Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 1915 insertions, 0 deletions

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
new file mode 100644
index 000000000..2cc730729
--- /dev/null
+++ b/drivers/vhost/net.c
@@ -0,0 +1,1915 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (C) 2009 Red Hat, Inc.
+ * Author: Michael S. Tsirkin <mst@redhat.com>
+ *
+ * virtio-net server in host kernel.
+ */
+
+#include <linux/compat.h>
+#include <linux/eventfd.h>
+#include <linux/vhost.h>
+#include <linux/virtio_net.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/mutex.h>
+#include <linux/workqueue.h>
+#include <linux/file.h>
+#include <linux/slab.h>
+#include <linux/sched/clock.h>
+#include <linux/sched/signal.h>
+#include <linux/vmalloc.h>
+
+#include <linux/net.h>
+#include <linux/if_packet.h>
+#include <linux/if_arp.h>
+#include <linux/if_tun.h>
+#include <linux/if_macvlan.h>
+#include <linux/if_tap.h>
+#include <linux/if_vlan.h>
+#include <linux/skb_array.h>
+#include <linux/skbuff.h>
+
+#include <net/sock.h>
+#include <net/xdp.h>
+
+#include "vhost.h"
+
+static int experimental_zcopytx = 0;
+module_param(experimental_zcopytx, int, 0444);
+MODULE_PARM_DESC(experimental_zcopytx, "Enable Zero Copy TX;"
+		                       " 1 -Enable; 0 - Disable");
+
+/* Max number of bytes transferred before requeueing the job.
+ * Using this limit prevents one virtqueue from starving others. */
+#define VHOST_NET_WEIGHT 0x80000
+
+/* Max number of packets transferred before requeueing the job.
+ * Using this limit prevents one virtqueue from starving others with small
+ * pkts.
+ */
+#define VHOST_NET_PKT_WEIGHT 256
+
+/* MAX number of TX used buffers for outstanding zerocopy */
+#define VHOST_MAX_PEND 128
+#define VHOST_GOODCOPY_LEN 256
+
+/*
+ * For transmit, used buffer len is unused; we override it to track buffer
+ * status internally; used for zerocopy tx only.
+ */
+/* Lower device DMA failed */
+#define VHOST_DMA_FAILED_LEN	((__force __virtio32)3)
+/* Lower device DMA done */
+#define VHOST_DMA_DONE_LEN	((__force __virtio32)2)
+/* Lower device DMA in progress */
+#define VHOST_DMA_IN_PROGRESS	((__force __virtio32)1)
+/* Buffer unused */
+#define VHOST_DMA_CLEAR_LEN	((__force __virtio32)0)
+
+#define VHOST_DMA_IS_DONE(len) ((__force u32)(len) >= (__force u32)VHOST_DMA_DONE_LEN)
+
+static const int vhost_net_bits[] = {
+	VHOST_FEATURES,
+	VHOST_NET_F_VIRTIO_NET_HDR,
+	VIRTIO_NET_F_MRG_RXBUF,
+	VIRTIO_F_ACCESS_PLATFORM,
+	VIRTIO_F_RING_RESET,
+	VIRTIO_F_IN_ORDER,
+	VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO,
+	VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO
+};
+
+enum {
+	VHOST_NET_BACKEND_FEATURES = (1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2)
+};
+
+enum {
+	VHOST_NET_VQ_RX = 0,
+	VHOST_NET_VQ_TX = 1,
+	VHOST_NET_VQ_MAX = 2,
+};
+
+struct vhost_net_ubuf_ref {
+	/* refcount follows semantics similar to kref:
+	 *  0: object is released
+	 *  1: no outstanding ubufs
+	 * >1: outstanding ubufs
+	 */
+	atomic_t refcount;
+	wait_queue_head_t wait;
+	struct vhost_virtqueue *vq;
+	struct rcu_head rcu;
+};
+
+#define VHOST_NET_BATCH 64
+struct vhost_net_buf {
+	void **queue;
+	int tail;
+	int head;
+};
+
+struct vhost_net_virtqueue {
+	struct vhost_virtqueue vq;
+	size_t vhost_hlen;
+	size_t sock_hlen;
+	/* vhost zerocopy support fields below: */
+	/* last used idx for outstanding DMA zerocopy buffers */
+	int upend_idx;
+	/* For TX, first used idx for DMA done zerocopy buffers
+	 * For RX, number of batched heads
+	 */
+	int done_idx;
+	/* Number of XDP frames batched */
+	int batched_xdp;
+	/* an array of userspace buffers info */
+	struct ubuf_info_msgzc *ubuf_info;
+	/* Reference counting for outstanding ubufs.
+	 * Protected by vq mutex. Writers must also take device mutex. */
+	struct vhost_net_ubuf_ref *ubufs;
+	struct ptr_ring *rx_ring;
+	struct vhost_net_buf rxq;
+	/* Batched XDP buffs */
+	struct xdp_buff *xdp;
+};
+
+struct vhost_net {
+	struct vhost_dev dev;
+	struct vhost_net_virtqueue vqs[VHOST_NET_VQ_MAX];
+	struct vhost_poll poll[VHOST_NET_VQ_MAX];
+	/* Number of TX recently submitted.
+	 * Protected by tx vq lock. */
+	unsigned tx_packets;
+	/* Number of times zerocopy TX recently failed.
+	 * Protected by tx vq lock. */
+	unsigned tx_zcopy_err;
+	/* Flush in progress. Protected by tx vq lock. */
+	bool tx_flush;
+	/* Private page frag cache */
+	struct page_frag_cache pf_cache;
+};
+
+static unsigned vhost_net_zcopy_mask __read_mostly;
+
+static void *vhost_net_buf_get_ptr(struct vhost_net_buf *rxq)
+{
+	if (rxq->tail != rxq->head)
+		return rxq->queue[rxq->head];
+	else
+		return NULL;
+}
+
+static int vhost_net_buf_get_size(struct vhost_net_buf *rxq)
+{
+	return rxq->tail - rxq->head;
+}
+
+static int vhost_net_buf_is_empty(struct vhost_net_buf *rxq)
+{
+	return rxq->tail == rxq->head;
+}
+
+static void *vhost_net_buf_consume(struct vhost_net_buf *rxq)
+{
+	void *ret = vhost_net_buf_get_ptr(rxq);
+	++rxq->head;
+	return ret;
+}
+
+static int vhost_net_buf_produce(struct sock *sk,
+				 struct vhost_net_virtqueue *nvq)
+{
+	struct file *file = sk->sk_socket->file;
+	struct vhost_net_buf *rxq = &nvq->rxq;
+
+	rxq->head = 0;
+	spin_lock(&nvq->rx_ring->consumer_lock);
+	rxq->tail = __ptr_ring_consume_batched(nvq->rx_ring, rxq->queue,
+					       VHOST_NET_BATCH);
+
+	if (rxq->tail)
+		tun_wake_queue(file, rxq->tail);
+
+	spin_unlock(&nvq->rx_ring->consumer_lock);
+	return rxq->tail;
+}
+
+static void vhost_net_buf_unproduce(struct vhost_net_virtqueue *nvq)
+{
