Commit graph

408 commits

Author SHA1 Message Date
Linus Torvalds
1654e95ee3 - Add the model number of a new, Raptor Lake CPU, to intel-family.h
- Do not log spurious corrected MCEs on SKL too, due to an erratum
 
 - Clarify the path of paravirt ops patches upstream
 
 - Add an optimization to avoid writing out AMX components to sigframes
 when former are in init state
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Merge tag 'x86_urgent_for_v5.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Borislav Petkov:

 - Add the model number of a new, Raptor Lake CPU, to intel-family.h

 - Do not log spurious corrected MCEs on SKL too, due to an erratum

 - Clarify the path of paravirt ops patches upstream

 - Add an optimization to avoid writing out AMX components to sigframes
   when former are in init state

* tag 'x86_urgent_for_v5.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/cpu: Add Raptor Lake to Intel family
  x86/mce: Add errata workaround for Skylake SKX37
  MAINTAINERS: Add some information to PARAVIRT_OPS entry
  x86/fpu: Optimize out sigframe xfeatures when in init state
2021-11-14 09:29:03 -08:00
Linus Torvalds
95faf6ba65 Driver core changes for 5.16-rc1
Here is the big set of driver core changes for 5.16-rc1.
 
 All of these have been in linux-next for a while now with no reported
 problems.
 
 Included in here are:
 	- big update and cleanup of the sysfs abi documentation files
 	  and scripts from Mauro.  We are almost at the place where we
 	  can properly check that the running kernel's sysfs abi is
 	  documented fully.
 	- firmware loader updates
 	- dyndbg updates
 	- kernfs cleanups and fixes from Christoph
 	- device property updates
 	- component fix
 	- other minor driver core cleanups and fixes
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'driver-core-5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core updates from Greg KH:
 "Here is the big set of driver core changes for 5.16-rc1.

  All of these have been in linux-next for a while now with no reported
  problems.

  Included in here are:

   - big update and cleanup of the sysfs abi documentation files and
     scripts from Mauro. We are almost at the place where we can
     properly check that the running kernel's sysfs abi is documented
     fully.

   - firmware loader updates

   - dyndbg updates

   - kernfs cleanups and fixes from Christoph

   - device property updates

   - component fix

   - other minor driver core cleanups and fixes"

* tag 'driver-core-5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (122 commits)
  device property: Drop redundant NULL checks
  x86/build: Tuck away built-in firmware under FW_LOADER
  vmlinux.lds.h: wrap built-in firmware support under FW_LOADER
  firmware_loader: move struct builtin_fw to the only place used
  x86/microcode: Use the firmware_loader built-in API
  firmware_loader: remove old DECLARE_BUILTIN_FIRMWARE()
  firmware_loader: formalize built-in firmware API
  component: do not leave master devres group open after bind
  dyndbg: refine verbosity 1-4 summary-detail
  gpiolib: acpi: Replace custom code with device_match_acpi_handle()
  i2c: acpi: Replace custom function with device_match_acpi_handle()
  driver core: Provide device_match_acpi_handle() helper
  dyndbg: fix spurious vNpr_info change
  dyndbg: no vpr-info on empty queries
  dyndbg: vpr-info on remove-module complete, not starting
  device property: Add missed header in fwnode.h
  Documentation: dyndbg: Improve cli param examples
  dyndbg: Remove support for ddebug_query param
  dyndbg: make dyndbg a known cli param
  dyndbg: show module in vpr-info in dd-exec-queries
  ...
2021-11-04 08:32:38 -07:00
Dave Hansen
30d02551ba x86/fpu: Optimize out sigframe xfeatures when in init state
tl;dr: AMX state is ~8k.  Signal frames can have space for this
~8k and each signal entry writes out all 8k even if it is zeros.
Skip writing zeros for AMX to speed up signal delivery by about
4% overall when AMX is in its init state.

This is a user-visible change to the sigframe ABI.

== Hardware XSAVE Background ==

XSAVE state components may be tracked by the processor as being
in their initial configuration.  Software can detect which
features are in this configuration by looking at the XSTATE_BV
field in an XSAVE buffer or with the XGETBV(1) instruction.

Both the XSAVE and XSAVEOPT instructions enumerate features s
being in the initial configuration via the XSTATE_BV field in the
XSAVE header,  However, XSAVEOPT declines to actually write
features in their initial configuration to the buffer.  XSAVE
writes the feature unconditionally, regardless of whether it is
in the initial configuration or not.

Basically, XSAVE users never need to inspect XSTATE_BV to
determine if the feature has been written to the buffer.
XSAVEOPT users *do* need to inspect XSTATE_BV.  They might also
need to clear out the buffer if they want to make an isolated
change to the state, like modifying one register.

== Software Signal / XSAVE Background ==

Signal frames have historically been written with XSAVE itself.
Each state is written in its entirety, regardless of being in its
initial configuration.

In other words, the signal frame ABI uses the XSAVE behavior, not
the XSAVEOPT behavior.

== Problem ==

This means that any application which has acquired permission to
use AMX via ARCH_REQ_XCOMP_PERM will write 8k of state to the
signal frame.  This 8k write will occur even when AMX was in its
initial configuration and software *knows* this because of
XSTATE_BV.

This problem also exists to a lesser degree with AVX-512 and its
2k of state.  However, AVX-512 use does not require
ARCH_REQ_XCOMP_PERM and is more likely to have existing users
which would be impacted by any change in behavior.

== Solution ==

Stop writing out AMX xfeatures which are in their initial state
to the signal frame.  This effectively makes the signal frame
XSAVE buffer look as if it were written with a combination of
XSAVEOPT and XSAVE behavior.  Userspace which handles XSAVEOPT-
style buffers should be able to handle this naturally.

For now, include only the AMX xfeatures: XTILE and XTILEDATA in
this new behavior.  These require new ABI to use anyway, which
makes their users very unlikely to be broken.  This XSAVEOPT-like
behavior should be expected for all future dynamic xfeatures.  It
may also be extended to legacy features like AVX-512 in the
future.

Only attempt this optimization on systems with dynamic features.
Disable dynamic feature support (XFD) if XGETBV1 is unavailable
by adding a CPUID dependency.

This has been measured to reduce the *overall* cycle cost of
signal delivery by about 4%.

Fixes: 2308ee57d9 ("x86/fpu/amx: Enable the AMX feature in 64-bit mode")
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: "Chang S. Bae" <chang.seok.bae@intel.com>
Link: https://lore.kernel.org/r/20211102224750.FA412E26@davehans-spike.ostc.intel.com
2021-11-03 22:42:35 +01:00
Linus Torvalds
624ad333d4 This is a relatively unexciting cycle for documentation.
- Some small scripts/kerneldoc fixes
 
  - More Chinese translation work, but at a much reduced rate.
 
  - The tip-tree maintainer's handbook
 
 ...plus the usual array of build fixes, typo fixes, etc.
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Merge tag 'docs-5.16' of git://git.lwn.net/linux

Pull documentation updates from Jonathan Corbet:
 "This is a relatively unexciting cycle for documentation.

   - Some small scripts/kerneldoc fixes

   - More Chinese translation work, but at a much reduced rate.

