migration: allow enabling mutilfd for specific protocol only

To: <quintela@redhat.com>, <dgilbert@redhat.com>, <qemu-devel@nongnu.org>
CC: Li Zhijian <lizhijian@cn.fujitsu.com>
Date: Sat, 31 Jul 2021 22:05:52 +0800 (5 weeks, 4 days, 17 hours ago)

And change the default to true so that in '-incoming defer' case, user is able
to change multifd capability.

Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

migration/migration.c

@@ -1237,6 +1237,14 @@ static bool migrate_caps_check(bool *cap_list,
         }
     }
 
+    /* incoming side only */
+    if (runstate_check(RUN_STATE_INMIGRATE) &&
+        !migrate_multifd_is_allowed() &&
+        cap_list[MIGRATION_CAPABILITY_MULTIFD]) {
+        error_setg(errp, "multifd is not supported by current protocol");
+        return false;
+    }
+
     return true;
 }
 

migration/multifd.c

@@ -868,7 +868,7 @@ static void multifd_new_send_channel_async(QIOTask *task, gpointer opaque)
     multifd_new_send_channel_cleanup(p, sioc, local_err);
 }
 
-static bool migrate_allow_multifd;
+static bool migrate_allow_multifd = true;
 void migrate_protocol_allow_multifd(bool allow)
 {
     migrate_allow_multifd = allow;