KVM: nSVM: Check for CR0.CD and CR0.NW on VMRUN of nested guests

According to section "Canonicalization and Consistency Checks" in APM vol. 2,
the following guest state combination is illegal:

	"CR0.CD is zero and CR0.NW is set"
Signed-off-by: NKrish Sadhukhan <krish.sadhukhan@oracle.com>
Message-Id: <20200409205035.16830-2-krish.sadhukhan@oracle.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/nested.c

@@ -207,6 +207,10 @@ static bool nested_vmcb_checks(struct vmcb *vmcb)
 	if ((vmcb->save.efer & EFER_SVME) == 0)
 		return false;
 
+	if (((vmcb->save.cr0 & X86_CR0_CD) == 0) &&
+	    (vmcb->save.cr0 & X86_CR0_NW))
+		return false;
+
 	if ((vmcb->control.intercept & (1ULL << INTERCEPT_VMRUN)) == 0)
 		return false;