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