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Some late arriving documentation changes. In particular, this contains the 

conversion of the x86 docs to RST, which has been in the works for some
 time but needed a couple of final tweaks.
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Merge tag 'docs-5.2a' of git://git.lwn.net/linux

Pull more documentation updates from Jonathan Corbet:
 "Some late arriving documentation changes. In particular, this contains
  the conversion of the x86 docs to RST, which has been in the works for
  some time but needed a couple of final tweaks"

* tag 'docs-5.2a' of git://git.lwn.net/linux: (29 commits)
  Documentation: x86: convert x86_64/machinecheck to reST
  Documentation: x86: convert x86_64/cpu-hotplug-spec to reST
  Documentation: x86: convert x86_64/fake-numa-for-cpusets to reST
  Documentation: x86: convert x86_64/5level-paging.txt to reST
  Documentation: x86: convert x86_64/mm.txt to reST
  Documentation: x86: convert x86_64/uefi.txt to reST
  Documentation: x86: convert x86_64/boot-options.txt to reST
  Documentation: x86: convert i386/IO-APIC.txt to reST
  Documentation: x86: convert usb-legacy-support.txt to reST
  Documentation: x86: convert orc-unwinder.txt to reST
  Documentation: x86: convert resctrl_ui.txt to reST
  Documentation: x86: convert microcode.txt to reST
  Documentation: x86: convert pti.txt to reST
  Documentation: x86: convert amd-memory-encryption.txt to reST
  Documentation: x86: convert intel_mpx.txt to reST
  Documentation: x86: convert protection-keys.txt to reST
  Documentation: x86: convert pat.txt to reST
  Documentation: x86: convert mtrr.txt to reST
  Documentation: x86: convert tlb.txt to reST
  Documentation: x86: convert zero-page.txt to reST
  ...
This commit is contained in:
Linus Torvalds 2019-05-10 13:24:53 -04:00
parent e290e6af1d afbd4d4247
commit 1fb3b526df
37 changed files with 2569 additions and 2019 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
Documentation/index.rst
View File

@ -112,6 +112,7 @@ implementation.
.. toctree::
:maxdepth: 2
x86/index
sh/index
Filesystem Documentation

11
Documentation/trace/histogram.rst
View File

@ -1915,7 +1915,10 @@ The following commonly-used handler.action pairs are available:
The 'matching.event' specification is simply the fully qualified
event name of the event that matches the target event for the
onmatch() functionality, in the form 'system.event_name'.
onmatch() functionality, in the form 'system.event_name'. Histogram
keys of both events are compared to find if events match. In case
multiple histogram keys are used, they all must match in the specified
order.
Finally, the number and type of variables/fields in the 'param
list' must match the number and types of the fields in the
@ -1978,9 +1981,9 @@ The following commonly-used handler.action pairs are available:
/sys/kernel/debug/tracing/events/sched/sched_waking/trigger
Then, when the corresponding thread is actually scheduled onto the
CPU by a sched_switch event, calculate the latency and use that
along with another variable and an event field to generate a
wakeup_latency synthetic event::
CPU by a sched_switch event (saved_pid matches next_pid), calculate
the latency and use that along with another variable and an event field
to generate a wakeup_latency synthetic event::
# echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0:\
onmatch(sched.sched_waking).wakeup_latency($wakeup_lat,\

60
Documentation/translations/it_IT/process/license-rules.rst
View File

@ -249,13 +249,13 @@ essere categorizzate in:
|
2. Licenze non raccomandate:
2. Licenze deprecate:
Questo tipo di licenze dovrebbero essere usate solo per codice già esistente
o quando si prende codice da altri progetti. Le licenze sono disponibili
nei sorgenti del kernel nella cartella::
LICENSES/other/
LICENSES/deprecated/
I file in questa cartella contengono il testo completo della licenza e i
`Metatag`_. Il nome di questi file è lo stesso usato come identificatore
@ -263,14 +263,14 @@ essere categorizzate in:
Esempi::
LICENSES/other/ISC
LICENSES/deprecated/ISC
Contiene il testo della licenza Internet System Consortium e i suoi
metatag::
LICENSES/other/ZLib
LICENSES/deprecated/GPL-1.0
Contiene il testo della licenza ZLIB e i suoi metatag.
Contiene il testo della versione 1 della licenza GPL e i suoi metatag.
Metatag:
@ -294,7 +294,55 @@ essere categorizzate in:
|
3. _`Eccezioni`:
3. Solo per doppie licenze
Queste licenze dovrebbero essere usate solamente per codice licenziato in
combinazione con un'altra licenza che solitamente è quella preferita.
Queste licenze sono disponibili nei sorgenti del kernel nella cartella::
LICENSES/dual
I file in questa cartella contengono il testo completo della rispettiva
licenza e i suoi `Metatags`_. I nomi dei file sono identici agli
identificatori di licenza SPDX che dovrebbero essere usati nei file
sorgenti.
Esempi::
LICENSES/dual/MPL-1.1
Questo file contiene il testo della versione 1.1 della licenza *Mozilla
Pulic License* e i metatag necessari::
LICENSES/dual/Apache-2.0
Questo file contiene il testo della versione 2.0 della licenza Apache e i
metatag necessari.
Metatag:
I requisiti per le 'altre' ('*other*') licenze sono identici a quelli per le
`Licenze raccomandate`_.
Esempio del formato del file::
Valid-License-Identifier: MPL-1.1
SPDX-URL: https://spdx.org/licenses/MPL-1.1.html
Usage-Guide:
Do NOT use. The MPL-1.1 is not GPL2 compatible. It may only be used for
dual-licensed files where the other license is GPL2 compatible.
If you end up using this it MUST be used together with a GPL2 compatible
license using "OR".
To use the Mozilla Public License version 1.1 put the following SPDX
tag/value pair into a comment according to the placement guidelines in
the licensing rules documentation:
SPDX-License-Identifier: MPL-1.1
License-Text:
Full license text
|
4. _`Eccezioni`:
Alcune licenze possono essere corrette con delle eccezioni che forniscono
diritti aggiuntivi. Queste eccezioni sono disponibili nei sorgenti del

13
Documentation/x86/amd-memory-encryption.txt → Documentation/x86/amd-memory-encryption.rst
View File

@ -1,3 +1,9 @@
.. SPDX-License-Identifier: GPL-2.0
=====================
AMD Memory Encryption
=====================
Secure Memory Encryption (SME) and Secure Encrypted Virtualization (SEV) are
features found on AMD processors.
@ -34,7 +40,7 @@ is operating in 64-bit or 32-bit PAE mode, in all other modes the SEV hardware
forces the memory encryption bit to 1.
Support for SME and SEV can be determined through the CPUID instruction. The
CPUID function 0x8000001f reports information related to SME:
CPUID function 0x8000001f reports information related to SME::
0x8000001f[eax]:
Bit[0] indicates support for SME
@ -48,14 +54,14 @@ CPUID function 0x8000001f reports information related to SME:
addresses)
If support for SME is present, MSR 0xc00100010 (MSR_K8_SYSCFG) can be used to
determine if SME is enabled and/or to enable memory encryption:
determine if SME is enabled and/or to enable memory encryption::
0xc0010010:
Bit[23] 0 = memory encryption features are disabled
1 = memory encryption features are enabled
If SEV is supported, MSR 0xc0010131 (MSR_AMD64_SEV) can be used to determine if
SEV is active:
SEV is active::
0xc0010131:
Bit[0] 0 = memory encryption is not active
@ -68,6 +74,7 @@ requirements for the system. If this bit is not set upon Linux startup then
Linux itself will not set it and memory encryption will not be possible.
The state of SME in the Linux kernel can be documented as follows:
- Supported:
The CPU supports SME (determined through CPUID instruction).

272
Documentation/x86/boot.txt → Documentation/x86/boot.rst
View File

@ -1,5 +1,8 @@
THE LINUX/x86 BOOT PROTOCOL
---------------------------
.. SPDX-License-Identifier: GPL-2.0
===========================
The Linux/x86 Boot Protocol
===========================
On the x86 platform, the Linux kernel uses a rather complicated boot
convention. This has evolved partially due to historical aspects, as
@ -10,65 +13,69 @@ real-mode DOS as a mainstream operating system.
Currently, the following versions of the Linux/x86 boot protocol exist.
Old kernels: zImage/Image support only. Some very early kernels
============= ============================================================
Old kernels zImage/Image support only. Some very early kernels
may not even support a command line.
Protocol 2.00: (Kernel 1.3.73) Added bzImage and initrd support, as
Protocol 2.00 (Kernel 1.3.73) Added bzImage and initrd support, as
well as a formalized way to communicate between the
boot loader and the kernel. setup.S made relocatable,
although the traditional setup area still assumed
writable.
Protocol 2.01: (Kernel 1.3.76) Added a heap overrun warning.
Protocol 2.01 (Kernel 1.3.76) Added a heap overrun warning.
Protocol 2.02: (Kernel 2.4.0-test3-pre3) New command line protocol.
Protocol 2.02 (Kernel 2.4.0-test3-pre3) New command line protocol.
Lower the conventional memory ceiling. No overwrite
of the traditional setup area, thus making booting
safe for systems which use the EBDA from SMM or 32-bit
BIOS entry points. zImage deprecated but still
supported.
Protocol 2.03: (Kernel 2.4.18-pre1) Explicitly makes the highest possible
Protocol 2.03 (Kernel 2.4.18-pre1) Explicitly makes the highest possible
initrd address available to the bootloader.
Protocol 2.04: (Kernel 2.6.14) Extend the syssize field to four bytes.
Protocol 2.04 (Kernel 2.6.14) Extend the syssize field to four bytes.
Protocol 2.05: (Kernel 2.6.20) Make protected mode kernel relocatable.
Protocol 2.05 (Kernel 2.6.20) Make protected mode kernel relocatable.
Introduce relocatable_kernel and kernel_alignment fields.
Protocol 2.06: (Kernel 2.6.22) Added a field that contains the size of
Protocol 2.06 (Kernel 2.6.22) Added a field that contains the size of
the boot command line.
Protocol 2.07: (Kernel 2.6.24) Added paravirtualised boot protocol.
Protocol 2.07 (Kernel 2.6.24) Added paravirtualised boot protocol.
Introduced hardware_subarch and hardware_subarch_data
and KEEP_SEGMENTS flag in load_flags.
Protocol 2.08: (Kernel 2.6.26) Added crc32 checksum and ELF format
Protocol 2.08 (Kernel 2.6.26) Added crc32 checksum and ELF format
payload. Introduced payload_offset and payload_length
fields to aid in locating the payload.
Protocol 2.09: (Kernel 2.6.26) Added a field of 64-bit physical
Protocol 2.09 (Kernel 2.6.26) Added a field of 64-bit physical
pointer to single linked list of struct setup_data.
Protocol 2.10: (Kernel 2.6.31) Added a protocol for relaxed alignment
Protocol 2.10 (Kernel 2.6.31) Added a protocol for relaxed alignment
beyond the kernel_alignment added, new init_size and
pref_address fields. Added extended boot loader IDs.
Protocol 2.11: (Kernel 3.6) Added a field for offset of EFI handover
Protocol 2.11 (Kernel 3.6) Added a field for offset of EFI handover
protocol entry point.
Protocol 2.12: (Kernel 3.8) Added the xloadflags field and extension fields
Protocol 2.12 (Kernel 3.8) Added the xloadflags field and extension fields
to struct boot_params for loading bzImage and ramdisk
above 4G in 64bit.
Protocol 2.13: (Kernel 3.14) Support 32- and 64-bit flags being set in
Protocol 2.13 (Kernel 3.14) Support 32- and 64-bit flags being set in
xloadflags to support booting a 64-bit kernel from 32-bit
EFI
============= ============================================================
**** MEMORY LAYOUT
Memory Layout
=============
The traditional memory map for the kernel loader, used for Image or
zImage kernels, typically looks like:
zImage kernels, typically looks like::
| |
0A0000 +------------------------+
@ -92,7 +99,6 @@ zImage kernels, typically looks like:
| BIOS use only |
000000 +------------------------+
When using bzImage, the protected-mode kernel was relocated to
0x100000 ("high memory"), and the kernel real-mode block (boot sector,
setup, and stack/heap) was made relocatable to any address between
@ -116,7 +122,7 @@ zImage or old bzImage kernels, which need data written into the
above the 0x9A000 point; too many BIOSes will break above that point.
For a modern bzImage kernel with boot protocol version >= 2.02, a
memory layout like the following is suggested:
memory layout like the following is suggested::
~ ~
| Protected-mode kernel |
@ -141,11 +147,11 @@ X +------------------------+
| BIOS use only |
000000 +------------------------+
... where the address X is as low as the design of the boot loader
permits.
... where the address X is as low as the design of the boot loader permits.
**** THE REAL-MODE KERNEL HEADER
The Real-Mode Kernel Header
===========================
In the following text, and anywhere in the kernel boot sequence, "a
sector" refers to 512 bytes. It is independent of the actual sector
@ -159,12 +165,12 @@ sectors (1K) and then examine the bootup sector size.
The header looks like:
Offset Proto Name Meaning
/Size
01F1/1 ALL(1 setup_sects The size of the setup in sectors
=========== ======== ===================== ============================================
Offset/Size Proto Name Meaning
=========== ======== ===================== ============================================
01F1/1 ALL(1) setup_sects The size of the setup in sectors
01F2/2 ALL root_flags If set, the root is mounted readonly
01F4/4 2.04+(2 syssize The size of the 32-bit code in 16-byte paras
01F4/4 2.04+(2) syssize The size of the 32-bit code in 16-byte paras
01F8/2 ALL ram_size DO NOT USE - for bootsect.S use only
01FA/2 ALL vid_mode Video mode control
01FC/2 ALL root_dev Default root device number
@ -183,8 +189,8 @@ Offset Proto Name Meaning
021C/4 2.00+ ramdisk_size initrd size (set by boot loader)
0220/4 2.00+ bootsect_kludge DO NOT USE - for bootsect.S use only
0224/2 2.01+ heap_end_ptr Free memory after setup end
0226/1 2.02+(3 ext_loader_ver Extended boot loader version
0227/1 2.02+(3 ext_loader_type Extended boot loader ID
0226/1 2.02+(3) ext_loader_ver Extended boot loader version
0227/1 2.02+(3) ext_loader_type Extended boot loader ID
0228/4 2.02+ cmd_line_ptr 32-bit pointer to the kernel command line
022C/4 2.03+ initrd_addr_max Highest legal initrd address
0230/4 2.05+ kernel_alignment Physical addr alignment required for kernel
@ -201,7 +207,9 @@ Offset Proto Name Meaning
0258/8 2.10+ pref_address Preferred loading address
0260/4 2.10+ init_size Linear memory required during initialization
0264/4 2.11+ handover_offset Offset of handover entry point
=========== ======== ===================== ============================================
.. note::
(1) For backwards compatibility, if the setup_sects field contains 0, the
real value is 4.
@ -213,7 +221,7 @@ Offset Proto Name Meaning
If the "HdrS" (0x53726448) magic number is not found at offset 0x202,
the boot protocol version is "old". Loading an old kernel, the
following parameters should be assumed:
following parameters should be assumed::
Image type = zImage
initrd not supported
@ -225,7 +233,8 @@ setting fields in the header, you must make sure only to set fields
supported by the protocol version in use.
**** DETAILS OF HEADER FIELDS
Details of Harder Fileds
========================
For each field, some are information from the kernel to the bootloader
("read"), some are expected to be filled out by the bootloader
@ -239,106 +248,132 @@ boot loaders can ignore those fields.
The byte order of all fields is littleendian (this is x86, after all.)
============ ===========
Field name: setup_sects
Type: read
Offset/size: 0x1f1/1
Protocol: ALL
============ ===========
The size of the setup code in 512-byte sectors. If this field is
0, the real value is 4. The real-mode code consists of the boot
sector (always one 512-byte sector) plus the setup code.
============ =================
Field name: root_flags
Type: modify (optional)
Offset/size: 0x1f2/2
Protocol: ALL
============ =================
If this field is nonzero, the root defaults to readonly. The use of
this field is deprecated; use the "ro" or "rw" options on the
command line instead.
============ ===============================================
Field name: syssize
Type: read
Offset/size: 0x1f4/4 (protocol 2.04+) 0x1f4/2 (protocol ALL)
Protocol: 2.04+
============ ===============================================
The size of the protected-mode code in units of 16-byte paragraphs.
For protocol versions older than 2.04 this field is only two bytes
wide, and therefore cannot be trusted for the size of a kernel if
the LOAD_HIGH flag is set.
============ ===============
Field name: ram_size
Type: kernel internal
Offset/size: 0x1f8/2
Protocol: ALL
============ ===============
This field is obsolete.
============ ===================
Field name: vid_mode
Type: modify (obligatory)
Offset/size: 0x1fa/2
============ ===================
Please see the section on SPECIAL COMMAND LINE OPTIONS.
============ =================
Field name: root_dev
Type: modify (optional)
Offset/size: 0x1fc/2
Protocol: ALL
============ =================
The default root device device number. The use of this field is
deprecated, use the "root=" option on the command line instead.
============ =========
Field name: boot_flag
Type: read
Offset/size: 0x1fe/2
Protocol: ALL
============ =========
Contains 0xAA55. This is the closest thing old Linux kernels have
to a magic number.
============ =======
Field name: jump
Type: read
Offset/size: 0x200/2
Protocol: 2.00+
============ =======
Contains an x86 jump instruction, 0xEB followed by a signed offset
relative to byte 0x202. This can be used to determine the size of
the header.
============ =======
Field name: header
Type: read
Offset/size: 0x202/4
Protocol: 2.00+
============ =======
Contains the magic number "HdrS" (0x53726448).
============ =======
Field name: version
Type: read
Offset/size: 0x206/2
Protocol: 2.00+
============ =======
Contains the boot protocol version, in (major << 8)+minor format,
e.g. 0x0204 for version 2.04, and 0x0a11 for a hypothetical version
10.17.
============ =================
Field name: realmode_swtch
Type: modify (optional)
Offset/size: 0x208/4
Protocol: 2.00+
============ =================
Boot loader hook (see ADVANCED BOOT LOADER HOOKS below.)
============ =============
Field name: start_sys_seg
Type: read
Offset/size: 0x20c/2
Protocol: 2.00+
============ =============
The load low segment (0x1000). Obsolete.
============ ==============
Field name: kernel_version
Type: read
Offset/size: 0x20e/2
Protocol: 2.00+
============ ==============
If set to a nonzero value, contains a pointer to a NUL-terminated
human-readable kernel version number string, less 0x200. This can
@ -348,17 +383,19 @@ Protocol: 2.00+
For example, if this value is set to 0x1c00, the kernel version
number string can be found at offset 0x1e00 in the kernel file.
This is a valid value if and only if the "setup_sects" field
contains the value 15 or higher, as:
contains the value 15 or higher, as::
0x1c00 < 15*0x200 (= 0x1e00) but
0x1c00 >= 14*0x200 (= 0x1c00)
0x1c00 >> 9 = 14, so the minimum value for setup_secs is 15.
0x1c00 >> 9 = 14, So the minimum value for setup_secs is 15.
============ ==================
Field name: type_of_loader
Type: write (obligatory)
Offset/size: 0x210/1
Protocol: 2.00+
============ ==================
If your boot loader has an assigned id (see table below), enter
0xTV here, where T is an identifier for the boot loader and V is
@ -369,7 +406,7 @@ Protocol: 2.00+
Similarly, the ext_loader_ver field can be used to provide more than
four bits for the bootloader version.
For example, for T = 0x15, V = 0x234, write:
For example, for T = 0x15, V = 0x234, write::
type_of_loader <- 0xE4
ext_loader_type <- 0x05
@ -377,9 +414,12 @@ Protocol: 2.00+
Assigned boot loader ids (hexadecimal):
0 LILO (0x00 reserved for pre-2.00 bootloader)
== =======================================
0 LILO
(0x00 reserved for pre-2.00 bootloader)
1 Loadlin
2 bootsect-loader (0x20, all other values reserved)
2 bootsect-loader
(0x20, all other values reserved)
3 Syslinux
4 Etherboot/gPXE/iPXE
5 ELILO
@ -393,52 +433,67 @@ Protocol: 2.00+
E Extended (see ext_loader_type)
F Special (0xFF = undefined)
10 Reserved
11 Minimal Linux Bootloader <http://sebastian-plotz.blogspot.de>
11 Minimal Linux Bootloader
<http://sebastian-plotz.blogspot.de>
12 OVMF UEFI virtualization stack
== =======================================
Please contact <hpa@zytor.com> if you need a bootloader ID
value assigned.
Please contact <hpa@zytor.com> if you need a bootloader ID value assigned.
============ ===================
Field name: loadflags
Type: modify (obligatory)
Offset/size: 0x211/1
Protocol: 2.00+
============ ===================
This field is a bitmask.
Bit 0 (read): LOADED_HIGH
- If 0, the protected-mode code is loaded at 0x10000.
- If 1, the protected-mode code is loaded at 0x100000.
Bit 1 (kernel internal): KASLR_FLAG
- Used internally by the compressed kernel to communicate
KASLR status to kernel proper.
If 1, KASLR enabled.
If 0, KASLR disabled.
- If 1, KASLR enabled.
- If 0, KASLR disabled.
Bit 5 (write): QUIET_FLAG
- If 0, print early messages.
- If 1, suppress early messages.
This requests to the kernel (decompressor and early
kernel) to not write early messages that require
accessing the display hardware directly.
Bit 6 (write): KEEP_SEGMENTS
Protocol: 2.07+
- If 0, reload the segment registers in the 32bit entry point.
- If 1, do not reload the segment registers in the 32bit entry point.
Assume that %cs %ds %ss %es are all set to flat segments with
a base of 0 (or the equivalent for their environment).
Bit 7 (write): CAN_USE_HEAP
Set this bit to 1 to indicate that the value entered in the
heap_end_ptr is valid. If this field is clear, some setup code
functionality will be disabled.
============ ===================
Field name: setup_move_size
Type: modify (obligatory)
Offset/size: 0x212/2
Protocol: 2.00-2.01
============ ===================
When using protocol 2.00 or 2.01, if the real mode kernel is not
loaded at 0x90000, it gets moved there later in the loading
@ -451,10 +506,12 @@ Protocol: 2.00-2.01
This field is can be ignored when the protocol is 2.02 or higher, or
if the real-mode code is loaded at 0x90000.
============ ========================
Field name: code32_start
Type: modify (optional, reloc)
Offset/size: 0x214/4
Protocol: 2.00+
============ ========================
The address to jump to in protected mode. This defaults to the load
address of the kernel, and can be used by the boot loader to
@ -462,47 +519,57 @@ Protocol: 2.00+
This field can be modified for two purposes:
1. as a boot loader hook (see ADVANCED BOOT LOADER HOOKS below.)
1. as a boot loader hook (see Advanced Boot Loader Hooks below.)
2. if a bootloader which does not install a hook loads a
relocatable kernel at a nonstandard address it will have to modify
this field to point to the load address.
============ ==================
Field name: ramdisk_image
Type: write (obligatory)
Offset/size: 0x218/4
Protocol: 2.00+
============ ==================
The 32-bit linear address of the initial ramdisk or ramfs. Leave at
zero if there is no initial ramdisk/ramfs.
============ ==================
Field name: ramdisk_size
Type: write (obligatory)
Offset/size: 0x21c/4
Protocol: 2.00+
============ ==================
Size of the initial ramdisk or ramfs. Leave at zero if there is no
initial ramdisk/ramfs.
============ ===============
Field name: bootsect_kludge
Type: kernel internal
Offset/size: 0x220/4
Protocol: 2.00+
============ ===============
This field is obsolete.
============ ==================
Field name: heap_end_ptr
Type: write (obligatory)
Offset/size: 0x224/2
Protocol: 2.01+
============ ==================
Set this field to the offset (from the beginning of the real-mode
code) of the end of the setup stack/heap, minus 0x0200.
============ ================
Field name: ext_loader_ver
Type: write (optional)
Offset/size: 0x226/1
Protocol: 2.02+
============ ================
This field is used as an extension of the version number in the
type_of_loader field. The total version number is considered to be
@ -514,10 +581,12 @@ Protocol: 2.02+
Kernels prior to 2.6.31 did not recognize this field, but it is safe
to write for protocol version 2.02 or higher.
============ =====================================================
Field name: ext_loader_type
Type: write (obligatory if (type_of_loader & 0xf0) == 0xe0)
Offset/size: 0x227/1
Protocol: 2.02+
============ =====================================================
This field is used as an extension of the type number in
type_of_loader field. If the type in type_of_loader is 0xE, then
@ -528,10 +597,12 @@ Protocol: 2.02+
Kernels prior to 2.6.31 did not recognize this field, but it is safe
to write for protocol version 2.02 or higher.
============ ==================
Field name: cmd_line_ptr
Type: write (obligatory)
Offset/size: 0x228/4
Protocol: 2.02+
============ ==================
Set this field to the linear address of the kernel command line.
The kernel command line can be located anywhere between the end of
@ -544,10 +615,12 @@ Protocol: 2.02+
zero, the kernel will assume that your boot loader does not support
the 2.02+ protocol.
============ ===============
Field name: initrd_addr_max
Type: read
Offset/size: 0x22c/4
Protocol: 2.03+
============ ===============
The maximum address that may be occupied by the initial
ramdisk/ramfs contents. For boot protocols 2.02 or earlier, this
@ -556,10 +629,12 @@ Protocol: 2.03+
your ramdisk is exactly 131072 bytes long and this field is
0x37FFFFFF, you can start your ramdisk at 0x37FE0000.)
============ ============================
Field name: kernel_alignment
Type: read/modify (reloc)
Offset/size: 0x230/4
Protocol: 2.05+ (read), 2.10+ (modify)
============ ============================
Alignment unit required by the kernel (if relocatable_kernel is
true.) A relocatable kernel that is loaded at an alignment
@ -571,25 +646,29 @@ Protocol: 2.05+ (read), 2.10+ (modify)
loader to modify this field to permit a lesser alignment. See the
min_alignment and pref_address field below.
============ ==================
Field name: relocatable_kernel
Type: read (reloc)
Offset/size: 0x234/1
Protocol: 2.05+
============ ==================
If this field is nonzero, the protected-mode part of the kernel can
be loaded at any address that satisfies the kernel_alignment field.
After loading, the boot loader must set the code32_start field to
point to the loaded code, or to a boot loader hook.
============ =============
Field name: min_alignment
Type: read (reloc)
Offset/size: 0x235/1
Protocol: 2.10+
============ =============
This field, if nonzero, indicates as a power of two the minimum
alignment required, as opposed to preferred, by the kernel to boot.
If a boot loader makes use of this field, it should update the
kernel_alignment field with the alignment unit desired; typically:
kernel_alignment field with the alignment unit desired; typically::
kernel_alignment = 1 << min_alignment
@ -597,44 +676,56 @@ Protocol: 2.10+
misaligned kernel. Therefore, a loader should typically try each
power-of-two alignment from kernel_alignment down to this alignment.
============ ==========
Field name: xloadflags
Type: read
Offset/size: 0x236/2
Protocol: 2.12+
============ ==========
This field is a bitmask.
Bit 0 (read): XLF_KERNEL_64
- If 1, this kernel has the legacy 64-bit entry point at 0x200.
Bit 1 (read): XLF_CAN_BE_LOADED_ABOVE_4G
- If 1, kernel/boot_params/cmdline/ramdisk can be above 4G.
Bit 2 (read): XLF_EFI_HANDOVER_32
- If 1, the kernel supports the 32-bit EFI handoff entry point
given at handover_offset.
Bit 3 (read): XLF_EFI_HANDOVER_64
- If 1, the kernel supports the 64-bit EFI handoff entry point
given at handover_offset + 0x200.
Bit 4 (read): XLF_EFI_KEXEC
- If 1, the kernel supports kexec EFI boot with EFI runtime support.
============ ============
Field name: cmdline_size
Type: read
Offset/size: 0x238/4
Protocol: 2.06+
============ ============
The maximum size of the command line without the terminating
zero. This means that the command line can contain at most
cmdline_size characters. With protocol version 2.05 and earlier, the
maximum size was 255.
============ ====================================
Field name: hardware_subarch
Type: write (optional, defaults to x86/PC)
Offset/size: 0x23c/4
Protocol: 2.07+
============ ====================================
In a paravirtualized environment the hardware low level architectural
pieces such as interrupt handling, page table handling, and
@ -643,25 +734,31 @@ Protocol: 2.07+
This field allows the bootloader to inform the kernel we are in one
one of those environments.
========== ==============================
0x00000000 The default x86/PC environment
0x00000001 lguest
0x00000002 Xen
0x00000003 Moorestown MID
0x00000004 CE4100 TV Platform
========== ==============================
============ =========================
Field name: hardware_subarch_data
Type: write (subarch-dependent)
Offset/size: 0x240/8
Protocol: 2.07+
============ =========================
A pointer to data that is specific to hardware subarch
This field is currently unused for the default x86/PC environment,
do not modify.
============ ==============
Field name: payload_offset
Type: read
Offset/size: 0x248/4
Protocol: 2.08+
============ ==============
If non-zero then this field contains the offset from the beginning
of the protected-mode code to the payload.
@ -674,22 +771,26 @@ Protocol: 2.08+
02 21). The uncompressed payload is currently always ELF (magic
number 7F 45 4C 46).
============ ==============
Field name: payload_length
Type: read
Offset/size: 0x24c/4
Protocol: 2.08+
============ ==============
The length of the payload.
============ ===============
Field name: setup_data
Type: write (special)
Offset/size: 0x250/8
Protocol: 2.09+
============ ===============
The 64-bit physical pointer to NULL terminated single linked list of
struct setup_data. This is used to define a more extensible boot
parameters passing mechanism. The definition of struct setup_data is
as follow:
as follow::
struct setup_data {
u64 next;
@ -708,10 +809,12 @@ Protocol: 2.09+
sure to consider the case where the linked list already contains
entries.
============ ============
Field name: pref_address
Type: read (reloc)
Offset/size: 0x258/8
Protocol: 2.10+
============ ============
This field, if nonzero, represents a preferred load address for the
kernel. A relocating bootloader should attempt to load at this
@ -720,9 +823,11 @@ Protocol: 2.10+
A non-relocatable kernel will unconditionally move itself and to run
at this address.
============ =======
Field name: init_size
Type: read
Offset/size: 0x260/4
============ =======
This field indicates the amount of linear contiguous memory starting
at the kernel runtime start address that the kernel needs before it
@ -731,16 +836,18 @@ Offset/size: 0x260/4
be used by a relocating boot loader to help select a safe load
address for the kernel.
The kernel runtime start address is determined by the following algorithm:
The kernel runtime start address is determined by the following algorithm::
if (relocatable_kernel)
runtime_start = align_up(load_address, kernel_alignment)
else
runtime_start = pref_address
============ ===============
Field name: handover_offset
Type: read
Offset/size: 0x264/4
============ ===============
This field is the offset from the beginning of the kernel image to
the EFI handover protocol entry point. Boot loaders using the EFI
@ -749,7 +856,8 @@ Offset/size: 0x264/4
See EFI HANDOVER PROTOCOL below for more details.
**** THE IMAGE CHECKSUM
The Image Checksum
==================
From boot protocol version 2.08 onwards the CRC-32 is calculated over
the entire file using the characteristic polynomial 0x04C11DB7 and an
@ -758,7 +866,8 @@ file; therefore the CRC of the file up to the limit specified in the
syssize field of the header is always 0.
**** THE KERNEL COMMAND LINE
The Kernel Command Line
=======================
The kernel command line has become an important way for the boot
loader to communicate with the kernel. Some of its options are also
@ -778,19 +887,20 @@ heap and 0xA0000.
If the protocol version is *not* 2.02 or higher, the kernel
command line is entered using the following protocol:
At offset 0x0020 (word), "cmd_line_magic", enter the magic
- At offset 0x0020 (word), "cmd_line_magic", enter the magic
number 0xA33F.
At offset 0x0022 (word), "cmd_line_offset", enter the offset
- At offset 0x0022 (word), "cmd_line_offset", enter the offset
of the kernel command line (relative to the start of the
real-mode kernel).
The kernel command line *must* be within the memory region
- The kernel command line *must* be within the memory region
covered by setup_move_size, so you may need to adjust this
field.
**** MEMORY LAYOUT OF THE REAL-MODE CODE
Memory Layout of The Real-Mode Code
===================================
The real-mode code requires a stack/heap to be set up, as well as
memory allocated for the kernel command line. This needs to be done
@ -806,7 +916,8 @@ segment has to be used:
- When loading a zImage kernel ((loadflags & 0x01) == 0).
- When loading a 2.01 or earlier boot protocol kernel.
-> For the 2.00 and 2.01 boot protocols, the real-mode code
.. note::
For the 2.00 and 2.01 boot protocols, the real-mode code
can be loaded at another address, but it is internally
relocated to 0x90000. For the "old" protocol, the
real-mode code must be loaded at 0x90000.
@ -822,24 +933,29 @@ The kernel command line should not be located below the real-mode
code, nor should it be located in high memory.
**** SAMPLE BOOT CONFIGURATION
Sample Boot Configuartion
=========================
As a sample configuration, assume the following layout of the real
mode segment:
mode segment.
When loading below 0x90000, use the entire segment:
============= ===================
0x0000-0x7fff Real mode kernel
0x8000-0xdfff Stack and heap
0xe000-0xffff Kernel command line
============= ===================
When loading at 0x90000 OR the protocol version is 2.01 or earlier:
============= ===================
0x0000-0x7fff Real mode kernel
0x8000-0x97ff Stack and heap
0x9800-0x9fff Kernel command line
============= ===================
Such a boot loader should enter the following fields in the header:
Such a boot loader should enter the following fields in the header::
unsigned long base_ptr; /* base address for real-mode segment */
@ -898,7 +1014,8 @@ Such a boot loader should enter the following fields in the header:
}
**** LOADING THE REST OF THE KERNEL
Loading The Rest of The Kernel
==============================
The 32-bit (non-real-mode) kernel starts at offset (setup_sects+1)*512
in the kernel file (again, if setup_sects == 0 the real value is 4.)
@ -906,7 +1023,7 @@ It should be loaded at address 0x10000 for Image/zImage kernels and
0x100000 for bzImage kernels.
The kernel is a bzImage kernel if the protocol >= 2.00 and the 0x01
bit (LOAD_HIGH) in the loadflags field is set:
bit (LOAD_HIGH) in the loadflags field is set::
is_bzImage = (protocol >= 0x0200) && (loadflags & 0x01);
load_address = is_bzImage ? 0x100000 : 0x10000;
@ -916,8 +1033,8 @@ the entire 0x10000-0x90000 range of memory. This means it is pretty
much a requirement for these kernels to load the real-mode part at
0x90000. bzImage kernels allow much more flexibility.
**** SPECIAL COMMAND LINE OPTIONS
Special Command Line Options
============================
If the command line provided by the boot loader is entered by the
user, the user may expect the following command line options to work.
@ -966,7 +1083,8 @@ or configuration-specified command line. Otherwise, "init=/bin/sh"
gets confused by the "auto" option.
**** RUNNING THE KERNEL
Running the Kernel
==================
The kernel is started by jumping to the kernel entry point, which is
located at *segment* offset 0x20 from the start of the real mode
@ -980,7 +1098,7 @@ interrupts should be disabled. Furthermore, to guard against bugs in
the kernel, it is recommended that the boot loader sets fs = gs = ds =
es = ss.
In our example from above, we would do:
In our example from above, we would do::
/* Note: in the case of the "old" kernel protocol, base_ptr must
be == 0x90000 at this point; see the previous sample code */
@ -1003,7 +1121,8 @@ switched off, especially if the loaded kernel has the floppy driver as
a demand-loaded module!
**** ADVANCED BOOT LOADER HOOKS
Advanced Boot Loader Hooks
==========================
If the boot loader runs in a particularly hostile environment (such as
LOADLIN, which runs under DOS) it may be impossible to follow the
@ -1032,7 +1151,8 @@ IMPORTANT: All the hooks are required to preserve %esp, %ebp, %esi and
(relocated, if appropriate.)
**** 32-bit BOOT PROTOCOL
32-bit Boot Protocol
====================
For machine with some new BIOS other than legacy BIOS, such as EFI,
LinuxBIOS, etc, and kexec, the 16-bit real mode setup code in kernel
@ -1045,7 +1165,7 @@ traditionally known as "zero page"). The memory for struct boot_params
should be allocated and initialized to all zero. Then the setup header
from offset 0x01f1 of kernel image on should be loaded into struct
boot_params and examined. The end of setup header can be calculated as
follow:
follow::
0x0202 + byte value at offset 0x0201
@ -1069,7 +1189,8 @@ must have read/write permission; CS must be __BOOT_CS and DS, ES, SS
must be __BOOT_DS; interrupt must be disabled; %esi must hold the base
address of the struct boot_params; %ebp, %edi and %ebx must be zero.
**** 64-bit BOOT PROTOCOL
64-bit Boot Protocol
====================
For machine with 64bit cpus and 64bit kernel, we could use 64bit bootloader
and we need a 64-bit boot protocol.
@ -1080,7 +1201,7 @@ traditionally known as "zero page"). The memory for struct boot_params
could be allocated anywhere (even above 4G) and initialized to all zero.
Then, the setup header at offset 0x01f1 of kernel image on should be
loaded into struct boot_params and examined. The end of setup header
can be calculated as follows:
can be calculated as follows::
0x0202 + byte value at offset 0x0201
@ -1107,7 +1228,8 @@ must have read/write permission; CS must be __BOOT_CS and DS, ES, SS
must be __BOOT_DS; interrupt must be disabled; %rsi must hold the base
address of the struct boot_params.
**** EFI HANDOVER PROTOCOL
EFI Handover Protocol
=====================
This protocol allows boot loaders to defer initialisation to the EFI
boot stub. The boot loader is required to load the kernel/initrd(s)
@ -1115,7 +1237,7 @@ from the boot media and jump to the EFI handover protocol entry point
which is hdr->handover_offset bytes from the beginning of
startup_{32,64}.
The function prototype for the handover entry point looks like this,
The function prototype for the handover entry point looks like this::
efi_main(void *handle, efi_system_table_t *table, struct boot_params *bp)
@ -1124,11 +1246,11 @@ firmware, 'table' is the EFI system table - these are the first two
arguments of the "handoff state" as described in section 2.3 of the
UEFI specification. 'bp' is the boot loader-allocated boot params.
The boot loader *must* fill out the following fields in bp,
The boot loader *must* fill out the following fields in bp::
o hdr.code32_start
o hdr.cmd_line_ptr
o hdr.ramdisk_image (if applicable)
o hdr.ramdisk_size (if applicable)
- hdr.code32_start
- hdr.cmd_line_ptr
- hdr.ramdisk_image (if applicable)
- hdr.ramdisk_size (if applicable)
All other fields should be zero.

