or indirect reply to the mail with the +report. The easiest way to do that: find the report in your "Sent" folder or the +mailing list archive and reply to it using your mailer's "Reply-all" function. +In that mail, use one of the following commands in a stand-alone paragraph (IOW: +use blank lines to separate one or multiple of these commands from the rest of +the mail's text). + + * Update when the regression started to happen, for example after performing a + bisection:: + + #regzbot introduced: 1f2e3d4c5d + + * Set or update the title:: + + #regzbot title: foo + + * Monitor a discussion or bugzilla.kernel.org ticket where additions aspects of + the issue or a fix are discussed::: + + #regzbot monitor: https://lore.kernel.org/r/30th.anniversary.repost@klaava.Helsinki.FI/ + #regzbot monitor: https://bugzilla.kernel.org/show_bug.cgi?id=123456789 + + * Point to a place with further details of interest, like a mailing list post + or a ticket in a bug tracker that are slightly related, but about a different + topic:: + + #regzbot link: https://bugzilla.kernel.org/show_bug.cgi?id=123456789 + + * Mark a regression as invalid:: + + #regzbot invalid: wasn't a regression, problem has always existed + +Regzbot supports a few other commands primarily used by developers or people +tracking regressions. They and more details about the aforementioned regzbot +commands can be found in the `getting started guide +<https://gitlab.com/knurd42/regzbot/-/blob/main/docs/getting_started.md>`_ and +the `reference documentation <https://gitlab.com/knurd42/regzbot/-/blob/main/docs/reference.md>`_ +for regzbot. + +.. + end-of-content +.. + This text is available under GPL-2.0+ or CC-BY-4.0, as stated at the top + of the file. If you want to distribute this text under CC-BY-4.0 only, + please use "The Linux kernel developers" for author attribution and link + this as source: + https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/Documentation/admin-guide/reporting-regressions.rst +.. + Note: Only the content of this RST file as found in the Linux kernel sources + is available under CC-BY-4.0, as versions of this text that were processed + (for example by the kernel's build system) might contain content taken from + files which use a more restrictive license. diff --git a/Documentation/admin-guide/rtc.rst b/Documentation/admin-guide/rtc.rst new file mode 100644 index 000000000..688c95b11 --- /dev/null +++ b/Documentation/admin-guide/rtc.rst @@ -0,0 +1,140 @@ +======================================= +Real Time Clock (RTC) Drivers for Linux +======================================= + +When Linux developers talk about a "Real Time Clock", they usually mean +something that tracks wall clock time and is battery backed so that it +works even with system power off. Such clocks will normally not track +the local time zone or daylight savings time -- unless they dual boot +with MS-Windows -- but will instead be set to Coordinated Universal Time +(UTC, formerly "Greenwich Mean Time"). + +The newest non-PC hardware tends to just count seconds, like the time(2) +system call reports, but RTCs also very commonly represent time using +the Gregorian calendar and 24 hour time, as reported by gmtime(3). + +Linux has two largely-compatible userspace RTC API families you may +need to know about: + + * /dev/rtc ... is the RTC provided by PC compatible systems, + so it's not very portable to non-x86 systems. + + * /dev/rtc0, /dev/rtc1 ... are part of a framework that's + supported by a wide variety of RTC chips on all systems. + +Programmers need to understand that the PC/AT functionality is not +always available, and some systems can do much more. That is, the +RTCs use the same API to make requests in both RTC frameworks (using +different filenames of course), but the hardware may not offer the +same functionality. For example, not every RTC is hooked up to an +IRQ, so they can't all issue alarms; and where standard PC RTCs can +only issue an alarm up to 24 hours in the future, other hardware may +be able to schedule one any time in the upcoming century. + + +Old PC/AT-Compatible driver: /dev/rtc +-------------------------------------- + +All PCs (even Alpha machines) have a Real Time Clock built into them. +Usually they are built into the chipset of the computer, but some may +actually have a Motorola MC146818 (or clone) on the board. This is the +clock that keeps the date and time while your computer is turned off. + +ACPI has standardized that MC146818 functionality, and extended it in +a few ways (enabling longer alarm periods, and wake-from-hibernate). +That functionality is NOT exposed in the old driver. + +However it can also be used to generate signals from a slow 2Hz to a +relatively fast 8192Hz, in increments of powers of two. These signals +are reported by interrupt number 8. (Oh! So *that* is what IRQ 8 is +for...) It can also function as a 24hr alarm, raising IRQ 8 when the +alarm goes off. The alarm can also be programmed to only check any +subset of the three programmable values, meaning that it could be set to +ring on the 30th second of the 30th minute of every hour, for example. +The clock can also be set to generate an interrupt upon every clock +update, thus generating a 1Hz signal. + +The interrupts are reported via /dev/rtc (major 10, minor 135, read only +character device) in the form of an unsigned long. The low byte contains +the type of interrupt (update-done, alarm-rang, or periodic) that was +raised, and the remaining bytes contain the number of interrupts since +the last read. Status information is reported through the pseudo-file +/proc/driver/rtc if the /proc filesystem was enabled. The driver has +built in locking so that only one process is allowed to have the /dev/rtc +interface open at a time. + +A user process can monitor these interrupts by doing a read(2) or a +select(2) on /dev/rtc -- either will block/stop the user process until +the next interrupt is received. This is useful for things like +reasonably high frequency data acquisition where one doesn't want to +burn up 100% CPU by polling gettimeofday etc. etc. + +At high frequencies, or under high loads, the user process should check +the number of interrupts received since the last read to determine if +there has been any interrupt "pileup" so to speak. Just for reference, a +typical 486-33 running a tight read loop on /dev/rtc will start to suffer +occasional interrupt pileup (i.e. > 1 IRQ event since last read) for +frequencies above 1024Hz. So you really should check the high bytes +of the value you read, especially at frequencies above that of the +normal timer interrupt, which is 100Hz. + +Programming and/or enabling interrupt frequencies greater than 64Hz is +only allowed by root. This is perhaps a bit conservative, but we don't want +an evil user generating lots of IRQs on a slow 386sx-16, where it might have +a negative impact on performance. This 64Hz limit can be changed by writing +a different value to /proc/sys/dev/rtc/max-user-freq. Note that the +interrupt handler is only a few lines of code to minimize any possibility +of this effect. + +Also, if the kernel time is synchronized with an external source, the +kernel will write the time back to the CMOS clock every 11 minutes. In +the process of doing this, the kernel briefly turns off RTC periodic +interrupts, so be aware of this if you are doing serious work. If you +don't synchronize the kernel time with an external source (via ntp or +whatever) then the kernel will keep its hands off the RTC, allowing you +exclusive access to the device for your applications. + +The alarm and/or interrupt frequency are programmed into the RTC via +various ioctl(2) calls as listed in ./include/linux/rtc.h +Rather than write 50 pages describing the ioctl() and so on, it is +perhaps more useful to include a small test program that demonstrates +how to use them, and demonstrates the features of the driver. This is +probably a lot more useful to people interested in writing applications +that will be using this driver. See the code at the end of this document. + +(The original /dev/rtc driver was written by Paul Gortmaker.) + + +New portable "RTC Class" drivers: /dev/rtcN +-------------------------------------------- + +Because Linux supports many non-ACPI and non-PC platforms, some of which +have more than one RTC style clock, it needed a more portable solution +than expecting a single battery-backed MC146818 clone on every system. +Accordingly, a new "RTC Class" framework has been defined. It offers +three different userspace interfaces: + + * /dev/rtcN ... much the same as the older /dev/rtc interface + + * /sys/class/rtc/rtcN ... sysfs attributes support readonly + access to some RTC attributes. + + * /proc/driver/rtc ... the system clock RTC may expose itself + using a procfs interface. If there is no RTC for the system clock, + rtc0 is used by default. More information is (currently) shown + here than through sysfs. + +The RTC Class framework supports a wide variety of RTCs, ranging from those +integrated into embeddable system-on-chip (SOC) processors to discrete chips +using I2C, SPI, or some other bus to communicate with the host CPU. There's +even support for PC-style RTCs ... including the features exposed on newer PCs +through ACPI. + +The new framework also removes the "one RTC per system" restriction. For +example, maybe the low-power battery-backed RTC is a discrete I2C chip, but +a high functionality RTC is integrated into the SOC. That system might read +the system clock from the discrete RTC, but use the integrated one for all +other tasks, because of its greater functionality. + +Check out tools/testing/selftests/rtc/rtctest.c for an example usage of the +ioctl interface. diff --git a/Documentation/admin-guide/serial-console.rst b/Documentation/admin-guide/serial-console.rst new file mode 100644 index 000000000..a3dfc2c66 --- /dev/null +++ b/Documentation/admin-guide/serial-console.rst @@ -0,0 +1,145 @@ +.. _serial_console: + +Linux Serial Console +==================== + +To use a serial port as console you need to compile the support into your +kernel - by default it is not compiled in. For PC style serial ports +it's the config option next to menu option: + +:menuselection:`Character devices --> Serial drivers --> 8250/16550 and compatible serial support --> Console on 8250/16550 and compatible serial port` + +You must compile serial support into the kernel and not as a module. + +It is possible to specify multiple devices for console output. You can +define a new kernel command line option to select which device(s) to +use for console output. + +The format of this option is:: + + console=device,options + + device: tty0 for the foreground virtual console + ttyX for any other virtual console + ttySx for a serial port + lp0 for the first parallel port + ttyUSB0 for the first USB serial device + + options: depend on the driver. For the serial port this + defines the baudrate/parity/bits/flow control of + the port, in the format BBBBPNF, where BBBB is the + speed, P is parity (n/o/e), N is number of bits, + and F is flow control ('r' for RTS). Default is + 9600n8. The maximum baudrate is 115200. + +You can specify multiple console= options on the kernel command line. + +The behavior is well defined when each device type is mentioned only once. +In this case, the output will appear on all requested consoles. And +the last device will be used when you open ``/dev/console``. +So, for example:: + + console=ttyS1,9600 console=tty0 + +defines that opening ``/dev/console`` will get you the current foreground +virtual console, and kernel messages will appear on both the VGA +console and the 2nd serial port (ttyS1 or COM2) at 9600 baud. + +The behavior is more complicated when the same device type is defined more +times. In this case, there are the following two rules: + +1. The output will appear only on the first device of each defined type. + +2. ``/dev/console`` will be associated with the first registered device. + Where the registration order depends on how kernel initializes various + subsystems. + + This rule is used also when the last console= parameter is not used + for other reasons. For example, because of a typo or because + the hardware is not available. + +The result might be surprising. For example, the following two command +lines have the same result:: + + console=ttyS1,9600 console=tty0 console=tty1 + console=tty0 console=ttyS1,9600 console=tty1 + +The kernel messages are printed only on ``tty0`` and ``ttyS1``. And +``/dev/console`` gets associated with ``tty0``. It is because kernel +tries to register graphical consoles before serial ones. It does it +because of the default behavior when no console device is specified, +see below. + +Note that the last ``console=tty1`` parameter still makes a difference. +The kernel command line is used also by systemd. It would use the last +defined ``tty1`` as the login console. + +If no console device is specified, the first device found capable of +acting as a system console will be used. At this time, the system +first looks for a VGA card and then for a serial port. So if you don't +have a VGA card in your system the first serial port will automatically +become the console. + +You will need to create a new device to use ``/dev/console``. The official +``/dev/console`` is now character device 5,1. + +(You can also use a network device as a console. See +``Documentation/networking/netconsole.rst`` for information on that.) + +Here's an example that will use ``/dev/ttyS1`` (COM2) as the console. +Replace the sample values as needed. + +1. Create ``/dev/console`` (real console) and ``/dev/tty0`` (master virtual + console):: + + cd /dev + rm -f console tty0 + mknod -m 622 console c 5 1 + mknod -m 622 tty0 c 4 0 + +2. LILO can also take input from a serial device. This is a very + useful option. To tell LILO to use the serial port: + In lilo.conf (global section):: + + serial = 1,9600n8 (ttyS1, 9600 bd, no parity, 8 bits) + +3. Adjust to kernel flags for the new kernel, + again in lilo.conf (kernel section):: + + append = "console=ttyS1,9600" + +4. Make sure a getty runs on the serial port so that you can login to + it once the system is done booting. This is done by adding a line + like this to ``/etc/inittab`` (exact syntax depends on your getty):: + + S1:23:respawn:/sbin/getty -L ttyS1 9600 vt100 + +5. Init and ``/etc/ioctl.save`` + + Sysvinit remembers its stty settings in a file in ``/etc``, called + ``/etc/ioctl.save``. REMOVE THIS FILE before using the serial + console for the first time, because otherwise init will probably + set the baudrate to 38400 (baudrate of the virtual console). + +6. ``/dev/console`` and X + Programs that want to do something with the virtual console usually + open ``/dev/console``. If you have created the new ``/dev/console`` device, + and your console is NOT the virtual console some programs will fail. + Those are programs that want to access the VT interface, and use + ``/dev/console instead of /dev/tty0``. Some of those programs are:: + + Xfree86, svgalib, gpm, SVGATextMode + + It should be fixed in modern versions of these programs though. + + Note that if you boot without a ``console=`` option (or with + ``console=/dev/tty0``), ``/dev/console`` is the same as ``/dev/tty0``. + In that case everything will still work. + +7. Thanks + + Thanks to Geert Uytterhoeven <geert@linux-m68k.org> + for porting the patches from 2.1.4x to 2.1.6x for taking care of + the integration of these patches into m68k, ppc and alpha. + +Miquel van Smoorenburg <miquels@cistron.nl>, 11-Jun-2000 diff --git a/Documentation/admin-guide/spkguide.txt b/Documentation/admin-guide/spkguide.txt new file mode 100644 index 000000000..74ea7f391 --- /dev/null +++ b/Documentation/admin-guide/spkguide.txt @@ -0,0 +1,1620 @@ + +The Speakup User's Guide +For Speakup 3.1.2 and Later +By Gene Collins +Updated by others +Last modified on Mon Sep 27 14:26:31 2010 +Document version 1.3 + +Copyright (c) 2005 Gene Collins +Copyright (c) 2008 Samuel Thibault +Copyright (c) 2009, 2010 the Speakup Team + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.2 or +any later version published by the Free Software Foundation; with no +Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A +copy of the license is included in the section entitled "GNU Free +Documentation License". + +Preface + +The purpose of this document is to familiarize users with the user +interface to Speakup, a Linux Screen Reader. If you need instructions +for installing or obtaining Speakup, visit the web site at +http://linux-speakup.org/. Speakup is a set of patches to the standard +Linux kernel source tree. It can be built as a series of modules, or as +a part of a monolithic kernel. These details are beyond the scope of +this manual, but the user may need to be aware of the module +capabilities, depending on how your system administrator has installed +Speakup. If Speakup is built as a part of a monolithic kernel, and the +user is using a hardware synthesizer, then Speakup will be able to +provide speech access from the time the kernel is loaded, until the time +the system is shutdown. This means that if you have obtained Linux +installation media for a distribution which includes Speakup as a part +of its kernel, you will be able, as a blind person, to install Linux +with speech access unaided by a sighted person. Again, these details +are beyond the scope of this manual, but the user should be aware of +them. See the web site mentioned above for further details. + +1. Starting Speakup + +If your system administrator has installed Speakup to work with your +specific synthesizer by default, then all you need to do to use Speakup +is to boot your system, and Speakup should come up talking. This +assumes of course that your synthesizer is a supported hardware +synthesizer, and that it is either installed in or connected to your +system, and is if necessary powered on. + +It is possible, however, that Speakup may have been compiled into the +kernel with no default synthesizer. It is even possible that your +kernel has been compiled with support for some of the supported +synthesizers and not others. If you find that this is the case, and +your synthesizer is supported but not available, complain to the person +who compiled and installed your kernel. Or better yet, go to the web +site, and learn how to patch Speakup into your own kernel source, and +build and install your own kernel. + +If your kernel has been compiled with Speakup, and has no default +synthesizer set, or you would like to use a different synthesizer than +the default one, then you may issue the following command at the boot +prompt of your boot loader. + +linux speakup.synth=ltlk + +This command would tell Speakup to look for and use a LiteTalk or +DoubleTalk LT at boot up. You may replace the ltlk synthesizer keyword +with the keyword for whatever synthesizer you wish to use. The +speakup.synth parameter will accept the following keywords, provided +that support for the related synthesizers has been built into the +kernel. + +acntsa -- Accent SA +acntpc -- Accent PC +apollo -- Apollo +audptr -- Audapter +bns -- Braille 'n Speak +dectlk -- DecTalk Express (old and new, db9 serial only) +decext -- DecTalk (old) External +dtlk -- DoubleTalk PC +keypc -- Keynote Gold PC +ltlk -- DoubleTalk LT, LiteTalk, or external Tripletalk (db9 serial only) +spkout -- Speak Out +txprt -- Transport +dummy -- Plain text terminal + +Note: Speakup does * NOT * support usb connections! Speakup also does * +NOT * support the internal Tripletalk! + +Speakup does support two other synthesizers, but because they work in +conjunction with other software, they must be loaded as modules after +their related software is loaded, and so are not available at boot up. +These are as follows: + +decpc -- DecTalk PC (not available at boot up) +soft -- One of several software synthesizers (not available at boot up) + +See the sections on loading modules and software synthesizers later in +this manual for further details. It should be noted here that the +speakup.synth boot parameter will have no effect if Speakup has been +compiled as modules. In order for Speakup modules to be loaded during +the boot process, such action must be configured by your system +administrator. This will mean that you will hear some, but not all, of +the bootup messages. + +2. Basic operation + +Once you have booted the system, and if necessary, have supplied the +proper bootup parameter for your synthesizer, Speakup will begin +talking as soon as the kernel is loaded. In fact, it will talk a lot! +It will speak all the boot up messages that the kernel prints on the +screen during the boot process. This is because Speakup is not a +separate screen reader, but is actually built into the operating +system. Since almost all console applications must print text on the +screen using the kernel, and must get their keyboard input through the +kernel, they are automatically handled properly by Speakup. There are a +few exceptions, but we'll come to those later. + +Note: In this guide I will refer to the numeric keypad as the keypad. +This is done because the speakupmap.map file referred to later in this +manual uses the term keypad instead of numeric keypad. Also I'm lazy +and would rather only type one word. So keypad it is. Got it? Good. + +Most of the Speakup review keys are located on the keypad at the far +right of the keyboard. The numlock key should be off, in order for these +to work. If you toggle the numlock on, the keypad will produce numbers, +which is exactly what you want for spreadsheets and such. For the +purposes of this guide, you should have the numlock turned off, which is +its default state at bootup. + +You probably won't want to listen to all the bootup messages every time +you start your system, though it's a good idea to listen to them at +least once, just so you'll know what kind of information is available to +you during the boot process. You can always review these messages after +bootup with the command: + +dmesg | more + +In order to speed the boot process, and to silence the speaking of the +bootup messages, just press the keypad enter key. This key is located +in the bottom right corner of the keypad. Speakup will shut up and stay +that way, until you press another key. + +You can check to see if the boot process has completed by pressing the 8 +key on the keypad, which reads the current line. This also has the +effect of starting Speakup talking again, so you can press keypad enter +to silence it again if the boot process has not completed. + +When the boot process is complete, you will arrive at a "login" prompt. +At this point, you'll need to type in your user id and password, as +provided by your system administrator. You will hear Speakup speak the +letters of your user id as you type it, but not the password. This is +because the password is not displayed on the screen for security +reasons. This has nothing to do with Speakup, it's a Linux security +feature. + +Once you've logged in, you can run any Linux command or program which is +allowed by your user id. Normal users will not be able to run programs +which require root privileges. + +When you are running a program or command, Speakup will automatically +speak new text as it arrives on the screen. You can at any time silence +the speech with keypad enter, or use any of the Speakup review keys. + +Here are some basic Speakup review keys, and a short description of what +they do. + +keypad 1 -- read previous character +keypad 2 -- read current character (pressing keypad 2 twice rapidly will speak + the current character phonetically) +keypad 3 -- read next character +keypad 4 -- read previous word +keypad 5 -- read current word (press twice rapidly to spell the current word) +keypad 6 -- read next word +keypad 7 -- read previous line +keypad 8 -- read current line (press twice rapidly to hear how much the + text on the current line is indented) +keypad 9 -- read next line +keypad period -- speak current cursor position and announce current + virtual console + +It's also worth noting that the insert key on the keypad is mapped +as the speakup key. Instead of pressing and releasing this key, as you +do under DOS or Windows, you hold it like a shift key, and press other +keys in combination with it. For example, repeatedly holding keypad +insert, from now on called speakup, and keypad enter will toggle the +speaking of new text on the screen on and off. This is not the same as +just pressing keypad enter by itself, which just silences the speech +until you hit another key. When you hit speakup plus keypad enter, +Speakup will say, "You turned me off.", or "Hey, that's better." When +Speakup is turned off, no new text on the screen will be spoken. You +can still use the reading controls to review the screen however. + +3. Using the Speakup Help System + +In order to enter the Speakup help system, press and hold the speakup +key (remember that this is the keypad insert key), and press the f1 key. +You will hear the message: + +"Press space to leave help, cursor up or down to scroll, or a letter to +go to commands in list." + +When you press the spacebar to leave the help system, you will hear: + +"Leaving help." + +While you are in the Speakup help system, you can scroll up or down +through the list of available commands using the cursor keys. The list +of commands is arranged in alphabetical order. If you wish to jump to +commands in a specific part of the alphabet, you may press the letter of +the alphabet you wish to jump to. + +You can also just explore by typing keyboard keys. Pressing keys will +cause Speakup to speak the command associated with that key. For +example, if you press the keypad 8 key, you will hear: + +"Keypad 8 is line, say current." + +You'll notice that some commands do not have keys assigned to them. +This is because they are very infrequently used commands, and are also +accessible through the sys system. We'll discuss the sys system later +in this manual. + +You'll also notice that some commands have two keys assigned to them. +This is because Speakup has a built in set of alternative key bindings +for laptop users. The alternate speakup key is the caps lock key. You +can press and hold the caps lock key, while pressing an alternate +speakup command key to activate the command. On most laptops, the +numeric keypad is defined as the keys in the j k l area of the keyboard. + +There is usually a function key which turns this keypad function on and +off, and some other key which controls the numlock state. Toggling the +keypad functionality on and off can become a royal pain. So, Speakup +gives you a simple way to get at an alternative set of key mappings for +your laptop. These are also available by default on desktop systems, +because Speakup does not know whether it is running on a desktop or +laptop. So you may choose which set of Speakup keys to use. Some +system administrators may have chosen to compile Speakup for a desktop +system without this set of alternate key bindings, but these details are +beyond the scope of this manual. To use the caps lock for its normal +purpose, hold the shift key while toggling the caps lock on and off. We +should note here, that holding the caps lock key and pressing the z key +will toggle the alternate j k l keypad on and off. + +4. Keys and Their Assigned Commands + +In this section, we'll go through a list of all the speakup keys and +commands. You can also get a list of commands and assigned keys from +the help system. + +The following list was taken from the speakupmap.map file. Key +assignments are on the left of the equal sign, and the associated +Speakup commands are on the right. The designation "spk" means to press +and hold the speakup key, a.k.a. keypad insert, a.k.a. caps lock, while +pressing the other specified key. + +spk key_f9 = punc_level_dec +spk key_f10 = punc_level_inc +spk key_f11 = reading_punc_dec +spk key_f12 = reading_punc_inc +spk key_1 = vol_dec +spk key_2 = vol_inc +spk key_3 = pitch_dec +spk key_4 = pitch_inc +spk key_5 = rate_dec +spk key_6 = rate_inc +key_kpasterisk = toggle_cursoring +spk key_kpasterisk = speakup_goto +spk key_f1 = speakup_help +spk key_f2 = set_win +spk key_f3 = clear_win +spk key_f4 = enable_win +spk key_f5 = edit_some +spk key_f6 = edit_most +spk key_f7 = edit_delim +spk key_f8 = edit_repeat +shift spk key_f9 = edit_exnum + key_kp7 = say_prev_line +spk key_kp7 = left_edge + key_kp8 = say_line +double key_kp8 = say_line_indent +spk key_kp8 = say_from_top + key_kp9 = say_next_line +spk key_kp9 = top_edge + key_kpminus = speakup_parked +spk key_kpminus = say_char_num + key_kp4 = say_prev_word +spk key_kp4 = say_from_left + key_kp5 = say_word +double key_kp5 = spell_word +spk key_kp5 = spell_phonetic + key_kp6 = say_next_word +spk key_kp6 = say_to_right + key_kpplus = say_screen +spk key_kpplus = say_win + key_kp1 = say_prev_char +spk key_kp1 = right_edge + key_kp2 = say_char +spk key_kp2 = say_to_bottom +double key_kp2 = say_phonetic_char + key_kp3 = say_next_char +spk key_kp3 = bottom_edge + key_kp0 = spk_key + key_kpdot = say_position +spk key_kpdot = say_attributes +key_kpenter = speakup_quiet +spk key_kpenter = speakup_off +key_sysrq = speech_kill + key_kpslash = speakup_cut +spk key_kpslash = speakup_paste +spk key_pageup = say_first_char +spk key_pagedown = say_last_char +key_capslock = spk_key + spk key_z = spk_lock +key_leftmeta = spk_key +ctrl spk key_0 = speakup_goto +spk key_u = say_prev_line +spk key_i = say_line +double spk key_i = say_line_indent +spk key_o = say_next_line +spk key_minus = speakup_parked +shift spk key_minus = say_char_num +spk key_j = say_prev_word +spk key_k = say_word +double spk key_k = spell_word +spk key_l = say_next_word +spk key_m = say_prev_char +spk key_comma = say_char +double spk key_comma = say_phonetic_char +spk key_dot = say_next_char +spk key_n = say_position + ctrl spk key_m = left_edge + ctrl spk key_y = top_edge + ctrl spk key_dot = right_edge +ctrl spk key_p = bottom_edge +spk key_apostrophe = say_screen +spk key_h = say_from_left +spk key_y = say_from_top +spk key_semicolon = say_to_right +spk key_p = say_to_bottom +spk key_slash = say_attributes + spk key_enter = speakup_quiet + ctrl spk key_enter = speakup_off + spk key_9 = speakup_cut +spk key_8 = speakup_paste +shift spk key_m = say_first_char + ctrl spk key_semicolon = say_last_char +spk key_r = read_all_doc + +5. The Speakup Sys System + +The Speakup screen reader also creates a speakup subdirectory as a part +of the sys system. + +As a convenience, run as root + +ln -s /sys/accessibility/speakup /speakup + +to directly access speakup parameters from /speakup. +You can see these entries by typing the command: + +ls -1 /speakup/* + +If you issue the above ls command, you will get back something like +this: + +/speakup/attrib_bleep +/speakup/bell_pos +/speakup/bleep_time +/speakup/bleeps +/speakup/cursor_time +/speakup/delimiters +/speakup/ex_num +/speakup/key_echo +/speakup/keymap +/speakup/no_interrupt +/speakup/punc_all +/speakup/punc_level +/speakup/punc_most +/speakup/punc_some +/speakup/reading_punc +/speakup/repeats +/speakup/say_control +/speakup/say_word_ctl +/speakup/silent +/speakup/spell_delay +/speakup/synth +/speakup/synth_direct +/speakup/version + +/speakup/i18n: +announcements +characters +chartab +colors +ctl_keys +formatted +function_names +key_names +states + +/speakup/soft: +caps_start +caps_stop +delay_time +direct +freq +full_time +jiffy_delta +pitch +inflection +punct +rate +tone +trigger_time +voice +vol + +Notice the two subdirectories of /speakup: /speakup/i18n and +/speakup/soft. +The i18n subdirectory is described in a later section. +The files under /speakup/soft represent settings that are specific to the +driver for the software synthesizer. If you use the LiteTalk, your +synthesizer-specific settings would be found in /speakup/ltlk. In other words, +a subdirectory named /speakup/KWD is created to hold parameters specific +to the device whose keyword is KWD. +These parameters include volume, rate, pitch, and others. + +In addition to using the Speakup hot keys to change such things as +volume, pitch, and rate, you can also echo values to the appropriate +entry in the /speakup directory. This is very useful, since it +lets you control Speakup parameters from within a script. How you +would write such scripts is somewhat beyond the scope of this manual, +but I will include a couple of simple examples here to give you a +general idea of what such scripts can do. + +Suppose for example, that you wanted to control both the punctuation +level and the reading punctuation level at the same time. For +simplicity, we'll call them punc0, punc1, punc2, and punc3. The scripts +might look something like this: + +#!/bin/bash +# punc0 +# set punc and reading punc levels to 0 +echo 0 >/speakup/punc_level +echo 0 >/speakup/reading_punc +echo Punctuation level set to 0. + +#!/bin/bash +# punc1 +# set punc and reading punc levels to 1 +echo 1 >/speakup/punc_level +echo 1 >/speakup/reading_punc +echo Punctuation level set to 1. + +#!/bin/bash +# punc2 +# set punc and reading punc levels to 2 +echo 2 >/speakup/punc_level +echo 2 >/speakup/reading_punc +echo Punctuation level set to 2. + +#!/bin/bash +# punc3 +# set punc and reading punc levels to 3 +echo 3 >/speakup/punc_level +echo 3 >/speakup/reading_punc +echo Punctuation level set to 3. + +If you were to store these four small scripts in a directory in your +path, perhaps /usr/local/bin, and set the permissions to 755 with the +chmod command, then you could change the default reading punc and +punctuation levels at the same time by issuing just one command. For +example, if you were to execute the punc3 command at your shell prompt, +then the reading punc and punc level would both get set to 3. + +I should note that the above scripts were written to work with bash, but +regardless of which shell you use, you should be able to do something +similar. + +The Speakup sys system also has another interesting use. You can echo +Speakup parameters into the sys system in a script during system +startup, and speakup will return to your preferred parameters every time +the system is rebooted. + +Most of the Speakup sys parameters can be manipulated by a regular user +on the system. However, there are a few parameters that are dangerous +enough that they should only be manipulated by the root user on your +system. There are even some parameters that are read only, and cannot +be written to at all. For example, the version entry in the Speakup +sys system is read only. This is because there is no reason for a user +to tamper with the version number which is reported by Speakup. Doing +an ls -l on /speakup/version will return this: + +-r--r--r-- 1 root root 0 Mar 21 13:46 /speakup/version + +As you can see, the version entry in the Speakup sys system is read +only, is owned by root, and belongs to the root group. Doing a cat of +/speakup/version will display the Speakup version number, like +this: + +cat /speakup/version +Speakup v-2.00 CVS: Thu Oct 21 10:38:21 EDT 2004 +synth dtlk version 1.1 + +The display shows the Speakup version number, along with the version +number of the driver for the current synthesizer. + +Looking at entries in the Speakup sys system can be useful in many +ways. For example, you might wish to know what level your volume is set +at. You could type: + +cat /speakup/KWD/vol +# Replace KWD with the keyword for your synthesizer, E.G., ltlk for LiteTalk. +5 + +The number five which comes back is the level at which the synthesizer +volume is set at. + +All the entries in the Speakup sys system are readable, some are +writable by root only, and some are writable by everyone. Unless you +know what you are doing, you should probably leave the ones that are +writable by root only alone. Most of the names are self explanatory. +Vol for controlling volume, pitch for pitch, inflection for pitch range, rate +for controlling speaking rate, etc. If you find one you aren't sure about, you +can post a query on the Speakup list. + +6. Changing Synthesizers + +It is possible to change to a different synthesizer while speakup is +running. In other words, it is not necessary to reboot the system +in order to use a different synthesizer. You can simply echo the +synthesizer keyword to the /speakup/synth sys entry. +Depending on your situation, you may wish to echo none to the synth +sys entry, to disable speech while one synthesizer is disconnected and +a second one is connected in its place. Then echo the keyword for the +new synthesizer into the synth sys entry in order to start speech +with the newly connected synthesizer. See the list of synthesizer +keywords in section 1 to find the keyword which matches your synth. + +7. Loading modules + +As mentioned earlier, Speakup can either be completely compiled into the +kernel, with the exception of the help module, or it can be compiled as +a series of modules. When compiled as modules, Speakup will only be +able to speak some of the bootup messages if your system administrator +has configured the system to load the modules at boot time. The modules +can be loaded after the file systems have been checked and mounted, or +from an initrd. There is a third possibility. Speakup can be compiled +with some components built into the kernel, and others as modules. As +we'll see in the next section, this is particularly useful when you are +working with software synthesizers. + +If Speakup is completely compiled as modules, then you must use the +modprobe command to load Speakup. You do this by loading the module for +the synthesizer driver you wish to use. The driver modules are all +named speakup_<keyword>, where <keyword> is the keyword for the +synthesizer you want. So, in order to load the driver for the DecTalk +Express, you would type the following command: + +modprobe speakup_dectlk + +Issuing this command would load the DecTalk Express driver and all other +related Speakup modules necessary to get Speakup up and running. + +To completely unload Speakup, again presuming that it is entirely built +as modules, you would give the command: + +modprobe -r speakup_dectlk + +The above command assumes you were running a DecTalk Express. If you +were using a different synth, then you would substitute its keyword in +place of dectlk. + +If you have multiple drivers loaded, you need to unload all of them, in +order to completely unload Speakup. +For example, if you have loaded both the dectlk and ltlk drivers, use the +command: +modprobe -r speakup_dectlk speakup_ltlk + +You cannot unload the driver for software synthesizers when a user-space +daemon is using /dev/softsynth. First, kill the daemon. Next, remove +the driver with the command: +modprobe -r speakup_soft + +Now, suppose we have a situation where the main Speakup component +is built into the kernel, and some or all of the drivers are built as +modules. Since the main part of Speakup is compiled into the kernel, a +partial Speakup sys system has been created which we can take advantage +of by simply echoing the synthesizer keyword into the +/speakup/synth sys entry. This will cause the kernel to +automatically load the appropriate driver module, and start Speakup +talking. To switch to another synth, just echo a new keyword to the +synth sys entry. For example, to load the DoubleTalk LT driver, +you would type: + +echo ltlk >/speakup/synth + +You can use the modprobe -r command to unload driver modules, regardless +of whether the main part of Speakup has been built into the kernel or +not. + +8. Using Software Synthesizers + +Using a software synthesizer requires that some other software be +installed and running on your system. For this reason, software +synthesizers are not available for use at bootup, or during a system +installation process. +There are two freely-available solutions for software speech: Espeakup and +Speech Dispatcher. +These are described in subsections 8.1 and 8.2, respectively. + +During the rest of this section, we assume that speakup_soft is either +built in to your kernel, or loaded as a module. + +If your system does not have udev installed , before you can use a +software synthesizer, you must have created the /dev/softsynth device. +If you have not already done so, issue the following commands as root: + +cd /dev +mknod softsynth c 10 26 + +While we are at it, we might just as well create the /dev/synth device, +which can be used to let user space programs send information to your +synthesizer. To create /dev/synth, change to the /dev directory, and +issue the following command as root: + +mknod synth c 10 25 + +of both. + +8.1. Espeakup + +Espeakup is a connector between Speakup and the eSpeak software synthesizer. +Espeakup may already be available as a package for your distribution +of Linux. If it is not packaged, you need to install it manually. +You can find it in the contrib/ subdirectory of the Speakup sources. +The filename is espeakup-$VERSION.tar.bz2, where $VERSION +depends on the current release of Espeakup. The Speakup 3.1.2 source +ships with version 0.71 of Espeakup. +The README file included with the Espeakup sources describes the process +of manual installation. + +Assuming that Espeakup is installed, either by the user or by the distributor, +follow these steps to use it. + +Tell Speakup to use the "soft driver: +echo soft > /speakup/synth + +Finally, start the espeakup program. There are two ways to do it. +Both require root privileges. + +If Espeakup was installed as a package for your Linux distribution, +you probably have a distribution-specific script that controls the operation +of the daemon. Look for a file named espeakup under /etc/init.d or +/etc/rc.d. Execute the following command with root privileges: +/etc/init.d/espeakup start +Replace init.d with rc.d, if your distribution uses scripts located under +/etc/rc.d. +Your distribution will also have a procedure for starting daemons at +boot-time, so it is possible to have software speech as soon as user-space +daemons are started by the bootup scripts. +These procedures are not described in this document. + +If you built Espeakup manually, the "make install" step placed the binary +under /usr/bin. +Run the following command as root: +/usr/bin/espeakup +Espeakup should start speaking. + +8.2. Speech Dispatcher + +For this option, you must have a package called +Speech Dispatcher running on your system, and it must be configured to +work with one of its supported software synthesizers. + +Two open source synthesizers you might use are Flite and Festival. You +might also choose to purchase the Software DecTalk from Fonix Sales Inc. +If you run a google search for Fonix, you'll find their web site. + +You can obtain a copy of Speech Dispatcher from free(b)soft at +http://www.freebsoft.org/. Follow the installation instructions that +come with Speech Dispatcher in order to install and configure Speech +Dispatcher. You can check out the web site for your Linux distribution +in order to get