It has:
1. Move comments close to what it want to comment.
2. Comments cleanup & improvement.
Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

When compiling with `make CC=clang HOSTCC=clang`, I was seeing warnings
that clang did not recognize -fno-delete-null-pointer-checks for HOSTCC
targets.  These were added in commit 61163efa ("kbuild: LLVMLinux:
Add Kbuild support for building kernel with Clang").

Clang does not support -fno-delete-null-pointer-checks, so adding it to
HOSTCFLAGS if HOSTCC is clang does not make sense.

It's not clear why the other warnings were disabled, and just for
HOSTCFLAGS, but I can remove them, add -Werror to HOSTCFLAGS and compile
with clang just fine.
Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Nick Desaulniers <nick.desaulniers@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

The top Makefile is divided into some sections such as mixed targets,
config targets, build targets, etc.

When we build mixed targets, Kbuild just invokes submake to process
them one by one.  In this case, compiler-related variables like CC,
KBUILD_CFLAGS, etc. are unneeded.

Check what kind of targets we are building first, and parse variables
for building only when necessary.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

The first "_all" occurrence around line 120 is only visible when
KBUILD_SRC is unset.

If O=... is specified, the working directory is relocated, then the
only second occurrence around line 193 is visible, that is not set
to PHONY.

Move the first one to an always visible place.  This clarifies "_all"
is our default target and it is always set to PHONY.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>

Since commit 5e538790 ("sparc,sparc64: unify Makefile"), hdr-arch
and SRCARCH always match.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>

This script does not need to create .version; it will be created by
scripts/link-vmlinux.sh later.  Clean-up the code slightly.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Since commit 1f2bfbd0 ("kbuild: link of vmlinux moved to a
script"), it is easy to increment .version without using a temporary
file .old_version.

I do not see anybody who creates the .tmp_version.  Probably it is a
left-over of commit 4e25d8bb ("[PATCH] kbuild: adjust .version
updating").  Just remove it.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

<generated/compile.h> is created (or updated) when Kbuild descends
into the init/ directory.  In parallel building from a pristine
source tree, there is no guarantee <generated/compile.h> exists when
arch/hexagon/kernel/ptrace.c is compiled.

For hexagon architecture, we know UTS_MACHINE is a fixed string
"hexagon", so let's hard-code it, like many architectures do.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Richard Kuo <rkuo@codeaurora.org>

Pull x86 fixes from Thomas Gleixner:
 "This contains the following fixes and improvements:

   - Avoid dereferencing an unprotected VMA pointer in the fault signal
     generation code

   - Fix inline asm call constraints for GCC 4.4

   - Use existing register variable to retrieve the stack pointer
     instead of forcing the compiler to create another indirect access
     which results in excessive extra 'mov %rsp, %<dst>' instructions

   - Disable branch profiling for the memory encryption code to prevent
     an early boot crash

   - Fix a sparse warning caused by casting the __user annotation in
     __get_user_asm_u64() away

   - Fix an off by one error in the loop termination of the error patch
     in the x86 sysfs init code

   - Add missing CPU IDs to various Intel specific drivers to enable the
     functionality on recent hardware

   - More (init) constification in the numachip code"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/asm: Use register variable to get stack pointer value
  x86/mm: Disable branch profiling in mem_encrypt.c
  x86/asm: Fix inline asm call constraints for GCC 4.4
  perf/x86/intel/uncore: Correct num_boxes for IIO and IRP
  perf/x86/intel/rapl: Add missing CPU IDs
  perf/x86/msr: Add missing CPU IDs
  perf/x86/intel/cstate: Add missing CPU IDs
  x86: Don't cast away the __user in __get_user_asm_u64()
  x86/sysfs: Fix off-by-one error in loop termination
  x86/mm: Fix fault error path using unsafe vma pointer
  x86/numachip: Add const and __initconst to numachip2_clockevent

Pull timer fixes from Thomas Gleixner:
 "This adds a new timer wheel function which is required for the
  conversion of the timer callback function from the 'unsigned long
  data' argument to 'struct timer_list *timer'. This conversion has two
  benefits:

   1) It makes struct timer_list smaller

   2) Many callers hand in a pointer to the timer or to the structure
      containing the timer, which happens via type casting both at setup
      and in the callback. This change gets rid of the typecasts.

