linux-kernel - Re: [PATCH V4 01/25] x86/cpufeatures: Enumerate Intel Hybrid Technology feature bit

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Date:   Fri, 2 Apr 2021 11:24:27 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     kan.liang@...ux.intel.com
Cc:     peterz@...radead.org, mingo@...nel.org,
        linux-kernel@...r.kernel.org, acme@...nel.org, tglx@...utronix.de,
        namhyung@...nel.org, jolsa@...hat.com, ak@...ux.intel.com,
        yao.jin@...ux.intel.com, alexander.shishkin@...ux.intel.com,
        adrian.hunter@...el.com,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH V4 01/25] x86/cpufeatures: Enumerate Intel Hybrid
 Technology feature bit

On Thu, Apr 01, 2021 at 05:10:28PM -0700, kan.liang@...ux.intel.com wrote:
> From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> 
> Add feature enumeration to identify a processor with Intel Hybrid
> Technology: one in which CPUs of more than one type are the same package.
> On a hybrid processor, all CPUs support the same homogeneous (i.e.,
> symmetric) instruction set. All CPUs enumerate the same features in CPUID.
> Thus, software (user space and kernel) can run and migrate to any CPU in
> the system as well as utilize any of the enumerated features without any
> change or special provisions. The main difference among CPUs in a hybrid
> processor are power and performance properties.
> 
> Cc: Andi Kleen <ak@...ux.intel.com>
> Cc: Kan Liang <kan.liang@...ux.intel.com>
> Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>
> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
> Cc: "Ravi V. Shankar" <ravi.v.shankar@...el.com>
> Cc: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> Cc: linux-kernel@...r.kernel.org
> Reviewed-by: Len Brown <len.brown@...el.com>
> Reviewed-by: Tony Luck <tony.luck@...el.com>
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> ---
> Changes since v3 (as part of patchset for perf change for Alderlake)
>  * None
> 
> Changes since V2 (as part of patchset for perf change for Alderlake)
>  * Don't show "hybrid_cpu" in /proc/cpuinfo (Boris)
> 
> Changes since v1 (as part of patchset for perf change for Alderlake)
>  * None
> 
> Changes since v1 (in a separate posting):
>  * Reworded commit message to clearly state what is Intel Hybrid
>    Technology. Stress that all CPUs can run the same instruction
>    set and support the same features.
> ---
>  arch/x86/include/asm/cpufeatures.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index cc96e26d69f7..1ba4a6e1690c 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -374,6 +374,7 @@
>  #define X86_FEATURE_MD_CLEAR		(18*32+10) /* VERW clears CPU buffers */
>  #define X86_FEATURE_TSX_FORCE_ABORT	(18*32+13) /* "" TSX_FORCE_ABORT */
>  #define X86_FEATURE_SERIALIZE		(18*32+14) /* SERIALIZE instruction */
> +#define X86_FEATURE_HYBRID_CPU		(18*32+15) /* "" This part has CPUs of more than one type */
>  #define X86_FEATURE_TSXLDTRK		(18*32+16) /* TSX Suspend Load Address Tracking */
>  #define X86_FEATURE_PCONFIG		(18*32+18) /* Intel PCONFIG */
>  #define X86_FEATURE_ARCH_LBR		(18*32+19) /* Intel ARCH LBR */
> -- 

Acked-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette