linux-kernel - [tip:perf/urgent] perf/x86/intel: Fix spurious NMI on fixed counter

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Date:   Sat, 13 Jul 2019 04:13:02 -0700
From:   tip-bot for Kan Liang <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, eranian@...gle.com,
        torvalds@...ux-foundation.org, peterz@...radead.org,
        tglx@...utronix.de, jolsa@...nel.org, vincent.weaver@...ne.edu,
        jolsa@...hat.com, mingo@...nel.org,
        alexander.shishkin@...ux.intel.com, ammy.yi@...el.com,
        acme@...hat.com, kan.liang@...ux.intel.com, stable@...r.kernel.org,
        hpa@...or.com
Subject: [tip:perf/urgent] perf/x86/intel: Fix spurious NMI on fixed counter

Commit-ID:  e4557c1a46b0d32746bd309e1941914b5a6912b4
Gitweb:     https://git.kernel.org/tip/e4557c1a46b0d32746bd309e1941914b5a6912b4
Author:     Kan Liang <kan.liang@...ux.intel.com>
AuthorDate: Tue, 25 Jun 2019 07:21:35 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Sat, 13 Jul 2019 11:21:29 +0200

perf/x86/intel: Fix spurious NMI on fixed counter

If a user first sample a PEBS event on a fixed counter, then sample a
non-PEBS event on the same fixed counter on Icelake, it will trigger
spurious NMI. For example:

  perf record -e 'cycles:p' -a
  perf record -e 'cycles' -a

The error message for spurious NMI:

  [June 21 15:38] Uhhuh. NMI received for unknown reason 30 on CPU 2.
  [    +0.000000] Do you have a strange power saving mode enabled?
  [    +0.000000] Dazed and confused, but trying to continue

The bug was introduced by the following commit:

  commit 6f55967ad9d9 ("perf/x86/intel: Fix race in intel_pmu_disable_event()")

The commit moves the intel_pmu_pebs_disable() after intel_pmu_disable_fixed(),
which returns immediately.  The related bit of PEBS_ENABLE MSR will never be
cleared for the fixed counter. Then a non-PEBS event runs on the fixed counter,
but the bit on PEBS_ENABLE is still set, which triggers spurious NMIs.

Check and disable PEBS for fixed counters after intel_pmu_disable_fixed().

Reported-by: Yi, Ammy <ammy.yi@...el.com>
Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Jiri Olsa <jolsa@...nel.org>
Cc: <stable@...r.kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Vince Weaver <vincent.weaver@...ne.edu>
Fixes: 6f55967ad9d9 ("perf/x86/intel: Fix race in intel_pmu_disable_event()")
Link: https://lkml.kernel.org/r/20190625142135.22112-1-kan.liang@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/events/intel/core.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index bda450ff51ee..9e911a96972b 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -2161,12 +2161,10 @@ static void intel_pmu_disable_event(struct perf_event *event)
 	cpuc->intel_ctrl_host_mask &= ~(1ull << hwc->idx);
 	cpuc->intel_cp_status &= ~(1ull << hwc->idx);
 
-	if (unlikely(hwc->config_base == MSR_ARCH_PERFMON_FIXED_CTR_CTRL)) {
+	if (unlikely(hwc->config_base == MSR_ARCH_PERFMON_FIXED_CTR_CTRL))
 		intel_pmu_disable_fixed(hwc);
-		return;
-	}
-
-	x86_pmu_disable_event(event);
+	else
+		x86_pmu_disable_event(event);
 
 	/*
 	 * Needs to be called after x86_pmu_disable_event,