<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux.git/arch/x86, branch v4.11</title>
<subtitle>Linux kernel source tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/'/>
<entry>
<title>Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip</title>
<updated>2017-04-30T18:44:18+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2017-04-30T18:44:18+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=97ce89f8a4eb15a1e82be419fcd6218fe4da1fbd'/>
<id>97ce89f8a4eb15a1e82be419fcd6218fe4da1fbd</id>
<content type='text'>
Pull x86 fixes from Thomas Gleixner:
 "The final fixes for 4.11:

   - prevent a triple fault with function graph tracing triggered via
     suspend to ram

   - prevent optimizing for size when function graph tracing is enabled
     and the compiler does not support -mfentry

   - prevent mwaitx() being called with a zero timeout as mwaitx() might
     never return. Observed on the new Ryzen CPUs"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Prevent timer value 0 for MWAITX
  x86/build: convert function graph '-Os' error to warning
  ftrace/x86: Fix triple fault with graph tracing and suspend-to-ram
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull x86 fixes from Thomas Gleixner:
 "The final fixes for 4.11:

   - prevent a triple fault with function graph tracing triggered via
     suspend to ram

   - prevent optimizing for size when function graph tracing is enabled
     and the compiler does not support -mfentry

   - prevent mwaitx() being called with a zero timeout as mwaitx() might
     never return. Observed on the new Ryzen CPUs"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Prevent timer value 0 for MWAITX
  x86/build: convert function graph '-Os' error to warning
  ftrace/x86: Fix triple fault with graph tracing and suspend-to-ram
</pre>
</div>
</content>
</entry>
<entry>
<title>Prevent timer value 0 for MWAITX</title>
<updated>2017-04-30T11:35:11+00:00</updated>
<author>
<name>Janakarajan Natarajan</name>
<email>Janakarajan.Natarajan@amd.com</email>
</author>
<published>2017-04-25T21:44:03+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=88d879d29f9cc0de2d930b584285638cdada6625'/>
<id>88d879d29f9cc0de2d930b584285638cdada6625</id>
<content type='text'>
Newer hardware has uncovered a bug in the software implementation of
using MWAITX for the delay function. A value of 0 for the timer is meant
to indicate that a timeout will not be used to exit MWAITX. On newer
hardware this can result in MWAITX never returning, resulting in NMI
soft lockup messages being printed. On older hardware, some of the other
conditions under which MWAITX can exit masked this issue. The AMD APM
does not currently document this and will be updated.

Please refer to http://marc.info/?l=kvm&amp;m=148950623231140 for
information regarding NMI soft lockup messages on an AMD Ryzen 1800X.
This has been root-caused as a 0 passed to MWAITX causing it to wait
indefinitely.

This change has the added benefit of avoiding the unnecessary setup of
MONITORX/MWAITX when the delay value is zero.

Signed-off-by: Janakarajan Natarajan &lt;Janakarajan.Natarajan@amd.com&gt;
Link: http://lkml.kernel.org/r/1493156643-29366-1-git-send-email-Janakarajan.Natarajan@amd.com
Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Newer hardware has uncovered a bug in the software implementation of
using MWAITX for the delay function. A value of 0 for the timer is meant
to indicate that a timeout will not be used to exit MWAITX. On newer
hardware this can result in MWAITX never returning, resulting in NMI
soft lockup messages being printed. On older hardware, some of the other
conditions under which MWAITX can exit masked this issue. The AMD APM
does not currently document this and will be updated.

Please refer to http://marc.info/?l=kvm&amp;m=148950623231140 for
information regarding NMI soft lockup messages on an AMD Ryzen 1800X.
This has been root-caused as a 0 passed to MWAITX causing it to wait
indefinitely.

This change has the added benefit of avoiding the unnecessary setup of
MONITORX/MWAITX when the delay value is zero.

