4 files changed, 398 insertions, 80 deletions

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 020cf17ab7e4..816725af281f 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -89,6 +89,7 @@
 #include <linux/types.h>
 #include <linux/bitops.h>
 #include <linux/cred.h>
+#include <linux/errqueue.h>
 #include <linux/init.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
@@ -110,6 +111,7 @@
 #include <linux/workqueue.h>
 #include <net/sock.h>
 #include <net/af_vsock.h>
+#include <uapi/linux/vm_sockets.h>
 
 static int __vsock_bind(struct sock *sk, struct sockaddr_vm *addr);
 static void vsock_sk_destruct(struct sock *sk);
@@ -1030,7 +1032,7 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock,
 	poll_wait(file, sk_sleep(sk), wait);
 	mask = 0;
 
-	if (sk->sk_err)
+	if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue))
 		/* Signify that there has been an error on this socket. */
 		mask |= EPOLLERR;
 
@@ -1404,6 +1406,17 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr,
 			goto out;
 		}
 
+		if (vsock_msgzerocopy_allow(transport)) {
+			set_bit(SOCK_SUPPORT_ZC, &sk->sk_socket->flags);
+		} else if (sock_flag(sk, SOCK_ZEROCOPY)) {
+			/* If this option was set before 'connect()',
+			 * when transport was unknown, check that this
+			 * feature is supported here.
+			 */
+			err = -EOPNOTSUPP;
+			goto out;
+		}
+
 		err = vsock_auto_bind(vsk);
 		if (err)
 			goto out;
@@ -1558,6 +1571,9 @@ static int vsock_accept(struct socket *sock, struct socket *newsock, int flags,
 		} else {
 			newsock->state = SS_CONNECTED;
 			sock_graft(connected, newsock);
+			if (vsock_msgzerocopy_allow(vconnected->transport))
+				set_bit(SOCK_SUPPORT_ZC,
+					&connected->sk_socket->flags);
 		}
 
 		release_sock(connected);
@@ -1635,7 +1651,7 @@ static int vsock_connectible_setsockopt(struct socket *sock,
 	const struct vsock_transport *transport;
 	u64 val;
 
-	if (level != AF_VSOCK)
+	if (level != AF_VSOCK && level != SOL_SOCKET)
 		return -ENOPROTOOPT;
 
 #define COPY_IN(_v)                                       \
@@ -1658,6 +1674,33 @@ static int vsock_connectible_setsockopt(struct socket *sock,
 
 	transport = vsk->transport;
 
+	if (level == SOL_SOCKET) {
+		int zerocopy;
+
+		if (optname != SO_ZEROCOPY) {
+			release_sock(sk);
+			return sock_setsockopt(sock, level, optname, optval, optlen);
+		}
+
+		/* Use 'int' type here, because variable to
+		 * set this option usually has this type.
+		 */
+		COPY_IN(zerocopy);
+
+		if (zerocopy < 0 || zerocopy > 1) {
+			err = -EINVAL;
+			goto exit;
+		}
+
+		if (transport && !vsock_msgzerocopy_allow(transport)) {
+			err = -EOPNOTSUPP;
+			goto exit;
+		}
+
+		sock_valbool_flag(sk, SOCK_ZEROCOPY, zerocopy);
+		goto exit;
+	}
+
 	switch (optname) {
 	case SO_VM_SOCKETS_BUFFER_SIZE:
 		COPY_IN(val);
@@ -1822,6 +1865,12 @@ static int vsock_connectible_sendmsg(struct socket *sock, struct msghdr *msg,
 		goto out;
 	}
 
+	if (msg->msg_flags & MSG_ZEROCOPY &&
+	    !vsock_msgzerocopy_allow(transport)) {
+		err = -EOPNOTSUPP;
+		goto out;
+	}
+
 	/* Wait for room in the produce queue to enqueue our user's data. */
 	timeout = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
 
