include/linux/memremap.h

   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 struct resource;
   8 struct device;
   9
  10 /**
  11  * struct vmem_altmap - pre-allocated storage for vmemmap_populate
  12  * @base_pfn: base of the entire dev_pagemap mapping
  13  * @reserve: pages mapped, but reserved for driver use (relative to @base)
  14  * @free: free pages set aside in the mapping for memmap storage
  15  * @align: pages reserved to meet allocation alignments
  16  * @alloc: track pages consumed, private to vmemmap_populate()
  17  */
  18 struct vmem_altmap {
  19         const unsigned long base_pfn;
  20         const unsigned long reserve;
  21         unsigned long free;
  22         unsigned long align;
  23         unsigned long alloc;
  24 };
  25
  26 /*
  27  * Specialize ZONE_DEVICE memory into multiple types each having differents
  28  * usage.
  29  *
  30  * MEMORY_DEVICE_PRIVATE:
  31  * Device memory that is not directly addressable by the CPU: CPU can neither
  32  * read nor write private memory. In this case, we do still have struct pages
  33  * backing the device memory. Doing so simplifies the implementation, but it is
  34  * important to remember that there are certain points at which the struct page
  35  * must be treated as an opaque object, rather than a "normal" struct page.
  36  *
  37  * A more complete discussion of unaddressable memory may be found in
  38  * include/linux/hmm.h and Documentation/vm/hmm.rst.
  39  *
  40  * MEMORY_DEVICE_FS_DAX:
  41  * Host memory that has similar access semantics as System RAM i.e. DMA
  42  * coherent and supports page pinning. In support of coordinating page
  43  * pinning vs other operations MEMORY_DEVICE_FS_DAX arranges for a
  44  * wakeup event whenever a page is unpinned and becomes idle. This
  45  * wakeup is used to coordinate physical address space management (ex:
  46  * fs truncate/hole punch) vs pinned pages (ex: device dma).
  47  *
  48  * MEMORY_DEVICE_DEVDAX:
  49  * Host memory that has similar access semantics as System RAM i.e. DMA
  50  * coherent and supports page pinning. In contrast to
  51  * MEMORY_DEVICE_FS_DAX, this memory is access via a device-dax
  52  * character device.
  53  *
  54  * MEMORY_DEVICE_PCI_P2PDMA:
  55  * Device memory residing in a PCI BAR intended for use with Peer-to-Peer
  56  * transactions.
  57  */
  58 enum memory_type {
  59         /* 0 is reserved to catch uninitialized type fields */
  60         MEMORY_DEVICE_PRIVATE = 1,
  61         MEMORY_DEVICE_FS_DAX,
  62         MEMORY_DEVICE_DEVDAX,
  63         MEMORY_DEVICE_PCI_P2PDMA,
  64 };
  65
  66 struct dev_pagemap_ops {
  67         /*
  68          * Called once the page refcount reaches 1.  (ZONE_DEVICE pages never
  69          * reach 0 refcount unless there is a refcount bug. This allows the
  70          * device driver to implement its own memory management.)
  71          */
  72         void (*page_free)(struct page *page);
  73
  74         /*
  75          * Transition the refcount in struct dev_pagemap to the dead state.
  76          */
  77         void (*kill)(struct dev_pagemap *pgmap);
  78
  79         /*
  80          * Wait for refcount in struct dev_pagemap to be idle and reap it.
  81          */
  82         void (*cleanup)(struct dev_pagemap *pgmap);
  83
  84         /*
  85          * Used for private (un-addressable) device memory only.  Must migrate
  86          * the page back to a CPU accessible page.
  87          */
  88         vm_fault_t (*migrate_to_ram)(struct vm_fault *vmf);
  89 };
  90
  91 #define PGMAP_ALTMAP_VALID      (1 << 0)
  92
  93 /**
  94  * struct dev_pagemap - metadata for ZONE_DEVICE mappings
  95  * @altmap: pre-allocated/reserved memory for vmemmap allocations
  96  * @res: physical address range covered by @ref
  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  * @dev: host device of the mapping for debug
 101  * @data: private data pointer for page_free()
 102  * @type: memory type: see MEMORY_* in memory_hotplug.h
 103  * @flags: PGMAP_* flags to specify defailed behavior
 104  * @ops: method table
 105  */
 106 struct dev_pagemap {
 107         struct vmem_altmap altmap;
 108         struct resource res;
 109         struct percpu_ref *ref;
 110         struct percpu_ref internal_ref;
 111         struct completion done;
 112         struct device *dev;
 113         enum memory_type type;
 114         unsigned int flags;
 115         u64 pci_p2pdma_bus_offset;
 116         const struct dev_pagemap_ops *ops;
 117 };
 118
 119 static inline struct vmem_altmap *pgmap_altmap(struct dev_pagemap *pgmap)
 120 {
 121         if (pgmap->flags & PGMAP_ALTMAP_VALID)
 122                 return &pgmap->altmap;
 123         return NULL;
 124 }
 125
 126 #ifdef CONFIG_ZONE_DEVICE
 127 void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
 128 void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap);
 129 struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
 130                 struct dev_pagemap *pgmap);
 131
 132 unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
 133 void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
 134 #else
 135 static inline void *devm_memremap_pages(struct device *dev,
 136                 struct dev_pagemap *pgmap)
 137 {
 138         /*
 139          * Fail attempts to call devm_memremap_pages() without
 140          * ZONE_DEVICE support enabled, this requires callers to fall
 141          * back to plain devm_memremap() based on config
 142          */
 143         WARN_ON_ONCE(1);
 144         return ERR_PTR(-ENXIO);
 145 }
 146
 147 static inline void devm_memunmap_pages(struct device *dev,
 148                 struct dev_pagemap *pgmap)
 149 {
 150 }
 151
 152 static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
 153                 struct dev_pagemap *pgmap)
 154 {
 155         return NULL;
 156 }
 157
 158 static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
 159 {
 160         return 0;
 161 }
 162
 163 static inline void vmem_altmap_free(struct vmem_altmap *altmap,
 164                 unsigned long nr_pfns)
 165 {
 166 }
 167 #endif /* CONFIG_ZONE_DEVICE */
 168
 169 static inline void put_dev_pagemap(struct dev_pagemap *pgmap)
 170 {
 171         if (pgmap)
 172                 percpu_ref_put(pgmap->ref);
 173 }
 174 #endif /* _LINUX_MEMREMAP_H_ */