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  1. 08 3月, 2016 1 次提交
    • K
      perf/x86/intel: Fix PEBS warning by only restoring active PMU in pmi · c3d266c8
      由 Kan Liang 提交于 
      This patch tries to fix a PEBS warning found in my stress test. The
following perf command can easily trigger the pebs warning or spurious
NMI error on Skylake/Broadwell/Haswell platforms:

  sudo perf record -e 'cpu/umask=0x04,event=0xc4/pp,cycles,branches,ref-cycles,cache-misses,cache-references' --call-graph fp -b -c1000 -a

Also the NMI watchdog must be enabled.

For this case, the events number is larger than counter number. So
perf has to do multiplexing.

In perf_mux_hrtimer_handler, it does perf_pmu_disable(), schedule out
old events, rotate_ctx, schedule in new events and finally
perf_pmu_enable().

If the old events include precise event, the MSR_IA32_PEBS_ENABLE
should be cleared when perf_pmu_disable().  The MSR_IA32_PEBS_ENABLE
should keep 0 until the perf_pmu_enable() is called and the new event is
precise event.

However, there is a corner case which could restore PEBS_ENABLE to
stale value during the above period. In perf_pmu_disable(), GLOBAL_CTRL
will be set to 0 to stop overflow and followed PMI. But there may be
pending PMI from an earlier overflow, which cannot be stopped. So even
GLOBAL_CTRL is cleared, the kernel still be possible to get PMI. At
the end of the PMI handler, __intel_pmu_enable_all() will be called,
which will restore the stale values if old events haven't scheduled
out.

Once the stale pebs value is set, it's impossible to be corrected if
the new events are non-precise. Because the pebs_enabled will be set
to 0. x86_pmu.enable_all() will ignore the MSR_IA32_PEBS_ENABLE
setting. As a result, the following NMI with stale PEBS_ENABLE
trigger pebs warning.

The pending PMI after enabled=0 will become harmless if the NMI handler
does not change the state. This patch checks cpuc->enabled in pmi and
only restore the state when PMU is active.

Here is the dump:

