linux-kernel - Re: [PATCH v4 1/2] x86/cpufeatures: Add "Allowed SEV Features" Feature

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Message-ID: <1d240cf7-a270-4cfa-b4bc-a41c8872416e@amd.com>
Date: Thu, 6 Mar 2025 06:28:50 +0100
From: "Gupta, Pankaj" <pankaj.gupta@....com>
To: Kim Phillips <kim.phillips@....com>, kvm@...r.kernel.org,
 linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org
Cc: Tom Lendacky <thomas.lendacky@....com>,
 Michael Roth <michael.roth@....com>, Ashish Kalra <ashish.kalra@....com>,
 "Nikunj A . Dadhania" <nikunj@....com>, Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
 <pbonzini@...hat.com>, Ingo Molnar <mingo@...hat.com>,
 "H. Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v4 1/2] x86/cpufeatures: Add "Allowed SEV Features"
 Feature

On 3/6/2025 1:38 AM, Kim Phillips wrote:
> From: Kishon Vijay Abraham I <kvijayab@....com>
> 
> Add CPU feature detection for "Allowed SEV Features" to allow the
> Hypervisor to enforce that SEV-ES and SEV-SNP guest VMs cannot
> enable features (via SEV_FEATURES) that the Hypervisor does not
> support or wish to be enabled.
> 
> Signed-off-by: Kishon Vijay Abraham I <kvijayab@....com>
> Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
> Signed-off-by: Kim Phillips <kim.phillips@....com>

Reviewed-by: Pankaj Gupta <pankaj.gupta@....com>

> ---
>   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 8f8aaf94dc00..6a12c8c48bd2 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -454,6 +454,7 @@
>   #define X86_FEATURE_DEBUG_SWAP		(19*32+14) /* "debug_swap" SEV-ES full debug state swap support */
>   #define X86_FEATURE_RMPREAD		(19*32+21) /* RMPREAD instruction */
>   #define X86_FEATURE_SEGMENTED_RMP	(19*32+23) /* Segmented RMP support */
> +#define X86_FEATURE_ALLOWED_SEV_FEATURES (19*32+27) /* Allowed SEV Features */
>   #define X86_FEATURE_SVSM		(19*32+28) /* "svsm" SVSM present */
>   #define X86_FEATURE_HV_INUSE_WR_ALLOWED	(19*32+30) /* Allow Write to in-use hypervisor-owned pages */
>