58
Documentation/x86/earlyprintk.txt → Documentation/x86/earlyprintk.rst
View File

@ -1,18 +1,24 @@
.. SPDX-License-Identifier: GPL-2.0
============
Early Printk
============
Mini-HOWTO for using the earlyprintk=dbgp boot option with a
USB2 Debug port key and a debug cable, on x86 systems.
You need two computers, the 'USB debug key' special gadget and
and two USB cables, connected like this:
and two USB cables, connected like this::
[host/target] <-------> [USB debug key] <-------> [client/console]
1. There are a number of specific hardware requirements:
Hardware requirements
=====================
a.) Host/target system needs to have USB debug port capability.
a) Host/target system needs to have USB debug port capability.
You can check this capability by looking at a 'Debug port' bit in
the lspci -vvv output:
the lspci -vvv output::
# lspci -vvv
...
@ -32,20 +38,20 @@ and two USB cables, connected like this:
Kernel modules: ehci-hcd
...
( If your system does not list a debug port capability then you probably
won't be able to use the USB debug key. )
.. note::
If your system does not list a debug port capability then you probably
won't be able to use the USB debug key.
b.) You also need a NetChip USB debug cable/key:
b) You also need a NetChip USB debug cable/key:
http://www.plxtech.com/products/NET2000/NET20DC/default.asp
This is a small blue plastic connector with two USB connections;
it draws power from its USB connections.
c.) You need a second client/console system with a high speed USB 2.0
port.
c) You need a second client/console system with a high speed USB 2.0 port.
d.) The NetChip device must be plugged directly into the physical
d) The NetChip device must be plugged directly into the physical
debug port on the "host/target" system. You cannot use a USB hub in
between the physical debug port and the "host/target" system.
@ -65,29 +71,31 @@ and two USB cables, connected like this:
to the hardware vendor, because there is no reason not to wire
this port into one of the physically accessible ports.
e.) It is also important to note, that many versions of the NetChip
e) It is also important to note, that many versions of the NetChip
device require the "client/console" system to be plugged into the
right hand side of the device (with the product logo facing up and
readable left to right). The reason being is that the 5 volt
power supply is taken from only one side of the device and it
must be the side that does not get rebooted.
2. Software requirements:
Software requirements
=====================
a.) On the host/target system:
a) On the host/target system:
You need to enable the following kernel config option:
You need to enable the following kernel config option::
CONFIG_EARLY_PRINTK_DBGP=y
And you need to add the boot command line: "earlyprintk=dbgp".
(If you are using Grub, append it to the 'kernel' line in
.. note::
If you are using Grub, append it to the 'kernel' line in
/etc/grub.conf. If you are using Grub2 on a BIOS firmware system,
append it to the 'linux' line in /boot/grub2/grub.cfg. If you are
using Grub2 on an EFI firmware system, append it to the 'linux'
or 'linuxefi' line in /boot/grub2/grub.cfg or
/boot/efi/EFI/<distro>/grub.cfg.)
/boot/efi/EFI/<distro>/grub.cfg.
On systems with more than one EHCI debug controller you must
specify the correct EHCI debug controller number. The ordering
@ -96,14 +104,15 @@ and two USB cables, connected like this:
controller. To use the second EHCI debug controller, you would
use the command line: "earlyprintk=dbgp1"
NOTE: normally earlyprintk console gets turned off once the
.. note::
normally earlyprintk console gets turned off once the
regular console is alive - use "earlyprintk=dbgp,keep" to keep
this channel open beyond early bootup. This can be useful for
debugging crashes under Xorg, etc.
b.) On the client/console system:
b) On the client/console system:
You should enable the following kernel config option:
You should enable the following kernel config option::
CONFIG_USB_SERIAL_DEBUG=y
@ -115,22 +124,23 @@ and two USB cables, connected like this:
it up to use /dev/ttyUSB0 - or use a raw 'cat /dev/ttyUSBx' to
see the raw output.
c.) On Nvidia Southbridge based systems: the kernel will try to probe
c) On Nvidia Southbridge based systems: the kernel will try to probe
and find out which port has a debug device connected.
3. Testing that it works fine:
Testing
=======
You can test the output by using earlyprintk=dbgp,keep and provoking
kernel messages on the host/target system. You can provoke a harmless
kernel message by for example doing:
kernel message by for example doing::
echo h > /proc/sysrq-trigger
On the host/target system you should see this help line in "dmesg" output:
On the host/target system you should see this help line in "dmesg" output::
SysRq : HELP : loglevel(0-9) reBoot Crashdump terminate-all-tasks(E) memory-full-oom-kill(F) kill-all-tasks(I) saK show-backtrace-all-active-cpus(L) show-memory-usage(M) nice-all-RT-tasks(N) powerOff show-registers(P) show-all-timers(Q) unRaw Sync show-task-states(T) Unmount show-blocked-tasks(W) dump-ftrace-buffer(Z)
On the client/console system do:
On the client/console system do::
cat /dev/ttyUSB0

10
Documentation/x86/entry_64.txt → Documentation/x86/entry_64.rst
View File

@ -1,3 +1,9 @@
.. SPDX-License-Identifier: GPL-2.0
==============
Kernel Entries
==============
This file documents some of the kernel entries in
arch/x86/entry/entry_64.S. A lot of this explanation is adapted from
an email from Ingo Molnar:
@ -59,7 +65,7 @@ Now, there's a secondary complication: there's a cheap way to test
which mode the CPU is in and an expensive way.
The cheap way is to pick this info off the entry frame on the kernel
stack, from the CS of the ptregs area of the kernel stack:
stack, from the CS of the ptregs area of the kernel stack::
xorl %ebx,%ebx
testl $3,CS+8(%rsp)
@ -67,7 +73,7 @@ stack, from the CS of the ptregs area of the kernel stack:
SWAPGS
The expensive (paranoid) way is to read back the MSR_GS_BASE value
(which is what SWAPGS modifies):
(which is what SWAPGS modifies)::
movl $1,%ebx
movl $MSR_GS_BASE,%ecx

79
Documentation/x86/exception-tables.txt → Documentation/x86/exception-tables.rst
View File

@ -1,4 +1,9 @@
Kernel level exception handling in Linux
.. SPDX-License-Identifier: GPL-2.0
===============================
Kernel level exception handling
===============================
Commentary by Joerg Pommnitz <joerg@raleigh.ibm.com>
When a process runs in kernel mode, it often has to access user
@ -25,7 +30,7 @@ How does this work?
Whenever the kernel tries to access an address that is currently not
accessible, the CPU generates a page fault exception and calls the
page fault handler
page fault handler::
void do_page_fault(struct pt_regs *regs, unsigned long error_code)
@ -57,10 +62,11 @@ as an example. The definition is somewhat hard to follow, so let's peek at
the code generated by the preprocessor and the compiler. I selected
the get_user call in drivers/char/sysrq.c for a detailed examination.
The original code in sysrq.c line 587:
The original code in sysrq.c line 587::
get_user(c, buf);
The preprocessor output (edited to become somewhat readable):
The preprocessor output (edited to become somewhat readable)::
(
{
@ -123,7 +129,7 @@ The preprocessor output (edited to become somewhat readable):
);
WOW! Black GCC/assembly magic. This is impossible to follow, so let's
see what code gcc generates:
see what code gcc generates::
> xorl %edx,%edx
> movl current_set,%eax
@ -154,7 +160,7 @@ understand. Can we? The actual user access is quite obvious. Thanks
to the unified address space we can just access the address in user
memory. But what does the .section stuff do?????
To understand this we have to look at the final kernel:
To understand this we have to look at the final kernel::
> objdump --section-headers vmlinux
>
@ -181,7 +187,7 @@ To understand this we have to look at the final kernel:
There are obviously 2 non standard ELF sections in the generated object
file. But first we want to find out what happened to our code in the
final kernel executable:
final kernel executable::
> objdump --disassemble --section=.text vmlinux
>
@ -199,7 +205,7 @@ final kernel executable:
The whole user memory access is reduced to 10 x86 machine instructions.
The instructions bracketed in the .section directives are no longer
in the normal execution path. They are located in a different section
of the executable file:
of the executable file::
> objdump --disassemble --section=.fixup vmlinux
>
@ -207,14 +213,15 @@ of the executable file:
> c0199ffa <.fixup+10ba> xorb %dl,%dl
> c0199ffc <.fixup+10bc> jmp c017e7a7 <do_con_write+e3>
And finally:
And finally::
> objdump --full-contents --section=__ex_table vmlinux
>
> c01aa7c4 93c017c0 e09f19c0 97c017c0 99c017c0 ................
> c01aa7d4 f6c217c0 e99f19c0 a5e717c0 f59f19c0 ................
> c01aa7e4 080a18c0 01a019c0 0a0a18c0 04a019c0 ................
or in human readable byte order:
or in human readable byte order::
> c01aa7c4 c017c093 c0199fe0 c017c097 c017c099 ................
> c01aa7d4 c017c2f6 c0199fe9 c017e7a5 c0199ff5 ................
@ -222,18 +229,22 @@ or in human readable byte order:
this is the interesting part!
> c01aa7e4 c0180a08 c019a001 c0180a0a c019a004 ................
What happened? The assembly directives
What happened? The assembly directives::
.section .fixup,"ax"
.section __ex_table,"a"
told the assembler to move the following code to the specified
sections in the ELF object file. So the instructions
sections in the ELF object file. So the instructions::
3: movl $-14,%eax
xorb %dl,%dl
jmp 2b
ended up in the .fixup section of the object file and the addresses
ended up in the .fixup section of the object file and the addresses::
.long 1b,3b
ended up in the __ex_table section of the object file. 1b and 3b
are local labels. The local label 1b (1b stands for next label 1
backward) is the address of the instruction that might fault, i.e.
@ -246,34 +257,38 @@ the fault, in our case the actual value is c0199ff5:
the original assembly code: > 3: movl $-14,%eax
and linked in vmlinux : > c0199ff5 <.fixup+10b5> movl $0xfffffff2,%eax
The assembly code
The assembly code::
> .section __ex_table,"a"
> .align 4
> .long 1b,3b
becomes the value pair
becomes the value pair::
> c01aa7d4 c017c2f6 c0199fe9 c017e7a5 c0199ff5 ................
^this is ^this is
1b 3b
c017e7a5,c0199ff5 in the exception table of the kernel.
So, what actually happens if a fault from kernel mode with no suitable
vma occurs?
1.) access to invalid address:
#. access to invalid address::
> c017e7a5 <do_con_write+e1> movb (%ebx),%dl
2.) MMU generates exception
3.) CPU calls do_page_fault
4.) do page fault calls search_exception_table (regs->eip == c017e7a5);
5.) search_exception_table looks up the address c017e7a5 in the
#. MMU generates exception
#. CPU calls do_page_fault
#. do page fault calls search_exception_table (regs->eip == c017e7a5);
#. search_exception_table looks up the address c017e7a5 in the
exception table (i.e. the contents of the ELF section __ex_table)
and returns the address of the associated fault handle code c0199ff5.
6.) do_page_fault modifies its own return address to point to the fault
#. do_page_fault modifies its own return address to point to the fault
handle code and returns.
7.) execution continues in the fault handling code.
8.) 8a) EAX becomes -EFAULT (== -14)
8b) DL becomes zero (the value we "read" from user space)
8c) execution continues at local label 2 (address of the
#. execution continues in the fault handling code.
#. a) EAX becomes -EFAULT (== -14)
b) DL becomes zero (the value we "read" from user space)
c) execution continues at local label 2 (address of the
instruction immediately after the faulting user access).
The steps 8a to 8c in a certain way emulate the faulting instruction.
@ -295,14 +310,15 @@ Things changed when 64-bit support was added to x86 Linux. Rather than
double the size of the exception table by expanding the two entries
from 32-bits to 64 bits, a clever trick was used to store addresses
as relative offsets from the table itself. The assembly code changed
from:
from::
.long 1b,3b
to:
.long (from) - .
.long (to) - .
and the C-code that uses these values converts back to absolute addresses
like this:
like this::
ex_insn_addr(const struct exception_table_entry *x)
{
@ -313,15 +329,18 @@ In v4.6 the exception table entry was expanded with a new field "handler".
This is also 32-bits wide and contains a third relative function
pointer which points to one of:
1) int ex_handler_default(const struct exception_table_entry *fixup)
1) ``int ex_handler_default(const struct exception_table_entry *fixup)``
This is legacy case that just jumps to the fixup code
2) int ex_handler_fault(const struct exception_table_entry *fixup)
2) ``int ex_handler_fault(const struct exception_table_entry *fixup)``
This case provides the fault number of the trap that occurred at
entry->insn. It is used to distinguish page faults from machine
check.
3) int ex_handler_ext(const struct exception_table_entry *fixup)
3) ``int ex_handler_ext(const struct exception_table_entry *fixup)``
This case is used for uaccess_err ... we need to set a flag
in the task structure. Before the handler functions existed this
case was handled by adding a large offset to the fixup to tag
it as special.
More functions can easily be added.

28
Documentation/x86/i386/IO-APIC.txt → Documentation/x86/i386/IO-APIC.rst
View File

@ -1,3 +1,11 @@
.. SPDX-License-Identifier: GPL-2.0
=======
IO-APIC
=======
:Author: Ingo Molnar <mingo@kernel.org>
Most (all) Intel-MP compliant SMP boards have the so-called 'IO-APIC',
which is an enhanced interrupt controller. It enables us to route
hardware interrupts to multiple CPUs, or to CPU groups. Without an
@ -13,9 +21,8 @@ usually worked around by the kernel. If your MP-compliant SMP board does
not boot Linux, then consult the linux-smp mailing list archives first.
If your box boots fine with enabled IO-APIC IRQs, then your
/proc/interrupts will look like this one:
/proc/interrupts will look like this one::
---------------------------->
hell:~> cat /proc/interrupts
CPU0
0: 1360293 IO-APIC-edge timer
@ -28,7 +35,6 @@ If your box boots fine with enabled IO-APIC IRQs, then your
NMI: 0
ERR: 0
hell:~>
<----------------------------
Some interrupts are still listed as 'XT PIC', but this is not a problem;
none of those IRQ sources is performance-critical.
@ -37,14 +43,14 @@ none of those IRQ sources is performance-critical.
In the unlikely case that your board does not create a working mp-table,
you can use the pirq= boot parameter to 'hand-construct' IRQ entries. This
is non-trivial though and cannot be automated. One sample /etc/lilo.conf
entry:
entry::
append="pirq=15,11,10"
The actual numbers depend on your system, on your PCI cards and on their
PCI slot position. Usually PCI slots are 'daisy chained' before they are
connected to the PCI chipset IRQ routing facility (the incoming PIRQ1-4
lines):
lines)::
,-. ,-. ,-. ,-. ,-.
PIRQ4 ----| |-. ,-| |-. ,-| |-. ,-| |--------| |
@ -56,7 +62,7 @@ lines):
PIRQ1 ----| |- `----| |- `----| |- `----| |--------| |
`-' `-' `-' `-' `-'
Every PCI card emits a PCI IRQ, which can be INTA, INTB, INTC or INTD:
Every PCI card emits a PCI IRQ, which can be INTA, INTB, INTC or INTD::
,-.
INTD--| |
@ -78,19 +84,19 @@ to have non shared interrupts). Slot5 should be used for videocards, they
do not use interrupts normally, thus they are not daisy chained either.
so if you have your SCSI card (IRQ11) in Slot1, Tulip card (IRQ9) in
Slot2, then you'll have to specify this pirq= line:
Slot2, then you'll have to specify this pirq= line::
append="pirq=11,9"
the following script tries to figure out such a default pirq= line from
your PCI configuration:
your PCI configuration::
echo -n pirq=; echo `scanpci | grep T_L | cut -c56-` | sed 's/ /,/g'
note that this script won't work if you have skipped a few slots or if your
board does not do default daisy-chaining. (or the IO-APIC has the PIRQ pins
connected in some strange way). E.g. if in the above case you have your SCSI
card (IRQ11) in Slot3, and have Slot1 empty:
card (IRQ11) in Slot3, and have Slot1 empty::
append="pirq=0,9,11"
@ -105,7 +111,7 @@ won't function properly (e.g. if it's inserted as a module).
If you have 2 PCI buses, then you can use up to 8 pirq values, although such
boards tend to have a good configuration.
Be prepared that it might happen that you need some strange pirq line:
Be prepared that it might happen that you need some strange pirq line::
append="pirq=0,0,0,0,0,0,9,11"
@ -115,5 +121,3 @@ Good luck and mail to linux-smp@vger.kernel.org or
linux-kernel@vger.kernel.org if you have any problems that are not covered
by this document.
-- mingo

10
Documentation/x86/i386/index.rst Normal file
View File

@ -0,0 +1,10 @@
.. SPDX-License-Identifier: GPL-2.0
============
i386 Support
============
.. toctree::
:maxdepth: 2
IO-APIC

30
Documentation/x86/index.rst Normal file
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@ -0,0 +1,30 @@
.. SPDX-License-Identifier: GPL-2.0
==========================
x86-specific Documentation
==========================
.. toctree::
:maxdepth: 2
:numbered:
boot
topology
exception-tables
kernel-stacks
entry_64
earlyprintk
orc-unwinder
zero-page
tlb
mtrr
pat
protection-keys
intel_mpx
amd-memory-encryption
pti
microcode
resctrl_ui
usb-legacy-support
i386/index
x86_64/index

40
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View File

@ -1,5 +1,11 @@
1. Intel(R) MPX Overview
========================
.. SPDX-License-Identifier: GPL-2.0
===========================================
Intel(R) Memory Protection Extensions (MPX)
===========================================
Intel(R) MPX Overview
=====================
Intel(R) Memory Protection Extensions (Intel(R) MPX) is a new capability
introduced into Intel Architecture. Intel MPX provides hardware features
@ -7,7 +13,7 @@ that can be used in conjunction with compiler changes to check memory
references, for those references whose compile-time normal intentions are
usurped at runtime due to buffer overflow or underflow.
You can tell if your CPU supports MPX by looking in /proc/cpuinfo:
You can tell if your CPU supports MPX by looking in /proc/cpuinfo::
cat /proc/cpuinfo | grep ' mpx '
@ -21,8 +27,8 @@ can be downloaded from
http://software.intel.com/en-us/articles/intel-software-development-emulator
2. How to get the advantage of MPX
==================================
How to get the advantage of MPX
===============================
For MPX to work, changes are required in the kernel, binutils and compiler.
No source changes are required for applications, just a recompile.
@ -84,14 +90,15 @@ Kernel MPX Code:
is unmapped.
3. How does MPX kernel code work
================================
How does MPX kernel code work
=============================
Handling #BR faults caused by MPX
---------------------------------
When MPX is enabled, there are 2 new situations that can generate
#BR faults.
* new bounds tables (BT) need to be allocated to save bounds.
* bounds violation caused by MPX instructions.
@ -124,9 +131,9 @@ the kernel. It can theoretically be done completely from userspace. Here
are a few ways this could be done. We don't think any of them are practical
in the real-world, but here they are.
Q: Can virtual space simply be reserved for the bounds tables so that we
:Q: Can virtual space simply be reserved for the bounds tables so that we
never have to allocate them?
A: MPX-enabled application will possibly create a lot of bounds tables in
:A: MPX-enabled application will possibly create a lot of bounds tables in
process address space to save bounds information. These tables can take
up huge swaths of memory (as much as 80% of the memory on the system)
even if we clean them up aggressively. In the worst-case scenario, the
@ -140,19 +147,19 @@ A: MPX-enabled application will possibly create a lot of bounds tables in
consumes 2GB of virtual *AND* physical memory. IOW, it's completely
infeasible to prepopulate bounds directories.
Q: Can we preallocate bounds table space at the same time memory is
:Q: Can we preallocate bounds table space at the same time memory is
allocated which might contain pointers that might eventually need
bounds tables?
A: This would work if we could hook the site of each and every memory
:A: This would work if we could hook the site of each and every memory
allocation syscall. This can be done for small, constrained applications.
But, it isn't practical at a larger scale since a given app has no
way of controlling how all the parts of the app might allocate memory
(think libraries). The kernel is really the only place to intercept
these calls.
Q: Could a bounds fault be handed to userspace and the tables allocated
:Q: Could a bounds fault be handed to userspace and the tables allocated
there in a signal handler instead of in the kernel?
A: mmap() is not on the list of safe async handler functions and even
:A: mmap() is not on the list of safe async handler functions and even
if mmap() would work it still requires locking or nasty tricks to
keep track of the allocation state there.
@ -167,7 +174,7 @@ If a #BR is generated due to a bounds violation caused by MPX.
We need to decode MPX instructions to get violation address and
set this address into extended struct siginfo.
The _sigfault field of struct siginfo is extended as follow:
The _sigfault field of struct siginfo is extended as follow::
87 /* SIGILL, SIGFPE, SIGSEGV, SIGBUS */
88 struct {
@ -209,6 +216,7 @@ Adding new prctl commands
Two new prctl commands are added to enable and disable MPX bounds tables
management in kernel.
::
155 #define PR_MPX_ENABLE_MANAGEMENT 43
156 #define PR_MPX_DISABLE_MANAGEMENT 44
@ -223,8 +231,8 @@ into struct mm_struct to be used in future during PR_MPX_ENABLE_MANAGEMENT
command execution.
4. Special rules
================
Special rules
=============
1) If userspace is requesting help from the kernel to do the management
of bounds tables, it may not create or modify entries in the bounds directory.