   - The tip-tree maintainer's handbook

  ...plus the usual array of build fixes, typo fixes, etc"

* tag 'docs-5.16' of git://git.lwn.net/linux: (53 commits)
  kernel-doc: support DECLARE_PHY_INTERFACE_MASK()
  docs/zh_CN: add core-api xarray translation
  docs/zh_CN: add core-api assoc_array translation
  speakup: Fix typo in documentation "boo" -> "boot"
  docs: submitting-patches: make section about the Link: tag more explicit
  docs: deprecated.rst: Clarify open-coded arithmetic with literals
  scripts: documentation-file-ref-check: fix bpf selftests path
  scripts: documentation-file-ref-check: ignore hidden files
  coding-style.rst: trivial: fix location of driver model macros
  docs: f2fs: fix text alignment
  docs/zh_CN add PCI pci.rst translation
  docs/zh_CN add PCI index.rst translation
  docs: translations: zh_CN: memory-hotplug.rst: fix a typo
  docs: translations: zn_CN: irq-affinity.rst: add a missing extension
  block: add documentation for inflight
  scripts: kernel-doc: Ignore __alloc_size() attribute
  docs: pdfdocs: Adjust \headheight for fancyhdr
  docs: UML: user_mode_linux_howto_v2 edits
  docs: use the lore redirector everywhere
  docs: proc.rst: mountinfo: align columns
  ...
2021-11-02 22:11:39 -07:00
Linus Torvalds
879dbe9ffe Add a SGX_IOC_VEPC_REMOVE ioctl to the /dev/sgx_vepc virt interface with
which EPC pages can be put back into their uninitialized state without
 having to reopen /dev/sgx_vepc, which could not be possible anymore
 after startup due to security policies.
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Merge tag 'x86_sgx_for_v5.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 SGX updates from Borislav Petkov:
 "Add a SGX_IOC_VEPC_REMOVE ioctl to the /dev/sgx_vepc virt interface
  with which EPC pages can be put back into their uninitialized state
  without having to reopen /dev/sgx_vepc, which could not be possible
  anymore after startup due to security policies"

* tag 'x86_sgx_for_v5.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/sgx/virt: implement SGX_IOC_VEPC_REMOVE ioctl
  x86/sgx/virt: extract sgx_vepc_remove_page
2021-11-01 15:54:07 -07:00
Chang S. Bae
d7a9590f60 Documentation/x86: Add documentation for using dynamic XSTATE features
Explain how dynamic XSTATE features can be enabled via the
architecture-specific prctl() along with dynamic sigframe size and
first use trap handling.

Fix:

Documentation/x86/xstate.rst:15: WARNING: Title underline too short.

as reported by Stephen Rothwell <sfr@canb.auug.org.au>

Originally-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211026091157.16711-1-chang.seok.bae@intel.com
2021-10-28 14:54:58 +02:00
Paolo Bonzini
ae095b16fc x86/sgx/virt: implement SGX_IOC_VEPC_REMOVE ioctl
For bare-metal SGX on real hardware, the hardware provides guarantees
SGX state at reboot.  For instance, all pages start out uninitialized.
The vepc driver provides a similar guarantee today for freshly-opened
vepc instances, but guests such as Windows expect all pages to be in
uninitialized state on startup, including after every guest reboot.

Some userspace implementations of virtual SGX would rather avoid having
to close and reopen the /dev/sgx_vepc file descriptor and re-mmap the
virtual EPC.  For example, they could sandbox themselves after the guest
starts and forbid further calls to open(), in order to mitigate exploits
from untrusted guests.

Therefore, add a ioctl that does this with EREMOVE.  Userspace can
invoke the ioctl to bring its vEPC pages back to uninitialized state.
There is a possibility that some pages fail to be removed if they are
SECS pages, and the child and SECS pages could be in separate vEPC
regions.  Therefore, the ioctl returns the number of EREMOVE failures,
telling userspace to try the ioctl again after it's done with all
vEPC regions.  A more verbose description of the correct usage and
the possible error conditions is documented in sgx.rst.

Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/20211021201155.1523989-3-pbonzini@redhat.com
2021-10-22 08:32:12 -07:00
Thorsten Leemhuis
a9d85efb25 docs: use the lore redirector everywhere
Change all links from using the lkml redirector to the lore redirector,
as the kernel.org admin recently indicated: we shouldn't be using
lkml.kernel.org anymore because the domain can create confusion, as it
indicates it is only valid for messages sent to the LKML; the convention
has been to use https://lore.kernel.org/r/msgid for this reason.

In this process also change three links from using http to https.

Link: https://lore.kernel.org/r/20211006170025.qw3glxvocczfuhar@meerkat.local
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ingo Molnar <mingo@redhat.com>
CC: Borislav Petkov <bp@alien8.de>
CC: Hu Haowen <src.res@email.cn>
CC: Alex Shi <alexs@kernel.org>
CC: Federico Vaga <federico.vaga@vaga.pv.it>
Signed-off-by: Thorsten Leemhuis <linux@leemhuis.info>
Reviewed-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
Link: https://lore.kernel.org/r/5bb55bac6ba10fafab19bf2b21572dd0e2f8cea2.1633593385.git.linux@leemhuis.info
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2021-10-12 13:58:19 -06:00
Mauro Carvalho Chehab
edfc8730ba ABI: sysfs-mce: add a new ABI file
Reduce the gap of missing ABIs for Intel servers with MCE
by adding a new ABI file.

The contents of this file comes from:
	Documentation/x86/x86_64/machinecheck.rst

Reviewed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/801a26985e32589eb78ba4b728d3e19fdea18f04.1632994837.git.mchehab+huawei@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-10-05 16:24:15 +02:00
Linus Torvalds
0f4b9289ba Another collection of documentation patches, mostly fixes but also includes
another set of traditional Chinese translations.
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Merge tag 'docs-5.15-2' of git://git.lwn.net/linux

Pull more documentation updates from Jonathan Corbet:
 "Another collection of documentation patches, mostly fixes but also
  includes another set of traditional Chinese translations"

* tag 'docs-5.15-2' of git://git.lwn.net/linux:
  docs: pdfdocs: Fix typo in CJK-language specific font settings
  docs: kernel-hacking: Remove inappropriate text
  docs/zh_TW: add translations for zh_TW/filesystems
  docs/zh_TW: add translations for zh_TW/cpu-freq
  docs/zh_TW: add translations for zh_TW/arm64
  docs/zh_CN: Modify the translator tag and fix the wrong word
  Documentation/features/vm: correct huge-vmap APIs
  Documentation: block: blk-mq: Fix small typo in multi-queue docs
  Documentation: in_irq() cleanup
  Documentation: arm: marvell: Add 88F6825 model into list
  Documentation/process/maintainer-pgp-guide: Replace broken link to PGP path finder
  Documentation: locking: fix references
  Documentation: Update details of The Linux Kernel Module Programming Guide
  docs: x86: Remove obsolete information about x86_64 vmalloc() faulting
  Documentation/process/applying-patches: Activate linux-next man hyperlink
2021-09-08 16:28:14 -07:00
Peilin Ye
251a7b3edc docs: x86: Remove obsolete information about x86_64 vmalloc() faulting
x86_64 vmalloc() mappings are no longer "synchronized" among page tables
via faulting since commit 6eb82f9940 ("x86/mm: Pre-allocate P4D/PUD
pages for vmalloc area"), since the corresponding P4D or PUD pages are
now preallocated at boot, by preallocate_vmalloc_pages().  Drop the
"lazily synchronized" description for less confusion.

While this file is x86_64-specific, it is worth noting that things are
different for x86_32, where vmalloc()-related changes to `init_mm.pgd` are
synchronized to all page tables in the system during runtime, via
arch_sync_kernel_mappings().  Unfortunately, this synchronization is
subject to race condition, which is further handled via faulting, see
vmalloc_fault().  See commit 4819e15f74 ("x86/mm/32: Bring back vmalloc
faulting on x86_32") for more details.

Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20210818220123.2623-1-yepeilin.cs@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2021-08-20 11:14:11 -06:00
Paul Gortmaker
12febc1818 x86/reboot: Document how to override DMI platform quirks
commit 5955633e91 ("x86/reboot: Skip DMI checks if reboot set by user")
made it so that it's not required to recompile the kernel in order to
bypass broken reboot quirks compiled into an image:

 * This variable is used privately to keep track of whether or not
 * reboot_type is still set to its default value (i.e., reboot= hasn't
 * been set on the command line).  This is needed so that we can
 * suppress DMI scanning for reboot quirks.  Without it, it's
 * impossible to override a faulty reboot quirk without recompiling.

