Re: [PATCH] perf/x86/intel: Fix spurious NMI on fixed counter
From: Jin, Yao
Date: Thu Jul 04 2019 - 20:23:41 EST
On 6/25/2019 10:58 PM, Jiri Olsa wrote:
On Tue, Jun 25, 2019 at 07:21:35AM -0700, kan.liang@xxxxxxxxxxxxxxx wrote:
From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
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@xxxxxxxxx>
Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
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@xxxxxxxxxx>
thanks,
jirka
Hi,
Could this fix be accepted?
Thanks
Jin Yao
/*
* Needs to be called after x86_pmu_disable_event,
--
2.14.5