Postcopy+spice: Pass spice migration data earlier

Spice hooks the migration status changes to figure out when to
transmit information to the new spice server; but the migration
status in postcopy doesn't quite fit - the destination starts
running before the end of the source migration.

It's not a case of hanging off the migration status change to
postcopy-active either, since that happens before we stop the
guest CPU.

Fix it by sending a notify just after sending the device state,
and adding a flag that can be tested by the notify receiver.

Symptom:
   spice handover doesn't work with the error:
   red_worker.c:11540:display_channel_wait_for_migrate_data: timeout

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Message-id: 1456161452-25318-1-git-send-email-dgilbert@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

include/migration/migration.h

diff --git a/include/migration/migration.h b/include/migration/migration.h
index 74684ad..97622e4 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -159,6 +159,8 @@
 
     /* Flag set once the migration has been asked to enter postcopy */
     bool start_postcopy;
+    /* Flag set after postcopy has sent the device state */
+    bool postcopy_after_devices;
 
     /* Flag set once the migration thread is running (and needs joining) */
     bool migration_thread_running;
@@ -212,6 +214,8 @@
 bool migration_has_failed(MigrationState *);
 /* True if outgoing migration has entered postcopy phase */
 bool migration_in_postcopy(MigrationState *);
+/* ...and after the device transmission */
+bool migration_in_postcopy_after_devices(MigrationState *);
 MigrationState *migrate_get_current(void);
 
 void migrate_compress_threads_create(void);