KVM: vmx: handle_cr ignores 32/64-bit mode

On 32-bit mode only bits [31:0] of the CR should be used for setting the CR
value.  Otherwise, the host may incorrectly assume the value is invalid if bits
[63:32] are not zero.  Moreover, the CR is currently being read twice when CR8
is used.  Last, nested mov-cr exiting is modified to handle the CR value
correctly as well.
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx.c

@@ -5058,7 +5058,7 @@ static int handle_cr(struct kvm_vcpu *vcpu)
 	reg = (exit_qualification >> 8) & 15;
 	switch ((exit_qualification >> 4) & 3) {
 	case 0: /* mov to cr */
-		val = kvm_register_read(vcpu, reg);
+		val = kvm_register_readl(vcpu, reg);
 		trace_kvm_cr_write(cr, val);
 		switch (cr) {
 		case 0:
@@ -5075,7 +5075,7 @@ static int handle_cr(struct kvm_vcpu *vcpu)
 			return 1;
 		case 8: {
 				u8 cr8_prev = kvm_get_cr8(vcpu);
-				u8 cr8 = kvm_register_read(vcpu, reg);
+				u8 cr8 = (u8)val;
 				err = kvm_set_cr8(vcpu, cr8);
 				kvm_complete_insn_gp(vcpu, err);
 				if (irqchip_in_kernel(vcpu->kvm))
@@ -6770,7 +6770,7 @@ static bool nested_vmx_exit_handled_cr(struct kvm_vcpu *vcpu,
 	unsigned long exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
 	int cr = exit_qualification & 15;
 	int reg = (exit_qualification >> 8) & 15;
-	unsigned long val = kvm_register_read(vcpu, reg);
+	unsigned long val = kvm_register_readl(vcpu, reg);
 
 	switch ((exit_qualification >> 4) & 3) {
 	case 0: /* mov to cr */