1 #ifndef _LINUX_MEMREMAP_H_
2 #define _LINUX_MEMREMAP_H_
4 #include <linux/ioport.h>
5 #include <linux/percpu-refcount.h>
7 #include <asm/pgtable.h>
13 * struct vmem_altmap - pre-allocated storage for vmemmap_populate
14 * @base_pfn: base of the entire dev_pagemap mapping
15 * @reserve: pages mapped, but reserved for driver use (relative to @base)
16 * @free: free pages set aside in the mapping for memmap storage
17 * @align: pages reserved to meet allocation alignments
18 * @alloc: track pages consumed, private to vmemmap_populate()
21 const unsigned long base_pfn
;
22 const unsigned long reserve
;
28 unsigned long vmem_altmap_offset(struct vmem_altmap
*altmap
);
29 void vmem_altmap_free(struct vmem_altmap
*altmap
, unsigned long nr_pfns
);
31 #ifdef CONFIG_ZONE_DEVICE
32 struct vmem_altmap
*to_vmem_altmap(unsigned long memmap_start
);
34 static inline struct vmem_altmap
*to_vmem_altmap(unsigned long memmap_start
)
41 * Specialize ZONE_DEVICE memory into multiple types each having differents
45 * Persistent device memory (pmem): struct page might be allocated in different
46 * memory and architecture might want to perform special actions. It is similar
47 * to regular memory, in that the CPU can access it transparently. However,
48 * it is likely to have different bandwidth and latency than regular memory.
49 * See Documentation/nvdimm/nvdimm.txt for more information.
51 * MEMORY_DEVICE_PRIVATE:
52 * Device memory that is not directly addressable by the CPU: CPU can neither
53 * read nor write private memory. In this case, we do still have struct pages
54 * backing the device memory. Doing so simplifies the implementation, but it is
55 * important to remember that there are certain points at which the struct page
56 * must be treated as an opaque object, rather than a "normal" struct page.
58 * A more complete discussion of unaddressable memory may be found in
59 * include/linux/hmm.h and Documentation/vm/hmm.txt.
61 * MEMORY_DEVICE_PUBLIC:
62 * Device memory that is cache coherent from device and CPU point of view. This
63 * is use on platform that have an advance system bus (like CAPI or CCIX). A
64 * driver can hotplug the device memory using ZONE_DEVICE and with that memory
65 * type. Any page of a process can be migrated to such memory. However no one
66 * should be allow to pin such memory so that it can always be evicted.
69 MEMORY_DEVICE_HOST
= 0,
70 MEMORY_DEVICE_PRIVATE
,
75 * For MEMORY_DEVICE_PRIVATE we use ZONE_DEVICE and extend it with two
80 * Additional notes about MEMORY_DEVICE_PRIVATE may be found in
81 * include/linux/hmm.h and Documentation/vm/hmm.txt. There is also a brief
82 * explanation in include/linux/memory_hotplug.h.
84 * The page_fault() callback must migrate page back, from device memory to
85 * system memory, so that the CPU can access it. This might fail for various
86 * reasons (device issues, device have been unplugged, ...). When such error
87 * conditions happen, the page_fault() callback must return VM_FAULT_SIGBUS and
88 * set the CPU page table entry to "poisoned".
90 * Note that because memory cgroup charges are transferred to the device memory,
91 * this should never fail due to memory restrictions. However, allocation
92 * of a regular system page might still fail because we are out of memory. If
93 * that happens, the page_fault() callback must return VM_FAULT_OOM.
95 * The page_fault() callback can also try to migrate back multiple pages in one
96 * chunk, as an optimization. It must, however, prioritize the faulting address
97 * over all the others.
100 * The page_free() callback is called once the page refcount reaches 1
101 * (ZONE_DEVICE pages never reach 0 refcount unless there is a refcount bug.
102 * This allows the device driver to implement its own memory management.)
104 * For MEMORY_DEVICE_PUBLIC only the page_free() callback matter.
106 typedef int (*dev_page_fault_t
)(struct vm_area_struct
*vma
,
108 const struct page
*page
,
111 typedef void (*dev_page_free_t
)(struct page
*page
, void *data
);
114 * struct dev_pagemap - metadata for ZONE_DEVICE mappings
115 * @page_fault: callback when CPU fault on an unaddressable device page
116 * @page_free: free page callback when page refcount reaches 1
117 * @altmap: pre-allocated/reserved memory for vmemmap allocations
118 * @res: physical address range covered by @ref
119 * @ref: reference count that pins the devm_memremap_pages() mapping
120 * @dev: host device of the mapping for debug
121 * @data: private data pointer for page_free()
122 * @type: memory type: see MEMORY_* in memory_hotplug.h
125 dev_page_fault_t page_fault
;
126 dev_page_free_t page_free
;
127 struct vmem_altmap
*altmap
;
128 const struct resource
*res
;
129 struct percpu_ref
*ref
;
132 enum memory_type type
;
135 #ifdef CONFIG_ZONE_DEVICE
136 void *devm_memremap_pages(struct device
*dev
, struct resource
*res
,
137 struct percpu_ref
*ref
, struct vmem_altmap
*altmap
);
138 struct dev_pagemap
*find_dev_pagemap(resource_size_t phys
);
140 static inline bool is_zone_device_page(const struct page
*page
);
142 static inline void *devm_memremap_pages(struct device
*dev
,
143 struct resource
*res
, struct percpu_ref
*ref
,
144 struct vmem_altmap
*altmap
)
147 * Fail attempts to call devm_memremap_pages() without
148 * ZONE_DEVICE support enabled, this requires callers to fall
149 * back to plain devm_memremap() based on config
152 return ERR_PTR(-ENXIO
);
155 static inline struct dev_pagemap
*find_dev_pagemap(resource_size_t phys
)
161 #if defined(CONFIG_DEVICE_PRIVATE) || defined(CONFIG_DEVICE_PUBLIC)
162 static inline bool is_device_private_page(const struct page
*page
)
164 return is_zone_device_page(page
) &&
165 page
->pgmap
->type
== MEMORY_DEVICE_PRIVATE
;
168 static inline bool is_device_public_page(const struct page
*page
)
170 return is_zone_device_page(page
) &&
171 page
->pgmap
->type
== MEMORY_DEVICE_PUBLIC
;
173 #endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
176 * get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn
177 * @pfn: page frame number to lookup page_map
178 * @pgmap: optional known pgmap that already has a reference
180 * @pgmap allows the overhead of a lookup to be bypassed when @pfn lands in the
183 static inline struct dev_pagemap
*get_dev_pagemap(unsigned long pfn
,
184 struct dev_pagemap
*pgmap
)
186 const struct resource
*res
= pgmap
? pgmap
->res
: NULL
;
187 resource_size_t phys
= PFN_PHYS(pfn
);
190 * In the cached case we're already holding a live reference so
191 * we can simply do a blind increment
193 if (res
&& phys
>= res
->start
&& phys
<= res
->end
) {
194 percpu_ref_get(pgmap
->ref
);
198 /* fall back to slow path lookup */
200 pgmap
= find_dev_pagemap(phys
);
201 if (pgmap
&& !percpu_ref_tryget_live(pgmap
->ref
))
208 static inline void put_dev_pagemap(struct dev_pagemap
*pgmap
)
211 percpu_ref_put(pgmap
->ref
);
213 #endif /* _LINUX_MEMREMAP_H_ */