vhost: allow to check in-flight packets for async vhost

This patch allows to check the amount of in-flight packets
for the vhost queue using async acceleration.

Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

doc/guides/prog_guide/vhost_lib.rst

@@ -281,6 +281,11 @@ The following is an overview of some key Vhost API functions:
   Poll enqueue completion status from async data path. Completed packets
   are returned to applications through ``pkts``.
 
+* ``rte_vhost_async_get_inflight(vid, queue_id)``
+
+  This function returns the amount of in-flight packets for the vhost
+  queue using async acceleration.
+
 Vhost-user Implementations
 --------------------------
 

lib/vhost/rte_vhost_async.h

@@ -193,4 +193,18 @@ __rte_experimental
 uint16_t rte_vhost_poll_enqueue_completed(int vid, uint16_t queue_id,
 		struct rte_mbuf **pkts, uint16_t count);
 
+/**
+ * This function returns the amount of in-flight packets for the vhost
+ * queue which uses async channel acceleration.
+ *
+ * @param vid
+ *  id of vhost device to enqueue data
+ * @param queue_id
+ *  queue id to enqueue data
+ * @return
+ *  the amount of in-flight packets on success; -1 on failure
+ */
+__rte_experimental
+int rte_vhost_async_get_inflight(int vid, uint16_t queue_id);
+
 #endif /* _RTE_VHOST_ASYNC_H_ */

lib/vhost/version.map

@@ -79,4 +79,7 @@ EXPERIMENTAL {
 
 	# added in 21.05
 	rte_vhost_get_negotiated_protocol_features;
+
+	# added in 21.08
+	rte_vhost_async_get_inflight;
 };

lib/vhost/vhost.c

@@ -1778,5 +1778,38 @@ out:
 	return ret;
 }
 
+int rte_vhost_async_get_inflight(int vid, uint16_t queue_id)
+{
+	struct vhost_virtqueue *vq;
+	struct virtio_net *dev = get_device(vid);
+	int ret = -1;
+
+	if (dev == NULL)
+		return ret;
+
+	if (queue_id >= VHOST_MAX_VRING)
+		return ret;
+
+	vq = dev->virtqueue[queue_id];
+
+	if (vq == NULL)
+		return ret;
+
+	if (!vq->async_registered)
+		return ret;
+
+	if (!rte_spinlock_trylock(&vq->access_lock)) {
+		VHOST_LOG_CONFIG(DEBUG, "Failed to check in-flight packets. "
+			"virt queue busy.\n");
+		return ret;
+	}
+
+	ret = vq->async_pkts_inflight_n;
+	rte_spinlock_unlock(&vq->access_lock);
+
+	return ret;
+
+}
+
 RTE_LOG_REGISTER_SUFFIX(vhost_config_log_level, config, INFO);
 RTE_LOG_REGISTER_SUFFIX(vhost_data_log_level, data, WARNING);