  Once the conversion is complete, which is planned for 4.15, the old
  setup function and the intermediate typecast in the new setup function
  go away along with the data field in struct timer_list.

  Merging this now into mainline allows a smooth queueing of the actual
  conversion in the affected maintainer trees without creating
  dependencies"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  um/time: Fixup namespace collision
  timer: Prepare to change timer callback argument type

Pull smp/hotplug fixes from Thomas Gleixner:
 "This addresses the fallout of the new lockdep mechanism which covers
  completions in the CPU hotplug code.

  The lockdep splats are false positives, but there is no way to
  annotate that reliably. The solution is to split the completions for
  CPU up and down, which requires some reshuffling of the failure
  rollback handling as well"

* 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  smp/hotplug: Hotplug state fail injection
  smp/hotplug: Differentiate the AP completion between up and down
  smp/hotplug: Differentiate the AP-work lockdep class between up and down
  smp/hotplug: Callback vs state-machine consistency
  smp/hotplug: Rewrite AP state machine core
  smp/hotplug: Allow external multi-instance rollback
  smp/hotplug: Add state diagram

Pull scheduler fixes from Thomas Gleixner:
 "The scheduler pull request comes with the following updates:

   - Prevent a divide by zero issue by validating the input value of
     sysctl_sched_time_avg

   - Make task state printing consistent all over the place and have
     explicit state characters for IDLE and PARKED so they wont be
     displayed as 'D' state which confuses tools"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/sysctl: Check user input value of sysctl_sched_time_avg
  sched/debug: Add explicit TASK_PARKED printing
  sched/debug: Ignore TASK_IDLE for SysRq-W
  sched/debug: Add explicit TASK_IDLE printing
  sched/tracing: Use common task-state helpers
  sched/tracing: Fix trace_sched_switch task-state printing
  sched/debug: Remove unused variable
  sched/debug: Convert TASK_state to hex
  sched/debug: Implement consistent task-state printing

Pull perf fixes from Thomas Gleixner:

 - Prevent a division by zero in the perf aux buffer handling

 - Sync kernel headers with perf tool headers

 - Fix a build failure in the syscalltbl code

 - Make the debug messages of perf report --call-graph work correctly

 - Make sure that all required perf files are in the MANIFEST for
   container builds

 - Fix the atrr.exclude kernel handling so it respects the
   perf_event_paranoid and the user permissions

 - Make perf test on s390x work correctly

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/aux: Only update ->aux_wakeup in non-overwrite mode
  perf test: Fix vmlinux failure on s390x part 2
  perf test: Fix vmlinux failure on s390x
  perf tools: Fix syscalltbl build failure
  perf report: Fix debug messages with --call-graph option
  perf evsel: Fix attr.exclude_kernel setting for default cycles:p
  tools include: Sync kernel ABI headers with tooling headers
  perf tools: Get all of tools/{arch,include}/ in the MANIFEST

Pull  locking fixes from Thomas Gleixner:
 "Two fixes for locking:

   - Plug a hole the pi_stat->owner serialization which was changed
     recently and failed to fixup two usage sites.

   - Prevent reordering of the rwsem_has_spinner() check vs the
     decrement of rwsem count in up_write() which causes a missed
     wakeup"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/rwsem-xadd: Fix missed wakeup due to reordering of load
  futex: Fix pi_state->owner serialization

Pull irq fixes from Thomas Gleixner:

 - Add a missing NULL pointer check in free_irq()

 - Fix a memory leak/memory corruption in the generic irq chip

 - Add missing rcu annotations for radix tree access

 - Use ffs instead of fls when extracting data from a chip register in
   the MIPS GIC irq driver

 - Fix the unmasking of IPI interrupts in the MIPS GIC driver so they
   end up at the target CPU and not at CPU0

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  irq/generic-chip: Don't replace domain's name
  irqdomain: Add __rcu annotations to radix tree accessors
  irqchip/mips-gic: Use effective affinity to unmask
  irqchip/mips-gic: Fix shifts to extract register fields
  genirq: Check __free_irq() return value for NULL

Pull objtool fixes from Thomas Gleixner:
 "Two small fixes for objtool:

   - Support frame pointer setup via 'lea (%rsp), %rbp' which was not
     yet supported and caused build warnings

   - Disable unreacahble warnings for GCC4.4 and older to avoid false
     positives caused by the compiler itself"

