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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
23enum 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
30struct pci_p2pdma {
31 struct gen_pool *pool;
32 bool p2pmem_published;
33 struct xarray map_types;
34};
35
36struct pci_p2pdma_pagemap {
37 struct dev_pagemap pgmap;
38 struct pci_dev *provider;
39 u64 bus_offset;
40};
41
42static struct pci_p2pdma_pagemap *to_p2p_pgmap(struct dev_pagemap *pgmap)
43{
44 return container_of(pgmap, struct pci_p2pdma_pagemap, pgmap);
45}
46
47static 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}
58static DEVICE_ATTR_RO(size);
59
60static 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}
71static DEVICE_ATTR_RO(available);
72
73static 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}
81static DEVICE_ATTR_RO(published);
82
83static struct attribute *p2pmem_attrs[] = {
84 &dev_attr_size.attr,
85 &dev_attr_available.attr,
86 &dev_attr_published.attr,
87 NULL,
88};
89
90static const struct attribute_group p2pmem_group = {
91 .attrs = p2pmem_attrs,
92 .name = "p2pmem",
93};
94
95static 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
112static 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
139out_pool_destroy:
140 pdev->p2pdma = NULL;
141 gen_pool_destroy(p2p->pool);
142out:
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 */
157int 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
215pages_free:
216 devm_memunmap_pages(&pdev->dev, pgmap);
217pgmap_free:
218 devm_kfree(&pdev->dev, pgmap);
219 return error;
220}
221EXPORT_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 */
228static 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 */
251static 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
268static 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
276static 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
295static 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 */
325static 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
340static 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
385check_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
413static 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 */
458static enum pci_p2pdma_map_type
459upstream_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
479static enum pci_p2pdma_map_type
480upstream_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 */
529int 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}
581EXPORT_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 */
587bool pci_has_p2pmem(struct pci_dev *pdev)
588{
589 return pdev->p2pdma && pdev->p2pdma->p2pmem_published;
590}
591EXPORT_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 */
610struct 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}
656EXPORT_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 */
665void *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 }
689out:
690 rcu_read_unlock();
691 return ret;
692}
693EXPORT_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 */
701void 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}
709EXPORT_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 */
717pci_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}
731EXPORT_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 */
741struct 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
761out_free_sg:
762 kfree(sg);
763 return NULL;
764}
765EXPORT_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 */
772void 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}
785EXPORT_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 */
798void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
799{
800 if (pdev->p2pdma)
801 pdev->p2pdma->p2pmem_published = publish;
802}
803EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
804
805static 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
815static 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 */
855int 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}
877EXPORT_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 */
888void 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}
906EXPORT_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 */
928int 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}
961EXPORT_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 */
975ssize_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}
986EXPORT_SYMBOL_GPL(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/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 dev_pagemap pgmap;
32 struct pci_dev *provider;
33 u64 bus_offset;
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 mapping
133 * such that rcu_read_unlock() can be done before inserting the
