memory: Alloc dispatch tree where topology is generared

This is to make next patches simpler.
Signed-off-by: NAlexey Kardashevskiy <aik@ozlabs.ru>
Message-Id: <20170921085110.25598-11-aik@ozlabs.ru>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

memory.c

@@ -743,6 +743,7 @@ static MemoryRegion *memory_region_get_flatview_root(MemoryRegion *mr)
 /* Render a memory topology into a list of disjoint absolute ranges. */
 static FlatView *generate_memory_topology(MemoryRegion *mr)
 {
+    int i;
     FlatView *view;
 
     view = flatview_new(mr);
@@ -753,6 +754,14 @@ static FlatView *generate_memory_topology(MemoryRegion *mr)
     }
     flatview_simplify(view);
 
+    view->dispatch = address_space_dispatch_new(view);
+    for (i = 0; i < view->nr; i++) {
+        MemoryRegionSection mrs =
+            section_from_flat_range(&view->ranges[i], view);
+        flatview_add_to_dispatch(view, &mrs);
+    }
+    address_space_dispatch_compact(view->dispatch);
+
     return view;
 }
 
@@ -926,15 +935,6 @@ static void address_space_update_topology(AddressSpace *as)
     FlatView *old_view = address_space_get_flatview(as);
     MemoryRegion *physmr = memory_region_get_flatview_root(old_view->root);
     FlatView *new_view = generate_memory_topology(physmr);
-    int i;
-
-    new_view->dispatch = address_space_dispatch_new(new_view);
-    for (i = 0; i < new_view->nr; i++) {
-        MemoryRegionSection mrs =
-            section_from_flat_range(&new_view->ranges[i], new_view);
-        flatview_add_to_dispatch(new_view, &mrs);
-    }
-    address_space_dispatch_compact(new_view->dispatch);
 
     if (!QTAILQ_EMPTY(&as->listeners)) {
         address_space_update_topology_pass(as, old_view, new_view, false);