+	struct vhost_net_buf *rxq = &nvq->rxq;
+
+	if (nvq->rx_ring && !vhost_net_buf_is_empty(rxq)) {
+		ptr_ring_unconsume(nvq->rx_ring, rxq->queue + rxq->head,
+				   vhost_net_buf_get_size(rxq),
+				   tun_ptr_free);
+		rxq->head = rxq->tail = 0;
+	}
+}
+
+static int vhost_net_buf_peek_len(void *ptr)
+{
+	if (tun_is_xdp_frame(ptr)) {
+		struct xdp_frame *xdpf = tun_ptr_to_xdp(ptr);
+
+		return xdpf->len;
+	}
+
+	return __skb_array_len_with_tag(ptr);
+}
+
+static int vhost_net_buf_peek(struct sock *sk,
+			      struct vhost_net_virtqueue *nvq)
+{
+	struct vhost_net_buf *rxq = &nvq->rxq;
+
+	if (!vhost_net_buf_is_empty(rxq))
+		goto out;
+
+	if (!vhost_net_buf_produce(sk, nvq))
+		return 0;
+
+out:
+	return vhost_net_buf_peek_len(vhost_net_buf_get_ptr(rxq));
+}
+
+static void vhost_net_buf_init(struct vhost_net_buf *rxq)
+{
+	rxq->head = rxq->tail = 0;
+}
+
+static void vhost_net_enable_zcopy(int vq)
+{
+	vhost_net_zcopy_mask |= 0x1 << vq;
+}
+
+static struct vhost_net_ubuf_ref *
+vhost_net_ubuf_alloc(struct vhost_virtqueue *vq, bool zcopy)
+{
+	struct vhost_net_ubuf_ref *ubufs;
+	/* No zero copy backend? Nothing to count. */
+	if (!zcopy)
+		return NULL;
+	ubufs = kmalloc_obj(*ubufs);
+	if (!ubufs)
+		return ERR_PTR(-ENOMEM);
+	atomic_set(&ubufs->refcount, 1);
+	init_waitqueue_head(&ubufs->wait);
+	ubufs->vq = vq;
+	return ubufs;
+}
+
+static int vhost_net_ubuf_put(struct vhost_net_ubuf_ref *ubufs)
+{
+	int r;
+
+	rcu_read_lock();
+	r = atomic_sub_return(1, &ubufs->refcount);
+	if (unlikely(!r))
+		wake_up(&ubufs->wait);
+	rcu_read_unlock();
+	return r;
+}
+
+static void vhost_net_ubuf_put_and_wait(struct vhost_net_ubuf_ref *ubufs)
+{
+	vhost_net_ubuf_put(ubufs);
+	wait_event(ubufs->wait, !atomic_read(&ubufs->refcount));
+}
+
+static void vhost_net_ubuf_put_wait_and_free(struct vhost_net_ubuf_ref *ubufs)
+{
+	vhost_net_ubuf_put_and_wait(ubufs);
+	kfree_rcu(ubufs, rcu);
+}
+
+static void vhost_net_clear_ubuf_info(struct vhost_net *n)
+{
+	int i;
+
+	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
+		kfree(n->vqs[i].ubuf_info);
+		n->vqs[i].ubuf_info = NULL;
+	}
+}
+
+static int vhost_net_set_ubuf_info(struct vhost_net *n)
+{
+	bool zcopy;
+	int i;
+
+	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
+		zcopy = vhost_net_zcopy_mask & (0x1 << i);
+		if (!zcopy)
+			continue;
+		n->vqs[i].ubuf_info =
+			kmalloc_objs(*n->vqs[i].ubuf_info, UIO_MAXIOV);
+		if  (!n->vqs[i].ubuf_info)
+			goto err;
+	}
+	return 0;
+
+err:
+	vhost_net_clear_ubuf_info(n);
+	return -ENOMEM;
+}
+
+static void vhost_net_vq_reset(struct vhost_net *n)
+{
+	int i;
+
+	vhost_net_clear_ubuf_info(n);
+
+	for (i = 0; i < VHOST_NET_VQ_MAX; i++) {
+		n->vqs[i].done_idx = 0;
+		n->vqs[i].upend_idx = 0;
+		n->vqs[i].ubufs = NULL;
+		n->vqs[i].vhost_hlen = 0;
+		n->vqs[i].sock_hlen = 0;
+		vhost_net_buf_init(&n->vqs[i].rxq);
+	}
+
+}
+
+static void vhost_net_tx_packet(struct vhost_net *net)
+{
+	++net->tx_packets;
+	if (net->tx_packets < 1024)
+		return;
+	net->tx_packets = 0;
+	net->tx_zcopy_err = 0;
+}
+
+static void vhost_net_tx_err(struct vhost_net *net)
+{
+	++net->tx_zcopy_err;
+}
+
+static bool vhost_net_tx_select_zcopy(struct vhost_net *net)
+{
+	/* TX flush waits for outstanding DMAs to be done.
+	 * Don't start new DMAs.
+	 */
+	return !net->tx_flush &&
+		net->tx_packets / 64 >= net->tx_zcopy_err;
+}
+
+static bool vhost_sock_zcopy(struct socket *sock)
+{
+	return unlikely(experimental_zcopytx) &&
+		sock_flag(sock->sk, SOCK_ZEROCOPY);
+}
+
+static bool vhost_sock_xdp(struct socket *sock)
+{
+	return sock_flag(sock->sk, SOCK_XDP);
+}
+
+/* In case of DMA done not in order in lower device driver for some reason.
+ * upend_idx is used to track end of used idx, done_idx is used to track head
+ * of used idx. Once lower device DMA done contiguously, we will signal KVM
+ * guest used idx.
+ */
+static void vhost_zerocopy_signal_used(struct vhost_net *net,
+				       struct vhost_virtqueue *vq)
+{
+	struct vhost_net_virtqueue *nvq =
+		container_of(vq, struct vhost_net_virtqueue, vq);
+	int i, add;
+	int j = 0;
+
+	for (i = nvq->done_idx; i != nvq->upend_idx; i = (i + 1) % UIO_MAXIOV) {
+		if (vq->heads[i].len == VHOST_DMA_FAILED_LEN)
+			vhost_net_tx_err(net);
+		if (VHOST_DMA_IS_DONE(vq->heads[i].len)) {
+			vq->heads[i].len = VHOST_DMA_CLEAR_LEN;
+			++j;
+		} else
+			break;
+	}
+	while (j) {
+		add = min(UIO_MAXIOV - nvq->done_idx, j);
+		vhost_add_used_and_signal_n(vq->dev, vq,
+					    &vq->heads[nvq->done_idx],
+					    NULL, add);
+		nvq->done_idx = (nvq->done_idx + add) % UIO_MAXIOV;
+		j -= add;
+	}
+}
+
+static void vhost_zerocopy_complete(struct sk_buff *skb,
+				    struct ubuf_info *ubuf_base, bool success)
+{
+	struct ubuf_info_msgzc *ubuf;
+	struct vhost_net_ubuf_ref *ubufs;
+	struct vhost_virtqueue *vq;
+	int cnt;
+
+	/* Only the final cloned skb reference completes the vhost descriptor. */
+	if (!refcount_dec_and_test(&ubuf_base->refcnt))
+		return;
+
+	ubuf = uarg_to_msgzc(ubuf_base);
+	ubufs = ubuf->ctx;
+	vq = ubufs->vq;
+
+	rcu_read_lock_bh();
+	/* set len to mark this desc buffers done DMA */
+	vq->heads[ubuf->desc].len = success ?
+		VHOST_DMA_DONE_LEN : VHOST_DMA_FAILED_LEN;
+	cnt = vhost_net_ubuf_put(ubufs);
+
+	/*
+	 * Trigger polling thread if guest stopped submitting new buffers:
+	 * in this case, the refcount after decrement will eventually reach 1.
+	 * We also trigger polling periodically after each 16 packets
+	 * (the value 16 here is more or less arbitrary, it's tuned to trigger
+	 * less than 10% of times).
