diff --git a/hw/xen/xen-hvm-common.c b/hw/xen/xen-hvm-common.c
index 52e2cce397..258014370e 100644
--- a/hw/xen/xen-hvm-common.c
+++ b/hw/xen/xen-hvm-common.c
@@ -1,5 +1,6 @@
 #include "qemu/osdep.h"
 #include "qemu/units.h"
+#include "qemu/bitops.h"
 #include "qemu/error-report.h"
 #include "qapi/error.h"
 #include "exec/target_long.h"
@@ -448,12 +449,14 @@ static void cpu_ioreq_config(XenIOState *state, ioreq_t *req)
 
 static void handle_ioreq(XenIOState *state, ioreq_t *req)
 {
+    size_t req_size_bits = req->size * BITS_PER_BYTE;
+
     trace_handle_ioreq(req, req->type, req->dir, req->df, req->data_is_ptr,
                        req->addr, req->data, req->count, req->size);
 
     if (!req->data_is_ptr && (req->dir == IOREQ_WRITE) &&
             (req->size < sizeof (target_ulong))) {
-        req->data &= ((target_ulong) 1 << (8 * req->size)) - 1;
+        req->data &= MAKE_64BIT_MASK(0, req_size_bits);
     }
 
     if (req->dir == IOREQ_WRITE)