[PATCH 5/5] migration: restore vmstate on migration failure

[Vladimir Sementsov-Ogievskiy]

1. Otherwise failed migration just drops guest-panicked state, which is
   not good for management software.

2. We do keep different paused states like guest-panicked during
   migration with help of global_state state.

3. We do restore running state on source when migration is cancelled or
   failed.

4. "postmigrate" state is documented as "guest is paused following a
   successful 'migrate'", so originally it's only for successful path
   and we never documented current behavior.

Let's restore paused states like guest-panicked in case of cancel or
fail too. Allow same transitions like for inmigrate state.

This commit changes the behavior that was introduced by commit
42da5550d6 "migration: set state to post-migrate on failure" and
provides a bit different fix on related
  https://bugzilla.redhat.com/show_bug.cgi?id=1355683

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
---
 migration/migration.c | 2 +-
 softmmu/runstate.c    | 8 +++++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 4ccb9f9f3b..951897554f 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -2804,7 +2804,7 @@ static void migration_iteration_finish(MigrationState *s)
             }
         } else {
             if (runstate_check(RUN_STATE_FINISH_MIGRATE)) {
-                runstate_set(RUN_STATE_POSTMIGRATE);
+                runstate_set(s->vm_old_state);
             }
         }
         break;
diff --git a/softmmu/runstate.c b/softmmu/runstate.c
index 0370230a5e..1957caf73f 100644
--- a/softmmu/runstate.c
+++ b/softmmu/runstate.c
@@ -121,7 +121,13 @@ static const RunStateTransition runstate_transitions_def[] 
= {
     { RUN_STATE_FINISH_MIGRATE, RUN_STATE_PAUSED },
     { RUN_STATE_FINISH_MIGRATE, RUN_STATE_POSTMIGRATE },
     { RUN_STATE_FINISH_MIGRATE, RUN_STATE_PRELAUNCH },
-    { RUN_STATE_FINISH_MIGRATE, RUN_STATE_COLO},
+    { RUN_STATE_FINISH_MIGRATE, RUN_STATE_COLO },
+    { RUN_STATE_FINISH_MIGRATE, RUN_STATE_INTERNAL_ERROR },
+    { RUN_STATE_FINISH_MIGRATE, RUN_STATE_IO_ERROR },
+    { RUN_STATE_FINISH_MIGRATE, RUN_STATE_SHUTDOWN },
+    { RUN_STATE_FINISH_MIGRATE, RUN_STATE_SUSPENDED },
+    { RUN_STATE_FINISH_MIGRATE, RUN_STATE_WATCHDOG },
+    { RUN_STATE_FINISH_MIGRATE, RUN_STATE_GUEST_PANICKED },
 
     { RUN_STATE_RESTORE_VM, RUN_STATE_RUNNING },
     { RUN_STATE_RESTORE_VM, RUN_STATE_PRELAUNCH },
-- 
2.34.1