KVM: x86: nSVM: don't copy virt_ext from vmcb12

These field correspond to features that we don't expose yet to L2

While currently there are no CVE worthy features in this field,
if AMD adds more features to this field, that could allow guest
escapes similar to CVE-2021-3653 and CVE-2021-3656.

Signed-off-by: Maxim Levitsky <[email protected]>
Message-Id: <[email protected]>
Cc: [email protected]
Signed-off-by: Paolo Bonzini <[email protected]>

Author: Maxim Levitsky

arch/x86/kvm/svm/nested.c

@@ -545,7 +545,6 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm *svm)
 		(svm->nested.ctl.int_ctl & int_ctl_vmcb12_bits) |
 		(svm->vmcb01.ptr->control.int_ctl & int_ctl_vmcb01_bits);
 
-	svm->vmcb->control.virt_ext            = svm->nested.ctl.virt_ext;
 	svm->vmcb->control.int_vector          = svm->nested.ctl.int_vector;
 	svm->vmcb->control.int_state           = svm->nested.ctl.int_state;
 	svm->vmcb->control.event_inj           = svm->nested.ctl.event_inj;