@@ -1921,6 +1970,9 @@ out_err:
 			err = total_written;
 	}
 out:
+	if (sk->sk_type == SOCK_STREAM)
+		err = sk_stream_error(sk, msg->msg_flags, err);
+
 	release_sock(sk);
 	return err;
 }
@@ -2134,6 +2186,10 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 	int err;
 
 	sk = sock->sk;
+
+	if (unlikely(flags & MSG_ERRQUEUE))
+		return sock_recv_errqueue(sk, msg, len, SOL_VSOCK, VSOCK_RECVERR);
+
 	vsk = vsock_sk(sk);
 	err = 0;
 
@@ -2301,6 +2357,12 @@ static int vsock_create(struct net *net, struct socket *sock,
 		}
 	}
 
+	/* SOCK_DGRAM doesn't have 'setsockopt' callback set in its
+	 * proto_ops, so there is no handler for custom logic.
+	 */
+	if (sock_type_connectible(sock->type))
+		set_bit(SOCK_CUSTOM_SOCKOPT, &sk->sk_socket->flags);
+
 	vsock_insert_unbound(vsk);
 
 	return 0;
diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index b80bf681327b..af5bab1acee1 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -63,6 +63,17 @@ struct virtio_vsock {
 
 	u32 guest_cid;
 	bool seqpacket_allow;
+
+	/* These fields are used only in tx path in function
+	 * 'virtio_transport_send_pkt_work()', so to save
+	 * stack space in it, place both of them here. Each
+	 * pointer from 'out_sgs' points to the corresponding
+	 * element in 'out_bufs' - this is initialized in
+	 * 'virtio_vsock_probe()'. Both fields are protected
+	 * by 'tx_lock'. +1 is needed for packet header.
+	 */
+	struct scatterlist *out_sgs[MAX_SKB_FRAGS + 1];
+	struct scatterlist out_bufs[MAX_SKB_FRAGS + 1];
 };
 
 static u32 virtio_transport_get_local_cid(void)
@@ -100,8 +111,8 @@ virtio_transport_send_pkt_work(struct work_struct *work)
 	vq = vsock->vqs[VSOCK_VQ_TX];
 
 	for (;;) {
-		struct scatterlist hdr, buf, *sgs[2];
 		int ret, in_sg = 0, out_sg = 0;
+		struct scatterlist **sgs;
 		struct sk_buff *skb;
 		bool reply;
 
@@ -111,12 +122,43 @@ virtio_transport_send_pkt_work(struct work_struct *work)
 
 		virtio_transport_deliver_tap_pkt(skb);
 		reply = virtio_vsock_skb_reply(skb);
-
-		sg_init_one(&hdr, virtio_vsock_hdr(skb), sizeof(*virtio_vsock_hdr(skb)));
-		sgs[out_sg++] = &hdr;
-		if (skb->len > 0) {
-			sg_init_one(&buf, skb->data, skb->len);
-			sgs[out_sg++] = &buf;
+		sgs = vsock->out_sgs;
+		sg_init_one(sgs[out_sg], virtio_vsock_hdr(skb),
+			    sizeof(*virtio_vsock_hdr(skb)));
+		out_sg++;
+
+		if (!skb_is_nonlinear(skb)) {
+			if (skb->len > 0) {
+				sg_init_one(sgs[out_sg], skb->data, skb->len);
+				out_sg++;
+			}
+		} else {
+			struct skb_shared_info *si;
+			int i;
+
+			/* If skb is nonlinear, then its buffer must contain
+			 * only header and nothing more. Data is stored in
+			 * the fragged part.
+			 */
+			WARN_ON_ONCE(skb_headroom(skb) != sizeof(*virtio_vsock_hdr(skb)));
+
+			si = skb_shinfo(skb);
+
+			for (i = 0; i < si->nr_frags; i++) {
+				skb_frag_t *skb_frag = &si->frags[i];
+				void *va;
+
+				/* We will use 'page_to_virt()' for the userspace page
+				 * here, because virtio or dma-mapping layers will call
+				 * 'virt_to_phys()' later to fill the buffer descriptor.
+				 * We don't touch memory at "virtual" address of this page.
+				 */
+				va = page_to_virt(skb_frag->bv_page);
+				sg_init_one(sgs[out_sg],
+					    va + skb_frag->bv_offset,
+					    skb_frag->bv_len);
+				out_sg++;
+			}
 		}
 
