net/9p/trans_xen.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * linux/fs/9p/trans_xen
   4  *
   5  * Xen transport layer.
   6  *
   7  * Copyright (C) 2017 by Stefano Stabellini <stefano@aporeto.com>
   8  */
   9
  10 #include <xen/events.h>
  11 #include <xen/grant_table.h>
  12 #include <xen/xen.h>
  13 #include <xen/xenbus.h>
  14 #include <xen/interface/io/9pfs.h>
  15
  16 #include <linux/module.h>
  17 #include <linux/spinlock.h>
  18 #include <net/9p/9p.h>
  19 #include <net/9p/client.h>
  20 #include <net/9p/transport.h>
  21
  22 #define XEN_9PFS_NUM_RINGS 2
  23 #define XEN_9PFS_RING_ORDER 9
  24 #define XEN_9PFS_RING_SIZE(ring)  XEN_FLEX_RING_SIZE(ring->intf->ring_order)
  25
  26 struct xen_9pfs_header {
  27         uint32_t size;
  28         uint8_t id;
  29         uint16_t tag;
  30
  31         /* uint8_t sdata[]; */
  32 } __attribute__((packed));
  33
  34 /* One per ring, more than one per 9pfs share */
  35 struct xen_9pfs_dataring {
  36         struct xen_9pfs_front_priv *priv;
  37
  38         struct xen_9pfs_data_intf *intf;
  39         grant_ref_t ref;
  40         int evtchn;
  41         int irq;
  42         /* protect a ring from concurrent accesses */
  43         spinlock_t lock;
  44
  45         struct xen_9pfs_data data;
  46         wait_queue_head_t wq;
  47         struct work_struct work;
  48 };
  49
  50 /* One per 9pfs share */
  51 struct xen_9pfs_front_priv {
  52         struct list_head list;
  53         struct xenbus_device *dev;
  54         char *tag;
  55         struct p9_client *client;
  56
  57         struct xen_9pfs_dataring *rings;
  58 };
  59
  60 static LIST_HEAD(xen_9pfs_devs);
  61 static DEFINE_RWLOCK(xen_9pfs_lock);
  62
  63 /* We don't currently allow canceling of requests */
  64 static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req)
  65 {
  66         return 1;
  67 }
  68
  69 static int p9_xen_create(struct p9_client *client, const char *addr, char *args)
  70 {
  71         struct xen_9pfs_front_priv *priv;
  72
  73         if (addr == NULL)
  74                 return -EINVAL;
  75
  76         read_lock(&xen_9pfs_lock);
  77         list_for_each_entry(priv, &xen_9pfs_devs, list) {
  78                 if (!strcmp(priv->tag, addr)) {
  79                         priv->client = client;
  80                         read_unlock(&xen_9pfs_lock);
  81                         return 0;
  82                 }
  83         }
  84         read_unlock(&xen_9pfs_lock);
  85         return -EINVAL;
  86 }
  87
  88 static void p9_xen_close(struct p9_client *client)
  89 {
  90         struct xen_9pfs_front_priv *priv;
  91
  92         read_lock(&xen_9pfs_lock);
  93         list_for_each_entry(priv, &xen_9pfs_devs, list) {
  94                 if (priv->client == client) {
  95                         priv->client = NULL;
  96                         read_unlock(&xen_9pfs_lock);
  97                         return;
  98                 }
  99         }
 100         read_unlock(&xen_9pfs_lock);
 101 }
 102
 103 static bool p9_xen_write_todo(struct xen_9pfs_dataring *ring, RING_IDX size)
 104 {
 105         RING_IDX cons, prod;
 106
 107         cons = ring->intf->out_cons;
 108         prod = ring->intf->out_prod;
 109         virt_mb();
 110
 111         return XEN_9PFS_RING_SIZE(ring) -
 112                 xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) >= size;
 113 }
 114
 115 static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
 116 {
 117         struct xen_9pfs_front_priv *priv;
 118         RING_IDX cons, prod, masked_cons, masked_prod;
 119         unsigned long flags;
 120         u32 size = p9_req->tc.size;
 121         struct xen_9pfs_dataring *ring;
 122         int num;
 123
 124         read_lock(&xen_9pfs_lock);
 125         list_for_each_entry(priv, &xen_9pfs_devs, list) {
 126                 if (priv->client == client)
 127                         break;
 128         }
 129         read_unlock(&xen_9pfs_lock);
 130         if (list_entry_is_head(priv, &xen_9pfs_devs, list))
 131                 return -EINVAL;
 132
 133         num = p9_req->tc.tag % XEN_9PFS_NUM_RINGS;
 134         ring = &priv->rings[num];
