Date:	Wed, 28 Apr 2010 13:57:12 -0700
From:	David L Stevens <dlstevens@...ibm.com>
To:	mst@...hat.com
Cc:	netdev@...r.kernel.org, kvm@...r.kernel.org,
	virtualization@...ts.osdl.org
Subject: [PATCHv7] add mergeable buffers support to vhost_net

This patch adds mergeable receive buffer support to vhost_net.

Signed-off-by: David L Stevens <dlstevens@...ibm.com>

diff -ruNp net-next-v0/drivers/vhost/net.c net-next-v7/drivers/vhost/net.c
--- net-next-v0/drivers/vhost/net.c	2010-04-24 21:36:54.000000000 -0700
+++ net-next-v7/drivers/vhost/net.c	2010-04-28 12:26:18.000000000 -0700
@@ -74,6 +74,23 @@ static int move_iovec_hdr(struct iovec *
 	}
 	return seg;
 }
+/* Copy iovec entries for len bytes from iovec. Return segments used. */
+static int copy_iovec_hdr(const struct iovec *from, struct iovec *to,
+			  size_t len, int iovcount)
+{
+	int seg = 0;
+	size_t size;
+	while (len && seg < iovcount) {
+		size = min(from->iov_len, len);
+		to->iov_base = from->iov_base;
+		to->iov_len = size;
+		len -= size;
+		++from;
+		++to;
+		++seg;
+	}
+	return seg;
+}
 
 /* Caller must have TX VQ lock */
 static void tx_poll_stop(struct vhost_net *net)
@@ -109,7 +126,7 @@ static void handle_tx(struct vhost_net *
 	};
 	size_t len, total_len = 0;
 	int err, wmem;
-	size_t hdr_size;
+	size_t vhost_hlen;
 	struct socket *sock = rcu_dereference(vq->private_data);
 	if (!sock)
 		return;
@@ -128,13 +145,13 @@ static void handle_tx(struct vhost_net *
 
 	if (wmem < sock->sk->sk_sndbuf / 2)
 		tx_poll_stop(net);
-	hdr_size = vq->hdr_size;
+	vhost_hlen = vq->vhost_hlen;
 
 	for (;;) {
-		head = vhost_get_vq_desc(&net->dev, vq, vq->iov,
-					 ARRAY_SIZE(vq->iov),
-					 &out, &in,
-					 NULL, NULL);
+		head = vhost_get_desc(&net->dev, vq, vq->iov,
+				      ARRAY_SIZE(vq->iov),
+				      &out, &in,
+				      NULL, NULL);
 		/* Nothing new?  Wait for eventfd to tell us they refilled. */
 		if (head == vq->num) {
 			wmem = atomic_read(&sock->sk->sk_wmem_alloc);
@@ -155,20 +172,20 @@ static void handle_tx(struct vhost_net *
 			break;
 		}
 		/* Skip header. TODO: support TSO. */
-		s = move_iovec_hdr(vq->iov, vq->hdr, hdr_size, out);
+		s = move_iovec_hdr(vq->iov, vq->hdr, vhost_hlen, out);
 		msg.msg_iovlen = out;
 		len = iov_length(vq->iov, out);
 		/* Sanity check */
 		if (!len) {
 			vq_err(vq, "Unexpected header len for TX: "
 			       "%zd expected %zd\n",
-			       iov_length(vq->hdr, s), hdr_size);
+			       iov_length(vq->hdr, s), vhost_hlen);
 			break;
 		}
 		/* TODO: Check specific error and bomb out unless ENOBUFS? */
 		err = sock->ops->sendmsg(NULL, sock, &msg, len);
 		if (unlikely(err < 0)) {
-			vhost_discard_vq_desc(vq);
+			vhost_discard_desc(vq, 1);
 			tx_poll_start(net, sock);
 			break;
 		}
@@ -187,12 +204,25 @@ static void handle_tx(struct vhost_net *
 	unuse_mm(net->dev.mm);
 }
 
+static int vhost_head_len(struct vhost_virtqueue *vq, struct sock *sk)
+{
+	struct sk_buff *head;
+	int len = 0;
+
+	lock_sock(sk);
+	head = skb_peek(&sk->sk_receive_queue);
+	if (head)
+		len = head->len + vq->sock_hlen;
+	release_sock(sk);
+	return len;
+}
+
 /* Expects to be always run from workqueue - which acts as
  * read-size critical section for our kind of RCU. */
 static void handle_rx(struct vhost_net *net)
 {
 	struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_RX];
-	unsigned head, out, in, log, s;
+	unsigned in, log, s;
 	struct vhost_log *vq_log;
 	struct msghdr msg = {
 		.msg_name = NULL,
@@ -203,14 +233,14 @@ static void handle_rx(struct vhost_net *
 		.msg_flags = MSG_DONTWAIT,
 	};
 
-	struct virtio_net_hdr hdr = {
-		.flags = 0,
-		.gso_type = VIRTIO_NET_HDR_GSO_NONE
+	struct virtio_net_hdr_mrg_rxbuf hdr = {
+		.hdr.flags = 0,
+		.hdr.gso_type = VIRTIO_NET_HDR_GSO_NONE
 	};
 
 	size_t len, total_len = 0;
-	int err;
-	size_t hdr_size;
+	int err, headcount, datalen;
+	size_t vhost_hlen;
 	struct socket *sock = rcu_dereference(vq->private_data);
 	if (!sock || skb_queue_empty(&sock->sk->sk_receive_queue))
 		return;
@@ -218,18 +248,19 @@ static void handle_rx(struct vhost_net *
 	use_mm(net->dev.mm);
 	mutex_lock(&vq->mutex);
 	vhost_disable_notify(vq);
-	hdr_size = vq->hdr_size;
+	vhost_hlen = vq->vhost_hlen;
 
 	vq_log = unlikely(vhost_has_feature(&net->dev, VHOST_F_LOG_ALL)) ?
 		vq->log : NULL;
 
-	for (;;) {
-		head = vhost_get_vq_desc(&net->dev, vq, vq->iov,
-					 ARRAY_SIZE(vq->iov),
-					 &out, &in,
-					 vq_log, &log);
+	while ((datalen = vhost_head_len(vq, sock->sk))) {
+		headcount = vhost_get_desc_n(vq, vq->heads,
+					     datalen + vhost_hlen,
+					     &in, vq_log, &log);
+		if (headcount < 0)
+			break;
 		/* OK, now we need to know about added descriptors. */
-		if (head == vq->num) {
+		if (!headcount) {
 			if (unlikely(vhost_enable_notify(vq))) {
 				/* They have slipped one in as we were
 				 * doing that: check again. */
@@ -241,46 +272,53 @@ static void handle_rx(struct vhost_net *
 			break;
 		}
 		/* We don't need to be notified again. */
-		if (out) {
-			vq_err(vq, "Unexpected descriptor format for RX: "
-			       "out %d, int %d\n",
-			       out, in);
-			break;
-		}
-		/* Skip header. TODO: support TSO/mergeable rx buffers. */
-		s = move_iovec_hdr(vq->iov, vq->hdr, hdr_size, in);
+		if (vhost_hlen)
+			/* Skip header. TODO: support TSO. */
+			s = move_iovec_hdr(vq->iov, vq->hdr, vhost_hlen, in);
+		else
+			s = copy_iovec_hdr(vq->iov, vq->hdr, vq->sock_hlen, in);
 		msg.msg_iovlen = in;
 		len = iov_length(vq->iov, in);
 		/* Sanity check */
 		if (!len) {
 			vq_err(vq, "Unexpected header len for RX: "
 			       "%zd expected %zd\n",
-			       iov_length(vq->hdr, s), hdr_size);
+			       iov_length(vq->hdr, s), vhost_hlen);
 			break;
 		}
 		err = sock->ops->recvmsg(NULL, sock, &msg,
 					 len, MSG_DONTWAIT | MSG_TRUNC);
 		/* TODO: Check specific error and bomb out unless EAGAIN? */
 		if (err < 0) {
-			vhost_discard_vq_desc(vq);
+			vhost_discard_desc(vq, headcount);
 			break;
 		}
-		/* TODO: Should check and handle checksum. */
-		if (err > len) {
-			pr_err("Discarded truncated rx packet: "
-			       " len %d > %zd\n", err, len);
-			vhost_discard_vq_desc(vq);
+		if (err != datalen) {
+			pr_err("Discarded rx packet: "
+			       " len %d, expected %zd\n", err, datalen);
+			vhost_discard_desc(vq, headcount);
 			continue;
 		}
 		len = err;
-		err = memcpy_toiovec(vq->hdr, (unsigned char *)&hdr, hdr_size);
-		if (err) {
-			vq_err(vq, "Unable to write vnet_hdr at addr %p: %d\n",
-			       vq->iov->iov_base, err);
+		if (vhost_hlen &&
+		    memcpy_toiovecend(vq->hdr, (unsigned char *)&hdr, 0,
+				      vhost_hlen)) {
+			vq_err(vq, "Unable to write vnet_hdr at addr %p\n",
+			       vq->iov->iov_base);
 			break;
 		}
-		len += hdr_size;
-		vhost_add_used_and_signal(&net->dev, vq, head, len);
+		/* TODO: Should check and handle checksum. */
+		if (vhost_has_feature(&net->dev, VIRTIO_NET_F_MRG_RXBUF) &&
+		    memcpy_toiovecend(vq->hdr, (unsigned char *)&headcount,
+				      offsetof(typeof(hdr), num_buffers),
+				      sizeof(hdr.num_buffers))) {
+			vq_err(vq, "Failed num_buffers write");
+			vhost_discard_desc(vq, headcount);
+			break;
+		}
+		len += vhost_hlen;
+		vhost_add_used_and_signal_n(&net->dev, vq, vq->heads,
+					    headcount);
 		if (unlikely(vq_log))
 			vhost_log_write(vq, vq_log, log, len);
 		total_len += len;
@@ -561,9 +599,21 @@ done:
 