+	 */
+	if (cnt <= 1 || !(cnt % 16))
+		vhost_poll_queue(&vq->poll);
+
+	rcu_read_unlock_bh();
+}
+
+static const struct ubuf_info_ops vhost_ubuf_ops = {
+	.complete = vhost_zerocopy_complete,
+};
+
+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_net_disable_vq(struct vhost_net *n,
+				 struct vhost_virtqueue *vq)
+{
+	struct vhost_net_virtqueue *nvq =
+		container_of(vq, struct vhost_net_virtqueue, vq);
+	struct vhost_poll *poll = n->poll + (nvq - n->vqs);
+	if (!vhost_vq_get_backend(vq))
+		return;
+	vhost_poll_stop(poll);
+}
+
+static int vhost_net_enable_vq(struct vhost_net *n,
+				struct vhost_virtqueue *vq)
+{
+	struct vhost_net_virtqueue *nvq =
+		container_of(vq, struct vhost_net_virtqueue, vq);
+	struct vhost_poll *poll = n->poll + (nvq - n->vqs);
+	struct socket *sock;
+
+	sock = vhost_vq_get_backend(vq);
+	if (!sock)
+		return 0;
+
+	return vhost_poll_start(poll, sock->file);
+}
+
+static void vhost_net_signal_used(struct vhost_net_virtqueue *nvq,
+				  unsigned int count)
+{
+	struct vhost_virtqueue *vq = &nvq->vq;
+	struct vhost_dev *dev = vq->dev;
+
+	if (!nvq->done_idx)
+		return;
+
+	vhost_add_used_and_signal_n(dev, vq, vq->heads,
+				    vq->nheads, count);
+	nvq->done_idx = 0;
+}
+
+static void vhost_tx_batch(struct vhost_net *net,
+			   struct vhost_net_virtqueue *nvq,
+			   struct socket *sock,
+			   struct msghdr *msghdr)
+{
+	struct vhost_virtqueue *vq = &nvq->vq;
+	bool in_order = vhost_has_feature(vq, VIRTIO_F_IN_ORDER);
+	struct tun_msg_ctl ctl = {
+		.type = TUN_MSG_PTR,
+		.num = nvq->batched_xdp,
+		.ptr = nvq->xdp,
+	};
+	int i, err;
+
+	if (in_order) {
+		vq->heads[0].len = 0;
+		vq->nheads[0] = nvq->done_idx;
+	}
+
+	if (nvq->batched_xdp == 0)
+		goto signal_used;
+
+	msghdr->msg_control = &ctl;
+	msghdr->msg_controllen = sizeof(ctl);
+	err = sock->ops->sendmsg(sock, msghdr, 0);
+	if (unlikely(err < 0)) {
+		vq_err(&nvq->vq, "Fail to batch sending packets\n");
+
+		/* free pages owned by XDP; since this is an unlikely error path,
+		 * keep it simple and avoid more complex bulk update for the
+		 * used pages
+		 */
+		for (i = 0; i < nvq->batched_xdp; ++i)
+			put_page(virt_to_head_page(nvq->xdp[i].data));
+		nvq->batched_xdp = 0;
+		nvq->done_idx = 0;
+		return;
+	}
+
+signal_used:
+	vhost_net_signal_used(nvq, in_order ? 1 : nvq->done_idx);
+	nvq->batched_xdp = 0;
+}
+
+static int sock_has_rx_data(struct socket *sock)
+{
+	if (unlikely(!sock))
+		return 0;
+
+	if (sock->ops->peek_len)
+		return sock->ops->peek_len(sock);
+
+	return skb_queue_empty(&sock->sk->sk_receive_queue);
+}
+
+static void vhost_net_busy_poll_try_queue(struct vhost_net *net,
+					  struct vhost_virtqueue *vq)
+{
+	if (!vhost_vq_avail_empty(&net->dev, vq)) {
+		vhost_poll_queue(&vq->poll);
+	} else if (unlikely(vhost_enable_notify(&net->dev, vq))) {
+		vhost_disable_notify(&net->dev, vq);
+		vhost_poll_queue(&vq->poll);
+	}
+}
+
+static void vhost_net_busy_poll(struct vhost_net *net,
+				struct vhost_virtqueue *rvq,
+				struct vhost_virtqueue *tvq,
+				bool *busyloop_intr,
+				bool poll_rx)
+{
+	unsigned long busyloop_timeout;
+	unsigned long endtime;
+	struct socket *sock;
+	struct vhost_virtqueue *vq = poll_rx ? tvq : rvq;
+
+	/* Try to hold the vq mutex of the paired virtqueue. We can't
+	 * use mutex_lock() here since we could not guarantee a
+	 * consistenet lock ordering.
+	 */
+	if (!mutex_trylock(&vq->mutex))
+		return;
+
+	vhost_disable_notify(&net->dev, vq);
+	sock = vhost_vq_get_backend(rvq);
+
+	busyloop_timeout = poll_rx ? rvq->busyloop_timeout:
+				     tvq->busyloop_timeout;
+
+	migrate_disable();
+	endtime = busy_clock() + busyloop_timeout;
+
+	while (vhost_can_busy_poll(endtime)) {
+		if (vhost_vq_has_work(vq)) {
+			*busyloop_intr = true;
+			break;
+		}
+
+		if ((sock_has_rx_data(sock) &&
+		     !vhost_vq_avail_empty(&net->dev, rvq)) ||
+		    !vhost_vq_avail_empty(&net->dev, tvq))
+			break;
+
+		cpu_relax();
+	}
+
+	migrate_enable();
+
+	if (poll_rx || sock_has_rx_data(sock))
+		vhost_net_busy_poll_try_queue(net, vq);
+	else if (!poll_rx) /* On tx here, sock has no rx data. */
+		vhost_enable_notify(&net->dev, rvq);
+
+	mutex_unlock(&vq->mutex);
+}
+
+static int vhost_net_tx_get_vq_desc(struct vhost_net *net,
+				    struct vhost_net_virtqueue *tnvq,
+				    unsigned int *out_num, unsigned int *in_num,
+				    struct msghdr *msghdr, bool *busyloop_intr,
+				    unsigned int *ndesc)
+{
+	struct vhost_net_virtqueue *rnvq = &net->vqs[VHOST_NET_VQ_RX];
+	struct vhost_virtqueue *rvq = &rnvq->vq;
+	struct vhost_virtqueue *tvq = &tnvq->vq;
+
+	int r = vhost_get_vq_desc_n(tvq, tvq->iov, ARRAY_SIZE(tvq->iov),
+				    out_num, in_num, NULL, NULL, ndesc);
+
+	if (r == tvq->num && tvq->busyloop_timeout) {
+		/* Flush batched packets first */
+		if (!vhost_sock_zcopy(vhost_vq_get_backend(tvq)))
+			vhost_tx_batch(net, tnvq,
+				       vhost_vq_get_backend(tvq),
+				       msghdr);
+
+		vhost_net_busy_poll(net, rvq, tvq, busyloop_intr, false);
+
+		r = vhost_get_vq_desc_n(tvq, tvq->iov, ARRAY_SIZE(tvq->iov),
+					out_num, in_num, NULL, NULL, ndesc);
+	}
+
+	return r;
+}
+
+static bool vhost_exceeds_maxpend(struct vhost_net *net)
+{
+	struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX];
+	struct vhost_virtqueue *vq = &nvq->vq;
+
+	return (nvq->upend_idx + UIO_MAXIOV - nvq->done_idx) % UIO_MAXIOV >
+	       min_t(unsigned int, VHOST_MAX_PEND, vq->num >> 2);
+}
+
+static size_t init_iov_iter(struct vhost_virtqueue *vq, struct iov_iter *iter,
+			    size_t hdr_size, int out)
+{
+	/* Skip header. TODO: support TSO. */
+	size_t len = iov_length(vq->iov, out);
+
+	iov_iter_init(iter, ITER_SOURCE, vq->iov, out, len);
+	iov_iter_advance(iter, hdr_size);
+
+	return iov_iter_count(iter);
+}
+
+static int get_tx_bufs(struct vhost_net *net,
+		       struct vhost_net_virtqueue *nvq,
+		       struct msghdr *msg,
+		       unsigned int *out, unsigned int *in,
+		       size_t *len, bool *busyloop_intr,
+		       unsigned int *ndesc)
+{
+	struct vhost_virtqueue *vq = &nvq->vq;
+	int ret;
+
+	ret = vhost_net_tx_get_vq_desc(net, nvq, out, in, msg,
+				       busyloop_intr, ndesc);
+
+	if (ret < 0 || ret == vq->num)
+		return ret;
+
+	if (*in) {
+		vq_err(vq, "Unexpected descriptor format for TX: out %d, int %d\n",
+			*out, *in);
+		return -EFAULT;
+	}
+
+	/* Sanity check */
+	*len = init_iov_iter(vq, &msg->msg_iter, nvq->vhost_hlen, *out);
+	if (*len == 0) {
+		vq_err(vq, "Unexpected header len for TX: %zd expected %zd\n",
+			*len, nvq->vhost_hlen);
+		return -EFAULT;
+	}
+
+	return ret;
+}
+
+static bool tx_can_batch(struct vhost_virtqueue *vq, size_t total_len)
+{
+	return total_len < VHOST_NET_WEIGHT &&
+	       !vhost_vq_avail_empty(vq->dev, vq);
