Re: [PATCH] perf/x86/intel: Keep anythread_deprecated capability

[Namhyung Kim <namhyung@kernel.org>]

Hello,

On Tue, Apr 14, 2026 at 10:09:58AM +0800, Mi, Dapeng wrote:
> 
> On 4/14/2026 5:29 AM, Namhyung Kim wrote:
> > In update_pmu_cap(), it reads MSR_IA32_PERF_CAPABILITIES on non-MTL CPUs
> > to update the PMU capabilities.  But it resets the anythread_deprecated
> > bit on GNR so I can see /sys/bus/event_source/devices/cpu/format/any
> > even if dmesg says AnyThread is deprecated.
> >
> >   # dmesg | grep -A10 AnyThread
> >   [   10.662423] Performance Events: XSAVE Architectural LBR, PEBS fmt5+-baseline,  AnyThread deprecated, Granite Rapids events, 32-deep LBR, full-width counters, Intel PMU driver.
> >   [   10.663172] ... version:                   5
> >   [   10.663173] ... bit width:                 48
> >   [   10.663174] ... generic counters:          8
> >   [   10.663174] ... generic bitmap:            00000000000000ff
> >   [   10.663175] ... fixed-purpose counters:    4
> >   [   10.663176] ... fixed-purpose bitmap:      000000000000000f
> >   [   10.663176] ... value mask:                0000ffffffffffff
> >   [   10.663177] ... max period:                00007fffffffffff
> >   [   10.663178] ... global_ctrl mask:          0001000f000000ff
> >   [   10.668979] signal: max sigframe size: 11952
> >
> > I guess it's not intentional and we want to keep deprecating anythread
> > on these machines.
> >
> > Fixes: 25c623f41438fafc ("perf/x86/intel: Parse CPUID archPerfmonExt leaves for non-hybrid CPUs")
> > Cc: Dapeng Mi <dapeng1.mi@linux.intel.com>
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > ---
> >  arch/x86/events/intel/core.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
> > index 4768236c054bbcf8..f1fae640cc8e5991 100644
> > --- a/arch/x86/events/intel/core.c
> > +++ b/arch/x86/events/intel/core.c
> > @@ -5945,8 +5945,12 @@ static void update_pmu_cap(struct pmu *pmu)
> >  	}
> >  
> >  	if (!intel_pmu_broken_perf_cap()) {
> > +		bool anythread = hybrid(pmu, intel_cap).anythread_deprecated;
> > +
> >  		/* Perf Metric (Bit 15) and PEBS via PT (Bit 16) are hybrid enumeration */
> >  		rdmsrq(MSR_IA32_PERF_CAPABILITIES, hybrid(pmu, intel_cap).capabilities);
> > +		/* It seems anythread_deprecated is deleted unintentionally */
> > +		hybrid(pmu, intel_cap).anythread_deprecated = anythread;
> >  	}
> >  }
> >  
> 
> Namhyung, thanks for reporting this issue. But it may be not the best way
> to fix the issue by restoring the anythread_deprecated bit in intel_cap. 
> 
> anythread_deprecated is enumerated in CPUID.0AH:EDX[15] instead of the
> PERF_CAPABILITIES MSR. There is no anythread_deprecated bit in
> PERF_CAPABILITIES MSR, It's not a good practice to
> define anythread_deprecated bit in perf_capabilities .
> 
> Maybe we can do this, remove the anythread_deprecated from
> perf_capabilities and directly depends on the CPUID.0AH:EDX[15] to check
> if anythread is deprecated.

Looks good to me.  You can add

Acked-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung

> 
> 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)
>                 x86_pmu.format_attrs = intel_arch_formats_attr;
> 
>         intel_pmu_check_event_constraints_all(NULL);
> diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
> index fad87d3c8b2c..01217c663dff 100644
> --- a/arch/x86/events/perf_event.h
> +++ b/arch/x86/events/perf_event.h
> @@ -660,7 +660,7 @@ union perf_capabilities {
>                 u64     perf_metrics:1;
>                 u64     pebs_output_pt_available:1;
>                 u64     pebs_timing_info:1;
> -               u64     anythread_deprecated:1;
> +               u64     __reserved:1;
>                 u64     rdpmc_metrics_clear:1;
>         };
>         u64     capabilities;
> 
> Not fully tested, only test on SPR and it looks good. 
> 
> Thanks.
> 
>