[PATCH 2/3 V7] KVM, SEV: Add support for SEV-ES intra host migration

[Peter Gonda <pgonda@google.com>]

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@google.com>
Reviewed-by: Marc Orr <marcorr@google.com>
Cc: Marc Orr <marcorr@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Wanpeng Li <wanpengli@tencent.com>
Cc: Jim Mattson <jmattson@google.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 arch/x86/kvm/svm/sev.c | 62 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 60 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 8db666a362d4..fac21a82e4de 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1545,6 +1545,59 @@ 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);
+
+		/*
+		 * Copy VMSA and GHCB fields from the source to the destination.
+		 * Clear them on the source to prevent the VM running and
+		 * changing the state of the VMSA/GHCB unexpectedly.
+		 */
+		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;
+		src_svm->vmcb->control.ghcb_gpa = 0;
+		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;
@@ -1556,7 +1609,7 @@ 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;
@@ -1582,13 +1635,18 @@ 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;
 
-- 
2.33.0.153.gba50c8fa24-goog