 		ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, GFP_KERNEL);
@@ -413,6 +455,42 @@ static void virtio_vsock_rx_done(struct virtqueue *vq)
 	queue_work(virtio_vsock_workqueue, &vsock->rx_work);
 }
 
+static bool virtio_transport_can_msgzerocopy(int bufs_num)
+{
+	struct virtio_vsock *vsock;
+	bool res = false;
+
+	rcu_read_lock();
+
+	vsock = rcu_dereference(the_virtio_vsock);
+	if (vsock) {
+		struct virtqueue *vq = vsock->vqs[VSOCK_VQ_TX];
+
+		/* Check that tx queue is large enough to keep whole
+		 * data to send. This is needed, because when there is
+		 * not enough free space in the queue, current skb to
+		 * send will be reinserted to the head of tx list of
+		 * the socket to retry transmission later, so if skb
+		 * is bigger than whole queue, it will be reinserted
+		 * again and again, thus blocking other skbs to be sent.
+		 * Each page of the user provided buffer will be added
+		 * as a single buffer to the tx virtqueue, so compare
+		 * number of pages against maximum capacity of the queue.
+		 */
+		if (bufs_num <= vq->num_max)
+			res = true;
+	}
+
+	rcu_read_unlock();
+
+	return res;
+}
+
+static bool virtio_transport_msgzerocopy_allow(void)
+{
+	return true;
+}
+
 static bool virtio_transport_seqpacket_allow(u32 remote_cid);
 
 static struct virtio_transport virtio_transport = {
@@ -446,6 +524,8 @@ static struct virtio_transport virtio_transport = {
 		.seqpacket_allow          = virtio_transport_seqpacket_allow,
 		.seqpacket_has_data       = virtio_transport_seqpacket_has_data,
 
+		.msgzerocopy_allow        = virtio_transport_msgzerocopy_allow,
+
 		.notify_poll_in           = virtio_transport_notify_poll_in,
 		.notify_poll_out          = virtio_transport_notify_poll_out,
 		.notify_recv_init         = virtio_transport_notify_recv_init,
@@ -462,6 +542,7 @@ static struct virtio_transport virtio_transport = {
 	},
 
 	.send_pkt = virtio_transport_send_pkt,
+	.can_msgzerocopy = virtio_transport_can_msgzerocopy,
 };
 
 static bool virtio_transport_seqpacket_allow(u32 remote_cid)
@@ -635,6 +716,7 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
 {
 	struct virtio_vsock *vsock = NULL;
 	int ret;
+	int i;
 
 	ret = mutex_lock_interruptible(&the_virtio_vsock_mutex);
 	if (ret)
@@ -677,6 +759,9 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
 	if (ret < 0)
 		goto out;
 
+	for (i = 0; i < ARRAY_SIZE(vsock->out_sgs); i++)
+		vsock->out_sgs[i] = &vsock->out_bufs[i];
+
 	rcu_assign_pointer(the_virtio_vsock, vsock);
 	virtio_vsock_vqs_start(vsock);
 
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 352d042b130b..e22c81435ef7 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -37,27 +37,89 @@ virtio_transport_get_ops(struct vsock_sock *vsk)
 	return container_of(t, struct virtio_transport, transport);
 }
 
-/* Returns a new packet on success, otherwise returns NULL.
- *
- * If NULL is returned, errp is set to a negative errno.
- */
-static struct sk_buff *
-virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info,
-			   size_t len,
-			   u32 src_cid,
-			   u32 src_port,
-			   u32 dst_cid,
-			   u32 dst_port)
-{
-	const size_t skb_len = VIRTIO_VSOCK_SKB_HEADROOM + len;
-	struct virtio_vsock_hdr *hdr;
-	struct sk_buff *skb;
-	void *payload;
-	int err;
+static bool virtio_transport_can_zcopy(const struct virtio_transport *t_ops,
+				       struct virtio_vsock_pkt_info *info,
+				       size_t pkt_len)
+{
+	struct iov_iter *iov_iter;
 
