4 files changed, 65 insertions, 3 deletions

diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
index 266079a3a646..34d0c4816141 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -1126,6 +1126,7 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)
 	void *base, *at, *top;
 	int bit;
 	short counts[MAX_PEBS_EVENTS] = {};
+	short error[MAX_PEBS_EVENTS] = {};
 
 	if (!x86_pmu.pebs_active)
 		return;
@@ -1169,20 +1170,33 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)
 			/* slow path */
 			pebs_status = p->status & cpuc->pebs_enabled;
 			pebs_status &= (1ULL << MAX_PEBS_EVENTS) - 1;
-			if (pebs_status != (1 << bit))
+			if (pebs_status != (1 << bit)) {
+				u8 i;
+
+				for_each_set_bit(i, (unsigned long *)&pebs_status,
+						 MAX_PEBS_EVENTS)
+					error[i]++;
 				continue;
+			}
 		}
 		counts[bit]++;
 	}
 
 	for (bit = 0; bit < x86_pmu.max_pebs_events; bit++) {
-		if (counts[bit] == 0)
+		if ((counts[bit] == 0) && (error[bit] == 0))
 			continue;
 		event = cpuc->events[bit];
 		WARN_ON_ONCE(!event);
 		WARN_ON_ONCE(!event->attr.precise_ip);
 
-		__intel_pmu_pebs_event(event, iregs, base, top, bit, counts[bit]);
+		/* log dropped samples number */
+		if (error[bit])
+			perf_log_lost_samples(event, error[bit]);
+
+		if (counts[bit]) {
+			__intel_pmu_pebs_event(event, iregs, base,
+					       top, bit, counts[bit]);
+		}
 	}
 }
 
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 5f192e1bc98e..a204d5266f5f 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -743,6 +743,9 @@ perf_event__output_id_sample(struct perf_event *event,
 			     struct perf_output_handle *handle,
 			     struct perf_sample_data *sample);
 
+extern void
+perf_log_lost_samples(struct perf_event *event, u64 lost);
+
 static inline bool is_sampling_event(struct perf_event *event)
 {
 	return event->attr.sample_period != 0;
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index c4622f1ce046..613ed9ad588f 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -802,6 +802,18 @@ enum perf_event_type {
 	 */
 	PERF_RECORD_ITRACE_START		= 12,
 
+	/*
+	 * Records the dropped/lost sample number.
+	 *
+	 * struct {
+	 *	struct perf_event_header	header;
+	 *
+	 *	u64				lost;
+	 *	struct sample_id		sample_id;
+	 * };
+	 */
+	PERF_RECORD_LOST_SAMPLES		= 13,
+
 	PERF_RECORD_MAX,			/* non-ABI */
 };
 
diff --git a/kernel/events/core.c b/kernel/events/core.c
index e499b4e43aff..9e0773d5d110 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5975,6 +5975,39 @@ void perf_event_aux_event(struct perf_event *event, unsigned long head,
 }
 
 /*
+ * Lost/dropped samples logging
+ */
+void perf_log_lost_samples(struct perf_event *event, u64 lost)
+{
+	struct perf_output_handle handle;
+	struct perf_sample_data sample;
+	int ret;
+
+	struct {
+		struct perf_event_header	header;
+		u64				lost;
+	} lost_samples_event = {
+		.header = {
+			.type = PERF_RECORD_LOST_SAMPLES,
+			.misc = 0,
+			.size = sizeof(lost_samples_event),
+		},
+		.lost		= lost,
+	};
+
+	perf_event_header__init_id(&lost_samples_event.header, &sample, event);
+
+	ret = perf_output_begin(&handle, event,
+				lost_samples_event.header.size);
+	if (ret)
+		return;
+
+	perf_output_put(&handle, lost_samples_event);
+	perf_event__output_id_sample(event, &handle, &sample);
+	perf_output_end(&handle);
+}
+
+/*
  * IRQ throttle logging
  */