Re: [PATCH v3] KVM: SEV: Disable SEV-SNP support on initialization failure

[Kalra, Ashish]

Hello Sean/Paolo,

On 5/12/2025 11:46 PM, Gupta, Pankaj wrote:
> On 5/13/2025 12:16 AM, Ashish Kalra wrote:
>> From: Ashish Kalra <ashish.kalra@xxxxxxx>
>>
>> During platform init, SNP initialization may fail for several reasons,
>> such as firmware command failures and incompatible versions. However,
>> the KVM capability may continue to advertise support for it.
>>
>> The platform may have SNP enabled but if SNP_INIT fails then SNP is
>> not supported by KVM.
>>
>> During KVM module initialization query the SNP platform status to obtain
>> the SNP initialization state and use it as an additional condition to
>> determine support for SEV-SNP.
>>
>> Co-developed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
>> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
>> Co-developed-by: Pratik R. Sampat <prsampat@xxxxxxx>
>> Signed-off-by: Pratik R. Sampat <prsampat@xxxxxxx>
>> Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
>> Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
> 
> LGTM
> 
> Reviewed-by: Pankaj Gupta <pankaj.gupta@xxxxxxx>
>

Can you please pull in this patch.

Thanks,
Ashish
 
>> ---
>>   arch/x86/kvm/svm/sev.c | 44 +++++++++++++++++++++++++++++++++---------
>>   1 file changed, 35 insertions(+), 9 deletions(-)
>>
>> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
>> index dea9480b9ff6..8c3b12e3de8c 100644
>> --- a/arch/x86/kvm/svm/sev.c
>> +++ b/arch/x86/kvm/svm/sev.c
>> @@ -2935,6 +2935,33 @@ void __init sev_set_cpu_caps(void)
>>       }
>>   }
>>   +static bool is_sev_snp_initialized(void)
>> +{
>> +    struct sev_user_data_snp_status *status;
>> +    struct sev_data_snp_addr buf;
>> +    bool initialized = false;
>> +    int ret, error = 0;
>> +
>> +    status = snp_alloc_firmware_page(GFP_KERNEL | __GFP_ZERO);
>> +    if (!status)
>> +        return false;
>> +
>> +    buf.address = __psp_pa(status);
>> +    ret = sev_do_cmd(SEV_CMD_SNP_PLATFORM_STATUS, &buf, &error);
>> +    if (ret) {
>> +        pr_err("SEV: SNP_PLATFORM_STATUS failed ret=%d, fw_error=%d (%#x)\n",
>> +               ret, error, error);
>> +        goto out;
>> +    }
>> +
>> +    initialized = !!status->state;
>> +
>> +out:
>> +    snp_free_firmware_page(status);
>> +
>> +    return initialized;
>> +}
>> +
>>   void __init sev_hardware_setup(void)
>>   {
>>       unsigned int eax, ebx, ecx, edx, sev_asid_count, sev_es_asid_count;
>> @@ -3039,6 +3066,14 @@ void __init sev_hardware_setup(void)
>>       sev_snp_supported = sev_snp_enabled && cc_platform_has(CC_ATTR_HOST_SEV_SNP);
>>     out:
>> +    if (sev_enabled) {
>> +        init_args.probe = true;
>> +        if (sev_platform_init(&init_args))
>> +            sev_supported = sev_es_supported = sev_snp_supported = false;
>> +        else if (sev_snp_supported)
>> +            sev_snp_supported = is_sev_snp_initialized();
>> +    }
>> +
>>       if (boot_cpu_has(X86_FEATURE_SEV))
>>           pr_info("SEV %s (ASIDs %u - %u)\n",
>>               sev_supported ? min_sev_asid <= max_sev_asid ? "enabled" :
>> @@ -3065,15 +3100,6 @@ void __init sev_hardware_setup(void)
>>       sev_supported_vmsa_features = 0;
>>       if (sev_es_debug_swap_enabled)
>>           sev_supported_vmsa_features |= SVM_SEV_FEAT_DEBUG_SWAP;
>> -
>> -    if (!sev_enabled)
>> -        return;
>> -
>> -    /*
>> -     * Do both SNP and SEV initialization at KVM module load.
>> -     */
>> -    init_args.probe = true;
>> -    sev_platform_init(&init_args);
>>   }
>>     void sev_hardware_unsetup(void)
>