net/9p/trans_xen.c

   1 /*
   2  * linux/fs/9p/trans_xen
   3  *
   4  * Xen transport layer.
   5  *
   6  * Copyright (C) 2017 by Stefano Stabellini <stefano@aporeto.com>
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License version 2
  10  * as published by the Free Software Foundation; or, when distributed
  11  * separately from the Linux kernel or incorporated into other
  12  * software packages, subject to the following license:
  13  *
  14  * Permission is hereby granted, free of charge, to any person obtaining a copy
  15  * of this source file (the "Software"), to deal in the Software without
  16  * restriction, including without limitation the rights to use, copy, modify,
  17  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  18  * and to permit persons to whom the Software is furnished to do so, subject to
  19  * the following conditions:
  20  *
  21  * The above copyright notice and this permission notice shall be included in
  22  * all copies or substantial portions of the Software.
  23  *
  24  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  25  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  26  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  27  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  28  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  29  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  30  * IN THE SOFTWARE.
  31  */
  32
  33 #include <xen/events.h>
  34 #include <xen/grant_table.h>
  35 #include <xen/xen.h>
  36 #include <xen/xenbus.h>
  37 #include <xen/interface/io/9pfs.h>
  38
  39 #include <linux/module.h>
  40 #include <linux/spinlock.h>
  41 #include <net/9p/9p.h>
  42 #include <net/9p/client.h>
  43 #include <net/9p/transport.h>
  44
  45 #define XEN_9PFS_NUM_RINGS 2
  46 #define XEN_9PFS_RING_ORDER 6
  47 #define XEN_9PFS_RING_SIZE  XEN_FLEX_RING_SIZE(XEN_9PFS_RING_ORDER)
  48
  49 struct xen_9pfs_header {
  50         uint32_t size;
  51         uint8_t id;
  52         uint16_t tag;
  53
  54         /* uint8_t sdata[]; */
  55 } __attribute__((packed));
  56
  57 /* One per ring, more than one per 9pfs share */
  58 struct xen_9pfs_dataring {
  59         struct xen_9pfs_front_priv *priv;
  60
  61         struct xen_9pfs_data_intf *intf;
  62         grant_ref_t ref;
  63         int evtchn;
  64         int irq;
  65         /* protect a ring from concurrent accesses */
  66         spinlock_t lock;
  67
  68         struct xen_9pfs_data data;
  69         wait_queue_head_t wq;
  70         struct work_struct work;
  71 };
  72
  73 /* One per 9pfs share */
  74 struct xen_9pfs_front_priv {
  75         struct list_head list;
  76         struct xenbus_device *dev;
  77         char *tag;
  78         struct p9_client *client;
  79
  80         int num_rings;
  81         struct xen_9pfs_dataring *rings;
  82 };
  83
  84 static LIST_HEAD(xen_9pfs_devs);
  85 static DEFINE_RWLOCK(xen_9pfs_lock);
  86
  87 /* We don't currently allow canceling of requests */
  88 static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req)
  89 {
  90         return 1;
  91 }
  92
  93 static int p9_xen_create(struct p9_client *client, const char *addr, char *args)
  94 {
  95         struct xen_9pfs_front_priv *priv;
  96
  97         if (addr == NULL)
  98                 return -EINVAL;
  99
 100         read_lock(&xen_9pfs_lock);
 101         list_for_each_entry(priv, &xen_9pfs_devs, list) {
 102                 if (!strcmp(priv->tag, addr)) {
 103                         priv->client = client;
 104                         read_unlock(&xen_9pfs_lock);
 105                         return 0;
 106                 }
 107         }
 108         read_unlock(&xen_9pfs_lock);
 109         return -EINVAL;
 110 }
 111
 112 static void p9_xen_close(struct p9_client *client)
 113 {
 114         struct xen_9pfs_front_priv *priv;
 115
 116         read_lock(&xen_9pfs_lock);
 117         list_for_each_entry(priv, &xen_9pfs_devs, list) {
 118                 if (priv->client == client) {
 119                         priv->client = NULL;
 120                         read_unlock(&xen_9pfs_lock);
 121                         return;
 122                 }
 123         }
 124         read_unlock(&xen_9pfs_lock);
 125 }
 126
 127 static bool p9_xen_write_todo(struct xen_9pfs_dataring *ring, RING_IDX size)
 128 {
 129         RING_IDX cons, prod;
 130
 131         cons = ring->intf->out_cons;
 132         prod = ring->intf->out_prod;
 133         virt_mb();
 134
 135         return XEN_9PFS_RING_SIZE -
 136                 xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE) >= size;
 137 }
 138
 139 static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
 140 {
 141         struct xen_9pfs_front_priv *priv = NULL;
 142         RING_IDX cons, prod, masked_cons, masked_prod;
 143         unsigned long flags;
 144         u32 size = p9_req->tc->size;
 145         struct xen_9pfs_dataring *ring;
 146         int num;
 147
 148         read_lock(&xen_9pfs_lock);
 149         list_for_each_entry(priv, &xen_9pfs_devs, list) {
 150                 if (priv->client == client)
 151                         break;
 152         }
 153         read_unlock(&xen_9pfs_lock);
 154         if (!priv || priv->client != client)
 155                 return -EINVAL;
 156
 157         num = p9_req->tc->tag % priv->num_rings;
 158         ring = &priv->rings[num];
 159
 160 again:
 161         while (wait_event_killable(ring->wq,
 162                                    p9_xen_write_todo(ring, size)) != 0)
 163                 ;
 164
 165         spin_lock_irqsave(&ring->lock, flags);
 166         cons = ring->intf->out_cons;
 167         prod = ring->intf->out_prod;
 168         virt_mb();
 169
 170         if (XEN_9PFS_RING_SIZE - xen_9pfs_queued(prod, cons,
 171                                                  XEN_9PFS_RING_SIZE) < size) {
 172                 spin_unlock_irqrestore(&ring->lock, flags);
 173                 goto again;
 174         }
 175
 176         masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE);
 177         masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
 178
 179         xen_9pfs_write_packet(ring->data.out, p9_req->tc->sdata, size,
 180                               &masked_prod, masked_cons, XEN_9PFS_RING_SIZE);
 181
 182         p9_req->status = REQ_STATUS_SENT;
 183         virt_wmb();                     /* write ring before updating pointer */
 184         prod += size;
 185         ring->intf->out_prod = prod;
 186         spin_unlock_irqrestore(&ring->lock, flags);
 187         notify_remote_via_irq(ring->irq);
 188
 189         return 0;
 190 }
 191
 192 static void p9_xen_response(struct work_struct *work)
 193 {
 194         struct xen_9pfs_front_priv *priv;
 195         struct xen_9pfs_dataring *ring;
 196         RING_IDX cons, prod, masked_cons, masked_prod;
 197         struct xen_9pfs_header h;
 198         struct p9_req_t *req;
 199         int status;
 200
 201         ring = container_of(work, struct xen_9pfs_dataring, work);
 202         priv = ring->priv;
 203
 204         while (1) {
 205                 cons = ring->intf->in_cons;
 206                 prod = ring->intf->in_prod;
 207                 virt_rmb();
 208
 209                 if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE) <
 210                     sizeof(h)) {
 211                         notify_remote_via_irq(ring->irq);
 212                         return;
 213                 }
 214
 215                 masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE);
 216                 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
 217
 218                 /* First, read just the header */
 219                 xen_9pfs_read_packet(&h, ring->data.in, sizeof(h),
 220                                      masked_prod, &masked_cons,
 221                                      XEN_9PFS_RING_SIZE);
 222
 223                 req = p9_tag_lookup(priv->client, h.tag);
 224                 if (!req || req->status != REQ_STATUS_SENT) {
 225                         dev_warn(&priv->dev->dev, "Wrong req tag=%x\n", h.tag);
 226                         cons += h.size;
 227                         virt_mb();
 228                         ring->intf->in_cons = cons;
 229                         continue;
 230                 }
 231
 232                 memcpy(req->rc, &h, sizeof(h));
 233                 req->rc->offset = 0;
 234
 235                 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
 236                 /* Then, read the whole packet (including the header) */
 237                 xen_9pfs_read_packet(req->rc->sdata, ring->data.in, h.size,
 238                                      masked_prod, &masked_cons,
 239                                      XEN_9PFS_RING_SIZE);
 240
 241                 virt_mb();
 242                 cons += h.size;
 243                 ring->intf->in_cons = cons;
 244
 245                 status = (req->status != REQ_STATUS_ERROR) ?
 246                         REQ_STATUS_RCVD : REQ_STATUS_ERROR;
 247
 248                 p9_client_cb(priv->client, req, status);
 249         }
 250 }
 251
 252 static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
 253 {
 254         struct xen_9pfs_dataring *ring = r;
 255
 256         if (!ring || !ring->priv->client) {
 257                 /* ignore spurious interrupt */
 258                 return IRQ_HANDLED;
 259         }
 260
 261         wake_up_interruptible(&ring->wq);
 262         schedule_work(&ring->work);
 263
 264         return IRQ_HANDLED;
 265 }
 266
 267 static struct p9_trans_module p9_xen_trans = {
 268         .name = "xen",
 269         .maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT),
 270         .def = 1,
 271         .create = p9_xen_create,
 272         .close = p9_xen_close,
 273         .request = p9_xen_request,
 274         .cancel = p9_xen_cancel,
 275         .owner = THIS_MODULE,
 276 };
 277
 278 static const struct xenbus_device_id xen_9pfs_front_ids[] = {
 279         { "9pfs" },
 280         { "" }
 281 };
 282
 283 static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
 284 {
 285         int i, j;
 286
 287         write_lock(&xen_9pfs_lock);
 288         list_del(&priv->list);
 289         write_unlock(&xen_9pfs_lock);
 290
 291         for (i = 0; i < priv->num_rings; i++) {
 292                 if (!priv->rings[i].intf)
 293                         break;
 294                 if (priv->rings[i].irq > 0)
 295                         unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
 296                 if (priv->rings[i].data.in) {
 297                         for (j = 0; j < (1 << XEN_9PFS_RING_ORDER); j++) {
 298                                 grant_ref_t ref;
 299
 300                                 ref = priv->rings[i].intf->ref[j];
 301                                 gnttab_end_foreign_access(ref, 0, 0);
 302                         }
 303                         free_pages((unsigned long)priv->rings[i].data.in,
 304                                    XEN_9PFS_RING_ORDER -
 305                                    (PAGE_SHIFT - XEN_PAGE_SHIFT));
 306                 }
 307                 gnttab_end_foreign_access(priv->rings[i].ref, 0, 0);
 308                 free_page((unsigned long)priv->rings[i].intf);
 309         }
 310         kfree(priv->rings);
 311         kfree(priv->tag);
 312         kfree(priv);
 313 }
 314
 315 static int xen_9pfs_front_remove(struct xenbus_device *dev)
 316 {
 317         struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
 318
 319         dev_set_drvdata(&dev->dev, NULL);
 320         xen_9pfs_front_free(priv);
 321         return 0;
 322 }
 323
 324 static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
 325                                          struct xen_9pfs_dataring *ring)
 326 {
 327         int i = 0;
 328         int ret = -ENOMEM;
 329         void *bytes = NULL;
 330
 331         init_waitqueue_head(&ring->wq);
 332         spin_lock_init(&ring->lock);
 333         INIT_WORK(&ring->work, p9_xen_response);
 334
 335         ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL);
 336         if (!ring->intf)
 337                 return ret;
 338         ret = gnttab_grant_foreign_access(dev->otherend_id,
 339                                           virt_to_gfn(ring->intf), 0);
 340         if (ret < 0)
 341                 goto out;
 342         ring->ref = ret;
 343         bytes = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
 344                         XEN_9PFS_RING_ORDER - (PAGE_SHIFT - XEN_PAGE_SHIFT));
 345         if (!bytes) {
 346                 ret = -ENOMEM;
 347                 goto out;
 348         }
 349         for (; i < (1 << XEN_9PFS_RING_ORDER); i++) {
 350                 ret = gnttab_grant_foreign_access(
 351                                 dev->otherend_id, virt_to_gfn(bytes) + i, 0);
 352                 if (ret < 0)
 353                         goto out;
 354                 ring->intf->ref[i] = ret;
 355         }
 356         ring->intf->ring_order = XEN_9PFS_RING_ORDER;
 357         ring->data.in = bytes;
 358         ring->data.out = bytes + XEN_9PFS_RING_SIZE;
 359
 360         ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
 361         if (ret)
 362                 goto out;
 363         ring->irq = bind_evtchn_to_irqhandler(ring->evtchn,
 364                                               xen_9pfs_front_event_handler,
 365                                               0, "xen_9pfs-frontend", ring);
 366         if (ring->irq >= 0)
 367                 return 0;
 368
 369         xenbus_free_evtchn(dev, ring->evtchn);
 370         ret = ring->irq;
 371 out:
 372         if (bytes) {
 373                 for (i--; i >= 0; i--)
 374                         gnttab_end_foreign_access(ring->intf->ref[i], 0, 0);
 375                 free_pages((unsigned long)bytes,
 376                            XEN_9PFS_RING_ORDER -
 377                            (PAGE_SHIFT - XEN_PAGE_SHIFT));
 378         }
 379         gnttab_end_foreign_access(ring->ref, 0, 0);
 380         free_page((unsigned long)ring->intf);
 381         return ret;
 382 }
 383
 384 static int xen_9pfs_front_probe(struct xenbus_device *dev,
 385                                 const struct xenbus_device_id *id)
 386 {
 387         int ret, i;
 388         struct xenbus_transaction xbt;
 389         struct xen_9pfs_front_priv *priv = NULL;
 390         char *versions;
 391         unsigned int max_rings, max_ring_order, len = 0;
 392
 393         versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
 394         if (!len)
 395                 return -EINVAL;
 396         if (strcmp(versions, "1")) {
 397                 kfree(versions);
 398                 return -EINVAL;
 399         }
 400         kfree(versions);
 401         max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
 402         if (max_rings < XEN_9PFS_NUM_RINGS)
 403                 return -EINVAL;
 404         max_ring_order = xenbus_read_unsigned(dev->otherend,
 405                                               "max-ring-page-order", 0);
 406         if (max_ring_order < XEN_9PFS_RING_ORDER)
 407                 return -EINVAL;
 408
 409         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 410         if (!priv)
 411                 return -ENOMEM;
 412
 413         priv->dev = dev;
 414         priv->num_rings = XEN_9PFS_NUM_RINGS;
 415         priv->rings = kcalloc(priv->num_rings, sizeof(*priv->rings),
 416                               GFP_KERNEL);
 417         if (!priv->rings) {
 418                 kfree(priv);
 419                 return -ENOMEM;
 420         }
 421
 422         for (i = 0; i < priv->num_rings; i++) {
 423                 priv->rings[i].priv = priv;
 424                 ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i]);
 425                 if (ret < 0)
 426                         goto error;
 427         }
 428
 429  again:
 430         ret = xenbus_transaction_start(&xbt);
 431         if (ret) {
 432                 xenbus_dev_fatal(dev, ret, "starting transaction");
 433                 goto error;
 434         }
 435         ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
 436         if (ret)
 437                 goto error_xenbus;
 438         ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
 439                             priv->num_rings);
 440         if (ret)
 441                 goto error_xenbus;
 442         for (i = 0; i < priv->num_rings; i++) {
 443                 char str[16];
 444
 445                 BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
 446                 sprintf(str, "ring-ref%u", i);
 447                 ret = xenbus_printf(xbt, dev->nodename, str, "%d",
 448                                     priv->rings[i].ref);
 449                 if (ret)
 450                         goto error_xenbus;
 451
 452                 sprintf(str, "event-channel-%u", i);
 453                 ret = xenbus_printf(xbt, dev->nodename, str, "%u",
 454                                     priv->rings[i].evtchn);
 455                 if (ret)
 456                         goto error_xenbus;
 457         }
 458         priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
 459         if (IS_ERR(priv->tag)) {
 460                 ret = PTR_ERR(priv->tag);
 461                 goto error_xenbus;
 462         }
 463         ret = xenbus_transaction_end(xbt, 0);
 464         if (ret) {
 465                 if (ret == -EAGAIN)
 466                         goto again;
 467                 xenbus_dev_fatal(dev, ret, "completing transaction");
 468                 goto error;
 469         }
 470
 471         write_lock(&xen_9pfs_lock);
 472         list_add_tail(&priv->list, &xen_9pfs_devs);
 473         write_unlock(&xen_9pfs_lock);
 474         dev_set_drvdata(&dev->dev, priv);
 475         xenbus_switch_state(dev, XenbusStateInitialised);
 476
 477         return 0;
 478
 479  error_xenbus:
 480         xenbus_transaction_end(xbt, 1);
 481         xenbus_dev_fatal(dev, ret, "writing xenstore");
 482  error:
 483         dev_set_drvdata(&dev->dev, NULL);
 484         xen_9pfs_front_free(priv);
 485         return ret;
 486 }
 487
 488 static int xen_9pfs_front_resume(struct xenbus_device *dev)
 489 {
 490         dev_warn(&dev->dev, "suspend/resume unsupported\n");
 491         return 0;
 492 }
 493
 494 static void xen_9pfs_front_changed(struct xenbus_device *dev,
 495                                    enum xenbus_state backend_state)
 496 {
 497         switch (backend_state) {
 498         case XenbusStateReconfiguring:
 499         case XenbusStateReconfigured:
 500         case XenbusStateInitialising:
 501         case XenbusStateInitialised:
 502         case XenbusStateUnknown:
 503                 break;
 504
 505         case XenbusStateInitWait:
 506                 break;
 507
 508         case XenbusStateConnected:
 509                 xenbus_switch_state(dev, XenbusStateConnected);
 510                 break;
 511
 512         case XenbusStateClosed:
 513                 if (dev->state == XenbusStateClosed)
 514                         break;
 515                 /* Missed the backend's CLOSING state -- fallthrough */
 516         case XenbusStateClosing:
 517                 xenbus_frontend_closed(dev);
 518                 break;
 519         }
 520 }
 521
 522 static struct xenbus_driver xen_9pfs_front_driver = {
 523         .ids = xen_9pfs_front_ids,
 524         .probe = xen_9pfs_front_probe,
 525         .remove = xen_9pfs_front_remove,
 526         .resume = xen_9pfs_front_resume,
 527         .otherend_changed = xen_9pfs_front_changed,
 528 };
 529
 530 static int p9_trans_xen_init(void)
 531 {
 532         if (!xen_domain())
 533                 return -ENODEV;
 534
 535         pr_info("Initialising Xen transport for 9pfs\n");
 536
 537         v9fs_register_trans(&p9_xen_trans);
 538         return xenbus_register_frontend(&xen_9pfs_front_driver);
 539 }
 540 module_init(p9_trans_xen_init);
 541
 542 static void p9_trans_xen_exit(void)
 543 {
 544         v9fs_unregister_trans(&p9_xen_trans);
 545         return xenbus_unregister_driver(&xen_9pfs_front_driver);
 546 }
 547 module_exit(p9_trans_xen_exit);
 548
 549 MODULE_AUTHOR("Stefano Stabellini <stefano@aporeto.com>");
 550 MODULE_DESCRIPTION("Xen Transport for 9P");
 551 MODULE_LICENSE("GPL");