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SubjectRe: [PATCH 1/3] perf/x86: Add new event for AUX output counter index
On Wed, Jun 30, 2021 at 12:21:07PM +0300, Adrian Hunter wrote:
> 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:

Right, bit yuck, but I suppose it works. The alternative is something
like:

static_call_cond(x86_pmu_assign)(event, idx);

but I'm not sure that's worth it, but it avoids stuffing even more intel
specific bits into the core.


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