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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_MEMREMAP_H_
3#define _LINUX_MEMREMAP_H_
4#include <linux/ioport.h>
5#include <linux/percpu-refcount.h>
6
7struct resource;
8struct device;
9
10/**
11 * struct vmem_altmap - pre-allocated storage for vmemmap_populate
12 * @base_pfn: base of the entire dev_pagemap mapping
13 * @reserve: pages mapped, but reserved for driver use (relative to @base)
14 * @free: free pages set aside in the mapping for memmap storage
15 * @align: pages reserved to meet allocation alignments
16 * @alloc: track pages consumed, private to vmemmap_populate()
17 */
18struct vmem_altmap {
19 const unsigned long base_pfn;
20 const unsigned long end_pfn;
21 const unsigned long reserve;
22 unsigned long free;
23 unsigned long align;
24 unsigned long alloc;
25};
26
27/*
28 * Specialize ZONE_DEVICE memory into multiple types each having differents
29 * usage.
30 *
31 * MEMORY_DEVICE_PRIVATE:
32 * Device memory that is not directly addressable by the CPU: CPU can neither
33 * read nor write private memory. In this case, we do still have struct pages
34 * backing the device memory. Doing so simplifies the implementation, but it is
35 * important to remember that there are certain points at which the struct page
36 * must be treated as an opaque object, rather than a "normal" struct page.
37 *
38 * A more complete discussion of unaddressable memory may be found in
39 * include/linux/hmm.h and Documentation/vm/hmm.rst.
40 *
41 * MEMORY_DEVICE_FS_DAX:
42 * Host memory that has similar access semantics as System RAM i.e. DMA
43 * coherent and supports page pinning. In support of coordinating page
44 * pinning vs other operations MEMORY_DEVICE_FS_DAX arranges for a
45 * wakeup event whenever a page is unpinned and becomes idle. This
46 * wakeup is used to coordinate physical address space management (ex:
47 * fs truncate/hole punch) vs pinned pages (ex: device dma).
48 *
49 * MEMORY_DEVICE_GENERIC:
50 * Host memory that has similar access semantics as System RAM i.e. DMA
51 * coherent and supports page pinning. This is for example used by DAX devices
52 * that expose memory using a character device.
53 *
54 * MEMORY_DEVICE_PCI_P2PDMA:
55 * Device memory residing in a PCI BAR intended for use with Peer-to-Peer
56 * transactions.
57 */
58enum memory_type {
59 /* 0 is reserved to catch uninitialized type fields */
60 MEMORY_DEVICE_PRIVATE = 1,
61 MEMORY_DEVICE_FS_DAX,
62 MEMORY_DEVICE_GENERIC,
63 MEMORY_DEVICE_PCI_P2PDMA,
64};
65
66struct dev_pagemap_ops {
67 /*
68 * Called once the page refcount reaches 1. (ZONE_DEVICE pages never
69 * reach 0 refcount unless there is a refcount bug. This allows the
70 * device driver to implement its own memory management.)
71 */
72 void (*page_free)(struct page *page);
73
74 /*
75 * Transition the refcount in struct dev_pagemap to the dead state.
76 */
77 void (*kill)(struct dev_pagemap *pgmap);
78
79 /*
80 * Wait for refcount in struct dev_pagemap to be idle and reap it.
81 */
82 void (*cleanup)(struct dev_pagemap *pgmap);
83
84 /*
85 * Used for private (un-addressable) device memory only. Must migrate
86 * the page back to a CPU accessible page.
87 */
88 vm_fault_t (*migrate_to_ram)(struct vm_fault *vmf);
89};
90
91#define PGMAP_ALTMAP_VALID (1 << 0)
92
93/**
94 * struct dev_pagemap - metadata for ZONE_DEVICE mappings
95 * @altmap: pre-allocated/reserved memory for vmemmap allocations
96 * @res: physical address range covered by @ref
97 * @ref: reference count that pins the devm_memremap_pages() mapping
98 * @internal_ref: internal reference if @ref is not provided by the caller
99 * @done: completion for @internal_ref
100 * @type: memory type: see MEMORY_* in memory_hotplug.h
101 * @flags: PGMAP_* flags to specify defailed behavior
102 * @ops: method table
103 * @owner: an opaque pointer identifying the entity that manages this
104 * instance. Used by various helpers to make sure that no
105 * foreign ZONE_DEVICE memory is accessed.
106 */
107struct dev_pagemap {
108 struct vmem_altmap altmap;
109 struct resource res;
110 struct percpu_ref *ref;
111 struct percpu_ref internal_ref;
112 struct completion done;
113 enum memory_type type;
114 unsigned int flags;
115 const struct dev_pagemap_ops *ops;
116 void *owner;
117};
118
119static inline struct vmem_altmap *pgmap_altmap(struct dev_pagemap *pgmap)
120{
121 if (pgmap->flags & PGMAP_ALTMAP_VALID)
122 return &pgmap->altmap;
123 return NULL;
124}
125
126#ifdef CONFIG_ZONE_DEVICE
127void *memremap_pages(struct dev_pagemap *pgmap, int nid);
128void memunmap_pages(struct dev_pagemap *pgmap);
129void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
130void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap);
131struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
132 struct dev_pagemap *pgmap);
133
134unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
135void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
136unsigned long memremap_compat_align(void);
137#else
138static inline void *devm_memremap_pages(struct device *dev,
139 struct dev_pagemap *pgmap)
140{
141 /*
142 * Fail attempts to call devm_memremap_pages() without
143 * ZONE_DEVICE support enabled, this requires callers to fall
144 * back to plain devm_memremap() based on config
145 */
146 WARN_ON_ONCE(1);
147 return ERR_PTR(-ENXIO);
148}
149
150static inline void devm_memunmap_pages(struct device *dev,
151 struct dev_pagemap *pgmap)
152{
153}
154
155static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
156 struct dev_pagemap *pgmap)
157{
158 return NULL;
159}
160
161static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
162{
163 return 0;
164}
165
166static inline void vmem_altmap_free(struct vmem_altmap *altmap,
167 unsigned long nr_pfns)
168{
169}
170
171/* when memremap_pages() is disabled all archs can remap a single page */
172static inline unsigned long memremap_compat_align(void)
173{
174 return PAGE_SIZE;
175}
176#endif /* CONFIG_ZONE_DEVICE */
177
178static inline void put_dev_pagemap(struct dev_pagemap *pgmap)
179{
180 if (pgmap)
181 percpu_ref_put(pgmap->ref);
182}
183
184#endif /* _LINUX_MEMREMAP_H_ */