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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 	const 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 having differents
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 	 * Transition the refcount in struct dev_pagemap to the dead state.
77 	 */
78 	void (*kill)(struct dev_pagemap *pgmap);
79 
80 	/*
81 	 * Wait for refcount in struct dev_pagemap to be idle and reap it.
82 	 */
83 	void (*cleanup)(struct dev_pagemap *pgmap);
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 #define PGMAP_ALTMAP_VALID	(1 << 0)
93 
94 /**
95  * struct dev_pagemap - metadata for ZONE_DEVICE mappings
96  * @altmap: pre-allocated/reserved memory for vmemmap allocations
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  * @nr_range: number of ranges to be mapped
107  * @range: range to be mapped when nr_range == 1
108  * @ranges: array of ranges to be mapped when nr_range > 1
109  */
110 struct dev_pagemap {
111 	struct vmem_altmap altmap;
112 	struct percpu_ref *ref;
113 	struct percpu_ref internal_ref;
114 	struct completion done;
115 	enum memory_type type;
116 	unsigned int flags;
117 	const struct dev_pagemap_ops *ops;
118 	void *owner;
119 	int nr_range;
120 	union {
121 		struct range range;
122 		struct range ranges[0];
123 	};
124 };
125 
pgmap_altmap(struct dev_pagemap * pgmap)126 static inline struct vmem_altmap *pgmap_altmap(struct dev_pagemap *pgmap)
127 {
128 	if (pgmap->flags & PGMAP_ALTMAP_VALID)
129 		return &pgmap->altmap;
130 	return NULL;
131 }
132 
133 #ifdef CONFIG_ZONE_DEVICE
134 void *memremap_pages(struct dev_pagemap *pgmap, int nid);
135 void memunmap_pages(struct dev_pagemap *pgmap);
136 void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
137 void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap);
138 struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
139 		struct dev_pagemap *pgmap);
140 bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn);
141 
142 unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
143 void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
144 unsigned long memremap_compat_align(void);
145 #else
devm_memremap_pages(struct device * dev,struct dev_pagemap * pgmap)146 static inline void *devm_memremap_pages(struct device *dev,
147 		struct dev_pagemap *pgmap)
148 {
149 	/*
150 	 * Fail attempts to call devm_memremap_pages() without
151 	 * ZONE_DEVICE support enabled, this requires callers to fall
152 	 * back to plain devm_memremap() based on config
153 	 */
154 	WARN_ON_ONCE(1);
155 	return ERR_PTR(-ENXIO);
156 }
157 
devm_memunmap_pages(struct device * dev,struct dev_pagemap * pgmap)158 static inline void devm_memunmap_pages(struct device *dev,
159 		struct dev_pagemap *pgmap)
160 {
161 }
162 
get_dev_pagemap(unsigned long pfn,struct dev_pagemap * pgmap)163 static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
164 		struct dev_pagemap *pgmap)
165 {
166 	return NULL;
167 }
168 
pgmap_pfn_valid(struct dev_pagemap * pgmap,unsigned long pfn)169 static inline bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn)
170 {
171 	return false;
172 }
173 
vmem_altmap_offset(struct vmem_altmap * altmap)174 static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
175 {
176 	return 0;
177 }
178 
vmem_altmap_free(struct vmem_altmap * altmap,unsigned long nr_pfns)179 static inline void vmem_altmap_free(struct vmem_altmap *altmap,
180 		unsigned long nr_pfns)
181 {
182 }
183 
184 /* when memremap_pages() is disabled all archs can remap a single page */
memremap_compat_align(void)185 static inline unsigned long memremap_compat_align(void)
186 {
187 	return PAGE_SIZE;
188 }
189 #endif /* CONFIG_ZONE_DEVICE */
190 
put_dev_pagemap(struct dev_pagemap * pgmap)191 static inline void put_dev_pagemap(struct dev_pagemap *pgmap)
192 {
193 	if (pgmap)
194 		percpu_ref_put(pgmap->ref);
195 }
196 
197 #endif /* _LINUX_MEMREMAP_H_ */
198