Don't iterate on precopy-only devices during postcopy

During the postcopy phase we must not call the iterate method on
precopy-only devices, since they may have done some cleanup during
the _complete call at the end of the precopy phase.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

include/sysemu/sysemu.h

@@ -109,7 +109,7 @@ bool qemu_savevm_state_blocked(Error **errp);
 void qemu_savevm_state_begin(QEMUFile *f,
                              const MigrationParams *params);
 void qemu_savevm_state_header(QEMUFile *f);
-int qemu_savevm_state_iterate(QEMUFile *f);
+int qemu_savevm_state_iterate(QEMUFile *f, bool postcopy);
 void qemu_savevm_state_cleanup(void);
 void qemu_savevm_state_complete_postcopy(QEMUFile *f);
 void qemu_savevm_state_complete_precopy(QEMUFile *f);

migration/migration.c

@@ -1628,7 +1628,7 @@ static void *migration_thread(void *opaque)
                     continue;
                 }
                 /* Just another iteration step */
-                qemu_savevm_state_iterate(s->file);
+                qemu_savevm_state_iterate(s->file, entered_postcopy);
             } else {
                 trace_migration_thread_low_pending(pending_size);
                 migration_completion(s, current_active_state,

migration/savevm.c

@@ -931,7 +931,7 @@ void qemu_savevm_state_begin(QEMUFile *f,
  *   0 : We haven't finished, caller have to go again
  *   1 : We have finished, we can go to complete phase
  */
-int qemu_savevm_state_iterate(QEMUFile *f)
+int qemu_savevm_state_iterate(QEMUFile *f, bool postcopy)
 {
     SaveStateEntry *se;
     int ret = 1;
@@ -946,6 +946,15 @@ int qemu_savevm_state_iterate(QEMUFile *f)
                 continue;
             }
         }
+        /*
+         * In the postcopy phase, any device that doesn't know how to
+         * do postcopy should have saved it's state in the _complete
+         * call that's already run, it might get confused if we call
+         * iterate afterwards.
+         */
+        if (postcopy && !se->ops->save_live_complete_postcopy) {
+            continue;
+        }
         if (qemu_file_rate_limit(f)) {
             return 0;
         }
@@ -1160,7 +1169,7 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp)
     qemu_mutex_lock_iothread();
 
     while (qemu_file_get_error(f) == 0) {
-        if (qemu_savevm_state_iterate(f) > 0) {
+        if (qemu_savevm_state_iterate(f, false) > 0) {
             break;
         }
     }