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 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 <stefano@aporeto.com>"); 542 MODULE_DESCRIPTION("Xen Transport for 9P"); 543 MODULE_LICENSE("GPL"); 544