vhost: vhost TX zero-copy support
[linux-2.6.git] / drivers / vhost / net.c
1 /* Copyright (C) 2009 Red Hat, Inc.
2  * Author: Michael S. Tsirkin <mst@redhat.com>
3  *
4  * This work is licensed under the terms of the GNU GPL, version 2.
5  *
6  * virtio-net server in host kernel.
7  */
8
9 #include <linux/compat.h>
10 #include <linux/eventfd.h>
11 #include <linux/vhost.h>
12 #include <linux/virtio_net.h>
13 #include <linux/miscdevice.h>
14 #include <linux/module.h>
15 #include <linux/moduleparam.h>
16 #include <linux/mutex.h>
17 #include <linux/workqueue.h>
18 #include <linux/rcupdate.h>
19 #include <linux/file.h>
20 #include <linux/slab.h>
21
22 #include <linux/net.h>
23 #include <linux/if_packet.h>
24 #include <linux/if_arp.h>
25 #include <linux/if_tun.h>
26 #include <linux/if_macvlan.h>
27
28 #include <net/sock.h>
29
30 #include "vhost.h"
31
32 static int experimental_zcopytx;
33 module_param(experimental_zcopytx, int, 0444);
34 MODULE_PARM_DESC(experimental_zcopytx, "Enable Experimental Zero Copy TX");
35
36 /* Max number of bytes transferred before requeueing the job.
37  * Using this limit prevents one virtqueue from starving others. */
38 #define VHOST_NET_WEIGHT 0x80000
39
40 /* MAX number of TX used buffers for outstanding zerocopy */
41 #define VHOST_MAX_PEND 128
42 #define VHOST_GOODCOPY_LEN 256
43
44 enum {
45         VHOST_NET_VQ_RX = 0,
46         VHOST_NET_VQ_TX = 1,
47         VHOST_NET_VQ_MAX = 2,
48 };
49
50 enum vhost_net_poll_state {
51         VHOST_NET_POLL_DISABLED = 0,
52         VHOST_NET_POLL_STARTED = 1,
53         VHOST_NET_POLL_STOPPED = 2,
54 };
55
56 struct vhost_net {
57         struct vhost_dev dev;
58         struct vhost_virtqueue vqs[VHOST_NET_VQ_MAX];
59         struct vhost_poll poll[VHOST_NET_VQ_MAX];
60         /* Tells us whether we are polling a socket for TX.
61          * We only do this when socket buffer fills up.
62          * Protected by tx vq lock. */
63         enum vhost_net_poll_state tx_poll_state;
64 };
65
66 static bool vhost_sock_zcopy(struct socket *sock)
67 {
68         return unlikely(experimental_zcopytx) &&
69                 sock_flag(sock->sk, SOCK_ZEROCOPY);
70 }
71
72 /* Pop first len bytes from iovec. Return number of segments used. */
73 static int move_iovec_hdr(struct iovec *from, struct iovec *to,
74                           size_t len, int iov_count)
75 {
76         int seg = 0;
77         size_t size;
78
79         while (len && seg < iov_count) {
80                 size = min(from->iov_len, len);
81                 to->iov_base = from->iov_base;
82                 to->iov_len = size;
83                 from->iov_len -= size;
84                 from->iov_base += size;
85                 len -= size;
86                 ++from;
87                 ++to;
88                 ++seg;
89         }
90         return seg;
91 }
92 /* Copy iovec entries for len bytes from iovec. */
93 static void copy_iovec_hdr(const struct iovec *from, struct iovec *to,
94                            size_t len, int iovcount)
95 {
96         int seg = 0;
97         size_t size;
98
99         while (len && seg < iovcount) {
100                 size = min(from->iov_len, len);
101                 to->iov_base = from->iov_base;
102                 to->iov_len = size;
103                 len -= size;
104                 ++from;
105                 ++to;
106                 ++seg;
107         }
108 }
109
110 /* Caller must have TX VQ lock */
111 static void tx_poll_stop(struct vhost_net *net)
112 {
113         if (likely(net->tx_poll_state != VHOST_NET_POLL_STARTED))
114                 return;
115         vhost_poll_stop(net->poll + VHOST_NET_VQ_TX);
116         net->tx_poll_state = VHOST_NET_POLL_STOPPED;
117 }
118
119 /* Caller must have TX VQ lock */
120 static void tx_poll_start(struct vhost_net *net, struct socket *sock)
