linux-kernel - [PATCH 5.15 224/279] KVM: SEV: Disallow COPY_ENC_CONTEXT

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Message-Id: <20211124115726.473855152@linuxfoundation.org>
Date:   Wed, 24 Nov 2021 12:58:31 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Peter Gonda <pgonda@...gle.com>,
        Marc Orr <marcorr@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Nathan Tempelman <natet@...gle.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 5.15 224/279] KVM: SEV: Disallow COPY_ENC_CONTEXT_FROM if target has created vCPUs

From: Sean Christopherson <seanjc@...gle.com>

commit 79b11142763791bdead8b6460052cbdde8e08e2f upstream.

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@...r.kernel.org
Cc: Peter Gonda <pgonda@...gle.com>
Cc: Marc Orr <marcorr@...gle.com>
Cc: Sean Christopherson <seanjc@...gle.com>
Cc: Nathan Tempelman <natet@...gle.com>
Cc: Brijesh Singh <brijesh.singh@....com>
Cc: Tom Lendacky <thomas.lendacky@....com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Message-Id: <20211109215101.2211373-2-seanjc@...gle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/kvm/svm/sev.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1787,7 +1787,12 @@ int svm_vm_copy_asid_from(struct kvm *kv
 	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;
 	}