 135
 136 again:
 137         while (wait_event_killable(ring->wq,
 138                                    p9_xen_write_todo(ring, size)) != 0)
 139                 ;
 140
 141         spin_lock_irqsave(&ring->lock, flags);
 142         cons = ring->intf->out_cons;
 143         prod = ring->intf->out_prod;
 144         virt_mb();
 145
 146         if (XEN_9PFS_RING_SIZE(ring) -
 147             xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) < size) {
 148                 spin_unlock_irqrestore(&ring->lock, flags);
 149                 goto again;
 150         }
 151
 152         masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
 153         masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
 154
 155         xen_9pfs_write_packet(ring->data.out, p9_req->tc.sdata, size,
 156                               &masked_prod, masked_cons,
 157                               XEN_9PFS_RING_SIZE(ring));
 158
 159         WRITE_ONCE(p9_req->status, REQ_STATUS_SENT);
 160         virt_wmb();                     /* write ring before updating pointer */
 161         prod += size;
 162         ring->intf->out_prod = prod;
 163         spin_unlock_irqrestore(&ring->lock, flags);
 164         notify_remote_via_irq(ring->irq);
 165         p9_req_put(client, p9_req);
 166
 167         return 0;
 168 }
 169
 170 static void p9_xen_response(struct work_struct *work)
 171 {
 172         struct xen_9pfs_front_priv *priv;
 173         struct xen_9pfs_dataring *ring;
 174         RING_IDX cons, prod, masked_cons, masked_prod;
 175         struct xen_9pfs_header h;
 176         struct p9_req_t *req;
 177         int status;
 178
 179         ring = container_of(work, struct xen_9pfs_dataring, work);
 180         priv = ring->priv;
 181
 182         while (1) {
 183                 cons = ring->intf->in_cons;
 184                 prod = ring->intf->in_prod;
 185                 virt_rmb();
 186
 187                 if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) <
 188                     sizeof(h)) {
 189                         notify_remote_via_irq(ring->irq);
 190                         return;
 191                 }
 192
 193                 masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
 194                 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
 195
 196                 /* First, read just the header */
 197                 xen_9pfs_read_packet(&h, ring->data.in, sizeof(h),
 198                                      masked_prod, &masked_cons,
 199                                      XEN_9PFS_RING_SIZE(ring));
 200
 201                 req = p9_tag_lookup(priv->client, h.tag);
 202                 if (!req || req->status != REQ_STATUS_SENT) {
 203                         dev_warn(&priv->dev->dev, "Wrong req tag=%x\n", h.tag);
 204                         cons += h.size;
 205                         virt_mb();
 206                         ring->intf->in_cons = cons;
 207                         continue;
 208                 }
 209
 210                 if (h.size > req->rc.capacity) {
 211                         dev_warn(&priv->dev->dev,
 212                                  "requested packet size too big: %d for tag %d with capacity %zd\n",
 213                                  h.size, h.tag, req->rc.capacity);
 214                         WRITE_ONCE(req->status, REQ_STATUS_ERROR);
 215                         goto recv_error;
 216                 }
 217
 218                 req->rc.size = h.size;
 219                 req->rc.id = h.id;
 220                 req->rc.tag = h.tag;
 221                 req->rc.offset = 0;
 222
 223                 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
 224                 /* Then, read the whole packet (including the header) */
 225                 xen_9pfs_read_packet(req->rc.sdata, ring->data.in, h.size,
 226                                      masked_prod, &masked_cons,
 227                                      XEN_9PFS_RING_SIZE(ring));
 228
 229 recv_error:
 230                 virt_mb();
 231                 cons += h.size;
 232                 ring->intf->in_cons = cons;
 233
 234                 status = (req->status != REQ_STATUS_ERROR) ?
