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 <[email protected]>
   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         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(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                 memcpy(&req->rc, &h, sizeof(h));
 212                 req->rc.offset = 0;
 213
 214                 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
 215                 /* Then, read the whole packet (including the header) */
 216                 xen_9pfs_read_packet(req->rc.sdata, ring->data.in, h.size,
 217                                      masked_prod, &masked_cons,
 218                                      XEN_9PFS_RING_SIZE(ring));
 219
 220                 virt_mb();
 221                 cons += h.size;
 222                 ring->intf->in_cons = cons;
 223
 224                 status = (req->status != REQ_STATUS_ERROR) ?
 225                         REQ_STATUS_RCVD : REQ_STATUS_ERROR;
 226
 227                 p9_client_cb(priv->client, req, status);
 228         }
 229 }
 230
 231 static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
 232 {
 233         struct xen_9pfs_dataring *ring = r;
 234
 235         if (!ring || !ring->priv->client) {
 236                 /* ignore spurious interrupt */
 237                 return IRQ_HANDLED;
 238         }
 239
 240         wake_up_interruptible(&ring->wq);
 241         schedule_work(&ring->work);
 242
 243         return IRQ_HANDLED;
 244 }
 245
 246 static struct p9_trans_module p9_xen_trans = {
 247         .name = "xen",
 248         .maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT - 2),
 249         .def = 1,
 250         .create = p9_xen_create,
 251         .close = p9_xen_close,
 252         .request = p9_xen_request,
 253         .cancel = p9_xen_cancel,
 254         .owner = THIS_MODULE,
 255 };
 256
 257 static const struct xenbus_device_id xen_9pfs_front_ids[] = {
 258         { "9pfs" },
 259         { "" }
 260 };
 261
 262 static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
 263 {
 264         int i, j;
 265
 266         write_lock(&xen_9pfs_lock);
 267         list_del(&priv->list);
 268         write_unlock(&xen_9pfs_lock);
 269
 270         for (i = 0; i < priv->num_rings; i++) {
 271                 if (!priv->rings[i].intf)
 272                         break;
 273                 if (priv->rings[i].irq > 0)
 274                         unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
 275                 if (priv->rings[i].data.in) {
 276                         for (j = 0;
 277                              j < (1 << priv->rings[i].intf->ring_order);
 278                              j++) {
 279                                 grant_ref_t ref;
 280
 281                                 ref = priv->rings[i].intf->ref[j];
 282                                 gnttab_end_foreign_access(ref, 0, 0);
 283                         }
 284                         free_pages((unsigned long)priv->rings[i].data.in,
 285                                    priv->rings[i].intf->ring_order -
 286                                    (PAGE_SHIFT - XEN_PAGE_SHIFT));
 287                 }
 288                 gnttab_end_foreign_access(priv->rings[i].ref, 0, 0);
 289                 free_page((unsigned long)priv->rings[i].intf);
 290         }
 291         kfree(priv->rings);
 292         kfree(priv->tag);
 293         kfree(priv);
 294 }
 295
 296 static int xen_9pfs_front_remove(struct xenbus_device *dev)
 297 {
 298         struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
 299
 300         dev_set_drvdata(&dev->dev, NULL);
 301         xen_9pfs_front_free(priv);
 302         return 0;
 303 }
 304
 305 static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
 306                                          struct xen_9pfs_dataring *ring,
 307                                          unsigned int order)
 308 {
 309         int i = 0;
 310         int ret = -ENOMEM;
 311         void *bytes = NULL;
 312
 313         init_waitqueue_head(&ring->wq);
 314         spin_lock_init(&ring->lock);
 315         INIT_WORK(&ring->work, p9_xen_response);
 316
 317         ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL);
 318         if (!ring->intf)
 319                 return ret;