-	skb = virtio_vsock_alloc_skb(skb_len, GFP_KERNEL);
-	if (!skb)
-		return NULL;
+	if (!info->msg)
+		return false;
+
+	iov_iter = &info->msg->msg_iter;
+
+	if (iov_iter->iov_offset)
+		return false;
+
+	/* We can't send whole iov. */
+	if (iov_iter->count > pkt_len)
+		return false;
+
+	/* Check that transport can send data in zerocopy mode. */
+	t_ops = virtio_transport_get_ops(info->vsk);
+
+	if (t_ops->can_msgzerocopy) {
+		int pages_in_iov = iov_iter_npages(iov_iter, MAX_SKB_FRAGS);
+		int pages_to_send = min(pages_in_iov, MAX_SKB_FRAGS);
+
+		/* +1 is for packet header. */
+		return t_ops->can_msgzerocopy(pages_to_send + 1);
+	}
+
+	return true;
+}
+
+static int virtio_transport_init_zcopy_skb(struct vsock_sock *vsk,
+					   struct sk_buff *skb,
+					   struct msghdr *msg,
+					   bool zerocopy)
+{
+	struct ubuf_info *uarg;
+
+	if (msg->msg_ubuf) {
+		uarg = msg->msg_ubuf;
+		net_zcopy_get(uarg);
+	} else {
+		struct iov_iter *iter = &msg->msg_iter;
+		struct ubuf_info_msgzc *uarg_zc;
+
+		uarg = msg_zerocopy_realloc(sk_vsock(vsk),
+					    iter->count,
+					    NULL);
+		if (!uarg)
+			return -1;
+
+		uarg_zc = uarg_to_msgzc(uarg);
+		uarg_zc->zerocopy = zerocopy ? 1 : 0;
+	}
+
+	skb_zcopy_init(skb, uarg);
+
+	return 0;
+}
+
+static int virtio_transport_fill_skb(struct sk_buff *skb,
+				     struct virtio_vsock_pkt_info *info,
+				     size_t len,
+				     bool zcopy)
+{
+	if (zcopy)
+		return __zerocopy_sg_from_iter(info->msg, NULL, skb,
+					       &info->msg->msg_iter,
+					       len);
+
+	return memcpy_from_msg(skb_put(skb, len), info->msg, len);
+}
+
+static void virtio_transport_init_hdr(struct sk_buff *skb,
+				      struct virtio_vsock_pkt_info *info,
+				      size_t payload_len,
+				      u32 src_cid,
+				      u32 src_port,
+				      u32 dst_cid,
+				      u32 dst_port)
+{
+	struct virtio_vsock_hdr *hdr;
 
 	hdr = virtio_vsock_hdr(skb);
 	hdr->type	= cpu_to_le16(info->type);
@@ -67,43 +129,28 @@ virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info,
 	hdr->src_port	= cpu_to_le32(src_port);
 	hdr->dst_port	= cpu_to_le32(dst_port);
 	hdr->flags	= cpu_to_le32(info->flags);
-	hdr->len	= cpu_to_le32(len);
-
-	if (info->msg && len > 0) {
-		payload = skb_put(skb, len);
-		err = memcpy_from_msg(payload, info->msg, len);
-		if (err)
-			goto out;
-
-		if (msg_data_left(info->msg) == 0 &&
-		    info->type == VIRTIO_VSOCK_TYPE_SEQPACKET) {
-			hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM);
-
-			if (info->msg->msg_flags & MSG_EOR)
-				hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
-		}
-	}
+	hdr->len	= cpu_to_le32(payload_len);
+}
 
-	if (info->reply)
-		virtio_vsock_skb_set_reply(skb);
+static void virtio_transport_copy_nonlinear_skb(const struct sk_buff *skb,
+						void *dst,
+						size_t len)
+{
+	struct iov_iter iov_iter = { 0 };
+	struct kvec kvec;
+	size_t to_copy;
 
-	trace_virtio_transport_alloc_pkt(src_cid, src_port,
-					 dst_cid, dst_port,
-					 len,
-					 info->type,
-					 info->op,
-					 info->flags);
+	kvec.iov_base = dst;
+	kvec.iov_len = len;
 
