linux-kernel - Re: [Patch v7 02/12] perf/x86/intel: Fix NULL event access and potential PEBS record loss

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Message-ID: <4bb0537b-8b8e-48fd-b777-0787b23a3b41@linux.intel.com>
Date: Mon, 6 Oct 2025 16:03:48 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Oliver Sang <oliver.sang@...el.com>
Cc: oe-lkp@...ts.linux.dev, lkp@...el.com,
 Kan Liang <kan.liang@...ux.intel.com>, linux-perf-users@...r.kernel.org,
 linux-kernel@...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>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Andi Kleen <ak@...ux.intel.com>, Eranian Stephane <eranian@...gle.com>,
 Dapeng Mi <dapeng1.mi@...el.com>
Subject: Re: [Patch v7 02/12] perf/x86/intel: Fix NULL event access and
 potential PEBS record loss


On 10/2/2025 3:09 PM, Oliver Sang wrote:
> hi, Dapeng,
>
> On Tue, Sep 30, 2025 at 02:19:25PM +0800, Mi, Dapeng wrote:
> [...]
>
>> Oops, it looks previous fix was incomplete. :(
>>
>> Oliver, could you please verify the new attached patch (Please apply this
>> patch on top of the whole patch series)? Thanks a lot for your effort. 
> we confirmed the patch fixed the warning we reported.
>
> Tested-by: kernel test robot <oliver.sang@...el.com>
>
> =========================================================================================
> compiler/cpufreq_governor/kconfig/option_a/rootfs/tbox_group/test/testcase:
>   gcc-12/performance/x86_64-rhel-9.4/Socket Activity/debian-12-x86_64-phoronix/lkp-csl-2sp7/stress-ng-1.11.0/phoronix-test-suite
>
> commit:
>   0c9567b36ae6f8 ("perf/x86: Remove redundant is_x86_event() prototype")
>   a7138973beb1d1 ("perf/x86/intel: Fix NULL event access and potential PEBS record loss")
>   81248d31dd384c ("perf/x86/intel: Add counter group support for arch-PEBS")
>   54701e916f6782 ("Fixup: perf/x86/intel: Fix NULL event access waring from test robot")
>
> 0c9567b36ae6f83c a7138973beb1d124386472663cf 81248d31dd384c71c3b6a6af25a 54701e916f6782039c2ea8adb4b
> ---------------- --------------------------- --------------------------- ---------------------------
>        fail:runs  %reproduction    fail:runs  %reproduction    fail:runs  %reproduction    fail:runs
>            |             |             |             |             |             |             |
>            :6          100%           6:6          100%           6:6            0%            :20    dmesg.WARNING:at_arch/x86/events/intel/ds.c:#intel_pmu_drain_pebs_nhm

Oliver, thanks a lot for confirm this. :)



>
>
>> diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
>> index 65908880f424..3dedf7a0acf6 100644
>> --- a/arch/x86/events/intel/ds.c
>> +++ b/arch/x86/events/intel/ds.c
>> @@ -2781,9 +2781,11 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs
>> *iregs, struct perf_sample_d
>>  
>>          /* PEBS v3 has more accurate status bits */
>>          if (x86_pmu.intel_cap.pebs_format >= 3) {
>> -            for_each_set_bit(bit, (unsigned long *)&pebs_status, size)
>> +            for_each_set_bit(bit, (unsigned long *)&pebs_status, size) {
>>                  counts[bit]++;
>> -
>> +                if (counts[bit] && !events[bit])
>> +                    events[bit] = cpuc->events[bit];
>> +            }
>>              continue;
>>          }
>>  
>> @@ -2821,8 +2823,11 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs
>> *iregs, struct perf_sample_d
>>           * If collision happened, the record will be dropped.
>>           */
>>          if (pebs_status != (1ULL << bit)) {
>> -            for_each_set_bit(i, (unsigned long *)&pebs_status, size)
>> +            for_each_set_bit(i, (unsigned long *)&pebs_status, size) {
>>                  error[i]++;
>> +                if (error[i] && !events[i])
>> +                    events[i] = cpuc->events[i];
>> +            }
>>              continue;
>>          }
>>