migration: add has_postcopy savevm handler

Now postcopy-able states are recognized by not NULL
save_live_complete_postcopy handler. But when we have several different
postcopy-able states, it is not convenient. Ram postcopy may be
disabled, while some other postcopy enabled, in this case Ram state
should behave as it is not postcopy-able.

This patch add separate has_postcopy handler to specify behaviour of
savevm state.
Signed-off-by: NVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

include/migration/register.h

@@ -24,6 +24,7 @@ typedef struct SaveVMHandlers {
 
     /* This runs both outside and inside the iothread lock.  */
     bool (*is_active)(void *opaque);
+    bool (*has_postcopy)(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

migration/ram.c

@@ -2849,11 +2849,17 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
     return ret;
 }
 
+static bool ram_has_postcopy(void *opaque)
+{
+    return migrate_postcopy_ram();
+}
+
 static SaveVMHandlers savevm_ram_handlers = {
     .save_setup = ram_save_setup,
     .save_live_iterate = ram_save_iterate,
     .save_live_complete_postcopy = ram_save_complete,
     .save_live_complete_precopy = ram_save_complete,
+    .has_postcopy = ram_has_postcopy,
     .save_live_pending = ram_save_pending,
     .load_state = ram_load,
     .save_cleanup = ram_save_cleanup,

migration/savevm.c

@@ -1008,7 +1008,8 @@ int qemu_savevm_state_iterate(QEMUFile *f, bool postcopy)
          * call that's already run, it might get confused if we call
          * iterate afterwards.
          */
-        if (postcopy && !se->ops->save_live_complete_postcopy) {
+        if (postcopy &&
+            !(se->ops->has_postcopy && se->ops->has_postcopy(se->opaque))) {
             continue;
         }
         if (qemu_file_rate_limit(f)) {
@@ -1097,7 +1098,8 @@ int qemu_savevm_state_complete_precopy(QEMUFile *f, bool iterable_only,
 
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
         if (!se->ops ||
-            (in_postcopy && se->ops->save_live_complete_postcopy) ||
+            (in_postcopy && se->ops->has_postcopy &&
+             se->ops->has_postcopy(se->opaque)) ||
             (in_postcopy && !iterable_only) ||
             !se->ops->save_live_complete_precopy) {
             continue;