a copy of either Flite or Festival. Your Linux +distribution may also have a precompiled Speech Dispatcher package. + +Once you've installed, configured, and tested Speech Dispatcher with your +chosen software synthesizer, you still need one more piece of software +in order to make things work. You need a package called speechd-up. +You get it from the free(b)soft web site mentioned above. After you've +compiled and installed speechd-up, you are almost ready to begin using +your software synthesizer. + +Now you can begin using your software synthesizer. In order to do so, +echo the soft keyword to the synth sys entry like this: + +echo soft >/speakup/synth + +Next run the speechd_up command like this: + +speechd_up & + +Your synth should now start talking, and you should be able to adjust +the pitch, rate, etc. + +9. Using The DecTalk PC Card + +The DecTalk PC card is an ISA card that is inserted into one of the ISA +slots in your computer. It requires that the DecTalk PC software be +installed on your computer, and that the software be loaded onto the +Dectalk PC card before it can be used. + +You can get the dec_pc.tgz file from the linux-speakup.org site. The +dec_pc.tgz file is in the ~ftp/pub/linux/speakup directory. + +After you have downloaded the dec_pc.tgz file, untar it in your home +directory, and read the Readme file in the newly created dec_pc +directory. + +The easiest way to get the software working is to copy the entire dec_pc +directory into /user/local/lib. To do this, su to root in your home +directory, and issue the command: + +cp dec_pc /usr/local/lib + +You will need to copy the dtload command from the dec_pc directory to a +directory in your path. Either /usr/bin or /usr/local/bin is a good +choice. + +You can now run the dtload command in order to load the DecTalk PC +software onto the card. After you have done this, echo the decpc +keyword to the synth entry in the sys system like this: + +echo decpc >/speakup/synth + +Your DecTalk PC should start talking, and then you can adjust the pitch, +rate, volume, voice, etc. The voice entry in the Speakup sys system +will accept a number from 0 through 7 for the DecTalk PC synthesizer, +which will give you access to some of the DecTalk voices. + +10. Using Cursor Tracking + +In Speakup version 2.0 and later, cursor tracking is turned on by +default. This means that when you are using an editor, Speakup will +automatically speak characters as you move left and right with the +cursor keys, and lines as you move up and down with the cursor keys. +This is the traditional sort of cursor tracking. +Recent versions of Speakup provide two additional ways to control the +text that is spoken when the cursor is moved: +"highlight tracking" and "read window." +They are described later in this section. +Sometimes, these modes get in your way, so you can disable cursor tracking +altogether. + +You may select among the various forms of cursor tracking using the keypad +asterisk key. +Each time you press this key, a new mode is selected, and Speakup speaks +the name of the new mode. The names for the four possible states of cursor +tracking are: "cursoring on", "highlight tracking", "read window", +and "cursoring off." The keypad asterisk key moves through the list of +modes in a circular fashion. + +If highlight tracking is enabled, Speakup tracks highlighted text, +rather than the cursor itself. When you move the cursor with the arrow keys, +Speakup speaks the currently highlighted information. +This is useful when moving through various menus and dialog boxes. +If cursor tracking isn't helping you while navigating a menu, +try highlight tracking. + +With the "read window" variety of cursor tracking, you can limit the text +that Speakup speaks by specifying a window of interest on the screen. +See section 15 for a description of the process of defining windows. +When you move the cursor via the arrow keys, Speakup only speaks +the contents of the window. This is especially helpful when you are hearing +superfluous speech. Consider the following example. + +Suppose that you are at a shell prompt. You use bash, and you want to +explore your command history using the up and down arrow keys. If you +have enabled cursor tracking, you will hear two pieces of information. +Speakup speaks both your shell prompt and the current entry from the +command history. You may not want to hear the prompt repeated +each time you move, so you can silence it by specifying a window. Find +the last line of text on the screen. Clear the current window by pressing +the key combination speakup f3. Use the review cursor to find the first +character that follows your shell prompt. Press speakup + f2 twice, to +define a one-line window. The boundaries of the window are the +character following the shell prompt and the end of the line. Now, cycle +through the cursor tracking modes using keypad asterisk, until Speakup +says "read window." Move through your history using your arrow keys. +You will notice that Speakup no longer speaks the redundant prompt. + +Some folks like to turn cursor tracking off while they are using the +lynx web browser. You definitely want to turn cursor tracking off when +you are using the alsamixer application. Otherwise, you won't be able +to hear your mixer settings while you are using the arrow keys. + +11. Cut and Paste + +One of Speakup's more useful features is the ability to cut and paste +text on the screen. This means that you can capture information from a +program, and paste that captured text into a different place in the +program, or into an entirely different program, which may even be +running on a different console. + +For example, in this manual, we have made references to several web +sites. It would be nice if you could cut and paste these urls into your +web browser. Speakup does this quite nicely. Suppose you wanted to +past the following url into your browser: + +http://linux-speakup.org/ + +Use the speakup review keys to position the reading cursor on the first +character of the above url. When the reading cursor is in position, +press the keypad slash key once. Speakup will say, "mark". Next, +position the reading cursor on the rightmost character of the above +url. Press the keypad slash key once again to actually cut the text +from the screen. Speakup will say, "cut". Although we call this +cutting, Speakup does not actually delete the cut text from the screen. +It makes a copy of the text in a special buffer for later pasting. + +Now that you have the url cut from the screen, you can paste it into +your browser, or even paste the url on a command line as an argument to +your browser. + +Suppose you want to start lynx and go to the Speakup site. + +You can switch to a different console with the alt left and right +arrows, or you can switch to a specific console by typing alt and a +function key. These are not Speakup commands, just standard Linux +console capabilities. + +Once you've changed to an appropriate console, and are at a shell prompt, +type the word lynx, followed by a space. Now press and hold the speakup +key, while you type the keypad slash character. The url will be pasted +onto the command line, just as though you had typed it in. Press the +enter key to execute the command. + +The paste buffer will continue to hold the cut information, until a new +mark and cut operation is carried out. This means you can paste the cut +information as many times as you like before doing another cut +operation. + +You are not limited to cutting and pasting only one line on the screen. +You can also cut and paste rectangular regions of the screen. Just +position the reading cursor at the top left corner of the text to be +cut, mark it with the keypad slash key, then position the reading cursor +at the bottom right corner of the region to be cut, and cut it with the +keypad slash key. + +12. Changing the Pronunciation of Characters + +Through the /speakup/i18n/characters sys entry, Speakup gives you the +ability to change how Speakup pronounces a given character. You could, +for example, change how some punctuation characters are spoken. You can +even change how Speakup will pronounce certain letters. + +You may, for example, wish to change how Speakup pronounces the z +character. The author of Speakup, Kirk Reiser, is Canadian, and thus +believes that the z should be pronounced zed. If you are an American, +you might wish to use the zee pronunciation instead of zed. You can +change the pronunciation of both the upper and lower case z with the +following two commands: + +echo 90 zee >/speakup/characters +echo 122 zee >/speakup/characters + +Let's examine the parts of the two previous commands. They are issued +at the shell prompt, and could be placed in a startup script. + +The word echo tells the shell that you want to have it display the +string of characters that follow the word echo. If you were to just +type: + +echo hello. + +You would get the word hello printed on your screen as soon as you +pressed the enter key. In this case, we are echoing strings that we +want to be redirected into the sys system. + +The numbers 90 and 122 in the above echo commands are the ascii numeric +values for the upper and lower case z, the characters we wish to change. + +The string zee is the pronunciation that we want Speakup to use for the +upper and lower case z. + +The > symbol redirects the output of the echo command to a file, just +like in DOS, or at the Windows command prompt. + +And finally, /speakup/i18n/characters is the file entry in the sys system +where we want the output to be directed. Speakup looks at the numeric +value of the character we want to change, and inserts the pronunciation +string into an internal table. + +You can look at the whole table with the following command: + +cat /speakup/i18n/characters + +Speakup will then print out the entire character pronunciation table. I +won't display it here, but leave you to look at it at your convenience. + +13. Mapping Keys + +Speakup has the capability of allowing you to assign or "map" keys to +internal Speakup commands. This section necessarily assumes you have a +Linux kernel source tree installed, and that it has been patched and +configured with Speakup. How you do this is beyond the scope of this +manual. For this information, visit the Speakup web site at +http://linux-speakup.org/. The reason you'll need the kernel source +tree patched with Speakup is that the genmap utility you'll need for +processing keymaps is in the +/usr/src/linux-<version_number>/drivers/char/speakup directory. The +<version_number> in the above directory path is the version number of +the Linux source tree you are working with. + +So ok, you've gone off and gotten your kernel source tree, and patched +and configured it. Now you can start manipulating keymaps. + +You can either use the +/usr/src/linux-<version_number>/drivers/char/speakup/speakupmap.map file +included with the Speakup source, or you can cut and paste the copy in +section 4 into a separate file. If you use the one in the Speakup +source tree, make sure you make a backup of it before you start making +changes. You have been warned! + +Suppose that you want to swap the key assignments for the Speakup +say_last_char and the Speakup say_first_char commands. The +speakupmap.map lists the key mappings for these two commands as follows: + +spk key_pageup = say_first_char +spk key_pagedown = say_last_char + +You can edit your copy of the speakupmap.map file and swap the command +names on the right side of the = (equals) sign. You did make a backup, +right? The new keymap lines would look like this: + +spk key_pageup = say_last_char +spk key_pagedown = say_first_char + +After you edit your copy of the speakupmap.map file, save it under a new +file name, perhaps newmap.map. Then exit your editor and return to the +shell prompt. + +You are now ready to load your keymap with your swapped key assignments. + Assuming that you saved your new keymap as the file newmap.map, you +would load your keymap into the sys system like this: + +/usr/src/linux-<version_number>/drivers/char/speakup/genmap newmap.map +>/speakup/keymap + +Remember to substitute your kernel version number for the +<version_number> in the above command. Also note that although the +above command wrapped onto two lines in this document, you should type +it all on one line. + +Your say first and say last characters should now be swapped. Pressing +speakup pagedown should read you the first non-whitespace character on +the line your reading cursor is in, and pressing speakup pageup should +read you the last character on the line your reading cursor is in. + +You should note that these new mappings will only stay in effect until +you reboot, or until you load another keymap. + +One final warning. If you try to load a partial map, you will quickly +find that all the mappings you didn't include in your file got deleted +from the working map. Be extremely careful, and always make a backup! +You have been warned! + +14. Internationalizing Speakup + +Speakup indicates various conditions to the user by speaking messages. +For instance, when you move to the left edge of the screen with the +review keys, Speakup says, "left." +Prior to version 3.1.0 of Speakup, all of these messages were in English, +and they could not be changed. If you used a non-English synthesizer, +you still heard English messages, such as "left" and "cursoring on." +In version 3.1.0 or higher, one may load translations for the various +messages via the /sys filesystem. + +The directory /speakup/i18n contains several collections of messages. +Each group of messages is stored in its own file. +The following section lists all of these files, along with a brief description +of each. + +14.1. Files Under the i18n Subdirectory + +* announcements: +This file contains various general announcements, most of which cannot +be categorized. You will find messages such as "You killed Speakup", +"I'm alive", "leaving help", "parked", "unparked", and others. +You will also find the names of the screen edges and cursor tracking modes +here. + +* characters: +See section 12 for a description of this file. + +* chartab: +See section 12. Unlike the rest of the files in the i18n subdirectory, +this one does not contain messages to be spoken. + +* colors: +When you use the "say attributes" function, Speakup says the name of the +foreground and background colors. These names come from the i18n/colors +file. + +* ctl_keys: +Here, you will find names of control keys. These are used with Speakup's +say_control feature. + +* formatted: +This group of messages contains embedded formatting codes, to specify +the type and width of displayed data. If you change these, you must +preserve all of the formatting codes, and they must appear in the order +used by the default messages. + +* function_names: +Here, you will find a list of names for Speakup functions. These are used +by the help system. For example, suppose that you have activated help mode, +and you pressed keypad 3. Speakup says: +"keypad 3 is character, say next." +The message "character, say next" names a Speakup function, and it +comes from this function_names file. + +* key_names: +Again, key_names is used by Speakup's help system. In the previous +example, Speakup said that you pressed "keypad 3." +This name came from the key_names file. + +* states: +This file contains names for key states. +Again, these are part of the help system. For instance, if you had pressed +speakup + keypad 3, you would hear: +"speakup keypad 3 is go to bottom edge." +The speakup key is depressed, so the name of the key state is speakup. +This part of the message comes from the states collection. + +14.2. Changing language + +14.2.1. Loading Your Own Messages + +The files under the i18n subdirectory all follow the same format. +They consist of lines, with one message per line. +Each message is represented by a number, followed by the text of the message. +The number is the position of the message in the given collection. +For example, if you view the file /speakup/i18n/colors, you will see the +following list: + +0 black +1 blue +2 green +3 cyan +4 red +5 magenta +6 yellow +7 white +8 grey + +You can change one message, or you can change a whole group. +To load a whole collection of messages from a new source, simply use +the cp command: +cp ~/my_colors /speakup/i18n/colors +You can change an individual message with the echo command, +as shown in the following example. + +The Spanish name for the color blue is azul. +Looking at the colors file, we see that the name "blue" is at position 1 +within the colors group. Let's change blue to azul: +echo '1 azul' > /speakup/i18n/colors +The next time that Speakup says message 1 from the colors group, it will +say "azul", rather than "blue." + +14.2.2. Choose a language + +In the future, translations into various languages will be made available, +and most users will just load the files necessary for their language. So far, +only French language is available beyond native Canadian English language. + +French is only available after you are logged in. + +Canadian English is the default language. To toggle another language, +download the source of Speakup and untar it in your home directory. The +following command should let you do this: + +tar xvjf speakup-<version>.tar.bz2 + +where <version> is the version number of the application. + +Next, change to the newly created directory, then into the tools/ directory, and +run the script speakup_setlocale. You are asked the language that you want to +use. Type the number associated to your language (e.g. fr for French) then press +Enter. Needed files are copied in the i18n directory. + +Note: the speakupconf must be installed on your system so that settings are saved. +Otherwise, you will have an error: your language will be loaded but you will +have to run the script again every time Speakup restarts. +See section 16.1. for information about speakupconf. + +You will have to repeat these steps for any change of locale, i.e. if you wish +change the speakup's language or charset (iso-8859-15 ou UTF-8). + +If you wish store the settings, note that at your next login, you will need to +do: + +speakup load + +Alternatively, you can add the above line to your file +~/.bashrc or ~/.bash_profile. + +If your system administrator himself ran the script, all the users will be able +to change from English to the language chosen by root and do directly +speakupconf load (or add this to the ~/.bashrc or +~/.bash_profile file). If there are several languages to handle, the +administrator (or every user) will have to run the first steps until speakupconf +save, choosing the appropriate language, in every user's home directory. Every +user will then be able to do speakupconf load, Speakup will load his own settings. + +14.3. No Support for Non-Western-European Languages + +As of the current release, Speakup only supports Western European languages. +Support for the extended characters used by languages outside of the Western +European family of languages is a work in progress. + +15. Using Speakup's Windowing Capability + +Speakup has the capability of defining and manipulating windows on the +screen. Speakup uses the term "Window", to mean a user defined area of +the screen. The key strokes for defining and manipulating Speakup +windows are as follows: + +speakup + f2 -- Set the bounds of the window. +Speakup + f3 -- clear the current window definition. +speakup + f4 -- Toggle window silence on and off. +speakup + keypad plus -- Say the currently defined window. + +These capabilities are useful for tracking a certain part of the screen +without rereading the whole screen, or for silencing a part of the +screen that is constantly changing, such as a clock or status line. + +There is no way to save these window settings, and you can only have one +window defined for each virtual console. There is also no way to have +windows automatically defined for specific applications. + +In order to define a window, use the review keys to move your reading +cursor to the beginning of the area you want to define. Then press +speakup + f2. Speakup will tell you that the window starts at the +indicated row and column position. Then move the reading cursor to the +end of the area to be defined as a window, and press speakup + f2 again. + If there is more than one line in the window, Speakup will tell you +that the window ends at the indicated row and column position. If there +is only one line in the window, then Speakup will tell you that the +window is the specified line on the screen. If you are only defining a +one line window, you can just press speakup + f2 twice after placing the +reading cursor on the line you want to define as a window. It is not +necessary to position the reading cursor at the end of the line in order +to define the whole line as a window. + +16. Tools for Controlling Speakup + +The speakup distribution includes extra tools (in the tools directory) +which were written to make speakup easier to use. This section will +briefly describe the use of these tools. + +16.1. Speakupconf + +speakupconf began life as a contribution from Steve Holmes, a member of +the speakup community. We would like to thank him for his work on the +early versions of this project. + +This script may be installed as part of your linux distribution, but if +it isn't, the recommended places to put it are /usr/local/bin or +/usr/bin. This script can be run by any user, so it does not require +root privileges. + +Speakupconf allows you to save and load your Speakup settings. It works +by reading and writing the /sys files described above. + +The directory that speakupconf uses to store your settings depends on +whether it is run from the root account. If you execute speakupconf as +root, it uses the directory /etc/speakup. Otherwise, it uses the directory +~/.speakup, where ~ is your home directory. +Anyone who needs to use Speakup from your console can load his own custom +settings with this script. + +speakupconf takes one required argument: load or save. +Use the command +speakupconf save +to save your Speakup settings, and +speakupconf load +to load them into Speakup. +A second argument may be specified to use an alternate directory to +load or save the speakup parameters. + +16.2. Talkwith + +Charles Hallenbeck, another member of the speakup community, wrote the +initial versions of this script, and we would also like to thank him for +his work on it. + +This script needs root privileges to run, so if it is not installed as +part of your linux distribution, the recommended places to install it +are /usr/local/sbin or /usr/sbin. + +Talkwith allows you to switch synthesizers on the fly. It takes a synthesizer +name as an argument. For instance, +talkwith dectlk +causes Speakup to use the DecTalk Express. If you wish to switch to a +software synthesizer, you must also indicate which daemon you wish to +use. There are two possible choices: +spd and espeakup. spd is an abbreviation for speechd-up. +If you wish to use espeakup for software synthesis, give the command +talkwith soft espeakup +To use speechd-up, type: +talkwith soft spd +Any arguments that follow the name of the daemon are passed to the daemon +when it is invoked. For instance: +talkwith espeakup --default-voice=fr +causes espeakup to use the French voice. +Note that talkwith must always be executed with root privileges. + +Talkwith does not attempt to load your settings after the new +synthesizer is activated. 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If the Document does not specify a version +number of this License, you may choose any version ever published (not +as a draft) by the Free Software Foundation. + + +ADDENDUM: How to use this License for your documents + +To use this License in a document you have written, include a copy of +the License in the document and put the following copyright and +license notices just after the title page: + + Copyright (c) YEAR YOUR NAME. + Permission is granted to copy, distribute and/or modify this document + under the terms of the GNU Free Documentation License, Version 1.2 + or any later version published by the Free Software Foundation; + with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. + A copy of the license is included in the section entitled "GNU + Free Documentation License". + +If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, +replace the "with...Texts." line with this: + + with the Invariant Sections being LIST THEIR TITLES, with the + Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. + +If you have Invariant Sections without Cover Texts, or some other +combination of the three, merge those two alternatives to suit the +situation. + +If your document contains nontrivial examples of program code, we +recommend releasing these examples in parallel under your choice of +free software license, such as the GNU General Public License, +to permit their use in free software. + +The End. diff --git a/Documentation/admin-guide/svga.rst b/Documentation/admin-guide/svga.rst new file mode 100644 index 000000000..9eb1e0738 --- /dev/null +++ b/Documentation/admin-guide/svga.rst @@ -0,0 +1,250 @@ +.. include:: <isonum.txt> + +================================= +Video Mode Selection Support 2.13 +================================= + +:Copyright: |copy| 1995--1999 Martin Mares, <mj@ucw.cz> + +Intro +~~~~~ + +This small document describes the "Video Mode Selection" feature which +allows the use of various special video modes supported by the video BIOS. Due +to usage of the BIOS, the selection is limited to boot time (before the +kernel decompression starts) and works only on 80X86 machines that are +booted through BIOS firmware (as opposed to through UEFI, kexec, etc.). + +.. note:: + + Short intro for the impatient: Just use vga=ask for the first time, + enter ``scan`` on the video mode prompt, pick the mode you want to use, + remember its mode ID (the four-digit hexadecimal number) and then + set the vga parameter to this number (converted to decimal first). + +The video mode to be used is selected by a kernel parameter which can be +specified in the kernel Makefile (the SVGA_MODE=... line) or by the "vga=..." +option of LILO (or some other boot loader you use) or by the "xrandr" utility +(present in standard Linux utility packages). You can use the following values +of this parameter:: + + NORMAL_VGA - Standard 80x25 mode available on all display adapters. + + EXTENDED_VGA - Standard 8-pixel font mode: 80x43 on EGA, 80x50 on VGA. + + ASK_VGA - Display a video mode menu upon startup (see below). + + 0..35 - Menu item number (when you have used the menu to view the list of + modes available on your adapter, you can specify the menu item you want + to use). 0..9 correspond to "0".."9", 10..35 to "a".."z". Warning: the + mode list displayed may vary as the kernel version changes, because the + modes are listed in a "first detected -- first displayed" manner. It's + better to use absolute mode numbers instead. + + 0x.... - Hexadecimal video mode ID (also displayed on the menu, see below + for exact meaning of the ID). Warning: LILO doesn't support + hexadecimal numbers -- you have to convert it to decimal manually. + +Menu +~~~~ + +The ASK_VGA mode causes the kernel to offer a video mode menu upon +bootup. It displays a "Press <RETURN> to see video modes available, <SPACE> +to continue or wait 30 secs" message. If you press <RETURN>, you enter the +menu, if you press <SPACE> or wait 30 seconds, the kernel will boot up in +the standard 80x25 mode. + +The menu looks like:: + + Video adapter: <name-of-detected-video-adapter> + Mode: COLSxROWS: + 0 0F00 80x25 + 1 0F01 80x50 + 2 0F02 80x43 + 3 0F03 80x26 + .... + Enter mode number or ``scan``: <flashing-cursor-here> + +<name-of-detected-video-adapter> tells what video adapter did Linux detect +-- it's either a generic adapter name (MDA, CGA, HGC, EGA, VGA, VESA VGA [a VGA +with VESA-compliant BIOS]) or a chipset name (e.g., Trident). Direct detection +of chipsets is turned off by default as it's inherently unreliable due to +absolutely insane PC design. + +"0 0F00 80x25" means that the first menu item (the menu items are numbered +from "0" to "9" and from "a" to "z") is a 80x25 mode with ID=0x0f00 (see the +next section for a description of mode IDs). + +<flashing-cursor-here> encourages you to enter the item number or mode ID +you wish to set and press <RETURN>. If the computer complains something about +"Unknown mode ID", it is trying to tell you that it isn't possible to set such +a mode. It's also possible to press only <RETURN> which leaves the current mode. + +The mode list usually contains a few basic modes and some VESA modes. In +case your chipset has been detected, some chipset-specific modes are shown as +well (some of these might be missing or unusable on your machine as different +BIOSes are often shipped with the same card and the mode numbers depend purely +on the VGA BIOS). + +The modes displayed on the menu are partially sorted: The list starts with +the standard modes (80x25 and 80x50) followed by "special" modes (80x28 and +80x43), local modes (if the local modes feature is enabled), VESA modes and +finally SVGA modes for the auto-detected adapter. + +If you are not happy with the mode list offered (e.g., if you think your card +is able to do more), you can enter "scan" instead of item number / mode ID. The +program will try to ask the BIOS for all possible video mode numbers and test +what happens then. The screen will be probably flashing wildly for some time and +strange noises will be heard from inside the monitor and so on and then, really +all consistent video modes supported by your BIOS will appear (plus maybe some +``ghost modes``). If you are afraid this could damage your monitor, don't use +this function. + +After scanning, the mode ordering is a bit different: the auto-detected SVGA +modes are not listed at all and the modes revealed by ``scan`` are shown before +all VESA modes. + +Mode IDs +~~~~~~~~ + +Because of the complexity of all the video stuff, the video mode IDs +used here are also a bit complex. A video mode ID is a 16-bit number usually +expressed in a hexadecimal notation (starting with "0x"). You can set a mode +by entering its mode directly if you know it even if it isn't shown on the menu. + +The ID numbers can be divided to those regions:: + + 0x0000 to 0x00ff - menu item references. 0x0000 is the first item. Don't use + outside the menu as this can change from boot to boot (especially if you + have used the ``scan`` feature). + + 0x0100 to 0x017f - standard BIOS modes. The ID is a BIOS video mode number + (as presented to INT 10, function 00) increased by 0x0100. + + 0x0200 to 0x08ff - VESA BIOS modes. The ID is a VESA mode ID increased by + 0x0100. All VESA modes should be autodetected and shown on the menu. + + 0x0900 to 0x09ff - Video7 special modes. Set by calling INT 0x10, AX=0x6f05. + (Usually 940=80x43, 941=132x25, 942=132x44, 943=80x60, 944=100x60, + 945=132x28 for the standard Video7 BIOS) + + 0x0f00 to 0x0fff - special modes (they are set by various tricks -- usually + by modifying one of the standard modes). Currently available: + 0x0f00 standard 80x25, don't reset mode if already set (=FFFF) + 0x0f01 standard with 8-point font: 80x43 on EGA, 80x50 on VGA + 0x0f02 VGA 80x43 (VGA switched to 350 scanlines with a 8-point font) + 0x0f03 VGA 80x28 (standard VGA scans, but 14-point font) + 0x0f04 leave current video mode + 0x0f05 VGA 80x30 (480 scans, 16-point font) + 0x0f06 VGA 80x34 (480 scans, 14-point font) + 0x0f07 VGA 80x60 (480 scans, 8-point font) + 0x0f08 Graphics hack (see the VIDEO_GFX_HACK paragraph below) + + 0x1000 to 0x7fff - modes specified by resolution. The code has a "0xRRCC" + form where RR is a number of rows and CC is a number of columns. + E.g., 0x1950 corresponds to a 80x25 mode, 0x2b84 to 132x43 etc. + This is the only fully portable way to refer to a non-standard mode, + but it relies on the mode being found and displayed on the menu + (remember that mode scanning is not done automatically). + + 0xff00 to 0xffff - aliases for backward compatibility: + 0xffff equivalent to 0x0f00 (standard 80x25) + 0xfffe equivalent to 0x0f01 (EGA 80x43 or VGA 80x50) + +If you add 0x8000 to the mode ID, the program will try to recalculate +vertical display timing according to mode parameters, which can be used to +eliminate some annoying bugs of certain VGA BIOSes (usually those used for +cards with S3 chipsets and old Cirrus Logic BIOSes) -- mainly extra lines at the +end of the display. + +Options +~~~~~~~ + +Build options for arch/x86/boot/* are selected by the kernel kconfig +utility and the kernel .config file. + +VIDEO_GFX_HACK - includes special hack for setting of graphics modes +to be used later by special drivers. +Allows to set _any_ BIOS mode including graphic ones and forcing specific +text screen resolution instead of peeking it from BIOS variables. Don't use +unless you think you know what you're doing. To activate this setup, use +mode number 0x0f08 (see the Mode IDs section above). + +Still doesn't work? +~~~~~~~~~~~~~~~~~~~ + +When the mode detection doesn't work (e.g., the mode list is incorrect or +the machine hangs instead of displaying the menu), try to switch off some of +the configuration options listed under "Options". If it fails, you can still use +your kernel with the video mode set directly via the kernel parameter. + +In either case, please send me a bug report containing what _exactly_ +happens and how do the configuration switches affect the behaviour of the bug. + +If you start Linux from M$-DOS, you might also use some DOS tools for +video mode setting. In this case, you must specify the 0x0f04 mode ("leave +current settings") to Linux, because if you don't and you use any non-standard +mode, Linux will switch to 80x25 automatically. + +If you set some extended mode and there's one or more extra lines on the +bottom of the display containing already scrolled-out text, your VGA BIOS +contains the most common video BIOS bug called "incorrect vertical display +end setting". Adding 0x8000 to the mode ID might fix the problem. Unfortunately, +this must be done manually -- no autodetection mechanisms are available. + +History +~~~~~~~ + +=============== ================================================================ +1.0 (??-Nov-95) First version supporting all adapters supported by the old + setup.S + Cirrus Logic 54XX. Present in some 1.3.4? kernels + and then removed due to instability on some machines. +2.0 (28-Jan-96) Rewritten from scratch. Cirrus Logic 64XX support added, almost + everything is configurable, the VESA support should be much more + stable, explicit mode numbering allowed, "scan" implemented etc. +2.1 (30-Jan-96) VESA modes moved to 0x200-0x3ff. Mode selection by resolution + supported. Few bugs fixed. VESA modes are listed prior to + modes supplied by SVGA autodetection as they are more reliable. + CLGD autodetect works better. Doesn't depend on 80x25 being + active when started. Scanning fixed. 80x43 (any VGA) added. + Code cleaned up. +2.2 (01-Feb-96) EGA 80x43 fixed. VESA extended to 0x200-0x4ff (non-standard 02XX + VESA modes work now). Display end bug workaround supported. + Special modes renumbered to allow adding of the "recalculate" + flag, 0xffff and 0xfffe became aliases instead of real IDs. + Screen contents retained during mode changes. +2.3 (15-Mar-96) Changed to work with 1.3.74 kernel. +2.4 (18-Mar-96) Added patches by Hans Lermen fixing a memory overwrite problem + with some boot loaders. Memory management rewritten to reflect + these changes. Unfortunately, screen contents retaining works + only with some loaders now. + Added a Tseng 132x60 mode. +2.5 (19-Mar-96) Fixed a VESA mode scanning bug introduced in 2.4. +2.6 (25-Mar-96) Some VESA BIOS errors not reported -- it fixes error reports on + several cards with broken VESA code (e.g., ATI VGA). +2.7 (09-Apr-96) - Accepted all VESA modes in range 0x100 to 0x7ff, because some + cards use very strange mode numbers. + - Added Realtek VGA modes (thanks to Gonzalo Tornaria). + - Hardware testing order slightly changed, tests based on ROM + contents done as first. + - Added support for special Video7 mode switching functions + (thanks to Tom Vander Aa). + - Added 480-scanline modes (especially useful for notebooks, + original version written by hhanemaa@cs.ruu.nl, patched by + Jeff Chua, rewritten by me). + - Screen store/restore fixed. +2.8 (14-Apr-96) - Previous release was not compilable without CONFIG_VIDEO_SVGA. + - Better recognition of text modes during mode scan. +2.9 (12-May-96) - Ignored VESA modes 0x80 - 0xff (more VESA BIOS bugs!) +2.10(11-Nov-96) - The whole thing made optional. + - Added the CONFIG_VIDEO_400_HACK switch. + - Added the CONFIG_VIDEO_GFX_HACK switch. + - Code cleanup. +2.11(03-May-97) - Yet another cleanup, now including also the documentation. + - Direct testing of SVGA adapters turned off by default, ``scan`` + offered explicitly on the prompt line. + - Removed the doc section describing adding of new probing + functions as I try to get rid of _all_ hardware probing here. +2.12(25-May-98) Added support for VESA frame buffer graphics. +2.13(14-May-99) Minor documentation fixes. +=============== ================================================================ diff --git a/Documentation/admin-guide/syscall-user-dispatch.rst b/Documentation/admin-guide/syscall-user-dispatch.rst new file mode 100644 index 000000000..e3cfffef5 --- /dev/null +++ b/Documentation/admin-guide/syscall-user-dispatch.rst @@ -0,0 +1,94 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================== +Syscall User Dispatch +===================== + +Background +---------- + +Compatibility layers like Wine need a way to efficiently emulate system +calls of only a part of their process - the part that has the +incompatible code - while being able to execute native syscalls without +a high performance penalty on the native part of the process. Seccomp +falls short on this task, since it has limited support to efficiently +filter syscalls based on memory regions, and it doesn't support removing +filters. Therefore a new mechanism is necessary. + +Syscall User Dispatch brings the filtering of the syscall dispatcher +address back to userspace. The application is in control of a flip +switch, indicating the current personality of the process. A +multiple-personality application can then flip the switch without +invoking the kernel, when crossing the compatibility layer API +boundaries, to enable/disable the syscall redirection and execute +syscalls directly (disabled) or send them to be emulated in userspace +through a SIGSYS. + +The goal of this design is to provide very quick compatibility layer +boundary crosses, which is achieved by not executing a syscall to change +personality every time the compatibility layer executes. Instead, a +userspace memory region exposed to the kernel indicates the current +personality, and the application simply modifies that variable to +configure the mechanism. + +There is a relatively high cost associated with handling signals on most +architectures, like x86, but at least for Wine, syscalls issued by +native Windows code are currently not known to be a performance problem, +since they are quite rare, at least for modern gaming applications. + +Since this mechanism is designed to capture syscalls issued by +non-native applications, it must function on syscalls whose invocation +ABI is completely unexpected to Linux. Syscall User Dispatch, therefore +doesn't rely on any of the syscall ABI to make the filtering. It uses +only the syscall dispatcher address and the userspace key. + +As the ABI of these intercepted syscalls is unknown to Linux, these +syscalls are not instrumentable via ptrace or the syscall tracepoints. + +Interface +--------- + +A thread can setup this mechanism on supported kernels by executing the +following prctl: + + prctl(PR_SET_SYSCALL_USER_DISPATCH, <op>, <offset>, <length>, [selector]) + +<op> is either PR_SYS_DISPATCH_ON or PR_SYS_DISPATCH_OFF, to enable and +disable the mechanism globally for that thread. When +PR_SYS_DISPATCH_OFF is used, the other fields must be zero. + +[<offset>, <offset>+<length>) delimit a memory region interval +from which syscalls are always executed directly, regardless of the +userspace selector. This provides a fast path for the C library, which +includes the most common syscall dispatchers in the native code +applications, and also provides a way for the signal handler to return +without triggering a nested SIGSYS on (rt\_)sigreturn. Users of this +interface should make sure that at least the signal trampoline code is +included in this region. In addition, for syscalls that implement the +trampoline code on the vDSO, that trampoline is never intercepted. + +[selector] is a pointer to a char-sized region in the process memory +region, that provides a quick way to enable disable syscall redirection +thread-wide, without the need to invoke the kernel directly. selector +can be set to SYSCALL_DISPATCH_FILTER_ALLOW or SYSCALL_DISPATCH_FILTER_BLOCK. +Any other value should terminate the program with a SIGSYS. + +Additionally, a tasks syscall user dispatch configuration can be peeked +and poked via the PTRACE_(GET|SET)_SYSCALL_USER_DISPATCH_CONFIG ptrace +requests. This is useful for checkpoint/restart software. + +Security Notes +-------------- + +Syscall User Dispatch provides functionality for compatibility layers to +quickly capture system calls issued by a non-native part of the +application, while not impacting the Linux native regions of the +process. It is not a mechanism for sandboxing system calls, and it +should not be seen as a security mechanism, since it is trivial for a +malicious application to subvert the mechanism by jumping to an allowed +dispatcher region prior to executing the syscall, or to discover the +address and modify the selector value. If the use case requires any +kind of security sandboxing, Seccomp should be used instead. + +Any fork or exec of the existing process resets the mechanism to +PR_SYS_DISPATCH_OFF. diff --git a/Documentation/admin-guide/sysctl/abi.rst b/Documentation/admin-guide/sysctl/abi.rst new file mode 100644 index 000000000..4e6db0a2a --- /dev/null +++ b/Documentation/admin-guide/sysctl/abi.rst @@ -0,0 +1,34 @@ +.. SPDX-License-Identifier: GPL-2.0+ + +================================ +Documentation for /proc/sys/abi/ +================================ + +.. See scripts/check-sysctl-docs to keep this up to date: +.. scripts/check-sysctl-docs -vtable="abi" \ +.. Documentation/admin-guide/sysctl/abi.rst \ +.. $(git grep -l register_sysctl_) + +Copyright (c) 2020, Stephen Kitt + +For general info, see Documentation/admin-guide/sysctl/index.rst. + +------------------------------------------------------------------------------ + +The files in ``/proc/sys/abi`` can be used to see and modify +ABI-related settings. + +Currently, these files might (depending