xref: /openbmc/linux/net/9p/trans_virtio.c (revision f6723b56)
1 /*
2  * The Virtio 9p transport driver
3  *
4  * This is a block based transport driver based on the lguest block driver
5  * code.
6  *
7  *  Copyright (C) 2007, 2008 Eric Van Hensbergen, IBM Corporation
8  *
9  *  Based on virtio console driver
10  *  Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
11  *
12  *  This program is free software; you can redistribute it and/or modify
13  *  it under the terms of the GNU General Public License version 2
14  *  as published by the Free Software Foundation.
15  *
16  *  This program is distributed in the hope that it will be useful,
17  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
18  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
19  *  GNU General Public License for more details.
20  *
21  *  You should have received a copy of the GNU General Public License
22  *  along with this program; if not, write to:
23  *  Free Software Foundation
24  *  51 Franklin Street, Fifth Floor
25  *  Boston, MA  02111-1301  USA
26  *
27  */
28 
29 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
30 
31 #include <linux/in.h>
32 #include <linux/module.h>
33 #include <linux/net.h>
34 #include <linux/ipv6.h>
35 #include <linux/errno.h>
36 #include <linux/kernel.h>
37 #include <linux/un.h>
38 #include <linux/uaccess.h>
39 #include <linux/inet.h>
40 #include <linux/idr.h>
41 #include <linux/file.h>
42 #include <linux/highmem.h>
43 #include <linux/slab.h>
44 #include <net/9p/9p.h>
45 #include <linux/parser.h>
46 #include <net/9p/client.h>
47 #include <net/9p/transport.h>
48 #include <linux/scatterlist.h>
49 #include <linux/swap.h>
50 #include <linux/virtio.h>
51 #include <linux/virtio_9p.h>
52 #include "trans_common.h"
53 
54 #define VIRTQUEUE_NUM	128
55 
56 /* a single mutex to manage channel initialization and attachment */
57 static DEFINE_MUTEX(virtio_9p_lock);
58 static DECLARE_WAIT_QUEUE_HEAD(vp_wq);
59 static atomic_t vp_pinned = ATOMIC_INIT(0);
60 
61 /**
62  * struct virtio_chan - per-instance transport information
63  * @initialized: whether the channel is initialized
64  * @inuse: whether the channel is in use
65  * @lock: protects multiple elements within this structure
66  * @client: client instance
67  * @vdev: virtio dev associated with this channel
68  * @vq: virtio queue associated with this channel
69  * @sg: scatter gather list which is used to pack a request (protected?)
70  *
71  * We keep all per-channel information in a structure.
72  * This structure is allocated within the devices dev->mem space.
73  * A pointer to the structure will get put in the transport private.
74  *
75  */
76 
77 struct virtio_chan {
78 	bool inuse;
79 
80 	spinlock_t lock;
81 
82 	struct p9_client *client;
83 	struct virtio_device *vdev;
84 	struct virtqueue *vq;
85 	int ring_bufs_avail;
86 	wait_queue_head_t *vc_wq;
87 	/* This is global limit. Since we don't have a global structure,
88 	 * will be placing it in each channel.
89 	 */
90 	unsigned long p9_max_pages;
91 	/* Scatterlist: can be too big for stack. */
92 	struct scatterlist sg[VIRTQUEUE_NUM];
93 
94 	int tag_len;
95 	/*
96 	 * tag name to identify a mount Non-null terminated
97 	 */
98 	char *tag;
99 
100 	struct list_head chan_list;
101 };
102 
103 static struct list_head virtio_chan_list;
104 
105 /* How many bytes left in this page. */
106 static unsigned int rest_of_page(void *data)
107 {
108 	return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
109 }
110 
111 /**
112  * p9_virtio_close - reclaim resources of a channel
113  * @client: client instance
114  *
115  * This reclaims a channel by freeing its resources and
116  * reseting its inuse flag.
117  *
118  */
119 
120 static void p9_virtio_close(struct p9_client *client)
121 {
122 	struct virtio_chan *chan = client->trans;
123 
124 	mutex_lock(&virtio_9p_lock);
125 	if (chan)
126 		chan->inuse = false;
127 	mutex_unlock(&virtio_9p_lock);
128 }
129 
130 /**
131  * req_done - callback which signals activity from the server
132  * @vq: virtio queue activity was received on
133  *
134  * This notifies us that the server has triggered some activity
135  * on the virtio channel - most likely a response to request we
136  * sent.  Figure out which requests now have responses and wake up
137  * those threads.