However, at the time it was not eally documented outside the source code,
and so this information isn't really available to the average user out
there.

The change is a little white lie and invented "reboot=default" since it is
easy to remember, and documents well.  The truth is that any random string
that is *not* a currently accepted string will work.

Since that doesn't document well for non-coders, and since it's unknown
what the future additions might be, lay claim on "default" since that is
exactly what it achieves.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210530162447.996461-3-paul.gortmaker@windriver.com
2021-08-12 12:06:58 +02:00
Paul Gortmaker
162a5284fa x86/reboot: Document the "reboot=pci" option
It is mentioned in the top level non-arch specific file but it was
overlooked here for x86.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210530162447.996461-2-paul.gortmaker@windriver.com
2021-08-12 12:06:58 +02:00
Linus Torvalds
1423e2660c Fixes and improvements for FPU handling on x86:
- Prevent sigaltstack out of bounds writes. The kernel unconditionally
     writes the FPU state to the alternate stack without checking whether
     the stack is large enough to accomodate it.
 
     Check the alternate stack size before doing so and in case it's too
     small force a SIGSEGV instead of silently corrupting user space data.
 
   - MINSIGSTKZ and SIGSTKSZ are constants in signal.h and have never been
     updated despite the fact that the FPU state which is stored on the
     signal stack has grown over time which causes trouble in the field
     when AVX512 is available on a CPU. The kernel does not expose the
     minimum requirements for the alternate stack size depending on the
     available and enabled CPU features.
 
     ARM already added an aux vector AT_MINSIGSTKSZ for the same reason.
     Add it to x86 as well
 
   - A major cleanup of the x86 FPU code. The recent discoveries of XSTATE
     related issues unearthed quite some inconsistencies, duplicated code
     and other issues.
 
     The fine granular overhaul addresses this, makes the code more robust
     and maintainable, which allows to integrate upcoming XSTATE related
     features in sane ways.
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Merge tag 'x86-fpu-2021-07-07' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fpu updates from Thomas Gleixner:
 "Fixes and improvements for FPU handling on x86:

   - Prevent sigaltstack out of bounds writes.

     The kernel unconditionally writes the FPU state to the alternate
     stack without checking whether the stack is large enough to
     accomodate it.

     Check the alternate stack size before doing so and in case it's too
     small force a SIGSEGV instead of silently corrupting user space
     data.

   - MINSIGSTKZ and SIGSTKSZ are constants in signal.h and have never
     been updated despite the fact that the FPU state which is stored on
     the signal stack has grown over time which causes trouble in the
     field when AVX512 is available on a CPU. The kernel does not expose
     the minimum requirements for the alternate stack size depending on
     the available and enabled CPU features.

     ARM already added an aux vector AT_MINSIGSTKSZ for the same reason.
     Add it to x86 as well.

   - A major cleanup of the x86 FPU code. The recent discoveries of
     XSTATE related issues unearthed quite some inconsistencies,
     duplicated code and other issues.

     The fine granular overhaul addresses this, makes the code more
     robust and maintainable, which allows to integrate upcoming XSTATE
     related features in sane ways"

* tag 'x86-fpu-2021-07-07' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (74 commits)
  x86/fpu/xstate: Clear xstate header in copy_xstate_to_uabi_buf() again
  x86/fpu/signal: Let xrstor handle the features to init
  x86/fpu/signal: Handle #PF in the direct restore path
  x86/fpu: Return proper error codes from user access functions
  x86/fpu/signal: Split out the direct restore code
  x86/fpu/signal: Sanitize copy_user_to_fpregs_zeroing()
  x86/fpu/signal: Sanitize the xstate check on sigframe
  x86/fpu/signal: Remove the legacy alignment check
  x86/fpu/signal: Move initial checks into fpu__restore_sig()
  x86/fpu: Mark init_fpstate __ro_after_init
  x86/pkru: Remove xstate fiddling from write_pkru()
  x86/fpu: Don't store PKRU in xstate in fpu_reset_fpstate()
  x86/fpu: Remove PKRU handling from switch_fpu_finish()
  x86/fpu: Mask PKRU from kernel XRSTOR[S] operations
  x86/fpu: Hook up PKRU into ptrace()
  x86/fpu: Add PKRU storage outside of task XSAVE buffer
  x86/fpu: Dont restore PKRU in fpregs_restore_userspace()
  x86/fpu: Rename xfeatures_mask_user() to xfeatures_mask_uabi()
  x86/fpu: Move FXSAVE_LEAK quirk info __copy_kernel_to_fpregs()
  x86/fpu: Rename __fpregs_load_activate() to fpregs_restore_userregs()
  ...
2021-07-07 11:12:01 -07:00
Linus Torvalds
233a806b00 This was a reasonably active cycle for documentation; this pull includes:
- Some kernel-doc cleanups.  That script is still regex onslaught from
    hell, but it has gotten a little better.
 
  - Improvements to the checkpatch docs, which are also used by the tool
    itself.
 
  - A major update to the pathname lookup documentation.
 
  - Elimination of :doc: markup, since our automarkup magic can create
    references from filenames without all the extra noise.
 
  - The flurry of Chinese translation activity continues.
 
 Plus, of course, the usual collection of updates, typo fixes, and warning
 fixes.
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Merge tag 'docs-5.14' of git://git.lwn.net/linux

Pull documentation updates from Jonathan Corbet:
 "This was a reasonably active cycle for documentation; this includes:

   - Some kernel-doc cleanups. That script is still regex onslaught from
     hell, but it has gotten a little better.

   - Improvements to the checkpatch docs, which are also used by the
     tool itself.

   - A major update to the pathname lookup documentation.

   - Elimination of :doc: markup, since our automarkup magic can create
     references from filenames without all the extra noise.

   - The flurry of Chinese translation activity continues.

  Plus, of course, the usual collection of updates, typo fixes, and
  warning fixes"

* tag 'docs-5.14' of git://git.lwn.net/linux: (115 commits)
  docs: path-lookup: use bare function() rather than literals
  docs: path-lookup: update symlink description
  docs: path-lookup: update get_link() ->follow_link description
  docs: path-lookup: update WALK_GET, WALK_PUT desc
  docs: path-lookup: no get_link()
  docs: path-lookup: update i_op->put_link and cookie description
  docs: path-lookup: i_op->follow_link replaced with i_op->get_link
  docs: path-lookup: Add macro name to symlink limit description
  docs: path-lookup: remove filename_mountpoint
  docs: path-lookup: update do_last() part
  docs: path-lookup: update path_mountpoint() part
  docs: path-lookup: update path_to_nameidata() part
  docs: path-lookup: update follow_managed() part
  docs: Makefile: Use CONFIG_SHELL not SHELL
  docs: Take a little noise out of the build process
  docs: x86: avoid using ReST :doc:`foo` markup
  docs: virt: kvm: s390-pv-boot.rst: avoid using ReST :doc:`foo` markup
  docs: userspace-api: landlock.rst: avoid using ReST :doc:`foo` markup
  docs: trace: ftrace.rst: avoid using ReST :doc:`foo` markup
  docs: trace: coresight: coresight.rst: avoid using ReST :doc:`foo` markup
  ...
2021-06-28 16:53:05 -07:00
Linus Torvalds
1b1cf8fe99 Changes in this cycle were:
- Add the "ratelimit:N" parameter to the split_lock_detect= boot option,
    to rate-limit the generation of bus-lock exceptions. This is both
    easier on system resources and kinder to offending applications than
    the current policy of outright killing them.
 