 static int vhost_net_set_features(struct vhost_net *n, u64 features)
 {
-	size_t hdr_size = features & (1 << VHOST_NET_F_VIRTIO_NET_HDR) ?
-		sizeof(struct virtio_net_hdr) : 0;
+	size_t vhost_hlen, sock_hlen, hdr_len;
 	int i;
+
+	hdr_len = (features & (1 << VIRTIO_NET_F_MRG_RXBUF)) ?
+			sizeof(struct virtio_net_hdr_mrg_rxbuf) :
+			sizeof(struct virtio_net_hdr);
+	if (features & (1 << VHOST_NET_F_VIRTIO_NET_HDR)) {
+		/* vhost provides vnet_hdr */
+		vhost_hlen = hdr_len;
+		sock_hlen = 0;
+	} else {
+		/* socket provides vnet_hdr */
+		vhost_hlen = 0;
+		sock_hlen = hdr_len;
+	}
 	mutex_lock(&n->dev.mutex);
 	if ((features & (1 << VHOST_F_LOG_ALL)) &&
 	    !vhost_log_access_ok(&n->dev)) {
@@ -574,7 +624,8 @@ static int vhost_net_set_features(struct
 	smp_wmb();
 	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
 		mutex_lock(&n->vqs[i].mutex);
-		n->vqs[i].hdr_size = hdr_size;
+		n->vqs[i].vhost_hlen = vhost_hlen;
+		n->vqs[i].sock_hlen = sock_hlen;
 		mutex_unlock(&n->vqs[i].mutex);
 	}
 	vhost_net_flush(n);
diff -ruNp net-next-v0/drivers/vhost/vhost.c net-next-v7/drivers/vhost/vhost.c
--- net-next-v0/drivers/vhost/vhost.c	2010-04-22 11:31:57.000000000 -0700
+++ net-next-v7/drivers/vhost/vhost.c	2010-04-28 11:16:13.000000000 -0700
@@ -114,7 +114,8 @@ static void vhost_vq_reset(struct vhost_
 	vq->used_flags = 0;
 	vq->log_used = false;
 	vq->log_addr = -1ull;
-	vq->hdr_size = 0;
+	vq->vhost_hlen = 0;
+	vq->sock_hlen = 0;
 	vq->private_data = NULL;
 	vq->log_base = NULL;
 	vq->error_ctx = NULL;
@@ -861,6 +862,53 @@ static unsigned get_indirect(struct vhos
 	return 0;
 }
 
