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-rw-r--r--arch/x86/include/asm/perf_event_p4.h1
-rw-r--r--arch/x86/kernel/cpu/perf_event_p4.c11
2 files changed, 9 insertions, 3 deletions
diff --git a/arch/x86/include/asm/perf_event_p4.h b/arch/x86/include/asm/perf_event_p4.h
index e2f6a99f14ab..cc29086e30cd 100644
--- a/arch/x86/include/asm/perf_event_p4.h
+++ b/arch/x86/include/asm/perf_event_p4.h
@@ -22,6 +22,7 @@
#define ARCH_P4_CNTRVAL_BITS (40)
#define ARCH_P4_CNTRVAL_MASK ((1ULL << ARCH_P4_CNTRVAL_BITS) - 1)
+#define ARCH_P4_UNFLAGGED_BIT ((1ULL) << (ARCH_P4_CNTRVAL_BITS - 1))
#define P4_ESCR_EVENT_MASK 0x7e000000U
#define P4_ESCR_EVENT_SHIFT 25
diff --git a/arch/x86/kernel/cpu/perf_event_p4.c b/arch/x86/kernel/cpu/perf_event_p4.c
index f7a0993c1e7c..ff751a9f182b 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)
return 1;
}
- /* it might be unflagged overflow */
- rdmsrl(hwc->event_base + hwc->idx, v);
- if (!(v & ARCH_P4_CNTRVAL_MASK))
+ /*
+ * In some circumstances the overflow might issue an NMI but did
+ * not set P4_CCCR_OVF bit. Because a counter holds a negative value
+ * we simply check for high bit being set, if it's cleared it means
+ * the counter has reached zero value and continued counting before
+ * real NMI signal was received:
+ */
+ if (!(v & ARCH_P4_UNFLAGGED_BIT))
return 1;
return 0;