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 page 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 page again.
82 */
83 void (*page_free)(struct page *page);
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#define PGMAP_ALTMAP_VALID (1 << 0)
105
106/**
107 * struct dev_pagemap - metadata for ZONE_DEVICE mappings
108 * @altmap: pre-allocated/reserved memory for vmemmap allocations
109 * @ref: reference count that pins the devm_memremap_pages() mapping
110 * @done: completion for @ref
111 * @type: memory type: see MEMORY_* in memory_hotplug.h
112 * @flags: PGMAP_* flags to specify defailed behavior
113 * @vmemmap_shift: structural definition of how the vmemmap page metadata
114 * is populated, specifically the metadata page order.
115 * A zero value (default) uses base pages as the vmemmap metadata
116 * representation. A bigger value will set up compound struct pages
117 * of the requested order value.
118 * @ops: method table
119 * @owner: an opaque pointer identifying the entity that manages this
120 * instance. Used by various helpers to make sure that no
121 * foreign ZONE_DEVICE memory is accessed.
122 * @nr_range: number of ranges to be mapped
123 * @range: range to be mapped when nr_range == 1
124 * @ranges: array of ranges to be mapped when nr_range > 1
125 */
126struct dev_pagemap {
127 struct vmem_altmap altmap;
128 struct percpu_ref ref;
129 struct completion done;
130 enum memory_type type;
131 unsigned int flags;
132 unsigned long vmemmap_shift;
133 const struct dev_pagemap_ops *ops;
134 void *owner;
135 int nr_range;
136 union {
137 struct range range;
138 struct range ranges[0];
139 };
140};
141
142static inline struct vmem_altmap *pgmap_altmap(struct dev_pagemap *pgmap)
143{
144 if (pgmap->flags & PGMAP_ALTMAP_VALID)
145 return &pgmap->altmap;
146 return NULL;
147}
148
149static inline unsigned long pgmap_vmemmap_nr(struct dev_pagemap *pgmap)
150{
151 return 1 << pgmap->vmemmap_shift;
152}
153
154static inline bool is_device_private_page(const struct page *page)
155{
156 return IS_ENABLED(CONFIG_DEVICE_PRIVATE) &&
157 is_zone_device_page(page) &&
158 page->pgmap->type == MEMORY_DEVICE_PRIVATE;
159}
160
161static inline bool folio_is_device_private(const struct folio *folio)
162{
163 return is_device_private_page(&folio->page);
164}
165
166static inline bool is_pci_p2pdma_page(const struct page *page)
167{
168 return IS_ENABLED(CONFIG_PCI_P2PDMA) &&
169 is_zone_device_page(page) &&
170 page->pgmap->type == MEMORY_DEVICE_PCI_P2PDMA;
171}
172
173static inline bool is_device_coherent_page(const struct page *page)
174{
175 return is_zone_device_page(page) &&
176 page->pgmap->type == MEMORY_DEVICE_COHERENT;
177}
178
179static inline bool folio_is_device_coherent(const struct folio *folio)
180{
181 return is_device_coherent_page(&folio->page);
182}
183
184#ifdef CONFIG_ZONE_DEVICE
185void *memremap_pages(struct dev_pagemap *pgmap, int nid);
186void memunmap_pages(struct dev_pagemap *pgmap);
187void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
188void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap);
189struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
190 struct dev_pagemap *pgmap);
191bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn);
192
193unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
194void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
195unsigned long memremap_compat_align(void);
196#else
197static inline void *devm_memremap_pages(struct device *dev,
198 struct dev_pagemap *pgmap)
199{
200 /*
201 * Fail attempts to call devm_memremap_pages() without
202 * ZONE_DEVICE support enabled, this requires callers to fall
203 * back to plain devm_memremap() based on config
204 */
205 WARN_ON_ONCE(1);
206 return ERR_PTR(-ENXIO);
207}
208
209static inline void devm_memunmap_pages(struct device *dev,
210 struct dev_pagemap *pgmap)
211{
212}
213
214static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
215 struct dev_pagemap *pgmap)
216{
217 return NULL;
218}
219
220static inline bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn)
221{
222 return false;
223}
224
225static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
226{
227 return 0;
228}
229
230static inline void vmem_altmap_free(struct vmem_altmap *altmap,
231 unsigned long nr_pfns)
232{
233}
234
235/* when memremap_pages() is disabled all archs can remap a single page */
236static inline unsigned long memremap_compat_align(void)
237{
238 return PAGE_SIZE;
239}
240#endif /* CONFIG_ZONE_DEVICE */
241
242static inline void put_dev_pagemap(struct dev_pagemap *pgmap)
243{
244 if (pgmap)
245 percpu_ref_put(&pgmap->ref);
246}
247
248#endif /* _LINUX_MEMREMAP_H_ */
249

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