linux-kernel - Re: [perf] crashing bug in icl_update_topdown

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Message-ID: <36b65ee5-4bce-4b15-91bc-52604bc8a046@linux.intel.com>
Date: Thu, 12 Jun 2025 10:47:30 -0400
From: "Liang, Kan" <kan.liang@...ux.intel.com>
To: Vince Weaver <vincent.weaver@...ne.edu>
Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [perf] crashing bug in icl_update_topdown_event



On 2025-06-11 3:28 p.m., Vince Weaver wrote:
> On Wed, 11 Jun 2025, Liang, Kan wrote:
> 
>>
>>
>> It seems an regression from the f9bdf1f95339 ("perf/x86/intel: Avoid
>> disable PMU if !cpuc->enabled in sample read").
>> The commit merged the intel_pmu_auto_reload_read() and
>> intel_pmu_read_topdown_event(). It's possible that a PEBS event 0x0400
>> runs on a ATOM CPU. So the PERF_X86_EVENT_AUTO_RELOAD is set for the
>> event. The is_topdown_event() also returns true.
>>
>> Does the below patch help?
>> It checks the PERF_X86_EVENT_TOPDOWN flag as well before invoking the
>> topdown functions.
> 
> With this patch applied my test case no longer crashes.
> 

Thanks for the test. I've posted a fix to LKML.
https://lore.kernel.org/linux-perf-users/20250612143818.2889040-1-kan.liang@linux.intel.com/

It's a little bit different from the one tested. Please check and
provide a 'tested-by' on the new patch if it works.Thanks,Kan