Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

17 files changed, 4026 insertions, 0 deletions

diff --git a/Documentation/arch/s390/3270.ChangeLog b/Documentation/arch/s390/3270.ChangeLog
new file mode 100644
index 0000000000..ecaf60b6c3
--- /dev/null
+++ b/Documentation/arch/s390/3270.ChangeLog
@@ -0,0 +1,44 @@
+ChangeLog for the UTS Global 3270-support patch
+
+Sep 2002:	Get bootup colors right on 3270 console
+	* In tubttybld.c, substantially revise ESC processing so that
+	  ESC sequences (especially coloring ones) and the strings
+	  they affect work as right as 3270 can get them.  Also, set
+	  screen height to omit the two rows used for input area, in
+	  tty3270_open() in tubtty.c.
+
+Sep 2002:	Dynamically get 3270 input buffer
+	* Oversize 3270 screen widths may exceed GEOM_MAXINPLEN columns,
+	  so get input-area buffer dynamically when sizing the device in
+	  tubmakemin() in tuball.c (if it's the console) or tty3270_open()
+	  in tubtty.c (if needed).  Change tubp->tty_input to be a
+	  pointer rather than an array, in tubio.h.
+
+Sep 2002:	Fix tubfs kmalloc()s
+	* Do read and write lengths correctly in fs3270_read()
+	  and fs3270_write(), while never asking kmalloc()
+	  for more than 0x800 bytes.  Affects tubfs.c and tubio.h.
+
+Sep 2002:	Recognize 3270 control unit type 3174
+	* Recognize control-unit type 0x3174 as well as 0x327?.
+	  The IBM 2047 device emulates a 3174 control unit.
+	  Modularize control-unit recognition in tuball.c by
+	  adding and invoking new tub3270_is_ours().
+
+Apr 2002:	Fix 3270 console reboot loop
+	* (Belated log entry) Fixed reboot loop if 3270 console,
+	  in tubtty.c:ttu3270_bh().
+
+Feb 6, 2001:
+	* This changelog is new
+	* tub3270 now supports 3270 console:
+		Specify y for CONFIG_3270 and y for CONFIG_3270_CONSOLE.
+		Support for 3215 will not appear if 3270 console support
+		is chosen.
+		NOTE:  The default is 3270 console support, NOT 3215.
+	* the components are remodularized: added source modules are
+	  tubttybld.c and tubttyscl.c, for screen-building code and
+	  scroll-timeout code.
+	* tub3270 source for this (2.4.0) version is #ifdeffed to
+	  build with both 2.4.0 and 2.2.16.2.
+	* color support and minimal other ESC-sequence support is added.
diff --git a/Documentation/arch/s390/3270.rst b/Documentation/arch/s390/3270.rst
new file mode 100644
index 0000000000..467eace914
--- /dev/null
+++ b/Documentation/arch/s390/3270.rst
@@ -0,0 +1,298 @@
+===============================
+IBM 3270 Display System support
+===============================
+
+This file describes the driver that supports local channel attachment
+of IBM 3270 devices.  It consists of three sections:
+
+	* Introduction
+	* Installation
+	* Operation
+
+
+Introduction
+============
+
+This paper describes installing and operating 3270 devices under
+Linux/390.  A 3270 device is a block-mode rows-and-columns terminal of
+which I'm sure hundreds of millions were sold by IBM and clonemakers
+twenty and thirty years ago.
+
+You may have 3270s in-house and not know it.  If you're using the
+VM-ESA operating system, define a 3270 to your virtual machine by using
+the command "DEF GRAF <hex-address>"  This paper presumes you will be
+defining four 3270s with the CP/CMS commands:
+
+	- DEF GRAF 620
+	- DEF GRAF 621
+	- DEF GRAF 622
+	- DEF GRAF 623
+
+Your network connection from VM-ESA allows you to use x3270, tn3270, or
+another 3270 emulator, started from an xterm window on your PC or
+workstation.  With the DEF GRAF command, an application such as xterm,
+and this Linux-390 3270 driver, you have another way of talking to your
+Linux box.
+
+This paper covers installation of the driver and operation of a
+dialed-in x3270.
+
+
+Installation
+============
+
+You install the driver by installing a patch, doing a kernel build, and
+running the configuration script (config3270.sh, in this directory).
+
+WARNING:  If you are using 3270 console support, you must rerun the
+configuration script every time you change the console's address (perhaps
+by using the condev= parameter in silo's /boot/parmfile).  More precisely,
+you should rerun the configuration script every time your set of 3270s,
+including the console 3270, changes subchannel identifier relative to
+one another.  ReIPL as soon as possible after running the configuration
+script and the resulting /tmp/mkdev3270.
+
+If you have chosen to make tub3270 a module, you add a line to a
+configuration file under /etc/modprobe.d/.  If you are working on a VM
+virtual machine, you can use DEF GRAF to define virtual 3270 devices.
+
+You may generate both 3270 and 3215 console support, or one or the
+other, or neither.  If you generate both, the console type under VM is
+not changed.  Use #CP Q TERM to see what the current console type is.
+Use #CP TERM CONMODE 3270 to change it to 3270.  If you generate only
+3270 console support, then the driver automatically converts your console
+at boot time to a 3270 if it is a 3215.
+
+In brief, these are the steps:
+
+	1. Install the tub3270 patch
+	2. (If a module) add a line to a file in `/etc/modprobe.d/*.conf`
+	3. (If VM) define devices with DEF GRAF
+	4. Reboot
+	5. Configure
+
+To test that everything works, assuming VM and x3270,
+
+	1. Bring up an x3270 window.
+	2. Use the DIAL command in that window.
+	3. You should immediately see a Linux login screen.
+
+Here are the installation steps in detail:
+
+	1.  The 3270 driver is a part of the official Linux kernel
+	source.  Build a tree with the kernel source and any necessary
+	patches.  Then do::
+
+		make oldconfig
+		(If you wish to disable 3215 console support, edit
+		.config; change CONFIG_TN3215's value to "n";
+		and rerun "make oldconfig".)
+		make image
+		make modules
+		make modules_install
+
+	2. (Perform this step only if you have configured tub3270 as a
+	module.)  Add a line to a file `/etc/modprobe.d/*.conf` to automatically
+	load the driver when it's needed.  With this line added, you will see
+	login prompts appear on your 3270s as soon as boot is complete (or
+	with emulated 3270s, as soon as you dial into your vm guest using the
+	command "DIAL <vmguestname>").  Since the line-mode major number is
+	227, the line to add should be::
+
+		alias char-major-227 tub3270
+
+	3. Define graphic devices to your vm guest machine, if you
+	haven't already.  Define them before you reboot (reipl):
+
+		- DEFINE GRAF 620
+		- DEFINE GRAF 621
+		- DEFINE GRAF 622
+		- DEFINE GRAF 623
+
+	4. Reboot.  The reboot process scans hardware devices, including
+	3270s, and this enables the tub3270 driver once loaded to respond
+	correctly to the configuration requests of the next step.  If
+	you have chosen 3270 console support, your console now behaves
+	as a 3270, not a 3215.
+
+	5. Run the 3270 configuration script config3270.  It is
+	distributed in this same directory, Documentation/arch/s390, as
+	config3270.sh.  Inspect the output script it produces,
+	/tmp/mkdev3270, and then run that script.  This will create the
+	necessary character special device files and make the necessary
+	changes to /etc/inittab.
+
+	Then notify /sbin/init that /etc/inittab has changed, by issuing
+	the telinit command with the q operand::
+
+		cd Documentation/arch/s390
+		sh config3270.sh
+		sh /tmp/mkdev3270
+		telinit q
+
+	This should be sufficient for your first time.  If your 3270
+	configuration has changed and you're reusing config3270, you
+	should follow these steps::
+
+		Change 3270 configuration
+		Reboot
+		Run config3270 and /tmp/mkdev3270
+		Reboot
+
+Here are the testing steps in detail:
+
+	1. Bring up an x3270 window, or use an actual hardware 3278 or
+	3279, or use the 3270 emulator of your choice.  You would be
+	running the emulator on your PC or workstation.  You would use
+	the command, for example::
+
+		x3270 vm-esa-domain-name &
+
+	if you wanted a 3278 Model 4 with 43 rows of 80 columns, the
+	default model number.  The driver does not take advantage of
+	extended attributes.
+
+	The screen you should now see contains a VM logo with input
+	lines near the bottom.  Use TAB to move to the bottom line,
+	probably labeled "COMMAND  ===>".
+
+	2. Use the DIAL command instead of the LOGIN command to connect
+	to one of the virtual 3270s you defined with the DEF GRAF
+	commands::
+
+		dial my-vm-guest-name
+
+	3. You should immediately see a login prompt from your
+	Linux-390 operating system.  If that does not happen, you would
+	see instead the line "DIALED TO my-vm-guest-name   0620".
+
+	To troubleshoot:  do these things.
+
+	A. Is the driver loaded?  Use the lsmod command (no operands)
+	to find out.  Probably it isn't.  Try loading it manually, with
+	the command "insmod tub3270".  Does that command give error
+	messages?  Ha!  There's your problem.
+
+	B. Is the /etc/inittab file modified as in installation step 3
+	above?  Use the grep command to find out; for instance, issue
+	"grep 3270 /etc/inittab".  Nothing found?  There's your
+	problem!
+
+	C. Are the device special files created, as in installation
+	step 2 above?  Use the ls -l command to find out; for instance,
+	issue "ls -l /dev/3270/tty620".  The output should start with the
+	letter "c" meaning character device and should contain "227, 1"
+	just to the left of the device name.  No such file?  no "c"?
+	Wrong major number?  Wrong minor number?  There's your
+	problem!
+
+	D. Do you get the message::
+
+		 "HCPDIA047E my-vm-guest-name 0620 does not exist"?
+
+	If so, you must issue the command "DEF GRAF 620" from your VM
+	3215 console and then reboot the system.
+
+
+
+OPERATION.
+==========
+
+The driver defines three areas on the 3270 screen:  the log area, the
+input area, and the status area.
+
+The log area takes up all but the bottom two lines of the screen.  The
+driver writes terminal output to it, starting at the top line and going
+down.  When it fills, the status area changes from "Linux Running" to
+"Linux More...".  After a scrolling timeout of (default) 5 sec, the
+screen clears and more output is written, from the top down.
+
+The input area extends from the beginning of the second-to-last screen
+line to the start of the status area.  You type commands in this area
+and hit ENTER to execute them.
+
+The status area initializes to "Linux Running" to give you a warm
+fuzzy feeling.  When the log area fills up and output awaits, it
+changes to "Linux More...".  At this time you can do several things or
+nothing.  If you do nothing, the screen will clear in (default) 5 sec
+and more output will appear.  You may hit ENTER with nothing typed in
+the input area to toggle between "Linux More..." and "Linux Holding",
+which indicates no scrolling will occur.  (If you hit ENTER with "Linux
+Running" and nothing typed, the application receives a newline.)
+
+You may change the scrolling timeout value.  For example, the following
+command line::
+
+	echo scrolltime=60 > /proc/tty/driver/tty3270
+
+changes the scrolling timeout value to 60 sec.  Set scrolltime to 0 if
+you wish to prevent scrolling entirely.
+
+Other things you may do when the log area fills up are:  hit PA2 to
+clear the log area and write more output to it, or hit CLEAR to clear
+the log area and the input area and write more output to the log area.
+
+Some of the Program Function (PF) and Program Attention (PA) keys are
+preassigned special functions.  The ones that are not yield an alarm
+when pressed.
+
+PA1 causes a SIGINT to the currently running application.  You may do
+the same thing from the input area, by typing "^C" and hitting ENTER.
+
+PA2 causes the log area to be cleared.  If output awaits, it is then
+written to the log area.
+
+PF3 causes an EOF to be received as input by the application.  You may
+cause an EOF also by typing "^D" and hitting ENTER.
+
+No PF key is preassigned to cause a job suspension, but you may cause a
+job suspension by typing "^Z" and hitting ENTER.  You may wish to
+assign this function to a PF key.  To make PF7 cause job suspension,
+execute the command::
+
+	echo pf7=^z > /proc/tty/driver/tty3270
+
+If the input you type does not end with the two characters "^n", the
+driver appends a newline character and sends it to the tty driver;
+otherwise the driver strips the "^n" and does not append a newline.
+The IBM 3215 driver behaves similarly.
+
+Pf10 causes the most recent command to be retrieved from the tube's
+command stack (default depth 20) and displayed in the input area.  You
+may hit PF10 again for the next-most-recent command, and so on.  A
+command is entered into the stack only when the input area is not made
+invisible (such as for password entry) and it is not identical to the
+current top entry.  PF10 rotates backward through the command stack;
+PF11 rotates forward.  You may assign the backward function to any PF
+key (or PA key, for that matter), say, PA3, with the command::
+
+	echo -e pa3=\\033k > /proc/tty/driver/tty3270
+
+This assigns the string ESC-k to PA3.  Similarly, the string ESC-j
+performs the forward function.  (Rationale:  In bash with vi-mode line
+editing, ESC-k and ESC-j retrieve backward and forward history.
+Suggestions welcome.)
+
+Is a stack size of twenty commands not to your liking?  Change it on
+the fly.  To change to saving the last 100 commands, execute the
+command::
+
+	echo recallsize=100 > /proc/tty/driver/tty3270
+
+Have a command you issue frequently?  Assign it to a PF or PA key!  Use
+the command::
+
+	echo pf24="mkdir foobar; cd foobar" > /proc/tty/driver/tty3270
+
+to execute the commands mkdir foobar and cd foobar immediately when you
+hit PF24.  Want to see the command line first, before you execute it?
+Use the -n option of the echo command::
+
+	echo -n pf24="mkdir foo; cd foo" > /proc/tty/driver/tty3270
+
+
+
+Happy testing!  I welcome any and all comments about this document, the
+driver, etc etc.
+
+Dick Hitt <rbh00@utsglobal.com>
diff --git a/Documentation/arch/s390/cds.rst b/Documentation/arch/s390/cds.rst
new file mode 100644
index 0000000000..bcad2a1424
--- /dev/null
+++ b/Documentation/arch/s390/cds.rst
@@ -0,0 +1,530 @@
+===========================
+Linux for S/390 and zSeries
+===========================
+
+Common Device Support (CDS)
+Device Driver I/O Support Routines
+
+Authors:
+	- Ingo Adlung
+	- Cornelia Huck
+
+Copyright, IBM Corp. 1999-2002
+
+Introduction
+============
+
+This document describes the common device support routines for Linux/390.
+Different than other hardware architectures, ESA/390 has defined a unified
+I/O access method. This gives relief to the device drivers as they don't
+have to deal with different bus types, polling versus interrupt
+processing, shared versus non-shared interrupt processing, DMA versus port
+I/O (PIO), and other hardware features more. However, this implies that
+either every single device driver needs to implement the hardware I/O
+attachment functionality itself, or the operating system provides for a
+unified method to access the hardware, providing all the functionality that
+every single device driver would have to provide itself.
+
+The document does not intend to explain the ESA/390 hardware architecture in
+every detail.This information can be obtained from the ESA/390 Principles of
+Operation manual (IBM Form. No. SA22-7201).
+
+In order to build common device support for ESA/390 I/O interfaces, a
+functional layer was introduced that provides generic I/O access methods to
+the hardware.
+
+The common device support layer comprises the I/O support routines defined
+below. Some of them implement common Linux device driver interfaces, while
+some of them are ESA/390 platform specific.
+
+Note:
+  In order to write a driver for S/390, you also need to look into the interface
+  described in Documentation/arch/s390/driver-model.rst.
+
+Note for porting drivers from 2.4:
+
+The major changes are:
+
+* The functions use a ccw_device instead of an irq (subchannel).
+* All drivers must define a ccw_driver (see driver-model.txt) and the associated
+  functions.
+* request_irq() and free_irq() are no longer done by the driver.
+* The oper_handler is (kindof) replaced by the probe() and set_online() functions
+  of the ccw_driver.
+* The not_oper_handler is (kindof) replaced by the remove() and set_offline()
+  functions of the ccw_driver.
+* The channel device layer is gone.
+* The interrupt handlers must be adapted to use a ccw_device as argument.
+  Moreover, they don't return a devstat, but an irb.
+* Before initiating an io, the options must be set via ccw_device_set_options().
+* Instead of calling read_dev_chars()/read_conf_data(), the driver issues
+  the channel program and handles the interrupt itself.
+
+ccw_device_get_ciw()
+   get commands from extended sense data.
+
+ccw_device_start(), ccw_device_start_timeout(), ccw_device_start_key(), ccw_device_start_key_timeout()
+   initiate an I/O request.
+
+ccw_device_resume()
+   resume channel program execution.
+
+ccw_device_halt()
+   terminate the current I/O request processed on the device.
+
+do_IRQ()
+   generic interrupt routine. This function is called by the interrupt entry
+   routine whenever an I/O interrupt is presented to the system. The do_IRQ()
+   routine determines the interrupt status and calls the device specific
+   interrupt handler according to the rules (flags) defined during I/O request
+   initiation with do_IO().
+
+The next chapters describe the functions other than do_IRQ() in more details.
+The do_IRQ() interface is not described, as it is called from the Linux/390
+first level interrupt handler only and does not comprise a device driver
+callable interface. Instead, the functional description of do_IO() also
+describes the input to the device specific interrupt handler.
+
+Note:
+	All explanations apply also to the 64 bit architecture s390x.
+
+
+Common Device Support (CDS) for Linux/390 Device Drivers
+========================================================
+
+General Information
+-------------------
+
+The following chapters describe the I/O related interface routines the
+Linux/390 common device support (CDS) provides to allow for device specific
+driver implementations on the IBM ESA/390 hardware platform. Those interfaces
+intend to provide the functionality required by every device driver
+implementation to allow to drive a specific hardware device on the ESA/390
+platform. Some of the interface routines are specific to Linux/390 and some
+of them can be found on other Linux platforms implementations too.
+Miscellaneous function prototypes, data declarations, and macro definitions
+can be found in the architecture specific C header file
+linux/arch/s390/include/asm/irq.h.
+
+Overview of CDS interface concepts
+----------------------------------
+
+Different to other hardware platforms, the ESA/390 architecture doesn't define
+interrupt lines managed by a specific interrupt controller and bus systems
+that may or may not allow for shared interrupts, DMA processing, etc.. Instead,
+the ESA/390 architecture has implemented a so called channel subsystem, that
+provides a unified view of the devices physically attached to the systems.
+Though the ESA/390 hardware platform knows about a huge variety of different
+peripheral attachments like disk devices (aka. DASDs), tapes, communication
+controllers, etc. they can all be accessed by a well defined access method and
+they are presenting I/O completion a unified way : I/O interruptions. Every
+single device is uniquely identified to the system by a so called subchannel,
+where the ESA/390 architecture allows for 64k devices be attached.
+
+Linux, however, was first built on the Intel PC architecture, with its two
+cascaded 8259 programmable interrupt controllers (PICs), that allow for a
+maximum of 15 different interrupt lines. All devices attached to such a system
+share those 15 interrupt levels. Devices attached to the ISA bus system must
+not share interrupt levels (aka. IRQs), as the ISA bus bases on edge triggered
+interrupts. MCA, EISA, PCI and other bus systems base on level triggered
+interrupts, and therewith allow for shared IRQs. However, if multiple devices
+present their hardware status by the same (shared) IRQ, the operating system
+has to call every single device driver registered on this IRQ in order to
+determine the device driver owning the device that raised the interrupt.
