linux-kernel - Re: [PATCH v2 1/2] x86/cpufeatures: Add HWP highest perf change feature flag

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Date: Mon, 24 Jun 2024 19:45:38 +0200
From: Borislav Petkov <bp@...en8.de>
To: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc: rafael@...nel.org, viresh.kumar@...aro.org, tglx@...utronix.de,
	mingo@...hat.com, dave.hansen@...ux.intel.com, hpa@...or.com,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	x86@...nel.org
Subject: Re: [PATCH v2 1/2] x86/cpufeatures: Add HWP highest perf change
 feature flag

On Mon, Jun 24, 2024 at 09:11:08AM -0700, Srinivas Pandruvada wrote:
> When CPUID[6].EAX[15] is set to 1, this CPU supports notification for
> HWP (Hardware P-states) highest performance change.
> 
> Add a feature flag to check if the CPU supports HWP highest performance
> change.
> 
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> ---
> v2:
> - Prevent display in /proc/cpuinfo flags as suggested by Borris
> 
>  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 3c7434329661..4cf929c457bb 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -361,6 +361,7 @@
>  #define X86_FEATURE_HWP_ACT_WINDOW	(14*32+ 9) /* HWP Activity Window */
>  #define X86_FEATURE_HWP_EPP		(14*32+10) /* HWP Energy Perf. Preference */
>  #define X86_FEATURE_HWP_PKG_REQ		(14*32+11) /* HWP Package Level Request */
> +#define X86_FEATURE_HWP_HIGHEST_PERF_CHANGE (14*32+15) /* "" HWP Highest perf change */

Yeah, in the meantime I made it even simpler:

https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?h=x86/cpu&id=78ce84b9e0a54a0c91a7449f321c1f852c0cd3fc

so in case you have to send your patch again, you can drop the "" too.

New flags are not exposed in /proc/cpuinfo by default after the above change.

Thx.

-- 
Regards/Gruss,
    Boris.

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