121 {
122         if (unlikely(net->tx_poll_state != VHOST_NET_POLL_STOPPED))
123                 return;
124         vhost_poll_start(net->poll + VHOST_NET_VQ_TX, sock->file);
125         net->tx_poll_state = VHOST_NET_POLL_STARTED;
126 }
127
128 /* Expects to be always run from workqueue - which acts as
129  * read-size critical section for our kind of RCU. */
130 static void handle_tx(struct vhost_net *net)
131 {
132         struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_TX];
133         unsigned out, in, s;
134         int head;
135         struct msghdr msg = {
136                 .msg_name = NULL,
137                 .msg_namelen = 0,
138                 .msg_control = NULL,
139                 .msg_controllen = 0,
140                 .msg_iov = vq->iov,
141                 .msg_flags = MSG_DONTWAIT,
142         };
143         size_t len, total_len = 0;
144         int err, wmem;
145         size_t hdr_size;
146         struct socket *sock;
147         struct vhost_ubuf_ref *uninitialized_var(ubufs);
148         bool zcopy;
149
150         /* TODO: check that we are running from vhost_worker? */
151         sock = rcu_dereference_check(vq->private_data, 1);
152         if (!sock)
153                 return;
154
155         wmem = atomic_read(&sock->sk->sk_wmem_alloc);
156         if (wmem >= sock->sk->sk_sndbuf) {
157                 mutex_lock(&vq->mutex);
158                 tx_poll_start(net, sock);
159                 mutex_unlock(&vq->mutex);
160                 return;
161         }
162
163         mutex_lock(&vq->mutex);
164         vhost_disable_notify(&net->dev, vq);
165
166         if (wmem < sock->sk->sk_sndbuf / 2)
167                 tx_poll_stop(net);
168         hdr_size = vq->vhost_hlen;
169         zcopy = vhost_sock_zcopy(sock);
170
171         for (;;) {
172                 /* Release DMAs done buffers first */
173                 if (zcopy)
174                         vhost_zerocopy_signal_used(vq);
175
176                 head = vhost_get_vq_desc(&net->dev, vq, vq->iov,
177                                          ARRAY_SIZE(vq->iov),
178                                          &out, &in,
179                                          NULL, NULL);
180                 /* On error, stop handling until the next kick. */
181                 if (unlikely(head < 0))
182                         break;
183                 /* Nothing new?  Wait for eventfd to tell us they refilled. */
184                 if (head == vq->num) {
185                         wmem = atomic_read(&sock->sk->sk_wmem_alloc);
186                         if (wmem >= sock->sk->sk_sndbuf * 3 / 4) {
187                                 tx_poll_start(net, sock);
188                                 set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
189                                 break;
190                         }
191                         /* If more outstanding DMAs, queue the work */
192                         if (unlikely(vq->upend_idx - vq->done_idx >
193                                      VHOST_MAX_PEND)) {
194                                 tx_poll_start(net, sock);
195                                 set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
196                                 break;
197                         }
198                         if (unlikely(vhost_enable_notify(&net->dev, vq))) {
199                                 vhost_disable_notify(&net->dev, vq);
200                                 continue;
201                         }
202                         break;
203                 }
204                 if (in) {
205                         vq_err(vq, "Unexpected descriptor format for TX: "
206                                "out %d, int %d\n", out, in);
207                         break;
