xref: /openbmc/linux/net/9p/trans_virtio.c (revision 9d56dd3b083a3bec56e9da35ce07baca81030b03)
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 #include <linux/in.h>
30 #include <linux/module.h>
31 #include <linux/net.h>
32 #include <linux/ipv6.h>
33 #include <linux/errno.h>
34 #include <linux/kernel.h>
35 #include <linux/un.h>
36 #include <linux/uaccess.h>
37 #include <linux/inet.h>
38 #include <linux/idr.h>
39 #include <linux/file.h>
40 #include <net/9p/9p.h>
41 #include <linux/parser.h>
42 #include <net/9p/client.h>
43 #include <net/9p/transport.h>
44 #include <linux/scatterlist.h>
45 #include <linux/virtio.h>
46 #include <linux/virtio_9p.h>
47 
48 #define VIRTQUEUE_NUM	128
49 
50 /* a single mutex to manage channel initialization and attachment */
51 static DEFINE_MUTEX(virtio_9p_lock);
52 /* global which tracks highest initialized channel */
53 static int chan_index;
54 
55 /**
56  * struct virtio_chan - per-instance transport information
57  * @initialized: whether the channel is initialized
58  * @inuse: whether the channel is in use
59  * @lock: protects multiple elements within this structure
60  * @client: client instance
61  * @vdev: virtio dev associated with this channel
62  * @vq: virtio queue associated with this channel
63  * @sg: scatter gather list which is used to pack a request (protected?)
64  *
65  * We keep all per-channel information in a structure.
66  * This structure is allocated within the devices dev->mem space.
67  * A pointer to the structure will get put in the transport private.
68  *
69  */
70 
71 static struct virtio_chan {
72 	bool initialized;
73 	bool inuse;
74 
75 	spinlock_t lock;
76 
77 	struct p9_client *client;
78 	struct virtio_device *vdev;
79 	struct virtqueue *vq;
80 
81 	/* Scatterlist: can be too big for stack. */
82 	struct scatterlist sg[VIRTQUEUE_NUM];
83 } channels[MAX_9P_CHAN];
84 
85 /* How many bytes left in this page. */
86 static unsigned int rest_of_page(void *data)
87 {
88 	return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
89 }
90 
91 /**
92  * p9_virtio_close - reclaim resources of a channel
93  * @client: client instance
94  *
95  * This reclaims a channel by freeing its resources and
96  * reseting its inuse flag.
97  *
98  */
99 
100 static void p9_virtio_close(struct p9_client *client)
101 {
102 	struct virtio_chan *chan = client->trans;
103 
104 	mutex_lock(&virtio_9p_lock);
105 	chan->inuse = false;
106 	mutex_unlock(&virtio_9p_lock);
107 }
108 
109 /**
110  * req_done - callback which signals activity from the server
111  * @vq: virtio queue activity was received on
112  *
113  * This notifies us that the server has triggered some activity
114  * on the virtio channel - most likely a response to request we
115  * sent.  Figure out which requests now have responses and wake up
116  * those threads.
117  *
118  * Bugs: could do with some additional sanity checking, but appears to work.
119  *
120  */
121 
122 static void req_done(struct virtqueue *vq)
123 {
124 	struct virtio_chan *chan = vq->vdev->priv;
125 	struct p9_fcall *rc;
126 	unsigned int len;
127 	struct p9_req_t *req;
128 
129 	P9_DPRINTK(P9_DEBUG_TRANS, ": request done\n");
130 
131 	while ((rc = chan->vq->vq_ops->get_buf(chan->vq, &len)) != NULL) {
132 		P9_DPRINTK(P9_DEBUG_TRANS, ": rc %p\n", rc);
133 		P9_DPRINTK(P9_DEBUG_TRANS, ": lookup tag %d\n", rc->tag);
134 		req = p9_tag_lookup(chan->client, rc->tag);
135 		req->status = REQ_STATUS_RCVD;
136 		p9_client_cb(chan->client, req);
137 	}
138 }
139 
140 /**
141  * pack_sg_list - pack a scatter gather list from a linear buffer
142  * @sg: scatter/gather list to pack into
143  * @start: which segment of the sg_list to start at
144  * @limit: maximum segment to pack data to
145  * @data: data to pack into scatter/gather list
146  * @count: amount of data to pack into the scatter/gather list
147  *
148  * sg_lists have multiple segments of various sizes.  This will pack
149  * arbitrary data into an existing scatter gather list, segmenting the
150  * data as necessary within constraints.
151  *
152  */
153 
154 static int
155 pack_sg_list(struct scatterlist *sg, int start, int limit, char *data,
156 								int count)
157 {
158 	int s;
159 	int index = start;
160 
161 	while (count) {
162 		s = rest_of_page(data);
163 		if (s > count)
164 			s = count;
165 		sg_set_buf(&sg[index++], data, s);
166 		count -= s;
167 		data += s;
168 		BUG_ON(index > limit);
169 	}
170 
171 	return index-start;
172 }
173 
174 /* We don't currently allow canceling of virtio requests */
175 static int p9_virtio_cancel(struct p9_client *client, struct p9_req_t *req)
176 {
177 	return 1;
178 }
179 
180 /**
181  * p9_virtio_request - issue a request
182  * @client: client instance issuing the request
183  * @req: request to be issued
184  *
185  */
186 
187 static int
188 p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
189 {
190 	int in, out;
191 	struct virtio_chan *chan = client->trans;
192 	char *rdata = (char *)req->rc+sizeof(struct p9_fcall);
193 
194 	P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request\n");
195 
196 	out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, req->tc->sdata,
197 								req->tc->size);
198 	in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata,
199 								client->msize);
200 
201 	req->status = REQ_STATUS_SENT;
202 
203 	if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, req->tc) < 0) {
204 		P9_DPRINTK(P9_DEBUG_TRANS,
205 			"9p debug: virtio rpc add_buf returned failure");
206 		return -EIO;
207 	}
208 
209 	chan->vq->vq_ops->kick(chan->vq);
210 
211 	P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request kicked\n");
212 	return 0;
213 }
214 
215 /**
216  * p9_virtio_probe - probe for existence of 9P virtio channels
217  * @vdev: virtio device to probe
218  *
219  * This probes for existing virtio channels.  At present only
220  * a single channel is in use, so in the future more work may need
221  * to be done here.
222  *
223  */
224 
225 static int p9_virtio_probe(struct virtio_device *vdev)
226 {
227 	int err;
228 	struct virtio_chan *chan;
229 	int index;
230 
231 	mutex_lock(&virtio_9p_lock);
232 	index = chan_index++;
233 	chan = &channels[index];
234 	mutex_unlock(&virtio_9p_lock);
235 
236 	if (chan_index > MAX_9P_CHAN) {
237 		printk(KERN_ERR "9p: virtio: Maximum channels exceeded\n");
238 		BUG();
239 		err = -ENOMEM;
240 		goto fail;
241 	}
242 
243 	chan->vdev = vdev;
244 
245 	/* We expect one virtqueue, for requests. */
246 	chan->vq = virtio_find_single_vq(vdev, req_done, "requests");
247 	if (IS_ERR(chan->vq)) {
248 		err = PTR_ERR(chan->vq);
249 		goto out_free_vq;
250 	}
251 	chan->vq->vdev->priv = chan;
252 	spin_lock_init(&chan->lock);
253 
254 	sg_init_table(chan->sg, VIRTQUEUE_NUM);
255 
256 	chan->inuse = false;
257 	chan->initialized = true;
258 	return 0;
259 
260 out_free_vq:
261 	vdev->config->del_vqs(vdev);
262 fail:
263 	mutex_lock(&virtio_9p_lock);
264 	chan_index--;
265 	mutex_unlock(&virtio_9p_lock);
266 	return err;
267 }
268 
269 
270 /**
271  * p9_virtio_create - allocate a new virtio channel
272  * @client: client instance invoking this transport
273  * @devname: string identifying the channel to connect to (unused)
274  * @args: args passed from sys_mount() for per-transport options (unused)
275  *
276  * This sets up a transport channel for 9p communication.  Right now
277  * we only match the first available channel, but eventually we couldlook up
278  * alternate channels by matching devname versus a virtio_config entry.
279  * We use a simple reference count mechanism to ensure that only a single
280  * mount has a channel open at a time.
281  *
282  * Bugs: doesn't allow identification of a specific channel
283  * to allocate, channels are allocated sequentially. This was
284  * a pragmatic decision to get things rolling, but ideally some
285  * way of identifying the channel to attach to would be nice
286  * if we are going to support multiple channels.
287  *
288  */
289 
290 static int
291 p9_virtio_create(struct p9_client *client, const char *devname, char *args)
292 {
293 	struct virtio_chan *chan = channels;
294 	int index = 0;
295 
296 	mutex_lock(&virtio_9p_lock);
297 	while (index < MAX_9P_CHAN) {
298 		if (chan->initialized && !chan->inuse) {
299 			chan->inuse = true;
300 			break;
301 		} else {
302 			index++;
303 			chan = &channels[index];
304 		}
305 	}
306 	mutex_unlock(&virtio_9p_lock);
307 
308 	if (index >= MAX_9P_CHAN) {
309 		printk(KERN_ERR "9p: no channels available\n");
310 		return -ENODEV;
311 	}
312 
313 	client->trans = (void *)chan;
314 	chan->client = client;
315 
316 	return 0;
317 }
318 
319 /**
320  * p9_virtio_remove - clean up resources associated with a virtio device
321  * @vdev: virtio device to remove
322  *
323  */
324 
325 static void p9_virtio_remove(struct virtio_device *vdev)
326 {
327 	struct virtio_chan *chan = vdev->priv;
328 
329 	BUG_ON(chan->inuse);
330 
331 	if (chan->initialized) {
332 		vdev->config->del_vqs(vdev);
333 		chan->initialized = false;
334 	}
335 }
336 
337 static struct virtio_device_id id_table[] = {
338 	{ VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
339 	{ 0 },
340 };
341 
342 /* The standard "struct lguest_driver": */
343 static struct virtio_driver p9_virtio_drv = {
344 	.driver.name = 	KBUILD_MODNAME,
345 	.driver.owner = THIS_MODULE,
346 	.id_table =	id_table,
347 	.probe = 	p9_virtio_probe,
348 	.remove =	p9_virtio_remove,
349 };
350 
351 static struct p9_trans_module p9_virtio_trans = {
352 	.name = "virtio",
353 	.create = p9_virtio_create,
354 	.close = p9_virtio_close,
355 	.request = p9_virtio_request,
356 	.cancel = p9_virtio_cancel,
357 	.maxsize = PAGE_SIZE*16,
358 	.def = 0,
359 	.owner = THIS_MODULE,
360 };
361 
362 /* The standard init function */
363 static int __init p9_virtio_init(void)
364 {
365 	int count;
366 
367 	for (count = 0; count < MAX_9P_CHAN; count++)
368 		channels[count].initialized = false;
369 
370 	v9fs_register_trans(&p9_virtio_trans);
371 	return register_virtio_driver(&p9_virtio_drv);
372 }
373 
374 static void __exit p9_virtio_cleanup(void)
375 {
376 	unregister_virtio_driver(&p9_virtio_drv);
377 	v9fs_unregister_trans(&p9_virtio_trans);
378 }
379 
380 module_init(p9_virtio_init);
381 module_exit(p9_virtio_cleanup);
382 
383 MODULE_DEVICE_TABLE(virtio, id_table);
384 MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
385 MODULE_DESCRIPTION("Virtio 9p Transport");
386 MODULE_LICENSE("GPL");
387