include/linux/memremap.h

   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         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
 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
 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
 158 static inline void devm_memunmap_pages(struct device *dev,
 159                 struct dev_pagemap *pgmap)
 160 {
 161 }
 162
 163 static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
 164                 struct dev_pagemap *pgmap)
 165 {
 166         return NULL;
 167 }
 168
 169 static inline bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn)
 170 {
 171         return false;
 172 }
 173
 174 static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
 175 {
 176         return 0;
 177 }
 178
 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 */
 185 static inline unsigned long memremap_compat_align(void)
 186 {
 187         return PAGE_SIZE;
 188 }
 189 #endif /* CONFIG_ZONE_DEVICE */
 190
 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_ */