  - Document the split-lock detection feature and its parameters.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-splitlock-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 splitlock updates from Ingo Molnar:

 - Add the "ratelimit:N" parameter to the split_lock_detect= boot
   option, to rate-limit the generation of bus-lock exceptions.

   This is both easier on system resources and kinder to offending
   applications than the current policy of outright killing them.

 - Document the split-lock detection feature and its parameters.

* tag 'x86-splitlock-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Documentation/x86: Add ratelimit in buslock.rst
  Documentation/admin-guide: Add bus lock ratelimit
  x86/bus_lock: Set rate limit for bus lock
  Documentation/x86: Add buslock.rst
2021-06-28 13:30:02 -07:00
Mauro Carvalho Chehab
0ffd643875 docs: x86: avoid using ReST :doc:foo markup
The :doc:`foo` tag is auto-generated via automarkup.py.
So, use the filename at the sources, instead of :doc:`foo`.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/17c68b5f1d72488431c77c1de9f13683fe9f536c.1623824363.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2021-06-17 13:24:39 -06:00
Hubert Jasudowicz
0e5a89dbb4 doc: Remove references to IBM Calgary
The Calgary IOMMU driver has been removed in

  90dc392fc4 ("x86: Remove the calgary IOMMU driver")

Clean up stale docs that refer to it.

Signed-off-by: Hubert Jasudowicz <hubert.jasudowicz@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/1bd2b57dd1db53df09e520b8170ff61418805de4.1623274832.git.hubert.jasudowicz@gmail.com
2021-06-10 18:19:36 +02:00
Chang S. Bae
1c33bb0507 x86/elf: Support a new ELF aux vector AT_MINSIGSTKSZ
Historically, signal.h defines MINSIGSTKSZ (2KB) and SIGSTKSZ (8KB), for
use by all architectures with sigaltstack(2). Over time, the hardware state
size grew, but these constants did not evolve. Today, literal use of these
constants on several architectures may result in signal stack overflow, and
thus user data corruption.

A few years ago, the ARM team addressed this issue by establishing
getauxval(AT_MINSIGSTKSZ). This enables the kernel to supply a value
at runtime that is an appropriate replacement on current and future
hardware.

Add getauxval(AT_MINSIGSTKSZ) support to x86, analogous to the support
added for ARM in

  94b07c1f8c ("arm64: signal: Report signal frame size to userspace via auxv").

Also, include a documentation to describe x86-specific auxiliary vectors.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Len Brown <len.brown@intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20210518200320.17239-4-chang.seok.bae@intel.com
2021-05-19 12:18:45 +02:00
Fenghua Yu
d28397eaf4 Documentation/x86: Add ratelimit in buslock.rst
ratelimit is a new command line option for bus lock handling. Add proper
documentation.

[ tglx: Massaged documentation ]

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20210419214958.4035512-5-fenghua.yu@intel.com
2021-05-18 16:39:31 +02:00
Fenghua Yu
1897907cca Documentation/x86: Add buslock.rst
Add buslock.rst to explain bus lock problem and how to detect and
handle it.

[ tglx: Included it into index.rst and added the missing include ... ]

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20210419214958.4035512-2-fenghua.yu@intel.com
2021-05-18 16:39:31 +02:00
Brijesh Singh
059e5c321a x86/msr: Rename MSR_K8_SYSCFG to MSR_AMD64_SYSCFG
The SYSCFG MSR continued being updated beyond the K8 family; drop the K8
name from it.

Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Joerg Roedel <jroedel@suse.de>
Link: https://lkml.kernel.org/r/20210427111636.1207-4-brijesh.singh@amd.com
2021-05-10 07:51:38 +02:00
Linus Torvalds
a3f53e8adf A few late-arriving documentation fixes, including some oprofile cleanup, a
kernel-doc fix, some regression-reporting updates, and the usual minor
 fixes.
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Merge tag 'docs-5.13-2' of git://git.lwn.net/linux

Pull documentation fixes from Jonathan Corbet:
 "A few late-arriving documentation fixes, including some oprofile
  cleanup, a kernel-doc fix, some regression-reporting updates, and the
  usual minor fixes"

* tag 'docs-5.13-2' of git://git.lwn.net/linux:
  Enlisted oprofile version line removed
  oprofiled version output line removed from the list
  Removed the oprofiled version option
  docs: reporting-issues.rst: CC subsystem and maintainers on regressions
  docs: correct URL to bios and kernel developer's guide
  docs/core-api: Consistent code style
  docs/zh_CN: Adjust order and content of zh_CN/index.rst
  Documentation: input: joydev file corrections
  docs: Fix typo in Documentation/x86/x86_64/5level-paging.rst
  kernel-doc: Add support for __deprecated
2021-05-06 08:33:54 -07:00
bilbao@vt.edu
6a79162fe5 docs: Fix typo in Documentation/x86/x86_64/5level-paging.rst
fix two typos in the documentation
(Documentation/x86/x86_64/5level-paging.rst), changing 'paing' for 'paging'
and using the right verbal form for plural on 'some vendors offer'.

Signed-off-by: Carlos Bilbao <bilbao@vt.edu>
Link: https://lore.kernel.org/r/2599991.mvXUDI8C0e@iron-maiden
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2021-04-27 13:03:30 -06:00
Sean Christopherson
540745ddbc x86/sgx: Introduce virtual EPC for use by KVM guests
Add a misc device /dev/sgx_vepc to allow userspace to allocate "raw"
Enclave Page Cache (EPC) without an associated enclave. The intended
and only known use case for raw EPC allocation is to expose EPC to a
KVM guest, hence the 'vepc' moniker, virt.{c,h} files and X86_SGX_KVM
Kconfig.

The SGX driver uses the misc device /dev/sgx_enclave to support
userspace in creating an enclave. Each file descriptor returned from
opening /dev/sgx_enclave represents an enclave. Unlike the SGX driver,
KVM doesn't control how the guest uses the EPC, therefore EPC allocated
to a KVM guest is not associated with an enclave, and /dev/sgx_enclave
is not suitable for allocating EPC for a KVM guest.

Having separate device nodes for the SGX driver and KVM virtual EPC also
allows separate permission control for running host SGX enclaves and KVM
SGX guests.

To use /dev/sgx_vepc to allocate a virtual EPC instance with particular
size, the hypervisor opens /dev/sgx_vepc, and uses mmap() with the
intended size to get an address range of virtual EPC. Then it may use
the address range to create one KVM memory slot as virtual EPC for
a guest.

Implement the "raw" EPC allocation in the x86 core-SGX subsystem via
/dev/sgx_vepc rather than in KVM. Doing so has two major advantages:

  - Does not require changes to KVM's uAPI, e.g. EPC gets handled as
    just another memory backend for guests.

  - EPC management is wholly contained in the SGX subsystem, e.g. SGX
    does not have to export any symbols, changes to reclaim flows don't
    need to be routed through KVM, SGX's dirty laundry doesn't have to
    get aired out for the world to see, and so on and so forth.

The virtual EPC pages allocated to guests are currently not reclaimable.
Reclaiming an EPC page used by enclave requires a special reclaim
mechanism separate from normal page reclaim, and that mechanism is not
supported for virutal EPC pages. Due to the complications of handling
reclaim conflicts between guest and host, reclaiming virtual EPC pages
is significantly more complex than basic support for SGX virtualization.