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  objtool: Support unoptimized frame pointer setup
  objtool: Skip unreachable warnings for GCC 4.4 and older

Pull mtd fixes from Boris Brezillon:

 - Fix partition alignment check in mtdcore.c

 - Fix a buffer overflow in the Atmel NAND driver

* tag 'mtd/fixes-for-4.14-rc3' of git://git.infradead.org/linux-mtd:
  mtd: nand: atmel: fix buffer overflow in atmel_pmecc_user
  mtd: Fix partition alignment check on multi-erasesize devices

Pull SCSI fixes from James Bottomley:
 "Eight mostly minor fixes for recently discovered issues in drivers"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  scsi: ILLEGAL REQUEST + ASC==27 => target failure
  scsi: aacraid: Add a small delay after IOP reset
  scsi: scsi_transport_fc: Also check for NOTPRESENT in fc_remote_port_add()
  scsi: scsi_transport_fc: set scsi_target_id upon rescan
  scsi: scsi_transport_iscsi: fix the issue that iscsi_if_rx doesn't parse nlmsg properly
  scsi: aacraid: error: testing array offset 'bus' after use
  scsi: lpfc: Don't return internal MBXERR_ERROR code from probe function
  scsi: aacraid: Fix 2T+ drives on SmartIOC-2000

Pull x86 platform drivers fix from Darren Hart:
 "Newly discovered species of fujitsu laptops break some assumptions
  about ACPI device pairings.

  fujitsu-laptop: Don't oops when FUJ02E3 is not present"

* tag 'platform-drivers-x86-v4.14-2' of git://git.infradead.org/linux-platform-drivers-x86:
  platform/x86: fujitsu-laptop: Don't oops when FUJ02E3 is not presnt

Merge tag 'led_fixes-4.14-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/j.anaszewski/linux-leds

Pull LED fixes from Jacek Anaszewski:
 "Four fixes for the as3645a LED flash controller and one update to
  MAINTAINERS"

* tag 'led_fixes-4.14-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/j.anaszewski/linux-leds:
  MAINTAINERS: Add entry for MediaTek PMIC LED driver
  as3645a: Unregister indicator LED on device unbind
  as3645a: Use integer numbers for parsing LEDs
  dt: bindings: as3645a: Use LED number to refer to LEDs
  as3645a: Use ams,input-max-microamp as documented in DT bindings

Pull waitid fix from Al Viro:
 "Fix infoleak in waitid()"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fix infoleak in waitid(2)

Pull btrfs fixes from David Sterba:
 "We've collected a bunch of isolated fixes, for crashes, user-visible
  behaviour or missing bits from other subsystem cleanups from the past.

  The overall number is not small but I was not able to make it
  significantly smaller. Most of the patches are supposed to go to
  stable"

* 'for-4.14-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: log csums for all modified extents
  Btrfs: fix unexpected result when dio reading corrupted blocks
  btrfs: Report error on removing qgroup if del_qgroup_item fails
  Btrfs: skip checksum when reading compressed data if some IO have failed
  Btrfs: fix kernel oops while reading compressed data
  Btrfs: use btrfs_op instead of bio_op in __btrfs_map_block
  Btrfs: do not backup tree roots when fsync
  btrfs: remove BTRFS_FS_QUOTA_DISABLING flag
  btrfs: propagate error to btrfs_cmp_data_prepare caller
  btrfs: prevent to set invalid default subvolid
  Btrfs: send: fix error number for unknown inode types
  btrfs: fix NULL pointer dereference from free_reloc_roots()
  btrfs: finish ordered extent cleaning if no progress is found
  btrfs: clear ordered flag on cleaning up ordered extents
  Btrfs: fix incorrect {node,sector}size endianness from BTRFS_IOC_FS_INFO
  Btrfs: do not reset bio->bi_ops while writing bio
  Btrfs: use the new helper wbc_to_write_flags

Pull MD fixes from Shaohua Li:
 "A few fixes for MD. Mainly fix a problem introduced in 4.13, which we
  retry bio for some code paths but not all in some situations"

* tag 'md/4.14-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/shli/md:
  md/raid5: cap worker count
  dm-raid: fix a race condition in request handling
  md: fix a race condition for flush request handling
  md: separate request handling

Pull PCI fixes from Bjorn Helgaas:

 - fix CONFIG_PCI=n build error (introduced in v4.14-rc1) (Geert
   Uytterhoeven)

 - fix a race in sysfs driver_override store/show (Nicolai Stange)

* tag 'pci-v4.14-fixes-3' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci:
  PCI: Fix race condition with driver_override
  PCI: Add dummy pci_acs_enabled() for CONFIG_PCI=n build

Pull drm fixes from Dave Airlie:
 "Regular fixes pull, some amdkfd, amdgpu, etnaviv, sun4i, qxl, tegra
  fixes.