 235                         REQ_STATUS_RCVD : REQ_STATUS_ERROR;
 236
 237                 p9_client_cb(priv->client, req, status);
 238         }
 239 }
 240
 241 static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
 242 {
 243         struct xen_9pfs_dataring *ring = r;
 244
 245         if (!ring || !ring->priv->client) {
 246                 /* ignore spurious interrupt */
 247                 return IRQ_HANDLED;
 248         }
 249
 250         wake_up_interruptible(&ring->wq);
 251         schedule_work(&ring->work);
 252
 253         return IRQ_HANDLED;
 254 }
 255
 256 static struct p9_trans_module p9_xen_trans = {
 257         .name = "xen",
 258         .maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT - 2),
 259         .pooled_rbuffers = false,
 260         .def = 1,
 261         .create = p9_xen_create,
 262         .close = p9_xen_close,
 263         .request = p9_xen_request,
 264         .cancel = p9_xen_cancel,
 265         .owner = THIS_MODULE,
 266 };
 267
 268 static const struct xenbus_device_id xen_9pfs_front_ids[] = {
 269         { "9pfs" },
 270         { "" }
 271 };
 272
 273 static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
 274 {
 275         int i, j;
 276
 277         write_lock(&xen_9pfs_lock);
 278         list_del(&priv->list);
 279         write_unlock(&xen_9pfs_lock);
 280
 281         for (i = 0; i < XEN_9PFS_NUM_RINGS; i++) {
 282                 struct xen_9pfs_dataring *ring = &priv->rings[i];
 283
 284                 cancel_work_sync(&ring->work);
 285
 286                 if (!priv->rings[i].intf)
 287                         break;
 288                 if (priv->rings[i].irq > 0)
 289                         unbind_from_irqhandler(priv->rings[i].irq, ring);
 290                 if (priv->rings[i].data.in) {
 291                         for (j = 0;
 292                              j < (1 << priv->rings[i].intf->ring_order);
 293                              j++) {
 294                                 grant_ref_t ref;
 295
 296                                 ref = priv->rings[i].intf->ref[j];
 297                                 gnttab_end_foreign_access(ref, NULL);
 298                         }
 299                         free_pages_exact(priv->rings[i].data.in,
 300                                    1UL << (priv->rings[i].intf->ring_order +
 301                                            XEN_PAGE_SHIFT));
 302                 }
 303                 gnttab_end_foreign_access(priv->rings[i].ref, NULL);
 304                 free_page((unsigned long)priv->rings[i].intf);
 305         }
 306         kfree(priv->rings);
 307         kfree(priv->tag);
 308         kfree(priv);
 309 }
 310
 311 static void xen_9pfs_front_remove(struct xenbus_device *dev)
 312 {
 313         struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
 314
 315         dev_set_drvdata(&dev->dev, NULL);
 316         xen_9pfs_front_free(priv);
 317 }
 318
 319 static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
 320                                          struct xen_9pfs_dataring *ring,
 321                                          unsigned int order)
 322 {
 323         int i = 0;
 324         int ret = -ENOMEM;
 325         void *bytes = NULL;
 326
 327         init_waitqueue_head(&ring->wq);
 328         spin_lock_init(&ring->lock);
 329         INIT_WORK(&ring->work, p9_xen_response);
 330
 331         ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL);
 332         if (!ring->intf)
 333                 return ret;
 334         ret = gnttab_grant_foreign_access(dev->otherend_id,
 335                                           virt_to_gfn(ring->intf), 0);
 336         if (ret < 0)
 337                 goto out;
 338         ring->ref = ret;
 339         bytes = alloc_pages_exact(1UL << (order + XEN_PAGE_SHIFT),
 340                                   GFP_KERNEL | __GFP_ZERO);
 341         if (!bytes) {
 342                 ret = -ENOMEM;
 343                 goto out;
 344         }
 345         for (; i < (1 << order); i++) {
 346                 ret = gnttab_grant_foreign_access(
 347                                 dev->otherend_id, virt_to_gfn(bytes) + i, 0);
