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1// SPDX-License-Identifier: GPL-2.02/*3 * PCI Peer 2 Peer DMA support.4 *5 * Copyright (c) 2016-2018, Logan Gunthorpe6 * Copyright (c) 2016-2017, Microsemi Corporation7 * Copyright (c) 2017, Christoph Hellwig8 * Copyright (c) 2018, Eideticom Inc.9 */10 11#define pr_fmt(fmt) "pci-p2pdma: " fmt12#include <linux/ctype.h>13#include <linux/dma-map-ops.h>14#include <linux/pci-p2pdma.h>15#include <linux/module.h>16#include <linux/slab.h>17#include <linux/genalloc.h>18#include <linux/memremap.h>19#include <linux/percpu-refcount.h>20#include <linux/random.h>21#include <linux/seq_buf.h>22#include <linux/xarray.h>23 24struct pci_p2pdma {25 struct gen_pool *pool;26 bool p2pmem_published;27 struct xarray map_types;28};29 30struct pci_p2pdma_pagemap {31 struct pci_dev *provider;32 u64 bus_offset;33 struct dev_pagemap pgmap;34};35 36static struct pci_p2pdma_pagemap *to_p2p_pgmap(struct dev_pagemap *pgmap)37{38 return container_of(pgmap, struct pci_p2pdma_pagemap, pgmap);39}40 41static ssize_t size_show(struct device *dev, struct device_attribute *attr,42 char *buf)43{44 struct pci_dev *pdev = to_pci_dev(dev);45 struct pci_p2pdma *p2pdma;46 size_t size = 0;47 48 rcu_read_lock();49 p2pdma = rcu_dereference(pdev->p2pdma);50 if (p2pdma && p2pdma->pool)51 size = gen_pool_size(p2pdma->pool);52 rcu_read_unlock();53 54 return sysfs_emit(buf, "%zd\n", size);55}56static DEVICE_ATTR_RO(size);57 58static ssize_t available_show(struct device *dev, struct device_attribute *attr,59 char *buf)60{61 struct pci_dev *pdev = to_pci_dev(dev);62 struct pci_p2pdma *p2pdma;63 size_t avail = 0;64 65 rcu_read_lock();66 p2pdma = rcu_dereference(pdev->p2pdma);67 if (p2pdma && p2pdma->pool)68 avail = gen_pool_avail(p2pdma->pool);69 rcu_read_unlock();70 71 return sysfs_emit(buf, "%zd\n", avail);72}73static DEVICE_ATTR_RO(available);74 75static ssize_t published_show(struct device *dev, struct device_attribute *attr,76 char *buf)77{78 struct pci_dev *pdev = to_pci_dev(dev);79 struct pci_p2pdma *p2pdma;80 bool published = false;81 82 rcu_read_lock();83 p2pdma = rcu_dereference(pdev->p2pdma);84 if (p2pdma)85 published = p2pdma->p2pmem_published;86 rcu_read_unlock();87 88 return sysfs_emit(buf, "%d\n", published);89}90static DEVICE_ATTR_RO(published);91 92static int p2pmem_alloc_mmap(struct file *filp, struct kobject *kobj,93 struct bin_attribute *attr, struct vm_area_struct *vma)94{95 struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj));96 size_t len = vma->vm_end - vma->vm_start;97 struct pci_p2pdma *p2pdma;98 struct percpu_ref *ref;99 unsigned long vaddr;100 void *kaddr;101 int ret;102 103 /* prevent private mappings from being established */104 if ((vma->vm_flags & VM_MAYSHARE) != VM_MAYSHARE) {105 pci_info_ratelimited(pdev,106 "%s: fail, attempted private mapping\n",107 current->comm);108 return -EINVAL;109 }110 111 if (vma->vm_pgoff) {112 pci_info_ratelimited(pdev,113 "%s: fail, attempted mapping with non-zero offset\n",114 current->comm);115 return -EINVAL;116 }117 118 rcu_read_lock();119 p2pdma = rcu_dereference(pdev->p2pdma);120 if (!p2pdma) {121 ret = -ENODEV;122 goto out;123 }124 125 kaddr = (void *)gen_pool_alloc_owner(p2pdma->pool, len, (void **)&ref);126 if (!kaddr) {127 ret = -ENOMEM;128 goto out;129 }130 131 /*132 * vm_insert_page() can sleep, so a reference is taken to mapping133 * such that rcu_read_unlock() can be done before inserting the134 * pages135 */136 if (unlikely(!percpu_ref_tryget_live_rcu(ref))) {137 ret = -ENODEV;138 goto out_free_mem;139 }140 rcu_read_unlock();141 142 for (vaddr = vma->vm_start; vaddr < vma->vm_end; vaddr += PAGE_SIZE) {143 ret = vm_insert_page(vma, vaddr, virt_to_page(kaddr));144 if (ret) {145 gen_pool_free(p2pdma->pool, (uintptr_t)kaddr, len);146 return ret;147 }148 percpu_ref_get(ref);149 put_page(virt_to_page(kaddr));150 kaddr += PAGE_SIZE;151 len -= PAGE_SIZE;152 }153 154 