text: /* Copyright (C) 2009 Red Hat, Inc.
   * Author: Michael S. Tsirkin <mst@redhat.com>
   *
   * This work is licensed under the terms of the GNU GPL, version 2.
   *
   * 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/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_vlan.h>
  
  #include <net/sock.h>
  
  #include "vhost.h"
  
  static int experimental_zcopytx = 1;
  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 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)
  
  enum {
  	VHOST_NET_FEATURES = VHOST_FEATURES |
  			 (1ULL << VHOST_NET_F_VIRTIO_NET_HDR) |
  			 (1ULL << VIRTIO_NET_F_MRG_RXBUF) |
  			 (1ULL << VIRTIO_F_IOMMU_PLATFORM)
  };
  
  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 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;
  	/* first used idx for DMA done zerocopy buffers */
  	int done_idx;
  	/* an array of userspace buffers info */
  	struct ubuf_info *ubuf_info;
  	/* Reference counting for outstanding ubufs.
  	 * Protected by vq mutex. Writers must also take device mutex. */
  	struct vhost_net_ubuf_ref *ubufs;
  };
  
  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;
  };
  
  static unsigned vhost_net_zcopy_mask __read_mostly;
  
  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(sizeof(*ubufs), GFP_KERNEL);
  	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 = atomic_sub_return(1, &ubufs->refcount);
  	if (unlikely(!r))
  		wake_up(&ubufs->wait);
  	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(ubufs);
  }
  
  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(sizeof(*n->vqs[i].ubuf_info) *
  					      UIO_MAXIOV, GFP_KERNEL);
  		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;
  	}
  
  }
  
  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);
  }
  
  /* 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], add);
  		nvq->done_idx = (nvq->done_idx + add) % UIO_MAXIOV;
  		j -= add;
  	}
  }
  
  static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success)
  {
  	struct vhost_net_ubuf_ref *ubufs = ubuf->ctx;
  	struct vhost_virtqueue *vq = ubufs->vq;
  	int cnt;
  
  	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 inline unsigned long busy_clock(void)
  {
  	return local_clock() >> 10;
  }
  
  static bool vhost_can_busy_poll(struct vhost_dev *dev,
  				unsigned long endtime)
  {
  	return likely(!need_resched()) &&
  	       likely(!time_after(busy_clock(), endtime)) &&
  	       likely(!signal_pending(current)) &&
  	       !vhost_has_work(dev);
  }
  
  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 (!vq->private_data)
  		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 = vq->private_data;
  	if (!sock)
  		return 0;
  
  	return vhost_poll_start(poll, sock->file);
  }
  
  static int vhost_net_tx_get_vq_desc(struct vhost_net *net,
  				    struct vhost_virtqueue *vq,
  				    struct iovec iov[], unsigned int iov_size,
  				    unsigned int *out_num, unsigned int *in_num)
  {
  	unsigned long uninitialized_var(endtime);
  	int r = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
  				  out_num, in_num, NULL, NULL);
  
  	if (r == vq->num && vq->busyloop_timeout) {
  		preempt_disable();
  		endtime = busy_clock() + vq->busyloop_timeout;
  		while (vhost_can_busy_poll(vq->dev, endtime) &&
  		       vhost_vq_avail_empty(vq->dev, vq))
  			cpu_relax_lowlatency();
  		preempt_enable();
  		r = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
  				      out_num, in_num, NULL, NULL);
  	}
  
  	return r;
  }
  
  /* 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;
  	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;
  	size_t hdr_size;
  	struct socket *sock;
  	struct vhost_net_ubuf_ref *uninitialized_var(ubufs);
  	bool zcopy, zcopy_used;
  
  	mutex_lock(&vq->mutex);
  	sock = vq->private_data;
  	if (!sock)
  		goto out;
  
  	if (!vq_iotlb_prefetch(vq))
  		goto out;
  
  	vhost_disable_notify(&net->dev, vq);
  
  	hdr_size = nvq->vhost_hlen;
  	zcopy = nvq->ubufs;
  
  	for (;;) {
  		/* Release DMAs done buffers first */
  		if (zcopy)
  			vhost_zerocopy_signal_used(net, vq);
  
