drivers/pci/p2pdma.c

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This source file includes following definitions.
to_p2p_pgmap
size_show
available_show
published_show
pci_p2pdma_release
pci_p2pdma_setup
pci_p2pdma_add_resource
find_parent_pci_dev
pci_bridge_has_acs_redir
seq_buf_print_bus_devfn
__host_bridge_whitelist
host_bridge_whitelist
__upstream_bridge_distance
map_types_idx
upstream_bridge_distance
upstream_bridge_distance_warn
pci_p2pdma_distance_many
pci_has_p2pmem
pci_p2pmem_find_many
pci_alloc_p2pmem
pci_free_p2pmem
pci_p2pmem_virt_to_bus
pci_p2pmem_alloc_sgl
pci_p2pmem_free_sgl
pci_p2pmem_publish
__pci_p2pdma_map_sg
pci_p2pdma_map_sg_attrs
pci_p2pdma_unmap_sg_attrs
pci_p2pdma_enable_store
pci_p2pdma_enable_show
   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * PCI Peer 2 Peer DMA support.
   4  *
   5  * Copyright (c) 2016-2018, Logan Gunthorpe
   6  * Copyright (c) 2016-2017, Microsemi Corporation
   7  * Copyright (c) 2017, Christoph Hellwig
   8  * Copyright (c) 2018, Eideticom Inc.
   9  */
  10 
  11 #define pr_fmt(fmt) "pci-p2pdma: " fmt
  12 #include <linux/ctype.h>
  13 #include <linux/pci-p2pdma.h>
  14 #include <linux/module.h>
  15 #include <linux/slab.h>
  16 #include <linux/genalloc.h>
  17 #include <linux/memremap.h>
  18 #include <linux/percpu-refcount.h>
  19 #include <linux/random.h>
  20 #include <linux/seq_buf.h>
  21 #include <linux/xarray.h>
  22 
  23 enum pci_p2pdma_map_type {
  24         PCI_P2PDMA_MAP_UNKNOWN = 0,
  25         PCI_P2PDMA_MAP_NOT_SUPPORTED,
  26         PCI_P2PDMA_MAP_BUS_ADDR,
  27         PCI_P2PDMA_MAP_THRU_HOST_BRIDGE,
  28 };
  29 
  30 struct pci_p2pdma {
  31         struct gen_pool *pool;
  32         bool p2pmem_published;
  33         struct xarray map_types;
  34 };
  35 
  36 struct pci_p2pdma_pagemap {
  37         struct dev_pagemap pgmap;
  38         struct pci_dev *provider;
  39         u64 bus_offset;
  40 };
  41 
  42 static struct pci_p2pdma_pagemap *to_p2p_pgmap(struct dev_pagemap *pgmap)
  43 {
  44         return container_of(pgmap, struct pci_p2pdma_pagemap, pgmap);
  45 }
  46 
  47 static ssize_t size_show(struct device *dev, struct device_attribute *attr,
  48                          char *buf)
  49 {
  50         struct pci_dev *pdev = to_pci_dev(dev);
  51         size_t size = 0;
  52 
  53         if (pdev->p2pdma->pool)
  54                 size = gen_pool_size(pdev->p2pdma->pool);
  55 
  56         return snprintf(buf, PAGE_SIZE, "%zd\n", size);
  57 }
  58 static DEVICE_ATTR_RO(size);
  59 
  60 static ssize_t available_show(struct device *dev, struct device_attribute *attr,
  61                               char *buf)
  62 {
  63         struct pci_dev *pdev = to_pci_dev(dev);
  64         size_t avail = 0;
  65 
  66         if (pdev->p2pdma->pool)
  67                 avail = gen_pool_avail(pdev->p2pdma->pool);
  68 
  69         return snprintf(buf, PAGE_SIZE, "%zd\n", avail);
  70 }
  71 static DEVICE_ATTR_RO(available);
  72 
  73 static ssize_t published_show(struct device *dev, struct device_attribute *attr,
  74                               char *buf)
  75 {
  76         struct pci_dev *pdev = to_pci_dev(dev);
  77 
  78         return snprintf(buf, PAGE_SIZE, "%d\n",
  79                         pdev->p2pdma->p2pmem_published);
  80 }
  81 static DEVICE_ATTR_RO(published);
  82 
  83 static struct attribute *p2pmem_attrs[] = {
  84         &dev_attr_size.attr,
  85         &dev_attr_available.attr,
  86         &dev_attr_published.attr,
  87         NULL,
  88 };
  89 
  90 static const struct attribute_group p2pmem_group = {
  91         .attrs = p2pmem_attrs,
  92         .name = "p2pmem",
  93 };
  94 
  95 static void pci_p2pdma_release(void *data)
  96 {
  97         struct pci_dev *pdev = data;
  98         struct pci_p2pdma *p2pdma = pdev->p2pdma;
  99 
 100         if (!p2pdma)
 101                 return;
 102 
 103         /* Flush and disable pci_alloc_p2p_mem() */
 104         pdev->p2pdma = NULL;
 105         synchronize_rcu();
 106 
 107         gen_pool_destroy(p2pdma->pool);
