exec: move listener from AddressSpaceDispatch to AddressSpace

This will help having two copies of AddressSpaceDispatch during the
recreation of the radix tree (one being built, and one that is complete
and will be protected by RCU).  We do not want to have to unregister and
re-register the listener.
Reviewed-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

exec.c

@@ -93,7 +93,6 @@ struct AddressSpaceDispatch {
      * The bottom level has pointers to MemoryRegionSections.
      */
     PhysPageEntry phys_map;
-    MemoryListener listener;
     AddressSpace *as;
 };
 
@@ -841,7 +840,8 @@ static void register_multipage(AddressSpaceDispatch *d,
 
 static void mem_add(MemoryListener *listener, MemoryRegionSection *section)
 {
-    AddressSpaceDispatch *d = container_of(listener, AddressSpaceDispatch, listener);
+    AddressSpace *as = container_of(listener, AddressSpace, dispatch_listener);
+    AddressSpaceDispatch *d = as->dispatch;
     MemoryRegionSection now = *section, remain = *section;
     Int128 page_size = int128_make64(TARGET_PAGE_SIZE);
 
@@ -1703,7 +1703,8 @@ static void io_mem_init(void)
 
 static void mem_begin(MemoryListener *listener)
 {
-    AddressSpaceDispatch *d = container_of(listener, AddressSpaceDispatch, listener);
+    AddressSpace *as = container_of(listener, AddressSpace, dispatch_listener);
+    AddressSpaceDispatch *d = as->dispatch;
 
     d->phys_map.ptr = PHYS_MAP_NODE_NIL;
 }
@@ -1772,22 +1773,22 @@ void address_space_init_dispatch(AddressSpace *as)
     AddressSpaceDispatch *d = g_new(AddressSpaceDispatch, 1);
 
     d->phys_map  = (PhysPageEntry) { .ptr = PHYS_MAP_NODE_NIL, .is_leaf = 0 };
-    d->listener = (MemoryListener) {
+    d->as = as;
+    as->dispatch = d;
+    as->dispatch_listener = (MemoryListener) {
         .begin = mem_begin,
         .region_add = mem_add,
         .region_nop = mem_add,
         .priority = 0,
     };
-    d->as = as;
-    as->dispatch = d;
-    memory_listener_register(&d->listener, as);
+    memory_listener_register(&as->dispatch_listener, as);
 }
 
 void address_space_destroy_dispatch(AddressSpace *as)
 {
     AddressSpaceDispatch *d = as->dispatch;
 
-    memory_listener_unregister(&d->listener);
+    memory_listener_unregister(&as->dispatch_listener);
     g_free(d);
     as->dispatch = NULL;
 }

include/exec/memory.h

@@ -209,6 +209,8 @@ struct AddressSpace {
     int ioeventfd_nb;
     struct MemoryRegionIoeventfd *ioeventfds;
     struct AddressSpaceDispatch *dispatch;
+    MemoryListener dispatch_listener;
+
     QTAILQ_ENTRY(AddressSpace) address_spaces_link;
 };