 348                 if (ret < 0)
 349                         goto out;
 350                 ring->intf->ref[i] = ret;
 351         }
 352         ring->intf->ring_order = order;
 353         ring->data.in = bytes;
 354         ring->data.out = bytes + XEN_FLEX_RING_SIZE(order);
 355
 356         ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
 357         if (ret)
 358                 goto out;
 359         ring->irq = bind_evtchn_to_irqhandler(ring->evtchn,
 360                                               xen_9pfs_front_event_handler,
 361                                               0, "xen_9pfs-frontend", ring);
 362         if (ring->irq >= 0)
 363                 return 0;
 364
 365         xenbus_free_evtchn(dev, ring->evtchn);
 366         ret = ring->irq;
 367 out:
 368         if (bytes) {
 369                 for (i--; i >= 0; i--)
 370                         gnttab_end_foreign_access(ring->intf->ref[i], NULL);
 371                 free_pages_exact(bytes, 1UL << (order + XEN_PAGE_SHIFT));
 372         }
 373         gnttab_end_foreign_access(ring->ref, NULL);
 374         free_page((unsigned long)ring->intf);
 375         return ret;
 376 }
 377
 378 static int xen_9pfs_front_init(struct xenbus_device *dev)
 379 {
 380         int ret, i;
 381         struct xenbus_transaction xbt;
 382         struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
 383         char *versions, *v;
 384         unsigned int max_rings, max_ring_order, len = 0;
 385
 386         versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
 387         if (IS_ERR(versions))
 388                 return PTR_ERR(versions);
 389         for (v = versions; *v; v++) {
 390                 if (simple_strtoul(v, &v, 10) == 1) {
 391                         v = NULL;
 392                         break;
 393                 }
 394         }
 395         if (v) {
 396                 kfree(versions);
 397                 return -EINVAL;
 398         }
 399         kfree(versions);
 400         max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
 401         if (max_rings < XEN_9PFS_NUM_RINGS)
 402                 return -EINVAL;
 403         max_ring_order = xenbus_read_unsigned(dev->otherend,
 404                                               "max-ring-page-order", 0);
 405         if (max_ring_order > XEN_9PFS_RING_ORDER)
 406                 max_ring_order = XEN_9PFS_RING_ORDER;
 407         if (p9_xen_trans.maxsize > XEN_FLEX_RING_SIZE(max_ring_order))
 408                 p9_xen_trans.maxsize = XEN_FLEX_RING_SIZE(max_ring_order) / 2;
 409
 410         priv->rings = kcalloc(XEN_9PFS_NUM_RINGS, sizeof(*priv->rings),
 411                               GFP_KERNEL);
 412         if (!priv->rings) {
 413                 kfree(priv);
 414                 return -ENOMEM;
 415         }
 416
 417         for (i = 0; i < XEN_9PFS_NUM_RINGS; i++) {
 418                 priv->rings[i].priv = priv;
 419                 ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i],
 420                                                     max_ring_order);
 421                 if (ret < 0)
 422                         goto error;
 423         }
 424
 425  again:
 426         ret = xenbus_transaction_start(&xbt);
 427         if (ret) {
 428                 xenbus_dev_fatal(dev, ret, "starting transaction");
 429                 goto error;
 430         }
 431         ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
 432         if (ret)
 433                 goto error_xenbus;
 434         ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
 435                             XEN_9PFS_NUM_RINGS);
 436         if (ret)
 437                 goto error_xenbus;
 438
 439         for (i = 0; i < XEN_9PFS_NUM_RINGS; i++) {
 440                 char str[16];
 441
 442                 BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
 443                 sprintf(str, "ring-ref%d", i);
 444                 ret = xenbus_printf(xbt, dev->nodename, str, "%d",
 445                                     priv->rings[i].ref);
 446                 if (ret)
 447                         goto error_xenbus;
 448
 449                 sprintf(str, "event-channel-%d", i);
