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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_MEMREMAP_H_
3#define _LINUX_MEMREMAP_H_
4
5#include <linux/mmzone.h>
6#include <linux/range.h>
7#include <linux/ioport.h>
8#include <linux/percpu-refcount.h>
9
10struct resource;
11struct device;
12
13/**
14 * struct vmem_altmap - pre-allocated storage for vmemmap_populate
15 * @base_pfn: base of the entire dev_pagemap mapping
16 * @reserve: pages mapped, but reserved for driver use (relative to @base)
17 * @free: free pages set aside in the mapping for memmap storage
18 * @align: pages reserved to meet allocation alignments
19 * @alloc: track pages consumed, private to vmemmap_populate()
20 */
21struct vmem_altmap {
22 unsigned long base_pfn;
23 const unsigned long end_pfn;
24 const unsigned long reserve;
25 unsigned long free;
26 unsigned long align;
27 unsigned long alloc;
28};
29
30/*
31 * Specialize ZONE_DEVICE memory into multiple types each has a different
32 * usage.
33 *
34 * MEMORY_DEVICE_PRIVATE:
35 * Device memory that is not directly addressable by the CPU: CPU can neither
36 * read nor write private memory. In this case, we do still have struct pages
37 * backing the device memory. Doing so simplifies the implementation, but it is
38 * important to remember that there are certain points at which the struct page
39 * must be treated as an opaque object, rather than a "normal" struct page.
40 *
41 * A more complete discussion of unaddressable memory may be found in
42 * include/linux/hmm.h and Documentation/mm/hmm.rst.
43 *
44 * MEMORY_DEVICE_COHERENT:
45 * Device memory that is cache coherent from device and CPU point of view. This
46 * is used on platforms that have an advanced system bus (like CAPI or CXL). A
47 * driver can hotplug the device memory using ZONE_DEVICE and with that memory
48 * type. Any page of a process can be migrated to such memory. However no one
49 * should be allowed to pin such memory so that it can always be evicted.
50 *
51 * MEMORY_DEVICE_FS_DAX:
52 * Host memory that has similar access semantics as System RAM i.e. DMA
53 * coherent and supports page pinning. In support of coordinating page
54 * pinning vs other operations MEMORY_DEVICE_FS_DAX arranges for a
55 * wakeup event whenever a page is unpinned and becomes idle. This
56 * wakeup is used to coordinate physical address space management (ex:
57 * fs truncate/hole punch) vs pinned pages (ex: device dma).
58 *
59 * MEMORY_DEVICE_GENERIC:
60 * Host memory that has similar access semantics as System RAM i.e. DMA
61 * coherent and supports page pinning. This is for example used by DAX devices
62 * that expose memory using a character device.
63 *
64 * MEMORY_DEVICE_PCI_P2PDMA:
65 * Device memory residing in a PCI BAR intended for use with Peer-to-Peer
66 * transactions.
67 */
68enum memory_type {
69 /* 0 is reserved to catch uninitialized type fields */
70 MEMORY_DEVICE_PRIVATE = 1,
71 MEMORY_DEVICE_COHERENT,
72 MEMORY_DEVICE_FS_DAX,
73 MEMORY_DEVICE_GENERIC,
74 MEMORY_DEVICE_PCI_P2PDMA,
75};
76
77struct dev_pagemap_ops {
78 /*
79 * Called once the folio refcount reaches 0. The reference count will be
80 * reset to one by the core code after the method is called to prepare
81 * for handing out the folio again.
82 */
83 void (*folio_free)(struct folio *folio);
84
85 /*
86 * Used for private (un-addressable) device memory only. Must migrate
87 * the page back to a CPU accessible page.
88 */
89 vm_fault_t (*migrate_to_ram)(struct vm_fault *vmf);
90
91 /*
92 * Handle the memory failure happens on a range of pfns. Notify the
93 * processes who are using these pfns, and try to recover the data on
94 * them if necessary. The mf_flags is finally passed to the recover
95 * function through the whole notify routine.
96 *
97 * When this is not implemented, or it returns -EOPNOTSUPP, the caller
98 * will fall back to a common handler called mf_generic_kill_procs().
99 */
100 int (*memory_failure)(struct dev_pagemap *pgmap, unsigned long pfn,
101 unsigned long nr_pages, int mf_flags);
102
103 /*
104 * Used for private (un-addressable) device memory only.
105 * This callback is used when a folio is split into
106 * a smaller folio
107 */
108 void (*folio_split)(struct folio *head, struct folio *tail);
109};
110
111#define PGMAP_ALTMAP_VALID (1 << 0)
112
113/**
114 * struct dev_pagemap - metadata for ZONE_DEVICE mappings
115 * @altmap: pre-allocated/reserved memory for vmemmap allocations
116 * @ref: reference count that pins the devm_memremap_pages() mapping
117 * @done: completion for @ref
118 * @type: memory type: see MEMORY_* above in memremap.h
119 * @flags: PGMAP_* flags to specify defailed behavior
120 * @vmemmap_shift: structural definition of how the vmemmap page metadata
121 * is populated, specifically the metadata page order.
122 * A zero value (default) uses base pages as the vmemmap metadata
123 * representation. A bigger value will set up compound struct pages
124 * of the requested order value.
125 * @ops: method table
126 * @owner: an opaque pointer identifying the entity that manages this
127 * instance. Used by various helpers to make sure that no
128 * foreign ZONE_DEVICE memory is accessed.
