diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 3086055bf681..3dcfecf858f3 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -518,6 +518,7 @@ static void power_pmu_bhrb_read(struct perf_event *event, struct cpu_hw_events *
 		}
 	}
 	cpuhw->bhrb_stack.nr = u_index;
+	cpuhw->bhrb_stack.hw_idx = -1ULL;
 	return;
 }
 
diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index 534c76606049..7639e2097101 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -585,6 +585,7 @@ static void intel_pmu_lbr_read_32(struct cpu_hw_events *cpuc)
 		cpuc->lbr_entries[i].reserved	= 0;
 	}
 	cpuc->lbr_stack.nr = i;
+	cpuc->lbr_stack.hw_idx = -1ULL;
 }
 
 /*
@@ -680,6 +681,7 @@ static void intel_pmu_lbr_read_64(struct cpu_hw_events *cpuc)
 		out++;
 	}
 	cpuc->lbr_stack.nr = out;
+	cpuc->lbr_stack.hw_idx = -1ULL;
 }
 
 void intel_pmu_lbr_read(void)
@@ -1120,6 +1122,7 @@ void intel_pmu_store_pebs_lbrs(struct pebs_lbr *lbr)
 	int i;
 
 	cpuc->lbr_stack.nr = x86_pmu.lbr_nr;
+	cpuc->lbr_stack.hw_idx = -1ULL;
 	for (i = 0; i < x86_pmu.lbr_nr; i++) {
 		u64 info = lbr->lbr[i].info;
 		struct perf_branch_entry *e = &cpuc->lbr_entries[i];
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 547773f5894e..68e21e828893 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -93,14 +93,26 @@ struct perf_raw_record {
 /*
  * branch stack layout:
  *  nr: number of taken branches stored in entries[]
+ *  hw_idx: The low level index of raw branch records
+ *          for the most recent branch.
+ *          -1ULL means invalid/unknown.
  *
  * Note that nr can vary from sample to sample
  * branches (to, from) are stored from most recent
  * to least recent, i.e., entries[0] contains the most
  * recent branch.
+ * The entries[] is an abstraction of raw branch records,
+ * which may not be stored in age order in HW, e.g. Intel LBR.
+ * The hw_idx is to expose the low level index of raw
+ * branch record for the most recent branch aka entries[0].
+ * The hw_idx index is between -1 (unknown) and max depth,
+ * which can be retrieved in /sys/devices/cpu/caps/branches.
+ * For the architectures whose raw branch records are
+ * already stored in age order, the hw_idx should be 0.
  */
 struct perf_branch_stack {
 	__u64				nr;
+	__u64				hw_idx;
 	struct perf_branch_entry	entries[0];
 };
 
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 377d794d3105..397cfd65b3fe 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -181,6 +181,8 @@ enum perf_branch_sample_type_shift {
 
 	PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT	= 16, /* save branch type */
 
+	PERF_SAMPLE_BRANCH_HW_INDEX_SHIFT	= 17, /* save low level index of raw branch records */
+
 	PERF_SAMPLE_BRANCH_MAX_SHIFT		/* non-ABI */
 };
 
@@ -208,6 +210,8 @@ enum perf_branch_sample_type {
 	PERF_SAMPLE_BRANCH_TYPE_SAVE	=
 		1U << PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT,
 
+	PERF_SAMPLE_BRANCH_HW_INDEX	= 1U << PERF_SAMPLE_BRANCH_HW_INDEX_SHIFT,
+
 	PERF_SAMPLE_BRANCH_MAX		= 1U << PERF_SAMPLE_BRANCH_MAX_SHIFT,
 };
 
@@ -853,7 +857,9 @@ enum perf_event_type {
 	 *	  char                  data[size];}&& PERF_SAMPLE_RAW
 	 *
 	 *	{ u64                   nr;
-	 *        { u64 from, to, flags } lbr[nr];} && PERF_SAMPLE_BRANCH_STACK
+	 *	  { u64	hw_idx; } && PERF_SAMPLE_BRANCH_HW_INDEX
+	 *        { u64 from, to, flags } lbr[nr];
+	 *      } && PERF_SAMPLE_BRANCH_STACK
 	 *
 	 * 	{ u64			abi; # enum perf_sample_regs_abi
 	 * 	  u64			regs[weight(mask)]; } && PERF_SAMPLE_REGS_USER
diff --git a/kernel/events/core.c b/kernel/events/core.c
index e453589da97c..3f1f77de7247 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6555,6 +6555,11 @@ static void perf_output_read(struct perf_output_handle *handle,
 		perf_output_read_one(handle, event, enabled, running);
 }
 
+static inline bool perf_sample_save_hw_index(struct perf_event *event)
+{
+	return event->attr.branch_sample_type & PERF_SAMPLE_BRANCH_HW_INDEX;
+}
+
 void perf_output_sample(struct perf_output_handle *handle,
 			struct perf_event_header *header,
 			struct perf_sample_data *data,
@@ -6643,6 +6648,8 @@ void perf_output_sample(struct perf_output_handle *handle,
 			     * sizeof(struct perf_branch_entry);
 
 			perf_output_put(handle, data->br_stack->nr);
+			if (perf_sample_save_hw_index(event))
+				perf_output_put(handle, data->br_stack->hw_idx);
 			perf_output_copy(handle, data->br_stack->entries, size);
 		} else {
 			/*
@@ -6836,6 +6843,9 @@ void perf_prepare_sample(struct perf_event_header *header,
 	if (sample_type & PERF_SAMPLE_BRANCH_STACK) {
 		int size = sizeof(u64); /* nr */
 		if (data->br_stack) {
+			if (perf_sample_save_hw_index(event))
+				size += sizeof(u64);
+
 			size += data->br_stack->nr
 			      * sizeof(struct perf_branch_entry);
 		}