+/* This is a multi-buffer version of vhost_get_desc
+ * @vq		- the relevant virtqueue
+ * datalen	- data length we'll be reading
+ * @iovcount	- returned count of io vectors we fill
+ * @log		- vhost log
+ * @log_num	- log offset
+ *	returns number of buffer heads allocated, negative on error
+ */
+int vhost_get_desc_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
+		     int datalen, unsigned *iovcount, struct vhost_log *log,
+		     unsigned int *log_num)
+{
+	unsigned int out, in;
+	int seg = 0;
+	int headcount = 0;
+	int r;
+
+	while (datalen > 0) {
+		if (headcount >= VHOST_NET_MAX_SG) {
+			r = -ENOBUFS;
+			goto err;
+		}
+		heads[headcount].id = vhost_get_desc(vq->dev, vq, vq->iov + seg,
+					      ARRAY_SIZE(vq->iov) - seg, &out,
+					      &in, log, log_num);
+		if (heads[headcount].id == vq->num) {
+			r = 0;
+			goto err;
+		}
+		if (out || in <= 0) {
+			vq_err(vq, "unexpected descriptor format for RX: "
+				"out %d, in %d\n", out, in);
+			r = -EINVAL;
+			goto err;
+		}
+		heads[headcount].len = iov_length(vq->iov + seg, in);
+		datalen -= heads[headcount].len;
+		++headcount;
+		seg += in;
+	}
+	*iovcount = seg;
+	return headcount;
+err:
+	vhost_discard_desc(vq, headcount);
+	return r;
+}
+
 /* This looks in the virtqueue and for the first available buffer, and converts
  * it to an iovec for convenient access.  Since descriptors consist of some
  * number of output then some number of input descriptors, it's actually two
@@ -868,7 +916,7 @@ static unsigned get_indirect(struct vhos
  *
  * This function returns the descriptor number found, or vq->num (which
  * is never a valid descriptor number) if none was found. */
-unsigned vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
+unsigned vhost_get_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
 			   struct iovec iov[], unsigned int iov_size,
 			   unsigned int *out_num, unsigned int *in_num,
 			   struct vhost_log *log, unsigned int *log_num)
@@ -986,9 +1034,9 @@ unsigned vhost_get_vq_desc(struct vhost_
 }
 
 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
-void vhost_discard_vq_desc(struct vhost_virtqueue *vq)
+void vhost_discard_desc(struct vhost_virtqueue *vq, int n)
 {
-	vq->last_avail_idx--;
+	vq->last_avail_idx -= n;
 }
 
 /* After we've used one of their buffers, we tell them about it.  We'll then
@@ -1033,6 +1081,68 @@ int vhost_add_used(struct vhost_virtqueu
 	return 0;
 }
 
+static void vhost_log_used(struct vhost_virtqueue *vq,
+			   struct vring_used_elem __user *used)
+{
+	/* Make sure data is seen before log. */
+	smp_wmb();
+	/* Log used ring entry write. */
+	log_write(vq->log_base,
+		  vq->log_addr +
+		   ((void __user *)used - (void __user *)vq->used),
+		  sizeof *used);
+	/* Log used index update. */
+	log_write(vq->log_base,
+		  vq->log_addr + offsetof(struct vring_used, idx),
+		  sizeof vq->used->idx);
+	if (vq->log_ctx)
+		eventfd_signal(vq->log_ctx, 1);
+}
+
+static int __vhost_add_used_n(struct vhost_virtqueue *vq,
+			    struct vring_used_elem *heads,
+			    unsigned count)
+{
+	struct vring_used_elem __user *used;
+	int start;
+
+	start = vq->last_used_idx % vq->num;
+	used = vq->used->ring + start;
+	if (copy_to_user(used, heads, count * sizeof *used)) {
+		vq_err(vq, "Failed to write used");
+		return -EFAULT;
+	}
+	/* Make sure buffer is written before we update index. */
+	smp_wmb();
+	if (put_user(vq->last_used_idx + count, &vq->used->idx)) {
+		vq_err(vq, "Failed to increment used idx");
+		return -EFAULT;
+	}
+	if (unlikely(vq->log_used))
+		vhost_log_used(vq, used);
+	vq->last_used_idx += count;
+	return 0;
+}
+
+/* After we've used one of their buffers, we tell them about it.  We'll then
+ * want to notify the guest, using eventfd. */
+int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
+		     unsigned count)
+{
+	int start, n, r;
+
+	start = vq->last_used_idx % vq->num;
+	n = vq->num - start;
+	if (n < count) {
+		r = __vhost_add_used_n(vq, heads, n);
+		if (r < 0)
+			return r;
+		heads += n;
+		count -= n;
+	}
+	return __vhost_add_used_n(vq, heads, count);
+}
+
 /* This actually signals the guest, using eventfd. */
 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
 {
@@ -1062,6 +1172,15 @@ void vhost_add_used_and_signal(struct vh
 	vhost_signal(dev, vq);
 }
 