+
+Up to kernel 2.4, Linux/390 used to provide interfaces via the IRQ (subchannel).
+For internal use of the common I/O layer, these are still there. However,
+device drivers should use the new calling interface via the ccw_device only.
+
+During its startup the Linux/390 system checks for peripheral devices. Each
+of those devices is uniquely defined by a so called subchannel by the ESA/390
+channel subsystem. While the subchannel numbers are system generated, each
+subchannel also takes a user defined attribute, the so called device number.
+Both subchannel number and device number cannot exceed 65535. During sysfs
+initialisation, the information about control unit type and device types that
+imply specific I/O commands (channel command words - CCWs) in order to operate
+the device are gathered. Device drivers can retrieve this set of hardware
+information during their initialization step to recognize the devices they
+support using the information saved in the struct ccw_device given to them.
+This methods implies that Linux/390 doesn't require to probe for free (not
+armed) interrupt request lines (IRQs) to drive its devices with. Where
+applicable, the device drivers can use issue the READ DEVICE CHARACTERISTICS
+ccw to retrieve device characteristics in its online routine.
+
+In order to allow for easy I/O initiation the CDS layer provides a
+ccw_device_start() interface that takes a device specific channel program (one
+or more CCWs) as input sets up the required architecture specific control blocks
+and initiates an I/O request on behalf of the device driver. The
+ccw_device_start() routine allows to specify whether it expects the CDS layer
+to notify the device driver for every interrupt it observes, or with final status
+only. See ccw_device_start() for more details. A device driver must never issue
+ESA/390 I/O commands itself, but must use the Linux/390 CDS interfaces instead.
+
+For long running I/O request to be canceled, the CDS layer provides the
+ccw_device_halt() function. Some devices require to initially issue a HALT
+SUBCHANNEL (HSCH) command without having pending I/O requests. This function is
+also covered by ccw_device_halt().
+
+
+get_ciw() - get command information word
+
+This call enables a device driver to get information about supported commands
+from the extended SenseID data.
+
+::
+
+  struct ciw *
+  ccw_device_get_ciw(struct ccw_device *cdev, __u32 cmd);
+
+====  ========================================================
+cdev  The ccw_device for which the command is to be retrieved.
+cmd   The command type to be retrieved.
+====  ========================================================
+
+ccw_device_get_ciw() returns:
+
+=====  ================================================================
+ NULL  No extended data available, invalid device or command not found.
+!NULL  The command requested.
+=====  ================================================================
+
+::
+
+  ccw_device_start() - Initiate I/O Request
+
+The ccw_device_start() routines is the I/O request front-end processor. All
+device driver I/O requests must be issued using this routine. A device driver
+must not issue ESA/390 I/O commands itself. Instead the ccw_device_start()
+routine provides all interfaces required to drive arbitrary devices.
+
+This description also covers the status information passed to the device
+driver's interrupt handler as this is related to the rules (flags) defined
+with the associated I/O request when calling ccw_device_start().
+
+::
+
+  int ccw_device_start(struct ccw_device *cdev,
+		       struct ccw1 *cpa,
+		       unsigned long intparm,
+		       __u8 lpm,
+		       unsigned long flags);
+  int ccw_device_start_timeout(struct ccw_device *cdev,
+			       struct ccw1 *cpa,
+			       unsigned long intparm,
+			       __u8 lpm,
+			       unsigned long flags,
+			       int expires);
+  int ccw_device_start_key(struct ccw_device *cdev,
+			   struct ccw1 *cpa,
+			   unsigned long intparm,
+			   __u8 lpm,
+			   __u8 key,
+			   unsigned long flags);
+  int ccw_device_start_key_timeout(struct ccw_device *cdev,
+				   struct ccw1 *cpa,
+				   unsigned long intparm,
+				   __u8 lpm,
+				   __u8 key,
+				   unsigned long flags,
+				   int expires);
+
+============= =============================================================
+cdev          ccw_device the I/O is destined for
+cpa           logical start address of channel program
+user_intparm  user specific interrupt information; will be presented
+	      back to the device driver's interrupt handler. Allows a
+	      device driver to associate the interrupt with a
+	      particular I/O request.
+lpm           defines the channel path to be used for a specific I/O
+	      request. A value of 0 will make cio use the opm.
+key           the storage key to use for the I/O (useful for operating on a
+	      storage with a storage key != default key)
+flag          defines the action to be performed for I/O processing
+expires       timeout value in jiffies. The common I/O layer will terminate
+	      the running program after this and call the interrupt handler
+	      with ERR_PTR(-ETIMEDOUT) as irb.
+============= =============================================================
+
+Possible flag values are:
+
+========================= =============================================
+DOIO_ALLOW_SUSPEND        channel program may become suspended
+DOIO_DENY_PREFETCH        don't allow for CCW prefetch; usually
+			  this implies the channel program might
+			  become modified
+DOIO_SUPPRESS_INTER       don't call the handler on intermediate status
+========================= =============================================
+
+The cpa parameter points to the first format 1 CCW of a channel program::
+
+  struct ccw1 {
+	__u8  cmd_code;/* command code */
+	__u8  flags;   /* flags, like IDA addressing, etc. */
+	__u16 count;   /* byte count */
+	__u32 cda;     /* data address */
+  } __attribute__ ((packed,aligned(8)));
+
+with the following CCW flags values defined:
+
+=================== =========================
+CCW_FLAG_DC         data chaining
+CCW_FLAG_CC         command chaining
+CCW_FLAG_SLI        suppress incorrect length
+CCW_FLAG_SKIP       skip
+CCW_FLAG_PCI        PCI
+CCW_FLAG_IDA        indirect addressing
+CCW_FLAG_SUSPEND    suspend
+=================== =========================
+
+
+Via ccw_device_set_options(), the device driver may specify the following
+options for the device:
+
+========================= ======================================
+DOIO_EARLY_NOTIFICATION   allow for early interrupt notification
+DOIO_REPORT_ALL           report all interrupt conditions
+========================= ======================================
+
+
+The ccw_device_start() function returns:
+
+======== ======================================================================
+      0  successful completion or request successfully initiated
+ -EBUSY  The device is currently processing a previous I/O request, or there is
+	 a status pending at the device.
+-ENODEV  cdev is invalid, the device is not operational or the ccw_device is
+	 not online.
+======== ======================================================================
+
+When the I/O request completes, the CDS first level interrupt handler will
+accumulate the status in a struct irb and then call the device interrupt handler.
+The intparm field will contain the value the device driver has associated with a
+particular I/O request. If a pending device status was recognized,
+intparm will be set to 0 (zero). This may happen during I/O initiation or delayed
+by an alert status notification. In any case this status is not related to the
+current (last) I/O request. In case of a delayed status notification no special
+interrupt will be presented to indicate I/O completion as the I/O request was
+never started, even though ccw_device_start() returned with successful completion.
+
+The irb may contain an error value, and the device driver should check for this
+first:
+
+========== =================================================================
+-ETIMEDOUT the common I/O layer terminated the request after the specified
+	   timeout value
+-EIO       the common I/O layer terminated the request due to an error state
+========== =================================================================
+
+If the concurrent sense flag in the extended status word (esw) in the irb is
+set, the field erw.scnt in the esw describes the number of device specific
+sense bytes available in the extended control word irb->scsw.ecw[]. No device
+sensing by the device driver itself is required.
+
+The device interrupt handler can use the following definitions to investigate
+the primary unit check source coded in sense byte 0 :
+
+======================= ====
+SNS0_CMD_REJECT         0x80
+SNS0_INTERVENTION_REQ   0x40
+SNS0_BUS_OUT_CHECK      0x20
+SNS0_EQUIPMENT_CHECK    0x10
+SNS0_DATA_CHECK         0x08
+SNS0_OVERRUN            0x04
+SNS0_INCOMPL_DOMAIN     0x01
+======================= ====
+
+Depending on the device status, multiple of those values may be set together.
+Please refer to the device specific documentation for details.
+
+The irb->scsw.cstat field provides the (accumulated) subchannel status :
+
+========================= ============================
+SCHN_STAT_PCI             program controlled interrupt
+SCHN_STAT_INCORR_LEN      incorrect length
+SCHN_STAT_PROG_CHECK      program check
+SCHN_STAT_PROT_CHECK      protection check
+SCHN_STAT_CHN_DATA_CHK    channel data check
+SCHN_STAT_CHN_CTRL_CHK    channel control check
+SCHN_STAT_INTF_CTRL_CHK   interface control check
+SCHN_STAT_CHAIN_CHECK     chaining check
+========================= ============================
+
+The irb->scsw.dstat field provides the (accumulated) device status :
+
+===================== =================
+DEV_STAT_ATTENTION    attention
+DEV_STAT_STAT_MOD     status modifier
+DEV_STAT_CU_END       control unit end
+DEV_STAT_BUSY         busy
+DEV_STAT_CHN_END      channel end
+DEV_STAT_DEV_END      device end
+DEV_STAT_UNIT_CHECK   unit check
+DEV_STAT_UNIT_EXCEP   unit exception
+===================== =================
+
+Please see the ESA/390 Principles of Operation manual for details on the
+individual flag meanings.
+
+Usage Notes:
+
+ccw_device_start() must be called disabled and with the ccw device lock held.
+
+The device driver is allowed to issue the next ccw_device_start() call from
+within its interrupt handler already. It is not required to schedule a
+bottom-half, unless a non deterministically long running error recovery procedure
+or similar needs to be scheduled. During I/O processing the Linux/390 generic
+I/O device driver support has already obtained the IRQ lock, i.e. the handler
+must not try to obtain it again when calling ccw_device_start() or we end in a
+deadlock situation!
+
+If a device driver relies on an I/O request to be completed prior to start the
+next it can reduce I/O processing overhead by chaining a NoOp I/O command
+CCW_CMD_NOOP to the end of the submitted CCW chain. This will force Channel-End
+and Device-End status to be presented together, with a single interrupt.
+However, this should be used with care as it implies the channel will remain
+busy, not being able to process I/O requests for other devices on the same
+channel. Therefore e.g. read commands should never use this technique, as the
+result will be presented by a single interrupt anyway.
+
+In order to minimize I/O overhead, a device driver should use the
+DOIO_REPORT_ALL  only if the device can report intermediate interrupt
+information prior to device-end the device driver urgently relies on. In this
+case all I/O interruptions are presented to the device driver until final
+status is recognized.
+
+If a device is able to recover from asynchronously presented I/O errors, it can
+perform overlapping I/O using the DOIO_EARLY_NOTIFICATION flag. While some
+devices always report channel-end and device-end together, with a single
+interrupt, others present primary status (channel-end) when the channel is
+ready for the next I/O request and secondary status (device-end) when the data
+transmission has been completed at the device.
+
+Above flag allows to exploit this feature, e.g. for communication devices that
+can handle lost data on the network to allow for enhanced I/O processing.
+
+Unless the channel subsystem at any time presents a secondary status interrupt,
+exploiting this feature will cause only primary status interrupts to be
+presented to the device driver while overlapping I/O is performed. When a
+secondary status without error (alert status) is presented, this indicates
+successful completion for all overlapping ccw_device_start() requests that have
+been issued since the last secondary (final) status.
+
+Channel programs that intend to set the suspend flag on a channel command word
+(CCW)  must start the I/O operation with the DOIO_ALLOW_SUSPEND option or the
+suspend flag will cause a channel program check. At the time the channel program
+becomes suspended an intermediate interrupt will be generated by the channel
+subsystem.
+
+ccw_device_resume() - Resume Channel Program Execution
+
+If a device driver chooses to suspend the current channel program execution by
+setting the CCW suspend flag on a particular CCW, the channel program execution
+is suspended. In order to resume channel program execution the CIO layer
+provides the ccw_device_resume() routine.
+
+::
+
+  int ccw_device_resume(struct ccw_device *cdev);
+
+====  ================================================
+cdev  ccw_device the resume operation is requested for
+====  ================================================
+
+The ccw_device_resume() function returns:
+
+=========   ==============================================
+	0   suspended channel program is resumed
+   -EBUSY   status pending
+  -ENODEV   cdev invalid or not-operational subchannel
+  -EINVAL   resume function not applicable
+-ENOTCONN   there is no I/O request pending for completion
+=========   ==============================================
+
+Usage Notes:
+
+Please have a look at the ccw_device_start() usage notes for more details on
+suspended channel programs.
+
+ccw_device_halt() - Halt I/O Request Processing
+
+Sometimes a device driver might need a possibility to stop the processing of
+a long-running channel program or the device might require to initially issue
+a halt subchannel (HSCH) I/O command. For those purposes the ccw_device_halt()
+command is provided.
+
+ccw_device_halt() must be called disabled and with the ccw device lock held.
+
+::
+
+  int ccw_device_halt(struct ccw_device *cdev,
+		      unsigned long intparm);
+
+=======  =====================================================
+cdev     ccw_device the halt operation is requested for
+intparm  interruption parameter; value is only used if no I/O
+	 is outstanding, otherwise the intparm associated with
+	 the I/O request is returned
+=======  =====================================================
+
+The ccw_device_halt() function returns:
+
+=======  ==============================================================
+      0  request successfully initiated
+-EBUSY   the device is currently busy, or status pending.
+-ENODEV  cdev invalid.
+-EINVAL  The device is not operational or the ccw device is not online.
+=======  ==============================================================
+
+Usage Notes:
+
+A device driver may write a never-ending channel program by writing a channel
+program that at its end loops back to its beginning by means of a transfer in
+channel (TIC)   command (CCW_CMD_TIC). Usually this is performed by network
+device drivers by setting the PCI CCW flag (CCW_FLAG_PCI). Once this CCW is
+executed a program controlled interrupt (PCI) is generated. The device driver
+can then perform an appropriate action. Prior to interrupt of an outstanding
+read to a network device (with or without PCI flag) a ccw_device_halt()
+is required to end the pending operation.
+
+::
+
+  ccw_device_clear() - Terminage I/O Request Processing
+
+In order to terminate all I/O processing at the subchannel, the clear subchannel
+(CSCH) command is used. It can be issued via ccw_device_clear().
+
+ccw_device_clear() must be called disabled and with the ccw device lock held.
+
+::
+
+  int ccw_device_clear(struct ccw_device *cdev, unsigned long intparm);
+
+======= ===============================================
+cdev    ccw_device the clear operation is requested for
+intparm interruption parameter (see ccw_device_halt())
+======= ===============================================
+
+The ccw_device_clear() function returns:
+
+=======  ==============================================================
+      0  request successfully initiated
+-ENODEV  cdev invalid
+-EINVAL  The device is not operational or the ccw device is not online.
+=======  ==============================================================
+
+Miscellaneous Support Routines
+------------------------------
+
+This chapter describes various routines to be used in a Linux/390 device
+driver programming environment.
+
+get_ccwdev_lock()
+
+Get the address of the device specific lock. This is then used in
+spin_lock() / spin_unlock() calls.
+
+::
+
+  __u8 ccw_device_get_path_mask(struct ccw_device *cdev);
+
+Get the mask of the path currently available for cdev.
diff --git a/Documentation/arch/s390/common_io.rst b/Documentation/arch/s390/common_io.rst
new file mode 100644
index 0000000000..6dcb40cb71
--- /dev/null
+++ b/Documentation/arch/s390/common_io.rst
@@ -0,0 +1,140 @@
+======================
+S/390 common I/O-Layer
+======================
+
+command line parameters, procfs and debugfs entries
+===================================================
+
+Command line parameters
+-----------------------
+
+* ccw_timeout_log
+
+  Enable logging of debug information in case of ccw device timeouts.
+
+* cio_ignore = device[,device[,..]]
+
+	device := {all | [!]ipldev | [!]condev | [!]<devno> | [!]<devno>-<devno>}
+
+  The given devices will be ignored by the common I/O-layer; no detection
+  and device sensing will be done on any of those devices. The subchannel to
+  which the device in question is attached will be treated as if no device was
+  attached.
+
+  An ignored device can be un-ignored later; see the "/proc entries"-section for
+  details.
+
+  The devices must be given either as bus ids (0.x.abcd) or as hexadecimal
+  device numbers (0xabcd or abcd, for 2.4 backward compatibility). If you
+  give a device number 0xabcd, it will be interpreted as 0.0.abcd.
+
+  You can use the 'all' keyword to ignore all devices. The 'ipldev' and 'condev'
+  keywords can be used to refer to the CCW based boot device and CCW console
+  device respectively (these are probably useful only when combined with the '!'
+  operator). The '!' operator will cause the I/O-layer to _not_ ignore a device.
+  The command line
+  is parsed from left to right.
+
+  For example::
+
+	cio_ignore=0.0.0023-0.0.0042,0.0.4711
+
+  will ignore all devices ranging from 0.0.0023 to 0.0.0042 and the device
+  0.0.4711, if detected.
+
+  As another example::
+
+	cio_ignore=all,!0.0.4711,!0.0.fd00-0.0.fd02
+
+  will ignore all devices but 0.0.4711, 0.0.fd00, 0.0.fd01, 0.0.fd02.
+
+  By default, no devices are ignored.
+
+
+/proc entries
+-------------
+
+* /proc/cio_ignore
+
+  Lists the ranges of devices (by bus id) which are ignored by common I/O.
+
+  You can un-ignore certain or all devices by piping to /proc/cio_ignore.
+  "free all" will un-ignore all ignored devices,
+  "free <device range>, <device range>, ..." will un-ignore the specified
+  devices.
+
+  For example, if devices 0.0.0023 to 0.0.0042 and 0.0.4711 are ignored,
+
+  - echo free 0.0.0030-0.0.0032 > /proc/cio_ignore
+    will un-ignore devices 0.0.0030 to 0.0.0032 and will leave devices 0.0.0023
+    to 0.0.002f, 0.0.0033 to 0.0.0042 and 0.0.4711 ignored;
+  - echo free 0.0.0041 > /proc/cio_ignore will furthermore un-ignore device
+    0.0.0041;
+  - echo free all > /proc/cio_ignore will un-ignore all remaining ignored
+    devices.
+
+  When a device is un-ignored, device recognition and sensing is performed and
+  the device driver will be notified if possible, so the device will become
+  available to the system. Note that un-ignoring is performed asynchronously.
+
+  You can also add ranges of devices to be ignored by piping to
+  /proc/cio_ignore; "add <device range>, <device range>, ..." will ignore the
+  specified devices.
+
+  Note: While already known devices can be added to the list of devices to be
+	ignored, there will be no effect on then. However, if such a device
+	disappears and then reappears, it will then be ignored. To make
+	known devices go away, you need the "purge" command (see below).
+
+  For example::
+
+	"echo add 0.0.a000-0.0.accc, 0.0.af00-0.0.afff > /proc/cio_ignore"
+
+  will add 0.0.a000-0.0.accc and 0.0.af00-0.0.afff to the list of ignored
+  devices.
