Adding upstream version 6.1.76.upstream/6.1.76upstream

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

9 files changed, 952 insertions, 0 deletions

diff --git a/Documentation/x86/x86_64/5level-paging.rst b/Documentation/x86/x86_64/5level-paging.rst
new file mode 100644
index 000000000..b792bbdc0
--- /dev/null
+++ b/Documentation/x86/x86_64/5level-paging.rst
@@ -0,0 +1,67 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==============
+5-level paging
+==============
+
+Overview
+========
+Original x86-64 was limited by 4-level paging to 256 TiB of virtual address
+space and 64 TiB of physical address space. We are already bumping into
+this limit: some vendors offer servers with 64 TiB of memory today.
+
+To overcome the limitation upcoming hardware will introduce support for
+5-level paging. It is a straight-forward extension of the current page
+table structure adding one more layer of translation.
+
+It bumps the limits to 128 PiB of virtual address space and 4 PiB of
+physical address space. This "ought to be enough for anybody" ©.
+
+QEMU 2.9 and later support 5-level paging.
+
+Virtual memory layout for 5-level paging is described in
+Documentation/x86/x86_64/mm.rst
+
+
+Enabling 5-level paging
+=======================
+CONFIG_X86_5LEVEL=y enables the feature.
+
+Kernel with CONFIG_X86_5LEVEL=y still able to boot on 4-level hardware.
+In this case additional page table level -- p4d -- will be folded at
+runtime.
+
+User-space and large virtual address space
+==========================================
+On x86, 5-level paging enables 56-bit userspace virtual address space.
+Not all user space is ready to handle wide addresses. It's known that
+at least some JIT compilers use higher bits in pointers to encode their
+information. It collides with valid pointers with 5-level paging and
+leads to crashes.
+
+To mitigate this, we are not going to allocate virtual address space
+above 47-bit by default.
+
+But userspace can ask for allocation from full address space by
+specifying hint address (with or without MAP_FIXED) above 47-bits.
+
+If hint address set above 47-bit, but MAP_FIXED is not specified, we try
+to look for unmapped area by specified address. If it's already
+occupied, we look for unmapped area in *full* address space, rather than
+from 47-bit window.
+
+A high hint address would only affect the allocation in question, but not
+any future mmap()s.
+
+Specifying high hint address on older kernel or on machine without 5-level
+paging support is safe. The hint will be ignored and kernel will fall back
+to allocation from 47-bit address space.
+
+This approach helps to easily make application's memory allocator aware
+about large address space without manually tracking allocated virtual
+address space.
+
+One important case we need to handle here is interaction with MPX.
+MPX (without MAWA extension) cannot handle addresses above 47-bit, so we
+need to make sure that MPX cannot be enabled we already have VMA above
+the boundary and forbid creating such VMAs once MPX is enabled.
diff --git a/Documentation/x86/x86_64/boot-options.rst b/Documentation/x86/x86_64/boot-options.rst
new file mode 100644
index 000000000..cbd14124a
--- /dev/null
+++ b/Documentation/x86/x86_64/boot-options.rst
@@ -0,0 +1,319 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===========================
+AMD64 Specific Boot Options
+===========================
+
+There are many others (usually documented in driver documentation), but
+only the AMD64 specific ones are listed here.
+
+Machine check
+=============
+Please see Documentation/x86/x86_64/machinecheck.rst for sysfs runtime tunables.
+
+   mce=off
+		Disable machine check
+   mce=no_cmci
+		Disable CMCI(Corrected Machine Check Interrupt) that
+		Intel processor supports.  Usually this disablement is
+		not recommended, but it might be handy if your hardware
+		is misbehaving.
+		Note that you'll get more problems without CMCI than with
+		due to the shared banks, i.e. you might get duplicated
+		error logs.
+   mce=dont_log_ce
+		Don't make logs for corrected errors.  All events reported
+		as corrected are silently cleared by OS.
+		This option will be useful if you have no interest in any
+		of corrected errors.
+   mce=ignore_ce
+		Disable features for corrected errors, e.g. polling timer
+		and CMCI.  All events reported as corrected are not cleared
+		by OS and remained in its error banks.
+		Usually this disablement is not recommended, however if
+		there is an agent checking/clearing corrected errors
+		(e.g. BIOS or hardware monitoring applications), conflicting
+		with OS's error handling, and you cannot deactivate the agent,
+		then this option will be a help.
+   mce=no_lmce
+		Do not opt-in to Local MCE delivery. Use legacy method
+		to broadcast MCEs.
+   mce=bootlog
+		Enable logging of machine checks left over from booting.
+		Disabled by default on AMD Fam10h and older because some BIOS
+		leave bogus ones.
+		If your BIOS doesn't do that it's a good idea to enable though
+		to make sure you log even machine check events that result
+		in a reboot. On Intel systems it is enabled by default.
+   mce=nobootlog
+		Disable boot machine check logging.
+   mce=monarchtimeout (number)
+		monarchtimeout:
+		Sets the time in us to wait for other CPUs on machine checks. 0
+		to disable.