 [ bp:
   - Massage commit message and comments
   - use cpu_feature_enabled()
   - vertically align struct members init
   - massage Virtual EPC clarification text
   - move Kconfig prompt to Virtualization ]

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Co-developed-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lkml.kernel.org/r/0c38ced8c8e5a69872db4d6a1c0dabd01e07cad7.1616136308.git.kai.huang@intel.com
2021-04-06 09:43:17 +02:00
Kai Huang
b0c7459be0 x86/sgx: Wipe out EREMOVE from sgx_free_epc_page()
EREMOVE takes a page and removes any association between that page and
an enclave. It must be run on a page before it can be added into another
enclave. Currently, EREMOVE is run as part of pages being freed into the
SGX page allocator. It is not expected to fail, as it would indicate a
use-after-free of EPC pages. Rather than add the page back to the pool
of available EPC pages, the kernel intentionally leaks the page to avoid
additional errors in the future.

However, KVM does not track how guest pages are used, which means that
SGX virtualization use of EREMOVE might fail. Specifically, it is
legitimate that EREMOVE returns SGX_CHILD_PRESENT for EPC assigned to
KVM guest, because KVM/kernel doesn't track SECS pages.

To allow SGX/KVM to introduce a more permissive EREMOVE helper and
to let the SGX virtualization code use the allocator directly, break
out the EREMOVE call from the SGX page allocator. Rename the original
sgx_free_epc_page() to sgx_encl_free_epc_page(), indicating that
it is used to free an EPC page assigned to a host enclave. Replace
sgx_free_epc_page() with sgx_encl_free_epc_page() in all call sites so
there's no functional change.

At the same time, improve the error message when EREMOVE fails, and
add documentation to explain to the user what that failure means and
to suggest to the user what to do when this bug happens in the case it
happens.

 [ bp: Massage commit message, fix typos and sanitize text, simplify. ]

Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lkml.kernel.org/r/20210325093057.122834-1-kai.huang@intel.com
2021-03-26 22:51:23 +01:00
Cao jin
bcadb65fd6 Documentation/x86/boot.rst: Correct the example of SETUP_INDIRECT
struct setup_data.len is the length of data field. In case of
SETUP_INDIRECT, it should be sizeof(setup_indirect).

Signed-off-by: Cao jin <jojing64@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Link: https://lore.kernel.org/r/20210127084911.63438-1-jojing64@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2021-01-28 15:25:31 -07:00
Linus Torvalds
ff6135959a A much quieter cycle for documentation (happily), with, one hopes, the bulk
of the churn behind us.  Significant stuff in this pull includes:
 
  - A set of new Chinese translations
  - Italian translation updates
  - A mechanism from Mauro to automatically format Documentation/features
    for the built docs
  - Automatic cross references without explicit :ref: markup
  - A new reset-controller document
  - An extensive new document on reporting problems from Thorsten
 
 That last patch also adds the CC-BY-4.0 license to LICENSES/dual; there was
 some discussion on this, but we seem to have consensus and an ack from Greg
 for that addition.
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Merge tag 'docs-5.11' of git://git.lwn.net/linux

Pull documentation updates from Jonathan Corbet:
 "A much quieter cycle for documentation (happily), with, one hopes, the
  bulk of the churn behind us. Significant stuff in this pull includes:

   - A set of new Chinese translations

   - Italian translation updates

   - A mechanism from Mauro to automatically format
     Documentation/features for the built docs

   - Automatic cross references without explicit :ref: markup

   - A new reset-controller document

   - An extensive new document on reporting problems from Thorsten

  That last patch also adds the CC-BY-4.0 license to LICENSES/dual;
  there was some discussion on this, but we seem to have consensus and
  an ack from Greg for that addition"

* tag 'docs-5.11' of git://git.lwn.net/linux: (50 commits)
  docs: fix broken cross reference in translations/zh_CN
  docs: Note that sphinx 1.7 will be required soon
  docs: update requirements to install six module
  docs: reporting-issues: move 'outdated, need help' note to proper place
  docs: Update documentation to reflect what TAINT_CPU_OUT_OF_SPEC means
  docs: add a reset controller chapter to the driver API docs
  docs: make reporting-bugs.rst obsolete
  docs: Add a new text describing how to report bugs
  LICENSES: Add the CC-BY-4.0 license
  Documentation: fix multiple typos found in the admin-guide subdirectory
  Documentation: fix typos found in admin-guide subdirectory
  kernel-doc: Fix example in Nested structs/unions
  docs: clean up sysctl/kernel: titles, version
  docs: trace: fix event state structure name
  docs: nios2: add missing ReST file
  scripts: get_feat.pl: reduce table width for all features output
  scripts: get_feat.pl: change the group by order
  scripts: get_feat.pl: make complete table more coincise
  scripts: kernel-doc: fix parsing function-like typedefs
  Documentation: fix typos found in process, dev-tools, and doc-guide subdirectories
  ...
2020-12-14 16:55:54 -08:00
Linus Torvalds
8ba27ae36b - Add logic to correct MBM total and local values fixing errata SKX99 and BDF102
(Fenghua Yu)
 
 - Cleanups.
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Merge tag 'x86_cache_for_v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 cache resource control updates from Borislav Petkov:

 - add logic to correct MBM total and local values fixing errata SKX99
   and BDF102 (Fenghua Yu)

 - cleanups

* tag 'x86_cache_for_v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/resctrl: Clean up unused function parameter in rmdir path
  x86/resctrl: Constify kernfs_ops
  x86/resctrl: Correct MBM total and local values
  Documentation/x86: Rename resctrl_ui.rst and add two errata to the file
2020-12-14 13:53:17 -08:00
Linus Torvalds
0d712978dc - Save the AMD's physical die ID into cpuinfo_x86.cpu_die_id and convert all
code to use it (Yazen Ghannam)
 
 - Remove a dead and unused TSEG region remapping workaround on AMD (Arvind Sankar)
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Merge tag 'x86_cpu_for_v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 cpuid updates from Borislav Petkov:
 "Only AMD-specific changes this time:

   - Save the AMD physical die ID into cpuinfo_x86.cpu_die_id and
     convert all code to use it (Yazen Ghannam)

   - Remove a dead and unused TSEG region remapping workaround on AMD
     (Arvind Sankar)"

* tag 'x86_cpu_for_v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/cpu/amd: Remove dead code for TSEG region remapping
  x86/topology: Set cpu_die_id only if DIE_TYPE found
  EDAC/mce_amd: Use struct cpuinfo_x86.cpu_die_id for AMD NodeId
  x86/CPU/AMD: Remove amd_get_nb_id()
  x86/CPU/AMD: Save AMD NodeId as cpu_die_id
2020-12-14 13:21:33 -08:00
Mauro Carvalho Chehab
ed13a92d0f docs: archis: add a per-architecture features list
Add a feature list matrix for each architecture to their
respective Kernel books.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/9c39d4dd93e05c0008205527d2c3450912f029ed.1606748711.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-12-03 15:10:15 -07:00
Yazen Ghannam
028c221ed1 x86/CPU/AMD: Save AMD NodeId as cpu_die_id
AMD systems provide a "NodeId" value that represents a global ID
indicating to which "Node" a logical CPU belongs. The "Node" is a
physical structure equivalent to a Die, and it should not be confused
with logical structures like NUMA nodes. Logical nodes can be adjusted
based on firmware or other settings whereas the physical nodes/dies are
fixed based on hardware topology.

The NodeId value can be used when a physical ID is needed by software.

Save the AMD NodeId to struct cpuinfo_x86.cpu_die_id. Use the value
from CPUID or MSR as appropriate. Default to phys_proc_id otherwise.
Do so for both AMD and Hygon systems.

Drop the node_id parameter from cacheinfo_*_init_llc_id() as it is no
longer needed.

Update the x86 topology documentation.

Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20201109210659.754018-2-Yazen.Ghannam@amd.com
2020-11-19 11:43:13 +01:00
Jarkko Sakkinen
3fa97bf001 Documentation/x86: Document SGX kernel architecture
Document the Intel SGX kernel architecture. The fine-grained architecture
details can be looked up from Intel SDM Volume 3D.

Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Jethro Beekman <jethro@fortanix.com>
Cc: linux-doc@vger.kernel.org
Link: https://lkml.kernel.org/r/20201112220135.165028-24-jarkko@kernel.org
2020-11-18 18:16:13 +01:00
Fenghua Yu
d1b22e36e3 Documentation/x86: Rename resctrl_ui.rst and add two errata to the file
Intel Memory Bandwidth Monitoring (MBM) counters may report system
memory bandwidth incorrectly on some Intel processors. This is reported
in documented in erratum SKX99, erratum BDF102 and in the RDT reference
manual, see Documentation/x86/index.rst.

To work around the errata, MBM total and local readings are corrected
using a correction factor table.

Since the correction factor table is not publicly documented anywhere,
document the table and the errata in Documentation/x86/resctrl.rst for
future reference.

 [ bp: Move web links to the doc, massage. ]

Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/20201014004927.1839452-2-fenghua.yu@intel.com
2020-10-27 16:47:00 +01:00
Linus Torvalds
c80e42a496 A handful of late-arriving documentation fixes.
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Merge tag 'docs-5.10-2' of git://git.lwn.net/linux

Pull documentation fixes from Jonathan Corbet:
 "A handful of late-arriving documentation fixes"

* tag 'docs-5.10-2' of git://git.lwn.net/linux:
  docs: Add two missing entries in vm sysctl index
  docs/vm: trivial fixes to several spelling mistakes
  docs: submitting-patches: describe preserving review/test tags
  Documentation: Chinese translation of Documentation/arm64/hugetlbpage.rst
  Documentation: x86: fix a missing word in x86_64/mm.rst.
  docs: driver-api: remove a duplicated index entry
  docs: lkdtm: Modernize and improve details
  docs: deprecated.rst: Expand str*cpy() replacement notes
  docs/cpu-load: format the example code.
2020-10-23 17:13:53 -07:00
Wei Lin Chang
d7a4c55b13 Documentation: x86: fix a missing word in x86_64/mm.rst.
This patch adds a missing word in x86/x86_64/mm.rst, without which
the note reads awkwardly.

Signed-off-by: Wei Lin Chang <r09922117@csie.ntu.edu.tw>
Link: https://lore.kernel.org/r/20201015062242.26296-1-r09922117@csie.ntu.edu.tw
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-10-21 15:14:36 -06:00
Linus Torvalds
f888bdf982 Devicetree updates for v5.10:
- Update dtc to upstream version v1.6.0-31-gcbca977ea121
 
 - dtx_diff help text reformatting
 
 - Speed-up validation time for binding and dtb checks using json for
   intermediate files
 
 - Add support for running yamllint on DT schema files
 
 - Remove old booting-without-of.rst
 
 - Extend the example schema to address common issues
 
 - Cleanup handling of additionalProperties/unevaluatedProperties
 
 - Ensure all DSI controller schemas reference dsi-controller.yaml
 
 - Vendor prefixes for Zealz, Wandbord/Technexion, Embest RIoT, Rex, DFI,
   and Cisco Meraki
 
 - Convert at25, SPMI bus, TI hwlock, HiSilicon Hi3660 USB3 PHY, Arm
   SP805 watchdog, Arm SP804, and Samsung 11-pin USB connector to DT
   schema
 
 - Convert HiSilicon SoC and syscon bindings to DT schema
 
 - Convert SiFive Risc-V L2 cache, PLIC, PRCI, and PWM to DT schema
 
 - Convert i.MX bindings for w1, crypto, rng, SIM, PM, DDR,
    SATA, vf610 GPIO, and UART to DT schema
 
 - Add i.MX 8M compatible strings
 
 - Add LM81 and DS1780 as trivial devices
 
 - Various missing properties added to fix dtb validation warnings
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Merge tag 'devicetree-for-5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux

Pull devicetree updates from Rob Herring:

 - Update dtc to upstream version v1.6.0-31-gcbca977ea121

 - dtx_diff help text reformatting

 - Speed-up validation time for binding and dtb checks using json for
   intermediate files

 - Add support for running yamllint on DT schema files

 - Remove old booting-without-of.rst

 - Extend the example schema to address common issues

 - Cleanup handling of additionalProperties/unevaluatedProperties

 - Ensure all DSI controller schemas reference dsi-controller.yaml

 - Vendor prefixes for Zealz, Wandbord/Technexion, Embest RIoT, Rex,
   DFI, and Cisco Meraki

 - Convert at25, SPMI bus, TI hwlock, HiSilicon Hi3660 USB3 PHY, Arm
   SP805 watchdog, Arm SP804, and Samsung 11-pin USB connector to DT
   schema

 - Convert HiSilicon SoC and syscon bindings to DT schema

 - Convert SiFive Risc-V L2 cache, PLIC, PRCI, and PWM to DT schema

 - Convert i.MX bindings for w1, crypto, rng, SIM, PM, DDR, SATA, vf610
   GPIO, and UART to DT schema

 - Add i.MX 8M compatible strings

 - Add LM81 and DS1780 as trivial devices

 - Various missing properties added to fix dtb validation warnings

* tag 'devicetree-for-5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux: (111 commits)
  dt-bindings: misc: explicitly add #address-cells for slave mode
  spi: dt-bindings: spi-controller: explicitly require #address-cells=<0> for slave mode
  dt: Remove booting-without-of.rst
  dt-bindings: update usb-c-connector example
  dt-bindings: arm: hisilicon: add missing properties into cpuctrl.yaml
  dt-bindings: arm: hisilicon: add missing properties into sysctrl.yaml
  dt-bindings: pwm: imx: document i.MX compatibles
  scripts/dtc: Update to upstream version v1.6.0-31-gcbca977ea121
  dt-bindings: Add running yamllint to dt_binding_check
  dt-bindings: powerpc: Add a schema for the 'sleep' property
  dt-bindings: pinctrl: sirf: Fix typo abitrary
  dt-bindings: pinctrl: qcom: Fix typo abitrary
  dt-bindings: Explicitly allow additional properties in common schemas
  dt-bindings: Use 'additionalProperties' instead of 'unevaluatedProperties'
  dt-bindings: Add missing 'unevaluatedProperties'
  Docs: Fixing spelling errors in Documentation/devicetree/bindings/
  dt-bindings: arm: hisilicon: convert Hi6220 domain controller bindings to json-schema
  dt-bindings: riscv: convert pwm bindings to json-schema
  dt-bindings: riscv: convert plic bindings to json-schema
  dt-bindings: fu540: prci: convert PRCI bindings to json-schema
  ...
2020-10-14 15:31:58 -07:00
Dan Williams
3b0d31011d x86/numa: add 'nohmat' option
Disable parsing of the HMAT for debug, to workaround broken platform
instances, or cases where it is otherwise not wanted.

[rdunlap@infradead.org: fix build when CONFIG_ACPI is not set]
  Link: https://lkml.kernel.org/r/70e5ee34-9809-a997-7b49-499e4be61307@infradead.org

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Brice Goglin <Brice.Goglin@inria.fr>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: David Airlie <airlied@linux.ie>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Jia He <justin.he@arm.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Paul Mackerras <paulus@ozlabs.org>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Will Deacon <will@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Hulk Robot <hulkci@huawei.com>
Cc: Jason Yan <yanaijie@huawei.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Link: https://lkml.kernel.org/r/159643095540.4062302.732962081968036212.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-10-13 18:38:27 -07:00
Rob Herring
441848282c dt: Remove booting-without-of.rst
booting-without-of.rst is an ancient document that first outlined
Flattened DeviceTree on PowerPC initially. The DT world has evolved a
lot in the 15 years since and booting-without-of.rst is pretty stale.
The name of the document itself is confusing if you don't understand the
evolution from real 'OpenFirmware'. Most of what booting-without-of.rst
contains is now in the DT specification (which evolved out of the
ePAPR). The few things that weren't documented in the DT specification
are now.

All that remains is the boot entry details, so let's move these to arch
specific documents. The exception is arm which already has the same
details documented.

Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-mips@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Signed-off-by: Rob Herring <robh@kernel.org>
2020-10-13 13:33:16 -05:00
Linus Torvalds
64743e652c * Misc cleanups to the resctrl code in preparation for the ARM side, by
James Morse.
 
 * Add support for controlling per-thread memory bandwidth throttling
 delay values on hw which supports it, by Fenghua Yu.
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Merge tag 'x86_cache_for_v5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 cache resource control updates from Borislav Petkov:

 - Misc cleanups to the resctrl code in preparation for the ARM side
   (James Morse)

 - Add support for controlling per-thread memory bandwidth throttling
   delay values on hw which supports it (Fenghua Yu)

* tag 'x86_cache_for_v5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/resctrl: Enable user to view thread or core throttling mode
  x86/resctrl: Enumerate per-thread MBA controls
  cacheinfo: Move resctrl's get_cache_id() to the cacheinfo header file
  x86/resctrl: Add struct rdt_cache::arch_has_{sparse, empty}_bitmaps
  x86/resctrl: Merge AMD/Intel parse_bw() calls
  x86/resctrl: Add struct rdt_membw::arch_needs_linear to explain AMD/Intel MBA difference
  x86/resctrl: Use is_closid_match() in more places
  x86/resctrl: Include pid.h
  x86/resctrl: Use container_of() in delayed_work handlers
  x86/resctrl: Fix stale comment
  x86/resctrl: Remove struct rdt_membw::max_delay
  x86/resctrl: Remove unused struct mbm_state::chunks_bw
2020-10-12 10:53:32 -07:00
Linus Torvalds
9e536c8179 * Ratelimit the message about writes to unrecognized MSRs so that they
don't spam the console log, by Chris Down.
 
 * Document how the /proc/cpuinfo machinery works for future reference,
 by Kyung Min Park, Ricardo Neri and Dave Hansen.
 
 * Correct the current NMI's duration calculation, by Libing Zhou.
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Merge tag 'x86_misc_for_v5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull misc x86 fixes fromm Borislav Petkov:

 - Ratelimit the message about writes to unrecognized MSRs so that they
   don't spam the console log (Chris Down)

 - Document how the /proc/cpuinfo machinery works for future reference
   (Kyung Min Park, Ricardo Neri and Dave Hansen)

 - Correct the current NMI's duration calculation (Libing Zhou)

* tag 'x86_misc_for_v5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/nmi: Fix nmi_handle() duration miscalculation
  Documentation/x86: Add documentation for /proc/cpuinfo feature flags
  x86/msr: Make source of unrecognised MSR writes unambiguous
  x86/msr: Prevent userspace MSR access from dominating the console
2020-10-12 10:42:23 -07:00
Linus Torvalds
ac74075e5d Initial support for sharing virtual addresses between the CPU and
devices which doesn't need pinning of pages for DMA anymore. Add support
 for the command submission to devices using new x86 instructions like
 ENQCMD{,S} and MOVDIR64B. In addition, add support for process address
 space identifiers (PASIDs) which are referenced by those command
 submission instructions along with the handling of the PASID state on
 context switch as another extended state. Work by Fenghua Yu, Ashok Raj,
 Yu-cheng Yu and Dave Jiang.
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Merge tag 'x86_pasid_for_5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 PASID updates from Borislav Petkov:
 "Initial support for sharing virtual addresses between the CPU and
  devices which doesn't need pinning of pages for DMA anymore.

  Add support for the command submission to devices using new x86
  instructions like ENQCMD{,S} and MOVDIR64B. In addition, add support
  for process address space identifiers (PASIDs) which are referenced by
  those command submission instructions along with the handling of the
  PASID state on context switch as another extended state.

  Work by Fenghua Yu, Ashok Raj, Yu-cheng Yu and Dave Jiang"

* tag 'x86_pasid_for_5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/asm: Add an enqcmds() wrapper for the ENQCMDS instruction
  x86/asm: Carve out a generic movdir64b() helper for general usage
  x86/mmu: Allocate/free a PASID
  x86/cpufeatures: Mark ENQCMD as disabled when configured out
  mm: Add a pasid member to struct mm_struct
  x86/msr-index: Define an IA32_PASID MSR
  x86/fpu/xstate: Add supervisor PASID state for ENQCMD
  x86/cpufeatures: Enumerate ENQCMD and ENQCMDS instructions
  Documentation/x86: Add documentation for SVA (Shared Virtual Addressing)
  iommu/vt-d: Change flags type to unsigned int in binding mm
  drm, iommu: Change type of pasid to u32
2020-10-12 10:40:34 -07:00
Heinrich Schuchardt
0c7689830e Documentation/x86: Fix incorrect references to zero-page.txt
The file zero-page.txt does not exit. Add links to zero-page.rst
instead.

 [ bp: Massage a bit. ]

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20201002190623.7489-1-xypron.glpk@gmx.de
2020-10-02 22:49:29 +02:00
Ashok Raj
4e7b11567d Documentation/x86: Add documentation for SVA (Shared Virtual Addressing)
ENQCMD and Data Streaming Accelerator (DSA) and all of their associated
features are a complicated stack with lots of interconnected pieces.
This documentation provides a big picture overview for all of the
features.

Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Co-developed-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/1600187413-163670-4-git-send-email-fenghua.yu@intel.com
2020-09-17 19:29:42 +02:00
Kyung Min Park
ea4e3bef4c Documentation/x86: Add documentation for /proc/cpuinfo feature flags
/proc/cpuinfo shows features which the kernel supports. Some of these
flags are derived from CPUID, and others are derived from other sources,
including some that are entirely software-based. Currently, there is
not any documentation in the kernel about how /proc/cpuinfo flags are
generated and what it means when they are missing.

Add documentation for /proc/cpuinfo feature flags enumeration.
Document how and when x86 feature flags are used. Also discuss what
their presence or absence mean for the kernel and users.

Suggested-by: Dave Hansen <dave.hansen@intel.com>
Co-developed-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Kyung Min Park <kyung.min.park@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/20200831183500.15481-1-kyung.min.park@intel.com
2020-09-01 11:07:15 +02:00
Fenghua Yu
29b6bd41ee x86/resctrl: Enable user to view thread or core throttling mode
Early Intel hardware implementations of Memory Bandwidth Allocation (MBA)
could only control bandwidth at the processor core level. This meant that
when two processes with different bandwidth allocations ran simultaneously
on the same core the hardware had to resolve this difference. It did so by
applying the higher throttling value (lower bandwidth) to both processes.

Newer implementations can apply different throttling values to each
thread on a core.

Introduce a new resctrl file, "thread_throttle_mode", on Intel systems
that shows to the user how throttling values are allocated, per-core or
per-thread.

On systems that support per-core throttling, the file will display "max".
On newer systems that support per-thread throttling, the file will display
"per-thread".

AMD confirmed in [1] that AMD bandwidth allocation is already at thread
level but that the AMD implementation does not use a memory delay
throttle mode. So to avoid confusion the thread throttling mode would be
UNDEFINED on AMD systems and the "thread_throttle_mode" file will not be
visible.

