[dpdk-dev] [PATCH v4 2/5] vhost: add unsafe API to drain pkts in async vhost

[Cheng Jiang <cheng1.jiang@intel.com>]

Applications need to stop DMA transfers and finish all the in-flight
pkts when in VM memory hot-plug case and async vhost is used. This
patch is to provide an unsafe API to drain in-flight pkts which are
submitted to DMA engine in vhost async data path.

Signed-off-by: Cheng Jiang <cheng1.jiang@intel.com>
---
 lib/vhost/rte_vhost_async.h | 24 ++++++++++
 lib/vhost/version.map       |  3 ++
 lib/vhost/virtio_net.c      | 90 +++++++++++++++++++++++++++----------
 3 files changed, 94 insertions(+), 23 deletions(-)

diff --git a/lib/vhost/rte_vhost_async.h b/lib/vhost/rte_vhost_async.h
index bc81cd0caa..fd622631b2 100644
--- a/lib/vhost/rte_vhost_async.h
+++ b/lib/vhost/rte_vhost_async.h
@@ -193,4 +193,28 @@ __rte_experimental
 uint16_t rte_vhost_poll_enqueue_completed(int vid, uint16_t queue_id,
 		struct rte_mbuf **pkts, uint16_t count);
 
+/**
+ * This function checks async completion status and empty all pakcets
+ * for a specific vhost device queue. Packets which are inflight will
+ * be returned in an array.
+ *
+ * @note This function does not perform any locking
+ *
+ * @param vid
+ *  id of vhost device to enqueue data
+ * @param queue_id
+ *  queue id to enqueue data
+ * @param pkts
+ *  blank array to get return packet pointer
+ * @param count
+ *  size of the packet array
+ * @param times
+ *  max number of poll attempts
+ * @return
+ *  num of packets returned
+ */
+__rte_experimental
+uint16_t rte_vhost_try_drain_queue_thread_unsafe(int vid, uint16_t queue_id,
+		struct rte_mbuf **pkts, uint16_t count, uint16_t times);
+
 #endif /* _RTE_VHOST_ASYNC_H_ */
diff --git a/lib/vhost/version.map b/lib/vhost/version.map
index 9103a23cd4..b8fc8770dd 100644
--- a/lib/vhost/version.map
+++ b/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_try_drain_queue_thread_unsafe;
 };
diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
index 8156796a46..9f541679b9 100644
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -2115,10 +2115,10 @@ write_back_completed_descs_packed(struct vhost_virtqueue *vq,
 	} while (nr_left > 0);
 }
 
-uint16_t rte_vhost_poll_enqueue_completed(int vid, uint16_t queue_id,
+static __rte_always_inline uint16_t
+vhost_poll_enqueue_completed(struct virtio_net *dev, uint16_t queue_id,
 		struct rte_mbuf **pkts, uint16_t count)
 {
-	struct virtio_net *dev = get_device(vid);
 	struct vhost_virtqueue *vq;
 	uint16_t n_pkts_cpl = 0, n_pkts_put = 0, n_descs = 0, n_buffers = 0;
 	uint16_t start_idx, pkts_idx, vq_size;
@@ -2126,26 +2126,8 @@ uint16_t rte_vhost_poll_enqueue_completed(int vid, uint16_t queue_id,
 	uint16_t from, i;
 	int32_t n_poll;
 
-	if (!dev)
-		return 0;
-
-	VHOST_LOG_DATA(DEBUG, "(%d) %s\n", dev->vid, __func__);
-	if (unlikely(!is_valid_virt_queue_idx(queue_id, 0, dev->nr_vring))) {
-		VHOST_LOG_DATA(ERR, "(%d) %s: invalid virtqueue idx %d.\n",
-			dev->vid, __func__, queue_id);
-		return 0;
-	}
-
 	vq = dev->virtqueue[queue_id];
 
-	if (unlikely(!vq->async_registered)) {
-		VHOST_LOG_DATA(ERR, "(%d) %s: async not registered for queue id %d.\n",
-			dev->vid, __func__, queue_id);
-		return 0;
-	}
-
-	rte_spinlock_lock(&vq->access_lock);
-
 	pkts_idx = vq->async_pkts_idx % vq->size;
 	pkts_info = vq->async_pkts_info;
 	vq_size = vq->size;
@@ -2153,7 +2135,7 @@ uint16_t rte_vhost_poll_enqueue_completed(int vid, uint16_t queue_id,
 		vq_size, vq->async_pkts_inflight_n);
 
 	if (count > vq->async_last_pkts_n) {
-		n_poll = vq->async_ops.check_completed_copies(vid,
+		n_poll = vq->async_ops.check_completed_copies(dev->vid,
 			queue_id, 0, count - vq->async_last_pkts_n);
 		if (n_poll >= 0) {
 			n_pkts_cpl = n_poll;
@@ -2168,7 +2150,7 @@ uint16_t rte_vhost_poll_enqueue_completed(int vid, uint16_t queue_id,
 	n_pkts_put = RTE_MIN(count, n_pkts_cpl);
 	if (unlikely(n_pkts_put == 0)) {
 		vq->async_last_pkts_n = n_pkts_cpl;
-		goto done;
+		return 0;
 	}
 
 	if (vq_is_packed(dev)) {
@@ -2207,12 +2189,74 @@ uint16_t rte_vhost_poll_enqueue_completed(int vid, uint16_t queue_id,
 			vq->last_async_desc_idx_split += n_descs;
 	}
 
-done:
+	return n_pkts_put;
+}
+
+uint16_t rte_vhost_poll_enqueue_completed(int vid, uint16_t queue_id,
+		struct rte_mbuf **pkts, uint16_t count)
+{
+	struct virtio_net *dev = get_device(vid);
+	struct vhost_virtqueue *vq;
+	uint16_t n_pkts_put = 0;
+
+	if (!dev)
+		return 0;
+
+	VHOST_LOG_DATA(DEBUG, "(%d) %s\n", dev->vid, __func__);
+	if (unlikely(!is_valid_virt_queue_idx(queue_id, 0, dev->nr_vring))) {
+		VHOST_LOG_DATA(ERR, "(%d) %s: invalid virtqueue idx %d.\n",
+			dev->vid, __func__, queue_id);
+		return 0;
+	}
+
+	vq = dev->virtqueue[queue_id];
+
+	if (unlikely(!vq->async_registered)) {
+		VHOST_LOG_DATA(ERR, "(%d) %s: async not registered for queue id %d.\n",
+			dev->vid, __func__, queue_id);
+		return 0;
+	}
+
+	rte_spinlock_lock(&vq->access_lock);
+
+	n_pkts_put = vhost_poll_enqueue_completed(dev, queue_id, pkts, count);
+
 	rte_spinlock_unlock(&vq->access_lock);
 
 	return n_pkts_put;
 }
 
+uint16_t rte_vhost_try_drain_queue_thread_unsafe(int vid, uint16_t queue_id,
+		struct rte_mbuf **pkts, uint16_t count, uint16_t times)
+{
+	struct virtio_net *dev = get_device(vid);
+	struct vhost_virtqueue *vq;
+	uint16_t n_cpl = 0;
+
+	if (!dev)
+		return 0;
+
+	VHOST_LOG_DATA(DEBUG, "(%d) %s\n", dev->vid, __func__);
+	if (unlikely(!is_valid_virt_queue_idx(queue_id, 0, dev->nr_vring))) {
+		VHOST_LOG_DATA(ERR, "(%d) %s: invalid virtqueue idx %d.\n",
+			dev->vid, __func__, queue_id);
+		return 0;
+	}
+
+	vq = dev->virtqueue[queue_id];
+
+	if (unlikely(!vq->async_registered)) {
+		VHOST_LOG_DATA(ERR, "(%d) %s: async not registered for queue id %d.\n",
+			dev->vid, __func__, queue_id);
+		return 0;
+	}
+
+	while ((n_cpl < count) && times--)
+		n_cpl += vhost_poll_enqueue_completed(dev, queue_id, pkts + n_cpl, count);
+
+	return n_cpl;
+}
+
 static __rte_always_inline uint32_t
 virtio_dev_rx_async_submit(struct virtio_net *dev, uint16_t queue_id,
 	struct rte_mbuf **pkts, uint32_t count,
-- 
2.29.2