memory: Sanity check that no listeners remain on a destroyed AddressSpace

At the moment, most AddressSpace objects last as long as the guest system
in practice, but that could well change in future.  In addition, for VFIO
we will be introducing some private per-AdressSpace information, which must
be disposed of before the AddressSpace itself is destroyed.

To reduce the chances of subtle bugs in this area, this patch adds
asssertions to ensure that when an AddressSpace is destroyed, there are no
remaining MemoryListeners using that AS as a filter.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/memory.c b/memory.c
index 3f1df238e200308972badb012503ee5ae034387a..678661e2bb3db2fb269ba13e3aca3415425ac14e 100644 (file)
--- a/memory.c
+++ b/memory.c
@@ -1722,12 +1722,19 @@ void address_space_init(AddressSpace *as, MemoryRegion *root, const char *name)
 
 void address_space_destroy(AddressSpace *as)
 {
+    MemoryListener *listener;
+
     /* Flush out anything from MemoryListeners listening in on this */
     memory_region_transaction_begin();
     as->root = NULL;
     memory_region_transaction_commit();
     QTAILQ_REMOVE(&address_spaces, as, address_spaces_link);
     address_space_destroy_dispatch(as);
+
+    QTAILQ_FOREACH(listener, &memory_listeners, link) {
+        assert(listener->address_space_filter != as);
+    }
+
     flatview_unref(as->current_map);
     g_free(as->name);
     g_free(as->ioeventfds);