  Call Trace:
   <NMI>  [<ffffffff813c3a2e>] dump_stack+0x63/0x85
   [<ffffffff810a46f2>] warn_slowpath_common+0x82/0xc0
   [<ffffffff810a483a>] warn_slowpath_null+0x1a/0x20
   [<ffffffff8100fe2e>] intel_pmu_drain_pebs_nhm+0x2be/0x320
   [<ffffffff8100caa9>] intel_pmu_handle_irq+0x279/0x460
   [<ffffffff810639b6>] ? native_write_msr_safe+0x6/0x40
   [<ffffffff811f290d>] ? vunmap_page_range+0x20d/0x330
   [<ffffffff811f2f11>] ?  unmap_kernel_range_noflush+0x11/0x20
   [<ffffffff8148379f>] ? ghes_copy_tofrom_phys+0x10f/0x2a0
   [<ffffffff814839c8>] ? ghes_read_estatus+0x98/0x170
   [<ffffffff81005a7d>] perf_event_nmi_handler+0x2d/0x50
   [<ffffffff810310b9>] nmi_handle+0x69/0x120
   [<ffffffff810316f6>] default_do_nmi+0xe6/0x100
   [<ffffffff810317f2>] do_nmi+0xe2/0x130
   [<ffffffff817aea71>] end_repeat_nmi+0x1a/0x1e
   [<ffffffff810639b6>] ? native_write_msr_safe+0x6/0x40
   [<ffffffff810639b6>] ? native_write_msr_safe+0x6/0x40
   [<ffffffff810639b6>] ? native_write_msr_safe+0x6/0x40
   <<EOE>>  <IRQ>  [<ffffffff81006df8>] ?  x86_perf_event_set_period+0xd8/0x180
   [<ffffffff81006eec>] x86_pmu_start+0x4c/0x100
   [<ffffffff8100722d>] x86_pmu_enable+0x28d/0x300
   [<ffffffff811994d7>] perf_pmu_enable.part.81+0x7/0x10
   [<ffffffff8119cb70>] perf_mux_hrtimer_handler+0x200/0x280
   [<ffffffff8119c970>] ?  __perf_install_in_context+0xc0/0xc0
   [<ffffffff8110f92d>] __hrtimer_run_queues+0xfd/0x280
   [<ffffffff811100d8>] hrtimer_interrupt+0xa8/0x190
   [<ffffffff81199080>] ?  __perf_read_group_add.part.61+0x1a0/0x1a0
   [<ffffffff81051bd8>] local_apic_timer_interrupt+0x38/0x60
   [<ffffffff817af01d>] smp_apic_timer_interrupt+0x3d/0x50
   [<ffffffff817ad15c>] apic_timer_interrupt+0x8c/0xa0
   <EOI>  [<ffffffff81199080>] ?  __perf_read_group_add.part.61+0x1a0/0x1a0
   [<ffffffff81123de5>] ?  smp_call_function_single+0xd5/0x130
   [<ffffffff81123ddb>] ?  smp_call_function_single+0xcb/0x130
   [<ffffffff81199080>] ?  __perf_read_group_add.part.61+0x1a0/0x1a0
   [<ffffffff8119765a>] event_function_call+0x10a/0x120
   [<ffffffff8119c660>] ? ctx_resched+0x90/0x90
   [<ffffffff811971e0>] ? cpu_clock_event_read+0x30/0x30
   [<ffffffff811976d0>] ? _perf_event_disable+0x60/0x60
   [<ffffffff8119772b>] _perf_event_enable+0x5b/0x70
   [<ffffffff81197388>] perf_event_for_each_child+0x38/0xa0
   [<ffffffff811976d0>] ? _perf_event_disable+0x60/0x60
   [<ffffffff811a0ffd>] perf_ioctl+0x12d/0x3c0
   [<ffffffff8134d855>] ? selinux_file_ioctl+0x95/0x1e0
   [<ffffffff8124a3a1>] do_vfs_ioctl+0xa1/0x5a0
   [<ffffffff81036d29>] ? sched_clock+0x9/0x10
   [<ffffffff8124a919>] SyS_ioctl+0x79/0x90
   [<ffffffff817ac4b2>] entry_SYSCALL_64_fastpath+0x1a/0xa4
  ---[ end trace aef202839fe9a71d ]---
  Uhhuh. NMI received for unknown reason 2d on CPU 2.
  Do you have a strange power saving mode enabled?
Signed-off-by: NKan Liang <kan.liang@intel.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/1457046448-6184-1-git-send-email-kan.liang@intel.com
[ Fixed various typos and other small details. ]
Signed-off-by: NIngo Molnar <mingo@kernel.org>
      c3d266c8
  3. 17 2月, 2016 1 次提交
  5. 09 2月, 2016 1 次提交
  7. 03 2月, 2016 1 次提交
  9. 06 1月, 2016 2 次提交
    • S
      perf/x86: Fix filter_events() bug with event mappings · 61b87cae
      由 Stephane Eranian 提交于 
      This patch fixes a bug in the filter_events() function.

The patch fixes the bug whereby if some mappings did not
exist, e.g., STALLED_CYCLES_FRONTEND, then any event after it
in the attrs array would disappear from the published list of
events in /sys/devices/cpu/events. This could be verified
easily on any system post SNB (which do not publish
STALLED_CYCLES_FRONTEND):

	$ ./perf stat -e cycles,ref-cycles true
	Performance counter stats for 'true':
              1,217,348      cycles
	<not supported>      ref-cycles

The problem is that in filter_events() there is an assumption
that the argument (attrs) is organized in increasing continuous
event indexes related to the event_map(). But if we remove the
non-supported events by shifing the position in the array, then
the lookup x86_pmu.event_map() needs to compensate for it, otherwise
we are looking up the wrong index. This patch corrects this problem
by compensating for the deleted events and with that ref-cycles
reappears (here shown on Haswell):