+}
+
+#define VHOST_NET_RX_PAD (NET_IP_ALIGN + NET_SKB_PAD)
+
+static int vhost_net_build_xdp(struct vhost_net_virtqueue *nvq,
+			       struct iov_iter *from)
+{
+	struct vhost_virtqueue *vq = &nvq->vq;
+	struct vhost_net *net = container_of(vq->dev, struct vhost_net,
+					     dev);
+	struct socket *sock = vhost_vq_get_backend(vq);
+	struct virtio_net_hdr *gso;
+	struct xdp_buff *xdp = &nvq->xdp[nvq->batched_xdp];
+	size_t len = iov_iter_count(from);
+	int headroom = vhost_sock_xdp(sock) ? XDP_PACKET_HEADROOM : 0;
+	int buflen = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+	int pad = SKB_DATA_ALIGN(VHOST_NET_RX_PAD + headroom + nvq->sock_hlen);
+	int sock_hlen = nvq->sock_hlen;
+	void *buf;
+	int copied;
+	int ret;
+
+	if (unlikely(len < nvq->sock_hlen))
+		return -EFAULT;
+
+	if (SKB_DATA_ALIGN(len + pad) +
+	    SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) > PAGE_SIZE)
+		return -ENOSPC;
+
+	buflen += SKB_DATA_ALIGN(len + pad);
+	buf = page_frag_alloc_align(&net->pf_cache, buflen, GFP_KERNEL,
+				    SMP_CACHE_BYTES);
+	if (unlikely(!buf))
+		return -ENOMEM;
+
+	copied = copy_from_iter(buf + pad - sock_hlen, len, from);
+	if (copied != len) {
+		ret = -EFAULT;
+		goto err;
+	}
+
+	if (!sock_hlen) {
+		memset(buf, 0, pad);
+		gso = buf;
+	} else {
+		gso = buf + pad - sock_hlen;
+	}
+
+	if ((gso->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
+	    vhost16_to_cpu(vq, gso->csum_start) +
+	    vhost16_to_cpu(vq, gso->csum_offset) + 2 >
+	    vhost16_to_cpu(vq, gso->hdr_len)) {
+		gso->hdr_len = cpu_to_vhost16(vq,
+			       vhost16_to_cpu(vq, gso->csum_start) +
+			       vhost16_to_cpu(vq, gso->csum_offset) + 2);
+
+		if (vhost16_to_cpu(vq, gso->hdr_len) > len) {
+			ret = -EINVAL;
+			goto err;
+		}
+	}
+
+	/* pad contains sock_hlen */
+	memcpy(buf, buf + pad - sock_hlen, sock_hlen);
+
+	xdp_init_buff(xdp, buflen, NULL);
+	xdp_prepare_buff(xdp, buf, pad, len - sock_hlen, true);
+
+	++nvq->batched_xdp;
+
+	return 0;
+
+err:
+	page_frag_free(buf);
+	return ret;
+}
+
+static void handle_tx_copy(struct vhost_net *net, struct socket *sock)
+{
+	struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX];
+	struct vhost_virtqueue *vq = &nvq->vq;
+	unsigned out, in;
+	int head;
+	struct msghdr msg = {
+		.msg_name = NULL,
+		.msg_namelen = 0,
+		.msg_control = NULL,
+		.msg_controllen = 0,
+		.msg_flags = MSG_DONTWAIT,
+	};
+	size_t len, total_len = 0;
+	int err;
+	int sent_pkts = 0;
+	bool sock_can_batch = (sock->sk->sk_sndbuf == INT_MAX);
+	bool in_order = vhost_has_feature(vq, VIRTIO_F_IN_ORDER);
+	unsigned int ndesc = 0;
+
+	do {
+		bool busyloop_intr = false;
+
+		if (nvq->done_idx == VHOST_NET_BATCH)
+			vhost_tx_batch(net, nvq, sock, &msg);
+
+		head = get_tx_bufs(net, nvq, &msg, &out, &in, &len,
+				   &busyloop_intr, &ndesc);
+		/* On error, stop handling until the next kick. */
+		if (unlikely(head < 0))
+			break;
+		/* Nothing new?  Wait for eventfd to tell us they refilled. */
+		if (head == vq->num) {
+			/* Flush batched packets to handle pending RX
+			 * work (if busyloop_intr is set) and to avoid
+			 * unnecessary virtqueue kicks.
+			 */
+			vhost_tx_batch(net, nvq, sock, &msg);
+			if (unlikely(busyloop_intr)) {
+				vhost_poll_queue(&vq->poll);
+			} else if (unlikely(vhost_enable_notify(&net->dev,
+								vq))) {
+				vhost_disable_notify(&net->dev, vq);
+				continue;
+			}
+			break;
+		}
+
+		total_len += len;
+
+		/* For simplicity, TX batching is only enabled if
+		 * sndbuf is unlimited.
+		 */
+		if (sock_can_batch) {
+			err = vhost_net_build_xdp(nvq, &msg.msg_iter);
+			if (!err) {
+				goto done;
+			} else if (unlikely(err != -ENOSPC)) {
+				vhost_tx_batch(net, nvq, sock, &msg);
+				vhost_discard_vq_desc(vq, 1, ndesc);
+				vhost_net_enable_vq(net, vq);
+				break;
+			}
+
+			if (nvq->batched_xdp) {
+				/* We can't build XDP buff, go for single
+				 * packet path but let's flush batched
+				 * packets.
+				 */
+				vhost_tx_batch(net, nvq, sock, &msg);
+			}
+			msg.msg_control = NULL;
+		} else {
+			if (tx_can_batch(vq, total_len))
+				msg.msg_flags |= MSG_MORE;
+			else
+				msg.msg_flags &= ~MSG_MORE;
+		}
+
+		err = sock->ops->sendmsg(sock, &msg, len);
+		if (unlikely(err < 0)) {
+			if (err == -EAGAIN || err == -ENOMEM || err == -ENOBUFS) {
+				vhost_discard_vq_desc(vq, 1, ndesc);
+				vhost_net_enable_vq(net, vq);
+				break;
+			}
+			pr_debug("Fail to send packet: err %d", err);
+		} else if (unlikely(err != len))
+			pr_debug("Truncated TX packet: len %d != %zd\n",
+				 err, len);
+done:
+		if (in_order) {
+			vq->heads[0].id = cpu_to_vhost32(vq, head);
+		} else {
+			vq->heads[nvq->done_idx].id = cpu_to_vhost32(vq, head);
+			vq->heads[nvq->done_idx].len = 0;
+		}
+		++nvq->done_idx;
+	} while (likely(!vhost_exceeds_weight(vq, ++sent_pkts, total_len)));
+
+	vhost_tx_batch(net, nvq, sock, &msg);
+}
+
+static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
+{
+	struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX];
+	struct vhost_virtqueue *vq = &nvq->vq;
+	unsigned out, in;
+	int head;
+	struct msghdr msg = {
+		.msg_name = NULL,
+		.msg_namelen = 0,
+		.msg_control = NULL,
+		.msg_controllen = 0,
+		.msg_flags = MSG_DONTWAIT,
+	};
+	struct tun_msg_ctl ctl;
+	size_t len, total_len = 0;
+	int err;
+	struct vhost_net_ubuf_ref *ubufs;
+	struct ubuf_info_msgzc *ubuf;
+	unsigned int ndesc = 0;
+	bool zcopy_used;
+	int sent_pkts = 0;
+
+	do {
+		bool busyloop_intr;
+
+		/* Release DMAs done buffers first */
+		vhost_zerocopy_signal_used(net, vq);
+
+		busyloop_intr = false;
+		head = get_tx_bufs(net, nvq, &msg, &out, &in, &len,
+				   &busyloop_intr, &ndesc);
+		/* On error, stop handling until the next kick. */
+		if (unlikely(head < 0))
+			break;
+		/* Nothing new?  Wait for eventfd to tell us they refilled. */
+		if (head == vq->num) {
+			if (unlikely(busyloop_intr)) {
+				vhost_poll_queue(&vq->poll);
+			} else if (unlikely(vhost_enable_notify(&net->dev, vq))) {
+				vhost_disable_notify(&net->dev, vq);
+				continue;
+			}
+			break;
+		}
+
+		zcopy_used = len >= VHOST_GOODCOPY_LEN
+			     && !vhost_exceeds_maxpend(net)
+			     && vhost_net_tx_select_zcopy(net);
+
+		/* use msg_control to pass vhost zerocopy ubuf info to skb */
+		if (zcopy_used) {
+			ubuf = nvq->ubuf_info + nvq->upend_idx;
+			vq->heads[nvq->upend_idx].id = cpu_to_vhost32(vq, head);
+			vq->heads[nvq->upend_idx].len = VHOST_DMA_IN_PROGRESS;
+			ubuf->ctx = nvq->ubufs;
+			ubuf->desc = nvq->upend_idx;
+			ubuf->ubuf.ops = &vhost_ubuf_ops;
+			ubuf->ubuf.flags = SKBFL_ZEROCOPY_FRAG;
+			refcount_set(&ubuf->ubuf.refcnt, 1);
+			msg.msg_control = &ctl;
+			ctl.type = TUN_MSG_UBUF;
+			ctl.ptr = &ubuf->ubuf;
+			msg.msg_controllen = sizeof(ctl);
+			ubufs = nvq->ubufs;
+			atomic_inc(&ubufs->refcount);
+			nvq->upend_idx = (nvq->upend_idx + 1) % UIO_MAXIOV;
+		} else {
+			msg.msg_control = NULL;
+			ubufs = NULL;
+		}
+		total_len += len;
+		if (tx_can_batch(vq, total_len) &&
+		    likely(!vhost_exceeds_maxpend(net))) {
+			msg.msg_flags |= MSG_MORE;
+		} else {
+			msg.msg_flags &= ~MSG_MORE;
+		}
+
+		err = sock->ops->sendmsg(sock, &msg, len);
+		if (unlikely(err < 0)) {
+			bool retry = err == -EAGAIN || err == -ENOMEM || err == -ENOBUFS;
+
+			if (zcopy_used) {
+				if (vq->heads[ubuf->desc].len == VHOST_DMA_IN_PROGRESS)
+					vhost_net_ubuf_put(ubufs);
+				if (retry)
+					nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
+						% UIO_MAXIOV;
+				else
+					vq->heads[ubuf->desc].len = VHOST_DMA_DONE_LEN;
+			}
+			if (retry) {
+				vhost_discard_vq_desc(vq, 1, ndesc);
+				vhost_net_enable_vq(net, vq);
+				break;
+			}
+			pr_debug("Fail to send packet: err %d", err);
+		} else if (unlikely(err != len))
+			pr_debug("Truncated TX packet: "
+				 " len %d != %zd\n", err, len);
+		if (!zcopy_used)
+			vhost_add_used_and_signal(&net->dev, vq, head, 0);
+		else
+			vhost_zerocopy_signal_used(net, vq);
+		vhost_net_tx_packet(net);
+	} while (likely(!vhost_exceeds_weight(vq, ++sent_pkts, total_len)));
+}
+
+/* Expects to be always run from workqueue - which acts as
+ * read-size critical section for our kind of RCU. */
+static void handle_tx(struct vhost_net *net)
+{
+	struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX];
+	struct vhost_virtqueue *vq = &nvq->vq;
+	struct socket *sock;
+
+	mutex_lock_nested(&vq->mutex, VHOST_NET_VQ_TX);
+	sock = vhost_vq_get_backend(vq);
+	if (!sock)
+		goto out;
+
+	if (!vq_meta_prefetch(vq))
+		goto out;
+
+	vhost_disable_notify(&net->dev, vq);
+	vhost_net_disable_vq(net, vq);
+
+	if (vhost_sock_zcopy(sock))
+		handle_tx_zerocopy(net, sock);
+	else
+		handle_tx_copy(net, sock);
+
+out:
+	mutex_unlock(&vq->mutex);
+}
+
+static int peek_head_len(struct vhost_net_virtqueue *rvq, struct sock *sk)
+{
+	struct sk_buff *head;
+	int len = 0;
+	unsigned long flags;
+
+	if (rvq->rx_ring)
+		return vhost_net_buf_peek(sk, rvq);
+
+	spin_lock_irqsave(&sk->sk_receive_queue.lock, flags);
+	head = skb_peek(&sk->sk_receive_queue);
+	if (likely(head)) {
+		len = head->len;
+		if (skb_vlan_tag_present(head))
+			len += VLAN_HLEN;
+	}
+
+	spin_unlock_irqrestore(&sk->sk_receive_queue.lock, flags);
+	return len;
+}
+
+static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk,
+				      bool *busyloop_intr, unsigned int *count)
+{
+	struct vhost_net_virtqueue *rnvq = &net->vqs[VHOST_NET_VQ_RX];
+	struct vhost_net_virtqueue *tnvq = &net->vqs[VHOST_NET_VQ_TX];
+	struct vhost_virtqueue *rvq = &rnvq->vq;
+	struct vhost_virtqueue *tvq = &tnvq->vq;
+	int len = peek_head_len(rnvq, sk);
+
+	if (!len && rvq->busyloop_timeout) {
+		/* Flush batched heads first */
+		vhost_net_signal_used(rnvq, *count);
+		*count = 0;
+		/* Both tx vq and rx socket were polled here */
+		vhost_net_busy_poll(net, rvq, tvq, busyloop_intr, true);
+
+		len = peek_head_len(rnvq, sk);
+	}
+
+	return len;
+}
+
+/* This is a multi-buffer version of vhost_get_desc, that works if
+ *	vq has read descriptors only.
+ * @nvq		- the relevant vhost_net virtqueue
+ * @datalen	- data length we'll be reading
+ * @iovcount	- returned count of io vectors we fill
+ * @log		- vhost log
+ * @log_num	- log offset
+ * @quota       - headcount quota, 1 for big buffer
+ *	returns number of buffer heads allocated, negative on error
+ */
+static int get_rx_bufs(struct vhost_net_virtqueue *nvq,
+		       struct vring_used_elem *heads,
+		       u16 *nheads,
+		       int datalen,
+		       unsigned *iovcount,
+		       struct vhost_log *log,
+		       unsigned *log_num,
+		       unsigned int quota,
+		       unsigned int *ndesc)
+{
+	struct vhost_virtqueue *vq = &nvq->vq;
+	bool in_order = vhost_has_feature(vq, VIRTIO_F_IN_ORDER);
+	unsigned int out, in, desc_num, n = 0;
+	int seg = 0;
+	int headcount = 0;
+	unsigned d;
+	int r, nlogs = 0;
+	/* len is always initialized before use since we are always called with
+	 * datalen > 0.
+	 */
+	u32 len;
+
+	while (datalen > 0 && headcount < quota) {
+		if (unlikely(seg >= UIO_MAXIOV)) {
+			r = -ENOBUFS;
+			goto err;
+		}
+		r = vhost_get_vq_desc_n(vq, vq->iov + seg,
+					ARRAY_SIZE(vq->iov) - seg, &out,
+					&in, log, log_num, &desc_num);
+		if (unlikely(r < 0))
+			goto err;
+
+		d = r;
+		if (d == vq->num) {
+			r = 0;
+			goto err;
+		}
+		if (unlikely(out || in <= 0)) {
+			vq_err(vq, "unexpected descriptor format for RX: "
+				"out %d, in %d\n", out, in);
+			r = -EINVAL;
+			goto err;
+		}
+		if (unlikely(log)) {
+			nlogs += *log_num;
+			log += *log_num;
+		}
+		len = iov_length(vq->iov + seg, in);
+		if (!in_order) {
+			heads[headcount].id = cpu_to_vhost32(vq, d);
+			heads[headcount].len = cpu_to_vhost32(vq, len);
+		}
+		++headcount;
+		datalen -= len;
+		seg += in;
+		n += desc_num;
+	}
+
+	*iovcount = seg;
+	if (unlikely(log))
+		*log_num = nlogs;
+
+	/* Detect overrun */
+	if (unlikely(datalen > 0)) {
+		r = UIO_MAXIOV + 1;
+		goto err;
+	}
+
+	if (!in_order)
+		heads[headcount - 1].len = cpu_to_vhost32(vq, len + datalen);
+	else {
+		heads[0].len = cpu_to_vhost32(vq, len + datalen);
+		heads[0].id = cpu_to_vhost32(vq, d);
+		nheads[0] = headcount;
+	}
+
+	*ndesc = n;
+
+	return headcount;
+err:
+	vhost_discard_vq_desc(vq, headcount, n);
+	return r;
+}
+
+/* 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_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_RX];
+	struct vhost_virtqueue *vq = &nvq->vq;
+	bool in_order = vhost_has_feature(vq, VIRTIO_F_IN_ORDER);
+	unsigned int count = 0;
+	unsigned in, log;
+	struct vhost_log *vq_log;
+	struct msghdr msg = {
+		.msg_name = NULL,
+		.msg_namelen = 0,
+		.msg_control = NULL, /* FIXME: get and handle RX aux data. */
+		.msg_controllen = 0,
+		.msg_flags = MSG_DONTWAIT,
+	};
+	struct virtio_net_hdr hdr = {
+		.flags = 0,
+		.gso_type = VIRTIO_NET_HDR_GSO_NONE
+	};
+	size_t total_len = 0;
+	int err, mergeable;
+	s16 headcount;
+	size_t vhost_hlen, sock_hlen;
+	size_t vhost_len, sock_len;
+	bool busyloop_intr = false;
+	bool set_num_buffers;
+	struct socket *sock;
+	struct iov_iter fixup;
+	__virtio16 num_buffers;
+	int recv_pkts = 0;
+	unsigned int ndesc;
+
+	mutex_lock_nested(&vq->mutex, VHOST_NET_VQ_RX);
+	sock = vhost_vq_get_backend(vq);
+	if (!sock)
+		goto out;
+
+	if (!vq_meta_prefetch(vq))
+		goto out;
+
+	vhost_disable_notify(&net->dev, vq);
+	vhost_net_disable_vq(net, vq);
+
+	vhost_hlen = nvq->vhost_hlen;
+	sock_hlen = nvq->sock_hlen;
+
+	vq_log = unlikely(vhost_has_feature(vq, VHOST_F_LOG_ALL)) ?