  I've got an outstanding pull for i915 but it wasn't on an rc2 base so
  I wanted to ship these out first, I might get to it before rc3 or I
  might not"

* tag 'drm-fixes-for-v4.14-rc3' of git://people.freedesktop.org/~airlied/linux:
  drm/tegra: trace: Fix path to include
  qxl: fix framebuffer unpinning
  drm/sun4i: cec: Enable back CEC-pin framework
  drm/amdkfd: Print event limit messages only once per process
  drm/amdkfd: Fix kernel-queue wrapping bugs
  drm/amdkfd: Fix incorrect destroy_mqd parameter
  drm/radeon: disable hard reset in hibernate for APUs
  drm/amdgpu: revert tile table update for oland
  etnaviv: fix gem object list corruption
  etnaviv: fix submit error path
  qxl: fix primary surface handling
  drm/amdkfd: check for null dev to avoid a null pointer dereference

Pull IOMMU fixes from Joerg Roedel:

 - A comment fix for 'struct iommu_ops'

 - Format string fixes for AMD IOMMU, unfortunatly I missed that during
   review.

 - Limit mediatek physical addresses to 32 bit for v7s to fix a warning
   triggered in io-page-table code.

 - Fix dma-sync in io-pgtable-arm-v7s code

* tag 'iommu-fixes-v4.14-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu:
  iommu: Fix comment for iommu_ops.map_sg
  iommu/amd: pr_err() strings should end with newlines
  iommu/mediatek: Limit the physical address in 32bit for v7s
  iommu/io-pgtable-arm-v7s: Need dma-sync while there is no QUIRK_NO_DMA

Pull arm64 fixes from Catalin Marinas:

 - SPsel register initialisation on reset as the architecture defines
   its state as unknown

 - Use READ_ONCE when dereferencing pmd_t pointers to avoid race
   conditions in page_vma_mapped_walk() (or fast GUP) with concurrent
   modifications of the page table

 - Avoid invoking the mm fault handling code for kernel addresses (check
   against TASK_SIZE) which would otherwise result in calling
   might_sleep() in atomic context

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: fault: Route pte translation faults via do_translation_fault
  arm64: mm: Use READ_ONCE when dereferencing pointer to pte table
  arm64: Make sure SPsel is always set

Pull xen fixes from Juergen Gross:

 - avoid a warning when compiling with clang

 - consider read-only bits in xen-pciback when writing to a BAR

 - fix a boot crash of pv-domains

* tag 'for-linus-4.14c-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen/mmu: Call xen_cleanhighmap() with 4MB aligned for page tables mapping
  xen-pciback: relax BAR sizing write value check
  x86/xen: clean up clang build warning

Pull kvm fixes from Paolo Bonzini:
 "Mixed bugfixes. Perhaps the most interesting one is a latent bug that
  was finally triggered by PCID support"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  kvm/x86: Handle async PF in RCU read-side critical sections
  KVM: nVMX: Fix nested #PF intends to break L1's vmlauch/vmresume
  KVM: VMX: use cmpxchg64
  KVM: VMX: simplify and fix vmx_vcpu_pi_load
  KVM: VMX: avoid double list add with VT-d posted interrupts
  KVM: VMX: extract __pi_post_block
  KVM: PPC: Book3S HV: Check for updated HDSISR on P9 HDSI exception
  KVM: nVMX: fix HOST_CR3/HOST_CR4 cache

kernel_waitid() can return a PID, an error or 0.  rusage is filled in the first
case and waitid(2) rusage should've been copied out exactly in that case, *not*
whenever kernel_waitid() has not returned an error.  Compat variant shares that
braino; none of kernel_wait4() callers do, so the below ought to fix it.
Reported-and-tested-by: Alexander Potapenko <glider@google.com>
Fixes: ce72a16f ("wait4(2)/waitid(2): separate copying rusage to userland")
Cc: stable@vger.kernel.org # v4.13
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Currently we use current_stack_pointer() function to get the value
of the stack pointer register. Since commit:

  f5caf621 ("x86/asm: Fix inline asm call constraints for Clang")

