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Message-Id: <20201126110922.317681-2-namhyung@kernel.org>
Date: Thu, 26 Nov 2020 20:09:22 +0900
From: Namhyung Kim <namhyung@...nel.org>
To: Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Thomas Gleixner <tglx@...utronix.de>,
Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...or.com>,
LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
Stephane Eranian <eranian@...gle.com>,
Kan Liang <kan.liang@...ux.intel.com>
Subject: [PATCH 2/2] perf/x86/intel: Check PEBS status correctly
From: Stephane Eranian <eranian@...gle.com>
The kernel cannot disambiguate when 2+ PEBS counters overflow at the
same time. This is what the comment for this code suggests. However,
I see the comparison is done with the unfiltered p->status which is a
copy of IA32_PERF_GLOBAL_STATUS at the time of the sample. This
register contains more than the PEBS counter overflow bits. It also
includes many other bits which could also be set.
Cc: Kan Liang <kan.liang@...ux.intel.com>
Signed-off-by: Stephane Eranian <eranian@...gle.com>
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
arch/x86/events/intel/ds.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 89dba588636e..485c5066f8b8 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1916,7 +1916,7 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs, struct perf_sample_d
* that caused the PEBS record. It's called collision.
* If collision happened, the record will be dropped.
*/
- if (p->status != (1ULL << bit)) {
+ if (pebs_status != (1ULL << bit)) {
for_each_set_bit(i, (unsigned long *)&pebs_status, size)
error[i]++;
continue;
--
2.29.2.454.gaff20da3a2-goog
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