-	if (info->vsk && !skb_set_owner_sk_safe(skb, sk_vsock(info->vsk))) {
-		WARN_ONCE(1, "failed to allocate skb on vsock socket with sk_refcnt == 0\n");
-		goto out;
-	}
+	iov_iter.iter_type = ITER_KVEC;
+	iov_iter.kvec = &kvec;
+	iov_iter.nr_segs = 1;
 
-	return skb;
+	to_copy = min_t(size_t, len, skb->len);
 
-out:
-	kfree_skb(skb);
-	return NULL;
+	skb_copy_datagram_iter(skb, VIRTIO_VSOCK_SKB_CB(skb)->offset,
+			       &iov_iter, to_copy);
 }
 
 /* Packet capture */
@@ -114,7 +161,6 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)
 	struct af_vsockmon_hdr *hdr;
 	struct sk_buff *skb;
 	size_t payload_len;
-	void *payload_buf;
 
 	/* A packet could be split to fit the RX buffer, so we can retrieve
 	 * the payload length from the header and the buffer pointer taking
@@ -122,7 +168,6 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)
 	 */
 	pkt_hdr = virtio_vsock_hdr(pkt);
 	payload_len = pkt->len;
-	payload_buf = pkt->data;
 
 	skb = alloc_skb(sizeof(*hdr) + sizeof(*pkt_hdr) + payload_len,
 			GFP_ATOMIC);
@@ -165,7 +210,13 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)
 	skb_put_data(skb, pkt_hdr, sizeof(*pkt_hdr));
 
 	if (payload_len) {
-		skb_put_data(skb, payload_buf, payload_len);
+		if (skb_is_nonlinear(pkt)) {
+			void *data = skb_put(skb, payload_len);
+
+			virtio_transport_copy_nonlinear_skb(pkt, data, payload_len);
+		} else {
+			skb_put_data(skb, pkt->data, payload_len);
+		}
 	}
 
 	return skb;
@@ -189,6 +240,82 @@ static u16 virtio_transport_get_type(struct sock *sk)
 		return VIRTIO_VSOCK_TYPE_SEQPACKET;
 }
 
+/* Returns new sk_buff on success, otherwise returns NULL. */
+static struct sk_buff *virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info,
+						  size_t payload_len,
+						  bool zcopy,
+						  u32 src_cid,
+						  u32 src_port,
+						  u32 dst_cid,
+						  u32 dst_port)
+{
+	struct vsock_sock *vsk;
+	struct sk_buff *skb;
+	size_t skb_len;
+
+	skb_len = VIRTIO_VSOCK_SKB_HEADROOM;
+
+	if (!zcopy)
+		skb_len += payload_len;
+
+	skb = virtio_vsock_alloc_skb(skb_len, GFP_KERNEL);
+	if (!skb)
+		return NULL;
+
+	virtio_transport_init_hdr(skb, info, payload_len, src_cid, src_port,
+				  dst_cid, dst_port);
+
+	vsk = info->vsk;
+
+	/* If 'vsk' != NULL then payload is always present, so we
+	 * will never call '__zerocopy_sg_from_iter()' below without
+	 * setting skb owner in 'skb_set_owner_w()'. The only case
+	 * when 'vsk' == NULL is VIRTIO_VSOCK_OP_RST control message
+	 * without payload.
+	 */
+	WARN_ON_ONCE(!(vsk && (info->msg && payload_len)) && zcopy);
+
+	/* Set owner here, because '__zerocopy_sg_from_iter()' uses
+	 * owner of skb without check to update 'sk_wmem_alloc'.
+	 */
+	if (vsk)
+		skb_set_owner_w(skb, sk_vsock(vsk));
+
+	if (info->msg && payload_len > 0) {
+		int err;
+
+		err = virtio_transport_fill_skb(skb, info, payload_len, zcopy);
+		if (err)
+			goto out;
+
+		if (msg_data_left(info->msg) == 0 &&
+		    info->type == VIRTIO_VSOCK_TYPE_SEQPACKET) {
+			struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
+
+			hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM);
+
+			if (info->msg->msg_flags & MSG_EOR)
+				hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
+		}
+	}
+
+	if (info->reply)
+		virtio_vsock_skb_set_reply(skb);
+
+	trace_virtio_transport_alloc_pkt(src_cid, src_port,
+					 dst_cid, dst_port,
+					 payload_len,
+					 info->type,
+					 info->op,
+					 info->flags,
+					 zcopy);
+
+	return skb;
+out:
+	kfree_skb(skb);
+	return NULL;
+}
+
 /* This function can only be used on connecting/connected sockets,
  * since a socket assigned to a transport is required.
  *
@@ -197,10 +324,12 @@ static u16 virtio_transport_get_type(struct sock *sk)
 static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
 					  struct virtio_vsock_pkt_info *info)
 {
+	u32 max_skb_len = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE;
 	u32 src_cid, src_port, dst_cid, dst_port;
 	const struct virtio_transport *t_ops;
 	struct virtio_vsock_sock *vvs;
 	u32 pkt_len = info->pkt_len;
+	bool can_zcopy = false;
 	u32 rest_len;
 	int ret;
 
