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Message-ID: <CAMkAt6oJVC=2X_9u4+g0vRhFPL3GV3GZT02bLBkoU4R39+cucQ@mail.gmail.com>
Date: Mon, 23 Aug 2021 10:38:48 -0600
From: Peter Gonda <pgonda@...gle.com>
To: Marc Orr <marcorr@...gle.com>
Cc: kvm list <kvm@...r.kernel.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <seanjc@...gle.com>,
David Rientjes <rientjes@...gle.com>,
"Dr . David Alan Gilbert" <dgilbert@...hat.com>,
Brijesh Singh <brijesh.singh@....com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2 V4] KVM, SEV: Add support for SEV-ES intra host migration
On Fri, Aug 20, 2021 at 3:01 PM Marc Orr <marcorr@...gle.com> wrote:
>
> On Thu, Aug 19, 2021 at 8:49 AM Peter Gonda <pgonda@...gle.com> 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@...gle.com>
> > Cc: Marc Orr <marcorr@...gle.com>
> > Cc: Paolo Bonzini <pbonzini@...hat.com>
> > Cc: Sean Christopherson <seanjc@...gle.com>
> > Cc: David Rientjes <rientjes@...gle.com>
> > Cc: Dr. David Alan Gilbert <dgilbert@...hat.com>
> > Cc: Brijesh Singh <brijesh.singh@....com>
> > Cc: Vitaly Kuznetsov <vkuznets@...hat.com>
> > Cc: Wanpeng Li <wanpengli@...cent.com>
> > Cc: Jim Mattson <jmattson@...gle.com>
> > Cc: Joerg Roedel <joro@...tes.org>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Ingo Molnar <mingo@...hat.com>
> > Cc: Borislav Petkov <bp@...en8.de>
> > Cc: "H. Peter Anvin" <hpa@...or.com>
> > Cc: kvm@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > ---
> > arch/x86/kvm/svm/sev.c | 58 +++++++++++++++++++++++++++++++++++++++---
> > 1 file changed, 55 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> > index 2d98b56b6f8c..970d75c34e9a 100644
> > --- a/arch/x86/kvm/svm/sev.c
> > +++ b/arch/x86/kvm/svm/sev.c
> > @@ -1554,6 +1554,53 @@ static void migrate_info_from(struct kvm_sev_info *dst,
> > list_replace_init(&src->regions_list, &dst->regions_list);
> > }
> >
> > +static int migrate_vmsa_from(struct kvm *dst, struct kvm *src)
> > +{
> > + int i, num_vcpus;
> > + struct kvm_vcpu *dst_vcpu, *src_vcpu;
> > + struct vcpu_svm *dst_svm, *src_svm;
> > +
> > + num_vcpus = atomic_read(&dst->online_vcpus);
> > + if (num_vcpus != atomic_read(&src->online_vcpus)) {
> > + pr_warn_ratelimited(
> > + "Source and target VMs must have same number of vCPUs.\n");
> > + return -EINVAL;
> > + }
> > +
> > + for (i = 0; i < num_vcpus; ++i) {
> > + src_vcpu = src->vcpus[i];
> > + if (!src_vcpu->arch.guest_state_protected) {
> > + pr_warn_ratelimited(
> > + "Source ES VM vCPUs must have protected state.\n");
> > + return -EINVAL;
> > + }
> > + }
> > +
> > + for (i = 0; i < num_vcpus; ++i) {
> > + src_vcpu = src->vcpus[i];
> > + src_svm = to_svm(src_vcpu);
> > + dst_vcpu = dst->vcpus[i];
> > + dst_svm = to_svm(dst_vcpu);
> > +
> > + dst_vcpu->vcpu_id = src_vcpu->vcpu_id;
> > + dst_svm->vmsa = src_svm->vmsa;
> > + src_svm->vmsa = NULL;
> > + dst_svm->ghcb = src_svm->ghcb;
> > + src_svm->ghcb = NULL;
> > + dst_svm->vmcb->control.ghcb_gpa =
> > + src_svm->vmcb->control.ghcb_gpa;
>
> Should we clear `src_svm->vmcb->control.ghcb_gpa`? (All the other
> fields in `srv_svm` that are copied are then cleared, except for this
> one.) Aside: Do we really need to clear all of the fields in `src_svm`
> after they're copied over? It might be worth adding a comment to
> explain why we're clearing them. It's not immediately obvious to me
> why we're doing that.
Cleared in the next version and added a comment. We don't want to
leave references for the source VM to edit the VMSA or GHCB after the
migration.
>
> > + dst_svm->ghcb_sa = src_svm->ghcb_sa;
> > + src_svm->ghcb_sa = NULL;
> > + dst_svm->ghcb_sa_len = src_svm->ghcb_sa_len;
> > + src_svm->ghcb_sa_len = 0;
> > + dst_svm->ghcb_sa_sync = src_svm->ghcb_sa_sync;
> > + src_svm->ghcb_sa_sync = false;
> > + dst_svm->ghcb_sa_free = src_svm->ghcb_sa_free;
> > + src_svm->ghcb_sa_free = false;
> > + }
> > + return 0;
> > +}
> > +
> > int svm_vm_migrate_from(struct kvm *kvm, unsigned int source_fd)
> > {
> > struct kvm_sev_info *dst_sev = &to_kvm_svm(kvm)->sev_info;
> > @@ -1565,7 +1612,7 @@ int svm_vm_migrate_from(struct kvm *kvm, unsigned int source_fd)
> > if (ret)
> > return ret;
> >
> > - if (!sev_guest(kvm) || sev_es_guest(kvm)) {
> > + if (!sev_guest(kvm)) {
> > ret = -EINVAL;
> > pr_warn_ratelimited("VM must be SEV enabled to migrate to.\n");
> > goto out_unlock;
> > @@ -1589,15 +1636,20 @@ int svm_vm_migrate_from(struct kvm *kvm, unsigned int source_fd)
> > if (ret)
> > goto out_fput;
> >
> > - if (!sev_guest(source_kvm) || sev_es_guest(source_kvm)) {
> > + if (!sev_guest(source_kvm)) {
> > ret = -EINVAL;
> > pr_warn_ratelimited(
> > "Source VM must be SEV enabled to migrate from.\n");
> > goto out_source;
> > }
> >
> > + if (sev_es_guest(kvm)) {
> > + ret = migrate_vmsa_from(kvm, source_kvm);
> > + if (ret)
> > + goto out_source;
> > + }
> > migrate_info_from(dst_sev, &to_kvm_svm(source_kvm)->sev_info);
> > - ret = 0;
> > + ret = 0;
>
> nit: looks like there's some space issue on this line. Since I believe
> this line was introduced in the previous patch, I wouldn't expect it
> to show up with a diff in patch #2.
Fixed thanks.
>
> > out_source:
> > svm_unlock_after_migration(source_kvm);
> > --
> > 2.33.0.rc1.237.g0d66db33f3-goog
>
> This patch looks good overall to me.
>
> Reviewed-by: Marc Orr <marcorr@...gle.com>
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