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Message-ID: <CAMkAt6r0ZsjS_XtVYnazC8-Z9bHQafLZ7QFq2NqcRQ2gZbUyPg@mail.gmail.com>
Date: Tue, 14 Jun 2022 10:30:10 -0600
From: Peter Gonda <pgonda@...gle.com>
To: "Kalra, Ashish" <Ashish.Kalra@....com>
Cc: Alper Gun <alpergun@...gle.com>,
Brijesh Singh <brijesh.singh@....com>,
"the arch/x86 maintainers" <x86@...nel.org>,
LKML <linux-kernel@...r.kernel.org>,
kvm list <kvm@...r.kernel.org>,
"linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
"Lendacky, Thomas" <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 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>,
"Roth, Michael" <Michael.Roth@....com>,
Vlastimil Babka <vbabka@...e.cz>,
"Kirill A . Shutemov" <kirill@...temov.name>,
Andi Kleen <ak@...ux.intel.com>,
Tony Luck <tony.luck@...el.com>, Marc Orr <marcorr@...gle.com>,
Sathyanarayanan Kuppuswamy
<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 Tue, Jun 14, 2022 at 10:11 AM Kalra, Ashish <Ashish.Kalra@....com> wrote:
>
> [AMD Official Use Only - General]
>
>
> -----Original Message-----
> From: Peter Gonda <pgonda@...gle.com>
> Sent: Tuesday, June 14, 2022 10:38 AM
> To: Kalra, Ashish <Ashish.Kalra@....com>
> Cc: Alper Gun <alpergun@...gle.com>; Brijesh Singh <brijesh.singh@....com>; Kalra, Ashish <Ashish.Kalra@....com>; the arch/x86 maintainers <x86@...nel.org>; LKML <linux-kernel@...r.kernel.org>; kvm list <kvm@...r.kernel.org>; linux-coco@...ts.linux.dev; linux-mm@...ck.org; Linux Crypto Mailing List <linux-crypto@...r.kernel.org>; Thomas Gleixner <tglx@...utronix.de>; Ingo Molnar <mingo@...hat.com>; Joerg Roedel <jroedel@...e.de>; Lendacky, Thomas <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 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>; Roth, Michael <Michael.Roth@....com>; Vlastimil Babka <vbabka@...e.cz>; Kirill A . Shutemov <kirill@...temov.name>; Andi Kleen <ak@...ux.intel.com>; Tony Luck <tony.luck@...el.com>; Marc Orr <marcorr@...gle.com>; Sathyanarayanan Kuppuswamy <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 6:21 PM Ashish Kalra <ashkalra@....com> wrote:
> >
> >
> > On 6/13/22 23:33, Alper Gun wrote:
> > > 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.
> > >
> > Ok, that makes sense.
> >
> > So the fix will be to call sev_platform_init() unconditionally here in
> > sev_guest_init(), and both sev_snp_init() and sev_platform_init() are
> > protected from being called again, so there won't be any issues if
> > these functions are invoked again at SNP/SEV VM launch if they have
> > been invoked earlier during module init.
>
> >That's one solution. I don't know if there is a downside to the system for enabling SEV if SNP is being enabled but another solution could be to just directly place a DF_FLUSH command instead of calling sev_platform_init().
>
> Actually sev_platform_init() is already called on module init if psp_init_on_probe is not false. Only need to ensure that SNP firmware is initialized first with SNP_INIT command.
But if psp_init_on_probe is false, sev_platform_init() isn't called
down this path. Alper has suggested we always call sev_platform_init()
but we could just place an SEV_DF_FLUSH command instead. Or am I still
missing something?
>
> Thanks,
> Ashish
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