 108         sysfs_remove_group(&pdev->dev.kobj, &p2pmem_group);
 109         xa_destroy(&p2pdma->map_types);
 110 }
 111 
 112 static int pci_p2pdma_setup(struct pci_dev *pdev)
 113 {
 114         int error = -ENOMEM;
 115         struct pci_p2pdma *p2p;
 116 
 117         p2p = devm_kzalloc(&pdev->dev, sizeof(*p2p), GFP_KERNEL);
 118         if (!p2p)
 119                 return -ENOMEM;
 120 
 121         xa_init(&p2p->map_types);
 122 
 123         p2p->pool = gen_pool_create(PAGE_SHIFT, dev_to_node(&pdev->dev));
 124         if (!p2p->pool)
 125                 goto out;
 126 
 127         error = devm_add_action_or_reset(&pdev->dev, pci_p2pdma_release, pdev);
 128         if (error)
 129                 goto out_pool_destroy;
 130 
 131         pdev->p2pdma = p2p;
 132 
 133         error = sysfs_create_group(&pdev->dev.kobj, &p2pmem_group);
 134         if (error)
 135                 goto out_pool_destroy;
 136 
 137         return 0;
 138 
 139 out_pool_destroy:
 140         pdev->p2pdma = NULL;
 141         gen_pool_destroy(p2p->pool);
 142 out:
 143         devm_kfree(&pdev->dev, p2p);
 144         return error;
 145 }
 146 
 147 /**
 148  * pci_p2pdma_add_resource - add memory for use as p2p memory
 149  * @pdev: the device to add the memory to
 150  * @bar: PCI BAR to add
 151  * @size: size of the memory to add, may be zero to use the whole BAR
 152  * @offset: offset into the PCI BAR
 153  *
 154  * The memory will be given ZONE_DEVICE struct pages so that it may
 155  * be used with any DMA request.
 156  */
 157 int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
 158                             u64 offset)
 159 {
 160         struct pci_p2pdma_pagemap *p2p_pgmap;
 161         struct dev_pagemap *pgmap;
 162         void *addr;
 163         int error;
 164 
 165         if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
 166                 return -EINVAL;
 167 
 168         if (offset >= pci_resource_len(pdev, bar))
 169                 return -EINVAL;
 170 
 171         if (!size)
 172                 size = pci_resource_len(pdev, bar) - offset;
 173 
 174         if (size + offset > pci_resource_len(pdev, bar))
 175                 return -EINVAL;
 176 
 177         if (!pdev->p2pdma) {
 178                 error = pci_p2pdma_setup(pdev);
 179                 if (error)
 180                         return error;
 181         }
 182 
 183         p2p_pgmap = devm_kzalloc(&pdev->dev, sizeof(*p2p_pgmap), GFP_KERNEL);
 184         if (!p2p_pgmap)
 185                 return -ENOMEM;
 186 
 187         pgmap = &p2p_pgmap->pgmap;
 188         pgmap->res.start = pci_resource_start(pdev, bar) + offset;
 189         pgmap->res.end = pgmap->res.start + size - 1;
 190         pgmap->res.flags = pci_resource_flags(pdev, bar);
 191         pgmap->type = MEMORY_DEVICE_PCI_P2PDMA;
 192 
 193         p2p_pgmap->provider = pdev;
 194         p2p_pgmap->bus_offset = pci_bus_address(pdev, bar) -
 195                 pci_resource_start(pdev, bar);
 196 
 197         addr = devm_memremap_pages(&pdev->dev, pgmap);
 198         if (IS_ERR(addr)) {
 199                 error = PTR_ERR(addr);
 200                 goto pgmap_free;
 201         }
 202 
 203         error = gen_pool_add_owner(pdev->p2pdma->pool, (unsigned long)addr,
 204                         pci_bus_address(pdev, bar) + offset,
 205                         resource_size(&pgmap->res), dev_to_node(&pdev->dev),
 206                         pgmap->ref);
 207         if (error)
 208                 goto pages_free;
 209 
 210         pci_info(pdev, "added peer-to-peer DMA memory %pR\n",
 211                  &pgmap->res);
 212 
 213         return 0;
 214 
 215 pages_free:
 216         devm_memunmap_pages(&pdev->dev, pgmap);
 217 pgmap_free:
 218         devm_kfree(&pdev->dev, pgmap);
 219         return error;
 220 }
 221 EXPORT_SYMBOL_GPL(pci_p2pdma_add_resource);
 222 
 223 /*
 224  * Note this function returns the parent PCI device with a
 225  * reference taken. It is the caller's responsibility to drop
 226  * the reference.