	$ perf stat -e ref-cycles,cycles true
	Performance counter stats for 'true':
         4,525,910      ref-cycles
         1,064,920      cycles
       0.002943888 seconds time elapsed
Signed-off-by: NStephane Eranian <eranian@google.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: jolsa@kernel.org
Cc: kan.liang@intel.com
Fixes: 8300daa2 ("perf/x86: Filter out undefined events from sysfs events attribute")
Link: http://lkml.kernel.org/r/1449516805-6637-1-git-send-email-eranian@google.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      61b87cae
    • A
      perf/x86: Use INST_RETIRED.PREC_DIST for cycles: ppp · 72469764
      由 Andi Kleen 提交于 
      Add a new 'three-p' precise level, that uses INST_RETIRED.PREC_DIST as
base. The basic mechanism of abusing the inverse cmask to get all
cycles works the same as before.

PREC_DIST is available on Sandy Bridge or later. It had some problems
on Sandy Bridge, so we only use it on IvyBridge and later. I tested it
on Broadwell and Skylake.

PREC_DIST has special support for avoiding shadow effects, which can
give better results compare to UOPS_RETIRED. The drawback is that
PREC_DIST can only schedule on counter 1, but that is ok for cycle
sampling, as there is normally no need to do multiple cycle sampling
runs in parallel. It is still possible to run perf top in parallel, as
that doesn't use precise mode. Also of course the multiplexing can
still allow parallel operation.

:pp stays with the previous event.

Example:

Sample a loop with 10 sqrt with old cycles:pp

	  0.14 │10:   sqrtps %xmm1,%xmm0     <--------------
	  9.13 │      sqrtps %xmm1,%xmm0
	 11.58 │      sqrtps %xmm1,%xmm0
	 11.51 │      sqrtps %xmm1,%xmm0
	  6.27 │      sqrtps %xmm1,%xmm0
	 10.38 │      sqrtps %xmm1,%xmm0
	 12.20 │      sqrtps %xmm1,%xmm0
	 12.74 │      sqrtps %xmm1,%xmm0
	  5.40 │      sqrtps %xmm1,%xmm0
	 10.14 │      sqrtps %xmm1,%xmm0
	 10.51 │    ↑ jmp    10

We expect all 10 sqrt to get roughly the sample number of samples.

But you can see that the instruction directly after the JMP is
systematically underestimated in the result, due to sampling shadow
effects.

With the new PREC_DIST based sampling this problem is gone and all
instructions show up roughly evenly:

	  9.51 │10:   sqrtps %xmm1,%xmm0
	 11.74 │      sqrtps %xmm1,%xmm0
	 11.84 │      sqrtps %xmm1,%xmm0
	  6.05 │      sqrtps %xmm1,%xmm0
	 10.46 │      sqrtps %xmm1,%xmm0
	 12.25 │      sqrtps %xmm1,%xmm0
	 12.18 │      sqrtps %xmm1,%xmm0
	  5.26 │      sqrtps %xmm1,%xmm0
	 10.13 │      sqrtps %xmm1,%xmm0
	 10.43 │      sqrtps %xmm1,%xmm0
	  0.16 │    ↑ jmp    10

Even with PREC_DIST there is still sampling skid and the result is not
completely even, but systematic shadow effects are significantly
reduced.

The improvements are mainly expected to make a difference in high IPC
code. With low IPC it should be similar.
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: hpa@zytor.com
Link: http://lkml.kernel.org/r/1448929689-13771-2-git-send-email-andi@firstfloor.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
      72469764
  11. 23 11月, 2015 2 次提交
    • A
      perf/x86: Optimize stack walk user accesses · 75925e1a
      由 Andi Kleen 提交于 
      Change the perf user stack walking to use the new
__copy_from_user_nmi(), and split each access into word sized transfer
sizes. This allows to inline the complete access and optimize it all
into a single load.

