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 * @vdev: virtio dev associated with this channel 61 * @vq: virtio queue associated with this channel 62 * @tagpool: accounting for tag ids (and request slots) 63 * @reqs: array of request slots 64 * @max_tag: current number of request_slots allocated 65 * @sg: scatter gather list which is used to pack a request (protected?) 66 * 67 * We keep all per-channel information in a structure. 68 * This structure is allocated within the devices dev->mem space. 69 * A pointer to the structure will get put in the transport private. 70 * 71 */ 72 73 static struct virtio_chan { 74 bool initialized; 75 bool inuse; 76 77 spinlock_t lock; 78 79 struct p9_client *client; 80 struct virtio_device *vdev; 81 struct virtqueue *vq; 82 83 /* Scatterlist: can be too big for stack. */ 84 struct scatterlist sg[VIRTQUEUE_NUM]; 85 } channels[MAX_9P_CHAN]; 86 87 /* How many bytes left in this page. */ 88 static unsigned int rest_of_page(void *data) 89 { 90 return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE); 91 } 92 93 /** 94 * p9_virtio_close - reclaim resources of a channel 95 * @trans: transport state 96 * 97 * This reclaims a channel by freeing its resources and 98 * reseting its inuse flag. 99 * 100 */ 101 102 static void p9_virtio_close(struct p9_client *client) 103 { 104 struct virtio_chan *chan = client->trans; 105 106 mutex_lock(&virtio_9p_lock); 107 chan->inuse = false; 108 mutex_unlock(&virtio_9p_lock); 109 } 110 111 /** 112 * req_done - callback which signals activity from the server 113 * @vq: virtio queue activity was received on 114 * 115 * This notifies us that the server has triggered some activity 116 * on the virtio channel - most likely a response to request we 117 * sent. Figure out which requests now have responses and wake up 118 * those threads. 119 * 120 * Bugs: could do with some additional sanity checking, but appears to work. 121 * 122 */ 123 124 static void req_done(struct virtqueue *vq) 125 { 126 struct virtio_chan *chan = vq->vdev->priv; 127 struct p9_fcall *rc; 128 unsigned int len; 129 struct p9_req_t *req; 130 131 P9_DPRINTK(P9_DEBUG_TRANS, ": request done\n"); 132 133 while ((rc = chan->vq->vq_ops->get_buf(chan->vq, &len)) != NULL) { 134 P9_DPRINTK(P9_DEBUG_TRANS, ": rc %p\n", rc); 135 P9_DPRINTK(P9_DEBUG_TRANS, ": lookup tag %d\n", rc->tag); 136 req = p9_tag_lookup(chan->client, rc->tag); 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 * @t: transport state 184 * @tc: &p9_fcall request to transmit 185 * @rc: &p9_fcall to put reponse into 186 * 187 */ 188 189 static int 190 p9_virtio_request(struct p9_client *client, struct p9_req_t *req) 191 { 192 int in, out; 193 struct virtio_chan *chan = client->trans; 194 char *rdata = (char *)req->rc+sizeof(struct p9_fcall); 195 196 P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request\n"); 197 198 out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, req->tc->sdata, 199 req->tc->size); 200 in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata, 201 client->msize); 202 203 req->status = REQ_STATUS_SENT; 204 205 if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, req->tc)) { 206 P9_DPRINTK(P9_DEBUG_TRANS, 207 "9p debug: virtio rpc add_buf returned failure"); 208 return -EIO; 209 } 210 211 chan->vq->vq_ops->kick(chan->vq); 212 213 P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request kicked\n"); 214 return 0; 215 } 216 217 /** 218 * p9_virtio_probe - probe for existence of 9P virtio channels 219 * @vdev: virtio device to probe 220 * 221 * This probes for existing virtio channels. At present only 222 * a single channel is in use, so in the future more work may need 223 * to be done here. 224 * 225 */ 226 227 static int p9_virtio_probe(struct virtio_device *vdev) 228 { 229 int err; 230 struct virtio_chan *chan; 231 int index; 232 233 mutex_lock(&virtio_9p_lock); 234 index = chan_index++; 235 chan = &channels[index]; 236 mutex_unlock(&virtio_9p_lock); 237 238 if (chan_index > MAX_9P_CHAN) { 239 printk(KERN_ERR "9p: virtio: Maximum channels exceeded\n"); 240 BUG(); 241 err = -ENOMEM; 242 goto fail; 243 } 244 245 chan->vdev = vdev; 246 247 /* We expect one virtqueue, for requests. */ 248 chan->vq = vdev->config->find_vq(vdev, 0, req_done); 249 if (IS_ERR(chan->vq)) { 250 err = PTR_ERR(chan->vq); 251 goto out_free_vq; 252 } 253 chan->vq->vdev->priv = chan; 254 spin_lock_init(&chan->lock); 255 256 sg_init_table(chan->sg, VIRTQUEUE_NUM); 257 258 chan->inuse = false; 259 chan->initialized = true; 260 return 0; 261 262 out_free_vq: 263 vdev->config->del_vq(chan->vq); 264 fail: 265 mutex_lock(&virtio_9p_lock); 266 chan_index--; 267 mutex_unlock(&virtio_9p_lock); 268 return err; 269 } 270 271 272 /** 273 * p9_virtio_create - allocate a new virtio channel 274 * @client: client instance invoking this transport 275 * @devname: string identifying the channel to connect to (unused) 276 * @args: args passed from sys_mount() for per-transport options (unused) 277 * 278 * This sets up a transport channel for 9p communication. Right now 279 * we only match the first available channel, but eventually we couldlook up 280 * alternate channels by matching devname versus a virtio_config entry. 281 * We use a simple reference count mechanism to ensure that only a single 282 * mount has a channel open at a time. 283 * 284 * Bugs: doesn't allow identification of a specific channel 285 * to allocate, channels are allocated sequentially. This was 286 * a pragmatic decision to get things rolling, but ideally some 287 * way of identifying the channel to attach to would be nice 288 * if we are going to support multiple channels. 289 * 290 */ 291 292 static int 293 p9_virtio_create(struct p9_client *client, const char *devname, char *args) 294 { 295 struct virtio_chan *chan = channels; 296 int index = 0; 297 298 mutex_lock(&virtio_9p_lock); 299 while (index < MAX_9P_CHAN) { 300 if (chan->initialized && !chan->inuse) { 301 chan->inuse = true; 302 break; 303 } else { 304 index++; 305 chan = &channels[index]; 306 } 307 } 308 mutex_unlock(&virtio_9p_lock); 309 310 if (index >= MAX_9P_CHAN) { 311 printk(KERN_ERR "9p: no channels available\n"); 312 return -ENODEV; 313 } 314 315 client->trans = (void *)chan; 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_vq(chan->vq); 335 chan->initialized = false; 336 } 337 } 338 339 #define VIRTIO_ID_9P 9 340 341 static struct virtio_device_id id_table[] = { 342 { VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID }, 343 { 0 }, 344 }; 345 346 /* The standard "struct lguest_driver": */ 347 static struct virtio_driver p9_virtio_drv = { 348 .driver.name = KBUILD_MODNAME, 349 .driver.owner = THIS_MODULE, 350 .id_table = id_table, 351 .probe = p9_virtio_probe, 352 .remove = p9_virtio_remove, 353 }; 354 355 static struct p9_trans_module p9_virtio_trans = { 356 .name = "virtio", 357 .create = p9_virtio_create, 358 .close = p9_virtio_close, 359 .request = p9_virtio_request, 360 .cancel = p9_virtio_cancel, 361 .maxsize = PAGE_SIZE*16, 362 .def = 0, 363 .owner = THIS_MODULE, 364 }; 365 366 /* The standard init function */ 367 static int __init p9_virtio_init(void) 368 { 369 int count; 370 371 for (count = 0; count < MAX_9P_CHAN; count++) 372 channels[count].initialized = false; 373 374 v9fs_register_trans(&p9_virtio_trans); 375 return register_virtio_driver(&p9_virtio_drv); 376 } 377 378 static void __exit p9_virtio_cleanup(void) 379 { 380 unregister_virtio_driver(&p9_virtio_drv); 381 v9fs_unregister_trans(&p9_virtio_trans); 382 } 383 384 module_init(p9_virtio_init); 385 module_exit(p9_virtio_cleanup); 386 387 MODULE_DEVICE_TABLE(virtio, id_table); 388 MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>"); 389 MODULE_DESCRIPTION("Virtio 9p Transport"); 390 MODULE_LICENSE("GPL"); 391