 450                 ret = xenbus_printf(xbt, dev->nodename, str, "%u",
 451                                     priv->rings[i].evtchn);
 452                 if (ret)
 453                         goto error_xenbus;
 454         }
 455         priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
 456         if (IS_ERR(priv->tag)) {
 457                 ret = PTR_ERR(priv->tag);
 458                 goto error_xenbus;
 459         }
 460         ret = xenbus_transaction_end(xbt, 0);
 461         if (ret) {
 462                 if (ret == -EAGAIN)
 463                         goto again;
 464                 xenbus_dev_fatal(dev, ret, "completing transaction");
 465                 goto error;
 466         }
 467
 468         xenbus_switch_state(dev, XenbusStateInitialised);
 469         return 0;
 470
 471  error_xenbus:
 472         xenbus_transaction_end(xbt, 1);
 473         xenbus_dev_fatal(dev, ret, "writing xenstore");
 474  error:
 475         xen_9pfs_front_free(priv);
 476         return ret;
 477 }
 478
 479 static int xen_9pfs_front_probe(struct xenbus_device *dev,
 480                                 const struct xenbus_device_id *id)
 481 {
 482         struct xen_9pfs_front_priv *priv = NULL;
 483
 484         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 485         if (!priv)
 486                 return -ENOMEM;
 487
 488         priv->dev = dev;
 489         dev_set_drvdata(&dev->dev, priv);
 490
 491         write_lock(&xen_9pfs_lock);
 492         list_add_tail(&priv->list, &xen_9pfs_devs);
 493         write_unlock(&xen_9pfs_lock);
 494
 495         return 0;
 496 }
 497
 498 static int xen_9pfs_front_resume(struct xenbus_device *dev)
 499 {
 500         dev_warn(&dev->dev, "suspend/resume unsupported\n");
 501         return 0;
 502 }
 503
 504 static void xen_9pfs_front_changed(struct xenbus_device *dev,
 505                                    enum xenbus_state backend_state)
 506 {
 507         switch (backend_state) {
 508         case XenbusStateReconfiguring:
 509         case XenbusStateReconfigured:
 510         case XenbusStateInitialising:
 511         case XenbusStateInitialised:
 512         case XenbusStateUnknown:
 513                 break;
 514
 515         case XenbusStateInitWait:
 516                 if (dev->state != XenbusStateInitialising)
 517                         break;
 518
 519                 xen_9pfs_front_init(dev);
 520                 break;
 521
 522         case XenbusStateConnected:
 523                 xenbus_switch_state(dev, XenbusStateConnected);
 524                 break;
 525
 526         case XenbusStateClosed:
 527                 if (dev->state == XenbusStateClosed)
 528                         break;
 529                 fallthrough;    /* Missed the backend's CLOSING state */
 530         case XenbusStateClosing:
 531                 xenbus_frontend_closed(dev);
 532                 break;
 533         }
 534 }
 535
 536 static struct xenbus_driver xen_9pfs_front_driver = {
 537         .ids = xen_9pfs_front_ids,
 538         .probe = xen_9pfs_front_probe,
 539         .remove = xen_9pfs_front_remove,
 540         .resume = xen_9pfs_front_resume,
 541         .otherend_changed = xen_9pfs_front_changed,
 542 };
 543
 544 static int __init p9_trans_xen_init(void)
 545 {
 546         int rc;
 547
 548         if (!xen_domain())
 549                 return -ENODEV;
 550
 551         pr_info("Initialising Xen transport for 9pfs\n");
 552
 553         v9fs_register_trans(&p9_xen_trans);
 554         rc = xenbus_register_frontend(&xen_9pfs_front_driver);
 555         if (rc)
 556                 v9fs_unregister_trans(&p9_xen_trans);
 557
 558         return rc;
 559 }
 560 module_init(p9_trans_xen_init);
 561 MODULE_ALIAS_9P("xen");
 562
 563 static void __exit p9_trans_xen_exit(void)
 564 {
 565         v9fs_unregister_trans(&p9_xen_trans);
 566         return xenbus_unregister_driver(&xen_9pfs_front_driver);
 567 }
 568 module_exit(p9_trans_xen_exit);
 569
 570 MODULE_ALIAS("xen:9pfs");
 571 MODULE_AUTHOR("Stefano Stabellini <stefano@aporeto.com>");
 572 MODULE_DESCRIPTION("Xen Transport for 9P");
 573 MODULE_LICENSE("GPL");