summaryrefslogtreecommitdiff
path: root/include/linux/memremap.h
blob: 79f8ba7c38940953182d05a59df970d06acc13fc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
#ifndef _LINUX_MEMREMAP_H_
#define _LINUX_MEMREMAP_H_
#include <linux/mm.h>
#include <linux/ioport.h>
#include <linux/percpu-refcount.h>

#include <asm/pgtable.h>

struct resource;
struct device;

/**
 * struct vmem_altmap - pre-allocated storage for vmemmap_populate
 * @base_pfn: base of the entire dev_pagemap mapping
 * @reserve: pages mapped, but reserved for driver use (relative to @base)
 * @free: free pages set aside in the mapping for memmap storage
 * @align: pages reserved to meet allocation alignments
 * @alloc: track pages consumed, private to vmemmap_populate()
 */
struct vmem_altmap {
	const unsigned long base_pfn;
	const unsigned long reserve;
	unsigned long free;
	unsigned long align;
	unsigned long alloc;
};

unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);

#ifdef CONFIG_ZONE_DEVICE
struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start);
#else
static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
{
	return NULL;
}
#endif

/*
 * Specialize ZONE_DEVICE memory into multiple types each having differents
 * usage.
 *
 * MEMORY_DEVICE_HOST:
 * Persistent device memory (pmem): struct page might be allocated in different
 * memory and architecture might want to perform special actions. It is similar
 * to regular memory, in that the CPU can access it transparently. However,
 * it is likely to have different bandwidth and latency than regular memory.
 * See Documentation/nvdimm/nvdimm.txt for more information.
 *
 * MEMORY_DEVICE_PRIVATE:
 * Device memory that is not directly addressable by the CPU: CPU can neither
 * read nor write private memory. In this case, we do still have struct pages
 * backing the device memory. Doing so simplifies the implementation, but it is
 * important to remember that there are certain points at which the struct page
 * must be treated as an opaque object, rather than a "normal" struct page.
 *
 * A more complete discussion of unaddressable memory may be found in
 * include/linux/hmm.h and Documentation/vm/hmm.txt.
 *
 * MEMORY_DEVICE_PUBLIC:
 * Device memory that is cache coherent from device and CPU point of view. This
 * is use on platform that have an advance system bus (like CAPI or CCIX). A
 * driver can hotplug the device memory using ZONE_DEVICE and with that memory
 * type. Any page of a process can be migrated to such memory. However no one
 * should be allow to pin such memory so that it can always be evicted.
 */
enum memory_type {
	MEMORY_DEVICE_HOST = 0,
	MEMORY_DEVICE_PRIVATE,
	MEMORY_DEVICE_PUBLIC,
};

/*
 * For MEMORY_DEVICE_PRIVATE we use ZONE_DEVICE and extend it with two
 * callbacks:
 *   page_fault()
 *   page_free()
 *
 * Additional notes about MEMORY_DEVICE_PRIVATE may be found in
 * include/linux/hmm.h and Documentation/vm/hmm.txt. There is also a brief
 * explanation in include/linux/memory_hotplug.h.
 *
 * The page_fault() callback must migrate page back, from device memory to
 * system memory, so that the CPU can access it. This might fail for various
 * reasons (device issues,  device have been unplugged, ...). When such error
 * conditions happen, the page_fault() callback must return VM_FAULT_SIGBUS and
 * set the CPU page table entry to "poisoned".
 *
 * Note that because memory cgroup charges are transferred to the device memory,
 * this should never fail due to memory restrictions. However, allocation
 * of a regular system page might still fail because we are out of memory. If
 * that happens, the page_fault() callback must return VM_FAULT_OOM.
 *
 * The page_fault() callback can also try to migrate back multiple pages in one
 * chunk, as an optimization. It must, however, prioritize the faulting address
 * over all the others.
 *
 *
 * The page_free() callback is called once the page refcount reaches 1
 * (ZONE_DEVICE pages never reach 0 refcount unless there is a refcount bug.
 * This allows the device driver to implement its own memory management.)
 *
 * For MEMORY_DEVICE_PUBLIC only the page_free() callback matter.
 */
typedef int (*dev_page_fault_t)(struct vm_area_struct *vma,
				unsigned long addr,
				const struct page *page,
				unsigned int flags,
				pmd_t *pmdp);
typedef void (*dev_page_free_t)(struct page *page, void *data);

/**
 * struct dev_pagemap - metadata for ZONE_DEVICE mappings
 * @page_fault: callback when CPU fault on an unaddressable device page
 * @page_free: free page callback when page refcount reaches 1
 * @altmap: pre-allocated/reserved memory for vmemmap allocations
 * @res: physical address range covered by @ref
 * @ref: reference count that pins the devm_memremap_pages() mapping
 * @dev: host device of the mapping for debug
 * @data: private data pointer for page_free()
 * @type: memory type: see MEMORY_* in memory_hotplug.h
 */
struct dev_pagemap {
	dev_page_fault_t page_fault;
	dev_page_free_t page_free;
	struct vmem_altmap *altmap;
	const struct resource *res;
	struct percpu_ref *ref;
	struct device *dev;
	void *data;
	enum memory_type type;
};

#ifdef CONFIG_ZONE_DEVICE
void *devm_memremap_pages(struct device *dev, struct resource *res,
		struct percpu_ref *ref, struct vmem_altmap *altmap);
struct dev_pagemap *find_dev_pagemap(resource_size_t phys);

static inline bool is_zone_device_page(const struct page *page);
#else
static inline void *devm_memremap_pages(struct device *dev,
		struct resource *res, struct percpu_ref *ref,
		struct vmem_altmap *altmap)
{
	/*
	 * Fail attempts to call devm_memremap_pages() without
	 * ZONE_DEVICE support enabled, this requires callers to fall
	 * back to plain devm_memremap() based on config
	 */
	WARN_ON_ONCE(1);
	return ERR_PTR(-ENXIO);
}

static inline struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
{
	return NULL;
}
#endif

#if defined(CONFIG_DEVICE_PRIVATE) || defined(CONFIG_DEVICE_PUBLIC)
static inline bool is_device_private_page(const struct page *page)
{
	return is_zone_device_page(page) &&
		page->pgmap->type == MEMORY_DEVICE_PRIVATE;
}

static inline bool is_device_public_page(const struct page *page)
{
	return is_zone_device_page(page) &&
		page->pgmap->type == MEMORY_DEVICE_PUBLIC;
}
#endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */

/**
 * get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn
 * @pfn: page frame number to lookup page_map
 * @pgmap: optional known pgmap that already has a reference
 *
 * @pgmap allows the overhead of a lookup to be bypassed when @pfn lands in the
 * same mapping.
 */
static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
		struct dev_pagemap *pgmap)
{
	const struct resource *res = pgmap ? pgmap->res : NULL;
	resource_size_t phys = PFN_PHYS(pfn);

	/*
	 * In the cached case we're already holding a live reference so
	 * we can simply do a blind increment
	 */
	if (res && phys >= res->start && phys <= res->end) {
		percpu_ref_get(pgmap->ref);
		return pgmap;
	}

	/* fall back to slow path lookup */
	rcu_read_lock();
	pgmap = find_dev_pagemap(phys);
	if (pgmap && !percpu_ref_tryget_live(pgmap->ref))
		pgmap = NULL;
	rcu_read_unlock();

	return pgmap;
}

static inline void put_dev_pagemap(struct dev_pagemap *pgmap)
{
	if (pgmap)
		percpu_ref_put(pgmap->ref);
}
#endif /* _LINUX_MEMREMAP_H_ */