[PATCH 2/2] perf/x86/intel: Check PEBS status correctly

[Namhyung Kim <namhyung@kernel.org>]

From: Stephane Eranian <eranian@google.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@linux.intel.com>
Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.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