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

[Namhyung Kim <namhyung@kernel.org>]

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?

Thanks,
Namhyung


>  		x86_pmu.format_attrs = intel_arch_formats_attr;
>