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  * @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");