softmmu/memory_mapping: never merge ranges accross memory regions

Let's make sure to not merge when different memory regions are involved.
Unlikely, but theoretically possible.

Acked-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Claudio Fontana <cfontana@suse.de>
Cc: Thomas Huth <thuth@redhat.com>
Cc: "Alex Bennée" <alex.bennee@linaro.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Laurent Vivier <lvivier@redhat.com>
Cc: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20210727082545.17934-3-david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

softmmu/memory_mapping.c

@@ -229,7 +229,8 @@ static void guest_phys_blocks_region_add(MemoryListener *listener,
 
         /* we want continuity in both guest-physical and host-virtual memory */
         if (predecessor->target_end < target_start ||
-            predecessor->host_addr + predecessor_size != host_addr) {
+            predecessor->host_addr + predecessor_size != host_addr ||
+            predecessor->mr != section->mr) {
             predecessor = NULL;
         }
     }