Signed-off-by: Janakarajan Natarajan &lt;Janakarajan.Natarajan@amd.com&gt;
Link: http://lkml.kernel.org/r/1493156643-29366-1-git-send-email-Janakarajan.Natarajan@amd.com
Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>x86/build: convert function graph '-Os' error to warning</title>
<updated>2017-04-19T07:57:23+00:00</updated>
<author>
<name>Josh Poimboeuf</name>
<email>jpoimboe@redhat.com</email>
</author>
<published>2017-04-18T21:44:29+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=a5859c6d7b6114fc0e52be40f7b0f5451c4aba93'/>
<id>a5859c6d7b6114fc0e52be40f7b0f5451c4aba93</id>
<content type='text'>
For pre-4.6.0 versions of GCC, which don't have '-mfentry', the
'-maccumulate-outgoing-args' option is required for function graph
tracing in order to avoid GCC bug 42109.

However, GCC ignores '-maccumulate-outgoing-args' when '-Os' is
also set.

Currently we force a build error to prevent that scenario, but that
breaks randconfigs.  So change the error to a warning which also
disables CONFIG_CC_OPTIMIZE_FOR_SIZE.

Reported-by: Andi Kleen &lt;andi@firstfloor.org&gt;
Signed-off-by: Josh Poimboeuf &lt;jpoimboe@redhat.com&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Steven Rostedt &lt;rostedt@goodmis.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: kbuild test robot &lt;fengguang.wu@intel.com&gt;
Cc: kbuild-all@01.org
Link: http://lkml.kernel.org/r/20170418214429.o7fbwbmf4nqosezy@treble
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
For pre-4.6.0 versions of GCC, which don't have '-mfentry', the
'-maccumulate-outgoing-args' option is required for function graph
tracing in order to avoid GCC bug 42109.

However, GCC ignores '-maccumulate-outgoing-args' when '-Os' is
also set.

Currently we force a build error to prevent that scenario, but that
breaks randconfigs.  So change the error to a warning which also
disables CONFIG_CC_OPTIMIZE_FOR_SIZE.

Reported-by: Andi Kleen &lt;andi@firstfloor.org&gt;
Signed-off-by: Josh Poimboeuf &lt;jpoimboe@redhat.com&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Steven Rostedt &lt;rostedt@goodmis.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: kbuild test robot &lt;fengguang.wu@intel.com&gt;
Cc: kbuild-all@01.org
Link: http://lkml.kernel.org/r/20170418214429.o7fbwbmf4nqosezy@treble
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>x86/mce: Make the MCE notifier a blocking one</title>
<updated>2017-04-18T20:23:48+00:00</updated>
<author>
<name>Vishal Verma</name>
<email>vishal.l.verma@intel.com</email>
</author>
<published>2017-04-18T18:42:35+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=0dc9c639e6553e39c13b2c0d54c8a1b098cb95e2'/>
<id>0dc9c639e6553e39c13b2c0d54c8a1b098cb95e2</id>
<content type='text'>
The NFIT MCE handler callback (for handling media errors on NVDIMMs)
takes a mutex to add the location of a memory error to a list. But since
the notifier call chain for machine checks (x86_mce_decoder_chain) is
atomic, we get a lockdep splat like:

  BUG: sleeping function called from invalid context at kernel/locking/mutex.c:620
  in_atomic(): 1, irqs_disabled(): 0, pid: 4, name: kworker/0:0
  [..]
  Call Trace:
   dump_stack
   ___might_sleep
   __might_sleep
   mutex_lock_nested
   ? __lock_acquire
   nfit_handle_mce
   notifier_call_chain
   atomic_notifier_call_chain
   ? atomic_notifier_call_chain
   mce_gen_pool_process

Convert the notifier to a blocking one which gets to run only in process
context.

Boris: remove the notifier call in atomic context in print_mce(). For
now, let's print the MCE on the atomic path so that we can make sure
they go out and get logged at least.

Fixes: 6839a6d96f4e ("nfit: do an ARS scrub on hitting a latent media error")
Reported-by: Ross Zwisler &lt;ross.zwisler@linux.intel.com&gt;
Signed-off-by: Vishal Verma &lt;vishal.l.verma@intel.com&gt;
Acked-by: Tony Luck &lt;tony.luck@intel.com&gt;
Cc: Dan Williams &lt;dan.j.williams@intel.com&gt;
Cc: linux-edac &lt;linux-edac@vger.kernel.org&gt;
Cc: x86-ml &lt;x86@kernel.org&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Link: http://lkml.kernel.org/r/20170411224457.24777-1-vishal.l.verma@intel.com
Signed-off-by: Borislav Petkov &lt;bp@suse.de&gt;
Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The NFIT MCE handler callback (for handling media errors on NVDIMMs)
takes a mutex to add the location of a memory error to a list. But since
the notifier call chain for machine checks (x86_mce_decoder_chain) is
atomic, we get a lockdep splat like:

  BUG: sleeping function called from invalid context at kernel/locking/mutex.c:620
  in_atomic(): 1, irqs_disabled(): 0, pid: 4, name: kworker/0:0
  [..]
  Call Trace:
   dump_stack
   ___might_sleep
   __might_sleep
   mutex_lock_nested
   ? __lock_acquire
   nfit_handle_mce
   notifier_call_chain
   atomic_notifier_call_chain
   ? atomic_notifier_call_chain
   mce_gen_pool_process

Convert the notifier to a blocking one which gets to run only in process
context.

Boris: remove the notifier call in atomic context in print_mce(). For
now, let's print the MCE on the atomic path so that we can make sure
they go out and get logged at least.

Fixes: 6839a6d96f4e ("nfit: do an ARS scrub on hitting a latent media error")
Reported-by: Ross Zwisler &lt;ross.zwisler@linux.intel.com&gt;
Signed-off-by: Vishal Verma &lt;vishal.l.verma@intel.com&gt;
Acked-by: Tony Luck &lt;tony.luck@intel.com&gt;
Cc: Dan Williams &lt;dan.j.williams@intel.com&gt;
Cc: linux-edac &lt;linux-edac@vger.kernel.org&gt;
Cc: x86-ml &lt;x86@kernel.org&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Link: http://lkml.kernel.org/r/20170411224457.24777-1-vishal.l.verma@intel.com
Signed-off-by: Borislav Petkov &lt;bp@suse.de&gt;
Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm</title>
<updated>2017-04-15T21:07:03+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2017-04-15T21:07:03+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=d5ff0814fda50f0306e102f39640cf5bb76af08e'/>
<id>d5ff0814fda50f0306e102f39640cf5bb76af08e</id>
<content type='text'>
Pull nvdimm fixes from Dan Williams:
 "A small crop of lockdep, sleeping while atomic, and other fixes /
  band-aids in advance of the full-blown reworks targeting the next
  merge window. The largest change here is "libnvdimm: fix blk free
  space accounting" which deletes a pile of buggy code that better
  testing would have caught before merging. The next change that is
  borderline too big for a late rc is switching the device-dax locking
  from rcu to srcu, I couldn't think of a smaller way to make that fix.

  The __copy_user_nocache fix will have a full replacement in 4.12 to
  move those pmem special case considerations into the pmem driver. The
  "libnvdimm: band aid btt vs clear poison locking" commit admits that
  our error clearing support for btt went in broken, so we just disable
  it in 4.11 and -stable. A replacement / full fix is in the pipeline
  for 4.12

  Some of these would have been caught earlier had DEBUG_ATOMIC_SLEEP
  been enabled on my development station. I wonder if we should have:

      config DEBUG_ATOMIC_SLEEP
        default PROVE_LOCKING

  ...since I mistakenly thought I got both with PROVE_LOCKING=y.

  These have received a build success notification from the 0day robot,
  and some have appeared in a -next release with no reported issues"

* 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  x86, pmem: fix broken __copy_user_nocache cache-bypass assumptions
  device-dax: switch to srcu, fix rcu_read_lock() vs pte allocation
  libnvdimm: band aid btt vs clear poison locking
  libnvdimm: fix reconfig_mutex, mmap_sem, and jbd2_handle lockdep splat
  libnvdimm: fix blk free space accounting
  acpi, nfit, libnvdimm: fix interleave set cookie calculation (64-bit comparison)
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull nvdimm fixes from Dan Williams:
 "A small crop of lockdep, sleeping while atomic, and other fixes /
  band-aids in advance of the full-blown reworks targeting the next
  merge window. The largest change here is "libnvdimm: fix blk free
  space accounting" which deletes a pile of buggy code that better
  testing would have caught before merging. The next change that is
  borderline too big for a late rc is switching the device-dax locking
  from rcu to srcu, I couldn't think of a smaller way to make that fix.