The main advantage is that this avoids the overhead of double page
faults.  When normal copy_from_user() fails it reexecutes the copy to
compute an accurate number of non copied bytes. This leads to
executing the expensive page fault twice.

While walking stacks having a fault at some point is relatively common
(typically when some part of the program isn't compiled with frame
pointers), so this is a large overhead.

With the optimized copies we avoid this problem because they only do
all accesses once. And of course they're much faster too when the
access does not fault because they're just single instructions instead
of complex function calls.

While profiling a kernel build with -g, the patch brings down the
average time of the PMI handler from 966ns to 552ns (-43%).
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/1445551641-13379-2-git-send-email-andi@firstfloor.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
      75925e1a
    • P
      treewide: Remove old email address · 90eec103
      由 Peter Zijlstra 提交于 
      There were still a number of references to my old Red Hat email
address in the kernel source. Remove these while keeping the
Red Hat copyright notices intact.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: NIngo Molnar <mingo@kernel.org>
      90eec103
  13. 13 9月, 2015 2 次提交
    • S
      perf/core: Drop PERF_EVENT_TXN · 8f3e5684
      由 Sukadev Bhattiprolu 提交于 
      We currently use PERF_EVENT_TXN flag to determine if we are in the middle
of a transaction. If in a transaction, we defer the schedulability checks
from pmu->add() operation to the pmu->commit() operation.

Now that we have "transaction types" (PERF_PMU_TXN_ADD, PERF_PMU_TXN_READ)
we can use the type to determine if we are in a transaction and drop the
PERF_EVENT_TXN flag.

When PERF_EVENT_TXN is dropped, the cpuhw->group_flag on some architectures
becomes unused, so drop that field as well.

This is an extension of the Powerpc patch from Peter Zijlstra to s390,
Sparc and x86 architectures.
Signed-off-by: NSukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/1441336073-22750-11-git-send-email-sukadev@linux.vnet.ibm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      8f3e5684
    • S
      perf/core: Add a 'flags' parameter to the PMU transactional interfaces · fbbe0701
      由 Sukadev Bhattiprolu 提交于 
      Currently, the PMU interface allows reading only one counter at a time.
But some PMUs like the 24x7 counters in Power, support reading several
counters at once. To leveage this functionality, extend the transaction
interface to support a "transaction type".

The first type, PERF_PMU_TXN_ADD, refers to the existing transactions,
i.e. used to _schedule_ all the events on the PMU as a group. A second
transaction type, PERF_PMU_TXN_READ, will be used in a follow-on patch,
by the 24x7 counters to read several counters at once.

Extend the transaction interfaces to the PMU to accept a 'txn_flags'
parameter and use this parameter to ignore any transactions that are
not of type PERF_PMU_TXN_ADD.

Thanks to Peter Zijlstra for his input.
Signed-off-by: NSukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
[peterz: s390 compile fix]
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: NMichael Ellerman <mpe@ellerman.id.au>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/1441336073-22750-3-git-send-email-sukadev@linux.vnet.ibm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      fbbe0701
  15. 04 8月, 2015 1 次提交
  17. 31 7月, 2015 2 次提交
    • A
      x86/ldt: Make modify_ldt() optional · a5b9e5a2
      由 Andy Lutomirski 提交于 
      The modify_ldt syscall exposes a large attack surface and is
unnecessary for modern userspace.  Make it optional.
Signed-off-by: NAndy Lutomirski <luto@kernel.org>
Reviewed-by: NKees Cook <keescook@chromium.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: security@kernel.org <security@kernel.org>
Cc: xen-devel <xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/a605166a771c343fd64802dece77a903507333bd.1438291540.git.luto@kernel.org
[ Made MATH_EMULATION dependent on MODIFY_LDT_SYSCALL. ]
Signed-off-by: NIngo Molnar <mingo@kernel.org>
      a5b9e5a2
    • A
      x86/ldt: Make modify_ldt synchronous · 37868fe1
      由 Andy Lutomirski 提交于 
      modify_ldt() has questionable locking and does not synchronize
threads.  Improve it: redesign the locking and synchronize all
threads' LDTs using an IPI on all modifications.

