KVM: x86: movnti minimum op size of 32-bit is not kept

If the operand-size prefix (0x66) is used in 64-bit mode, the emulator would
assume the destination operand is 64-bit, when it should be 32-bit.

Reminder: movnti does not support 16-bit operands and its default operand size
is 32-bit.
Signed-off-by: NNadav Amit <namit@cs.technion.ac.il>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/emulate.c

@@ -4836,8 +4836,8 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
 		break;
 	case 0xc3:		/* movnti */
 		ctxt->dst.bytes = ctxt->op_bytes;
-		ctxt->dst.val = (ctxt->op_bytes == 4) ? (u32) ctxt->src.val :
-							(u64) ctxt->src.val;
+		ctxt->dst.val = (ctxt->op_bytes == 8) ? (u64) ctxt->src.val :
+							(u32) ctxt->src.val;
 		break;
 	default:
 		goto cannot_emulate;