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Message-ID: <20190625145834.GA8480@krava>
Date: Tue, 25 Jun 2019 16:58:34 +0200
From: Jiri Olsa <jolsa@...hat.com>
To: kan.liang@...ux.intel.com
Cc: mingo@...hat.com, jolsa@...nel.org, peterz@...radead.org,
linux-kernel@...r.kernel.org, ak@...ux.intel.com
Subject: Re: [PATCH] perf/x86/intel: Fix spurious NMI on fixed counter
On Tue, Jun 25, 2019 at 07:21:35AM -0700, kan.liang@...ux.intel.com wrote:
> From: Kan Liang <kan.liang@...ux.intel.com>
>
> 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 issue 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 trigger spurious NMI.
>
> Check and disable PEBS for fixed counter after intel_pmu_disable_fixed().
>
> Reported-by: Yi, Ammy <ammy.yi@...el.com>
> Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
> Fixes: 6f55967ad9d9 ("perf/x86/intel: Fix race in intel_pmu_disable_event()")
> ---
> 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 4377bf6a6f82..464316218b77 100644
> --- a/arch/x86/events/intel/core.c
> +++ b/arch/x86/events/intel/core.c
> @@ -2160,12 +2160,10 @@ 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);
>
oops, I overlooed this, looks good
Acked-by: Jiri Olsa <jolsa@...nel.org>
thanks,
jirka
> /*
> * Needs to be called after x86_pmu_disable_event,
> --
> 2.14.5
>
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