From 457f01abae3db9bf5bd44a02bdfd9940eabbc2e3 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Tue, 9 Nov 2021 21:50:56 +0000
Subject: [PATCH 3/6] KVM: SEV: Disallow COPY_ENC_CONTEXT_FROM if target has
 created vCPUs
Git-commit: 79b11142763791bdead8b6460052cbdde8e08e2f
Patch-mainline: v5.16-rc2
References: bsc#1194526

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: stable@vger.kernel.org
Cc: Peter Gonda <pgonda@google.com>
Cc: Marc Orr <marcorr@google.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Nathan Tempelman <natet@google.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211109215101.2211373-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Li Zhang <lizhang@suse.de>
---
 arch/x86/kvm/svm/sev.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 18b4940bef05..1a36636b07c8 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1993,7 +1993,12 @@ 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;
 	}
-- 
2.31.1