138  *
139  * Bugs: could do with some additional sanity checking, but appears to work.
140  *
141  */
142 
143 static void req_done(struct virtqueue *vq)
144 {
145 	struct virtio_chan *chan = vq->vdev->priv;
146 	struct p9_fcall *rc;
147 	unsigned int len;
148 	struct p9_req_t *req;
149 	unsigned long flags;
150 
151 	p9_debug(P9_DEBUG_TRANS, ": request done\n");
152 
153 	while (1) {
154 		spin_lock_irqsave(&chan->lock, flags);
155 		rc = virtqueue_get_buf(chan->vq, &len);
156 		if (rc == NULL) {
157 			spin_unlock_irqrestore(&chan->lock, flags);
158 			break;
159 		}
160 		chan->ring_bufs_avail = 1;
161 		spin_unlock_irqrestore(&chan->lock, flags);
162 		/* Wakeup if anyone waiting for VirtIO ring space. */
163 		wake_up(chan->vc_wq);
164 		p9_debug(P9_DEBUG_TRANS, ": rc %p\n", rc);
165 		p9_debug(P9_DEBUG_TRANS, ": lookup tag %d\n", rc->tag);
166 		req = p9_tag_lookup(chan->client, rc->tag);
167 		req->status = REQ_STATUS_RCVD;
168 		p9_client_cb(chan->client, req);
169 	}
170 }
171 
172 /**
173  * pack_sg_list - pack a scatter gather list from a linear buffer
174  * @sg: scatter/gather list to pack into
175  * @start: which segment of the sg_list to start at
176  * @limit: maximum segment to pack data to
177  * @data: data to pack into scatter/gather list
178  * @count: amount of data to pack into the scatter/gather list
179  *
180  * sg_lists have multiple segments of various sizes.  This will pack
181  * arbitrary data into an existing scatter gather list, segmenting the
182  * data as necessary within constraints.
183  *
184  */
185 
186 static int pack_sg_list(struct scatterlist *sg, int start,
187 			int limit, char *data, int count)
188 {
189 	int s;
190 	int index = start;
191 
192 	while (count) {
193 		s = rest_of_page(data);
194 		if (s > count)
195 			s = count;
196 		BUG_ON(index > limit);
197 		/* Make sure we don't terminate early. */
198 		sg_unmark_end(&sg[index]);
199 		sg_set_buf(&sg[index++], data, s);
200 		count -= s;
201 		data += s;
202 	}
203 	if (index-start)
204 		sg_mark_end(&sg[index - 1]);
205 	return index-start;
206 }
207 
208 /* We don't currently allow canceling of virtio requests */
209 static int p9_virtio_cancel(struct p9_client *client, struct p9_req_t *req)
210 {
211 	return 1;
212 }
213 
214 /**
215  * pack_sg_list_p - Just like pack_sg_list. Instead of taking a buffer,
216  * this takes a list of pages.
217  * @sg: scatter/gather list to pack into
218  * @start: which segment of the sg_list to start at
219  * @pdata: a list of pages to add into sg.
220  * @nr_pages: number of pages to pack into the scatter/gather list
221  * @data: data to pack into scatter/gather list
222  * @count: amount of data to pack into the scatter/gather list
223  */
224 static int
225 pack_sg_list_p(struct scatterlist *sg, int start, int limit,
226 	       struct page **pdata, int nr_pages, char *data, int count)
227 {
228 	int i = 0, s;
229 	int data_off;
230 	int index = start;
231 
232 	BUG_ON(nr_pages > (limit - start));
233 	/*
234 	 * if the first page doesn't start at
235 	 * page boundary find the offset
236 	 */
237 	data_off = offset_in_page(data);
238 	while (nr_pages) {
239 		s = rest_of_page(data);
240 		if (s > count)
241 			s = count;
242 		/* Make sure we don't terminate early. */
243 		sg_unmark_end(&sg[index]);
244 		sg_set_page(&sg[index++], pdata[i++], s, data_off);
245 		data_off = 0;
246 		data += s;
247 		count -= s;
248 		nr_pages--;
249 	}
250 
251 	if (index-start)
252 		sg_mark_end(&sg[index - 1]);
253 	return index - start;
254 }
255 
256 /**
257  * p9_virtio_request - issue a request
258  * @client: client instance issuing the request
259  * @req: request to be issued
260  *
261  */
262 
263 static int
264 p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
265 {
266 	int err;
267 	int in, out, out_sgs, in_sgs;
268 	unsigned long flags;
269 	struct virtio_chan *chan = client->trans;
270 	struct scatterlist *sgs[2];
271 
272 	p9_debug(P9_DEBUG_TRANS, "9p debug: virtio request\n");
273 
274 	req->status = REQ_STATUS_SENT;
275 req_retry:
276 	spin_lock_irqsave(&chan->lock, flags);
277 
278 	out_sgs = in_sgs = 0;
279 	/* Handle out VirtIO ring buffers */
280 	out = pack_sg_list(chan->sg, 0,
281 			   VIRTQUEUE_NUM, req->tc->sdata, req->tc->size);
282 	if (out)
283 		sgs[out_sgs++] = chan->sg;
284 
285 	in = pack_sg_list(chan->sg, out,
286 			  VIRTQUEUE_NUM, req->rc->sdata, req->rc->capacity);
287 	if (in)
288 		sgs[out_sgs + in_sgs++] = chan->sg + out;
289 
290 	err = virtqueue_add_sgs(chan->vq, sgs, out_sgs, in_sgs, req->tc,
291 				GFP_ATOMIC);
292 	if (err < 0) {
293 		if (err == -ENOSPC) {
294 			chan->ring_bufs_avail = 0;
295 			spin_unlock_irqrestore(&chan->lock, flags);
296 			err = wait_event_interruptible(*chan->vc_wq,
297 							chan->ring_bufs_avail);
298 			if (err  == -ERESTARTSYS)
299 				return err;
300 
301 			p9_debug(P9_DEBUG_TRANS, "Retry virtio request\n");
302 			goto req_retry;
303 		} else {
304 			spin_unlock_irqrestore(&chan->lock, flags);
305 			p9_debug(P9_DEBUG_TRANS,
306 				 "virtio rpc add_sgs returned failure\n");
307 			return -EIO;
308 		}
309 	}
310 	virtqueue_kick(chan->vq);
311 	spin_unlock_irqrestore(&chan->lock, flags);
312 
313 	p9_debug(P9_DEBUG_TRANS, "virtio request kicked\n");
314 	return 0;
315 }
316 
317 static int p9_get_mapped_pages(struct virtio_chan *chan,
318 			       struct page **pages, char *data,
319 			       int nr_pages, int write, int kern_buf)
320 {
321 	int err;
322 	if (!kern_buf) {
323 		/*
324 		 * We allow only p9_max_pages pinned. We wait for the
325 		 * Other zc request to finish here
326 		 */
327 		if (atomic_read(&vp_pinned) >= chan->p9_max_pages) {
328 			err = wait_event_interruptible(vp_wq,
329 			      (atomic_read(&vp_pinned) < chan->p9_max_pages));
330 			if (err == -ERESTARTSYS)
331 				return err;
332 		}
333 		err = p9_payload_gup(data, &nr_pages, pages, write);
334 		if (err < 0)
335 			return err;
336 		atomic_add(nr_pages, &vp_pinned);
337 	} else {
338 		/* kernel buffer, no need to pin pages */
339 		int s, index = 0;
340 		int count = nr_pages;
341 		while (nr_pages) {
342 			s = rest_of_page(data);
343 			if (is_vmalloc_addr(data))
344 				pages[index++] = vmalloc_to_page(data);
345 			else
346 				pages[index++] = kmap_to_page(data);
347 			data += s;
348 			nr_pages--;
349 		}
350 		nr_pages = count;
351 	}
352 	return nr_pages;
353 }
354 
355 /**
356  * p9_virtio_zc_request - issue a zero copy request
357  * @client: client instance issuing the request
358  * @req: request to be issued
359  * @uidata: user bffer that should be ued for zero copy read
360  * @uodata: user buffer that shoud be user for zero copy write
361  * @inlen: read buffer size
362  * @olen: write buffer size
363  * @hdrlen: reader header size, This is the size of response protocol data
364  *
365  */
366 static int
367 p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
368 		     char *uidata, char *uodata, int inlen,
369 		     int outlen, int in_hdr_len, int kern_buf)
370 {
371 	int in, out, err, out_sgs, in_sgs;
372 	unsigned long flags;
373 	int in_nr_pages = 0, out_nr_pages = 0;
374 	struct page **in_pages = NULL, **out_pages = NULL;
375 	struct virtio_chan *chan = client->trans;
376 	struct scatterlist *sgs[4];
377 
378 	p9_debug(P9_DEBUG_TRANS, "virtio request\n");
379 
380 	if (uodata) {
381 		out_nr_pages = p9_nr_pages(uodata, outlen);
382 		out_pages = kmalloc(sizeof(struct page *) * out_nr_pages,
383 				    GFP_NOFS);
384 		if (!out_pages) {
385 			err = -ENOMEM;
386 			goto err_out;
387 		}
388 		out_nr_pages = p9_get_mapped_pages(chan, out_pages, uodata,
389 						   out_nr_pages, 0, kern_buf);
390 		if (out_nr_pages < 0) {
391 			err = out_nr_pages;
392 			kfree(out_pages);
393 			out_pages = NULL;
394 			goto err_out;
395 		}
396 	}
397 	if (uidata) {
398 		in_nr_pages = p9_nr_pages(uidata, inlen);
399 		in_pages = kmalloc(sizeof(struct page *) * in_nr_pages,
400 				   GFP_NOFS);
401 		if (!in_pages) {
402 			err = -ENOMEM;
403 			goto err_out;
404 		}
405 		in_nr_pages = p9_get_mapped_pages(chan, in_pages, uidata,
406 						  in_nr_pages, 1, kern_buf);
407 		if (in_nr_pages < 0) {
408 			err = in_nr_pages;
409 			kfree(in_pages);
410 			in_pages = NULL;
411 			goto err_out;
412 		}
413 	}
414 	req->status = REQ_STATUS_SENT;
415 req_retry_pinned:
416 	spin_lock_irqsave(&chan->lock, flags);
417 
418 	out_sgs = in_sgs = 0;
419 
420 	/* out data */
421 	out = pack_sg_list(chan->sg, 0,
422 			   VIRTQUEUE_NUM, req->tc->sdata, req->tc->size);
423 
424 	if (out)
425 		sgs[out_sgs++] = chan->sg;
426 
427 	if (out_pages) {
428 		sgs[out_sgs++] = chan->sg + out;
429 		out += pack_sg_list_p(chan->sg, out, VIRTQUEUE_NUM,
430 				      out_pages, out_nr_pages, uodata, outlen);
431 	}
432 
433 	/*
434 	 * Take care of in data
435 	 * For example TREAD have 11.
436 	 * 11 is the read/write header = PDU Header(7) + IO Size (4).
437 	 * Arrange in such a way that server places header in the
438 	 * alloced memory and payload onto the user buffer.
439 	 */
440 	in = pack_sg_list(chan->sg, out,
441 			  VIRTQUEUE_NUM, req->rc->sdata, in_hdr_len);
442 	if (in)
443 		sgs[out_sgs + in_sgs++] = chan->sg + out;
444 
445 	if (in_pages) {
446 		sgs[out_sgs + in_sgs++] = chan->sg + out + in;
447 		in += pack_sg_list_p(chan->sg, out + in, VIRTQUEUE_NUM,
448 				     in_pages, in_nr_pages, uidata, inlen);
449 	}
450 
451 	BUG_ON(out_sgs + in_sgs > ARRAY_SIZE(sgs));
452 	err = virtqueue_add_sgs(chan->vq, sgs, out_sgs, in_sgs, req->tc,
453 				GFP_ATOMIC);
454 	if (err < 0) {
455 		if (err == -ENOSPC) {
456 			chan->ring_bufs_avail = 0;
457 			spin_unlock_irqrestore(&chan->lock, flags);
458 			err = wait_event_interruptible(*chan->vc_wq,
459 						       chan->ring_bufs_avail);
460 			if (err  == -ERESTARTSYS)
461 				goto err_out;
462 
463 			p9_debug(P9_DEBUG_TRANS, "Retry virtio request\n");
464 			goto req_retry_pinned;
465 		} else {
466 			spin_unlock_irqrestore(&chan->lock, flags);
467 			p9_debug(P9_DEBUG_TRANS,
468 				 "virtio rpc add_sgs returned failure\n");
469 			err = -EIO;
470 			goto err_out;
471 		}
472 	}
473 	virtqueue_kick(chan->vq);
474 	spin_unlock_irqrestore(&chan->lock, flags);
475 	p9_debug(P9_DEBUG_TRANS, "virtio request kicked\n");
476 	err = wait_event_interruptible(*req->wq,
477 				       req->status >= REQ_STATUS_RCVD);
478 	/*
479 	 * Non kernel buffers are pinned, unpin them
480 	 */
481 err_out:
482 	if (!kern_buf) {
483 		if (in_pages) {
484 			p9_release_pages(in_pages, in_nr_pages);
485 			atomic_sub(in_nr_pages, &vp_pinned);
486 		}
487 		if (out_pages) {
488 			p9_release_pages(out_pages, out_nr_pages);
489 			atomic_sub(out_nr_pages, &vp_pinned);
490 		}
491 		/* wakeup anybody waiting for slots to pin pages */
492 		wake_up(&vp_wq);
493 	}
494 	kfree(in_pages);
495 	kfree(out_pages);
496 	return err;
497 }
498 
499 static ssize_t p9_mount_tag_show(struct device *dev,
500 				struct device_attribute *attr, char *buf)
501 {
502 	struct virtio_chan *chan;
503 	struct virtio_device *vdev;
504 
505 	vdev = dev_to_virtio(dev);
506 	chan = vdev->priv;
507 
508 	return snprintf(buf, chan->tag_len + 1, "%s", chan->tag);
509 }
510 
511 static DEVICE_ATTR(mount_tag, 0444, p9_mount_tag_show, NULL);
512 
513 /**
514  * p9_virtio_probe - probe for existence of 9P virtio channels
515  * @vdev: virtio device to probe
516  *
517  * This probes for existing virtio channels.
518  *
519  */
520 
521 static int p9_virtio_probe(struct virtio_device *vdev)
522 {
523 	__u16 tag_len;
524 	char *tag;
525 	int err;
526 	struct virtio_chan *chan;
527 
528 	chan = kmalloc(sizeof(struct virtio_chan), GFP_KERNEL);
529 	if (!chan) {
530 		pr_err("Failed to allocate virtio 9P channel\n");
531 		err = -ENOMEM;
532 		goto fail;
533 	}
534 
535 	chan->vdev = vdev;
536 
537 	/* We expect one virtqueue, for requests. */
538 	chan->vq = virtio_find_single_vq(vdev, req_done, "requests");
539 	if (IS_ERR(chan->vq)) {
540 		err = PTR_ERR(chan->vq);
541 		goto out_free_vq;
542 	}
543 	chan->vq->vdev->priv = chan;
544 	spin_lock_init(&chan->lock);
545 
546 	sg_init_table(chan->sg, VIRTQUEUE_NUM);
547 
548 	chan->inuse = false;
549 	if (virtio_has_feature(vdev, VIRTIO_9P_MOUNT_TAG)) {
550 		virtio_cread(vdev, struct virtio_9p_config, tag_len, &tag_len);
551 	} else {
552 		err = -EINVAL;
553 		goto out_free_vq;
554 	}
555 	tag = kmalloc(tag_len, GFP_KERNEL);
556 	if (!tag) {
557 		err = -ENOMEM;
558 		goto out_free_vq;
559 	}
560 
561 	virtio_cread_bytes(vdev, offsetof(struct virtio_9p_config, tag),
562 			   tag, tag_len);
563 	chan->tag = tag;
564 	chan->tag_len = tag_len;
565 	err = sysfs_create_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
566 	if (err) {
567 		goto out_free_tag;
568 	}
569 	chan->vc_wq = kmalloc(sizeof(wait_queue_head_t), GFP_KERNEL);
570 	if (!chan->vc_wq) {
571 		err = -ENOMEM;
572 		goto out_free_tag;
573 	}
574 	init_waitqueue_head(chan->vc_wq);
575 	chan->ring_bufs_avail = 1;
576 	/* Ceiling limit to avoid denial of service attacks */
577 	chan->p9_max_pages = nr_free_buffer_pages()/4;
578 
579 	mutex_lock(&virtio_9p_lock);
580 	list_add_tail(&chan->chan_list, &virtio_chan_list);
581 	mutex_unlock(&virtio_9p_lock);
582 
583 	/* Let udev rules use the new mount_tag attribute. */
584 	kobject_uevent(&(vdev->dev.kobj), KOBJ_CHANGE);
585 
586 	return 0;
587 
588 out_free_tag:
589 	kfree(tag);
590 out_free_vq:
591 	vdev->config->del_vqs(vdev);
592 	kfree(chan);
593 fail:
594 	return err;
595 }
596 
597 
598 /**
599  * p9_virtio_create - allocate a new virtio channel
600  * @client: client instance invoking this transport
601  * @devname: string identifying the channel to connect to (unused)
602  * @args: args passed from sys_mount() for per-transport options (unused)
603  *
604  * This sets up a transport channel for 9p communication.  Right now
605  * we only match the first available channel, but eventually we couldlook up
606  * alternate channels by matching devname versus a virtio_config entry.