+   mce=bios_cmci_threshold
+		Don't overwrite the bios-set CMCI threshold. This boot option
+		prevents Linux from overwriting the CMCI threshold set by the
+		bios. Without this option, Linux always sets the CMCI
+		threshold to 1. Enabling this may make memory predictive failure
+		analysis less effective if the bios sets thresholds for memory
+		errors since we will not see details for all errors.
+   mce=recovery
+		Force-enable recoverable machine check code paths
+
+   nomce (for compatibility with i386)
+		same as mce=off
+
+   Everything else is in sysfs now.
+
+APICs
+=====
+
+   apic
+	Use IO-APIC. Default
+
+   noapic
+	Don't use the IO-APIC.
+
+   disableapic
+	Don't use the local APIC
+
+   nolapic
+     Don't use the local APIC (alias for i386 compatibility)
+
+   pirq=...
+	See Documentation/x86/i386/IO-APIC.rst
+
+   noapictimer
+	Don't set up the APIC timer
+
+   no_timer_check
+	Don't check the IO-APIC timer. This can work around
+	problems with incorrect timer initialization on some boards.
+
+   apicpmtimer
+	Do APIC timer calibration using the pmtimer. Implies
+	apicmaintimer. Useful when your PIT timer is totally broken.
+
+Timing
+======
+
+  notsc
+    Deprecated, use tsc=unstable instead.
+
+  nohpet
+    Don't use the HPET timer.
+
+Idle loop
+=========
+
+  idle=poll
+    Don't do power saving in the idle loop using HLT, but poll for rescheduling
+    event. This will make the CPUs eat a lot more power, but may be useful
+    to get slightly better performance in multiprocessor benchmarks. It also
+    makes some profiling using performance counters more accurate.
+    Please note that on systems with MONITOR/MWAIT support (like Intel EM64T
+    CPUs) this option has no performance advantage over the normal idle loop.
+    It may also interact badly with hyperthreading.
+
+Rebooting
+=========
+
+   reboot=b[ios] | t[riple] | k[bd] | a[cpi] | e[fi] | p[ci] [, [w]arm | [c]old]
+      bios
+        Use the CPU reboot vector for warm reset
+      warm
+        Don't set the cold reboot flag
+      cold
+        Set the cold reboot flag
+      triple
+        Force a triple fault (init)
+      kbd
+        Use the keyboard controller. cold reset (default)
+      acpi
+        Use the ACPI RESET_REG in the FADT. If ACPI is not configured or
+        the ACPI reset does not work, the reboot path attempts the reset
+        using the keyboard controller.
+      efi
+        Use efi reset_system runtime service. If EFI is not configured or
+        the EFI reset does not work, the reboot path attempts the reset using
+        the keyboard controller.
+      pci
+        Use a write to the PCI config space register 0xcf9 to trigger reboot.
+
+   Using warm reset will be much faster especially on big memory
+   systems because the BIOS will not go through the memory check.
+   Disadvantage is that not all hardware will be completely reinitialized
+   on reboot so there may be boot problems on some systems.
+
+   reboot=force
+     Don't stop other CPUs on reboot. This can make reboot more reliable
+     in some cases.
+
+   reboot=default
+     There are some built-in platform specific "quirks" - you may see:
+     "reboot: <name> series board detected. Selecting <type> for reboots."
+     In the case where you think the quirk is in error (e.g. you have
+     newer BIOS, or newer board) using this option will ignore the built-in
+     quirk table, and use the generic default reboot actions.
+
+NUMA
+====
+
+  numa=off
+    Only set up a single NUMA node spanning all memory.
+
+  numa=noacpi
+    Don't parse the SRAT table for NUMA setup
+
+  numa=nohmat
+    Don't parse the HMAT table for NUMA setup, or soft-reserved memory
+    partitioning.
+
+  numa=fake=<size>[MG]
+    If given as a memory unit, fills all system RAM with nodes of
+    size interleaved over physical nodes.
+
+  numa=fake=<N>
+    If given as an integer, fills all system RAM with N fake nodes
+    interleaved over physical nodes.
+
+  numa=fake=<N>U
+    If given as an integer followed by 'U', it will divide each
+    physical node into N emulated nodes.
+
+ACPI
+====
+
+  acpi=off
+    Don't enable ACPI
+  acpi=ht
+    Use ACPI boot table parsing, but don't enable ACPI interpreter
+  acpi=force
+    Force ACPI on (currently not needed)
+  acpi=strict
+    Disable out of spec ACPI workarounds.
+  acpi_sci={edge,level,high,low}
+    Set up ACPI SCI interrupt.
+  acpi=noirq
+    Don't route interrupts
+  acpi=nocmcff
+    Disable firmware first mode for corrected errors. This
+    disables parsing the HEST CMC error source to check if
+    firmware has set the FF flag. This may result in
+    duplicate corrected error reports.
+
+PCI
+===
+
+  pci=off
+    Don't use PCI
+  pci=conf1
+    Use conf1 access.
+  pci=conf2
+    Use conf2 access.
+  pci=rom
+    Assign ROMs.
