KVM: VMX: WARN on a MOV CR3 exit w/ unrestricted guest

CR3 load/store exiting are always off when unrestricted guest
is enabled.  WARN on the associated CR3 VMEXIT to detect code
that would re-introduce CR3 load/store exiting for unrestricted
guest.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/kvm/vmx.c

@@ -6377,6 +6377,7 @@ static int handle_cr(struct kvm_vcpu *vcpu)
 			err = handle_set_cr0(vcpu, val);
 			return kvm_complete_insn_gp(vcpu, err);
 		case 3:
+			WARN_ON_ONCE(enable_unrestricted_guest);
 			err = kvm_set_cr3(vcpu, val);
 			return kvm_complete_insn_gp(vcpu, err);
 		case 4:
@@ -6409,6 +6410,7 @@ static int handle_cr(struct kvm_vcpu *vcpu)
 	case 1: /*mov from cr*/
 		switch (cr) {
 		case 3:
+			WARN_ON_ONCE(enable_unrestricted_guest);
 			val = kvm_read_cr3(vcpu);
 			kvm_register_write(vcpu, reg, val);
 			trace_kvm_cr_read(cr, val);