 227  */
 228 static struct pci_dev *find_parent_pci_dev(struct device *dev)
 229 {
 230         struct device *parent;
 231 
 232         dev = get_device(dev);
 233 
 234         while (dev) {
 235                 if (dev_is_pci(dev))
 236                         return to_pci_dev(dev);
 237 
 238                 parent = get_device(dev->parent);
 239                 put_device(dev);
 240                 dev = parent;
 241         }
 242 
 243         return NULL;
 244 }
 245 
 246 /*
 247  * Check if a PCI bridge has its ACS redirection bits set to redirect P2P
 248  * TLPs upstream via ACS. Returns 1 if the packets will be redirected
 249  * upstream, 0 otherwise.
 250  */
 251 static int pci_bridge_has_acs_redir(struct pci_dev *pdev)
 252 {
 253         int pos;
 254         u16 ctrl;
 255 
 256         pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ACS);
 257         if (!pos)
 258                 return 0;
 259 
 260         pci_read_config_word(pdev, pos + PCI_ACS_CTRL, &ctrl);
 261 
 262         if (ctrl & (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC))
 263                 return 1;
 264 
 265         return 0;
 266 }
 267 
 268 static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev)
 269 {
 270         if (!buf)
 271                 return;
 272 
 273         seq_buf_printf(buf, "%s;", pci_name(pdev));
 274 }
 275 
 276 static const struct pci_p2pdma_whitelist_entry {
 277         unsigned short vendor;
 278         unsigned short device;
 279         enum {
 280                 REQ_SAME_HOST_BRIDGE    = 1 << 0,
 281         } flags;
 282 } pci_p2pdma_whitelist[] = {
 283         /* AMD ZEN */
 284         {PCI_VENDOR_ID_AMD,     0x1450, 0},
 285 
 286         /* Intel Xeon E5/Core i7 */
 287         {PCI_VENDOR_ID_INTEL,   0x3c00, REQ_SAME_HOST_BRIDGE},
 288         {PCI_VENDOR_ID_INTEL,   0x3c01, REQ_SAME_HOST_BRIDGE},
 289         /* Intel Xeon E7 v3/Xeon E5 v3/Core i7 */
 290         {PCI_VENDOR_ID_INTEL,   0x2f00, REQ_SAME_HOST_BRIDGE},
 291         {PCI_VENDOR_ID_INTEL,   0x2f01, REQ_SAME_HOST_BRIDGE},
 292         {}
 293 };
 294 
 295 static bool __host_bridge_whitelist(struct pci_host_bridge *host,
 296                                     bool same_host_bridge)
 297 {
 298         struct pci_dev *root = pci_get_slot(host->bus, PCI_DEVFN(0, 0));
 299         const struct pci_p2pdma_whitelist_entry *entry;
 300         unsigned short vendor, device;
 301 
 302         if (!root)
 303                 return false;
 304 
 305         vendor = root->vendor;
 306         device = root->device;
 307         pci_dev_put(root);
 308 
 309         for (entry = pci_p2pdma_whitelist; entry->vendor; entry++) {
 310                 if (vendor != entry->vendor || device != entry->device)
 311                         continue;
 312                 if (entry->flags & REQ_SAME_HOST_BRIDGE && !same_host_bridge)
 313                         return false;
 314 
 315                 return true;
 316         }
 317 
 318         return false;
 319 }
 320 
 321 /*
 322  * If we can't find a common upstream bridge take a look at the root
 323  * complex and compare it to a whitelist of known good hardware.
 324  */
 325 static bool host_bridge_whitelist(struct pci_dev *a, struct pci_dev *b)
 326 {
 327         struct pci_host_bridge *host_a = pci_find_host_bridge(a->bus);
 328         struct pci_host_bridge *host_b = pci_find_host_bridge(b->bus);
 329 
 330         if (host_a == host_b)
 331                 return __host_bridge_whitelist(host_a, true);
 332 
 333         if (__host_bridge_whitelist(host_a, false) &&
 334             __host_bridge_whitelist(host_b, false))
 335                 return true;
 336 
 337         return false;
 338 }
 339 
 340 static enum pci_p2pdma_map_type
 341 __upstream_bridge_distance(struct pci_dev *provider, struct pci_dev *client,
 342                 int *dist, bool *acs_redirects, struct seq_buf *acs_list)
 343 {
 344         struct pci_dev *a = provider, *b = client, *bb;
 345         int dist_a = 0;
 346         int dist_b = 0;
 347         int acs_cnt = 0;
 348 
 349         if (acs_redirects)
 350                 *acs_redirects = false;
 351 
 352         /*
 353          * Note, we don't need to take references to devices returned by
 354          * pci_upstream_bridge() seeing we hold a reference to a child
 355          * device which will already hold a reference to the upstream bridge.
 356          */
 357 
 358         while (a) {
 359                 dist_b = 0;
 360 
 361                 if (pci_bridge_has_acs_redir(a)) {
 362                         seq_buf_print_bus_devfn(acs_list, a);
 363                         acs_cnt++;
 364                 }
 365 
 366                 bb = b;
 367 
 368                 while (bb) {
 369                         if (a == bb)
 370                                 goto check_b_path_acs;
 371 
 372                         bb = pci_upstream_bridge(bb);
 373                         dist_b++;
 374                 }
 375 
 376                 a = pci_upstream_bridge(a);
 377                 dist_a++;
 378         }
 379 
 380         if (dist)
 381                 *dist = dist_a + dist_b;
 382 
 383         return PCI_P2PDMA_MAP_THRU_HOST_BRIDGE;
 384 
 385 check_b_path_acs:
 386         bb = b;
 387 
 388         while (bb) {
 389                 if (a == bb)
 390                         break;
 391 
 392                 if (pci_bridge_has_acs_redir(bb)) {
 393                         seq_buf_print_bus_devfn(acs_list, bb);
 394                         acs_cnt++;
 395                 }
 396 
 397                 bb = pci_upstream_bridge(bb);
 398         }
 399 
 400         if (dist)
 401                 *dist = dist_a + dist_b;
 402 
 403         if (acs_cnt) {
 404                 if (acs_redirects)
 405                         *acs_redirects = true;
 406 
 407                 return PCI_P2PDMA_MAP_THRU_HOST_BRIDGE;
 408         }
 409 
 410         return PCI_P2PDMA_MAP_BUS_ADDR;
 411 }
 412 
 413 static unsigned long map_types_idx(struct pci_dev *client)
 414 {
 415         return (pci_domain_nr(client->bus) << 16) |
 416                 (client->bus->number << 8) | client->devfn;
 417 }
 418 
 419 /*
 420  * Find the distance through the nearest common upstream bridge between
 421  * two PCI devices.
 422  *
 423  * If the two devices are the same device then 0 will be returned.
 424  *
 425  * If there are two virtual functions of the same device behind the same
 426  * bridge port then 2 will be returned (one step down to the PCIe switch,
 427  * then one step back to the same device).
 428  *
 429  * In the case where two devices are connected to the same PCIe switch, the
 430  * value 4 will be returned. This corresponds to the following PCI tree:
 431  *
 432  *     -+  Root Port
 433  *      \+ Switch Upstream Port
 434  *       +-+ Switch Downstream Port
 435  *       + \- Device A
 436  *       \-+ Switch Downstream Port
 437  *         \- Device B
 438  *
 439  * The distance is 4 because we traverse from Device A through the downstream
 440  * port of the switch, to the common upstream port, back up to the second
 441  * downstream port and then to Device B.
 442  *
 443  * Any two devices that cannot communicate using p2pdma will return
 444  * PCI_P2PDMA_MAP_NOT_SUPPORTED.
 445  *
 446  * Any two devices that have a data path that goes through the host bridge
 447  * will consult a whitelist. If the host bridges are on the whitelist,
 448  * this function will return PCI_P2PDMA_MAP_THRU_HOST_BRIDGE.
 449  *
 450  * If either bridge is not on the whitelist this function returns
 451  * PCI_P2PDMA_MAP_NOT_SUPPORTED.
 452  *
 453  * If a bridge which has any ACS redirection bits set is in the path,
 454  * acs_redirects will be set to true. In this case, a list of all infringing
 455  * bridge addresses will be populated in acs_list (assuming it's non-null)
 456  * for printk purposes.
 457  */
 458 static enum pci_p2pdma_map_type
 459 upstream_bridge_distance(struct pci_dev *provider, struct pci_dev *client,
 460                 int *dist, bool *acs_redirects, struct seq_buf *acs_list)
 461 {
 462         enum pci_p2pdma_map_type map_type;
 463 
 464         map_type = __upstream_bridge_distance(provider, client, dist,
 465                                               acs_redirects, acs_list);
 466 
 467         if (map_type == PCI_P2PDMA_MAP_THRU_HOST_BRIDGE) {
 468                 if (!host_bridge_whitelist(provider, client))
 469                         map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
 470         }
 471 
 472         if (provider->p2pdma)
 473                 xa_store(&provider->p2pdma->map_types, map_types_idx(client),
 474                          xa_mk_value(map_type), GFP_KERNEL);
 475 
 476         return map_type;
 477 }
 478 
 479 static enum pci_p2pdma_map_type
 480 upstream_bridge_distance_warn(struct pci_dev *provider, struct pci_dev *client,
 481                               int *dist)
 482 {
 483         struct seq_buf acs_list;
 484         bool acs_redirects;
 485         int ret;
 486 
 487         seq_buf_init(&acs_list, kmalloc(PAGE_SIZE, GFP_KERNEL), PAGE_SIZE);
 488         if (!acs_list.buffer)
 489                 return -ENOMEM;
 490 
 491         ret = upstream_bridge_distance(provider, client, dist, &acs_redirects,
 492                                        &acs_list);
 493         if (acs_redirects) {
 494                 pci_warn(client, "ACS redirect is set between the client and provider (%s)\n",
 495                          pci_name(provider));
 496                 /* Drop final semicolon */
 497                 acs_list.buffer[acs_list.len-1] = 0;
 498                 pci_warn(client, "to disable ACS redirect for this path, add the kernel parameter: pci=disable_acs_redir=%s\n",
 499                          acs_list.buffer);
 500         }
 501 
 502         if (ret == PCI_P2PDMA_MAP_NOT_SUPPORTED) {
 503                 pci_warn(client, "cannot be used for peer-to-peer DMA as the client and provider (%s) do not share an upstream bridge or whitelisted host bridge\n",
 504                          pci_name(provider));
 505         }
 506 
 507         kfree(acs_list.buffer);
 508 
 509         return ret;
 510 }
 511 
 512 /**
 513  * pci_p2pdma_distance_many - Determine the cumulative distance between
 514  *      a p2pdma provider and the clients in use.