on your configuration) +show up in ``/proc/sys/kernel``: + +.. contents:: :local: + +vsyscall32 (x86) +================ + +Determines whether the kernels maps a vDSO page into 32-bit processes; +can be set to 1 to enable, or 0 to disable. Defaults to enabled if +``CONFIG_COMPAT_VDSO`` is set, disabled otherwise. + +This controls the same setting as the ``vdso32`` kernel boot +parameter. diff --git a/Documentation/admin-guide/sysctl/fs.rst b/Documentation/admin-guide/sysctl/fs.rst new file mode 100644 index 000000000..a321b84ec --- /dev/null +++ b/Documentation/admin-guide/sysctl/fs.rst @@ -0,0 +1,334 @@ +=============================== +Documentation for /proc/sys/fs/ +=============================== + +Copyright (c) 1998, 1999, Rik van Riel <riel@nl.linux.org> + +Copyright (c) 2009, Shen Feng<shen@cn.fujitsu.com> + +For general info and legal blurb, please look in intro.rst. + +------------------------------------------------------------------------------ + +This file contains documentation for the sysctl files and directories +in ``/proc/sys/fs/``. + +The files in this directory can be used to tune and monitor +miscellaneous and general things in the operation of the Linux +kernel. Since some of the files *can* be used to screw up your +system, it is advisable to read both documentation and source +before actually making adjustments. + +1. /proc/sys/fs +=============== + +Currently, these files might (depending on your configuration) +show up in ``/proc/sys/fs``: + +.. contents:: :local: + + +aio-nr & aio-max-nr +------------------- + +``aio-nr`` shows the current system-wide number of asynchronous io +requests. ``aio-max-nr`` allows you to change the maximum value +``aio-nr`` can grow to. If ``aio-nr`` reaches ``aio-nr-max`` then +``io_setup`` will fail with ``EAGAIN``. Note that raising +``aio-max-nr`` does not result in the +pre-allocation or re-sizing of any kernel data structures. + + +dentry-state +------------ + +This file shows the values in ``struct dentry_stat``, as defined in +``linux/include/linux/dcache.h``:: + + struct dentry_stat_t dentry_stat { + int nr_dentry; + int nr_unused; + int age_limit; /* age in seconds */ + int want_pages; /* pages requested by system */ + int nr_negative; /* # of unused negative dentries */ + int dummy; /* Reserved for future use */ + }; + +Dentries are dynamically allocated and deallocated. + +``nr_dentry`` shows the total number of dentries allocated (active ++ unused). ``nr_unused shows`` the number of dentries that are not +actively used, but are saved in the LRU list for future reuse. + +``age_limit`` is the age in seconds after which dcache entries +can be reclaimed when memory is short and ``want_pages`` is +nonzero when ``shrink_dcache_pages()`` has been called and the +dcache isn't pruned yet. + +``nr_negative`` shows the number of unused dentries that are also +negative dentries which do not map to any files. Instead, +they help speeding up rejection of non-existing files provided +by the users. + + +file-max & file-nr +------------------ + +The value in ``file-max`` denotes the maximum number of file- +handles that the Linux kernel will allocate. When you get lots +of error messages about running out of file handles, you might +want to increase this limit. + +Historically,the kernel was able to allocate file handles +dynamically, but not to free them again. The three values in +``file-nr`` denote the number of allocated file handles, the number +of allocated but unused file handles, and the maximum number of +file handles. Linux 2.6 and later always reports 0 as the number of free +file handles -- this is not an error, it just means that the +number of allocated file handles exactly matches the number of +used file handles. + +Attempts to allocate more file descriptors than ``file-max`` are +reported with ``printk``, look for:: + + VFS: file-max limit <number> reached + +in the kernel logs. + + +inode-nr & inode-state +---------------------- + +As with file handles, the kernel allocates the inode structures +dynamically, but can't free them yet. + +The file ``inode-nr`` contains the first two items from +``inode-state``, so we'll skip to that file... + +``inode-state`` contains three actual numbers and four dummies. +The actual numbers are, in order of appearance, ``nr_inodes``, +``nr_free_inodes`` and ``preshrink``. + +``nr_inodes`` stands for the number of inodes the system has +allocated. + +``nr_free_inodes`` represents the number of free inodes (?) and +preshrink is nonzero when the +system needs to prune the inode list instead of allocating +more. + + +mount-max +--------- + +This denotes the maximum number of mounts that may exist +in a mount namespace. + + +nr_open +------- + +This denotes the maximum number of file-handles a process can +allocate. Default value is 1024*1024 (1048576) which should be +enough for most machines. Actual limit depends on ``RLIMIT_NOFILE`` +resource limit. + + +overflowgid & overflowuid +------------------------- + +Some filesystems only support 16-bit UIDs and GIDs, although in Linux +UIDs and GIDs are 32 bits. When one of these filesystems is mounted +with writes enabled, any UID or GID that would exceed 65535 is translated +to a fixed value before being written to disk. + +These sysctls allow you to change the value of the fixed UID and GID. +The default is 65534. + + +pipe-user-pages-hard +-------------------- + +Maximum total number of pages a non-privileged user may allocate for pipes. +Once this limit is reached, no new pipes may be allocated until usage goes +below the limit again. When set to 0, no limit is applied, which is the default +setting. + + +pipe-user-pages-soft +-------------------- + +Maximum total number of pages a non-privileged user may allocate for pipes +before the pipe size gets limited to a single page. Once this limit is reached, +new pipes will be limited to a single page in size for this user in order to +limit total memory usage, and trying to increase them using ``fcntl()`` will be +denied until usage goes below the limit again. The default value allows to +allocate up to 1024 pipes at their default size. When set to 0, no limit is +applied. + + +protected_fifos +--------------- + +The intent of this protection is to avoid unintentional writes to +an attacker-controlled FIFO, where a program expected to create a regular +file. + +When set to "0", writing to FIFOs is unrestricted. + +When set to "1" don't allow ``O_CREAT`` open on FIFOs that we don't own +in world writable sticky directories, unless they are owned by the +owner of the directory. + +When set to "2" it also applies to group writable sticky directories. + +This protection is based on the restrictions in Openwall. + + +protected_hardlinks +-------------------- + +A long-standing class of security issues is the hardlink-based +time-of-check-time-of-use race, most commonly seen in world-writable +directories like ``/tmp``. The common method of exploitation of this flaw +is to cross privilege boundaries when following a given hardlink (i.e. a +root process follows a hardlink created by another user). Additionally, +on systems without separated partitions, this stops unauthorized users +from "pinning" vulnerable setuid/setgid files against being upgraded by +the administrator, or linking to special files. + +When set to "0", hardlink creation behavior is unrestricted. + +When set to "1" hardlinks cannot be created by users if they do not +already own the source file, or do not have read/write access to it. + +This protection is based on the restrictions in Openwall and grsecurity. + + +protected_regular +----------------- + +This protection is similar to `protected_fifos`_, but it +avoids writes to an attacker-controlled regular file, where a program +expected to create one. + +When set to "0", writing to regular files is unrestricted. + +When set to "1" don't allow ``O_CREAT`` open on regular files that we +don't own in world writable sticky directories, unless they are +owned by the owner of the directory. + +When set to "2" it also applies to group writable sticky directories. + + +protected_symlinks +------------------ + +A long-standing class of security issues is the symlink-based +time-of-check-time-of-use race, most commonly seen in world-writable +directories like ``/tmp``. The common method of exploitation of this flaw +is to cross privilege boundaries when following a given symlink (i.e. a +root process follows a symlink belonging to another user). For a likely +incomplete list of hundreds of examples across the years, please see: +https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=/tmp + +When set to "0", symlink following behavior is unrestricted. + +When set to "1" symlinks are permitted to be followed only when outside +a sticky world-writable directory, or when the uid of the symlink and +follower match, or when the directory owner matches the symlink's owner. + +This protection is based on the restrictions in Openwall and grsecurity. + + +suid_dumpable +------------- + +This value can be used to query and set the core dump mode for setuid +or otherwise protected/tainted binaries. The modes are + += ========== =============================================================== +0 (default) Traditional behaviour. Any process which has changed + privilege levels or is execute only will not be dumped. +1 (debug) All processes dump core when possible. The core dump is + owned by the current user and no security is applied. This is + intended for system debugging situations only. + Ptrace is unchecked. + This is insecure as it allows regular users to examine the + memory contents of privileged processes. +2 (suidsafe) Any binary which normally would not be dumped is dumped + anyway, but only if the ``core_pattern`` kernel sysctl (see + :ref:`Documentation/admin-guide/sysctl/kernel.rst <core_pattern>`) + is set to + either a pipe handler or a fully qualified path. (For more + details on this limitation, see CVE-2006-2451.) This mode is + appropriate when administrators are attempting to debug + problems in a normal environment, and either have a core dump + pipe handler that knows to treat privileged core dumps with + care, or specific directory defined for catching core dumps. + If a core dump happens without a pipe handler or fully + qualified path, a message will be emitted to syslog warning + about the lack of a correct setting. += ========== =============================================================== + + + +2. /proc/sys/fs/binfmt_misc +=========================== + +Documentation for the files in ``/proc/sys/fs/binfmt_misc`` is +in Documentation/admin-guide/binfmt-misc.rst. + + +3. /proc/sys/fs/mqueue - POSIX message queues filesystem +======================================================== + + +The "mqueue" filesystem provides the necessary kernel features to enable the +creation of a user space library that implements the POSIX message queues +API (as noted by the MSG tag in the POSIX 1003.1-2001 version of the System +Interfaces specification.) + +The "mqueue" filesystem contains values for determining/setting the +amount of resources used by the file system. + +``/proc/sys/fs/mqueue/queues_max`` is a read/write file for +setting/getting the maximum number of message queues allowed on the +system. + +``/proc/sys/fs/mqueue/msg_max`` is a read/write file for +setting/getting the maximum number of messages in a queue value. In +fact it is the limiting value for another (user) limit which is set in +``mq_open`` invocation. This attribute of a queue must be less than +or equal to ``msg_max``. + +``/proc/sys/fs/mqueue/msgsize_max`` is a read/write file for +setting/getting the maximum message size value (it is an attribute of +every message queue, set during its creation). + +``/proc/sys/fs/mqueue/msg_default`` is a read/write file for +setting/getting the default number of messages in a queue value if the +``attr`` parameter of ``mq_open(2)`` is ``NULL``. If it exceeds +``msg_max``, the default value is initialized to ``msg_max``. + +``/proc/sys/fs/mqueue/msgsize_default`` is a read/write file for +setting/getting the default message size value if the ``attr`` +parameter of ``mq_open(2)`` is ``NULL``. If it exceeds +``msgsize_max``, the default value is initialized to ``msgsize_max``. + +4. /proc/sys/fs/epoll - Configuration options for the epoll interface +===================================================================== + +This directory contains configuration options for the epoll(7) interface. + +max_user_watches +---------------- + +Every epoll file descriptor can store a number of files to be monitored +for event readiness. Each one of these monitored files constitutes a "watch". +This configuration option sets the maximum number of "watches" that are +allowed for each user. +Each "watch" costs roughly 90 bytes on a 32-bit kernel, and roughly 160 bytes +on a 64-bit one. +The current default value for ``max_user_watches`` is 4% of the +available low memory, divided by the "watch" cost in bytes. diff --git a/Documentation/admin-guide/sysctl/index.rst b/Documentation/admin-guide/sysctl/index.rst new file mode 100644 index 000000000..03346f98c --- /dev/null +++ b/Documentation/admin-guide/sysctl/index.rst @@ -0,0 +1,98 @@ +=========================== +Documentation for /proc/sys +=========================== + +Copyright (c) 1998, 1999, Rik van Riel <riel@nl.linux.org> + +------------------------------------------------------------------------------ + +'Why', I hear you ask, 'would anyone even _want_ documentation +for them sysctl files? If anybody really needs it, it's all in +the source...' + +Well, this documentation is written because some people either +don't know they need to tweak something, or because they don't +have the time or knowledge to read the source code. + +Furthermore, the programmers who built sysctl have built it to +be actually used, not just for the fun of programming it :-) + +------------------------------------------------------------------------------ + +Legal blurb: + +As usual, there are two main things to consider: + +1. you get what you pay for +2. it's free + +The consequences are that I won't guarantee the correctness of +this document, and if you come to me complaining about how you +screwed up your system because of wrong documentation, I won't +feel sorry for you. I might even laugh at you... + +But of course, if you _do_ manage to screw up your system using +only the sysctl options used in this file, I'd like to hear of +it. Not only to have a great laugh, but also to make sure that +you're the last RTFMing person to screw up. + +In short, e-mail your suggestions, corrections and / or horror +stories to: <riel@nl.linux.org> + +Rik van Riel. + +-------------------------------------------------------------- + +Introduction +============ + +Sysctl is a means of configuring certain aspects of the kernel +at run-time, and the /proc/sys/ directory is there so that you +don't even need special tools to do it! +In fact, there are only four things needed to use these config +facilities: + +- a running Linux system +- root access +- common sense (this is especially hard to come by these days) +- knowledge of what all those values mean + +As a quick 'ls /proc/sys' will show, the directory consists of +several (arch-dependent?) subdirs. Each subdir is mainly about +one part of the kernel, so you can do configuration on a piece +by piece basis, or just some 'thematic frobbing'. + +This documentation is about: + +=============== =============================================================== +abi/ execution domains & personalities +debug/ <empty> +dev/ device specific information (eg dev/cdrom/info) +fs/ specific filesystems + filehandle, inode, dentry and quota tuning + binfmt_misc <Documentation/admin-guide/binfmt-misc.rst> +kernel/ global kernel info / tuning + miscellaneous stuff +net/ networking stuff, for documentation look in: + <Documentation/networking/> +proc/ <empty> +sunrpc/ SUN Remote Procedure Call (NFS) +vm/ memory management tuning + buffer and cache management +user/ Per user per user namespace limits +=============== =============================================================== + +These are the subdirs I have on my system. There might be more +or other subdirs in another setup. If you see another dir, I'd +really like to hear about it :-) + +.. toctree:: + :maxdepth: 1 + + abi + fs + kernel + net + sunrpc + user + vm diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst new file mode 100644 index 000000000..cf33de56d --- /dev/null +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -0,0 +1,1666 @@ +=================================== +Documentation for /proc/sys/kernel/ +=================================== + +.. See scripts/check-sysctl-docs to keep this up to date + + +Copyright (c) 1998, 1999, Rik van Riel <riel@nl.linux.org> + +Copyright (c) 2009, Shen Feng<shen@cn.fujitsu.com> + +For general info and legal blurb, please look in +Documentation/admin-guide/sysctl/index.rst. + +------------------------------------------------------------------------------ + +This file contains documentation for the sysctl files in +``/proc/sys/kernel/``. + +The files in this directory can be used to tune and monitor +miscellaneous and general things in the operation of the Linux +kernel. Since some of the files *can* be used to screw up your +system, it is advisable to read both documentation and source +before actually making adjustments. + +Currently, these files might (depending on your configuration) +show up in ``/proc/sys/kernel``: + +.. contents:: :local: + + +acct +==== + +:: + + highwater lowwater frequency + +If BSD-style process accounting is enabled these values control +its behaviour. If free space on filesystem where the log lives +goes below ``lowwater``\ % accounting suspends. If free space gets +above ``highwater``\ % accounting resumes. ``frequency`` determines +how often do we check the amount of free space (value is in +seconds). Default: + +:: + + 4 2 30 + +That is, suspend accounting if free space drops below 2%; resume it +if it increases to at least 4%; consider information about amount of +free space valid for 30 seconds. + + +acpi_video_flags +================ + +See Documentation/power/video.rst. This allows the video resume mode to be set, +in a similar fashion to the ``acpi_sleep`` kernel parameter, by +combining the following values: + += ======= +1 s3_bios +2 s3_mode +4 s3_beep += ======= + +arch +==== + +The machine hardware name, the same output as ``uname -m`` +(e.g. ``x86_64`` or ``aarch64``). + +auto_msgmni +=========== + +This variable has no effect and may be removed in future kernel +releases. Reading it always returns 0. +Up to Linux 3.17, it enabled/disabled automatic recomputing of +`msgmni`_ +upon memory add/remove or upon IPC namespace creation/removal. +Echoing "1" into this file enabled msgmni automatic recomputing. +Echoing "0" turned it off. The default value was 1. + + +bootloader_type (x86 only) +========================== + +This gives the bootloader type number as indicated by the bootloader, +shifted left by 4, and OR'd with the low four bits of the bootloader +version. The reason for this encoding is that this used to match the +``type_of_loader`` field in the kernel header; the encoding is kept for +backwards compatibility. That is, if the full bootloader type number +is 0x15 and the full version number is 0x234, this file will contain +the value 340 = 0x154. + +See the ``type_of_loader`` and ``ext_loader_type`` fields in +Documentation/arch/x86/boot.rst for additional information. + + +bootloader_version (x86 only) +============================= + +The complete bootloader version number. In the example above, this +file will contain the value 564 = 0x234. + +See the ``type_of_loader`` and ``ext_loader_ver`` fields in +Documentation/arch/x86/boot.rst for additional information. + + +bpf_stats_enabled +================= + +Controls whether the kernel should collect statistics on BPF programs +(total time spent running, number of times run...). Enabling +statistics causes a slight reduction in performance on each program +run. The statistics can be seen using ``bpftool``. + += =================================== +0 Don't collect statistics (default). +1 Collect statistics. += =================================== + + +cad_pid +======= + +This is the pid which will be signalled on reboot (notably, by +Ctrl-Alt-Delete). Writing a value to this file which doesn't +correspond to a running process will result in ``-ESRCH``. + +See also `ctrl-alt-del`_. + + +cap_last_cap +============ + +Highest valid capability of the running kernel. Exports +``CAP_LAST_CAP`` from the kernel. + + +.. _core_pattern: + +core_pattern +============ + +``core_pattern`` is used to specify a core dumpfile pattern name. + +* max length 127 characters; default value is "core" +* ``core_pattern`` is used as a pattern template for the output + filename; certain string patterns (beginning with '%') are + substituted with their actual values. +* backward compatibility with ``core_uses_pid``: + + If ``core_pattern`` does not include "%p" (default does not) + and ``core_uses_pid`` is set, then .PID will be appended to + the filename. + +* corename format specifiers + + ======== ========================================== + %<NUL> '%' is dropped + %% output one '%' + %p pid + %P global pid (init PID namespace) + %i tid + %I global tid (init PID namespace) + %u uid (in initial user namespace) + %g gid (in initial user namespace) + %d dump mode, matches ``PR_SET_DUMPABLE`` and + ``/proc/sys/fs/suid_dumpable`` + %s signal number + %t UNIX time of dump + %h hostname + %e executable filename (may be shortened, could be changed by prctl etc) + %f executable filename + %E executable path + %c maximum size of core file by resource limit RLIMIT_CORE + %C CPU the task ran on + %<OTHER> both are dropped + ======== ========================================== + +* If the first character of the pattern is a '|', the kernel will treat + the rest of the pattern as a command to run. The core dump will be + written to the standard input of that program instead of to a file. + + +core_pipe_limit +=============== + +This sysctl is only applicable when `core_pattern`_ is configured to +pipe core files to a user space helper (when the first character of +``core_pattern`` is a '|', see above). +When collecting cores via a pipe to an application, it is occasionally +useful for the collecting application to gather data about the +crashing process from its ``/proc/pid`` directory. +In order to do this safely, the kernel must wait for the collecting +process to exit, so as not to remove the crashing processes proc files +prematurely. +This in turn creates the possibility that a misbehaving userspace +collecting process can block the reaping of a crashed process simply +by never exiting. +This sysctl defends against that. +It defines how many concurrent crashing processes may be piped to user +space applications in parallel. +If this value is exceeded, then those crashing processes above that +value are noted via the kernel log and their cores are skipped. +0 is a special value, indicating that unlimited processes may be +captured in parallel, but that no waiting will take place (i.e. the +collecting process is not guaranteed access to ``/proc/<crashing +pid>/``). +This value defaults to 0. + + +core_uses_pid +============= + +The default coredump filename is "core". By setting +``core_uses_pid`` to 1, the coredump filename becomes core.PID. +If `core_pattern`_ does not include "%p" (default does not) +and ``core_uses_pid`` is set, then .PID will be appended to +the filename. + + +ctrl-alt-del +============ + +When the value in this file is 0, ctrl-alt-del is trapped and +sent to the ``init(1)`` program to handle a graceful restart. +When, however, the value is > 0, Linux's reaction to a Vulcan +Nerve Pinch (tm) will be an immediate reboot, without even +syncing its dirty buffers. + +Note: + when a program (like dosemu) has the keyboard in 'raw' + mode, the ctrl-alt-del is intercepted by the program before it + ever reaches the kernel tty layer, and it's up to the program + to decide what to do with it. + + +dmesg_restrict +============== + +This toggle indicates whether unprivileged users are prevented +from using ``dmesg(8)`` to view messages from the kernel's log +buffer. +When ``dmesg_restrict`` is set to 0 there are no restrictions. +When ``dmesg_restrict`` is set to 1, users must have +``CAP_SYSLOG`` to use ``dmesg(8)``. + +The kernel config option ``CONFIG_SECURITY_DMESG_RESTRICT`` sets the +default value of ``dmesg_restrict``. + + +domainname & hostname +===================== + +These files can be used to set the NIS/YP domainname and the +hostname of your box in exactly the same way as the commands +domainname and hostname, i.e.:: + + # echo "darkstar" > /proc/sys/kernel/hostname + # echo "mydomain" > /proc/sys/kernel/domainname + +has the same effect as:: + + # hostname "darkstar" + # domainname "mydomain" + +Note, however, that the classic darkstar.frop.org has the +hostname "darkstar" and DNS (Internet Domain Name Server) +domainname "frop.org", not to be confused with the NIS (Network +Information Service) or YP (Yellow Pages) domainname. These two +domain names are in general different. For a detailed discussion +see the ``hostname(1)`` man page. + + +firmware_config +=============== + +See Documentation/driver-api/firmware/fallback-mechanisms.rst. + +The entries in this directory allow the firmware loader helper +fallback to be controlled: + +* ``force_sysfs_fallback``, when set to 1, forces the use of the + fallback; +* ``ignore_sysfs_fallback``, when set to 1, ignores any fallback. + + +ftrace_dump_on_oops +=================== + +Determines whether ``ftrace_dump()`` should be called on an oops (or +kernel panic). This will output the contents of the ftrace buffers to +the console. This is very useful for capturing traces that lead to +crashes and outputting them to a serial console. + += =================================================== +0 Disabled (default). +1 Dump buffers of all CPUs. +2 Dump the buffer of the CPU that triggered the oops. += =================================================== + + +ftrace_enabled, stack_tracer_enabled +==================================== + +See Documentation/trace/ftrace.rst. + + +hardlockup_all_cpu_backtrace +============================ + +This value controls the hard lockup detector behavior when a hard +lockup condition is detected as to whether or not to gather further +debug information. If enabled, arch-specific all-CPU stack dumping +will be initiated. + += ============================================ +0 Do nothing. This is the default behavior. +1 On detection capture more debug information. += ============================================ + + +hardlockup_panic +================ + +This parameter can be used to control whether the kernel panics +when a hard lockup is detected. + += =========================== +0 Don't panic on hard lockup. +1 Panic on hard lockup. += =========================== + +See Documentation/admin-guide/lockup-watchdogs.rst for more information. +This can also be set using the nmi_watchdog kernel parameter. + + +hotplug +======= + +Path for the hotplug policy agent. +Default value is ``CONFIG_UEVENT_HELPER_PATH``, which in turn defaults +to the empty string. + +This file only exists when ``CONFIG_UEVENT_HELPER`` is enabled. Most +modern systems rely exclusively on the netlink-based uevent source and +don't need this. + + +hung_task_all_cpu_backtrace +=========================== + +If this option is set, the kernel will send an NMI to all CPUs to dump +their backtraces when a hung task is detected. This file shows up if +CONFIG_DETECT_HUNG_TASK and CONFIG_SMP are enabled. + +0: Won't show all CPUs backtraces when a hung task is detected. +This is the default behavior. + +1: Will non-maskably interrupt all CPUs and dump their backtraces when +a hung task is detected. + + +hung_task_panic +=============== + +Controls the kernel's behavior when a hung task is detected. +This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled. + += ================================================= +0 Continue operation. This is the default behavior. +1 Panic immediately. += ================================================= + + +hung_task_check_count +===================== + +The upper bound on the number of tasks that are checked. +This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled. + + +hung_task_timeout_secs +====================== + +When a task in D state did not get scheduled +for more than this value report a warning. +This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled. + +0 means infinite timeout, no checking is done. + +Possible values to set are in range {0:``LONG_MAX``/``HZ``}. + + +hung_task_check_interval_secs +============================= + +Hung task check interval. If hung task checking is enabled +(see `hung_task_timeout_secs`_), the check is done every +``hung_task_check_interval_secs`` seconds. +This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled. + +0 (default) means use ``hung_task_timeout_secs`` as checking +interval. + +Possible values to set are in range {0:``LONG_MAX``/``HZ``}. + + +hung_task_warnings +================== + +The maximum number of warnings to report. During a check interval +if a hung task is detected, this value is decreased by 1. +When this value reaches 0, no more warnings will be reported. +This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled. + +-1: report an infinite number of warnings. + + +hyperv_record_panic_msg +======================= + +Controls whether the panic kmsg data should be reported to Hyper-V. + += ========================================================= +0 Do not report panic kmsg data. +1 Report the panic kmsg data. This is the default behavior. += ========================================================= + + +ignore-unaligned-usertrap +========================= + +On architectures where unaligned accesses cause traps, and where this +feature is supported (``CONFIG_SYSCTL_ARCH_UNALIGN_NO_WARN``; +currently, ``arc``, ``ia64`` and ``loongarch``), controls whether all +unaligned traps are logged. + += ============================================================= +0 Log all unaligned accesses. +1 Only warn the first time a process traps. This is the default + setting. += ============================================================= + +See also `unaligned-trap`_ and `unaligned-dump-stack`_. On ``ia64``, +this allows system administrators to override the +``IA64_THREAD_UAC_NOPRINT`` ``prctl`` and avoid logs being flooded. + + +io_uring_disabled +================= + +Prevents all processes from creating new io_uring instances. Enabling this +shrinks the kernel's attack surface. + += ====================================================================== +0 All processes can create io_uring instances as normal. This is the + default setting. +1 io_uring creation is disabled (io_uring_setup() will fail with + -EPERM) for unprivileged processes not in the io_uring_group group. + Existing io_uring instances can still be used. See the + documentation for io_uring_group for more information. +2 io_uring creation is disabled for all processes. io_uring_setup() + always fails with -EPERM. Existing io_uring instances can still be + used. += ====================================================================== + + +io_uring_group +============== + +When io_uring_disabled is set to 1, a process must either be +privileged (CAP_SYS_ADMIN) or be in the io_uring_group group in order +to create an io_uring instance. If io_uring_group is set to -1 (the +default), only processes with the CAP_SYS_ADMIN capability may create +io_uring instances. + + +kexec_load_disabled +=================== + +A toggle indicating if the syscalls ``kexec_load`` and +``kexec_file_load`` have been disabled. +This value defaults to 0 (false: ``kexec_*load`` enabled), but can be +set to 1 (true: ``kexec_*load`` disabled). +Once true, kexec can no longer be used, and the toggle cannot be set +back to false. +This allows a kexec image to be loaded before disabling the syscall, +allowing a system to set up (and later use) an image without it being +altered. +Generally used together with the `modules_disabled`_ sysctl. + +kexec_load_limit_panic +====================== + +This parameter specifies a limit to the number of times the syscalls +``kexec_load`` and ``kexec_file_load`` can be called with a crash +image. It can only be set with a more restrictive value than the +current one. + +== ====================================================== +-1 Unlimited calls to kexec. This is the default setting. +N Number of calls left. +== ====================================================== + +kexec_load_limit_reboot +======================= + +Similar functionality as ``kexec_load_limit_panic``, but for a normal +image. + +kptr_restrict +============= + +This toggle indicates whether restrictions are placed on +exposing kernel addresses via ``/proc`` and other interfaces. + +When ``kptr_restrict`` is set to 0 (the default) the address is hashed +before printing. +(This is the equivalent to %p.) + +When ``kptr_restrict`` is set to 1, kernel pointers printed using the +%pK format specifier will be replaced with 0s unless the user has +``CAP_SYSLOG`` and effective user and group ids are equal to the real +ids. +This is because %pK checks are done at read() time rather than open() +time, so if permissions are elevated between the open() and the read() +(e.g via a setuid binary) then %pK will not leak kernel pointers to +unprivileged users. +Note, this is a temporary solution only. +The correct long-term solution is to do the permission checks at +open() time. +Consider removing world read permissions from files that use %pK, and +using `dmesg_restrict`_ to protect against uses of %pK in ``dmesg(8)`` +if leaking kernel pointer values to unprivileged users is a concern. + +When ``kptr_restrict`` is set to 2, kernel pointers printed using +%pK will be replaced with 0s regardless of privileges. + + +modprobe +======== + +The full path to the usermode helper for autoloading kernel modules, +by default ``CONFIG_MODPROBE_PATH``, which in turn defaults to +"/sbin/modprobe". This binary is executed when the kernel requests a +module. For example, if userspace passes an unknown filesystem type +to mount(), then the kernel will automatically request the +corresponding filesystem module by executing this usermode helper. +This usermode helper should insert the needed module into the kernel. + +This sysctl only affects module autoloading. It has no effect on the +ability to explicitly insert modules. + +This sysctl can be used to debug module loading requests:: + + echo '#! /bin/sh' > /tmp/modprobe + echo 'echo "$@" >> /tmp/modprobe.log' >> /tmp/modprobe + echo 'exec /sbin/modprobe "$@"' >> /tmp/modprobe + chmod a+x /tmp/modprobe + echo /tmp/modprobe > /proc/sys/kernel/modprobe + +Alternatively, if this sysctl is set to the empty string, then module +autoloading is completely disabled. The kernel will not try to +execute a usermode helper at all, nor will it call the +kernel_module_request LSM hook. + +If CONFIG_STATIC_USERMODEHELPER=y is set in the kernel configuration, +then the configured static usermode helper overrides this sysctl, +except that the empty string is still accepted to completely disable +module autoloading as described above. + +modules_disabled +================ + +A toggle value indicating if modules are allowed to be loaded +in an otherwise modular kernel. This toggle defaults to off +(0), but can be set true (1). Once true, modules can be +neither loaded nor unloaded, and the toggle cannot be set back +to false. Generally used with the `kexec_load_disabled`_ toggle. + + +.. _msgmni: + +msgmax, msgmnb, and msgmni +========================== + +``msgmax`` is the maximum size of an IPC message, in bytes. 8192 by +default (``MSGMAX``). + +``msgmnb`` is the maximum size of an IPC queue, in bytes. 16384 by +default (``MSGMNB``). + +``msgmni`` is the maximum number of IPC queues. 32000 by default +(``MSGMNI``). + + +msg_next_id, sem_next_id, and shm_next_id (System V IPC) +======================================================== + +These three toggles allows to specify desired id for next allocated IPC +object: message, semaphore or shared memory respectively. + +By default they are equal to -1, which means generic allocation logic. +Possible values to set are in range {0:``INT_MAX``}. + +Notes: + 1) kernel doesn't guarantee, that new object will have desired id. So, + it's up to userspace, how to handle an object with "wrong" id. + 2) Toggle with non-default value will be set back to -1 by kernel after + successful IPC object allocation. If an IPC object allocation syscall + fails, it is undefined if the value remains unmodified or is reset to -1. + + +ngroups_max +=========== + +Maximum number of supplementary groups, _i.e._ the maximum size which +``setgroups`` will accept. Exports ``NGROUPS_MAX`` from the kernel. + + + +nmi_watchdog +============ + +This parameter can be used to control the NMI watchdog +(i.e. the hard lockup detector) on x86 systems. + += ================================= +0 Disable the hard lockup detector. +1 Enable the hard lockup detector. += ================================= + +The hard lockup detector monitors each CPU for its ability to respond to +timer interrupts. The mechanism utilizes CPU performance counter registers +that are programmed to generate Non-Maskable Interrupts (NMIs) periodically +while a CPU is busy. Hence, the alternative name 'NMI watchdog'. + +The NMI watchdog is disabled by default if the kernel is running as a guest +in a KVM virtual machine. This default can be overridden by adding:: + + nmi_watchdog=1 + +to the guest kernel command line (see +Documentation/admin-guide/kernel-parameters.rst). + + +nmi_wd_lpm_factor (PPC only) +============================ + +Factor to apply to the NMI watchdog timeout (only when ``nmi_watchdog`` is +set to 1). This factor represents the percentage added to +``watchdog_thresh`` when calculating the NMI watchdog timeout during an +LPM. The soft lockup timeout is not impacted. + +A value of 0 means no change. The default value is 200 meaning the NMI +watchdog is set to 30s (based on ``watchdog_thresh`` equal to 10). + + +numa_balancing +============== + +Enables/disables and configures automatic page fault based NUMA memory +balancing. Memory is moved automatically to nodes that access it often. +The value to set can be the result of ORing the following: + += ================================= +0 NUMA_BALANCING_DISABLED +1 NUMA_BALANCING_NORMAL +2 NUMA_BALANCING_MEMORY_TIERING += ================================= + +Or NUMA_BALANCING_NORMAL to optimize page placement among different +NUMA nodes to reduce remote accessing. On NUMA machines, there is a +performance penalty if remote memory is accessed by a CPU. When this +feature is enabled the kernel samples what task thread is accessing +memory by periodically unmapping pages and later trapping a page +fault. At the time of the page fault, it is determined if the data +being accessed should be migrated to a local memory node. + +The unmapping of pages and trapping faults incur additional overhead that +ideally is offset by improved memory locality but there is no universal +guarantee. If the target workload is already bound to NUMA nodes then this +feature should be disabled. + +Or NUMA_BALANCING_MEMORY_TIERING to optimize page placement among +different types of memory (represented as different NUMA nodes) to +place the hot pages in the fast memory. This is implemented based on +unmapping and page fault too. + +numa_balancing_promote_rate_limit_MBps +====================================== + +Too high promotion/demotion throughput between different memory types +may hurt application latency. This can be used to rate limit the +promotion throughput. The per-node max promotion throughput in MB/s +will be limited to be no more than the set value. + +A rule of thumb is to set this to less than 1/10 of the PMEM node +write bandwidth. + +oops_all_cpu_backtrace +====================== + +If this option is set, the kernel will send an NMI to all CPUs to dump +their backtraces when an oops event occurs. It should be used as a last +resort in case a panic cannot be triggered (to protect VMs running, for +example) or kdump can't be collected. This file shows up if CONFIG_SMP +is enabled. + +0: Won't show all CPUs backtraces when an oops is detected. +This is the default behavior. + +1: Will non-maskably interrupt all CPUs and dump their backtraces when +an oops event is detected. + + +oops_limit +========== + +Number of kernel oopses after which the kernel should panic when +``panic_on_oops`` is not set. Setting this to 0 disables checking +the count. Setting this to 1 has the same effect as setting +``panic_on_oops=1``. The default value is 10000. + + +osrelease, ostype & version +=========================== + +:: + + # cat osrelease + 2.1.88 + # cat ostype + Linux + # cat version + #5 Wed Feb 25 21:49:24 MET 1998 + +The files ``osrelease`` and ``ostype`` should be clear enough. +``version`` +needs a little more clarification however. The '#5' means that +this is the fifth kernel built from this source base and the +date behind it indicates the time the kernel was built. +The only way to tune these values is to rebuild the kernel :-) + + +overflowgid & overflowuid +========================= + +if your architecture did not always support 32-bit UIDs (i.e. arm, +i386, m68k, sh, and sparc32), a fixed UID and GID will be returned to +applications that use the old 16-bit UID/GID system calls, if the +actual UID or GID would exceed 65535. + +These sysctls allow you to change the value of the fixed UID and GID. +The default is 65534. + + +panic +===== + +The value in this file determines the behaviour of the kernel on a +panic: + +* if zero, the kernel will loop forever; +* if negative, the kernel will reboot immediately; +* if positive, the kernel will reboot after the corresponding number + of seconds. + +When you use the software watchdog, the recommended setting is 60. + + +panic_on_io_nmi +=============== + +Controls the kernel's behavior when a CPU receives an NMI caused by +an IO error. + += ================================================================== +0 Try to continue operation (default). +1 Panic immediately. The IO error triggered an NMI. This indicates a + serious system condition which could result in IO data corruption. + Rather than continuing, panicking might be a better choice. Some + servers issue this sort of NMI when the dump button is pushed, + and you can use this option to take a crash dump. += ================================================================== + + +panic_on_oops +============= + +Controls the kernel's behaviour when an oops or BUG is encountered. + += =================================================================== +0 Try to continue operation. +1 Panic immediately. If the `panic` sysctl is also non-zero then the + machine will be rebooted. += =================================================================== + + +panic_on_stackoverflow +====================== + +Controls the kernel's behavior when detecting the overflows of +kernel, IRQ and exception stacks except a user stack. +This file shows up if ``CONFIG_DEBUG_STACKOVERFLOW`` is enabled. + += ========================== +0 Try to continue operation. +1 Panic immediately. += ========================== + + +panic_on_unrecovered_nmi +======================== + +The default Linux behaviour on an NMI of either memory or unknown is +to continue operation. For many environments such as scientific +computing it is preferable that the box is taken out and the error +dealt with than an uncorrected parity/ECC error get propagated. + +A small number of systems do generate NMIs for bizarre random reasons +such as power management so the default is off. That sysctl works like +the existing panic controls already in that directory. + + +panic_on_warn +============= + +Calls panic() in the WARN() path when set to 1. This is useful to avoid +a kernel rebuild when attempting to kdump at the location of a WARN(). + += ================================================ +0 Only WARN(), default behaviour. +1 Call panic() after printing out WARN() location. += ================================================ + + +panic_print +=========== + +Bitmask for printing system info when panic happens. User can chose +combination of the following bits: + +===== ============================================ +bit 0 print all tasks info +bit 1 print system memory info +bit 2 print timer info +bit 3 print locks info if ``CONFIG_LOCKDEP`` is on +bit 4 print ftrace buffer +bit 5 print all printk messages in buffer +bit 6 print all CPUs backtrace (if available in the arch) +===== ============================================ + +So for example to print tasks and memory info on panic, user can:: + + echo 3 > /proc/sys/kernel/panic_print + + +panic_on_rcu_stall +================== + +When set to 1, calls panic() after RCU stall detection messages. This +is useful to define the root cause of RCU stalls using a vmcore. + += ============================================================ +0 Do not panic() when RCU stall takes place, default behavior. +1 panic() after printing RCU stall messages. += ============================================================ + +max_rcu_stall_to_panic +====================== + +When ``panic_on_rcu_stall`` is set to 1, this value determines the +number of times that RCU can stall before panic() is called. + +When ``panic_on_rcu_stall`` is set to 0, this value is has no effect. + +perf_cpu_time_max_percent +========================= + +Hints to the kernel how much CPU time it should be allowed to +use to handle perf sampling events. If the perf subsystem +is informed that its samples are exceeding this limit, it +will drop its sampling frequency to attempt to reduce its CPU +usage. + +Some perf sampling happens in NMIs. If these samples +unexpectedly take too long to execute, the NMIs can become +stacked up next to each other so much that nothing else is +allowed to execute. + +===== ======================================================== +0 Disable the mechanism. Do not monitor or correct perf's + sampling rate no matter how CPU time it takes. + +1-100 Attempt to throttle perf's sample rate to this + percentage of CPU. Note: the kernel calculates an + "expected" length of each sample event. 