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"); 554