+		vq->log : NULL;
+	mergeable = vhost_has_feature(vq, VIRTIO_NET_F_MRG_RXBUF);
+	set_num_buffers = mergeable ||
+			  vhost_has_feature(vq, VIRTIO_F_VERSION_1);
+
+	do {
+		sock_len = vhost_net_rx_peek_head_len(net, sock->sk,
+						      &busyloop_intr, &count);
+		if (!sock_len)
+			break;
+		sock_len += sock_hlen;
+		vhost_len = sock_len + vhost_hlen;
+		headcount = get_rx_bufs(nvq, vq->heads + count,
+					vq->nheads + count,
+					vhost_len, &in, vq_log, &log,
+					likely(mergeable) ? UIO_MAXIOV : 1,
+					&ndesc);
+		/* On error, stop handling until the next kick. */
+		if (unlikely(headcount < 0))
+			goto out;
+		/* OK, now we need to know about added descriptors. */
+		if (!headcount) {
+			if (unlikely(busyloop_intr)) {
+				vhost_poll_queue(&vq->poll);
+			} else if (unlikely(vhost_enable_notify(&net->dev, vq))) {
+				/* They have slipped one in as we were
+				 * doing that: check again. */
+				vhost_disable_notify(&net->dev, vq);
+				continue;
+			}
+			/* Nothing new?  Wait for eventfd to tell us
+			 * they refilled. */
+			goto out;
+		}
+		busyloop_intr = false;
+		if (nvq->rx_ring)
+			msg.msg_control = vhost_net_buf_consume(&nvq->rxq);
+		/* On overrun, truncate and discard */
+		if (unlikely(headcount > UIO_MAXIOV)) {
+			iov_iter_init(&msg.msg_iter, ITER_DEST, vq->iov, 1, 1);
+			err = sock->ops->recvmsg(sock, &msg,
+						 1, MSG_DONTWAIT | MSG_TRUNC);
+			pr_debug("Discarded rx packet: len %zd\n", sock_len);
+			continue;
+		}
+		/* We don't need to be notified again. */
+		iov_iter_init(&msg.msg_iter, ITER_DEST, vq->iov, in, vhost_len);
+		fixup = msg.msg_iter;
+		if (unlikely((vhost_hlen))) {
+			/* We will supply the header ourselves
+			 * TODO: support TSO.
+			 */
+			iov_iter_advance(&msg.msg_iter, vhost_hlen);
+		}
+		err = sock->ops->recvmsg(sock, &msg,
+					 sock_len, MSG_DONTWAIT | MSG_TRUNC);
+		/* Userspace might have consumed the packet meanwhile:
+		 * it's not supposed to do this usually, but might be hard
+		 * to prevent. Discard data we got (if any) and keep going. */
+		if (unlikely(err != sock_len)) {
+			pr_debug("Discarded rx packet: "
+				 " len %d, expected %zd\n", err, sock_len);
+			vhost_discard_vq_desc(vq, headcount, ndesc);
+			continue;
+		}
+		/* Supply virtio_net_hdr if VHOST_NET_F_VIRTIO_NET_HDR */
+		if (unlikely(vhost_hlen)) {
+			if (copy_to_iter(&hdr, sizeof(hdr),
+					 &fixup) != sizeof(hdr)) {
+				vq_err(vq, "Unable to write vnet_hdr "
+				       "at addr %p\n", vq->iov->iov_base);
+				goto out;
+			}
+		} else {
+			/* Header came from socket; we'll need to patch
+			 * ->num_buffers over if VIRTIO_NET_F_MRG_RXBUF
+			 */
+			iov_iter_advance(&fixup, sizeof(hdr));
+		}
+		/* TODO: Should check and handle checksum. */
+
+		num_buffers = cpu_to_vhost16(vq, headcount);
+		if (likely(set_num_buffers) &&
+		    copy_to_iter(&num_buffers, sizeof num_buffers,
+				 &fixup) != sizeof num_buffers) {
+			vq_err(vq, "Failed num_buffers write");
+			vhost_discard_vq_desc(vq, headcount, ndesc);
+			goto out;
+		}
+		nvq->done_idx += headcount;
+		count += in_order ? 1 : headcount;
+		if (nvq->done_idx > VHOST_NET_BATCH) {
+			vhost_net_signal_used(nvq, count);
+			count = 0;
+		}
+		if (unlikely(vq_log))
+			vhost_log_write(vq, vq_log, log, vhost_len,
+					vq->iov, in);
+		total_len += vhost_len;
+	} while (likely(!vhost_exceeds_weight(vq, ++recv_pkts, total_len)));
+
+	if (unlikely(busyloop_intr))
+		vhost_poll_queue(&vq->poll);
+	else if (!sock_len)
+		vhost_net_enable_vq(net, vq);
+out:
+	vhost_net_signal_used(nvq, count);
+	mutex_unlock(&vq->mutex);
+}
+
+static void handle_tx_kick(struct vhost_work *work)
+{
+	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
+						  poll.work);
+	struct vhost_net *net = container_of(vq->dev, struct vhost_net, dev);
+
+	handle_tx(net);
+}
+
+static void handle_rx_kick(struct vhost_work *work)
+{
+	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
+						  poll.work);
+	struct vhost_net *net = container_of(vq->dev, struct vhost_net, dev);
+
+	handle_rx(net);
+}
+
+static void handle_tx_net(struct vhost_work *work)
+{
+	struct vhost_net *net = container_of(work, struct vhost_net,
+					     poll[VHOST_NET_VQ_TX].work);
+	handle_tx(net);
+}
+
+static void handle_rx_net(struct vhost_work *work)
+{
+	struct vhost_net *net = container_of(work, struct vhost_net,
+					     poll[VHOST_NET_VQ_RX].work);
+	handle_rx(net);
+}
+
+static int vhost_net_open(struct inode *inode, struct file *f)
+{
+	struct vhost_net *n;
+	struct vhost_dev *dev;
+	struct vhost_virtqueue **vqs;
+	void **queue;
+	struct xdp_buff *xdp;
+	int i;
+
+	n = kvmalloc_obj(*n, GFP_KERNEL | __GFP_RETRY_MAYFAIL);
+	if (!n)
+		return -ENOMEM;
+	vqs = kmalloc_objs(*vqs, VHOST_NET_VQ_MAX);
+	if (!vqs) {
+		kvfree(n);
+		return -ENOMEM;
+	}
+
+	queue = kmalloc_array(VHOST_NET_BATCH, sizeof(void *),
+			      GFP_KERNEL);
+	if (!queue) {
+		kfree(vqs);
+		kvfree(n);
+		return -ENOMEM;
+	}
+	n->vqs[VHOST_NET_VQ_RX].rxq.queue = queue;
+
+	xdp = kmalloc_objs(*xdp, VHOST_NET_BATCH);
+	if (!xdp) {
+		kfree(vqs);
+		kvfree(n);
+		kfree(queue);
+		return -ENOMEM;
+	}
+	n->vqs[VHOST_NET_VQ_TX].xdp = xdp;
+
+	dev = &n->dev;
+	vqs[VHOST_NET_VQ_TX] = &n->vqs[VHOST_NET_VQ_TX].vq;
+	vqs[VHOST_NET_VQ_RX] = &n->vqs[VHOST_NET_VQ_RX].vq;
+	n->vqs[VHOST_NET_VQ_TX].vq.handle_kick = handle_tx_kick;
+	n->vqs[VHOST_NET_VQ_RX].vq.handle_kick = handle_rx_kick;
+	for (i = 0; i < VHOST_NET_VQ_MAX; i++) {
+		n->vqs[i].ubufs = NULL;
+		n->vqs[i].ubuf_info = NULL;
+		n->vqs[i].upend_idx = 0;
+		n->vqs[i].done_idx = 0;
+		n->vqs[i].batched_xdp = 0;
+		n->vqs[i].vhost_hlen = 0;
+		n->vqs[i].sock_hlen = 0;
+		n->vqs[i].rx_ring = NULL;
+		vhost_net_buf_init(&n->vqs[i].rxq);
+	}
+	vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX,
+		       UIO_MAXIOV + VHOST_NET_BATCH,
+		       VHOST_NET_PKT_WEIGHT, VHOST_NET_WEIGHT, true,
+		       NULL);
+
+	vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, EPOLLOUT, dev,
+			vqs[VHOST_NET_VQ_TX]);
+	vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, EPOLLIN, dev,
+			vqs[VHOST_NET_VQ_RX]);
+
+	f->private_data = n;
+	page_frag_cache_init(&n->pf_cache);
+
+	return 0;
+}
+
+static struct socket *vhost_net_stop_vq(struct vhost_net *n,
