linux-kernel - Re: [PATCH v5 1/9] KVM: SEV: Disable SEV-SNP on FW validation failure

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Message-ID: <85ikq4msup.fsf@amd.com>
Date: Fri, 24 Jan 2025 10:03:26 +0000
From: Nikunj A Dadhania <nikunj@....com>
To: "Pratik R. Sampat" <prsampat@....com>, <linux-kernel@...r.kernel.org>,
	<x86@...nel.org>, <kvm@...r.kernel.org>, <linux-crypto@...r.kernel.org>,
	<linux-kselftest@...r.kernel.org>
CC: <seanjc@...gle.com>, <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>, <michael.roth@....com>, <sraithal@....com>,
	<prsampat@....com>
Subject: Re: [PATCH v5 1/9] KVM: SEV: Disable SEV-SNP on FW validation failure

"Pratik R. Sampat" <prsampat@....com> writes:

> On incompatible firmware versions, SEV-SNP support is pulled and the
> setup is not performed. However, the platform and subsequently the KVM
> capability may continue to advertise support for it. Disable support for
> SEV-SNP if the FW version validation fails.
>
> Fixes: 1dfe571c12cf ("KVM: SEV: Add initial SEV-SNP support")
> Suggested-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Pratik R. Sampat <prsampat@....com>

Reviewed-by: Nikunj A Dadhania <nikunj@....com>

> ---
>  arch/x86/kvm/svm/sev.c       | 4 +++-
>  drivers/crypto/ccp/sev-dev.c | 6 ++++++
>  include/linux/psp-sev.h      | 3 +++
>  3 files changed, 12 insertions(+), 1 deletion(-)
>
> 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);
> +}
> +EXPORT_SYMBOL_GPL(snp_fw_valid);
> +
>  static void sev_irq_handler(int irq, void *data, unsigned int status)
>  {
>  	struct sev_device *sev = data;
> diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
> index 903ddfea8585..e841a8fbbb15 100644
> --- a/include/linux/psp-sev.h
> +++ b/include/linux/psp-sev.h
> @@ -945,6 +945,7 @@ int sev_do_cmd(int cmd, void *data, int *psp_ret);
>  void *psp_copy_user_blob(u64 uaddr, u32 len);
>  void *snp_alloc_firmware_page(gfp_t mask);
>  void snp_free_firmware_page(void *addr);
> +bool snp_fw_valid(void);
>  
>  #else	/* !CONFIG_CRYPTO_DEV_SP_PSP */
>  
> @@ -979,6 +980,8 @@ static inline void *snp_alloc_firmware_page(gfp_t mask)
>  
>  static inline void snp_free_firmware_page(void *addr) { }
>  
> +static inline bool snp_fw_valid(void) { return false; }
> +
>  #endif	/* CONFIG_CRYPTO_DEV_SP_PSP */
>  
>  #endif	/* __PSP_SEV_H__ */
> -- 
> 2.43.0