migrate_add_blocker() can fail (e.g. if migration is already in
progress), in which case it returns a negative value and populates
its errp argument with the reason.

The previous code ignored the return value. Pass &error_fatal so
that on failure QEMU exits cleanly with an informative error message
rather than continuing in an inconsistent state.

Resolves: CID 1645470
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Tested-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Trieu Huynh <vikingtc4@gmail.com>
---
v2:
- Pass &error_fatal instead of returning NULL: the plugin has no
  recovery path, QEMU should exit cleanly with an error message.
  (Peter Maydell, Pierrick Bouvier)
- Remove manual error_free(migration_blocker) + migration_blocker = NULL:
  migrate_add_blocker() already does this on failure. (Peter Maydell)
---
 plugins/api-system.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/plugins/api-system.c b/plugins/api-system.c
index 9a70b9caa6..fbf905cd63 100644
--- a/plugins/api-system.c
+++ b/plugins/api-system.c
@@ -108,7 +108,7 @@ const void *qemu_plugin_request_time_control(void)
         has_control = true;
         error_setg(&migration_blocker,
                    "TCG plugin time control does not support migration");
-        migrate_add_blocker(&migration_blocker, NULL);
+        migrate_add_blocker(&migration_blocker, &error_fatal);
         return &has_control;
     }
     return NULL;
-- 
2.43.0