net/9p/trans_virtio.c

   1 /*
   2  * The Guest 9p transport driver
   3  *
   4  * This is a block based transport driver based on the lguest block driver
   5  * code.
   6  *
   7  */
   8 /*
   9  *  Copyright (C) 2007 Eric Van Hensbergen, IBM Corporation
  10  *
  11  *  Based on virtio console driver
  12  *  Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
  13  *
  14  *  This program is free software; you can redistribute it and/or modify
  15  *  it under the terms of the GNU General Public License version 2
  16  *  as published by the Free Software Foundation.
  17  *
  18  *  This program is distributed in the hope that it will be useful,
  19  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21  *  GNU General Public License for more details.
  22  *
  23  *  You should have received a copy of the GNU General Public License
  24  *  along with this program; if not, write to:
  25  *  Free Software Foundation
  26  *  51 Franklin Street, Fifth Floor
  27  *  Boston, MA  02111-1301  USA
  28  *
  29  */
  30
  31 #include <linux/in.h>
  32 #include <linux/module.h>
  33 #include <linux/net.h>
  34 #include <linux/ipv6.h>
  35 #include <linux/errno.h>
  36 #include <linux/kernel.h>
  37 #include <linux/un.h>
  38 #include <linux/uaccess.h>
  39 #include <linux/inet.h>
  40 #include <linux/idr.h>
  41 #include <linux/file.h>
  42 #include <net/9p/9p.h>
  43 #include <linux/parser.h>
  44 #include <net/9p/transport.h>
  45 #include <linux/scatterlist.h>
  46 #include <linux/virtio.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 DECLARE_MUTEX(virtio_9p_lock);
  53 /* global which tracks highest initialized channel */
  54 static int chan_index;
  55
  56 #define P9_INIT_MAXTAG  16
  57
  58 #define REQ_STATUS_IDLE 0
  59 #define REQ_STATUS_SENT 1
  60 #define REQ_STATUS_RCVD 2
  61 #define REQ_STATUS_FLSH 3
  62
  63 struct p9_req_t {
  64         int status;
  65         wait_queue_head_t *wq;
  66 };
  67
  68 /* We keep all per-channel information in a structure.
  69  * This structure is allocated within the devices dev->mem space.
  70  * A pointer to the structure will get put in the transport private.
  71  */
  72 static struct virtio_chan {
  73         bool initialized;               /* channel is initialized */
  74         bool inuse;                     /* channel is in use */
  75
  76         spinlock_t lock;
  77
  78         struct virtio_device *vdev;
  79         struct virtqueue *vq;
  80
  81         struct p9_idpool *tagpool;
  82         struct p9_req_t *reqs;
  83         int max_tag;
  84
  85         /* Scatterlist: can be too big for stack. */
  86         struct scatterlist sg[VIRTQUEUE_NUM];
  87 } channels[MAX_9P_CHAN];
  88
  89 /* Lookup requests by tag */
  90 static struct p9_req_t *p9_lookup_tag(struct virtio_chan *c, u16 tag)
  91 {
  92         /* This looks up the original request by tag so we know which
  93          * buffer to read the data into */
  94         tag++;
  95
  96         while (tag >= c->max_tag) {
  97                 int old_max = c->max_tag;
  98                 int count;
  99
 100                 if (c->max_tag)
 101                         c->max_tag *= 2;
 102                 else
 103                         c->max_tag = P9_INIT_MAXTAG;
 104
 105                 c->reqs = krealloc(c->reqs, sizeof(struct p9_req_t)*c->max_tag,
 106                                                                 GFP_ATOMIC);
 107                 if (!c->reqs) {
 108                         printk(KERN_ERR "Couldn't grow tag array\n");
 109                         BUG();
 110                 }
 111                 for (count = old_max; count < c->max_tag; count++) {
 112                         c->reqs[count].status = REQ_STATUS_IDLE;
 113                         c->reqs[count].wq = kmalloc(sizeof(wait_queue_head_t),
 114                                                                 GFP_ATOMIC);
 115                         if (!c->reqs[count].wq) {
 116                                 printk(KERN_ERR "Couldn't grow tag array\n");
 117                                 BUG();
 118                         }
 119                         init_waitqueue_head(c->reqs[count].wq);
 120                 }
 121         }
 122
 123         return &c->reqs[tag];
 124 }
 125
 126
 127 /* How many bytes left in this page. */
 128 static unsigned int rest_of_page(void *data)
 129 {
 130         return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
 131 }
 132
 133 static void p9_virtio_close(struct p9_trans *trans)
 134 {
 135         struct virtio_chan *chan = trans->priv;
 136         int count;
 137         unsigned int flags;
 138
 139         spin_lock_irqsave(&chan->lock, flags);
 140         p9_idpool_destroy(chan->tagpool);
 141         for (count = 0; count < chan->max_tag; count++)
 142                 kfree(chan->reqs[count].wq);
 143         kfree(chan->reqs);
 144         chan->max_tag = 0;
 145         spin_unlock_irqrestore(&chan->lock, flags);
 146
 147         down(&virtio_9p_lock);
 148         chan->inuse = false;
 149         up(&virtio_9p_lock);
 150
 151         kfree(trans);
 152 }
 153
 154 static void req_done(struct virtqueue *vq)
 155 {
 156         struct virtio_chan *chan = vq->vdev->priv;
