migration: add is_active_iterate handler

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>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 20180313180320.339796-10-vsementsov@virtuozzo.com

diff --git a/include/migration/register.h b/include/migration/register.h
index 9436a87..f6f12f9 100644 (file)
--- a/include/migration/register.h
+++ b/include/migration/register.h
@@ -26,6 +26,15 @@ typedef struct SaveVMHandlers {
     bool (*is_active)(void *opaque);
     bool (*has_postcopy)(void *opaque);
 
+    /* is_active_iterate
+     * If it is not NULL then qemu_savevm_state_iterate will skip iteration if
+     * it returns false. For example, it is needed for only-postcopy-states,
+     * which needs to be handled by qemu_savevm_state_setup and
+     * qemu_savevm_state_pending, but do not need iterations until not in
+     * postcopy stage.
+     */
+    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
      * use data that is local to the migration thread or protected

diff --git a/migration/savevm.c b/migration/savevm.c
index cd5944b..a60819e 100644 (file)
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1028,6 +1028,11 @@ 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