16
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@ -1,5 +1,11 @@
.. SPDX-License-Identifier: GPL-2.0
=============
Kernel Stacks
=============
Kernel stacks on x86-64 bit
---------------------------
===========================
Most of the text from Keith Owens, hacked by AK
@ -57,7 +63,7 @@ IST events with the same code to be nested. However in most cases, the
stack size allocated to an IST assumes no nesting for the same code.
If that assumption is ever broken then the stacks will become corrupt.
The currently assigned IST stacks are :-
The currently assigned IST stacks are:
* ESTACK_DF. EXCEPTION_STKSZ (PAGE_SIZE).
@ -103,7 +109,7 @@ For more details see the Intel IA32 or AMD AMD64 architecture manuals.
Printing backtraces on x86
--------------------------
==========================
The question about the '?' preceding function names in an x86 stacktrace
keeps popping up, here's an indepth explanation. It helps if the reader
@ -113,7 +119,7 @@ arch/x86/kernel/dumpstack.c.
Adapted from Ingo's mail, Message-ID: <20150521101614.GA10889@gmail.com>:
We always scan the full kernel stack for return addresses stored on
the kernel stack(s) [*], from stack top to stack bottom, and print out
the kernel stack(s) [1]_, from stack top to stack bottom, and print out
anything that 'looks like' a kernel text address.
If it fits into the frame pointer chain, we print it without a question
@ -141,6 +147,6 @@ that look like kernel text addresses, so if debug information is wrong,
we still print out the real call chain as well - just with more question
marks than ideal.
[*] For things like IRQ and IST stacks, we also scan those stacks, in
.. [1] For things like IRQ and IST stacks, we also scan those stacks, in
the right order, and try to cross from one stack into another
reconstructing the call chain. This works most of the time.

38
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@ -1,7 +1,11 @@
The Linux Microcode Loader
.. SPDX-License-Identifier: GPL-2.0
Authors: Fenghua Yu <fenghua.yu@intel.com>
Borislav Petkov <bp@suse.de>
==========================
The Linux Microcode Loader
==========================
:Authors: - Fenghua Yu <fenghua.yu@intel.com>
- Borislav Petkov <bp@suse.de>
The kernel has a x86 microcode loading facility which is supposed to
provide microcode loading methods in the OS. Potential use cases are
@ -10,8 +14,8 @@ and updating the microcode on long-running systems without rebooting.
The loader supports three loading methods:
1. Early load microcode
=======================
Early load microcode
====================
The kernel can update microcode very early during boot. Loading
microcode early can fix CPU issues before they are observed during
@ -26,8 +30,10 @@ loader parses the combined initrd image during boot.
The microcode files in cpio name space are:
on Intel: kernel/x86/microcode/GenuineIntel.bin
on AMD : kernel/x86/microcode/AuthenticAMD.bin
on Intel:
kernel/x86/microcode/GenuineIntel.bin
on AMD :
kernel/x86/microcode/AuthenticAMD.bin
During BSP (BootStrapping Processor) boot (pre-SMP), the kernel
scans the microcode file in the initrd. If microcode matching the
@ -42,8 +48,8 @@ Here's a crude example how to prepare an initrd with microcode (this is
normally done automatically by the distribution, when recreating the
initrd, so you don't really have to do it yourself. It is documented
here for future reference only).
::
---
#!/bin/bash
if [ -z "$1" ]; then
@ -76,15 +82,15 @@ here for future reference only).
cat ucode.cpio $INITRD.orig > $INITRD
rm -rf $TMPDIR
---
The system needs to have the microcode packages installed into
/lib/firmware or you need to fixup the paths above if yours are
somewhere else and/or you've downloaded them directly from the processor
vendor's site.
2. Late loading
===============
Late loading
============
There are two legacy user space interfaces to load microcode, either through
/dev/cpu/microcode or through /sys/devices/system/cpu/microcode/reload file
@ -94,7 +100,7 @@ The /dev/cpu/microcode method is deprecated because it needs a special
userspace tool for that.
The easier method is simply installing the microcode packages your distro
supplies and running:
supplies and running::
# echo 1 > /sys/devices/system/cpu/microcode/reload
@ -104,19 +110,19 @@ The loading mechanism looks for microcode blobs in
/lib/firmware/{intel-ucode,amd-ucode}. The default distro installation
packages already put them there.
3. Builtin microcode
====================
Builtin microcode
=================
The loader supports also loading of a builtin microcode supplied through
the regular builtin firmware method CONFIG_EXTRA_FIRMWARE. Only 64-bit is
currently supported.
Here's an example:
Here's an example::
CONFIG_EXTRA_FIRMWARE="intel-ucode/06-3a-09 amd-ucode/microcode_amd_fam15h.bin"
CONFIG_EXTRA_FIRMWARE_DIR="/lib/firmware"
This basically means, you have the following tree structure locally:
This basically means, you have the following tree structure locally::
/lib/firmware/
|-- amd-ucode

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@ -0,0 +1,354 @@
.. SPDX-License-Identifier: GPL-2.0
=========================================
MTRR (Memory Type Range Register) control
=========================================
:Authors: - Richard Gooch <rgooch@atnf.csiro.au> - 3 Jun 1999
- Luis R. Rodriguez <mcgrof@do-not-panic.com> - April 9, 2015
Phasing out MTRR use
====================
MTRR use is replaced on modern x86 hardware with PAT. Direct MTRR use by
drivers on Linux is now completely phased out, device drivers should use
arch_phys_wc_add() in combination with ioremap_wc() to make MTRR effective on
non-PAT systems while a no-op but equally effective on PAT enabled systems.
Even if Linux does not use MTRRs directly, some x86 platform firmware may still
set up MTRRs early before booting the OS. They do this as some platform
firmware may still have implemented access to MTRRs which would be controlled
and handled by the platform firmware directly. An example of platform use of
MTRRs is through the use of SMI handlers, one case could be for fan control,
the platform code would need uncachable access to some of its fan control
registers. Such platform access does not need any Operating System MTRR code in
place other than mtrr_type_lookup() to ensure any OS specific mapping requests
are aligned with platform MTRR setup. If MTRRs are only set up by the platform
firmware code though and the OS does not make any specific MTRR mapping
requests mtrr_type_lookup() should always return MTRR_TYPE_INVALID.
For details refer to :doc:`pat`.
.. tip::
On Intel P6 family processors (Pentium Pro, Pentium II and later)
the Memory Type Range Registers (MTRRs) may be used to control
processor access to memory ranges. This is most useful when you have
a video (VGA) card on a PCI or AGP bus. Enabling write-combining
allows bus write transfers to be combined into a larger transfer
before bursting over the PCI/AGP bus. This can increase performance
of image write operations 2.5 times or more.
The Cyrix 6x86, 6x86MX and M II processors have Address Range
Registers (ARRs) which provide a similar functionality to MTRRs. For
these, the ARRs are used to emulate the MTRRs.
The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
MTRRs. These are supported. The AMD Athlon family provide 8 Intel
style MTRRs.
The Centaur C6 (WinChip) has 8 MCRs, allowing write-combining. These
are supported.
The VIA Cyrix III and VIA C3 CPUs offer 8 Intel style MTRRs.
The CONFIG_MTRR option creates a /proc/mtrr file which may be used
to manipulate your MTRRs. Typically the X server should use
this. This should have a reasonably generic interface so that
similar control registers on other processors can be easily
supported.
There are two interfaces to /proc/mtrr: one is an ASCII interface
which allows you to read and write. The other is an ioctl()
interface. The ASCII interface is meant for administration. The
ioctl() interface is meant for C programs (i.e. the X server). The
interfaces are described below, with sample commands and C code.
Reading MTRRs from the shell
============================
::
% cat /proc/mtrr
reg00: base=0x00000000 ( 0MB), size= 128MB: write-back, count=1
reg01: base=0x08000000 ( 128MB), size= 64MB: write-back, count=1
Creating MTRRs from the C-shell::
# echo "base=0xf8000000 size=0x400000 type=write-combining" >! /proc/mtrr
or if you use bash::
# echo "base=0xf8000000 size=0x400000 type=write-combining" >| /proc/mtrr
And the result thereof::
% cat /proc/mtrr
reg00: base=0x00000000 ( 0MB), size= 128MB: write-back, count=1
reg01: base=0x08000000 ( 128MB), size= 64MB: write-back, count=1
reg02: base=0xf8000000 (3968MB), size= 4MB: write-combining, count=1
This is for video RAM at base address 0xf8000000 and size 4 megabytes. To
find out your base address, you need to look at the output of your X
server, which tells you where the linear framebuffer address is. A
typical line that you may get is::
(--) S3: PCI: 968 rev 0, Linear FB @ 0xf8000000
Note that you should only use the value from the X server, as it may
move the framebuffer base address, so the only value you can trust is
that reported by the X server.
To find out the size of your framebuffer (what, you don't actually
know?), the following line will tell you::
(--) S3: videoram: 4096k
That's 4 megabytes, which is 0x400000 bytes (in hexadecimal).
A patch is being written for XFree86 which will make this automatic:
in other words the X server will manipulate /proc/mtrr using the
ioctl() interface, so users won't have to do anything. If you use a
commercial X server, lobby your vendor to add support for MTRRs.
Creating overlapping MTRRs
==========================
::
%echo "base=0xfb000000 size=0x1000000 type=write-combining" >/proc/mtrr
%echo "base=0xfb000000 size=0x1000 type=uncachable" >/proc/mtrr
And the results::
% cat /proc/mtrr
reg00: base=0x00000000 ( 0MB), size= 64MB: write-back, count=1
reg01: base=0xfb000000 (4016MB), size= 16MB: write-combining, count=1
reg02: base=0xfb000000 (4016MB), size= 4kB: uncachable, count=1
Some cards (especially Voodoo Graphics boards) need this 4 kB area
excluded from the beginning of the region because it is used for
registers.
NOTE: You can only create type=uncachable region, if the first
region that you created is type=write-combining.
Removing MTRRs from the C-shel
==============================
::
% echo "disable=2" >! /proc/mtrr
or using bash::
% echo "disable=2" >| /proc/mtrr
Reading MTRRs from a C program using ioctl()'s
==============================================
::
/* mtrr-show.c
Source file for mtrr-show (example program to show MTRRs using ioctl()'s)
Copyright (C) 1997-1998 Richard Gooch
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
Richard Gooch may be reached by email at rgooch@atnf.csiro.au
The postal address is:
Richard Gooch, c/o ATNF, P. O. Box 76, Epping, N.S.W., 2121, Australia.
*/
/*
This program will use an ioctl() on /proc/mtrr to show the current MTRR
settings. This is an alternative to reading /proc/mtrr.
Written by Richard Gooch 17-DEC-1997
Last updated by Richard Gooch 2-MAY-1998
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <asm/mtrr.h>
#define TRUE 1
#define FALSE 0
#define ERRSTRING strerror (errno)
static char *mtrr_strings[MTRR_NUM_TYPES] =
{
"uncachable", /* 0 */
"write-combining", /* 1 */
"?", /* 2 */
"?", /* 3 */
"write-through", /* 4 */
"write-protect", /* 5 */
"write-back", /* 6 */
};
int main ()
{
int fd;
struct mtrr_gentry gentry;
if ( ( fd = open ("/proc/mtrr", O_RDONLY, 0) ) == -1 )
{
if (errno == ENOENT)
{
fputs ("/proc/mtrr not found: not supported or you don't have a PPro?\n",
stderr);
exit (1);
}
fprintf (stderr, "Error opening /proc/mtrr\t%s\n", ERRSTRING);
exit (2);
}
for (gentry.regnum = 0; ioctl (fd, MTRRIOC_GET_ENTRY, &gentry) == 0;
++gentry.regnum)
{
if (gentry.size < 1)
{
fprintf (stderr, "Register: %u disabled\n", gentry.regnum);
continue;
}
fprintf (stderr, "Register: %u base: 0x%lx size: 0x%lx type: %s\n",
gentry.regnum, gentry.base, gentry.size,
mtrr_strings[gentry.type]);
}
if (errno == EINVAL) exit (0);
fprintf (stderr, "Error doing ioctl(2) on /dev/mtrr\t%s\n", ERRSTRING);
exit (3);
} /* End Function main */
Creating MTRRs from a C programme using ioctl()'s
=================================================
::
/* mtrr-add.c
Source file for mtrr-add (example programme to add an MTRRs using ioctl())
Copyright (C) 1997-1998 Richard Gooch
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
Richard Gooch may be reached by email at rgooch@atnf.csiro.au
The postal address is:
Richard Gooch, c/o ATNF, P. O. Box 76, Epping, N.S.W., 2121, Australia.
*/
/*
This programme will use an ioctl() on /proc/mtrr to add an entry. The first
available mtrr is used. This is an alternative to writing /proc/mtrr.
Written by Richard Gooch 17-DEC-1997
Last updated by Richard Gooch 2-MAY-1998
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <asm/mtrr.h>
#define TRUE 1
#define FALSE 0
#define ERRSTRING strerror (errno)
static char *mtrr_strings[MTRR_NUM_TYPES] =
{
"uncachable", /* 0 */
"write-combining", /* 1 */
"?", /* 2 */
"?", /* 3 */
"write-through", /* 4 */
"write-protect", /* 5 */
"write-back", /* 6 */
};
int main (int argc, char **argv)
{
int fd;
struct mtrr_sentry sentry;
if (argc != 4)
{
fprintf (stderr, "Usage:\tmtrr-add base size type\n");
exit (1);
}
sentry.base = strtoul (argv[1], NULL, 0);
sentry.size = strtoul (argv[2], NULL, 0);
for (sentry.type = 0; sentry.type < MTRR_NUM_TYPES; ++sentry.type)
{
if (strcmp (argv[3], mtrr_strings[sentry.type]) == 0) break;
}
if (sentry.type >= MTRR_NUM_TYPES)
{
fprintf (stderr, "Illegal type: \"%s\"\n", argv[3]);
exit (2);
}
if ( ( fd = open ("/proc/mtrr", O_WRONLY, 0) ) == -1 )
{
if (errno == ENOENT)
{
fputs ("/proc/mtrr not found: not supported or you don't have a PPro?\n",
stderr);
exit (3);
}
fprintf (stderr, "Error opening /proc/mtrr\t%s\n", ERRSTRING);
exit (4);
}
if (ioctl (fd, MTRRIOC_ADD_ENTRY, &sentry) == -1)
{
fprintf (stderr, "Error doing ioctl(2) on /dev/mtrr\t%s\n", ERRSTRING);
exit (5);
}
fprintf (stderr, "Sleeping for 5 seconds so you can see the new entry\n");
sleep (5);
close (fd);
fputs ("I've just closed /proc/mtrr so now the new entry should be gone\n",
stderr);
} /* End Function main */