This will dramatically slow down modify_ldt in multithreaded
programs, but there shouldn't be any multithreaded programs that
care about modify_ldt's performance in the first place.

This fixes some fallout from the CVE-2015-5157 fixes.
Signed-off-by: NAndy Lutomirski <luto@kernel.org>
Reviewed-by: NBorislav Petkov <bp@suse.de>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: security@kernel.org <security@kernel.org>
Cc: <stable@vger.kernel.org>
Cc: xen-devel <xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/4c6978476782160600471bd865b318db34c7b628.1438291540.git.luto@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
      37868fe1
  19. 06 7月, 2015 1 次提交
  21. 30 6月, 2015 1 次提交
    • P
      perf/x86: Fix 'active_events' imbalance · 93472aff
      由 Peter Zijlstra 提交于 
      Commit 1b7b938f ("perf/x86/intel: Fix PMI handling for Intel PT") conditionally
increments active_events in x86_add_exclusive() but unconditionally decrements in
x86_del_exclusive().

These extra decrements can lead to the situation where
active_events is zero and thus the PMI handler is 'disabled'
while we have active events on the PMU generating PMIs.

This leads to a truckload of:

  Uhhuh. NMI received for unknown reason 21 on CPU 28.
  Do you have a strange power saving mode enabled?
  Dazed and confused, but trying to continue

messages and generally messes up perf.

Remove the condition on the increment, double increment balanced
by a double decrement is perfectly fine.

Restructure the code a little bit to make the unconditional inc
a bit more natural.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: alexander.shishkin@linux.intel.com
Cc: brgerst@gmail.com
Cc: dvlasenk@redhat.com
Cc: luto@amacapital.net
Cc: oleg@redhat.com
Fixes: 1b7b938f ("perf/x86/intel: Fix PMI handling for Intel PT")
Link: http://lkml.kernel.org/r/20150624144750.GJ18673@twins.programming.kicks-ass.netSigned-off-by: NIngo Molnar <mingo@kernel.org>
      93472aff
  23. 19 6月, 2015 2 次提交
    • A
      perf/x86/intel: Fix PMI handling for Intel PT · 1b7b938f
      由 Alexander Shishkin 提交于 
      Intel PT is a separate PMU and it is not using any of the x86_pmu
code paths, which means in particular that the active_events counter
remains intact when new PT events are created.

However, PT uses the generic x86_pmu PMI handler for its PMI handling needs.

The problem here is that the latter checks active_events and in case of it
being zero, exits without calling the actual x86_pmu.handle_nmi(), which
results in unknown NMI errors and massive data loss for PT.

The effect is not visible if there are other perf events in the system
at the same time that keep active_events counter non-zero, for instance
if the NMI watchdog is running, so one needs to disable it to reproduce
the problem.

At the same time, the active_events counter besides doing what the name
suggests also implicitly serves as a PMC hardware and DS area reference
counter.

This patch adds a separate reference counter for the PMC hardware, leaving
active_events for actually counting the events and makes sure it also
counts PT and BTS events.
Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@infradead.org
Cc: adrian.hunter@intel.com
Link: http://lkml.kernel.org/r/87k2v92t0s.fsf@ashishki-desk.ger.corp.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      1b7b938f
    • A
      perf/x86/intel/bts: Fix DS area sharing with x86_pmu events · 6b099d9b
      由 Alexander Shishkin 提交于 
      Currently, the intel_bts driver relies on the DS area allocated by the x86_pmu
code in its event_init() path, which is a bug: creating a BTS event while
no x86_pmu events are present results in a NULL pointer dereference.

The same DS area is also used by PEBS sampling, which makes it quite a bit
trickier to have a separate one for intel_bts' purposes.

