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