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
7 #include <asm/pgtable.h>
8
9 struct resource;
10 struct device;
11
12 /**
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()
19 */
20 struct vmem_altmap {
21 const unsigned long base_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_PUBLIC:
43 * Device memory that is cache coherent from device and CPU point of view. This
44 * is use on platform that have an advance system bus (like CAPI or CCIX). A
45 * driver can hotplug the device memory using ZONE_DEVICE and with that memory
46 * type. Any page of a process can be migrated to such memory. However no one
47 * should be allow to pin such memory so that it can always be evicted.
48 *
49 * MEMORY_DEVICE_FS_DAX:
50 * Host memory that has similar access semantics as System RAM i.e. DMA
51 * coherent and supports page pinning. In support of coordinating page
52 * pinning vs other operations MEMORY_DEVICE_FS_DAX arranges for a
53 * wakeup event whenever a page is unpinned and becomes idle. This
54 * wakeup is used to coordinate physical address space management (ex:
55 * fs truncate/hole punch) vs pinned pages (ex: device dma).
56 */
57 enum memory_type {
58 MEMORY_DEVICE_PRIVATE = 1,
59 MEMORY_DEVICE_PUBLIC,
60 MEMORY_DEVICE_FS_DAX,
61 };
62
63 /*
64 * For MEMORY_DEVICE_PRIVATE we use ZONE_DEVICE and extend it with two
65 * callbacks:
66 * page_fault()
67 * page_free()
68 *
69 * Additional notes about MEMORY_DEVICE_PRIVATE may be found in
70 * include/linux/hmm.h and Documentation/vm/hmm.rst. There is also a brief
71 * explanation in include/linux/memory_hotplug.h.
72 *
73 * The page_fault() callback must migrate page back, from device memory to
74 * system memory, so that the CPU can access it. This might fail for various
75 * reasons (device issues, device have been unplugged, ...). When such error
76 * conditions happen, the page_fault() callback must return VM_FAULT_SIGBUS and
77 * set the CPU page table entry to "poisoned".
78 *
79 * Note that because memory cgroup charges are transferred to the device memory,
80 * this should never fail due to memory restrictions. However, allocation
81 * of a regular system page might still fail because we are out of memory. If
82 * that happens, the page_fault() callback must return VM_FAULT_OOM.
83 *
84 * The page_fault() callback can also try to migrate back multiple pages in one
85 * chunk, as an optimization. It must, however, prioritize the faulting address
86 * over all the others.
87 *
88 *
89 * The page_free() callback is called once the page refcount reaches 1
90 * (ZONE_DEVICE pages never reach 0 refcount unless there is a refcount bug.
91 * This allows the device driver to implement its own memory management.)
92 *
93 * For MEMORY_DEVICE_PUBLIC only the page_free() callback matter.
94 */
95 typedef int (*dev_page_fault_t)(struct vm_area_struct *vma,
96 unsigned long addr,
97 const struct page *page,
98 unsigned int flags,
99 pmd_t *pmdp);
100 typedef void (*dev_page_free_t)(struct page *page, void *data);
101
102 /**
103 * struct dev_pagemap - metadata for ZONE_DEVICE mappings
104 * @page_fault: callback when CPU fault on an unaddressable device page
105 * @page_free: free page callback when page refcount reaches 1
106 * @altmap: pre-allocated/reserved memory for vmemmap allocations
107 * @res: physical address range covered by @ref
108 * @ref: reference count that pins the devm_memremap_pages() mapping
109 * @dev: host device of the mapping for debug
110 * @data: private data pointer for page_free()
111 * @type: memory type: see MEMORY_* in memory_hotplug.h
112 */
113 struct dev_pagemap {
114 dev_page_fault_t page_fault;
115 dev_page_free_t page_free;
116 struct vmem_altmap altmap;
117 bool altmap_valid;
118 struct resource res;
119 struct percpu_ref *ref;
120 struct device *dev;
121 void *data;
122 enum memory_type type;
123 };
124
125 #ifdef CONFIG_ZONE_DEVICE
126 void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
127 struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
128 struct dev_pagemap *pgmap);
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 #else
devm_memremap_pages(struct device * dev,struct dev_pagemap * pgmap)133 static inline void *devm_memremap_pages(struct device *dev,
134 struct dev_pagemap *pgmap)
135 {
136 /*
137 * Fail attempts to call devm_memremap_pages() without
138 * ZONE_DEVICE support enabled, this requires callers to fall
139 * back to plain devm_memremap() based on config
140 */
141 WARN_ON_ONCE(1);
142 return ERR_PTR(-ENXIO);
143 }
144
get_dev_pagemap(unsigned long pfn,struct dev_pagemap * pgmap)145 static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
146 struct dev_pagemap *pgmap)
147 {
148 return NULL;
149 }
150
vmem_altmap_offset(struct vmem_altmap * altmap)151 static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
152 {
153 return 0;
154 }
155
vmem_altmap_free(struct vmem_altmap * altmap,unsigned long nr_pfns)156 static inline void vmem_altmap_free(struct vmem_altmap *altmap,
157 unsigned long nr_pfns)
158 {
159 }
160 #endif /* CONFIG_ZONE_DEVICE */
161
put_dev_pagemap(struct dev_pagemap * pgmap)162 static inline void put_dev_pagemap(struct dev_pagemap *pgmap)
163 {
164 if (pgmap)
165 percpu_ref_put(pgmap->ref);
166 }
167 #endif /* _LINUX_MEMREMAP_H_ */
168