+  pci=assign-busses
+    Assign busses
+  pci=irqmask=MASK
+    Set PCI interrupt mask to MASK
+  pci=lastbus=NUMBER
+    Scan up to NUMBER busses, no matter what the mptable says.
+  pci=noacpi
+    Don't use ACPI to set up PCI interrupt routing.
+
+IOMMU (input/output memory management unit)
+===========================================
+Multiple x86-64 PCI-DMA mapping implementations exist, for example:
+
+   1. <kernel/dma/direct.c>: use no hardware/software IOMMU at all
+      (e.g. because you have < 3 GB memory).
+      Kernel boot message: "PCI-DMA: Disabling IOMMU"
+
+   2. <arch/x86/kernel/amd_gart_64.c>: AMD GART based hardware IOMMU.
+      Kernel boot message: "PCI-DMA: using GART IOMMU"
+
+   3. <arch/x86_64/kernel/pci-swiotlb.c> : Software IOMMU implementation. Used
+      e.g. if there is no hardware IOMMU in the system and it is need because
+      you have >3GB memory or told the kernel to us it (iommu=soft))
+      Kernel boot message: "PCI-DMA: Using software bounce buffering
+      for IO (SWIOTLB)"
+
+::
+
+  iommu=[<size>][,noagp][,off][,force][,noforce]
+  [,memaper[=<order>]][,merge][,fullflush][,nomerge]
+  [,noaperture]
+
+General iommu options:
+
+    off
+      Don't initialize and use any kind of IOMMU.
+    noforce
+      Don't force hardware IOMMU usage when it is not needed. (default).
+    force
+      Force the use of the hardware IOMMU even when it is
+      not actually needed (e.g. because < 3 GB memory).
+    soft
+      Use software bounce buffering (SWIOTLB) (default for
+      Intel machines). This can be used to prevent the usage
+      of an available hardware IOMMU.
+
+iommu options only relevant to the AMD GART hardware IOMMU:
+
+    <size>
+      Set the size of the remapping area in bytes.
+    allowed
+      Overwrite iommu off workarounds for specific chipsets.
+    fullflush
+      Flush IOMMU on each allocation (default).
+    nofullflush
+      Don't use IOMMU fullflush.
+    memaper[=<order>]
+      Allocate an own aperture over RAM with size 32MB<<order.
+      (default: order=1, i.e. 64MB)
+    merge
+      Do scatter-gather (SG) merging. Implies "force" (experimental).
+    nomerge
+      Don't do scatter-gather (SG) merging.
+    noaperture
+      Ask the IOMMU not to touch the aperture for AGP.
+    noagp
+      Don't initialize the AGP driver and use full aperture.
+    panic
+      Always panic when IOMMU overflows.
+
+iommu options only relevant to the software bounce buffering (SWIOTLB) IOMMU
+implementation:
+
+    swiotlb=<slots>[,force,noforce]
+      <slots>
+        Prereserve that many 2K slots for the software IO bounce buffering.
+      force
+        Force all IO through the software TLB.
+      noforce
+        Do not initialize the software TLB.
+
+
+Miscellaneous
+=============
+
+  nogbpages
+    Do not use GB pages for kernel direct mappings.
+  gbpages
+    Use GB pages for kernel direct mappings.
+
+
+AMD SEV (Secure Encrypted Virtualization)
+=========================================
+Options relating to AMD SEV, specified via the following format:
+
+::
+
+   sev=option1[,option2]
+
+The available options are:
+
+   debug
+     Enable debug messages.
diff --git a/Documentation/x86/x86_64/cpu-hotplug-spec.rst b/Documentation/x86/x86_64/cpu-hotplug-spec.rst
new file mode 100644
index 000000000..8d1c91f0c
--- /dev/null
+++ b/Documentation/x86/x86_64/cpu-hotplug-spec.rst
@@ -0,0 +1,24 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===================================================
+Firmware support for CPU hotplug under Linux/x86-64
+===================================================
+
+Linux/x86-64 supports CPU hotplug now. For various reasons Linux wants to
+know in advance of boot time the maximum number of CPUs that could be plugged
+into the system. ACPI 3.0 currently has no official way to supply
+this information from the firmware to the operating system.
+
+In ACPI each CPU needs an LAPIC object in the MADT table (5.2.11.5 in the
+ACPI 3.0 specification).  ACPI already has the concept of disabled LAPIC
+objects by setting the Enabled bit in the LAPIC object to zero.
+
+For CPU hotplug Linux/x86-64 expects now that any possible future hotpluggable
+CPU is already available in the MADT. If the CPU is not available yet
+it should have its LAPIC Enabled bit set to 0. Linux will use the number
+of disabled LAPICs to compute the maximum number of future CPUs.
+
+In the worst case the user can overwrite this choice using a command line
+option (additional_cpus=...), but it is recommended to supply the correct
+number (or a reasonable approximation of it, with erring towards more not less)
+in the MADT to avoid manual configuration.
diff --git a/Documentation/x86/x86_64/fake-numa-for-cpusets.rst b/Documentation/x86/x86_64/fake-numa-for-cpusets.rst
new file mode 100644
index 000000000..ff9bcfd2c
--- /dev/null
+++ b/Documentation/x86/x86_64/fake-numa-for-cpusets.rst
@@ -0,0 +1,78 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=====================
+Fake NUMA For CPUSets
+=====================
+
+:Author: David Rientjes <rientjes@cs.washington.edu>
+
+Using numa=fake and CPUSets for Resource Management
+
+This document describes how the numa=fake x86_64 command-line option can be used
+in conjunction with cpusets for coarse memory management.  Using this feature,
+you can create fake NUMA nodes that represent contiguous chunks of memory and
+assign them to cpusets and their attached tasks.  This is a way of limiting the
+amount of system memory that are available to a certain class of tasks.
+
+For more information on the features of cpusets, see
+Documentation/admin-guide/cgroup-v1/cpusets.rst.
+There are a number of different configurations you can use for your needs.  For
+more information on the numa=fake command line option and its various ways of
+configuring fake nodes, see Documentation/x86/x86_64/boot-options.rst.
+
+For the purposes of this introduction, we'll assume a very primitive NUMA
+emulation setup of "numa=fake=4*512,".  This will split our system memory into
+four equal chunks of 512M each that we can now use to assign to cpusets.  As
+you become more familiar with using this combination for resource control,
+you'll determine a better setup to minimize the number of nodes you have to deal
+with.
+
+A machine may be split as follows with "numa=fake=4*512," as reported by dmesg::
+
+	Faking node 0 at 0000000000000000-0000000020000000 (512MB)
+	Faking node 1 at 0000000020000000-0000000040000000 (512MB)
+	Faking node 2 at 0000000040000000-0000000060000000 (512MB)
+	Faking node 3 at 0000000060000000-0000000080000000 (512MB)
+	...
+	On node 0 totalpages: 130975
+	On node 1 totalpages: 131072
+	On node 2 totalpages: 131072
+	On node 3 totalpages: 131072
+
+Now following the instructions for mounting the cpusets filesystem from
+Documentation/admin-guide/cgroup-v1/cpusets.rst, you can assign fake nodes (i.e. contiguous memory
+address spaces) to individual cpusets::
+
+	[root@xroads /]# mkdir exampleset
+	[root@xroads /]# mount -t cpuset none exampleset
+	[root@xroads /]# mkdir exampleset/ddset
+	[root@xroads /]# cd exampleset/ddset
+	[root@xroads /exampleset/ddset]# echo 0-1 > cpus
+	[root@xroads /exampleset/ddset]# echo 0-1 > mems
+
+Now this cpuset, 'ddset', will only allowed access to fake nodes 0 and 1 for
+memory allocations (1G).
+
+You can now assign tasks to these cpusets to limit the memory resources
+available to them according to the fake nodes assigned as mems::
+
+	[root@xroads /exampleset/ddset]# echo $$ > tasks
+	[root@xroads /exampleset/ddset]# dd if=/dev/zero of=tmp bs=1024 count=1G
+	[1] 13425
+
+Notice the difference between the system memory usage as reported by
+/proc/meminfo between the restricted cpuset case above and the unrestricted
+case (i.e. running the same 'dd' command without assigning it to a fake NUMA
+cpuset):
+
+	========	============	==========
+	Name		Unrestricted	Restricted
+	========	============	==========
+	MemTotal	3091900 kB	3091900 kB
+	MemFree		42113 kB	1513236 kB
+	========	============	==========
+
+This allows for coarse memory management for the tasks you assign to particular
+cpusets.  Since cpusets can form a hierarchy, you can create some pretty
+interesting combinations of use-cases for various classes of tasks for your
+memory management needs.
diff --git a/Documentation/x86/x86_64/fsgs.rst b/Documentation/x86/x86_64/fsgs.rst
new file mode 100644
index 000000000..50960e09e
--- /dev/null
+++ b/Documentation/x86/x86_64/fsgs.rst
@@ -0,0 +1,199 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Using FS and GS segments in user space applications
+===================================================
+
+The x86 architecture supports segmentation. Instructions which access
+memory can use segment register based addressing mode. The following
+notation is used to address a byte within a segment:
+
+  Segment-register:Byte-address
+
+The segment base address is added to the Byte-address to compute the
+resulting virtual address which is accessed. This allows to access multiple
+instances of data with the identical Byte-address, i.e. the same code. The
+selection of a particular instance is purely based on the base-address in
+the segment register.
+
+In 32-bit mode the CPU provides 6 segments, which also support segment
+limits. The limits can be used to enforce address space protections.
+
+In 64-bit mode the CS/SS/DS/ES segments are ignored and the base address is
+always 0 to provide a full 64bit address space. The FS and GS segments are
+still functional in 64-bit mode.
+
+Common FS and GS usage
+------------------------------
+
+The FS segment is commonly used to address Thread Local Storage (TLS). FS
+is usually managed by runtime code or a threading library. Variables
+declared with the '__thread' storage class specifier are instantiated per
+thread and the compiler emits the FS: address prefix for accesses to these
+variables. Each thread has its own FS base address so common code can be
+used without complex address offset calculations to access the per thread
+instances. Applications should not use FS for other purposes when they use
+runtimes or threading libraries which manage the per thread FS.
+
+The GS segment has no common use and can be used freely by
+applications. GCC and Clang support GS based addressing via address space
+identifiers.
+
+Reading and writing the FS/GS base address
+------------------------------------------
+
+There exist two mechanisms to read and write the FS/GS base address:
+
+ - the arch_prctl() system call
+
+ - the FSGSBASE instruction family
+
+Accessing FS/GS base with arch_prctl()
+--------------------------------------
+
+ The arch_prctl(2) based mechanism is available on all 64-bit CPUs and all
+ kernel versions.
+
+ Reading the base:
+
+   arch_prctl(ARCH_GET_FS, &fsbase);
+   arch_prctl(ARCH_GET_GS, &gsbase);
+
+ Writing the base:
+
+   arch_prctl(ARCH_SET_FS, fsbase);
+   arch_prctl(ARCH_SET_GS, gsbase);
+
+ The ARCH_SET_GS prctl may be disabled depending on kernel configuration
+ and security settings.
+
+Accessing FS/GS base with the FSGSBASE instructions
+---------------------------------------------------
+
+ With the Ivy Bridge CPU generation Intel introduced a new set of
+ instructions to access the FS and GS base registers directly from user
+ space. These instructions are also supported on AMD Family 17H CPUs. The
+ following instructions are available:
+
+  =============== ===========================
+  RDFSBASE %reg   Read the FS base register
+  RDGSBASE %reg   Read the GS base register
+  WRFSBASE %reg   Write the FS base register
+  WRGSBASE %reg   Write the GS base register
+  =============== ===========================
+
+ The instructions avoid the overhead of the arch_prctl() syscall and allow
+ more flexible usage of the FS/GS addressing modes in user space
+ applications. This does not prevent conflicts between threading libraries
+ and runtimes which utilize FS and applications which want to use it for
+ their own purpose.
+
+FSGSBASE instructions enablement
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ The instructions are enumerated in CPUID leaf 7, bit 0 of EBX. If
+ available /proc/cpuinfo shows 'fsgsbase' in the flag entry of the CPUs.
+
+ The availability of the instructions does not enable them
+ automatically. The kernel has to enable them explicitly in CR4. The
+ reason for this is that older kernels make assumptions about the values in
+ the GS register and enforce them when GS base is set via
+ arch_prctl(). Allowing user space to write arbitrary values to GS base
+ would violate these assumptions and cause malfunction.
+
+ On kernels which do not enable FSGSBASE the execution of the FSGSBASE
+ instructions will fault with a #UD exception.
+
+ The kernel provides reliable information about the enabled state in the
+ ELF AUX vector. If the HWCAP2_FSGSBASE bit is set in the AUX vector, the
+ kernel has FSGSBASE instructions enabled and applications can use them.
+ The following code example shows how this detection works::
+
+   #include <sys/auxv.h>
+   #include <elf.h>
+
+   /* Will be eventually in asm/hwcap.h */
+   #ifndef HWCAP2_FSGSBASE
+   #define HWCAP2_FSGSBASE        (1 << 1)
+   #endif
+
+   ....
+
+   unsigned val = getauxval(AT_HWCAP2);
+
+   if (val & HWCAP2_FSGSBASE)
+        printf("FSGSBASE enabled\n");
+
+FSGSBASE instructions compiler support
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+GCC version 4.6.4 and newer provide instrinsics for the FSGSBASE
+instructions. Clang 5 supports them as well.
+
+  =================== ===========================
+  _readfsbase_u64()   Read the FS base register
+  _readfsbase_u64()   Read the GS base register
+  _writefsbase_u64()  Write the FS base register
+  _writegsbase_u64()  Write the GS base register
+  =================== ===========================
+
+To utilize these instrinsics <immintrin.h> must be included in the source
+code and the compiler option -mfsgsbase has to be added.
+
+Compiler support for FS/GS based addressing
+-------------------------------------------
+
+GCC version 6 and newer provide support for FS/GS based addressing via
+Named Address Spaces. GCC implements the following address space
+identifiers for x86:
+
+  ========= ====================================
+  __seg_fs  Variable is addressed relative to FS
+  __seg_gs  Variable is addressed relative to GS
+  ========= ====================================
+
+The preprocessor symbols __SEG_FS and __SEG_GS are defined when these
+address spaces are supported. Code which implements fallback modes should
+check whether these symbols are defined. Usage example::
+
+  #ifdef __SEG_GS
+
+  long data0 = 0;
+  long data1 = 1;
+
+  long __seg_gs *ptr;
+
+  /* Check whether FSGSBASE is enabled by the kernel (HWCAP2_FSGSBASE) */
+  ....
