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>
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;
29 * Specialize ZONE_DEVICE memory into multiple types each having differents
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.
39 * A more complete discussion of unaddressable memory may be found in
40 * include/linux/hmm.h and Documentation/vm/hmm.rst.
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.
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).
57 * MEMORY_DEVICE_PCI_P2PDMA:
58 * Device memory residing in a PCI BAR intended for use with Peer-to-Peer
62 MEMORY_DEVICE_PRIVATE = 1,
65 MEMORY_DEVICE_PCI_P2PDMA,
69 * For MEMORY_DEVICE_PRIVATE we use ZONE_DEVICE and extend it with two
74 * Additional notes about MEMORY_DEVICE_PRIVATE may be found in
75 * include/linux/hmm.h and Documentation/vm/hmm.rst. There is also a brief
76 * explanation in include/linux/memory_hotplug.h.
78 * The page_fault() callback must migrate page back, from device memory to
79 * system memory, so that the CPU can access it. This might fail for various
80 * reasons (device issues, device have been unplugged, ...). When such error
81 * conditions happen, the page_fault() callback must return VM_FAULT_SIGBUS and
82 * set the CPU page table entry to "poisoned".
84 * Note that because memory cgroup charges are transferred to the device memory,
85 * this should never fail due to memory restrictions. However, allocation
86 * of a regular system page might still fail because we are out of memory. If
87 * that happens, the page_fault() callback must return VM_FAULT_OOM.
89 * The page_fault() callback can also try to migrate back multiple pages in one
90 * chunk, as an optimization. It must, however, prioritize the faulting address
91 * over all the others.
94 * The page_free() callback is called once the page refcount reaches 1
95 * (ZONE_DEVICE pages never reach 0 refcount unless there is a refcount bug.
96 * This allows the device driver to implement its own memory management.)
98 * For MEMORY_DEVICE_PUBLIC only the page_free() callback matter.
100 typedef int (*dev_page_fault_t)(struct vm_area_struct *vma,
102 const struct page *page,
105 typedef void (*dev_page_free_t)(struct page *page, void *data);
108 * struct dev_pagemap - metadata for ZONE_DEVICE mappings
109 * @page_fault: callback when CPU fault on an unaddressable device page
110 * @page_free: free page callback when page refcount reaches 1
111 * @altmap: pre-allocated/reserved memory for vmemmap allocations
112 * @res: physical address range covered by @ref
113 * @ref: reference count that pins the devm_memremap_pages() mapping
114 * @dev: host device of the mapping for debug
115 * @data: private data pointer for page_free()
116 * @type: memory type: see MEMORY_* in memory_hotplug.h
119 dev_page_fault_t page_fault;
120 dev_page_free_t page_free;
121 struct vmem_altmap altmap;
124 struct percpu_ref *ref;
127 enum memory_type type;
128 u64 pci_p2pdma_bus_offset;
131 #ifdef CONFIG_ZONE_DEVICE
132 void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
133 struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
134 struct dev_pagemap *pgmap);
136 unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
137 void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
139 static inline void *devm_memremap_pages(struct device *dev,
140 struct dev_pagemap *pgmap)
143 * Fail attempts to call devm_memremap_pages() without
144 * ZONE_DEVICE support enabled, this requires callers to fall
145 * back to plain devm_memremap() based on config
148 return ERR_PTR(-ENXIO);
151 static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
152 struct dev_pagemap *pgmap)
157 static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
162 static inline void vmem_altmap_free(struct vmem_altmap *altmap,
163 unsigned long nr_pfns)
166 #endif /* CONFIG_ZONE_DEVICE */
168 static inline void put_dev_pagemap(struct dev_pagemap *pgmap)
171 percpu_ref_put(pgmap->ref);
173 #endif /* _LINUX_MEMREMAP_H_ */