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_ids.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 DEFINE_MUTEX(virtio_9p_lock);
  53 /* global which tracks highest initialized channel */
  54 static int chan_index;
  55
  56 /**
  57  * struct virtio_chan - per-instance transport information
  58  * @initialized: whether the channel is initialized
  59  * @inuse: whether the channel is in use
  60  * @lock: protects multiple elements within this structure
  61  * @client: client instance
  62  * @vdev: virtio dev associated with this channel
  63  * @vq: virtio queue associated with this channel
  64  * @sg: scatter gather list which is used to pack a request (protected?)
  65  *
  66  * We keep all per-channel information in a structure.
  67  * This structure is allocated within the devices dev->mem space.
  68  * A pointer to the structure will get put in the transport private.
  69  *
  70  */
  71
  72 static struct virtio_chan {
  73         bool initialized;
  74         bool inuse;
  75
  76         spinlock_t lock;
  77
  78         struct p9_client *client;
  79         struct virtio_device *vdev;
  80         struct virtqueue *vq;
  81
  82         /* Scatterlist: can be too big for stack. */
  83         struct scatterlist sg[VIRTQUEUE_NUM];
  84 } channels[MAX_9P_CHAN];
  85
  86 /* How many bytes left in this page. */
  87 static unsigned int rest_of_page(void *data)
  88 {
  89         return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
  90 }
  91
  92 /**
  93  * p9_virtio_close - reclaim resources of a channel
  94  * @client: client instance
  95  *
  96  * This reclaims a channel by freeing its resources and
  97  * reseting its inuse flag.
  98  *
  99  */
 100
 101 static void p9_virtio_close(struct p9_client *client)
 102 {
 103         struct virtio_chan *chan = client->trans;
 104
 105         mutex_lock(&virtio_9p_lock);
 106         chan->inuse = false;
 107         mutex_unlock(&virtio_9p_lock);
 108 }
 109
 110 /**
 111  * req_done - callback which signals activity from the server
 112  * @vq: virtio queue activity was received on
 113  *
 114  * This notifies us that the server has triggered some activity
 115  * on the virtio channel - most likely a response to request we
 116  * sent.  Figure out which requests now have responses and wake up
 117  * those threads.
 118  *
 119  * Bugs: could do with some additional sanity checking, but appears to work.
 120  *
 121  */
 122
 123 static void req_done(struct virtqueue *vq)
 124 {
 125         struct virtio_chan *chan = vq->vdev->priv;
 126         struct p9_fcall *rc;
 127         unsigned int len;
 128         struct p9_req_t *req;
 129
 130         P9_DPRINTK(P9_DEBUG_TRANS, ": request done\n");
 131
 132         while ((rc = chan->vq->vq_ops->get_buf(chan->vq, &len)) != NULL) {
 133                 P9_DPRINTK(P9_DEBUG_TRANS, ": rc %p\n", rc);
 134                 P9_DPRINTK(P9_DEBUG_TRANS, ": lookup tag %d\n", rc->tag);
 135                 req = p9_tag_lookup(chan->client, rc->tag);
 136                 req->status = REQ_STATUS_RCVD;
 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  * @client: client instance issuing the request
 184  * @req: request to be issued
 185  *
 186  */
 187
 188 static int
 189 p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
 190 {
 191         int in, out;
 192         struct virtio_chan *chan = client->trans;
 193         char *rdata = (char *)req->rc+sizeof(struct p9_fcall);
 194
 195         P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request\n");
 196
 197         out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, req->tc->sdata,
 198                                                                 req->tc->size);
 199         in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata,
 200                                                                 client->msize);
 201
 202         req->status = REQ_STATUS_SENT;
 203
 204         if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, req->tc) < 0) {
 205                 P9_DPRINTK(P9_DEBUG_TRANS,
 206                         "9p debug: virtio rpc add_buf returned failure");
 207                 return -EIO;
 208         }
 209
 210         chan->vq->vq_ops->kick(chan->vq);
 211
 212         P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request kicked\n");
 213         return 0;
 214 }
 215
 216 /**
 217  * p9_virtio_probe - probe for existence of 9P virtio channels
 218  * @vdev: virtio device to probe
 219  *
 220  * This probes for existing virtio channels.  At present only
 221  * a single channel is in use, so in the future more work may need
 222  * to be done here.
 223  *
 224  */
 225
 226 static int p9_virtio_probe(struct virtio_device *vdev)
 227 {
 228         int err;
 229         struct virtio_chan *chan;
 230         int index;
 231
 232         mutex_lock(&virtio_9p_lock);
 233         index = chan_index++;
 234         chan = &channels[index];
 235         mutex_unlock(&virtio_9p_lock);
 236
 237         if (chan_index > MAX_9P_CHAN) {
 238                 printk(KERN_ERR "9p: virtio: Maximum channels exceeded\n");
 239                 BUG();
 240                 err = -ENOMEM;
 241                 goto fail;
 242         }
 243
 244         chan->vdev = vdev;
 245
 246         /* We expect one virtqueue, for requests. */
 247         chan->vq = virtio_find_single_vq(vdev, req_done, "requests");
 248         if (IS_ERR(chan->vq)) {
 249                 err = PTR_ERR(chan->vq);
 250                 goto out_free_vq;
 251         }
 252         chan->vq->vdev->priv = chan;
 253         spin_lock_init(&chan->lock);
 254
 255         sg_init_table(chan->sg, VIRTQUEUE_NUM);
 256
 257         chan->inuse = false;
 258         chan->initialized = true;
 259         return 0;
 260
 261 out_free_vq:
 262         vdev->config->del_vqs(vdev);
 263 fail:
 264         mutex_lock(&virtio_9p_lock);
 265         chan_index--;
 266         mutex_unlock(&virtio_9p_lock);
 267         return err;
 268 }
 269
 270
 271 /**
 272  * p9_virtio_create - allocate a new virtio channel
 273  * @client: client instance invoking this transport
 274  * @devname: string identifying the channel to connect to (unused)
 275  * @args: args passed from sys_mount() for per-transport options (unused)
 276  *
 277  * This sets up a transport channel for 9p communication.  Right now
 278  * we only match the first available channel, but eventually we couldlook up
 279  * alternate channels by matching devname versus a virtio_config entry.
 280  * We use a simple reference count mechanism to ensure that only a single
 281  * mount has a channel open at a time.
 282  *
 283  * Bugs: doesn't allow identification of a specific channel
 284  * to allocate, channels are allocated sequentially. This was
 285  * a pragmatic decision to get things rolling, but ideally some
 286  * way of identifying the channel to attach to would be nice
 287  * if we are going to support multiple channels.
 288  *
 289  */
 290
 291 static int
 292 p9_virtio_create(struct p9_client *client, const char *devname, char *args)
 293 {
 294         struct virtio_chan *chan = channels;
 295         int index = 0;
 296
 297         mutex_lock(&virtio_9p_lock);
 298         while (index < MAX_9P_CHAN) {
 299                 if (chan->initialized && !chan->inuse) {
 300                         chan->inuse = true;
 301                         break;
 302                 } else {
 303                         index++;
 304                         chan = &channels[index];
 305                 }
 306         }
 307         mutex_unlock(&virtio_9p_lock);
 308
 309         if (index >= MAX_9P_CHAN) {
 310                 printk(KERN_ERR "9p: no channels available\n");
 311                 return -ENODEV;
 312         }
 313
 314         client->trans = (void *)chan;
 315         chan->client = client;
 316
 317         return 0;
 318 }
 319
 320 /**
 321  * p9_virtio_remove - clean up resources associated with a virtio device
 322  * @vdev: virtio device to remove
 323  *
 324  */
 325
 326 static void p9_virtio_remove(struct virtio_device *vdev)
 327 {
 328         struct virtio_chan *chan = vdev->priv;
 329
 330         BUG_ON(chan->inuse);
 331
 332         if (chan->initialized) {
 333                 vdev->config->del_vqs(vdev);
 334                 chan->initialized = false;
 335         }
 336 }
 337
 338 static struct virtio_device_id id_table[] = {
 339         { VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
 340         { 0 },
 341 };
 342
 343 /* The standard "struct lguest_driver": */
 344 static struct virtio_driver p9_virtio_drv = {
 345         .driver.name =  KBUILD_MODNAME,
 346         .driver.owner = THIS_MODULE,
 347         .id_table =     id_table,
 348         .probe =        p9_virtio_probe,
 349         .remove =       p9_virtio_remove,
 350 };
 351
 352 static struct p9_trans_module p9_virtio_trans = {
 353         .name = "virtio",
 354         .create = p9_virtio_create,
 355         .close = p9_virtio_close,
 356         .request = p9_virtio_request,
 357         .cancel = p9_virtio_cancel,
 358         .maxsize = PAGE_SIZE*16,
 359         .def = 0,
 360         .owner = THIS_MODULE,
 361 };
 362
 363 /* The standard init function */
 364 static int __init p9_virtio_init(void)
 365 {
 366         int count;
 367
 368         for (count = 0; count < MAX_9P_CHAN; count++)
 369                 channels[count].initialized = false;
 370
 371         v9fs_register_trans(&p9_virtio_trans);
 372         return register_virtio_driver(&p9_virtio_drv);
 373 }
 374
 375 static void __exit p9_virtio_cleanup(void)
 376 {
 377         unregister_virtio_driver(&p9_virtio_drv);
 378         v9fs_unregister_trans(&p9_virtio_trans);
 379 }
 380
 381 module_init(p9_virtio_init);
 382 module_exit(p9_virtio_cleanup);
 383
 384 MODULE_DEVICE_TABLE(virtio, id_table);
 385 MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
 386 MODULE_DESCRIPTION("Virtio 9p Transport");
 387 MODULE_LICENSE("GPL");