  		/* If more outstanding DMAs, queue the work.
  		 * Handle upend_idx wrap around
  		 */
  		if (unlikely((nvq->upend_idx + vq->num - VHOST_MAX_PEND)
  			      % UIO_MAXIOV == nvq->done_idx))
  			break;
  
  		head = vhost_net_tx_get_vq_desc(net, vq, vq->iov,
  						ARRAY_SIZE(vq->iov),
  						&out, &in);
  		/* 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(vhost_enable_notify(&net->dev, vq))) {
  				vhost_disable_notify(&net->dev, vq);
  				continue;
  			}
  			break;
  		}
  		if (in) {
  			vq_err(vq, "Unexpected descriptor format for TX: "
  			       "out %d, int %d\n", out, in);
  			break;
  		}
  		/* Skip header. TODO: support TSO. */
  		len = iov_length(vq->iov, out);
  		iov_iter_init(&msg.msg_iter, WRITE, vq->iov, out, len);
  		iov_iter_advance(&msg.msg_iter, hdr_size);
  		/* Sanity check */
  		if (!msg_data_left(&msg)) {
  			vq_err(vq, "Unexpected header len for TX: "
  			       "%zd expected %zd\n",
  			       len, hdr_size);
  			break;
  		}
  		len = msg_data_left(&msg);
  
  		zcopy_used = zcopy && len >= VHOST_GOODCOPY_LEN
  				   && (nvq->upend_idx + 1) % UIO_MAXIOV !=
  				      nvq->done_idx
  				   && vhost_net_tx_select_zcopy(net);
  
  		/* use msg_control to pass vhost zerocopy ubuf info to skb */
  		if (zcopy_used) {
  			struct ubuf_info *ubuf;
  			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->callback = vhost_zerocopy_callback;
  			ubuf->ctx = nvq->ubufs;
  			ubuf->desc = nvq->upend_idx;
  			msg.msg_control = ubuf;
  			msg.msg_controllen = sizeof(ubuf);
  			ubufs = nvq->ubufs;
  			atomic_inc(&ubufs->refcount);
  			nvq->upend_idx = (nvq->upend_idx + 1) % UIO_MAXIOV;
  		} else {
  			msg.msg_control = NULL;
  			ubufs = NULL;
  		}
  		/* TODO: Check specific error and bomb out unless ENOBUFS? */
  		err = sock->ops->sendmsg(sock, &msg, len);
  		if (unlikely(err < 0)) {
  			if (zcopy_used) {
  				vhost_net_ubuf_put(ubufs);
  				nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
  					% UIO_MAXIOV;
  			}
  			vhost_discard_vq_desc(vq, 1);
  			break;
  		}
  		if (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);
  		total_len += len;
  		vhost_net_tx_packet(net);
  		if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
  			vhost_poll_queue(&vq->poll);
  			break;
  		}
  	}
  out:
  	mutex_unlock(&vq->mutex);
  }
  
  static int peek_head_len(struct sock *sk)
  {
  	struct socket *sock = sk->sk_socket;
  	struct sk_buff *head;
  	int len = 0;
  	unsigned long flags;
  
  	if (sock->ops->peek_len)
  		return sock->ops->peek_len(sock);
  
  	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 sk_has_rx_data(struct sock *sk)
  {
  	struct socket *sock = sk->sk_socket;
  
  	if (sock->ops->peek_len)
  		return sock->ops->peek_len(sock);
  
  	return skb_queue_empty(&sk->sk_receive_queue);
  }
  
  static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk)
  {
  	struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX];
  	struct vhost_virtqueue *vq = &nvq->vq;
  	unsigned long uninitialized_var(endtime);
  	int len = peek_head_len(sk);
  
  	if (!len && vq->busyloop_timeout) {
  		/* Both tx vq and rx socket were polled here */
  		mutex_lock_nested(&vq->mutex, 1);
  		vhost_disable_notify(&net->dev, vq);
  
  		preempt_disable();
  		endtime = busy_clock() + vq->busyloop_timeout;
  
  		while (vhost_can_busy_poll(&net->dev, endtime) &&
  		       !sk_has_rx_data(sk) &&
  		       vhost_vq_avail_empty(&net->dev, vq))
  			cpu_relax_lowlatency();
  
  		preempt_enable();
  
