KVM: SEV: Disallow COPY_ENC_CONTEXT_FROM if target has created vCPUs

Reject COPY_ENC_CONTEXT_FROM if the destination VM has created vCPUs.
KVM relies on SEV activation to occur before vCPUs are created, e.g. to
set VMCB flags and intercepts correctly.

Fixes: 54526d1fd593 ("KVM: x86: Support KVM VMs sharing SEV context")
Cc: [email protected]
Cc: Peter Gonda <[email protected]>
Cc: Marc Orr <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Nathan Tempelman <[email protected]>
Cc: Brijesh Singh <[email protected]>
Cc: Tom Lendacky <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

1 files changed, 6 insertions, 1 deletions

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 3e2769855e51..eeec499e4372 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1775,7 +1775,12 @@ int svm_vm_copy_asid_from(struct kvm *kvm, unsigned int source_fd)
 	mutex_unlock(&source_kvm->lock);
 	mutex_lock(&kvm->lock);
 
-	if (sev_guest(kvm)) {
+	/*
+	 * Disallow out-of-band SEV/SEV-ES init if the target is already an
+	 * SEV guest, or if vCPUs have been created.  KVM relies on vCPUs being
+	 * created after SEV/SEV-ES initialization, e.g. to init intercepts.
+	 */
+	if (sev_guest(kvm) || kvm->created_vcpus) {
 		ret = -EINVAL;
 		goto e_mirror_unlock;
 	}