 515  * @provider: p2pdma provider to check against the client list
 516  * @clients: array of devices to check (NULL-terminated)
 517  * @num_clients: number of clients in the array
 518  * @verbose: if true, print warnings for devices when we return -1
 519  *
 520  * Returns -1 if any of the clients are not compatible, otherwise returns a
 521  * positive number where a lower number is the preferable choice. (If there's
 522  * one client that's the same as the provider it will return 0, which is best
 523  * choice).
 524  *
 525  * "compatible" means the provider and the clients are either all behind
 526  * the same PCI root port or the host bridges connected to each of the devices
 527  * are listed in the 'pci_p2pdma_whitelist'.
 528  */
 529 int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients,
 530                              int num_clients, bool verbose)
 531 {
 532         bool not_supported = false;
 533         struct pci_dev *pci_client;
 534         int total_dist = 0;
 535         int distance;
 536         int i, ret;
 537 
 538         if (num_clients == 0)
 539                 return -1;
 540 
 541         for (i = 0; i < num_clients; i++) {
 542                 if (IS_ENABLED(CONFIG_DMA_VIRT_OPS) &&
 543                     clients[i]->dma_ops == &dma_virt_ops) {
 544                         if (verbose)
 545                                 dev_warn(clients[i],
 546                                          "cannot be used for peer-to-peer DMA because the driver makes use of dma_virt_ops\n");
 547                         return -1;
 548                 }
 549 
 550                 pci_client = find_parent_pci_dev(clients[i]);
 551                 if (!pci_client) {
 552                         if (verbose)
 553                                 dev_warn(clients[i],
 554                                          "cannot be used for peer-to-peer DMA as it is not a PCI device\n");
 555                         return -1;
 556                 }
 557 
 558                 if (verbose)
 559                         ret = upstream_bridge_distance_warn(provider,
 560                                         pci_client, &distance);
 561                 else
 562                         ret = upstream_bridge_distance(provider, pci_client,
 563                                                        &distance, NULL, NULL);
 564 
 565                 pci_dev_put(pci_client);
 566 
 567                 if (ret == PCI_P2PDMA_MAP_NOT_SUPPORTED)
 568                         not_supported = true;
 569 
 570                 if (not_supported && !verbose)
 571                         break;
 572 
 573                 total_dist += distance;
 574         }
 575 
 576         if (not_supported)
 577                 return -1;
 578 
 579         return total_dist;
 580 }
 581 EXPORT_SYMBOL_GPL(pci_p2pdma_distance_many);
 582 
 583 /**
 584  * pci_has_p2pmem - check if a given PCI device has published any p2pmem
 585  * @pdev: PCI device to check
 586  */
 587 bool pci_has_p2pmem(struct pci_dev *pdev)
 588 {
 589         return pdev->p2pdma && pdev->p2pdma->p2pmem_published;
 590 }
 591 EXPORT_SYMBOL_GPL(pci_has_p2pmem);
 592 
 593 /**
 594  * pci_p2pmem_find - find a peer-to-peer DMA memory device compatible with
 595  *      the specified list of clients and shortest distance (as determined
 596  *      by pci_p2pmem_dma())
 597  * @clients: array of devices to check (NULL-terminated)
 598  * @num_clients: number of client devices in the list
 599  *
 600  * If multiple devices are behind the same switch, the one "closest" to the
 601  * client devices in use will be chosen first. (So if one of the providers is
 602  * the same as one of the clients, that provider will be used ahead of any
 603  * other providers that are unrelated). If multiple providers are an equal
 604  * distance away, one will be chosen at random.
 605  *
 606  * Returns a pointer to the PCI device with a reference taken (use pci_dev_put
 607  * to return the reference) or NULL if no compatible device is found. The
 608  * found provider will also be assigned to the client list.
 609  */
 610 struct pci_dev *pci_p2pmem_find_many(struct device **clients, int num_clients)
 611 {
 612         struct pci_dev *pdev = NULL;
 613         int distance;
 614         int closest_distance = INT_MAX;
 615         struct pci_dev **closest_pdevs;
 616         int dev_cnt = 0;
 617         const int max_devs = PAGE_SIZE / sizeof(*closest_pdevs);
 618         int i;
 619 
 620         closest_pdevs = kmalloc(PAGE_SIZE, GFP_KERNEL);
 621         if (!closest_pdevs)
 622                 return NULL;
 623 
 624         while ((pdev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, pdev))) {
 625                 if (!pci_has_p2pmem(pdev))
 626                         continue;
 627 
 628                 distance = pci_p2pdma_distance_many(pdev, clients,
 629                                                     num_clients, false);
 630                 if (distance < 0 || distance > closest_distance)
 631                         continue;
 632 
 633                 if (distance == closest_distance && dev_cnt >= max_devs)
 634                         continue;
 635 
 636                 if (distance < closest_distance) {
 637                         for (i = 0; i < dev_cnt; i++)
 638                                 pci_dev_put(closest_pdevs[i]);
 639 
 640                         dev_cnt = 0;
 641                         closest_distance = distance;
 642                 }
 643 
 644                 closest_pdevs[dev_cnt++] = pci_dev_get(pdev);
 645         }
 646 
 647         if (dev_cnt)
 648                 pdev = pci_dev_get(closest_pdevs[prandom_u32_max(dev_cnt)]);
 649 
 650         for (i = 0; i < dev_cnt; i++)
 651                 pci_dev_put(closest_pdevs[i]);
 652 
 653         kfree(closest_pdevs);
 654         return pdev;
 655 }
 656 EXPORT_SYMBOL_GPL(pci_p2pmem_find_many);
 657 
 658 /**
 659  * pci_alloc_p2p_mem - allocate peer-to-peer DMA memory
 660  * @pdev: the device to allocate memory from
 661  * @size: number of bytes to allocate
 662  *
 663  * Returns the allocated memory or NULL on error.
 664  */
 665 void *pci_alloc_p2pmem(struct pci_dev *pdev, size_t size)
 666 {
 667         void *ret = NULL;
 668         struct percpu_ref *ref;
 669 
 670         /*
 671          * Pairs with synchronize_rcu() in pci_p2pdma_release() to
 672          * ensure pdev->p2pdma is non-NULL for the duration of the
 673          * read-lock.
 674          */
 675         rcu_read_lock();
 676         if (unlikely(!pdev->p2pdma))
 677                 goto out;
 678 
 679         ret = (void *)gen_pool_alloc_owner(pdev->p2pdma->pool, size,
 680                         (void **) &ref);
 681         if (!ret)
 682                 goto out;
 683 
 684         if (unlikely(!percpu_ref_tryget_live(ref))) {
 685                 gen_pool_free(pdev->p2pdma->pool, (unsigned long) ret, size);
 686                 ret = NULL;
 687                 goto out;
 688         }
 689 out:
 690         rcu_read_unlock();
 691         return ret;
 692 }
 693 EXPORT_SYMBOL_GPL(pci_alloc_p2pmem);
 694 
 695 /**
 696  * pci_free_p2pmem - free peer-to-peer DMA memory
 697  * @pdev: the device the memory was allocated from
 698  * @addr: address of the memory that was allocated
 699  * @size: number of bytes that were allocated
 700  */
 701 void pci_free_p2pmem(struct pci_dev *pdev, void *addr, size_t size)
 702 {
 703         struct percpu_ref *ref;
 704 
 705         gen_pool_free_owner(pdev->p2pdma->pool, (uintptr_t)addr, size,
 706                         (void **) &ref);
 707         percpu_ref_put(ref);
 708 }
 709 EXPORT_SYMBOL_GPL(pci_free_p2pmem);
 710 
 711 /**
 712  * pci_virt_to_bus - return the PCI bus address for a given virtual
 713  *      address obtained with pci_alloc_p2pmem()
 714  * @pdev: the device the memory was allocated from
 715  * @addr: address of the memory that was allocated
 716  */
 717 pci_bus_addr_t pci_p2pmem_virt_to_bus(struct pci_dev *pdev, void *addr)
 718 {
 719         if (!addr)
 720                 return 0;
 721         if (!pdev->p2pdma)
 722                 return 0;
 723 
 724         /*
 725          * Note: when we added the memory to the pool we used the PCI
 726          * bus address as the physical address. So gen_pool_virt_to_phys()
 727          * actually returns the bus address despite the misleading name.
 728          */
 729         return gen_pool_virt_to_phys(pdev->p2pdma->pool, (unsigned long)addr);
 730 }
 731 EXPORT_SYMBOL_GPL(pci_p2pmem_virt_to_bus);
 732 
 733 /**
 734  * pci_p2pmem_alloc_sgl - allocate peer-to-peer DMA memory in a scatterlist
 735  * @pdev: the device to allocate memory from
 736  * @nents: the number of SG entries in the list
 737  * @length: number of bytes to allocate
 738  *
 739  * Return: %NULL on error or &struct scatterlist pointer and @nents on success
 740  */
 741 struct scatterlist *pci_p2pmem_alloc_sgl(struct pci_dev *pdev,
 742                                          unsigned int *nents, u32 length)
 743 {
 744         struct scatterlist *sg;
 745         void *addr;
 746 
 747         sg = kzalloc(sizeof(*sg), GFP_KERNEL);
 748         if (!sg)
 749                 return NULL;
 750 
 751         sg_init_table(sg, 1);
 752 
 753         addr = pci_alloc_p2pmem(pdev, length);
 754         if (!addr)
 755                 goto out_free_sg;
 756 
 757         sg_set_buf(sg, addr, length);
 758         *nents = 1;
 759         return sg;
 760 
 761 out_free_sg:
 762         kfree(sg);
 763         return NULL;
 764 }
 765 EXPORT_SYMBOL_GPL(pci_p2pmem_alloc_sgl);
 766 
 767 /**
 768  * pci_p2pmem_free_sgl - free a scatterlist allocated by pci_p2pmem_alloc_sgl()
 769  * @pdev: the device to allocate memory from
 770  * @sgl: the allocated scatterlist
 771  */
 772 void pci_p2pmem_free_sgl(struct pci_dev *pdev, struct scatterlist *sgl)
 773 {
 774         struct scatterlist *sg;
 775         int count;
 776 
 777         for_each_sg(sgl, sg, INT_MAX, count) {
 778                 if (!sg)
 779                         break;
 780 
 781                 pci_free_p2pmem(pdev, sg_virt(sg), sg->length);
 782         }
 783         kfree(sgl);
 784 }
 785 EXPORT_SYMBOL_GPL(pci_p2pmem_free_sgl);
 786 
 787 /**
 788  * pci_p2pmem_publish - publish the peer-to-peer DMA memory for use by
 789  *      other devices with pci_p2pmem_find()
 790  * @pdev: the device with peer-to-peer DMA memory to publish
 791  * @publish: set to true to publish the memory, false to unpublish it
 792  *
 793  * Published memory can be used by other PCI device drivers for
 794  * peer-2-peer DMA operations. Non-published memory is reserved for
 795  * exclusive use of the device driver that registers the peer-to-peer
 796  * memory.
 797  */
 798 void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
 799 {
 800         if (pdev->p2pdma)
 801                 pdev->p2pdma->p2pmem_published = publish;
 802 }
 803 EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
 804 
 805 static enum pci_p2pdma_map_type pci_p2pdma_map_type(struct pci_dev *provider,
 806                                                     struct pci_dev *client)
 807 {
 808         if (!provider->p2pdma)
 809                 return PCI_P2PDMA_MAP_NOT_SUPPORTED;
 810 
 811         return xa_to_value(xa_load(&provider->p2pdma->map_types,
 812                                    map_types_idx(client)));
 813 }
 814 
 815 static int __pci_p2pdma_map_sg(struct pci_p2pdma_pagemap *p2p_pgmap,
 816                 struct device *dev, struct scatterlist *sg, int nents)
 817 {
 818         struct scatterlist *s;
 819         phys_addr_t paddr;
 820         int i;
 821 
 822         /*
 823          * p2pdma mappings are not compatible with devices that use
 824          * dma_virt_ops. If the upper layers do the right thing
 825          * this should never happen because it will be prevented
 826          * by the check in pci_p2pdma_distance_many()
 827          */
 828         if (WARN_ON_ONCE(IS_ENABLED(CONFIG_DMA_VIRT_OPS) &&
 829                          dev->dma_ops == &dma_virt_ops))
 830                 return 0;
 831 
 832         for_each_sg(sg, s, nents, i) {
 833                 paddr = sg_phys(s);
 834 
 835                 s->dma_address = paddr - p2p_pgmap->bus_offset;
 836                 sg_dma_len(s) = s->length;
 837         }
 838 
 839         return nents;
 840 }
 841 
 842 /**
 843  * pci_p2pdma_map_sg - map a PCI peer-to-peer scatterlist for DMA
 844  * @dev: device doing the DMA request
 845  * @sg: scatter list to map
 846  * @nents: elements in the scatterlist
 847  * @dir: DMA direction
 848  * @attrs: DMA attributes passed to dma_map_sg() (if called)
 849  *
 850  * Scatterlists mapped with this function should be unmapped using
 851  * pci_p2pdma_unmap_sg_attrs().
 852  *
 853  * Returns the number of SG entries mapped or 0 on error.
 854  */
 855 int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
 856                 int nents, enum dma_data_direction dir, unsigned long attrs)
 857 {
 858         struct pci_p2pdma_pagemap *p2p_pgmap =
 859                 to_p2p_pgmap(sg_page(sg)->pgmap);
 860         struct pci_dev *client;
 861 
 862         if (WARN_ON_ONCE(!dev_is_pci(dev)))
 863                 return 0;
 864 
 865         client = to_pci_dev(dev);
 866 
 867         switch (pci_p2pdma_map_type(p2p_pgmap->provider, client)) {
 868         case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE:
 869                 return dma_map_sg_attrs(dev, sg, nents, dir, attrs);
 870         case PCI_P2PDMA_MAP_BUS_ADDR:
 871                 return __pci_p2pdma_map_sg(p2p_pgmap, dev, sg, nents);
 872         default:
 873                 WARN_ON_ONCE(1);
 874                 return 0;
 875         }
 876 }
 877 EXPORT_SYMBOL_GPL(pci_p2pdma_map_sg_attrs);
 878 
 879 /**
 880  * pci_p2pdma_unmap_sg - unmap a PCI peer-to-peer scatterlist that was
 881  *      mapped with pci_p2pdma_map_sg()
 882  * @dev: device doing the DMA request
 883  * @sg: scatter list to map
 884  * @nents: number of elements returned by pci_p2pdma_map_sg()
 885  * @dir: DMA direction
 886  * @attrs: DMA attributes passed to dma_unmap_sg() (if called)
 887  */
 888 void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
 889                 int nents, enum dma_data_direction dir, unsigned long attrs)
 890 {
 891         struct pci_p2pdma_pagemap *p2p_pgmap =
 892                 to_p2p_pgmap(sg_page(sg)->pgmap);
 893         enum pci_p2pdma_map_type map_type;
 894         struct pci_dev *client;
 895 
 896         if (WARN_ON_ONCE(!dev_is_pci(dev)))
 897                 return;
 898 
 899         client = to_pci_dev(dev);
 900 
 901         map_type = pci_p2pdma_map_type(p2p_pgmap->provider, client);
 902 
 903         if (map_type == PCI_P2PDMA_MAP_THRU_HOST_BRIDGE)
 904                 dma_unmap_sg_attrs(dev, sg, nents, dir, attrs);
 905 }
 906 EXPORT_SYMBOL_GPL(pci_p2pdma_unmap_sg_attrs);
 907 
 908 /**
 909  * pci_p2pdma_enable_store - parse a configfs/sysfs attribute store
 910  *              to enable p2pdma
 911  * @page: contents of the value to be stored
 912  * @p2p_dev: returns the PCI device that was selected to be used
 913  *              (if one was specified in the stored value)
 914  * @use_p2pdma: returns whether to enable p2pdma or not
 915  *
 916  * Parses an attribute value to decide whether to enable p2pdma.
 917  * The value can select a PCI device (using its full BDF device
 918  * name) or a boolean (in any format strtobool() accepts). A false
 919  * value disables p2pdma, a true value expects the caller
 920  * to automatically find a compatible device and specifying a PCI device
 921  * expects the caller to use the specific provider.
 922  *
 923  * pci_p2pdma_enable_show() should be used as the show operation for
 924  * the attribute.
 925  *
 926  * Returns 0 on success
 927  */
 928 int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,
 929                             bool *use_p2pdma)
 930 {
 931         struct device *dev;
 932 
 933         dev = bus_find_device_by_name(&pci_bus_type, NULL, page);
 934         if (dev) {
 935                 *use_p2pdma = true;
 936                 *p2p_dev = to_pci_dev(dev);
 937 
 938                 if (!pci_has_p2pmem(*p2p_dev)) {
 939                         pci_err(*p2p_dev,
 940                                 "PCI device has no peer-to-peer memory: %s\n",
 941                                 page);
 942                         pci_dev_put(*p2p_dev);
 943                         return -ENODEV;
 944                 }
 945 
 946                 return 0;
 947         } else if ((page[0] == '0' || page[0] == '1') && !iscntrl(page[1])) {
 948                 /*
 949                  * If the user enters a PCI device that  doesn't exist
 950                  * like "0000:01:00.1", we don't want strtobool to think
 951                  * it's a '0' when it's clearly not what the user wanted.
 952                  * So we require 0's and 1's to be exactly one character.
 953                  */
 954         } else if (!strtobool(page, use_p2pdma)) {
 955                 return 0;
 956         }
 957 
 958         pr_err("No such PCI device: %.*s\n", (int)strcspn(page, "\n"), page);
 959         return -ENODEV;
 960 }
 961 EXPORT_SYMBOL_GPL(pci_p2pdma_enable_store);
 962 
 963 /**
 964  * pci_p2pdma_enable_show - show a configfs/sysfs attribute indicating
 965  *              whether p2pdma is enabled
 966  * @page: contents of the stored value
 967  * @p2p_dev: the selected p2p device (NULL if no device is selected)
 968  * @use_p2pdma: whether p2pdma has been enabled
 969  *
 970  * Attributes that use pci_p2pdma_enable_store() should use this function
 971  * to show the value of the attribute.
 972  *
 973  * Returns 0 on success
 974  */
 975 ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,
 976                                bool use_p2pdma)
 977 {
 978         if (!use_p2pdma)
 979                 return sprintf(page, "0\n");
 980 
 981         if (!p2p_dev)
 982                 return sprintf(page, "1\n");
 983 
 984         return sprintf(page, "%s\n", pci_name(p2p_dev));
 985 }
 986 EXPORT_SYMBOL_GPL(pci_p2pdma_enable_show);
/* [<][>][^][v][top][bottom][index][help] */
root/drivers/pci/p2pdma.c

DEFINITIONS
