[dpdk-dev] [PATCH 1/2] 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. And enable it in
vhost example.

Signed-off-by: Cheng Jiang <cheng1.jiang@intel.com>
---
 examples/vhost/main.c       | 48 +++++++++++++++++++-
 examples/vhost/main.h       |  1 +
 lib/vhost/rte_vhost_async.h | 22 +++++++++
 lib/vhost/version.map       |  3 ++
 lib/vhost/virtio_net.c      | 90 +++++++++++++++++++++++++++----------
 5 files changed, 139 insertions(+), 25 deletions(-)

diff --git a/examples/vhost/main.c b/examples/vhost/main.c
index d2179eadb9..70bb67c7f8 100644
--- a/examples/vhost/main.c
+++ b/examples/vhost/main.c
@@ -851,8 +851,11 @@ complete_async_pkts(struct vhost_dev *vdev)
 
 	complete_count = rte_vhost_poll_enqueue_completed(vdev->vid,
 					VIRTIO_RXQ, p_cpl, MAX_PKT_BURST);
-	if (complete_count)
+	if (complete_count) {
 		free_pkts(p_cpl, complete_count);
+		__atomic_sub_fetch(&vdev->pkts_inflight, complete_count, __ATOMIC_SEQ_CST);
+	}
+
 }
 
 static __rte_always_inline void
@@ -895,6 +898,7 @@ drain_vhost(struct vhost_dev *vdev)
 		complete_async_pkts(vdev);
 		ret = rte_vhost_submit_enqueue_burst(vdev->vid, VIRTIO_RXQ,
 					m, nr_xmit, m_cpu_cpl, &cpu_cpl_nr);
+		__atomic_add_fetch(&vdev->pkts_inflight, ret - cpu_cpl_nr, __ATOMIC_SEQ_CST);
 
 		if (cpu_cpl_nr)
 			free_pkts(m_cpu_cpl, cpu_cpl_nr);
@@ -1226,6 +1230,9 @@ drain_eth_rx(struct vhost_dev *vdev)
 		enqueue_count = rte_vhost_submit_enqueue_burst(vdev->vid,
 					VIRTIO_RXQ, pkts, rx_count,
 					m_cpu_cpl, &cpu_cpl_nr);
+		__atomic_add_fetch(&vdev->pkts_inflight, enqueue_count - cpu_cpl_nr,
+					__ATOMIC_SEQ_CST);
+
 		if (cpu_cpl_nr)
 			free_pkts(m_cpu_cpl, cpu_cpl_nr);
 
@@ -1397,8 +1404,15 @@ destroy_device(int vid)
 		"(%d) device has been removed from data core\n",
 		vdev->vid);
 
-	if (async_vhost_driver)
+	if (async_vhost_driver) {
+		uint16_t n_pkt = 0;
+		struct rte_mbuf *m_cpl[vdev->pkts_inflight];
+		n_pkt = rte_vhost_drain_queue_thread_unsafe(vid, VIRTIO_RXQ, m_cpl,
+							vdev->pkts_inflight);
+
+		free_pkts(m_cpl, n_pkt);
 		rte_vhost_async_channel_unregister(vid, VIRTIO_RXQ);
+	}
 
 	rte_free(vdev);
 }
@@ -1487,6 +1501,35 @@ new_device(int vid)
 	return 0;
 }
 
+static int
+vring_state_changed(int vid, uint16_t queue_id, int enable)
+{
+	struct vhost_dev *vdev = NULL;
+
+	TAILQ_FOREACH(vdev, &vhost_dev_list, global_vdev_entry) {
+		if (vdev->vid == vid)
+			break;
+	}
+	if (!vdev)
+		return -1;
+
+	if (queue_id != VIRTIO_RXQ)
+		return 0;
+
+	if (async_vhost_driver) {
+		if (!enable) {
+			uint16_t n_pkt;
+			struct rte_mbuf *m_cpl[vdev->pkts_inflight];
+
+			n_pkt = rte_vhost_drain_queue_thread_unsafe(vid, queue_id,
+							m_cpl, vdev->pkts_inflight);
+			free_pkts(m_cpl, n_pkt);
+		}
+	}
+
+	return 0;
+}
+
 /*
  * These callback allow devices to be added to the data core when configuration
  * has been fully complete.
@@ -1495,6 +1538,7 @@ static const struct vhost_device_ops virtio_net_device_ops =
 {
 	.new_device =  new_device,
 	.destroy_device = destroy_device,
+	.vring_state_changed = vring_state_changed,
 };
 
 /*
diff --git a/examples/vhost/main.h b/examples/vhost/main.h
index 0ccdce4b4a..e7b1ac60a6 100644
--- a/examples/vhost/main.h
+++ b/examples/vhost/main.h
@@ -51,6 +51,7 @@ struct vhost_dev {
 	uint64_t features;
 	size_t hdr_len;
 	uint16_t nr_vrings;
+	uint16_t pkts_inflight;
 	struct rte_vhost_memory *mem;
 	struct device_statistics stats;
 	TAILQ_ENTRY(vhost_dev) global_vdev_entry;
diff --git a/lib/vhost/rte_vhost_async.h b/lib/vhost/rte_vhost_async.h
index 6faa31f5ad..041f40cf04 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 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
+ * @return
+ *  num of packets returned
+ */
+__rte_experimental
+uint16_t rte_vhost_drain_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..f480f188af 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_drain_queue_thread_unsafe;
 };
diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
index 8da8a86a10..793510974a 100644
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -2082,36 +2082,18 @@ 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;
 	struct async_inflight_info *pkts_info;
 	uint16_t from, i;
 
-	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;
@@ -2119,14 +2101,14 @@ 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_pkts_cpl = vq->async_ops.check_completed_copies(vid,
+		n_pkts_cpl = vq->async_ops.check_completed_copies(dev->vid,
 			queue_id, 0, count - vq->async_last_pkts_n);
 	n_pkts_cpl += vq->async_last_pkts_n;
 
 	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)) {
@@ -2165,12 +2147,74 @@ 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_drain_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 = count;
+
+	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 (count)
+		count -= vhost_poll_enqueue_completed(dev, queue_id, pkts, count);
+
+	return n_pkts;
+}
+
 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