+
+  You can remove already known but now ignored devices via::
+
+	"echo purge > /proc/cio_ignore"
+
+  All devices ignored but still registered and not online (= not in use)
+  will be deregistered and thus removed from the system.
+
+  The devices can be specified either by bus id (0.x.abcd) or, for 2.4 backward
+  compatibility, by the device number in hexadecimal (0xabcd or abcd). Device
+  numbers given as 0xabcd will be interpreted as 0.0.abcd.
+
+* /proc/cio_settle
+
+  A write request to this file is blocked until all queued cio actions are
+  handled. This will allow userspace to wait for pending work affecting
+  device availability after changing cio_ignore or the hardware configuration.
+
+* For some of the information present in the /proc filesystem in 2.4 (namely,
+  /proc/subchannels and /proc/chpids), see driver-model.txt.
+  Information formerly in /proc/irq_count is now in /proc/interrupts.
+
+
+debugfs entries
+---------------
+
+* /sys/kernel/debug/s390dbf/cio_*/ (S/390 debug feature)
+
+  Some views generated by the debug feature to hold various debug outputs.
+
+  - /sys/kernel/debug/s390dbf/cio_crw/sprintf
+    Messages from the processing of pending channel report words (machine check
+    handling).
+
+  - /sys/kernel/debug/s390dbf/cio_msg/sprintf
+    Various debug messages from the common I/O-layer.
+
+  - /sys/kernel/debug/s390dbf/cio_trace/hex_ascii
+    Logs the calling of functions in the common I/O-layer and, if applicable,
+    which subchannel they were called for, as well as dumps of some data
+    structures (like irb in an error case).
+
+  The level of logging can be changed to be more or less verbose by piping to
+  /sys/kernel/debug/s390dbf/cio_*/level a number between 0 and 6; see the
+  documentation on the S/390 debug feature (Documentation/arch/s390/s390dbf.rst)
+  for details.
diff --git a/Documentation/arch/s390/config3270.sh b/Documentation/arch/s390/config3270.sh
new file mode 100644
index 0000000000..515e2f4314
--- /dev/null
+++ b/Documentation/arch/s390/config3270.sh
@@ -0,0 +1,76 @@
+#!/bin/sh
+#
+# config3270 -- Autoconfigure /dev/3270/* and /etc/inittab
+#
+#       Usage:
+#               config3270
+#
+#       Output:
+#               /tmp/mkdev3270
+#
+#       Operation:
+#               1. Run this script
+#               2. Run the script it produces: /tmp/mkdev3270
+#               3. Issue "telinit q" or reboot, as appropriate.
+#
+P=/proc/tty/driver/tty3270
+ROOT=
+D=$ROOT/dev
+SUBD=3270
+TTY=$SUBD/tty
+TUB=$SUBD/tub
+SCR=$ROOT/tmp/mkdev3270
+SCRTMP=$SCR.a
+GETTYLINE=:2345:respawn:/sbin/mingetty
+INITTAB=$ROOT/etc/inittab
+NINITTAB=$ROOT/etc/NEWinittab
+OINITTAB=$ROOT/etc/OLDinittab
+ADDNOTE=\\"# Additional mingettys for the 3270/tty* driver, tub3270 ---\\"
+
+if ! ls $P > /dev/null 2>&1; then
+	modprobe tub3270 > /dev/null 2>&1
+fi
+ls $P > /dev/null 2>&1 || exit 1
+
+# Initialize two files, one for /dev/3270 commands and one
+# to replace the /etc/inittab file (old one saved in OLDinittab)
+echo "#!/bin/sh" > $SCR || exit 1
+echo " " >> $SCR
+echo "# Script built by /sbin/config3270" >> $SCR
+if [ ! -d /dev/dasd ]; then
+	echo rm -rf "$D/$SUBD/*" >> $SCR
+fi
+echo "grep -v $TTY $INITTAB > $NINITTAB" > $SCRTMP || exit 1
+echo "echo $ADDNOTE >> $NINITTAB" >> $SCRTMP
+if [ ! -d /dev/dasd ]; then
+	echo mkdir -p $D/$SUBD >> $SCR
+fi
+
+# Now query the tub3270 driver for 3270 device information
+# and add appropriate mknod and mingetty lines to our files
+echo what=config > $P
+while read devno maj min;do
+	if [ $min = 0 ]; then
+		fsmaj=$maj
+		if [ ! -d /dev/dasd ]; then
+			echo mknod $D/$TUB c $fsmaj 0 >> $SCR
+			echo chmod 666 $D/$TUB >> $SCR
+		fi
+	elif [ $maj = CONSOLE ]; then
+		if [ ! -d /dev/dasd ]; then
+			echo mknod $D/$TUB$devno c $fsmaj $min >> $SCR
+		fi
+	else
+		if [ ! -d /dev/dasd ]; then
+			echo mknod $D/$TTY$devno c $maj $min >>$SCR
+			echo mknod $D/$TUB$devno c $fsmaj $min >> $SCR
+		fi
+		echo "echo t$min$GETTYLINE $TTY$devno >> $NINITTAB" >> $SCRTMP
+	fi
+done < $P
+
+echo mv $INITTAB $OINITTAB >> $SCRTMP || exit 1
+echo mv $NINITTAB $INITTAB >> $SCRTMP
+cat $SCRTMP >> $SCR
+rm $SCRTMP
+exit 0
diff --git a/Documentation/arch/s390/driver-model.rst b/Documentation/arch/s390/driver-model.rst
new file mode 100644
index 0000000000..ad4bc2dbea
--- /dev/null
+++ b/Documentation/arch/s390/driver-model.rst
@@ -0,0 +1,328 @@
+=============================
+S/390 driver model interfaces
+=============================
+
+1. CCW devices
+--------------
+
+All devices which can be addressed by means of ccws are called 'CCW devices' -
+even if they aren't actually driven by ccws.
+
+All ccw devices are accessed via a subchannel, this is reflected in the
+structures under devices/::
+
+  devices/
+     - system/
+     - css0/
+	   - 0.0.0000/0.0.0815/
+	   - 0.0.0001/0.0.4711/
+	   - 0.0.0002/
+	   - 0.1.0000/0.1.1234/
+	   ...
+	   - defunct/
+
+In this example, device 0815 is accessed via subchannel 0 in subchannel set 0,
+device 4711 via subchannel 1 in subchannel set 0, and subchannel 2 is a non-I/O
+subchannel. Device 1234 is accessed via subchannel 0 in subchannel set 1.
+
+The subchannel named 'defunct' does not represent any real subchannel on the
+system; it is a pseudo subchannel where disconnected ccw devices are moved to
+if they are displaced by another ccw device becoming operational on their
+former subchannel. The ccw devices will be moved again to a proper subchannel
+if they become operational again on that subchannel.
+
+You should address a ccw device via its bus id (e.g. 0.0.4711); the device can
+be found under bus/ccw/devices/.
+
+All ccw devices export some data via sysfs.
+
+cutype:
+	The control unit type / model.
+
+devtype:
+	The device type / model, if applicable.
+
+availability:
+	      Can be 'good' or 'boxed'; 'no path' or 'no device' for
+	      disconnected devices.
+
+online:
+	    An interface to set the device online and offline.
+	    In the special case of the device being disconnected (see the
+	    notify function under 1.2), piping 0 to online will forcibly delete
+	    the device.
+
+The device drivers can add entries to export per-device data and interfaces.
+
+There is also some data exported on a per-subchannel basis (see under
+bus/css/devices/):
+
+chpids:
+	Via which chpids the device is connected.
+
+pimpampom:
+	The path installed, path available and path operational masks.
+
+There also might be additional data, for example for block devices.
+
+
+1.1 Bringing up a ccw device
+----------------------------
+
+This is done in several steps.
+
+a. Each driver can provide one or more parameter interfaces where parameters can
+   be specified. These interfaces are also in the driver's responsibility.
+b. After a. has been performed, if necessary, the device is finally brought up
+   via the 'online' interface.
+
+
+1.2 Writing a driver for ccw devices
+------------------------------------
+
+The basic struct ccw_device and struct ccw_driver data structures can be found
+under include/asm/ccwdev.h::
+
+  struct ccw_device {
+	spinlock_t *ccwlock;
+	struct ccw_device_private *private;
+	struct ccw_device_id id;
+
+	struct ccw_driver *drv;
+	struct device dev;
+	int online;
+
+	void (*handler) (struct ccw_device *dev, unsigned long intparm,
+			 struct irb *irb);
+  };
+
+  struct ccw_driver {
+	struct module *owner;
+	struct ccw_device_id *ids;
+	int (*probe) (struct ccw_device *);
+	int (*remove) (struct ccw_device *);
+	int (*set_online) (struct ccw_device *);
+	int (*set_offline) (struct ccw_device *);
+	int (*notify) (struct ccw_device *, int);
+	struct device_driver driver;
+	char *name;
+  };
+
+The 'private' field contains data needed for internal i/o operation only, and
+is not available to the device driver.
+
+Each driver should declare in a MODULE_DEVICE_TABLE into which CU types/models
+and/or device types/models it is interested. This information can later be found
+in the struct ccw_device_id fields::
+
+  struct ccw_device_id {
+	__u16   match_flags;
+
+	__u16   cu_type;
+	__u16   dev_type;
+	__u8    cu_model;
+	__u8    dev_model;
+
+	unsigned long driver_info;
+  };
+
+The functions in ccw_driver should be used in the following way:
+
+probe:
+	 This function is called by the device layer for each device the driver
+	 is interested in. The driver should only allocate private structures
+	 to put in dev->driver_data and create attributes (if needed). Also,
+	 the interrupt handler (see below) should be set here.
+
+::
+
+  int (*probe) (struct ccw_device *cdev);
+
+Parameters:
+		cdev
+			- the device to be probed.
+
+
+remove:
+	 This function is called by the device layer upon removal of the driver,
+	 the device or the module. The driver should perform cleanups here.
+
+::
+
+  int (*remove) (struct ccw_device *cdev);
+
+Parameters:
+		cdev
+			- the device to be removed.
+
+
+set_online:
+	    This function is called by the common I/O layer when the device is
+	    activated via the 'online' attribute. The driver should finally
+	    setup and activate the device here.
+
+::
+
+  int (*set_online) (struct ccw_device *);
+
+Parameters:
+		cdev
+			- the device to be activated. The common layer has
+			  verified that the device is not already online.
+
+
+set_offline: This function is called by the common I/O layer when the device is
+	     de-activated via the 'online' attribute. The driver should shut
+	     down the device, but not de-allocate its private data.
+
+::
+
+  int (*set_offline) (struct ccw_device *);
+
+Parameters:
+		cdev
+			- the device to be deactivated. The common layer has
+			   verified that the device is online.
+
+
+notify:
+	This function is called by the common I/O layer for some state changes
+	of the device.
+
+	Signalled to the driver are:
+
+	* In online state, device detached (CIO_GONE) or last path gone
+	  (CIO_NO_PATH). The driver must return !0 to keep the device; for
+	  return code 0, the device will be deleted as usual (also when no
+	  notify function is registered). If the driver wants to keep the
+	  device, it is moved into disconnected state.
+	* In disconnected state, device operational again (CIO_OPER). The
+	  common I/O layer performs some sanity checks on device number and
+	  Device / CU to be reasonably sure if it is still the same device.
+	  If not, the old device is removed and a new one registered. By the
+	  return code of the notify function the device driver signals if it
+	  wants the device back: !0 for keeping, 0 to make the device being
+	  removed and re-registered.
+
+::
+
+  int (*notify) (struct ccw_device *, int);
+
+Parameters:
+		cdev
+			- the device whose state changed.
+
+		event
+			- the event that happened. This can be one of CIO_GONE,
+			  CIO_NO_PATH or CIO_OPER.
+
+The handler field of the struct ccw_device is meant to be set to the interrupt
+handler for the device. In order to accommodate drivers which use several
+distinct handlers (e.g. multi subchannel devices), this is a member of ccw_device
+instead of ccw_driver.
+The handler is registered with the common layer during set_online() processing
+before the driver is called, and is deregistered during set_offline() after the
+driver has been called. Also, after registering / before deregistering, path
+grouping resp. disbanding of the path group (if applicable) are performed.
+
+::
+
+  void (*handler) (struct ccw_device *dev, unsigned long intparm, struct irb *irb);
+
+Parameters:     dev     - the device the handler is called for
+		intparm - the intparm which allows the device driver to identify
+			  the i/o the interrupt is associated with, or to recognize
+			  the interrupt as unsolicited.
+		irb     - interruption response block which contains the accumulated
+			  status.
+
+The device driver is called from the common ccw_device layer and can retrieve
+information about the interrupt from the irb parameter.
+
+
+1.3 ccwgroup devices
+--------------------
+
+The ccwgroup mechanism is designed to handle devices consisting of multiple ccw
+devices, like lcs or ctc.
+
+The ccw driver provides a 'group' attribute. Piping bus ids of ccw devices to
+this attributes creates a ccwgroup device consisting of these ccw devices (if
+possible). This ccwgroup device can be set online or offline just like a normal
+ccw device.
+
+Each ccwgroup device also provides an 'ungroup' attribute to destroy the device
+again (only when offline). This is a generic ccwgroup mechanism (the driver does
+not need to implement anything beyond normal removal routines).
+
+A ccw device which is a member of a ccwgroup device carries a pointer to the
+ccwgroup device in the driver_data of its device struct. This field must not be
+touched by the driver - it should use the ccwgroup device's driver_data for its
+private data.
+
+To implement a ccwgroup driver, please refer to include/asm/ccwgroup.h. Keep in
+mind that most drivers will need to implement both a ccwgroup and a ccw
+driver.
+
+
+2. Channel paths
+-----------------
+
+Channel paths show up, like subchannels, under the channel subsystem root (css0)
+and are called 'chp0.<chpid>'. They have no driver and do not belong to any bus.
+Please note, that unlike /proc/chpids in 2.4, the channel path objects reflect
+only the logical state and not the physical state, since we cannot track the
+latter consistently due to lacking machine support (we don't need to be aware
+of it anyway).
+
+status
+       - Can be 'online' or 'offline'.
+	 Piping 'on' or 'off' sets the chpid logically online/offline.
+	 Piping 'on' to an online chpid triggers path reprobing for all devices
+	 the chpid connects to. This can be used to force the kernel to re-use
+	 a channel path the user knows to be online, but the machine hasn't
+	 created a machine check for.
+
+type
+       - The physical type of the channel path.
+
+shared
+       - Whether the channel path is shared.
+
+cmg
+       - The channel measurement group.
+
+3. System devices
+-----------------
+
+3.1 xpram
+---------
+
+xpram shows up under devices/system/ as 'xpram'.
+
+3.2 cpus
+--------
+
+For each cpu, a directory is created under devices/system/cpu/. Each cpu has an
+attribute 'online' which can be 0 or 1.
+
+
+4. Other devices
+----------------
+
+4.1 Netiucv
+-----------
+
+The netiucv driver creates an attribute 'connection' under
+bus/iucv/drivers/netiucv. Piping to this attribute creates a new netiucv
+connection to the specified host.
+
+Netiucv connections show up under devices/iucv/ as "netiucv<ifnum>". The interface
+number is assigned sequentially to the connections defined via the 'connection'
+attribute.
+
+user
+    - shows the connection partner.
+
+buffer
+    - maximum buffer size. Pipe to it to change buffer size.
diff --git a/Documentation/arch/s390/features.rst b/Documentation/arch/s390/features.rst
new file mode 100644
index 0000000000..2883dc9506
--- /dev/null
+++ b/Documentation/arch/s390/features.rst
@@ -0,0 +1,3 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+.. kernel-feat:: features s390
diff --git a/Documentation/arch/s390/index.rst b/Documentation/arch/s390/index.rst
new file mode 100644
index 0000000000..73c79bf586
--- /dev/null
+++ b/Documentation/arch/s390/index.rst
@@ -0,0 +1,30 @@
+=================
+s390 Architecture
+=================
+
+.. toctree::
+    :maxdepth: 1
+
+    cds
+    3270
+    driver-model
+    monreader
+    qeth
+    s390dbf
+    vfio-ap
+    vfio-ap-locking
+    vfio-ccw
+    zfcpdump
+    common_io
+    pci
+
+    text_files
+
+    features
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`
diff --git a/Documentation/arch/s390/monreader.rst b/Documentation/arch/s390/monreader.rst
new file mode 100644
index 0000000000..21cdfb699b
--- /dev/null
+++ b/Documentation/arch/s390/monreader.rst
@@ -0,0 +1,212 @@
+=================================================
+Linux API for read access to z/VM Monitor Records
+=================================================
+
+Date  : 2004-Nov-26
+
+Author: Gerald Schaefer (geraldsc@de.ibm.com)
+
+
+
+
+Description
+===========
+This item delivers a new Linux API in the form of a misc char device that is
+usable from user space and allows read access to the z/VM Monitor Records
+collected by the `*MONITOR` System Service of z/VM.
+
+
+User Requirements
+=================
+The z/VM guest on which you want to access this API needs to be configured in
+order to allow IUCV connections to the `*MONITOR` service, i.e. it needs the
+IUCV `*MONITOR` statement in its user entry. If the monitor DCSS to be used is
+restricted (likely), you also need the NAMESAVE <DCSS NAME> statement.
+This item will use the IUCV device driver to access the z/VM services, so you
+need a kernel with IUCV support. You also need z/VM version 4.4 or 5.1.
+
+There are two options for being able to load the monitor DCSS (examples assume
+that the monitor DCSS begins at 144 MB and ends at 152 MB). You can query the
+location of the monitor DCSS with the Class E privileged CP command Q NSS MAP
+(the values BEGPAG and ENDPAG are given in units of 4K pages).
+
+See also "CP Command and Utility Reference" (SC24-6081-00) for more information
+on the DEF STOR and Q NSS MAP commands, as well as "Saved Segments Planning
+and Administration" (SC24-6116-00) for more information on DCSSes.
+
+1st option:
+-----------
+You can use the CP command DEF STOR CONFIG to define a "memory hole" in your
+guest virtual storage around the address range of the DCSS.
+
+Example: DEF STOR CONFIG 0.140M 200M.200M
+
+This defines two blocks of storage, the first is 140MB in size an begins at
+address 0MB, the second is 200MB in size and begins at address 200MB,
+resulting in a total storage of 340MB. Note that the first block should
+always start at 0 and be at least 64MB in size.
+
+2nd option:
+-----------
+Your guest virtual storage has to end below the starting address of the DCSS
+and you have to specify the "mem=" kernel parameter in your parmfile with a
+value greater than the ending address of the DCSS.
+
+Example::
+
+	DEF STOR 140M
+
+This defines 140MB storage size for your guest, the parameter "mem=160M" is
+added to the parmfile.
+
+
+User Interface
+==============
+The char device is implemented as a kernel module named "monreader",
+which can be loaded via the modprobe command, or it can be compiled into the
+kernel instead. There is one optional module (or kernel) parameter, "mondcss",
+to specify the name of the monitor DCSS. If the module is compiled into the
+kernel, the kernel parameter "monreader.mondcss=<DCSS NAME>" can be specified
+in the parmfile.
