linux-kernel - Re: [PATCH v11 13/20] x86/cc: Add CC_ATTR_GUEST_SECURE

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Message-ID: <96333d79-8ec3-44bf-7b74-33c67ff2d0df@amd.com>
Date: Fri, 13 Sep 2024 10:21:24 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Nikunj A Dadhania <nikunj@....com>, linux-kernel@...r.kernel.org,
 bp@...en8.de, x86@...nel.org, kvm@...r.kernel.org
Cc: mingo@...hat.com, tglx@...utronix.de, dave.hansen@...ux.intel.com,
 pgonda@...gle.com, seanjc@...gle.com, pbonzini@...hat.com
Subject: Re: [PATCH v11 13/20] x86/cc: Add CC_ATTR_GUEST_SECURE_TSC

On 7/31/24 10:08, Nikunj A Dadhania wrote:
> Add confidential compute platform attribute CC_ATTR_GUEST_SECURE_TSC that
> can be used by the guest to query whether the Secure TSC feature is active.
> 
> Signed-off-by: Nikunj A Dadhania <nikunj@....com>
> ---
>  include/linux/cc_platform.h | 8 ++++++++
>  arch/x86/coco/core.c        | 3 +++
>  2 files changed, 11 insertions(+)
> 
> diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
> index caa4b4430634..96dc61846c9d 100644
> --- a/include/linux/cc_platform.h
> +++ b/include/linux/cc_platform.h
> @@ -88,6 +88,14 @@ enum cc_attr {
>  	 * enabled to run SEV-SNP guests.
>  	 */
>  	CC_ATTR_HOST_SEV_SNP,
> +
> +	/**
> +	 * @CC_ATTR_GUEST_SECURE_TSC: Secure TSC is active.
> +	 *
> +	 * The platform/OS is running as a guest/virtual machine and actively
> +	 * using AMD SEV-SNP Secure TSC feature.
> +	 */
> +	CC_ATTR_GUEST_SECURE_TSC,

If this is specifically used for the AMD feature, as opposed to a generic
"does your system have a secure TSC", then it should probably be
CC_ATTR_GUEST_SNP_SECURE_TSC or CC_ATTR_GUEST_SEV_SNP_SECURE_TSC.

Thanks,
Tom

>  };
>  
>  #ifdef CONFIG_ARCH_HAS_CC_PLATFORM
> diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
> index 0f81f70aca82..00df00e2cb4a 100644
> --- a/arch/x86/coco/core.c
> +++ b/arch/x86/coco/core.c
> @@ -100,6 +100,9 @@ static bool noinstr amd_cc_platform_has(enum cc_attr attr)
>  	case CC_ATTR_HOST_SEV_SNP:
>  		return cc_flags.host_sev_snp;
>  
> +	case CC_ATTR_GUEST_SECURE_TSC:
> +		return sev_status & MSR_AMD64_SNP_SECURE_TSC;
> +
>  	default:
>  		return false;
>  	}