[dpdk-dev] [PATCH v6 2/5] vhost: add unsafe API to clear packets in async vhost

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

Applications need to stop DMA transfers and finish all the inflight
packets when in VM memory hot-plug case and async vhost is used. This
patch is to provide an unsafe API to clear inflight packets 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 | 22 +++++++++
 lib/vhost/version.map       |  3 ++
 lib/vhost/virtio_net.c      | 93 +++++++++++++++++++++++++++----------
 3 files changed, 94 insertions(+), 24 deletions(-)

diff --git a/lib/vhost/rte_vhost_async.h b/lib/vhost/rte_vhost_async.h
index e964d83837..9961e4970e 100644
--- a/lib/vhost/rte_vhost_async.h
+++ b/lib/vhost/rte_vhost_async.h
@@ -193,4 +193,26 @@ __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 clear packets 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 clear data
+ * @param queue_id
+ *  Queue id to clear data
+ * @param pkts
+ *  Blank array to get return packet pointer
+ * @param count
+ *  Size of the packet array
+ * @return
+ *  Number of packets returned
+ */
+__rte_experimental
+uint16_t rte_vhost_clear_queue_thread_unsafe(int vid, uint16_t queue_id,
+		struct rte_mbuf **pkts, uint16_t count);
+
 #endif /* _RTE_VHOST_ASYNC_H_ */
diff --git a/lib/vhost/version.map b/lib/vhost/version.map
index 9103a23cd4..8dcf9e802a 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_clear_queue_thread_unsafe;
 };
diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
index 16ae4d9e19..29f91f9ad4 100644
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -2117,10 +2117,10 @@ 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;
@@ -2128,26 +2128,8 @@ uint16_t rte_vhost_poll_enqueue_completed(int vid, uint16_t queue_id,
 	uint16_t from, i;
 	int32_t n_cpl;
 
-	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;
@@ -2155,7 +2137,7 @@ 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_cpl = vq->async_ops.check_completed_copies(vid,
+		n_cpl = vq->async_ops.check_completed_copies(dev->vid,
 			queue_id, 0, count - vq->async_last_pkts_n);
 		if (n_cpl >= 0) {
 			n_pkts_cpl = n_cpl;
@@ -2171,7 +2153,7 @@ 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)) {
@@ -2210,10 +2192,73 @@ 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_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;
+	}
+
+	rte_spinlock_lock(&vq->access_lock);
+
+	n_pkts_cpl = vhost_poll_enqueue_completed(dev, queue_id, pkts, count);
+
 	rte_spinlock_unlock(&vq->access_lock);
 
-	return n_pkts_put;
+	return n_pkts_cpl;
+}
+
+uint16_t
+rte_vhost_clear_queue_thread_unsafe(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_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;
+	}
+
+	n_pkts_cpl = vhost_poll_enqueue_completed(dev, queue_id, pkts, count);
+
+	return n_pkts_cpl;
 }
 
 static __rte_always_inline uint32_t
-- 
2.29.2