1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_MEMREMAP_H_
3 #define _LINUX_MEMREMAP_H_
4 #include <linux/range.h>
5 #include <linux/ioport.h>
6 #include <linux/percpu-refcount.h>
7
8 struct resource;
9 struct device;
10
11 /**
12 * struct vmem_altmap - pre-allocated storage for vmemmap_populate
13 * @base_pfn: base of the entire dev_pagemap mapping
14 * @reserve: pages mapped, but reserved for driver use (relative to @base)
15 * @free: free pages set aside in the mapping for memmap storage
16 * @align: pages reserved to meet allocation alignments
17 * @alloc: track pages consumed, private to vmemmap_populate()
18 */
19 struct vmem_altmap {
20 unsigned long base_pfn;
21 const unsigned long end_pfn;
22 const unsigned long reserve;
23 unsigned long free;
24 unsigned long align;
25 unsigned long alloc;
26 };
27
28 /*
29 * Specialize ZONE_DEVICE memory into multiple types each has a different
30 * usage.
31 *
32 * MEMORY_DEVICE_PRIVATE:
33 * Device memory that is not directly addressable by the CPU: CPU can neither
34 * read nor write private memory. In this case, we do still have struct pages
35 * backing the device memory. Doing so simplifies the implementation, but it is
36 * important to remember that there are certain points at which the struct page
37 * must be treated as an opaque object, rather than a "normal" struct page.
38 *
39 * A more complete discussion of unaddressable memory may be found in
40 * include/linux/hmm.h and Documentation/vm/hmm.rst.
41 *
42 * MEMORY_DEVICE_FS_DAX:
43 * Host memory that has similar access semantics as System RAM i.e. DMA
44 * coherent and supports page pinning. In support of coordinating page
45 * pinning vs other operations MEMORY_DEVICE_FS_DAX arranges for a
46 * wakeup event whenever a page is unpinned and becomes idle. This
47 * wakeup is used to coordinate physical address space management (ex:
48 * fs truncate/hole punch) vs pinned pages (ex: device dma).
49 *
50 * MEMORY_DEVICE_GENERIC:
51 * Host memory that has similar access semantics as System RAM i.e. DMA
52 * coherent and supports page pinning. This is for example used by DAX devices
53 * that expose memory using a character device.
54 *
55 * MEMORY_DEVICE_PCI_P2PDMA:
56 * Device memory residing in a PCI BAR intended for use with Peer-to-Peer
57 * transactions.
58 */
59 enum memory_type {
60 /* 0 is reserved to catch uninitialized type fields */
61 MEMORY_DEVICE_PRIVATE = 1,
62 MEMORY_DEVICE_FS_DAX,
63 MEMORY_DEVICE_GENERIC,
64 MEMORY_DEVICE_PCI_P2PDMA,
65 };
66
67 struct dev_pagemap_ops {
68 /*
69 * Called once the page refcount reaches 1. (ZONE_DEVICE pages never
70 * reach 0 refcount unless there is a refcount bug. This allows the
71 * device driver to implement its own memory management.)
72 */
73 void (*page_free)(struct page *page);
74
75 /*
76 * Used for private (un-addressable) device memory only. Must migrate
77 * the page back to a CPU accessible page.
78 */
79 vm_fault_t (*migrate_to_ram)(struct vm_fault *vmf);
80 };
81
82 #define PGMAP_ALTMAP_VALID (1 << 0)
83
84 /**
85 * struct dev_pagemap - metadata for ZONE_DEVICE mappings
86 * @altmap: pre-allocated/reserved memory for vmemmap allocations
87 * @ref: reference count that pins the devm_memremap_pages() mapping
88 * @done: completion for @ref
89 * @type: memory type: see MEMORY_* in memory_hotplug.h
90 * @flags: PGMAP_* flags to specify defailed behavior
91 * @ops: method table
92 * @owner: an opaque pointer identifying the entity that manages this
93 * instance. Used by various helpers to make sure that no
94 * foreign ZONE_DEVICE memory is accessed.
95 * @nr_range: number of ranges to be mapped
96 * @range: range to be mapped when nr_range == 1
97 * @ranges: array of ranges to be mapped when nr_range > 1
98 */
99 struct dev_pagemap {
100 struct vmem_altmap altmap;
101 struct percpu_ref ref;
102 struct completion done;
103 enum memory_type type;
104 unsigned int flags;
105 const struct dev_pagemap_ops *ops;
106 void *owner;
107 int nr_range;
108 union {
109 struct range range;
110 struct range ranges[0];
111 };
112 };
113
pgmap_altmap(struct dev_pagemap * pgmap)114 static inline struct vmem_altmap *pgmap_altmap(struct dev_pagemap *pgmap)
115 {
116 if (pgmap->flags & PGMAP_ALTMAP_VALID)
117 return &pgmap->altmap;
118 return NULL;
119 }
120
121 #ifdef CONFIG_ZONE_DEVICE
122 void *memremap_pages(struct dev_pagemap *pgmap, int nid);
123 void memunmap_pages(struct dev_pagemap *pgmap);
124 void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
125 void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap);
126 struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
127 struct dev_pagemap *pgmap);
128 bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn);
129
130 unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
131 void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
132 unsigned long memremap_compat_align(void);
133 #else
devm_memremap_pages(struct device * dev,struct dev_pagemap * pgmap)134 static inline void *devm_memremap_pages(struct device *dev,
135 struct dev_pagemap *pgmap)
136 {
137 /*
138 * Fail attempts to call devm_memremap_pages() without
139 * ZONE_DEVICE support enabled, this requires callers to fall
140 * back to plain devm_memremap() based on config
141 */
142 WARN_ON_ONCE(1);
143 return ERR_PTR(-ENXIO);
144 }
145
devm_memunmap_pages(struct device * dev,struct dev_pagemap * pgmap)146 static inline void devm_memunmap_pages(struct device *dev,
147 struct dev_pagemap *pgmap)
148 {
149 }
150
get_dev_pagemap(unsigned long pfn,struct dev_pagemap * pgmap)151 static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
152 struct dev_pagemap *pgmap)
153 {
154 return NULL;
155 }
156
pgmap_pfn_valid(struct dev_pagemap * pgmap,unsigned long pfn)157 static inline bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn)
158 {
159 return false;
160 }
161
vmem_altmap_offset(struct vmem_altmap * altmap)162 static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
163 {
164 return 0;
165 }
166
vmem_altmap_free(struct vmem_altmap * altmap,unsigned long nr_pfns)167 static inline void vmem_altmap_free(struct vmem_altmap *altmap,
168 unsigned long nr_pfns)
169 {
170 }
171
172 /* when memremap_pages() is disabled all archs can remap a single page */
memremap_compat_align(void)173 static inline unsigned long memremap_compat_align(void)
174 {
175 return PAGE_SIZE;
176 }
177 #endif /* CONFIG_ZONE_DEVICE */
178
put_dev_pagemap(struct dev_pagemap * pgmap)179 static inline void put_dev_pagemap(struct dev_pagemap *pgmap)
180 {
181 if (pgmap)
182 percpu_ref_put(&pgmap->ref);
183 }
184
185 #endif /* _LINUX_MEMREMAP_H_ */
186