  The __copy_user_nocache fix will have a full replacement in 4.12 to
  move those pmem special case considerations into the pmem driver. The
  "libnvdimm: band aid btt vs clear poison locking" commit admits that
  our error clearing support for btt went in broken, so we just disable
  it in 4.11 and -stable. A replacement / full fix is in the pipeline
  for 4.12

  Some of these would have been caught earlier had DEBUG_ATOMIC_SLEEP
  been enabled on my development station. I wonder if we should have:

      config DEBUG_ATOMIC_SLEEP
        default PROVE_LOCKING

  ...since I mistakenly thought I got both with PROVE_LOCKING=y.

  These have received a build success notification from the 0day robot,
  and some have appeared in a -next release with no reported issues"

* 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  x86, pmem: fix broken __copy_user_nocache cache-bypass assumptions
  device-dax: switch to srcu, fix rcu_read_lock() vs pte allocation
  libnvdimm: band aid btt vs clear poison locking
  libnvdimm: fix reconfig_mutex, mmap_sem, and jbd2_handle lockdep splat
  libnvdimm: fix blk free space accounting
  acpi, nfit, libnvdimm: fix interleave set cookie calculation (64-bit comparison)
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip</title>
<updated>2017-04-15T00:00:01+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2017-04-15T00:00:01+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=91174391bf5a368c9837b63b84d7f5a813efd719'/>
<id>91174391bf5a368c9837b63b84d7f5a813efd719</id>
<content type='text'>
Pull x86 fixes from Thomas Gleixner:
 "A set of small fixes for x86:

   - fix locking in RDT to prevent memory leaks and freeing in use
     memory

   - prevent setting invalid values for vdso32_enabled which cause
     inconsistencies for user space resulting in application crashes.

   - plug a race in the vdso32 code between fork and sysctl which causes
     inconsistencies for user space resulting in application crashes.

   - make MPX signal delivery work in compat mode

   - make the dmesg output of traps and faults readable again"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/intel_rdt: Fix locking in rdtgroup_schemata_write()
  x86/debug: Fix the printk() debug output of signal_fault(), do_trap() and do_general_protection()
  x86/vdso: Plug race between mapping and ELF header setup
  x86/vdso: Ensure vdso32_enabled gets set to valid values only
  x86/signals: Fix lower/upper bound reporting in compat siginfo
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull x86 fixes from Thomas Gleixner:
 "A set of small fixes for x86:

   - fix locking in RDT to prevent memory leaks and freeing in use
     memory

   - prevent setting invalid values for vdso32_enabled which cause
     inconsistencies for user space resulting in application crashes.

   - plug a race in the vdso32 code between fork and sysctl which causes
     inconsistencies for user space resulting in application crashes.

   - make MPX signal delivery work in compat mode

   - make the dmesg output of traps and faults readable again"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/intel_rdt: Fix locking in rdtgroup_schemata_write()
  x86/debug: Fix the printk() debug output of signal_fault(), do_trap() and do_general_protection()
  x86/vdso: Plug race between mapping and ELF header setup
  x86/vdso: Ensure vdso32_enabled gets set to valid values only
  x86/signals: Fix lower/upper bound reporting in compat siginfo
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip</title>
<updated>2017-04-14T23:58:38+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2017-04-14T23:58:38+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=07c7016de7896493e95bef64fe913ac849509d6e'/>
<id>07c7016de7896493e95bef64fe913ac849509d6e</id>
<content type='text'>
Pull perf fixes from Thomas Gleixner:
 "Two small fixes for perf:

   - the move to support cross arch annotation introduced per arch
     initialization requirements, fullfill them for s/390 (Christian
     Borntraeger)

   - add the missing initialization to the LBR entries to avoid exposing
     random or stale data"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86: Avoid exposing wrong/stale data in intel_pmu_lbr_read_32()
  perf annotate s390: Fix perf annotate error -95 (4.10 regression)
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull perf fixes from Thomas Gleixner:
 "Two small fixes for perf:

   - the move to support cross arch annotation introduced per arch
     initialization requirements, fullfill them for s/390 (Christian
     Borntraeger)

   - add the missing initialization to the LBR entries to avoid exposing
     random or stale data"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86: Avoid exposing wrong/stale data in intel_pmu_lbr_read_32()
  perf annotate s390: Fix perf annotate error -95 (4.10 regression)
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'efi-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip</title>
<updated>2017-04-14T23:55:33+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2017-04-14T23:55:33+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=f399ecb4b49b3b6afb5bbb613bfa3728682a3e4f'/>
<id>f399ecb4b49b3b6afb5bbb613bfa3728682a3e4f</id>
<content type='text'>
Pull EFI fixes from Thomas Gleixner:
 "Three fixes from EFI land:

   - prevent accessing a Graphic Output Device (GOP) which the kernel
     does not know to handle

   - prevent PCI reconfiguration to modify a BAR which covers the
     framebuffer because that's already in use through the EFI GOP
     interface

   - avoid reserving EFI runtime regions as this results in bogus memory
     mappings"

* 'efi-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/efi: Don't try to reserve runtime regions
  efi/fb: Avoid reconfiguration of BAR that covers the framebuffer
  efi/libstub: Skip GOP with PIXEL_BLT_ONLY format
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull EFI fixes from Thomas Gleixner:
 "Three fixes from EFI land:

   - prevent accessing a Graphic Output Device (GOP) which the kernel
     does not know to handle

   - prevent PCI reconfiguration to modify a BAR which covers the
     framebuffer because that's already in use through the EFI GOP
     interface

   - avoid reserving EFI runtime regions as this results in bogus memory
     mappings"

* 'efi-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/efi: Don't try to reserve runtime regions
  efi/fb: Avoid reconfiguration of BAR that covers the framebuffer
  efi/libstub: Skip GOP with PIXEL_BLT_ONLY format
</pre>
</div>
</content>
</entry>
<entry>
<title>ftrace/x86: Fix triple fault with graph tracing and suspend-to-ram</title>
<updated>2017-04-14T09:48:51+00:00</updated>
<author>
<name>Josh Poimboeuf</name>
<email>jpoimboe@redhat.com</email>
</author>
<published>2017-04-13T22:53:55+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=34a477e5297cbaa6ecc6e17c042a866e1cbe80d6'/>
<id>34a477e5297cbaa6ecc6e17c042a866e1cbe80d6</id>
<content type='text'>
On x86-32, with CONFIG_FIRMWARE and multiple CPUs, if you enable function
graph tracing and then suspend to RAM, it will triple fault and reboot when
it resumes.

The first fault happens when booting a secondary CPU:

startup_32_smp()
  load_ucode_ap()
    prepare_ftrace_return()
      ftrace_graph_is_dead()
        (accesses 'kill_ftrace_graph')

The early head_32.S code calls into load_ucode_ap(), which has an an
ftrace hook, so it calls prepare_ftrace_return(), which calls
ftrace_graph_is_dead(), which tries to access the global
'kill_ftrace_graph' variable with a virtual address, causing a fault
because the CPU is still in real mode.

The fix is to add a check in prepare_ftrace_return() to make sure it's
running in protected mode before continuing.  The check makes sure the
stack pointer is a virtual kernel address.  It's a bit of a hack, but
it's not very intrusive and it works well enough.

For reference, here are a few other (more difficult) ways this could
have potentially been fixed:

- Move startup_32_smp()'s call to load_ucode_ap() down to *after* paging
  is enabled.  (No idea what that would break.)

- Track down load_ucode_ap()'s entire callee tree and mark all the
  functions 'notrace'.  (Probably not realistic.)

- Pause graph tracing in ftrace_suspend_notifier_call() or bringup_cpu()
  or __cpu_up(), and ensure that the pause facility can be queried from
  real mode.

