xref: /openbmc/linux/mm/memremap.c (revision 223ec6ab)
1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright(c) 2015 Intel Corporation. All rights reserved. */
3 #include <linux/device.h>
4 #include <linux/io.h>
5 #include <linux/kasan.h>
6 #include <linux/memory_hotplug.h>
7 #include <linux/memremap.h>
8 #include <linux/pfn_t.h>
9 #include <linux/swap.h>
10 #include <linux/mmzone.h>
11 #include <linux/swapops.h>
12 #include <linux/types.h>
13 #include <linux/wait_bit.h>
14 #include <linux/xarray.h>
15 #include "internal.h"
16 
17 static DEFINE_XARRAY(pgmap_array);
18 
19 /*
20  * The memremap() and memremap_pages() interfaces are alternately used
21  * to map persistent memory namespaces. These interfaces place different
22  * constraints on the alignment and size of the mapping (namespace).
23  * memremap() can map individual PAGE_SIZE pages. memremap_pages() can
24  * only map subsections (2MB), and at least one architecture (PowerPC)
25  * the minimum mapping granularity of memremap_pages() is 16MB.
26  *
27  * The role of memremap_compat_align() is to communicate the minimum
28  * arch supported alignment of a namespace such that it can freely
29  * switch modes without violating the arch constraint. Namely, do not
30  * allow a namespace to be PAGE_SIZE aligned since that namespace may be
31  * reconfigured into a mode that requires SUBSECTION_SIZE alignment.
32  */
33 #ifndef CONFIG_ARCH_HAS_MEMREMAP_COMPAT_ALIGN
memremap_compat_align(void)34 unsigned long memremap_compat_align(void)
35 {
36 	return SUBSECTION_SIZE;
37 }
38 EXPORT_SYMBOL_GPL(memremap_compat_align);
39 #endif
40 
41 #ifdef CONFIG_FS_DAX
42 DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
43 EXPORT_SYMBOL(devmap_managed_key);
44 
devmap_managed_enable_put(struct dev_pagemap * pgmap)45 static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
46 {
47 	if (pgmap->type == MEMORY_DEVICE_FS_DAX)
48 		static_branch_dec(&devmap_managed_key);
49 }
50 
devmap_managed_enable_get(struct dev_pagemap * pgmap)51 static void devmap_managed_enable_get(struct dev_pagemap *pgmap)
52 {
53 	if (pgmap->type == MEMORY_DEVICE_FS_DAX)
54 		static_branch_inc(&devmap_managed_key);
55 }
56 #else
devmap_managed_enable_get(struct dev_pagemap * pgmap)57 static void devmap_managed_enable_get(struct dev_pagemap *pgmap)
58 {
59 }
devmap_managed_enable_put(struct dev_pagemap * pgmap)60 static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
61 {
62 }
63 #endif /* CONFIG_FS_DAX */
64 
pgmap_array_delete(struct range * range)65 static void pgmap_array_delete(struct range *range)
66 {
67 	xa_store_range(&pgmap_array, PHYS_PFN(range->start), PHYS_PFN(range->end),
68 			NULL, GFP_KERNEL);
69 	synchronize_rcu();
70 }
71 
pfn_first(struct dev_pagemap * pgmap,int range_id)72 static unsigned long pfn_first(struct dev_pagemap *pgmap, int range_id)
73 {
74 	struct range *range = &pgmap->ranges[range_id];
75 	unsigned long pfn = PHYS_PFN(range->start);
76 
77 	if (range_id)
78 		return pfn;
79 	return pfn + vmem_altmap_offset(pgmap_altmap(pgmap));
80 }
81 
pgmap_pfn_valid(struct dev_pagemap * pgmap,unsigned long pfn)82 bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn)
83 {
84 	int i;
85 
86 	for (i = 0; i < pgmap->nr_range; i++) {
87 		struct range *range = &pgmap->ranges[i];
88 
89 		if (pfn >= PHYS_PFN(range->start) &&
90 		    pfn <= PHYS_PFN(range->end))
91 			return pfn >= pfn_first(pgmap, i);
92 	}
93 
94 	return false;
95 }
96 
pfn_end(struct dev_pagemap * pgmap,int range_id)97 static unsigned long pfn_end(struct dev_pagemap *pgmap, int range_id)
98 {
99 	const struct range *range = &pgmap->ranges[range_id];
100 
101 	return (range->start + range_len(range)) >> PAGE_SHIFT;
102 }
103 
pfn_len(struct dev_pagemap * pgmap,unsigned long range_id)104 static unsigned long pfn_len(struct dev_pagemap *pgmap, unsigned long range_id)
105 {
106 	return (pfn_end(pgmap, range_id) -
107 		pfn_first(pgmap, range_id)) >> pgmap->vmemmap_shift;
108 }
109 
pageunmap_range(struct dev_pagemap * pgmap,int range_id)110 static void pageunmap_range(struct dev_pagemap *pgmap, int range_id)
111 {
112 	struct range *range = &pgmap->ranges[range_id];
113 	struct page *first_page;
114 
115 	/* make sure to access a memmap that was actually initialized */
116 	first_page = pfn_to_page(pfn_first(pgmap, range_id));
117 
118 	/* pages are dead and unused, undo the arch mapping */
119 	mem_hotplug_begin();
120 	remove_pfn_range_from_zone(page_zone(first_page), PHYS_PFN(range->start),
121 				   PHYS_PFN(range_len(range)));
122 	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
123 		__remove_pages(PHYS_PFN(range->start),
124 			       PHYS_PFN(range_len(range)), NULL);
125 	} else {
126 		arch_remove_memory(range->start, range_len(range),
127 				pgmap_altmap(pgmap));
128 		kasan_remove_zero_shadow(__va(range->start), range_len(range));
129 	}
130 	mem_hotplug_done();
131 
132 	untrack_pfn(NULL, PHYS_PFN(range->start), range_len(range), true);
133 	pgmap_array_delete(range);
134 }
135 
memunmap_pages(struct dev_pagemap * pgmap)136 void memunmap_pages(struct dev_pagemap *pgmap)
137 {
138 	int i;
139 
140 	percpu_ref_kill(&pgmap->ref);
141 	if (pgmap->type != MEMORY_DEVICE_PRIVATE &&
142 	    pgmap->type != MEMORY_DEVICE_COHERENT)
143 		for (i = 0; i < pgmap->nr_range; i++)
144 			percpu_ref_put_many(&pgmap->ref, pfn_len(pgmap, i));
145 
146 	wait_for_completion(&pgmap->done);
147 
148 	for (i = 0; i < pgmap->nr_range; i++)
149 		pageunmap_range(pgmap, i);
150 	percpu_ref_exit(&pgmap->ref);
151 
152 	WARN_ONCE(pgmap->altmap.alloc, "failed to free all reserved pages\n");
153 	devmap_managed_enable_put(pgmap);
154 }
155 EXPORT_SYMBOL_GPL(memunmap_pages);
156 
devm_memremap_pages_release(void * data)157 static void devm_memremap_pages_release(void *data)
158 {
159 	memunmap_pages(data);
160 }
161 
dev_pagemap_percpu_release(struct percpu_ref * ref)162 static void dev_pagemap_percpu_release(struct percpu_ref *ref)
163 {
164 	struct dev_pagemap *pgmap = container_of(ref, struct dev_pagemap, ref);
165 
166 	complete(&pgmap->done);
167 }
168 
pagemap_range(struct dev_pagemap * pgmap,struct mhp_params * params,int range_id,int nid)169 static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params,
170 		int range_id, int nid)
171 {
172 	const bool is_private = pgmap->type == MEMORY_DEVICE_PRIVATE;
173 	struct range *range = &pgmap->ranges[range_id];
174 	struct dev_pagemap *conflict_pgmap;
175 	int error, is_ram;
176 
177 	if (WARN_ONCE(pgmap_altmap(pgmap) && range_id > 0,
178 				"altmap not supported for multiple ranges\n"))
179 		return -EINVAL;
180 
181 	conflict_pgmap = get_dev_pagemap(PHYS_PFN(range->start), NULL);
182 	if (conflict_pgmap) {
183 		WARN(1, "Conflicting mapping in same section\n");
184 		put_dev_pagemap(conflict_pgmap);
185 		return -ENOMEM;
186 	}
187 
188 	conflict_pgmap = get_dev_pagemap(PHYS_PFN(range->end), NULL);
189 	if (conflict_pgmap) {
190 		WARN(1, "Conflicting mapping in same section\n");
191 		put_dev_pagemap(conflict_pgmap);
192 		return -ENOMEM;
193 	}
194 
195 	is_ram = region_intersects(range->start, range_len(range),
196 		IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);
197 
198 	if (is_ram != REGION_DISJOINT) {
199 		WARN_ONCE(1, "attempted on %s region %#llx-%#llx\n",
200 				is_ram == REGION_MIXED ? "mixed" : "ram",
201 				range->start, range->end);
202 		return -ENXIO;
203 	}
204 
205 	error = xa_err(xa_store_range(&pgmap_array, PHYS_PFN(range->start),
206 				PHYS_PFN(range->end), pgmap, GFP_KERNEL));
207 	if (error)
208 		return error;
209 
210 	if (nid < 0)
211 		nid = numa_mem_id();
212 
213 	error = track_pfn_remap(NULL, &params->pgprot, PHYS_PFN(range->start), 0,
214 			range_len(range));
215 	if (error)
216 		goto err_pfn_remap;
217 
218 	if (!mhp_range_allowed(range->start, range_len(range), !is_private)) {
219 		error = -EINVAL;
220 		goto err_kasan;
221 	}
222 
223 	mem_hotplug_begin();
224 
225 	/*
226 	 * For device private memory we call add_pages() as we only need to
227 	 * allocate and initialize struct page for the device memory. More-
228 	 * over the device memory is un-accessible thus we do not want to
229 	 * create a linear mapping for the memory like arch_add_memory()
230 	 * would do.
231 	 *
232 	 * For all other device memory types, which are accessible by
233 	 * the CPU, we do want the linear mapping and thus use
234 	 * arch_add_memory().
235 	 */
236 	if (is_private) {
237 		error = add_pages(nid, PHYS_PFN(range->start),
238 				PHYS_PFN(range_len(range)), params);
239 	} else {
240 		error = kasan_add_zero_shadow(__va(range->start), range_len(range));
241 		if (error) {
242 			mem_hotplug_done();
243 			goto err_kasan;
244 		}
245 
246 		error = arch_add_memory(nid, range->start, range_len(range),
247 					params);
248 	}
249 
250 	if (!error) {
251 		struct zone *zone;
252 
253 		zone = &NODE_DATA(nid)->node_zones[ZONE_DEVICE];
254 		move_pfn_range_to_zone(zone, PHYS_PFN(range->start),
255 				PHYS_PFN(range_len(range)), params->altmap,
256 				MIGRATE_MOVABLE);
257 	}
258 
259 	mem_hotplug_done();
260 	if (error)
261 		goto err_add_memory;
262 
263 	/*
264 	 * Initialization of the pages has been deferred until now in order
265 	 * to allow us to do the work while not holding the hotplug lock.
266 	 */
267 	memmap_init_zone_device(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
268 				PHYS_PFN(range->start),
269 				PHYS_PFN(range_len(range)), pgmap);
270 	if (pgmap->type != MEMORY_DEVICE_PRIVATE &&
271 	    pgmap->type != MEMORY_DEVICE_COHERENT)
272 		percpu_ref_get_many(&pgmap->ref, pfn_len(pgmap, range_id));
273 	return 0;
274 
275 err_add_memory:
276 	if (!is_private)
277 		kasan_remove_zero_shadow(__va(range->start), range_len(range));
278 err_kasan:
279 	untrack_pfn(NULL, PHYS_PFN(range->start), range_len(range), true);
280 err_pfn_remap:
281 	pgmap_array_delete(range);
282 	return error;
283 }
284 
285 
286 /*
287  * Not device managed version of devm_memremap_pages, undone by
288  * memunmap_pages().  Please use devm_memremap_pages if you have a struct
289  * device available.
290  */
memremap_pages(struct dev_pagemap * pgmap,int nid)291 void *memremap_pages(struct dev_pagemap *pgmap, int nid)
292 {
293 	struct mhp_params params = {
294 		.altmap = pgmap_altmap(pgmap),
295 		.pgmap = pgmap,
296 		.pgprot = PAGE_KERNEL,
297 	};
298 	const int nr_range = pgmap->nr_range;
299 	int error, i;
300 
301 	if (WARN_ONCE(!nr_range, "nr_range must be specified\n"))
302 		return ERR_PTR(-EINVAL);
303 
304 	switch (pgmap->type) {
305 	case MEMORY_DEVICE_PRIVATE:
306 		if (!IS_ENABLED(CONFIG_DEVICE_PRIVATE)) {
307 			WARN(1, "Device private memory not supported\n");
308 			return ERR_PTR(-EINVAL);
309 		}
310 		if (!pgmap->ops || !pgmap->ops->migrate_to_ram) {
311 			WARN(1, "Missing migrate_to_ram method\n");
312 			return ERR_PTR(-EINVAL);
313 		}
314 		if (!pgmap->ops->page_free) {
315 			WARN(1, "Missing page_free method\n");
316 			return ERR_PTR(-EINVAL);
317 		}
318 		if (!pgmap->owner) {
319 			WARN(1, "Missing owner\n");
320 			return ERR_PTR(-EINVAL);
321 		}
322 		break;
323 	case MEMORY_DEVICE_COHERENT:
324 		if (!pgmap->ops->page_free) {
325 			WARN(1, "Missing page_free method\n");
326 			return ERR_PTR(-EINVAL);
327 		}
328 		if (!pgmap->owner) {
329 			WARN(1, "Missing owner\n");
330 			return ERR_PTR(-EINVAL);
331 		}
332 		break;
333 	case MEMORY_DEVICE_FS_DAX:
334 		if (IS_ENABLED(CONFIG_FS_DAX_LIMITED)) {
335 			WARN(1, "File system DAX not supported\n");
336 			return ERR_PTR(-EINVAL);
337 		}
338 		params.pgprot = pgprot_decrypted(params.pgprot);
339 		break;
340 	case MEMORY_DEVICE_GENERIC:
341 		break;
342 	case MEMORY_DEVICE_PCI_P2PDMA:
343 		params.pgprot = pgprot_noncached(params.pgprot);
344 		break;
345 	default:
346 		WARN(1, "Invalid pgmap type %d\n", pgmap->type);
347 		break;
348 	}
349 
350 	init_completion(&pgmap->done);
351 	error = percpu_ref_init(&pgmap->ref, dev_pagemap_percpu_release, 0,
352 				GFP_KERNEL);
353 	if (error)
354 		return ERR_PTR(error);
355 
356 	devmap_managed_enable_get(pgmap);
357 
358 	/*
359 	 * Clear the pgmap nr_range as it will be incremented for each
360 	 * successfully processed range. This communicates how many
361 	 * regions to unwind in the abort case.
362 	 */
363 	pgmap->nr_range = 0;
364 	error = 0;
365 	for (i = 0; i < nr_range; i++) {
366 		error = pagemap_range(pgmap, &params, i, nid);
367 		if (error)
368 			break;
369 		pgmap->nr_range++;
370 	}
371 
372 	if (i < nr_range) {
373 		memunmap_pages(pgmap);
374 		pgmap->nr_range = nr_range;
375 		return ERR_PTR(error);
376 	}
377 
378 	return __va(pgmap->ranges[0].start);
379 }
380 EXPORT_SYMBOL_GPL(memremap_pages);
381 
382 /**
383  * devm_memremap_pages - remap and provide memmap backing for the given resource
384  * @dev: hosting device for @res
385  * @pgmap: pointer to a struct dev_pagemap
386  *
387  * Notes:
388  * 1/ At a minimum the range and type members of @pgmap must be initialized
389  *    by the caller before passing it to this function
390  *
391  * 2/ The altmap field may optionally be initialized, in which case
392  *    PGMAP_ALTMAP_VALID must be set in pgmap->flags.
393  *
394  * 3/ The ref field may optionally be provided, in which pgmap->ref must be
395  *    'live' on entry and will be killed and reaped at
396  *    devm_memremap_pages_release() time, or if this routine fails.
397  *
398  * 4/ range is expected to be a host memory range that could feasibly be
399  *    treated as a "System RAM" range, i.e. not a device mmio range, but
400  *    this is not enforced.
401  */
devm_memremap_pages(struct device * dev,struct dev_pagemap * pgmap)402 void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
403 {
404 	int error;
405 	void *ret;
406 
407 	ret = memremap_pages(pgmap, dev_to_node(dev));
408 	if (IS_ERR(ret))
409 		return ret;
410 
411 	error = devm_add_action_or_reset(dev, devm_memremap_pages_release,
412 			pgmap);
413 	if (error)
414 		return ERR_PTR(error);
415 	return ret;
416 }
417 EXPORT_SYMBOL_GPL(devm_memremap_pages);
418 
devm_memunmap_pages(struct device * dev,struct dev_pagemap * pgmap)419 void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap)
420 {
421 	devm_release_action(dev, devm_memremap_pages_release, pgmap);
422 }
423 EXPORT_SYMBOL_GPL(devm_memunmap_pages);
424 
vmem_altmap_offset(struct vmem_altmap * altmap)425 unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
426 {
427 	/* number of pfns from base where pfn_to_page() is valid */
428 	if (altmap)
429 		return altmap->reserve + altmap->free;
430 	return 0;
431 }
432 
vmem_altmap_free(struct vmem_altmap * altmap,unsigned long nr_pfns)433 void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns)
434 {
435 	altmap->alloc -= nr_pfns;
436 }
437 
438 /**
439  * get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn
440  * @pfn: page frame number to lookup page_map
441  * @pgmap: optional known pgmap that already has a reference
442  *
443  * If @pgmap is non-NULL and covers @pfn it will be returned as-is.  If @pgmap
444  * is non-NULL but does not cover @pfn the reference to it will be released.
445  */
get_dev_pagemap(unsigned long pfn,struct dev_pagemap * pgmap)446 struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
447 		struct dev_pagemap *pgmap)
448 {
449 	resource_size_t phys = PFN_PHYS(pfn);
450 
451 	/*
452 	 * In the cached case we're already holding a live reference.
453 	 */
454 	if (pgmap) {
455 		if (phys >= pgmap->range.start && phys <= pgmap->range.end)
456 			return pgmap;
457 		put_dev_pagemap(pgmap);
458 	}
459 
460 	/* fall back to slow path lookup */
461 	rcu_read_lock();
462 	pgmap = xa_load(&pgmap_array, PHYS_PFN(phys));
463 	if (pgmap && !percpu_ref_tryget_live_rcu(&pgmap->ref))
464 		pgmap = NULL;
465 	rcu_read_unlock();
466 
467 	return pgmap;
468 }
469 EXPORT_SYMBOL_GPL(get_dev_pagemap);
470 
free_zone_device_page(struct page * page)471 void free_zone_device_page(struct page *page)
472 {
473 	if (WARN_ON_ONCE(!page->pgmap->ops || !page->pgmap->ops->page_free))
474 		return;
475 
476 	mem_cgroup_uncharge(page_folio(page));
477 
478 	/*
479 	 * Note: we don't expect anonymous compound pages yet. Once supported
480 	 * and we could PTE-map them similar to THP, we'd have to clear
481 	 * PG_anon_exclusive on all tail pages.
482 	 */
483 	VM_BUG_ON_PAGE(PageAnon(page) && PageCompound(page), page);
484 	if (PageAnon(page))
485 		__ClearPageAnonExclusive(page);
486 
487 	/*
488 	 * When a device managed page is freed, the page->mapping field
489 	 * may still contain a (stale) mapping value. For example, the
490 	 * lower bits of page->mapping may still identify the page as an
491 	 * anonymous page. Ultimately, this entire field is just stale
492 	 * and wrong, and it will cause errors if not cleared.  One
493 	 * example is:
494 	 *
495 	 *  migrate_vma_pages()
496 	 *    migrate_vma_insert_page()
497 	 *      page_add_new_anon_rmap()
498 	 *        __page_set_anon_rmap()
499 	 *          ...checks page->mapping, via PageAnon(page) call,
500 	 *            and incorrectly concludes that the page is an
501 	 *            anonymous page. Therefore, it incorrectly,
502 	 *            silently fails to set up the new anon rmap.
503 	 *
504 	 * For other types of ZONE_DEVICE pages, migration is either
505 	 * handled differently or not done at all, so there is no need
506 	 * to clear page->mapping.
507 	 */
508 	page->mapping = NULL;
509 	page->pgmap->ops->page_free(page);
510 
511 	if (page->pgmap->type != MEMORY_DEVICE_PRIVATE &&
512 	    page->pgmap->type != MEMORY_DEVICE_COHERENT)
513 		/*
514 		 * Reset the page count to 1 to prepare for handing out the page
515 		 * again.
516 		 */
517 		set_page_count(page, 1);
518 	else
519 		put_dev_pagemap(page->pgmap);
520 }
521 
zone_device_page_init(struct page * page)522 void zone_device_page_init(struct page *page)
523 {
524 	/*
525 	 * Drivers shouldn't be allocating pages after calling
526 	 * memunmap_pages().
527 	 */
528 	WARN_ON_ONCE(!percpu_ref_tryget_live(&page->pgmap->ref));
529 	set_page_count(page, 1);
530 	lock_page(page);
531 }
532 EXPORT_SYMBOL_GPL(zone_device_page_init);
533 
534 #ifdef CONFIG_FS_DAX
__put_devmap_managed_page_refs(struct page * page,int refs)535 bool __put_devmap_managed_page_refs(struct page *page, int refs)
536 {
537 	if (page->pgmap->type != MEMORY_DEVICE_FS_DAX)
538 		return false;
539 
540 	/*
541 	 * fsdax page refcounts are 1-based, rather than 0-based: if
542 	 * refcount is 1, then the page is free and the refcount is
543 	 * stable because nobody holds a reference on the page.
544 	 */
545 	if (page_ref_sub_return(page, refs) == 1)
546 		wake_up_var(&page->_refcount);
547 	return true;
548 }
549 EXPORT_SYMBOL(__put_devmap_managed_page_refs);
550 #endif /* CONFIG_FS_DAX */
551