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