+
+The default name for the DCSS is "MONDCSS" if none is specified. In case that
+there are other users already connected to the `*MONITOR` service (e.g.
+Performance Toolkit), the monitor DCSS is already defined and you have to use
+the same DCSS. The CP command Q MONITOR (Class E privileged) shows the name
+of the monitor DCSS, if already defined, and the users connected to the
+`*MONITOR` service.
+Refer to the "z/VM Performance" book (SC24-6109-00) on how to create a monitor
+DCSS if your z/VM doesn't have one already, you need Class E privileges to
+define and save a DCSS.
+
+Example:
+--------
+
+::
+
+	modprobe monreader mondcss=MYDCSS
+
+This loads the module and sets the DCSS name to "MYDCSS".
+
+NOTE:
+-----
+This API provides no interface to control the `*MONITOR` service, e.g. specify
+which data should be collected. This can be done by the CP command MONITOR
+(Class E privileged), see "CP Command and Utility Reference".
+
+Device nodes with udev:
+-----------------------
+After loading the module, a char device will be created along with the device
+node /<udev directory>/monreader.
+
+Device nodes without udev:
+--------------------------
+If your distribution does not support udev, a device node will not be created
+automatically and you have to create it manually after loading the module.
+Therefore you need to know the major and minor numbers of the device. These
+numbers can be found in /sys/class/misc/monreader/dev.
+
+Typing cat /sys/class/misc/monreader/dev will give an output of the form
+<major>:<minor>. The device node can be created via the mknod command, enter
+mknod <name> c <major> <minor>, where <name> is the name of the device node
+to be created.
+
+Example:
+--------
+
+::
+
+	# modprobe monreader
+	# cat /sys/class/misc/monreader/dev
+	10:63
+	# mknod /dev/monreader c 10 63
+
+This loads the module with the default monitor DCSS (MONDCSS) and creates a
+device node.
+
+File operations:
+----------------
+The following file operations are supported: open, release, read, poll.
+There are two alternative methods for reading: either non-blocking read in
+conjunction with polling, or blocking read without polling. IOCTLs are not
+supported.
+
+Read:
+-----
+Reading from the device provides a 12 Byte monitor control element (MCE),
+followed by a set of one or more contiguous monitor records (similar to the
+output of the CMS utility MONWRITE without the 4K control blocks). The MCE
+contains information on the type of the following record set (sample/event
+data), the monitor domains contained within it and the start and end address
+of the record set in the monitor DCSS. The start and end address can be used
+to determine the size of the record set, the end address is the address of the
+last byte of data. The start address is needed to handle "end-of-frame" records
+correctly (domain 1, record 13), i.e. it can be used to determine the record
+start offset relative to a 4K page (frame) boundary.
+
+See "Appendix A: `*MONITOR`" in the "z/VM Performance" document for a description
+of the monitor control element layout. The layout of the monitor records can
+be found here (z/VM 5.1): https://www.vm.ibm.com/pubs/mon510/index.html
+
+The layout of the data stream provided by the monreader device is as follows::
+
+	...
+	<0 byte read>
+	<first MCE>              \
+	<first set of records>    |
+	...                       |- data set
+	<last MCE>                |
+	<last set of records>    /
+	<0 byte read>
+	...
+
+There may be more than one combination of MCE and corresponding record set
+within one data set and the end of each data set is indicated by a successful
+read with a return value of 0 (0 byte read).
+Any received data must be considered invalid until a complete set was
+read successfully, including the closing 0 byte read. Therefore you should
+always read the complete set into a buffer before processing the data.
+
+The maximum size of a data set can be as large as the size of the
+monitor DCSS, so design the buffer adequately or use dynamic memory allocation.
+The size of the monitor DCSS will be printed into syslog after loading the
+module. You can also use the (Class E privileged) CP command Q NSS MAP to
+list all available segments and information about them.
+
+As with most char devices, error conditions are indicated by returning a
+negative value for the number of bytes read. In this case, the errno variable
+indicates the error condition:
+
+EIO:
+     reply failed, read data is invalid and the application
+     should discard the data read since the last successful read with 0 size.
+EFAULT:
+	copy_to_user failed, read data is invalid and the application should
+	discard the data read since the last successful read with 0 size.
+EAGAIN:
+	occurs on a non-blocking read if there is no data available at the
+	moment. There is no data missing or corrupted, just try again or rather
+	use polling for non-blocking reads.
+EOVERFLOW:
+	   message limit reached, the data read since the last successful
+	   read with 0 size is valid but subsequent records may be missing.
+
+In the last case (EOVERFLOW) there may be missing data, in the first two cases
+(EIO, EFAULT) there will be missing data. It's up to the application if it will
+continue reading subsequent data or rather exit.
+
+Open:
+-----
+Only one user is allowed to open the char device. If it is already in use, the
+open function will fail (return a negative value) and set errno to EBUSY.
+The open function may also fail if an IUCV connection to the `*MONITOR` service
+cannot be established. In this case errno will be set to EIO and an error
+message with an IPUSER SEVER code will be printed into syslog. The IPUSER SEVER
+codes are described in the "z/VM Performance" book, Appendix A.
+
+NOTE:
+-----
+As soon as the device is opened, incoming messages will be accepted and they
+will account for the message limit, i.e. opening the device without reading
+from it will provoke the "message limit reached" error (EOVERFLOW error code)
+eventually.
diff --git a/Documentation/arch/s390/pci.rst b/Documentation/arch/s390/pci.rst
new file mode 100644
index 0000000000..d5755484d8
--- /dev/null
+++ b/Documentation/arch/s390/pci.rst
@@ -0,0 +1,133 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=========
+S/390 PCI
+=========
+
+Authors:
+        - Pierre Morel
+
+Copyright, IBM Corp. 2020
+
+
+Command line parameters and debugfs entries
+===========================================
+
+Command line parameters
+-----------------------
+
+* nomio
+
+  Do not use PCI Mapped I/O (MIO) instructions.
+
+* norid
+
+  Ignore the RID field and force use of one PCI domain per PCI function.
+
+debugfs entries
+---------------
+
+The S/390 debug feature (s390dbf) generates views to hold various debug results in sysfs directories of the form:
+
+ * /sys/kernel/debug/s390dbf/pci_*/
+
+For example:
+
+  - /sys/kernel/debug/s390dbf/pci_msg/sprintf
+    Holds messages from the processing of PCI events, like machine check handling
+    and setting of global functionality, like UID checking.
+
+  Change the level of logging to be more or less verbose by piping
+  a number between 0 and 6 to  /sys/kernel/debug/s390dbf/pci_*/level. For
+  details, see the documentation on the S/390 debug feature at
+  Documentation/arch/s390/s390dbf.rst.
+
+Sysfs entries
+=============
+
+Entries specific to zPCI functions and entries that hold zPCI information.
+
+* /sys/bus/pci/slots/XXXXXXXX
+
+  The slot entries are set up using the function identifier (FID) of the
+  PCI function. The format depicted as XXXXXXXX above is 8 hexadecimal digits
+  with 0 padding and lower case hexadecimal digits.
+
+  - /sys/bus/pci/slots/XXXXXXXX/power
+
+  A physical function that currently supports a virtual function cannot be
+  powered off until all virtual functions are removed with:
+  echo 0 > /sys/bus/pci/devices/XXXX:XX:XX.X/sriov_numvf
+
+* /sys/bus/pci/devices/XXXX:XX:XX.X/
+
+  - function_id
+    A zPCI function identifier that uniquely identifies the function in the Z server.
+
+  - function_handle
+    Low-level identifier used for a configured PCI function.
+    It might be useful for debugging.
+
+  - pchid
+    Model-dependent location of the I/O adapter.
+
+  - pfgid
+    PCI function group ID, functions that share identical functionality
+    use a common identifier.
+    A PCI group defines interrupts, IOMMU, IOTLB, and DMA specifics.
+
+  - vfn
+    The virtual function number, from 1 to N for virtual functions,
+    0 for physical functions.
+
+  - pft
+    The PCI function type
+
+  - port
+    The port corresponds to the physical port the function is attached to.
+    It also gives an indication of the physical function a virtual function
+    is attached to.
+
+  - uid
+    The user identifier (UID) may be defined as part of the machine
+    configuration or the z/VM or KVM guest configuration. If the accompanying
+    uid_is_unique attribute is 1 the platform guarantees that the UID is unique
+    within that instance and no devices with the same UID can be attached
+    during the lifetime of the system.
+
+  - uid_is_unique
+    Indicates whether the user identifier (UID) is guaranteed to be and remain
+    unique within this Linux instance.
+
+  - pfip/segmentX
+    The segments determine the isolation of a function.
+    They correspond to the physical path to the function.
+    The more the segments are different, the more the functions are isolated.
+
+Enumeration and hotplug
+=======================
+
+The PCI address consists of four parts: domain, bus, device and function,
+and is of this form: DDDD:BB:dd.f
+
+* When not using multi-functions (norid is set, or the firmware does not
+  support multi-functions):
+
+  - There is only one function per domain.
+
+  - The domain is set from the zPCI function's UID as defined during the
+    LPAR creation.
+
+* When using multi-functions (norid parameter is not set),
+  zPCI functions are addressed differently:
+
+  - There is still only one bus per domain.
+
+  - There can be up to 256 functions per bus.
+
+  - The domain part of the address of all functions for
+    a multi-Function device is set from the zPCI function's UID as defined
+    in the LPAR creation for the function zero.
+
+  - New functions will only be ready for use after the function zero
+    (the function with devfn 0) has been enumerated.
diff --git a/Documentation/arch/s390/qeth.rst b/Documentation/arch/s390/qeth.rst
new file mode 100644
index 0000000000..f02fdaa68d
--- /dev/null
+++ b/Documentation/arch/s390/qeth.rst
@@ -0,0 +1,64 @@
+=============================
+IBM s390 QDIO Ethernet Driver
+=============================
+
+OSA and HiperSockets Bridge Port Support
+========================================
+
+Uevents
+-------
+
+To generate the events the device must be assigned a role of either
+a primary or a secondary Bridge Port. For more information, see
+"z/VM Connectivity, SC24-6174".
+
+When run on an OSA or HiperSockets Bridge Capable Port hardware, and the state
+of some configured Bridge Port device on the channel changes, a udev
+event with ACTION=CHANGE is emitted on behalf of the corresponding
+ccwgroup device. The event has the following attributes:
+
+BRIDGEPORT=statechange
+  indicates that the Bridge Port device changed
+  its state.
+
+ROLE={primary|secondary|none}
+  the role assigned to the port.
+
+STATE={active|standby|inactive}
+  the newly assumed state of the port.
+
+When run on HiperSockets Bridge Capable Port hardware with host address
+notifications enabled, a udev event with ACTION=CHANGE is emitted.
+It is emitted on behalf of the corresponding ccwgroup device when a host
+or a VLAN is registered or unregistered on the network served by the device.
+The event has the following attributes:
+
+BRIDGEDHOST={reset|register|deregister|abort}
+  host address
+  notifications are started afresh, a new host or VLAN is registered or
+  deregistered on the Bridge Port HiperSockets channel, or address
+  notifications are aborted.
+
+VLAN=numeric-vlan-id
+  VLAN ID on which the event occurred. Not included
+  if no VLAN is involved in the event.
+
+MAC=xx:xx:xx:xx:xx:xx
+  MAC address of the host that is being registered
+  or deregistered from the HiperSockets channel. Not reported if the
+  event reports the creation or destruction of a VLAN.
+
+NTOK_BUSID=x.y.zzzz
+  device bus ID (CSSID, SSID and device number).
+
+NTOK_IID=xx
+  device IID.
+
+NTOK_CHPID=xx
+  device CHPID.
+
+NTOK_CHID=xxxx
+  device channel ID.
+
+Note that the `NTOK_*` attributes refer to devices other than  the one
+connected to the system on which the OS is running.
diff --git a/Documentation/arch/s390/s390dbf.rst b/Documentation/arch/s390/s390dbf.rst
new file mode 100644
index 0000000000..af8bdc3629
--- /dev/null
+++ b/Documentation/arch/s390/s390dbf.rst
@@ -0,0 +1,478 @@
+==================
+S390 Debug Feature
+==================
+
+files:
+      - arch/s390/kernel/debug.c
+      - arch/s390/include/asm/debug.h
+
+Description:
+------------
+The goal of this feature is to provide a kernel debug logging API
+where log records can be stored efficiently in memory, where each component
+(e.g. device drivers) can have one separate debug log.
+One purpose of this is to inspect the debug logs after a production system crash
+in order to analyze the reason for the crash.
+
+If the system still runs but only a subcomponent which uses dbf fails,
+it is possible to look at the debug logs on a live system via the Linux
+debugfs filesystem.
+
+The debug feature may also very useful for kernel and driver development.
+
+Design:
+-------
+Kernel components (e.g. device drivers) can register themselves at the debug
+feature with the function call :c:func:`debug_register()`.
+This function initializes a
+debug log for the caller. For each debug log exists a number of debug areas
+where exactly one is active at one time.  Each debug area consists of contiguous
+pages in memory. In the debug areas there are stored debug entries (log records)
+which are written by event- and exception-calls.
+
+An event-call writes the specified debug entry to the active debug
+area and updates the log pointer for the active area. If the end
+of the active debug area is reached, a wrap around is done (ring buffer)
+and the next debug entry will be written at the beginning of the active
+debug area.
+
+An exception-call writes the specified debug entry to the log and
+switches to the next debug area. This is done in order to be sure
+that the records which describe the origin of the exception are not
+overwritten when a wrap around for the current area occurs.
+
+The debug areas themselves are also ordered in form of a ring buffer.
+When an exception is thrown in the last debug area, the following debug
+entries are then written again in the very first area.
+
+There are four versions for the event- and exception-calls: One for
+logging raw data, one for text, one for numbers (unsigned int and long),
+and one for sprintf-like formatted strings.
+
+Each debug entry contains the following data:
+
+- Timestamp
+- Cpu-Number of calling task
+- Level of debug entry (0...6)
+- Return Address to caller
+- Flag, if entry is an exception or not
+
+The debug logs can be inspected in a live system through entries in
+the debugfs-filesystem. Under the toplevel directory "``s390dbf``" there is
+a directory for each registered component, which is named like the
+corresponding component. The debugfs normally should be mounted to
+``/sys/kernel/debug`` therefore the debug feature can be accessed under
+``/sys/kernel/debug/s390dbf``.
+
+The content of the directories are files which represent different views
+to the debug log. Each component can decide which views should be
+used through registering them with the function :c:func:`debug_register_view()`.
+Predefined views for hex/ascii and sprintf data are provided.
+It is also possible to define other views. The content of
+a view can be inspected simply by reading the corresponding debugfs file.
+
+All debug logs have an actual debug level (range from 0 to 6).
+The default level is 3. Event and Exception functions have a :c:data:`level`
+parameter. Only debug entries with a level that is lower or equal
+than the actual level are written to the log. This means, when
+writing events, high priority log entries should have a low level
+value whereas low priority entries should have a high one.
+The actual debug level can be changed with the help of the debugfs-filesystem
+through writing a number string "x" to the ``level`` debugfs file which is
+provided for every debug log. Debugging can be switched off completely
+by using "-" on the ``level`` debugfs file.
+
+Example::
+
+	> echo "-" > /sys/kernel/debug/s390dbf/dasd/level
+
+It is also possible to deactivate the debug feature globally for every
+debug log. You can change the behavior using  2 sysctl parameters in
+``/proc/sys/s390dbf``:
+
+There are currently 2 possible triggers, which stop the debug feature
+globally. The first possibility is to use the ``debug_active`` sysctl. If
+set to 1 the debug feature is running. If ``debug_active`` is set to 0 the
+debug feature is turned off.
+
+The second trigger which stops the debug feature is a kernel oops.
+That prevents the debug feature from overwriting debug information that
+happened before the oops. After an oops you can reactivate the debug feature
+by piping 1 to ``/proc/sys/s390dbf/debug_active``. Nevertheless, it's not
+suggested to use an oopsed kernel in a production environment.
+
+If you want to disallow the deactivation of the debug feature, you can use
+the ``debug_stoppable`` sysctl. If you set ``debug_stoppable`` to 0 the debug
+feature cannot be stopped. If the debug feature is already stopped, it
+will stay deactivated.
+
+Kernel Interfaces:
+------------------
+
+.. kernel-doc:: arch/s390/kernel/debug.c
+.. kernel-doc:: arch/s390/include/asm/debug.h
+
+Predefined views:
+-----------------
+
+.. code-block:: c
+
+  extern struct debug_view debug_hex_ascii_view;
+
+  extern struct debug_view debug_sprintf_view;
+
+Examples
+--------
+
+.. code-block:: c
+
+  /*
+   * hex_ascii-view Example
+   */
+
+  #include <linux/init.h>
+  #include <asm/debug.h>
+
+  static debug_info_t *debug_info;
+
+  static int init(void)
+  {
+      /* register 4 debug areas with one page each and 4 byte data field */
+
+      debug_info = debug_register("test", 1, 4, 4 );
+      debug_register_view(debug_info, &debug_hex_ascii_view);
+
+      debug_text_event(debug_info, 4 , "one ");
+      debug_int_exception(debug_info, 4, 4711);
+      debug_event(debug_info, 3, &debug_info, 4);
+
+      return 0;
+  }
+
+  static void cleanup(void)
+  {
+      debug_unregister(debug_info);
+  }
+
+  module_init(init);
+  module_exit(cleanup);
+
+.. code-block:: c
+
+  /*
+   * sprintf-view Example
+   */
+
+  #include <linux/init.h>
+  #include <asm/debug.h>
+
+  static debug_info_t *debug_info;
+
+  static int init(void)
+  {
+      /* register 4 debug areas with one page each and data field for */
+      /* format string pointer + 2 varargs (= 3 * sizeof(long))       */
+
+      debug_info = debug_register("test", 1, 4, sizeof(long) * 3);
+      debug_register_view(debug_info, &debug_sprintf_view);
+
+      debug_sprintf_event(debug_info, 2 , "first event in %s:%i\n",__FILE__,__LINE__);
+      debug_sprintf_exception(debug_info, 1, "pointer to debug info: %p\n",&debug_info);
+
+      return 0;
+  }
+
+  static void cleanup(void)
+  {
+      debug_unregister(debug_info);
+  }
+
+  module_init(init);
+  module_exit(cleanup);
+
+Debugfs Interface
+-----------------
+Views to the debug logs can be investigated through reading the corresponding
+debugfs-files:
+
+Example::
+
+  > ls /sys/kernel/debug/s390dbf/dasd
+  flush  hex_ascii  level pages
+  > cat /sys/kernel/debug/s390dbf/dasd/hex_ascii | sort -k2,2 -s
+  00 00974733272:680099 2 - 02 0006ad7e  07 ea 4a 90 | ....
+  00 00974733272:682210 2 - 02 0006ade6  46 52 45 45 | FREE
+  00 00974733272:682213 2 - 02 0006adf6  07 ea 4a 90 | ....
+  00 00974733272:682281 1 * 02 0006ab08  41 4c 4c 43 | EXCP
+  01 00974733272:682284 2 - 02 0006ab16  45 43 4b 44 | ECKD
+  01 00974733272:682287 2 - 02 0006ab28  00 00 00 04 | ....
