linux-kernel - Re: [PATCH V5 04/25] perf/x86/intel: Hybrid PMU support for perf capabilities

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Date:   Thu, 8 Apr 2021 14:24:30 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:     mingo@...nel.org, linux-kernel@...r.kernel.org, acme@...nel.org,
        tglx@...utronix.de, bp@...en8.de, namhyung@...nel.org,
        jolsa@...hat.com, ak@...ux.intel.com, yao.jin@...ux.intel.com,
        adrian.hunter@...el.com, ricardo.neri-calderon@...ux.intel.com
Subject: Re: [PATCH V5 04/25] perf/x86/intel: Hybrid PMU support for perf
 capabilities



On 4/8/2021 9:40 AM, Peter Zijlstra wrote:
>> @@ -4330,7 +4347,7 @@ static int intel_pmu_check_period(struct perf_event *event, u64 value)
>>   
>>   static int intel_pmu_aux_output_match(struct perf_event *event)
>>   {
>> -	if (!x86_pmu.intel_cap.pebs_output_pt_available)
>> +	if (!intel_pmu_has_cap(event, PERF_CAP_PT_IDX))
>>   		return 0;
>>   
>>   	return is_intel_pt_event(event);
> these sites can have !event->pmu ?


I don't think the event->pmu can be NULL, but it could be pt_pmu.pmu.
If so, it should be a problem.

I think I will still use the x86_pmu.intel_cap.pebs_output_pt_available 
here in V6. The worst case is that we lost the PEBS via PT support on 
the small core for now.

I guess Alexander may provide a separate patch later to enable the PEBS 
via PT support on the ADL small core.

Thanks,
Kan