+
+  /* Set GS base to point to data0 */
+  _writegsbase_u64(&data0);
+
+  /* Access offset 0 of GS */
+  ptr = 0;
+  printf("data0 = %ld\n", *ptr);
+
+  /* Set GS base to point to data1 */
+  _writegsbase_u64(&data1);
+  /* ptr still addresses offset 0! */
+  printf("data1 = %ld\n", *ptr);
+
+
+Clang does not provide the GCC address space identifiers, but it provides
+address spaces via an attribute based mechanism in Clang 2.6 and newer
+versions:
+
+ ==================================== =====================================
+  __attribute__((address_space(256))  Variable is addressed relative to GS
+  __attribute__((address_space(257))  Variable is addressed relative to FS
+ ==================================== =====================================
+
+FS/GS based addressing with inline assembly
+-------------------------------------------
+
+In case the compiler does not support address spaces, inline assembly can
+be used for FS/GS based addressing mode::
+
+	mov %fs:offset, %reg
+	mov %gs:offset, %reg
+
+	mov %reg, %fs:offset
+	mov %reg, %gs:offset
diff --git a/Documentation/x86/x86_64/index.rst b/Documentation/x86/x86_64/index.rst
new file mode 100644
index 000000000..a56070fc8
--- /dev/null
+++ b/Documentation/x86/x86_64/index.rst
@@ -0,0 +1,17 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==============
+x86_64 Support
+==============
+
+.. toctree::
+   :maxdepth: 2
+
+   boot-options
+   uefi
+   mm
+   5level-paging
+   fake-numa-for-cpusets
+   cpu-hotplug-spec
+   machinecheck
+   fsgs
diff --git a/Documentation/x86/x86_64/machinecheck.rst b/Documentation/x86/x86_64/machinecheck.rst
new file mode 100644
index 000000000..cea12ee97
--- /dev/null
+++ b/Documentation/x86/x86_64/machinecheck.rst
@@ -0,0 +1,33 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============================================================
+Configurable sysfs parameters for the x86-64 machine check code
+===============================================================
+
+Machine checks report internal hardware error conditions detected
+by the CPU. Uncorrected errors typically cause a machine check
+(often with panic), corrected ones cause a machine check log entry.
+
+Machine checks are organized in banks (normally associated with
+a hardware subsystem) and subevents in a bank. The exact meaning
+of the banks and subevent is CPU specific.
+
+mcelog knows how to decode them.
+
+When you see the "Machine check errors logged" message in the system
+log then mcelog should run to collect and decode machine check entries
+from /dev/mcelog. Normally mcelog should be run regularly from a cronjob.
+
+Each CPU has a directory in /sys/devices/system/machinecheck/machinecheckN
+(N = CPU number).
+
+The directory contains some configurable entries. See
+Documentation/ABI/testing/sysfs-mce for more details.
+
+TBD document entries for AMD threshold interrupt configuration
+
+For more details about the x86 machine check architecture
+see the Intel and AMD architecture manuals from their developer websites.
+
+For more details about the architecture
+see http://one.firstfloor.org/~andi/mce.pdf
diff --git a/Documentation/x86/x86_64/mm.rst b/Documentation/x86/x86_64/mm.rst
new file mode 100644
index 000000000..9798676bb
--- /dev/null
+++ b/Documentation/x86/x86_64/mm.rst
@@ -0,0 +1,157 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================
+Memory Management
+=================
+
+Complete virtual memory map with 4-level page tables
+====================================================
+
+.. note::
+
+ - Negative addresses such as "-23 TB" are absolute addresses in bytes, counted down
+   from the top of the 64-bit address space. It's easier to understand the layout
+   when seen both in absolute addresses and in distance-from-top notation.
+
+   For example 0xffffe90000000000 == -23 TB, it's 23 TB lower than the top of the
+   64-bit address space (ffffffffffffffff).
+
+   Note that as we get closer to the top of the address space, the notation changes
+   from TB to GB and then MB/KB.
+
+ - "16M TB" might look weird at first sight, but it's an easier way to visualize size
+   notation than "16 EB", which few will recognize at first sight as 16 exabytes.
+   It also shows it nicely how incredibly large 64-bit address space is.
+
+::
+
+  ========================================================================================================================
+      Start addr    |   Offset   |     End addr     |  Size   | VM area description
+  ========================================================================================================================
+                    |            |                  |         |
+   0000000000000000 |    0       | 00007fffffffffff |  128 TB | user-space virtual memory, different per mm
+  __________________|____________|__________________|_________|___________________________________________________________
+                    |            |                  |         |
+   0000800000000000 | +128    TB | ffff7fffffffffff | ~16M TB | ... huge, almost 64 bits wide hole of non-canonical
+                    |            |                  |         |     virtual memory addresses up to the -128 TB
+                    |            |                  |         |     starting offset of kernel mappings.