+					struct vhost_virtqueue *vq)
+{
+	struct socket *sock;
+	struct vhost_net_virtqueue *nvq =
+		container_of(vq, struct vhost_net_virtqueue, vq);
+
+	mutex_lock(&vq->mutex);
+	sock = vhost_vq_get_backend(vq);
+	vhost_net_disable_vq(n, vq);
+	vhost_vq_set_backend(vq, NULL);
+	vhost_net_buf_unproduce(nvq);
+	nvq->rx_ring = NULL;
+	mutex_unlock(&vq->mutex);
+	return sock;
+}
+
+static void vhost_net_stop(struct vhost_net *n, struct socket **tx_sock,
+			   struct socket **rx_sock)
+{
+	*tx_sock = vhost_net_stop_vq(n, &n->vqs[VHOST_NET_VQ_TX].vq);
+	*rx_sock = vhost_net_stop_vq(n, &n->vqs[VHOST_NET_VQ_RX].vq);
+}
+
+static void vhost_net_flush(struct vhost_net *n)
+{
+	vhost_dev_flush(&n->dev);
+	if (n->vqs[VHOST_NET_VQ_TX].ubufs) {
+		mutex_lock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);
+		n->tx_flush = true;
+		mutex_unlock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);
+		/* Wait for all lower device DMAs done. */
+		vhost_net_ubuf_put_and_wait(n->vqs[VHOST_NET_VQ_TX].ubufs);
+		mutex_lock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);
+		n->tx_flush = false;
+		atomic_set(&n->vqs[VHOST_NET_VQ_TX].ubufs->refcount, 1);
+		mutex_unlock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);
+	}
+}
+
+static int vhost_net_release(struct inode *inode, struct file *f)
+{
+	struct vhost_net *n = f->private_data;
+	struct socket *tx_sock;
+	struct socket *rx_sock;
+
+	vhost_net_stop(n, &tx_sock, &rx_sock);
+	vhost_net_flush(n);
+	vhost_dev_stop(&n->dev);
+	vhost_dev_cleanup(&n->dev);
+	vhost_net_vq_reset(n);
+	if (tx_sock)
+		sockfd_put(tx_sock);
+	if (rx_sock)
+		sockfd_put(rx_sock);
+	/* Make sure no callbacks are outstanding */
+	synchronize_rcu();
+	/* We do an extra flush before freeing memory,
+	 * since jobs can re-queue themselves. */
+	vhost_net_flush(n);
+	kfree(n->vqs[VHOST_NET_VQ_RX].rxq.queue);
+	kfree(n->vqs[VHOST_NET_VQ_TX].xdp);
+	kfree(n->dev.vqs);
+	page_frag_cache_drain(&n->pf_cache);
+	kvfree(n);
+	return 0;
+}
+
+static struct socket *get_raw_socket(int fd)
+{
+	int r;
+	struct socket *sock = sockfd_lookup(fd, &r);
+
+	if (!sock)
+		return ERR_PTR(-ENOTSOCK);
+
+	/* Parameter checking */
+	if (sock->sk->sk_type != SOCK_RAW) {
+		r = -ESOCKTNOSUPPORT;
+		goto err;
+	}
+
+	if (sock->sk->sk_family != AF_PACKET) {
+		r = -EPFNOSUPPORT;
+		goto err;
+	}
+	return sock;
+err:
+	sockfd_put(sock);
+	return ERR_PTR(r);
+}
+
+static struct ptr_ring *get_tap_ptr_ring(struct file *file)
+{
+	struct ptr_ring *ring;
+	ring = tun_get_tx_ring(file);
+	if (!IS_ERR(ring))
+		goto out;
+	ring = tap_get_ptr_ring(file);
+	if (!IS_ERR(ring))
+		goto out;
+	ring = NULL;
+out:
+	return ring;
+}
+
+static struct socket *get_tap_socket(int fd)
+{
+	struct file *file = fget(fd);
+	struct socket *sock;
+
+	if (!file)
+		return ERR_PTR(-EBADF);
+	sock = tun_get_socket(file);
+	if (!IS_ERR(sock))
+		return sock;
+	sock = tap_get_socket(file);
+	if (IS_ERR(sock))
+		fput(file);
+	return sock;
+}
+
+static struct socket *get_socket(int fd)
+{
+	struct socket *sock;
+
+	/* special case to disable backend */
+	if (fd == -1)
+		return NULL;
+	sock = get_raw_socket(fd);
+	if (!IS_ERR(sock))
+		return sock;
+	sock = get_tap_socket(fd);
+	if (!IS_ERR(sock))
+		return sock;
+	return ERR_PTR(-ENOTSOCK);
+}
+
+static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
+{
+	struct socket *sock, *oldsock;
+	struct vhost_virtqueue *vq;
+	struct vhost_net_virtqueue *nvq;
+	struct vhost_net_ubuf_ref *ubufs, *oldubufs = NULL;
+	int r;
+
+	mutex_lock(&n->dev.mutex);
+	r = vhost_dev_check_owner(&n->dev);
+	if (r)
+		goto err;
+
+	if (index >= VHOST_NET_VQ_MAX) {
+		r = -ENOBUFS;
+		goto err;
+	}
+	vq = &n->vqs[index].vq;
+	nvq = &n->vqs[index];
+	mutex_lock(&vq->mutex);
+
+	if (fd == -1)
+		vhost_clear_msg(&n->dev);
+
+	/* Verify that ring has been setup correctly. */
+	if (!vhost_vq_access_ok(vq)) {
+		r = -EFAULT;
+		goto err_vq;
+	}
+	sock = get_socket(fd);
+	if (IS_ERR(sock)) {
+		r = PTR_ERR(sock);
+		goto err_vq;
+	}
+
+	/* start polling new socket */
+	oldsock = vhost_vq_get_backend(vq);
+	if (sock != oldsock) {
+		ubufs = vhost_net_ubuf_alloc(vq,
+					     sock && vhost_sock_zcopy(sock));
+		if (IS_ERR(ubufs)) {
+			r = PTR_ERR(ubufs);
+			goto err_ubufs;
+		}
+
+		vhost_net_disable_vq(n, vq);
+		vhost_vq_set_backend(vq, sock);
+		vhost_net_buf_unproduce(nvq);
+		r = vhost_vq_init_access(vq);
+		if (r)
+			goto err_used;
+		r = vhost_net_enable_vq(n, vq);
+		if (r)
+			goto err_used;
+		if (index == VHOST_NET_VQ_RX) {
+			if (sock)
+				nvq->rx_ring = get_tap_ptr_ring(sock->file);
+			else
+				nvq->rx_ring = NULL;
+		}
+
+		oldubufs = nvq->ubufs;
+		nvq->ubufs = ubufs;
+
+		n->tx_packets = 0;
+		n->tx_zcopy_err = 0;
+		n->tx_flush = false;
+	}
+
+	mutex_unlock(&vq->mutex);
+
+	if (oldubufs) {
+		vhost_net_ubuf_put_wait_and_free(oldubufs);
+		mutex_lock(&vq->mutex);
+		vhost_zerocopy_signal_used(n, vq);
+		mutex_unlock(&vq->mutex);
+	}
+
+	if (oldsock) {
+		vhost_dev_flush(&n->dev);
+		sockfd_put(oldsock);
+	}
+
+	mutex_unlock(&n->dev.mutex);
+	return 0;
+
+err_used:
+	vhost_vq_set_backend(vq, oldsock);
+	vhost_net_enable_vq(n, vq);
+	if (ubufs)
+		vhost_net_ubuf_put_wait_and_free(ubufs);
+err_ubufs:
+	if (sock)
+		sockfd_put(sock);
+err_vq:
+	mutex_unlock(&vq->mutex);
+err:
+	mutex_unlock(&n->dev.mutex);
+	return r;
+}
+
+static long vhost_net_reset_owner(struct vhost_net *n)
+{
+	struct socket *tx_sock = NULL;
+	struct socket *rx_sock = NULL;
+	long err;
+	struct vhost_iotlb *umem;
+
+	mutex_lock(&n->dev.mutex);
+	err = vhost_dev_check_owner(&n->dev);
+	if (err)
+		goto done;
+	umem = vhost_dev_reset_owner_prepare();
+	if (!umem) {
+		err = -ENOMEM;
+		goto done;
+	}
+	vhost_net_stop(n, &tx_sock, &rx_sock);
+	vhost_net_flush(n);
+	vhost_dev_stop(&n->dev);
+	vhost_dev_reset_owner(&n->dev, umem);
+	vhost_net_vq_reset(n);
+done:
+	mutex_unlock(&n->dev.mutex);
+	if (tx_sock)
+		sockfd_put(tx_sock);
+	if (rx_sock)
+		sockfd_put(rx_sock);
+	return err;
+}
+
+static int vhost_net_set_features(struct vhost_net *n, const u64 *features)
+{
+	size_t vhost_hlen, sock_hlen, hdr_len;
+	int i;
+
+	hdr_len = virtio_features_test_bit(features, VIRTIO_NET_F_MRG_RXBUF) ||
+		  virtio_features_test_bit(features, VIRTIO_F_VERSION_1) ?