208                 }
209                 /* Skip header. TODO: support TSO. */
210                 s = move_iovec_hdr(vq->iov, vq->hdr, hdr_size, out);
211                 msg.msg_iovlen = out;
212                 len = iov_length(vq->iov, out);
213                 /* Sanity check */
214                 if (!len) {
215                         vq_err(vq, "Unexpected header len for TX: "
216                                "%zd expected %zd\n",
217                                iov_length(vq->hdr, s), hdr_size);
218                         break;
219                 }
220                 /* use msg_control to pass vhost zerocopy ubuf info to skb */
221                 if (zcopy) {
222                         vq->heads[vq->upend_idx].id = head;
223                         if (len < VHOST_GOODCOPY_LEN) {
224                                 /* copy don't need to wait for DMA done */
225                                 vq->heads[vq->upend_idx].len =
226                                                         VHOST_DMA_DONE_LEN;
227                                 msg.msg_control = NULL;
228                                 msg.msg_controllen = 0;
229                                 ubufs = NULL;
230                         } else {
231                                 struct ubuf_info *ubuf = &vq->ubuf_info[head];
232
233                                 vq->heads[vq->upend_idx].len = len;
234                                 ubuf->callback = vhost_zerocopy_callback;
235                                 ubuf->arg = vq->ubufs;
236                                 ubuf->desc = vq->upend_idx;
237                                 msg.msg_control = ubuf;
238                                 msg.msg_controllen = sizeof(ubuf);
239                                 ubufs = vq->ubufs;
240                                 kref_get(&ubufs->kref);
241                         }
242                         vq->upend_idx = (vq->upend_idx + 1) % UIO_MAXIOV;
243                 }
244                 /* TODO: Check specific error and bomb out unless ENOBUFS? */
245                 err = sock->ops->sendmsg(NULL, sock, &msg, len);
246                 if (unlikely(err < 0)) {
247                         if (zcopy) {
248                                 if (ubufs)
249                                         vhost_ubuf_put(ubufs);
250                                 vq->upend_idx = ((unsigned)vq->upend_idx - 1) %
251                                         UIO_MAXIOV;
252                         }
253                         vhost_discard_vq_desc(vq, 1);
254                         tx_poll_start(net, sock);
255                         break;
256                 }
257                 if (err != len)
258                         pr_debug("Truncated TX packet: "
259                                  " len %d != %zd\n", err, len);
260                 if (!zcopy)
261                         vhost_add_used_and_signal(&net->dev, vq, head, 0);
262                 total_len += len;
263                 if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
264                         vhost_poll_queue(&vq->poll);
265                         break;
266                 }
267         }
268
269         mutex_unlock(&vq->mutex);
270 }
271
272 static int peek_head_len(struct sock *sk)
273 {
274         struct sk_buff *head;
275         int len = 0;
276         unsigned long flags;
277
278         spin_lock_irqsave(&sk->sk_receive_queue.lock, flags);
279         head = skb_peek(&sk->sk_receive_queue);
280         if (likely(head))
281                 len = head->len;
282         spin_unlock_irqrestore(&sk->sk_receive_queue.lock, flags);
283         return len;
284 }
285
286 /* This is a multi-buffer version of vhost_get_desc, that works if
287  *      vq has read descriptors only.