+  __________________|____________|__________________|_________|___________________________________________________________
+                                                              |
+                                                              | Kernel-space virtual memory, shared between all processes:
+  ____________________________________________________________|___________________________________________________________
+                    |            |                  |         |
+   ffff800000000000 | -128    TB | ffff87ffffffffff |    8 TB | ... guard hole, also reserved for hypervisor
+   ffff880000000000 | -120    TB | ffff887fffffffff |  0.5 TB | LDT remap for PTI
+   ffff888000000000 | -119.5  TB | ffffc87fffffffff |   64 TB | direct mapping of all physical memory (page_offset_base)
+   ffffc88000000000 |  -55.5  TB | ffffc8ffffffffff |  0.5 TB | ... unused hole
+   ffffc90000000000 |  -55    TB | ffffe8ffffffffff |   32 TB | vmalloc/ioremap space (vmalloc_base)
+   ffffe90000000000 |  -23    TB | ffffe9ffffffffff |    1 TB | ... unused hole
+   ffffea0000000000 |  -22    TB | ffffeaffffffffff |    1 TB | virtual memory map (vmemmap_base)
+   ffffeb0000000000 |  -21    TB | ffffebffffffffff |    1 TB | ... unused hole
+   ffffec0000000000 |  -20    TB | fffffbffffffffff |   16 TB | KASAN shadow memory
+  __________________|____________|__________________|_________|____________________________________________________________
+                                                              |
+                                                              | Identical layout to the 56-bit one from here on:
+  ____________________________________________________________|____________________________________________________________
+                    |            |                  |         |
+   fffffc0000000000 |   -4    TB | fffffdffffffffff |    2 TB | ... unused hole
+                    |            |                  |         | vaddr_end for KASLR
+   fffffe0000000000 |   -2    TB | fffffe7fffffffff |  0.5 TB | cpu_entry_area mapping
+   fffffe8000000000 |   -1.5  TB | fffffeffffffffff |  0.5 TB | ... unused hole
+   ffffff0000000000 |   -1    TB | ffffff7fffffffff |  0.5 TB | %esp fixup stacks
+   ffffff8000000000 | -512    GB | ffffffeeffffffff |  444 GB | ... unused hole
+   ffffffef00000000 |  -68    GB | fffffffeffffffff |   64 GB | EFI region mapping space
+   ffffffff00000000 |   -4    GB | ffffffff7fffffff |    2 GB | ... unused hole
+   ffffffff80000000 |   -2    GB | ffffffff9fffffff |  512 MB | kernel text mapping, mapped to physical address 0
+   ffffffff80000000 |-2048    MB |                  |         |
+   ffffffffa0000000 |-1536    MB | fffffffffeffffff | 1520 MB | module mapping space
+   ffffffffff000000 |  -16    MB |                  |         |
+      FIXADDR_START | ~-11    MB | ffffffffff5fffff | ~0.5 MB | kernel-internal fixmap range, variable size and offset
+   ffffffffff600000 |  -10    MB | ffffffffff600fff |    4 kB | legacy vsyscall ABI
+   ffffffffffe00000 |   -2    MB | ffffffffffffffff |    2 MB | ... unused hole
+  __________________|____________|__________________|_________|___________________________________________________________
+
+
+Complete virtual memory map with 5-level page tables
+====================================================
+
+.. note::
+
+ - With 56-bit addresses, user-space memory gets expanded by a factor of 512x,
+   from 0.125 PB to 64 PB. All kernel mappings shift down to the -64 PB starting
+   offset and many of the regions expand to support the much larger physical
+   memory supported.
+
+::
+
+  ========================================================================================================================
+      Start addr    |   Offset   |     End addr     |  Size   | VM area description
+  ========================================================================================================================
+                    |            |                  |         |
+   0000000000000000 |    0       | 00ffffffffffffff |   64 PB | user-space virtual memory, different per mm
+  __________________|____________|__________________|_________|___________________________________________________________
+                    |            |                  |         |
+   0100000000000000 |  +64    PB | feffffffffffffff | ~16K PB | ... huge, still almost 64 bits wide hole of non-canonical
+                    |            |                  |         |     virtual memory addresses up to the -64 PB
+                    |            |                  |         |     starting offset of kernel mappings.