+  01 00974733272:682289 2 - 02 0006ab3e  00 00 00 20 | ...
+  01 00974733272:682297 2 - 02 0006ad7e  07 ea 4a 90 | ....
+  01 00974733272:684384 2 - 00 0006ade6  46 52 45 45 | FREE
+  01 00974733272:684388 2 - 00 0006adf6  07 ea 4a 90 | ....
+
+See section about predefined views for explanation of the above output!
+
+Changing the debug level
+------------------------
+
+Example::
+
+
+  > cat /sys/kernel/debug/s390dbf/dasd/level
+  3
+  > echo "5" > /sys/kernel/debug/s390dbf/dasd/level
+  > cat /sys/kernel/debug/s390dbf/dasd/level
+  5
+
+Flushing debug areas
+--------------------
+Debug areas can be flushed with piping the number of the desired
+area (0...n) to the debugfs file "flush". When using "-" all debug areas
+are flushed.
+
+Examples:
+
+1. Flush debug area 0::
+
+     > echo "0" > /sys/kernel/debug/s390dbf/dasd/flush
+
+2. Flush all debug areas::
+
+     > echo "-" > /sys/kernel/debug/s390dbf/dasd/flush
+
+Changing the size of debug areas
+------------------------------------
+It is possible the change the size of debug areas through piping
+the number of pages to the debugfs file "pages". The resize request will
+also flush the debug areas.
+
+Example:
+
+Define 4 pages for the debug areas of debug feature "dasd"::
+
+  > echo "4" > /sys/kernel/debug/s390dbf/dasd/pages
+
+Stopping the debug feature
+--------------------------
+Example:
+
+1. Check if stopping is allowed::
+
+     > cat /proc/sys/s390dbf/debug_stoppable
+
+2. Stop debug feature::
+
+     > echo 0 > /proc/sys/s390dbf/debug_active
+
+crash Interface
+----------------
+The ``crash`` tool since v5.1.0 has a built-in command
+``s390dbf`` to display all the debug logs or export them to the file system.
+With this tool it is possible
+to investigate the debug logs on a live system and with a memory dump after
+a system crash.
+
+Investigating raw memory
+------------------------
+One last possibility to investigate the debug logs at a live
+system and after a system crash is to look at the raw memory
+under VM or at the Service Element.
+It is possible to find the anchor of the debug-logs through
+the ``debug_area_first`` symbol in the System map. Then one has
+to follow the correct pointers of the data-structures defined
+in debug.h and find the debug-areas in memory.
+Normally modules which use the debug feature will also have
+a global variable with the pointer to the debug-logs. Following
+this pointer it will also be possible to find the debug logs in
+memory.
+
+For this method it is recommended to use '16 * x + 4' byte (x = 0..n)
+for the length of the data field in :c:func:`debug_register()` in
+order to see the debug entries well formatted.
+
+
+Predefined Views
+----------------
+
+There are two predefined views: hex_ascii and sprintf.
+The hex_ascii view shows the data field in hex and ascii representation
+(e.g. ``45 43 4b 44 | ECKD``).
+
+The sprintf view formats the debug entries in the same way as the sprintf
+function would do. The sprintf event/exception functions write to the
+debug entry a pointer to the format string (size = sizeof(long))
+and for each vararg a long value. So e.g. for a debug entry with a format
+string plus two varargs one would need to allocate a (3 * sizeof(long))
+byte data area in the debug_register() function.
+
+IMPORTANT:
+  Using "%s" in sprintf event functions is dangerous. You can only
+  use "%s" in the sprintf event functions, if the memory for the passed string
+  is available as long as the debug feature exists. The reason behind this is
+  that due to performance considerations only a pointer to the string is stored
+  in  the debug feature. If you log a string that is freed afterwards, you will
+  get an OOPS when inspecting the debug feature, because then the debug feature
+  will access the already freed memory.
+
+NOTE:
+  If using the sprintf view do NOT use other event/exception functions
+  than the sprintf-event and -exception functions.
+
+The format of the hex_ascii and sprintf view is as follows:
+
+- Number of area
+- Timestamp (formatted as seconds and microseconds since 00:00:00 Coordinated
+  Universal Time (UTC), January 1, 1970)
+- level of debug entry
+- Exception flag (* = Exception)
+- Cpu-Number of calling task
+- Return Address to caller
+- data field
+
+A typical line of the hex_ascii view will look like the following (first line
+is only for explanation and will not be displayed when 'cating' the view)::
+
+  area  time           level exception cpu caller    data (hex + ascii)
+  --------------------------------------------------------------------------
+  00    00964419409:440690 1 -         00  88023fe
+
+
+Defining views
+--------------
+
+Views are specified with the 'debug_view' structure. There are defined
+callback functions which are used for reading and writing the debugfs files:
+
+.. code-block:: c
+
+  struct debug_view {
+	char name[DEBUG_MAX_PROCF_LEN];
+	debug_prolog_proc_t* prolog_proc;
+	debug_header_proc_t* header_proc;
+	debug_format_proc_t* format_proc;
+	debug_input_proc_t*  input_proc;
+	void*                private_data;
+  };
+
+where:
+
+.. code-block:: c
+
+  typedef int (debug_header_proc_t) (debug_info_t* id,
+				     struct debug_view* view,
+				     int area,
+				     debug_entry_t* entry,
+				     char* out_buf);
+
+  typedef int (debug_format_proc_t) (debug_info_t* id,
+				     struct debug_view* view, char* out_buf,
+				     const char* in_buf);
+  typedef int (debug_prolog_proc_t) (debug_info_t* id,
+				     struct debug_view* view,
+				     char* out_buf);
+  typedef int (debug_input_proc_t) (debug_info_t* id,
+				    struct debug_view* view,
+				    struct file* file, const char* user_buf,
+				    size_t in_buf_size, loff_t* offset);
+
+
+The "private_data" member can be used as pointer to view specific data.
+It is not used by the debug feature itself.
+
+The output when reading a debugfs file is structured like this::
+
+  "prolog_proc output"
+
+  "header_proc output 1"  "format_proc output 1"
+  "header_proc output 2"  "format_proc output 2"
+  "header_proc output 3"  "format_proc output 3"
+  ...
+
+When a view is read from the debugfs, the Debug Feature calls the
+'prolog_proc' once for writing the prolog.
+Then 'header_proc' and 'format_proc' are called for each
+existing debug entry.
+
+The input_proc can be used to implement functionality when it is written to
+the view (e.g. like with ``echo "0" > /sys/kernel/debug/s390dbf/dasd/level``).
+
+For header_proc there can be used the default function
+:c:func:`debug_dflt_header_fn()` which is defined in debug.h.
+and which produces the same header output as the predefined views.
+E.g::
+
+  00 00964419409:440761 2 - 00 88023ec
+
+In order to see how to use the callback functions check the implementation
+of the default views!
+
+Example:
+
+.. code-block:: c
+
+  #include <asm/debug.h>
+
+  #define UNKNOWNSTR "data: %08x"
+
+  const char* messages[] =
+  {"This error...........\n",
+   "That error...........\n",
+   "Problem..............\n",
+   "Something went wrong.\n",
+   "Everything ok........\n",
+   NULL
+  };
+
+  static int debug_test_format_fn(
+     debug_info_t *id, struct debug_view *view,
+     char *out_buf, const char *in_buf
+  )
+  {
+    int i, rc = 0;
+
+    if (id->buf_size >= 4) {
+       int msg_nr = *((int*)in_buf);
+       if (msg_nr < sizeof(messages) / sizeof(char*) - 1)
+	  rc += sprintf(out_buf, "%s", messages[msg_nr]);
+       else
+	  rc += sprintf(out_buf, UNKNOWNSTR, msg_nr);
+    }
+    return rc;
+  }
+
+  struct debug_view debug_test_view = {
+    "myview",                 /* name of view */
+    NULL,                     /* no prolog */
+    &debug_dflt_header_fn,    /* default header for each entry */
+    &debug_test_format_fn,    /* our own format function */
+    NULL,                     /* no input function */
+    NULL                      /* no private data */
+  };
+
+test:
+=====
+
+.. code-block:: c
+
+  debug_info_t *debug_info;
+  int i;
+  ...
+  debug_info = debug_register("test", 0, 4, 4);
+  debug_register_view(debug_info, &debug_test_view);
+  for (i = 0; i < 10; i ++)
+    debug_int_event(debug_info, 1, i);
+
+::
+
+  > cat /sys/kernel/debug/s390dbf/test/myview
+  00 00964419734:611402 1 - 00 88042ca   This error...........
+  00 00964419734:611405 1 - 00 88042ca   That error...........
+  00 00964419734:611408 1 - 00 88042ca   Problem..............
+  00 00964419734:611411 1 - 00 88042ca   Something went wrong.
+  00 00964419734:611414 1 - 00 88042ca   Everything ok........
+  00 00964419734:611417 1 - 00 88042ca   data: 00000005
+  00 00964419734:611419 1 - 00 88042ca   data: 00000006
+  00 00964419734:611422 1 - 00 88042ca   data: 00000007
+  00 00964419734:611425 1 - 00 88042ca   data: 00000008
+  00 00964419734:611428 1 - 00 88042ca   data: 00000009
diff --git a/Documentation/arch/s390/text_files.rst b/Documentation/arch/s390/text_files.rst
new file mode 100644
index 0000000000..c94d05d4fa
--- /dev/null
+++ b/Documentation/arch/s390/text_files.rst
@@ -0,0 +1,11 @@
+ibm 3270 changelog
+------------------
+
+.. include:: 3270.ChangeLog
+    :literal:
+
+ibm 3270 config3270.sh
+----------------------
+
+.. literalinclude:: config3270.sh
+    :language: shell
diff --git a/Documentation/arch/s390/vfio-ap-locking.rst b/Documentation/arch/s390/vfio-ap-locking.rst
new file mode 100644
index 0000000000..0dfcdb562e
--- /dev/null
+++ b/Documentation/arch/s390/vfio-ap-locking.rst
@@ -0,0 +1,115 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+======================
+VFIO AP Locks Overview
+======================
+This document describes the locks that are pertinent to the secure operation
+of the vfio_ap device driver. Throughout this document, the following variables
+will be used to denote instances of the structures herein described:
+
+.. code-block:: c
+
+  struct ap_matrix_dev *matrix_dev;
+  struct ap_matrix_mdev *matrix_mdev;
+  struct kvm *kvm;
+
+The Matrix Devices Lock (drivers/s390/crypto/vfio_ap_private.h)
+---------------------------------------------------------------
+
+.. code-block:: c
+
+  struct ap_matrix_dev {
+  	...
+  	struct list_head mdev_list;
+  	struct mutex mdevs_lock;
+  	...
+  }
+
+The Matrix Devices Lock (matrix_dev->mdevs_lock) is implemented as a global
+mutex contained within the single object of struct ap_matrix_dev. This lock
+controls access to all fields contained within each matrix_mdev
+(matrix_dev->mdev_list). This lock must be held while reading from, writing to
+or using the data from a field contained within a matrix_mdev instance
+representing one of the vfio_ap device driver's mediated devices.
+
+The KVM Lock (include/linux/kvm_host.h)
+---------------------------------------
+
+.. code-block:: c
+
+  struct kvm {
+  	...
+  	struct mutex lock;
+  	...
+  }
+
+The KVM Lock (kvm->lock) controls access to the state data for a KVM guest. This
+lock must be held by the vfio_ap device driver while one or more AP adapters,
+domains or control domains are being plugged into or unplugged from the guest.
+
+The KVM pointer is stored in the in the matrix_mdev instance
+(matrix_mdev->kvm = kvm) containing the state of the mediated device that has
+been attached to the KVM guest.
+
+The Guests Lock (drivers/s390/crypto/vfio_ap_private.h)
+-----------------------------------------------------------
+
+.. code-block:: c
+
+  struct ap_matrix_dev {
+  	...
+  	struct list_head mdev_list;
+  	struct mutex guests_lock;
+  	...
+  }
+
+The Guests Lock (matrix_dev->guests_lock) controls access to the
+matrix_mdev instances (matrix_dev->mdev_list) that represent mediated devices
+that hold the state for the mediated devices that have been attached to a
+KVM guest. This lock must be held:
+
+1. To control access to the KVM pointer (matrix_mdev->kvm) while the vfio_ap
+   device driver is using it to plug/unplug AP devices passed through to the KVM
+   guest.
+
+2. To add matrix_mdev instances to or remove them from matrix_dev->mdev_list.
+   This is necessary to ensure the proper locking order when the list is perused
+   to find an ap_matrix_mdev instance for the purpose of plugging/unplugging
+   AP devices passed through to a KVM guest.
+
+   For example, when a queue device is removed from the vfio_ap device driver,
+   if the adapter is passed through to a KVM guest, it will have to be
+   unplugged. In order to figure out whether the adapter is passed through,
+   the matrix_mdev object to which the queue is assigned will have to be
+   found. The KVM pointer (matrix_mdev->kvm) can then be used to determine if
+   the mediated device is passed through (matrix_mdev->kvm != NULL) and if so,
+   to unplug the adapter.
+
+It is not necessary to take the Guests Lock to access the KVM pointer if the
+pointer is not used to plug/unplug devices passed through to the KVM guest;
+however, in this case, the Matrix Devices Lock (matrix_dev->mdevs_lock) must be
+held in order to access the KVM pointer since it is set and cleared under the
+protection of the Matrix Devices Lock. A case in point is the function that
+handles interception of the PQAP(AQIC) instruction sub-function. This handler
+needs to access the KVM pointer only for the purposes of setting or clearing IRQ
+resources, so only the matrix_dev->mdevs_lock needs to be held.
+
+The PQAP Hook Lock (arch/s390/include/asm/kvm_host.h)
+-----------------------------------------------------
+
+.. code-block:: c
+
+  typedef int (*crypto_hook)(struct kvm_vcpu *vcpu);
+
+  struct kvm_s390_crypto {
+  	...
+  	struct rw_semaphore pqap_hook_rwsem;
+  	crypto_hook *pqap_hook;
+  	...
+  };
+
+The PQAP Hook Lock is a r/w semaphore that controls access to the function
+pointer of the handler ``(*kvm->arch.crypto.pqap_hook)`` to invoke when the
+PQAP(AQIC) instruction sub-function is intercepted by the host. The lock must be
+held in write mode when pqap_hook value is set, and in read mode when the
+pqap_hook function is called.
diff --git a/Documentation/arch/s390/vfio-ap.rst b/Documentation/arch/s390/vfio-ap.rst
new file mode 100644
index 0000000000..929ee1c1c9
--- /dev/null
+++ b/Documentation/arch/s390/vfio-ap.rst
@@ -0,0 +1,1069 @@
+===============================
+Adjunct Processor (AP) facility
+===============================
+
+
+Introduction
+============
+The Adjunct Processor (AP) facility is an IBM Z cryptographic facility comprised
+of three AP instructions and from 1 up to 256 PCIe cryptographic adapter cards.
+The AP devices provide cryptographic functions to all CPUs assigned to a
+linux system running in an IBM Z system LPAR.
+
+The AP adapter cards are exposed via the AP bus. The motivation for vfio-ap
+is to make AP cards available to KVM guests using the VFIO mediated device
+framework. This implementation relies considerably on the s390 virtualization
+facilities which do most of the hard work of providing direct access to AP
+devices.
+
+AP Architectural Overview
+=========================
+To facilitate the comprehension of the design, let's start with some
+definitions:
+
+* AP adapter
+
+  An AP adapter is an IBM Z adapter card that can perform cryptographic
+  functions. There can be from 0 to 256 adapters assigned to an LPAR. Adapters
+  assigned to the LPAR in which a linux host is running will be available to
+  the linux host. Each adapter is identified by a number from 0 to 255; however,
+  the maximum adapter number is determined by machine model and/or adapter type.
+  When installed, an AP adapter is accessed by AP instructions executed by any
+  CPU.
+
+  The AP adapter cards are assigned to a given LPAR via the system's Activation
+  Profile which can be edited via the HMC. When the linux host system is IPL'd
+  in the LPAR, the AP bus detects the AP adapter cards assigned to the LPAR and
+  creates a sysfs device for each assigned adapter. For example, if AP adapters
+  4 and 10 (0x0a) are assigned to the LPAR, the AP bus will create the following
+  sysfs device entries::
+
+    /sys/devices/ap/card04
+    /sys/devices/ap/card0a
+
+  Symbolic links to these devices will also be created in the AP bus devices
+  sub-directory::
+
+    /sys/bus/ap/devices/[card04]
+    /sys/bus/ap/devices/[card04]
+
+* AP domain
+
+  An adapter is partitioned into domains. An adapter can hold up to 256 domains
+  depending upon the adapter type and hardware configuration. A domain is
+  identified by a number from 0 to 255; however, the maximum domain number is
+  determined by machine model and/or adapter type.. A domain can be thought of
+  as a set of hardware registers and memory used for processing AP commands. A
+  domain can be configured with a secure private key used for clear key
+  encryption. A domain is classified in one of two ways depending upon how it
+  may be accessed:
+
+    * Usage domains are domains that are targeted by an AP instruction to
+      process an AP command.
+
+    * Control domains are domains that are changed by an AP command sent to a
+      usage domain; for example, to set the secure private key for the control
+      domain.
+
+  The AP usage and control domains are assigned to a given LPAR via the system's
+  Activation Profile which can be edited via the HMC. When a linux host system
+  is IPL'd in the LPAR, the AP bus module detects the AP usage and control
+  domains assigned to the LPAR. The domain number of each usage domain and
+  adapter number of each AP adapter are combined to create AP queue devices
+  (see AP Queue section below). The domain number of each control domain will be
+  represented in a bitmask and stored in a sysfs file
+  /sys/bus/ap/ap_control_domain_mask. The bits in the mask, from most to least
+  significant bit, correspond to domains 0-255.
+
+* AP Queue
+
+  An AP queue is the means by which an AP command is sent to a usage domain
+  inside a specific adapter. An AP queue is identified by a tuple
+  comprised of an AP adapter ID (APID) and an AP queue index (APQI). The
+  APQI corresponds to a given usage domain number within the adapter. This tuple
+  forms an AP Queue Number (APQN) uniquely identifying an AP queue. AP
+  instructions include a field containing the APQN to identify the AP queue to
+  which the AP command is to be sent for processing.
+
+  The AP bus will create a sysfs device for each APQN that can be derived from
+  the cross product of the AP adapter and usage domain numbers detected when the
+  AP bus module is loaded. For example, if adapters 4 and 10 (0x0a) and usage
+  domains 6 and 71 (0x47) are assigned to the LPAR, the AP bus will create the
+  following sysfs entries::
+
+    /sys/devices/ap/card04/04.0006
+    /sys/devices/ap/card04/04.0047
+    /sys/devices/ap/card0a/0a.0006
+    /sys/devices/ap/card0a/0a.0047
+
+  The following symbolic links to these devices will be created in the AP bus
+  devices subdirectory::
+
+    /sys/bus/ap/devices/[04.0006]
+    /sys/bus/ap/devices/[04.0047]
+    /sys/bus/ap/devices/[0a.0006]
+    /sys/bus/ap/devices/[0a.0047]
+
+* AP Instructions:
+
+  There are three AP instructions:
+
+  * NQAP: to enqueue an AP command-request message to a queue
+  * DQAP: to dequeue an AP command-reply message from a queue
+  * PQAP: to administer the queues
+
+  AP instructions identify the domain that is targeted to process the AP
+  command; this must be one of the usage domains. An AP command may modify a
+  domain that is not one of the usage domains, but the modified domain
+  must be one of the control domains.