... we have a stack register variable declared. It can be used instead of
current_stack_pointer() function which allows to optimize away some
excessive "mov %rsp, %<dst>" instructions:

 -mov    %rsp,%rdx
 -sub    %rdx,%rax
 -cmp    $0x3fff,%rax
 -ja     ffffffff810722fd <ist_begin_non_atomic+0x2d>

 +sub    %rsp,%rax
 +cmp    $0x3fff,%rax
 +ja     ffffffff810722fa <ist_begin_non_atomic+0x2a>

Remove current_stack_pointer(), rename __asm_call_sp to current_stack_pointer
and use it instead of the removed function.
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170929141537.29167-1-aryabinin@virtuozzo.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

Some routines in mem_encrypt.c are called very early in the boot process,
e.g. sme_encrypt_kernel(). When CONFIG_TRACE_BRANCH_PROFILING=y is defined
the resulting branch profiling associated with the check to see if SME is
active results in a kernel crash. Disable branch profiling for
mem_encrypt.c by defining DISABLE_BRANCH_PROFILING before including any
header files.
Reported-by: kernel test robot <lkp@01.org>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Borislav Petkov <bp@suse.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170929162419.6016.53390.stgit@tlendack-t1.amdoffice.netSigned-off-by: Ingo Molnar <mingo@kernel.org>

Merge tag 'perf-urgent-for-mingo-4.14-20170928' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/urgent

Pull perf/urgent fixes from Arnaldo Carvalho de Melo:

- Fix syscalltbl build failure (Akemi Yagi)

- Fix attr.exclude_kernel setting for default cycles:p, this time for
  !root with kernel.perf_event_paranoid = -1 (Arnaldo Carvalho de Melo)

- Sync kernel ABI headers with tooling headers (Ingo Molnar)

- Remove misleading debug messages with --call-graph option (Mengting Zhang)

- Revert vmlinux symbol resolution patches for s390x (Thomas Richter)
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Merge branch 'fixes-v4.14-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security

Pull keys fixes from James Morris:
 "Notable here is a rewrite of big_key crypto by Jason Donenfeld to
  address some issues in the original code.

  From Jason's commit log:
   "This started out as just replacing the use of crypto/rng with
    get_random_bytes_wait, so that we wouldn't use bad randomness at
    boot time. But, upon looking further, it appears that there were
    even deeper underlying cryptographic problems, and that this seems
    to have been committed with very little crypto review. So, I rewrote
    the whole thing, trying to keep to the conventions introduced by the
    previous author, to fix these cryptographic flaws."

  There has been positive review of the new code by Eric Biggers and
  Herbert Xu, and it passes basic testing via the keyutils test suite.
  Eric also manually tested it.

  Generally speaking, we likely need to improve the amount of crypto
  review for kernel crypto users including keys (I'll post a note
  separately to ksummit-discuss)"

* 'fixes-v4.14-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  security/keys: rewrite all of big_key crypto
  security/keys: properly zero out sensitive key material in big_key
  KEYS: use kmemdup() in request_key_auth_new()
  KEYS: restrict /proc/keys by credentials at open time
  KEYS: reset parent each time before searching key_user_tree
  KEYS: prevent KEYCTL_READ on negative key
  KEYS: prevent creating a different user's keyrings
  KEYS: fix writing past end of user-supplied buffer in keyring_read()
  KEYS: fix key refcount leak in keyctl_read_key()
  KEYS: fix key refcount leak in keyctl_assume_authority()
  KEYS: don't revoke uninstantiated key in request_key_auth_new()
  KEYS: fix cred refcount leak in request_key_auth_new()

We currently route pte translation faults via do_page_fault, which elides
the address check against TASK_SIZE before invoking the mm fault handling
code. However, this can cause issues with the path walking code in
conjunction with our word-at-a-time implementation because
load_unaligned_zeropad can end up faulting in kernel space if it reads
across a page boundary and runs into a page fault (e.g. by attempting to
read from a guard region).

