[RFC v1 3/6] vhost/vsock: add support for vhost dgram.

[Jiang Wang <jiang.wang@bytedance.com>]

This patch supports dgram on vhost side, including
tx and rx. The vhost send packets asynchronously.

Signed-off-by: Jiang Wang <jiang.wang@bytedance.com>
---
 drivers/vhost/vsock.c | 199 +++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 173 insertions(+), 26 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 81d064601093..d366463be6d4 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -28,7 +28,10 @@
  * small pkts.
  */
 #define VHOST_VSOCK_PKT_WEIGHT 256
+#define VHOST_VSOCK_DGRM_MAX_PENDING_PKT 128
 
+/* Max wait time in busy poll in microseconds */
+#define VHOST_VSOCK_BUSY_POLL_TIMEOUT 20
 enum {
 	VHOST_VSOCK_FEATURES = VHOST_FEATURES |
 			       (1ULL << VIRTIO_F_ACCESS_PLATFORM) |
@@ -45,7 +48,7 @@ static DEFINE_READ_MOSTLY_HASHTABLE(vhost_vsock_hash, 8);
 
 struct vhost_vsock {
 	struct vhost_dev dev;
-	struct vhost_virtqueue vqs[2];
+	struct vhost_virtqueue vqs[4];
 
 	/* Link to global vhost_vsock_hash, writes use vhost_vsock_mutex */
 	struct hlist_node hash;
@@ -54,6 +57,11 @@ struct vhost_vsock {
 	spinlock_t send_pkt_list_lock;
 	struct list_head send_pkt_list;	/* host->guest pending packets */
 
+	spinlock_t dgram_send_pkt_list_lock;
+	struct list_head dgram_send_pkt_list;	/* host->guest pending packets */
+	struct vhost_work dgram_send_pkt_work;
+	int  dgram_used; /*pending packets to be send */
+
 	atomic_t queued_replies;
 
 	u32 guest_cid;
@@ -90,10 +98,22 @@ static void
 vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 			    struct vhost_virtqueue *vq)
 {
-	struct vhost_virtqueue *tx_vq = &vsock->vqs[VSOCK_VQ_TX];
+	struct vhost_virtqueue *tx_vq;
 	int pkts = 0, total_len = 0;
 	bool added = false;
 	bool restart_tx = false;
+	spinlock_t *lock;
+	struct list_head *send_pkt_list;
+
+	if (vq == &vsock->vqs[VSOCK_VQ_RX]) {
+		tx_vq = &vsock->vqs[VSOCK_VQ_TX];
+		lock = &vsock->send_pkt_list_lock;
+		send_pkt_list = &vsock->send_pkt_list;
+	} else {
+		tx_vq = &vsock->vqs[VSOCK_VQ_DGRAM_TX];
+		lock = &vsock->dgram_send_pkt_list_lock;
+		send_pkt_list = &vsock->dgram_send_pkt_list;
+	}
 
 	mutex_lock(&vq->mutex);
 
@@ -113,36 +133,48 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 		size_t nbytes;
 		size_t iov_len, payload_len;
 		int head;
+		bool is_dgram = false;
 
-		spin_lock_bh(&vsock->send_pkt_list_lock);
-		if (list_empty(&vsock->send_pkt_list)) {
-			spin_unlock_bh(&vsock->send_pkt_list_lock);
+		spin_lock_bh(lock);
+		if (list_empty(send_pkt_list)) {
+			spin_unlock_bh(lock);
 			vhost_enable_notify(&vsock->dev, vq);
 			break;
 		}
 
-		pkt = list_first_entry(&vsock->send_pkt_list,
+		pkt = list_first_entry(send_pkt_list,
 				       struct virtio_vsock_pkt, list);
 		list_del_init(&pkt->list);
-		spin_unlock_bh(&vsock->send_pkt_list_lock);
+		spin_unlock_bh(lock);
+
+		if (pkt->hdr.type == VIRTIO_VSOCK_TYPE_DGRAM)
+			is_dgram = true;
 
 		head = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
 					 &out, &in, NULL, NULL);
 		if (head < 0) {
-			spin_lock_bh(&vsock->send_pkt_list_lock);
-			list_add(&pkt->list, &vsock->send_pkt_list);
-			spin_unlock_bh(&vsock->send_pkt_list_lock);
+			spin_lock_bh(lock);
+			list_add(&pkt->list, send_pkt_list);
+			spin_unlock_bh(lock);
 			break;
 		}
 
 		if (head == vq->num) {
-			spin_lock_bh(&vsock->send_pkt_list_lock);
-			list_add(&pkt->list, &vsock->send_pkt_list);
-			spin_unlock_bh(&vsock->send_pkt_list_lock);
+			if (is_dgram) {
+				virtio_transport_free_pkt(pkt);
+				vq_err(vq, "Dgram virtqueue is full!");
+				spin_lock_bh(lock);
+				vsock->dgram_used--;
+				spin_unlock_bh(lock);
+				break;
+			}
+			spin_lock_bh(lock);
+			list_add(&pkt->list, send_pkt_list);
+			spin_unlock_bh(lock);
 