@@ -229,15 +358,30 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
 	if (pkt_len == 0 && info->op == VIRTIO_VSOCK_OP_RW)
 		return pkt_len;
 
+	if (info->msg) {
+		/* If zerocopy is not enabled by 'setsockopt()', we behave as
+		 * there is no MSG_ZEROCOPY flag set.
+		 */
+		if (!sock_flag(sk_vsock(vsk), SOCK_ZEROCOPY))
+			info->msg->msg_flags &= ~MSG_ZEROCOPY;
+
+		if (info->msg->msg_flags & MSG_ZEROCOPY)
+			can_zcopy = virtio_transport_can_zcopy(t_ops, info, pkt_len);
+
+		if (can_zcopy)
+			max_skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE,
+					    (MAX_SKB_FRAGS * PAGE_SIZE));
+	}
+
 	rest_len = pkt_len;
 
 	do {
 		struct sk_buff *skb;
 		size_t skb_len;
 
-		skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE, rest_len);
+		skb_len = min(max_skb_len, rest_len);
 
-		skb = virtio_transport_alloc_skb(info, skb_len,
+		skb = virtio_transport_alloc_skb(info, skb_len, can_zcopy,
 						 src_cid, src_port,
 						 dst_cid, dst_port);
 		if (!skb) {
@@ -245,6 +389,21 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
 			break;
 		}
 
+		/* We process buffer part by part, allocating skb on
+		 * each iteration. If this is last skb for this buffer
+		 * and MSG_ZEROCOPY mode is in use - we must allocate
+		 * completion for the current syscall.
+		 */
+		if (info->msg && info->msg->msg_flags & MSG_ZEROCOPY &&
+		    skb_len == rest_len && info->op == VIRTIO_VSOCK_OP_RW) {
+			if (virtio_transport_init_zcopy_skb(vsk, skb,
+							    info->msg,
+							    can_zcopy)) {
+				ret = -ENOMEM;
+				break;
+			}
+		}
+
 		virtio_transport_inc_tx_pkt(vvs, skb);
 
 		ret = t_ops->send_pkt(skb);
@@ -364,9 +523,10 @@ virtio_transport_stream_do_peek(struct vsock_sock *vsk,
 		spin_unlock_bh(&vvs->rx_lock);
 
 		/* sk_lock is held by caller so no one else can dequeue.
-		 * Unlock rx_lock since memcpy_to_msg() may sleep.
+		 * Unlock rx_lock since skb_copy_datagram_iter() may sleep.
 		 */
-		err = memcpy_to_msg(msg, skb->data, bytes);
+		err = skb_copy_datagram_iter(skb, VIRTIO_VSOCK_SKB_CB(skb)->offset,
+					     &msg->msg_iter, bytes);
 		if (err)
 			goto out;
 
@@ -410,25 +570,27 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
 	while (total < len && !skb_queue_empty(&vvs->rx_queue)) {
 		skb = skb_peek(&vvs->rx_queue);
 
-		bytes = len - total;
-		if (bytes > skb->len)
-			bytes = skb->len;
+		bytes = min_t(size_t, len - total,
+			      skb->len - VIRTIO_VSOCK_SKB_CB(skb)->offset);
 
