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

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Message-ID: <704f6604-547b-f7ca-ad45-2afd2dd70456@maine.edu>
Date: Wed, 11 Jun 2025 15:28:30 -0400 (EDT)
From: Vince Weaver <vincent.weaver@...ne.edu>
To: "Liang, Kan" <kan.liang@...ux.intel.com>
cc: Vince Weaver <vincent.weaver@...ne.edu>, 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 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,

Vince Weaver
vincent.weaver@...ne.edu