linux-kernel - Re: [PATCH Part2 v5 23/45] KVM: SVM: Add KVM_SNP

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Message-ID: <CABpDEun0rjrNVCGZDXd8SO3tfZi-2ku3mit2XMGLwCsijbF9tg@mail.gmail.com>
Date:   Mon, 13 Jun 2022 16:33:46 -0700
From:   Alper Gun <alpergun@...gle.com>
To:     Ashish Kalra <ashkalra@....com>
Cc:     Brijesh Singh <brijesh.singh@....com>, Ashish.Kalra@....com,
        x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Borislav Petkov <bp@...en8.de>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>, tony.luck@...el.com,
        Marc Orr <marcorr@...gle.com>,
        sathyanarayanan.kuppuswamy@...ux.intel.com,
        Pavan Kumar Paluri <papaluri@....com>
Subject: Re: [PATCH Part2 v5 23/45] KVM: SVM: Add KVM_SNP_INIT command

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