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 if (chan) 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 client->status = Connected; 316 chan->client = client; 317 318 return 0; 319 } 320 321 /** 322 * p9_virtio_remove - clean up resources associated with a virtio device 323 * @vdev: virtio device to remove 324 * 325 */ 326 327 static void p9_virtio_remove(struct virtio_device *vdev) 328 { 329 struct virtio_chan *chan = vdev->priv; 330 331 BUG_ON(chan->inuse); 332 333 if (chan->initialized) { 334 vdev->config->del_vqs(vdev); 335 chan->initialized = false; 336 } 337 } 338 339 static struct virtio_device_id id_table[] = { 340 { VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID }, 341 { 0 }, 342 }; 343 344 /* The standard "struct lguest_driver": */ 345 static struct virtio_driver p9_virtio_drv = { 346 .driver.name = KBUILD_MODNAME, 347 .driver.owner = THIS_MODULE, 348 .id_table = id_table, 349 .probe = p9_virtio_probe, 350 .remove = p9_virtio_remove, 351 }; 352 353 static struct p9_trans_module p9_virtio_trans = { 354 .name = "virtio", 355 .create = p9_virtio_create, 356 .close = p9_virtio_close, 357 .request = p9_virtio_request, 358 .cancel = p9_virtio_cancel, 359 .maxsize = PAGE_SIZE*16, 360 .def = 0, 361 .owner = THIS_MODULE, 362 }; 363 364 /* The standard init function */ 365 static int __init p9_virtio_init(void) 366 { 367 int count; 368 369 for (count = 0; count < MAX_9P_CHAN; count++) 370 channels[count].initialized = false; 371 372 v9fs_register_trans(&p9_virtio_trans); 373 return register_virtio_driver(&p9_virtio_drv); 374 } 375 376 static void __exit p9_virtio_cleanup(void) 377 { 378 unregister_virtio_driver(&p9_virtio_drv); 379 v9fs_unregister_trans(&p9_virtio_trans); 380 } 381 382 module_init(p9_virtio_init); 383 module_exit(p9_virtio_cleanup); 384 385 MODULE_DEVICE_TABLE(virtio, id_table); 386 MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>"); 387 MODULE_DESCRIPTION("Virtio 9p Transport"); 388 MODULE_LICENSE("GPL"); 389