 		/* sk_lock is held by caller so no one else can dequeue.
-		 * Unlock rx_lock since memcpy_to_msg() may sleep.
+		 * Unlock rx_lock since skb_copy_datagram_iter() may sleep.
 		 */
 		spin_unlock_bh(&vvs->rx_lock);
 
-		err = memcpy_to_msg(msg, skb->data, bytes);
+		err = skb_copy_datagram_iter(skb,
+					     VIRTIO_VSOCK_SKB_CB(skb)->offset,
+					     &msg->msg_iter, bytes);
 		if (err)
 			goto out;
 
 		spin_lock_bh(&vvs->rx_lock);
 
 		total += bytes;
-		skb_pull(skb, bytes);
 
-		if (skb->len == 0) {
+		VIRTIO_VSOCK_SKB_CB(skb)->offset += bytes;
+
+		if (skb->len == VIRTIO_VSOCK_SKB_CB(skb)->offset) {
 			u32 pkt_len = le32_to_cpu(virtio_vsock_hdr(skb)->len);
 
 			virtio_transport_dec_rx_pkt(vvs, pkt_len);
@@ -492,9 +654,10 @@ virtio_transport_seqpacket_do_peek(struct vsock_sock *vsk,
 			spin_unlock_bh(&vvs->rx_lock);
 
 			/* sk_lock is held by caller so no one else can dequeue.
-			 * Unlock rx_lock since memcpy_to_msg() may sleep.
+			 * Unlock rx_lock since skb_copy_datagram_iter() may sleep.
 			 */
-			err = memcpy_to_msg(msg, skb->data, bytes);
+			err = skb_copy_datagram_iter(skb, VIRTIO_VSOCK_SKB_CB(skb)->offset,
+						     &msg->msg_iter, bytes);
 			if (err)
 				return err;
 
@@ -553,11 +716,13 @@ static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
 				int err;
 
 				/* sk_lock is held by caller so no one else can dequeue.
-				 * Unlock rx_lock since memcpy_to_msg() may sleep.
+				 * Unlock rx_lock since skb_copy_datagram_iter() may sleep.
 				 */
 				spin_unlock_bh(&vvs->rx_lock);
 
-				err = memcpy_to_msg(msg, skb->data, bytes_to_copy);
+				err = skb_copy_datagram_iter(skb, 0,
+							     &msg->msg_iter,
+							     bytes_to_copy);
 				if (err) {
 					/* Copy of message failed. Rest of
 					 * fragments will be freed without copy.
@@ -954,7 +1119,7 @@ static int virtio_transport_reset_no_sock(const struct virtio_transport *t,
 	if (!t)
 		return -ENOTCONN;
 
-	reply = virtio_transport_alloc_skb(&info, 0,
+	reply = virtio_transport_alloc_skb(&info, 0, false,
 					   le64_to_cpu(hdr->dst_cid),
 					   le32_to_cpu(hdr->dst_port),
 					   le64_to_cpu(hdr->src_cid),
diff --git a/net/vmw_vsock/vsock_loopback.c b/net/vmw_vsock/vsock_loopback.c
index 5c6360df1f31..048640167411 100644
--- a/net/vmw_vsock/vsock_loopback.c
+++ b/net/vmw_vsock/vsock_loopback.c
@@ -47,6 +47,10 @@ static int vsock_loopback_cancel_pkt(struct vsock_sock *vsk)
 }
 
 static bool vsock_loopback_seqpacket_allow(u32 remote_cid);
+static bool vsock_loopback_msgzerocopy_allow(void)
+{
+	return true;
+}
 
 static struct virtio_transport loopback_transport = {
 	.transport = {
@@ -79,6 +83,8 @@ static struct virtio_transport loopback_transport = {
 		.seqpacket_allow          = vsock_loopback_seqpacket_allow,
 		.seqpacket_has_data       = virtio_transport_seqpacket_has_data,
 
+		.msgzerocopy_allow        = vsock_loopback_msgzerocopy_allow,
+
 		.notify_poll_in           = virtio_transport_notify_poll_in,
 		.notify_poll_out          = virtio_transport_notify_poll_out,
 		.notify_recv_init         = virtio_transport_notify_recv_init,