  		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);
  		}
  
  		mutex_unlock(&vq->mutex);
  
  		len = peek_head_len(sk);
  	}
  
  	return len;
  }
  
  /* This is a multi-buffer version of vhost_get_desc, that works if
   *	vq has read descriptors only.
   * @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
   * @quota       - headcount quota, 1 for big buffer
   *	returns number of buffer heads allocated, negative on error
   */
  static int get_rx_bufs(struct vhost_virtqueue *vq,
  		       struct vring_used_elem *heads,
  		       int datalen,
  		       unsigned *iovcount,
  		       struct vhost_log *log,
  		       unsigned *log_num,
  		       unsigned int quota)
  {
  	unsigned int out, in;
  	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 uninitialized_var(len);
  
  	while (datalen > 0 && headcount < quota) {
  		if (unlikely(seg >= UIO_MAXIOV)) {
  			r = -ENOBUFS;
  			goto err;
  		}
  		r = vhost_get_vq_desc(vq, vq->iov + seg,
  				      ARRAY_SIZE(vq->iov) - seg, &out,
  				      &in, log, log_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;
  		}
  		heads[headcount].id = cpu_to_vhost32(vq, d);
  		len = iov_length(vq->iov + seg, in);
  		heads[headcount].len = cpu_to_vhost32(vq, len);
  		datalen -= len;
  		++headcount;
  		seg += in;
  	}
  	heads[headcount - 1].len = cpu_to_vhost32(vq, len + datalen);
  	*iovcount = seg;
  	if (unlikely(log))
  		*log_num = nlogs;
  
  	/* Detect overrun */
  	if (unlikely(datalen > 0)) {
  		r = UIO_MAXIOV + 1;
  		goto err;
  	}
  	return headcount;
  err:
  	vhost_discard_vq_desc(vq, headcount);
  	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;
  	unsigned uninitialized_var(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;
  	struct socket *sock;
  	struct iov_iter fixup;
  	__virtio16 num_buffers;
  
  	mutex_lock_nested(&vq->mutex, 0);
  	sock = vq->private_data;
  	if (!sock)
  		goto out;
  
  	if (!vq_iotlb_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);
  
  	while ((sock_len = vhost_net_rx_peek_head_len(net, sock->sk))) {
  		sock_len += sock_hlen;
  		vhost_len = sock_len + vhost_hlen;
  		headcount = get_rx_bufs(vq, vq->heads, vhost_len,
  					&in, vq_log, &log,
  					likely(mergeable) ? UIO_MAXIOV : 1);
  		/* On error, stop handling until the next kick. */
  		if (unlikely(headcount < 0))
  			goto out;
  		/* On overrun, truncate and discard */
  		if (unlikely(headcount > UIO_MAXIOV)) {
  			iov_iter_init(&msg.msg_iter, READ, 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;
  		}
  		/* OK, now we need to know about added descriptors. */
  		if (!headcount) {
  			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;
  		}
  		/* We don't need to be notified again. */
  		iov_iter_init(&msg.msg_iter, READ, 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);
  			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(mergeable) &&
  		    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);
  			goto out;
  		}
  		vhost_add_used_and_signal_n(&net->dev, vq, vq->heads,
  					    headcount);
  		if (unlikely(vq_log))
  			vhost_log_write(vq, vq_log, log, vhost_len);
  		total_len += vhost_len;
  		if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
  			vhost_poll_queue(&vq->poll);
  			goto out;
  		}
  	}
  	vhost_net_enable_vq(net, vq);
  out:
  	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;
  	int i;
  
  	n = kmalloc(sizeof *n, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
  	if (!n) {
  		n = vmalloc(sizeof *n);
  		if (!n)
  			return -ENOMEM;
  	}
  	vqs = kmalloc(VHOST_NET_VQ_MAX * sizeof(*vqs), GFP_KERNEL);
  	if (!vqs) {
  		kvfree(n);
  		return -ENOMEM;
  	}
  
