net/9p/trans_virtio.c

   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");