memory: support stateless memory listeners

Current memory listeners are incremental; that is, they are expected to
maintain their own state, and receive callbacks for changes to that state.

This patch adds support for stateless listeners; these work by receiving
a ->begin() callback (which tells them that new state is coming), a
sequence of ->region_add() and ->region_nop() callbacks, and then a
->commit() callback which signifies the end of the new state.  They should
ignore ->region_del() callbacks.

Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/hw/vhost.c b/hw/vhost.c
index 01f676a959..8d3ba5b608 100644
--- a/hw/vhost.c
+++ b/hw/vhost.c
@@ -436,6 +436,14 @@ static bool vhost_section(MemoryRegionSection *section)
         && memory_region_is_ram(section->mr);
 }
 
+static void vhost_begin(MemoryListener *listener)
+{
+}
+
+static void vhost_commit(MemoryListener *listener)
+{
+}
+
 static void vhost_region_add(MemoryListener *listener,
                              MemoryRegionSection *section)
 {
@@ -476,6 +484,11 @@ static void vhost_region_del(MemoryListener *listener,
     }
 }
 
+static void vhost_region_nop(MemoryListener *listener,
+                             MemoryRegionSection *section)
+{
+}
+
 static int vhost_virtqueue_set_addr(struct vhost_dev *dev,
                                     struct vhost_virtqueue *vq,
                                     unsigned idx, bool enable_log)
@@ -756,8 +769,11 @@ int vhost_dev_init(struct vhost_dev *hdev, int devfd, bool force)
     hdev->features = features;
 
     hdev->memory_listener = (MemoryListener) {
+        .begin = vhost_begin,
+        .commit = vhost_commit,
         .region_add = vhost_region_add,
         .region_del = vhost_region_del,
+        .region_nop = vhost_region_nop,
         .log_start = vhost_log_start,
         .log_stop = vhost_log_stop,
         .log_sync = vhost_log_sync,