Re: [PATCH] perf/x86/intel: Remove anythread_deprecated bit from perf_capabilities

["Mi, Dapeng" <dapeng1.mi@linux.intel.com>]

On 4/21/2026 5:23 AM, Namhyung Kim wrote:
> On Wed, Apr 15, 2026 at 10:10:10AM +0800, Dapeng Mi wrote:
>> AnyThread mode deprecation is enumerated by CPUID.0AH:EDX[15] instead of
>> PERF_CAPABILITIES MSR. It's not a good practice to define a bit to
>> represent "anythread deprecation" in perf_capabilities. It leads to the
>> anythread_deprecated bit could be overwritten by the real value of
>> PERF_CAPABILITIES MSR, just like the below code in update_pmu_cap() does.
>>
>> ```
>> if (!intel_pmu_broken_perf_cap()) {
>> 	/* Perf Metric (Bit 15) and PEBS via PT (Bit 16) are hybrid enumeration */
>> 	rdmsrq(MSR_IA32_PERF_CAPABILITIES, hybrid(pmu, intel_cap).capabilities);
>> }
>> ```
>>
>> It leads to the anythread_deprecated bit is cleared to 0 and the "any"
>> attribute is incorrectly shown in the /sys/devices/cpu/format/ folder on
>> these support Perfmon v6 platforms, like Clearwater Forest.
>>
>> ```
>> $grep . /sys/devices/cpu/format/*
>> /sys/devices/cpu/format/acr_mask:config2:0-63
>> /sys/devices/cpu/format/any:config:21
>> /sys/devices/cpu/format/cmask:config:24-31
>> ```
>>
>> So remove the anythread_deprecated bit from perf_capabilities structure
>> and directly depends on CPUID.0AH:EDX[15] to judge if anythread is
>> deprecated.
>>
>> Cc: stable@vger.kernel.org
>> Reported-by: Namhyung Kim <namhyung@kernel.org>
>> Fixes: cadbaa039b99 ("perf/x86/intel: Make anythread filter support conditional")
>> Acked-by: Namhyung Kim <namhyung@kernel.org>
>> Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
>> ---
>>  arch/x86/events/intel/core.c | 9 +++------
>>  arch/x86/events/perf_event.h | 2 +-
>>  2 files changed, 4 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
>> index 793335c3ce78..450c63165a22 100644
>> --- a/arch/x86/events/intel/core.c
>> +++ b/arch/x86/events/intel/core.c
>> @@ -7612,11 +7612,8 @@ __init int intel_pmu_init(void)
>>  
>>  	x86_add_quirk(intel_arch_events_quirk); /* Install first, so it runs last */
>>  
>> -	if (version >= 5) {
>> -		x86_pmu.intel_cap.anythread_deprecated = edx.split.anythread_deprecated;
>> -		if (x86_pmu.intel_cap.anythread_deprecated)
>> -			pr_cont(" AnyThread deprecated, ");
>> -	}
>> +	if (version >= 5 && edx.split.anythread_deprecated)
>> +		pr_cont(" AnyThread deprecated, ");
>>  
>>  	/* The perf side of core PMU is ready to support the mediated vPMU. */
>>  	x86_get_pmu(smp_processor_id())->capabilities |= PERF_PMU_CAP_MEDIATED_VPMU;
>> @@ -8467,7 +8464,7 @@ __init int intel_pmu_init(void)
>>  				      &x86_pmu.intel_ctrl);
>>  
>>  	/* AnyThread may be deprecated on arch perfmon v5 or later */
>> -	if (x86_pmu.intel_cap.anythread_deprecated)
>> +	if (edx.split.anythread_deprecated)
> Do we need to check the version here as well?

hmm, it should be enough to only check the CPUID
"edx.split.anythread_deprecated" bit  in practice. But if we want to follow
the SDM 100%, the version check should be added here.

I would add an version check here. Thanks.


>
> Thanks,
> Namhyung
>
>
>>  		x86_pmu.format_attrs = intel_arch_formats_attr;
>>