288  * @vq          - the relevant virtqueue
289  * @datalen     - data length we'll be reading
290  * @iovcount    - returned count of io vectors we fill
291  * @log         - vhost log
292  * @log_num     - log offset
293  * @quota       - headcount quota, 1 for big buffer
294  *      returns number of buffer heads allocated, negative on error
295  */
296 static int get_rx_bufs(struct vhost_virtqueue *vq,
297                        struct vring_used_elem *heads,
298                        int datalen,
299                        unsigned *iovcount,
300                        struct vhost_log *log,
301                        unsigned *log_num,
302                        unsigned int quota)
303 {
304         unsigned int out, in;
305         int seg = 0;
306         int headcount = 0;
307         unsigned d;
308         int r, nlogs = 0;
309
310         while (datalen > 0 && headcount < quota) {
311                 if (unlikely(seg >= UIO_MAXIOV)) {
312                         r = -ENOBUFS;
313                         goto err;
314                 }
315                 d = vhost_get_vq_desc(vq->dev, vq, vq->iov + seg,
316                                       ARRAY_SIZE(vq->iov) - seg, &out,
317                                       &in, log, log_num);
318                 if (d == vq->num) {
319                         r = 0;
320                         goto err;
321                 }
322                 if (unlikely(out || in <= 0)) {
323                         vq_err(vq, "unexpected descriptor format for RX: "
324                                 "out %d, in %d\n", out, in);
325                         r = -EINVAL;
326                         goto err;
327                 }
328                 if (unlikely(log)) {
329                         nlogs += *log_num;
330                         log += *log_num;
331                 }
332                 heads[headcount].id = d;
333                 heads[headcount].len = iov_length(vq->iov + seg, in);
334                 datalen -= heads[headcount].len;
335                 ++headcount;
336                 seg += in;
337         }
338         heads[headcount - 1].len += datalen;
339         *iovcount = seg;
340         if (unlikely(log))
341                 *log_num = nlogs;
342         return headcount;
343 err:
344         vhost_discard_vq_desc(vq, headcount);
345         return r;
346 }
347
348 /* Expects to be always run from workqueue - which acts as
349  * read-size critical section for our kind of RCU. */
350 static void handle_rx(struct vhost_net *net)
351 {
352         struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_RX];
353         unsigned uninitialized_var(in), log;
354         struct vhost_log *vq_log;
355         struct msghdr msg = {
356                 .msg_name = NULL,
357                 .msg_namelen = 0,
358                 .msg_control = NULL, /* FIXME: get and handle RX aux data. */
359                 .msg_controllen = 0,
360                 .msg_iov = vq->iov,
361                 .msg_flags = MSG_DONTWAIT,
362         };
363         struct virtio_net_hdr_mrg_rxbuf hdr = {
364                 .hdr.flags = 0,
365                 .hdr.gso_type = VIRTIO_NET_HDR_GSO_NONE
366         };
367         size_t total_len = 0;
368         int err, headcount, mergeable;
369         size_t vhost_hlen, sock_hlen;
370         size_t vhost_len, sock_len;
371         /* TODO: check that we are running from vhost_worker? */
372         struct socket *sock = rcu_dereference_check(vq->private_data, 1);
373
374         if (!sock)
375                 return;
376
377         mutex_lock(&vq->mutex);
378         vhost_disable_notify(&net->dev, vq);
379         vhost_hlen = vq->vhost_hlen;
380         sock_hlen = vq->sock_hlen;
381
382         vq_log = unlikely(vhost_has_feature(&net->dev, VHOST_F_LOG_ALL)) ?
383                 vq->log : NULL;
384         mergeable = vhost_has_feature(&net->dev, VIRTIO_NET_F_MRG_RXBUF);
385
386         while ((sock_len = peek_head_len(sock->sk))) {
387                 sock_len += sock_hlen;
388                 vhost_len = sock_len + vhost_hlen;
389                 headcount = get_rx_bufs(vq, vq->heads, vhost_len,
390                                         &in, vq_log, &log,
391                                         likely(mergeable) ? UIO_MAXIOV : 1);
392                 /* On error, stop handling until the next kick. */
393                 if (unlikely(headcount < 0))
394                         break;
395                 /* OK, now we need to know about added descriptors. */
396                 if (!headcount) {
397                         if (unlikely(vhost_enable_notify(&net->dev, vq))) {
398                                 /* They have slipped one in as we were
399                                  * doing that: check again. */
400                                 vhost_disable_notify(&net->dev, vq);
401                                 continue;
402                         }
403                         /* Nothing new?  Wait for eventfd to tell us
404                          * they refilled. */
405                         break;
406                 }
407                 /* We don't need to be notified again. */
408                 if (unlikely((vhost_hlen)))
409                         /* Skip header. TODO: support TSO. */
410                         move_iovec_hdr(vq->iov, vq->hdr, vhost_hlen, in);
411                 else
412                         /* Copy the header for use in VIRTIO_NET_F_MRG_RXBUF:
413                          * needed because recvmsg can modify msg_iov. */
414                         copy_iovec_hdr(vq->iov, vq->hdr, sock_hlen, in);
415                 msg.msg_iovlen = in;
416                 err = sock->ops->recvmsg(NULL, sock, &msg,
417                                          sock_len, MSG_DONTWAIT | MSG_TRUNC);
418                 /* Userspace might have consumed the packet meanwhile:
419                  * it's not supposed to do this usually, but might be hard
420                  * to prevent. Discard data we got (if any) and keep going. */
421                 if (unlikely(err != sock_len)) {
422                         pr_debug("Discarded rx packet: "
423                                  " len %d, expected %zd\n", err, sock_len);
424                         vhost_discard_vq_desc(vq, headcount);
425                         continue;
426                 }
427                 if (unlikely(vhost_hlen) &&
428                     memcpy_toiovecend(vq->hdr, (unsigned char *)&hdr, 0,
429                                       vhost_hlen)) {
430                         vq_err(vq, "Unable to write vnet_hdr at addr %p\n",
431                                vq->iov->iov_base);
432                         break;
433                 }
434                 /* TODO: Should check and handle checksum. */
435                 if (likely(mergeable) &&
436                     memcpy_toiovecend(vq->hdr, (unsigned char *)&headcount,
437                                       offsetof(typeof(hdr), num_buffers),
438                                       sizeof hdr.num_buffers)) {
439                         vq_err(vq, "Failed num_buffers write");
440                         vhost_discard_vq_desc(vq, headcount);
441                         break;
442                 }
443                 vhost_add_used_and_signal_n(&net->dev, vq, vq->heads,
444                                             headcount);
445                 if (unlikely(vq_log))
446                         vhost_log_write(vq, vq_log, log, vhost_len);
447                 total_len += vhost_len;
448                 if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
449                         vhost_poll_queue(&vq->poll);
450                         break;
451                 }
452         }
453
454         mutex_unlock(&vq->mutex);
455 }
456
457 static void handle_tx_kick(struct vhost_work *work)
458 {
459         struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
460                                                   poll.work);
461         struct vhost_net *net = container_of(vq->dev, struct vhost_net, dev);
462
463         handle_tx(net);
464 }
465
466 static void handle_rx_kick(struct vhost_work *work)
467 {
468         struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
469                                                   poll.work);
470         struct vhost_net *net = container_of(vq->dev, struct vhost_net, dev);
471
472         handle_rx(net);
473 }
474
475 static void handle_tx_net(struct vhost_work *work)
476 {
477         struct vhost_net *net = container_of(work, struct vhost_net,
478                                              poll[VHOST_NET_VQ_TX].work);
479         handle_tx(net);
480 }
481
482 static void handle_rx_net(struct vhost_work *work)
483 {