+
+AP and SIE
+==========
+Let's now take a look at how AP instructions executed on a guest are interpreted
+by the hardware.
+
+A satellite control block called the Crypto Control Block (CRYCB) is attached to
+our main hardware virtualization control block. The CRYCB contains an AP Control
+Block (APCB) that has three fields to identify the adapters, usage domains and
+control domains assigned to the KVM guest:
+
+* The AP Mask (APM) field is a bit mask that identifies the AP adapters assigned
+  to the KVM guest. Each bit in the mask, from left to right, corresponds to
+  an APID from 0-255. If a bit is set, the corresponding adapter is valid for
+  use by the KVM guest.
+
+* The AP Queue Mask (AQM) field is a bit mask identifying the AP usage domains
+  assigned to the KVM guest. Each bit in the mask, from left to right,
+  corresponds to an AP queue index (APQI) from 0-255. If a bit is set, the
+  corresponding queue is valid for use by the KVM guest.
+
+* The AP Domain Mask field is a bit mask that identifies the AP control domains
+  assigned to the KVM guest. The ADM bit mask controls which domains can be
+  changed by an AP command-request message sent to a usage domain from the
+  guest. Each bit in the mask, from left to right, corresponds to a domain from
+  0-255. If a bit is set, the corresponding domain can be modified by an AP
+  command-request message sent to a usage domain.
+
+If you recall from the description of an AP Queue, AP instructions include
+an APQN to identify the AP queue to which an AP command-request message is to be
+sent (NQAP and PQAP instructions), or from which a command-reply message is to
+be received (DQAP instruction). The validity of an APQN is defined by the matrix
+calculated from the APM and AQM; it is the Cartesian product of all assigned
+adapter numbers (APM) with all assigned queue indexes (AQM). For example, if
+adapters 1 and 2 and usage domains 5 and 6 are assigned to a guest, the APQNs
+(1,5), (1,6), (2,5) and (2,6) will be valid for the guest.
+
+The APQNs can provide secure key functionality - i.e., a private key is stored
+on the adapter card for each of its domains - so each APQN must be assigned to
+at most one guest or to the linux host::
+
+   Example 1: Valid configuration:
+   ------------------------------
+   Guest1: adapters 1,2  domains 5,6
+   Guest2: adapter  1,2  domain 7
+
+   This is valid because both guests have a unique set of APQNs:
+      Guest1 has APQNs (1,5), (1,6), (2,5), (2,6);
+      Guest2 has APQNs (1,7), (2,7)
+
+   Example 2: Valid configuration:
+   ------------------------------
+   Guest1: adapters 1,2 domains 5,6
+   Guest2: adapters 3,4 domains 5,6
+
+   This is also valid because both guests have a unique set of APQNs:
+      Guest1 has APQNs (1,5), (1,6), (2,5), (2,6);
+      Guest2 has APQNs (3,5), (3,6), (4,5), (4,6)
+
+   Example 3: Invalid configuration:
+   --------------------------------
+   Guest1: adapters 1,2  domains 5,6
+   Guest2: adapter  1    domains 6,7
+
+   This is an invalid configuration because both guests have access to
+   APQN (1,6).
+
+The Design
+==========
+The design introduces three new objects:
+
+1. AP matrix device
+2. VFIO AP device driver (vfio_ap.ko)
+3. VFIO AP mediated pass-through device
+
+The VFIO AP device driver
+-------------------------
+The VFIO AP (vfio_ap) device driver serves the following purposes:
+
+1. Provides the interfaces to secure APQNs for exclusive use of KVM guests.
+
+2. Sets up the VFIO mediated device interfaces to manage a vfio_ap mediated
+   device and creates the sysfs interfaces for assigning adapters, usage
+   domains, and control domains comprising the matrix for a KVM guest.
+
+3. Configures the APM, AQM and ADM in the APCB contained in the CRYCB referenced
+   by a KVM guest's SIE state description to grant the guest access to a matrix
+   of AP devices
+
+Reserve APQNs for exclusive use of KVM guests
+---------------------------------------------
+The following block diagram illustrates the mechanism by which APQNs are
+reserved::
+
+				+------------------+
+		 7 remove       |                  |
+	   +--------------------> cex4queue driver |
+	   |                    |                  |
+	   |                    +------------------+
+	   |
+	   |
+	   |                    +------------------+          +----------------+
+	   |  5 register driver |                  | 3 create |                |
+	   |   +---------------->   Device core    +---------->  matrix device |
+	   |   |                |                  |          |                |
+	   |   |                +--------^---------+          +----------------+
+	   |   |                         |
+	   |   |                         +-------------------+
+	   |   | +-----------------------------------+       |
+	   |   | |      4 register AP driver         |       | 2 register device
+	   |   | |                                   |       |
+  +--------+---+-v---+                      +--------+-------+-+
+  |                  |                      |                  |
+  |      ap_bus      +--------------------- >  vfio_ap driver  |
+  |                  |       8 probe        |                  |
+  +--------^---------+                      +--^--^------------+
+  6 edit   |                                   |  |
+    apmask |     +-----------------------------+  | 11 mdev create
+    aqmask |     |           1 modprobe           |
+  +--------+-----+---+           +----------------+-+         +----------------+
+  |                  |           |                  |10 create|     mediated   |
+  |      admin       |           | VFIO device core |--------->     matrix     |
+  |                  +           |                  |         |     device     |
+  +------+-+---------+           +--------^---------+         +--------^-------+
+	 | |                              |                            |
+	 | | 9 create vfio_ap-passthrough |                            |
+	 | +------------------------------+                            |
+	 +-------------------------------------------------------------+
+		     12  assign adapter/domain/control domain
+
+The process for reserving an AP queue for use by a KVM guest is:
+
+1. The administrator loads the vfio_ap device driver
+2. The vfio-ap driver during its initialization will register a single 'matrix'
+   device with the device core. This will serve as the parent device for
+   all vfio_ap mediated devices used to configure an AP matrix for a guest.
+3. The /sys/devices/vfio_ap/matrix device is created by the device core
+4. The vfio_ap device driver will register with the AP bus for AP queue devices
+   of type 10 and higher (CEX4 and newer). The driver will provide the vfio_ap
+   driver's probe and remove callback interfaces. Devices older than CEX4 queues
+   are not supported to simplify the implementation by not needlessly
+   complicating the design by supporting older devices that will go out of
+   service in the relatively near future, and for which there are few older
+   systems around on which to test.
+5. The AP bus registers the vfio_ap device driver with the device core
+6. The administrator edits the AP adapter and queue masks to reserve AP queues
+   for use by the vfio_ap device driver.
+7. The AP bus removes the AP queues reserved for the vfio_ap driver from the
+   default zcrypt cex4queue driver.
+8. The AP bus probes the vfio_ap device driver to bind the queues reserved for
+   it.
+9. The administrator creates a passthrough type vfio_ap mediated device to be
+   used by a guest
+10. The administrator assigns the adapters, usage domains and control domains
+    to be exclusively used by a guest.
+
+Set up the VFIO mediated device interfaces
+------------------------------------------
+The VFIO AP device driver utilizes the common interfaces of the VFIO mediated
+device core driver to:
+
+* Register an AP mediated bus driver to add a vfio_ap mediated device to and
+  remove it from a VFIO group.
+* Create and destroy a vfio_ap mediated device
+* Add a vfio_ap mediated device to and remove it from the AP mediated bus driver
+* Add a vfio_ap mediated device to and remove it from an IOMMU group
+
+The following high-level block diagram shows the main components and interfaces
+of the VFIO AP mediated device driver::
+
+   +-------------+
+   |             |
+   | +---------+ | mdev_register_driver() +--------------+
+   | |  Mdev   | +<-----------------------+              |
+   | |  bus    | |                        | vfio_mdev.ko |
+   | | driver  | +----------------------->+              |<-> VFIO user
+   | +---------+ |    probe()/remove()    +--------------+    APIs
+   |             |
+   |  MDEV CORE  |
+   |   MODULE    |
+   |   mdev.ko   |
+   | +---------+ | mdev_register_parent() +--------------+
+   | |Physical | +<-----------------------+              |
+   | | device  | |                        |  vfio_ap.ko  |<-> matrix
+   | |interface| +----------------------->+              |    device
+   | +---------+ |       callback         +--------------+
+   +-------------+
+
+During initialization of the vfio_ap module, the matrix device is registered
+with an 'mdev_parent_ops' structure that provides the sysfs attribute
+structures, mdev functions and callback interfaces for managing the mediated
+matrix device.
+
+* sysfs attribute structures:
+
+  supported_type_groups
+    The VFIO mediated device framework supports creation of user-defined
+    mediated device types. These mediated device types are specified
+    via the 'supported_type_groups' structure when a device is registered
+    with the mediated device framework. The registration process creates the
+    sysfs structures for each mediated device type specified in the
+    'mdev_supported_types' sub-directory of the device being registered. Along
+    with the device type, the sysfs attributes of the mediated device type are
+    provided.
+
+    The VFIO AP device driver will register one mediated device type for
+    passthrough devices:
+
+      /sys/devices/vfio_ap/matrix/mdev_supported_types/vfio_ap-passthrough
+
+    Only the read-only attributes required by the VFIO mdev framework will
+    be provided::
+
+	... name
+	... device_api
+	... available_instances
+	... device_api
+
+    Where:
+
+	* name:
+	    specifies the name of the mediated device type
+	* device_api:
+	    the mediated device type's API
+	* available_instances:
+	    the number of vfio_ap mediated passthrough devices
+	    that can be created
+	* device_api:
+	    specifies the VFIO API
+  mdev_attr_groups
+    This attribute group identifies the user-defined sysfs attributes of the
+    mediated device. When a device is registered with the VFIO mediated device
+    framework, the sysfs attribute files identified in the 'mdev_attr_groups'
+    structure will be created in the vfio_ap mediated device's directory. The
+    sysfs attributes for a vfio_ap mediated device are:
+
+    assign_adapter / unassign_adapter:
+      Write-only attributes for assigning/unassigning an AP adapter to/from the
+      vfio_ap mediated device. To assign/unassign an adapter, the APID of the
+      adapter is echoed into the respective attribute file.
+    assign_domain / unassign_domain:
+      Write-only attributes for assigning/unassigning an AP usage domain to/from
+      the vfio_ap mediated device. To assign/unassign a domain, the domain
+      number of the usage domain is echoed into the respective attribute
+      file.
+    matrix:
+      A read-only file for displaying the APQNs derived from the Cartesian
+      product of the adapter and domain numbers assigned to the vfio_ap mediated
+      device.
+    guest_matrix:
+      A read-only file for displaying the APQNs derived from the Cartesian
+      product of the adapter and domain numbers assigned to the APM and AQM
+      fields respectively of the KVM guest's CRYCB. This may differ from the
+      the APQNs assigned to the vfio_ap mediated device if any APQN does not
+      reference a queue device bound to the vfio_ap device driver (i.e., the
+      queue is not in the host's AP configuration).
+    assign_control_domain / unassign_control_domain:
+      Write-only attributes for assigning/unassigning an AP control domain
+      to/from the vfio_ap mediated device. To assign/unassign a control domain,
+      the ID of the domain to be assigned/unassigned is echoed into the
+      respective attribute file.
+    control_domains:
+      A read-only file for displaying the control domain numbers assigned to the
+      vfio_ap mediated device.
+
+* functions:
+
+  create:
+    allocates the ap_matrix_mdev structure used by the vfio_ap driver to:
+
+    * Store the reference to the KVM structure for the guest using the mdev
+    * Store the AP matrix configuration for the adapters, domains, and control
+      domains assigned via the corresponding sysfs attributes files
+    * Store the AP matrix configuration for the adapters, domains and control
+      domains available to a guest. A guest may not be provided access to APQNs
+      referencing queue devices that do not exist, or are not bound to the
+      vfio_ap device driver.
+
+  remove:
+    deallocates the vfio_ap mediated device's ap_matrix_mdev structure.
+    This will be allowed only if a running guest is not using the mdev.
+
+* callback interfaces
+
+  open_device:
+    The vfio_ap driver uses this callback to register a
+    VFIO_GROUP_NOTIFY_SET_KVM notifier callback function for the matrix mdev
+    devices. The open_device callback is invoked by userspace to connect the
+    VFIO iommu group for the matrix mdev device to the MDEV bus. Access to the
+    KVM structure used to configure the KVM guest is provided via this callback.
+    The KVM structure, is used to configure the guest's access to the AP matrix
+    defined via the vfio_ap mediated device's sysfs attribute files.
+
+  close_device:
+    unregisters the VFIO_GROUP_NOTIFY_SET_KVM notifier callback function for the
+    matrix mdev device and deconfigures the guest's AP matrix.
+
+  ioctl:
+    this callback handles the VFIO_DEVICE_GET_INFO and VFIO_DEVICE_RESET ioctls
+    defined by the vfio framework.
+
+Configure the guest's AP resources
+----------------------------------
+Configuring the AP resources for a KVM guest will be performed when the
+VFIO_GROUP_NOTIFY_SET_KVM notifier callback is invoked. The notifier
+function is called when userspace connects to KVM. The guest's AP resources are
+configured via its APCB by:
+
+* Setting the bits in the APM corresponding to the APIDs assigned to the
+  vfio_ap mediated device via its 'assign_adapter' interface.
+* Setting the bits in the AQM corresponding to the domains assigned to the
+  vfio_ap mediated device via its 'assign_domain' interface.
+* Setting the bits in the ADM corresponding to the domain dIDs assigned to the
+  vfio_ap mediated device via its 'assign_control_domains' interface.
+
+The linux device model precludes passing a device through to a KVM guest that
+is not bound to the device driver facilitating its pass-through. Consequently,
+an APQN that does not reference a queue device bound to the vfio_ap device
+driver will not be assigned to a KVM guest's matrix. The AP architecture,
+however, does not provide a means to filter individual APQNs from the guest's
+matrix, so the adapters, domains and control domains assigned to vfio_ap
+mediated device via its sysfs 'assign_adapter', 'assign_domain' and
+'assign_control_domain' interfaces will be filtered before providing the AP
+configuration to a guest:
+
+* The APIDs of the adapters, the APQIs of the domains and the domain numbers of
+  the control domains assigned to the matrix mdev that are not also assigned to
+  the host's AP configuration will be filtered.
+
+* Each APQN derived from the Cartesian product of the APIDs and APQIs assigned
+  to the vfio_ap mdev is examined and if any one of them does not reference a
+  queue device bound to the vfio_ap device driver, the adapter will not be
+  plugged into the guest (i.e., the bit corresponding to its APID will not be
+  set in the APM of the guest's APCB).
+
+The CPU model features for AP
+-----------------------------
+The AP stack relies on the presence of the AP instructions as well as three
+facilities: The AP Facilities Test (APFT) facility; the AP Query
+Configuration Information (QCI) facility; and the AP Queue Interruption Control
+facility. These features/facilities are made available to a KVM guest via the
+following CPU model features:
+
+1. ap: Indicates whether the AP instructions are installed on the guest. This
+   feature will be enabled by KVM only if the AP instructions are installed
+   on the host.
+
+2. apft: Indicates the APFT facility is available on the guest. This facility
+   can be made available to the guest only if it is available on the host (i.e.,
+   facility bit 15 is set).
+
+3. apqci: Indicates the AP QCI facility is available on the guest. This facility
+   can be made available to the guest only if it is available on the host (i.e.,
+   facility bit 12 is set).
+
+4. apqi: Indicates AP Queue Interruption Control faclity is available on the
+   guest. This facility can be made available to the guest only if it is
+   available on the host (i.e., facility bit 65 is set).
+
+Note: If the user chooses to specify a CPU model different than the 'host'
+model to QEMU, the CPU model features and facilities need to be turned on
+explicitly; for example::
+
+     /usr/bin/qemu-system-s390x ... -cpu z13,ap=on,apqci=on,apft=on,apqi=on
+
+A guest can be precluded from using AP features/facilities by turning them off
+explicitly; for example::
+
+     /usr/bin/qemu-system-s390x ... -cpu host,ap=off,apqci=off,apft=off,apqi=off
+
+Note: If the APFT facility is turned off (apft=off) for the guest, the guest
+will not see any AP devices. The zcrypt device drivers on the guest that
+register for type 10 and newer AP devices - i.e., the cex4card and cex4queue
+device drivers - need the APFT facility to ascertain the facilities installed on
+a given AP device. If the APFT facility is not installed on the guest, then no
+adapter or domain devices will get created by the AP bus running on the
+guest because only type 10 and newer devices can be configured for guest use.
+
+Example
+=======
+Let's now provide an example to illustrate how KVM guests may be given
+access to AP facilities. For this example, we will show how to configure
+three guests such that executing the lszcrypt command on the guests would
+look like this:
+
+Guest1
+------
+=========== ===== ============
+CARD.DOMAIN TYPE  MODE
+=========== ===== ============
+05          CEX5C CCA-Coproc
+05.0004     CEX5C CCA-Coproc
+05.00ab     CEX5C CCA-Coproc
+06          CEX5A Accelerator
+06.0004     CEX5A Accelerator
+06.00ab     CEX5A Accelerator
+=========== ===== ============
+
+Guest2
+------
+=========== ===== ============
+CARD.DOMAIN TYPE  MODE
+=========== ===== ============
+05          CEX5C CCA-Coproc
+05.0047     CEX5C CCA-Coproc
+05.00ff     CEX5C CCA-Coproc
+=========== ===== ============
+
+Guest3
+------
+=========== ===== ============
+CARD.DOMAIN TYPE  MODE
+=========== ===== ============
+06          CEX5A Accelerator
+06.0047     CEX5A Accelerator
+06.00ff     CEX5A Accelerator
+=========== ===== ============
+
+These are the steps:
+
+1. Install the vfio_ap module on the linux host. The dependency chain for the
+   vfio_ap module is:
+   * iommu
+   * s390
+   * zcrypt
+   * vfio
+   * vfio_mdev
+   * vfio_mdev_device
+   * KVM
+
+   To build the vfio_ap module, the kernel build must be configured with the
+   following Kconfig elements selected:
+   * IOMMU_SUPPORT
+   * S390
+   * ZCRYPT
+   * VFIO
+   * KVM
+
+   If using make menuconfig select the following to build the vfio_ap module::
+
+     -> Device Drivers
+	-> IOMMU Hardware Support
+	   select S390 AP IOMMU Support
+	-> VFIO Non-Privileged userspace driver framework
+	   -> Mediated device driver frramework
+	      -> VFIO driver for Mediated devices
+     -> I/O subsystem
+	-> VFIO support for AP devices
+
+2. Secure the AP queues to be used by the three guests so that the host can not
+   access them. To secure them, there are two sysfs files that specify
+   bitmasks marking a subset of the APQN range as usable only by the default AP
+   queue device drivers. All remaining APQNs are available for use by
+   any other device driver. The vfio_ap device driver is currently the only
+   non-default device driver. The location of the sysfs files containing the
+   masks are::
+
+     /sys/bus/ap/apmask
+     /sys/bus/ap/aqmask
+
+   The 'apmask' is a 256-bit mask that identifies a set of AP adapter IDs
+   (APID). Each bit in the mask, from left to right, corresponds to an APID from
+   0-255. If a bit is set, the APID belongs to the subset of APQNs marked as
+   available only to the default AP queue device drivers.