329
Documentation/x86/mtrr.txt
View File

@ -1,329 +0,0 @@
MTRR (Memory Type Range Register) control
Richard Gooch <rgooch@atnf.csiro.au> - 3 Jun 1999
Luis R. Rodriguez <mcgrof@do-not-panic.com> - April 9, 2015
===============================================================================
Phasing out MTRR use
MTRR use is replaced on modern x86 hardware with PAT. Direct MTRR use by
drivers on Linux is now completely phased out, device drivers should use
arch_phys_wc_add() in combination with ioremap_wc() to make MTRR effective on
non-PAT systems while a no-op but equally effective on PAT enabled systems.
Even if Linux does not use MTRRs directly, some x86 platform firmware may still
set up MTRRs early before booting the OS. They do this as some platform
firmware may still have implemented access to MTRRs which would be controlled
and handled by the platform firmware directly. An example of platform use of
MTRRs is through the use of SMI handlers, one case could be for fan control,
the platform code would need uncachable access to some of its fan control
registers. Such platform access does not need any Operating System MTRR code in
place other than mtrr_type_lookup() to ensure any OS specific mapping requests
are aligned with platform MTRR setup. If MTRRs are only set up by the platform
firmware code though and the OS does not make any specific MTRR mapping
requests mtrr_type_lookup() should always return MTRR_TYPE_INVALID.
For details refer to Documentation/x86/pat.txt.
===============================================================================
On Intel P6 family processors (Pentium Pro, Pentium II and later)
the Memory Type Range Registers (MTRRs) may be used to control
processor access to memory ranges. This is most useful when you have
a video (VGA) card on a PCI or AGP bus. Enabling write-combining
allows bus write transfers to be combined into a larger transfer
before bursting over the PCI/AGP bus. This can increase performance
of image write operations 2.5 times or more.
The Cyrix 6x86, 6x86MX and M II processors have Address Range
Registers (ARRs) which provide a similar functionality to MTRRs. For
these, the ARRs are used to emulate the MTRRs.
The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
MTRRs. These are supported. The AMD Athlon family provide 8 Intel
style MTRRs.
The Centaur C6 (WinChip) has 8 MCRs, allowing write-combining. These
are supported.
The VIA Cyrix III and VIA C3 CPUs offer 8 Intel style MTRRs.
The CONFIG_MTRR option creates a /proc/mtrr file which may be used
to manipulate your MTRRs. Typically the X server should use
this. This should have a reasonably generic interface so that
similar control registers on other processors can be easily
supported.
There are two interfaces to /proc/mtrr: one is an ASCII interface
which allows you to read and write. The other is an ioctl()
interface. The ASCII interface is meant for administration. The
ioctl() interface is meant for C programs (i.e. the X server). The
interfaces are described below, with sample commands and C code.
===============================================================================
Reading MTRRs from the shell:
% cat /proc/mtrr
reg00: base=0x00000000 ( 0MB), size= 128MB: write-back, count=1
reg01: base=0x08000000 ( 128MB), size= 64MB: write-back, count=1
===============================================================================
Creating MTRRs from the C-shell:
# echo "base=0xf8000000 size=0x400000 type=write-combining" >! /proc/mtrr
or if you use bash:
# echo "base=0xf8000000 size=0x400000 type=write-combining" >| /proc/mtrr
And the result thereof:
% cat /proc/mtrr
reg00: base=0x00000000 ( 0MB), size= 128MB: write-back, count=1
reg01: base=0x08000000 ( 128MB), size= 64MB: write-back, count=1
reg02: base=0xf8000000 (3968MB), size= 4MB: write-combining, count=1
This is for video RAM at base address 0xf8000000 and size 4 megabytes. To
find out your base address, you need to look at the output of your X
server, which tells you where the linear framebuffer address is. A
typical line that you may get is:
(--) S3: PCI: 968 rev 0, Linear FB @ 0xf8000000
Note that you should only use the value from the X server, as it may
move the framebuffer base address, so the only value you can trust is
that reported by the X server.
To find out the size of your framebuffer (what, you don't actually
know?), the following line will tell you:
(--) S3: videoram: 4096k
That's 4 megabytes, which is 0x400000 bytes (in hexadecimal).
A patch is being written for XFree86 which will make this automatic:
in other words the X server will manipulate /proc/mtrr using the
ioctl() interface, so users won't have to do anything. If you use a
commercial X server, lobby your vendor to add support for MTRRs.
===============================================================================
Creating overlapping MTRRs:
%echo "base=0xfb000000 size=0x1000000 type=write-combining" >/proc/mtrr
%echo "base=0xfb000000 size=0x1000 type=uncachable" >/proc/mtrr
And the results: cat /proc/mtrr
reg00: base=0x00000000 ( 0MB), size= 64MB: write-back, count=1
reg01: base=0xfb000000 (4016MB), size= 16MB: write-combining, count=1
reg02: base=0xfb000000 (4016MB), size= 4kB: uncachable, count=1
Some cards (especially Voodoo Graphics boards) need this 4 kB area
excluded from the beginning of the region because it is used for
registers.
NOTE: You can only create type=uncachable region, if the first
region that you created is type=write-combining.
===============================================================================
Removing MTRRs from the C-shell:
% echo "disable=2" >! /proc/mtrr
or using bash:
% echo "disable=2" >| /proc/mtrr
===============================================================================
Reading MTRRs from a C program using ioctl()'s:
/* mtrr-show.c
Source file for mtrr-show (example program to show MTRRs using ioctl()'s)
Copyright (C) 1997-1998 Richard Gooch
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
Richard Gooch may be reached by email at rgooch@atnf.csiro.au
The postal address is:
Richard Gooch, c/o ATNF, P. O. Box 76, Epping, N.S.W., 2121, Australia.
*/
/*
This program will use an ioctl() on /proc/mtrr to show the current MTRR
settings. This is an alternative to reading /proc/mtrr.
Written by Richard Gooch 17-DEC-1997
Last updated by Richard Gooch 2-MAY-1998
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <asm/mtrr.h>
#define TRUE 1
#define FALSE 0
#define ERRSTRING strerror (errno)
static char *mtrr_strings[MTRR_NUM_TYPES] =
{
"uncachable", /* 0 */
"write-combining", /* 1 */
"?", /* 2 */
"?", /* 3 */
"write-through", /* 4 */
"write-protect", /* 5 */
"write-back", /* 6 */
};
int main ()
{
int fd;
struct mtrr_gentry gentry;
if ( ( fd = open ("/proc/mtrr", O_RDONLY, 0) ) == -1 )
{
if (errno == ENOENT)
{
fputs ("/proc/mtrr not found: not supported or you don't have a PPro?\n",
stderr);
exit (1);
}
fprintf (stderr, "Error opening /proc/mtrr\t%s\n", ERRSTRING);
exit (2);
}
for (gentry.regnum = 0; ioctl (fd, MTRRIOC_GET_ENTRY, &gentry) == 0;
++gentry.regnum)
{
if (gentry.size < 1)
{
fprintf (stderr, "Register: %u disabled\n", gentry.regnum);
continue;
}
fprintf (stderr, "Register: %u base: 0x%lx size: 0x%lx type: %s\n",
gentry.regnum, gentry.base, gentry.size,
mtrr_strings[gentry.type]);
}
if (errno == EINVAL) exit (0);
fprintf (stderr, "Error doing ioctl(2) on /dev/mtrr\t%s\n", ERRSTRING);
exit (3);
} /* End Function main */
===============================================================================
Creating MTRRs from a C programme using ioctl()'s:
/* mtrr-add.c
Source file for mtrr-add (example programme to add an MTRRs using ioctl())
Copyright (C) 1997-1998 Richard Gooch
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
Richard Gooch may be reached by email at rgooch@atnf.csiro.au
The postal address is:
Richard Gooch, c/o ATNF, P. O. Box 76, Epping, N.S.W., 2121, Australia.
*/
/*
This programme will use an ioctl() on /proc/mtrr to add an entry. The first
available mtrr is used. This is an alternative to writing /proc/mtrr.
Written by Richard Gooch 17-DEC-1997
Last updated by Richard Gooch 2-MAY-1998
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <asm/mtrr.h>
#define TRUE 1
#define FALSE 0
#define ERRSTRING strerror (errno)
static char *mtrr_strings[MTRR_NUM_TYPES] =
{
"uncachable", /* 0 */
"write-combining", /* 1 */
"?", /* 2 */
"?", /* 3 */
"write-through", /* 4 */
"write-protect", /* 5 */
"write-back", /* 6 */
};
int main (int argc, char **argv)
{
int fd;
struct mtrr_sentry sentry;
if (argc != 4)
{
fprintf (stderr, "Usage:\tmtrr-add base size type\n");
exit (1);
}
sentry.base = strtoul (argv[1], NULL, 0);
sentry.size = strtoul (argv[2], NULL, 0);
for (sentry.type = 0; sentry.type < MTRR_NUM_TYPES; ++sentry.type)
{
if (strcmp (argv[3], mtrr_strings[sentry.type]) == 0) break;
}
if (sentry.type >= MTRR_NUM_TYPES)
{
fprintf (stderr, "Illegal type: \"%s\"\n", argv[3]);
exit (2);
}
if ( ( fd = open ("/proc/mtrr", O_WRONLY, 0) ) == -1 )
{
if (errno == ENOENT)
{
fputs ("/proc/mtrr not found: not supported or you don't have a PPro?\n",
stderr);
exit (3);
}
fprintf (stderr, "Error opening /proc/mtrr\t%s\n", ERRSTRING);
exit (4);
}
if (ioctl (fd, MTRRIOC_ADD_ENTRY, &sentry) == -1)
{
fprintf (stderr, "Error doing ioctl(2) on /dev/mtrr\t%s\n", ERRSTRING);
exit (5);
}
fprintf (stderr, "Sleeping for 5 seconds so you can see the new entry\n");
sleep (5);
close (fd);
fputs ("I've just closed /proc/mtrr so now the new entry should be gone\n",
stderr);
} /* End Function main */
===============================================================================

27
Documentation/x86/orc-unwinder.txt → Documentation/x86/orc-unwinder.rst
View File

@ -1,8 +1,11 @@
.. SPDX-License-Identifier: GPL-2.0
============
ORC unwinder
============
Overview
--------
========
The kernel CONFIG_UNWINDER_ORC option enables the ORC unwinder, which is
similar in concept to a DWARF unwinder. The difference is that the
@ -23,12 +26,12 @@ correlate instruction addresses with their stack states at run time.
ORC vs frame pointers
---------------------
=====================
With frame pointers enabled, GCC adds instrumentation code to every
function in the kernel. The kernel's .text size increases by about
3.2%, resulting in a broad kernel-wide slowdown. Measurements by Mel
Gorman [1] have shown a slowdown of 5-10% for some workloads.
Gorman [1]_ have shown a slowdown of 5-10% for some workloads.
In contrast, the ORC unwinder has no effect on text size or runtime
performance, because the debuginfo is out of band. So if you disable
@ -55,7 +58,7 @@ depending on the kernel config.
ORC vs DWARF
------------
============
ORC debuginfo's advantage over DWARF itself is that it's much simpler.
It gets rid of the complex DWARF CFI state machine and also gets rid of
@ -65,7 +68,7 @@ mission critical oops code.
The simpler debuginfo format also enables the unwinder to be much faster
than DWARF, which is important for perf and lockdep. In a basic
performance test by Jiri Slaby [2], the ORC unwinder was about 20x
performance test by Jiri Slaby [2]_, the ORC unwinder was about 20x
faster than an out-of-tree DWARF unwinder. (Note: That measurement was
taken before some performance tweaks were added, which doubled
performance, so the speedup over DWARF may be closer to 40x.)
@ -85,7 +88,7 @@ still be able to control the format, e.g. no complex state machines.
ORC unwind table generation
---------------------------
===========================
The ORC data is generated by objtool. With the existing compile-time
stack metadata validation feature, objtool already follows all code
@ -133,7 +136,7 @@ objtool follows GCC code quite well.
Unwinder implementation details
-------------------------------
===============================
Objtool generates the ORC data by integrating with the compile-time
stack metadata validation feature, which is described in detail in
@ -154,7 +157,7 @@ subset of the table needs to be searched.
Etymology
---------
=========
Orcs, fearsome creatures of medieval folklore, are the Dwarves' natural
enemies. Similarly, the ORC unwinder was created in opposition to the
@ -162,7 +165,7 @@ complexity and slowness of DWARF.
"Although Orcs rarely consider multiple solutions to a problem, they do
excel at getting things done because they are creatures of action, not
thought." [3] Similarly, unlike the esoteric DWARF unwinder, the
thought." [3]_ Similarly, unlike the esoteric DWARF unwinder, the
veracious ORC unwinder wastes no time or siloconic effort decoding
variable-length zero-extended unsigned-integer byte-coded
state-machine-based debug information entries.
@ -174,6 +177,6 @@ brutal, unyielding efficiency.
ORC stands for Oops Rewind Capability.
[1] https://lkml.kernel.org/r/20170602104048.jkkzssljsompjdwy@suse.de
[2] https://lkml.kernel.org/r/d2ca5435-6386-29b8-db87-7f227c2b713a@suse.cz
[3] http://dustin.wikidot.com/half-orcs-and-orcs
.. [1] https://lkml.kernel.org/r/20170602104048.jkkzssljsompjdwy@suse.de
.. [2] https://lkml.kernel.org/r/d2ca5435-6386-29b8-db87-7f227c2b713a@suse.cz
.. [3] http://dustin.wikidot.com/half-orcs-and-orcs

242
Documentation/x86/pat.rst Normal file
View File

@ -0,0 +1,242 @@
.. SPDX-License-Identifier: GPL-2.0
==========================
PAT (Page Attribute Table)
==========================
x86 Page Attribute Table (PAT) allows for setting the memory attribute at the
page level granularity. PAT is complementary to the MTRR settings which allows
for setting of memory types over physical address ranges. However, PAT is
more flexible than MTRR due to its capability to set attributes at page level
and also due to the fact that there are no hardware limitations on number of
such attribute settings allowed. Added flexibility comes with guidelines for
not having memory type aliasing for the same physical memory with multiple
virtual addresses.
PAT allows for different types of memory attributes. The most commonly used
ones that will be supported at this time are:
=== ==============
WB Write-back
UC Uncached
WC Write-combined
WT Write-through
UC- Uncached Minus
=== ==============
PAT APIs
========
There are many different APIs in the kernel that allows setting of memory
attributes at the page level. In order to avoid aliasing, these interfaces
should be used thoughtfully. Below is a table of interfaces available,
their intended usage and their memory attribute relationships. Internally,
these APIs use a reserve_memtype()/free_memtype() interface on the physical
address range to avoid any aliasing.
+------------------------+----------+--------------+------------------+
| API | RAM | ACPI,... | Reserved/Holes |
+------------------------+----------+--------------+------------------+
| ioremap | -- | UC- | UC- |
+------------------------+----------+--------------+------------------+
| ioremap_cache | -- | WB | WB |
+------------------------+----------+--------------+------------------+
| ioremap_uc | -- | UC | UC |
+------------------------+----------+--------------+------------------+
| ioremap_nocache | -- | UC- | UC- |
+------------------------+----------+--------------+------------------+
| ioremap_wc | -- | -- | WC |
+------------------------+----------+--------------+------------------+
| ioremap_wt | -- | -- | WT |
+------------------------+----------+--------------+------------------+
| set_memory_uc, | UC- | -- | -- |
| set_memory_wb | | | |
+------------------------+----------+--------------+------------------+
| set_memory_wc, | WC | -- | -- |
| set_memory_wb | | | |
+------------------------+----------+--------------+------------------+
| set_memory_wt, | WT | -- | -- |
| set_memory_wb | | | |
+------------------------+----------+--------------+------------------+
| pci sysfs resource | -- | -- | UC- |
+------------------------+----------+--------------+------------------+
| pci sysfs resource_wc | -- | -- | WC |
| is IORESOURCE_PREFETCH | | | |
+------------------------+----------+--------------+------------------+
| pci proc | -- | -- | UC- |
| !PCIIOC_WRITE_COMBINE | | | |
+------------------------+----------+--------------+------------------+
| pci proc | -- | -- | WC |
| PCIIOC_WRITE_COMBINE | | | |
+------------------------+----------+--------------+------------------+
| /dev/mem | -- | WB/WC/UC- | WB/WC/UC- |
| read-write | | | |
+------------------------+----------+--------------+------------------+
| /dev/mem | -- | UC- | UC- |
| mmap SYNC flag | | | |
+------------------------+----------+--------------+------------------+
| /dev/mem | -- | WB/WC/UC- | WB/WC/UC- |
| mmap !SYNC flag | | | |
| and | |(from existing| (from existing |
| any alias to this area | |alias) | alias) |
+------------------------+----------+--------------+------------------+
| /dev/mem | -- | WB | WB |
| mmap !SYNC flag | | | |
| no alias to this area | | | |
| and | | | |
| MTRR says WB | | | |
+------------------------+----------+--------------+------------------+
| /dev/mem | -- | -- | UC- |
| mmap !SYNC flag | | | |
| no alias to this area | | | |
| and | | | |
| MTRR says !WB | | | |
+------------------------+----------+--------------+------------------+
Advanced APIs for drivers
=========================
A. Exporting pages to users with remap_pfn_range, io_remap_pfn_range,
vmf_insert_pfn.
Drivers wanting to export some pages to userspace do it by using mmap
interface and a combination of:
1) pgprot_noncached()
2) io_remap_pfn_range() or remap_pfn_range() or vmf_insert_pfn()
With PAT support, a new API pgprot_writecombine is being added. So, drivers can
continue to use the above sequence, with either pgprot_noncached() or
pgprot_writecombine() in step 1, followed by step 2.
In addition, step 2 internally tracks the region as UC or WC in memtype
list in order to ensure no conflicting mapping.
Note that this set of APIs only works with IO (non RAM) regions. If driver
wants to export a RAM region, it has to do set_memory_uc() or set_memory_wc()
as step 0 above and also track the usage of those pages and use set_memory_wb()
before the page is freed to free pool.
MTRR effects on PAT / non-PAT systems
=====================================
The following table provides the effects of using write-combining MTRRs when
using ioremap*() calls on x86 for both non-PAT and PAT systems. Ideally
mtrr_add() usage will be phased out in favor of arch_phys_wc_add() which will
be a no-op on PAT enabled systems. The region over which a arch_phys_wc_add()
is made, should already have been ioremapped with WC attributes or PAT entries,
this can be done by using ioremap_wc() / set_memory_wc(). Devices which
combine areas of IO memory desired to remain uncacheable with areas where
write-combining is desirable should consider use of ioremap_uc() followed by
set_memory_wc() to white-list effective write-combined areas. Such use is
nevertheless discouraged as the effective memory type is considered
implementation defined, yet this strategy can be used as last resort on devices
with size-constrained regions where otherwise MTRR write-combining would
otherwise not be effective.
::
==== ======= === ========================= =====================
MTRR Non-PAT PAT Linux ioremap value Effective memory type
==== ======= === ========================= =====================
PAT Non-PAT | PAT
|PCD |
||PWT |
||| |
WC 000 WB _PAGE_CACHE_MODE_WB WC | WC
WC 001 WC _PAGE_CACHE_MODE_WC WC* | WC
WC 010 UC- _PAGE_CACHE_MODE_UC_MINUS WC* | UC
WC 011 UC _PAGE_CACHE_MODE_UC UC | UC
==== ======= === ========================= =====================
(*) denotes implementation defined and is discouraged
.. note:: -- in the above table mean "Not suggested usage for the API". Some
of the --'s are strictly enforced by the kernel. Some others are not really
enforced today, but may be enforced in future.
For ioremap and pci access through /sys or /proc - The actual type returned
can be more restrictive, in case of any existing aliasing for that address.
For example: If there is an existing uncached mapping, a new ioremap_wc can
return uncached mapping in place of write-combine requested.
set_memory_[uc|wc|wt] and set_memory_wb should be used in pairs, where driver
will first make a region uc, wc or wt and switch it back to wb after use.
Over time writes to /proc/mtrr will be deprecated in favor of using PAT based
interfaces. Users writing to /proc/mtrr are suggested to use above interfaces.
Drivers should use ioremap_[uc|wc] to access PCI BARs with [uc|wc] access
types.
Drivers should use set_memory_[uc|wc|wt] to set access type for RAM ranges.
PAT debugging
=============
With CONFIG_DEBUG_FS enabled, PAT memtype list can be examined by::
# mount -t debugfs debugfs /sys/kernel/debug
# cat /sys/kernel/debug/x86/pat_memtype_list
PAT memtype list:
uncached-minus @ 0x7fadf000-0x7fae0000
uncached-minus @ 0x7fb19000-0x7fb1a000
uncached-minus @ 0x7fb1a000-0x7fb1b000
uncached-minus @ 0x7fb1b000-0x7fb1c000
uncached-minus @ 0x7fb1c000-0x7fb1d000
uncached-minus @ 0x7fb1d000-0x7fb1e000
uncached-minus @ 0x7fb1e000-0x7fb25000
uncached-minus @ 0x7fb25000-0x7fb26000
uncached-minus @ 0x7fb26000-0x7fb27000
uncached-minus @ 0x7fb27000-0x7fb28000
uncached-minus @ 0x7fb28000-0x7fb2e000
uncached-minus @ 0x7fb2e000-0x7fb2f000
uncached-minus @ 0x7fb2f000-0x7fb30000
uncached-minus @ 0x7fb31000-0x7fb32000
uncached-minus @ 0x80000000-0x90000000
This list shows physical address ranges and various PAT settings used to
access those physical address ranges.
Another, more verbose way of getting PAT related debug messages is with
"debugpat" boot parameter. With this parameter, various debug messages are
printed to dmesg log.
PAT Initialization
==================
The following table describes how PAT is initialized under various
configurations. The PAT MSR must be updated by Linux in order to support WC
and WT attributes. Otherwise, the PAT MSR has the value programmed in it
by the firmware. Note, Xen enables WC attribute in the PAT MSR for guests.
==== ===== ========================== ========= =======
MTRR PAT Call Sequence PAT State PAT MSR
==== ===== ========================== ========= =======
E E MTRR -> PAT init Enabled OS
E D MTRR -> PAT init Disabled -
D E MTRR -> PAT disable Disabled BIOS
D D MTRR -> PAT disable Disabled -
- np/E PAT -> PAT disable Disabled BIOS
- np/D PAT -> PAT disable Disabled -
E !P/E MTRR -> PAT init Disabled BIOS
D !P/E MTRR -> PAT disable Disabled BIOS
!M !P/E MTRR stub -> PAT disable Disabled BIOS
==== ===== ========================== ========= =======
Legend
========= =======================================
E Feature enabled in CPU
D Feature disabled/unsupported in CPU
np "nopat" boot option specified
!P CONFIG_X86_PAT option unset
!M CONFIG_MTRR option unset
Enabled PAT state set to enabled
Disabled PAT state set to disabled
OS PAT initializes PAT MSR with OS setting
BIOS PAT keeps PAT MSR with BIOS setting
========= =======================================