100 here means + 100% of that expected length. Even if this is set to + 100, you may still see sample throttling if this + length is exceeded. Set to 0 if you truly do not care + how much CPU is consumed. +===== ======================================================== + + +perf_event_paranoid +=================== + +Controls use of the performance events system by unprivileged +users (without CAP_PERFMON). The default value is 2. + +For backward compatibility reasons access to system performance +monitoring and observability remains open for CAP_SYS_ADMIN +privileged processes but CAP_SYS_ADMIN usage for secure system +performance monitoring and observability operations is discouraged +with respect to CAP_PERFMON use cases. + +=== ================================================================== + -1 Allow use of (almost) all events by all users. + + Ignore mlock limit after perf_event_mlock_kb without + ``CAP_IPC_LOCK``. + +>=0 Disallow ftrace function tracepoint by users without + ``CAP_PERFMON``. + + Disallow raw tracepoint access by users without ``CAP_PERFMON``. + +>=1 Disallow CPU event access by users without ``CAP_PERFMON``. + +>=2 Disallow kernel profiling by users without ``CAP_PERFMON``. +=== ================================================================== + + +perf_event_max_stack +==================== + +Controls maximum number of stack frames to copy for (``attr.sample_type & +PERF_SAMPLE_CALLCHAIN``) configured events, for instance, when using +'``perf record -g``' or '``perf trace --call-graph fp``'. + +This can only be done when no events are in use that have callchains +enabled, otherwise writing to this file will return ``-EBUSY``. + +The default value is 127. + + +perf_event_mlock_kb +=================== + +Control size of per-cpu ring buffer not counted against mlock limit. + +The default value is 512 + 1 page + + +perf_event_max_contexts_per_stack +================================= + +Controls maximum number of stack frame context entries for +(``attr.sample_type & PERF_SAMPLE_CALLCHAIN``) configured events, for +instance, when using '``perf record -g``' or '``perf trace --call-graph fp``'. + +This can only be done when no events are in use that have callchains +enabled, otherwise writing to this file will return ``-EBUSY``. + +The default value is 8. + + +perf_user_access (arm64 and riscv only) +======================================= + +Controls user space access for reading perf event counters. + +arm64 +===== + +The default value is 0 (access disabled). + +When set to 1, user space can read performance monitor counter registers +directly. + +See Documentation/arch/arm64/perf.rst for more information. + +riscv +===== + +When set to 0, user space access is disabled. + +The default value is 1, user space can read performance monitor counter +registers through perf, any direct access without perf intervention will trigger +an illegal instruction. + +When set to 2, which enables legacy mode (user space has direct access to cycle +and insret CSRs only). Note that this legacy value is deprecated and will be +removed once all user space applications are fixed. + +Note that the time CSR is always directly accessible to all modes. + +pid_max +======= + +PID allocation wrap value. When the kernel's next PID value +reaches this value, it wraps back to a minimum PID value. +PIDs of value ``pid_max`` or larger are not allocated. + + +ns_last_pid +=========== + +The last pid allocated in the current (the one task using this sysctl +lives in) pid namespace. When selecting a pid for a next task on fork +kernel tries to allocate a number starting from this one. + + +powersave-nap (PPC only) +======================== + +If set, Linux-PPC will use the 'nap' mode of powersaving, +otherwise the 'doze' mode will be used. + + +============================================================== + +printk +====== + +The four values in printk denote: ``console_loglevel``, +``default_message_loglevel``, ``minimum_console_loglevel`` and +``default_console_loglevel`` respectively. + +These values influence printk() behavior when printing or +logging error messages. See '``man 2 syslog``' for more info on +the different loglevels. + +======================== ===================================== +console_loglevel messages with a higher priority than + this will be printed to the console +default_message_loglevel messages without an explicit priority + will be printed with this priority +minimum_console_loglevel minimum (highest) value to which + console_loglevel can be set +default_console_loglevel default value for console_loglevel +======================== ===================================== + + +printk_delay +============ + +Delay each printk message in ``printk_delay`` milliseconds + +Value from 0 - 10000 is allowed. + + +printk_ratelimit +================ + +Some warning messages are rate limited. ``printk_ratelimit`` specifies +the minimum length of time between these messages (in seconds). +The default value is 5 seconds. + +A value of 0 will disable rate limiting. + + +printk_ratelimit_burst +====================== + +While long term we enforce one message per `printk_ratelimit`_ +seconds, we do allow a burst of messages to pass through. +``printk_ratelimit_burst`` specifies the number of messages we can +send before ratelimiting kicks in. + +The default value is 10 messages. + + +printk_devkmsg +============== + +Control the logging to ``/dev/kmsg`` from userspace: + +========= ============================================= +ratelimit default, ratelimited +on unlimited logging to /dev/kmsg from userspace +off logging to /dev/kmsg disabled +========= ============================================= + +The kernel command line parameter ``printk.devkmsg=`` overrides this and is +a one-time setting until next reboot: once set, it cannot be changed by +this sysctl interface anymore. + +============================================================== + + +pty +=== + +See Documentation/filesystems/devpts.rst. + + +random +====== + +This is a directory, with the following entries: + +* ``boot_id``: a UUID generated the first time this is retrieved, and + unvarying after that; + +* ``uuid``: a UUID generated every time this is retrieved (this can + thus be used to generate UUIDs at will); + +* ``entropy_avail``: the pool's entropy count, in bits; + +* ``poolsize``: the entropy pool size, in bits; + +* ``urandom_min_reseed_secs``: obsolete (used to determine the minimum + number of seconds between urandom pool reseeding). This file is + writable for compatibility purposes, but writing to it has no effect + on any RNG behavior; + +* ``write_wakeup_threshold``: when the entropy count drops below this + (as a number of bits), processes waiting to write to ``/dev/random`` + are woken up. This file is writable for compatibility purposes, but + writing to it has no effect on any RNG behavior. + + +randomize_va_space +================== + +This option can be used to select the type of process address +space randomization that is used in the system, for architectures +that support this feature. + +== =========================================================================== +0 Turn the process address space randomization off. This is the + default for architectures that do not support this feature anyways, + and kernels that are booted with the "norandmaps" parameter. + +1 Make the addresses of mmap base, stack and VDSO page randomized. + This, among other things, implies that shared libraries will be + loaded to random addresses. Also for PIE-linked binaries, the + location of code start is randomized. This is the default if the + ``CONFIG_COMPAT_BRK`` option is enabled. + +2 Additionally enable heap randomization. This is the default if + ``CONFIG_COMPAT_BRK`` is disabled. + + There are a few legacy applications out there (such as some ancient + versions of libc.so.5 from 1996) that assume that brk area starts + just after the end of the code+bss. These applications break when + start of the brk area is randomized. There are however no known + non-legacy applications that would be broken this way, so for most + systems it is safe to choose full randomization. + + Systems with ancient and/or broken binaries should be configured + with ``CONFIG_COMPAT_BRK`` enabled, which excludes the heap from process + address space randomization. +== =========================================================================== + + +real-root-dev +============= + +See Documentation/admin-guide/initrd.rst. + + +reboot-cmd (SPARC only) +======================= + +??? This seems to be a way to give an argument to the Sparc +ROM/Flash boot loader. Maybe to tell it what to do after +rebooting. ??? + + +sched_energy_aware +================== + +Enables/disables Energy Aware Scheduling (EAS). EAS starts +automatically on platforms where it can run (that is, +platforms with asymmetric CPU topologies and having an Energy +Model available). If your platform happens to meet the +requirements for EAS but you do not want to use it, change +this value to 0. + +task_delayacct +=============== + +Enables/disables task delay accounting (see +Documentation/accounting/delay-accounting.rst. Enabling this feature incurs +a small amount of overhead in the scheduler but is useful for debugging +and performance tuning. It is required by some tools such as iotop. + +sched_schedstats +================ + +Enables/disables scheduler statistics. Enabling this feature +incurs a small amount of overhead in the scheduler but is +useful for debugging and performance tuning. + +sched_util_clamp_min +==================== + +Max allowed *minimum* utilization. + +Default value is 1024, which is the maximum possible value. + +It means that any requested uclamp.min value cannot be greater than +sched_util_clamp_min, i.e., it is restricted to the range +[0:sched_util_clamp_min]. + +sched_util_clamp_max +==================== + +Max allowed *maximum* utilization. + +Default value is 1024, which is the maximum possible value. + +It means that any requested uclamp.max value cannot be greater than +sched_util_clamp_max, i.e., it is restricted to the range +[0:sched_util_clamp_max]. + +sched_util_clamp_min_rt_default +=============================== + +By default Linux is tuned for performance. Which means that RT tasks always run +at the highest frequency and most capable (highest capacity) CPU (in +heterogeneous systems). + +Uclamp achieves this by setting the requested uclamp.min of all RT tasks to +1024 by default, which effectively boosts the tasks to run at the highest +frequency and biases them to run on the biggest CPU. + +This knob allows admins to change the default behavior when uclamp is being +used. In battery powered devices particularly, running at the maximum +capacity and frequency will increase energy consumption and shorten the battery +life. + +This knob is only effective for RT tasks which the user hasn't modified their +requested uclamp.min value via sched_setattr() syscall. + +This knob will not escape the range constraint imposed by sched_util_clamp_min +defined above. + +For example if + + sched_util_clamp_min_rt_default = 800 + sched_util_clamp_min = 600 + +Then the boost will be clamped to 600 because 800 is outside of the permissible +range of [0:600]. This could happen for instance if a powersave mode will +restrict all boosts temporarily by modifying sched_util_clamp_min. As soon as +this restriction is lifted, the requested sched_util_clamp_min_rt_default +will take effect. + +seccomp +======= + +See Documentation/userspace-api/seccomp_filter.rst. + + +sg-big-buff +=========== + +This file shows the size of the generic SCSI (sg) buffer. +You can't tune it just yet, but you could change it on +compile time by editing ``include/scsi/sg.h`` and changing +the value of ``SG_BIG_BUFF``. + +There shouldn't be any reason to change this value. If +you can come up with one, you probably know what you +are doing anyway :) + + +shmall +====== + +This parameter sets the total amount of shared memory pages that +can be used system wide. Hence, ``shmall`` should always be at least +``ceil(shmmax/PAGE_SIZE)``. + +If you are not sure what the default ``PAGE_SIZE`` is on your Linux +system, you can run the following command:: + + # getconf PAGE_SIZE + + +shmmax +====== + +This value can be used to query and set the run time limit +on the maximum shared memory segment size that can be created. +Shared memory segments up to 1Gb are now supported in the +kernel. This value defaults to ``SHMMAX``. + + +shmmni +====== + +This value determines the maximum number of shared memory segments. +4096 by default (``SHMMNI``). + + +shm_rmid_forced +=============== + +Linux lets you set resource limits, including how much memory one +process can consume, via ``setrlimit(2)``. Unfortunately, shared memory +segments are allowed to exist without association with any process, and +thus might not be counted against any resource limits. If enabled, +shared memory segments are automatically destroyed when their attach +count becomes zero after a detach or a process termination. It will +also destroy segments that were created, but never attached to, on exit +from the process. The only use left for ``IPC_RMID`` is to immediately +destroy an unattached segment. Of course, this breaks the way things are +defined, so some applications might stop working. Note that this +feature will do you no good unless you also configure your resource +limits (in particular, ``RLIMIT_AS`` and ``RLIMIT_NPROC``). Most systems don't +need this. + +Note that if you change this from 0 to 1, already created segments +without users and with a dead originative process will be destroyed. + + +sysctl_writes_strict +==================== + +Control how file position affects the behavior of updating sysctl values +via the ``/proc/sys`` interface: + + == ====================================================================== + -1 Legacy per-write sysctl value handling, with no printk warnings. + Each write syscall must fully contain the sysctl value to be + written, and multiple writes on the same sysctl file descriptor + will rewrite the sysctl value, regardless of file position. + 0 Same behavior as above, but warn about processes that perform writes + to a sysctl file descriptor when the file position is not 0. + 1 (default) Respect file position when writing sysctl strings. Multiple + writes will append to the sysctl value buffer. Anything past the max + length of the sysctl value buffer will be ignored. Writes to numeric + sysctl entries must always be at file position 0 and the value must + be fully contained in the buffer sent in the write syscall. + == ====================================================================== + + +softlockup_all_cpu_backtrace +============================ + +This value controls the soft lockup detector thread's behavior +when a soft lockup condition is detected as to whether or not +to gather further debug information. If enabled, each cpu will +be issued an NMI and instructed to capture stack trace. + +This feature is only applicable for architectures which support +NMI. + += ============================================ +0 Do nothing. This is the default behavior. +1 On detection capture more debug information. += ============================================ + + +softlockup_panic +================= + +This parameter can be used to control whether the kernel panics +when a soft lockup is detected. + += ============================================ +0 Don't panic on soft lockup. +1 Panic on soft lockup. += ============================================ + +This can also be set using the softlockup_panic kernel parameter. + + +soft_watchdog +============= + +This parameter can be used to control the soft lockup detector. + += ================================= +0 Disable the soft lockup detector. +1 Enable the soft lockup detector. += ================================= + +The soft lockup detector monitors CPUs for threads that are hogging the CPUs +without rescheduling voluntarily, and thus prevent the 'migration/N' threads +from running, causing the watchdog work fail to execute. The mechanism depends +on the CPUs ability to respond to timer interrupts which are needed for the +watchdog work to be queued by the watchdog timer function, otherwise the NMI +watchdog — if enabled — can detect a hard lockup condition. + + +split_lock_mitigate (x86 only) +============================== + +On x86, each "split lock" imposes a system-wide performance penalty. On larger +systems, large numbers of split locks from unprivileged users can result in +denials of service to well-behaved and potentially more important users. + +The kernel mitigates these bad users by detecting split locks and imposing +penalties: forcing them to wait and only allowing one core to execute split +locks at a time. + +These mitigations can make those bad applications unbearably slow. Setting +split_lock_mitigate=0 may restore some application performance, but will also +increase system exposure to denial of service attacks from split lock users. + += =================================================================== +0 Disable the mitigation mode - just warns the split lock on kernel log + and exposes the system to denials of service from the split lockers. +1 Enable the mitigation mode (this is the default) - penalizes the split + lockers with intentional performance degradation. += =================================================================== + + +stack_erasing +============= + +This parameter can be used to control kernel stack erasing at the end +of syscalls for kernels built with ``CONFIG_GCC_PLUGIN_STACKLEAK``. + +That erasing reduces the information which kernel stack leak bugs +can reveal and blocks some uninitialized stack variable attacks. +The tradeoff is the performance impact: on a single CPU system kernel +compilation sees a 1% slowdown, other systems and workloads may vary. + += ==================================================================== +0 Kernel stack erasing is disabled, STACKLEAK_METRICS are not updated. +1 Kernel stack erasing is enabled (default), it is performed before + returning to the userspace at the end of syscalls. += ==================================================================== + + +stop-a (SPARC only) +=================== + +Controls Stop-A: + += ==================================== +0 Stop-A has no effect. +1 Stop-A breaks to the PROM (default). += ==================================== + +Stop-A is always enabled on a panic, so that the user can return to +the boot PROM. + + +sysrq +===== + +See Documentation/admin-guide/sysrq.rst. + + +tainted +======= + +Non-zero if the kernel has been tainted. Numeric values, which can be +ORed together. The letters are seen in "Tainted" line of Oops reports. + +====== ===== ============================================================== + 1 `(P)` proprietary module was loaded + 2 `(F)` module was force loaded + 4 `(S)` kernel running on an out of specification system + 8 `(R)` module was force unloaded + 16 `(M)` processor reported a Machine Check Exception (MCE) + 32 `(B)` bad page referenced or some unexpected page flags + 64 `(U)` taint requested by userspace application + 128 `(D)` kernel died recently, i.e. there was an OOPS or BUG + 256 `(A)` an ACPI table was overridden by user + 512 `(W)` kernel issued warning + 1024 `(C)` staging driver was loaded + 2048 `(I)` workaround for bug in platform firmware applied + 4096 `(O)` externally-built ("out-of-tree") module was loaded + 8192 `(E)` unsigned module was loaded + 16384 `(L)` soft lockup occurred + 32768 `(K)` kernel has been live patched + 65536 `(X)` Auxiliary taint, defined and used by for distros +131072 `(T)` The kernel was built with the struct randomization plugin +====== ===== ============================================================== + +See Documentation/admin-guide/tainted-kernels.rst for more information. + +Note: + writes to this sysctl interface will fail with ``EINVAL`` if the kernel is + booted with the command line option ``panic_on_taint=<bitmask>,nousertaint`` + and any of the ORed together values being written to ``tainted`` match with + the bitmask declared on panic_on_taint. + See Documentation/admin-guide/kernel-parameters.rst for more details on + that particular kernel command line option and its optional + ``nousertaint`` switch. + +threads-max +=========== + +This value controls the maximum number of threads that can be created +using ``fork()``. + +During initialization the kernel sets this value such that even if the +maximum number of threads is created, the thread structures occupy only +a part (1/8th) of the available RAM pages. + +The minimum value that can be written to ``threads-max`` is 1. + +The maximum value that can be written to ``threads-max`` is given by the +constant ``FUTEX_TID_MASK`` (0x3fffffff). + +If a value outside of this range is written to ``threads-max`` an +``EINVAL`` error occurs. + + +traceoff_on_warning +=================== + +When set, disables tracing (see Documentation/trace/ftrace.rst) when a +``WARN()`` is hit. + + +tracepoint_printk +================= + +When tracepoints are sent to printk() (enabled by the ``tp_printk`` +boot parameter), this entry provides runtime control:: + + echo 0 > /proc/sys/kernel/tracepoint_printk + +will stop tracepoints from being sent to printk(), and:: + + echo 1 > /proc/sys/kernel/tracepoint_printk + +will send them to printk() again. + +This only works if the kernel was booted with ``tp_printk`` enabled. + +See Documentation/admin-guide/kernel-parameters.rst and +Documentation/trace/boottime-trace.rst. + + +.. _unaligned-dump-stack: + +unaligned-dump-stack (ia64) +=========================== + +When logging unaligned accesses, controls whether the stack is +dumped. + += =================================================== +0 Do not dump the stack. This is the default setting. +1 Dump the stack. += =================================================== + +See also `ignore-unaligned-usertrap`_. + + +unaligned-trap +============== + +On architectures where unaligned accesses cause traps, and where this +feature is supported (``CONFIG_SYSCTL_ARCH_UNALIGN_ALLOW``; currently, +``arc``, ``parisc`` and ``loongarch``), controls whether unaligned traps +are caught and emulated (instead of failing). + += ======================================================== +0 Do not emulate unaligned accesses. +1 Emulate unaligned accesses. This is the default setting. += ======================================================== + +See also `ignore-unaligned-usertrap`_. + + +unknown_nmi_panic +================= + +The value in this file affects behavior of handling NMI. When the +value is non-zero, unknown NMI is trapped and then panic occurs. At +that time, kernel debugging information is displayed on console. + +NMI switch that most IA32 servers have fires unknown NMI up, for +example. If a system hangs up, try pressing the NMI switch. + + +unprivileged_bpf_disabled +========================= + +Writing 1 to this entry will disable unprivileged calls to ``bpf()``; +once disabled, calling ``bpf()`` without ``CAP_SYS_ADMIN`` or ``CAP_BPF`` +will return ``-EPERM``. Once set to 1, this can't be cleared from the +running kernel anymore. + +Writing 2 to this entry will also disable unprivileged calls to ``bpf()``, +however, an admin can still change this setting later on, if needed, by +writing 0 or 1 to this entry. + +If ``BPF_UNPRIV_DEFAULT_OFF`` is enabled in the kernel config, then this +entry will default to 2 instead of 0. + += ============================================================= +0 Unprivileged calls to ``bpf()`` are enabled +1 Unprivileged calls to ``bpf()`` are disabled without recovery +2 Unprivileged calls to ``bpf()`` are disabled += ============================================================= + + +warn_limit +========== + +Number of kernel warnings after which the kernel should panic when +``panic_on_warn`` is not set. Setting this to 0 disables checking +the warning count. Setting this to 1 has the same effect as setting +``panic_on_warn=1``. The default value is 0. + + +watchdog +======== + +This parameter can be used to disable or enable the soft lockup detector +*and* the NMI watchdog (i.e. the hard lockup detector) at the same time. + += ============================== +0 Disable both lockup detectors. +1 Enable both lockup detectors. += ============================== + +The soft lockup detector and the NMI watchdog can also be disabled or +enabled individually, using the ``soft_watchdog`` and ``nmi_watchdog`` +parameters. +If the ``watchdog`` parameter is read, for example by executing:: + + cat /proc/sys/kernel/watchdog + +the output of this command (0 or 1) shows the logical OR of +``soft_watchdog`` and ``nmi_watchdog``. + + +watchdog_cpumask +================ + +This value can be used to control on which cpus the watchdog may run. +The default cpumask is all possible cores, but if ``NO_HZ_FULL`` is +enabled in the kernel config, and cores are specified with the +``nohz_full=`` boot argument, those cores are excluded by default. +Offline cores can be included in this mask, and if the core is later +brought online, the watchdog will be started based on the mask value. + +Typically this value would only be touched in the ``nohz_full`` case +to re-enable cores that by default were not running the watchdog, +if a kernel lockup was suspected on those cores. + +The argument value is the standard cpulist format for cpumasks, +so for example to enable the watchdog on cores 0, 2, 3, and 4 you +might say:: + + echo 0,2-4 > /proc/sys/kernel/watchdog_cpumask + + +watchdog_thresh +=============== + +This value can be used to control the frequency of hrtimer and NMI +events and the soft and hard lockup thresholds. The default threshold +is 10 seconds. + +The softlockup threshold is (``2 * watchdog_thresh``). Setting this +tunable to zero will disable lockup detection altogether. diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst new file mode 100644 index 000000000..487756324 --- /dev/null +++ b/Documentation/admin-guide/sysctl/net.rst @@ -0,0 +1,505 @@ +================================ +Documentation for /proc/sys/net/ +================================ + +Copyright + +Copyright (c) 1999 + + - Terrehon Bowden <terrehon@pacbell.net> + - Bodo Bauer <bb@ricochet.net> + +Copyright (c) 2000 + + - Jorge Nerin <comandante@zaralinux.com> + +Copyright (c) 2009 + + - Shen Feng <shen@cn.fujitsu.com> + +For general info and legal blurb, please look in index.rst. + +------------------------------------------------------------------------------ + +This file contains the documentation for the sysctl files in +/proc/sys/net + +The interface to the networking parts of the kernel is located in +/proc/sys/net. The following table shows all possible subdirectories. You may +see only some of them, depending on your kernel's configuration. + + +Table : Subdirectories in /proc/sys/net + + ========= =================== = ========== =================== + Directory Content Directory Content + ========= =================== = ========== =================== + 802 E802 protocol mptcp Multipath TCP + appletalk Appletalk protocol netfilter Network Filter + ax25 AX25 netrom NET/ROM + bridge Bridging rose X.25 PLP layer + core General parameter tipc TIPC + ethernet Ethernet protocol unix Unix domain sockets + ipv4 IP version 4 x25 X.25 protocol + ipv6 IP version 6 + ========= =================== = ========== =================== + +1. /proc/sys/net/core - Network core options +============================================ + +bpf_jit_enable +-------------- + +This enables the BPF Just in Time (JIT) compiler. BPF is a flexible +and efficient infrastructure allowing to execute bytecode at various +hook points. It is used in a number of Linux kernel subsystems such +as networking (e.g. XDP, tc), tracing (e.g. kprobes, uprobes, tracepoints) +and security (e.g. seccomp). LLVM has a BPF back end that can compile +restricted C into a sequence of BPF instructions. After program load +through bpf(2) and passing a verifier in the kernel, a JIT will then +translate these BPF proglets into native CPU instructions. There are +two flavors of JITs, the newer eBPF JIT currently supported on: + + - x86_64 + - x86_32 + - arm64 + - arm32 + - ppc64 + - ppc32 + - sparc64 + - mips64 + - s390x + - riscv64 + - riscv32 + +And the older cBPF JIT supported on the following archs: + + - mips + - sparc + +eBPF JITs are a superset of cBPF JITs, meaning the kernel will +migrate cBPF instructions into eBPF instructions and then JIT +compile them transparently. Older cBPF JITs can only translate +tcpdump filters, seccomp rules, etc, but not mentioned eBPF +programs loaded through bpf(2). + +Values: + + - 0 - disable the JIT (default value) + - 1 - enable the JIT + - 2 - enable the JIT and ask the compiler to emit traces on kernel log. + +bpf_jit_harden +-------------- + +This enables hardening for the BPF JIT compiler. Supported are eBPF +JIT backends. Enabling hardening trades off performance, but can +mitigate JIT spraying. + +Values: + + - 0 - disable JIT hardening (default value) + - 1 - enable JIT hardening for unprivileged users only + - 2 - enable JIT hardening for all users + +where "privileged user" in this context means a process having +CAP_BPF or CAP_SYS_ADMIN in the root user name space. + +bpf_jit_kallsyms +---------------- + +When BPF JIT compiler is enabled, then compiled images are unknown +addresses to the kernel, meaning they neither show up in traces nor +in /proc/kallsyms. This enables export of these addresses, which can +be used for debugging/tracing. If bpf_jit_harden is enabled, this +feature is disabled. + +Values : + + - 0 - disable JIT kallsyms export (default value) + - 1 - enable JIT kallsyms export for privileged users only + +bpf_jit_limit +------------- + +This enforces a global limit for memory allocations to the BPF JIT +compiler in order to reject unprivileged JIT requests once it has +been surpassed. bpf_jit_limit contains the value of the global limit +in bytes. + +dev_weight +---------- + +The maximum number of packets that kernel can handle on a NAPI interrupt, +it's a Per-CPU variable. For drivers that support LRO or GRO_HW, a hardware +aggregated packet is counted as one packet in this context. + +Default: 64 + +dev_weight_rx_bias +------------------ + +RPS (e.g. RFS, aRFS) processing is competing with the registered NAPI poll function +of the driver for the per softirq cycle netdev_budget. This parameter influences +the proportion of the configured netdev_budget that is spent on RPS based packet +processing during RX softirq cycles. It is further meant for making current +dev_weight adaptable for asymmetric CPU needs on RX/TX side of the network stack. +(see dev_weight_tx_bias) It is effective on a per CPU basis. Determination is based +on dev_weight and is calculated multiplicative (dev_weight * dev_weight_rx_bias). + +Default: 1 + +dev_weight_tx_bias +------------------ + +Scales the maximum number of packets that can be processed during a TX softirq cycle. +Effective on a per CPU basis. Allows scaling of current dev_weight for asymmetric +net stack processing needs. Be careful to avoid making TX softirq processing a CPU hog. + +Calculation is based on dev_weight (dev_weight * dev_weight_tx_bias). + +Default: 1 + +default_qdisc +------------- + +The default queuing discipline to use for network devices. This allows +overriding the default of pfifo_fast with an alternative. Since the default +queuing discipline is created without additional parameters so is best suited +to queuing disciplines that work well without configuration like stochastic +fair queue (sfq), CoDel (codel) or fair queue CoDel (fq_codel). Don't use +queuing disciplines like Hierarchical Token Bucket or Deficit Round Robin +which require setting up classes and bandwidths. Note that physical multiqueue +interfaces still use mq as root qdisc, which in turn uses this default for its +leaves. Virtual devices (like e.g. lo or veth) ignore this setting and instead +default to noqueue. + +Default: pfifo_fast + +busy_read +--------- + +Low latency busy poll timeout for socket reads. (needs CONFIG_NET_RX_BUSY_POLL) +Approximate time in us to busy loop waiting for packets on the device queue. +This sets the default value of the SO_BUSY_POLL socket option. +Can be set or overridden per socket by setting socket option SO_BUSY_POLL, +which is the preferred method of enabling. If you need to enable the feature +globally via sysctl, a value of 50 is recommended. + +Will increase power usage. + +Default: 0 (off) + +busy_poll +---------------- +Low latency busy poll timeout for poll and select. (needs CONFIG_NET_RX_BUSY_POLL) +Approximate time in us to busy loop waiting for events. +Recommended value depends on the number of sockets you poll on. +For several sockets 50, for several hundreds 100. +For more than that you probably want to use epoll. +Note that only sockets with SO_BUSY_POLL set will be busy polled, +so you want to either selectively set SO_BUSY_POLL on those sockets or set +sysctl.net.busy_read globally. + +Will increase power usage. + +Default: 0 (off) + +rmem_default +------------ + +The default setting of the socket receive buffer in bytes. + +rmem_max +-------- + +The maximum receive socket buffer size in bytes. + +rps_default_mask +---------------- + +The default RPS CPU mask used on newly created network devices. An empty +mask means RPS disabled by default. + +tstamp_allow_data +----------------- +Allow processes to receive tx timestamps looped together with the original +packet contents. If disabled, transmit timestamp requests from unprivileged +processes are dropped unless socket option SOF_TIMESTAMPING_OPT_TSONLY is set. + +Default: 1 (on) + + +wmem_default +------------ + +The default setting (in bytes) of the socket send buffer. + +wmem_max +-------- + +The maximum send socket buffer size in bytes. + +message_burst and message_cost +------------------------------ + +These parameters are used to limit the warning messages written to the kernel +log from the networking code. They enforce a rate limit to make a +denial-of-service attack impossible. A higher message_cost factor, results in +fewer messages that will be written. Message_burst controls when messages will +be dropped. The default settings limit warning messages to one every five +seconds. + +warnings +-------- + +This sysctl is now unused. + +This was used to control console messages from the networking stack that +occur because of problems on the network like duplicate address or bad +checksums. + +These messages are now emitted at KERN_DEBUG and can generally be enabled +and controlled by the dynamic_debug facility. + +netdev_budget +------------- + +Maximum number of packets taken from all interfaces in one polling cycle (NAPI +poll). In one polling cycle interfaces which are registered to polling are +probed in a round-robin manner. Also, a polling cycle may not exceed +netdev_budget_usecs microseconds, even if netdev_budget has not been +exhausted. + +netdev_budget_usecs +--------------------- + +Maximum number of microseconds in one NAPI polling cycle. Polling +will exit when either netdev_budget_usecs have elapsed during the +poll cycle or the number of packets processed reaches netdev_budget. + +netdev_max_backlog +------------------ + +Maximum number of packets, queued on the INPUT side, when the interface +receives packets faster than kernel can process them. + +netdev_rss_key +-------------- + +RSS (Receive Side Scaling) enabled drivers use a 40 bytes host key that is +randomly generated. +Some user space might need to gather its content even if drivers do not +provide ethtool -x support yet. + +:: + + myhost:~# cat /proc/sys/net/core/netdev_rss_key + 84:50:f4:00:a8:15:d1:a7:e9:7f:1d:60:35:c7:47:25:42:97:74:ca:56:bb:b6:a1:d8: ... (52 bytes total) + +File contains nul bytes if no driver ever called netdev_rss_key_fill() function. + +Note: + /proc/sys/net/core/netdev_rss_key contains 52 bytes of key, + but most drivers only use 40 bytes of it. + +:: + + myhost:~# ethtool -x eth0 + RX flow hash indirection table for eth0 with 8 RX ring(s): + 0: 0 1 2 3 4 5 6 7 + RSS hash key: + 84:50:f4:00:a8:15:d1:a7:e9:7f:1d:60:35:c7:47:25:42:97:74:ca:56:bb:b6:a1:d8:43:e3:c9:0c:fd:17:55:c2:3a:4d:69:ed:f1:42:89 + +netdev_tstamp_prequeue +---------------------- + +If set to 0, RX packet timestamps can be sampled after RPS processing, when +the target CPU processes packets. It might give some delay on timestamps, but +permit to distribute the load on several cpus. + +If set to 1 (default), timestamps are sampled as soon as possible, before +queueing. + +netdev_unregister_timeout_secs +------------------------------ + +Unregister network device timeout in seconds. +This option controls the timeout (in seconds) used to issue a warning while +waiting for a network device refcount to drop to 0 during device +unregistration. A lower value may be useful during bisection to detect +a leaked reference faster. A larger value may be useful to prevent false +warnings on slow/loaded systems. +Default value is 10, minimum 1, maximum 3600. + +skb_defer_max +------------- + +Max size (in skbs) of the per-cpu list of skbs being freed +by the cpu which allocated them. Used by TCP stack so far. + +Default: 64 + +optmem_max +---------- + +Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence +of struct cmsghdr structures with appended data. + +fb_tunnels_only_for_init_net +---------------------------- + +Controls if fallback tunnels (like tunl0, gre0, gretap0, erspan0, +sit0, ip6tnl0, ip6gre0) are automatically created. There are 3 possibilities +(a) value = 0; respective fallback tunnels are created when module is +loaded in every net namespaces (backward compatible behavior). +(b) value = 1; [kcmd value: initns] respective fallback tunnels are +created only in init net namespace and every other net namespace will +not have them. +(c) value = 2; [kcmd value: none] fallback tunnels are not created +when a module is loaded in any of the net namespace. Setting value to +"2" is pointless after boot if these modules are built-in, so there is +a kernel command-line option that can change this default. Please refer to +Documentation/admin-guide/kernel-parameters.txt for additional details. + +Not creating fallback tunnels gives control to userspace to create +whatever is needed only and avoid creating devices which are redundant. + +Default : 0 (for compatibility reasons) + +devconf_inherit_init_net +------------------------ + +Controls if a new network namespace should inherit all current +settings under /proc/sys/net/{ipv4,ipv6}/conf/{all,default}/. By +default, we keep the current behavior: for IPv4 we inherit all current +settings from init_net and for IPv6 we reset all settings to default. + +If set to 1, both IPv4 and IPv6 settings are forced to inherit from +current ones in init_net. If set to 2, both IPv4 and IPv6 settings are +forced to reset to their default values. If set to 3, both IPv4 and IPv6 +settings are forced to inherit from current ones in the netns where this +new netns has been created. + +Default : 0 (for compatibility reasons) + +txrehash +-------- + +Controls default hash rethink behaviour on socket when SO_TXREHASH option is set +to SOCK_TXREHASH_DEFAULT (i. e. not overridden by setsockopt). + +If set to 1 (default), hash rethink is performed on listening socket. +If set to 0, hash rethink is not performed. + +gro_normal_batch +---------------- + +Maximum number of