Re: [PATCH v12 09/19] x86/cc: Add CC_ATTR_GUEST_SNP_SECURE_TSC

[Tom Lendacky <thomas.lendacky@amd.com>]

On 10/9/24 04:28, Nikunj A Dadhania wrote:
> Add confidential compute platform attribute CC_ATTR_GUEST_SNP_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@amd.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

(Although, this can probably be squashed into the next patch where it is
first used)

> ---
>  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..cb7103dc124f 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_SNP_SECURE_TSC: SNP 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_SNP_SECURE_TSC,
>  };
>  
>  #ifdef CONFIG_ARCH_HAS_CC_PLATFORM
> diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
> index 0f81f70aca82..5b9a358a3254 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_SNP_SECURE_TSC:
> +		return sev_status & MSR_AMD64_SNP_SECURE_TSC;
> +
>  	default:
>  		return false;
>  	}