In the case of such a fault, load_unaligned_zeropad has registered a
fixup to shift the valid data and pad with zeroes, however the abort is
reported as a level 3 translation fault and we dispatch it straight to
do_page_fault, despite it being a kernel address. This results in calling
a sleeping function from atomic context:

  BUG: sleeping function called from invalid context at arch/arm64/mm/fault.c:313
  in_atomic(): 0, irqs_disabled(): 0, pid: 10290
  Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
  [...]
  [<ffffff8e016cd0cc>] ___might_sleep+0x134/0x144
  [<ffffff8e016cd158>] __might_sleep+0x7c/0x8c
  [<ffffff8e016977f0>] do_page_fault+0x140/0x330
  [<ffffff8e01681328>] do_mem_abort+0x54/0xb0
  Exception stack(0xfffffffb20247a70 to 0xfffffffb20247ba0)
  [...]
  [<ffffff8e016844fc>] el1_da+0x18/0x78
  [<ffffff8e017f399c>] path_parentat+0x44/0x88
  [<ffffff8e017f4c9c>] filename_parentat+0x5c/0xd8
  [<ffffff8e017f5044>] filename_create+0x4c/0x128
  [<ffffff8e017f59e4>] SyS_mkdirat+0x50/0xc8
  [<ffffff8e01684e30>] el0_svc_naked+0x24/0x28
  Code: 36380080 d5384100 f9400800 9402566d (d4210000)
  ---[ end trace 2d01889f2bca9b9f ]---

Fix this by dispatching all translation faults to do_translation_faults,
which avoids invoking the page fault logic for faults on kernel addresses.

Cc: <stable@vger.kernel.org>
Reported-by: Ankit Jain <ankijain@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

On kernels built with support for transparent huge pages, different CPUs
can access the PMD concurrently due to e.g. fast GUP or page_vma_mapped_walk
and they must take care to use READ_ONCE to avoid value tearing or caching
of stale values by the compiler. Unfortunately, these functions call into
our pgtable macros, which don't use READ_ONCE, and compiler caching has
been observed to cause the following crash during ext4 writeback:

PC is at check_pte+0x20/0x170
LR is at page_vma_mapped_walk+0x2e0/0x540
[...]
Process doio (pid: 2463, stack limit = 0xffff00000f2e8000)
Call trace:
[<ffff000008233328>] check_pte+0x20/0x170
[<ffff000008233758>] page_vma_mapped_walk+0x2e0/0x540
[<ffff000008234adc>] page_mkclean_one+0xac/0x278
[<ffff000008234d98>] rmap_walk_file+0xf0/0x238
[<ffff000008236e74>] rmap_walk+0x64/0xa0
[<ffff0000082370c8>] page_mkclean+0x90/0xa8
[<ffff0000081f3c64>] clear_page_dirty_for_io+0x84/0x2a8
[<ffff00000832f984>] mpage_submit_page+0x34/0x98
[<ffff00000832fb4c>] mpage_process_page_bufs+0x164/0x170
[<ffff00000832fc8c>] mpage_prepare_extent_to_map+0x134/0x2b8
[<ffff00000833530c>] ext4_writepages+0x484/0xe30
[<ffff0000081f6ab4>] do_writepages+0x44/0xe8
[<ffff0000081e5bd4>] __filemap_fdatawrite_range+0xbc/0x110
[<ffff0000081e5e68>] file_write_and_wait_range+0x48/0xd8
[<ffff000008324310>] ext4_sync_file+0x80/0x4b8
[<ffff0000082bd434>] vfs_fsync_range+0x64/0xc0
[<ffff0000082332b4>] SyS_msync+0x194/0x1e8

This is because page_vma_mapped_walk loads the PMD twice before calling
pte_offset_map: the first time without READ_ONCE (where it gets all zeroes
due to a concurrent pmdp_invalidate) and the second time with READ_ONCE
(where it sees a valid table pointer due to a concurrent pmd_populate).
However, the compiler inlines everything and caches the first value in
a register, which is subsequently used in pte_offset_phys which returns
a junk pointer that is later dereferenced when attempting to access the
relevant pte.

This patch fixes the issue by using READ_ONCE in pte_offset_phys to ensure
that a stale value is not used. Whilst this is a point fix for a known
failure (and simple to backport), a full fix moving all of our page table
accessors over to {READ,WRITE}_ONCE and consistently using READ_ONCE in
page_vma_mapped_walk is in the works for a future kernel release.