230
Documentation/x86/pat.txt
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@ -1,230 +0,0 @@
PAT (Page Attribute Table)
x86 Page Attribute Table (PAT) allows for setting the memory attribute at the
page level granularity. PAT is complementary to the MTRR settings which allows
for setting of memory types over physical address ranges. However, PAT is
more flexible than MTRR due to its capability to set attributes at page level
and also due to the fact that there are no hardware limitations on number of
such attribute settings allowed. Added flexibility comes with guidelines for
not having memory type aliasing for the same physical memory with multiple
virtual addresses.
PAT allows for different types of memory attributes. The most commonly used
ones that will be supported at this time are Write-back, Uncached,
Write-combined, Write-through and Uncached Minus.
PAT APIs
--------
There are many different APIs in the kernel that allows setting of memory
attributes at the page level. In order to avoid aliasing, these interfaces
should be used thoughtfully. Below is a table of interfaces available,
their intended usage and their memory attribute relationships. Internally,
these APIs use a reserve_memtype()/free_memtype() interface on the physical
address range to avoid any aliasing.
-------------------------------------------------------------------
API | RAM | ACPI,... | Reserved/Holes |
-----------------------|----------|------------|------------------|
| | | |
ioremap | -- | UC- | UC- |
| | | |
ioremap_cache | -- | WB | WB |
| | | |
ioremap_uc | -- | UC | UC |
| | | |
ioremap_nocache | -- | UC- | UC- |
| | | |
ioremap_wc | -- | -- | WC |
| | | |
ioremap_wt | -- | -- | WT |
| | | |
set_memory_uc | UC- | -- | -- |
set_memory_wb | | | |
| | | |
set_memory_wc | WC | -- | -- |
set_memory_wb | | | |
| | | |
set_memory_wt | WT | -- | -- |
set_memory_wb | | | |
| | | |
pci sysfs resource | -- | -- | UC- |
| | | |
pci sysfs resource_wc | -- | -- | WC |
is IORESOURCE_PREFETCH| | | |
| | | |
pci proc | -- | -- | UC- |
!PCIIOC_WRITE_COMBINE | | | |
| | | |
pci proc | -- | -- | WC |
PCIIOC_WRITE_COMBINE | | | |
| | | |
/dev/mem | -- | WB/WC/UC- | WB/WC/UC- |
read-write | | | |
| | | |
/dev/mem | -- | UC- | UC- |
mmap SYNC flag | | | |
| | | |
/dev/mem | -- | WB/WC/UC- | WB/WC/UC- |
mmap !SYNC flag | |(from exist-| (from exist- |
and | | ing alias)| ing alias) |
any alias to this area| | | |
| | | |
/dev/mem | -- | WB | WB |
mmap !SYNC flag | | | |
no alias to this area | | | |
and | | | |
MTRR says WB | | | |
| | | |
/dev/mem | -- | -- | UC- |
mmap !SYNC flag | | | |
no alias to this area | | | |
and | | | |
MTRR says !WB | | | |
| | | |
-------------------------------------------------------------------
Advanced APIs for drivers
-------------------------
A. Exporting pages to users with remap_pfn_range, io_remap_pfn_range,
vmf_insert_pfn
Drivers wanting to export some pages to userspace do it by using mmap
interface and a combination of
1) pgprot_noncached()
2) io_remap_pfn_range() or remap_pfn_range() or vmf_insert_pfn()
With PAT support, a new API pgprot_writecombine is being added. So, drivers can
continue to use the above sequence, with either pgprot_noncached() or
pgprot_writecombine() in step 1, followed by step 2.
In addition, step 2 internally tracks the region as UC or WC in memtype
list in order to ensure no conflicting mapping.
Note that this set of APIs only works with IO (non RAM) regions. If driver
wants to export a RAM region, it has to do set_memory_uc() or set_memory_wc()
as step 0 above and also track the usage of those pages and use set_memory_wb()
before the page is freed to free pool.
MTRR effects on PAT / non-PAT systems
-------------------------------------
The following table provides the effects of using write-combining MTRRs when
using ioremap*() calls on x86 for both non-PAT and PAT systems. Ideally
mtrr_add() usage will be phased out in favor of arch_phys_wc_add() which will
be a no-op on PAT enabled systems. The region over which a arch_phys_wc_add()
is made, should already have been ioremapped with WC attributes or PAT entries,
this can be done by using ioremap_wc() / set_memory_wc(). Devices which
combine areas of IO memory desired to remain uncacheable with areas where
write-combining is desirable should consider use of ioremap_uc() followed by
set_memory_wc() to white-list effective write-combined areas. Such use is
nevertheless discouraged as the effective memory type is considered
implementation defined, yet this strategy can be used as last resort on devices
with size-constrained regions where otherwise MTRR write-combining would
otherwise not be effective.
----------------------------------------------------------------------
MTRR Non-PAT PAT Linux ioremap value Effective memory type
----------------------------------------------------------------------
Non-PAT | PAT
PAT
|PCD
||PWT
|||
WC 000 WB _PAGE_CACHE_MODE_WB WC | WC
WC 001 WC _PAGE_CACHE_MODE_WC WC* | WC
WC 010 UC- _PAGE_CACHE_MODE_UC_MINUS WC* | UC
WC 011 UC _PAGE_CACHE_MODE_UC UC | UC
----------------------------------------------------------------------
(*) denotes implementation defined and is discouraged
Notes:
-- in the above table mean "Not suggested usage for the API". Some of the --'s
are strictly enforced by the kernel. Some others are not really enforced
today, but may be enforced in future.
For ioremap and pci access through /sys or /proc - The actual type returned
can be more restrictive, in case of any existing aliasing for that address.
For example: If there is an existing uncached mapping, a new ioremap_wc can
return uncached mapping in place of write-combine requested.
set_memory_[uc|wc|wt] and set_memory_wb should be used in pairs, where driver
will first make a region uc, wc or wt and switch it back to wb after use.
Over time writes to /proc/mtrr will be deprecated in favor of using PAT based
interfaces. Users writing to /proc/mtrr are suggested to use above interfaces.
Drivers should use ioremap_[uc|wc] to access PCI BARs with [uc|wc] access
types.
Drivers should use set_memory_[uc|wc|wt] to set access type for RAM ranges.
PAT debugging
-------------
With CONFIG_DEBUG_FS enabled, PAT memtype list can be examined by
# mount -t debugfs debugfs /sys/kernel/debug
# cat /sys/kernel/debug/x86/pat_memtype_list
PAT memtype list:
uncached-minus @ 0x7fadf000-0x7fae0000
uncached-minus @ 0x7fb19000-0x7fb1a000
uncached-minus @ 0x7fb1a000-0x7fb1b000
uncached-minus @ 0x7fb1b000-0x7fb1c000
uncached-minus @ 0x7fb1c000-0x7fb1d000
uncached-minus @ 0x7fb1d000-0x7fb1e000
uncached-minus @ 0x7fb1e000-0x7fb25000
uncached-minus @ 0x7fb25000-0x7fb26000
uncached-minus @ 0x7fb26000-0x7fb27000
uncached-minus @ 0x7fb27000-0x7fb28000
uncached-minus @ 0x7fb28000-0x7fb2e000
uncached-minus @ 0x7fb2e000-0x7fb2f000
uncached-minus @ 0x7fb2f000-0x7fb30000
uncached-minus @ 0x7fb31000-0x7fb32000
uncached-minus @ 0x80000000-0x90000000
This list shows physical address ranges and various PAT settings used to
access those physical address ranges.
Another, more verbose way of getting PAT related debug messages is with
"debugpat" boot parameter. With this parameter, various debug messages are
printed to dmesg log.
PAT Initialization
------------------
The following table describes how PAT is initialized under various
configurations. The PAT MSR must be updated by Linux in order to support WC
and WT attributes. Otherwise, the PAT MSR has the value programmed in it
by the firmware. Note, Xen enables WC attribute in the PAT MSR for guests.
MTRR PAT Call Sequence PAT State PAT MSR
=========================================================
E E MTRR -> PAT init Enabled OS
E D MTRR -> PAT init Disabled -
D E MTRR -> PAT disable Disabled BIOS
D D MTRR -> PAT disable Disabled -
- np/E PAT -> PAT disable Disabled BIOS
- np/D PAT -> PAT disable Disabled -
E !P/E MTRR -> PAT init Disabled BIOS
D !P/E MTRR -> PAT disable Disabled BIOS
!M !P/E MTRR stub -> PAT disable Disabled BIOS
Legend
------------------------------------------------
E Feature enabled in CPU
D Feature disabled/unsupported in CPU
np "nopat" boot option specified
!P CONFIG_X86_PAT option unset
!M CONFIG_MTRR option unset
Enabled PAT state set to enabled
Disabled PAT state set to disabled
OS PAT initializes PAT MSR with OS setting
BIOS PAT keeps PAT MSR with BIOS setting

31
Documentation/x86/protection-keys.txt → Documentation/x86/protection-keys.rst
View File

@ -1,3 +1,9 @@
.. SPDX-License-Identifier: GPL-2.0
======================
Memory Protection Keys
======================
Memory Protection Keys for Userspace (PKU aka PKEYs) is a feature
which is found on Intel's Skylake "Scalable Processor" Server CPUs.
It will be avalable in future non-server parts.
@ -23,9 +29,10 @@ even though there is theoretically space in the PAE PTEs. These
permissions are enforced on data access only and have no effect on
instruction fetches.
=========================== Syscalls ===========================
Syscalls
========
There are 3 system calls which directly interact with pkeys:
There are 3 system calls which directly interact with pkeys::
int pkey_alloc(unsigned long flags, unsigned long init_access_rights)
int pkey_free(int pkey);
@ -37,6 +44,7 @@ pkey_alloc(). An application calls the WRPKRU instruction
directly in order to change access permissions to memory covered
with a key. In this example WRPKRU is wrapped by a C function
called pkey_set().
::
int real_prot = PROT_READ|PROT_WRITE;
pkey = pkey_alloc(0, PKEY_DISABLE_WRITE);
@ -45,43 +53,44 @@ called pkey_set().
... application runs here
Now, if the application needs to update the data at 'ptr', it can
gain access, do the update, then remove its write access:
gain access, do the update, then remove its write access::
pkey_set(pkey, 0); // clear PKEY_DISABLE_WRITE
*ptr = foo; // assign something
pkey_set(pkey, PKEY_DISABLE_WRITE); // set PKEY_DISABLE_WRITE again
Now when it frees the memory, it will also free the pkey since it
is no longer in use:
is no longer in use::
munmap(ptr, PAGE_SIZE);
pkey_free(pkey);
(Note: pkey_set() is a wrapper for the RDPKRU and WRPKRU instructions.
.. note:: pkey_set() is a wrapper for the RDPKRU and WRPKRU instructions.
An example implementation can be found in
tools/testing/selftests/x86/protection_keys.c)
tools/testing/selftests/x86/protection_keys.c.
=========================== Behavior ===========================
Behavior
========
The kernel attempts to make protection keys consistent with the
behavior of a plain mprotect(). For instance if you do this:
behavior of a plain mprotect(). For instance if you do this::
mprotect(ptr, size, PROT_NONE);
something(ptr);
you can expect the same effects with protection keys when doing this:
you can expect the same effects with protection keys when doing this::
pkey = pkey_alloc(0, PKEY_DISABLE_WRITE | PKEY_DISABLE_READ);
pkey_mprotect(ptr, size, PROT_READ|PROT_WRITE, pkey);
something(ptr);
That should be true whether something() is a direct access to 'ptr'
like:
like::
*ptr = foo;
or when the kernel does the access on the application's behalf like
with a read():
with a read()::
read(fd, ptr, 1);

17
Documentation/x86/pti.txt → Documentation/x86/pti.rst
View File

@ -1,9 +1,15 @@
.. SPDX-License-Identifier: GPL-2.0
==========================
Page Table Isolation (PTI)
==========================
Overview
========
Page Table Isolation (pti, previously known as KAISER[1]) is a
Page Table Isolation (pti, previously known as KAISER [1]_) is a
countermeasure against attacks on the shared user/kernel address
space such as the "Meltdown" approach[2].
space such as the "Meltdown" approach [2]_.
To mitigate this class of attacks, we create an independent set of
page tables for use only when running userspace applications. When
@ -60,6 +66,7 @@ Protection against side-channel attacks is important. But,
this protection comes at a cost:
1. Increased Memory Use
a. Each process now needs an order-1 PGD instead of order-0.
(Consumes an additional 4k per process).
b. The 'cpu_entry_area' structure must be 2MB in size and 2MB
@ -68,6 +75,7 @@ this protection comes at a cost:
is decompressed, but no space in the kernel image itself.
2. Runtime Cost
a. CR3 manipulation to switch between the page table copies
must be done at interrupt, syscall, and exception entry
and exit (it can be skipped when the kernel is interrupted,
@ -142,6 +150,7 @@ ideally doing all of these in parallel:
interrupted, including nested NMIs. Using "-c" boosts the rate of
NMIs, and using two -c with separate counters encourages nested NMIs
and less deterministic behavior.
::
while true; do perf record -c 10000 -e instructions,cycles -a sleep 10; done
@ -182,5 +191,5 @@ that are worth noting here.
tended to be TLB invalidation issues. Usually invalidating
the wrong PCID, or otherwise missing an invalidation.
1. https://gruss.cc/files/kaiser.pdf
2. https://meltdownattack.com/meltdown.pdf
.. [1] https://gruss.cc/files/kaiser.pdf
.. [2] https://meltdownattack.com/meltdown.pdf

242
Documentation/x86/resctrl_ui.txt → Documentation/x86/resctrl_ui.rst
View File

@ -1,32 +1,43 @@
.. SPDX-License-Identifier: GPL-2.0
.. include:: <isonum.txt>
===========================================
User Interface for Resource Control feature
===========================================
:Copyright: |copy| 2016 Intel Corporation
:Authors: - Fenghua Yu <fenghua.yu@intel.com>
- Tony Luck <tony.luck@intel.com>
- Vikas Shivappa <vikas.shivappa@intel.com>
Intel refers to this feature as Intel Resource Director Technology(Intel(R) RDT).
AMD refers to this feature as AMD Platform Quality of Service(AMD QoS).
Copyright (C) 2016 Intel Corporation
Fenghua Yu <fenghua.yu@intel.com>
Tony Luck <tony.luck@intel.com>
Vikas Shivappa <vikas.shivappa@intel.com>
This feature is enabled by the CONFIG_X86_CPU_RESCTRL and the x86 /proc/cpuinfo
flag bits:
RDT (Resource Director Technology) Allocation - "rdt_a"
CAT (Cache Allocation Technology) - "cat_l3", "cat_l2"
CDP (Code and Data Prioritization ) - "cdp_l3", "cdp_l2"
CQM (Cache QoS Monitoring) - "cqm_llc", "cqm_occup_llc"
MBM (Memory Bandwidth Monitoring) - "cqm_mbm_total", "cqm_mbm_local"
MBA (Memory Bandwidth Allocation) - "mba"
To use the feature mount the file system:
============================================= ================================
RDT (Resource Director Technology) Allocation "rdt_a"
CAT (Cache Allocation Technology) "cat_l3", "cat_l2"
CDP (Code and Data Prioritization) "cdp_l3", "cdp_l2"
CQM (Cache QoS Monitoring) "cqm_llc", "cqm_occup_llc"
MBM (Memory Bandwidth Monitoring) "cqm_mbm_total", "cqm_mbm_local"
MBA (Memory Bandwidth Allocation) "mba"
============================================= ================================
To use the feature mount the file system::
# mount -t resctrl resctrl [-o cdp[,cdpl2][,mba_MBps]] /sys/fs/resctrl
mount options are:
"cdp": Enable code/data prioritization in L3 cache allocations.
"cdpl2": Enable code/data prioritization in L2 cache allocations.
"mba_MBps": Enable the MBA Software Controller(mba_sc) to specify MBA
"cdp":
Enable code/data prioritization in L3 cache allocations.
"cdpl2":
Enable code/data prioritization in L2 cache allocations.
"mba_MBps":
Enable the MBA Software Controller(mba_sc) to specify MBA
bandwidth in MBps
L2 and L3 CDP are controlled seperately.
@ -44,7 +55,7 @@ For more details on the behavior of the interface during monitoring
and allocation, see the "Resource alloc and monitor groups" section.
Info directory
--------------
==============
The 'info' directory contains information about the enabled
resources. Each resource has its own subdirectory. The subdirectory
@ -56,71 +67,87 @@ allocation:
Cache resource(L3/L2) subdirectory contains the following files
related to allocation:
"num_closids": The number of CLOSIDs which are valid for this
"num_closids":
The number of CLOSIDs which are valid for this
resource. The kernel uses the smallest number of
CLOSIDs of all enabled resources as limit.
"cbm_mask": The bitmask which is valid for this resource.
"cbm_mask":
The bitmask which is valid for this resource.
This mask is equivalent to 100%.
"min_cbm_bits": The minimum number of consecutive bits which
"min_cbm_bits":
The minimum number of consecutive bits which
must be set when writing a mask.
"shareable_bits": Bitmask of shareable resource with other executing
"shareable_bits":
Bitmask of shareable resource with other executing
entities (e.g. I/O). User can use this when
setting up exclusive cache partitions. Note that
some platforms support devices that have their
own settings for cache use which can over-ride
these bits.
"bit_usage": Annotated capacity bitmasks showing how all
"bit_usage":
Annotated capacity bitmasks showing how all
instances of the resource are used. The legend is:
"0" - Corresponding region is unused. When the system's
"0":
Corresponding region is unused. When the system's
resources have been allocated and a "0" is found
in "bit_usage" it is a sign that resources are
wasted.
"H" - Corresponding region is used by hardware only
"H":
Corresponding region is used by hardware only
but available for software use. If a resource
has bits set in "shareable_bits" but not all
of these bits appear in the resource groups'
schematas then the bits appearing in
"shareable_bits" but no resource group will
be marked as "H".
"X" - Corresponding region is available for sharing and
"X":
Corresponding region is available for sharing and
used by hardware and software. These are the
bits that appear in "shareable_bits" as
well as a resource group's allocation.
"S" - Corresponding region is used by software
"S":
Corresponding region is used by software
and available for sharing.
"E" - Corresponding region is used exclusively by
"E":
Corresponding region is used exclusively by
one resource group. No sharing allowed.
"P" - Corresponding region is pseudo-locked. No
"P":
Corresponding region is pseudo-locked. No
sharing allowed.
Memory bandwitdh(MB) subdirectory contains the following files
with respect to allocation:
"min_bandwidth": The minimum memory bandwidth percentage which
"min_bandwidth":
The minimum memory bandwidth percentage which
user can request.
"bandwidth_gran": The granularity in which the memory bandwidth
"bandwidth_gran":
The granularity in which the memory bandwidth
percentage is allocated. The allocated
b/w percentage is rounded off to the next
control step available on the hardware. The
available bandwidth control steps are:
min_bandwidth + N * bandwidth_gran.
"delay_linear": Indicates if the delay scale is linear or
"delay_linear":
Indicates if the delay scale is linear or
non-linear. This field is purely informational
only.
If RDT monitoring is available there will be an "L3_MON" directory
with the following files:
"num_rmids": The number of RMIDs available. This is the
"num_rmids":
The number of RMIDs available. This is the
upper bound for how many "CTRL_MON" + "MON"
groups can be created.
"mon_features": Lists the monitoring events if
"mon_features":
Lists the monitoring events if
monitoring is enabled for the resource.
"max_threshold_occupancy":
@ -134,6 +161,7 @@ via the file system (making new directories or writing to any of the
control files). If the command was successful, it will read as "ok".
If the command failed, it will provide more information that can be
conveyed in the error returns from file operations. E.g.
::
# echo L3:0=f7 > schemata
bash: echo: write error: Invalid argument
@ -141,7 +169,7 @@ conveyed in the error returns from file operations. E.g.
mask f7 has non-consecutive 1-bits
Resource alloc and monitor groups
---------------------------------
=================================
Resource groups are represented as directories in the resctrl file
system. The default group is the root directory which, immediately
@ -226,6 +254,7 @@ When monitoring is enabled all MON groups will also contain:
Resource allocation rules
-------------------------
When a task is running the following rules define which resources are
available to it:
@ -252,7 +281,7 @@ Resource monitoring rules
Notes on cache occupancy monitoring and control
-----------------------------------------------
===============================================
When moving a task from one group to another you should remember that
this only affects *new* cache allocations by the task. E.g. you may have
a task in a monitor group showing 3 MB of cache occupancy. If you move
@ -321,7 +350,7 @@ of the capacity of the cache. You could partition the cache into four
equal parts with masks: 0x1f, 0x3e0, 0x7c00, 0xf8000.
Memory bandwidth Allocation and monitoring
------------------------------------------
==========================================
For Memory bandwidth resource, by default the user controls the resource
by indicating the percentage of total memory bandwidth.
@ -369,7 +398,7 @@ In order to mitigate this and make the interface more user friendly,
resctrl added support for specifying the bandwidth in MBps as well. The
kernel underneath would use a software feedback mechanism or a "Software
Controller(mba_sc)" which reads the actual bandwidth using MBM counters
and adjust the memowy bandwidth percentages to ensure
and adjust the memowy bandwidth percentages to ensure::
"actual bandwidth < user specified bandwidth".
@ -380,14 +409,14 @@ sections.
L3 schemata file details (code and data prioritization disabled)
----------------------------------------------------------------
With CDP disabled the L3 schemata format is:
With CDP disabled the L3 schemata format is::
L3:<cache_id0>=<cbm>;<cache_id1>=<cbm>;...
L3 schemata file details (CDP enabled via mount option to resctrl)
------------------------------------------------------------------
When CDP is enabled L3 control is split into two separate resources
so you can specify independent masks for code and data like this:
so you can specify independent masks for code and data like this::
L3data:<cache_id0>=<cbm>;<cache_id1>=<cbm>;...
L3code:<cache_id0>=<cbm>;<cache_id1>=<cbm>;...
@ -395,7 +424,7 @@ so you can specify independent masks for code and data like this:
L2 schemata file details
------------------------
L2 cache does not support code and data prioritization, so the
schemata format is always:
schemata format is always::
L2:<cache_id0>=<cbm>;<cache_id1>=<cbm>;...
@ -403,6 +432,7 @@ Memory bandwidth Allocation (default mode)
------------------------------------------
Memory b/w domain is L3 cache.
::
MB:<cache_id0>=bandwidth0;<cache_id1>=bandwidth1;...
@ -410,6 +440,7 @@ Memory bandwidth Allocation specified in MBps
---------------------------------------------
Memory bandwidth domain is L3 cache.
::
MB:<cache_id0>=bw_MBps0;<cache_id1>=bw_MBps1;...
@ -418,6 +449,7 @@ Reading/writing the schemata file
Reading the schemata file will show the state of all resources
on all domains. When writing you only need to specify those values
which you wish to change. E.g.
::
# cat schemata
L3DATA:0=fffff;1=fffff;2=fffff;3=fffff
@ -428,7 +460,7 @@ L3DATA:0=fffff;1=fffff;2=3c0;3=fffff
L3CODE:0=fffff;1=fffff;2=fffff;3=fffff
Cache Pseudo-Locking
--------------------
====================
CAT enables a user to specify the amount of cache space that an
application can fill. Cache pseudo-locking builds on the fact that a
CPU can still read and write data pre-allocated outside its current
@ -442,6 +474,7 @@ a region of memory with reduced average read latency.
The creation of a cache pseudo-locked region is triggered by a request
from the user to do so that is accompanied by a schemata of the region
to be pseudo-locked. The cache pseudo-locked region is created as follows:
- Create a CAT allocation CLOSNEW with a CBM matching the schemata
from the user of the cache region that will contain the pseudo-locked
memory. This region must not overlap with any current CAT allocation/CLOS
@ -480,6 +513,7 @@ initial mmap() handling, there is no enforcement afterwards and the
application self needs to ensure it remains affine to the correct cores.
Pseudo-locking is accomplished in two stages:
1) During the first stage the system administrator allocates a portion
of cache that should be dedicated to pseudo-locking. At this time an
equivalent portion of memory is allocated, loaded into allocated
@ -506,7 +540,7 @@ by user space in order to obtain access to the pseudo-locked memory region.
An example of cache pseudo-locked region creation and usage can be found below.
Cache Pseudo-Locking Debugging Interface
---------------------------------------
----------------------------------------
The pseudo-locking debugging interface is enabled by default (if
CONFIG_DEBUG_FS is enabled) and can be found in /sys/kernel/debug/resctrl.
@ -514,6 +548,7 @@ There is no explicit way for the kernel to test if a provided memory
location is present in the cache. The pseudo-locking debugging interface uses
the tracing infrastructure to provide two ways to measure cache residency of
the pseudo-locked region:
1) Memory access latency using the pseudo_lock_mem_latency tracepoint. Data
from these measurements are best visualized using a hist trigger (see
example below). In this test the pseudo-locked region is traversed at
@ -529,24 +564,30 @@ it in debugfs as /sys/kernel/debug/resctrl/<newdir>. A single
write-only file, pseudo_lock_measure, is present in this directory. The
measurement of the pseudo-locked region depends on the number written to this
debugfs file:
1 - writing "1" to the pseudo_lock_measure file will trigger the latency
1:
writing "1" to the pseudo_lock_measure file will trigger the latency
measurement captured in the pseudo_lock_mem_latency tracepoint. See
example below.
2 - writing "2" to the pseudo_lock_measure file will trigger the L2 cache
2:
writing "2" to the pseudo_lock_measure file will trigger the L2 cache
residency (cache hits and misses) measurement captured in the
pseudo_lock_l2 tracepoint. See example below.
3 - writing "3" to the pseudo_lock_measure file will trigger the L3 cache
3:
writing "3" to the pseudo_lock_measure file will trigger the L3 cache
residency (cache hits and misses) measurement captured in the
pseudo_lock_l3 tracepoint.
All measurements are recorded with the tracing infrastructure. This requires
the relevant tracepoints to be enabled before the measurement is triggered.
Example of latency debugging interface:
Example of latency debugging interface
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In this example a pseudo-locked region named "newlock" was created. Here is
how we can measure the latency in cycles of reading from this region and
visualize this data with a histogram that is available if CONFIG_HIST_TRIGGERS
is set:
is set::
# :> /sys/kernel/debug/tracing/trace
# echo 'hist:keys=latency' > /sys/kernel/debug/tracing/events/resctrl/pseudo_lock_mem_latency/trigger
# echo 1 > /sys/kernel/debug/tracing/events/resctrl/pseudo_lock_mem_latency/enable
@ -574,10 +615,12 @@ Totals:
Entries: 9
Dropped: 0
Example of cache hits/misses debugging:
Example of cache hits/misses debugging
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In this example a pseudo-locked region named "newlock" was created on the L2
cache of a platform. Here is how we can obtain details of the cache hits
and misses using the platform's precision counters.
::
# :> /sys/kernel/debug/tracing/trace
# echo 1 > /sys/kernel/debug/tracing/events/resctrl/pseudo_lock_l2/enable
@ -597,13 +640,15 @@ and misses using the platform's precision counters.
pseudo_lock_mea-1672 [002] .... 3132.860500: pseudo_lock_l2: hits=4097 miss=0
Examples for RDT allocation usage:
Examples for RDT allocation usage
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1) Example 1
Example 1
---------
On a two socket machine (one L3 cache per socket) with just four bits
for cache bit masks, minimum b/w of 10% with a memory bandwidth
granularity of 10%
granularity of 10%.
::
# mount -t resctrl resctrl /sys/fs/resctrl
# cd /sys/fs/resctrl
@ -628,6 +673,7 @@ the b/w accordingly.
If the MBA is specified in MB(megabytes) then user can enter the max b/w in MB
rather than the percentage values.
::
# echo "L3:0=3;1=c\nMB:0=1024;1=500" > /sys/fs/resctrl/p0/schemata
# echo "L3:0=3;1=3\nMB:0=1024;1=500" > /sys/fs/resctrl/p1/schemata
@ -635,26 +681,28 @@ rather than the percentage values.
In the above example the tasks in "p1" and "p0" on socket 0 would use a max b/w
of 1024MB where as on socket 1 they would use 500MB.
Example 2
---------
2) Example 2
Again two sockets, but this time with a more realistic 20-bit mask.
Two real time tasks pid=1234 running on processor 0 and pid=5678 running on
processor 1 on socket 0 on a 2-socket and dual core machine. To avoid noisy
neighbors, each of the two real-time tasks exclusively occupies one quarter
of L3 cache on socket 0.
::
# mount -t resctrl resctrl /sys/fs/resctrl
# cd /sys/fs/resctrl
First we reset the schemata for the default group so that the "upper"
50% of the L3 cache on socket 0 and 50% of memory b/w cannot be used by
ordinary tasks:
ordinary tasks::
# echo "L3:0=3ff;1=fffff\nMB:0=50;1=100" > schemata
Next we make a resource group for our first real time task and give
it access to the "top" 25% of the cache on socket 0.
::
# mkdir p0
# echo "L3:0=f8000;1=fffff" > p0/schemata
@ -663,11 +711,12 @@ Finally we move our first real time task into this resource group. We
also use taskset(1) to ensure the task always runs on a dedicated CPU
on socket 0. Most uses of resource groups will also constrain which
processors tasks run on.
::
# echo 1234 > p0/tasks
# taskset -cp 1 1234
Ditto for the second real time task (with the remaining 25% of cache):
Ditto for the second real time task (with the remaining 25% of cache)::
# mkdir p1
# echo "L3:0=7c00;1=fffff" > p1/schemata
@ -678,37 +727,39 @@ For the same 2 socket system with memory b/w resource and CAT L3 the
schemata would look like(Assume min_bandwidth 10 and bandwidth_gran is
10):
For our first real time task this would request 20% memory b/w on socket
0.
For our first real time task this would request 20% memory b/w on socket 0.
::
# echo -e "L3:0=f8000;1=fffff\nMB:0=20;1=100" > p0/schemata
For our second real time task this would request an other 20% memory b/w
on socket 0.
::
# echo -e "L3:0=f8000;1=fffff\nMB:0=20;1=100" > p0/schemata
Example 3
---------
3) Example 3
A single socket system which has real-time tasks running on core 4-7 and
non real-time workload assigned to core 0-3. The real-time tasks share text
and data, so a per task association is not required and due to interaction
with the kernel it's desired that the kernel on these cores shares L3 with
the tasks.
::
# mount -t resctrl resctrl /sys/fs/resctrl
# cd /sys/fs/resctrl
First we reset the schemata for the default group so that the "upper"
50% of the L3 cache on socket 0, and 50% of memory bandwidth on socket 0
cannot be used by ordinary tasks:
cannot be used by ordinary tasks::
# echo "L3:0=3ff\nMB:0=50" > schemata
Next we make a resource group for our real time cores and give it access
to the "top" 50% of the cache on socket 0 and 50% of memory bandwidth on
socket 0.
::
# mkdir p0
# echo "L3:0=ffc00\nMB:0=50" > p0/schemata
@ -717,11 +768,11 @@ Finally we move core 4-7 over to the new group and make sure that the
kernel and the tasks running there get 50% of the cache. They should
also get 50% of memory bandwidth assuming that the cores 4-7 are SMT
siblings and only the real time threads are scheduled on the cores 4-7.
::
# echo F0 > p0/cpus
Example 4
---------
4) Example 4
The resource groups in previous examples were all in the default "shareable"
mode allowing sharing of their cache allocations. If one resource group
@ -732,18 +783,20 @@ In this example a new exclusive resource group will be created on a L2 CAT
system with two L2 cache instances that can be configured with an 8-bit
capacity bitmask. The new exclusive resource group will be configured to use
25% of each cache instance.
::
# mount -t resctrl resctrl /sys/fs/resctrl/
# cd /sys/fs/resctrl
First, we observe that the default group is configured to allocate to all L2
cache:
cache::
# cat schemata
L2:0=ff;1=ff
We could attempt to create the new resource group at this point, but it will
fail because of the overlap with the schemata of the default group:
fail because of the overlap with the schemata of the default group::
# mkdir p0
# echo 'L2:0=0x3;1=0x3' > p0/schemata
# cat p0/mode
@ -756,6 +809,8 @@ schemata overlaps
To ensure that there is no overlap with another resource group the default
resource group's schemata has to change, making it possible for the new
resource group to become exclusive.
::
# echo 'L2:0=0xfc;1=0xfc' > schemata
# echo exclusive > p0/mode
# grep . p0/*
@ -765,7 +820,8 @@ p0/schemata:L2:0=03;1=03
p0/size:L2:0=262144;1=262144
A new resource group will on creation not overlap with an exclusive resource
group:
group::
# mkdir p1
# grep . p1/*
p1/cpus:0
@ -773,28 +829,32 @@ p1/mode:shareable
p1/schemata:L2:0=fc;1=fc
p1/size:L2:0=786432;1=786432
The bit_usage will reflect how the cache is used:
The bit_usage will reflect how the cache is used::
# cat info/L2/bit_usage
0=SSSSSSEE;1=SSSSSSEE
A resource group cannot be forced to overlap with an exclusive resource group:
A resource group cannot be forced to overlap with an exclusive resource group::
# echo 'L2:0=0x1;1=0x1' > p1/schemata
-sh: echo: write error: Invalid argument
# cat info/last_cmd_status
overlaps with exclusive group
Example of Cache Pseudo-Locking
-------------------------------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Lock portion of L2 cache from cache id 1 using CBM 0x3. Pseudo-locked
region is exposed at /dev/pseudo_lock/newlock that can be provided to
application for argument to mmap().
::
# mount -t resctrl resctrl /sys/fs/resctrl/
# cd /sys/fs/resctrl
Ensure that there are bits available that can be pseudo-locked, since only
unused bits can be pseudo-locked the bits to be pseudo-locked needs to be
removed from the default resource group's schemata:
removed from the default resource group's schemata::
# cat info/L2/bit_usage
0=SSSSSSSS;1=SSSSSSSS
# echo 'L2:1=0xfc' > schemata
@ -803,7 +863,7 @@ removed from the default resource group's schemata:
Create a new resource group that will be associated with the pseudo-locked
region, indicate that it will be used for a pseudo-locked region, and
configure the requested pseudo-locked region capacity bitmask:
configure the requested pseudo-locked region capacity bitmask::
# mkdir newlock
# echo pseudo-locksetup > newlock/mode
@ -811,7 +871,7 @@ configure the requested pseudo-locked region capacity bitmask:
On success the resource group's mode will change to pseudo-locked, the
bit_usage will reflect the pseudo-locked region, and the character device
exposing the pseudo-locked region will exist:
exposing the pseudo-locked region will exist::
# cat newlock/mode
pseudo-locked
@ -820,6 +880,8 @@ pseudo-locked
# ls -l /dev/pseudo_lock/newlock
crw------- 1 root root 243, 0 Apr 3 05:01 /dev/pseudo_lock/newlock
::
/*
* Example code to access one page of pseudo-locked cache region
* from user space.
@ -921,7 +983,7 @@ Read lock:
B) If success read the directory structure.
C) funlock
Example with bash:
Example with bash::
# Atomically read directory structure
$ flock -s /sys/fs/resctrl/ find /sys/fs/resctrl
@ -936,7 +998,7 @@ echo mask > /sys/fs/resctrl/newres/schemata
$ flock /sys/fs/resctrl/ ./create-dir.sh
Example with C:
Example with C::
/*
* Example code do take advisory locks
@ -999,8 +1061,8 @@ void main(void)
resctrl_release_lock(fd);
}
Examples for RDT Monitoring along with allocation usage:
Examples for RDT Monitoring along with allocation usage
=======================================================
Reading monitored data
----------------------
Reading an event file (for ex: mon_data/mon_L3_00/llc_occupancy) would
@ -1009,9 +1071,9 @@ group or CTRL_MON group.
Example 1 (Monitor CTRL_MON group and subset of tasks in CTRL_MON group)
---------
------------------------------------------------------------------------
On a two socket machine (one L3 cache per socket) with just four bits
for cache bit masks
for cache bit masks::
# mount -t resctrl resctrl /sys/fs/resctrl
# cd /sys/fs/resctrl
@ -1029,6 +1091,7 @@ Tasks that are under the control of group "p0" may only allocate from the
Tasks in group "p1" use the "lower" 50% of cache on both sockets.
Create monitor groups and assign a subset of tasks to each monitor group.
::
# cd /sys/fs/resctrl/p1/mon_groups
# mkdir m11 m12
@ -1036,6 +1099,7 @@ Create monitor groups and assign a subset of tasks to each monitor group.
# echo 5679 > m12/tasks
fetch data (data shown in bytes)
::
# cat m11/mon_data/mon_L3_00/llc_occupancy
16234000
@ -1045,13 +1109,14 @@ fetch data (data shown in bytes)
16789000
The parent ctrl_mon group shows the aggregated data.
::
# cat /sys/fs/resctrl/p1/mon_data/mon_l3_00/llc_occupancy
31234000
Example 2 (Monitor a task from its creation)
---------
On a two socket machine (one L3 cache per socket)
--------------------------------------------
On a two socket machine (one L3 cache per socket)::
# mount -t resctrl resctrl /sys/fs/resctrl
# cd /sys/fs/resctrl
@ -1059,17 +1124,18 @@ On a two socket machine (one L3 cache per socket)
An RMID is allocated to the group once its created and hence the <cmd>
below is monitored from its creation.
::
# echo $$ > /sys/fs/resctrl/p1/tasks
# <cmd>
Fetch the data
Fetch the data::
# cat /sys/fs/resctrl/p1/mon_data/mon_l3_00/llc_occupancy
31789000
Example 3 (Monitor without CAT support or before creating CAT groups)
---------
---------------------------------------------------------------------
Assume a system like HSW has only CQM and no CAT support. In this case
the resctrl will still mount but cannot create CTRL_MON directories.
@ -1078,6 +1144,7 @@ able to monitor all tasks including kernel threads.
This can also be used to profile jobs cache size footprint before being
able to allocate them to different allocation groups.
::
# mount -t resctrl resctrl /sys/fs/resctrl
# cd /sys/fs/resctrl
@ -1090,6 +1157,7 @@ able to allocate them to different allocation groups.
Monitor the groups separately and also get per domain data. From the
below its apparent that the tasks are mostly doing work on
domain(socket) 0.
::
# cat /sys/fs/resctrl/mon_groups/m01/mon_L3_00/llc_occupancy
31234000
@ -1107,15 +1175,17 @@ Example 4 (Monitor real time tasks)
A single socket system which has real time tasks running on cores 4-7
and non real time tasks on other cpus. We want to monitor the cache
occupancy of the real time threads on these cores.
::
# mount -t resctrl resctrl /sys/fs/resctrl
# cd /sys/fs/resctrl
# mkdir p1
Move the cpus 4-7 over to p1
Move the cpus 4-7 over to p1::
# echo f0 > p1/cpus
View the llc occupancy snapshot
View the llc occupancy snapshot::
# cat /sys/fs/resctrl/p1/mon_data/mon_L3_00/llc_occupancy
11234000

16
Documentation/x86/tlb.txt → Documentation/x86/tlb.rst
View File

@ -1,5 +1,12 @@
.. SPDX-License-Identifier: GPL-2.0
=======
The TLB
=======
When the kernel unmaps or modified the attributes of a range of
memory, it has two choices:
1. Flush the entire TLB with a two-instruction sequence. This is
a quick operation, but it causes collateral damage: TLB entries
from areas other than the one we are trying to flush will be
@ -10,6 +17,7 @@ memory, it has two choices:
damage to other TLB entries.
Which method to do depends on a few things:
1. The size of the flush being performed. A flush of the entire
address space is obviously better performed by flushing the
entire TLB than doing 2^48/PAGE_SIZE individual flushes.
@ -33,7 +41,7 @@ well. There is essentially no "right" point to choose.
You may be doing too many individual invalidations if you see the
invlpg instruction (or instructions _near_ it) show up high in
profiles. If you believe that individual invalidations being
called too often, you can lower the tunable:
called too often, you can lower the tunable::
/sys/kernel/debug/x86/tlb_single_page_flush_ceiling
@ -43,7 +51,7 @@ Setting it to 1 is a very conservative setting and it should
never need to be 0 under normal circumstances.
Despite the fact that a single individual flush on x86 is
guaranteed to flush a full 2MB [1], hugetlbfs always uses the full
guaranteed to flush a full 2MB [1]_, hugetlbfs always uses the full
flushes. THP is treated exactly the same as normal memory.
You might see invlpg inside of flush_tlb_mm_range() show up in
@ -54,7 +62,7 @@ Essentially, you are balancing the cycles you spend doing invlpg
with the cycles that you spend refilling the TLB later.
You can measure how expensive TLB refills are by using
performance counters and 'perf stat', like this:
performance counters and 'perf stat', like this::
perf stat -e
cpu/event=0x8,umask=0x84,name=dtlb_load_misses_walk_duration/,
@ -70,6 +78,6 @@ be there in some form. You can use pmu-tools 'ocperf list'
(https://github.com/andikleen/pmu-tools) to find the right
counters for a given CPU.
1. A footnote in Intel's SDM "4.10.4.2 Recommended Invalidation"
.. [1] A footnote in Intel's SDM "4.10.4.2 Recommended Invalidation"
says: "One execution of INVLPG is sufficient even for a page
with size greater than 4 KBytes."

40
Documentation/x86/topology.txt → Documentation/x86/topology.rst
View File

@ -1,3 +1,6 @@
.. SPDX-License-Identifier: GPL-2.0
============
x86 Topology
============
@ -33,8 +36,8 @@ The topology of a system is described in the units of:
- cores
- threads
* Package:
Package
=======
Packages contain a number of cores plus shared resources, e.g. DRAM
controller, shared caches etc.
@ -66,6 +69,7 @@ The topology of a system is described in the units of:
- cpu_llc_id:
A per-CPU variable containing:
- On Intel, the first APIC ID of the list of CPUs sharing the Last Level
Cache
@ -73,8 +77,8 @@ The topology of a system is described in the units of:
Cache. In general, it is a number identifying an LLC uniquely on the
system.
* Cores:
Cores
=====
A core consists of 1 or more threads. It does not matter whether the threads
are SMT- or CMT-type threads.
@ -86,13 +90,13 @@ The topology of a system is described in the units of:
- smp_num_siblings:
The number of threads in a core. The number of threads in a package can be
calculated by:
calculated by::
threads_per_package = cpuinfo_x86.x86_max_cores * smp_num_siblings
* Threads:
Threads
=======
A thread is a single scheduling unit. It's the equivalent to a logical Linux
CPU.
@ -129,41 +133,41 @@ The topology of a system is described in the units of:
System topology examples
========================
Note:
.. note::
The alternative Linux CPU enumeration depends on how the BIOS enumerates the
threads. Many BIOSes enumerate all threads 0 first and then all threads 1.
That has the "advantage" that the logical Linux CPU numbers of threads 0 stay
the same whether threads are enabled or not. That's merely an implementation
detail and has no practical impact.
1) Single Package, Single Core
1) Single Package, Single Core::
[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
2) Single Package, Dual Core
a) One thread per core
a) One thread per core::
[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
-> [core 1] -> [thread 0] -> Linux CPU 1
b) Two threads per core
b) Two threads per core::
[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
-> [thread 1] -> Linux CPU 1
-> [core 1] -> [thread 0] -> Linux CPU 2
-> [thread 1] -> Linux CPU 3
Alternative enumeration:
Alternative enumeration::
[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
-> [thread 1] -> Linux CPU 2
-> [core 1] -> [thread 0] -> Linux CPU 1
-> [thread 1] -> Linux CPU 3
AMD nomenclature for CMT systems:
AMD nomenclature for CMT systems::
[node 0] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 0
-> [Compute Unit Core 1] -> Linux CPU 1
@ -172,7 +176,7 @@ detail and has no practical impact.
4) Dual Package, Dual Core
a) One thread per core
a) One thread per core::
[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
-> [core 1] -> [thread 0] -> Linux CPU 1
@ -180,7 +184,7 @@ detail and has no practical impact.
[package 1] -> [core 0] -> [thread 0] -> Linux CPU 2
-> [core 1] -> [thread 0] -> Linux CPU 3
b) Two threads per core
b) Two threads per core::
[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
-> [thread 1] -> Linux CPU 1
@ -192,7 +196,7 @@ detail and has no practical impact.
-> [core 1] -> [thread 0] -> Linux CPU 6
-> [thread 1] -> Linux CPU 7
Alternative enumeration:
Alternative enumeration::
[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
-> [thread 1] -> Linux CPU 4
@ -204,7 +208,7 @@ detail and has no practical impact.
-> [core 1] -> [thread 0] -> Linux CPU 3
-> [thread 1] -> Linux CPU 7
AMD nomenclature for CMT systems:
AMD nomenclature for CMT systems::
[node 0] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 0
-> [Compute Unit Core 1] -> Linux CPU 1

20
Documentation/x86/usb-legacy-support.txt → Documentation/x86/usb-legacy-support.rst
View File

@ -1,7 +1,11 @@
USB Legacy support
~~~~~~~~~~~~~~~~~~
Vojtech Pavlik <vojtech@suse.cz>, January 2004
.. SPDX-License-Identifier: GPL-2.0
==================
USB Legacy support
==================
:Author: Vojtech Pavlik <vojtech@suse.cz>, January 2004
Also known as "USB Keyboard" or "USB Mouse support" in the BIOS Setup is a
@ -27,18 +31,20 @@ It has several drawbacks, though:
Solutions:
Problem 1) can be solved by loading the USB drivers prior to loading the
Problem 1)
can be solved by loading the USB drivers prior to loading the
PS/2 mouse driver. Since the PS/2 mouse driver is in 2.6 compiled into
the kernel unconditionally, this means the USB drivers need to be
compiled-in, too.
Problem 2) can currently only be solved by either disabling HIGHMEM64G
Problem 2)
can currently only be solved by either disabling HIGHMEM64G
in the kernel config or USB Legacy support in the BIOS. A BIOS update
could help, but so far no such update exists.
Problem 3) is usually fixed by a BIOS update. Check the board
Problem 3)
is usually fixed by a BIOS update. Check the board
manufacturers web site. If an update is not available, disable USB
Legacy support in the BIOS. If this alone doesn't help, try also adding
idle=poll on the kernel command line. The BIOS may be entering the SMM
on the HLT instruction as well.

16
Documentation/x86/x86_64/5level-paging.txt → Documentation/x86/x86_64/5level-paging.rst
View File

@ -1,5 +1,11 @@
== Overview ==
.. SPDX-License-Identifier: GPL-2.0
==============
5-level paging
==============
Overview
========
Original x86-64 was limited by 4-level paing to 256 TiB of virtual address
space and 64 TiB of physical address space. We are already bumping into
this limit: some vendors offers servers with 64 TiB of memory today.
@ -16,16 +22,17 @@ QEMU 2.9 and later support 5-level paging.
Virtual memory layout for 5-level paging is described in
Documentation/x86/x86_64/mm.txt
== Enabling 5-level paging ==
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 ==
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
@ -58,4 +65,3 @@ 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.

335
Documentation/x86/x86_64/boot-options.rst Normal file
View File

@ -0,0 +1,335 @@
.. 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 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=tolerancelevel[,monarchtimeout] (number,number)
tolerance levels:
0: always panic on uncorrected errors, log corrected errors
1: panic or SIGBUS on uncorrected errors, log corrected errors
2: SIGBUS or log uncorrected errors, log corrected errors
3: never panic or SIGBUS, log all errors (for testing only)
Default is 1
Can be also set using sysfs which is preferable.
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.txt
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] [, [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.
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.
Non Executable Mappings
=======================
noexec=on|off
on
Enable(default)
off
Disable
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=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. <lib/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)"
4. <arch/x86_64/pci-calgary.c> : IBM Calgary hardware IOMMU. Used in IBM
pSeries and xSeries servers. This hardware IOMMU supports DMA address
mapping with memory protection, etc.
Kernel boot message: "PCI-DMA: Using Calgary IOMMU"
::
iommu=[<size>][,noagp][,off][,force][,noforce]
[,memaper[=<order>]][,merge][,fullflush][,nomerge]
[,noaperture][,calgary]
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.
calgary
Use the Calgary IOMMU if it is available
iommu options only relevant to the software bounce buffering (SWIOTLB) IOMMU
implementation:
swiotlb=<pages>[,force]
<pages>
Prereserve that many 128K pages for the software IO bounce buffering.
force
Force all IO through the software TLB.
Settings for the IBM Calgary hardware IOMMU currently found in IBM
pSeries and xSeries machines
calgary=[64k,128k,256k,512k,1M,2M,4M,8M]
Set the size of each PCI slot's translation table when using the
Calgary IOMMU. This is the size of the translation table itself
in main memory. The smallest table, 64k, covers an IO space of
32MB; the largest, 8MB table, can cover an IO space of 4GB.
Normally the kernel will make the right choice by itself.
calgary=[translate_empty_slots]
Enable translation even on slots that have no devices attached to
them, in case a device will be hotplugged in the future.
calgary=[disable=<PCI bus number>]
Disable translation on a given PHB. For
example, the built-in graphics adapter resides on the first bridge
(PCI bus number 0); if translation (isolation) is enabled on this
bridge, X servers that access the hardware directly from user
space might stop working. Use this option if you have devices that
are accessed from userspace directly on some PCI host bridge.
panic
Always panic when IOMMU overflows
Miscellaneous
=============
nogbpages
Do not use GB pages for kernel direct mappings.
gbpages
Use GB pages for kernel direct mappings.

278
Documentation/x86/x86_64/boot-options.txt
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@ -1,278 +0,0 @@
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 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=tolerancelevel[,monarchtimeout] (number,number)
tolerance levels:
0: always panic on uncorrected errors, log corrected errors
1: panic or SIGBUS on uncorrected errors, log corrected errors
2: SIGBUS or log uncorrected errors, log corrected errors
3: never panic or SIGBUS, log all errors (for testing only)
Default is 1
Can be also set using sysfs which is preferable.
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.txt
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] [, [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.
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.
Non Executable Mappings
noexec=on|off
on Enable(default)
off Disable
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=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. <lib/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)"
4. <arch/x86_64/pci-calgary.c> : IBM Calgary hardware IOMMU. Used in IBM
pSeries and xSeries servers. This hardware IOMMU supports DMA address
mapping with memory protection, etc.
Kernel boot message: "PCI-DMA: Using Calgary IOMMU"
iommu=[<size>][,noagp][,off][,force][,noforce]
[,memaper[=<order>]][,merge][,fullflush][,nomerge]
[,noaperture][,calgary]
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.
calgary Use the Calgary IOMMU if it is available
iommu options only relevant to the software bounce buffering (SWIOTLB) IOMMU
implementation:
swiotlb=<pages>[,force]
<pages> Prereserve that many 128K pages for the software IO
bounce buffering.
force Force all IO through the software TLB.
Settings for the IBM Calgary hardware IOMMU currently found in IBM
pSeries and xSeries machines:
calgary=[64k,128k,256k,512k,1M,2M,4M,8M]
calgary=[translate_empty_slots]
calgary=[disable=<PCI bus number>]
panic Always panic when IOMMU overflows
64k,...,8M - Set the size of each PCI slot's translation table
when using the Calgary IOMMU. This is the size of the translation
table itself in main memory. The smallest table, 64k, covers an IO
space of 32MB; the largest, 8MB table, can cover an IO space of
4GB. Normally the kernel will make the right choice by itself.
translate_empty_slots - Enable translation even on slots that have
no devices attached to them, in case a device will be hotplugged
in the future.
disable=<PCI bus number> - Disable translation on a given PHB. For
example, the built-in graphics adapter resides on the first bridge
(PCI bus number 0); if translation (isolation) is enabled on this
bridge, X servers that access the hardware directly from user
space might stop working. Use this option if you have devices that
are accessed from userspace directly on some PCI host bridge.
Miscellaneous
nogbpages
Do not use GB pages for kernel direct mappings.
gbpages
Use GB pages for kernel direct mappings.

5
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@ -1,5 +1,8 @@
.. 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

25
Documentation/x86/x86_64/fake-numa-for-cpusets → Documentation/x86/x86_64/fake-numa-for-cpusets.rst
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@ -1,5 +1,12 @@
.. 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
Written by David Rientjes <rientjes@cs.washington.edu>
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,
@ -20,7 +27,7 @@ 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:
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)
@ -34,7 +41,7 @@ A machine may be split as follows with "numa=fake=4*512," as reported by dmesg:
Now following the instructions for mounting the cpusets filesystem from
Documentation/cgroup-v1/cpusets.txt, you can assign fake nodes (i.e. contiguous memory
address spaces) to individual cpusets:
address spaces) to individual cpusets::
[root@xroads /]# mkdir exampleset
[root@xroads /]# mount -t cpuset none exampleset
@ -47,7 +54,7 @@ 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:
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
@ -57,9 +64,13 @@ 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):
Unrestricted Restricted
MemTotal: 3091900 kB 3091900 kB
MemFree: 42113 kB 1513236 kB
======== ============ ==========
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

16
Documentation/x86/x86_64/index.rst Normal file
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@ -0,0 +1,16 @@
.. 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

10
Documentation/x86/x86_64/machinecheck → Documentation/x86/x86_64/machinecheck.rst
View File

@ -1,5 +1,8 @@
.. SPDX-License-Identifier: GPL-2.0
Configurable sysfs parameters for the x86-64 machine check code.
===============================================================
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
@ -16,14 +19,13 @@ 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)
(N = CPU number).
The directory contains some configurable entries:
Entries:
bankNctl
(N bank number)
64bit Hex bitmask enabling/disabling specific subevents for bank N
When a bit in the bitmask is zero then the respective
subevent will not be reported.

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@ -0,0 +1,161 @@
.. SPDX-License-Identifier: GPL-2.0
================
Memory Managment
================
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 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).
vmalloc space is lazily synchronized into the different PML4/PML5 pages of
the processes using the page fault handler, with init_top_pgt as
reference.
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

153
Documentation/x86/x86_64/mm.txt
View File

@ -1,153 +0,0 @@
====================================================
Complete virtual memory map with 4-level page tables
====================================================
Notes:
- 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 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
====================================================
Notes:
- 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).
vmalloc space is lazily synchronized into the different PML4/PML5 pages of
the processes using the page fault handler, with init_top_pgt as
reference.
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

30
Documentation/x86/x86_64/uefi.txt → Documentation/x86/x86_64/uefi.rst
View File

@ -1,5 +1,8 @@
.. 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.
@ -14,29 +17,42 @@ with EFI firmware and specifications are listed below.
3. x86_64 platform with EFI/UEFI firmware.
Mechanics:
Mechanics
---------
- Build the kernel with the following configuration.
- 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.
be selected::
CONFIG_EFI=y
CONFIG_EFI_VARS=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
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
add_efi_memmap
include EFI memory map of available physical RAM

45
Documentation/x86/zero-page.rst Normal file
View File

@ -0,0 +1,45 @@
.. SPDX-License-Identifier: GPL-2.0
=========
Zero Page
=========
The additional fields in struct boot_params as a part of 32-bit boot
protocol of kernel. These should be filled by bootloader or 16-bit
real-mode setup code of the kernel. References/settings to it mainly
are in::
arch/x86/include/uapi/asm/bootparam.h
=========== ===== ======================= =================================================
Offset/Size Proto Name Meaning
000/040 ALL screen_info Text mode or frame buffer information
(struct screen_info)
040/014 ALL apm_bios_info APM BIOS information (struct apm_bios_info)
058/008 ALL tboot_addr Physical address of tboot shared page
060/010 ALL ist_info Intel SpeedStep (IST) BIOS support information
(struct ist_info)
080/010 ALL hd0_info hd0 disk parameter, OBSOLETE!!
090/010 ALL hd1_info hd1 disk parameter, OBSOLETE!!
0A0/010 ALL sys_desc_table System description table (struct sys_desc_table),
OBSOLETE!!
0B0/010 ALL olpc_ofw_header OLPC's OpenFirmware CIF and friends
0C0/004 ALL ext_ramdisk_image ramdisk_image high 32bits
0C4/004 ALL ext_ramdisk_size ramdisk_size high 32bits
0C8/004 ALL ext_cmd_line_ptr cmd_line_ptr high 32bits
140/080 ALL edid_info Video mode setup (struct edid_info)
1C0/020 ALL efi_info EFI 32 information (struct efi_info)
1E0/004 ALL alt_mem_k Alternative mem check, in KB
1E4/004 ALL scratch Scratch field for the kernel setup code
1E8/001 ALL e820_entries Number of entries in e820_table (below)
1E9/001 ALL eddbuf_entries Number of entries in eddbuf (below)
1EA/001 ALL edd_mbr_sig_buf_entries Number of entries in edd_mbr_sig_buffer
(below)
1EB/001 ALL kbd_status Numlock is enabled
1EC/001 ALL secure_boot Secure boot is enabled in the firmware
1EF/001 ALL sentinel Used to detect broken bootloaders
290/040 ALL edd_mbr_sig_buffer EDD MBR signatures
2D0/A00 ALL e820_table E820 memory map table
(array of struct e820_entry)
D00/1EC ALL eddbuf EDD data (array of struct edd_info)
=========== ===== ======================= =================================================

40
Documentation/x86/zero-page.txt
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@ -1,40 +0,0 @@
The additional fields in struct boot_params as a part of 32-bit boot
protocol of kernel. These should be filled by bootloader or 16-bit
real-mode setup code of the kernel. References/settings to it mainly
are in:
arch/x86/include/uapi/asm/bootparam.h
Offset Proto Name Meaning
/Size
000/040 ALL screen_info Text mode or frame buffer information
(struct screen_info)
040/014 ALL apm_bios_info APM BIOS information (struct apm_bios_info)
058/008 ALL tboot_addr Physical address of tboot shared page
060/010 ALL ist_info Intel SpeedStep (IST) BIOS support information
(struct ist_info)
080/010 ALL hd0_info hd0 disk parameter, OBSOLETE!!
090/010 ALL hd1_info hd1 disk parameter, OBSOLETE!!
0A0/010 ALL sys_desc_table System description table (struct sys_desc_table),
OBSOLETE!!
0B0/010 ALL olpc_ofw_header OLPC's OpenFirmware CIF and friends
0C0/004 ALL ext_ramdisk_image ramdisk_image high 32bits
0C4/004 ALL ext_ramdisk_size ramdisk_size high 32bits
0C8/004 ALL ext_cmd_line_ptr cmd_line_ptr high 32bits
140/080 ALL edid_info Video mode setup (struct edid_info)
1C0/020 ALL efi_info EFI 32 information (struct efi_info)
1E0/004 ALL alt_mem_k Alternative mem check, in KB
1E4/004 ALL scratch Scratch field for the kernel setup code
1E8/001 ALL e820_entries Number of entries in e820_table (below)
1E9/001 ALL eddbuf_entries Number of entries in eddbuf (below)
1EA/001 ALL edd_mbr_sig_buf_entries Number of entries in edd_mbr_sig_buffer
(below)
1EB/001 ALL kbd_status Numlock is enabled
1EC/001 ALL secure_boot Secure boot is enabled in the firmware
1EF/001 ALL sentinel Used to detect broken bootloaders
290/040 ALL edd_mbr_sig_buffer EDD MBR signatures
2D0/A00 ALL e820_table E820 memory map table
(array of struct e820_entry)
D00/1EC ALL eddbuf EDD data (array of struct edd_info)