+  __________________|____________|__________________|_________|___________________________________________________________
+                                                              |
+                                                              | Kernel-space virtual memory, shared between all processes:
+  ____________________________________________________________|___________________________________________________________
+                    |            |                  |         |
+   ff00000000000000 |  -64    PB | ff0fffffffffffff |    4 PB | ... guard hole, also reserved for hypervisor
+   ff10000000000000 |  -60    PB | ff10ffffffffffff | 0.25 PB | LDT remap for PTI
+   ff11000000000000 |  -59.75 PB | ff90ffffffffffff |   32 PB | direct mapping of all physical memory (page_offset_base)
+   ff91000000000000 |  -27.75 PB | ff9fffffffffffff | 3.75 PB | ... unused hole
+   ffa0000000000000 |  -24    PB | ffd1ffffffffffff | 12.5 PB | vmalloc/ioremap space (vmalloc_base)
+   ffd2000000000000 |  -11.5  PB | ffd3ffffffffffff |  0.5 PB | ... unused hole
+   ffd4000000000000 |  -11    PB | ffd5ffffffffffff |  0.5 PB | virtual memory map (vmemmap_base)
+   ffd6000000000000 |  -10.5  PB | ffdeffffffffffff | 2.25 PB | ... unused hole
+   ffdf000000000000 |   -8.25 PB | fffffbffffffffff |   ~8 PB | KASAN shadow memory
+  __________________|____________|__________________|_________|____________________________________________________________
+                                                              |
+                                                              | Identical layout to the 47-bit one from here on:
+  ____________________________________________________________|____________________________________________________________
+                    |            |                  |         |
+   fffffc0000000000 |   -4    TB | fffffdffffffffff |    2 TB | ... unused hole
+                    |            |                  |         | vaddr_end for KASLR
+   fffffe0000000000 |   -2    TB | fffffe7fffffffff |  0.5 TB | cpu_entry_area mapping
+   fffffe8000000000 |   -1.5  TB | fffffeffffffffff |  0.5 TB | ... unused hole
+   ffffff0000000000 |   -1    TB | ffffff7fffffffff |  0.5 TB | %esp fixup stacks
+   ffffff8000000000 | -512    GB | ffffffeeffffffff |  444 GB | ... unused hole
+   ffffffef00000000 |  -68    GB | fffffffeffffffff |   64 GB | EFI region mapping space
+   ffffffff00000000 |   -4    GB | ffffffff7fffffff |    2 GB | ... unused hole
+   ffffffff80000000 |   -2    GB | ffffffff9fffffff |  512 MB | kernel text mapping, mapped to physical address 0
+   ffffffff80000000 |-2048    MB |                  |         |
+   ffffffffa0000000 |-1536    MB | fffffffffeffffff | 1520 MB | module mapping space
+   ffffffffff000000 |  -16    MB |                  |         |
+      FIXADDR_START | ~-11    MB | ffffffffff5fffff | ~0.5 MB | kernel-internal fixmap range, variable size and offset
+   ffffffffff600000 |  -10    MB | ffffffffff600fff |    4 kB | legacy vsyscall ABI
+   ffffffffffe00000 |   -2    MB | ffffffffffffffff |    2 MB | ... unused hole
+  __________________|____________|__________________|_________|___________________________________________________________
+
+Architecture defines a 64-bit virtual address. Implementations can support
+less. Currently supported are 48- and 57-bit virtual addresses. Bits 63
+through to the most-significant implemented bit are sign extended.
+This causes hole between user space and kernel addresses if you interpret them
+as unsigned.
+
+The direct mapping covers all memory in the system up to the highest
+memory address (this means in some cases it can also include PCI memory
+holes).
+
+We map EFI runtime services in the 'efi_pgd' PGD in a 64Gb large virtual
+memory window (this size is arbitrary, it can be raised later if needed).
+The mappings are not part of any other kernel PGD and are only available
+during EFI runtime calls.
+
+Note that if CONFIG_RANDOMIZE_MEMORY is enabled, the direct mapping of all
+physical memory, vmalloc/ioremap space and virtual memory map are randomized.
+Their order is preserved but their base will be offset early at boot time.
+
+Be very careful vs. KASLR when changing anything here. The KASLR address
+range must not overlap with anything except the KASAN shadow area, which is
+correct as KASAN disables KASLR.
+
+For both 4- and 5-level layouts, the STACKLEAK_POISON value in the last 2MB
+hole: ffffffffffff4111
diff --git a/Documentation/x86/x86_64/uefi.rst b/Documentation/x86/x86_64/uefi.rst
new file mode 100644
index 000000000..fbc30c9a0
--- /dev/null
+++ b/Documentation/x86/x86_64/uefi.rst
@@ -0,0 +1,58 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=====================================
+General note on [U]EFI x86_64 support
+=====================================
+
+The nomenclature EFI and UEFI are used interchangeably in this document.
+
+Although the tools below are _not_ needed for building the kernel,
+the needed bootloader support and associated tools for x86_64 platforms
+with EFI firmware and specifications are listed below.
+
+1. UEFI specification:  http://www.uefi.org
+
+2. Booting Linux kernel on UEFI x86_64 platform requires bootloader
+   support. Elilo with x86_64 support can be used.
+
+3. x86_64 platform with EFI/UEFI firmware.
+
+Mechanics
+---------
+
+- Build the kernel with the following configuration::
+
+	CONFIG_FB_EFI=y
+	CONFIG_FRAMEBUFFER_CONSOLE=y
+
+  If EFI runtime services are expected, the following configuration should
+  be selected::
+
+	CONFIG_EFI=y
+	CONFIG_EFIVAR_FS=y or m		# optional
+
+- Create a VFAT partition on the disk
+- Copy the following to the VFAT partition:
+
+	elilo bootloader with x86_64 support, elilo configuration file,
+	kernel image built in first step and corresponding
+	initrd. Instructions on building elilo and its dependencies
+	can be found in the elilo sourceforge project.
+
+- Boot to EFI shell and invoke elilo choosing the kernel image built
+  in first step.
+- If some or all EFI runtime services don't work, you can try following
+  kernel command line parameters to turn off some or all EFI runtime
+  services.
+
+	noefi
+		turn off all EFI runtime services
+	reboot_type=k
+		turn off EFI reboot runtime service
+
+- If the EFI memory map has additional entries not in the E820 map,
+  you can include those entries in the kernels memory map of available
+  physical RAM by using the following kernel command line parameter.
+
+	add_efi_memmap
+		include EFI memory map of available physical RAM