Cc: Jon Masters <jcm@redhat.com>
Cc: Timur Tabi <timur@codeaurora.org>
Cc: <stable@vger.kernel.org>
Fixes: f27176cf ("mm: convert page_mkclean_one() to use page_vma_mapped_walk()")
Tested-by: Richard Ruigrok <rruigrok@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Sasha Levin reported a WARNING:

| WARNING: CPU: 0 PID: 6974 at kernel/rcu/tree_plugin.h:329
| rcu_preempt_note_context_switch kernel/rcu/tree_plugin.h:329 [inline]
| WARNING: CPU: 0 PID: 6974 at kernel/rcu/tree_plugin.h:329
| rcu_note_context_switch+0x16c/0x2210 kernel/rcu/tree.c:458
...
| CPU: 0 PID: 6974 Comm: syz-fuzzer Not tainted 4.13.0-next-20170908+ #246
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
| 1.10.1-1ubuntu1 04/01/2014
| Call Trace:
...
| RIP: 0010:rcu_preempt_note_context_switch kernel/rcu/tree_plugin.h:329 [inline]
| RIP: 0010:rcu_note_context_switch+0x16c/0x2210 kernel/rcu/tree.c:458
| RSP: 0018:ffff88003b2debc8 EFLAGS: 00010002
| RAX: 0000000000000001 RBX: 1ffff1000765bd85 RCX: 0000000000000000
| RDX: 1ffff100075d7882 RSI: ffffffffb5c7da20 RDI: ffff88003aebc410
| RBP: ffff88003b2def30 R08: dffffc0000000000 R09: 0000000000000001
| R10: 0000000000000000 R11: 0000000000000000 R12: ffff88003b2def08
| R13: 0000000000000000 R14: ffff88003aebc040 R15: ffff88003aebc040
| __schedule+0x201/0x2240 kernel/sched/core.c:3292
| schedule+0x113/0x460 kernel/sched/core.c:3421
| kvm_async_pf_task_wait+0x43f/0x940 arch/x86/kernel/kvm.c:158
| do_async_page_fault+0x72/0x90 arch/x86/kernel/kvm.c:271
| async_page_fault+0x22/0x30 arch/x86/entry/entry_64.S:1069
| RIP: 0010:format_decode+0x240/0x830 lib/vsprintf.c:1996
| RSP: 0018:ffff88003b2df520 EFLAGS: 00010283
| RAX: 000000000000003f RBX: ffffffffb5d1e141 RCX: ffff88003b2df670
| RDX: 0000000000000001 RSI: dffffc0000000000 RDI: ffffffffb5d1e140
| RBP: ffff88003b2df560 R08: dffffc0000000000 R09: 0000000000000000
| R10: ffff88003b2df718 R11: 0000000000000000 R12: ffff88003b2df5d8
| R13: 0000000000000064 R14: ffffffffb5d1e140 R15: 0000000000000000
| vsnprintf+0x173/0x1700 lib/vsprintf.c:2136
| sprintf+0xbe/0xf0 lib/vsprintf.c:2386
| proc_self_get_link+0xfb/0x1c0 fs/proc/self.c:23
| get_link fs/namei.c:1047 [inline]
| link_path_walk+0x1041/0x1490 fs/namei.c:2127
...

This happened when the host hit a page fault, and delivered it as in an
async page fault, while the guest was in an RCU read-side critical
section.  The guest then tries to reschedule in kvm_async_pf_task_wait(),
but rcu_preempt_note_context_switch() would treat the reschedule as a
sleep in RCU read-side critical section, which is not allowed (even in
preemptible RCU).  Thus the WARN.

To cure this, make kvm_async_pf_task_wait() go to the halt path if the
PF happens in a RCU read-side critical section.
Reported-by: Sasha Levin <levinsasha928@gmail.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