+
+   The 'aqmask' is a 256-bit mask that identifies a set of AP queue indexes
+   (APQI). Each bit in the mask, from left to right, corresponds to an APQI from
+   0-255. If a bit is set, the APQI belongs to the subset of APQNs marked as
+   available only to the default AP queue device drivers.
+
+   The Cartesian product of the APIDs corresponding to the bits set in the
+   apmask and the APQIs corresponding to the bits set in the aqmask comprise
+   the subset of APQNs that can be used only by the host default device drivers.
+   All other APQNs are available to the non-default device drivers such as the
+   vfio_ap driver.
+
+   Take, for example, the following masks::
+
+      apmask:
+      0x7d00000000000000000000000000000000000000000000000000000000000000
+
+      aqmask:
+      0x8000000000000000000000000000000000000000000000000000000000000000
+
+   The masks indicate:
+
+   * Adapters 1, 2, 3, 4, 5, and 7 are available for use by the host default
+     device drivers.
+
+   * Domain 0 is available for use by the host default device drivers
+
+   * The subset of APQNs available for use only by the default host device
+     drivers are:
+
+     (1,0), (2,0), (3,0), (4.0), (5,0) and (7,0)
+
+   * All other APQNs are available for use by the non-default device drivers.
+
+   The APQN of each AP queue device assigned to the linux host is checked by the
+   AP bus against the set of APQNs derived from the Cartesian product of APIDs
+   and APQIs marked as available to the default AP queue device drivers. If a
+   match is detected,  only the default AP queue device drivers will be probed;
+   otherwise, the vfio_ap device driver will be probed.
+
+   By default, the two masks are set to reserve all APQNs for use by the default
+   AP queue device drivers. There are two ways the default masks can be changed:
+
+   1. The sysfs mask files can be edited by echoing a string into the
+      respective sysfs mask file in one of two formats:
+
+      * An absolute hex string starting with 0x - like "0x12345678" - sets
+	the mask. If the given string is shorter than the mask, it is padded
+	with 0s on the right; for example, specifying a mask value of 0x41 is
+	the same as specifying::
+
+	   0x4100000000000000000000000000000000000000000000000000000000000000
+
+	Keep in mind that the mask reads from left to right, so the mask
+	above identifies device numbers 1 and 7 (01000001).
+
+	If the string is longer than the mask, the operation is terminated with
+	an error (EINVAL).
+
+      * Individual bits in the mask can be switched on and off by specifying
+	each bit number to be switched in a comma separated list. Each bit
+	number string must be prepended with a ('+') or minus ('-') to indicate
+	the corresponding bit is to be switched on ('+') or off ('-'). Some
+	valid values are:
+
+	   - "+0"    switches bit 0 on
+	   - "-13"   switches bit 13 off
+	   - "+0x41" switches bit 65 on
+	   - "-0xff" switches bit 255 off
+
+	The following example:
+
+	      +0,-6,+0x47,-0xf0
+
+	Switches bits 0 and 71 (0x47) on
+
+	Switches bits 6 and 240 (0xf0) off
+
+	Note that the bits not specified in the list remain as they were before
+	the operation.
+
+   2. The masks can also be changed at boot time via parameters on the kernel
+      command line like this:
+
+	 ap.apmask=0xffff ap.aqmask=0x40
+
+	 This would create the following masks::
+
+	    apmask:
+	    0xffff000000000000000000000000000000000000000000000000000000000000
+
+	    aqmask:
+	    0x4000000000000000000000000000000000000000000000000000000000000000
+
+	 Resulting in these two pools::
+
+	    default drivers pool:    adapter 0-15, domain 1
+	    alternate drivers pool:  adapter 16-255, domains 0, 2-255
+
+   **Note:**
+   Changing a mask such that one or more APQNs will be taken from a vfio_ap
+   mediated device (see below) will fail with an error (EBUSY). A message
+   is logged to the kernel ring buffer which can be viewed with the 'dmesg'
+   command. The output identifies each APQN flagged as 'in use' and identifies
+   the vfio_ap mediated device to which it is assigned; for example:
+
+   Userspace may not re-assign queue 05.0054 already assigned to 62177883-f1bb-47f0-914d-32a22e3a8804
+   Userspace may not re-assign queue 04.0054 already assigned to cef03c3c-903d-4ecc-9a83-40694cb8aee4
+
+Securing the APQNs for our example
+----------------------------------
+   To secure the AP queues 05.0004, 05.0047, 05.00ab, 05.00ff, 06.0004, 06.0047,
+   06.00ab, and 06.00ff for use by the vfio_ap device driver, the corresponding
+   APQNs can be removed from the default masks using either of the following
+   commands::
+
+      echo -5,-6 > /sys/bus/ap/apmask
+
+      echo -4,-0x47,-0xab,-0xff > /sys/bus/ap/aqmask
+
+   Or the masks can be set as follows::
+
+      echo 0xf9ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff \
+      > apmask
+
+      echo 0xf7fffffffffffffffeffffffffffffffffffffffffeffffffffffffffffffffe \
+      > aqmask
+
+   This will result in AP queues 05.0004, 05.0047, 05.00ab, 05.00ff, 06.0004,
+   06.0047, 06.00ab, and 06.00ff getting bound to the vfio_ap device driver. The
+   sysfs directory for the vfio_ap device driver will now contain symbolic links
+   to the AP queue devices bound to it::
+
+     /sys/bus/ap
+     ... [drivers]
+     ...... [vfio_ap]
+     ......... [05.0004]
+     ......... [05.0047]
+     ......... [05.00ab]
+     ......... [05.00ff]
+     ......... [06.0004]
+     ......... [06.0047]
+     ......... [06.00ab]
+     ......... [06.00ff]
+
+   Keep in mind that only type 10 and newer adapters (i.e., CEX4 and later)
+   can be bound to the vfio_ap device driver. The reason for this is to
+   simplify the implementation by not needlessly complicating the design by
+   supporting older devices that will go out of service in the relatively near
+   future and for which there are few older systems on which to test.
+
+   The administrator, therefore, must take care to secure only AP queues that
+   can be bound to the vfio_ap device driver. The device type for a given AP
+   queue device can be read from the parent card's sysfs directory. For example,
+   to see the hardware type of the queue 05.0004:
+
+     cat /sys/bus/ap/devices/card05/hwtype
+
+   The hwtype must be 10 or higher (CEX4 or newer) in order to be bound to the
+   vfio_ap device driver.
+
+3. Create the mediated devices needed to configure the AP matrixes for the
+   three guests and to provide an interface to the vfio_ap driver for
+   use by the guests::
+
+     /sys/devices/vfio_ap/matrix/
+     --- [mdev_supported_types]
+     ------ [vfio_ap-passthrough] (passthrough vfio_ap mediated device type)
+     --------- create
+     --------- [devices]
+
+   To create the mediated devices for the three guests::
+
+	uuidgen > create
+	uuidgen > create
+	uuidgen > create
+
+	or
+
+	echo $uuid1 > create
+	echo $uuid2 > create
+	echo $uuid3 > create
+
+   This will create three mediated devices in the [devices] subdirectory named
+   after the UUID written to the create attribute file. We call them $uuid1,
+   $uuid2 and $uuid3 and this is the sysfs directory structure after creation::
+
+     /sys/devices/vfio_ap/matrix/
+     --- [mdev_supported_types]
+     ------ [vfio_ap-passthrough]
+     --------- [devices]
+     ------------ [$uuid1]
+     --------------- assign_adapter
+     --------------- assign_control_domain
+     --------------- assign_domain
+     --------------- matrix
+     --------------- unassign_adapter
+     --------------- unassign_control_domain
+     --------------- unassign_domain
+
+     ------------ [$uuid2]
+     --------------- assign_adapter
+     --------------- assign_control_domain
+     --------------- assign_domain
+     --------------- matrix
+     --------------- unassign_adapter
+     ----------------unassign_control_domain
+     ----------------unassign_domain
+
+     ------------ [$uuid3]
+     --------------- assign_adapter
+     --------------- assign_control_domain
+     --------------- assign_domain
+     --------------- matrix
+     --------------- unassign_adapter
+     ----------------unassign_control_domain
+     ----------------unassign_domain
+
+   Note *****: The vfio_ap mdevs do not persist across reboots unless the
+               mdevctl tool is used to create and persist them.
+
+4. The administrator now needs to configure the matrixes for the mediated
+   devices $uuid1 (for Guest1), $uuid2 (for Guest2) and $uuid3 (for Guest3).
+
+   This is how the matrix is configured for Guest1::
+
+      echo 5 > assign_adapter
+      echo 6 > assign_adapter
+      echo 4 > assign_domain
+      echo 0xab > assign_domain
+
+   Control domains can similarly be assigned using the assign_control_domain
+   sysfs file.
+
+   If a mistake is made configuring an adapter, domain or control domain,
+   you can use the unassign_xxx files to unassign the adapter, domain or
+   control domain.
+
+   To display the matrix configuration for Guest1::
+
+	 cat matrix
+
+   To display the matrix that is or will be assigned to Guest1::
+
+	 cat guest_matrix
+
+   This is how the matrix is configured for Guest2::
+
+      echo 5 > assign_adapter
+      echo 0x47 > assign_domain
+      echo 0xff > assign_domain
+
+   This is how the matrix is configured for Guest3::
+
+      echo 6 > assign_adapter
+      echo 0x47 > assign_domain
+      echo 0xff > assign_domain
+
+   In order to successfully assign an adapter:
+
+   * The adapter number specified must represent a value from 0 up to the
+     maximum adapter number configured for the system. If an adapter number
+     higher than the maximum is specified, the operation will terminate with
+     an error (ENODEV).
+
+     Note: The maximum adapter number can be obtained via the sysfs
+	   /sys/bus/ap/ap_max_adapter_id attribute file.
+
+   * Each APQN derived from the Cartesian product of the APID of the adapter
+     being assigned and the APQIs of the domains previously assigned:
+
+     - Must only be available to the vfio_ap device driver as specified in the
+       sysfs /sys/bus/ap/apmask and /sys/bus/ap/aqmask attribute files. If even
+       one APQN is reserved for use by the host device driver, the operation
+       will terminate with an error (EADDRNOTAVAIL).
+
+     - Must NOT be assigned to another vfio_ap mediated device. If even one APQN
+       is assigned to another vfio_ap mediated device, the operation will
+       terminate with an error (EBUSY).
+
+     - Must NOT be assigned while the sysfs /sys/bus/ap/apmask and
+       sys/bus/ap/aqmask attribute files are being edited or the operation may
+       terminate with an error (EBUSY).
+
+   In order to successfully assign a domain:
+
+   * The domain number specified must represent a value from 0 up to the
+     maximum domain number configured for the system. If a domain number
+     higher than the maximum is specified, the operation will terminate with
+     an error (ENODEV).
+
+     Note: The maximum domain number can be obtained via the sysfs
+	   /sys/bus/ap/ap_max_domain_id attribute file.
+
+    * Each APQN derived from the Cartesian product of the APQI of the domain
+      being assigned and the APIDs of the adapters previously assigned:
+
+     - Must only be available to the vfio_ap device driver as specified in the
+       sysfs /sys/bus/ap/apmask and /sys/bus/ap/aqmask attribute files. If even
+       one APQN is reserved for use by the host device driver, the operation
+       will terminate with an error (EADDRNOTAVAIL).
+
+     - Must NOT be assigned to another vfio_ap mediated device. If even one APQN
+       is assigned to another vfio_ap mediated device, the operation will
+       terminate with an error (EBUSY).
+
+     - Must NOT be assigned while the sysfs /sys/bus/ap/apmask and
+       sys/bus/ap/aqmask attribute files are being edited or the operation may
+       terminate with an error (EBUSY).
+
+   In order to successfully assign a control domain:
+
+   * The domain number specified must represent a value from 0 up to the maximum
+     domain number configured for the system. If a control domain number higher
+     than the maximum is specified, the operation will terminate with an
+     error (ENODEV).
+
+5. Start Guest1::
+
+     /usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on,apqi=on \
+	-device vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid1 ...
+
+7. Start Guest2::
+
+     /usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on,apqi=on \
+	-device vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid2 ...
+
+7. Start Guest3::
+
+     /usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on,apqi=on \
+	-device vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid3 ...
+
+When the guest is shut down, the vfio_ap mediated devices may be removed.
+
+Using our example again, to remove the vfio_ap mediated device $uuid1::
+
+   /sys/devices/vfio_ap/matrix/
+      --- [mdev_supported_types]
+      ------ [vfio_ap-passthrough]
+      --------- [devices]
+      ------------ [$uuid1]
+      --------------- remove
+
+::
+
+   echo 1 > remove
+
+This will remove all of the matrix mdev device's sysfs structures including
+the mdev device itself. To recreate and reconfigure the matrix mdev device,
+all of the steps starting with step 3 will have to be performed again. Note
+that the remove will fail if a guest using the vfio_ap mdev is still running.
+
+It is not necessary to remove a vfio_ap mdev, but one may want to
+remove it if no guest will use it during the remaining lifetime of the linux
+host. If the vfio_ap mdev is removed, one may want to also reconfigure
+the pool of adapters and queues reserved for use by the default drivers.
+
+Hot plug/unplug support:
+========================
+An adapter, domain or control domain may be hot plugged into a running KVM
+guest by assigning it to the vfio_ap mediated device being used by the guest if
+the following conditions are met:
+
+* The adapter, domain or control domain must also be assigned to the host's
+  AP configuration.
+
+* Each APQN derived from the Cartesian product comprised of the APID of the
+  adapter being assigned and the APQIs of the domains assigned must reference a
+  queue device bound to the vfio_ap device driver.
+
+* To hot plug a domain, each APQN derived from the Cartesian product
+  comprised of the APQI of the domain being assigned and the APIDs of the
+  adapters assigned must reference a queue device bound to the vfio_ap device
+  driver.
+
+An adapter, domain or control domain may be hot unplugged from a running KVM
+guest by unassigning it from the vfio_ap mediated device being used by the
+guest.
+
+Over-provisioning of AP queues for a KVM guest:
+===============================================
+Over-provisioning is defined herein as the assignment of adapters or domains to
+a vfio_ap mediated device that do not reference AP devices in the host's AP
+configuration. The idea here is that when the adapter or domain becomes
+available, it will be automatically hot-plugged into the KVM guest using
+the vfio_ap mediated device to which it is assigned as long as each new APQN
+resulting from plugging it in references a queue device bound to the vfio_ap
+device driver.
+
+Limitations
+===========
+Live guest migration is not supported for guests using AP devices without
+intervention by a system administrator. Before a KVM guest can be migrated,
+the vfio_ap mediated device must be removed. Unfortunately, it can not be
+removed manually (i.e., echo 1 > /sys/devices/vfio_ap/matrix/$UUID/remove) while
+the mdev is in use by a KVM guest. If the guest is being emulated by QEMU,
+its mdev can be hot unplugged from the guest in one of two ways:
+
+1. If the KVM guest was started with libvirt, you can hot unplug the mdev via
+   the following commands:
+
+      virsh detach-device <guestname> <path-to-device-xml>
+
+      For example, to hot unplug mdev 62177883-f1bb-47f0-914d-32a22e3a8804 from
+      the guest named 'my-guest':
+
+         virsh detach-device my-guest ~/config/my-guest-hostdev.xml
+
+            The contents of my-guest-hostdev.xml:
+
+.. code-block:: xml
+
+            <hostdev mode='subsystem' type='mdev' managed='no' model='vfio-ap'>
+              <source>
+                <address uuid='62177883-f1bb-47f0-914d-32a22e3a8804'/>
+              </source>
+            </hostdev>
+
+
+      virsh qemu-monitor-command <guest-name> --hmp "device-del <device-id>"
+
+      For example, to hot unplug the vfio_ap mediated device identified on the
+      qemu command line with 'id=hostdev0' from the guest named 'my-guest':
+
+.. code-block:: sh
+
+         virsh qemu-monitor-command my-guest --hmp "device_del hostdev0"
+
+2. A vfio_ap mediated device can be hot unplugged by attaching the qemu monitor
+   to the guest and using the following qemu monitor command:
+
+      (QEMU) device-del id=<device-id>
+
+      For example, to hot unplug the vfio_ap mediated device that was specified
+      on the qemu command line with 'id=hostdev0' when the guest was started:
+
+         (QEMU) device-del id=hostdev0
+
+After live migration of the KVM guest completes, an AP configuration can be
+restored to the KVM guest by hot plugging a vfio_ap mediated device on the target
+system into the guest in one of two ways:
+
+1. If the KVM guest was started with libvirt, you can hot plug a matrix mediated
+   device into the guest via the following virsh commands:
+
+   virsh attach-device <guestname> <path-to-device-xml>
+
+      For example, to hot plug mdev 62177883-f1bb-47f0-914d-32a22e3a8804 into
+      the guest named 'my-guest':
+
+         virsh attach-device my-guest ~/config/my-guest-hostdev.xml
+
+            The contents of my-guest-hostdev.xml:
+
+.. code-block:: xml
+
+            <hostdev mode='subsystem' type='mdev' managed='no' model='vfio-ap'>
+              <source>
+                <address uuid='62177883-f1bb-47f0-914d-32a22e3a8804'/>
+              </source>
+            </hostdev>
+
+
+   virsh qemu-monitor-command <guest-name> --hmp \
+   "device_add vfio-ap,sysfsdev=<path-to-mdev>,id=<device-id>"
+
+      For example, to hot plug the vfio_ap mediated device
+      62177883-f1bb-47f0-914d-32a22e3a8804 into the guest named 'my-guest' with
+      device-id hostdev0:
+
+      virsh qemu-monitor-command my-guest --hmp \
+      "device_add vfio-ap,\
+      sysfsdev=/sys/devices/vfio_ap/matrix/62177883-f1bb-47f0-914d-32a22e3a8804,\
+      id=hostdev0"
+
+2. A vfio_ap mediated device can be hot plugged by attaching the qemu monitor
+   to the guest and using the following qemu monitor command:
+
+      (qemu) device_add "vfio-ap,sysfsdev=<path-to-mdev>,id=<device-id>"
+
+      For example, to plug the vfio_ap mediated device
+      62177883-f1bb-47f0-914d-32a22e3a8804 into the guest with the device-id
+      hostdev0:
+
+         (QEMU) device-add "vfio-ap,\
+         sysfsdev=/sys/devices/vfio_ap/matrix/62177883-f1bb-47f0-914d-32a22e3a8804,\
+         id=hostdev0"
diff --git a/Documentation/arch/s390/vfio-ccw.rst b/Documentation/arch/s390/vfio-ccw.rst
new file mode 100644
index 0000000000..42960b7b0d
--- /dev/null
+++ b/Documentation/arch/s390/vfio-ccw.rst
@@ -0,0 +1,445 @@
+==================================
+vfio-ccw: the basic infrastructure
+==================================
+
+Introduction
+------------
+
+Here we describe the vfio support for I/O subchannel devices for
+Linux/s390. Motivation for vfio-ccw is to passthrough subchannels to a
+virtual machine, while vfio is the means.