 			/* We cannot finish yet if more buffers snuck in while
-			 * re-enabling notify.
-			 */
+			* re-enabling notify.
+			*/
 			if (unlikely(vhost_enable_notify(&vsock->dev, vq))) {
 				vhost_disable_notify(&vsock->dev, vq);
 				continue;
@@ -153,6 +185,12 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 		if (out) {
 			virtio_transport_free_pkt(pkt);
 			vq_err(vq, "Expected 0 output buffers, got %u\n", out);
+			if (is_dgram) {
+				spin_lock_bh(lock);
+				vsock->dgram_used--;
+				spin_unlock_bh(lock);
+			}
+
 			break;
 		}
 
@@ -160,6 +198,18 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 		if (iov_len < sizeof(pkt->hdr)) {
 			virtio_transport_free_pkt(pkt);
 			vq_err(vq, "Buffer len [%zu] too small\n", iov_len);
+			if (is_dgram) {
+				spin_lock_bh(lock);
+				vsock->dgram_used--;
+				spin_unlock_bh(lock);
+			}
+			break;
+		}
+
+		if (iov_len < pkt->len - pkt->off &&
+			vq == &vsock->vqs[VSOCK_VQ_DGRAM_RX]) {
+			virtio_transport_free_pkt(pkt);
+			vq_err(vq, "Buffer len [%zu] too small for dgram\n", iov_len);
 			break;
 		}
 
@@ -179,6 +229,11 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 		if (nbytes != sizeof(pkt->hdr)) {
 			virtio_transport_free_pkt(pkt);
 			vq_err(vq, "Faulted on copying pkt hdr\n");
+			if (is_dgram) {
+				spin_lock_bh(lock);
+				vsock->dgram_used--;
+				spin_unlock_bh(lock);
+			}
 			break;
 		}
 
@@ -204,16 +259,17 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 		/* If we didn't send all the payload we can requeue the packet
 		 * to send it with the next available buffer.
 		 */
-		if (pkt->off < pkt->len) {
+		if ((pkt->off < pkt->len)
+			&& (vq == &vsock->vqs[VSOCK_VQ_RX])) {
 			/* We are queueing the same virtio_vsock_pkt to handle
 			 * the remaining bytes, and we want to deliver it
 			 * to monitoring devices in the next iteration.
 			 */
 			pkt->tap_delivered = false;
 
-			spin_lock_bh(&vsock->send_pkt_list_lock);
-			list_add(&pkt->list, &vsock->send_pkt_list);
-			spin_unlock_bh(&vsock->send_pkt_list_lock);
+			spin_lock_bh(lock);
+			list_add(&pkt->list, send_pkt_list);
+			spin_unlock_bh(lock);
 		} else {
 			if (pkt->reply) {
 				int val;
@@ -228,6 +284,11 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 			}
 
 			virtio_transport_free_pkt(pkt);
+			if (is_dgram) {
+				spin_lock_bh(lock);
+				vsock->dgram_used--;
+				spin_unlock_bh(lock);
+			}
 		}
 	} while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));
 	if (added)
@@ -251,11 +312,25 @@ static void vhost_transport_send_pkt_work(struct vhost_work *work)
 	vhost_transport_do_send_pkt(vsock, vq);
 }
 
+static void vhost_transport_dgram_send_pkt_work(struct vhost_work *work)
+{
+	struct vhost_virtqueue *vq;
+	struct vhost_vsock *vsock;
+
+	vsock = container_of(work, struct vhost_vsock, dgram_send_pkt_work);
+	vq = &vsock->vqs[VSOCK_VQ_DGRAM_RX];
+
+	vhost_transport_do_send_pkt(vsock, vq);
+}
+
 static int
 vhost_transport_send_pkt(struct virtio_vsock_pkt *pkt)
 {
 	struct vhost_vsock *vsock;
 	int len = pkt->len;
+	spinlock_t *lock;
+	struct list_head *send_pkt_list;
+	struct vhost_work *work;
 
 	rcu_read_lock();
 
