xref: /openbmc/linux/net/9p/trans_virtio.c (revision e8e0929d)
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_ids.h>
47 #include <linux/virtio_9p.h>
48 
49 #define VIRTQUEUE_NUM	128
50 
51 /* a single mutex to manage channel initialization and attachment */
52 static DEFINE_MUTEX(virtio_9p_lock);
53 /* global which tracks highest initialized channel */
54 static int chan_index;
55 
56 /**
57  * struct virtio_chan - per-instance transport information
58  * @initialized: whether the channel is initialized
59  * @inuse: whether the channel is in use
60  * @lock: protects multiple elements within this structure
61  * @client: client instance
62  * @vdev: virtio dev associated with this channel
63  * @vq: virtio queue associated with this channel
64  * @sg: scatter gather list which is used to pack a request (protected?)
65  *
66  * We keep all per-channel information in a structure.
67  * This structure is allocated within the devices dev->mem space.
68  * A pointer to the structure will get put in the transport private.
69  *
70  */
71 
72 static struct virtio_chan {
73 	bool initialized;
74 	bool inuse;
75 
76 	spinlock_t lock;
77 
78 	struct p9_client *client;
79 	struct virtio_device *vdev;
80 	struct virtqueue *vq;
81 
82 	/* Scatterlist: can be too big for stack. */
83 	struct scatterlist sg[VIRTQUEUE_NUM];
84 } channels[MAX_9P_CHAN];
85 
86 /* How many bytes left in this page. */
87 static unsigned int rest_of_page(void *data)
88 {
89 	return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
90 }
91 
92 /**
93  * p9_virtio_close - reclaim resources of a channel
94  * @client: client instance
95  *
96  * This reclaims a channel by freeing its resources and
97  * reseting its inuse flag.
98  *
99  */
100 
101 static void p9_virtio_close(struct p9_client *client)
102 {
103 	struct virtio_chan *chan = client->trans;
104 
105 	mutex_lock(&virtio_9p_lock);
106 	chan->inuse = false;
107 	mutex_unlock(&virtio_9p_lock);
108 }
109 
110 /**
111  * req_done - callback which signals activity from the server
112  * @vq: virtio queue activity was received on
113  *
114  * This notifies us that the server has triggered some activity
115  * on the virtio channel - most likely a response to request we
116  * sent.  Figure out which requests now have responses and wake up
117  * those threads.
118  *
119  * Bugs: could do with some additional sanity checking, but appears to work.
120  *
121  */
122 
123 static void req_done(struct virtqueue *vq)
124 {
125 	struct virtio_chan *chan = vq->vdev->priv;
126 	struct p9_fcall *rc;
127 	unsigned int len;
128 	struct p9_req_t *req;
129 
130 	P9_DPRINTK(P9_DEBUG_TRANS, ": request done\n");
131 
132 	while ((rc = chan->vq->vq_ops->get_buf(chan->vq, &len)) != NULL) {
133 		P9_DPRINTK(P9_DEBUG_TRANS, ": rc %p\n", rc);
134 		P9_DPRINTK(P9_DEBUG_TRANS, ": lookup tag %d\n", rc->tag);
135 		req = p9_tag_lookup(chan->client, rc->tag);
136 		req->status = REQ_STATUS_RCVD;
137 		p9_client_cb(chan->client, req);
138 	}
139 }
140 
141 /**
142  * pack_sg_list - pack a scatter gather list from a linear buffer
143  * @sg: scatter/gather list to pack into
144  * @start: which segment of the sg_list to start at
145  * @limit: maximum segment to pack data to
146  * @data: data to pack into scatter/gather list
147  * @count: amount of data to pack into the scatter/gather list
148  *
149  * sg_lists have multiple segments of various sizes.  This will pack
150  * arbitrary data into an existing scatter gather list, segmenting the
151  * data as necessary within constraints.
152  *
153  */
154 
155 static int
156 pack_sg_list(struct scatterlist *sg, int start, int limit, char *data,
157 								int count)
158 {
159 	int s;
160 	int index = start;
161 
162 	while (count) {
163 		s = rest_of_page(data);
164 		if (s > count)
165 			s = count;
166 		sg_set_buf(&sg[index++], data, s);
167 		count -= s;
168 		data += s;
169 		BUG_ON(index > limit);
170 	}
171 
172 	return index-start;
173 }
174 
175 /* We don't currently allow canceling of virtio requests */
176 static int p9_virtio_cancel(struct p9_client *client, struct p9_req_t *req)
177 {
178 	return 1;
179 }
180 
181 /**
182  * p9_virtio_request - issue a request
183  * @client: client instance issuing the request
184  * @req: request to be issued
185  *
186  */
187 
188 static int
189 p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
190 {
191 	int in, out;
192 	struct virtio_chan *chan = client->trans;
193 	char *rdata = (char *)req->rc+sizeof(struct p9_fcall);
194 
195 	P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request\n");
196 
197 	out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, req->tc->sdata,
198 								req->tc->size);
199 	in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata,
200 								client->msize);
201 
202 	req->status = REQ_STATUS_SENT;
203 
204 	if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, req->tc) < 0) {
205 		P9_DPRINTK(P9_DEBUG_TRANS,
206 			"9p debug: virtio rpc add_buf returned failure");
207 		return -EIO;
208 	}
209 
210 	chan->vq->vq_ops->kick(chan->vq);
211 
212 	P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request kicked\n");
213 	return 0;
214 }
215 
216 /**
217  * p9_virtio_probe - probe for existence of 9P virtio channels
218  * @vdev: virtio device to probe
219  *
220  * This probes for existing virtio channels.  At present only
221  * a single channel is in use, so in the future more work may need
222  * to be done here.
223  *
224  */
225 
226 static int p9_virtio_probe(struct virtio_device *vdev)
227 {
228 	int err;
229 	struct virtio_chan *chan;
230 	int index;
231 
232 	mutex_lock(&virtio_9p_lock);
233 	index = chan_index++;
234 	chan = &channels[index];
235 	mutex_unlock(&virtio_9p_lock);
236 
237 	if (chan_index > MAX_9P_CHAN) {
238 		printk(KERN_ERR "9p: virtio: Maximum channels exceeded\n");
239 		BUG();
240 		err = -ENOMEM;
241 		goto fail;
242 	}
243 
244 	chan->vdev = vdev;
245 
246 	/* We expect one virtqueue, for requests. */
247 	chan->vq = virtio_find_single_vq(vdev, req_done, "requests");
248 	if (IS_ERR(chan->vq)) {
249 		err = PTR_ERR(chan->vq);
250 		goto out_free_vq;
251 	}
252 	chan->vq->vdev->priv = chan;
253 	spin_lock_init(&chan->lock);
254 
255 	sg_init_table(chan->sg, VIRTQUEUE_NUM);
256 
257 	chan->inuse = false;
258 	chan->initialized = true;
259 	return 0;
260 
261 out_free_vq:
262 	vdev->config->del_vqs(vdev);
263 fail:
264 	mutex_lock(&virtio_9p_lock);
265 	chan_index--;
266 	mutex_unlock(&virtio_9p_lock);
267 	return err;
268 }
269 
270 
271 /**
272  * p9_virtio_create - allocate a new virtio channel
273  * @client: client instance invoking this transport
274  * @devname: string identifying the channel to connect to (unused)
275  * @args: args passed from sys_mount() for per-transport options (unused)
276  *
277  * This sets up a transport channel for 9p communication.  Right now
278  * we only match the first available channel, but eventually we couldlook up
279  * alternate channels by matching devname versus a virtio_config entry.
280  * We use a simple reference count mechanism to ensure that only a single
281  * mount has a channel open at a time.
282  *
283  * Bugs: doesn't allow identification of a specific channel
284  * to allocate, channels are allocated sequentially. This was
285  * a pragmatic decision to get things rolling, but ideally some
286  * way of identifying the channel to attach to would be nice
287  * if we are going to support multiple channels.
288  *
289  */
290 
291 static int
292 p9_virtio_create(struct p9_client *client, const char *devname, char *args)
293 {
294 	struct virtio_chan *chan = channels;
295 	int index = 0;
296 
297 	mutex_lock(&virtio_9p_lock);
298 	while (index < MAX_9P_CHAN) {
299 		if (chan->initialized && !chan->inuse) {
300 			chan->inuse = true;
301 			break;
302 		} else {
303 			index++;
304 			chan = &channels[index];
305 		}
306 	}
307 	mutex_unlock(&virtio_9p_lock);
308 
309 	if (index >= MAX_9P_CHAN) {
310 		printk(KERN_ERR "9p: no channels available\n");
311 		return -ENODEV;
312 	}
313 
314 	client->trans = (void *)chan;
315 	chan->client = client;
316 
317 	return 0;
318 }
319 
320 /**
321  * p9_virtio_remove - clean up resources associated with a virtio device
322  * @vdev: virtio device to remove
323  *
324  */
325 
326 static void p9_virtio_remove(struct virtio_device *vdev)
327 {
328 	struct virtio_chan *chan = vdev->priv;
329 
330 	BUG_ON(chan->inuse);
331 
332 	if (chan->initialized) {
333 		vdev->config->del_vqs(vdev);
334 		chan->initialized = false;
335 	}
336 }
337 
338 static struct virtio_device_id id_table[] = {
339 	{ VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
340 	{ 0 },
341 };
342 
343 /* The standard "struct lguest_driver": */
344 static struct virtio_driver p9_virtio_drv = {
345 	.driver.name = 	KBUILD_MODNAME,
346 	.driver.owner = THIS_MODULE,
347 	.id_table =	id_table,
348 	.probe = 	p9_virtio_probe,
349 	.remove =	p9_virtio_remove,
350 };
351 
352 static struct p9_trans_module p9_virtio_trans = {
353 	.name = "virtio",
354 	.create = p9_virtio_create,
355 	.close = p9_virtio_close,
356 	.request = p9_virtio_request,
357 	.cancel = p9_virtio_cancel,
358 	.maxsize = PAGE_SIZE*16,
359 	.def = 0,
360 	.owner = THIS_MODULE,
361 };
362 
363 /* The standard init function */
364 static int __init p9_virtio_init(void)
365 {
366 	int count;
367 
368 	for (count = 0; count < MAX_9P_CHAN; count++)
369 		channels[count].initialized = false;
370 
371 	v9fs_register_trans(&p9_virtio_trans);
372 	return register_virtio_driver(&p9_virtio_drv);
373 }
374 
375 static void __exit p9_virtio_cleanup(void)
376 {
377 	unregister_virtio_driver(&p9_virtio_drv);
378 	v9fs_unregister_trans(&p9_virtio_trans);
379 }
380 
381 module_init(p9_virtio_init);
382 module_exit(p9_virtio_cleanup);
383 
384 MODULE_DEVICE_TABLE(virtio, id_table);
385 MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
386 MODULE_DESCRIPTION("Virtio 9p Transport");
387 MODULE_LICENSE("GPL");
388