+
+Different than other hardware architectures, s390 has defined a unified
+I/O access method, which is so called Channel I/O. It has its own access
+patterns:
+
+- Channel programs run asynchronously on a separate (co)processor.
+- The channel subsystem will access any memory designated by the caller
+  in the channel program directly, i.e. there is no iommu involved.
+
+Thus when we introduce vfio support for these devices, we realize it
+with a mediated device (mdev) implementation. The vfio mdev will be
+added to an iommu group, so as to make itself able to be managed by the
+vfio framework. And we add read/write callbacks for special vfio I/O
+regions to pass the channel programs from the mdev to its parent device
+(the real I/O subchannel device) to do further address translation and
+to perform I/O instructions.
+
+This document does not intend to explain the s390 I/O architecture in
+every detail. More information/reference could be found here:
+
+- A good start to know Channel I/O in general:
+  https://en.wikipedia.org/wiki/Channel_I/O
+- s390 architecture:
+  s390 Principles of Operation manual (IBM Form. No. SA22-7832)
+- The existing QEMU code which implements a simple emulated channel
+  subsystem could also be a good reference. It makes it easier to follow
+  the flow.
+  qemu/hw/s390x/css.c
+
+For vfio mediated device framework:
+- Documentation/driver-api/vfio-mediated-device.rst
+
+Motivation of vfio-ccw
+----------------------
+
+Typically, a guest virtualized via QEMU/KVM on s390 only sees
+paravirtualized virtio devices via the "Virtio Over Channel I/O
+(virtio-ccw)" transport. This makes virtio devices discoverable via
+standard operating system algorithms for handling channel devices.
+
+However this is not enough. On s390 for the majority of devices, which
+use the standard Channel I/O based mechanism, we also need to provide
+the functionality of passing through them to a QEMU virtual machine.
+This includes devices that don't have a virtio counterpart (e.g. tape
+drives) or that have specific characteristics which guests want to
+exploit.
+
+For passing a device to a guest, we want to use the same interface as
+everybody else, namely vfio. We implement this vfio support for channel
+devices via the vfio mediated device framework and the subchannel device
+driver "vfio_ccw".
+
+Access patterns of CCW devices
+------------------------------
+
+s390 architecture has implemented a so called channel subsystem, that
+provides a unified view of the devices physically attached to the
+systems. Though the s390 hardware platform knows about a huge variety of
+different peripheral attachments like disk devices (aka. DASDs), tapes,
+communication controllers, etc. They can all be accessed by a well
+defined access method and they are presenting I/O completion a unified
+way: I/O interruptions.
+
+All I/O requires the use of channel command words (CCWs). A CCW is an
+instruction to a specialized I/O channel processor. A channel program is
+a sequence of CCWs which are executed by the I/O channel subsystem.  To
+issue a channel program to the channel subsystem, it is required to
+build an operation request block (ORB), which can be used to point out
+the format of the CCW and other control information to the system. The
+operating system signals the I/O channel subsystem to begin executing
+the channel program with a SSCH (start sub-channel) instruction. The
+central processor is then free to proceed with non-I/O instructions
+until interrupted. The I/O completion result is received by the
+interrupt handler in the form of interrupt response block (IRB).
+
+Back to vfio-ccw, in short:
+
+- ORBs and channel programs are built in guest kernel (with guest
+  physical addresses).
+- ORBs and channel programs are passed to the host kernel.
+- Host kernel translates the guest physical addresses to real addresses
+  and starts the I/O with issuing a privileged Channel I/O instruction
+  (e.g SSCH).
+- channel programs run asynchronously on a separate processor.
+- I/O completion will be signaled to the host with I/O interruptions.
+  And it will be copied as IRB to user space to pass it back to the
+  guest.
+
+Physical vfio ccw device and its child mdev
+-------------------------------------------
+
+As mentioned above, we realize vfio-ccw with a mdev implementation.
+
+Channel I/O does not have IOMMU hardware support, so the physical
+vfio-ccw device does not have an IOMMU level translation or isolation.
+
+Subchannel I/O instructions are all privileged instructions. When
+handling the I/O instruction interception, vfio-ccw has the software
+policing and translation how the channel program is programmed before
+it gets sent to hardware.
+
+Within this implementation, we have two drivers for two types of
+devices:
+
+- The vfio_ccw driver for the physical subchannel device.
+  This is an I/O subchannel driver for the real subchannel device.  It
+  realizes a group of callbacks and registers to the mdev framework as a
+  parent (physical) device. As a consequence, mdev provides vfio_ccw a
+  generic interface (sysfs) to create mdev devices. A vfio mdev could be
+  created by vfio_ccw then and added to the mediated bus. It is the vfio
+  device that added to an IOMMU group and a vfio group.
+  vfio_ccw also provides an I/O region to accept channel program
+  request from user space and store I/O interrupt result for user
+  space to retrieve. To notify user space an I/O completion, it offers
+  an interface to setup an eventfd fd for asynchronous signaling.
+
+- The vfio_mdev driver for the mediated vfio ccw device.
+  This is provided by the mdev framework. It is a vfio device driver for
+  the mdev that created by vfio_ccw.
+  It realizes a group of vfio device driver callbacks, adds itself to a
+  vfio group, and registers itself to the mdev framework as a mdev
+  driver.
+  It uses a vfio iommu backend that uses the existing map and unmap
+  ioctls, but rather than programming them into an IOMMU for a device,
+  it simply stores the translations for use by later requests. This
+  means that a device programmed in a VM with guest physical addresses
+  can have the vfio kernel convert that address to process virtual
+  address, pin the page and program the hardware with the host physical
+  address in one step.
+  For a mdev, the vfio iommu backend will not pin the pages during the
+  VFIO_IOMMU_MAP_DMA ioctl. Mdev framework will only maintain a database
+  of the iova<->vaddr mappings in this operation. And they export a
+  vfio_pin_pages and a vfio_unpin_pages interfaces from the vfio iommu
+  backend for the physical devices to pin and unpin pages by demand.
+
+Below is a high Level block diagram::
+
+ +-------------+
+ |             |
+ | +---------+ | mdev_register_driver() +--------------+
+ | |  Mdev   | +<-----------------------+              |
+ | |  bus    | |                        | vfio_mdev.ko |
+ | | driver  | +----------------------->+              |<-> VFIO user
+ | +---------+ |    probe()/remove()    +--------------+    APIs
+ |             |
+ |  MDEV CORE  |
+ |   MODULE    |
+ |   mdev.ko   |
+ | +---------+ | mdev_register_parent() +--------------+
+ | |Physical | +<-----------------------+              |
+ | | device  | |                        |  vfio_ccw.ko |<-> subchannel
+ | |interface| +----------------------->+              |     device
+ | +---------+ |       callback         +--------------+
+ +-------------+
+
+The process of how these work together.
+
+1. vfio_ccw.ko drives the physical I/O subchannel, and registers the
+   physical device (with callbacks) to mdev framework.
+   When vfio_ccw probing the subchannel device, it registers device
+   pointer and callbacks to the mdev framework. Mdev related file nodes
+   under the device node in sysfs would be created for the subchannel
+   device, namely 'mdev_create', 'mdev_destroy' and
+   'mdev_supported_types'.
+2. Create a mediated vfio ccw device.
+   Use the 'mdev_create' sysfs file, we need to manually create one (and
+   only one for our case) mediated device.
+3. vfio_mdev.ko drives the mediated ccw device.
+   vfio_mdev is also the vfio device driver. It will probe the mdev and
+   add it to an iommu_group and a vfio_group. Then we could pass through
+   the mdev to a guest.
+
+
+VFIO-CCW Regions
+----------------
+
+The vfio-ccw driver exposes MMIO regions to accept requests from and return
+results to userspace.
+
+vfio-ccw I/O region
+-------------------
+
+An I/O region is used to accept channel program request from user
+space and store I/O interrupt result for user space to retrieve. The
+definition of the region is::
+
+  struct ccw_io_region {
+  #define ORB_AREA_SIZE 12
+	  __u8    orb_area[ORB_AREA_SIZE];
+  #define SCSW_AREA_SIZE 12
+	  __u8    scsw_area[SCSW_AREA_SIZE];
+  #define IRB_AREA_SIZE 96
+	  __u8    irb_area[IRB_AREA_SIZE];
+	  __u32   ret_code;
+  } __packed;
+
+This region is always available.
+
+While starting an I/O request, orb_area should be filled with the
+guest ORB, and scsw_area should be filled with the SCSW of the Virtual
+Subchannel.
+
+irb_area stores the I/O result.
+
+ret_code stores a return code for each access of the region. The following
+values may occur:
+
+``0``
+  The operation was successful.
+
+``-EOPNOTSUPP``
+  The ORB specified transport mode or the
+  SCSW specified a function other than the start function.
+
+``-EIO``
+  A request was issued while the device was not in a state ready to accept
+  requests, or an internal error occurred.
+
+``-EBUSY``
+  The subchannel was status pending or busy, or a request is already active.
+
+``-EAGAIN``
+  A request was being processed, and the caller should retry.
+
+``-EACCES``
+  The channel path(s) used for the I/O were found to be not operational.
+
+``-ENODEV``
+  The device was found to be not operational.
+
+``-EINVAL``
+  The orb specified a chain longer than 255 ccws, or an internal error
+  occurred.
+
+
+vfio-ccw cmd region
+-------------------
+
+The vfio-ccw cmd region is used to accept asynchronous instructions
+from userspace::
+
+  #define VFIO_CCW_ASYNC_CMD_HSCH (1 << 0)
+  #define VFIO_CCW_ASYNC_CMD_CSCH (1 << 1)
+  struct ccw_cmd_region {
+         __u32 command;
+         __u32 ret_code;
+  } __packed;
+
+This region is exposed via region type VFIO_REGION_SUBTYPE_CCW_ASYNC_CMD.
+
+Currently, CLEAR SUBCHANNEL and HALT SUBCHANNEL use this region.
+
+command specifies the command to be issued; ret_code stores a return code
+for each access of the region. The following values may occur:
+
+``0``
+  The operation was successful.
+
+``-ENODEV``
+  The device was found to be not operational.
+
+``-EINVAL``
+  A command other than halt or clear was specified.
+
+``-EIO``
+  A request was issued while the device was not in a state ready to accept
+  requests.
+
+``-EAGAIN``
+  A request was being processed, and the caller should retry.
+
+``-EBUSY``
+  The subchannel was status pending or busy while processing a halt request.
+
+vfio-ccw schib region
+---------------------
+
+The vfio-ccw schib region is used to return Subchannel-Information
+Block (SCHIB) data to userspace::
+
+  struct ccw_schib_region {
+  #define SCHIB_AREA_SIZE 52
+         __u8 schib_area[SCHIB_AREA_SIZE];
+  } __packed;
+
+This region is exposed via region type VFIO_REGION_SUBTYPE_CCW_SCHIB.
+
+Reading this region triggers a STORE SUBCHANNEL to be issued to the
+associated hardware.
+
+vfio-ccw crw region
+---------------------
+
+The vfio-ccw crw region is used to return Channel Report Word (CRW)
+data to userspace::
+
+  struct ccw_crw_region {
+         __u32 crw;
+         __u32 pad;
+  } __packed;
+
+This region is exposed via region type VFIO_REGION_SUBTYPE_CCW_CRW.
+
+Reading this region returns a CRW if one that is relevant for this
+subchannel (e.g. one reporting changes in channel path state) is
+pending, or all zeroes if not. If multiple CRWs are pending (including
+possibly chained CRWs), reading this region again will return the next
+one, until no more CRWs are pending and zeroes are returned. This is
+similar to how STORE CHANNEL REPORT WORD works.
+
+vfio-ccw operation details
+--------------------------
+
+vfio-ccw follows what vfio-pci did on the s390 platform and uses
+vfio-iommu-type1 as the vfio iommu backend.
+
+* CCW translation APIs
+  A group of APIs (start with `cp_`) to do CCW translation. The CCWs
+  passed in by a user space program are organized with their guest
+  physical memory addresses. These APIs will copy the CCWs into kernel
+  space, and assemble a runnable kernel channel program by updating the
+  guest physical addresses with their corresponding host physical addresses.
+  Note that we have to use IDALs even for direct-access CCWs, as the
+  referenced memory can be located anywhere, including above 2G.
+
+* vfio_ccw device driver
+  This driver utilizes the CCW translation APIs and introduces
+  vfio_ccw, which is the driver for the I/O subchannel devices you want
+  to pass through.
+  vfio_ccw implements the following vfio ioctls::
+
+    VFIO_DEVICE_GET_INFO
+    VFIO_DEVICE_GET_IRQ_INFO
+    VFIO_DEVICE_GET_REGION_INFO
+    VFIO_DEVICE_RESET
+    VFIO_DEVICE_SET_IRQS
+
+  This provides an I/O region, so that the user space program can pass a
+  channel program to the kernel, to do further CCW translation before
+  issuing them to a real device.
+  This also provides the SET_IRQ ioctl to setup an event notifier to
+  notify the user space program the I/O completion in an asynchronous
+  way.
+
+The use of vfio-ccw is not limited to QEMU, while QEMU is definitely a
+good example to get understand how these patches work. Here is a little
+bit more detail how an I/O request triggered by the QEMU guest will be
+handled (without error handling).
+
+Explanation:
+
+- Q1-Q7: QEMU side process.
+- K1-K5: Kernel side process.
+
+Q1.
+    Get I/O region info during initialization.
+
+Q2.
+    Setup event notifier and handler to handle I/O completion.
+
+... ...
+
+Q3.
+    Intercept a ssch instruction.
+Q4.
+    Write the guest channel program and ORB to the I/O region.
+
+    K1.
+	Copy from guest to kernel.
+    K2.
+	Translate the guest channel program to a host kernel space
+	channel program, which becomes runnable for a real device.
+    K3.
+	With the necessary information contained in the orb passed in
+	by QEMU, issue the ccwchain to the device.
+    K4.
+	Return the ssch CC code.
+Q5.
+    Return the CC code to the guest.
+
+... ...
+
+    K5.
+	Interrupt handler gets the I/O result and write the result to
+	the I/O region.
+    K6.
+	Signal QEMU to retrieve the result.
+
+Q6.
+    Get the signal and event handler reads out the result from the I/O
+    region.
+Q7.
+    Update the irb for the guest.
+
+Limitations
+-----------
+
+The current vfio-ccw implementation focuses on supporting basic commands
+needed to implement block device functionality (read/write) of DASD/ECKD
+device only. Some commands may need special handling in the future, for
+example, anything related to path grouping.
+
+DASD is a kind of storage device. While ECKD is a data recording format.
+More information for DASD and ECKD could be found here:
+https://en.wikipedia.org/wiki/Direct-access_storage_device
+https://en.wikipedia.org/wiki/Count_key_data
+
+Together with the corresponding work in QEMU, we can bring the passed
+through DASD/ECKD device online in a guest now and use it as a block
+device.
+
+The current code allows the guest to start channel programs via
+START SUBCHANNEL, and to issue HALT SUBCHANNEL, CLEAR SUBCHANNEL,
+and STORE SUBCHANNEL.
+
+Currently all channel programs are prefetched, regardless of the
+p-bit setting in the ORB.  As a result, self modifying channel
+programs are not supported.  For this reason, IPL has to be handled as
+a special case by a userspace/guest program; this has been implemented
+in QEMU's s390-ccw bios as of QEMU 4.1.
+
+vfio-ccw supports classic (command mode) channel I/O only. Transport
+mode (HPF) is not supported.
+
+QDIO subchannels are currently not supported. Classic devices other than
+DASD/ECKD might work, but have not been tested.
+
+Reference
+---------
+1. ESA/s390 Principles of Operation manual (IBM Form. No. SA22-7832)
+2. ESA/390 Common I/O Device Commands manual (IBM Form. No. SA22-7204)
+3. https://en.wikipedia.org/wiki/Channel_I/O
+4. Documentation/arch/s390/cds.rst
+5. Documentation/driver-api/vfio.rst
+6. Documentation/driver-api/vfio-mediated-device.rst
diff --git a/Documentation/arch/s390/zfcpdump.rst b/Documentation/arch/s390/zfcpdump.rst
new file mode 100644
index 0000000000..a61de7aa87
--- /dev/null
+++ b/Documentation/arch/s390/zfcpdump.rst
@@ -0,0 +1,50 @@
+==================================
+The s390 SCSI dump tool (zfcpdump)
+==================================
+
+System z machines (z900 or higher) provide hardware support for creating system
+dumps on SCSI disks. The dump process is initiated by booting a dump tool, which
+has to create a dump of the current (probably crashed) Linux image. In order to
+not overwrite memory of the crashed Linux with data of the dump tool, the
+hardware saves some memory plus the register sets of the boot CPU before the
+dump tool is loaded. There exists an SCLP hardware interface to obtain the saved
+memory afterwards. Currently 32 MB are saved.
+
+This zfcpdump implementation consists of a Linux dump kernel together with
+a user space dump tool, which are loaded together into the saved memory region
+below 32 MB. zfcpdump is installed on a SCSI disk using zipl (as contained in
+the s390-tools package) to make the device bootable. The operator of a Linux
+system can then trigger a SCSI dump by booting the SCSI disk, where zfcpdump
+resides on.
+
+The user space dump tool accesses the memory of the crashed system by means
+of the /proc/vmcore interface. This interface exports the crashed system's
+memory and registers in ELF core dump format. To access the memory which has
+been saved by the hardware SCLP requests will be created at the time the data
+is needed by /proc/vmcore. The tail part of the crashed systems memory which
+has not been stashed by hardware can just be copied from real memory.
+
+To build a dump enabled kernel the kernel config option CONFIG_CRASH_DUMP
+has to be set.
+
+To get a valid zfcpdump kernel configuration use "make zfcpdump_defconfig".
+
+The s390 zipl tool looks for the zfcpdump kernel and optional initrd/initramfs
+under the following locations:
+
+* kernel:  <zfcpdump directory>/zfcpdump.image
+* ramdisk: <zfcpdump directory>/zfcpdump.rd
+
+The zfcpdump directory is defined in the s390-tools package.
+
+The user space application of zfcpdump can reside in an intitramfs or an
+initrd. It can also be included in a built-in kernel initramfs. The application
+reads from /proc/vmcore or zcore/mem and writes the system dump to a SCSI disk.
+
+The s390-tools package version 1.24.0 and above builds an external zfcpdump
+initramfs with a user space application that writes the dump to a SCSI
+partition.
+
+For more information on how to use zfcpdump refer to the s390 'Using the Dump
+Tools' book, which is available from IBM Knowledge Center:
+https://www.ibm.com/support/knowledgecenter/linuxonibm/liaaf/lnz_r_dt.html