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, priv->dev); 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 return 0; 469 470 error_xenbus: 471 xenbus_transaction_end(xbt, 1); 472 xenbus_dev_fatal(dev, ret, "writing xenstore"); 473 error: 474 xen_9pfs_front_free(priv); 475 return ret; 476 } 477 478 static int xen_9pfs_front_probe(struct xenbus_device *dev, 479 const struct xenbus_device_id *id) 480 { 481 struct xen_9pfs_front_priv *priv = NULL; 482 483 priv = kzalloc(sizeof(*priv), GFP_KERNEL); 484 if (!priv) 485 return -ENOMEM; 486 487 priv->dev = dev; 488 dev_set_drvdata(&dev->dev, priv); 489 490 write_lock(&xen_9pfs_lock); 491 list_add_tail(&priv->list, &xen_9pfs_devs); 492 write_unlock(&xen_9pfs_lock); 493 494 return 0; 495 } 496 497 static int xen_9pfs_front_resume(struct xenbus_device *dev) 498 { 499 dev_warn(&dev->dev, "suspend/resume unsupported\n"); 500 return 0; 501 } 502 503 static void xen_9pfs_front_changed(struct xenbus_device *dev, 504 enum xenbus_state backend_state) 505 { 506 switch (backend_state) { 507 case XenbusStateReconfiguring: 508 case XenbusStateReconfigured: 509 case XenbusStateInitialising: 510 case XenbusStateInitialised: 511 case XenbusStateUnknown: 512 break; 513 514 case XenbusStateInitWait: 515 if (!xen_9pfs_front_init(dev)) 516 xenbus_switch_state(dev, XenbusStateInitialised); 517 break; 518 519 case XenbusStateConnected: 520 xenbus_switch_state(dev, XenbusStateConnected); 521 break; 522 523 case XenbusStateClosed: 524 if (dev->state == XenbusStateClosed) 525 break; 526 fallthrough; /* Missed the backend's CLOSING state */ 527 case XenbusStateClosing: 528 xenbus_frontend_closed(dev); 529 break; 530 } 531 } 532 533 static struct xenbus_driver xen_9pfs_front_driver = { 534 .ids = xen_9pfs_front_ids, 535 .probe = xen_9pfs_front_probe, 536 .remove = xen_9pfs_front_remove, 537 .resume = xen_9pfs_front_resume, 538 .otherend_changed = xen_9pfs_front_changed, 539 }; 540 541 static int __init p9_trans_xen_init(void) 542 { 543 int rc; 544 545 if (!xen_domain()) 546 return -ENODEV; 547 548 pr_info("Initialising Xen transport for 9pfs\n"); 549 550 v9fs_register_trans(&p9_xen_trans); 551 rc = xenbus_register_frontend(&xen_9pfs_front_driver); 552 if (rc) 553 v9fs_unregister_trans(&p9_xen_trans); 554 555 return rc; 556 } 557 module_init(p9_trans_xen_init); 558 MODULE_ALIAS_9P("xen"); 559 560 static void __exit p9_trans_xen_exit(void) 561 { 562 v9fs_unregister_trans(&p9_xen_trans); 563 return xenbus_unregister_driver(&xen_9pfs_front_driver); 564 } 565 module_exit(p9_trans_xen_exit); 566 567 MODULE_ALIAS("xen:9pfs"); 568 MODULE_AUTHOR("Stefano Stabellini <stefano@aporeto.com>"); 569 MODULE_DESCRIPTION("Xen Transport for 9P"); 570 MODULE_LICENSE("GPL"); 571