484         struct vhost_net *net = container_of(work, struct vhost_net,
485                                              poll[VHOST_NET_VQ_RX].work);
486         handle_rx(net);
487 }
488
489 static int vhost_net_open(struct inode *inode, struct file *f)
490 {
491         struct vhost_net *n = kmalloc(sizeof *n, GFP_KERNEL);
492         struct vhost_dev *dev;
493         int r;
494
495         if (!n)
496                 return -ENOMEM;
497
498         dev = &n->dev;
499         n->vqs[VHOST_NET_VQ_TX].handle_kick = handle_tx_kick;
500         n->vqs[VHOST_NET_VQ_RX].handle_kick = handle_rx_kick;
501         r = vhost_dev_init(dev, n->vqs, VHOST_NET_VQ_MAX);
502         if (r < 0) {
503                 kfree(n);
504                 return r;
505         }
506
507         vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, POLLOUT, dev);
508         vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, POLLIN, dev);
509         n->tx_poll_state = VHOST_NET_POLL_DISABLED;
510
511         f->private_data = n;
512
513         return 0;
514 }
515
516 static void vhost_net_disable_vq(struct vhost_net *n,
517                                  struct vhost_virtqueue *vq)
518 {
519         if (!vq->private_data)
520                 return;
521         if (vq == n->vqs + VHOST_NET_VQ_TX) {
522                 tx_poll_stop(n);
523                 n->tx_poll_state = VHOST_NET_POLL_DISABLED;
524         } else
525                 vhost_poll_stop(n->poll + VHOST_NET_VQ_RX);
526 }
527
528 static void vhost_net_enable_vq(struct vhost_net *n,
529                                 struct vhost_virtqueue *vq)
530 {
531         struct socket *sock;
532
533         sock = rcu_dereference_protected(vq->private_data,
534                                          lockdep_is_held(&vq->mutex));
535         if (!sock)
536                 return;
537         if (vq == n->vqs + VHOST_NET_VQ_TX) {
538                 n->tx_poll_state = VHOST_NET_POLL_STOPPED;
539                 tx_poll_start(n, sock);
540         } else
541                 vhost_poll_start(n->poll + VHOST_NET_VQ_RX, sock->file);
542 }
543
544 static struct socket *vhost_net_stop_vq(struct vhost_net *n,
545                                         struct vhost_virtqueue *vq)
546 {
547         struct socket *sock;
548
549         mutex_lock(&vq->mutex);
550         sock = rcu_dereference_protected(vq->private_data,
551                                          lockdep_is_held(&vq->mutex));
552         vhost_net_disable_vq(n, vq);
553         rcu_assign_pointer(vq->private_data, NULL);
554         mutex_unlock(&vq->mutex);
555         return sock;
556 }
557
558 static void vhost_net_stop(struct vhost_net *n, struct socket **tx_sock,
559                            struct socket **rx_sock)
560 {
561         *tx_sock = vhost_net_stop_vq(n, n->vqs + VHOST_NET_VQ_TX);
562         *rx_sock = vhost_net_stop_vq(n, n->vqs + VHOST_NET_VQ_RX);
563 }
564
565 static void vhost_net_flush_vq(struct vhost_net *n, int index)
566 {
567         vhost_poll_flush(n->poll + index);
568         vhost_poll_flush(&n->dev.vqs[index].poll);
569 }
570
571 static void vhost_net_flush(struct vhost_net *n)
572 {
573         vhost_net_flush_vq(n, VHOST_NET_VQ_TX);
574         vhost_net_flush_vq(n, VHOST_NET_VQ_RX);
575 }
576
577 static int vhost_net_release(struct inode *inode, struct file *f)
578 {
579         struct vhost_net *n = f->private_data;
580         struct socket *tx_sock;
581         struct socket *rx_sock;
582
583         vhost_net_stop(n, &tx_sock, &rx_sock);
584         vhost_net_flush(n);
585         vhost_dev_cleanup(&n->dev);
586         if (tx_sock)
587                 fput(tx_sock->file);
588         if (rx_sock)
589                 fput(rx_sock->file);
590         /* We do an extra flush before freeing memory,
591          * since jobs can re-queue themselves. */
592         vhost_net_flush(n);
593         kfree(n);
594         return 0;
595 }
596
597 static struct socket *get_raw_socket(int fd)
598 {
599         struct {
600                 struct sockaddr_ll sa;
601                 char  buf[MAX_ADDR_LEN];
602         } uaddr;
603         int uaddr_len = sizeof uaddr, r;
604         struct socket *sock = sockfd_lookup(fd, &r);
605
606         if (!sock)
607                 return ERR_PTR(-ENOTSOCK);
608
609         /* Parameter checking */
610         if (sock->sk->sk_type != SOCK_RAW) {
611                 r = -ESOCKTNOSUPPORT;
