linux-kernel - Re: [PATCH v3 03/14] x86/cpufeatures: add X86_FEATURE_WORKLOAD

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Message-ID: <ZxCW3bLUQhMqv9Rp@BLRRASHENOY1.amd.com>
Date: Thu, 17 Oct 2024 10:17:25 +0530
From: "Gautham R. Shenoy" <gautham.shenoy@....com>
To: Mario Limonciello <mario.limonciello@....com>
Cc: Borislav Petkov <bp@...en8.de>, Hans de Goede <hdegoede@...hat.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	x86@...nel.org, Perry Yuan <perry.yuan@....com>,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-pm@...r.kernel.org, platform-driver-x86@...r.kernel.org,
	Shyam Sundar S K <Shyam-sundar.S-k@....com>
Subject: Re: [PATCH v3 03/14] x86/cpufeatures: add X86_FEATURE_WORKLOAD_CLASS
 feature bit

On Tue, Oct 15, 2024 at 04:36:34PM -0500, Mario Limonciello wrote:
> From: Perry Yuan <perry.yuan@....com>
> 
> Add new feature bit that indicates support for workload based
> heuristic feedback to OS for scheduling decisions.
> When the bit set, threads are classified during runtime into
> enumerated classes. The classes represent thread performance/power
> characteristics that may benefit from special scheduling behaviors.
> 
> Signed-off-by: Perry Yuan <perry.yuan@....com>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>


> ---
>  arch/x86/include/asm/cpufeatures.h | 1 +
>  arch/x86/kernel/cpu/scattered.c    | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index cea1ed82aeb4..3e8e67b8ec7a 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -474,6 +474,7 @@
>  #define X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT (21*32+ 4) /* Clear branch history at vmexit using SW loop */
>  #define X86_FEATURE_FAST_CPPC		(21*32 + 5) /* AMD Fast CPPC */
>  #define X86_FEATURE_HETERO_CORE_TOPOLOGY	(21*32 + 6) /* Heterogeneous Core Topology */
> +#define X86_FEATURE_WORKLOAD_CLASS	(21*32 + 7) /* Workload Classification */
>  
>  /*
>   * BUG word(s)
> diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
> index 3bba55323163..b6547bab9e23 100644
> --- a/arch/x86/kernel/cpu/scattered.c
> +++ b/arch/x86/kernel/cpu/scattered.c
> @@ -49,6 +49,7 @@ static const struct cpuid_bit cpuid_bits[] = {
>  	{ X86_FEATURE_MBA,		CPUID_EBX,  6, 0x80000008, 0 },
>  	{ X86_FEATURE_SMBA,		CPUID_EBX,  2, 0x80000020, 0 },
>  	{ X86_FEATURE_BMEC,		CPUID_EBX,  3, 0x80000020, 0 },
> +	{ X86_FEATURE_WORKLOAD_CLASS,   CPUID_EAX,  22, 0x80000021, 0 },
>  	{ X86_FEATURE_PERFMON_V2,	CPUID_EAX,  0, 0x80000022, 0 },
>  	{ X86_FEATURE_AMD_LBR_V2,	CPUID_EAX,  1, 0x80000022, 0 },
>  	{ X86_FEATURE_AMD_LBR_PMC_FREEZE,	CPUID_EAX,  2, 0x80000022, 0 },
> -- 
> 2.43.0
>