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    Subject[PATCH 5.2 354/413] perf/x86/intel: Fix spurious NMI on fixed counter
    Date
    From: Kan Liang <kan.liang@linux.intel.com>

    commit e4557c1a46b0d32746bd309e1941914b5a6912b4 upstream.

    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@intel.com>
    Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Acked-by: Jiri Olsa <jolsa@kernel.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>
    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@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/events/intel/core.c | 8 +++-----
    1 file changed, 3 insertions(+), 5 deletions(-)

    --- a/arch/x86/events/intel/core.c
    +++ b/arch/x86/events/intel/core.c
    @@ -2161,12 +2161,10 @@ static void intel_pmu_disable_event(stru
    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,

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