Re: [PATCH Part2 v5 23/45] KVM: SVM: Add KVM_SNP_INIT command

Ashish Kalra
2022-06-13T23:15:14Z

Hello Alper,

On 6/13/22 20:58, Alper Gun wrote:
> static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
>> {
>> + bool es_active = (argp->id == KVM_SEV_ES_INIT || argp->id == KVM_SEV_SNP_INIT);
>> struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
>> - bool es_active = argp->id == KVM_SEV_ES_INIT;
>> + bool snp_active = argp->id == KVM_SEV_SNP_INIT;
>> int asid, ret;
>>
>> if (kvm->created_vcpus)
>> @@ -249,12 +269,22 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
>> return ret;
>>
>> sev->es_active = es_active;
>> + sev->snp_active = snp_active;
>> asid = sev_asid_new(sev);
>> if (asid < 0)
>> goto e_no_asid;
>> sev->asid = asid;
>>
>> - ret = sev_platform_init(&argp->error);
>> + if (snp_active) {
>> + ret = verify_snp_init_flags(kvm, argp);
>> + if (ret)
>> + goto e_free;
>> +
>> + ret = sev_snp_init(&argp->error);
>> + } else {
>> + ret = sev_platform_init(&argp->error);
> After SEV INIT_EX support patches, SEV may be initialized in the platform late.
> In my tests, if SEV has not been initialized in the platform yet, SNP
> VMs fail with SEV_DF_FLUSH required error. I tried calling
> SEV_DF_FLUSH right after the SNP platform init but this time it failed
> later on the SNP launch update command with SEV_RET_INVALID_PARAM
> error. Looks like there is another dependency on SEV platform
> initialization.
>
> Calling sev_platform_init for SNP VMs fixes the problem in our tests.

Trying to get some more context for this issue.

When you say after SEV_INIT_EX support patches, SEV may be initialized
in the platform late, do you mean sev_pci_init()->sev_snp_init() ...
sev_platform_init() code path has still not executed on the host BSP ?

Before launching the first SNP/SEV guest launch after INIT, we need to
issue SEV_CMD_DF_FLUSH command.

I assume that we will always be initially doing SNP firmware
initialization with SNP_INIT command followed by sev_platform_init(), if
SNP is enabled on boot CPU.

Thanks, Ashish