612                 goto err;
613         }
614
615         r = sock->ops->getname(sock, (struct sockaddr *)&uaddr.sa,
616                                &uaddr_len, 0);
617         if (r)
618                 goto err;
619
620         if (uaddr.sa.sll_family != AF_PACKET) {
621                 r = -EPFNOSUPPORT;
622                 goto err;
623         }
624         return sock;
625 err:
626         fput(sock->file);
627         return ERR_PTR(r);
628 }
629
630 static struct socket *get_tap_socket(int fd)
631 {
632         struct file *file = fget(fd);
633         struct socket *sock;
634
635         if (!file)
636                 return ERR_PTR(-EBADF);
637         sock = tun_get_socket(file);
638         if (!IS_ERR(sock))
639                 return sock;
640         sock = macvtap_get_socket(file);
641         if (IS_ERR(sock))
642                 fput(file);
643         return sock;
644 }
645
646 static struct socket *get_socket(int fd)
647 {
648         struct socket *sock;
649
650         /* special case to disable backend */
651         if (fd == -1)
652                 return NULL;
653         sock = get_raw_socket(fd);
654         if (!IS_ERR(sock))
655                 return sock;
656         sock = get_tap_socket(fd);
657         if (!IS_ERR(sock))
658                 return sock;
659         return ERR_PTR(-ENOTSOCK);
660 }
661
662 static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
663 {
664         struct socket *sock, *oldsock;
665         struct vhost_virtqueue *vq;
666         struct vhost_ubuf_ref *ubufs, *oldubufs = NULL;
667         int r;
668
669         mutex_lock(&n->dev.mutex);
670         r = vhost_dev_check_owner(&n->dev);
671         if (r)
672                 goto err;
673
674         if (index >= VHOST_NET_VQ_MAX) {
675                 r = -ENOBUFS;
676                 goto err;
677         }
678         vq = n->vqs + index;
679         mutex_lock(&vq->mutex);
680
681         /* Verify that ring has been setup correctly. */
682         if (!vhost_vq_access_ok(vq)) {
683                 r = -EFAULT;
684                 goto err_vq;
685         }
686         sock = get_socket(fd);
687         if (IS_ERR(sock)) {
688                 r = PTR_ERR(sock);
689                 goto err_vq;
690         }
691
692         /* start polling new socket */
693         oldsock = rcu_dereference_protected(vq->private_data,
694                                             lockdep_is_held(&vq->mutex));
695         if (sock != oldsock) {
696                 ubufs = vhost_ubuf_alloc(vq, sock && vhost_sock_zcopy(sock));
697                 if (IS_ERR(ubufs)) {
698                         r = PTR_ERR(ubufs);
699                         goto err_ubufs;
700                 }
701                 oldubufs = vq->ubufs;
702                 vq->ubufs = ubufs;
703                 vhost_net_disable_vq(n, vq);
704                 rcu_assign_pointer(vq->private_data, sock);
705                 vhost_net_enable_vq(n, vq);
706         }
707
708         mutex_unlock(&vq->mutex);
709
710         if (oldubufs)
711                 vhost_ubuf_put_and_wait(oldubufs);
712
713         if (oldsock) {
714                 vhost_net_flush_vq(n, index);
715                 fput(oldsock->file);
716         }
717
718         mutex_unlock(&n->dev.mutex);
719         return 0;
720
721 err_ubufs:
722         fput(sock->file);
723 err_vq:
724         mutex_unlock(&vq->mutex);
725 err:
726         mutex_unlock(&n->dev.mutex);
727         return r;
728 }
729
730 static long vhost_net_reset_owner(struct vhost_net *n)
731 {
732         struct socket *tx_sock = NULL;
733         struct socket *rx_sock = NULL;
734         long err;
735
736         mutex_lock(&n->dev.mutex);
737         err = vhost_dev_check_owner(&n->dev);
738         if (err)
739                 goto done;
740         vhost_net_stop(n, &tx_sock, &rx_sock);
741         vhost_net_flush(n);
742         err = vhost_dev_reset_owner(&n->dev);
743 done:
744         mutex_unlock(&n->dev.mutex);
745         if (tx_sock)
746                 fput(tx_sock->file);
747         if (rx_sock)
748                 fput(rx_sock->file);
749         return err;
750 }
751
752 static int vhost_net_set_features(struct vhost_net *n, u64 features)
753 {
754         size_t vhost_hlen, sock_hlen, hdr_len;
755         int i;
756
757         hdr_len = (features & (1 << VIRTIO_NET_F_MRG_RXBUF)) ?