the segments to batch up on output of GRO. When a packet +exits GRO, either as a coalesced superframe or as an original packet which +GRO has decided not to coalesce, it is placed on a per-NAPI list. This +list is then passed to the stack when the number of segments reaches the +gro_normal_batch limit. + +high_order_alloc_disable +------------------------ + +By default the allocator for page frags tries to use high order pages (order-3 +on x86). While the default behavior gives good results in most cases, some users +might have hit a contention in page allocations/freeing. This was especially +true on older kernels (< 5.14) when high-order pages were not stored on per-cpu +lists. This allows to opt-in for order-0 allocation instead but is now mostly of +historical importance. + +Default: 0 + +2. /proc/sys/net/unix - Parameters for Unix domain sockets +---------------------------------------------------------- + +There is only one file in this directory. +unix_dgram_qlen limits the max number of datagrams queued in Unix domain +socket's buffer. It will not take effect unless PF_UNIX flag is specified. + + +3. /proc/sys/net/ipv4 - IPV4 settings +------------------------------------- +Please see: Documentation/networking/ip-sysctl.rst and +Documentation/admin-guide/sysctl/net.rst for descriptions of these entries. + + +4. Appletalk +------------ + +The /proc/sys/net/appletalk directory holds the Appletalk configuration data +when Appletalk is loaded. The configurable parameters are: + +aarp-expiry-time +---------------- + +The amount of time we keep an ARP entry before expiring it. Used to age out +old hosts. + +aarp-resolve-time +----------------- + +The amount of time we will spend trying to resolve an Appletalk address. + +aarp-retransmit-limit +--------------------- + +The number of times we will retransmit a query before giving up. + +aarp-tick-time +-------------- + +Controls the rate at which expires are checked. + +The directory /proc/net/appletalk holds the list of active Appletalk sockets +on a machine. + +The fields indicate the DDP type, the local address (in network:node format) +the remote address, the size of the transmit pending queue, the size of the +received queue (bytes waiting for applications to read) the state and the uid +owning the socket. + +/proc/net/atalk_iface lists all the interfaces configured for appletalk.It +shows the name of the interface, its Appletalk address, the network range on +that address (or network number for phase 1 networks), and the status of the +interface. + +/proc/net/atalk_route lists each known network route. It lists the target +(network) that the route leads to, the router (may be directly connected), the +route flags, and the device the route is using. + +5. TIPC +------- + +tipc_rmem +--------- + +The TIPC protocol now has a tunable for the receive memory, similar to the +tcp_rmem - i.e. a vector of 3 INTEGERs: (min, default, max) + +:: + + # cat /proc/sys/net/tipc/tipc_rmem + 4252725 34021800 68043600 + # + +The max value is set to CONN_OVERLOAD_LIMIT, and the default and min values +are scaled (shifted) versions of that same value. Note that the min value +is not at this point in time used in any meaningful way, but the triplet is +preserved in order to be consistent with things like tcp_rmem. + +named_timeout +------------- + +TIPC name table updates are distributed asynchronously in a cluster, without +any form of transaction handling. This means that different race scenarios are +possible. One such is that a name withdrawal sent out by one node and received +by another node may arrive after a second, overlapping name publication already +has been accepted from a third node, although the conflicting updates +originally may have been issued in the correct sequential order. +If named_timeout is nonzero, failed topology updates will be placed on a defer +queue until another event arrives that clears the error, or until the timeout +expires. Value is in milliseconds. diff --git a/Documentation/admin-guide/sysctl/sunrpc.rst b/Documentation/admin-guide/sysctl/sunrpc.rst new file mode 100644 index 000000000..09780a682 --- /dev/null +++ b/Documentation/admin-guide/sysctl/sunrpc.rst @@ -0,0 +1,25 @@ +=================================== +Documentation for /proc/sys/sunrpc/ +=================================== + +kernel version 2.2.10 + +Copyright (c) 1998, 1999, Rik van Riel <riel@nl.linux.org> + +For general info and legal blurb, please look in index.rst. + +------------------------------------------------------------------------------ + +This file contains the documentation for the sysctl files in +/proc/sys/sunrpc and is valid for Linux kernel version 2.2. + +The files in this directory can be used to (re)set the debug +flags of the SUN Remote Procedure Call (RPC) subsystem in +the Linux kernel. This stuff is used for NFS, KNFSD and +maybe a few other things as well. + +The files in there are used to control the debugging flags: +rpc_debug, nfs_debug, nfsd_debug and nlm_debug. + +These flags are for kernel hackers only. You should read the +source code in net/sunrpc/ for more information. diff --git a/Documentation/admin-guide/sysctl/user.rst b/Documentation/admin-guide/sysctl/user.rst new file mode 100644 index 000000000..c45824589 --- /dev/null +++ b/Documentation/admin-guide/sysctl/user.rst @@ -0,0 +1,84 @@ +================================= +Documentation for /proc/sys/user/ +================================= + +kernel version 4.9.0 + +Copyright (c) 2016 Eric Biederman <ebiederm@xmission.com> + +------------------------------------------------------------------------------ + +This file contains the documentation for the sysctl files in +/proc/sys/user. + +The files in this directory can be used to override the default +limits on the number of namespaces and other objects that have +per user per user namespace limits. + +The primary purpose of these limits is to stop programs that +malfunction and attempt to create a ridiculous number of objects, +before the malfunction becomes a system wide problem. It is the +intention that the defaults of these limits are set high enough that +no program in normal operation should run into these limits. + +The creation of per user per user namespace objects are charged to +the user in the user namespace who created the object and +verified to be below the per user limit in that user namespace. + +The creation of objects is also charged to all of the users +who created user namespaces the creation of the object happens +in (user namespaces can be nested) and verified to be below the per user +limits in the user namespaces of those users. + +This recursive counting of created objects ensures that creating a +user namespace does not allow a user to escape their current limits. + +Currently, these files are in /proc/sys/user: + +max_cgroup_namespaces +===================== + + The maximum number of cgroup namespaces that any user in the current + user namespace may create. + +max_ipc_namespaces +================== + + The maximum number of ipc namespaces that any user in the current + user namespace may create. + +max_mnt_namespaces +================== + + The maximum number of mount namespaces that any user in the current + user namespace may create. + +max_net_namespaces +================== + + The maximum number of network namespaces that any user in the + current user namespace may create. + +max_pid_namespaces +================== + + The maximum number of pid namespaces that any user in the current + user namespace may create. + +max_time_namespaces +=================== + + The maximum number of time namespaces that any user in the current + user namespace may create. + +max_user_namespaces +=================== + + The maximum number of user namespaces that any user in the current + user namespace may create. + +max_uts_namespaces +================== + + The maximum number of user namespaces that any user in the current + user namespace may create. diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst new file mode 100644 index 000000000..45ba1f4dc --- /dev/null +++ b/Documentation/admin-guide/sysctl/vm.rst @@ -0,0 +1,1046 @@ +=============================== +Documentation for /proc/sys/vm/ +=============================== + +kernel version 2.6.29 + +Copyright (c) 1998, 1999, Rik van Riel <riel@nl.linux.org> + +Copyright (c) 2008 Peter W. Morreale <pmorreale@novell.com> + +For general info and legal blurb, please look in index.rst. + +------------------------------------------------------------------------------ + +This file contains the documentation for the sysctl files in +/proc/sys/vm and is valid for Linux kernel version 2.6.29. + +The files in this directory can be used to tune the operation +of the virtual memory (VM) subsystem of the Linux kernel and +the writeout of dirty data to disk. + +Default values and initialization routines for most of these +files can be found in mm/swap.c. + +Currently, these files are in /proc/sys/vm: + +- admin_reserve_kbytes +- compact_memory +- compaction_proactiveness +- compact_unevictable_allowed +- dirty_background_bytes +- dirty_background_ratio +- dirty_bytes +- dirty_expire_centisecs +- dirty_ratio +- dirtytime_expire_seconds +- dirty_writeback_centisecs +- drop_caches +- extfrag_threshold +- highmem_is_dirtyable +- hugetlb_shm_group +- laptop_mode +- legacy_va_layout +- lowmem_reserve_ratio +- max_map_count +- memory_failure_early_kill +- memory_failure_recovery +- min_free_kbytes +- min_slab_ratio +- min_unmapped_ratio +- mmap_min_addr +- mmap_rnd_bits +- mmap_rnd_compat_bits +- nr_hugepages +- nr_hugepages_mempolicy +- nr_overcommit_hugepages +- nr_trim_pages (only if CONFIG_MMU=n) +- numa_zonelist_order +- oom_dump_tasks +- oom_kill_allocating_task +- overcommit_kbytes +- overcommit_memory +- overcommit_ratio +- page-cluster +- page_lock_unfairness +- panic_on_oom +- percpu_pagelist_high_fraction +- stat_interval +- stat_refresh +- numa_stat +- swappiness +- unprivileged_userfaultfd +- user_reserve_kbytes +- vfs_cache_pressure +- watermark_boost_factor +- watermark_scale_factor +- zone_reclaim_mode + + +admin_reserve_kbytes +==================== + +The amount of free memory in the system that should be reserved for users +with the capability cap_sys_admin. + +admin_reserve_kbytes defaults to min(3% of free pages, 8MB) + +That should provide enough for the admin to log in and kill a process, +if necessary, under the default overcommit 'guess' mode. + +Systems running under overcommit 'never' should increase this to account +for the full Virtual Memory Size of programs used to recover. Otherwise, +root may not be able to log in to recover the system. + +How do you calculate a minimum useful reserve? + +sshd or login + bash (or some other shell) + top (or ps, kill, etc.) + +For overcommit 'guess', we can sum resident set sizes (RSS). +On x86_64 this is about 8MB. + +For overcommit 'never', we can take the max of their virtual sizes (VSZ) +and add the sum of their RSS. +On x86_64 this is about 128MB. + +Changing this takes effect whenever an application requests memory. + + +compact_memory +============== + +Available only when CONFIG_COMPACTION is set. When 1 is written to the file, +all zones are compacted such that free memory is available in contiguous +blocks where possible. This can be important for example in the allocation of +huge pages although processes will also directly compact memory as required. + +compaction_proactiveness +======================== + +This tunable takes a value in the range [0, 100] with a default value of +20. This tunable determines how aggressively compaction is done in the +background. Write of a non zero value to this tunable will immediately +trigger the proactive compaction. Setting it to 0 disables proactive compaction. + +Note that compaction has a non-trivial system-wide impact as pages +belonging to different processes are moved around, which could also lead +to latency spikes in unsuspecting applications. The kernel employs +various heuristics to avoid wasting CPU cycles if it detects that +proactive compaction is not being effective. + +Be careful when setting it to extreme values like 100, as that may +cause excessive background compaction activity. + +compact_unevictable_allowed +=========================== + +Available only when CONFIG_COMPACTION is set. When set to 1, compaction is +allowed to examine the unevictable lru (mlocked pages) for pages to compact. +This should be used on systems where stalls for minor page faults are an +acceptable trade for large contiguous free memory. Set to 0 to prevent +compaction from moving pages that are unevictable. Default value is 1. +On CONFIG_PREEMPT_RT the default value is 0 in order to avoid a page fault, due +to compaction, which would block the task from becoming active until the fault +is resolved. + + +dirty_background_bytes +====================== + +Contains the amount of dirty memory at which the background kernel +flusher threads will start writeback. + +Note: + dirty_background_bytes is the counterpart of dirty_background_ratio. Only + one of them may be specified at a time. When one sysctl is written it is + immediately taken into account to evaluate the dirty memory limits and the + other appears as 0 when read. + + +dirty_background_ratio +====================== + +Contains, as a percentage of total available memory that contains free pages +and reclaimable pages, the number of pages at which the background kernel +flusher threads will start writing out dirty data. + +The total available memory is not equal to total system memory. + + +dirty_bytes +=========== + +Contains the amount of dirty memory at which a process generating disk writes +will itself start writeback. + +Note: dirty_bytes is the counterpart of dirty_ratio. Only one of them may be +specified at a time. When one sysctl is written it is immediately taken into +account to evaluate the dirty memory limits and the other appears as 0 when +read. + +Note: the minimum value allowed for dirty_bytes is two pages (in bytes); any +value lower than this limit will be ignored and the old configuration will be +retained. + + +dirty_expire_centisecs +====================== + +This tunable is used to define when dirty data is old enough to be eligible +for writeout by the kernel flusher threads. It is expressed in 100'ths +of a second. Data which has been dirty in-memory for longer than this +interval will be written out next time a flusher thread wakes up. + + +dirty_ratio +=========== + +Contains, as a percentage of total available memory that contains free pages +and reclaimable pages, the number of pages at which a process which is +generating disk writes will itself start writing out dirty data. + +The total available memory is not equal to total system memory. + + +dirtytime_expire_seconds +======================== + +When a lazytime inode is constantly having its pages dirtied, the inode with +an updated timestamp will never get chance to be written out. And, if the +only thing that has happened on the file system is a dirtytime inode caused +by an atime update, a worker will be scheduled to make sure that inode +eventually gets pushed out to disk. This tunable is used to define when dirty +inode is old enough to be eligible for writeback by the kernel flusher threads. +And, it is also used as the interval to wakeup dirtytime_writeback thread. + + +dirty_writeback_centisecs +========================= + +The kernel flusher threads will periodically wake up and write `old` data +out to disk. This tunable expresses the interval between those wakeups, in +100'ths of a second. + +Setting this to zero disables periodic writeback altogether. + + +drop_caches +=========== + +Writing to this will cause the kernel to drop clean caches, as well as +reclaimable slab objects like dentries and inodes. Once dropped, their +memory becomes free. + +To free pagecache:: + + echo 1 > /proc/sys/vm/drop_caches + +To free reclaimable slab objects (includes dentries and inodes):: + + echo 2 > /proc/sys/vm/drop_caches + +To free slab objects and pagecache:: + + echo 3 > /proc/sys/vm/drop_caches + +This is a non-destructive operation and will not free any dirty objects. +To increase the number of objects freed by this operation, the user may run +`sync` prior to writing to /proc/sys/vm/drop_caches. This will minimize the +number of dirty objects on the system and create more candidates to be +dropped. + +This file is not a means to control the growth of the various kernel caches +(inodes, dentries, pagecache, etc...) These objects are automatically +reclaimed by the kernel when memory is needed elsewhere on the system. + +Use of this file can cause performance problems. Since it discards cached +objects, it may cost a significant amount of I/O and CPU to recreate the +dropped objects, especially if they were under heavy use. Because of this, +use outside of a testing or debugging environment is not recommended. + +You may see informational messages in your kernel log when this file is +used:: + + cat (1234): drop_caches: 3 + +These are informational only. They do not mean that anything is wrong +with your system. To disable them, echo 4 (bit 2) into drop_caches. + + +extfrag_threshold +================= + +This parameter affects whether the kernel will compact memory or direct +reclaim to satisfy a high-order allocation. The extfrag/extfrag_index file in +debugfs shows what the fragmentation index for each order is in each zone in +the system. Values tending towards 0 imply allocations would fail due to lack +of memory, values towards 1000 imply failures are due to fragmentation and -1 +implies that the allocation will succeed as long as watermarks are met. + +The kernel will not compact memory in a zone if the +fragmentation index is <= extfrag_threshold. The default value is 500. + + +highmem_is_dirtyable +==================== + +Available only for systems with CONFIG_HIGHMEM enabled (32b systems). + +This parameter controls whether the high memory is considered for dirty +writers throttling. This is not the case by default which means that +only the amount of memory directly visible/usable by the kernel can +be dirtied. As a result, on systems with a large amount of memory and +lowmem basically depleted writers might be throttled too early and +streaming writes can get very slow. + +Changing the value to non zero would allow more memory to be dirtied +and thus allow writers to write more data which can be flushed to the +storage more effectively. Note this also comes with a risk of pre-mature +OOM killer because some writers (e.g. direct block device writes) can +only use the low memory and they can fill it up with dirty data without +any throttling. + + +hugetlb_shm_group +================= + +hugetlb_shm_group contains group id that is allowed to create SysV +shared memory segment using hugetlb page. + + +laptop_mode +=========== + +laptop_mode is a knob that controls "laptop mode". All the things that are +controlled by this knob are discussed in Documentation/admin-guide/laptops/laptop-mode.rst. + + +legacy_va_layout +================ + +If non-zero, this sysctl disables the new 32-bit mmap layout - the kernel +will use the legacy (2.4) layout for all processes. + + +lowmem_reserve_ratio +==================== + +For some specialised workloads on highmem machines it is dangerous for +the kernel to allow process memory to be allocated from the "lowmem" +zone. This is because that memory could then be pinned via the mlock() +system call, or by unavailability of swapspace. + +And on large highmem machines this lack of reclaimable lowmem memory +can be fatal. + +So the Linux page allocator has a mechanism which prevents allocations +which *could* use highmem from using too much lowmem. This means that +a certain amount of lowmem is defended from the possibility of being +captured into pinned user memory. + +(The same argument applies to the old 16 megabyte ISA DMA region. This +mechanism will also defend that region from allocations which could use +highmem or lowmem). + +The `lowmem_reserve_ratio` tunable determines how aggressive the kernel is +in defending these lower zones. + +If you have a machine which uses highmem or ISA DMA and your +applications are using mlock(), or if you are running with no swap then +you probably should change the lowmem_reserve_ratio setting. + +The lowmem_reserve_ratio is an array. You can see them by reading this file:: + + % cat /proc/sys/vm/lowmem_reserve_ratio + 256 256 32 + +But, these values are not used directly. The kernel calculates # of protection +pages for each zones from them. These are shown as array of protection pages +in /proc/zoneinfo like the following. (This is an example of x86-64 box). +Each zone has an array of protection pages like this:: + + Node 0, zone DMA + pages free 1355 + min 3 + low 3 + high 4 + : + : + numa_other 0 + protection: (0, 2004, 2004, 2004) + ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + pagesets + cpu: 0 pcp: 0 + : + +These protections are added to score to judge whether this zone should be used +for page allocation or should be reclaimed. + +In this example, if normal pages (index=2) are required to this DMA zone and +watermark[WMARK_HIGH] is used for watermark, the kernel judges this zone should +not be used because pages_free(1355) is smaller than watermark + protection[2] +(4 + 2004 = 2008). If this protection value is 0, this zone would be used for +normal page requirement. If requirement is DMA zone(index=0), protection[0] +(=0) is used. + +zone[i]'s protection[j] is calculated by following expression:: + + (i < j): + zone[i]->protection[j] + = (total sums of managed_pages from zone[i+1] to zone[j] on the node) + / lowmem_reserve_ratio[i]; + (i = j): + (should not be protected. = 0; + (i > j): + (not necessary, but looks 0) + +The default values of lowmem_reserve_ratio[i] are + + === ==================================== + 256 (if zone[i] means DMA or DMA32 zone) + 32 (others) + === ==================================== + +As above expression, they are reciprocal number of ratio. +256 means 1/256. # of protection pages becomes about "0.39%" of total managed +pages of higher zones on the node. + +If you would like to protect more pages, smaller values are effective. +The minimum value is 1 (1/1 -> 100%). The value less than 1 completely +disables protection of the pages. + + +max_map_count: +============== + +This file contains the maximum number of memory map areas a process +may have. Memory map areas are used as a side-effect of calling +malloc, directly by mmap, mprotect, and madvise, and also when loading +shared libraries. + +While most applications need less than a thousand maps, certain +programs, particularly malloc debuggers, may consume lots of them, +e.g., up to one or two maps per allocation. + +The default value is 65530. + + +memory_failure_early_kill: +========================== + +Control how to kill processes when uncorrected memory error (typically +a 2bit error in a memory module) is detected in the background by hardware +that cannot be handled by the kernel. In some cases (like the page +still having a valid copy on disk) the kernel will handle the failure +transparently without affecting any applications. But if there is +no other up-to-date copy of the data it will kill to prevent any data +corruptions from propagating. + +1: Kill all processes that have the corrupted and not reloadable page mapped +as soon as the corruption is detected. Note this is not supported +for a few types of pages, like kernel internally allocated data or +the swap cache, but works for the majority of user pages. + +0: Only unmap the corrupted page from all processes and only kill a process +who tries to access it. + +The kill is done using a catchable SIGBUS with BUS_MCEERR_AO, so processes can +handle this if they want to. + +This is only active on architectures/platforms with advanced machine +check handling and depends on the hardware capabilities. + +Applications can override this setting individually with the PR_MCE_KILL prctl + + +memory_failure_recovery +======================= + +Enable memory failure recovery (when supported by the platform) + +1: Attempt recovery. + +0: Always panic on a memory failure. + + +min_free_kbytes +=============== + +This is used to force the Linux VM to keep a minimum number +of kilobytes free. The VM uses this number to compute a +watermark[WMARK_MIN] value for each lowmem zone in the system. +Each lowmem zone gets a number of reserved free pages based +proportionally on its size. + +Some minimal amount of memory is needed to satisfy PF_MEMALLOC +allocations; if you set this to lower than 1024KB, your system will +become subtly broken, and prone to deadlock under high loads. + +Setting this too high will OOM your machine instantly. + + +min_slab_ratio +============== + +This is available only on NUMA kernels. + +A percentage of the total pages in each zone. On Zone reclaim +(fallback from the local zone occurs) slabs will be reclaimed if more +than this percentage of pages in a zone are reclaimable slab pages. +This insures that the slab growth stays under control even in NUMA +systems that rarely perform global reclaim. + +The default is 5 percent. + +Note that slab reclaim is triggered in a per zone / node fashion. +The process of reclaiming slab memory is currently not node specific +and may not be fast. + + +min_unmapped_ratio +================== + +This is available only on NUMA kernels. + +This is a percentage of the total pages in each zone. Zone reclaim will +only occur if more than this percentage of pages are in a state that +zone_reclaim_mode allows to be reclaimed. + +If zone_reclaim_mode has the value 4 OR'd, then the percentage is compared +against all file-backed unmapped pages including swapcache pages and tmpfs +files. Otherwise, only unmapped pages backed by normal files but not tmpfs +files and similar are considered. + +The default is 1 percent. + + +mmap_min_addr +============= + +This file indicates the amount of address space which a user process will +be restricted from mmapping. Since kernel null dereference bugs could +accidentally operate based on the information in the first couple of pages +of memory userspace processes should not be allowed to write to them. By +default this value is set to 0 and no protections will be enforced by the +security module. Setting this value to something like 64k will allow the +vast majority of applications to work correctly and provide defense in depth +against future potential kernel bugs. + + +mmap_rnd_bits +============= + +This value can be used to select the number of bits to use to +determine the random offset to the base address of vma regions +resulting from mmap allocations on architectures which support +tuning address space randomization. This value will be bounded +by the architecture's minimum and maximum supported values. + +This value can be changed after boot using the +/proc/sys/vm/mmap_rnd_bits tunable + + +mmap_rnd_compat_bits +==================== + +This value can be used to select the number of bits to use to +determine the random offset to the base address of vma regions +resulting from mmap allocations for applications run in +compatibility mode on architectures which support tuning address +space randomization. This value will be bounded by the +architecture's minimum and maximum supported values. + +This value can be changed after boot using the +/proc/sys/vm/mmap_rnd_compat_bits tunable + + +nr_hugepages +============ + +Change the minimum size of the hugepage pool. + +See Documentation/admin-guide/mm/hugetlbpage.rst + + +hugetlb_optimize_vmemmap +======================== + +This knob is not available when the size of 'struct page' (a structure defined +in include/linux/mm_types.h) is not power of two (an unusual system config could +result in this). + +Enable (set to 1) or disable (set to 0) HugeTLB Vmemmap Optimization (HVO). + +Once enabled, the vmemmap pages of subsequent allocation of HugeTLB pages from +buddy allocator will be optimized (7 pages per 2MB HugeTLB page and 4095 pages +per 1GB HugeTLB page), whereas already allocated HugeTLB pages will not be +optimized. When those optimized HugeTLB pages are freed from the HugeTLB pool +to the buddy allocator, the vmemmap pages representing that range needs to be +remapped again and the vmemmap pages discarded earlier need to be rellocated +again. If your use case is that HugeTLB pages are allocated 'on the fly' (e.g. +never explicitly allocating HugeTLB pages with 'nr_hugepages' but only set +'nr_overcommit_hugepages', those overcommitted HugeTLB pages are allocated 'on +the fly') instead of being pulled from the HugeTLB pool, you should weigh the +benefits of memory savings against the more overhead (~2x slower than before) +of allocation or freeing HugeTLB pages between the HugeTLB pool and the buddy +allocator. Another behavior to note is that if the system is under heavy memory +pressure, it could prevent the user from freeing HugeTLB pages from the HugeTLB +pool to the buddy allocator since the allocation of vmemmap pages could be +failed, you have to retry later if your system encounter this situation. + +Once disabled, the vmemmap pages of subsequent allocation of HugeTLB pages from +buddy allocator will not be optimized meaning the extra overhead at allocation +time from buddy allocator disappears, whereas already optimized HugeTLB pages +will not be affected. If you want to make sure there are no optimized HugeTLB +pages, you can set "nr_hugepages" to 0 first and then disable this. Note that +writing 0 to nr_hugepages will make any "in use" HugeTLB pages become surplus +pages. So, those surplus pages are still optimized until they are no longer +in use. You would need to wait for those surplus pages to be released before +there are no optimized pages in the system. + + +nr_hugepages_mempolicy +====================== + +Change the size of the hugepage pool at run-time on a specific +set of NUMA nodes. + +See Documentation/admin-guide/mm/hugetlbpage.rst + + +nr_overcommit_hugepages +======================= + +Change the maximum size of the hugepage pool. The maximum is +nr_hugepages + nr_overcommit_hugepages. + +See Documentation/admin-guide/mm/hugetlbpage.rst + + +nr_trim_pages +============= + +This is available only on NOMMU kernels. + +This value adjusts the excess page trimming behaviour of power-of-2 aligned +NOMMU mmap allocations. + +A value of 0 disables trimming of allocations entirely, while a value of 1 +trims excess pages aggressively. Any value >= 1 acts as the watermark where +trimming of allocations is initiated. + +The default value is 1. + +See Documentation/admin-guide/mm/nommu-mmap.rst for more information. + + +numa_zonelist_order +=================== + +This sysctl is only for NUMA and it is deprecated. Anything but +Node order will fail! + +'where the memory is allocated from' is controlled by zonelists. + +(This documentation ignores ZONE_HIGHMEM/ZONE_DMA32 for simple explanation. +you may be able to read ZONE_DMA as ZONE_DMA32...) + +In non-NUMA case, a zonelist for GFP_KERNEL is ordered as following. +ZONE_NORMAL -> ZONE_DMA +This means that a memory allocation request for GFP_KERNEL will +get memory from ZONE_DMA only when ZONE_NORMAL is not available. + +In NUMA case, you can think of following 2 types of order. +Assume 2 node NUMA and below is zonelist of Node(0)'s GFP_KERNEL:: + + (A) Node(0) ZONE_NORMAL -> Node(0) ZONE_DMA -> Node(1) ZONE_NORMAL + (B) Node(0) ZONE_NORMAL -> Node(1) ZONE_NORMAL -> Node(0) ZONE_DMA. + +Type(A) offers the best locality for processes on Node(0), but ZONE_DMA +will be used before ZONE_NORMAL exhaustion. This increases possibility of +out-of-memory(OOM) of ZONE_DMA because ZONE_DMA is tend to be small. + +Type(B) cannot offer the best locality but is more robust against OOM of +the DMA zone. + +Type(A) is called as "Node" order. Type (B) is "Zone" order. + +"Node order" orders the zonelists by node, then by zone within each node. +Specify "[Nn]ode" for node order + +"Zone Order" orders the zonelists by zone type, then by node within each +zone. Specify "[Zz]one" for zone order. + +Specify "[Dd]efault" to request automatic configuration. + +On 32-bit, the Normal zone needs to be preserved for allocations accessible +by the kernel, so "zone" order will be selected. + +On 64-bit, devices that require DMA32/DMA are relatively rare, so "node" +order will be selected. + +Default order is recommended unless this is causing problems for your +system/application. + + +oom_dump_tasks +============== + +Enables a system-wide task dump (excluding kernel threads) to be produced +when the kernel performs an OOM-killing and includes such information as +pid, uid, tgid, vm size, rss, pgtables_bytes, swapents, oom_score_adj +score, and name. This is helpful to determine why the OOM killer was +invoked, to identify the rogue task that caused it, and to determine why +the OOM killer chose the task it did to kill. + +If this is set to zero, this information is suppressed. On very +large systems with thousands of tasks it may not be feasible to dump +the memory state information for each one. Such systems should not +be forced to incur a performance penalty in OOM conditions when the +information may not be desired. + +If this is set to non-zero, this information is shown whenever the +OOM killer actually kills a memory-hogging task. + +The default value is 1 (enabled). + + +oom_kill_allocating_task +======================== + +This enables or disables killing the OOM-triggering task in +out-of-memory situations. + +If this is set to zero, the OOM killer will scan through the entire +tasklist and select a task based on heuristics to kill. This normally +selects a rogue memory-hogging task that frees up a large amount of +memory when killed. + +If this is set to non-zero, the OOM killer simply kills the task that +triggered the out-of-memory condition. This avoids the expensive +tasklist scan. + +If panic_on_oom is selected, it takes precedence over whatever value +is used in oom_kill_allocating_task. + +The default value is 0. + + +overcommit_kbytes +================= + +When overcommit_memory is set to 2, the committed address space is not +permitted to exceed swap plus this amount of physical RAM. See below. + +Note: overcommit_kbytes is the counterpart of overcommit_ratio. Only one +of them may be specified at a time. Setting one disables the other (which +then appears as 0 when read). + + +overcommit_memory +================= + +This value contains a flag that enables memory overcommitment. + +When this flag is 0, the kernel attempts to estimate the amount +of free memory left when userspace requests more memory. + +When this flag is 1, the kernel pretends there is always enough +memory until it actually runs out. + +When this flag is 2, the kernel uses a "never overcommit" +policy that attempts to prevent any overcommit of memory. +Note that user_reserve_kbytes affects this policy. + +This feature can be very useful because there are a lot of +programs that malloc() huge amounts of memory "just-in-case" +and don't use much of it. + +The default value is 0. + +See Documentation/mm/overcommit-accounting.rst and +mm/util.c::__vm_enough_memory() for more information. + + +overcommit_ratio +================ + +When overcommit_memory is set to 2, the committed address +space is not permitted to exceed swap plus this percentage +of physical RAM. See above. + + +page-cluster +============ + +page-cluster controls the number of pages up to which consecutive pages +are read in from swap in a single attempt. This is the swap counterpart +to page cache readahead. +The mentioned consecutivity is not in terms of virtual/physical addresses, +but consecutive on swap space - that means they were swapped out together. + +It is a logarithmic value - setting it to zero means "1 page", setting +it to 1 means "2 pages", setting it to 2 means "4 pages", etc. +Zero disables swap readahead completely. + +The default value is three (eight pages at a time). There may be some +small benefits in tuning this to a different value if your workload is +swap-intensive. + +Lower values mean lower latencies for initial faults, but at the same time +extra faults and I/O delays for following faults if they would have been part of +that consecutive pages readahead would have brought in. + + +page_lock_unfairness +==================== + +This value determines the number of times that the page lock can be +stolen from under a waiter. After the lock is stolen the number of times +specified in this file (default is 5), the "fair lock handoff" semantics +will apply, and the waiter will only be awakened if the lock can be taken. + +panic_on_oom +============ + +This enables or disables panic on out-of-memory feature. + +If this is set to 0, the kernel will kill some rogue process, +called oom_killer. Usually, oom_killer can kill rogue processes and +system will survive. + +If this is set to 1, the kernel panics when out-of-memory happens. +However, if a process limits using nodes by mempolicy/cpusets, +and those nodes become memory exhaustion status, one process +may be killed by oom-killer. No panic occurs in this case. +Because other nodes' memory may be free. This means system total status +may be not fatal yet. + +If this is set to 2, the kernel panics compulsorily even on the +above-mentioned. Even oom happens under memory cgroup, the whole +system panics. + +The default value is 0. + +1 and 2 are for failover of clustering. Please select either +according to your policy of failover. + +panic_on_oom=2+kdump gives you very strong tool to investigate +why oom happens. You can get snapshot. + + +percpu_pagelist_high_fraction +============================= + +This is the fraction of pages in each zone that are can be stored to +per-cpu page lists. It is an upper boundary that is divided depending +on the number of online CPUs. The min value for this is 8 which means +that we do not allow more than 1/8th of pages in each zone to be stored +on per-cpu page lists. This entry only changes the value of hot per-cpu +page lists. A user can specify a number like 100 to allocate 1/100th of +each zone between per-cpu lists. + +The batch value of each per-cpu page list remains the same regardless of +the value of the high fraction so allocation latencies are unaffected. + +The initial value is zero. Kernel uses this value to set the high pcp->high +mark based on the low watermark for the zone and the number of local +online CPUs. If the user writes '0' to this sysctl, it will revert to +this default behavior. + + +stat_interval +============= + +The time interval between which vm statistics are updated. The default +is 1 second. + + +stat_refresh +============ + +Any read or write (by root only) flushes all the per-cpu vm statistics +into their global totals, for more accurate reports when testing +e.g. cat /proc/sys/vm/stat_refresh /proc/meminfo + +As a side-effect, it also checks for negative totals (elsewhere reported +as 0) and "fails" with EINVAL if any are found, with a warning in dmesg. +(At time of writing, a few stats are known sometimes to be found negative, +with no ill effects: errors and warnings on these stats are suppressed.) + + +numa_stat +========= + +This interface allows runtime configuration of numa statistics. + +When page allocation performance becomes a bottleneck and you can tolerate +some possible tool breakage and decreased numa counter precision, you can +do:: + + echo 0 > /proc/sys/vm/numa_stat + +When page allocation performance is not a bottleneck and you want all +tooling to work, you can do:: + + echo 1 > /proc/sys/vm/numa_stat + + +swappiness +========== + +This control is used to define the rough relative IO cost of swapping +and filesystem paging, as a value between 0 and 200. At 100, the VM +assumes equal IO cost and will thus apply memory pressure to the page +cache and swap-backed pages equally; lower values signify more +expensive swap IO, higher values indicates cheaper. + +Keep in mind that filesystem IO patterns under memory pressure tend to +be more efficient than swap's random IO. An optimal value will require +experimentation and will also be workload-dependent. + +The default value is 60. + +For in-memory swap, like zram or zswap, as well as hybrid setups that +have swap on faster devices than the filesystem, values beyond 100 can +be considered. For example, if the random IO against the swap device +is on average 2x faster than IO from the filesystem, swappiness should +be 133 (x + 2x = 200, 2x = 133.33). + +At 0, the kernel will not initiate swap until the amount of free and +file-backed pages is less than the high watermark in a zone. + + +unprivileged_userfaultfd +======================== + +This flag controls the mode in which unprivileged users can use the +userfaultfd system calls. Set this to 0 to restrict unprivileged users +to handle page faults in user mode only. In this case, users without +SYS_CAP_PTRACE must pass UFFD_USER_MODE_ONLY in order for userfaultfd to +succeed. Prohibiting use of userfaultfd for handling faults from kernel +mode may make certain vulnerabilities more difficult to exploit. + +Set this to 1 to allow unprivileged users to use the userfaultfd system +calls without any restrictions. + +The default value is 0. + +Another way to control permissions for userfaultfd is to use +/dev/userfaultfd instead of userfaultfd(2). See +Documentation/admin-guide/mm/userfaultfd.rst. + +user_reserve_kbytes +=================== + +When overcommit_memory is set to 2, "never overcommit" mode, reserve +min(3% of current process size, user_reserve_kbytes) of free memory. +This is intended to prevent a user from starting a single memory hogging +process, such that they cannot recover (kill the hog). + +user_reserve_kbytes defaults to min(3% of the current process size, 128MB). + +If this is reduced to zero, then the user will be allowed to allocate +all free memory with a single process, minus admin_reserve_kbytes. +Any subsequent attempts to execute a command will result in +"fork: Cannot allocate memory". + +Changing this takes effect whenever an application requests memory. + + +vfs_cache_pressure +================== + +This percentage value controls the tendency of the kernel to reclaim +the memory which is used for caching of directory and inode objects. + +At the default value of vfs_cache_pressure=100 the kernel will attempt to +reclaim dentries and inodes at a "fair" rate with respect to pagecache and +swapcache reclaim. Decreasing vfs_cache_pressure causes the kernel to prefer +to retain dentry and inode caches. When vfs_cache_pressure=0, the kernel will +never reclaim dentries and inodes due to memory pressure and this can easily +lead to out-of-memory conditions. Increasing vfs_cache_pressure beyond 100 +causes the kernel to prefer to reclaim dentries and inodes. + +Increasing vfs_cache_pressure significantly beyond 100 may have negative +performance impact. Reclaim code needs to take various locks to find freeable +directory and inode objects. With