linux-kernel - Re: [PATCH v6 1/9] KVM: SEV: Disable SEV-SNP on FW validation failure

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Message-ID: <Z6v_UjzEpSMyMZN2@google.com>
Date: Tue, 11 Feb 2025 17:54:26 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: "Pratik R. Sampat" <prsampat@....com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org, 
	linux-crypto@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	pbonzini@...hat.com, thomas.lendacky@....com, tglx@...utronix.de, 
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com, shuah@...nel.org, 
	pgonda@...gle.com, ashish.kalra@....com, nikunj@....com, pankaj.gupta@....com, 
	michael.roth@....com, sraithal@....com
Subject: Re: [PATCH v6 1/9] KVM: SEV: Disable SEV-SNP on FW validation failure

On Mon, Feb 03, 2025, Pratik R. Sampat wrote:
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 0f04f365885c..b709c2f0945c 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -3040,7 +3040,9 @@ void __init sev_hardware_setup(void)
>  	sev_es_asid_count = min_sev_asid - 1;
>  	WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV_ES, sev_es_asid_count));
>  	sev_es_supported = true;
> -	sev_snp_supported = sev_snp_enabled && cc_platform_has(CC_ATTR_HOST_SEV_SNP);
> +	sev_snp_supported = (sev_snp_enabled &&
> +			    cc_platform_has(CC_ATTR_HOST_SEV_SNP) &&
> +			    snp_fw_valid());
>  
>  out:
>  	if (boot_cpu_has(X86_FEATURE_SEV))
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index af018afd9cd7..b45cd60c19b0 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -122,6 +122,12 @@ static inline bool sev_version_greater_or_equal(u8 maj, u8 min)
>  	return false;
>  }
>  
> +bool snp_fw_valid(void)
> +{
> +	return sev_version_greater_or_equal(SNP_MIN_API_MAJOR, SNP_MIN_API_MINOR);

This lacks any sense of abstraction.  KVM doesn't care if the firmware is valid,
KVM only cares if SNP is support.  KVM _must_ run after ASP initialization[*],
so I'm pretty sure KVM just needs a way to query sev->snp_initialized.

[*] https://lore.kernel.org/all/f78ddb64087df27e7bcb1ae0ab53f55aa0804fab.1739226950.git.ashish.kalra@amd.com