xen: ignore I/O memory regions

Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/xen-all.c b/xen-all.c
index dd52f02..a58a397 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -989,7 +989,7 @@
 
     state->memory_listener = xen_memory_listener;
     QLIST_INIT(&state->physmap);
-    memory_listener_register(&state->memory_listener, NULL);
+    memory_listener_register(&state->memory_listener, get_system_memory());
     state->log_for_dirtybit = NULL;
 
     /* Initialize backend core & drivers */