129 * @nr_range: number of ranges to be mapped
130 * @range: range to be mapped when nr_range == 1
131 * @ranges: array of ranges to be mapped when nr_range > 1
132 */
133struct dev_pagemap {
134 struct vmem_altmap altmap;
135 struct percpu_ref ref;
136 struct completion done;
137 enum memory_type type;
138 unsigned int flags;
139 unsigned long vmemmap_shift;
140 const struct dev_pagemap_ops *ops;
141 void *owner;
142 int nr_range;
143 union {
144 struct range range;
145 DECLARE_FLEX_ARRAY(struct range, ranges);
146 };
147};
148
149static inline bool pgmap_has_memory_failure(struct dev_pagemap *pgmap)
150{
151 return pgmap->ops && pgmap->ops->memory_failure;
152}
153
154static inline struct vmem_altmap *pgmap_altmap(struct dev_pagemap *pgmap)
155{
156 if (pgmap->flags & PGMAP_ALTMAP_VALID)
157 return &pgmap->altmap;
158 return NULL;
159}
160
161static inline unsigned long pgmap_vmemmap_nr(struct dev_pagemap *pgmap)
162{
163 return 1 << pgmap->vmemmap_shift;
164}
165
166static inline bool folio_is_device_private(const struct folio *folio)
167{
168 return IS_ENABLED(CONFIG_DEVICE_PRIVATE) &&
169 folio_is_zone_device(folio) &&
170 folio->pgmap->type == MEMORY_DEVICE_PRIVATE;
171}
172
173static inline bool is_device_private_page(const struct page *page)
174{
175 return IS_ENABLED(CONFIG_DEVICE_PRIVATE) &&
176 folio_is_device_private(page_folio(page));
177}
178
179static inline bool folio_is_pci_p2pdma(const struct folio *folio)
180{
181 return IS_ENABLED(CONFIG_PCI_P2PDMA) &&
182 folio_is_zone_device(folio) &&
183 folio->pgmap->type == MEMORY_DEVICE_PCI_P2PDMA;
184}
185
186static inline void *folio_zone_device_data(const struct folio *folio)
187{
188 VM_WARN_ON_FOLIO(!folio_is_device_private(folio), folio);
189 return folio->page.zone_device_data;
190}
191
192static inline void folio_set_zone_device_data(struct folio *folio, void *data)
193{
194 VM_WARN_ON_FOLIO(!folio_is_device_private(folio), folio);
195 folio->page.zone_device_data = data;
196}
197
198static inline bool is_pci_p2pdma_page(const struct page *page)
199{
200 return IS_ENABLED(CONFIG_PCI_P2PDMA) &&
201 folio_is_pci_p2pdma(page_folio(page));
202}
203
204static inline bool folio_is_device_coherent(const struct folio *folio)
205{
206 return folio_is_zone_device(folio) &&
207 folio->pgmap->type == MEMORY_DEVICE_COHERENT;
208}
209
210static inline bool is_device_coherent_page(const struct page *page)
211{
212 return folio_is_device_coherent(page_folio(page));
213}
214
215static inline bool folio_is_fsdax(const struct folio *folio)
216{
217 return folio_is_zone_device(folio) &&
218 folio->pgmap->type == MEMORY_DEVICE_FS_DAX;
219}
220
221static inline bool is_fsdax_page(const struct page *page)
222{
223 return folio_is_fsdax(page_folio(page));
224}
225
226#ifdef CONFIG_ZONE_DEVICE
227void zone_device_page_init(struct page *page, struct dev_pagemap *pgmap,
228 unsigned int order);
229void *memremap_pages(struct dev_pagemap *pgmap, int nid);
230void memunmap_pages(struct dev_pagemap *pgmap);
231void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
232void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap);
233struct dev_pagemap *get_dev_pagemap(unsigned long pfn);
234bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn);
235
236unsigned long memremap_compat_align(void);
237
238static inline void zone_device_folio_init(struct folio *folio,
239 struct dev_pagemap *pgmap,
240 unsigned int order)
241{
242 zone_device_page_init(page: &folio->page, pgmap, order);
243 if (order)
244 folio_set_large_rmappable(folio);
245}
246
247static inline void zone_device_private_split_cb(struct folio *original_folio,
248 struct folio *new_folio)
249{
250 if (folio_is_device_private(folio: original_folio)) {
251 if (!original_folio->pgmap->ops->folio_split) {
252 if (new_folio) {
253 new_folio->pgmap = original_folio->pgmap;
254 new_folio->page.mapping =
255 original_folio->page.mapping;
256 }
257 } else {
258 original_folio->pgmap->ops->folio_split(original_folio,
259 new_folio);
260 }
261 }
262}
263
264#else
265static inline void *devm_memremap_pages(struct device *dev,
266 struct dev_pagemap *pgmap)
267{
268 /*
269 * Fail attempts to call devm_memremap_pages() without
270 * ZONE_DEVICE support enabled, this requires callers to fall
271 * back to plain devm_memremap() based on config
272 */
273 WARN_ON_ONCE(1);
274 return ERR_PTR(-ENXIO);
275}
276
277static inline void devm_memunmap_pages(struct device *dev,
278 struct dev_pagemap *pgmap)
279{
280}
281
282static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn)
283{
284 return NULL;
285}
286
287static inline bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn)
288{
289 return false;
290}
291
292/* when memremap_pages() is disabled all archs can remap a single page */
293static inline unsigned long memremap_compat_align(void)
294{
295 return PAGE_SIZE;
296}
297
298static inline void zone_device_private_split_cb(struct folio *original_folio,
299 struct folio *new_folio)
300{
301}
302#endif /* CONFIG_ZONE_DEVICE */
303
304static inline void put_dev_pagemap(struct dev_pagemap *pgmap)
305{
306 if (pgmap)
307 percpu_ref_put(ref: &pgmap->ref);
308}
309
310#endif /* _LINUX_MEMREMAP_H_ */
311

source code of linux/include/linux/memremap.h