Only-postcopy savevm states (dirty-bitmap) don't need live iteration, so
to disable them and stop transporting empty sections there is a new
savevm handler.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
---
 include/migration/register.h | 1 +
 migration/savevm.c           | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/include/migration/register.h b/include/migration/register.h
index ebf68992dd..3655341544 100644
--- a/include/migration/register.h
+++ b/include/migration/register.h
@@ -25,6 +25,7 @@ typedef struct SaveVMHandlers {
     /* This runs both outside and inside the iothread lock.  */
     bool (*is_active)(void *opaque);
     bool (*has_postcopy)(void *opaque);
+    bool (*is_active_iterate)(void *opaque);
 
     /* This runs outside the iothread lock in the migration case, and
      * within the lock in the savevm case.  The callback had better only
diff --git a/migration/savevm.c b/migration/savevm.c
index 0ab036489a..f03ee02f67 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1024,6 +1024,11 @@ int qemu_savevm_state_iterate(QEMUFile *f, bool postcopy)
                 continue;
             }
         }
+        if (se->ops && se->ops->is_active_iterate) {
+            if (!se->ops->is_active_iterate(se->opaque)) {
+                continue;
+            }
+        }
         /*
          * In the postcopy phase, any device that doesn't know how to
          * do postcopy should have saved it's state in the _complete
-- 
2.11.1