diff --git a/xen-all.c b/xen-all.c
index 61def2ec8f..f76b051eee 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -712,7 +712,8 @@ static void cpu_ioreq_pio(ioreq_t *req)
 
             for (i = 0; i < req->count; i++) {
                 tmp = do_inp(req->addr, req->size);
-                cpu_physical_memory_write(req->data + (sign * i * req->size),
+                cpu_physical_memory_write(
+                        req->data + (sign * i * (int64_t)req->size),
                         (uint8_t *) &tmp, req->size);
             }
         }
@@ -723,7 +724,8 @@ static void cpu_ioreq_pio(ioreq_t *req)
             for (i = 0; i < req->count; i++) {
                 uint32_t tmp = 0;
 
-                cpu_physical_memory_read(req->data + (sign * i * req->size),
+                cpu_physical_memory_read(
+                        req->data + (sign * i * (int64_t)req->size),
                         (uint8_t*) &tmp, req->size);
                 do_outp(req->addr, req->size, tmp);
             }
@@ -740,12 +742,14 @@ static void cpu_ioreq_move(ioreq_t *req)
     if (!req->data_is_ptr) {
         if (req->dir == IOREQ_READ) {
             for (i = 0; i < req->count; i++) {
-                cpu_physical_memory_read(req->addr + (sign * i * req->size),
+                cpu_physical_memory_read(
+                        req->addr + (sign * i * (int64_t)req->size),
                         (uint8_t *) &req->data, req->size);
             }
         } else if (req->dir == IOREQ_WRITE) {
             for (i = 0; i < req->count; i++) {
-                cpu_physical_memory_write(req->addr + (sign * i * req->size),
+                cpu_physical_memory_write(
+                        req->addr + (sign * i * (int64_t)req->size),
                         (uint8_t *) &req->data, req->size);
             }
         }
@@ -754,16 +758,20 @@ static void cpu_ioreq_move(ioreq_t *req)
 
         if (req->dir == IOREQ_READ) {
             for (i = 0; i < req->count; i++) {
-                cpu_physical_memory_read(req->addr + (sign * i * req->size),
+                cpu_physical_memory_read(
+                        req->addr + (sign * i * (int64_t)req->size),
                         (uint8_t*) &tmp, req->size);
-                cpu_physical_memory_write(req->data + (sign * i * req->size),
+                cpu_physical_memory_write(
+                        req->data + (sign * i * (int64_t)req->size),
                         (uint8_t*) &tmp, req->size);
             }
         } else if (req->dir == IOREQ_WRITE) {
             for (i = 0; i < req->count; i++) {
-                cpu_physical_memory_read(req->data + (sign * i * req->size),
+                cpu_physical_memory_read(
+                        req->data + (sign * i * (int64_t)req->size),
                         (uint8_t*) &tmp, req->size);
-                cpu_physical_memory_write(req->addr + (sign * i * req->size),
+                cpu_physical_memory_write(
+                        req->addr + (sign * i * (int64_t)req->size),
                         (uint8_t*) &tmp, req->size);
             }
         }