+/* multi-buffer version of vhost_add_used_and_signal */
+void vhost_add_used_and_signal_n(struct vhost_dev *dev,
+				 struct vhost_virtqueue *vq,
+				 struct vring_used_elem *heads, unsigned count)
+{
+	vhost_add_used_n(vq, heads, count);
+	vhost_signal(dev, vq);
+}
+
 /* OK, now we need to know about added descriptors. */
 bool vhost_enable_notify(struct vhost_virtqueue *vq)
 {
@@ -1086,7 +1205,7 @@ bool vhost_enable_notify(struct vhost_vi
 		return false;
 	}
 
-	return avail_idx != vq->last_avail_idx;
+	return avail_idx != vq->avail_idx;
 }
 
 /* We don't need to be notified again. */
diff -ruNp net-next-v0/drivers/vhost/vhost.h net-next-v7/drivers/vhost/vhost.h
--- net-next-v0/drivers/vhost/vhost.h	2010-04-24 21:37:41.000000000 -0700
+++ net-next-v7/drivers/vhost/vhost.h	2010-04-26 10:35:25.000000000 -0700
@@ -84,7 +84,9 @@ struct vhost_virtqueue {
 	struct iovec indirect[VHOST_NET_MAX_SG];
 	struct iovec iov[VHOST_NET_MAX_SG];
 	struct iovec hdr[VHOST_NET_MAX_SG];
-	size_t hdr_size;
+	size_t vhost_hlen;
+	size_t sock_hlen;
+	struct vring_used_elem heads[VHOST_NET_MAX_SG];
 	/* We use a kind of RCU to access private pointer.
 	 * All readers access it from workqueue, which makes it possible to
 	 * flush the workqueue instead of synchronize_rcu. Therefore readers do
@@ -120,16 +122,23 @@ long vhost_dev_ioctl(struct vhost_dev *,
 int vhost_vq_access_ok(struct vhost_virtqueue *vq);
 int vhost_log_access_ok(struct vhost_dev *);
 
-unsigned vhost_get_vq_desc(struct vhost_dev *, struct vhost_virtqueue *,
+int vhost_get_desc_n(struct vhost_virtqueue *, struct vring_used_elem *heads,
+		     int datalen, unsigned int *iovcount, struct vhost_log *log,
+		     unsigned int *log_num);
+unsigned vhost_get_desc(struct vhost_dev *, struct vhost_virtqueue *,
 			   struct iovec iov[], unsigned int iov_count,
 			   unsigned int *out_num, unsigned int *in_num,
 			   struct vhost_log *log, unsigned int *log_num);
-void vhost_discard_vq_desc(struct vhost_virtqueue *);
+void vhost_discard_desc(struct vhost_virtqueue *, int);
 
 int vhost_add_used(struct vhost_virtqueue *, unsigned int head, int len);
-void vhost_signal(struct vhost_dev *, struct vhost_virtqueue *);
+int vhost_add_used_n(struct vhost_virtqueue *, struct vring_used_elem *heads,
+		     unsigned count);
 void vhost_add_used_and_signal(struct vhost_dev *, struct vhost_virtqueue *,
-			       unsigned int head, int len);
+			       unsigned int id, int len);
+void vhost_add_used_and_signal_n(struct vhost_dev *, struct vhost_virtqueue *,
+			       struct vring_used_elem *heads, unsigned count);
+void vhost_signal(struct vhost_dev *, struct vhost_virtqueue *);
 void vhost_disable_notify(struct vhost_virtqueue *);
 bool vhost_enable_notify(struct vhost_virtqueue *);
 
@@ -149,7 +158,8 @@ enum {
 	VHOST_FEATURES = (1 << VIRTIO_F_NOTIFY_ON_EMPTY) |
 			 (1 << VIRTIO_RING_F_INDIRECT_DESC) |
 			 (1 << VHOST_F_LOG_ALL) |
-			 (1 << VHOST_NET_F_VIRTIO_NET_HDR),
+			 (1 << VHOST_NET_F_VIRTIO_NET_HDR) |
+			 (1 << VIRTIO_NET_F_MRG_RXBUF),
 };
 
 static inline int vhost_has_feature(struct vhost_dev *dev, int bit)


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