vfs_cache_pressure=1000, it will look for +ten times more freeable objects than there are. + + +watermark_boost_factor +====================== + +This factor controls the level of reclaim when memory is being fragmented. +It defines the percentage of the high watermark of a zone that will be +reclaimed if pages of different mobility are being mixed within pageblocks. +The intent is that compaction has less work to do in the future and to +increase the success rate of future high-order allocations such as SLUB +allocations, THP and hugetlbfs pages. + +To make it sensible with respect to the watermark_scale_factor +parameter, the unit is in fractions of 10,000. The default value of +15,000 means that up to 150% of the high watermark will be reclaimed in the +event of a pageblock being mixed due to fragmentation. The level of reclaim +is determined by the number of fragmentation events that occurred in the +recent past. If this value is smaller than a pageblock then a pageblocks +worth of pages will be reclaimed (e.g. 2MB on 64-bit x86). A boost factor +of 0 will disable the feature. + + +watermark_scale_factor +====================== + +This factor controls the aggressiveness of kswapd. It defines the +amount of memory left in a node/system before kswapd is woken up and +how much memory needs to be free before kswapd goes back to sleep. + +The unit is in fractions of 10,000. The default value of 10 means the +distances between watermarks are 0.1% of the available memory in the +node/system. The maximum value is 3000, or 30% of memory. + +A high rate of threads entering direct reclaim (allocstall) or kswapd +going to sleep prematurely (kswapd_low_wmark_hit_quickly) can indicate +that the number of free pages kswapd maintains for latency reasons is +too small for the allocation bursts occurring in the system. This knob +can then be used to tune kswapd aggressiveness accordingly. + + +zone_reclaim_mode +================= + +Zone_reclaim_mode allows someone to set more or less aggressive approaches to +reclaim memory when a zone runs out of memory. If it is set to zero then no +zone reclaim occurs. Allocations will be satisfied from other zones / nodes +in the system. + +This is value OR'ed together of + += =================================== +1 Zone reclaim on +2 Zone reclaim writes dirty pages out +4 Zone reclaim swaps pages += =================================== + +zone_reclaim_mode is disabled by default. For file servers or workloads +that benefit from having their data cached, zone_reclaim_mode should be +left disabled as the caching effect is likely to be more important than +data locality. + +Consider enabling one or more zone_reclaim mode bits if it's known that the +workload is partitioned such that each partition fits within a NUMA node +and that accessing remote memory would cause a measurable performance +reduction. The page allocator will take additional actions before +allocating off node pages. + +Allowing zone reclaim to write out pages stops processes that are +writing large amounts of data from dirtying pages on other nodes. Zone +reclaim will write out dirty pages if a zone fills up and so effectively +throttle the process. This may decrease the performance of a single process +since it cannot use all of system memory to buffer the outgoing writes +anymore but it preserve the memory on other nodes so that the performance +of other processes running on other nodes will not be affected. + +Allowing regular swap effectively restricts allocations to the local +node unless explicitly overridden by memory policies or cpuset +configurations. diff --git a/Documentation/admin-guide/sysfs-rules.rst b/Documentation/admin-guide/sysfs-rules.rst new file mode 100644 index 000000000..abad33526 --- /dev/null +++ b/Documentation/admin-guide/sysfs-rules.rst @@ -0,0 +1,192 @@ +Rules on how to access information in sysfs +=========================================== + +The kernel-exported sysfs exports internal kernel implementation details +and depends on internal kernel structures and layout. It is agreed upon +by the kernel developers that the Linux kernel does not provide a stable +internal API. Therefore, there are aspects of the sysfs interface that +may not be stable across kernel releases. + +To minimize the risk of breaking users of sysfs, which are in most cases +low-level userspace applications, with a new kernel release, the users +of sysfs must follow some rules to use an as-abstract-as-possible way to +access this filesystem. The current udev and HAL programs already +implement this and users are encouraged to plug, if possible, into the +abstractions these programs provide instead of accessing sysfs directly. + +But if you really do want or need to access sysfs directly, please follow +the following rules and then your programs should work with future +versions of the sysfs interface. + +- Do not use libsysfs + It makes assumptions about sysfs which are not true. Its API does not + offer any abstraction, it exposes all the kernel driver-core + implementation details in its own API. Therefore it is not better than + reading directories and opening the files yourself. + Also, it is not actively maintained, in the sense of reflecting the + current kernel development. The goal of providing a stable interface + to sysfs has failed; it causes more problems than it solves. It + violates many of the rules in this document. + +- sysfs is always at ``/sys`` + Parsing ``/proc/mounts`` is a waste of time. Other mount points are a + system configuration bug you should not try to solve. For test cases, + possibly support a ``SYSFS_PATH`` environment variable to overwrite the + application's behavior, but never try to search for sysfs. Never try + to mount it, if you are not an early boot script. + +- devices are only "devices" + There is no such thing like class-, bus-, physical devices, + interfaces, and such that you can rely on in userspace. Everything is + just simply a "device". Class-, bus-, physical, ... types are just + kernel implementation details which should not be expected by + applications that look for devices in sysfs. + + The properties of a device are: + + - devpath (``/devices/pci0000:00/0000:00:1d.1/usb2/2-2/2-2:1.0``) + + - identical to the DEVPATH value in the event sent from the kernel + at device creation and removal + - the unique key to the device at that point in time + - the kernel's path to the device directory without the leading + ``/sys``, and always starting with a slash + - all elements of a devpath must be real directories. Symlinks + pointing to /sys/devices must always be resolved to their real + target and the target path must be used to access the device. + That way the devpath to the device matches the devpath of the + kernel used at event time. + - using or exposing symlink values as elements in a devpath string + is a bug in the application + + - kernel name (``sda``, ``tty``, ``0000:00:1f.2``, ...) + + - a directory name, identical to the last element of the devpath + - applications need to handle spaces and characters like ``!`` in + the name + + - subsystem (``block``, ``tty``, ``pci``, ...) + + - simple string, never a path or a link + - retrieved by reading the "subsystem"-link and using only the + last element of the target path + + - driver (``tg3``, ``ata_piix``, ``uhci_hcd``) + + - a simple string, which may contain spaces, never a path or a + link + - it is retrieved by reading the "driver"-link and using only the + last element of the target path + - devices which do not have "driver"-link just do not have a + driver; copying the driver value in a child device context is a + bug in the application + + - attributes + + - the files in the device directory or files below subdirectories + of the same device directory + - accessing attributes reached by a symlink pointing to another device, + like the "device"-link, is a bug in the application + + Everything else is just a kernel driver-core implementation detail + that should not be assumed to be stable across kernel releases. + +- Properties of parent devices never belong into a child device. + Always look at the parent devices themselves for determining device + context properties. If the device ``eth0`` or ``sda`` does not have a + "driver"-link, then this device does not have a driver. Its value is empty. + Never copy any property of the parent-device into a child-device. Parent + device properties may change dynamically without any notice to the + child device. + +- Hierarchy in a single device tree + There is only one valid place in sysfs where hierarchy can be examined + and this is below: ``/sys/devices.`` + It is planned that all device directories will end up in the tree + below this directory. + +- Classification by subsystem + There are currently three places for classification of devices: + ``/sys/block,`` ``/sys/class`` and ``/sys/bus.`` It is planned that these will + not contain any device directories themselves, but only flat lists of + symlinks pointing to the unified ``/sys/devices`` tree. + All three places have completely different rules on how to access + device information. It is planned to merge all three + classification directories into one place at ``/sys/subsystem``, + following the layout of the bus directories. All buses and + classes, including the converted block subsystem, will show up + there. + The devices belonging to a subsystem will create a symlink in the + "devices" directory at ``/sys/subsystem/<name>/devices``, + + If ``/sys/subsystem`` exists, ``/sys/bus``, ``/sys/class`` and ``/sys/block`` + can be ignored. If it does not exist, you always have to scan all three + places, as the kernel is free to move a subsystem from one place to + the other, as long as the devices are still reachable by the same + subsystem name. + + Assuming ``/sys/class/<subsystem>`` and ``/sys/bus/<subsystem>``, or + ``/sys/block`` and ``/sys/class/block`` are not interchangeable is a bug in + the application. + +- Block + The converted block subsystem at ``/sys/class/block`` or + ``/sys/subsystem/block`` will contain the links for disks and partitions + at the same level, never in a hierarchy. Assuming the block subsystem to + contain only disks and not partition devices in the same flat list is + a bug in the application. + +- "device"-link and <subsystem>:<kernel name>-links + Never depend on the "device"-link. The "device"-link is a workaround + for the old layout, where class devices are not created in + ``/sys/devices/`` like the bus devices. If the link-resolving of a + device directory does not end in ``/sys/devices/``, you can use the + "device"-link to find the parent devices in ``/sys/devices/``, That is the + single valid use of the "device"-link; it must never appear in any + path as an element. Assuming the existence of the "device"-link for + a device in ``/sys/devices/`` is a bug in the application. + Accessing ``/sys/class/net/eth0/device`` is a bug in the application. + + Never depend on the class-specific links back to the ``/sys/class`` + directory. These links are also a workaround for the design mistake + that class devices are not created in ``/sys/devices.`` If a device + directory does not contain directories for child devices, these links + may be used to find the child devices in ``/sys/class.`` That is the single + valid use of these links; they must never appear in any path as an + element. Assuming the existence of these links for devices which are + real child device directories in the ``/sys/devices`` tree is a bug in + the application. + + It is planned to remove all these links when all class device + directories live in ``/sys/devices.`` + +- Position of devices along device chain can change. + Never depend on a specific parent device position in the devpath, + or the chain of parent devices. The kernel is free to insert devices into + the chain. You must always request the parent device you are looking for + by its subsystem value. You need to walk up the chain until you find + the device that matches the expected subsystem. Depending on a specific + position of a parent device or exposing relative paths using ``../`` to + access the chain of parents is a bug in the application. + +- When reading and writing sysfs device attribute files, avoid dependency + on specific error codes wherever possible. This minimizes coupling to + the error handling implementation within the kernel. + + In general, failures to read or write sysfs device attributes shall + propagate errors wherever possible. Common errors include, but are not + limited to: + + ``-EIO``: The read or store operation is not supported, typically + returned by the sysfs system itself if the read or store pointer + is ``NULL``. + + ``-ENXIO``: The read or store operation failed + + Error codes will not be changed without good reason, and should a change + to error codes result in user-space breakage, it will be fixed, or the + the offending change will be reverted. + + Userspace applications can, however, expect the format and contents of + the attribute files to remain consistent in the absence of a version + attribute change in the context of a given attribute. diff --git a/Documentation/admin-guide/sysrq.rst b/Documentation/admin-guide/sysrq.rst new file mode 100644 index 000000000..51906e473 --- /dev/null +++ b/Documentation/admin-guide/sysrq.rst @@ -0,0 +1,294 @@ +Linux Magic System Request Key Hacks +==================================== + +Documentation for sysrq.c + +What is the magic SysRq key? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +It is a 'magical' key combo you can hit which the kernel will respond to +regardless of whatever else it is doing, unless it is completely locked up. + +How do I enable the magic SysRq key? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +You need to say "yes" to 'Magic SysRq key (CONFIG_MAGIC_SYSRQ)' when +configuring the kernel. When running a kernel with SysRq compiled in, +/proc/sys/kernel/sysrq controls the functions allowed to be invoked via +the SysRq key. The default value in this file is set by the +CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE config symbol, which itself defaults +to 1. Here is the list of possible values in /proc/sys/kernel/sysrq: + + - 0 - disable sysrq completely + - 1 - enable all functions of sysrq + - >1 - bitmask of allowed sysrq functions (see below for detailed function + description):: + + 2 = 0x2 - enable control of console logging level + 4 = 0x4 - enable control of keyboard (SAK, unraw) + 8 = 0x8 - enable debugging dumps of processes etc. + 16 = 0x10 - enable sync command + 32 = 0x20 - enable remount read-only + 64 = 0x40 - enable signalling of processes (term, kill, oom-kill) + 128 = 0x80 - allow reboot/poweroff + 256 = 0x100 - allow nicing of all RT tasks + +You can set the value in the file by the following command:: + + echo "number" >/proc/sys/kernel/sysrq + +The number may be written here either as decimal or as hexadecimal +with the 0x prefix. CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE must always be +written in hexadecimal. + +Note that the value of ``/proc/sys/kernel/sysrq`` influences only the invocation +via a keyboard. Invocation of any operation via ``/proc/sysrq-trigger`` is +always allowed (by a user with admin privileges). + +How do I use the magic SysRq key? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +On x86 + You press the key combo :kbd:`ALT-SysRq-<command key>`. + + .. note:: + Some + keyboards may not have a key labeled 'SysRq'. The 'SysRq' key is + also known as the 'Print Screen' key. Also some keyboards cannot + handle so many keys being pressed at the same time, so you might + have better luck with press :kbd:`Alt`, press :kbd:`SysRq`, + release :kbd:`SysRq`, press :kbd:`<command key>`, release everything. + +On SPARC + You press :kbd:`ALT-STOP-<command key>`, I believe. + +On the serial console (PC style standard serial ports only) + You send a ``BREAK``, then within 5 seconds a command key. Sending + ``BREAK`` twice is interpreted as a normal BREAK. + +On PowerPC + Press :kbd:`ALT - Print Screen` (or :kbd:`F13`) - :kbd:`<command key>`. + :kbd:`Print Screen` (or :kbd:`F13`) - :kbd:`<command key>` may suffice. + +On other + If you know of the key combos for other architectures, please + submit a patch to be included in this section. + +On all + Write a character to /proc/sysrq-trigger. e.g.:: + + echo t > /proc/sysrq-trigger + +The :kbd:`<command key>` is case sensitive. + +What are the 'command' keys? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +=========== =================================================================== +Command Function +=========== =================================================================== +``b`` Will immediately reboot the system without syncing or unmounting + your disks. + +``c`` Will perform a system crash and a crashdump will be taken + if configured. + +``d`` Shows all locks that are held. + +``e`` Send a SIGTERM to all processes, except for init. + +``f`` Will call the oom killer to kill a memory hog process, but do not + panic if nothing can be killed. + +``g`` Used by kgdb (kernel debugger) + +``h`` Will display help (actually any other key than those listed + here will display help. but ``h`` is easy to remember :-) + +``i`` Send a SIGKILL to all processes, except for init. + +``j`` Forcibly "Just thaw it" - filesystems frozen by the FIFREEZE ioctl. + +``k`` Secure Access Key (SAK) Kills all programs on the current virtual + console. NOTE: See important comments below in SAK section. + +``l`` Shows a stack backtrace for all active CPUs. + +``m`` Will dump current memory info to your console. + +``n`` Used to make RT tasks nice-able + +``o`` Will shut your system off (if configured and supported). + +``p`` Will dump the current registers and flags to your console. + +``q`` Will dump per CPU lists of all armed hrtimers (but NOT regular + timer_list timers) and detailed information about all + clockevent devices. + +``r`` Turns off keyboard raw mode and sets it to XLATE. + +``s`` Will attempt to sync all mounted filesystems. + +``t`` Will dump a list of current tasks and their information to your + console. + +``u`` Will attempt to remount all mounted filesystems read-only. + +``v`` Forcefully restores framebuffer console +``v`` Causes ETM buffer dump [ARM-specific] + +``w`` Dumps tasks that are in uninterruptible (blocked) state. + +``x`` Used by xmon interface on ppc/powerpc platforms. + Show global PMU Registers on sparc64. + Dump all TLB entries on MIPS. + +``y`` Show global CPU Registers [SPARC-64 specific] + +``z`` Dump the ftrace buffer + +``0``-``9`` Sets the console log level, controlling which kernel messages + will be printed to your console. (``0``, for example would make + it so that only emergency messages like PANICs or OOPSes would + make it to your console.) +=========== =================================================================== + +Okay, so what can I use them for? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Well, unraw(r) is very handy when your X server or a svgalib program crashes. + +sak(k) (Secure Access Key) is useful when you want to be sure there is no +trojan program running at console which could grab your password +when you would try to login. It will kill all programs on given console, +thus letting you make sure that the login prompt you see is actually +the one from init, not some trojan program. + +.. important:: + + In its true form it is not a true SAK like the one in a + c2 compliant system, and it should not be mistaken as + such. + +It seems others find it useful as (System Attention Key) which is +useful when you want to exit a program that will not let you switch consoles. +(For example, X or a svgalib program.) + +``reboot(b)`` is good when you're unable to shut down, it is an equivalent +of pressing the "reset" button. + +``crash(c)`` can be used to manually trigger a crashdump when the system is hung. +Note that this just triggers a crash if there is no dump mechanism available. + +``sync(s)`` is handy before yanking removable medium or after using a rescue +shell that provides no graceful shutdown -- it will ensure your data is +safely written to the disk. Note that the sync hasn't taken place until you see +the "OK" and "Done" appear on the screen. + +``umount(u)`` can be used to mark filesystems as properly unmounted. From the +running system's point of view, they will be remounted read-only. The remount +isn't complete until you see the "OK" and "Done" message appear on the screen. + +The loglevels ``0``-``9`` are useful when your console is being flooded with +kernel messages you do not want to see. Selecting ``0`` will prevent all but +the most urgent kernel messages from reaching your console. (They will +still be logged if syslogd/klogd are alive, though.) + +``term(e)`` and ``kill(i)`` are useful if you have some sort of runaway process +you are unable to kill any other way, especially if it's spawning other +processes. + +"just thaw ``it(j)``" is useful if your system becomes unresponsive due to a +frozen (probably root) filesystem via the FIFREEZE ioctl. + +Sometimes SysRq seems to get 'stuck' after using it, what can I do? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +When this happens, try tapping shift, alt and control on both sides of the +keyboard, and hitting an invalid sysrq sequence again. (i.e., something like +:kbd:`alt-sysrq-z`). + +Switching to another virtual console (:kbd:`ALT+Fn`) and then back again +should also help. + +I hit SysRq, but nothing seems to happen, what's wrong? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +There are some keyboards that produce a different keycode for SysRq than the +pre-defined value of 99 +(see ``KEY_SYSRQ`` in ``include/uapi/linux/input-event-codes.h``), or +which don't have a SysRq key at all. In these cases, run ``showkey -s`` to find +an appropriate scancode sequence, and use ``setkeycodes <sequence> 99`` to map +this sequence to the usual SysRq code (e.g., ``setkeycodes e05b 99``). It's +probably best to put this command in a boot script. Oh, and by the way, you +exit ``showkey`` by not typing anything for ten seconds. + +I want to add SysRQ key events to a module, how does it work? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +In order to register a basic function with the table, you must first include +the header ``include/linux/sysrq.h``, this will define everything else you need. +Next, you must create a ``sysrq_key_op`` struct, and populate it with A) the key +handler function you will use, B) a help_msg string, that will print when SysRQ +prints help, and C) an action_msg string, that will print right before your +handler is called. Your handler must conform to the prototype in 'sysrq.h'. + +After the ``sysrq_key_op`` is created, you can call the kernel function +``register_sysrq_key(int key, const struct sysrq_key_op *op_p);`` this will +register the operation pointed to by ``op_p`` at table key 'key', +if that slot in the table is blank. At module unload time, you must call +the function ``unregister_sysrq_key(int key, const struct sysrq_key_op *op_p)``, +which will remove the key op pointed to by 'op_p' from the key 'key', if and +only if it is currently registered in that slot. This is in case the slot has +been overwritten since you registered it. + +The Magic SysRQ system works by registering key operations against a key op +lookup table, which is defined in 'drivers/tty/sysrq.c'. This key table has +a number of operations registered into it at compile time, but is mutable, +and 2 functions are exported for interface to it:: + + register_sysrq_key and unregister_sysrq_key. + +Of course, never ever leave an invalid pointer in the table. I.e., when +your module that called register_sysrq_key() exits, it must call +unregister_sysrq_key() to clean up the sysrq key table entry that it used. +Null pointers in the table are always safe. :) + +If for some reason you feel the need to call the handle_sysrq function from +within a function called by handle_sysrq, you must be aware that you are in +a lock (you are also in an interrupt handler, which means don't sleep!), so +you must call ``__handle_sysrq_nolock`` instead. + +When I hit a SysRq key combination only the header appears on the console? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Sysrq output is subject to the same console loglevel control as all +other console output. This means that if the kernel was booted 'quiet' +as is common on distro kernels the output may not appear on the actual +console, even though it will appear in the dmesg buffer, and be accessible +via the dmesg command and to the consumers of ``/proc/kmsg``. As a specific +exception the header line from the sysrq command is passed to all console +consumers as if the current loglevel was maximum. If only the header +is emitted it is almost certain that the kernel loglevel is too low. +Should you require the output on the console channel then you will need +to temporarily up the console loglevel using :kbd:`alt-sysrq-8` or:: + + echo 8 > /proc/sysrq-trigger + +Remember to return the loglevel to normal after triggering the sysrq +command you are interested in. + +I have more questions, who can I ask? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Just ask them on the linux-kernel mailing list: + linux-kernel@vger.kernel.org + +Credits +~~~~~~~ + +- Written by Mydraal <vulpyne@vulpyne.net> +- Updated by Adam Sulmicki <adam@cfar.umd.edu> +- Updated by Jeremy M. Dolan <jmd@turbogeek.org> 2001/01/28 10:15:59 +- Added to by Crutcher Dunnavant <crutcher+kernel@datastacks.com> diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst new file mode 100644 index 000000000..92a8a07f5 --- /dev/null +++ b/Documentation/admin-guide/tainted-kernels.rst @@ -0,0 +1,184 @@ +Tainted kernels +--------------- + +The kernel will mark itself as 'tainted' when something occurs that might be +relevant later when investigating problems. Don't worry too much about this, +most of the time it's not a problem to run a tainted kernel; the information is +mainly of interest once someone wants to investigate some problem, as its real +cause might be the event that got the kernel tainted. That's why bug reports +from tainted kernels will often be ignored by developers, hence try to reproduce +problems with an untainted kernel. + +Note the kernel will remain tainted even after you undo what caused the taint +(i.e. unload a proprietary kernel module), to indicate the kernel remains not +trustworthy. That's also why the kernel will print the tainted state when it +notices an internal problem (a 'kernel bug'), a recoverable error +('kernel oops') or a non-recoverable error ('kernel panic') and writes debug +information about this to the logs ``dmesg`` outputs. It's also possible to +check the tainted state at runtime through a file in ``/proc/``. + + +Tainted flag in bugs, oops or panics messages +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +You find the tainted state near the top in a line starting with 'CPU:'; if or +why the kernel was tainted is shown after the Process ID ('PID:') and a shortened +name of the command ('Comm:') that triggered the event:: + + BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 + Oops: 0002 [#1] SMP PTI + CPU: 0 PID: 4424 Comm: insmod Tainted: P W O 4.20.0-0.rc6.fc30 #1 + Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 + RIP: 0010:my_oops_init+0x13/0x1000 [kpanic] + [...] + +You'll find a 'Not tainted: ' there if the kernel was not tainted at the +time of the event; if it was, then it will print 'Tainted: ' and characters +either letters or blanks. In above example it looks like this:: + + Tainted: P W O + +The meaning of those characters is explained in the table below. In this case +the kernel got tainted earlier because a proprietary Module (``P``) was loaded, +a warning occurred (``W``), and an externally-built module was loaded (``O``). +To decode other letters use the table below. + + +Decoding tainted state at runtime +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +At runtime, you can query the tainted state by reading +``cat /proc/sys/kernel/tainted``. If that returns ``0``, the kernel is not +tainted; any other number indicates the reasons why it is. The easiest way to +decode that number is the script ``tools/debugging/kernel-chktaint``, which your +distribution might ship as part of a package called ``linux-tools`` or +``kernel-tools``; if it doesn't you can download the script from +`git.kernel.org <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/tools/debugging/kernel-chktaint>`_ +and execute it with ``sh kernel-chktaint``, which would print something like +this on the machine that had the statements in the logs that were quoted earlier:: + + Kernel is Tainted for following reasons: + * Proprietary module was loaded (#0) + * Kernel issued warning (#9) + * Externally-built ('out-of-tree') module was loaded (#12) + See Documentation/admin-guide/tainted-kernels.rst in the Linux kernel or + https://www.kernel.org/doc/html/latest/admin-guide/tainted-kernels.html for + a more details explanation of the various taint flags. + Raw taint value as int/string: 4609/'P W O ' + +You can try to decode the number yourself. That's easy if there was only one +reason that got your kernel tainted, as in this case you can find the number +with the table below. If there were multiple reasons you need to decode the +number, as it is a bitfield, where each bit indicates the absence or presence of +a particular type of taint. It's best to leave that to the aforementioned +script, but if you need something quick you can use this shell command to check +which bits are set:: + + $ for i in $(seq 18); do echo $(($i-1)) $(($(cat /proc/sys/kernel/tainted)>>($i-1)&1));done + +Table for decoding tainted state +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +=== === ====== ======================================================== +Bit Log Number Reason that got the kernel tainted +=== === ====== ======================================================== + 0 G/P 1 proprietary module was loaded + 1 _/F 2 module was force loaded + 2 _/S 4 kernel running on an out of specification system + 3 _/R 8 module was force unloaded + 4 _/M 16 processor reported a Machine Check Exception (MCE) + 5 _/B 32 bad page referenced or some unexpected page flags + 6 _/U 64 taint requested by userspace application + 7 _/D 128 kernel died recently, i.e. there was an OOPS or BUG + 8 _/A 256 ACPI table overridden by user + 9 _/W 512 kernel issued warning + 10 _/C 1024 staging driver was loaded + 11 _/I 2048 workaround for bug in platform firmware applied + 12 _/O 4096 externally-built ("out-of-tree") module was loaded + 13 _/E 8192 unsigned module was loaded + 14 _/L 16384 soft lockup occurred + 15 _/K 32768 kernel has been live patched + 16 _/X 65536 auxiliary taint, defined for and used by distros + 17 _/T 131072 kernel was built with the struct randomization plugin + 18 _/N 262144 an in-kernel test has been run +=== === ====== ======================================================== + +Note: The character ``_`` is representing a blank in this table to make reading +easier. + +More detailed explanation for tainting +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + + 0) ``G`` if all modules loaded have a GPL or compatible license, ``P`` if + any proprietary module has been loaded. Modules without a + MODULE_LICENSE or with a MODULE_LICENSE that is not recognised by + insmod as GPL compatible are assumed to be proprietary. + + 1) ``F`` if any module was force loaded by ``insmod -f``, ``' '`` if all + modules were loaded normally. + + 2) ``S`` if the kernel is running on a processor or system that is out of + specification: hardware has been put into an unsupported configuration, + therefore proper execution cannot be guaranteed. + Kernel will be tainted if, for example: + + - on x86: PAE is forced through forcepae on intel CPUs (such as Pentium M) + which do not report PAE but may have a functional implementation, an SMP + kernel is running on non officially capable SMP Athlon CPUs, MSRs are + being poked at from userspace. + - on arm: kernel running on certain CPUs (such as Keystone 2) without + having certain kernel features enabled. + - on arm64: there are mismatched hardware features between CPUs, the + bootloader has booted CPUs in different modes. + - certain drivers are being used on non supported architectures (such as + scsi/snic on something else than x86_64, scsi/ips on non + x86/x86_64/itanium, have broken firmware settings for the + irqchip/irq-gic on arm64 ...). + - x86/x86_64: Microcode late loading is dangerous and will result in + tainting the kernel. It requires that all CPUs rendezvous to make sure + the update happens when the system is as quiescent as possible. However, + a higher priority MCE/SMI/NMI can move control flow away from that + rendezvous and interrupt the update, which can be detrimental to the + machine. + + 3) ``R`` if a module was force unloaded by ``rmmod -f``, ``' '`` if all + modules were unloaded normally. + + 4) ``M`` if any processor has reported a Machine Check Exception, + ``' '`` if no Machine Check Exceptions have occurred. + + 5) ``B`` If a page-release function has found a bad page reference or some + unexpected page flags. This indicates a hardware problem or a kernel bug; + there should be other information in the log indicating why this tainting + occurred. + + 6) ``U`` if a user or user application specifically requested that the + Tainted flag be set, ``' '`` otherwise. + + 7) ``D`` if the kernel has died recently, i.e. there was an OOPS or BUG. + + 8) ``A`` if an ACPI table has been overridden. + + 9) ``W`` if a warning has previously been issued by the kernel. + (Though some warnings may set more specific taint flags.) + + 10) ``C`` if a staging driver has been loaded. + + 11) ``I`` if the kernel is working around a severe bug in the platform + firmware (BIOS or similar). + + 12) ``O`` if an externally-built ("out-of-tree") module has been loaded. + + 13) ``E`` if an unsigned module has been loaded in a kernel supporting + module signature. + + 14) ``L`` if a soft lockup has previously occurred on the system. + + 15) ``K`` if the kernel has been live patched. + + 16) ``X`` Auxiliary taint, defined for and used by Linux distributors. + + 17) ``T`` Kernel was build with the randstruct plugin, which can intentionally + produce extremely unusual kernel structure layouts (even performance + pathological ones), which is important to know when debugging. Set at + build time. diff --git a/Documentation/admin-guide/thermal/index.rst b/Documentation/admin-guide/thermal/index.rst new file mode 100644 index 000000000..193b7b01a --- /dev/null +++ b/Documentation/admin-guide/thermal/index.rst @@ -0,0 +1,8 @@ +================= +Thermal Subsystem +================= + +.. toctree:: + :maxdepth: 1 + + intel_powerclamp diff --git a/Documentation/admin-guide/thermal/intel_powerclamp.rst b/Documentation/admin-guide/thermal/intel_powerclamp.rst new file mode 100644 index 000000000..08509b978 --- /dev/null +++ b/Documentation/admin-guide/thermal/intel_powerclamp.rst @@ -0,0 +1,345 @@ +======================= +Intel Powerclamp Driver +======================= + +By: + - Arjan van de Ven <arjan@linux.intel.com> + - Jacob Pan <jacob.jun.pan@linux.intel.com> + +.. Contents: + + (*) Introduction + - Goals and Objectives + + (*) Theory of Operation + - Idle Injection + - Calibration + + (*) Performance Analysis + - Effectiveness and Limitations + - Power vs Performance + - Scalability + - Calibration + - Comparison with Alternative Techniques + + (*) Usage and Interfaces + - Generic Thermal Layer (sysfs) + - Kernel APIs (TBD) + + (*) Module Parameters + +INTRODUCTION +============ + +Consider the situation where a system’s power consumption must be +reduced at runtime, due to power budget, thermal constraint, or noise +level, and where active cooling is not preferred. Software managed +passive power reduction must be performed to prevent the hardware +actions that are designed for catastrophic scenarios. + +Currently, P-states, T-states (clock modulation), and CPU offlining +are used for CPU throttling. + +On Intel CPUs, C-states provide effective power reduction, but so far +they’re only used opportunistically, based on workload. With the +development of intel_powerclamp driver, the method of synchronizing +idle injection across all online CPU threads was introduced. The goal +is to achieve forced and controllable C-state residency. + +Test/Analysis has been made in the areas of power, performance, +scalability, and user experience. In many cases, clear advantage is +shown over taking the CPU offline or modulating the CPU clock. + + +THEORY OF OPERATION +=================== + +Idle Injection +-------------- + +On modern Intel processors (Nehalem or later), package level C-state +residency is available in MSRs, thus also available to the kernel. + +These MSRs are:: + + #define MSR_PKG_C2_RESIDENCY 0x60D + #define MSR_PKG_C3_RESIDENCY 0x3F8 + #define MSR_PKG_C6_RESIDENCY 0x3F9 + #define MSR_PKG_C7_RESIDENCY 0x3FA + +If the kernel can also inject idle time to the system, then a +closed-loop control system can be established that manages package +level C-state. The intel_powerclamp driver is conceived as such a +control system, where the target set point is a user-selected idle +ratio (based on power reduction), and the error is the difference +between the actual package level C-state residency ratio and the target idle +ratio. + +Injection is controlled by high priority kernel threads, spawned for +each online CPU. + +These kernel threads, with SCHED_FIFO class, are created to perform +clamping actions of controlled duty ratio and duration. Each per-CPU +thread synchronizes its idle time and duration, based on the rounding +of jiffies, so accumulated errors can be prevented to avoid a jittery +effect. Threads are also bound to the CPU such that they cannot be +migrated, unless the CPU is taken offline. In this case, threads +belong to the offlined CPUs will be terminated immediately. + +Running as SCHED_FIFO and relatively high priority, also allows such +scheme to work for both preemptible and non-preemptible kernels. +Alignment of idle time around jiffies ensures scalability for HZ +values. This effect can be better visualized using a Perf timechart. +The following diagram shows the behavior of kernel thread +kidle_inject/cpu. During idle injection, it runs monitor/mwait idle +for a given "duration", then relinquishes the CPU to other tasks, +until the next time interval. + +The NOHZ schedule tick is disabled during idle time, but interrupts +are not masked. Tests show that the extra wakeups from scheduler tick +have a dramatic impact on the effectiveness of the powerclamp driver +on large scale systems (Westmere system with 80 processors). + +:: + + CPU0 + ____________ ____________ + kidle_inject/0 | sleep | mwait | sleep | + _________| |________| |_______ + duration + CPU1 + ____________ ____________ + kidle_inject/1 | sleep | mwait | sleep | + _________| |________| |_______ + ^ + | + | + roundup(jiffies, interval) + +Only one CPU is allowed to collect statistics and update global +control parameters. This CPU is referred to as the controlling CPU in +this document. The controlling CPU is elected at runtime, with a +policy that favors BSP, taking into account the possibility of a CPU +hot-plug. + +In terms of dynamics of the idle control system, package level idle +time is considered largely as a non-causal system where its behavior +cannot be based on the past or current input. Therefore, the +intel_powerclamp driver attempts to enforce the desired idle time +instantly as given input (target idle ratio). After injection, +powerclamp monitors the actual idle for a given time window and adjust +the next injection accordingly to avoid over/under correction. + +When used in a causal control system, such as a temperature control, +it is up to the user of this driver to implement algorithms where +past samples and outputs are included in the feedback. For example, a +PID-based thermal controller can use the powerclamp driver to +maintain a desired target temperature, based on integral and +derivative gains of the past samples. + + + +Calibration +----------- +During scalability testing, it is observed that synchronized actions +among CPUs become challenging as the number of cores grows. This is +also true for the ability of a system to enter package level C-states. + +To make sure the intel_powerclamp driver scales well, online +calibration is implemented. The goals for doing such a calibration +are: + +a) determine the effective range of idle injection ratio +b) determine the amount of compensation needed at each target ratio + +Compensation to each target ratio consists of two parts: + + a) steady state error compensation + + This is to offset the error occurring when the system can + enter idle without extra wakeups (such as external interrupts). + + b) dynamic error compensation + + When an excessive amount of wakeups occurs during idle, an + additional idle ratio can be added to quiet interrupts, by + slowing down CPU activities. + +A debugfs file is provided for the user to examine compensation +progress and results, such as on a Westmere system:: + + [jacob@nex01 ~]$ cat + /sys/kernel/debug/intel_powerclamp/powerclamp_calib + controlling cpu: 0 + pct confidence steady dynamic (compensation) + 0 0 0 0 + 1 1 0 0 + 2 1 1 0 + 3 3 1 0 + 4 3 1 0 + 5 3 1 0 + 6 3 1 0 + 7 3 1 0 + 8 3 1 0 + ... + 30 3 2 0 + 31 3 2 0 + 32 3 1 0 + 33 3 2 0 + 34 3 1 0 + 35 3 2 0 + 36 3 1 0 + 37 3 2 0 + 38 3 1 0 + 39 3 2 0 + 40 3 3 0 + 41 3 1 0 + 42 3 2 0 + 43 3 1 0 + 44 3 1 0 + 45 3 2 0 + 46 3 3 0 + 47 3 0 0 + 48 3 2 0 + 49 3 3 0 + +Calibration occurs during runtime. No offline method is available. +Steady state compensation is used only when confidence levels of all +adjacent ratios have reached satisfactory level. A confidence level +is accumulated based on clean data collected at runtime. Data +collected during a period without extra interrupts is considered +clean. + +To compensate for excessive amounts of wakeup during idle, additional +idle time is injected when such a condition is detected. Currently, +we have a simple algorithm to double the injection ratio. A possible +enhancement might be to throttle the offending IRQ, such as delaying +EOI for level triggered interrupts. But it is a challenge to be +non-intrusive to the scheduler or the IRQ core code. + + +CPU Online/Offline +------------------ +Per-CPU kernel threads are started/stopped upon receiving +notifications of CPU hotplug activities. The intel_powerclamp driver +keeps track of clamping kernel threads, even after they are migrated +to other CPUs, after a CPU offline event. + + +Performance Analysis +==================== +This section describes the general performance data collected on +multiple systems, including Westmere (80P) and Ivy Bridge (4P, 8P). + +Effectiveness and Limitations +----------------------------- +The maximum range that idle injection is allowed is capped at 50 +percent. As mentioned earlier, since interrupts are allowed during +forced idle time, excessive interrupts could result in less +effectiveness. The extreme case would be doing a ping -f to generated +flooded network interrupts without much CPU acknowledgement. In this +case, little can be done from the idle injection threads. In most +normal cases, such as scp a large file, applications can be throttled +by the powerclamp driver, since slowing down the CPU also slows down +network protocol processing, which in turn reduces interrupts. + +When control parameters change at runtime by the controlling CPU, it +may take an additional period for the rest of the CPUs to catch up +with the changes. During this time, idle injection is out of sync, +thus not able to enter package C- states at the expected ratio. But +this effect is minor, in that in most cases change to the target +ratio is updated much less frequently than the idle injection +frequency. + +Scalability +----------- +Tests also show a minor, but measurable, difference between the 4P/8P +Ivy Bridge system and the 80P Westmere server under 50% idle ratio. +More compensation is needed on Westmere for the same amount of +target idle ratio. The compensation also increases as the idle ratio +gets larger. The above reason constitutes the need for the +calibration code. + +On the IVB 8P system, compared to an offline CPU, powerclamp can +achieve up to 40% better performance per watt. (measured by a spin +counter summed over per CPU counting threads spawned for all running +CPUs). + +Usage and Interfaces +==================== +The powerclamp driver is registered to the generic thermal layer as a +cooling device. Currently, it’s not bound to any thermal zones:: + + jacob@chromoly:/sys/class/thermal/cooling_device14$ grep . * + cur_state:0 + max_state:50 + type:intel_powerclamp + +cur_state allows user to set the desired idle percentage. Writing 0 to +cur_state will stop idle injection. Writing a value between 1 and +max_state will start the idle injection. Reading cur_state returns the +actual and current idle percentage. This may not be the same value +set by the user in that current idle percentage depends on workload +and includes natural idle. When idle injection is disabled, reading +cur_state returns value -1 instead of 0 which is to avoid confusing +100% busy state with the disabled state. + +Example usage: + +- To inject 25% idle time:: + + $ sudo sh -c "echo 25 > /sys/class/thermal/cooling_device80/cur_state + +If the system is not busy and has more than 25% idle time already, +then the powerclamp driver will not start idle injection. Using Top +will not show idle injection kernel threads. + +If the system is busy (spin test below) and has less than 25% natural +idle time, powerclamp kernel threads will do idle injection. Forced +idle time is accounted as normal idle in that common code path is +taken as the idle task. + +In this example, 24.1% idle is shown. This helps the system admin or +user determine the cause of slowdown, when a powerclamp driver is in action:: + + + Tasks: 197 total, 1 running, 196 sleeping, 0 stopped, 0 zombie + Cpu(s): 71.2%us, 4.7%sy, 0.0%ni, 24.