@@ -267,14 +342,38 @@ vhost_transport_send_pkt(struct virtio_vsock_pkt *pkt)
 		return -ENODEV;
 	}
 
+	if (pkt->hdr.type == VIRTIO_VSOCK_TYPE_STREAM) {
+		lock = &vsock->send_pkt_list_lock;
+		send_pkt_list = &vsock->send_pkt_list;
+		work = &vsock->send_pkt_work;
+	} else if (pkt->hdr.type == VIRTIO_VSOCK_TYPE_DGRAM) {
+		lock = &vsock->dgram_send_pkt_list_lock;
+		send_pkt_list = &vsock->dgram_send_pkt_list;
+		work = &vsock->dgram_send_pkt_work;
+	} else {
+		rcu_read_unlock();
+		virtio_transport_free_pkt(pkt);
+		return -EINVAL;
+	}
+
+
 	if (pkt->reply)
 		atomic_inc(&vsock->queued_replies);
 
-	spin_lock_bh(&vsock->send_pkt_list_lock);
-	list_add_tail(&pkt->list, &vsock->send_pkt_list);
-	spin_unlock_bh(&vsock->send_pkt_list_lock);
+	spin_lock_bh(lock);
+	if (pkt->hdr.type == VIRTIO_VSOCK_TYPE_DGRAM) {
+		if (vsock->dgram_used  == VHOST_VSOCK_DGRM_MAX_PENDING_PKT)
+			len = -ENOMEM;
+		else {
+			vsock->dgram_used++;
+			list_add_tail(&pkt->list, send_pkt_list);
+		}
+	} else
+		list_add_tail(&pkt->list, send_pkt_list);
 
-	vhost_work_queue(&vsock->dev, &vsock->send_pkt_work);
+	spin_unlock_bh(lock);
+
+	vhost_work_queue(&vsock->dev, work);
 
 	rcu_read_unlock();
 	return len;
@@ -355,7 +454,8 @@ vhost_vsock_alloc_pkt(struct vhost_virtqueue *vq,
 		return NULL;
 	}
 
-	if (le16_to_cpu(pkt->hdr.type) == VIRTIO_VSOCK_TYPE_STREAM)
+	if (le16_to_cpu(pkt->hdr.type) == VIRTIO_VSOCK_TYPE_STREAM
+		|| le16_to_cpu(pkt->hdr.type) == VIRTIO_VSOCK_TYPE_DGRAM)
 		pkt->len = le32_to_cpu(pkt->hdr.len);
 
 	/* No payload */
@@ -442,6 +542,18 @@ static struct virtio_transport vhost_transport = {
 	.send_pkt = vhost_transport_send_pkt,
 };
 
+static inline unsigned long busy_clock(void)
+{
+	return local_clock() >> 10;
+}
+
+static bool vhost_can_busy_poll(unsigned long endtime)
+{
+	return likely(!need_resched() && !time_after(busy_clock(), endtime) &&
+		      !signal_pending(current));
+}
+
+
 static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
 {
 	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
@@ -452,6 +564,8 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
 	int head, pkts = 0, total_len = 0;
 	unsigned int out, in;
 	bool added = false;
+	unsigned long busyloop_timeout = VHOST_VSOCK_BUSY_POLL_TIMEOUT;
+	unsigned long endtime;
 
 	mutex_lock(&vq->mutex);
 
@@ -461,11 +575,14 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
 	if (!vq_meta_prefetch(vq))
 		goto out;
 
+	endtime = busy_clock() + busyloop_timeout;
 	vhost_disable_notify(&vsock->dev, vq);
+	preempt_disable();
 	do {
 		u32 len;
 
