vhost: take worker or vq for flushing

This patch has the core work flush function take a worker. When we
support multiple workers we can then flush each worker during device
removal, stoppage, etc. It also adds a helper to flush specific
virtqueues, so vhost-scsi can flush IO vqs from it's ctl vq.
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Message-Id: <20230626232307.97930-7-michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/vhost.c

@@ -265,16 +265,27 @@ bool vhost_vq_work_queue(struct vhost_virtqueue *vq, struct vhost_work *work)
 }
 EXPORT_SYMBOL_GPL(vhost_vq_work_queue);
 
-void vhost_dev_flush(struct vhost_dev *dev)
+static void vhost_worker_flush(struct vhost_worker *worker)
 {
 	struct vhost_flush_struct flush;
 
 	init_completion(&flush.wait_event);
 	vhost_work_init(&flush.work, vhost_flush_work);
 
-	if (vhost_work_queue(dev, &flush.work))
+	if (vhost_worker_queue(worker, &flush.work))
 		wait_for_completion(&flush.wait_event);
 }
+
+void vhost_vq_flush(struct vhost_virtqueue *vq)
+{
+	vhost_worker_flush(vq->worker);
+}
+EXPORT_SYMBOL_GPL(vhost_vq_flush);
+
+void vhost_dev_flush(struct vhost_dev *dev)
+{
+	vhost_worker_flush(dev->worker);
+}
 EXPORT_SYMBOL_GPL(vhost_dev_flush);
 
 /* A lockless hint for busy polling code to exit the loop */

drivers/vhost/vhost.h

@@ -198,6 +198,7 @@ int vhost_get_vq_desc(struct vhost_virtqueue *,
 		      struct vhost_log *log, unsigned int *log_num);
 void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
 
+void vhost_vq_flush(struct vhost_virtqueue *vq);
 bool vhost_vq_work_queue(struct vhost_virtqueue *vq, struct vhost_work *work);
 bool vhost_vq_has_work(struct vhost_virtqueue *vq);
 bool vhost_vq_is_setup(struct vhost_virtqueue *vq);