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

[Chen, Zide]

On 4/20/2026 5:51 PM, Mi, Dapeng wrote:
> 
> 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@xxxxxxxxxxxxxxx
>>> Reported-by: Namhyung Kim <namhyung@xxxxxxxxxx>
>>> Fixes: cadbaa039b99 ("perf/x86/intel: Make anythread filter support conditional")
>>> Acked-by: Namhyung Kim <namhyung@xxxxxxxxxx>
>>> Signed-off-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
>>> ---
>>>  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.

How about merging pr_cont(" AnyThread deprecated, ") to here? No need to
repeat "if (version >= 5 && edx.split.anythread_deprecated)" twice in
one single API.


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