Originally-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lkml.kernel.org/r/1598296281-127595-3-git-send-email-fenghua.yu@intel.com
Link: [1] https://lore.kernel.org/lkml/18d277fd-6523-319c-d560-66b63ff606b8@amd.com
2020-08-26 17:53:22 +02:00
Linus Torvalds
2324d50d05 It's been a busy cycle for documentation - hopefully the busiest for a
while to come.  Changes include:
 
  - Some new Chinese translations
 
  - Progress on the battle against double words words and non-HTTPS URLs
 
  - Some block-mq documentation
 
  - More RST conversions from Mauro.  At this point, that task is
    essentially complete, so we shouldn't see this kind of churn again for a
    while.  Unless we decide to switch to asciidoc or something...:)
 
  - Lots of typo fixes, warning fixes, and more.
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Merge tag 'docs-5.9' of git://git.lwn.net/linux

Pull documentation updates from Jonathan Corbet:
 "It's been a busy cycle for documentation - hopefully the busiest for a
  while to come. Changes include:

   - Some new Chinese translations

   - Progress on the battle against double words words and non-HTTPS
     URLs

   - Some block-mq documentation

   - More RST conversions from Mauro. At this point, that task is
     essentially complete, so we shouldn't see this kind of churn again
     for a while. Unless we decide to switch to asciidoc or
     something...:)

   - Lots of typo fixes, warning fixes, and more"

* tag 'docs-5.9' of git://git.lwn.net/linux: (195 commits)
  scripts/kernel-doc: optionally treat warnings as errors
  docs: ia64: correct typo
  mailmap: add entry for <alobakin@marvell.com>
  doc/zh_CN: add cpu-load Chinese version
  Documentation/admin-guide: tainted-kernels: fix spelling mistake
  MAINTAINERS: adjust kprobes.rst entry to new location
  devices.txt: document rfkill allocation
  PCI: correct flag name
  docs: filesystems: vfs: correct flag name
  docs: filesystems: vfs: correct sync_mode flag names
  docs: path-lookup: markup fixes for emphasis
  docs: path-lookup: more markup fixes
  docs: path-lookup: fix HTML entity mojibake
  CREDITS: Replace HTTP links with HTTPS ones
  docs: process: Add an example for creating a fixes tag
  doc/zh_CN: add Chinese translation prefer section
  doc/zh_CN: add clearing-warn-once Chinese version
  doc/zh_CN: add admin-guide index
  doc:it_IT: process: coding-style.rst: Correct __maybe_unused compiler label
  futex: MAINTAINERS: Re-add selftests directory
  ...
2020-08-04 22:47:54 -07:00
Linus Torvalds
4da9f33026 Support for FSGSBASE. Almost 5 years after the first RFC to support it,
this has been brought into a shape which is maintainable and actually
 works.
 
 This final version was done by Sasha Levin who took it up after Intel
 dropped the ball. Sasha discovered that the SGX (sic!) offerings out there
 ship rogue kernel modules enabling FSGSBASE behind the kernels back which
 opens an instantanious unpriviledged root hole.
 
 The FSGSBASE instructions provide a considerable speedup of the context
 switch path and enable user space to write GSBASE without kernel
 interaction. This enablement requires careful handling of the exception
 entries which go through the paranoid entry path as they cannot longer rely
 on the assumption that user GSBASE is positive (as enforced via prctl() on
 non FSGSBASE enabled systemn). All other entries (syscalls, interrupts and
 exceptions) can still just utilize SWAPGS unconditionally when the entry
 comes from user space. Converting these entries to use FSGSBASE has no
 benefit as SWAPGS is only marginally slower than WRGSBASE and locating and
 retrieving the kernel GSBASE value is not a free operation either. The real
 benefit of RD/WRGSBASE is the avoidance of the MSR reads and writes.
 
 The changes come with appropriate selftests and have held up in field
 testing against the (sanitized) Graphene-SGX driver.
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Merge tag 'x86-fsgsbase-2020-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fsgsbase from Thomas Gleixner:
 "Support for FSGSBASE. Almost 5 years after the first RFC to support
  it, this has been brought into a shape which is maintainable and
  actually works.

  This final version was done by Sasha Levin who took it up after Intel
  dropped the ball. Sasha discovered that the SGX (sic!) offerings out
  there ship rogue kernel modules enabling FSGSBASE behind the kernels
  back which opens an instantanious unpriviledged root hole.

  The FSGSBASE instructions provide a considerable speedup of the
  context switch path and enable user space to write GSBASE without
  kernel interaction. This enablement requires careful handling of the
  exception entries which go through the paranoid entry path as they
  can no longer rely on the assumption that user GSBASE is positive (as
  enforced via prctl() on non FSGSBASE enabled systemn).

  All other entries (syscalls, interrupts and exceptions) can still just
  utilize SWAPGS unconditionally when the entry comes from user space.
  Converting these entries to use FSGSBASE has no benefit as SWAPGS is
  only marginally slower than WRGSBASE and locating and retrieving the
  kernel GSBASE value is not a free operation either. The real benefit
  of RD/WRGSBASE is the avoidance of the MSR reads and writes.

  The changes come with appropriate selftests and have held up in field
  testing against the (sanitized) Graphene-SGX driver"

* tag 'x86-fsgsbase-2020-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (21 commits)
  x86/fsgsbase: Fix Xen PV support
  x86/ptrace: Fix 32-bit PTRACE_SETREGS vs fsbase and gsbase
  selftests/x86/fsgsbase: Add a missing memory constraint
  selftests/x86/fsgsbase: Fix a comment in the ptrace_write_gsbase test
  selftests/x86: Add a syscall_arg_fault_64 test for negative GSBASE
  selftests/x86/fsgsbase: Test ptracer-induced GS base write with FSGSBASE
  selftests/x86/fsgsbase: Test GS selector on ptracer-induced GS base write
  Documentation/x86/64: Add documentation for GS/FS addressing mode
  x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2
  x86/cpu: Enable FSGSBASE on 64bit by default and add a chicken bit
  x86/entry/64: Handle FSGSBASE enabled paranoid entry/exit
  x86/entry/64: Introduce the FIND_PERCPU_BASE macro
  x86/entry/64: Switch CR3 before SWAPGS in paranoid entry
  x86/speculation/swapgs: Check FSGSBASE in enabling SWAPGS mitigation
  x86/process/64: Use FSGSBASE instructions on thread copy and ptrace
  x86/process/64: Use FSBSBASE in switch_to() if available
  x86/process/64: Make save_fsgs_for_kvm() ready for FSGSBASE
  x86/fsgsbase/64: Enable FSGSBASE instructions in helper functions
  x86/fsgsbase/64: Add intrinsics for FSGSBASE instructions
  x86/cpu: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE
  ...
2020-08-04 21:16:22 -07:00
Nick Terrell
fb46d057db x86: Add support for ZSTD compressed kernel
- Add support for zstd compressed kernel

- Define __DISABLE_EXPORTS in Makefile

- Remove __DISABLE_EXPORTS definition from kaslr.c

- Bump the heap size for zstd.

- Update the documentation.

Integrates the ZSTD decompression code to the x86 pre-boot code.

Zstandard requires slightly more memory during the kernel decompression
on x86 (192 KB vs 64 KB), and the memory usage is independent of the
window size.

__DISABLE_EXPORTS is now defined in the Makefile, which covers both
the existing use in kaslr.c, and the use needed by the zstd decompressor
in misc.c.

This patch has been boot tested with both a zstd and gzip compressed
kernel on i386 and x86_64 using buildroot and QEMU.

Additionally, this has been tested in production on x86_64 devices.
We saw a 2 second boot time reduction by switching kernel compression
from xz to zstd.

Signed-off-by: Nick Terrell <terrelln@fb.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200730190841.2071656-7-nickrterrell@gmail.com
2020-07-31 11:49:09 +02:00
Randy Dunlap
bfbc7e5c92 Documentation: x86: earlyprintk: drop doubled words
Drop the doubled word "and".

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lore.kernel.org/r/20200703213107.30758-2-rdunlap@infradead.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-07-13 09:47:38 -06:00