Reported-by: Paul Menzel &lt;pmenzel@molgen.mpg.de&gt;
Signed-off-by: Josh Poimboeuf &lt;jpoimboe@redhat.com&gt;
Tested-by: Paul Menzel &lt;pmenzel@molgen.mpg.de&gt;
Reviewed-by: Steven Rostedt (VMware) &lt;rostedt@goodmis.org&gt;
Cc: "Rafael J . Wysocki" &lt;rjw@rjwysocki.net&gt;
Cc: linux-acpi@vger.kernel.org
Cc: Borislav Petkov &lt;bp@alien8.de&gt;
Cc: stable@kernel.org
Cc: Len Brown &lt;lenb@kernel.org&gt;
Link: http://lkml.kernel.org/r/5c1272269a580660703ed2eccf44308e790c7a98.1492123841.git.jpoimboe@redhat.com
Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
On x86-32, with CONFIG_FIRMWARE and multiple CPUs, if you enable function
graph tracing and then suspend to RAM, it will triple fault and reboot when
it resumes.

The first fault happens when booting a secondary CPU:

startup_32_smp()
  load_ucode_ap()
    prepare_ftrace_return()
      ftrace_graph_is_dead()
        (accesses 'kill_ftrace_graph')

The early head_32.S code calls into load_ucode_ap(), which has an an
ftrace hook, so it calls prepare_ftrace_return(), which calls
ftrace_graph_is_dead(), which tries to access the global
'kill_ftrace_graph' variable with a virtual address, causing a fault
because the CPU is still in real mode.

The fix is to add a check in prepare_ftrace_return() to make sure it's
running in protected mode before continuing.  The check makes sure the
stack pointer is a virtual kernel address.  It's a bit of a hack, but
it's not very intrusive and it works well enough.

For reference, here are a few other (more difficult) ways this could
have potentially been fixed:

- Move startup_32_smp()'s call to load_ucode_ap() down to *after* paging
  is enabled.  (No idea what that would break.)

- Track down load_ucode_ap()'s entire callee tree and mark all the
  functions 'notrace'.  (Probably not realistic.)

- Pause graph tracing in ftrace_suspend_notifier_call() or bringup_cpu()
  or __cpu_up(), and ensure that the pause facility can be queried from
  real mode.

Reported-by: Paul Menzel &lt;pmenzel@molgen.mpg.de&gt;
Signed-off-by: Josh Poimboeuf &lt;jpoimboe@redhat.com&gt;
Tested-by: Paul Menzel &lt;pmenzel@molgen.mpg.de&gt;
Reviewed-by: Steven Rostedt (VMware) &lt;rostedt@goodmis.org&gt;
Cc: "Rafael J . Wysocki" &lt;rjw@rjwysocki.net&gt;
Cc: linux-acpi@vger.kernel.org
Cc: Borislav Petkov &lt;bp@alien8.de&gt;
Cc: stable@kernel.org
Cc: Len Brown &lt;lenb@kernel.org&gt;
Link: http://lkml.kernel.org/r/5c1272269a580660703ed2eccf44308e790c7a98.1492123841.git.jpoimboe@redhat.com
Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>perf/x86: Avoid exposing wrong/stale data in intel_pmu_lbr_read_32()</title>
<updated>2017-04-14T08:18:00+00:00</updated>
<author>
<name>Peter Zijlstra</name>
<email>peterz@infradead.org</email>
</author>
<published>2017-04-11T08:10:28+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=f2200ac311302fcdca6556fd0c5127eab6c65a3e'/>
<id>f2200ac311302fcdca6556fd0c5127eab6c65a3e</id>
<content type='text'>
When the perf_branch_entry::{in_tx,abort,cycles} fields were added,
intel_pmu_lbr_read_32() wasn't updated to initialize them.

Signed-off-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: linux-kernel@vger.kernel.org
Cc: &lt;stable@vger.kernel.org&gt;
Fixes: 135c5612c460 ("perf/x86/intel: Support Haswell/v4 LBR format")
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
When the perf_branch_entry::{in_tx,abort,cycles} fields were added,
intel_pmu_lbr_read_32() wasn't updated to initialize them.

Signed-off-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: linux-kernel@vger.kernel.org
Cc: &lt;stable@vger.kernel.org&gt;
Fixes: 135c5612c460 ("perf/x86/intel: Support Haswell/v4 LBR format")
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
</pre>
</div>
</content>
</entry>
</feed>
