Re: [PATCH 3/5 V10] KVM: SEV: Add support for SEV-ES intra host migration

[Tom Lendacky]

On 10/20/21 3:43 PM, Peter Gonda wrote:
> On Fri, Oct 15, 2021 at 3:36 PM Tom Lendacky <thomas.lendacky@xxxxxxx> wrote:
> > On 10/12/21 3:48 PM, Peter Gonda wrote:
> > > For SEV-ES to work with intra host migration the VMSAs, GHCB metadata,
> > > and other SEV-ES info needs to be preserved along with the guest's
> > > memory.
> > >
> > > Signed-off-by: Peter Gonda <pgonda@xxxxxxxxxx>
> > > Reviewed-by: Marc Orr <marcorr@xxxxxxxxxx>
> > > Cc: Marc Orr <marcorr@xxxxxxxxxx>
> > > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > > Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
> > > Cc: David Rientjes <rientjes@xxxxxxxxxx>
> > > Cc: Dr. David Alan Gilbert <dgilbert@xxxxxxxxxx>
> > > Cc: Brijesh Singh <brijesh.singh@xxxxxxx>
> > > Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
> > > Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> > > Cc: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> > > Cc: Jim Mattson <jmattson@xxxxxxxxxx>
> > > Cc: Joerg Roedel <joro@xxxxxxxxxx>
> > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > > Cc: Borislav Petkov <bp@xxxxxxxxx>
> > > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> > > Cc: kvm@xxxxxxxxxxxxxxx
> > > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > > ---
> > >    arch/x86/kvm/svm/sev.c | 48 +++++++++++++++++++++++++++++++++++++++++-
> > >    1 file changed, 47 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> > > index 42ff1ccfe1dc..a486ab08a766 100644
> > > --- a/arch/x86/kvm/svm/sev.c
> > > +++ b/arch/x86/kvm/svm/sev.c
> > > @@ -1600,6 +1600,46 @@ static void sev_migrate_from(struct kvm_sev_info *dst,
> > >        list_replace_init(&src->regions_list, &dst->regions_list);
> > >    }
> > >
> > > +static int sev_es_migrate_from(struct kvm *dst, struct kvm *src)
> > > +{
> > > +     int i;
> > > +     struct kvm_vcpu *dst_vcpu, *src_vcpu;
> > > +     struct vcpu_svm *dst_svm, *src_svm;
> > > +
> > > +     if (atomic_read(&src->online_vcpus) != atomic_read(&dst->online_vcpus))
> > > +             return -EINVAL;
> > > +
> > > +     kvm_for_each_vcpu(i, src_vcpu, src) {
> > > +             if (!src_vcpu->arch.guest_state_protected)
> > > +                     return -EINVAL;
> > > +     }
> > > +
> > > +     kvm_for_each_vcpu(i, src_vcpu, src) {
> > > +             src_svm = to_svm(src_vcpu);
> > > +             dst_vcpu = kvm_get_vcpu(dst, i);
> > > +             dst_svm = to_svm(dst_vcpu);
> > > +
> > > +             /*
> > > +              * Transfer VMSA and GHCB state to the destination.  Nullify and
> > > +              * clear source fields as appropriate, the state now belongs to
> > > +              * the destination.
> > > +              */
> > > +             dst_vcpu->vcpu_id = src_vcpu->vcpu_id;
> > > +             memcpy(&dst_svm->sev_es, &src_svm->sev_es,
> > > +                    sizeof(dst_svm->sev_es));
> > > +             dst_svm->vmcb->control.ghcb_gpa =
> > > +                             src_svm->vmcb->control.ghcb_gpa;
> > > +             dst_svm->vmcb->control.vmsa_pa = __pa(dst_svm->sev_es.vmsa);
> > > +             dst_vcpu->arch.guest_state_protected = true;
> >
> > Maybe just add a blank line here to separate the setting and clearing
> > (only if you have to do another version).
> >
> > > +             src_svm->vmcb->control.ghcb_gpa = 0;
> > > +             src_svm->vmcb->control.vmsa_pa = 0;
> > > +             src_vcpu->arch.guest_state_protected = false;
> >
> > In the previous patch you were clearing some of the fields that are now in
> > the vcpu_sev_es_state. Did you want to memset that to zero now?
>
> Oops, making that an easy memset was one of the pros of the |sev_es|
> refactor. Will fix and add newline in V11.

And totally up to you, but I think you can replace the memcpy() above with 
a direct assignment, if you want:

	dst_svm->sev_es = src_svm->sev_es;

Thanks,
Tom

> > Thanks,
> > Tom
> >
> > > +     }
> > > +     to_kvm_svm(src)->sev_info.es_active = false;
> > > +
> > > +     return 0;
> > > +}
> > > +