 157         struct p9_fcall *rc;
 158         unsigned int len;
 159         unsigned long flags;
 160         struct p9_req_t *req;
 161
 162         spin_lock_irqsave(&chan->lock, flags);
 163         while ((rc = chan->vq->vq_ops->get_buf(chan->vq, &len)) != NULL) {
 164                 req = p9_lookup_tag(chan, rc->tag);
 165                 req->status = REQ_STATUS_RCVD;
 166                 wake_up(req->wq);
 167         }
 168         /* In case queue is stopped waiting for more buffers. */
 169         spin_unlock_irqrestore(&chan->lock, flags);
 170 }
 171
 172 static int
 173 pack_sg_list(struct scatterlist *sg, int start, int limit, char *data,
 174                                                                 int count)
 175 {
 176         int s;
 177         int index = start;
 178
 179         while (count) {
 180                 s = rest_of_page(data);
 181                 if (s > count)
 182                         s = count;
 183                 sg_set_buf(&sg[index++], data, s);
 184                 count -= s;
 185                 data += s;
 186                 BUG_ON(index > limit);
 187         }
 188
 189         return index-start;
 190 }
 191
 192 static int
 193 p9_virtio_rpc(struct p9_trans *t, struct p9_fcall *tc, struct p9_fcall **rc)
 194 {
 195         int in, out;
 196         int n, err, size;
 197         struct virtio_chan *chan = t->priv;
 198         char *rdata;
 199         struct p9_req_t *req;
 200         unsigned long flags;
 201
 202         if (*rc == NULL) {
 203                 *rc = kmalloc(sizeof(struct p9_fcall) + t->msize, GFP_KERNEL);
 204                 if (!*rc)
 205                         return -ENOMEM;
 206         }
 207
 208         rdata = (char *)*rc+sizeof(struct p9_fcall);
 209
 210         n = P9_NOTAG;
 211         if (tc->id != P9_TVERSION) {
 212                 n = p9_idpool_get(chan->tagpool);
 213                 if (n < 0)
 214                         return -ENOMEM;
 215         }
 216
 217         spin_lock_irqsave(&chan->lock, flags);
 218         req = p9_lookup_tag(chan, n);
 219         spin_unlock_irqrestore(&chan->lock, flags);
 220
 221         p9_set_tag(tc, n);
 222
 223         P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio rpc tag %d\n", n);
 224
 225         out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, tc->sdata, tc->size);
 226         in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata, t->msize);
 227
 228         req->status = REQ_STATUS_SENT;
 229
 230         if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, tc)) {
 231                 P9_DPRINTK(P9_DEBUG_TRANS,
 232                         "9p debug: virtio rpc add_buf returned failure");
 233                 return -EIO;
 234         }
 235
 236         chan->vq->vq_ops->kick(chan->vq);
 237
 238         wait_event(*req->wq, req->status == REQ_STATUS_RCVD);
 239
 240         size = le32_to_cpu(*(__le32 *) rdata);
 241
 242         err = p9_deserialize_fcall(rdata, size, *rc, t->extended);
 243         if (err < 0) {
 244                 P9_DPRINTK(P9_DEBUG_TRANS,
 245                         "9p debug: virtio rpc deserialize returned %d\n", err);
 246                 return err;
 247         }
 248
 249 #ifdef CONFIG_NET_9P_DEBUG
 250         if ((p9_debug_level&P9_DEBUG_FCALL) == P9_DEBUG_FCALL) {
 251                 char buf[150];
 252
 253                 p9_printfcall(buf, sizeof(buf), *rc, t->extended);
 254                 printk(KERN_NOTICE ">>> %p %s\n", t, buf);
 255         }
 256 #endif
 257
 258         if (n != P9_NOTAG && p9_idpool_check(n, chan->tagpool))
 259                 p9_idpool_put(n, chan->tagpool);
 260
 261         req->status = REQ_STATUS_IDLE;
 262
 263         return 0;
 264 }
 265
 266 static int p9_virtio_probe(struct virtio_device *vdev)
 267 {
 268         int err;
 269         struct virtio_chan *chan;
 270         int index;
 271
 272         down(&virtio_9p_lock);
 273         index = chan_index++;
 274         chan = &channels[index];
 275         up(&virtio_9p_lock);
 276
 277         if (chan_index > MAX_9P_CHAN) {
 278                 printk(KERN_ERR "9p: virtio: Maximum channels exceeded\n");
 279                 BUG();
 280                 err = -ENOMEM;
 281                 goto fail;
 282         }
 283
 284         chan->vdev = vdev;
 285
 286         /* We expect one virtqueue, for requests. */
 287         chan->vq = vdev->config->find_vq(vdev, 0, req_done);
 288         if (IS_ERR(chan->vq)) {
 289                 err = PTR_ERR(chan->vq);
 290                 goto out_free_vq;
 291         }
 292         chan->vq->vdev->priv = chan;
 293         spin_lock_init(&chan->lock);
 294
 295         sg_init_table(chan->sg, VIRTQUEUE_NUM);
 296
 297         chan->inuse = false;
 298         chan->initialized = true;
 299         return 0;
 300
 301 out_free_vq:
 302         vdev->config->del_vq(chan->vq);
 303 fail:
 304         down(&virtio_9p_lock);
 305         chan_index--;
 306         up(&virtio_9p_lock);
 307         return err;
 308 }
 309
 310 /* This sets up a transport channel for 9p communication.  Right now
 311  * we only match the first available channel, but eventually we couldlook up
 312  * alternate channels by matching devname versus a virtio_config entry.
 313  * We use a simple reference count mechanism to ensure that only a single
 314  * mount has a channel open at a time. */
 315 static struct p9_trans *
 316 p9_virtio_create(const char *devname, char *args, int msize,
 317                                                         unsigned char extended)
 318 {
 319         struct p9_trans *trans;
 320         struct virtio_chan *chan = channels;
 321         int index = 0;
 322
 323         down(&virtio_9p_lock);
 324         while (index < MAX_9P_CHAN) {
 325                 if (chan->initialized && !chan->inuse) {
 326                         chan->inuse = true;
 327                         break;
 328                 } else {
 329                         index++;
 330                         chan = &channels[index];
 331                 }
 332         }
 333         up(&virtio_9p_lock);
 334
 335         if (index >= MAX_9P_CHAN) {
 336                 printk(KERN_ERR "9p: no channels available\n");
 337                 return ERR_PTR(-ENODEV);
 338         }
 339
 340         chan->tagpool = p9_idpool_create();
 341         if (IS_ERR(chan->tagpool)) {
 342                 printk(KERN_ERR "9p: couldn't allocate tagpool\n");
 343                 return ERR_PTR(-ENOMEM);
 344         }
 345         p9_idpool_get(chan->tagpool); /* reserve tag 0 */
 346         chan->max_tag = 0;
 347         chan->reqs = NULL;
 348
 349         trans = kmalloc(sizeof(struct p9_trans), GFP_KERNEL);
 350         if (!trans) {
 351                 printk(KERN_ERR "9p: couldn't allocate transport\n");
 352                 return ERR_PTR(-ENOMEM);
 353         }
 354         trans->extended = extended;
 355         trans->msize = msize;
 356         trans->close = p9_virtio_close;
 357         trans->rpc = p9_virtio_rpc;
 358         trans->priv = chan;
 359
 360         return trans;
 361 }
 362
 363 static void p9_virtio_remove(struct virtio_device *vdev)
 364 {
 365         struct virtio_chan *chan = vdev->priv;
 366
 367         BUG_ON(chan->inuse);
 368
 369         if (chan->initialized) {
 370                 vdev->config->del_vq(chan->vq);
 371                 chan->initialized = false;
 372         }
 373 }
 374
 375 #define VIRTIO_ID_9P 9
 376
 377 static struct virtio_device_id id_table[] = {
 378         { VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
 379         { 0 },
 380 };
 381
 382 /* The standard "struct lguest_driver": */
 383 static struct virtio_driver p9_virtio_drv = {
 384         .driver.name =  KBUILD_MODNAME,
 385         .driver.owner = THIS_MODULE,
 386         .id_table =     id_table,
 387         .probe =        p9_virtio_probe,
 388         .remove =       p9_virtio_remove,
 389 };
 390
 391 static struct p9_trans_module p9_virtio_trans = {
 392         .name = "virtio",
 393         .create = p9_virtio_create,
 394         .maxsize = PAGE_SIZE*16,
 395         .def = 0,
 396 };
 397
 398 /* The standard init function */
 399 static int __init p9_virtio_init(void)
 400 {
 401         int count;
 402
 403         for (count = 0; count < MAX_9P_CHAN; count++)
 404                 channels[count].initialized = false;
 405
 406         v9fs_register_trans(&p9_virtio_trans);
 407         return register_virtio_driver(&p9_virtio_drv);
 408 }
 409
 410 static void __exit p9_virtio_cleanup(void)
 411 {
 412         unregister_virtio_driver(&p9_virtio_drv);
 413 }
 414
 415 module_init(p9_virtio_init);
 416 module_exit(p9_virtio_cleanup);
 417
 418 MODULE_DEVICE_TABLE(virtio, id_table);
 419 MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
 420 MODULE_DESCRIPTION("Virtio 9p Transport");
 421 MODULE_LICENSE("GPL");