134 * pages
135 */
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 check
169 * that the file size is greater than the mmap size before allowing
170 * the mmap to continue. To work around this, just set the size
171 * 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 struct percpu_ref *ref;
198
199 gen_pool_free_owner(pgmap->provider->p2pdma->pool,
200 (uintptr_t)page_to_virt(page), PAGE_SIZE,
201 (void **)&ref);
202 percpu_ref_put(ref);
203}
204
205static const struct dev_pagemap_ops p2pdma_pgmap_ops = {
206 .page_free = p2pdma_page_free,
207};
208
209static void pci_p2pdma_release(void *data)
210{
211 struct pci_dev *pdev = data;
212 struct pci_p2pdma *p2pdma;
213
214 p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
215 if (!p2pdma)
216 return;
217
218 /* Flush and disable pci_alloc_p2p_mem() */
219 pdev->p2pdma = NULL;
220 synchronize_rcu();
221
222 gen_pool_destroy(p2pdma->pool);
223 sysfs_remove_group(&pdev->dev.kobj, &p2pmem_group);
224 xa_destroy(&p2pdma->map_types);
225}
226
227static int pci_p2pdma_setup(struct pci_dev *pdev)
228{
229 int error = -ENOMEM;
230 struct pci_p2pdma *p2p;
231
232 p2p = devm_kzalloc(&pdev->dev, sizeof(*p2p), GFP_KERNEL);
233 if (!p2p)
234 return -ENOMEM;
235
236 xa_init(&p2p->map_types);
237
238 p2p->pool = gen_pool_create(PAGE_SHIFT, dev_to_node(&pdev->dev));
239 if (!p2p->pool)
240 goto out;
241
242 error = devm_add_action_or_reset(&pdev->dev, pci_p2pdma_release, pdev);
243 if (error)
244 goto out_pool_destroy;
245
246 error = sysfs_create_group(&pdev->dev.kobj, &p2pmem_group);
247 if (error)
248 goto out_pool_destroy;
249
250 rcu_assign_pointer(pdev->p2pdma, p2p);
251 return 0;
252
253out_pool_destroy:
254 gen_pool_destroy(p2p->pool);
255out:
256 devm_kfree(&pdev->dev, p2p);
257 return error;
258}
259
260static void pci_p2pdma_unmap_mappings(void *data)
261{
262 struct pci_dev *pdev = data;
263
264 /*
265 * Removing the alloc attribute from sysfs will call
266 * unmap_mapping_range() on the inode, teardown any existing userspace
267 * mappings and prevent new ones from being created.
268 */
269 sysfs_remove_file_from_group(&pdev->dev.kobj, &p2pmem_alloc_attr.attr,
270 p2pmem_group.name);
271}
272
273/**
274 * pci_p2pdma_add_resource - add memory for use as p2p memory
275 * @pdev: the device to add the memory to
276 * @bar: PCI BAR to add
277 * @size: size of the memory to add, may be zero to use the whole BAR
278 * @offset: offset into the PCI BAR
279 *
280 * The memory will be given ZONE_DEVICE struct pages so that it may
281 * be used with any DMA request.
282 */
283int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
284 u64 offset)
285{
286 struct pci_p2pdma_pagemap *p2p_pgmap;
287 struct dev_pagemap *pgmap;
288 struct pci_p2pdma *p2pdma;
289 void *addr;
290 int error;
291
292 if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
293 return -EINVAL;
294
295 if (offset >= pci_resource_len(pdev, bar))
296 return -EINVAL;
297
298 if (!size)
299 size = pci_resource_len(pdev, bar) - offset;
300
301 if (size + offset > pci_resource_len(pdev, bar))
302 return -EINVAL;
303
304 if (!pdev->p2pdma) {
305 error = pci_p2pdma_setup(pdev);
306 if (error)
307 return error;
308 }
309
310 p2p_pgmap = devm_kzalloc(&pdev->dev, sizeof(*p2p_pgmap), GFP_KERNEL);
311 if (!p2p_pgmap)
312 return -ENOMEM;
313
314 pgmap = &p2p_pgmap->pgmap;
315 pgmap->range.start = pci_resource_start(pdev, bar) + offset;
316 pgmap->range.end = pgmap->range.start + size - 1;
317 pgmap->nr_range = 1;
318 pgmap->type = MEMORY_DEVICE_PCI_P2PDMA;
319 pgmap->ops = &p2pdma_pgmap_ops;
320
321 p2p_pgmap->provider = pdev;
322 p2p_pgmap->bus_offset = pci_bus_address(pdev, bar) -
323 pci_resource_start(pdev, bar);
324
325 addr = devm_memremap_pages(&pdev->dev, pgmap);
326 if (IS_ERR(addr)) {
327 error = PTR_ERR(addr);
328 goto pgmap_free;
329 }
330
331 error = devm_add_action_or_reset(&pdev->dev, pci_p2pdma_unmap_mappings,
332 pdev);
333 if (error)
334 goto pages_free;
335
336 p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
337 error = gen_pool_add_owner(p2pdma->pool, (unsigned long)addr,
338 pci_bus_address(pdev, bar) + offset,
339 range_len(&pgmap->range), dev_to_node(&pdev->dev),
340 &pgmap->ref);
341 if (error)
342 goto pages_free;
343
344 pci_info(pdev, "added peer-to-peer DMA memory %#llx-%#llx\n",
345 pgmap->range.start, pgmap->range.end);
346
347 return 0;
348
349pages_free:
350 devm_memunmap_pages(&pdev->dev, pgmap);
351pgmap_free:
352 devm_kfree(&pdev->dev, pgmap);
353 return error;
354}
355EXPORT_SYMBOL_GPL(pci_p2pdma_add_resource);
356
357/*
358 * Note this function returns the parent PCI device with a
359 * reference taken. It is the caller's responsibility to drop
360 * the reference.
361 */
362static struct pci_dev *find_parent_pci_dev(struct device *dev)
363{
364 struct device *parent;
365
366 dev = get_device(dev);
367
368 while (dev) {
369 if (dev_is_pci(dev))
370 return to_pci_dev(dev);
371
372 parent = get_device(dev->parent);
373 put_device(dev);
374 dev = parent;
375 }
376
377 return NULL;
378}
379
380/*
381 * Check if a PCI bridge has its ACS redirection bits set to redirect P2P
382 * TLPs upstream via ACS. Returns 1 if the packets will be redirected
383 * upstream, 0 otherwise.
384 */
385static int pci_bridge_has_acs_redir(struct pci_dev *pdev)
386{
387 int pos;
388 u16 ctrl;
389
390 pos = pdev->acs_cap;
391 if (!pos)
392 return 0;
393
394 pci_read_config_word(pdev, pos + PCI_ACS_CTRL, &ctrl);
395
396 if (ctrl & (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC))
397 return 1;
398
399 return 0;
400}
401
402static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev)
403{
404 if (!buf)
405 return;
406
407 seq_buf_printf(buf, "%s;", pci_name(pdev));
408}
409
410static bool cpu_supports_p2pdma(void)
411{
412#ifdef CONFIG_X86
413 struct cpuinfo_x86 *c = &cpu_data(0);
414
415 /* Any AMD CPU whose family ID is Zen or newer supports p2pdma */
416 if (c->x86_vendor == X86_VENDOR_AMD && c->x86 >= 0x17)
417 return true;
418#endif
419
420 return false;
421}
422
423static const struct pci_p2pdma_whitelist_entry {
424 unsigned short vendor;
425 unsigned short device;
426 enum {
427 REQ_SAME_HOST_BRIDGE = 1 << 0,
428 } flags;
429} pci_p2pdma_whitelist[] = {
430 /* Intel Xeon E5/Core i7 */
431 {PCI_VENDOR_ID_INTEL, 0x3c00, REQ_SAME_HOST_BRIDGE},
432 {PCI_VENDOR_ID_INTEL, 0x3c01, REQ_SAME_HOST_BRIDGE},
433 /* Intel Xeon E7 v3/Xeon E5 v3/Core i7 */
434 {PCI_VENDOR_ID_INTEL, 0x2f00, REQ_SAME_HOST_BRIDGE},
435 {PCI_VENDOR_ID_INTEL, 0x2f01, REQ_SAME_HOST_BRIDGE},
436 /* Intel SkyLake-E */
437 {PCI_VENDOR_ID_INTEL, 0x2030, 0},
438 {PCI_VENDOR_ID_INTEL, 0x2031, 0},
439 {PCI_VENDOR_ID_INTEL, 0x2032, 0},
440 {PCI_VENDOR_ID_INTEL, 0x2033, 0},
441 {PCI_VENDOR_ID_INTEL, 0x2020, 0},
442 {PCI_VENDOR_ID_INTEL, 0x09a2, 0},
443 {}
444};
445
446/*
447 * If the first device on host's root bus is either devfn 00.0 or a PCIe
448 * Root Port, return it. Otherwise return NULL.
449 *
450 * We often use a devfn 00.0 "host bridge" in the pci_p2pdma_whitelist[]
451 * (though there is no PCI/PCIe requirement for such a device). On some
452 * platforms, e.g., Intel Skylake, there is no such host bridge device, and
453 * pci_p2pdma_whitelist[] may contain a Root Port at any devfn.
454 *
455 * This function is similar to pci_get_slot(host->bus, 0), but it does
456 * not take the pci_bus_sem lock since __host_bridge_whitelist() must not
457 * sleep.
458 *
459 * For this to be safe, the caller should hold a reference to a device on the
460 * bridge, which should ensure the host_bridge device will not be freed
461 * or removed from the head of the devices list.
462 */
463static struct pci_dev *pci_host_bridge_dev(struct pci_host_bridge *host)
464{
465 struct pci_dev *root;
466
467 root = list_first_entry_or_null(&host->bus->devices,
468 struct pci_dev, bus_list);
469
470 if (!root)
471 return NULL;
472
473 if (root->devfn == PCI_DEVFN(0, 0))
474 return root;
475
476 if (pci_pcie_type(root) == PCI_EXP_TYPE_ROOT_PORT)
477 return root;
478
479 return NULL;
480}
481
482static bool __host_bridge_whitelist(struct pci_host_bridge *host,
483 bool same_host_bridge, bool warn)
484{
485 struct pci_dev *root = pci_host_bridge_dev(host);
486 const struct pci_p2pdma_whitelist_entry *entry;
487 unsigned short vendor, device;
488
489 if (!root)
490 return false;
491
492 vendor = root->vendor;
493 device = root->device;
494
495 for (entry = pci_p2pdma_whitelist; entry->vendor; entry++) {
496 if (vendor != entry->vendor || device != entry->device)
497 continue;
498 if (entry->flags & REQ_SAME_HOST_BRIDGE && !same_host_bridge)
499 return false;
500
501 return true;
502 }
503
504 if (warn)
505 pci_warn(root, "Host bridge not in P2PDMA whitelist: %04x:%04x\n",
506 vendor, device);
507
508 return false;
509}
510
511/*
512 * If we can't find a common upstream bridge take a look at the root
513 * complex and compare it to a whitelist of known good hardware.
514 */
515static bool host_bridge_whitelist(struct pci_dev *a, struct pci_dev *b,
516 bool warn)
517{
518 struct pci_host_bridge *host_a = pci_find_host_bridge(a->bus);
519 struct pci_host_bridge *host_b = pci_find_host_bridge(b->bus);
520
521 if (host_a == host_b)
522 return __host_bridge_whitelist(host_a, true, warn);
523
524 if (__host_bridge_whitelist(host_a, false, warn) &&
525 __host_bridge_whitelist(host_b, false, warn))
526 return true;
527
528 return false;
529}
530
531static unsigned long map_types_idx(struct pci_dev *client)
532{
533 return (pci_domain_nr(client->bus) << 16) |
534 (client->bus->number << 8) | client->devfn;
535}
536
537/*
538 * Calculate the P2PDMA mapping type and distance between two PCI devices.
539 *
540 * If the two devices are the same PCI function, return
541 * PCI_P2PDMA_MAP_BUS_ADDR and a distance of 0.
542 *
543 * If they are two functions of the same device, return
544 * PCI_P2PDMA_MAP_BUS_ADDR and a distance of 2 (one hop up to the bridge,
545 * then one hop back down to another function of the same device).
546 *
547 * In the case where two devices are connected to the same PCIe switch,
548 * return a distance of 4. This corresponds to the following PCI tree:
549 *
550 * -+ Root Port
551 * \+ Switch Upstream Port
552 * +-+ Switch Downstream Port 0
553 * + \- Device A
554 * \-+ Switch Downstream Port 1
555 * \- Device B
556 *
557 * The distance is 4 because we traverse from Device A to Downstream Port 0
558 * to the common Switch Upstream Port, back down to Downstream Port 1 and
559 * then to Device B. The mapping type returned depends on the ACS
560 * redirection setting of the ports along the path.
561 *
562 * If ACS redirect is set on any port in the path, traffic between the
563 * devices will go through the host bridge, so return
564 * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE; otherwise return
565 * PCI_P2PDMA_MAP_BUS_ADDR.
566 *
567 * Any two devices that have a data path that goes through the host bridge
568 * will consult a whitelist. If the host bridge is in the whitelist, return
569 * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE with the distance set to the number of
570 * ports per above. If the device is not in the whitelist, return
571 * PCI_P2PDMA_MAP_NOT_SUPPORTED.
572 */
573static enum pci_p2pdma_map_type
574calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
575 int *dist, bool verbose)
576{
577 enum pci_p2pdma_map_type map_type = PCI_P2PDMA_MAP_THRU_HOST_BRIDGE;
578 struct pci_dev *a = provider, *b = client, *bb;
579 bool acs_redirects = false;
580 struct pci_p2pdma *p2pdma;
581 struct seq_buf acs_list;
582 int acs_cnt = 0;
583 int dist_a = 0;
584 int dist_b = 0;
585 char buf[128];
586
587 seq_buf_init(&acs_list, buf, sizeof(buf));
588
589 /*
590 * Note, we don't need to take references to devices returned by
591 * pci_upstream_bridge() seeing we hold a reference to a child
592 * device which will already hold a reference to the upstream bridge.
593 */
594 while (a) {
595 dist_b = 0;
596
597 if (pci_bridge_has_acs_redir(a)) {
598 seq_buf_print_bus_devfn(&acs_list, a);
599 acs_cnt++;
600 }
601
602 bb = b;
603
604 while (bb) {
605 if (a == bb)
606 goto check_b_path_acs;
607
608 bb = pci_upstream_bridge(bb);
609 dist_b++;
610 }
611
612 a = pci_upstream_bridge(a);
613 dist_a++;
614 }
615
616 *dist = dist_a + dist_b;
617 goto map_through_host_bridge;
618
619check_b_path_acs:
620 bb = b;
621
622 while (bb) {
623 if (a == bb)
624 break;
625
626 if (pci_bridge_has_acs_redir(bb)) {
627 seq_buf_print_bus_devfn(&acs_list, bb);
628 acs_cnt++;
629 }
630
631 bb = pci_upstream_bridge(bb);
632 }
633
634 *dist = dist_a + dist_b;
635
636 if (!acs_cnt) {
637 map_type = PCI_P2PDMA_MAP_BUS_ADDR;
638 goto done;
639 }
640
641 if (verbose) {
642 acs_list.buffer[acs_list.len-1] = 0; /* drop final semicolon */
643 pci_warn(client, "ACS redirect is set between the client and provider (%s)\n",
644 pci_name(provider));
645 pci_warn(client, "to disable ACS redirect for this path, add the kernel parameter: pci=disable_acs_redir=%s\n",
646 acs_list.buffer);
647 }
648 acs_redirects = true;
649
650map_through_host_bridge:
651 if (!cpu_supports_p2pdma() &&
652 !host_bridge_whitelist(provider, client, acs_redirects)) {
653 if (verbose)
654 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",
655 pci_name(provider));
656 map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
657 }
658done:
659 rcu_read_lock();
660 p2pdma = rcu_dereference(provider->p2pdma);
661 if (p2pdma)
662 xa_store(&p2pdma->map_types, map_types_idx(client),
663 xa_mk_value(map_type), GFP_KERNEL);
664 rcu_read_unlock();
665 return map_type;
666}
667
668/**
669 * pci_p2pdma_distance_many - Determine the cumulative distance between
670 * a p2pdma provider and the clients in use.
671 * @provider: p2pdma provider to check against the client list
672 * @clients: array of devices to check (NULL-terminated)
673 * @num_clients: number of clients in the array
674 * @verbose: if true, print warnings for devices when we return -1
675 *
676 * Returns -1 if any of the clients are not compatible, otherwise returns a
677 * positive number where a lower number is the preferable choice. (If there's
678 * one client that's the same as the provider it will return 0, which is best
679 * choice).
680 *
681 * "compatible" means the provider and the clients are either all behind
682 * the same PCI root port or the host bridges connected to each of the devices
683 * are listed in the 'pci_p2pdma_whitelist'.
684 */
685int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients,
686 int num_clients, bool verbose)
687{
688 enum pci_p2pdma_map_type map;
689 bool not_supported = false;
690 struct pci_dev *pci_client;
691 int total_dist = 0;
692 int i, distance;
693
694 if (num_clients == 0)
695 return -1;
696
697 for (i = 0; i < num_clients; i++) {
698 pci_client = find_parent_pci_dev(clients[i]);
699 if (!pci_client) {
700 if (verbose)
701 dev_warn(clients[i],
702 "cannot be used for peer-to-peer DMA as it is not a PCI device\n");
703 return -1;
704 }
705
706 map = calc_map_type_and_dist(provider, pci_client, &distance,
707 verbose);
708
709 pci_dev_put(pci_client);
710
711 if (map == PCI_P2PDMA_MAP_NOT_SUPPORTED)
712 not_supported = true;
713
714 if (not_supported && !verbose)
715 break;
716
717 total_dist += distance;
718 }
719
720 if (not_supported)
721 return -1;
722
723 return total_dist;
724}
725EXPORT_SYMBOL_GPL(pci_p2pdma_distance_many);
726
727/**
728 * pci_has_p2pmem - check if a given PCI device has published any p2pmem
729 * @pdev: PCI device to check
730 */
731bool pci_has_p2pmem(struct pci_dev *pdev)
732{
733 struct pci_p2pdma *p2pdma;
734 bool res;
735
736 rcu_read_lock();
737 p2pdma = rcu_dereference(pdev->p2pdma);
738 res = p2pdma && p2pdma->p2pmem_published;
739 rcu_read_unlock();
740
741 return res;
742}
743EXPORT_SYMBOL_GPL(pci_has_p2pmem);
744
745/**
746 * pci_p2pmem_find_many - find a peer-to-peer DMA memory device compatible with
747 * the specified list of clients and shortest distance (as determined
748 * by pci_p2pmem_dma())
749 * @clients: array of devices to check (NULL-terminated)
750 * @num_clients: number of client devices in the list
751 *
752 * If multiple devices are behind the same switch, the one "closest" to the
753 * client devices in use will be chosen first. (So if one of the providers is
754 * the same as one of the clients, that provider will be used ahead of any
755 * other providers that are unrelated). If multiple providers are an equal
756 * distance away, one will be chosen at random.
757 *
758 * Returns a pointer to the PCI device with a reference taken (use pci_dev_put
759 * to return the reference) or NULL if no compatible device is found. The
760 * 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 memory
812 * @pdev: the device to allocate memory from
813 * @size: number of bytes to allocate
814 *
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() to
825 * ensure pdev->p2pdma is non-NULL for the duration of the
826 * 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 goto out;
841 }
842out:
843 rcu_read_unlock();
844 return ret;
845}
846EXPORT_SYMBOL_GPL(pci_alloc_p2pmem);
847
848/**
849 * pci_free_p2pmem - free peer-to-peer DMA memory
850 * @pdev: the device the memory was allocated from
851 * @addr: address of the memory that was allocated
852 * @size: number of bytes that were allocated
853 */
854void pci_free_p2pmem(struct pci_dev *pdev, void *addr, size_t size)
855{
856 struct percpu_ref *ref;
857 struct pci_p2pdma *p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
858
859 gen_pool_free_owner(p2pdma->pool, (uintptr_t)addr, size,
860 (void **) &ref);
861 percpu_ref_put(ref);
862}
863EXPORT_SYMBOL_GPL(pci_free_p2pmem);
864
865/**
866 * pci_p2pmem_virt_to_bus - return the PCI bus address for a given virtual
867 * address obtained with pci_alloc_p2pmem()
868 * @pdev: the device the memory was allocated from
869 * @addr: address of the memory that was allocated
870 */
871pci_bus_addr_t pci_p2pmem_virt_to_bus(struct pci_dev *pdev, void *addr)
872{
873 struct pci_p2pdma *p2pdma;
874
875 if (!addr)
876 return 0;
877
878 p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
879 if (!p2pdma)
880 return 0;
881
882 /*
883 * Note: when we added the memory to the pool we used the PCI
884 * bus address as the physical address. So gen_pool_virt_to_phys()
885 * actually returns the bus address despite the misleading name.
886 */
887 return gen_pool_virt_to_phys(p2pdma->pool, (unsigned long)addr);
888}
889EXPORT_SYMBOL_GPL(pci_p2pmem_virt_to_bus);
890
891/**
892 * pci_p2pmem_alloc_sgl - allocate peer-to-peer DMA memory in a scatterlist
893 * @pdev: the device to allocate memory from
894 * @nents: the number of SG entries in the list
895 * @length: number of bytes to allocate
896 *
897 * Return: %NULL on error or &struct scatterlist pointer and @nents on success
898 */
899struct scatterlist *pci_p2pmem_alloc_sgl(struct pci_dev *pdev,
900 unsigned int *nents, u32 length)
901{
902 struct scatterlist *sg;
903 void *addr;
904
905 sg = kmalloc(sizeof(*sg), GFP_KERNEL);
906 if (!sg)
907 return NULL;
908
909 sg_init_table(sg, 1);
910
911 addr = pci_alloc_p2pmem(pdev, length);
912 if (!addr)
913 goto out_free_sg;
914
915 sg_set_buf(sg, addr, length);
916 *nents = 1;
917 return sg;
918
919out_free_sg:
920 kfree(sg);
921 return NULL;
922}
923EXPORT_SYMBOL_GPL(pci_p2pmem_alloc_sgl);
924
925/**
926 * pci_p2pmem_free_sgl - free a scatterlist allocated by pci_p2pmem_alloc_sgl()
927 * @pdev: the device to allocate memory from
928 * @sgl: the allocated scatterlist
929 */
930void pci_p2pmem_free_sgl(struct pci_dev *pdev, struct scatterlist *sgl)
931{
932 struct scatterlist *sg;
933 int count;
934
935 for_each_sg(sgl, sg, INT_MAX, count) {
936 if (!sg)
937 break;
938
939 pci_free_p2pmem(pdev, sg_virt(sg), sg->length);
940 }
941 kfree(sgl);
942}
943EXPORT_SYMBOL_GPL(pci_p2pmem_free_sgl);
944
945/**
946 * pci_p2pmem_publish - publish the peer-to-peer DMA memory for use by
947 * other devices with pci_p2pmem_find()
948 * @pdev: the device with peer-to-peer DMA memory to publish
949 * @publish: set to true to publish the memory, false to unpublish it
950 *
951 * Published memory can be used by other PCI device drivers for
952 * peer-2-peer DMA operations. Non-published memory is reserved for
953 * exclusive use of the device driver that registers the peer-to-peer
954 * memory.
955 */
956void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
957{
958 struct pci_p2pdma *p2pdma;
959
960 rcu_read_lock();
961 p2pdma = rcu_dereference(pdev->p2pdma);
962 if (p2pdma)
963 p2pdma->p2pmem_published = publish;
964 rcu_read_unlock();
965}
966EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
967
968static enum pci_p2pdma_map_type pci_p2pdma_map_type(struct dev_pagemap *pgmap,
969 struct device *dev)
970{
971 enum pci_p2pdma_map_type type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
972 struct pci_dev *provider = to_p2p_pgmap(pgmap)->provider;
973 struct pci_dev *client;
974 struct pci_p2pdma *p2pdma;
975 int dist;
976
977 if (!provider->p2pdma)
978 return PCI_P2PDMA_MAP_NOT_SUPPORTED;
979
980 if (!dev_is_pci(dev))
981 return PCI_P2PDMA_MAP_NOT_SUPPORTED;
982
983 client = to_pci_dev(dev);
984
985 rcu_read_lock();
986 p2pdma = rcu_dereference(provider->p2pdma);
987
988 if (p2pdma)
989 type = xa_to_value(xa_load(&p2pdma->map_types,
990 map_types_idx(client)));
991 rcu_read_unlock();
992
993 if (type == PCI_P2PDMA_MAP_UNKNOWN)
994 return calc_map_type_and_dist(provider, client, &dist, true);
995
996 return type;
997}
998
999/**
1000 * pci_p2pdma_map_segment - map an sg segment determining the mapping type
1001 * @state: State structure that should be declared outside of the for_each_sg()
1002 * loop and initialized to zero.
1003 * @dev: DMA device that's doing the mapping operation
1004 * @sg: scatterlist segment to map
1005 *
1006 * This is a helper to be used by non-IOMMU dma_map_sg() implementations where
1007 * the sg segment is the same for the page_link and the dma_address.
1008 *
1009 * Attempt to map a single segment in an SGL with the PCI bus address.
1010 * The segment must point to a PCI P2PDMA page and thus must be
1011 * wrapped in a is_pci_p2pdma_page(sg_page(sg)) check.
1012 *
1013 * Returns the type of mapping used and maps the page if the type is
1014 * PCI_P2PDMA_MAP_BUS_ADDR.
1015 */
1016enum pci_p2pdma_map_type
1017pci_p2pdma_map_segment(struct pci_p2pdma_map_state *state, struct device *dev,
1018 struct scatterlist *sg)
1019{
1020 if (state->pgmap != sg_page(sg)->pgmap) {
1021 state->pgmap = sg_page(sg)->pgmap;
1022 state->map = pci_p2pdma_map_type(state->pgmap, dev);
1023 state->bus_off = to_p2p_pgmap(state->pgmap)->bus_offset;
1024 }
1025
1026 if (state->map == PCI_P2PDMA_MAP_BUS_ADDR) {
1027 sg->dma_address = sg_phys(sg) + state->bus_off;
1028 sg_dma_len(sg) = sg->length;
1029 sg_dma_mark_bus_address(sg);
1030 }
1031
1032 return state->map;
1033}
1034
1035/**
1036 * pci_p2pdma_enable_store - parse a configfs/sysfs attribute store
1037 * to enable p2pdma
1038 * @page: contents of the value to be stored
1039 * @p2p_dev: returns the PCI device that was selected to be used
1040 * (if one was specified in the stored value)
1041 * @use_p2pdma: returns whether to enable p2pdma or not
1042 *
1043 * Parses an attribute value to decide whether to enable p2pdma.
1044 * The value can select a PCI device (using its full BDF device
1045 * name) or a boolean (in any format kstrtobool() accepts). A false
1046 * value disables p2pdma, a true value expects the caller
1047 * to automatically find a compatible device and specifying a PCI device
1048 * expects the caller to use the specific provider.
1049 *
1050 * pci_p2pdma_enable_show() should be used as the show operation for
1051 * the attribute.
1052 *
1053 * Returns 0 on success
1054 */
1055int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,
1056 bool *use_p2pdma)
1057{
1058 struct device *dev;
1059
1060 dev = bus_find_device_by_name(&pci_bus_type, NULL, page);
1061 if (dev) {
1062 *use_p2pdma = true;
1063 *p2p_dev = to_pci_dev(dev);
1064
1065 if (!pci_has_p2pmem(*p2p_dev)) {
1066 pci_err(*p2p_dev,
1067 "PCI device has no peer-to-peer memory: %s\n",
1068 page);
1069 pci_dev_put(*p2p_dev);
1070 return -ENODEV;
1071 }
1072
1073 return 0;
1074 } else if ((page[0] == '0' || page[0] == '1') && !iscntrl(page[1])) {
1075 /*
1076 * If the user enters a PCI device that doesn't exist
1077 * like "0000:01:00.1", we don't want kstrtobool to think
1078 * it's a '0' when it's clearly not what the user wanted.
1079 * So we require 0's and 1's to be exactly one character.
1080 */
1081 } else if (!kstrtobool(page, use_p2pdma)) {
1082 return 0;
1083 }
1084
1085 pr_err("No such PCI device: %.*s\n", (int)strcspn(page, "\n"), page);
1086 return -ENODEV;
1087}
1088EXPORT_SYMBOL_GPL(pci_p2pdma_enable_store);
1089
1090/**
1091 * pci_p2pdma_enable_show - show a configfs/sysfs attribute indicating
1092 * whether p2pdma is enabled
1093 * @page: contents of the stored value
1094 * @p2p_dev: the selected p2p device (NULL if no device is selected)
1095 * @use_p2pdma: whether p2pdma has been enabled
1096 *
1097 * Attributes that use pci_p2pdma_enable_store() should use this function
1098 * to show the value of the attribute.
1099 *
1100 * Returns 0 on success
1101 */
1102ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,
1103 bool use_p2pdma)
1104{
1105 if (!use_p2pdma)
1106 return sprintf(page, "0\n");
1107
1108 if (!p2p_dev)
1109 return sprintf(page, "1\n");
1110
1111 return sprintf(page, "%s\n", pci_name(p2p_dev));
1112}
1113EXPORT_SYMBOL_GPL(pci_p2pdma_enable_show);