 320         ret = gnttab_grant_foreign_access(dev->otherend_id,
 321                                           virt_to_gfn(ring->intf), 0);
 322         if (ret < 0)
 323                 goto out;
 324         ring->ref = ret;
 325         bytes = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
 326                         order - (PAGE_SHIFT - XEN_PAGE_SHIFT));
 327         if (!bytes) {
 328                 ret = -ENOMEM;
 329                 goto out;
 330         }
 331         for (; i < (1 << order); i++) {
 332                 ret = gnttab_grant_foreign_access(
 333                                 dev->otherend_id, virt_to_gfn(bytes) + i, 0);
 334                 if (ret < 0)
 335                         goto out;
 336                 ring->intf->ref[i] = ret;
 337         }
 338         ring->intf->ring_order = order;
 339         ring->data.in = bytes;
 340         ring->data.out = bytes + XEN_FLEX_RING_SIZE(order);
 341
 342         ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
 343         if (ret)
 344                 goto out;
 345         ring->irq = bind_evtchn_to_irqhandler(ring->evtchn,
 346                                               xen_9pfs_front_event_handler,
 347                                               0, "xen_9pfs-frontend", ring);
 348         if (ring->irq >= 0)
 349                 return 0;
 350
 351         xenbus_free_evtchn(dev, ring->evtchn);
 352         ret = ring->irq;
 353 out:
 354         if (bytes) {
 355                 for (i--; i >= 0; i--)
 356                         gnttab_end_foreign_access(ring->intf->ref[i], 0, 0);
 357                 free_pages((unsigned long)bytes,
 358                            ring->intf->ring_order -
 359                            (PAGE_SHIFT - XEN_PAGE_SHIFT));
 360         }
 361         gnttab_end_foreign_access(ring->ref, 0, 0);
 362         free_page((unsigned long)ring->intf);
 363         return ret;
 364 }
 365
 366 static int xen_9pfs_front_probe(struct xenbus_device *dev,
 367                                 const struct xenbus_device_id *id)
 368 {
 369         int ret, i;
 370         struct xenbus_transaction xbt;
 371         struct xen_9pfs_front_priv *priv = NULL;
 372         char *versions;
 373         unsigned int max_rings, max_ring_order, len = 0;
 374
 375         versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
 376         if (IS_ERR(versions))
 377                 return PTR_ERR(versions);
 378         if (strcmp(versions, "1")) {
 379                 kfree(versions);
 380                 return -EINVAL;
 381         }
 382         kfree(versions);
 383         max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
 384         if (max_rings < XEN_9PFS_NUM_RINGS)
 385                 return -EINVAL;
 386         max_ring_order = xenbus_read_unsigned(dev->otherend,
 387                                               "max-ring-page-order", 0);
 388         if (max_ring_order > XEN_9PFS_RING_ORDER)
 389                 max_ring_order = XEN_9PFS_RING_ORDER;
 390         if (p9_xen_trans.maxsize > XEN_FLEX_RING_SIZE(max_ring_order))
 391                 p9_xen_trans.maxsize = XEN_FLEX_RING_SIZE(max_ring_order) / 2;
 392
 393         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 394         if (!priv)
 395                 return -ENOMEM;
 396
 397         priv->dev = dev;
 398         priv->num_rings = XEN_9PFS_NUM_RINGS;
 399         priv->rings = kcalloc(priv->num_rings, sizeof(*priv->rings),
 400                               GFP_KERNEL);
 401         if (!priv->rings) {
 402                 kfree(priv);
 403                 return -ENOMEM;
 404         }
 405
 406         for (i = 0; i < priv->num_rings; i++) {
 407                 priv->rings[i].priv = priv;
 408                 ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i],
 409                                                     max_ring_order);
 410                 if (ret < 0)
 411                         goto error;
 412         }
 413
 414  again:
 415         ret = xenbus_transaction_start(&xbt);
 416         if (ret) {
 417                 xenbus_dev_fatal(dev, ret, "starting transaction");
 418                 goto error;
 419         }
 420         ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
 421         if (ret)
