linux-kernel - Re: [PATCH 1/3] perf/x86: Add new event for AUX output counter index

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Date:   Wed, 30 Jun 2021 12:21:07 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>, Leo Yan <leo.yan@...aro.org>,
        Kan Liang <kan.liang@...ux.intel.com>, x86@...nel.org,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] perf/x86: Add new event for AUX output counter index

On 25/06/21 4:15 pm, Peter Zijlstra wrote:
> On Wed, Jun 09, 2021 at 05:20:53PM +0300, Adrian Hunter wrote:
> 
>> +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: