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 9
  47 #define XEN_9PFS_RING_SIZE(ring)  XEN_FLEX_RING_SIZE(ring->intf->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(ring) -
 136                 xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) >= 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;
 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 (list_entry_is_head(priv, &xen_9pfs_devs, list))
 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(ring) -
 171             xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) < size) {
 172                 spin_unlock_irqrestore(&ring->lock, flags);
 173                 goto again;
 174         }
 175
 176         masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
 177         masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
 178
 179         xen_9pfs_write_packet(ring->data.out, p9_req->tc.sdata, size,
 180                               &masked_prod, masked_cons,
 181                               XEN_9PFS_RING_SIZE(ring));
 182
 183         p9_req->status = REQ_STATUS_SENT;
 184         virt_wmb();                     /* write ring before updating pointer */
 185         prod += size;
 186         ring->intf->out_prod = prod;
 187         spin_unlock_irqrestore(&ring->lock, flags);
 188         notify_remote_via_irq(ring->irq);
 189         p9_req_put(client, p9_req);
 190
 191         return 0;
 192 }
 193
 194 static void p9_xen_response(struct work_struct *work)
 195 {
 196         struct xen_9pfs_front_priv *priv;
 197         struct xen_9pfs_dataring *ring;
 198         RING_IDX cons, prod, masked_cons, masked_prod;
 199         struct xen_9pfs_header h;
 200         struct p9_req_t *req;
 201         int status;
 202
 203         ring = container_of(work, struct xen_9pfs_dataring, work);
 204         priv = ring->priv;
 205
 206         while (1) {
 207                 cons = ring->intf->in_cons;
 208                 prod = ring->intf->in_prod;
 209                 virt_rmb();
 210
 211                 if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) <
 212                     sizeof(h)) {
 213                         notify_remote_via_irq(ring->irq);
 214                         return;
 215                 }
 216
 217                 masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
 218                 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
 219
 220                 /* First, read just the header */
 221                 xen_9pfs_read_packet(&h, ring->data.in, sizeof(h),
 222                                      masked_prod, &masked_cons,
 223                                      XEN_9PFS_RING_SIZE(ring));
 224
 225                 req = p9_tag_lookup(priv->client, h.tag);
 226                 if (!req || req->status != REQ_STATUS_SENT) {
 227                         dev_warn(&priv->dev->dev, "Wrong req tag=%x\n", h.tag);
 228                         cons += h.size;
 229                         virt_mb();
 230                         ring->intf->in_cons = cons;
 231                         continue;
 232                 }
 233
 234                 if (h.size > req->rc.capacity) {
 235                         dev_warn(&priv->dev->dev,
 236                                  "requested packet size too big: %d for tag %d with capacity %zd\n",
 237                                  h.size, h.tag, req->rc.capacity);
 238                         req->status = REQ_STATUS_ERROR;
 239                         goto recv_error;
 240                 }
 241
 242                 memcpy(&req->rc, &h, sizeof(h));
 243                 req->rc.offset = 0;
 244
 245                 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
 246                 /* Then, read the whole packet (including the header) */
 247                 xen_9pfs_read_packet(req->rc.sdata, ring->data.in, h.size,
 248                                      masked_prod, &masked_cons,
 249                                      XEN_9PFS_RING_SIZE(ring));
 250
 251 recv_error:
 252                 virt_mb();
 253                 cons += h.size;
 254                 ring->intf->in_cons = cons;
 255
 256                 status = (req->status != REQ_STATUS_ERROR) ?
 257                         REQ_STATUS_RCVD : REQ_STATUS_ERROR;
 258
 259                 p9_client_cb(priv->client, req, status);
 260         }
 261 }
 262
 263 static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
 264 {
 265         struct xen_9pfs_dataring *ring = r;
 266
 267         if (!ring || !ring->priv->client) {
 268                 /* ignore spurious interrupt */
 269                 return IRQ_HANDLED;
 270         }
 271
 272         wake_up_interruptible(&ring->wq);
 273         schedule_work(&ring->work);
 274
 275         return IRQ_HANDLED;
 276 }
 277
 278 static struct p9_trans_module p9_xen_trans = {
 279         .name = "xen",
 280         .maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT - 2),
 281         .def = 1,
 282         .create = p9_xen_create,
 283         .close = p9_xen_close,
 284         .request = p9_xen_request,
 285         .cancel = p9_xen_cancel,
 286         .owner = THIS_MODULE,
 287 };
 288
 289 static const struct xenbus_device_id xen_9pfs_front_ids[] = {
 290         { "9pfs" },
 291         { "" }
 292 };
 293
 294 static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
 295 {
 296         int i, j;
 297
 298         write_lock(&xen_9pfs_lock);
 299         list_del(&priv->list);
 300         write_unlock(&xen_9pfs_lock);
 301
 302         for (i = 0; i < priv->num_rings; i++) {
 303                 struct xen_9pfs_dataring *ring = &priv->rings[i];
 304
 305                 cancel_work_sync(&ring->work);
 306
 307                 if (!priv->rings[i].intf)
 308                         break;
 309                 if (priv->rings[i].irq > 0)
 310                         unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
 311                 if (priv->rings[i].data.in) {
 312                         for (j = 0;
 313                              j < (1 << priv->rings[i].intf->ring_order);
 314                              j++) {
 315                                 grant_ref_t ref;
 316
 317                                 ref = priv->rings[i].intf->ref[j];
 318                                 gnttab_end_foreign_access(ref, 0, 0);
 319                         }
 320                         free_pages_exact(priv->rings[i].data.in,
 321                                    1UL << (priv->rings[i].intf->ring_order +
 322                                            XEN_PAGE_SHIFT));
 323                 }
 324                 gnttab_end_foreign_access(priv->rings[i].ref, 0, 0);
 325                 free_page((unsigned long)priv->rings[i].intf);
 326         }
 327         kfree(priv->rings);
 328         kfree(priv->tag);
 329         kfree(priv);
 330 }
 331
 332 static int xen_9pfs_front_remove(struct xenbus_device *dev)
 333 {
 334         struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
 335
 336         dev_set_drvdata(&dev->dev, NULL);
 337         xen_9pfs_front_free(priv);
 338         return 0;
 339 }
 340
 341 static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
 342                                          struct xen_9pfs_dataring *ring,
 343                                          unsigned int order)
 344 {
 345         int i = 0;
 346         int ret = -ENOMEM;
 347         void *bytes = NULL;
 348
 349         init_waitqueue_head(&ring->wq);
 350         spin_lock_init(&ring->lock);
 351         INIT_WORK(&ring->work, p9_xen_response);
 352
 353         ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL);
 354         if (!ring->intf)
 355                 return ret;
 356         ret = gnttab_grant_foreign_access(dev->otherend_id,
 357                                           virt_to_gfn(ring->intf), 0);
 358         if (ret < 0)
 359                 goto out;
 360         ring->ref = ret;
 361         bytes = alloc_pages_exact(1UL << (order + XEN_PAGE_SHIFT),
 362                                   GFP_KERNEL | __GFP_ZERO);
 363         if (!bytes) {
 364                 ret = -ENOMEM;
 365                 goto out;
 366         }
 367         for (; i < (1 << order); i++) {
 368                 ret = gnttab_grant_foreign_access(
 369                                 dev->otherend_id, virt_to_gfn(bytes) + i, 0);
 370                 if (ret < 0)
 371                         goto out;
 372                 ring->intf->ref[i] = ret;
 373         }
 374         ring->intf->ring_order = order;
 375         ring->data.in = bytes;
 376         ring->data.out = bytes + XEN_FLEX_RING_SIZE(order);
 377
 378         ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
 379         if (ret)
 380                 goto out;
 381         ring->irq = bind_evtchn_to_irqhandler(ring->evtchn,
 382                                               xen_9pfs_front_event_handler,
 383                                               0, "xen_9pfs-frontend", ring);
 384         if (ring->irq >= 0)
 385                 return 0;
 386
 387         xenbus_free_evtchn(dev, ring->evtchn);
 388         ret = ring->irq;
 389 out:
 390         if (bytes) {
 391                 for (i--; i >= 0; i--)
 392                         gnttab_end_foreign_access(ring->intf->ref[i], 0, 0);
 393                 free_pages_exact(bytes, 1UL << (order + XEN_PAGE_SHIFT));
 394         }
 395         gnttab_end_foreign_access(ring->ref, 0, 0);
 396         free_page((unsigned long)ring->intf);
 397         return ret;
 398 }
 399
 400 static int xen_9pfs_front_init(struct xenbus_device *dev)
 401 {
 402         int ret, i;
 403         struct xenbus_transaction xbt;
 404         struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
 405         char *versions, *v;
 406         unsigned int max_rings, max_ring_order, len = 0;
 407
 408         versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
 409         if (IS_ERR(versions))
 410                 return PTR_ERR(versions);
 411         for (v = versions; *v; v++) {
 412                 if (simple_strtoul(v, &v, 10) == 1) {
 413                         v = NULL;
 414                         break;
 415                 }
 416         }
 417         if (v) {
 418                 kfree(versions);
 419                 return -EINVAL;
 420         }
 421         kfree(versions);
 422         max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
 423         if (max_rings < XEN_9PFS_NUM_RINGS)
 424                 return -EINVAL;
 425         max_ring_order = xenbus_read_unsigned(dev->otherend,
 426                                               "max-ring-page-order", 0);
 427         if (max_ring_order > XEN_9PFS_RING_ORDER)
 428                 max_ring_order = XEN_9PFS_RING_ORDER;
 429         if (p9_xen_trans.maxsize > XEN_FLEX_RING_SIZE(max_ring_order))
 430                 p9_xen_trans.maxsize = XEN_FLEX_RING_SIZE(max_ring_order) / 2;
 431
 432         priv->num_rings = XEN_9PFS_NUM_RINGS;
 433         priv->rings = kcalloc(priv->num_rings, sizeof(*priv->rings),
 434                               GFP_KERNEL);
 435         if (!priv->rings) {
 436                 kfree(priv);
 437                 return -ENOMEM;
 438         }
 439
 440         for (i = 0; i < priv->num_rings; i++) {
 441                 priv->rings[i].priv = priv;
 442                 ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i],
 443                                                     max_ring_order);
 444                 if (ret < 0)
 445                         goto error;
 446         }
 447
 448  again:
 449         ret = xenbus_transaction_start(&xbt);
 450         if (ret) {
 451                 xenbus_dev_fatal(dev, ret, "starting transaction");
 452                 goto error;
 453         }
 454         ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
 455         if (ret)
 456                 goto error_xenbus;
 457         ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
 458                             priv->num_rings);
 459         if (ret)
 460                 goto error_xenbus;
 461         for (i = 0; i < priv->num_rings; i++) {
 462                 char str[16];
 463
 464                 BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
 465                 sprintf(str, "ring-ref%d", i);
 466                 ret = xenbus_printf(xbt, dev->nodename, str, "%d",
 467                                     priv->rings[i].ref);
 468                 if (ret)
 469                         goto error_xenbus;
 470
 471                 sprintf(str, "event-channel-%d", i);
 472                 ret = xenbus_printf(xbt, dev->nodename, str, "%u",
 473                                     priv->rings[i].evtchn);
 474                 if (ret)
 475                         goto error_xenbus;
 476         }
 477         priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
 478         if (IS_ERR(priv->tag)) {
 479                 ret = PTR_ERR(priv->tag);
 480                 goto error_xenbus;
 481         }
 482         ret = xenbus_transaction_end(xbt, 0);
 483         if (ret) {
 484                 if (ret == -EAGAIN)
 485                         goto again;
 486                 xenbus_dev_fatal(dev, ret, "completing transaction");
 487                 goto error;
 488         }
 489
 490         return 0;
 491
 492  error_xenbus:
 493         xenbus_transaction_end(xbt, 1);
 494         xenbus_dev_fatal(dev, ret, "writing xenstore");
 495  error:
 496         xen_9pfs_front_free(priv);
 497         return ret;
 498 }
 499
 500 static int xen_9pfs_front_probe(struct xenbus_device *dev,
 501                                 const struct xenbus_device_id *id)
 502 {
 503         struct xen_9pfs_front_priv *priv = NULL;
 504
 505         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 506         if (!priv)
 507                 return -ENOMEM;
 508
 509         priv->dev = dev;
 510         dev_set_drvdata(&dev->dev, priv);
 511
 512         write_lock(&xen_9pfs_lock);
 513         list_add_tail(&priv->list, &xen_9pfs_devs);
 514         write_unlock(&xen_9pfs_lock);
 515
 516         return 0;
 517 }
 518
 519 static int xen_9pfs_front_resume(struct xenbus_device *dev)
 520 {
 521         dev_warn(&dev->dev, "suspend/resume unsupported\n");
 522         return 0;
 523 }
 524
 525 static void xen_9pfs_front_changed(struct xenbus_device *dev,
 526                                    enum xenbus_state backend_state)
 527 {
 528         switch (backend_state) {
 529         case XenbusStateReconfiguring:
 530         case XenbusStateReconfigured:
 531         case XenbusStateInitialising:
 532         case XenbusStateInitialised:
 533         case XenbusStateUnknown:
 534                 break;
 535
 536         case XenbusStateInitWait:
 537                 if (!xen_9pfs_front_init(dev))
 538                         xenbus_switch_state(dev, XenbusStateInitialised);
 539                 break;
 540
 541         case XenbusStateConnected:
 542                 xenbus_switch_state(dev, XenbusStateConnected);
 543                 break;
 544
 545         case XenbusStateClosed:
 546                 if (dev->state == XenbusStateClosed)
 547                         break;
 548                 fallthrough;    /* Missed the backend's CLOSING state */
 549         case XenbusStateClosing:
 550                 xenbus_frontend_closed(dev);
 551                 break;
 552         }
 553 }
 554
 555 static struct xenbus_driver xen_9pfs_front_driver = {
 556         .ids = xen_9pfs_front_ids,
 557         .probe = xen_9pfs_front_probe,
 558         .remove = xen_9pfs_front_remove,
 559         .resume = xen_9pfs_front_resume,
 560         .otherend_changed = xen_9pfs_front_changed,
 561 };
 562
 563 static int p9_trans_xen_init(void)
 564 {
 565         int rc;
 566
 567         if (!xen_domain())
 568                 return -ENODEV;
 569
 570         pr_info("Initialising Xen transport for 9pfs\n");
 571
 572         v9fs_register_trans(&p9_xen_trans);
 573         rc = xenbus_register_frontend(&xen_9pfs_front_driver);
 574         if (rc)
 575                 v9fs_unregister_trans(&p9_xen_trans);
 576
 577         return rc;
 578 }
 579 module_init(p9_trans_xen_init);
 580
 581 static void p9_trans_xen_exit(void)
 582 {
 583         v9fs_unregister_trans(&p9_xen_trans);
 584         return xenbus_unregister_driver(&xen_9pfs_front_driver);
 585 }
 586 module_exit(p9_trans_xen_exit);
 587
 588 MODULE_AUTHOR("Stefano Stabellini <stefano@aporeto.com>");
 589 MODULE_DESCRIPTION("Xen Transport for 9P");
 590 MODULE_LICENSE("GPL");