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 */ p9_xen_cancel(struct p9_client * client,struct p9_req_t * req)65 static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req) 66 { 67 return 1; 68 } 69 p9_xen_create(struct p9_client * client,const char * addr,char * args)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 p9_xen_close(struct p9_client * client)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 p9_xen_write_todo(struct xen_9pfs_dataring * ring,RING_IDX size)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 p9_xen_request(struct p9_client * client,struct p9_req_t * p9_req)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 p9_xen_response(struct work_struct * work)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 xen_9pfs_front_event_handler(int irq,void * r)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 xen_9pfs_front_free(struct xen_9pfs_front_priv * priv)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 struct xen_9pfs_dataring *ring = &priv->rings[i]; 284 285 cancel_work_sync(&ring->work); 286 287 if (!priv->rings[i].intf) 288 break; 289 if (priv->rings[i].irq > 0) 290 unbind_from_irqhandler(priv->rings[i].irq, ring); 291 if (priv->rings[i].data.in) { 292 for (j = 0; 293 j < (1 << priv->rings[i].intf->ring_order); 294 j++) { 295 grant_ref_t ref; 296 297 ref = priv->rings[i].intf->ref[j]; 298 gnttab_end_foreign_access(ref, NULL); 299 } 300 free_pages_exact(priv->rings[i].data.in, 301 1UL << (priv->rings[i].intf->ring_order + 302 XEN_PAGE_SHIFT)); 303 } 304 gnttab_end_foreign_access(priv->rings[i].ref, NULL); 305 free_page((unsigned long)priv->rings[i].intf); 306 } 307 kfree(priv->rings); 308 kfree(priv->tag); 309 kfree(priv); 310 } 311 xen_9pfs_front_remove(struct xenbus_device * dev)312 static void xen_9pfs_front_remove(struct xenbus_device *dev) 313 { 314 struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev); 315 316 dev_set_drvdata(&dev->dev, NULL); 317 xen_9pfs_front_free(priv); 318 } 319 xen_9pfs_front_alloc_dataring(struct xenbus_device * dev,struct xen_9pfs_dataring * ring,unsigned int order)320 static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev, 321 struct xen_9pfs_dataring *ring, 322 unsigned int order) 323 { 324 int i = 0; 325 int ret = -ENOMEM; 326 void *bytes = NULL; 327 328 init_waitqueue_head(&ring->wq); 329 spin_lock_init(&ring->lock); 330 INIT_WORK(&ring->work, p9_xen_response); 331 332 ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL); 333 if (!ring->intf) 334 return ret; 335 ret = gnttab_grant_foreign_access(dev->otherend_id, 336 virt_to_gfn(ring->intf), 0); 337 if (ret < 0) 338 goto out; 339 ring->ref = ret; 340 bytes = alloc_pages_exact(1UL << (order + XEN_PAGE_SHIFT), 341 GFP_KERNEL | __GFP_ZERO); 342 if (!bytes) { 343 ret = -ENOMEM; 344 goto out; 345 } 346 for (; i < (1 << order); i++) { 347 ret = gnttab_grant_foreign_access( 348 dev->otherend_id, virt_to_gfn(bytes) + i, 0); 349 if (ret < 0) 350 goto out; 351 ring->intf->ref[i] = ret; 352 } 353 ring->intf->ring_order = order; 354 ring->data.in = bytes; 355 ring->data.out = bytes + XEN_FLEX_RING_SIZE(order); 356 357 ret = xenbus_alloc_evtchn(dev, &ring->evtchn); 358 if (ret) 359 goto out; 360 ring->irq = bind_evtchn_to_irqhandler(ring->evtchn, 361 xen_9pfs_front_event_handler, 362 0, "xen_9pfs-frontend", ring); 363 if (ring->irq >= 0) 364 return 0; 365 366 xenbus_free_evtchn(dev, ring->evtchn); 367 ret = ring->irq; 368 out: 369 if (bytes) { 370 for (i--; i >= 0; i--) 371 gnttab_end_foreign_access(ring->intf->ref[i], NULL); 372 free_pages_exact(bytes, 1UL << (order + XEN_PAGE_SHIFT)); 373 } 374 gnttab_end_foreign_access(ring->ref, NULL); 375 free_page((unsigned long)ring->intf); 376 return ret; 377 } 378 xen_9pfs_front_init(struct xenbus_device * dev)379 static int xen_9pfs_front_init(struct xenbus_device *dev) 380 { 381 int ret, i; 382 struct xenbus_transaction xbt; 383 struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev); 384 char *versions, *v; 385 unsigned int max_rings, max_ring_order, len = 0; 386 387 versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len); 388 if (IS_ERR(versions)) 389 return PTR_ERR(versions); 390 for (v = versions; *v; v++) { 391 if (simple_strtoul(v, &v, 10) == 1) { 392 v = NULL; 393 break; 394 } 395 } 396 if (v) { 397 kfree(versions); 398 return -EINVAL; 399 } 400 kfree(versions); 401 max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0); 402 if (max_rings < XEN_9PFS_NUM_RINGS) 403 return -EINVAL; 404 max_ring_order = xenbus_read_unsigned(dev->otherend, 405 "max-ring-page-order", 0); 406 if (max_ring_order > XEN_9PFS_RING_ORDER) 407 max_ring_order = XEN_9PFS_RING_ORDER; 408 if (p9_xen_trans.maxsize > XEN_FLEX_RING_SIZE(max_ring_order)) 409 p9_xen_trans.maxsize = XEN_FLEX_RING_SIZE(max_ring_order) / 2; 410 411 priv->num_rings = XEN_9PFS_NUM_RINGS; 412 priv->rings = kcalloc(priv->num_rings, sizeof(*priv->rings), 413 GFP_KERNEL); 414 if (!priv->rings) { 415 kfree(priv); 416 return -ENOMEM; 417 } 418 419 for (i = 0; i < priv->num_rings; i++) { 420 priv->rings[i].priv = priv; 421 ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i], 422 max_ring_order); 423 if (ret < 0) 424 goto error; 425 } 426 427 again: 428 ret = xenbus_transaction_start(&xbt); 429 if (ret) { 430 xenbus_dev_fatal(dev, ret, "starting transaction"); 431 goto error; 432 } 433 ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1); 434 if (ret) 435 goto error_xenbus; 436 ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u", 437 priv->num_rings); 438 if (ret) 439 goto error_xenbus; 440 for (i = 0; i < priv->num_rings; i++) { 441 char str[16]; 442 443 BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9); 444 sprintf(str, "ring-ref%d", i); 445 ret = xenbus_printf(xbt, dev->nodename, str, "%d", 446 priv->rings[i].ref); 447 if (ret) 448 goto error_xenbus; 449 450 sprintf(str, "event-channel-%d", i); 451 ret = xenbus_printf(xbt, dev->nodename, str, "%u", 452 priv->rings[i].evtchn); 453 if (ret) 454 goto error_xenbus; 455 } 456 priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL); 457 if (IS_ERR(priv->tag)) { 458 ret = PTR_ERR(priv->tag); 459 goto error_xenbus; 460 } 461 ret = xenbus_transaction_end(xbt, 0); 462 if (ret) { 463 if (ret == -EAGAIN) 464 goto again; 465 xenbus_dev_fatal(dev, ret, "completing transaction"); 466 goto error; 467 } 468 469 xenbus_switch_state(dev, XenbusStateInitialised); 470 return 0; 471 472 error_xenbus: 473 xenbus_transaction_end(xbt, 1); 474 xenbus_dev_fatal(dev, ret, "writing xenstore"); 475 error: 476 xen_9pfs_front_free(priv); 477 return ret; 478 } 479 xen_9pfs_front_probe(struct xenbus_device * dev,const struct xenbus_device_id * id)480 static int xen_9pfs_front_probe(struct xenbus_device *dev, 481 const struct xenbus_device_id *id) 482 { 483 struct xen_9pfs_front_priv *priv = NULL; 484 485 priv = kzalloc(sizeof(*priv), GFP_KERNEL); 486 if (!priv) 487 return -ENOMEM; 488 489 priv->dev = dev; 490 dev_set_drvdata(&dev->dev, priv); 491 492 write_lock(&xen_9pfs_lock); 493 list_add_tail(&priv->list, &xen_9pfs_devs); 494 write_unlock(&xen_9pfs_lock); 495 496 return 0; 497 } 498 xen_9pfs_front_resume(struct xenbus_device * dev)499 static int xen_9pfs_front_resume(struct xenbus_device *dev) 500 { 501 dev_warn(&dev->dev, "suspend/resume unsupported\n"); 502 return 0; 503 } 504 xen_9pfs_front_changed(struct xenbus_device * dev,enum xenbus_state backend_state)505 static void xen_9pfs_front_changed(struct xenbus_device *dev, 506 enum xenbus_state backend_state) 507 { 508 switch (backend_state) { 509 case XenbusStateReconfiguring: 510 case XenbusStateReconfigured: 511 case XenbusStateInitialising: 512 case XenbusStateInitialised: 513 case XenbusStateUnknown: 514 break; 515 516 case XenbusStateInitWait: 517 if (dev->state != XenbusStateInitialising) 518 break; 519 520 xen_9pfs_front_init(dev); 521 break; 522 523 case XenbusStateConnected: 524 xenbus_switch_state(dev, XenbusStateConnected); 525 break; 526 527 case XenbusStateClosed: 528 if (dev->state == XenbusStateClosed) 529 break; 530 fallthrough; /* Missed the backend's CLOSING state */ 531 case XenbusStateClosing: 532 xenbus_frontend_closed(dev); 533 break; 534 } 535 } 536 537 static struct xenbus_driver xen_9pfs_front_driver = { 538 .ids = xen_9pfs_front_ids, 539 .probe = xen_9pfs_front_probe, 540 .remove = xen_9pfs_front_remove, 541 .resume = xen_9pfs_front_resume, 542 .otherend_changed = xen_9pfs_front_changed, 543 }; 544 p9_trans_xen_init(void)545 static int __init p9_trans_xen_init(void) 546 { 547 int rc; 548 549 if (!xen_domain()) 550 return -ENODEV; 551 552 pr_info("Initialising Xen transport for 9pfs\n"); 553 554 v9fs_register_trans(&p9_xen_trans); 555 rc = xenbus_register_frontend(&xen_9pfs_front_driver); 556 if (rc) 557 v9fs_unregister_trans(&p9_xen_trans); 558 559 return rc; 560 } 561 module_init(p9_trans_xen_init); 562 MODULE_ALIAS_9P("xen"); 563 p9_trans_xen_exit(void)564 static void __exit p9_trans_xen_exit(void) 565 { 566 v9fs_unregister_trans(&p9_xen_trans); 567 return xenbus_unregister_driver(&xen_9pfs_front_driver); 568 } 569 module_exit(p9_trans_xen_exit); 570 571 MODULE_ALIAS("xen:9pfs"); 572 MODULE_AUTHOR("Stefano Stabellini <stefano@aporeto.com>"); 573 MODULE_DESCRIPTION("Xen Transport for 9P"); 574 MODULE_LICENSE("GPL"); 575