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

Alper Gun
2022-06-14T18:58:31Z

Let me summarize what I tried.

1- when using psp_init_probe false, the SNP VM fails in
SNP_LAUNCH_START step with error SEV_RET_DFFLUSH_REQUIRED(15).
2- added SEV_DF_FLUSH just after SNP platform init and it didn't fail
in launch start but failed later during SNP_LAUNCH_UPDATE with
SEV_RET_INVALID_PARAM(22)
3- added SNP_DF_FLUSH just after SNP platform init and it failed again
during SNP_LAUNCH_UPDATE with SEV_RET_INVALID_PARAM(22)
4- added sev_platform_init for SNP VMs and it worked.

For me DF_FLUSH alone didn' help boot a VM. I don't know yet why sev
platform status impacts the SNP VM, but sev_platform_init fixes the
problem.

On Tue, Jun 14, 2022 at 10:16 AM Kalra, Ashish <Ashish.Kalra@amd.com> wrote:
>
> [AMD Official Use Only - General]
>
> Hello Alper, Peter,
>
> -----Original Message-----
> From: Peter Gonda <pgonda@google.com>
> Sent: Tuesday, June 14, 2022 11:30 AM
> To: Kalra, Ashish <Ashish.Kalra@amd.com>
> Cc: Alper Gun <alpergun@google.com>; Brijesh Singh <brijesh.singh@amd.com>; the arch/x86 maintainers <x86@kernel.org>; LKML <linux-kernel@vger.kernel.org>; kvm list <kvm@vger.kernel.org>; linux-coco@lists.linux.dev; linux-mm@kvack.org; Linux Crypto Mailing List <linux-crypto@vger.kernel.org>; Thomas Gleixner <tglx@linutronix.de>; Ingo Molnar <mingo@redhat.com>; Joerg Roedel <jroedel@suse.de>; Lendacky, Thomas <Thomas.Lendacky@amd.com>; H. Peter Anvin <hpa@zytor.com>; Ard Biesheuvel <ardb@kernel.org>; Paolo Bonzini <pbonzini@redhat.com>; Sean Christopherson <seanjc@google.com>; Vitaly Kuznetsov <vkuznets@redhat.com>; Wanpeng Li <wanpengli@tencent.com>; Jim Mattson <jmattson@google.com>; Andy Lutomirski <luto@kernel.org>; Dave Hansen <dave.hansen@linux.intel.com>; Sergio Lopez <slp@redhat.com>; Peter Zijlstra <peterz@infradead.org>; Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>; David Rientjes <rientjes@google.com>; Dov Murik <dovmurik@linux.ibm.com>; Tobin Feldman-Fitzthum <tobin@ibm.com>; Borislav Petkov <bp@alien8.de>; Roth, Michael <Michael.Roth@amd.com>; Vlastimil Babka <vbabka@suse.cz>; Kirill A . Shutemov <kirill@shutemov.name>; Andi Kleen <ak@linux.intel.com>; Tony Luck <tony.luck@intel.com>; Marc Orr <marcorr@google.com>; Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@linux.intel.com>; Pavan Kumar Paluri <papaluri@amd.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@amd.com> wrote:
> >
> > [AMD Official Use Only - General]
> >
> >
> > -----Original Message-----
> > From: Peter Gonda <pgonda@google.com>
> > Sent: Tuesday, June 14, 2022 10:38 AM
> > To: Kalra, Ashish <Ashish.Kalra@amd.com>
> > Cc: Alper Gun <alpergun@google.com>; Brijesh Singh
> > <brijesh.singh@amd.com>; Kalra, Ashish <Ashish.Kalra@amd.com>; the
> > arch/x86 maintainers <x86@kernel.org>; LKML
> > <linux-kernel@vger.kernel.org>; kvm list <kvm@vger.kernel.org>;
> > linux-coco@lists.linux.dev; linux-mm@kvack.org; Linux Crypto Mailing
> > List <linux-crypto@vger.kernel.org>; Thomas Gleixner
> > <tglx@linutronix.de>; Ingo Molnar <mingo@redhat.com>; Joerg Roedel
> > <jroedel@suse.de>; Lendacky, Thomas <Thomas.Lendacky@amd.com>; H.
> > Peter Anvin <hpa@zytor.com>; Ard Biesheuvel <ardb@kernel.org>; Paolo
> > Bonzini <pbonzini@redhat.com>; Sean Christopherson
> > <seanjc@google.com>; Vitaly Kuznetsov <vkuznets@redhat.com>; Wanpeng
> > Li <wanpengli@tencent.com>; Jim Mattson <jmattson@google.com>; Andy
> > Lutomirski <luto@kernel.org>; Dave Hansen
> > <dave.hansen@linux.intel.com>; Sergio Lopez <slp@redhat.com>; Peter
> > Zijlstra <peterz@infradead.org>; Srinivas Pandruvada
> > <srinivas.pandruvada@linux.intel.com>; David Rientjes
> > <rientjes@google.com>; Dov Murik <dovmurik@linux.ibm.com>; Tobin
> > Feldman-Fitzthum <tobin@ibm.com>; Borislav Petkov <bp@alien8.de>;
> > Roth, Michael <Michael.Roth@amd.com>; Vlastimil Babka
> > <vbabka@suse.cz>; Kirill A . Shutemov <kirill@shutemov.name>; Andi
> > Kleen <ak@linux.intel.com>; Tony Luck <tony.luck@intel.com>; Marc Orr
> > <marcorr@google.com>; Sathyanarayanan Kuppuswamy
> > <sathyanarayanan.kuppuswamy@linux.intel.com>; Pavan Kumar Paluri
> > <papaluri@amd.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@amd.com> wrote:
> > >
> > >
> > > On 6/13/22 23:33, Alper Gun wrote:
> > > > 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.
> > > >
> > > 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?
>
> >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.
>
> Are you getting the DLFLUSH_REQUIRED error after the SNP activate command ?
>
> Also did you use the SEV_DF_FLUSH command or the SNP_DF_FLUSH command ?
>
> With SNP you need to use SNP_DF_FLUSH command.
>
> Thanks,
> Ashish