vfio/migration: Skip log_sync during migration SETUP state

Currently, VFIO log_sync can be issued while migration is in SETUP
state. However, doing this log_sync is at best redundant and at worst
can fail.

Redundant -- all RAM is marked dirty in migration SETUP state and is
transferred only after migration is set to ACTIVE state, so doing
log_sync during migration SETUP is pointless.

Can fail -- there is a time window, between setting migration state to
SETUP and starting dirty tracking by RAM save_live_setup handler, during
which dirty tracking is still not started. Any VFIO log_sync call that
is issued during this time window will fail. For example, this error can
be triggered by migrating a VM when a GUI is active, which constantly
calls log_sync.

Fix it by skipping VFIO log_sync while migration is in SETUP state.

Fixes: 758b96b61d5c ("vfio/migrate: Move switch of dirty tracking into vfio_memory_listener")
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Link: https://lore.kernel.org/r/20230403130000.6422-1-avihaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 4d01ea3515156670a99c3b69ccdfef295d33ace9..78358ede27645e9013f29b6577304df76ba039de 100644 (file)
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -478,7 +478,8 @@ static bool vfio_devices_all_dirty_tracking(VFIOContainer *container)
     VFIODevice *vbasedev;
     MigrationState *ms = migrate_get_current();
 
-    if (!migration_is_setup_or_active(ms->state)) {
+    if (ms->state != MIGRATION_STATUS_ACTIVE &&
+        ms->state != MIGRATION_STATUS_DEVICE) {
         return false;
     }