linux-kernel - Re: [PATCH 1/4] perf/x86/intel/lbr: use setup_clear_cpu_cap instead of clear_cpu

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Message-ID: <84c84de9-f5f1-1f8c-fa7c-6a416ea3373e@intel.com>
Date:   Wed, 22 Jun 2022 07:58:12 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>, linux-kernel@...r.kernel.org
Cc:     "Chang S. Bae" <chang.seok.bae@...el.com>,
        Jiri Olsa <jolsa@...nel.org>, linux-perf-users@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "David S. Miller" <davem@...emloft.net>,
        Borislav Petkov <bp@...en8.de>,
        Kees Cook <keescook@...omium.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Jane Malalane <jane.malalane@...rix.com>,
        Tony Luck <tony.luck@...el.com>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        "open list:CRYPTO API" <linux-crypto@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "Liang, Kan" <kan.liang@...ux.intel.com>
Subject: Re: [PATCH 1/4] perf/x86/intel/lbr: use setup_clear_cpu_cap instead
 of clear_cpu_cap

On 6/22/22 07:48, Maxim Levitsky wrote:
> clear_cpu_cap(&boot_cpu_data) is very similar to setup_clear_cpu_cap
> except that the latter also sets a bit in 'cpu_caps_cleared' which
> later clears the same cap in secondary cpus, which is likely
> what is meant here.
> 
> Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>

Seems like a:

Fixes: 47125db27e47 ("perf/x86/intel/lbr: Support Architectural LBR")

would be in order.

Kan, does this change look right to you?

>  arch/x86/events/intel/lbr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
> index 13179f31fe10fa..b08715172309a7 100644
> --- a/arch/x86/events/intel/lbr.c
> +++ b/arch/x86/events/intel/lbr.c
> @@ -1860,7 +1860,7 @@ void __init intel_pmu_arch_lbr_init(void)
>  	return;
>  
>  clear_arch_lbr:
> -	clear_cpu_cap(&boot_cpu_data, X86_FEATURE_ARCH_LBR);
> +	setup_clear_cpu_cap(X86_FEATURE_ARCH_LBR);
>  }
>  
>  /**