758                         sizeof(struct virtio_net_hdr_mrg_rxbuf) :
759                         sizeof(struct virtio_net_hdr);
760         if (features & (1 << VHOST_NET_F_VIRTIO_NET_HDR)) {
761                 /* vhost provides vnet_hdr */
762                 vhost_hlen = hdr_len;
763                 sock_hlen = 0;
764         } else {
765                 /* socket provides vnet_hdr */
766                 vhost_hlen = 0;
767                 sock_hlen = hdr_len;
768         }
769         mutex_lock(&n->dev.mutex);
770         if ((features & (1 << VHOST_F_LOG_ALL)) &&
771             !vhost_log_access_ok(&n->dev)) {
772                 mutex_unlock(&n->dev.mutex);
773                 return -EFAULT;
774         }
775         n->dev.acked_features = features;
776         smp_wmb();
777         for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
778                 mutex_lock(&n->vqs[i].mutex);
779                 n->vqs[i].vhost_hlen = vhost_hlen;
780                 n->vqs[i].sock_hlen = sock_hlen;
781                 mutex_unlock(&n->vqs[i].mutex);
782         }
783         vhost_net_flush(n);
784         mutex_unlock(&n->dev.mutex);
785         return 0;
786 }
787
788 static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
789                             unsigned long arg)
790 {
791         struct vhost_net *n = f->private_data;
792         void __user *argp = (void __user *)arg;
793         u64 __user *featurep = argp;
794         struct vhost_vring_file backend;
795         u64 features;
796         int r;
797
798         switch (ioctl) {
799         case VHOST_NET_SET_BACKEND:
800                 if (copy_from_user(&backend, argp, sizeof backend))
801                         return -EFAULT;
802                 return vhost_net_set_backend(n, backend.index, backend.fd);
803         case VHOST_GET_FEATURES:
804                 features = VHOST_FEATURES;
805                 if (copy_to_user(featurep, &features, sizeof features))
806                         return -EFAULT;
807                 return 0;
808         case VHOST_SET_FEATURES:
809                 if (copy_from_user(&features, featurep, sizeof features))
810                         return -EFAULT;
811                 if (features & ~VHOST_FEATURES)
812                         return -EOPNOTSUPP;
813                 return vhost_net_set_features(n, features);
814         case VHOST_RESET_OWNER:
815                 return vhost_net_reset_owner(n);
816         default:
817                 mutex_lock(&n->dev.mutex);
818                 r = vhost_dev_ioctl(&n->dev, ioctl, arg);
819                 vhost_net_flush(n);
820                 mutex_unlock(&n->dev.mutex);
821                 return r;
822         }
823 }
824
825 #ifdef CONFIG_COMPAT
826 static long vhost_net_compat_ioctl(struct file *f, unsigned int ioctl,
827                                    unsigned long arg)
828 {
829         return vhost_net_ioctl(f, ioctl, (unsigned long)compat_ptr(arg));
830 }
831 #endif
832
833 static const struct file_operations vhost_net_fops = {
834         .owner          = THIS_MODULE,
835         .release        = vhost_net_release,
836         .unlocked_ioctl = vhost_net_ioctl,
837 #ifdef CONFIG_COMPAT
838         .compat_ioctl   = vhost_net_compat_ioctl,
839 #endif
840         .open           = vhost_net_open,
841         .llseek         = noop_llseek,
842 };
843
844 static struct miscdevice vhost_net_misc = {
845         MISC_DYNAMIC_MINOR,
846         "vhost-net",
847         &vhost_net_fops,
848 };
849
850 static int vhost_net_init(void)
851 {
852         if (experimental_zcopytx)
853                 vhost_enable_zcopy(VHOST_NET_VQ_TX);
854         return misc_register(&vhost_net_misc);
855 }
856 module_init(vhost_net_init);
857
858 static void vhost_net_exit(void)
859 {
860         misc_deregister(&vhost_net_misc);
861 }
862 module_exit(vhost_net_exit);
863
864 MODULE_VERSION("0.0.1");
865 MODULE_LICENSE("GPL v2");
866 MODULE_AUTHOR("Michael S. Tsirkin");
867 MODULE_DESCRIPTION("Host kernel accelerator for virtio net");