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st + Mem: 3943228k total, 1689632k used, 2253596k free, 74960k buffers + Swap: 4087804k total, 0k used, 4087804k free, 945336k cached + + PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND + 3352 jacob 20 0 262m 644 428 S 286 0.0 0:17.16 spin + 3341 root -51 0 0 0 0 D 25 0.0 0:01.62 kidle_inject/0 + 3344 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/3 + 3342 root -51 0 0 0 0 D 25 0.0 0:01.61 kidle_inject/1 + 3343 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/2 + 2935 jacob 20 0 696m 125m 35m S 5 3.3 0:31.11 firefox + 1546 root 20 0 158m 20m 6640 S 3 0.5 0:26.97 Xorg + 2100 jacob 20 0 1223m 88m 30m S 3 2.3 0:23.68 compiz + +Tests have shown that by using the powerclamp driver as a cooling +device, a PID based userspace thermal controller can manage to +control CPU temperature effectively, when no other thermal influence +is added. For example, a UltraBook user can compile the kernel under +certain temperature (below most active trip points). + +Module Parameters +================= + +``cpumask`` (RW) + A bit mask of CPUs to inject idle. The format of the bitmask is same as + used in other subsystems like in /proc/irq/\*/smp_affinity. The mask is + comma separated 32 bit groups. Each CPU is one bit. For example for a 256 + CPU system the full mask is: + ffffffff,ffffffff,ffffffff,ffffffff,ffffffff,ffffffff,ffffffff,ffffffff + + The rightmost mask is for CPU 0-32. + +``max_idle`` (RW) + Maximum injected idle time to the total CPU time ratio in percent range + from 1 to 100. Even if the cooling device max_state is always 100 (100%), + this parameter allows to add a max idle percent limit. The default is 50, + to match the current implementation of powerclamp driver. Also doesn't + allow value more than 75, if the cpumask includes every CPU present in + the system. diff --git a/Documentation/admin-guide/thunderbolt.rst b/Documentation/admin-guide/thunderbolt.rst new file mode 100644 index 000000000..2ed79f41a --- /dev/null +++ b/Documentation/admin-guide/thunderbolt.rst @@ -0,0 +1,336 @@ +.. SPDX-License-Identifier: GPL-2.0 + +====================== + USB4 and Thunderbolt +====================== +USB4 is the public specification based on Thunderbolt 3 protocol with +some differences at the register level among other things. Connection +manager is an entity running on the host router (host controller) +responsible for enumerating routers and establishing tunnels. A +connection manager can be implemented either in firmware or software. +Typically PCs come with a firmware connection manager for Thunderbolt 3 +and early USB4 capable systems. Apple systems on the other hand use +software connection manager and the later USB4 compliant devices follow +the suit. + +The Linux Thunderbolt driver supports both and can detect at runtime which +connection manager implementation is to be used. To be on the safe side the +software connection manager in Linux also advertises security level +``user`` which means PCIe tunneling is disabled by default. The +documentation below applies to both implementations with the exception that +the software connection manager only supports ``user`` security level and +is expected to be accompanied with an IOMMU based DMA protection. + +Security levels and how to use them +----------------------------------- +The interface presented here is not meant for end users. Instead there +should be a userspace tool that handles all the low-level details, keeps +a database of the authorized devices and prompts users for new connections. + +More details about the sysfs interface for Thunderbolt devices can be +found in ``Documentation/ABI/testing/sysfs-bus-thunderbolt``. + +Those users who just want to connect any device without any sort of +manual work can add following line to +``/etc/udev/rules.d/99-local.rules``:: + + ACTION=="add", SUBSYSTEM=="thunderbolt", ATTR{authorized}=="0", ATTR{authorized}="1" + +This will authorize all devices automatically when they appear. However, +keep in mind that this bypasses the security levels and makes the system +vulnerable to DMA attacks. + +Starting with Intel Falcon Ridge Thunderbolt controller there are 4 +security levels available. Intel Titan Ridge added one more security level +(usbonly). The reason for these is the fact that the connected devices can +be DMA masters and thus read contents of the host memory without CPU and OS +knowing about it. There are ways to prevent this by setting up an IOMMU but +it is not always available for various reasons. + +Some USB4 systems have a BIOS setting to disable PCIe tunneling. This is +treated as another security level (nopcie). + +The security levels are as follows: + + none + All devices are automatically connected by the firmware. No user + approval is needed. In BIOS settings this is typically called + *Legacy mode*. + + user + User is asked whether the device is allowed to be connected. + Based on the device identification information available through + ``/sys/bus/thunderbolt/devices``, the user then can make the decision. + In BIOS settings this is typically called *Unique ID*. + + secure + User is asked whether the device is allowed to be connected. In + addition to UUID the device (if it supports secure connect) is sent + a challenge that should match the expected one based on a random key + written to the ``key`` sysfs attribute. In BIOS settings this is + typically called *One time saved key*. + + dponly + The firmware automatically creates tunnels for Display Port and + USB. No PCIe tunneling is done. In BIOS settings this is + typically called *Display Port Only*. + + usbonly + The firmware automatically creates tunnels for the USB controller and + Display Port in a dock. All PCIe links downstream of the dock are + removed. + + nopcie + PCIe tunneling is disabled/forbidden from the BIOS. Available in some + USB4 systems. + +The current security level can be read from +``/sys/bus/thunderbolt/devices/domainX/security`` where ``domainX`` is +the Thunderbolt domain the host controller manages. There is typically +one domain per Thunderbolt host controller. + +If the security level reads as ``user`` or ``secure`` the connected +device must be authorized by the user before PCIe tunnels are created +(e.g the PCIe device appears). + +Each Thunderbolt device plugged in will appear in sysfs under +``/sys/bus/thunderbolt/devices``. The device directory carries +information that can be used to identify the particular device, +including its name and UUID. + +Authorizing devices when security level is ``user`` or ``secure`` +----------------------------------------------------------------- +When a device is plugged in it will appear in sysfs as follows:: + + /sys/bus/thunderbolt/devices/0-1/authorized - 0 + /sys/bus/thunderbolt/devices/0-1/device - 0x8004 + /sys/bus/thunderbolt/devices/0-1/device_name - Thunderbolt to FireWire Adapter + /sys/bus/thunderbolt/devices/0-1/vendor - 0x1 + /sys/bus/thunderbolt/devices/0-1/vendor_name - Apple, Inc. + /sys/bus/thunderbolt/devices/0-1/unique_id - e0376f00-0300-0100-ffff-ffffffffffff + +The ``authorized`` attribute reads 0 which means no PCIe tunnels are +created yet. The user can authorize the device by simply entering:: + + # echo 1 > /sys/bus/thunderbolt/devices/0-1/authorized + +This will create the PCIe tunnels and the device is now connected. + +If the device supports secure connect, and the domain security level is +set to ``secure``, it has an additional attribute ``key`` which can hold +a random 32-byte value used for authorization and challenging the device in +future connects:: + + /sys/bus/thunderbolt/devices/0-3/authorized - 0 + /sys/bus/thunderbolt/devices/0-3/device - 0x305 + /sys/bus/thunderbolt/devices/0-3/device_name - AKiTiO Thunder3 PCIe Box + /sys/bus/thunderbolt/devices/0-3/key - + /sys/bus/thunderbolt/devices/0-3/vendor - 0x41 + /sys/bus/thunderbolt/devices/0-3/vendor_name - inXtron + /sys/bus/thunderbolt/devices/0-3/unique_id - dc010000-0000-8508-a22d-32ca6421cb16 + +Notice the key is empty by default. + +If the user does not want to use secure connect they can just ``echo 1`` +to the ``authorized`` attribute and the PCIe tunnels will be created in +the same way as in the ``user`` security level. + +If the user wants to use secure connect, the first time the device is +plugged a key needs to be created and sent to the device:: + + # key=$(openssl rand -hex 32) + # echo $key > /sys/bus/thunderbolt/devices/0-3/key + # echo 1 > /sys/bus/thunderbolt/devices/0-3/authorized + +Now the device is connected (PCIe tunnels are created) and in addition +the key is stored on the device NVM. + +Next time the device is plugged in the user can verify (challenge) the +device using the same key:: + + # echo $key > /sys/bus/thunderbolt/devices/0-3/key + # echo 2 > /sys/bus/thunderbolt/devices/0-3/authorized + +If the challenge the device returns back matches the one we expect based +on the key, the device is connected and the PCIe tunnels are created. +However, if the challenge fails no tunnels are created and error is +returned to the user. + +If the user still wants to connect the device they can either approve +the device without a key or write a new key and write 1 to the +``authorized`` file to get the new key stored on the device NVM. + +De-authorizing devices +---------------------- +It is possible to de-authorize devices by writing ``0`` to their +``authorized`` attribute. This requires support from the connection +manager implementation and can be checked by reading domain +``deauthorization`` attribute. If it reads ``1`` then the feature is +supported. + +When a device is de-authorized the PCIe tunnel from the parent device +PCIe downstream (or root) port to the device PCIe upstream port is torn +down. This is essentially the same thing as PCIe hot-remove and the PCIe +toplogy in question will not be accessible anymore until the device is +authorized again. If there is storage such as NVMe or similar involved, +there is a risk for data loss if the filesystem on that storage is not +properly shut down. You have been warned! + +DMA protection utilizing IOMMU +------------------------------ +Recent systems from 2018 and forward with Thunderbolt ports may natively +support IOMMU. This means that Thunderbolt security is handled by an IOMMU +so connected devices cannot access memory regions outside of what is +allocated for them by drivers. When Linux is running on such system it +automatically enables IOMMU if not enabled by the user already. These +systems can be identified by reading ``1`` from +``/sys/bus/thunderbolt/devices/domainX/iommu_dma_protection`` attribute. + +The driver does not do anything special in this case but because DMA +protection is handled by the IOMMU, security levels (if set) are +redundant. For this reason some systems ship with security level set to +``none``. Other systems have security level set to ``user`` in order to +support downgrade to older OS, so users who want to automatically +authorize devices when IOMMU DMA protection is enabled can use the +following ``udev`` rule:: + + ACTION=="add", SUBSYSTEM=="thunderbolt", ATTRS{iommu_dma_protection}=="1", ATTR{authorized}=="0", ATTR{authorized}="1" + +Upgrading NVM on Thunderbolt device, host or retimer +---------------------------------------------------- +Since most of the functionality is handled in firmware running on a +host controller or a device, it is important that the firmware can be +upgraded to the latest where possible bugs in it have been fixed. +Typically OEMs provide this firmware from their support site. + +There is also a central site which has links where to download firmware +for some machines: + + `Thunderbolt Updates <https://thunderbolttechnology.net/updates>`_ + +Before you upgrade firmware on a device, host or retimer, please make +sure it is a suitable upgrade. Failing to do that may render the device +in a state where it cannot be used properly anymore without special +tools! + +Host NVM upgrade on Apple Macs is not supported. + +Once the NVM image has been downloaded, you need to plug in a +Thunderbolt device so that the host controller appears. It does not +matter which device is connected (unless you are upgrading NVM on a +device - then you need to connect that particular device). + +Note an OEM-specific method to power the controller up ("force power") may +be available for your system in which case there is no need to plug in a +Thunderbolt device. + +After that we can write the firmware to the non-active parts of the NVM +of the host or device. As an example here is how Intel NUC6i7KYK (Skull +Canyon) Thunderbolt controller NVM is upgraded:: + + # dd if=KYK_TBT_FW_0018.bin of=/sys/bus/thunderbolt/devices/0-0/nvm_non_active0/nvmem + +Once the operation completes we can trigger NVM authentication and +upgrade process as follows:: + + # echo 1 > /sys/bus/thunderbolt/devices/0-0/nvm_authenticate + +If no errors are returned, the host controller shortly disappears. Once +it comes back the driver notices it and initiates a full power cycle. +After a while the host controller appears again and this time it should +be fully functional. + +We can verify that the new NVM firmware is active by running the following +commands:: + + # cat /sys/bus/thunderbolt/devices/0-0/nvm_authenticate + 0x0 + # cat /sys/bus/thunderbolt/devices/0-0/nvm_version + 18.0 + +If ``nvm_authenticate`` contains anything other than 0x0 it is the error +code from the last authentication cycle, which means the authentication +of the NVM image failed. + +Note names of the NVMem devices ``nvm_activeN`` and ``nvm_non_activeN`` +depend on the order they are registered in the NVMem subsystem. N in +the name is the identifier added by the NVMem subsystem. + +Upgrading on-board retimer NVM when there is no cable connected +--------------------------------------------------------------- +If the platform supports, it may be possible to upgrade the retimer NVM +firmware even when there is nothing connected to the USB4 +ports. When this is the case the ``usb4_portX`` devices have two special +attributes: ``offline`` and ``rescan``. The way to upgrade the firmware +is to first put the USB4 port into offline mode:: + + # echo 1 > /sys/bus/thunderbolt/devices/0-0/usb4_port1/offline + +This step makes sure the port does not respond to any hotplug events, +and also ensures the retimers are powered on. The next step is to scan +for the retimers:: + + # echo 1 > /sys/bus/thunderbolt/devices/0-0/usb4_port1/rescan + +This enumerates and adds the on-board retimers. Now retimer NVM can be +upgraded in the same way than with cable connected (see previous +section). However, the retimer is not disconnected as we are offline +mode) so after writing ``1`` to ``nvm_authenticate`` one should wait for +5 or more seconds before running rescan again:: + + # echo 1 > /sys/bus/thunderbolt/devices/0-0/usb4_port1/rescan + +This point if everything went fine, the port can be put back to +functional state again:: + + # echo 0 > /sys/bus/thunderbolt/devices/0-0/usb4_port1/offline + +Upgrading NVM when host controller is in safe mode +-------------------------------------------------- +If the existing NVM is not properly authenticated (or is missing) the +host controller goes into safe mode which means that the only available +functionality is flashing a new NVM image. When in this mode, reading +``nvm_version`` fails with ``ENODATA`` and the device identification +information is missing. + +To recover from this mode, one needs to flash a valid NVM image to the +host controller in the same way it is done in the previous chapter. + +Networking over Thunderbolt cable +--------------------------------- +Thunderbolt technology allows software communication between two hosts +connected by a Thunderbolt cable. + +It is possible to tunnel any kind of traffic over a Thunderbolt link but +currently we only support Apple ThunderboltIP protocol. + +If the other host is running Windows or macOS, the only thing you need to +do is to connect a Thunderbolt cable between the two hosts; the +``thunderbolt-net`` driver is loaded automatically. If the other host is +also Linux you should load ``thunderbolt-net`` manually on one host (it +does not matter which one):: + + # modprobe thunderbolt-net + +This triggers module load on the other host automatically. If the driver +is built-in to the kernel image, there is no need to do anything. + +The driver will create one virtual ethernet interface per Thunderbolt +port which are named like ``thunderbolt0`` and so on. From this point +you can either use standard userspace tools like ``ifconfig`` to +configure the interface or let your GUI handle it automatically. + +Forcing power +------------- +Many OEMs include a method that can be used to force the power of a +Thunderbolt controller to an "On" state even if nothing is connected. +If supported by your machine this will be exposed by the WMI bus with +a sysfs attribute called "force_power". + +For example the intel-wmi-thunderbolt driver exposes this attribute in: + /sys/bus/wmi/devices/86CCFD48-205E-4A77-9C48-2021CBEDE341/force_power + + To force the power to on, write 1 to this attribute file. + To disable force power, write 0 to this attribute file. + +Note: it's currently not possible to query the force power state of a platform. diff --git a/Documentation/admin-guide/ufs.rst b/Documentation/admin-guide/ufs.rst new file mode 100644 index 000000000..55d15297f --- /dev/null +++ b/Documentation/admin-guide/ufs.rst @@ -0,0 +1,68 @@ +========= +Using UFS +========= + +mount -t ufs -o ufstype=type_of_ufs device dir + + +UFS Options +=========== + +ufstype=type_of_ufs + UFS is a file system widely used in different operating systems. + The problem are differences among implementations. Features of + some implementations are undocumented, so its hard to recognize + type of ufs automatically. That's why user must specify type of + ufs manually by mount option ufstype. Possible values are: + + old + old format of ufs + default value, supported as read-only + + 44bsd + used in FreeBSD, NetBSD, OpenBSD + supported as read-write + + ufs2 + used in FreeBSD 5.x + supported as read-write + + 5xbsd + synonym for ufs2 + + sun + used in SunOS (Solaris) + supported as read-write + + sunx86 + used in SunOS for Intel (Solarisx86) + supported as read-write + + hp + used in HP-UX + supported as read-only + + nextstep + used in NextStep + supported as read-only + + nextstep-cd + used for NextStep CDROMs (block_size == 2048) + supported as read-only + + openstep + used in OpenStep + supported as read-only + + +Possible Problems +----------------- + +See next section, if you have any. + + +Bug Reports +----------- + +Any ufs bug report you can send to daniel.pirkl@email.cz or +to dushistov@mail.ru (do not send partition tables bug reports). diff --git a/Documentation/admin-guide/unicode.rst b/Documentation/admin-guide/unicode.rst new file mode 100644 index 000000000..cba7e5017 --- /dev/null +++ b/Documentation/admin-guide/unicode.rst @@ -0,0 +1,188 @@ +Unicode support +=============== + + Last update: 2005-01-17, version 1.4 + +Note: The original version of this document, which was maintained at +lanana.org as part of the Linux Assigned Names And Numbers Authority +(LANANA) project, is no longer existent. So, this version in the +mainline Linux kernel is now the maintained main document. + +Introduction +------------ + +The Linux kernel code has been rewritten to use Unicode to map +characters to fonts. By downloading a single Unicode-to-font table, +both the eight-bit character sets and UTF-8 mode are changed to use +the font as indicated. + +This changes the semantics of the eight-bit character tables subtly. +The four character tables are now: + +=============== =============================== ================ +Map symbol Map name Escape code (G0) +=============== =============================== ================ +LAT1_MAP Latin-1 (ISO 8859-1) ESC ( B +GRAF_MAP DEC VT100 pseudographics ESC ( 0 +IBMPC_MAP IBM code page 437 ESC ( U +USER_MAP User defined ESC ( K +=============== =============================== ================ + +In particular, ESC ( U is no longer "straight to font", since the font +might be completely different than the IBM character set. This +permits for example the use of block graphics even with a Latin-1 font +loaded. + +Note that although these codes are similar to ISO 2022, neither the +codes nor their uses match ISO 2022; Linux has two 8-bit codes (G0 and +G1), whereas ISO 2022 has four 7-bit codes (G0-G3). + +In accordance with the Unicode standard/ISO 10646 the range U+F000 to +U+F8FF has been reserved for OS-wide allocation (the Unicode Standard +refers to this as a "Corporate Zone", since this is inaccurate for +Linux we call it the "Linux Zone"). U+F000 was picked as the starting +point since it lets the direct-mapping area start on a large power of +two (in case 1024- or 2048-character fonts ever become necessary). +This leaves U+E000 to U+EFFF as End User Zone. + +[v1.2]: The Unicodes range from U+F000 and up to U+F7FF have been +hard-coded to map directly to the loaded font, bypassing the +translation table. The user-defined map now defaults to U+F000 to +U+F0FF, emulating the previous behaviour. In practice, this range +might be shorter; for example, vgacon can only handle 256-character +(U+F000..U+F0FF) or 512-character (U+F000..U+F1FF) fonts. + + +Actual characters assigned in the Linux Zone +-------------------------------------------- + +In addition, the following characters not present in Unicode 1.1.4 +have been defined; these are used by the DEC VT graphics map. [v1.2] +THIS USE IS OBSOLETE AND SHOULD NO LONGER BE USED; PLEASE SEE BELOW. + +====== ====================================== +U+F800 DEC VT GRAPHICS HORIZONTAL LINE SCAN 1 +U+F801 DEC VT GRAPHICS HORIZONTAL LINE SCAN 3 +U+F803 DEC VT GRAPHICS HORIZONTAL LINE SCAN 7 +U+F804 DEC VT GRAPHICS HORIZONTAL LINE SCAN 9 +====== ====================================== + +The DEC VT220 uses a 6x10 character matrix, and these characters form +a smooth progression in the DEC VT graphics character set. I have +omitted the scan 5 line, since it is also used as a block-graphics +character, and hence has been coded as U+2500 FORMS LIGHT HORIZONTAL. + +[v1.3]: These characters have been officially added to Unicode 3.2.0; +they are added at U+23BA, U+23BB, U+23BC, U+23BD. Linux now uses the +new values. + +[v1.2]: The following characters have been added to represent common +keyboard symbols that are unlikely to ever be added to Unicode proper +since they are horribly vendor-specific. This, of course, is an +excellent example of horrible design. + +====== ====================================== +U+F810 KEYBOARD SYMBOL FLYING FLAG +U+F811 KEYBOARD SYMBOL PULLDOWN MENU +U+F812 KEYBOARD SYMBOL OPEN APPLE +U+F813 KEYBOARD SYMBOL SOLID APPLE +====== ====================================== + +Klingon language support +------------------------ + +In 1996, Linux was the first operating system in the world to add +support for the artificial language Klingon, created by Marc Okrand +for the "Star Trek" television series. This encoding was later +adopted by the ConScript Unicode Registry and proposed (but ultimately +rejected) for inclusion in Unicode Plane 1. Thus, it remains as a +Linux/CSUR private assignment in the Linux Zone. + +This encoding has been endorsed by the Klingon Language Institute. +For more information, contact them at: + + http://www.kli.org/ + +Since the characters in the beginning of the Linux CZ have been more +of the dingbats/symbols/forms type and this is a language, I have +located it at the end, on a 16-cell boundary in keeping with standard +Unicode practice. + +.. note:: + + This range is now officially managed by the ConScript Unicode + Registry. The normative reference is at: + + https://www.evertype.com/standards/csur/klingon.html + +Klingon has an alphabet of 26 characters, a positional numeric writing +system with 10 digits, and is written left-to-right, top-to-bottom. + +Several glyph forms for the Klingon alphabet have been proposed. +However, since the set of symbols appear to be consistent throughout, +with only the actual shapes being different, in keeping with standard +Unicode practice these differences are considered font variants. + +====== ======================================================= +U+F8D0 KLINGON LETTER A +U+F8D1 KLINGON LETTER B +U+F8D2 KLINGON LETTER CH +U+F8D3 KLINGON LETTER D +U+F8D4 KLINGON LETTER E +U+F8D5 KLINGON LETTER GH +U+F8D6 KLINGON LETTER H +U+F8D7 KLINGON LETTER I +U+F8D8 KLINGON LETTER J +U+F8D9 KLINGON LETTER L +U+F8DA KLINGON LETTER M +U+F8DB KLINGON LETTER N +U+F8DC KLINGON LETTER NG +U+F8DD KLINGON LETTER O +U+F8DE KLINGON LETTER P +U+F8DF KLINGON LETTER Q + - Written <q> in standard Okrand Latin transliteration +U+F8E0 KLINGON LETTER QH + - Written <Q> in standard Okrand Latin transliteration +U+F8E1 KLINGON LETTER R +U+F8E2 KLINGON LETTER S +U+F8E3 KLINGON LETTER T +U+F8E4 KLINGON LETTER TLH +U+F8E5 KLINGON LETTER U +U+F8E6 KLINGON LETTER V +U+F8E7 KLINGON LETTER W +U+F8E8 KLINGON LETTER Y +U+F8E9 KLINGON LETTER GLOTTAL STOP + +U+F8F0 KLINGON DIGIT ZERO +U+F8F1 KLINGON DIGIT ONE +U+F8F2 KLINGON DIGIT TWO +U+F8F3 KLINGON DIGIT THREE +U+F8F4 KLINGON DIGIT FOUR +U+F8F5 KLINGON DIGIT FIVE +U+F8F6 KLINGON DIGIT SIX +U+F8F7 KLINGON DIGIT SEVEN +U+F8F8 KLINGON DIGIT EIGHT +U+F8F9 KLINGON DIGIT NINE + +U+F8FD KLINGON COMMA +U+F8FE KLINGON FULL STOP +U+F8FF KLINGON SYMBOL FOR EMPIRE +====== ======================================================= + +Other Fictional and Artificial Scripts +-------------------------------------- + +Since the assignment of the Klingon Linux Unicode block, a registry of +fictional and artificial scripts has been established by John Cowan +<jcowan@reutershealth.com> and Michael Everson <everson@evertype.com>. +The ConScript Unicode Registry is accessible at: + + https://www.evertype.com/standards/csur/ + +The ranges used fall at the low end of the End User Zone and can hence +not be normatively assigned, but it is recommended that people who +wish to encode fictional scripts use these codes, in the interest of +interoperability. For Klingon, CSUR has adopted the Linux encoding. +The CSUR people are driving adding Tengwar and Cirth into Unicode +Plane 1; the addition of Klingon to Unicode Plane 1 has been rejected +and so the above encoding remains official. diff --git a/Documentation/admin-guide/vga-softcursor.rst b/Documentation/admin-guide/vga-softcursor.rst new file mode 100644 index 000000000..f52175457 --- /dev/null +++ b/Documentation/admin-guide/vga-softcursor.rst @@ -0,0 +1,62 @@ +Software cursor for VGA +======================= + +by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz> +and Martin Mares <mj@atrey.karlin.mff.cuni.cz> + +Linux now has some ability to manipulate cursor appearance. Normally, +you can set the size of hardware cursor. You can now play a few new +tricks: you can make your cursor look like a non-blinking red block, +make it inverse background of the character it's over or to highlight +that character and still choose whether the original hardware cursor +should remain visible or not. There may be other things I have never +thought of. + +The cursor appearance is controlled by a ``<ESC>[?1;2;3c`` escape sequence +where 1, 2 and 3 are parameters described below. If you omit any of them, +they will default to zeroes. + +first Parameter + specifies cursor size:: + + 0=default + 1=invisible + 2=underline, + ... + 8=full block + + 16 if you want the software cursor to be applied + + 32 if you want to always change the background color + + 64 if you dislike having the background the same as the + foreground. + + Highlights are ignored for the last two flags. + +second parameter + selects character attribute bits you want to change + (by simply XORing them with the value of this parameter). On standard + VGA, the high four bits specify background and the low four the + foreground. In both groups, low three bits set color (as in normal + color codes used by the console) and the most significant one turns + on highlight (or sometimes blinking -- it depends on the configuration + of your VGA). + +third parameter + consists of character attribute bits you want to set. + + Bit setting takes place before bit toggling, so you can simply clear a + bit by including it in both the set mask and the toggle mask. + +Examples +-------- + +To get normal blinking underline, use:: + + echo -e '\033[?2c' + +To get blinking block, use:: + + echo -e '\033[?6c' + +To get red non-blinking block, use:: + + echo -e '\033[?17;0;64c' diff --git a/Documentation/admin-guide/video-output.rst b/Documentation/admin-guide/video-output.rst new file mode 100644 index 000000000..56d6fa2e2 --- /dev/null +++ b/Documentation/admin-guide/video-output.rst @@ -0,0 +1,34 @@ +Video Output Switcher Control +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +2006 luming.yu@intel.com + +The output sysfs class driver provides an abstract video output layer that +can be used to hook platform specific methods to enable/disable video output +device through common sysfs interface. For example, on my IBM ThinkPad T42 +laptop, The ACPI video driver registered its output devices and read/write +method for 'state' with output sysfs class. The user interface under sysfs is:: + + linux:/sys/class/video_output # tree . + . + |-- CRT0 + | |-- device -> ../../../devices/pci0000:00/0000:00:01.0 + | |-- state + | |-- subsystem -> ../../../class/video_output + | `-- uevent + |-- DVI0 + | |-- device -> ../../../devices/pci0000:00/0000:00:01.0 + | |-- state + | |-- subsystem -> ../../../class/video_output + | `-- uevent + |-- LCD0 + | |-- device -> ../../../devices/pci0000:00/0000:00:01.0 + | |-- state + | |-- subsystem -> ../../../class/video_output + | `-- uevent + `-- TV0 + |-- device -> ../../../devices/pci0000:00/0000:00:01.0 + |-- state + |-- subsystem -> ../../../class/video_output + `-- uevent + diff --git a/Documentation/admin-guide/workload-tracing.rst b/Documentation/admin-guide/workload-tracing.rst new file mode 100644 index 000000000..b2e254ec8 --- /dev/null +++ b/Documentation/admin-guide/workload-tracing.rst @@ -0,0 +1,606 @@ +.. SPDX-License-Identifier: (GPL-2.0+ OR CC-BY-4.0) + +====================================================== +Discovering Linux kernel subsystems used by a workload +====================================================== + +:Authors: - Shuah Khan <skhan@linuxfoundation.org> + - Shefali Sharma <sshefali021@gmail.com> +:maintained-by: Shuah Khan <skhan@linuxfoundation.org> + +Key Points +========== + + * Understanding system resources necessary to build and run a workload + is important. + * Linux tracing and strace can be used to discover the system resources + in use by a workload. The completeness of the system usage information + depends on the completeness of coverage of a workload. + * Performance and security of the operating system can be analyzed with + the help of tools such as: + `perf <https://man7.org/linux/man-pages/man1/perf.1.html>`_, + `stress-ng <https://www.mankier.com/1/stress-ng>`_, + `paxtest <https://github.com/opntr/paxtest-freebsd>`_. + * Once we discover and understand the workload needs, we can focus on them + to avoid regressions and use it to evaluate safety considerations. + +Methodology +=========== + +`strace <https://man7.org/linux/man-pages/man1/strace.1.html>`_ is a +diagnostic, instructional, and debugging tool and can be used to discover +the system resources in use by a workload. Once we discover and understand +the workload needs, we can focus on them to avoid regressions and use it +to evaluate safety considerations. We use strace tool to trace workloads. + +This method of tracing using strace tells us the system calls invoked by +the workload and doesn't include all the system calls that can be invoked +by it. In addition, this tracing method tells us just the code paths within +these system calls that are invoked. As an example, if a workload opens a +file and reads from it successfully, then the success path is the one that +is traced. Any error paths in that system call will not be traced. If there +is a workload that provides full coverage of a workload then the method +outlined here will trace and find all possible code paths. The completeness +of the system usage information depends on the completeness of coverage of a +workload. + +The goal is tracing a workload on a system running a default kernel without +requiring custom kernel installs. + +How do we gather fine-grained system information? +================================================= + +strace tool can be used to trace system calls made by a process and signals +it receives. System calls are the fundamental interface between an +application and the operating system kernel. They enable a program to +request services from the kernel. For instance, the open() system call in +Linux is used to provide access to a file in the file system. strace enables +us to track all the system calls made by an application. It lists all the +system calls made by a process and their resulting output. + +You can generate profiling data combining strace and perf record tools to +record the events and information associated with a process. This provides +insight into the process. "perf annotate" tool generates the statistics of +each instruction of the program. This document goes over the details of how +to gather fine-grained information on a workload's usage of system resources. + +We used strace to trace the perf, stress-ng, paxtest workloads to illustrate +our methodology to discover resources used by a workload. This process can +be applied to trace other workloads. + +Getting the system ready for tracing +==================================== + +Before we can get started we will show you how to get your system ready. +We assume that you have a Linux distribution running on a physical system +or a virtual machine. Most distributions will include strace command. Let’s +install other tools that aren’t usually included to build Linux kernel. +Please note that the following works on Debian based distributions. You +might have to find equivalent packages on other Linux distributions. + +Install tools to build Linux kernel and tools in kernel repository. +scripts/ver_linux is a good way to check if your system already has +the necessary tools:: + + sudo apt-get build-essentials flex bison yacc + sudo apt install libelf-dev systemtap-sdt-dev libaudit-dev libslang2-dev libperl-dev libdw-dev + +cscope is a good tool to browse kernel sources. Let's install it now:: + + sudo apt-get install cscope + +Install stress-ng and paxtest:: + + apt-get install stress-ng + apt-get install paxtest + +Workload overview +================= + +As mentioned earlier, we used strace to trace perf bench, stress-ng and +paxtest workloads to show how to analyze a workload and identify Linux +subsystems used by these workloads. Let's start with an overview of these +three workloads to get a better understanding of what they do and how to +use them. + +perf bench (all) workload +------------------------- + +The perf bench command contains multiple multi-threaded microkernel +benchmarks for executing different subsystems in the Linux kernel and +system calls. This allows us to easily measure the impact of changes, +which can help mitigate performance regressions. It also acts as a common +benchmarking framework, enabling developers to easily create test cases, +integrate transparently, and use performance-rich tooling subsystems. + +Stress-ng netdev stressor workload +---------------------------------- + +stress-ng is used for performing stress testing on the kernel. It allows +you to exercise various physical subsystems of the computer, as well as +interfaces of the OS kernel, using "stressor-s". They are available for +CPU, CPU cache, devices, I/O, interrupts, file system, memory, network, +operating system, pipelines, schedulers, and virtual machines. Please refer +to the `stress-ng man-page <https://www.mankier.com/1/stress-ng>`_ to +find the description of all the available stressor-s. The netdev stressor +starts specified number (N) of workers that exercise various netdevice +ioctl commands across all the available network devices. + +paxtest kiddie workload +----------------------- + +paxtest is a program that tests buffer overflows in the kernel. It tests +kernel enforcements over memory usage. Generally, execution in some memory +segments makes buffer overflows possible. It runs a set of programs that +attempt to subvert memory usage. It is used as a regression test suite for +PaX, but might be useful to test other memory protection patches for the +kernel. We used paxtest kiddie mode which looks for simple vulnerabilities. + +What is strace and how do we use it? +==================================== + +As mentioned earlier, strace which is a useful diagnostic, instructional, +and debugging tool and can be used to discover the system resources in use +by a workload. It can be used: + + * To see how a process interacts with the kernel. + * To see why a process is failing or hanging. + * For reverse engineering a process. + * To find the files on which a program depends. + * For analyzing the performance of an application. + * For troubleshooting various problems related to the operating system. + +In addition, strace can generate run-time statistics on times, calls, and +errors for each system call and report a summary when program exits, +suppressing the regular output. This attempts to show system time (CPU time +spent running in the kernel) independent of wall clock time. We plan to use +these features to get information on workload system usage. + +strace command supports basic, verbose, and stats modes. strace command when +run in verbose mode gives more detailed information about the system calls +invoked by a process. + +Running strace -c generates a report of the percentage of time spent in each +system call, the total time in seconds, the microseconds per call, the total +number of calls, the count of each system call that has failed with an error +and the type of system call made. + + * Usage: strace <command we want to trace> + * Verbose mode usage: strace -v <command> + * Gather statistics: strace -c <command> + +We used the “-c” option to gather fine-grained run-time statistics in use +by three workloads we have chose for this analysis. + + * perf + * stress-ng + * paxtest + +What is cscope and how do we use it? +==================================== + +Now let’s look at `cscope <https://cscope.sourceforge.net/>`_, a command +line tool for browsing C, C++ or Java code-bases. We can use it to find +all the references to a symbol, global definitions, functions called by a +function, functions calling a function, text strings, regular expression +patterns, files including a file. + +We can use cscope to find which system call belongs to which subsystem. +This way we can find the kernel subsystems used by a process when it is +executed. + +Let’s checkout the latest Linux repository and build cscope database:: + + git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git linux + cd linux + cscope -R -p10 # builds cscope.out database before starting browse session + cscope -d -p10 # starts browse session on cscope.out database + +Note: Run "cscope -R -p10" to build the database and c"scope -d -p10" to +enter into the browsing session. cscope by default cscope.out database. +To get out of this mode press ctrl+d. -p option is used to specify the +number of file path components to display. -p10 is optimal for browsing +kernel sources. + +What is perf and how do we use it? +================================== + +Perf is an analysis tool based on Linux 2.6+ systems, which abstracts the +CPU hardware difference in performance measurement