-		if (!vhost_vsock_more_replies(vsock)) {
+		if (vq == &vsock->vqs[VSOCK_VQ_TX]
+			&& !vhost_vsock_more_replies(vsock)) {
 			/* Stop tx until the device processes already
 			 * pending replies.  Leave tx virtqueue
 			 * callbacks disabled.
@@ -479,6 +596,11 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
 			break;
 
 		if (head == vq->num) {
+			if (vhost_can_busy_poll(endtime)) {
+				cpu_relax();
+				continue;
+			}
+
 			if (unlikely(vhost_enable_notify(&vsock->dev, vq))) {
 				vhost_disable_notify(&vsock->dev, vq);
 				continue;
@@ -510,6 +632,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
 		total_len += len;
 		added = true;
 	} while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));
+	preempt_enable();
 
 no_more_replies:
 	if (added)
@@ -565,6 +688,7 @@ static int vhost_vsock_start(struct vhost_vsock *vsock)
 	 * let's kick the send worker to send them.
 	 */
 	vhost_work_queue(&vsock->dev, &vsock->send_pkt_work);
+	vhost_work_queue(&vsock->dev, &vsock->dgram_send_pkt_work);
 
 	mutex_unlock(&vsock->dev.mutex);
 	return 0;
@@ -639,8 +763,14 @@ static int vhost_vsock_dev_open(struct inode *inode, struct file *file)
 
 	vqs[VSOCK_VQ_TX] = &vsock->vqs[VSOCK_VQ_TX];
 	vqs[VSOCK_VQ_RX] = &vsock->vqs[VSOCK_VQ_RX];
+	vqs[VSOCK_VQ_DGRAM_TX] = &vsock->vqs[VSOCK_VQ_DGRAM_TX];
+	vqs[VSOCK_VQ_DGRAM_RX] = &vsock->vqs[VSOCK_VQ_DGRAM_RX];
 	vsock->vqs[VSOCK_VQ_TX].handle_kick = vhost_vsock_handle_tx_kick;
 	vsock->vqs[VSOCK_VQ_RX].handle_kick = vhost_vsock_handle_rx_kick;
+	vsock->vqs[VSOCK_VQ_DGRAM_TX].handle_kick =
+						vhost_vsock_handle_tx_kick;
+	vsock->vqs[VSOCK_VQ_DGRAM_RX].handle_kick =
+						vhost_vsock_handle_rx_kick;
 
 	vhost_dev_init(&vsock->dev, vqs, ARRAY_SIZE(vsock->vqs),
 		       UIO_MAXIOV, VHOST_VSOCK_PKT_WEIGHT,
@@ -650,6 +780,11 @@ static int vhost_vsock_dev_open(struct inode *inode, struct file *file)
 	spin_lock_init(&vsock->send_pkt_list_lock);
 	INIT_LIST_HEAD(&vsock->send_pkt_list);
 	vhost_work_init(&vsock->send_pkt_work, vhost_transport_send_pkt_work);
+	spin_lock_init(&vsock->dgram_send_pkt_list_lock);
+	INIT_LIST_HEAD(&vsock->dgram_send_pkt_list);
+	vhost_work_init(&vsock->dgram_send_pkt_work,
+			vhost_transport_dgram_send_pkt_work);
+
 	return 0;
 
 out:
@@ -665,6 +800,7 @@ static void vhost_vsock_flush(struct vhost_vsock *vsock)
 		if (vsock->vqs[i].handle_kick)
 			vhost_poll_flush(&vsock->vqs[i].poll);
 	vhost_work_flush(&vsock->dev, &vsock->send_pkt_work);
+	vhost_work_flush(&vsock->dev, &vsock->dgram_send_pkt_work);
 }
 
 static void vhost_vsock_reset_orphans(struct sock *sk)
@@ -724,6 +860,17 @@ static int vhost_vsock_dev_release(struct inode *inode, struct file *file)
 	}
 	spin_unlock_bh(&vsock->send_pkt_list_lock);
 
+	spin_lock_bh(&vsock->dgram_send_pkt_list_lock);
+	while (!list_empty(&vsock->dgram_send_pkt_list)) {
+		struct virtio_vsock_pkt *pkt;
+
+		pkt = list_first_entry(&vsock->dgram_send_pkt_list,
+				struct virtio_vsock_pkt, list);
+		list_del_init(&pkt->list);
+		virtio_transport_free_pkt(pkt);
+	}
+	spin_unlock_bh(&vsock->dgram_send_pkt_list_lock);
+
 	vhost_dev_cleanup(&vsock->dev);
 	kfree(vsock->dev.vqs);
 	vhost_vsock_free(vsock);
@@ -906,7 +1053,7 @@ static int __init vhost_vsock_init(void)
 	int ret;
 
 	ret = vsock_core_register(&vhost_transport.transport,
-				  VSOCK_TRANSPORT_F_H2G);
+				  VSOCK_TRANSPORT_F_H2G | VSOCK_TRANSPORT_F_DGRAM);
 	if (ret < 0)
 		return ret;
 	return misc_register(&vhost_vsock_misc);
-- 
2.11.0