On 1/12/26 23:19, Stefan Hajnoczi wrote:
On Mon, Jan 12, 2026 at 04:45:03PM +0500, Alexandr Moshkov wrote:
During inter-host migration, waiting for disk requests to be drained
in the vhost-user backend can incur significant downtime.
This can be avoided if QEMU migrates the inflight region in
vhost-user-blk.
Thus, during the qemu migration, with feature flag the vhost-user
back-end can immediately stop vrings, so all in-flight requests will be
migrated to another host.
Signed-off-by: Alexandr Moshkov <[email protected]>
---
hw/block/vhost-user-blk.c | 28 ++++++++++++++++++++++++++++
include/hw/virtio/vhost-user-blk.h | 1 +
2 files changed, 29 insertions(+)
diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index a8fd90480a..5e44f6253c 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -656,6 +656,28 @@ static struct vhost_dev
*vhost_user_blk_get_vhost(VirtIODevice *vdev)
return &s->dev;
}
+static bool vhost_user_blk_inflight_needed(void *opaque)
+{
+ struct VHostUserBlk *s = opaque;
+
+ bool inflight_drain = vhost_dev_has_feature(&s->dev,
+ VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT);
VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT must only be negotiated
when inflight_migration is enabled. Otherwise the backend will use this
feature even though vhost_user_blk_inflight_needed() skips migrating the
in-flight region.
Oh, I understand now. I'll fix this too, thanks!