This patch makes intel_bts driver use the same DS allocation and reference
counting code as x86_pmu to make sure it is always present when either
intel_bts or x86_pmu need it.
Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@infradead.org
Cc: adrian.hunter@intel.com
Link: http://lkml.kernel.org/r/1434024837-9916-2-git-send-email-alexander.shishkin@linux.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      6b099d9b
  25. 07 6月, 2015 1 次提交
  27. 27 5月, 2015 5 次提交
    • P
      perf/x86: Simplify the x86_schedule_events() logic · 8736e548
      由 Peter Zijlstra 提交于 
      	!x && y == ! (x || !y)
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: NIngo Molnar <mingo@kernel.org>
      8736e548
    • P
      perf/x86/intel: Remove intel_excl_states::init_state · 43ef205b
      由 Peter Zijlstra 提交于 
      For some obscure reason intel_{start,stop}_scheduling() copy the HT
state to an intermediate array. This would make sense if we ever were
to make changes to it which we'd have to discard.

Except we don't. By the time we call intel_commit_scheduling() we're;
as the name implies; committed to them. We'll never back out.

A further hint its pointless is that stop_scheduling() unconditionally
publishes the state.

So the intermediate array is pointless, modify the state in place and
kill the extra array.

And remove the pointless array initialization: INTEL_EXCL_UNUSED == 0.

Note; all is serialized by intel_excl_cntr::lock.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: NIngo Molnar <mingo@kernel.org>
      43ef205b
    • D
      perf/x86: Tweak broken BIOS rules during check_hw_exists() · 68ab7476
      由 Don Zickus 提交于 
      I stumbled upon an AMD box that had the BIOS using a hardware performance
counter. Instead of printing out a warning and continuing, it failed and
blocked further perf counter usage.

Looking through the history, I found this commit:

  a5ebe0ba ("perf/x86: Check all MSRs before passing hw check")

which tweaked the rules for a Xen guest on an almost identical box and now
changed the behaviour.

Unfortunately the rules were tweaked incorrectly and will always lead to
MSR failures even though the MSRs are completely fine.

What happens now is in arch/x86/kernel/cpu/perf_event.c::check_hw_exists():

<snip>
        for (i = 0; i < x86_pmu.num_counters; i++) {
                reg = x86_pmu_config_addr(i);
                ret = rdmsrl_safe(reg, &val);
                if (ret)
                        goto msr_fail;
                if (val & ARCH_PERFMON_EVENTSEL_ENABLE) {
                        bios_fail = 1;
                        val_fail = val;
                        reg_fail = reg;
                }
        }

<snip>
        /*
         * Read the current value, change it and read it back to see if it
         * matches, this is needed to detect certain hardware emulators
         * (qemu/kvm) that don't trap on the MSR access and always return 0s.
         */
        reg = x86_pmu_event_addr(0);
				^^^^

if the first perf counter is enabled, then this routine will always fail
because the counter is running. :-(

        if (rdmsrl_safe(reg, &val))
                goto msr_fail;
        val ^= 0xffffUL;
        ret = wrmsrl_safe(reg, val);
        ret |= rdmsrl_safe(reg, &val_new);
        if (ret || val != val_new)
                goto msr_fail;

The above bios_fail used to be a 'goto' which is why it worked in the past.

Further, most vendors have migrated to using fixed counters to hide their
evilness hence this problem rarely shows up now days except on a few old boxes.

I fixed my problem and kept the spirit of the original Xen fix, by recording a
safe non-enable register to be used safely for the reading/writing check.
Because it is not enabled, this passes on bare metal boxes (like metal), but
should continue to throw an msr_fail on Xen guests because the register isn't
emulated yet.

Now I get a proper bios_fail error message and Xen should still see their
msr_fail message (untested).
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Signed-off-by: NPeter 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: george.dunlap@eu.citrix.com
Cc: konrad.wilk@oracle.com
Link: http://lkml.kernel.org/r/1431976608-56970-1-git-send-email-dzickus@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      68ab7476
    • P
      perf/x86: Improve HT workaround GP counter constraint · cc1790cf
      由 Peter Zijlstra 提交于 
      The (SNB/IVB/HSW) HT bug only affects events that can be programmed
onto GP counters, therefore we should only limit the number of GP
counters that can be used per cpu -- iow we should not constrain the
FP counters.

Furthermore, we should only enfore such a limit when there are in fact
exclusive events being scheduled on either sibling.
Reported-by: NVince Weaver <vincent.weaver@maine.edu>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
[ Fixed build fail for the !CONFIG_CPU_SUP_INTEL case. ]
Signed-off-by: NIngo Molnar <mingo@kernel.org>
      cc1790cf
    • P
      perf/x86: Fix event/group validation · b371b594
      由 Peter Zijlstra 提交于 
      Commit 43b45780 ("perf/x86: Reduce stack usage of
x86_schedule_events()") violated the rule that 'fake' scheduling; as
used for event/group validation; should not change the event state.

This went mostly un-noticed because repeated calls of
x86_pmu::get_event_constraints() would give the same result. And
x86_pmu::put_event_constraints() would mostly not do anything.

Commit e979121b ("perf/x86/intel: Implement cross-HT corruption
bug workaround") made the situation much worse by actually setting the
event->hw.constraint value to NULL, so when validation and actual
scheduling interact we get NULL ptr derefs.

Fix it by removing the constraint pointer from the event and move it
back to an array, this time in cpuc instead of on the stack.

validate_group()
  x86_schedule_events()
    event->hw.constraint = c; # store

      <context switch>
        perf_task_event_sched_in()
          ...
            x86_schedule_events();
              event->hw.constraint = c2; # store

              ...

              put_event_constraints(event); # assume failure to schedule
                intel_put_event_constraints()
                  event->hw.constraint = NULL;

      <context switch end>

    c = event->hw.constraint; # read -> NULL

    if (!test_bit(hwc->idx, c->idxmsk)) # <- *BOOM* NULL deref

This in particular is possible when the event in question is a
cpu-wide event and group-leader, where the validate_group() tries to
add an event to the group.
Reported-by: NVince Weaver <vincent.weaver@maine.edu>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Hunter <ahh@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maria Dimakopoulou <maria.n.dimakopoulou@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 43b45780 ("perf/x86: Reduce stack usage of x86_schedule_events()")
Fixes: e979121b ("perf/x86/intel: Implement cross-HT corruption bug workaround")
Signed-off-by: NIngo Molnar <mingo@kernel.org>
      b371b594
  29. 02 4月, 2015 7 次提交
  31. 31 3月, 2015 1 次提交
    • I
      x86/asm/entry: Remove user_mode_ignore_vm86() · 55474c48
      由 Ingo Molnar 提交于 
      user_mode_ignore_vm86() can be used instead of user_mode(), in
places where we have already done a v8086_mode() security
check of ptregs.

But doing this check in the wrong place would be a bug that
could result in security problems, and also the naming still
isn't very clear.

Furthermore, it only affects 32-bit kernels, while most
development happens on 64-bit kernels.

If we replace them with user_mode() checks then the cost is only
a very minor increase in various slowpaths:

   text             data   bss     dec              hex    filename
   10573391         703562 1753042 13029995         c6d26b vmlinux.o.before
   10573423         703562 1753042 13030027         c6d28b vmlinux.o.after

So lets get rid of this distinction once and for all.
Acked-by: NBorislav Petkov <bp@suse.de>
Acked-by: NAndy Lutomirski <luto@kernel.org>
Cc: Andrew Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brad Spengler <spender@grsecurity.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150329090233.GA1963@gmail.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      55474c48
  33. 27 3月, 2015 3 次提交
    • P
      perf: Add per event clockid support · 34f43927
      由 Peter Zijlstra 提交于 
      While thinking on the whole clock discussion it occurred to me we have
two distinct uses of time:

 1) the tracking of event/ctx/cgroup enabled/running/stopped times
    which includes the self-monitoring support in struct
    perf_event_mmap_page.

