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[PULL,17/47] vfio/migration: Don't emit STOP_COPY VFIO migration QAPI event twice

Message ID 20240522095442.195243-18-clg@redhat.com
State New
Headers show
Series [PULL,01/47] vfio: Add Error** argument to .set_dirty_page_tracking() handler | expand

Commit Message

Cédric Le Goater May 22, 2024, 9:54 a.m. UTC 
From: Avihai Horon <avihaih@nvidia.com>

When migrating a VFIO device that supports pre-copy, it is transitioned
to STOP_COPY twice: once in vfio_vmstate_change() and second time in
vfio_save_complete_precopy().

The second transition is harmless, as it's a STOP_COPY->STOP_COPY no-op
transition. However, with the newly added VFIO migration QAPI event, the
STOP_COPY event is undesirably emitted twice.

Prevent this by returning early in vfio_migration_set_state() if
new_state is the same as current device state.

Note that the STOP_COPY transition in vfio_save_complete_precopy() is
essential for VFIO devices that don't support pre-copy, for migrating an
already stopped guest and for snapshots.

Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
 hw/vfio/migration.c | 4 ++++
 1 file changed, 4 insertions(+)
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Patch

diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index af579b868d7caa726fde1eeb73c832ebc3136a7a..56edffaf6251e28e39ef32991394697abb1b9e55 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -150,6 +150,10 @@  static int vfio_migration_set_state(VFIODevice *vbasedev,
         g_strdup_printf("%s: Failed setting device state to %s.",
                         vbasedev->name, mig_state_to_str(new_state));
 
+    if (new_state == migration->device_state) {
+        return 0;
+    }
+
     feature->argsz = sizeof(buf);
     feature->flags =
         VFIO_DEVICE_FEATURE_SET | VFIO_DEVICE_FEATURE_MIG_DEVICE_STATE;