 422                 goto error_xenbus;
 423         ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
 424                             priv->num_rings);
 425         if (ret)
 426                 goto error_xenbus;
 427         for (i = 0; i < priv->num_rings; i++) {
 428                 char str[16];
 429
 430                 BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
 431                 sprintf(str, "ring-ref%d", i);
 432                 ret = xenbus_printf(xbt, dev->nodename, str, "%d",
 433                                     priv->rings[i].ref);
 434                 if (ret)
 435                         goto error_xenbus;
 436
 437                 sprintf(str, "event-channel-%d", i);
 438                 ret = xenbus_printf(xbt, dev->nodename, str, "%u",
 439                                     priv->rings[i].evtchn);
 440                 if (ret)
 441                         goto error_xenbus;
 442         }
 443         priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
 444         if (IS_ERR(priv->tag)) {
 445                 ret = PTR_ERR(priv->tag);
 446                 goto error_xenbus;
 447         }
 448         ret = xenbus_transaction_end(xbt, 0);
 449         if (ret) {
 450                 if (ret == -EAGAIN)
 451                         goto again;
 452                 xenbus_dev_fatal(dev, ret, "completing transaction");
 453                 goto error;
 454         }
 455
 456         write_lock(&xen_9pfs_lock);
 457         list_add_tail(&priv->list, &xen_9pfs_devs);
 458         write_unlock(&xen_9pfs_lock);
 459         dev_set_drvdata(&dev->dev, priv);
 460         xenbus_switch_state(dev, XenbusStateInitialised);
 461
 462         return 0;
 463
 464  error_xenbus:
 465         xenbus_transaction_end(xbt, 1);
 466         xenbus_dev_fatal(dev, ret, "writing xenstore");
 467  error:
 468         dev_set_drvdata(&dev->dev, NULL);
 469         xen_9pfs_front_free(priv);
 470         return ret;
 471 }
 472
 473 static int xen_9pfs_front_resume(struct xenbus_device *dev)
 474 {
 475         dev_warn(&dev->dev, "suspend/resume unsupported\n");
 476         return 0;
 477 }
 478
 479 static void xen_9pfs_front_changed(struct xenbus_device *dev,
 480                                    enum xenbus_state backend_state)
 481 {
 482         switch (backend_state) {
 483         case XenbusStateReconfiguring:
 484         case XenbusStateReconfigured:
 485         case XenbusStateInitialising:
 486         case XenbusStateInitialised:
 487         case XenbusStateUnknown:
 488                 break;
 489
 490         case XenbusStateInitWait:
 491                 break;
 492
 493         case XenbusStateConnected:
 494                 xenbus_switch_state(dev, XenbusStateConnected);
 495                 break;
 496
 497         case XenbusStateClosed:
 498                 if (dev->state == XenbusStateClosed)
 499                         break;
 500                 fallthrough;    /* Missed the backend's CLOSING state */
 501         case XenbusStateClosing:
 502                 xenbus_frontend_closed(dev);
 503                 break;
 504         }
 505 }
 506
 507 static struct xenbus_driver xen_9pfs_front_driver = {
 508         .ids = xen_9pfs_front_ids,
 509         .probe = xen_9pfs_front_probe,
 510         .remove = xen_9pfs_front_remove,
 511         .resume = xen_9pfs_front_resume,
 512         .otherend_changed = xen_9pfs_front_changed,
 513 };
 514
 515 static int p9_trans_xen_init(void)
 516 {
 517         int rc;
 518
 519         if (!xen_domain())
 520                 return -ENODEV;
 521
 522         pr_info("Initialising Xen transport for 9pfs\n");
 523
 524         v9fs_register_trans(&p9_xen_trans);
 525         rc = xenbus_register_frontend(&xen_9pfs_front_driver);
 526         if (rc)
 527                 v9fs_unregister_trans(&p9_xen_trans);
 528
 529         return rc;
 530 }
 531 module_init(p9_trans_xen_init);
 532 MODULE_ALIAS_9P("xen");
 533
 534 static void p9_trans_xen_exit(void)
 535 {
 536         v9fs_unregister_trans(&p9_xen_trans);
 537         return xenbus_unregister_driver(&xen_9pfs_front_driver);
 538 }
 539 module_exit(p9_trans_xen_exit);
 540
 541 MODULE_AUTHOR("Stefano Stabellini <[email protected]>");
 542 MODULE_DESCRIPTION("Xen Transport for 9P");
 543 MODULE_LICENSE("GPL");