------------[ cut here ]------------
 WARNING: CPU: 4 PID: 5280 at /home/kernel/linux/arch/x86/kvm//vmx.c:11394 nested_vmx_vmexit+0xc2b/0xd70 [kvm_intel]
 CPU: 4 PID: 5280 Comm: qemu-system-x86 Tainted: G        W  OE   4.13.0+ #17
 RIP: 0010:nested_vmx_vmexit+0xc2b/0xd70 [kvm_intel]
 Call Trace:
  ? emulator_read_emulated+0x15/0x20 [kvm]
  ? segmented_read+0xae/0xf0 [kvm]
  vmx_inject_page_fault_nested+0x60/0x70 [kvm_intel]
  ? vmx_inject_page_fault_nested+0x60/0x70 [kvm_intel]
  x86_emulate_instruction+0x733/0x810 [kvm]
  vmx_handle_exit+0x2f4/0xda0 [kvm_intel]
  ? kvm_arch_vcpu_ioctl_run+0xd2f/0x1c60 [kvm]
  kvm_arch_vcpu_ioctl_run+0xdab/0x1c60 [kvm]
  ? kvm_arch_vcpu_load+0x62/0x230 [kvm]
  kvm_vcpu_ioctl+0x340/0x700 [kvm]
  ? kvm_vcpu_ioctl+0x340/0x700 [kvm]
  ? __fget+0xfc/0x210
  do_vfs_ioctl+0xa4/0x6a0
  ? __fget+0x11d/0x210
  SyS_ioctl+0x79/0x90
  entry_SYSCALL_64_fastpath+0x23/0xc2

A nested #PF is triggered during L0 emulating instruction for L2. However, it
doesn't consider we should not break L1's vmlauch/vmresme. This patch fixes
it by queuing the #PF exception instead ,requesting an immediate VM exit from
L2 and keeping the exception for L1 pending for a subsequent nested VM exit.

This should actually work all the time, making vmx_inject_page_fault_nested
totally unnecessary.  However, that's not working yet, so this patch can work
around the issue in the meanwhile.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

System will hang if user set sysctl_sched_time_avg to 0:

  [root@XXX ~]# sysctl kernel.sched_time_avg_ms=0

  Stack traceback for pid 0
  0xffff883f6406c600 0 0 1 3 R 0xffff883f6406cf50 *swapper/3
  ffff883f7ccc3ae8 0000000000000018 ffffffff810c4dd0 0000000000000000
  0000000000017800 ffff883f7ccc3d78 0000000000000003 ffff883f7ccc3bf8
  ffffffff810c4fc9 ffff883f7ccc3c08 00000000810c5043 ffff883f7ccc3c08
  Call Trace:
  <IRQ> [<ffffffff810c4dd0>] ? update_group_capacity+0x110/0x200
  [<ffffffff810c4fc9>] ? update_sd_lb_stats+0x109/0x600
  [<ffffffff810c5507>] ? find_busiest_group+0x47/0x530
  [<ffffffff810c5b84>] ? load_balance+0x194/0x900
  [<ffffffff810ad5ca>] ? update_rq_clock.part.83+0x1a/0xe0
  [<ffffffff810c6d42>] ? rebalance_domains+0x152/0x290
  [<ffffffff810c6f5c>] ? run_rebalance_domains+0xdc/0x1d0
  [<ffffffff8108a75b>] ? __do_softirq+0xfb/0x320
  [<ffffffff8108ac85>] ? irq_exit+0x125/0x130
  [<ffffffff810b3a17>] ? scheduler_ipi+0x97/0x160
  [<ffffffff81052709>] ? smp_reschedule_interrupt+0x29/0x30
  [<ffffffff8173a1be>] ? reschedule_interrupt+0x6e/0x80
   <EOI> [<ffffffff815bc83c>] ? cpuidle_enter_state+0xcc/0x230
  [<ffffffff815bc80c>] ? cpuidle_enter_state+0x9c/0x230
  [<ffffffff815bc9d7>] ? cpuidle_enter+0x17/0x20
  [<ffffffff810cd6dc>] ? cpu_startup_entry+0x38c/0x420
  [<ffffffff81053373>] ? start_secondary+0x173/0x1e0

Because divide-by-zero error happens in function:

update_group_capacity()
  update_cpu_capacity()
    scale_rt_capacity()
     {
          ...
          total = sched_avg_period() + delta;
          used = div_u64(avg, total);
          ...
     }

To fix this issue, check user input value of sysctl_sched_time_avg, keep
it unchanged when hitting invalid input, and set the minimum limit of
sysctl_sched_time_avg to 1 ms.
Reported-by: James Puthukattukaran <james.puthukattukaran@oracle.com>
Signed-off-by: Ethan Zhao <ethan.zhao@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: efault@gmx.de
Cc: ethan.kernel@gmail.com
Cc: keescook@chromium.org
Cc: mcgrof@kernel.org
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/1504504774-18253-1-git-send-email-ethan.zhao@oracle.comSigned-off-by: Ingo Molnar <mingo@kernel.org>