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

Alper Gun
2022-06-13T23:34:02Z

On Mon, Jun 13, 2022 at 4:15 PM Ashish Kalra <ashkalra@amd.com> wrote:
>
> 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 ?
>

Correct, INIT_EX requires the file system to be ready and there is a
ccp module param to call it only when needed.

MODULE_PARM_DESC(psp_init_on_probe, " if true, the PSP will be
initialized on module init. Else the PSP will be initialized on the
first command requiring it");

If this module param is false, it won't initialize SEV on the platform
until the first SEV VM.

> 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
>