On 25/06/21 4:15 pm, Peter Zijlstra wrote:

quoted

On Wed, Jun 09, 2021 at 05:20:53PM +0300, Adrian Hunter wrote:

quoted

+static void intel_pmu_report_aux_output_id(struct perf_event *event)
+{
+	struct hw_perf_event *hwc = &event->hw;
+
+	/*
+	 * So long as all PEBS-via-PT events for a recording session are
+	 * scheduled together, then only changes to hwc->idx need be reported.
+	 */
+	if (hwc->idx != hwc->idx_reported) {
+		hwc->idx_reported = hwc->idx;
+		perf_report_aux_output_id(event, hwc->idx);
+	}
+}

AFAICT you want a callback in x86_assign_hw_event(), is that so?

Yes, or open-coded e.g.

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 8f71dd72ef95..46dac45298d1 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c

@@ -1207,6 +1207,11 @@ static int collect_events(struct cpu_hw_events *cpuc, struct perf_event *leader,
 	return n;
 }
 
+static inline bool report_aux_output_id(struct perf_event *event)
+{
+	return is_pebs_pt(event);
+}
+
 static inline void x86_assign_hw_event(struct perf_event *event,
 				struct cpu_hw_events *cpuc, int i)
 {

@@ -1217,6 +1222,9 @@ static inline void x86_assign_hw_event(struct perf_event *event,
 	hwc->last_cpu = smp_processor_id();
 	hwc->last_tag = ++cpuc->tags[i];
 
+	if (report_aux_output_id(event))
+		perf_report_aux_output_id(event, idx);
+
 	switch (hwc->idx) {
 	case INTEL_PMC_IDX_FIXED_BTS:
 	case INTEL_PMC_IDX_FIXED_VLBR: