[mirror_ubuntu-focal-kernel.git] / net / 9p / trans_virtio.c

/*
 * The Guest 9p transport driver
 *
 * This is a block based transport driver based on the lguest block driver
 * code.
 *
 */
/*
 *  Copyright (C) 2007 Eric Van Hensbergen, IBM Corporation
 *
 *  Based on virtio console driver
 *  Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to:
 *  Free Software Foundation
 *  51 Franklin Street, Fifth Floor
 *  Boston, MA  02111-1301  USA
 *
 */

#include <linux/in.h>
#include <linux/module.h>
#include <linux/net.h>
#include <linux/ipv6.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/un.h>
#include <linux/uaccess.h>
#include <linux/inet.h>
#include <linux/idr.h>
#include <linux/file.h>
#include <net/9p/9p.h>
#include <linux/parser.h>
#include <net/9p/transport.h>
#include <linux/scatterlist.h>
#include <linux/virtio.h>
#include <linux/virtio_9p.h>

#define VIRTQUEUE_NUM	128

/* a single mutex to manage channel initialization and attachment */
static DECLARE_MUTEX(virtio_9p_lock);
/* global which tracks highest initialized channel */
static int chan_index;

#define P9_INIT_MAXTAG	16

#define REQ_STATUS_IDLE	0
#define REQ_STATUS_SENT 1
#define REQ_STATUS_RCVD 2
#define REQ_STATUS_FLSH 3

struct p9_req_t {
	int status;
	wait_queue_head_t *wq;
};

/* We keep all per-channel information in a structure.
 * This structure is allocated within the devices dev->mem space.
 * A pointer to the structure will get put in the transport private.
 */
static struct virtio_chan {
	bool initialized;		/* channel is initialized */
	bool inuse;			/* channel is in use */

	spinlock_t lock;

	struct virtio_device *vdev;
	struct virtqueue *vq;

	struct p9_idpool *tagpool;
	struct p9_req_t *reqs;
	int max_tag;

	/* Scatterlist: can be too big for stack. */
	struct scatterlist sg[VIRTQUEUE_NUM];
} channels[MAX_9P_CHAN];

/* Lookup requests by tag */
static struct p9_req_t *p9_lookup_tag(struct virtio_chan *c, u16 tag)
{
	/* This looks up the original request by tag so we know which
	 * buffer to read the data into */
	tag++;

	while (tag >= c->max_tag) {
		int old_max = c->max_tag;
		int count;

		if (c->max_tag)
			c->max_tag *= 2;
		else
			c->max_tag = P9_INIT_MAXTAG;

		c->reqs = krealloc(c->reqs, sizeof(struct p9_req_t)*c->max_tag,
								GFP_ATOMIC);
		if (!c->reqs) {
			printk(KERN_ERR "Couldn't grow tag array\n");
			BUG();
		}
		for (count = old_max; count < c->max_tag; count++) {
			c->reqs[count].status = REQ_STATUS_IDLE;
			c->reqs[count].wq = kmalloc(sizeof(wait_queue_t),
								GFP_ATOMIC);
			if (!c->reqs[count].wq) {
				printk(KERN_ERR "Couldn't grow tag array\n");
				BUG();
			}
			init_waitqueue_head(c->reqs[count].wq);
		}
	}

	return &c->reqs[tag];
}


/* How many bytes left in this page. */
static unsigned int rest_of_page(void *data)
{
	return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
}

static int p9_virtio_write(struct p9_trans *trans, void *buf, int count)
{
	/* Only use the rpc mechanism for now */
	return count;
}

static int p9_virtio_read(struct p9_trans *trans, void *buf, int count)
{
	/* Only use the rpc mechanism for now */
	return 0;
}

/* The poll function is used by 9p transports to determine if there
 * is there is activity available on a particular channel.  In our case
 * we use it to wait for a callback from the input routines.
 */
static unsigned int
p9_virtio_poll(struct p9_trans *trans, struct poll_table_struct *pt)
{
	/* Only use the rpc mechanism for now */
	return 0;
}

static void p9_virtio_close(struct p9_trans *trans)
{
	struct virtio_chan *chan = trans->priv;
	int count;
	unsigned int flags;

	spin_lock_irqsave(&chan->lock, flags);
	p9_idpool_destroy(chan->tagpool);
	for (count = 0; count < chan->max_tag; count++)
		kfree(chan->reqs[count].wq);
	kfree(chan->reqs);
	chan->max_tag = 0;
	spin_unlock_irqrestore(&chan->lock, flags);

	down(&virtio_9p_lock);
	chan->inuse = false;
	up(&virtio_9p_lock);

	kfree(trans);
}

static void req_done(struct virtqueue *vq)
{
	struct virtio_chan *chan = vq->vdev->priv;
	struct p9_fcall *rc;
	unsigned int len;
	unsigned long flags;
	struct p9_req_t *req;

	spin_lock_irqsave(&chan->lock, flags);
	while ((rc = chan->vq->vq_ops->get_buf(chan->vq, &len)) != NULL) {
		req = p9_lookup_tag(chan, rc->tag);
		req->status = REQ_STATUS_RCVD;
		wake_up(req->wq);
	}
	/* In case queue is stopped waiting for more buffers. */
	spin_unlock_irqrestore(&chan->lock, flags);
}

static int
pack_sg_list(struct scatterlist *sg, int start, int limit, char *data,
								int count)
{
	int s;
	int index = start;

	while (count) {
		s = rest_of_page(data);
		if (s > count)
			s = count;
		sg_set_buf(&sg[index++], data, s);
		count -= s;
		data += s;
		if (index > limit)
			BUG();
	}

	return index-start;
}

static int
p9_virtio_rpc(struct p9_trans *t, struct p9_fcall *tc, struct p9_fcall **rc,
		int msize, int dotu)
{
	int in, out;
	int n, err, size;
	struct virtio_chan *chan = t->priv;
	char *rdata;
	struct p9_req_t *req;
	unsigned long flags;

	if (*rc == NULL) {
		*rc = kmalloc(sizeof(struct p9_fcall) + msize, GFP_KERNEL);
		if (!*rc)
			return -ENOMEM;
	}

	rdata = (char *)*rc+sizeof(struct p9_fcall);

	spin_lock_irqsave(&chan->lock, flags);
	n = P9_NOTAG;
	if (tc->id != P9_TVERSION) {
		n = p9_idpool_get(chan->tagpool);
		if (n < 0)
			return -ENOMEM;
	}

	req = p9_lookup_tag(chan, n);
	spin_unlock_irqrestore(&chan->lock, flags);

	p9_set_tag(tc, n);

	P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio rpc tag %d\n", n);

	out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, tc->sdata, tc->size);
	in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata, msize);

	req->status = REQ_STATUS_SENT;

	if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, tc)) {
		P9_DPRINTK(P9_DEBUG_TRANS,
			"9p debug: virtio rpc add_buf returned failure");
		return -EIO;
	}

	chan->vq->vq_ops->kick(chan->vq);

	wait_event(*req->wq, req->status == REQ_STATUS_RCVD);

	size = le32_to_cpu(*(__le32 *) rdata);

	err = p9_deserialize_fcall(rdata, size, *rc, dotu);
	if (err < 0) {
		P9_DPRINTK(P9_DEBUG_TRANS,
			"9p debug: virtio rpc deserialize returned %d\n", err);
		return err;
	}

#ifdef CONFIG_NET_9P_DEBUG
	if ((p9_debug_level&P9_DEBUG_FCALL) == P9_DEBUG_FCALL) {
		char buf[150];

		p9_printfcall(buf, sizeof(buf), *rc, dotu);
		printk(KERN_NOTICE ">>> %p %s\n", t, buf);
	}
#endif

	if (n != P9_NOTAG && p9_idpool_check(n, chan->tagpool))
		p9_idpool_put(n, chan->tagpool);

	req->status = REQ_STATUS_IDLE;

	return 0;
}

static int p9_virtio_probe(struct virtio_device *vdev)
{
	int err;
	struct virtio_chan *chan;
	int index;

	down(&virtio_9p_lock);
	index = chan_index++;
	chan = &channels[index];
	up(&virtio_9p_lock);

	if (chan_index > MAX_9P_CHAN) {
		printk(KERN_ERR "9p: virtio: Maximum channels exceeded\n");
		BUG();
		err = -ENOMEM;
		goto fail;
	}

	chan->vdev = vdev;

	/* We expect one virtqueue, for requests. */
	chan->vq = vdev->config->find_vq(vdev, 0, req_done);
	if (IS_ERR(chan->vq)) {
		err = PTR_ERR(chan->vq);
		goto out_free_vq;
	}
	chan->vq->vdev->priv = chan;
	spin_lock_init(&chan->lock);

	sg_init_table(chan->sg, VIRTQUEUE_NUM);

	chan->inuse = false;
	chan->initialized = true;
	return 0;

out_free_vq:
	vdev->config->del_vq(chan->vq);
fail:
	down(&virtio_9p_lock);
	chan_index--;
	up(&virtio_9p_lock);
	return err;
}

/* This sets up a transport channel for 9p communication.  Right now
 * we only match the first available channel, but eventually we couldlook up
 * alternate channels by matching devname versus a virtio_config entry.
 * We use a simple reference count mechanism to ensure that only a single
 * mount has a channel open at a time. */
static struct p9_trans *p9_virtio_create(const char *devname, char *args)
{
	struct p9_trans *trans;
	struct virtio_chan *chan = channels;
	int index = 0;

	down(&virtio_9p_lock);
	while (index < MAX_9P_CHAN) {
		if (chan->initialized && !chan->inuse) {
			chan->inuse = true;
			break;
		} else {
			index++;
			chan = &channels[index];
		}
	}
	up(&virtio_9p_lock);

	if (index >= MAX_9P_CHAN) {
		printk(KERN_ERR "9p: no channels available\n");
		return ERR_PTR(-ENODEV);
	}

	chan->tagpool = p9_idpool_create();
	if (IS_ERR(chan->tagpool)) {
		printk(KERN_ERR "9p: couldn't allocate tagpool\n");
		return ERR_PTR(-ENOMEM);
	}
	p9_idpool_get(chan->tagpool); /* reserve tag 0 */
	chan->max_tag = 0;
	chan->reqs = NULL;

	trans = kmalloc(sizeof(struct p9_trans), GFP_KERNEL);
	if (!trans) {
		printk(KERN_ERR "9p: couldn't allocate transport\n");
		return ERR_PTR(-ENOMEM);
	}

	trans->write = p9_virtio_write;
	trans->read = p9_virtio_read;
	trans->close = p9_virtio_close;
	trans->poll = p9_virtio_poll;
	trans->rpc = p9_virtio_rpc;
	trans->priv = chan;

	return trans;
}

#define VIRTIO_ID_9P 9

static struct virtio_device_id id_table[] = {
	{ VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
	{ 0 },
};

/* The standard "struct lguest_driver": */
static struct virtio_driver p9_virtio_drv = {
	.driver.name = 	KBUILD_MODNAME,
	.driver.owner = THIS_MODULE,
	.id_table =	id_table,
	.probe = 	p9_virtio_probe,
};

static struct p9_trans_module p9_virtio_trans = {
	.name = "virtio",
	.create = p9_virtio_create,
	.maxsize = PAGE_SIZE*16,
	.def = 0,
};

/* The standard init function */
static int __init p9_virtio_init(void)
{
	int count;

	for (count = 0; count < MAX_9P_CHAN; count++)
		channels[count].initialized = false;

	v9fs_register_trans(&p9_virtio_trans);
	return register_virtio_driver(&p9_virtio_drv);
}

module_init(p9_virtio_init);

MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
MODULE_DESCRIPTION("Virtio 9p Transport");
MODULE_LICENSE("GPL");
Commit	Line	Data
b530cc79 EVH	1	/*
	2	* The Guest 9p transport driver
	3	*
e2735b77 EVH	4	* This is a block based transport driver based on the lguest block driver
e2735b77 EVH	5	* code.
b530cc79 EVH	6	*
	7	*/
	8	/*
	9	* Copyright (C) 2007 Eric Van Hensbergen, IBM Corporation
	10	*
	11	* Based on virtio console driver
	12	* Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
	13	*
	14	* This program is free software; you can redistribute it and/or modify
	15	* it under the terms of the GNU General Public License version 2
	16	* as published by the Free Software Foundation.
	17	*
	18	* This program is distributed in the hope that it will be useful,
	19	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	20	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	21	* GNU General Public License for more details.
	22	*
	23	* You should have received a copy of the GNU General Public License
	24	* along with this program; if not, write to:
	25	* Free Software Foundation
	26	* 51 Franklin Street, Fifth Floor
	27	* Boston, MA 02111-1301 USA
	28	*
	29	*/
	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 <net/9p/9p.h>
	43	#include <linux/parser.h>
	44	#include <net/9p/transport.h>
	45	#include <linux/scatterlist.h>
	46	#include <linux/virtio.h>
	47	#include <linux/virtio_9p.h>
	48
e2735b77 EVH	49	#define VIRTQUEUE_NUM 128
e2735b77 EVH	50
b530cc79 EVH	51	/* a single mutex to manage channel initialization and attachment */
	52	static DECLARE_MUTEX(virtio_9p_lock);
	53	/* global which tracks highest initialized channel */
	54	static int chan_index;
	55
e2735b77 EVH	56	#define P9_INIT_MAXTAG 16
	57
	58	#define REQ_STATUS_IDLE 0
	59	#define REQ_STATUS_SENT 1
	60	#define REQ_STATUS_RCVD 2
	61	#define REQ_STATUS_FLSH 3
	62
	63	struct p9_req_t {
	64	int status;
	65	wait_queue_head_t *wq;
	66	};
	67
b530cc79 EVH	68	/* We keep all per-channel information in a structure.
	69	* This structure is allocated within the devices dev->mem space.
	70	* A pointer to the structure will get put in the transport private.
	71	*/
	72	static struct virtio_chan {
	73	bool initialized; /* channel is initialized */
	74	bool inuse; /* channel is in use */
	75
e2735b77 EVH	76	spinlock_t lock;
e2735b77 EVH	77
b530cc79	78	struct virtio_device *vdev;
e2735b77	79	struct virtqueue *vq;
b530cc79	80
e2735b77 EVH	81	struct p9_idpool *tagpool;
	82	struct p9_req_t *reqs;
	83	int max_tag;
b530cc79	84
e2735b77 EVH	85	/* Scatterlist: can be too big for stack. */
e2735b77 EVH	86	struct scatterlist sg[VIRTQUEUE_NUM];
b530cc79 EVH	87	} channels[MAX_9P_CHAN];
b530cc79 EVH	88
e2735b77 EVH	89	/* Lookup requests by tag */
	90	static struct p9_req_t p9_lookup_tag(struct virtio_chan c, u16 tag)
	91	{
	92	/* This looks up the original request by tag so we know which
	93	* buffer to read the data into */
	94	tag++;
	95
	96	while (tag >= c->max_tag) {
	97	int old_max = c->max_tag;
	98	int count;
	99
	100	if (c->max_tag)
	101	c->max_tag *= 2;
	102	else
	103	c->max_tag = P9_INIT_MAXTAG;
	104
	105	c->reqs = krealloc(c->reqs, sizeof(struct p9_req_t)*c->max_tag,
	106	GFP_ATOMIC);
	107	if (!c->reqs) {
	108	printk(KERN_ERR "Couldn't grow tag array\n");
	109	BUG();
	110	}
	111	for (count = old_max; count < c->max_tag; count++) {
	112	c->reqs[count].status = REQ_STATUS_IDLE;
	113	c->reqs[count].wq = kmalloc(sizeof(wait_queue_t),
	114	GFP_ATOMIC);
	115	if (!c->reqs[count].wq) {
	116	printk(KERN_ERR "Couldn't grow tag array\n");
	117	BUG();
	118	}
	119	init_waitqueue_head(c->reqs[count].wq);
	120	}
	121	}
	122
	123	return &c->reqs[tag];
	124	}
	125
	126
b530cc79 EVH	127	/* How many bytes left in this page. */
	128	static unsigned int rest_of_page(void *data)
	129	{
	130	return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
	131	}
	132
	133	static int p9_virtio_write(struct p9_trans trans, void buf, int count)
	134	{
e2735b77 EVH	135	/* Only use the rpc mechanism for now */
	136	return count;
	137	}
b530cc79	138
e2735b77 EVH	139	static int p9_virtio_read(struct p9_trans trans, void buf, int count)
	140	{
	141	/* Only use the rpc mechanism for now */
	142	return 0;
	143	}
b530cc79	144
e2735b77 EVH	145	/* The poll function is used by 9p transports to determine if there
	146	* is there is activity available on a particular channel. In our case
	147	* we use it to wait for a callback from the input routines.
	148	*/
	149	static unsigned int
	150	p9_virtio_poll(struct p9_trans trans, struct poll_table_struct pt)
	151	{
	152	/* Only use the rpc mechanism for now */
	153	return 0;
	154	}
b530cc79	155
e2735b77 EVH	156	static void p9_virtio_close(struct p9_trans *trans)
	157	{
	158	struct virtio_chan *chan = trans->priv;
	159	int count;
	160	unsigned int flags;
b530cc79	161
e2735b77 EVH	162	spin_lock_irqsave(&chan->lock, flags);
	163	p9_idpool_destroy(chan->tagpool);
	164	for (count = 0; count < chan->max_tag; count++)
	165	kfree(chan->reqs[count].wq);
	166	kfree(chan->reqs);
	167	chan->max_tag = 0;
	168	spin_unlock_irqrestore(&chan->lock, flags);
b530cc79	169
e2735b77 EVH	170	down(&virtio_9p_lock);
	171	chan->inuse = false;
	172	up(&virtio_9p_lock);
b530cc79	173
e2735b77	174	kfree(trans);
b530cc79 EVH	175	}
b530cc79 EVH	176
e2735b77	177	static void req_done(struct virtqueue *vq)
b530cc79	178	{
e2735b77 EVH	179	struct virtio_chan *chan = vq->vdev->priv;
	180	struct p9_fcall *rc;
	181	unsigned int len;
	182	unsigned long flags;
	183	struct p9_req_t *req;
	184
	185	spin_lock_irqsave(&chan->lock, flags);
	186	while ((rc = chan->vq->vq_ops->get_buf(chan->vq, &len)) != NULL) {
	187	req = p9_lookup_tag(chan, rc->tag);
	188	req->status = REQ_STATUS_RCVD;
	189	wake_up(req->wq);
	190	}
	191	/* In case queue is stopped waiting for more buffers. */
	192	spin_unlock_irqrestore(&chan->lock, flags);
	193	}
b530cc79	194
e2735b77 EVH	195	static int
	196	pack_sg_list(struct scatterlist sg, int start, int limit, char data,
	197	int count)
	198	{
	199	int s;
	200	int index = start;
	201
	202	while (count) {
	203	s = rest_of_page(data);
	204	if (s > count)
	205	s = count;
	206	sg_set_buf(&sg[index++], data, s);
	207	count -= s;
	208	data += s;
	209	if (index > limit)
	210	BUG();
	211	}
b530cc79	212
e2735b77	213	return index-start;
b530cc79 EVH	214	}
b530cc79 EVH	215
e2735b77 EVH	216	static int
	217	p9_virtio_rpc(struct p9_trans t, struct p9_fcall tc, struct p9_fcall **rc,
	218	int msize, int dotu)
b530cc79	219	{
e2735b77 EVH	220	int in, out;
	221	int n, err, size;
	222	struct virtio_chan *chan = t->priv;
	223	char *rdata;
	224	struct p9_req_t *req;
	225	unsigned long flags;
	226
	227	if (*rc == NULL) {
	228	*rc = kmalloc(sizeof(struct p9_fcall) + msize, GFP_KERNEL);
	229	if (!*rc)
	230	return -ENOMEM;
	231	}
b530cc79	232
e2735b77	233	rdata = (char )rc+sizeof(struct p9_fcall);
b530cc79	234
e2735b77 EVH	235	spin_lock_irqsave(&chan->lock, flags);
	236	n = P9_NOTAG;
	237	if (tc->id != P9_TVERSION) {
	238	n = p9_idpool_get(chan->tagpool);
	239	if (n < 0)
	240	return -ENOMEM;
b530cc79 EVH	241	}
b530cc79 EVH	242
e2735b77 EVH	243	req = p9_lookup_tag(chan, n);
e2735b77 EVH	244	spin_unlock_irqrestore(&chan->lock, flags);
b530cc79	245
e2735b77	246	p9_set_tag(tc, n);
b530cc79	247
e2735b77	248	P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio rpc tag %d\n", n);
b530cc79	249
e2735b77 EVH	250	out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, tc->sdata, tc->size);
e2735b77 EVH	251	in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata, msize);
b530cc79	252
e2735b77	253	req->status = REQ_STATUS_SENT;
b530cc79	254
e2735b77 EVH	255	if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, tc)) {
	256	P9_DPRINTK(P9_DEBUG_TRANS,
	257	"9p debug: virtio rpc add_buf returned failure");
	258	return -EIO;
	259	}
b530cc79	260
e2735b77	261	chan->vq->vq_ops->kick(chan->vq);
b530cc79	262
e2735b77	263	wait_event(*req->wq, req->status == REQ_STATUS_RCVD);
b530cc79	264
e2735b77	265	size = le32_to_cpu((__le32 ) rdata);
b530cc79	266
e2735b77 EVH	267	err = p9_deserialize_fcall(rdata, size, *rc, dotu);
	268	if (err < 0) {
	269	P9_DPRINTK(P9_DEBUG_TRANS,
	270	"9p debug: virtio rpc deserialize returned %d\n", err);
	271	return err;
	272	}
b530cc79	273
e2735b77 EVH	274	#ifdef CONFIG_NET_9P_DEBUG
	275	if ((p9_debug_level&P9_DEBUG_FCALL) == P9_DEBUG_FCALL) {
	276	char buf[150];
b530cc79	277
e2735b77 EVH	278	p9_printfcall(buf, sizeof(buf), *rc, dotu);
	279	printk(KERN_NOTICE ">>> %p %s\n", t, buf);
	280	}
	281	#endif
b530cc79	282
e2735b77 EVH	283	if (n != P9_NOTAG && p9_idpool_check(n, chan->tagpool))
e2735b77 EVH	284	p9_idpool_put(n, chan->tagpool);
b530cc79	285
e2735b77	286	req->status = REQ_STATUS_IDLE;
b530cc79	287
e2735b77	288	return 0;
b530cc79 EVH	289	}
b530cc79 EVH	290
e2735b77	291	static int p9_virtio_probe(struct virtio_device *vdev)
b530cc79 EVH	292	{
	293	int err;
	294	struct virtio_chan *chan;
	295	int index;
	296
	297	down(&virtio_9p_lock);
	298	index = chan_index++;
	299	chan = &channels[index];
	300	up(&virtio_9p_lock);
	301
	302	if (chan_index > MAX_9P_CHAN) {
	303	printk(KERN_ERR "9p: virtio: Maximum channels exceeded\n");
	304	BUG();
b530cc79 EVH	305	err = -ENOMEM;
	306	goto fail;
	307	}
	308
e2735b77	309	chan->vdev = vdev;
b530cc79	310
e2735b77 EVH	311	/* We expect one virtqueue, for requests. */
	312	chan->vq = vdev->config->find_vq(vdev, 0, req_done);
	313	if (IS_ERR(chan->vq)) {
	314	err = PTR_ERR(chan->vq);
	315	goto out_free_vq;
b530cc79	316	}
e2735b77 EVH	317	chan->vq->vdev->priv = chan;
e2735b77 EVH	318	spin_lock_init(&chan->lock);
b530cc79	319
e2735b77	320	sg_init_table(chan->sg, VIRTQUEUE_NUM);
b530cc79	321
b530cc79 EVH	322	chan->inuse = false;
b530cc79 EVH	323	chan->initialized = true;
b530cc79 EVH	324	return 0;
b530cc79 EVH	325
e2735b77 EVH	326	out_free_vq:
e2735b77 EVH	327	vdev->config->del_vq(chan->vq);
b530cc79 EVH	328	fail:
	329	down(&virtio_9p_lock);
	330	chan_index--;
	331	up(&virtio_9p_lock);
	332	return err;
	333	}
	334
	335	/* This sets up a transport channel for 9p communication. Right now
	336	* we only match the first available channel, but eventually we couldlook up
	337	* alternate channels by matching devname versus a virtio_config entry.
	338	* We use a simple reference count mechanism to ensure that only a single
	339	* mount has a channel open at a time. */
	340	static struct p9_trans p9_virtio_create(const char devname, char *args)
	341	{
	342	struct p9_trans *trans;
b530cc79	343	struct virtio_chan *chan = channels;
e2735b77	344	int index = 0;
b530cc79 EVH	345
	346	down(&virtio_9p_lock);
	347	while (index < MAX_9P_CHAN) {
	348	if (chan->initialized && !chan->inuse) {
	349	chan->inuse = true;
	350	break;
	351	} else {
	352	index++;
	353	chan = &channels[index];
	354	}
	355	}
	356	up(&virtio_9p_lock);
	357
	358	if (index >= MAX_9P_CHAN) {
e2735b77 EVH	359	printk(KERN_ERR "9p: no channels available\n");
	360	return ERR_PTR(-ENODEV);
	361	}
	362
	363	chan->tagpool = p9_idpool_create();
	364	if (IS_ERR(chan->tagpool)) {
	365	printk(KERN_ERR "9p: couldn't allocate tagpool\n");
	366	return ERR_PTR(-ENOMEM);
b530cc79	367	}
e2735b77 EVH	368	p9_idpool_get(chan->tagpool); /* reserve tag 0 */
	369	chan->max_tag = 0;
	370	chan->reqs = NULL;
b530cc79 EVH	371
	372	trans = kmalloc(sizeof(struct p9_trans), GFP_KERNEL);
	373	if (!trans) {
	374	printk(KERN_ERR "9p: couldn't allocate transport\n");
	375	return ERR_PTR(-ENOMEM);
	376	}
	377
	378	trans->write = p9_virtio_write;
	379	trans->read = p9_virtio_read;
	380	trans->close = p9_virtio_close;
	381	trans->poll = p9_virtio_poll;
e2735b77	382	trans->rpc = p9_virtio_rpc;
b530cc79 EVH	383	trans->priv = chan;
	384
	385	return trans;
	386	}
	387
	388	#define VIRTIO_ID_9P 9
	389
	390	static struct virtio_device_id id_table[] = {
	391	{ VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
	392	{ 0 },
	393	};
	394
	395	/* The standard "struct lguest_driver": */
	396	static struct virtio_driver p9_virtio_drv = {
	397	.driver.name = KBUILD_MODNAME,
	398	.driver.owner = THIS_MODULE,
	399	.id_table = id_table,
	400	.probe = p9_virtio_probe,
	401	};
	402
	403	static struct p9_trans_module p9_virtio_trans = {
	404	.name = "virtio",
	405	.create = p9_virtio_create,
e2735b77	406	.maxsize = PAGE_SIZE*16,
b530cc79 EVH	407	.def = 0,
	408	};
	409
	410	/* The standard init function */
	411	static int __init p9_virtio_init(void)
	412	{
	413	int count;
	414
	415	for (count = 0; count < MAX_9P_CHAN; count++)
	416	channels[count].initialized = false;
	417
	418	v9fs_register_trans(&p9_virtio_trans);
	419	return register_virtio_driver(&p9_virtio_drv);
	420	}
	421
	422	module_init(p9_virtio_init);
	423
	424	MODULE_DEVICE_TABLE(virtio, id_table);
	425	MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
	426	MODULE_DESCRIPTION("Virtio 9p Transport");
	427	MODULE_LICENSE("GPL");