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Message-ID: <CAA03e5Hx_BW806LRnsm7jL6tH2YdwVZ2x49UsNe3M93_Kz0WXg@mail.gmail.com>
Date: Fri, 20 Aug 2021 14:00:57 -0700
From: Marc Orr <marcorr@...gle.com>
To: Peter Gonda <pgonda@...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 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.
> + 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.
> 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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