  	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].vhost_hlen = 0;
  		n->vqs[i].sock_hlen = 0;
  	}
  	vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);
  
  	vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, POLLOUT, dev);
  	vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, POLLIN, dev);
  
  	f->private_data = n;
  
  	return 0;
  }
  
  static struct socket *vhost_net_stop_vq(struct vhost_net *n,
  					struct vhost_virtqueue *vq)
  {
  	struct socket *sock;
  
  	mutex_lock(&vq->mutex);
  	sock = vq->private_data;
  	vhost_net_disable_vq(n, vq);
  	vq->private_data = 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_vq(struct vhost_net *n, int index)
  {
  	vhost_poll_flush(n->poll + index);
  	vhost_poll_flush(&n->vqs[index].vq.poll);
  }
  
  static void vhost_net_flush(struct vhost_net *n)
  {
  	vhost_net_flush_vq(n, VHOST_NET_VQ_TX);
  	vhost_net_flush_vq(n, VHOST_NET_VQ_RX);
  	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, false);
  	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_bh();
  	/* We do an extra flush before freeing memory,
  	 * since jobs can re-queue themselves. */
  	vhost_net_flush(n);
  	kfree(n->dev.vqs);
  	kvfree(n);
  	return 0;
  }
  
  static struct socket *get_raw_socket(int fd)
  {
  	struct {
  		struct sockaddr_ll sa;
  		char  buf[MAX_ADDR_LEN];
  	} uaddr;
  	int uaddr_len = sizeof uaddr, 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;
  	}
  
  	r = sock->ops->getname(sock, (struct sockaddr *)&uaddr.sa,
  			       &uaddr_len, 0);
  	if (r)
  		goto err;
  
  	if (uaddr.sa.sll_family != AF_PACKET) {
  		r = -EPFNOSUPPORT;
  		goto err;
  	}
  	return sock;
  err:
  	sockfd_put(sock);
  	return ERR_PTR(r);
  }
  
  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 = macvtap_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);
  
  	/* 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 = vq->private_data;
  	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);
  		vq->private_data = sock;
  		r = vhost_vq_init_access(vq);
  		if (r)
  			goto err_used;
  		r = vhost_net_enable_vq(n, vq);
  		if (r)
  			goto err_used;
  
  		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_net_flush_vq(n, index);
  		sockfd_put(oldsock);
  	}
  
  	mutex_unlock(&n->dev.mutex);
  	return 0;
  
  err_used:
  	vq->private_data = 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_umem *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, u64 features)
  {
  	size_t vhost_hlen, sock_hlen, hdr_len;
  	int i;
  
  	hdr_len = (features & ((1ULL << VIRTIO_NET_F_MRG_RXBUF) |
  			       (1ULL << VIRTIO_F_VERSION_1))) ?
  			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))
  		goto out_unlock;
  
  	if ((features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))) {
  		if (vhost_init_device_iotlb(&n->dev, true))
  			goto out_unlock;
  	}
  
  	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
  		mutex_lock(&n->vqs[i].vq.mutex);
  		n->vqs[i].vq.acked_features = 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)
  {
  	struct vhost_net *n = f->private_data;
  	void __user *argp = (void __user *)arg;
  	u64 __user *featurep = argp;
  	struct vhost_vring_file backend;
  	u64 features;
  	int r;
  
  	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;
  		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)
  			return -EOPNOTSUPP;
  		return vhost_net_set_features(n, features);
  	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;
  	}
  }
  
  #ifdef CONFIG_COMPAT
  static long vhost_net_compat_ioctl(struct file *f, unsigned int ioctl,
  				   unsigned long arg)
  {
  	return vhost_net_ioctl(f, ioctl, (unsigned long)compat_ptr(arg));
  }
  #endif
  
  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 unsigned int 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,
  #ifdef CONFIG_COMPAT
  	.compat_ioctl   = vhost_net_compat_ioctl,
  #endif
  	.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 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 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");
  