 2) the actual timestamps visible in the data records.

And we've been conflating them.

The first is all about tracking time deltas, nobody should really care
in what time base that happens, its all relative information, as long
as its internally consistent it works.

The second however is what people are worried about when having to
merge their data with external sources. And here we have the
discussion on MONOTONIC vs MONOTONIC_RAW etc..

Where MONOTONIC is good for correlating between machines (static
offset), MONOTNIC_RAW is required for correlating against a fixed rate
hardware clock.

This means configurability; now 1) makes that hard because it needs to
be internally consistent across groups of unrelated events; which is
why we had to have a global perf_clock().

However, for 2) it doesn't really matter, perf itself doesn't care
what it writes into the buffer.

The below patch makes the distinction between these two cases by
adding perf_event_clock() which is used for the second case. It
further makes this configurable on a per-event basis, but adds a few
sanity checks such that we cannot combine events with different clocks
in confusing ways.

And since we then have per-event configurability we might as well
retain the 'legacy' behaviour as a default.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@kernel.org>
      34f43927
    • D
      perf/x86: Remove redundant calls to perf_pmu_{dis|en}able() · 9332d250
      由 David Ahern 提交于 
      perf_pmu_disable() is called before pmu->add() and perf_pmu_enable() is called
afterwards. No need to call these inside of x86_pmu_add() as well.
Signed-off-by: NDavid Ahern <dsahern@gmail.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1424281543-67335-1-git-send-email-dsahern@gmail.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      9332d250
    • A
      perf/x86/intel: Add INST_RETIRED.ALL workarounds · 294fe0f5
      由 Andi Kleen 提交于 
      On Broadwell INST_RETIRED.ALL cannot be used with any period
that doesn't have the lowest 6 bits cleared. And the period
should not be smaller than 128.

This is erratum BDM11 and BDM55:

  http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/5th-gen-core-family-spec-update.pdf

BDM11: When using a period < 100; we may get incorrect PEBS/PMI
interrupts and/or an invalid counter state.
BDM55: When bit0-5 of the period are !0 we may get redundant PEBS
records on overflow.

Add a new callback to enforce this, and set it for Broadwell.

How does this handle the case when an app requests a specific
period with some of the bottom bits set?

Short answer:

Any useful instruction sampling period needs to be 4-6 orders
of magnitude larger than 128, as an PMI every 128 instructions
would instantly overwhelm the system and be throttled.
So the +-64 error from this is really small compared to the
period, much smaller than normal system jitter.

Long answer (by Peterz):

IFF we guarantee perf_event_attr::sample_period >= 128.

Suppose we start out with sample_period=192; then we'll set period_left
to 192, we'll end up with left = 128 (we truncate the lower bits). We
get an interrupt, find that period_left = 64 (>0 so we return 0 and
don't get an overflow handler), up that to 128. Then we trigger again,
at n=256. Then we find period_left = -64 (<=0 so we return 1 and do get
an overflow). We increment with sample_period so we get left = 128. We
fire again, at n=384, period_left = 0 (<=0 so we return 1 and get an
overflow). And on and on.

So while the individual interrupts are 'wrong' we get then with
interval=256,128 in exactly the right ratio to average out at 192. And
this works for everything >=128.

So the num_samples*fixed_period thing is still entirely correct +- 127,
which is good enough I'd say, as you already have that error anyhow.

So no need to 'fix' the tools, al we need to do is refuse to create
INST_RETIRED:ALL events with sample_period < 128.
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
[ Updated comments and changelog a bit. ]
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1424225886-18652-3-git-send-email-andi@firstfloor.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
      294fe0f5
  35. 23 3月, 2015 2 次提交
  37. 19 2月, 2015 4 次提交