in Linux, and provides +a simple command line interface. Perf is based on the perf_events interface +exported by the kernel. It is very useful for profiling the system and +finding performance bottlenecks in an application. + +If you haven't already checked out the Linux mainline repository, you can do +so and then build kernel and perf tool:: + + git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git linux + cd linux + make -j3 all + cd tools/perf + make + +Note: The perf command can be built without building the kernel in the +repository and can be run on older kernels. However matching the kernel +and perf revisions gives more accurate information on the subsystem usage. + +We used "perf stat" and "perf bench" options. For a detailed information on +the perf tool, run "perf -h". + +perf stat +--------- +The perf stat command generates a report of various hardware and software +events. It does so with the help of hardware counter registers found in +modern CPUs that keep the count of these activities. "perf stat cal" shows +stats for cal command. + +Perf bench +---------- +The perf bench command contains multiple multi-threaded microkernel +benchmarks for executing different subsystems in the Linux kernel and +system calls. This allows us to easily measure the impact of changes, +which can help mitigate performance regressions. It also acts as a common +benchmarking framework, enabling developers to easily create test cases, +integrate transparently, and use performance-rich tooling. + +"perf bench all" command runs the following benchmarks: + + * sched/messaging + * sched/pipe + * syscall/basic + * mem/memcpy + * mem/memset + +What is stress-ng and how do we use it? +======================================= + +As mentioned earlier, stress-ng is used for performing stress testing on +the kernel. It allows you to exercise various physical subsystems of the +computer, as well as interfaces of the OS kernel, using stressor-s. They +are available for CPU, CPU cache, devices, I/O, interrupts, file system, +memory, network, operating system, pipelines, schedulers, and virtual +machines. + +The netdev stressor starts N workers that exercise various netdevice ioctl +commands across all the available network devices. The following ioctls are +exercised: + + * SIOCGIFCONF, SIOCGIFINDEX, SIOCGIFNAME, SIOCGIFFLAGS + * SIOCGIFADDR, SIOCGIFNETMASK, SIOCGIFMETRIC, SIOCGIFMTU + * SIOCGIFHWADDR, SIOCGIFMAP, SIOCGIFTXQLEN + +The following command runs the stressor:: + + stress-ng --netdev 1 -t 60 --metrics command. + +We can use the perf record command to record the events and information +associated with a process. This command records the profiling data in the +perf.data file in the same directory. + +Using the following commands you can record the events associated with the +netdev stressor, view the generated report perf.data and annotate the to +view the statistics of each instruction of the program:: + + perf record stress-ng --netdev 1 -t 60 --metrics command. + perf report + perf annotate + +What is paxtest and how do we use it? +===================================== + +paxtest is a program that tests buffer overflows in the kernel. It tests +kernel enforcements over memory usage. Generally, execution in some memory +segments makes buffer overflows possible. It runs a set of programs that +attempt to subvert memory usage. It is used as a regression test suite for +PaX, and will be useful to test other memory protection patches for the +kernel. + +paxtest provides kiddie and blackhat modes. The paxtest kiddie mode runs +in normal mode, whereas the blackhat mode tries to get around the protection +of the kernel testing for vulnerabilities. We focus on the kiddie mode here +and combine "paxtest kiddie" run with "perf record" to collect CPU stack +traces for the paxtest kiddie run to see which function is calling other +functions in the performance profile. Then the "dwarf" (DWARF's Call Frame +Information) mode can be used to unwind the stack. + +The following command can be used to view resulting report in call-graph +format:: + + perf record --call-graph dwarf paxtest kiddie + perf report --stdio + +Tracing workloads +================= + +Now that we understand the workloads, let's start tracing them. + +Tracing perf bench all workload +------------------------------- + +Run the following command to trace perf bench all workload:: + + strace -c perf bench all + +**System Calls made by the workload** + +The below table shows the system calls invoked by the workload, number of +times each system call is invoked, and the corresponding Linux subsystem. + ++-------------------+-----------+-----------------+-------------------------+ +| System Call | # calls | Linux Subsystem | System Call (API) | ++===================+===========+=================+=========================+ +| getppid | 10000001 | Process Mgmt | sys_getpid() | ++-------------------+-----------+-----------------+-------------------------+ +| clone | 1077 | Process Mgmt. | sys_clone() | ++-------------------+-----------+-----------------+-------------------------+ +| prctl | 23 | Process Mgmt. | sys_prctl() | ++-------------------+-----------+-----------------+-------------------------+ +| prlimit64 | 7 | Process Mgmt. | sys_prlimit64() | ++-------------------+-----------+-----------------+-------------------------+ +| getpid | 10 | Process Mgmt. | sys_getpid() | ++-------------------+-----------+-----------------+-------------------------+ +| uname | 3 | Process Mgmt. | sys_uname() | ++-------------------+-----------+-----------------+-------------------------+ +| sysinfo | 1 | Process Mgmt. | sys_sysinfo() | ++-------------------+-----------+-----------------+-------------------------+ +| getuid | 1 | Process Mgmt. | sys_getuid() | ++-------------------+-----------+-----------------+-------------------------+ +| getgid | 1 | Process Mgmt. | sys_getgid() | ++-------------------+-----------+-----------------+-------------------------+ +| geteuid | 1 | Process Mgmt. | sys_geteuid() | ++-------------------+-----------+-----------------+-------------------------+ +| getegid | 1 | Process Mgmt. | sys_getegid | ++-------------------+-----------+-----------------+-------------------------+ +| close | 49951 | Filesystem | sys_close() | ++-------------------+-----------+-----------------+-------------------------+ +| pipe | 604 | Filesystem | sys_pipe() | ++-------------------+-----------+-----------------+-------------------------+ +| openat | 48560 | Filesystem | sys_opennat() | ++-------------------+-----------+-----------------+-------------------------+ +| fstat | 8338 | Filesystem | sys_fstat() | ++-------------------+-----------+-----------------+-------------------------+ +| stat | 1573 | Filesystem | sys_stat() | ++-------------------+-----------+-----------------+-------------------------+ +| pread64 | 9646 | Filesystem | sys_pread64() | ++-------------------+-----------+-----------------+-------------------------+ +| getdents64 | 1873 | Filesystem | sys_getdents64() | ++-------------------+-----------+-----------------+-------------------------+ +| access | 3 | Filesystem | sys_access() | ++-------------------+-----------+-----------------+-------------------------+ +| lstat | 1880 | Filesystem | sys_lstat() | ++-------------------+-----------+-----------------+-------------------------+ +| lseek | 6 | Filesystem | sys_lseek() | ++-------------------+-----------+-----------------+-------------------------+ +| ioctl | 3 | Filesystem | sys_ioctl() | ++-------------------+-----------+-----------------+-------------------------+ +| dup2 | 1 | Filesystem | sys_dup2() | ++-------------------+-----------+-----------------+-------------------------+ +| execve | 2 | Filesystem | sys_execve() | ++-------------------+-----------+-----------------+-------------------------+ +| fcntl | 8779 | Filesystem | sys_fcntl() | ++-------------------+-----------+-----------------+-------------------------+ +| statfs | 1 | Filesystem | sys_statfs() | ++-------------------+-----------+-----------------+-------------------------+ +| epoll_create | 2 | Filesystem | sys_epoll_create() | ++-------------------+-----------+-----------------+-------------------------+ +| epoll_ctl | 64 | Filesystem | sys_epoll_ctl() | ++-------------------+-----------+-----------------+-------------------------+ +| newfstatat | 8318 | Filesystem | sys_newfstatat() | ++-------------------+-----------+-----------------+-------------------------+ +| eventfd2 | 192 | Filesystem | sys_eventfd2() | ++-------------------+-----------+-----------------+-------------------------+ +| mmap | 243 | Memory Mgmt. | sys_mmap() | ++-------------------+-----------+-----------------+-------------------------+ +| mprotect | 32 | Memory Mgmt. | sys_mprotect() | ++-------------------+-----------+-----------------+-------------------------+ +| brk | 21 | Memory Mgmt. | sys_brk() | ++-------------------+-----------+-----------------+-------------------------+ +| munmap | 128 | Memory Mgmt. | sys_munmap() | ++-------------------+-----------+-----------------+-------------------------+ +| set_mempolicy | 156 | Memory Mgmt. | sys_set_mempolicy() | ++-------------------+-----------+-----------------+-------------------------+ +| set_tid_address | 1 | Process Mgmt. | sys_set_tid_address() | ++-------------------+-----------+-----------------+-------------------------+ +| set_robust_list | 1 | Futex | sys_set_robust_list() | ++-------------------+-----------+-----------------+-------------------------+ +| futex | 341 | Futex | sys_futex() | ++-------------------+-----------+-----------------+-------------------------+ +| sched_getaffinity | 79 | Scheduler | sys_sched_getaffinity() | ++-------------------+-----------+-----------------+-------------------------+ +| sched_setaffinity | 223 | Scheduler | sys_sched_setaffinity() | ++-------------------+-----------+-----------------+-------------------------+ +| socketpair | 202 | Network | sys_socketpair() | ++-------------------+-----------+-----------------+-------------------------+ +| rt_sigprocmask | 21 | Signal | sys_rt_sigprocmask() | ++-------------------+-----------+-----------------+-------------------------+ +| rt_sigaction | 36 | Signal | sys_rt_sigaction() | ++-------------------+-----------+-----------------+-------------------------+ +| rt_sigreturn | 2 | Signal | sys_rt_sigreturn() | ++-------------------+-----------+-----------------+-------------------------+ +| wait4 | 889 | Time | sys_wait4() | ++-------------------+-----------+-----------------+-------------------------+ +| clock_nanosleep | 37 | Time | sys_clock_nanosleep() | ++-------------------+-----------+-----------------+-------------------------+ +| capget | 4 | Capability | sys_capget() | ++-------------------+-----------+-----------------+-------------------------+ + +Tracing stress-ng netdev stressor workload +------------------------------------------ + +Run the following command to trace stress-ng netdev stressor workload:: + + strace -c stress-ng --netdev 1 -t 60 --metrics + +**System Calls made by the workload** + +The below table shows the system calls invoked by the workload, number of +times each system call is invoked, and the corresponding Linux subsystem. + ++-------------------+-----------+-----------------+-------------------------+ +| System Call | # calls | Linux Subsystem | System Call (API) | ++===================+===========+=================+=========================+ +| openat | 74 | Filesystem | sys_openat() | ++-------------------+-----------+-----------------+-------------------------+ +| close | 75 | Filesystem | sys_close() | ++-------------------+-----------+-----------------+-------------------------+ +| read | 58 | Filesystem | sys_read() | ++-------------------+-----------+-----------------+-------------------------+ +| fstat | 20 | Filesystem | sys_fstat() | ++-------------------+-----------+-----------------+-------------------------+ +| flock | 10 | Filesystem | sys_flock() | ++-------------------+-----------+-----------------+-------------------------+ +| write | 7 | Filesystem | sys_write() | ++-------------------+-----------+-----------------+-------------------------+ +| getdents64 | 8 | Filesystem | sys_getdents64() | ++-------------------+-----------+-----------------+-------------------------+ +| pread64 | 8 | Filesystem | sys_pread64() | ++-------------------+-----------+-----------------+-------------------------+ +| lseek | 1 | Filesystem | sys_lseek() | ++-------------------+-----------+-----------------+-------------------------+ +| access | 2 | Filesystem | sys_access() | ++-------------------+-----------+-----------------+-------------------------+ +| getcwd | 1 | Filesystem | sys_getcwd() | ++-------------------+-----------+-----------------+-------------------------+ +| execve | 1 | Filesystem | sys_execve() | ++-------------------+-----------+-----------------+-------------------------+ +| mmap | 61 | Memory Mgmt. | sys_mmap() | ++-------------------+-----------+-----------------+-------------------------+ +| munmap | 3 | Memory Mgmt. | sys_munmap() | ++-------------------+-----------+-----------------+-------------------------+ +| mprotect | 20 | Memory Mgmt. | sys_mprotect() | ++-------------------+-----------+-----------------+-------------------------+ +| mlock | 2 | Memory Mgmt. | sys_mlock() | ++-------------------+-----------+-----------------+-------------------------+ +| brk | 3 | Memory Mgmt. | sys_brk() | ++-------------------+-----------+-----------------+-------------------------+ +| rt_sigaction | 21 | Signal | sys_rt_sigaction() | ++-------------------+-----------+-----------------+-------------------------+ +| rt_sigprocmask | 1 | Signal | sys_rt_sigprocmask() | ++-------------------+-----------+-----------------+-------------------------+ +| sigaltstack | 1 | Signal | sys_sigaltstack() | ++-------------------+-----------+-----------------+-------------------------+ +| rt_sigreturn | 1 | Signal | sys_rt_sigreturn() | ++-------------------+-----------+-----------------+-------------------------+ +| getpid | 8 | Process Mgmt. | sys_getpid() | ++-------------------+-----------+-----------------+-------------------------+ +| prlimit64 | 5 | Process Mgmt. | sys_prlimit64() | ++-------------------+-----------+-----------------+-------------------------+ +| arch_prctl | 2 | Process Mgmt. | sys_arch_prctl() | ++-------------------+-----------+-----------------+-------------------------+ +| sysinfo | 2 | Process Mgmt. | sys_sysinfo() | ++-------------------+-----------+-----------------+-------------------------+ +| getuid | 2 | Process Mgmt. | sys_getuid() | ++-------------------+-----------+-----------------+-------------------------+ +| uname | 1 | Process Mgmt. | sys_uname() | ++-------------------+-----------+-----------------+-------------------------+ +| setpgid | 1 | Process Mgmt. | sys_setpgid() | ++-------------------+-----------+-----------------+-------------------------+ +| getrusage | 1 | Process Mgmt. | sys_getrusage() | ++-------------------+-----------+-----------------+-------------------------+ +| geteuid | 1 | Process Mgmt. | sys_geteuid() | ++-------------------+-----------+-----------------+-------------------------+ +| getppid | 1 | Process Mgmt. | sys_getppid() | ++-------------------+-----------+-----------------+-------------------------+ +| sendto | 3 | Network | sys_sendto() | ++-------------------+-----------+-----------------+-------------------------+ +| connect | 1 | Network | sys_connect() | ++-------------------+-----------+-----------------+-------------------------+ +| socket | 1 | Network | sys_socket() | ++-------------------+-----------+-----------------+-------------------------+ +| clone | 1 | Process Mgmt. | sys_clone() | ++-------------------+-----------+-----------------+-------------------------+ +| set_tid_address | 1 | Process Mgmt. | sys_set_tid_address() | ++-------------------+-----------+-----------------+-------------------------+ +| wait4 | 2 | Time | sys_wait4() | ++-------------------+-----------+-----------------+-------------------------+ +| alarm | 1 | Time | sys_alarm() | ++-------------------+-----------+-----------------+-------------------------+ +| set_robust_list | 1 | Futex | sys_set_robust_list() | ++-------------------+-----------+-----------------+-------------------------+ + +Tracing paxtest kiddie workload +------------------------------- + +Run the following command to trace paxtest kiddie workload:: + + strace -c paxtest kiddie + +**System Calls made by the workload** + +The below table shows the system calls invoked by the workload, number of +times each system call is invoked, and the corresponding Linux subsystem. + ++-------------------+-----------+-----------------+----------------------+ +| System Call | # calls | Linux Subsystem | System Call (API) | ++===================+===========+=================+======================+ +| read | 3 | Filesystem | sys_read() | ++-------------------+-----------+-----------------+----------------------+ +| write | 11 | Filesystem | sys_write() | ++-------------------+-----------+-----------------+----------------------+ +| close | 41 | Filesystem | sys_close() | ++-------------------+-----------+-----------------+----------------------+ +| stat | 24 | Filesystem | sys_stat() | ++-------------------+-----------+-----------------+----------------------+ +| fstat | 2 | Filesystem | sys_fstat() | ++-------------------+-----------+-----------------+----------------------+ +| pread64 | 6 | Filesystem | sys_pread64() | ++-------------------+-----------+-----------------+----------------------+ +| access | 1 | Filesystem | sys_access() | ++-------------------+-----------+-----------------+----------------------+ +| pipe | 1 | Filesystem | sys_pipe() | ++-------------------+-----------+-----------------+----------------------+ +| dup2 | 24 | Filesystem | sys_dup2() | ++-------------------+-----------+-----------------+----------------------+ +| execve | 1 | Filesystem | sys_execve() | ++-------------------+-----------+-----------------+----------------------+ +| fcntl | 26 | Filesystem | sys_fcntl() | ++-------------------+-----------+-----------------+----------------------+ +| openat | 14 | Filesystem | sys_openat() | ++-------------------+-----------+-----------------+----------------------+ +| rt_sigaction | 7 | Signal | sys_rt_sigaction() | ++-------------------+-----------+-----------------+----------------------+ +| rt_sigreturn | 38 | Signal | sys_rt_sigreturn() | ++-------------------+-----------+-----------------+----------------------+ +| clone | 38 | Process Mgmt. | sys_clone() | ++-------------------+-----------+-----------------+----------------------+ +| wait4 | 44 | Time | sys_wait4() | ++-------------------+-----------+-----------------+----------------------+ +| mmap | 7 | Memory Mgmt. | sys_mmap() | ++-------------------+-----------+-----------------+----------------------+ +| mprotect | 3 | Memory Mgmt. | sys_mprotect() | ++-------------------+-----------+-----------------+----------------------+ +| munmap | 1 | Memory Mgmt. | sys_munmap() | ++-------------------+-----------+-----------------+----------------------+ +| brk | 3 | Memory Mgmt. | sys_brk() | ++-------------------+-----------+-----------------+----------------------+ +| getpid | 1 | Process Mgmt. | sys_getpid() | ++-------------------+-----------+-----------------+----------------------+ +| getuid | 1 | Process Mgmt. | sys_getuid() | ++-------------------+-----------+-----------------+----------------------+ +| getgid | 1 | Process Mgmt. | sys_getgid() | ++-------------------+-----------+-----------------+----------------------+ +| geteuid | 2 | Process Mgmt. | sys_geteuid() | ++-------------------+-----------+-----------------+----------------------+ +| getegid | 1 | Process Mgmt. | sys_getegid() | ++-------------------+-----------+-----------------+----------------------+ +| getppid | 1 | Process Mgmt. | sys_getppid() | ++-------------------+-----------+-----------------+----------------------+ +| arch_prctl | 2 | Process Mgmt. | sys_arch_prctl() | ++-------------------+-----------+-----------------+----------------------+ + +Conclusion +========== + +This document is intended to be used as a guide on how to gather fine-grained +information on the resources in use by workloads using strace. + +References +========== + + * `Discovery Linux Kernel Subsystems used by OpenAPS <https://elisa.tech/blog/2022/02/02/discovery-linux-kernel-subsystems-used-by-openaps>`_ + * `ELISA-White-Papers-Discovering Linux kernel subsystems used by a workload <https://github.com/elisa-tech/ELISA-White-Papers/blob/master/Processes/Discovering_Linux_kernel_subsystems_used_by_a_workload.md>`_ + * `strace <https://man7.org/linux/man-pages/man1/strace.1.html>`_ + * `perf <https://man7.org/linux/man-pages/man1/perf.1.html>`_ + * `paxtest README <https://github.com/opntr/paxtest-freebsd/blob/hardenedbsd/0.9.14-hbsd/README>`_ + * `stress-ng <https://www.mankier.com/1/stress-ng>`_ + * `Monitoring and managing system status and performance <https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/monitoring_and_managing_system_status_and_performance/index>`_ diff --git a/Documentation/admin-guide/xfs.rst b/Documentation/admin-guide/xfs.rst new file mode 100644 index 000000000..b67772cf3 --- /dev/null +++ b/Documentation/admin-guide/xfs.rst @@ -0,0 +1,544 @@ +.. SPDX-License-Identifier: GPL-2.0 + +====================== +The SGI XFS Filesystem +====================== + +XFS is a high performance journaling filesystem which originated +on the SGI IRIX platform. It is completely multi-threaded, can +support large files and large filesystems, extended attributes, +variable block sizes, is extent based, and makes extensive use of +Btrees (directories, extents, free space) to aid both performance +and scalability. + +Refer to the documentation at https://xfs.wiki.kernel.org/ +for further details. This implementation is on-disk compatible +with the IRIX version of XFS. + + +Mount Options +============= + +When mounting an XFS filesystem, the following options are accepted. + + allocsize=size + Sets the buffered I/O end-of-file preallocation size when + doing delayed allocation writeout (default size is 64KiB). + Valid values for this option are page size (typically 4KiB) + through to 1GiB, inclusive, in power-of-2 increments. + + The default behaviour is for dynamic end-of-file + preallocation size, which uses a set of heuristics to + optimise the preallocation size based on the current + allocation patterns within the file and the access patterns + to the file. Specifying a fixed ``allocsize`` value turns off + the dynamic behaviour. + + attr2 or noattr2 + The options enable/disable an "opportunistic" improvement to + be made in the way inline extended attributes are stored + on-disk. When the new form is used for the first time when + ``attr2`` is selected (either when setting or removing extended + attributes) the on-disk superblock feature bit field will be + updated to reflect this format being in use. + + The default behaviour is determined by the on-disk feature + bit indicating that ``attr2`` behaviour is active. If either + mount option is set, then that becomes the new default used + by the filesystem. + + CRC enabled filesystems always use the ``attr2`` format, and so + will reject the ``noattr2`` mount option if it is set. + + discard or nodiscard (default) + Enable/disable the issuing of commands to let the block + device reclaim space freed by the filesystem. This is + useful for SSD devices, thinly provisioned LUNs and virtual + machine images, but may have a performance impact. + + Note: It is currently recommended that you use the ``fstrim`` + application to ``discard`` unused blocks rather than the ``discard`` + mount option because the performance impact of this option + is quite severe. + + grpid/bsdgroups or nogrpid/sysvgroups (default) + These options define what group ID a newly created file + gets. When ``grpid`` is set, it takes the group ID of the + directory in which it is created; otherwise it takes the + ``fsgid`` of the current process, unless the directory has the + ``setgid`` bit set, in which case it takes the ``gid`` from the + parent directory, and also gets the ``setgid`` bit set if it is + a directory itself. + + filestreams + Make the data allocator use the filestreams allocation mode + across the entire filesystem rather than just on directories + configured to use it. + + ikeep or noikeep (default) + When ``ikeep`` is specified, XFS does not delete empty inode + clusters and keeps them around on disk. When ``noikeep`` is + specified, empty inode clusters are returned to the free + space pool. + + inode32 or inode64 (default) + When ``inode32`` is specified, it indicates that XFS limits + inode creation to locations which will not result in inode + numbers with more than 32 bits of significance. + + When ``inode64`` is specified, it indicates that XFS is allowed + to create inodes at any location in the filesystem, + including those which will result in inode numbers occupying + more than 32 bits of significance. + + ``inode32`` is provided for backwards compatibility with older + systems and applications, since 64 bits inode numbers might + cause problems for some applications that cannot handle + large inode numbers. If applications are in use which do + not handle inode numbers bigger than 32 bits, the ``inode32`` + option should be specified. + + largeio or nolargeio (default) + If ``nolargeio`` is specified, the optimal I/O reported in + ``st_blksize`` by **stat(2)** will be as small as possible to allow + user applications to avoid inefficient read/modify/write + I/O. This is typically the page size of the machine, as + this is the granularity of the page cache. + + If ``largeio`` is specified, a filesystem that was created with a + ``swidth`` specified will return the ``swidth`` value (in bytes) + in ``st_blksize``. If the filesystem does not have a ``swidth`` + specified but does specify an ``allocsize`` then ``allocsize`` + (in bytes) will be returned instead. Otherwise the behaviour + is the same as if ``nolargeio`` was specified. + + logbufs=value + Set the number of in-memory log buffers. Valid numbers + range from 2-8 inclusive. + + The default value is 8 buffers. + + If the memory cost of 8 log buffers is too high on small + systems, then it may be reduced at some cost to performance + on metadata intensive workloads. The ``logbsize`` option below + controls the size of each buffer and so is also relevant to + this case. + + logbsize=value + Set the size of each in-memory log buffer. The size may be + specified in bytes, or in kilobytes with a "k" suffix. + Valid sizes for version 1 and version 2 logs are 16384 (16k) + and 32768 (32k). Valid sizes for version 2 logs also + include 65536 (64k), 131072 (128k) and 262144 (256k). The + logbsize must be an integer multiple of the log + stripe unit configured at **mkfs(8)** time. + + The default value for version 1 logs is 32768, while the + default value for version 2 logs is MAX(32768, log_sunit). + + logdev=device and rtdev=device + Use an external log (metadata journal) and/or real-time device. + An XFS filesystem has up to three parts: a data section, a log + section, and a real-time section. The real-time section is + optional, and the log section can be separate from the data + section or contained within it. + + noalign + Data allocations will not be aligned at stripe unit + boundaries. This is only relevant to filesystems created + with non-zero data alignment parameters (``sunit``, ``swidth``) by + **mkfs(8)**. + + norecovery + The filesystem will be mounted without running log recovery. + If the filesystem was not cleanly unmounted, it is likely to + be inconsistent when mounted in ``norecovery`` mode. + Some files or directories may not be accessible because of this. + Filesystems mounted ``norecovery`` must be mounted read-only or + the mount will fail. + + nouuid + Don't check for double mounted file systems using the file + system ``uuid``. This is useful to mount LVM snapshot volumes, + and often used in combination with ``norecovery`` for mounting + read-only snapshots. + + noquota + Forcibly turns off all quota accounting and enforcement + within the filesystem. + + uquota/usrquota/uqnoenforce/quota + User disk quota accounting enabled, and limits (optionally) + enforced. Refer to **xfs_quota(8)** for further details. + + gquota/grpquota/gqnoenforce + Group disk quota accounting enabled and limits (optionally) + enforced. Refer to **xfs_quota(8)** for further details. + + pquota/prjquota/pqnoenforce + Project disk quota accounting enabled and limits (optionally) + enforced. Refer to **xfs_quota(8)** for further details. + + sunit=value and swidth=value + Used to specify the stripe unit and width for a RAID device + or a stripe volume. "value" must be specified in 512-byte + block units. These options are only relevant to filesystems + that were created with non-zero data alignment parameters. + + The ``sunit`` and ``swidth`` parameters specified must be compatible + with the existing filesystem alignment characteristics. In + general, that means the only valid changes to ``sunit`` are + increasing it by a power-of-2 multiple. Valid ``swidth`` values + are any integer multiple of a valid ``sunit`` value. + + Typically the only time these mount options are necessary if + after an underlying RAID device has had its geometry + modified, such as adding a new disk to a RAID5 lun and + reshaping it. + + swalloc + Data allocations will be rounded up to stripe width boundaries + when the current end of file is being extended and the file + size is larger than the stripe width size. + + wsync + When specified, all filesystem namespace operations are + executed synchronously. This ensures that when the namespace + operation (create, unlink, etc) completes, the change to the + namespace is on stable storage. This is useful in HA setups + where failover must not result in clients seeing + inconsistent namespace presentation during or after a + failover event. + +Deprecation of V4 Format +======================== + +The V4 filesystem format lacks certain features that are supported by +the V5 format, such as metadata checksumming, strengthened metadata +verification, and the ability to store timestamps past the year 2038. +Because of this, the V4 format is deprecated. All users should upgrade +by backing up their files, reformatting, and restoring from the backup. + +Administrators and users can detect a V4 filesystem by running xfs_info +against a filesystem mountpoint and checking for a string containing +"crc=". If no such string is found, please upgrade xfsprogs to the +latest version and try again. + +The deprecation will take place in two parts. Support for mounting V4 +filesystems can now be disabled at kernel build time via Kconfig option. +The option will default to yes until September 2025, at which time it +will be changed to default to no. In September 2030, support will be +removed from the codebase entirely. + +Note: Distributors may choose to withdraw V4 format support earlier than +the dates listed above. + +Deprecated Mount Options +======================== + +============================ ================ + Name Removal Schedule +============================ ================ +Mounting with V4 filesystem September 2030 +Mounting ascii-ci filesystem September 2030 +ikeep/noikeep September 2025 +attr2/noattr2 September 2025 +============================ ================ + + +Removed Mount Options +===================== + +=========================== ======= + Name Removed +=========================== ======= + delaylog/nodelaylog v4.0 + ihashsize v4.0 + irixsgid v4.0 + osyncisdsync/osyncisosync v4.0 + barrier v4.19 + nobarrier v4.19 +=========================== ======= + +sysctls +======= + +The following sysctls are available for the XFS filesystem: + + fs.xfs.stats_clear (Min: 0 Default: 0 Max: 1) + Setting this to "1" clears accumulated XFS statistics + in /proc/fs/xfs/stat. It then immediately resets to "0". + + fs.xfs.xfssyncd_centisecs (Min: 100 Default: 3000 Max: 720000) + The interval at which the filesystem flushes metadata + out to disk and runs internal cache cleanup routines. + + fs.xfs.filestream_centisecs (Min: 1 Default: 3000 Max: 360000) + The interval at which the filesystem ages filestreams cache + references and returns timed-out AGs back to the free stream + pool. + + fs.xfs.speculative_prealloc_lifetime + (Units: seconds Min: 1 Default: 300 Max: 86400) + The interval at which the background scanning for inodes + with unused speculative preallocation runs. The scan + removes unused preallocation from clean inodes and releases + the unused space back to the free pool. + + fs.xfs.speculative_cow_prealloc_lifetime + This is an alias for speculative_prealloc_lifetime. + + fs.xfs.error_level (Min: 0 Default: 3 Max: 11) + A volume knob for error reporting when internal errors occur. + This will generate detailed messages & backtraces for filesystem + shutdowns, for example. Current threshold values are: + + XFS_ERRLEVEL_OFF: 0 + XFS_ERRLEVEL_LOW: 1 + XFS_ERRLEVEL_HIGH: 5 + + fs.xfs.panic_mask (Min: 0 Default: 0 Max: 511) + Causes certain error conditions to call BUG(). Value is a bitmask; + OR together the tags which represent errors which should cause panics: + + XFS_NO_PTAG 0 + XFS_PTAG_IFLUSH 0x00000001 + XFS_PTAG_LOGRES 0x00000002 + XFS_PTAG_AILDELETE 0x00000004 + XFS_PTAG_ERROR_REPORT 0x00000008 + XFS_PTAG_SHUTDOWN_CORRUPT 0x00000010 + XFS_PTAG_SHUTDOWN_IOERROR 0x00000020 + XFS_PTAG_SHUTDOWN_LOGERROR 0x00000040 + XFS_PTAG_FSBLOCK_ZERO 0x00000080 + XFS_PTAG_VERIFIER_ERROR 0x00000100 + + This option is intended for debugging only. + + fs.xfs.irix_symlink_mode (Min: 0 Default: 0 Max: 1) + Controls whether symlinks are created with mode 0777 (default) + or whether their mode is affected by the umask (irix mode). + + fs.xfs.irix_sgid_inherit (Min: 0 Default: 0 Max: 1) + Controls files created in SGID directories. + If the group ID of the new file does not match the effective group + ID or one of the supplementary group IDs of the parent dir, the + ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl + is set. + + fs.xfs.inherit_sync (Min: 0 Default: 1 Max: 1) + Setting this to "1" will cause the "sync" flag set + by the **xfs_io(8)** chattr command on a directory to be + inherited by files in that directory. + + fs.xfs.inherit_nodump (Min: 0 Default: 1 Max: 1) + Setting this to "1" will cause the "nodump" flag set + by the **xfs_io(8)** chattr command on a directory to be + inherited by files in that directory. + + fs.xfs.inherit_noatime (Min: 0 Default: 1 Max: 1) + Setting this to "1" will cause the "noatime" flag set + by the **xfs_io(8)** chattr command on a directory to be + inherited by files in that directory. + + fs.xfs.inherit_nosymlinks (Min: 0 Default: 1 Max: 1) + Setting this to "1" will cause the "nosymlinks" flag set + by the **xfs_io(8)** chattr command on a directory to be + inherited by files in that directory. + + fs.xfs.inherit_nodefrag (Min: 0 Default: 1 Max: 1) + Setting this to "1" will cause the "nodefrag" flag set + by the **xfs_io(8)** chattr command on a directory to be + inherited by files in that directory. + + fs.xfs.rotorstep (Min: 1 Default: 1 Max: 256) + In "inode32" allocation mode, this option determines how many + files the allocator attempts to allocate in the same allocation + group before moving to the next allocation group. The intent + is to control the rate at which the allocator moves between + allocation groups when allocating extents for new files. + +Deprecated Sysctls +================== + +=========================================== ================ + Name Removal Schedule +=========================================== ================ +fs.xfs.irix_sgid_inherit September 2025 +fs.xfs.irix_symlink_mode September 2025 +fs.xfs.speculative_cow_prealloc_lifetime September 2025 +=========================================== ================ + + +Removed Sysctls +=============== + +============================= ======= + Name Removed +============================= ======= + fs.xfs.xfsbufd_centisec v4.0 + fs.xfs.age_buffer_centisecs v4.0 +============================= ======= + +Error handling +============== + +XFS can act differently according to the type of error found during its +operation. The implementation introduces the following concepts to the error +handler: + + -failure speed: + Defines how fast XFS should propagate an error upwards when a specific + error is found during the filesystem operation. It can propagate + immediately, after a defined number of retries, after a set time period, + or simply retry forever. + + -error classes: + Specifies the subsystem the error configuration will apply to, such as + metadata IO or memory allocation. Different subsystems will have + different error handlers for which behaviour can be configured. + + -error handlers: + Defines the behavior for a specific error. + +The filesystem behavior during an error can be set via ``sysfs`` files. Each +error handler works independently - the first condition met by an error handler +for a specific class will cause the error to be propagated rather than reset and +retried. + +The action taken by the filesystem when the error is propagated is context +dependent - it may cause a shut down in the case of an unrecoverable error, +it may be reported back to userspace, or it may even be ignored because +there's nothing useful we can with the error or anyone we can report it to (e.g. +during unmount). + +The configuration files are organized into the following hierarchy for each +mounted filesystem: + + /sys/fs/xfs/<dev>/error/<class>/<error>/ + +Where: + <dev> + The short device name of the mounted filesystem. This is the same device + name that shows up in XFS kernel error messages as "XFS(<dev>): ..." + + <class> + The subsystem the error configuration belongs to. As of 4.9, the defined + classes are: + + - "metadata": applies metadata buffer write IO + + <error> + The individual error handler configurations. + + +Each filesystem has "global" error configuration options defined in their top +level directory: + + /sys/fs/xfs/<dev>/error/ + + fail_at_unmount (Min: 0 Default: 1 Max: 1) + Defines the filesystem error behavior at unmount time. + + If set to a value of 1, XFS will override all other error configurations + during unmount and replace them with "immediate fail" characteristics. + i.e. no retries, no retry timeout. This will always allow unmount to + succeed when there are persistent errors present. + + If set to 0, the configured retry behaviour will continue until all + retries and/or timeouts have been exhausted. This will delay unmount + completion when there are persistent errors, and it may prevent the + filesystem from ever unmounting fully in the case of "retry forever" + handler configurations. + + Note: there is no guarantee that fail_at_unmount can be set while an + unmount is in progress. It is possible that the ``sysfs`` entries are + removed by the unmounting filesystem before a "retry forever" error + handler configuration causes unmount to hang, and hence the filesystem + must be configured appropriately before unmount begins to prevent + unmount hangs. + +Each filesystem has specific error class handlers that define the error +propagation behaviour for specific errors. There is also a "default" error +handler defined, which defines the behaviour for all errors that don't have +specific handlers defined. Where multiple retry constraints are configured for +a single error, the first retry configuration that expires will cause the error +to be propagated. The handler configurations are found in the directory: + + /sys/fs/xfs/<dev>/error/<class>/<error>/ + + max_retries (Min: -1 Default: Varies Max: INTMAX) + Defines the allowed number of retries of a specific error before + the filesystem will propagate the error. The retry count for a given + error context (e.g. a specific metadata buffer) is reset every time + there is a successful completion of the operation. + + Setting the value to "-1" will cause XFS to retry forever for this + specific error. + + Setting the value to "0" will cause XFS to fail immediately when the + specific error is reported. + + Setting the value to "N" (where 0 < N < Max) will make XFS retry the + operation "N" times before propagating the error. + + retry_timeout_seconds (Min: -1 Default: Varies Max: 1 day) + Define the amount of time (in seconds) that the filesystem is + allowed to retry its operations when the specific error is + found. + + Setting the value to "-1" will allow XFS to retry forever for this + specific error. + + Setting the value to "0" will cause XFS to fail immediately when the + specific error is reported. + + Setting the value to "N" (where 0 < N < Max) will allow XFS to retry the + operation for up to "N" seconds before propagating the error. + +**Note:** The default behaviour for a specific error handler is dependent on both +the class and error context. For example, the default values for +"metadata/ENODEV" are "0" rather than "-1" so that this error handler defaults +to "fail immediately" behaviour. This is done because ENODEV is a fatal, +unrecoverable error no matter how many times the metadata IO is retried. + +Workqueue Concurrency +===================== + +XFS uses kernel workqueues to parallelize metadata update processes. This +enables it to take advantage of storage hardware that can service many IO +operations simultaneously. This interface exposes internal implementation +details of XFS, and as such is explicitly not part of any userspace API/ABI +guarantee the kernel may give userspace. These are undocumented features of +the generic workqueue implementation XFS uses for concurrency, and they are +provided here purely for diagnostic and tuning purposes and may change at any +time in the future. + +The control knobs for a filesystem's workqueues are organized by task at hand +and the short name of the data device. They all can be found in: + + /sys/bus/workqueue/devices/${task}!${device} + +================ =========== + Task Description +================ =========== + xfs_iwalk-$pid Inode scans of the entire filesystem. Currently limited to + mount time quotacheck. + xfs-gc Background garbage collection of disk space that have been + speculatively allocated beyond EOF or for staging copy on + write operations. +================ =========== + +For example, the knobs for the quotacheck workqueue for /dev/nvme0n1 would be +found in /sys/bus/workqueue/devices/xfs_iwalk-1111!nvme0n1/. + +The interesting knobs for XFS workqueues are as follows: + +============ =========== + Knob Description +============ =========== + max_active Maximum number of background threads that can be started to + run the work. + cpumask CPUs upon which the threads are allowed to run. + nice Relative priority of scheduling the threads. These are the + same nice levels that can be applied to userspace processes. +============ =========== |
