[PATCH RFC 1/9] migration/vfio: Remove BQL implication in vfio_multifd_switchover_start()

[Peter Xu <peterx@redhat.com>]

We may switch to a BQL-free loadvm model.  Be prepared with it.

Cc: Cédric Le Goater <clg@redhat.com>
Cc: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 hw/vfio/migration-multifd.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/hw/vfio/migration-multifd.c b/hw/vfio/migration-multifd.c
index e4785031a7..8dc8444f0d 100644
--- a/hw/vfio/migration-multifd.c
+++ b/hw/vfio/migration-multifd.c
@@ -763,16 +763,21 @@ int vfio_multifd_switchover_start(VFIODevice *vbasedev)
 {
     VFIOMigration *migration = vbasedev->migration;
     VFIOMultifd *multifd = migration->multifd;
+    bool bql_is_locked = bql_locked();
 
     assert(multifd);
 
     /* The lock order is load_bufs_mutex -> BQL so unlock BQL here first */
-    bql_unlock();
+    if (bql_is_locked) {
+        bql_unlock();
+    }
     WITH_QEMU_LOCK_GUARD(&multifd->load_bufs_mutex) {
         assert(!multifd->load_bufs_thread_running);
         multifd->load_bufs_thread_running = true;
     }
-    bql_lock();
+    if (bql_is_locked) {
+        bql_lock();
+    }
 
     qemu_loadvm_start_load_thread(vfio_load_bufs_thread, vbasedev);
 
-- 
2.50.1