percpu_ref_put(ref);155 156 return 0;157out_free_mem:158 gen_pool_free(p2pdma->pool, (uintptr_t)kaddr, len);159out:160 rcu_read_unlock();161 return ret;162}163 164static struct bin_attribute p2pmem_alloc_attr = {165 .attr = { .name = "allocate", .mode = 0660 },166 .mmap = p2pmem_alloc_mmap,167 /*168 * Some places where we want to call mmap (ie. python) will check169 * that the file size is greater than the mmap size before allowing170 * the mmap to continue. To work around this, just set the size171 * to be very large.172 */173 .size = SZ_1T,174};175 176static struct attribute *p2pmem_attrs[] = {177 &dev_attr_size.attr,178 &dev_attr_available.attr,179 &dev_attr_published.attr,180 NULL,181};182 183static struct bin_attribute *p2pmem_bin_attrs[] = {184 &p2pmem_alloc_attr,185 NULL,186};187 188static const struct attribute_group p2pmem_group = {189 .attrs = p2pmem_attrs,190 .bin_attrs = p2pmem_bin_attrs,191 .name = "p2pmem",192};193 194static void p2pdma_page_free(struct page *page)195{196 struct pci_p2pdma_pagemap *pgmap = to_p2p_pgmap(page->pgmap);197 /* safe to dereference while a reference is held to the percpu ref */198 struct pci_p2pdma *p2pdma =199 rcu_dereference_protected(pgmap->provider->p2pdma, 1);200 struct percpu_ref *ref;201 202 gen_pool_free_owner(p2pdma->pool, (uintptr_t)page_to_virt(page),203 PAGE_SIZE, (void **)&ref);204 percpu_ref_put(ref);205}206 207static const struct dev_pagemap_ops p2pdma_pgmap_ops = {208 .page_free = p2pdma_page_free,209};210 211static void pci_p2pdma_release(void *data)212{213 struct pci_dev *pdev = data;214 struct pci_p2pdma *p2pdma;215 216 p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);217 if (!p2pdma)218 return;219 220 /* Flush and disable pci_alloc_p2p_mem() */221 pdev->p2pdma = NULL;222 synchronize_rcu();223 224 gen_pool_destroy(p2pdma->pool);225 sysfs_remove_group(&pdev->dev.kobj, &p2pmem_group);226 xa_destroy(&p2pdma->map_types);227}228 229static int pci_p2pdma_setup(struct pci_dev *pdev)230{231 int error = -ENOMEM;232 struct pci_p2pdma *p2p;233 234 p2p = devm_kzalloc(&pdev->dev, sizeof(*p2p), GFP_KERNEL);235 if (!p2p)236 return -ENOMEM;237 238 xa_init(&p2p->map_types);239 240 p2p->pool = gen_pool_create(PAGE_SHIFT, dev_to_node(&pdev->dev));241 if (!p2p->pool)242 goto out;243 244 error = devm_add_action_or_reset(&pdev->dev, pci_p2pdma_release, pdev);245 if (error)246 goto out_pool_destroy;247 248 error = sysfs_create_group(&pdev->dev.kobj, &p2pmem_group);249 if (error)250 goto out_pool_destroy;251 252 rcu_assign_pointer(pdev->p2pdma, p2p);253 return 0;254 255out_pool_destroy:256 gen_pool_destroy(p2p->pool);257out:258 devm_kfree(&pdev->dev, p2p);259 return error;260}261 262static void pci_p2pdma_unmap_mappings(void *data)263{264 struct pci_dev *pdev = data;265 266 /*267 * Removing the alloc attribute from sysfs will call268 * unmap_mapping_range() on the inode, teardown any existing userspace269 * mappings and prevent new ones from being created.270 */271 sysfs_remove_file_from_group(&pdev->dev.kobj, &p2pmem_alloc_attr.attr,272 p2pmem_group.name);273}274 275/**276 * pci_p2pdma_add_resource - add memory for use as p2p memory277 * @pdev: the device to add the memory to278 * @bar: PCI BAR to add279 * @size: size of the memory to add, may be zero to use the whole BAR280 * @offset: offset into the PCI BAR281 *282 * The memory will be given ZONE_DEVICE struct pages so that it may283 * be used with any DMA request.284 */285int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,286 u64 offset)287{288 struct pci_p2pdma_pagemap *p2p_pgmap;289 struct dev_pagemap *pgmap;290 struct pci_p2pdma *p2pdma;291 void *addr;292 int error;293 294 if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))295 return -EINVAL;296 297 if (offset >= pci_resource_len(pdev, bar))298 return -EINVAL;299 300 if (!size)301 size = pci_resource_len(pdev, bar) - offset;302 303 if (size + offset > pci_resource_len(pdev, bar))304 return -EINVAL;305 306 if (!pdev->p2pdma) {307 error = pci_p2pdma_setup(pdev);308 if (error)309 return error;310 }311 312 p2p_pgmap = devm_kzalloc(&pdev->dev, sizeof(*p2p_pgmap), GFP_KERNEL);313 if (!p2p_pgmap)314 return -ENOMEM;315 316 pgmap = &p2p_pgmap->pgmap;317 pgmap->range.start = pci_resource_start(pdev, bar) + offset;318 pgmap->range.end = pgmap->range.start + size - 1;319 pgmap->nr_range = 1;320 pgmap->type = MEMORY_DEVICE_PCI_P2PDMA;321 pgmap->ops = &p2pdma_pgmap_ops;322 323 p2p_pgmap->provider = pdev;324 p2p_pgmap->bus_offset = pci_bus_address(pdev, bar) -325 pci_resource_start(pdev, bar);326 327 addr = devm_memremap_pages(&pdev->dev, pgmap);328 if (IS_ERR(addr)) {329 error = PTR_ERR(addr);330 goto pgmap_free;331 }332 333 error = devm_add_action_or_reset(&pdev->dev, pci_p2pdma_unmap_mappings,334 pdev);335 if (error)336 goto pages_free;337 338 p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);339 error = gen_pool_add_owner(p2pdma->pool, (unsigned long)addr,340 pci_bus_address(pdev, bar) + offset,341 range_len(&pgmap->range), dev_to_node(&pdev->dev),342 &pgmap->ref);343 if (error)344 goto pages_free;345 346 pci_info(pdev, "added peer-to-peer DMA memory %#llx-%#llx\n",347 pgmap->range.start, pgmap->range.end);348 349 return 0;350 351pages_free:352 devm_memunmap_pages(&pdev->dev, pgmap);353pgmap_free:354 devm_kfree(&pdev->dev, pgmap);355 return error;356}357EXPORT_SYMBOL_GPL(pci_p2pdma_add_resource);358 359/*360 * Note this function returns the parent PCI device with a361 * reference taken. It is the caller's responsibility to drop362 * the reference.363 */364static struct pci_dev *find_parent_pci_dev(struct device *dev)365{366 struct device *parent;367 368 dev = get_device(dev);369 370 while (dev) {371 if (dev_is_pci(dev))372 return to_pci_dev(dev);373 374 parent = get_device(dev->parent);375 put_device(dev);376 dev = parent;377 }378 379 return NULL;380}381 382/*383 * Check if a PCI bridge has its ACS redirection bits set to redirect P2P384 * TLPs upstream via ACS. Returns 1 if the packets will be redirected385 * upstream, 0 otherwise.386 */387static int pci_bridge_has_acs_redir(struct pci_dev *pdev)388{389 int pos;390 u16 ctrl;391 392 pos = pdev->acs_cap;393 if (!pos)394 return 0;395 396 pci_read_config_word(pdev, pos + PCI_ACS_CTRL, &ctrl);397 398 if (ctrl & (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC))399 return 1;400 401 return 0;402}403 404static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev)405{406 if (!buf)407 return;408 409 seq_buf_printf(buf, "%s;", pci_name(pdev));410}411 412static bool cpu_supports_p2pdma(void)413{414#ifdef CONFIG_X86415 struct cpuinfo_x86 *c = &cpu_data(0);416 417 /* Any AMD CPU whose family ID is Zen or newer supports p2pdma */418 if (c->x86_vendor == X86_VENDOR_AMD && c->x86 >= 0x17)419 return true;420#endif421 422 return false;423}424 425static const struct pci_p2pdma_whitelist_entry {426 unsigned short vendor;427 unsigned short device;428 enum {429 REQ_SAME_HOST_BRIDGE = 1 << 0,430 } flags;431} pci_p2pdma_whitelist[] = {432 /* Intel Xeon E5/Core i7 */433 {PCI_VENDOR_ID_INTEL, 0x3c00, REQ_SAME_HOST_BRIDGE},434 {PCI_VENDOR_ID_INTEL, 0x3c01, REQ_SAME_HOST_BRIDGE},435 /* Intel Xeon E7 v3/Xeon E5 v3/Core i7 */436 {PCI_VENDOR_ID_INTEL, 0x2f00, REQ_SAME_HOST_BRIDGE},437 {PCI_VENDOR_ID_INTEL, 0x2f01, REQ_SAME_HOST_BRIDGE},438 /* Intel Skylake-E */439 {PCI_VENDOR_ID_INTEL, 0x2030, 0},440 {PCI_VENDOR_ID_INTEL, 0x2031, 0},441 {PCI_VENDOR_ID_INTEL, 0x2032, 0},442 {PCI_VENDOR_ID_INTEL, 0x2033, 0},443 {PCI_VENDOR_ID_INTEL, 0x2020, 0},444 {PCI_VENDOR_ID_INTEL, 0x09a2, 0},445 {}446};447 448/*449 * If the first device on host's root bus is either devfn 00.0 or a PCIe450 * Root Port, return it. Otherwise return NULL.451 *452 * We often use a devfn 00.0 "host bridge" in the pci_p2pdma_whitelist[]453 * (though there is no PCI/PCIe requirement for such a device). On some454 * platforms, e.g., Intel Skylake, there is no such host bridge device, and455 * pci_p2pdma_whitelist[] may contain a Root Port at any devfn.456 *457 * This function is similar to pci_get_slot(host->bus, 0), but it does458 * not take the pci_bus_sem lock since __host_bridge_whitelist() must not459 * sleep.460 *461 * For this to be safe, the caller should hold a reference to a device on the462 * bridge, which should ensure the host_bridge device will not be freed463 * or removed from the head of the devices list.464 */465static struct pci_dev *pci_host_bridge_dev(struct pci_host_bridge *host)466{467 struct pci_dev *root;468 469 root = list_first_entry_or_null(&host->bus->devices,470 struct pci_dev, bus_list);471 472 if (!root)473 return NULL;474 475 if (root->devfn == PCI_DEVFN(0, 0))476 return root;477 478 if (pci_pcie_type(root) == PCI_EXP_TYPE_ROOT_PORT)479 return root;480 481 return NULL;482}483 484static bool __host_bridge_whitelist(struct pci_host_bridge *host,485 bool same_host_bridge, bool warn)486{487 struct pci_dev *root = pci_host_bridge_dev(host);488 const struct pci_p2pdma_whitelist_entry *entry;489 unsigned short vendor, device;490 491 if (!root)492 return false;493 494 vendor = root->vendor;495 device = root->device;496 497 for (entry = pci_p2pdma_whitelist; entry->vendor; entry++) {498 if (vendor != entry->vendor || device != entry->device)499 continue;500 if (entry->flags & REQ_SAME_HOST_BRIDGE && !same_host_bridge)501 return false;502 503 return true;504 }505 506 if (warn)507 pci_warn(root, "Host bridge not in P2PDMA whitelist: %04x:%04x\n",508 vendor, device);509 510 return false;511}512 513/*514 * If we can't find a common upstream bridge take a look at the root515 * complex and compare it to a whitelist of known good hardware.516 */517static bool host_bridge_whitelist(struct pci_dev *a, struct pci_dev *b,518 bool warn)519{520 struct pci_host_bridge *host_a = pci_find_host_bridge(a->bus);521 struct pci_host_bridge *host_b = pci_find_host_bridge(b->bus);522 523 if (host_a == host_b)524 return __host_bridge_whitelist(host_a, true, warn);525 526 if (__host_bridge_whitelist(host_a, false, warn) &&527 __host_bridge_whitelist(host_b, false, warn))528 return true;529 530 return false;531}532 533static unsigned long map_types_idx(struct pci_dev *client)534{535 return (pci_domain_nr(client->bus) << 16) | pci_dev_id(client);536}537 538/*539 * Calculate the P2PDMA mapping type and distance between two PCI devices.540 *541 * If the two devices are the same PCI function, return542 * PCI_P2PDMA_MAP_BUS_ADDR and a distance of 0.543 *544 * If they are two functions of the same device, return545 * PCI_P2PDMA_MAP_BUS_ADDR and a distance of 2 (one hop up to the bridge,546 * then one hop back down to another function of the same device).547 *548 * In the case where two devices are connected to the same PCIe switch,549 * return a distance of 4. This corresponds to the following PCI tree:550 *551 * -+ Root Port552 * \+ Switch Upstream Port553 * +-+ Switch Downstream Port 0554 * + \- Device A555 * \-+ Switch Downstream Port 1556 * \- Device B557 *558 * The distance is 4 because we traverse from Device A to Downstream Port 0559 * to the common Switch Upstream Port, back down to Downstream Port 1 and560 * then to Device B. The mapping type returned depends on the ACS561 * redirection setting of the ports along the path.562 *563 * If ACS redirect is set on any port in the path, traffic between the564 * devices will go through the host bridge, so return565 * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE; otherwise return566 * PCI_P2PDMA_MAP_BUS_ADDR.567 *568 * Any two devices that have a data path that goes through the host bridge569 * will consult a whitelist. If the host bridge is in the whitelist, return570 * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE with the distance set to the number of571 * ports per above. If the device is not in the whitelist, return572 * PCI_P2PDMA_MAP_NOT_SUPPORTED.573 */574static enum pci_p2pdma_map_type575calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,576 int *dist, bool verbose)577{578 enum pci_p2pdma_map_type map_type = PCI_P2PDMA_MAP_THRU_HOST_BRIDGE;579 struct pci_dev *a = provider, *b = client, *bb;580 bool acs_redirects = false;581 struct pci_p2pdma *p2pdma;582 struct seq_buf acs_list;583 int acs_cnt = 0;584 int dist_a = 0;585 int dist_b = 0;586 char buf[128];587 588 seq_buf_init(&acs_list, buf, sizeof(buf));589 590 /*591 * Note, we don't need to take references to devices returned by592 * pci_upstream_bridge() seeing we hold a reference to a child593 * device which will already hold a reference to the upstream bridge.594 */595 while (a) {596 dist_b = 0;597 598 if (pci_bridge_has_acs_redir(a)) {599 seq_buf_print_bus_devfn(&acs_list, a);600 acs_cnt++;601 }602 603 bb = b;604 605 while (bb) {606 if (a == bb)607 goto check_b_path_acs;608 609 bb = pci_upstream_bridge(bb);610 dist_b++;611 }612 613 a = pci_upstream_bridge(a);614 dist_a++;615 }616 617 *dist = dist_a + dist_b;618 goto map_through_host_bridge;619 620check_b_path_acs:621 bb = b;622 623 while (bb) {624 if (a == bb)625 break;626 627 if (pci_bridge_has_acs_redir(bb)) {628 seq_buf_print_bus_devfn(&acs_list, bb);629 acs_cnt++;630 }631 632 bb = pci_upstream_bridge(bb);633 }634 635 *dist = dist_a + dist_b;636 637 if (!acs_cnt) {638 map_type = PCI_P2PDMA_MAP_BUS_ADDR;639 goto done;640 }641 642 if (verbose) {643 acs_list.buffer[acs_list.len-1] = 0; /* drop final semicolon */644 pci_warn(client, "ACS redirect is set between the client and provider (%s)\n",645 pci_name(provider));646 pci_warn(client, "to disable ACS redirect for this path, add the kernel parameter: pci=disable_acs_redir=%s\n",647 acs_list.buffer);648 }649 acs_redirects = true;650 651map_through_host_bridge:652 if (!cpu_supports_p2pdma() &&653 !host_bridge_whitelist(provider, client, acs_redirects)) {654 if (verbose)655 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",656 pci_name(provider));657 map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED;658 }659done:660 rcu_read_lock();661 p2pdma = rcu_dereference(provider->p2pdma);662 if (p2pdma)663 xa_store(&p2pdma->map_types, map_types_idx(client),664 xa_mk_value(map_type), GFP_ATOMIC);665 rcu_read_unlock();666 return map_type;667}668 669/**670 * pci_p2pdma_distance_many - Determine the cumulative distance between671 * a p2pdma provider and the clients in use.672 * @provider: p2pdma provider to check against the client list673 * @clients: array of devices to check (NULL-terminated)674 * @num_clients: number of clients in the array675 * @verbose: if true, print warnings for devices when we return -1676 *677 * Returns -1 if any of the clients are not compatible, otherwise returns a678 * positive number where a lower number is the preferable choice. (If there's679 * one client that's the same as the provider it will return 0, which is best680 * choice).681 *682 * "compatible" means the provider and the clients are either all behind683 * the same PCI root port or the host bridges connected to each of the devices684 * are listed in the 'pci_p2pdma_whitelist'.685 */686int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients,687 int num_clients, bool verbose)688{689 enum pci_p2pdma_map_type map;690 bool not_supported = false;691 struct pci_dev *pci_client;692 int total_dist = 0;693 int i, distance;694 695 if (num_clients == 0)696 return -1;697 698 for (i = 0; i < num_clients; i++) {699 pci_client = find_parent_pci_dev(clients[i]);700 if (!pci_client) {701 if (verbose)702 dev_warn(clients[i],703 "cannot be used for peer-to-peer DMA as it is not a PCI device\n");704 return -1;705 }706 707 map = calc_map_type_and_dist(provider, pci_client, &distance,708 verbose);709 710 pci_dev_put(pci_client);711 712 if (map == PCI_P2PDMA_MAP_NOT_SUPPORTED)713 not_supported = true;714 715 if (not_supported && !verbose)716 break;717 718 total_dist += distance;719 }720 721 if (not_supported)722 return -1;723 724 return total_dist;725}726EXPORT_SYMBOL_GPL(pci_p2pdma_distance_many);727 728/**729 * pci_has_p2pmem - check if a given PCI device has published any p2pmem730 * @pdev: PCI device to check731 */732bool pci_has_p2pmem(struct pci_dev *pdev)733{734 struct pci_p2pdma *p2pdma;735 bool res;736 737 rcu_read_lock();738 p2pdma = rcu_dereference(pdev->p2pdma);739 res = p2pdma && p2pdma->p2pmem_published;740 rcu_read_unlock();741 742 return res;743}744EXPORT_SYMBOL_GPL(pci_has_p2pmem);745 746/**747 * pci_p2pmem_find_many - find a peer-to-peer DMA memory device compatible with748 * the specified list of clients and shortest distance749 * @clients: array of devices to check (NULL-terminated)750 * @num_clients: number of client devices in the list751 *752 * If multiple devices are behind the same switch, the one "closest" to the753 * client devices in use will be chosen first. (So if one of the providers is754 * the same as one of the clients, that provider will be used ahead of any755 * other providers that are unrelated). If multiple providers are an equal756 * distance away, one will be chosen at random.757 *758 * Returns a pointer to the PCI device with a reference taken (use pci_dev_put759 * to return the reference) or NULL if no compatible device is found. The760 * found provider will also be assigned to the client list.761 */762struct pci_dev *pci_p2pmem_find_many(struct device **clients, int num_clients)763{764 struct pci_dev *pdev = NULL;765 int distance;766 int closest_distance = INT_MAX;767 struct pci_dev **closest_pdevs;768 int dev_cnt = 0;769 const int max_devs = PAGE_SIZE / sizeof(*closest_pdevs);770 int i;771 772 closest_pdevs = kmalloc(PAGE_SIZE, GFP_KERNEL);773 if (!closest_pdevs)774 return NULL;775 776 for_each_pci_dev(pdev) {777 if (!pci_has_p2pmem(pdev))778 continue;779 780 distance = pci_p2pdma_distance_many(pdev, clients,781 num_clients, false);782 if (distance < 0 || distance > closest_distance)783 continue;784 785 if (distance == closest_distance && dev_cnt >= max_devs)786 continue;787 788 if (distance < closest_distance) {789 for (i = 0; i < dev_cnt; i++)790 pci_dev_put(closest_pdevs[i]);791 792 dev_cnt = 0;793 closest_distance = distance;794 }795 796 closest_pdevs[dev_cnt++] = pci_dev_get(pdev);797 }798 799 if (dev_cnt)800 pdev = pci_dev_get(closest_pdevs[get_random_u32_below(dev_cnt)]);801 802 for (i = 0; i < dev_cnt; i++)803 pci_dev_put(closest_pdevs[i]);804 805 kfree(closest_pdevs);806 return pdev;807}808EXPORT_SYMBOL_GPL(pci_p2pmem_find_many);809 810/**811 * pci_alloc_p2pmem - allocate peer-to-peer DMA memory812 * @pdev: the device to allocate memory from813 * @size: number of bytes to allocate814 *815 * Returns the allocated memory or NULL on error.816 */817void *pci_alloc_p2pmem(struct pci_dev *pdev, size_t size)818{819 void *ret = NULL;820 struct percpu_ref *ref;821 struct pci_p2pdma *p2pdma;822 823 /*824 * Pairs with synchronize_rcu() in pci_p2pdma_release() to825 * ensure pdev->p2pdma is non-NULL for the duration of the826 * read-lock.827 */828 rcu_read_lock();829 p2pdma = rcu_dereference(pdev->p2pdma);830 if (unlikely(!p2pdma))831 goto out;832 833 ret = (void *)gen_pool_alloc_owner(p2pdma->pool, size, (void **) &ref);834 if (!ret)835 goto out;836 837 if (unlikely(!percpu_ref_tryget_live_rcu(ref))) {838 gen_pool_free(p2pdma->pool, (unsigned long) ret, size);839 ret = NULL;840 }841out:842 rcu_read_unlock();843 return ret;844}845EXPORT_SYMBOL_GPL(pci_alloc_p2pmem);846 847/**848 * pci_free_p2pmem - free peer-to-peer DMA memory849 * @pdev: the device the memory was allocated from850 * @addr: address of the memory that was allocated851 * @size: number of bytes that were allocated852 */853void pci_free_p2pmem(struct pci_dev *pdev, void *addr, size_t size)854{855 struct percpu_ref *ref;856 struct pci_p2pdma *p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);857 858 gen_pool_free_owner(p2pdma->pool, (uintptr_t)addr, size,859 (void **) &ref);860 percpu_ref_put(ref);861}862EXPORT_SYMBOL_GPL(pci_free_p2pmem);863 864/**865 * pci_p2pmem_virt_to_bus - return the PCI bus address for a given virtual866 * address obtained with pci_alloc_p2pmem()867 * @pdev: the device the memory was allocated from868 * @addr: address of the memory that was allocated869 */870pci_bus_addr_t pci_p2pmem_virt_to_bus(struct pci_dev *pdev, void *addr)871{872 struct pci_p2pdma *p2pdma;873 874 if (!addr)875 return 0;876 877 p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);878 if (!p2pdma)879 return 0;880 881 /*882 * Note: when we added the memory to the pool we used the PCI883 * bus address as the physical address. So gen_pool_virt_to_phys()884 * actually returns the bus address despite the misleading name.885 */886 return gen_pool_virt_to_phys(p2pdma->pool, (unsigned long)addr);887}888EXPORT_SYMBOL_GPL(pci_p2pmem_virt_to_bus);889 890/**891 * pci_p2pmem_alloc_sgl - allocate peer-to-peer DMA memory in a scatterlist892 * @pdev: the device to allocate memory from893 * @nents: the number of SG entries in the list894 * @length: number of bytes to allocate895 *896 * Return: %NULL on error or &struct scatterlist pointer and @nents on success897 */898struct scatterlist *pci_p2pmem_alloc_sgl(struct pci_dev *pdev,899 unsigned int *nents, u32 length)900{901 struct scatterlist *sg;902 void *addr;903 904 sg = kmalloc(sizeof(*sg), GFP_KERNEL);905 if (!sg)906 return NULL;907 908 sg_init_table(sg, 1);909 910 addr = pci_alloc_p2pmem(pdev, length);911 if (!addr)912 goto out_free_sg;913 914 sg_set_buf(sg, addr, length);915 *nents = 1;916 return sg;917 918out_free_sg:919 kfree(sg);920 return NULL;921}922EXPORT_SYMBOL_GPL(pci_p2pmem_alloc_sgl);923 924/**925 * pci_p2pmem_free_sgl - free a scatterlist allocated by pci_p2pmem_alloc_sgl()926 * @pdev: the device to allocate memory from927 * @sgl: the allocated scatterlist928 */929void pci_p2pmem_free_sgl(struct pci_dev *pdev, struct scatterlist *sgl)930{931 struct scatterlist *sg;932 int count;933 934 for_each_sg(sgl, sg, INT_MAX, count) {935 if (!sg)936 break;937 938 pci_free_p2pmem(pdev, sg_virt(sg), sg->length);939 }940 kfree(sgl);941}942EXPORT_SYMBOL_GPL(pci_p2pmem_free_sgl);943 944/**945 * pci_p2pmem_publish - publish the peer-to-peer DMA memory for use by946 * other devices with pci_p2pmem_find()947 * @pdev: the device with peer-to-peer DMA memory to publish948 * @publish: set to true to publish the memory, false to unpublish it949 *950 * Published memory can be used by other PCI device drivers for951 * peer-2-peer DMA operations. Non-published memory is reserved for952 * exclusive use of the device driver that registers the peer-to-peer953 * memory.954 */955void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)956{957 struct pci_p2pdma *p2pdma;958 959 rcu_read_lock();960 p2pdma = rcu_dereference(pdev->p2pdma);961 if (p2pdma)962 p2pdma->p2pmem_published = publish;963 rcu_read_unlock();964}965EXPORT_SYMBOL_GPL(pci_p2pmem_publish);966 967static enum pci_p2pdma_map_type pci_p2pdma_map_type(struct dev_pagemap *pgmap,968 struct device *dev)969{970 enum pci_p2pdma_map_type type = PCI_P2PDMA_MAP_NOT_SUPPORTED;971 struct pci_dev *provider = to_p2p_pgmap(pgmap)->provider;972 struct pci_dev *client;973 struct pci_p2pdma *p2pdma;974 int dist;975 976 if (!provider->p2pdma)977 return PCI_P2PDMA_MAP_NOT_SUPPORTED;978 979 if (!dev_is_pci(dev))980 return PCI_P2PDMA_MAP_NOT_SUPPORTED;981 982 client = to_pci_dev(dev);983 984 rcu_read_lock();985 p2pdma = rcu_dereference(provider->p2pdma);986 987 if (p2pdma)988 type = xa_to_value(xa_load(&p2pdma->map_types,989 map_types_idx(client)));990 rcu_read_unlock();991 992 if (type == PCI_P2PDMA_MAP_UNKNOWN)993 return calc_map_type_and_dist(provider, client, &dist, true);994 995 return type;996}997 998/**999 * pci_p2pdma_map_segment - map an sg segment determining the mapping type1000 * @state: State structure that should be declared outside of the for_each_sg()1001 * loop and initialized to zero.1002 * @dev: DMA device that's doing the mapping operation1003 * @sg: scatterlist segment to map1004 *1005 * This is a helper to be used by non-IOMMU dma_map_sg() implementations where1006 * the sg segment is the same for the page_link and the dma_address.1007 *1008 * Attempt to map a single segment in an SGL with the PCI bus address.1009 * The segment must point to a PCI P2PDMA page and thus must be1010 * wrapped in a is_pci_p2pdma_page(sg_page(sg)) check.1011 *1012 * Returns the type of mapping used and maps the page if the type is1013 * PCI_P2PDMA_MAP_BUS_ADDR.1014 */1015enum pci_p2pdma_map_type1016pci_p2pdma_map_segment(struct pci_p2pdma_map_state *state, struct device *dev,1017 struct scatterlist *sg)1018{1019 if (state->pgmap != sg_page(sg)->pgmap) {1020 state->pgmap = sg_page(sg)->pgmap;1021 state->map = pci_p2pdma_map_type(state->pgmap, dev);1022 state->bus_off = to_p2p_pgmap(state->pgmap)->bus_offset;1023 }1024 1025 if (state->map == PCI_P2PDMA_MAP_BUS_ADDR) {1026 sg->dma_address = sg_phys(sg) + state->bus_off;1027 sg_dma_len(sg) = sg->length;1028 sg_dma_mark_bus_address(sg);1029 }1030 1031 return state->map;1032}1033 1034/**1035 * pci_p2pdma_enable_store - parse a configfs/sysfs attribute store1036 * to enable p2pdma1037 * @page: contents of the value to be stored1038 * @p2p_dev: returns the PCI device that was selected to be used1039 * (if one was specified in the stored value)1040 * @use_p2pdma: returns whether to enable p2pdma or not1041 *1042 * Parses an attribute value to decide whether to enable p2pdma.1043 * The value can select a PCI device (using its full BDF device1044 * name) or a boolean (in any format kstrtobool() accepts). A false1045 * value disables p2pdma, a true value expects the caller1046 * to automatically find a compatible device and specifying a PCI device1047 * expects the caller to use the specific provider.1048 *1049 * pci_p2pdma_enable_show() should be used as the show operation for1050 * the attribute.1051 *1052 * Returns 0 on success1053 */1054int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,1055 bool *use_p2pdma)1056{1057 struct device *dev;1058 1059 dev = bus_find_device_by_name(&pci_bus_type, NULL, page);1060 if (dev) {1061 *use_p2pdma = true;1062 *p2p_dev = to_pci_dev(dev);1063 1064 if (!pci_has_p2pmem(*p2p_dev)) {1065 pci_err(*p2p_dev,1066 "PCI device has no peer-to-peer memory: %s\n",1067 page);1068 pci_dev_put(*p2p_dev);1069 return -ENODEV;1070 }1071 1072 return 0;1073 } else if ((page[0] == '0' || page[0] == '1') && !iscntrl(page[1])) {1074 /*1075 * If the user enters a PCI device that doesn't exist1076 * like "0000:01:00.1", we don't want kstrtobool to think1077 * it's a '0' when it's clearly not what the user wanted.1078 * So we require 0's and 1's to be exactly one character.1079 */1080 } else if (!kstrtobool(page, use_p2pdma)) {1081 return 0;1082 }1083 1084 pr_err("No such PCI device: %.*s\n", (int)strcspn(page, "\n"), page);1085 return -ENODEV;1086}1087EXPORT_SYMBOL_GPL(pci_p2pdma_enable_store);1088 1089/**1090 * pci_p2pdma_enable_show - show a configfs/sysfs attribute indicating1091 * whether p2pdma is enabled1092 * @page: contents of the stored value1093 * @p2p_dev: the selected p2p device (NULL if no device is selected)1094 * @use_p2pdma: whether p2pdma has been enabled1095 *1096 * Attributes that use pci_p2pdma_enable_store() should use this function1097 * to show the value of the attribute.1098 *1099 * Returns 0 on success1100 */1101ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,1102 bool use_p2pdma)1103{1104 if (!use_p2pdma)1105 return sprintf(page, "0\n");1106 1107 if (!p2p_dev)1108 return sprintf(page, "1\n");1109 1110 return sprintf(page, "%s\n", pci_name(p2p_dev));1111}1112EXPORT_SYMBOL_GPL(pci_p2pdma_enable_show);1113