[PULL 61/65] migration: Display error in query-migrate irrelevant of status

[Juan Quintela]

From: Peter Xu <peterx@redhat.com>

Display it as long as being set, irrelevant of FAILED status.  E.g., it may
also be applicable to PAUSED stage of postcopy, to provide hint on what has
gone wrong.

The error_mutex seems to be overlooked when referencing the error, add it
to be very safe.

This will change QAPI behavior by showing up error message outside !FAILED
status, but it's intended and doesn't expect to break anyone.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2018404
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231004220240.167175-2-peterx@redhat.com>
---
 qapi/migration.json   | 5 ++---
 migration/migration.c | 8 +++++---
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/qapi/migration.json b/qapi/migration.json
index d8f3bbd7b0..d7dfaa5db9 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -230,9 +230,8 @@
 #     throttled during auto-converge.  This is only present when
 #     auto-converge has started throttling guest cpus.  (Since 2.7)
 #
-# @error-desc: the human readable error description string, when
-#     @status is 'failed'. Clients should not attempt to parse the
-#     error strings.  (Since 2.7)
+# @error-desc: the human readable error description string. Clients
+#     should not attempt to parse the error strings.  (Since 2.7)
 #
 # @postcopy-blocktime: total time when all vCPU were blocked during
 #     postcopy live migration.  This is only present when the
diff --git a/migration/migration.c b/migration/migration.c
index 2057e42134..57f9e9ed0c 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1060,9 +1060,6 @@ static void fill_source_migration_info(MigrationInfo 
*info)
         break;
     case MIGRATION_STATUS_FAILED:
         info->has_status = true;
-        if (s->error) {
-            info->error_desc = g_strdup(error_get_pretty(s->error));
-        }
         break;
     case MIGRATION_STATUS_CANCELLED:
         info->has_status = true;
@@ -1072,6 +1069,11 @@ static void fill_source_migration_info(MigrationInfo 
*info)
         break;
     }
     info->status = state;
+
+    QEMU_LOCK_GUARD(&s->error_mutex);
+    if (s->error) {
+        info->error_desc = g_strdup(error_get_pretty(s->error));
+    }
 }
 
 static void fill_destination_migration_info(MigrationInfo *info)
-- 
2.41.0