[PATCH V1 2/3] migration: fix suspended runstate

[Steve Sistare]

Migration of a guest in the suspended state is broken.  The incoming
migration code automatically tries to wake the guest, which IMO is
wrong -- the guest should end migration in the same state it started.
Further, the wakeup is done by calling qemu_system_wakeup_request(), which
bypasses vm_start().  The guest appears to be in the running state, but
it is not.

To fix, leave the guest in the suspended state, but call
qemu_system_start_on_wakeup_request() so the guest is properly resumed
later, when the client sends a system_wakeup command.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 migration/migration.c | 11 ++++-------
 softmmu/runstate.c    |  1 +
 2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 17b4b47..851fe6d 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -496,6 +496,10 @@ static void process_incoming_migration_bh(void *opaque)
         vm_start();
     } else {
         runstate_set(global_state_get_runstate());
+        if (runstate_check(RUN_STATE_SUSPENDED)) {
+            /* Force vm_start to be called later. */
+            qemu_system_start_on_wakeup_request();
+        }
     }
     /*
      * This must happen after any state changes since as soon as an external
@@ -2101,7 +2105,6 @@ static int postcopy_start(MigrationState *ms)
     qemu_mutex_lock_iothread();
     trace_postcopy_start_set_run();
 
-    qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER, NULL);
     global_state_store();
     ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
     if (ret < 0) {
@@ -2307,7 +2310,6 @@ static void migration_completion(MigrationState *s)
     if (s->state == MIGRATION_STATUS_ACTIVE) {
         qemu_mutex_lock_iothread();
         s->downtime_start = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
-        qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER, NULL);
 
         s->vm_old_state = runstate_get();
         global_state_store();
@@ -3102,11 +3104,6 @@ static void *bg_migration_thread(void *opaque)
 
     qemu_mutex_lock_iothread();
 
-    /*
-     * If VM is currently in suspended state, then, to make a valid runstate
-     * transition in vm_stop_force_state() we need to wakeup it up.
-     */
-    qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER, NULL);
     s->vm_old_state = runstate_get();
 
     global_state_store();
diff --git a/softmmu/runstate.c b/softmmu/runstate.c
index e127b21..771896c 100644
--- a/softmmu/runstate.c
+++ b/softmmu/runstate.c
@@ -159,6 +159,7 @@ static const RunStateTransition runstate_transitions_def[] 
= {
     { RUN_STATE_RUNNING, RUN_STATE_SUSPENDED },
     { RUN_STATE_SUSPENDED, RUN_STATE_RUNNING },
     { RUN_STATE_SUSPENDED, RUN_STATE_FINISH_MIGRATE },
+    { RUN_STATE_SUSPENDED, RUN_STATE_PAUSED },
     { RUN_STATE_SUSPENDED, RUN_STATE_PRELAUNCH },
     { RUN_STATE_SUSPENDED, RUN_STATE_COLO},
 
-- 
1.8.3.1