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Date: Tue, 14 Jun 2022 17:16:53 +0000
From: "Kalra, Ashish" <Ashish.Kalra@....com>
To: Peter Gonda <pgonda@...gle.com>
CC: Alper Gun <alpergun@...gle.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>
Subject: RE: [PATCH Part2 v5 23/45] KVM: SVM: Add KVM_SNP_INIT command
[AMD Official Use Only - General]
Hello Alper, Peter,
-----Original Message-----
From: Peter Gonda <pgonda@...gle.com>
Sent: Tuesday, June 14, 2022 11:30 AM
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-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?
>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
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