+		  sizeof(struct virtio_net_hdr_mrg_rxbuf) :
+		  sizeof(struct virtio_net_hdr);
+
+	if (virtio_features_test_bit(features,
+				     VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO) ||
+	    virtio_features_test_bit(features,
+				     VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO))
+		hdr_len = sizeof(struct virtio_net_hdr_v1_hash_tunnel);
+
+	if (virtio_features_test_bit(features, 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 (virtio_features_test_bit(features, VHOST_F_LOG_ALL) &&
+	    !vhost_log_access_ok(&n->dev))
+		goto out_unlock;
+
+	if (virtio_features_test_bit(features, VIRTIO_F_ACCESS_PLATFORM)) {
+		if (vhost_init_device_iotlb(&n->dev))
+			goto out_unlock;
+	} else {
+		vhost_clear_device_iotlb(&n->dev);
+	}
+
+	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
+		mutex_lock(&n->vqs[i].vq.mutex);
+		virtio_features_copy(n->vqs[i].vq.acked_features_array,
+				     features);
+		n->vqs[i].vhost_hlen = vhost_hlen;
+		n->vqs[i].sock_hlen = sock_hlen;
+		mutex_unlock(&n->vqs[i].vq.mutex);
+	}
+	mutex_unlock(&n->dev.mutex);
+	return 0;
+
+out_unlock:
+	mutex_unlock(&n->dev.mutex);
+	return -EFAULT;
+}
+
+static long vhost_net_set_owner(struct vhost_net *n)
+{
+	int r;
+
+	mutex_lock(&n->dev.mutex);
+	if (vhost_dev_has_owner(&n->dev)) {
+		r = -EBUSY;
+		goto out;
+	}
+	r = vhost_net_set_ubuf_info(n);
+	if (r)
+		goto out;
+	r = vhost_dev_set_owner(&n->dev);
+	if (r)
+		vhost_net_clear_ubuf_info(n);
+	vhost_net_flush(n);
+out:
+	mutex_unlock(&n->dev.mutex);
+	return r;
+}
+
+static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
+			    unsigned long arg)
+{
+	const DEFINE_VHOST_FEATURES_ARRAY(vhost_net_features, vhost_net_bits);
+	u64 all_features[VIRTIO_FEATURES_U64S];
+	struct vhost_net *n = f->private_data;
+	void __user *argp = (void __user *)arg;
+	u64 __user *featurep = argp;
+	struct vhost_vring_file backend;
+	u64 features, count, copied;
+	int r, i;
+
+	switch (ioctl) {
+	case VHOST_NET_SET_BACKEND:
+		if (copy_from_user(&backend, argp, sizeof backend))
+			return -EFAULT;
+		return vhost_net_set_backend(n, backend.index, backend.fd);
+	case VHOST_GET_FEATURES:
+		features = vhost_net_features[0];
+		if (copy_to_user(featurep, &features, sizeof features))
+			return -EFAULT;
+		return 0;
+	case VHOST_SET_FEATURES:
+		if (copy_from_user(&features, featurep, sizeof features))
+			return -EFAULT;
+		if (features & ~vhost_net_features[0])
+			return -EOPNOTSUPP;
+
+		virtio_features_from_u64(all_features, features);
+		return vhost_net_set_features(n, all_features);
+	case VHOST_GET_FEATURES_ARRAY:
+		if (copy_from_user(&count, featurep, sizeof(count)))
+			return -EFAULT;
+
+		/* Copy the net features, up to the user-provided buffer size */
+		argp += sizeof(u64);
+		copied = min(count, (u64)VIRTIO_FEATURES_U64S);
+		if (copy_to_user(argp, vhost_net_features,
+				 copied * sizeof(u64)))
+			return -EFAULT;
+
+		/* Zero the trailing space provided by user-space, if any */
+		if (clear_user(argp + size_mul(copied, sizeof(u64)),
+			       size_mul(count - copied, sizeof(u64))))
+			return -EFAULT;
+		return 0;
+	case VHOST_SET_FEATURES_ARRAY:
+		if (copy_from_user(&count, featurep, sizeof(count)))
+			return -EFAULT;
+
+		virtio_features_zero(all_features);
+		argp += sizeof(u64);
+		copied = min(count, (u64)VIRTIO_FEATURES_U64S);
+		if (copy_from_user(all_features, argp, copied * sizeof(u64)))
+			return -EFAULT;
+
+		/*
+		 * Any feature specified by user-space above
+		 * VIRTIO_FEATURES_BITS is not supported by definition.
+		 */
+		for (i = copied; i < count; ++i) {
+			if (copy_from_user(&features, featurep + 1 + i,
+					   sizeof(features)))
+				return -EFAULT;
+			if (features)
+				return -EOPNOTSUPP;
+		}
+
+		for (i = 0; i < VIRTIO_FEATURES_U64S; i++)
+			if (all_features[i] & ~vhost_net_features[i])
+				return -EOPNOTSUPP;
+
+		return vhost_net_set_features(n, all_features);
+	case VHOST_GET_BACKEND_FEATURES:
+		features = VHOST_NET_BACKEND_FEATURES;
+		if (copy_to_user(featurep, &features, sizeof(features)))
+			return -EFAULT;
+		return 0;
+	case VHOST_SET_BACKEND_FEATURES:
+		if (copy_from_user(&features, featurep, sizeof(features)))
+			return -EFAULT;
+		if (features & ~VHOST_NET_BACKEND_FEATURES)
+			return -EOPNOTSUPP;
+		vhost_set_backend_features(&n->dev, features);
+		return 0;
+	case VHOST_RESET_OWNER:
+		return vhost_net_reset_owner(n);
+	case VHOST_SET_OWNER:
+		return vhost_net_set_owner(n);
+	default:
+		mutex_lock(&n->dev.mutex);
+		r = vhost_dev_ioctl(&n->dev, ioctl, argp);
+		if (r == -ENOIOCTLCMD)
+			r = vhost_vring_ioctl(&n->dev, ioctl, argp);
+		else
+			vhost_net_flush(n);
+		mutex_unlock(&n->dev.mutex);
+		return r;
+	}
+}
+
+static ssize_t vhost_net_chr_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct file *file = iocb->ki_filp;
+	struct vhost_net *n = file->private_data;
+	struct vhost_dev *dev = &n->dev;
+	int noblock = file->f_flags & O_NONBLOCK;
+
+	return vhost_chr_read_iter(dev, to, noblock);
+}
+
+static ssize_t vhost_net_chr_write_iter(struct kiocb *iocb,
+					struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct vhost_net *n = file->private_data;
+	struct vhost_dev *dev = &n->dev;
+
+	return vhost_chr_write_iter(dev, from);
+}
+
+static __poll_t vhost_net_chr_poll(struct file *file, poll_table *wait)
+{
+	struct vhost_net *n = file->private_data;
+	struct vhost_dev *dev = &n->dev;
+
+	return vhost_chr_poll(file, dev, wait);
+}
+
+static const struct file_operations vhost_net_fops = {
+	.owner          = THIS_MODULE,
+	.release        = vhost_net_release,
+	.read_iter      = vhost_net_chr_read_iter,
+	.write_iter     = vhost_net_chr_write_iter,
+	.poll           = vhost_net_chr_poll,
+	.unlocked_ioctl = vhost_net_ioctl,
+	.compat_ioctl   = compat_ptr_ioctl,
+	.open           = vhost_net_open,
+	.llseek		= noop_llseek,
+};
+
+static struct miscdevice vhost_net_misc = {
+	.minor = VHOST_NET_MINOR,
+	.name = "vhost-net",
+	.fops = &vhost_net_fops,
+};
+
+static int __init vhost_net_init(void)
+{
+	if (experimental_zcopytx)
+		vhost_net_enable_zcopy(VHOST_NET_VQ_TX);
+	return misc_register(&vhost_net_misc);
+}
+module_init(vhost_net_init);
+
+static void __exit vhost_net_exit(void)
+{
+	misc_deregister(&vhost_net_misc);
+}
+module_exit(vhost_net_exit);
+
+MODULE_VERSION("0.0.1");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Michael S. Tsirkin");
+MODULE_DESCRIPTION("Host kernel accelerator for virtio net");
+MODULE_ALIAS_MISCDEV(VHOST_NET_MINOR);
+MODULE_ALIAS("devname:vhost-net");