607  * We use a simple reference count mechanism to ensure that only a single
608  * mount has a channel open at a time.
609  *
610  */
611 
612 static int
613 p9_virtio_create(struct p9_client *client, const char *devname, char *args)
614 {
615 	struct virtio_chan *chan;
616 	int ret = -ENOENT;
617 	int found = 0;
618 
619 	mutex_lock(&virtio_9p_lock);
620 	list_for_each_entry(chan, &virtio_chan_list, chan_list) {
621 		if (!strncmp(devname, chan->tag, chan->tag_len) &&
622 		    strlen(devname) == chan->tag_len) {
623 			if (!chan->inuse) {
624 				chan->inuse = true;
625 				found = 1;
626 				break;
627 			}
628 			ret = -EBUSY;
629 		}
630 	}
631 	mutex_unlock(&virtio_9p_lock);
632 
633 	if (!found) {
634 		pr_err("no channels available\n");
635 		return ret;
636 	}
637 
638 	client->trans = (void *)chan;
639 	client->status = Connected;
640 	chan->client = client;
641 
642 	return 0;
643 }
644 
645 /**
646  * p9_virtio_remove - clean up resources associated with a virtio device
647  * @vdev: virtio device to remove
648  *
649  */
650 
651 static void p9_virtio_remove(struct virtio_device *vdev)
652 {
653 	struct virtio_chan *chan = vdev->priv;
654 
655 	if (chan->inuse)
656 		p9_virtio_close(chan->client);
657 	vdev->config->del_vqs(vdev);
658 
659 	mutex_lock(&virtio_9p_lock);
660 	list_del(&chan->chan_list);
661 	mutex_unlock(&virtio_9p_lock);
662 	sysfs_remove_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
663 	kobject_uevent(&(vdev->dev.kobj), KOBJ_CHANGE);
664 	kfree(chan->tag);
665 	kfree(chan->vc_wq);
666 	kfree(chan);
667 
668 }
669 
670 static struct virtio_device_id id_table[] = {
671 	{ VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
672 	{ 0 },
673 };
674 
675 static unsigned int features[] = {
676 	VIRTIO_9P_MOUNT_TAG,
677 };
678 
679 /* The standard "struct lguest_driver": */
680 static struct virtio_driver p9_virtio_drv = {
681 	.feature_table  = features,
682 	.feature_table_size = ARRAY_SIZE(features),
683 	.driver.name    = KBUILD_MODNAME,
684 	.driver.owner	= THIS_MODULE,
685 	.id_table	= id_table,
686 	.probe		= p9_virtio_probe,
687 	.remove		= p9_virtio_remove,
688 };
689 
690 static struct p9_trans_module p9_virtio_trans = {
691 	.name = "virtio",
692 	.create = p9_virtio_create,
693 	.close = p9_virtio_close,
694 	.request = p9_virtio_request,
695 	.zc_request = p9_virtio_zc_request,
696 	.cancel = p9_virtio_cancel,
697 	/*
698 	 * We leave one entry for input and one entry for response
699 	 * headers. We also skip one more entry to accomodate, address
700 	 * that are not at page boundary, that can result in an extra
701 	 * page in zero copy.
702 	 */
703 	.maxsize = PAGE_SIZE * (VIRTQUEUE_NUM - 3),
704 	.def = 1,
705 	.owner = THIS_MODULE,
706 };
707 
708 /* The standard init function */
709 static int __init p9_virtio_init(void)
710 {
711 	INIT_LIST_HEAD(&virtio_chan_list);
712 
713 	v9fs_register_trans(&p9_virtio_trans);
714 	return register_virtio_driver(&p9_virtio_drv);
715 }
716 
717 static void __exit p9_virtio_cleanup(void)
718 {
719 	unregister_virtio_driver(&p9_virtio_drv);
720 	v9fs_unregister_trans(&p9_virtio_trans);
721 }
722 
723 module_init(p9_virtio_init);
724 module_exit(p9_virtio_cleanup);
725 
726 MODULE_DEVICE_TABLE(virtio, id_table);
727 MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
728 MODULE_DESCRIPTION("Virtio 9p Transport");
729 MODULE_LICENSE("GPL");
730