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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 
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 
to_p2p_pgmap(struct dev_pagemap * pgmap)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 
size_show(struct device * dev,struct device_attribute * attr,char * buf)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 	struct pci_p2pdma *p2pdma;
52 	size_t size = 0;
53 
54 	rcu_read_lock();
55 	p2pdma = rcu_dereference(pdev->p2pdma);
56 	if (p2pdma && p2pdma->pool)
57 		size = gen_pool_size(p2pdma->pool);
58 	rcu_read_unlock();
59 
60 	return sysfs_emit(buf, "%zd\n", size);
61 }
62 static DEVICE_ATTR_RO(size);
63 
available_show(struct device * dev,struct device_attribute * attr,char * buf)64 static ssize_t available_show(struct device *dev, struct device_attribute *attr,
65 			      char *buf)
66 {
67 	struct pci_dev *pdev = to_pci_dev(dev);
68 	struct pci_p2pdma *p2pdma;
69 	size_t avail = 0;
70 
71 	rcu_read_lock();
72 	p2pdma = rcu_dereference(pdev->p2pdma);
73 	if (p2pdma && p2pdma->pool)
74 		avail = gen_pool_avail(p2pdma->pool);
75 	rcu_read_unlock();
76 
77 	return sysfs_emit(buf, "%zd\n", avail);
78 }
79 static DEVICE_ATTR_RO(available);
80 
published_show(struct device * dev,struct device_attribute * attr,char * buf)81 static ssize_t published_show(struct device *dev, struct device_attribute *attr,
82 			      char *buf)
83 {
84 	struct pci_dev *pdev = to_pci_dev(dev);
85 	struct pci_p2pdma *p2pdma;
86 	bool published = false;
87 
88 	rcu_read_lock();
89 	p2pdma = rcu_dereference(pdev->p2pdma);
90 	if (p2pdma)
91 		published = p2pdma->p2pmem_published;
92 	rcu_read_unlock();
93 
94 	return sysfs_emit(buf, "%d\n", published);
95 }
96 static DEVICE_ATTR_RO(published);
97 
98 static struct attribute *p2pmem_attrs[] = {
99 	&dev_attr_size.attr,
100 	&dev_attr_available.attr,
101 	&dev_attr_published.attr,
102 	NULL,
103 };
104 
105 static const struct attribute_group p2pmem_group = {
106 	.attrs = p2pmem_attrs,
107 	.name = "p2pmem",
108 };
109 
pci_p2pdma_release(void * data)110 static void pci_p2pdma_release(void *data)
111 {
112 	struct pci_dev *pdev = data;
113 	struct pci_p2pdma *p2pdma;
114 
115 	p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
116 	if (!p2pdma)
117 		return;
118 
119 	/* Flush and disable pci_alloc_p2p_mem() */
120 	pdev->p2pdma = NULL;
121 	synchronize_rcu();
122 
123 	gen_pool_destroy(p2pdma->pool);
124 	sysfs_remove_group(&pdev->dev.kobj, &p2pmem_group);
125 	xa_destroy(&p2pdma->map_types);
126 }
127 
pci_p2pdma_setup(struct pci_dev * pdev)128 static int pci_p2pdma_setup(struct pci_dev *pdev)
129 {
130 	int error = -ENOMEM;
131 	struct pci_p2pdma *p2p;
132 
133 	p2p = devm_kzalloc(&pdev->dev, sizeof(*p2p), GFP_KERNEL);
134 	if (!p2p)
135 		return -ENOMEM;
136 
137 	xa_init(&p2p->map_types);
138 
139 	p2p->pool = gen_pool_create(PAGE_SHIFT, dev_to_node(&pdev->dev));
140 	if (!p2p->pool)
141 		goto out;
142 
143 	error = devm_add_action_or_reset(&pdev->dev, pci_p2pdma_release, pdev);
144 	if (error)
145 		goto out_pool_destroy;
146 
147 	error = sysfs_create_group(&pdev->dev.kobj, &p2pmem_group);
148 	if (error)
149 		goto out_pool_destroy;
150 
151 	rcu_assign_pointer(pdev->p2pdma, p2p);
152 	return 0;
153 
154 out_pool_destroy:
155 	gen_pool_destroy(p2p->pool);
156 out:
157 	devm_kfree(&pdev->dev, p2p);
158 	return error;
159 }
160 
161 /**
162  * pci_p2pdma_add_resource - add memory for use as p2p memory
163  * @pdev: the device to add the memory to
164  * @bar: PCI BAR to add
165  * @size: size of the memory to add, may be zero to use the whole BAR
166  * @offset: offset into the PCI BAR
167  *
168  * The memory will be given ZONE_DEVICE struct pages so that it may
169  * be used with any DMA request.
170  */
pci_p2pdma_add_resource(struct pci_dev * pdev,int bar,size_t size,u64 offset)171 int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
172 			    u64 offset)
173 {
174 	struct pci_p2pdma_pagemap *p2p_pgmap;
175 	struct dev_pagemap *pgmap;
176 	struct pci_p2pdma *p2pdma;
177 	void *addr;
178 	int error;
179 
180 	if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
181 		return -EINVAL;
182 
183 	if (offset >= pci_resource_len(pdev, bar))
184 		return -EINVAL;
185 
186 	if (!size)
187 		size = pci_resource_len(pdev, bar) - offset;
188 
189 	if (size + offset > pci_resource_len(pdev, bar))
190 		return -EINVAL;
191 
192 	if (!pdev->p2pdma) {
193 		error = pci_p2pdma_setup(pdev);
194 		if (error)
195 			return error;
196 	}
197 
198 	p2p_pgmap = devm_kzalloc(&pdev->dev, sizeof(*p2p_pgmap), GFP_KERNEL);
199 	if (!p2p_pgmap)
200 		return -ENOMEM;
201 
202 	pgmap = &p2p_pgmap->pgmap;
203 	pgmap->range.start = pci_resource_start(pdev, bar) + offset;
204 	pgmap->range.end = pgmap->range.start + size - 1;
205 	pgmap->nr_range = 1;
206 	pgmap->type = MEMORY_DEVICE_PCI_P2PDMA;
207 
208 	p2p_pgmap->provider = pdev;
209 	p2p_pgmap->bus_offset = pci_bus_address(pdev, bar) -
210 		pci_resource_start(pdev, bar);
211 
212 	addr = devm_memremap_pages(&pdev->dev, pgmap);
213 	if (IS_ERR(addr)) {
214 		error = PTR_ERR(addr);
215 		goto pgmap_free;
216 	}
217 
218 	p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
219 	error = gen_pool_add_owner(p2pdma->pool, (unsigned long)addr,
220 			pci_bus_address(pdev, bar) + offset,
221 			range_len(&pgmap->range), dev_to_node(&pdev->dev),
222 			&pgmap->ref);
223 	if (error)
224 		goto pages_free;
225 
226 	pci_info(pdev, "added peer-to-peer DMA memory %#llx-%#llx\n",
227 		 pgmap->range.start, pgmap->range.end);
228 
229 	return 0;
230 
231 pages_free:
232 	devm_memunmap_pages(&pdev->dev, pgmap);
233 pgmap_free:
234 	devm_kfree(&pdev->dev, pgmap);
235 	return error;
236 }
237 EXPORT_SYMBOL_GPL(pci_p2pdma_add_resource);
238 
239 /*
240  * Note this function returns the parent PCI device with a
241  * reference taken. It is the caller's responsibility to drop
242  * the reference.
243  */
find_parent_pci_dev(struct device * dev)244 static struct pci_dev *find_parent_pci_dev(struct device *dev)
245 {
246 	struct device *parent;
247 
248 	dev = get_device(dev);
249 
250 	while (dev) {
251 		if (dev_is_pci(dev))
252 			return to_pci_dev(dev);
253 
254 		parent = get_device(dev->parent);
255 		put_device(dev);
256 		dev = parent;
257 	}
258 
259 	return NULL;
260 }
261 
262 /*
263  * Check if a PCI bridge has its ACS redirection bits set to redirect P2P
264  * TLPs upstream via ACS. Returns 1 if the packets will be redirected
265  * upstream, 0 otherwise.
266  */
pci_bridge_has_acs_redir(struct pci_dev * pdev)267 static int pci_bridge_has_acs_redir(struct pci_dev *pdev)
268 {
269 	int pos;
270 	u16 ctrl;
271 
272 	pos = pdev->acs_cap;
273 	if (!pos)
274 		return 0;
275 
276 	pci_read_config_word(pdev, pos + PCI_ACS_CTRL, &ctrl);
277 
278 	if (ctrl & (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC))
279 		return 1;
280 
281 	return 0;
282 }
283 
seq_buf_print_bus_devfn(struct seq_buf * buf,struct pci_dev * pdev)284 static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev)
285 {
286 	if (!buf)
287 		return;
288 
289 	seq_buf_printf(buf, "%s;", pci_name(pdev));
290 }
291 
cpu_supports_p2pdma(void)292 static bool cpu_supports_p2pdma(void)
293 {
294 #ifdef CONFIG_X86
295 	struct cpuinfo_x86 *c = &cpu_data(0);
296 
297 	/* Any AMD CPU whose family ID is Zen or newer supports p2pdma */
298 	if (c->x86_vendor == X86_VENDOR_AMD && c->x86 >= 0x17)
299 		return true;
300 #endif
301 
302 	return false;
303 }
304 
305 static const struct pci_p2pdma_whitelist_entry {
306 	unsigned short vendor;
307 	unsigned short device;
308 	enum {
309 		REQ_SAME_HOST_BRIDGE	= 1 << 0,
310 	} flags;
311 } pci_p2pdma_whitelist[] = {
312 	/* Intel Xeon E5/Core i7 */
313 	{PCI_VENDOR_ID_INTEL,	0x3c00, REQ_SAME_HOST_BRIDGE},
314 	{PCI_VENDOR_ID_INTEL,	0x3c01, REQ_SAME_HOST_BRIDGE},
315 	/* Intel Xeon E7 v3/Xeon E5 v3/Core i7 */
316 	{PCI_VENDOR_ID_INTEL,	0x2f00, REQ_SAME_HOST_BRIDGE},
317 	{PCI_VENDOR_ID_INTEL,	0x2f01, REQ_SAME_HOST_BRIDGE},
318 	/* Intel SkyLake-E */
319 	{PCI_VENDOR_ID_INTEL,	0x2030, 0},
320 	{PCI_VENDOR_ID_INTEL,	0x2031, 0},
321 	{PCI_VENDOR_ID_INTEL,	0x2032, 0},
322 	{PCI_VENDOR_ID_INTEL,	0x2033, 0},
323 	{PCI_VENDOR_ID_INTEL,	0x2020, 0},
324 	{}
325 };
326 
327 /*
328  * This lookup function tries to find the PCI device corresponding to a given
329  * host bridge.
330  *
331  * It assumes the host bridge device is the first PCI device in the
332  * bus->devices list and that the devfn is 00.0. These assumptions should hold
333  * for all the devices in the whitelist above.
334  *
335  * This function is equivalent to pci_get_slot(host->bus, 0), however it does
336  * not take the pci_bus_sem lock seeing __host_bridge_whitelist() must not
337  * sleep.
338  *
339  * For this to be safe, the caller should hold a reference to a device on the
340  * bridge, which should ensure the host_bridge device will not be freed
341  * or removed from the head of the devices list.
342  */
pci_host_bridge_dev(struct pci_host_bridge * host)343 static struct pci_dev *pci_host_bridge_dev(struct pci_host_bridge *host)
344 {
345 	struct pci_dev *root;
346 
347 	root = list_first_entry_or_null(&host->bus->devices,
348 					struct pci_dev, bus_list);
349 
350 	if (!root)
351 		return NULL;
352 	if (root->devfn != PCI_DEVFN(0, 0))
353 		return NULL;
354 
355 	return root;
356 }
357 
__host_bridge_whitelist(struct pci_host_bridge * host,bool same_host_bridge,bool warn)358 static bool __host_bridge_whitelist(struct pci_host_bridge *host,
359 				    bool same_host_bridge, bool warn)
360 {
361 	struct pci_dev *root = pci_host_bridge_dev(host);
362 	const struct pci_p2pdma_whitelist_entry *entry;
363 	unsigned short vendor, device;
364 
365 	if (!root)
366 		return false;
367 
368 	vendor = root->vendor;
369 	device = root->device;
370 
371 	for (entry = pci_p2pdma_whitelist; entry->vendor; entry++) {
372 		if (vendor != entry->vendor || device != entry->device)
373 			continue;
374 		if (entry->flags & REQ_SAME_HOST_BRIDGE && !same_host_bridge)
375 			return false;
376 
377 		return true;
378 	}
379 
380 	if (warn)
381 		pci_warn(root, "Host bridge not in P2PDMA whitelist: %04x:%04x\n",
382 			 vendor, device);
383 
384 	return false;
385 }
386 
387 /*
388  * If we can't find a common upstream bridge take a look at the root
389  * complex and compare it to a whitelist of known good hardware.
390  */
host_bridge_whitelist(struct pci_dev * a,struct pci_dev * b,bool warn)391 static bool host_bridge_whitelist(struct pci_dev *a, struct pci_dev *b,
392 				  bool warn)
393 {
394 	struct pci_host_bridge *host_a = pci_find_host_bridge(a->bus);
395 	struct pci_host_bridge *host_b = pci_find_host_bridge(b->bus);
396 
397 	if (host_a == host_b)
398 		return __host_bridge_whitelist(host_a, true, warn);
399 
400 	if (__host_bridge_whitelist(host_a, false, warn) &&
401 	    __host_bridge_whitelist(host_b, false, warn))
402 		return true;
403 
404 	return false;
405 }
406 
map_types_idx(struct pci_dev * client)407 static unsigned long map_types_idx(struct pci_dev *client)
408 {
409 	return (pci_domain_nr(client->bus) << 16) |
410 		(client->bus->number << 8) | client->devfn;
411 }
412 
413 /*
414  * Calculate the P2PDMA mapping type and distance between two PCI devices.
415  *
416  * If the two devices are the same PCI function, return
417  * PCI_P2PDMA_MAP_BUS_ADDR and a distance of 0.
418  *
419  * If they are two functions of the same device, return
420  * PCI_P2PDMA_MAP_BUS_ADDR and a distance of 2 (one hop up to the bridge,
421  * then one hop back down to another function of the same device).
422  *
423  * In the case where two devices are connected to the same PCIe switch,
424  * return a distance of 4. This corresponds to the following PCI tree:
425  *
426  *     -+  Root Port
427  *      \+ Switch Upstream Port
428  *       +-+ Switch Downstream Port 0
429  *       + \- Device A
430  *       \-+ Switch Downstream Port 1
431  *         \- Device B
432  *
433  * The distance is 4 because we traverse from Device A to Downstream Port 0
434  * to the common Switch Upstream Port, back down to Downstream Port 1 and
435  * then to Device B. The mapping type returned depends on the ACS
436  * redirection setting of the ports along the path.
437  *
438  * If ACS redirect is set on any port in the path, traffic between the
439  * devices will go through the host bridge, so return
440  * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE; otherwise return
441  * PCI_P2PDMA_MAP_BUS_ADDR.
442  *
443  * Any two devices that have a data path that goes through the host bridge
444  * will consult a whitelist. If the host bridge is in the whitelist, return
445  * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE with the distance set to the number of
446  * ports per above. If the device is not in the whitelist, return
447  * PCI_P2PDMA_MAP_NOT_SUPPORTED.
448  */
449 static enum pci_p2pdma_map_type
calc_map_type_and_dist(struct pci_dev * provider,struct pci_dev * client,int * dist,bool verbose)450 calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
451 		int *dist, bool verbose)
452 {
453 	enum pci_p2pdma_map_type map_type = PCI_P2PDMA_MAP_THRU_HOST_BRIDGE;
454 	struct pci_dev *a = provider, *b = client, *bb;
455 	bool acs_redirects = false;
456 	struct pci_p2pdma *p2pdma;
457 	struct seq_buf acs_list;
458 	int acs_cnt = 0;
459 	int dist_a = 0;
460 	int dist_b = 0;
461 	char buf[128];
462 
463 	seq_buf_init(&acs_list, buf, sizeof(buf));
464 
465 	/*
466 	 * Note, we don't need to take references to devices returned by
467 	 * pci_upstream_bridge() seeing we hold a reference to a child
468 	 * device which will already hold a reference to the upstream bridge.
469 	 */
470 	while (a) {
471 		dist_b = 0;
472 
473 		if (pci_bridge_has_acs_redir(a)) {
474 			seq_buf_print_bus_devfn(&acs_list, a);
475 			acs_cnt++;
476 		}
477 
478 		bb = b;
479 
480 		while (bb) {
481 			if (a == bb)
482 				goto check_b_path_acs;
483 
484 			bb = pci_upstream_bridge(bb);
485 			dist_b++;
486 		}
487 
488 		a = pci_upstream_bridge(a);
489 		dist_a++;
490 	}
491 
492 	*dist = dist_a + dist_b;
493 	goto map_through_host_bridge;
494 
495 check_b_path_acs:
496 	bb = b;
497 
498 	while (bb) {
499 		if (a == bb)
500 			break;
501 
502 		if (pci_bridge_has_acs_redir(bb)) {
503 			seq_buf_print_bus_devfn(&acs_list, bb);
504 			acs_cnt++;
505 		}
506 
507 		bb = pci_upstream_bridge(bb);
508 	}
509 
510 	*dist = dist_a + dist_b;
511 
512 	if (!acs_cnt) {
513 		map_type = PCI_P2PDMA_MAP_BUS_ADDR;
514 		goto done;
515 	}
516 
517 	if (verbose) {
518 		acs_list.buffer[acs_list.len-1] = 0; /* drop final semicolon */
519 		pci_warn(client, "ACS redirect is set between the client and provider (%s)\n",
520 			 pci_name(provider));
521 		pci_warn(client, "to disable ACS redirect for this path, add the kernel parameter: pci=disable_acs_redir=%s\n",
522 			 acs_list.buffer);
523 	}
524 	acs_redirects = true;
525 
526 map_through_host_bridge:
527 	if (!cpu_supports_p2pdma() &&
528 	    !host_bridge_whitelist(provider, client, acs_redirects)) {
529 		if (verbose)
530 			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",
531 				 pci_name(provider));
532 		map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
533 	}
534 done:
535 	rcu_read_lock();
536 	p2pdma = rcu_dereference(provider->p2pdma);
537 	if (p2pdma)
538 		xa_store(&p2pdma->map_types, map_types_idx(client),
539 			 xa_mk_value(map_type), GFP_KERNEL);
540 	rcu_read_unlock();
541 	return map_type;
542 }
543 
544 /**
545  * pci_p2pdma_distance_many - Determine the cumulative distance between
546  *	a p2pdma provider and the clients in use.
547  * @provider: p2pdma provider to check against the client list
548  * @clients: array of devices to check (NULL-terminated)
549  * @num_clients: number of clients in the array
550  * @verbose: if true, print warnings for devices when we return -1
551  *
552  * Returns -1 if any of the clients are not compatible, otherwise returns a
553  * positive number where a lower number is the preferable choice. (If there's
554  * one client that's the same as the provider it will return 0, which is best
555  * choice).
556  *
557  * "compatible" means the provider and the clients are either all behind
558  * the same PCI root port or the host bridges connected to each of the devices
559  * are listed in the 'pci_p2pdma_whitelist'.
560  */
pci_p2pdma_distance_many(struct pci_dev * provider,struct device ** clients,int num_clients,bool verbose)561 int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients,
562 			     int num_clients, bool verbose)
563 {
564 	enum pci_p2pdma_map_type map;
565 	bool not_supported = false;
566 	struct pci_dev *pci_client;
567 	int total_dist = 0;
568 	int i, distance;
569 
570 	if (num_clients == 0)
571 		return -1;
572 
573 	for (i = 0; i < num_clients; i++) {
574 		pci_client = find_parent_pci_dev(clients[i]);
575 		if (!pci_client) {
576 			if (verbose)
577 				dev_warn(clients[i],
578 					 "cannot be used for peer-to-peer DMA as it is not a PCI device\n");
579 			return -1;
580 		}
581 
582 		map = calc_map_type_and_dist(provider, pci_client, &distance,
583 					     verbose);
584 
585 		pci_dev_put(pci_client);
586 
587 		if (map == PCI_P2PDMA_MAP_NOT_SUPPORTED)
588 			not_supported = true;
589 
590 		if (not_supported && !verbose)
591 			break;
592 
593 		total_dist += distance;
594 	}
595 
596 	if (not_supported)
597 		return -1;
598 
599 	return total_dist;
600 }
601 EXPORT_SYMBOL_GPL(pci_p2pdma_distance_many);
602 
603 /**
604  * pci_has_p2pmem - check if a given PCI device has published any p2pmem
605  * @pdev: PCI device to check
606  */
pci_has_p2pmem(struct pci_dev * pdev)607 bool pci_has_p2pmem(struct pci_dev *pdev)
608 {
609 	struct pci_p2pdma *p2pdma;
610 	bool res;
611 
612 	rcu_read_lock();
613 	p2pdma = rcu_dereference(pdev->p2pdma);
614 	res = p2pdma && p2pdma->p2pmem_published;
615 	rcu_read_unlock();
616 
617 	return res;
618 }
619 EXPORT_SYMBOL_GPL(pci_has_p2pmem);
620 
621 /**
622  * pci_p2pmem_find_many - find a peer-to-peer DMA memory device compatible with
623  *	the specified list of clients and shortest distance (as determined
624  *	by pci_p2pmem_dma())
625  * @clients: array of devices to check (NULL-terminated)
626  * @num_clients: number of client devices in the list
627  *
628  * If multiple devices are behind the same switch, the one "closest" to the
629  * client devices in use will be chosen first. (So if one of the providers is
630  * the same as one of the clients, that provider will be used ahead of any
631  * other providers that are unrelated). If multiple providers are an equal
632  * distance away, one will be chosen at random.
633  *
634  * Returns a pointer to the PCI device with a reference taken (use pci_dev_put
635  * to return the reference) or NULL if no compatible device is found. The
636  * found provider will also be assigned to the client list.
637  */
pci_p2pmem_find_many(struct device ** clients,int num_clients)638 struct pci_dev *pci_p2pmem_find_many(struct device **clients, int num_clients)
639 {
640 	struct pci_dev *pdev = NULL;
641 	int distance;
642 	int closest_distance = INT_MAX;
643 	struct pci_dev **closest_pdevs;
644 	int dev_cnt = 0;
645 	const int max_devs = PAGE_SIZE / sizeof(*closest_pdevs);
646 	int i;
647 
648 	closest_pdevs = kmalloc(PAGE_SIZE, GFP_KERNEL);
649 	if (!closest_pdevs)
650 		return NULL;
651 
652 	while ((pdev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, pdev))) {
653 		if (!pci_has_p2pmem(pdev))
654 			continue;
655 
656 		distance = pci_p2pdma_distance_many(pdev, clients,
657 						    num_clients, false);
658 		if (distance < 0 || distance > closest_distance)
659 			continue;
660 
661 		if (distance == closest_distance && dev_cnt >= max_devs)
662 			continue;
663 
664 		if (distance < closest_distance) {
665 			for (i = 0; i < dev_cnt; i++)
666 				pci_dev_put(closest_pdevs[i]);
667 
668 			dev_cnt = 0;
669 			closest_distance = distance;
670 		}
671 
672 		closest_pdevs[dev_cnt++] = pci_dev_get(pdev);
673 	}
674 
675 	if (dev_cnt)
676 		pdev = pci_dev_get(closest_pdevs[prandom_u32_max(dev_cnt)]);
677 
678 	for (i = 0; i < dev_cnt; i++)
679 		pci_dev_put(closest_pdevs[i]);
680 
681 	kfree(closest_pdevs);
682 	return pdev;
683 }
684 EXPORT_SYMBOL_GPL(pci_p2pmem_find_many);
685 
686 /**
687  * pci_alloc_p2pmem - allocate peer-to-peer DMA memory
688  * @pdev: the device to allocate memory from
689  * @size: number of bytes to allocate
690  *
691  * Returns the allocated memory or NULL on error.
692  */
pci_alloc_p2pmem(struct pci_dev * pdev,size_t size)693 void *pci_alloc_p2pmem(struct pci_dev *pdev, size_t size)
694 {
695 	void *ret = NULL;
696 	struct percpu_ref *ref;
697 	struct pci_p2pdma *p2pdma;
698 
699 	/*
700 	 * Pairs with synchronize_rcu() in pci_p2pdma_release() to
701 	 * ensure pdev->p2pdma is non-NULL for the duration of the
702 	 * read-lock.
703 	 */
704 	rcu_read_lock();
705 	p2pdma = rcu_dereference(pdev->p2pdma);
706 	if (unlikely(!p2pdma))
707 		goto out;
708 
709 	ret = (void *)gen_pool_alloc_owner(p2pdma->pool, size, (void **) &ref);
710 	if (!ret)
711 		goto out;
712 
713 	if (unlikely(!percpu_ref_tryget_live(ref))) {
714 		gen_pool_free(p2pdma->pool, (unsigned long) ret, size);
715 		ret = NULL;
716 		goto out;
717 	}
718 out:
719 	rcu_read_unlock();
720 	return ret;
721 }
722 EXPORT_SYMBOL_GPL(pci_alloc_p2pmem);
723 
724 /**
725  * pci_free_p2pmem - free peer-to-peer DMA memory
726  * @pdev: the device the memory was allocated from
727  * @addr: address of the memory that was allocated
728  * @size: number of bytes that were allocated
729  */
pci_free_p2pmem(struct pci_dev * pdev,void * addr,size_t size)730 void pci_free_p2pmem(struct pci_dev *pdev, void *addr, size_t size)
731 {
732 	struct percpu_ref *ref;
733 	struct pci_p2pdma *p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
734 
735 	gen_pool_free_owner(p2pdma->pool, (uintptr_t)addr, size,
736 			(void **) &ref);
737 	percpu_ref_put(ref);
738 }
739 EXPORT_SYMBOL_GPL(pci_free_p2pmem);
740 
741 /**
742  * pci_p2pmem_virt_to_bus - return the PCI bus address for a given virtual
743  *	address obtained with pci_alloc_p2pmem()
744  * @pdev: the device the memory was allocated from
745  * @addr: address of the memory that was allocated
746  */
pci_p2pmem_virt_to_bus(struct pci_dev * pdev,void * addr)747 pci_bus_addr_t pci_p2pmem_virt_to_bus(struct pci_dev *pdev, void *addr)
748 {
749 	struct pci_p2pdma *p2pdma;
750 
751 	if (!addr)
752 		return 0;
753 
754 	p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
755 	if (!p2pdma)
756 		return 0;
757 
758 	/*
759 	 * Note: when we added the memory to the pool we used the PCI
760 	 * bus address as the physical address. So gen_pool_virt_to_phys()
761 	 * actually returns the bus address despite the misleading name.
762 	 */
763 	return gen_pool_virt_to_phys(p2pdma->pool, (unsigned long)addr);
764 }
765 EXPORT_SYMBOL_GPL(pci_p2pmem_virt_to_bus);
766 
767 /**
768  * pci_p2pmem_alloc_sgl - allocate peer-to-peer DMA memory in a scatterlist
769  * @pdev: the device to allocate memory from
770  * @nents: the number of SG entries in the list
771  * @length: number of bytes to allocate
772  *
773  * Return: %NULL on error or &struct scatterlist pointer and @nents on success
774  */
pci_p2pmem_alloc_sgl(struct pci_dev * pdev,unsigned int * nents,u32 length)775 struct scatterlist *pci_p2pmem_alloc_sgl(struct pci_dev *pdev,
776 					 unsigned int *nents, u32 length)
777 {
778 	struct scatterlist *sg;
779 	void *addr;
780 
781 	sg = kmalloc(sizeof(*sg), GFP_KERNEL);
782 	if (!sg)
783 		return NULL;
784 
785 	sg_init_table(sg, 1);
786 
787 	addr = pci_alloc_p2pmem(pdev, length);
788 	if (!addr)
789 		goto out_free_sg;
790 
791 	sg_set_buf(sg, addr, length);
792 	*nents = 1;
793 	return sg;
794 
795 out_free_sg:
796 	kfree(sg);
797 	return NULL;
798 }
799 EXPORT_SYMBOL_GPL(pci_p2pmem_alloc_sgl);
800 
801 /**
802  * pci_p2pmem_free_sgl - free a scatterlist allocated by pci_p2pmem_alloc_sgl()
803  * @pdev: the device to allocate memory from
804  * @sgl: the allocated scatterlist
805  */
pci_p2pmem_free_sgl(struct pci_dev * pdev,struct scatterlist * sgl)806 void pci_p2pmem_free_sgl(struct pci_dev *pdev, struct scatterlist *sgl)
807 {
808 	struct scatterlist *sg;
809 	int count;
810 
811 	for_each_sg(sgl, sg, INT_MAX, count) {
812 		if (!sg)
813 			break;
814 
815 		pci_free_p2pmem(pdev, sg_virt(sg), sg->length);
816 	}
817 	kfree(sgl);
818 }
819 EXPORT_SYMBOL_GPL(pci_p2pmem_free_sgl);
820 
821 /**
822  * pci_p2pmem_publish - publish the peer-to-peer DMA memory for use by
823  *	other devices with pci_p2pmem_find()
824  * @pdev: the device with peer-to-peer DMA memory to publish
825  * @publish: set to true to publish the memory, false to unpublish it
826  *
827  * Published memory can be used by other PCI device drivers for
828  * peer-2-peer DMA operations. Non-published memory is reserved for
829  * exclusive use of the device driver that registers the peer-to-peer
830  * memory.
831  */
pci_p2pmem_publish(struct pci_dev * pdev,bool publish)832 void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
833 {
834 	struct pci_p2pdma *p2pdma;
835 
836 	rcu_read_lock();
837 	p2pdma = rcu_dereference(pdev->p2pdma);
838 	if (p2pdma)
839 		p2pdma->p2pmem_published = publish;
840 	rcu_read_unlock();
841 }
842 EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
843 
pci_p2pdma_map_type(struct dev_pagemap * pgmap,struct device * dev)844 static enum pci_p2pdma_map_type pci_p2pdma_map_type(struct dev_pagemap *pgmap,
845 						    struct device *dev)
846 {
847 	enum pci_p2pdma_map_type type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
848 	struct pci_dev *provider = to_p2p_pgmap(pgmap)->provider;
849 	struct pci_dev *client;
850 	struct pci_p2pdma *p2pdma;
851 
852 	if (!provider->p2pdma)
853 		return PCI_P2PDMA_MAP_NOT_SUPPORTED;
854 
855 	if (!dev_is_pci(dev))
856 		return PCI_P2PDMA_MAP_NOT_SUPPORTED;
857 
858 	client = to_pci_dev(dev);
859 
860 	rcu_read_lock();
861 	p2pdma = rcu_dereference(provider->p2pdma);
862 
863 	if (p2pdma)
864 		type = xa_to_value(xa_load(&p2pdma->map_types,
865 					   map_types_idx(client)));
866 	rcu_read_unlock();
867 	return type;
868 }
869 
__pci_p2pdma_map_sg(struct pci_p2pdma_pagemap * p2p_pgmap,struct device * dev,struct scatterlist * sg,int nents)870 static int __pci_p2pdma_map_sg(struct pci_p2pdma_pagemap *p2p_pgmap,
871 		struct device *dev, struct scatterlist *sg, int nents)
872 {
873 	struct scatterlist *s;
874 	int i;
875 
876 	for_each_sg(sg, s, nents, i) {
877 		s->dma_address = sg_phys(s) - p2p_pgmap->bus_offset;
878 		sg_dma_len(s) = s->length;
879 	}
880 
881 	return nents;
882 }
883 
884 /**
885  * pci_p2pdma_map_sg_attrs - map a PCI peer-to-peer scatterlist for DMA
886  * @dev: device doing the DMA request
887  * @sg: scatter list to map
888  * @nents: elements in the scatterlist
889  * @dir: DMA direction
890  * @attrs: DMA attributes passed to dma_map_sg() (if called)
891  *
892  * Scatterlists mapped with this function should be unmapped using
893  * pci_p2pdma_unmap_sg_attrs().
894  *
895  * Returns the number of SG entries mapped or 0 on error.
896  */
pci_p2pdma_map_sg_attrs(struct device * dev,struct scatterlist * sg,int nents,enum dma_data_direction dir,unsigned long attrs)897 int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
898 		int nents, enum dma_data_direction dir, unsigned long attrs)
899 {
900 	struct pci_p2pdma_pagemap *p2p_pgmap =
901 		to_p2p_pgmap(sg_page(sg)->pgmap);
902 
903 	switch (pci_p2pdma_map_type(sg_page(sg)->pgmap, dev)) {
904 	case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE:
905 		return dma_map_sg_attrs(dev, sg, nents, dir, attrs);
906 	case PCI_P2PDMA_MAP_BUS_ADDR:
907 		return __pci_p2pdma_map_sg(p2p_pgmap, dev, sg, nents);
908 	default:
909 		WARN_ON_ONCE(1);
910 		return 0;
911 	}
912 }
913 EXPORT_SYMBOL_GPL(pci_p2pdma_map_sg_attrs);
914 
915 /**
916  * pci_p2pdma_unmap_sg_attrs - unmap a PCI peer-to-peer scatterlist that was
917  *	mapped with pci_p2pdma_map_sg()
918  * @dev: device doing the DMA request
919  * @sg: scatter list to map
920  * @nents: number of elements returned by pci_p2pdma_map_sg()
921  * @dir: DMA direction
922  * @attrs: DMA attributes passed to dma_unmap_sg() (if called)
923  */
pci_p2pdma_unmap_sg_attrs(struct device * dev,struct scatterlist * sg,int nents,enum dma_data_direction dir,unsigned long attrs)924 void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
925 		int nents, enum dma_data_direction dir, unsigned long attrs)
926 {
927 	enum pci_p2pdma_map_type map_type;
928 
929 	map_type = pci_p2pdma_map_type(sg_page(sg)->pgmap, dev);
930 
931 	if (map_type == PCI_P2PDMA_MAP_THRU_HOST_BRIDGE)
932 		dma_unmap_sg_attrs(dev, sg, nents, dir, attrs);
933 }
934 EXPORT_SYMBOL_GPL(pci_p2pdma_unmap_sg_attrs);
935 
936 /**
937  * pci_p2pdma_enable_store - parse a configfs/sysfs attribute store
938  *		to enable p2pdma
939  * @page: contents of the value to be stored
940  * @p2p_dev: returns the PCI device that was selected to be used
941  *		(if one was specified in the stored value)
942  * @use_p2pdma: returns whether to enable p2pdma or not
943  *
944  * Parses an attribute value to decide whether to enable p2pdma.
945  * The value can select a PCI device (using its full BDF device
946  * name) or a boolean (in any format strtobool() accepts). A false
947  * value disables p2pdma, a true value expects the caller
948  * to automatically find a compatible device and specifying a PCI device
949  * expects the caller to use the specific provider.
950  *
951  * pci_p2pdma_enable_show() should be used as the show operation for
952  * the attribute.
953  *
954  * Returns 0 on success
955  */
pci_p2pdma_enable_store(const char * page,struct pci_dev ** p2p_dev,bool * use_p2pdma)956 int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,
957 			    bool *use_p2pdma)
958 {
959 	struct device *dev;
960 
961 	dev = bus_find_device_by_name(&pci_bus_type, NULL, page);
962 	if (dev) {
963 		*use_p2pdma = true;
964 		*p2p_dev = to_pci_dev(dev);
965 
966 		if (!pci_has_p2pmem(*p2p_dev)) {
967 			pci_err(*p2p_dev,
968 				"PCI device has no peer-to-peer memory: %s\n",
969 				page);
970 			pci_dev_put(*p2p_dev);
971 			return -ENODEV;
972 		}
973 
974 		return 0;
975 	} else if ((page[0] == '0' || page[0] == '1') && !iscntrl(page[1])) {
976 		/*
977 		 * If the user enters a PCI device that  doesn't exist
978 		 * like "0000:01:00.1", we don't want strtobool to think
979 		 * it's a '0' when it's clearly not what the user wanted.
980 		 * So we require 0's and 1's to be exactly one character.
981 		 */
982 	} else if (!strtobool(page, use_p2pdma)) {
983 		return 0;
984 	}
985 
986 	pr_err("No such PCI device: %.*s\n", (int)strcspn(page, "\n"), page);
987 	return -ENODEV;
988 }
989 EXPORT_SYMBOL_GPL(pci_p2pdma_enable_store);
990 
991 /**
992  * pci_p2pdma_enable_show - show a configfs/sysfs attribute indicating
993  *		whether p2pdma is enabled
994  * @page: contents of the stored value
995  * @p2p_dev: the selected p2p device (NULL if no device is selected)
996  * @use_p2pdma: whether p2pdma has been enabled
997  *
998  * Attributes that use pci_p2pdma_enable_store() should use this function
999  * to show the value of the attribute.
1000  *
1001  * Returns 0 on success
1002  */
pci_p2pdma_enable_show(char * page,struct pci_dev * p2p_dev,bool use_p2pdma)1003 ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,
1004 			       bool use_p2pdma)
1005 {
1006 	if (!use_p2pdma)
1007 		return sprintf(page, "0\n");
1008 
1009 	if (!p2p_dev)
1010 		return sprintf(page, "1\n");
1011 
1012 	return sprintf(page, "%s\n", pci_name(p2p_dev));
1013 }
1014 EXPORT_SYMBOL_GPL(pci_p2pdma_enable_show);
1015