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-rw-r--r--arch/x86/kernel/cpu/perf_event_p4.c11
1 files changed, 8 insertions, 3 deletions
diff --git a/arch/x86/kernel/cpu/perf_event_p4.c b/arch/x86/kernel/cpu/perf_event_p4.c
index f7a0993c1e7..ff751a9f182 100644
--- a/arch/x86/kernel/cpu/perf_event_p4.c
+++ b/arch/x86/kernel/cpu/perf_event_p4.c
@@ -770,9 +770,14 @@ static inline int p4_pmu_clear_cccr_ovf(struct hw_perf_event *hwc)
770 return 1; 770 return 1;
771 } 771 }
772 772
773 /* it might be unflagged overflow */ 773 /*
774 rdmsrl(hwc->event_base + hwc->idx, v); 774 * In some circumstances the overflow might issue an NMI but did
775 if (!(v & ARCH_P4_CNTRVAL_MASK)) 775 * not set P4_CCCR_OVF bit. Because a counter holds a negative value
776 * we simply check for high bit being set, if it's cleared it means
777 * the counter has reached zero value and continued counting before
778 * real NMI signal was received:
779 */
780 if (!(v & ARCH_P4_UNFLAGGED_BIT))
776 return 1; 781 return 1;
777 782
778 return 0; 783 return 0;