include/linux/memremap.h

   1 #ifndef _LINUX_MEMREMAP_H_
   2 #define _LINUX_MEMREMAP_H_
   3 #include <linux/mm.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 unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
  29 void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
  30
  31 #ifdef CONFIG_ZONE_DEVICE
  32 struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start);
  33 #else
  34 static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
  35 {
  36         return NULL;
  37 }
  38 #endif
  39
  40 /*
  41  * Specialize ZONE_DEVICE memory into multiple types each having differents
  42  * usage.
  43  *
  44  * MEMORY_DEVICE_HOST:
  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.
  50  *
  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.
  57  *
  58  * A more complete discussion of unaddressable memory may be found in
  59  * include/linux/hmm.h and Documentation/vm/hmm.txt.
  60  *
  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.
  67  */
  68 enum memory_type {
  69         MEMORY_DEVICE_HOST = 0,
  70         MEMORY_DEVICE_PRIVATE,
  71         MEMORY_DEVICE_PUBLIC,
  72 };
  73
  74 /*
  75  * For MEMORY_DEVICE_PRIVATE we use ZONE_DEVICE and extend it with two
  76  * callbacks:
  77  *   page_fault()
  78  *   page_free()
  79  *
  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.
  83  *
  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".
  89  *
  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.
  94  *
  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.
  98  *
  99  *
 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.)
 103  *
 104  * For MEMORY_DEVICE_PUBLIC only the page_free() callback matter.
 105  */
 106 typedef int (*dev_page_fault_t)(struct vm_area_struct *vma,
 107                                 unsigned long addr,
 108                                 const struct page *page,
 109                                 unsigned int flags,
 110                                 pmd_t *pmdp);
 111 typedef void (*dev_page_free_t)(struct page *page, void *data);
 112
 113 /**
 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
 123  */
 124 struct dev_pagemap {
 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;
 130         struct device *dev;
 131         void *data;
 132         enum memory_type type;
 133 };
 134
 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);
 139
 140 static inline bool is_zone_device_page(const struct page *page);
 141 #else
 142 static inline void *devm_memremap_pages(struct device *dev,
 143                 struct resource *res, struct percpu_ref *ref,
 144                 struct vmem_altmap *altmap)
 145 {
 146         /*
 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
 150          */
 151         WARN_ON_ONCE(1);
 152         return ERR_PTR(-ENXIO);
 153 }
 154
 155 static inline struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
 156 {
 157         return NULL;
 158 }
 159 #endif
 160
 161 #if defined(CONFIG_DEVICE_PRIVATE) || defined(CONFIG_DEVICE_PUBLIC)
 162 static inline bool is_device_private_page(const struct page *page)
 163 {
 164         return is_zone_device_page(page) &&
 165                 page->pgmap->type == MEMORY_DEVICE_PRIVATE;
 166 }
 167
 168 static inline bool is_device_public_page(const struct page *page)
 169 {
 170         return is_zone_device_page(page) &&
 171                 page->pgmap->type == MEMORY_DEVICE_PUBLIC;
 172 }
 173 #endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
 174
 175 /**
 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
 179  *
 180  * @pgmap allows the overhead of a lookup to be bypassed when @pfn lands in the
 181  * same mapping.
 182  */
 183 static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
 184                 struct dev_pagemap *pgmap)
 185 {
 186         const struct resource *res = pgmap ? pgmap->res : NULL;
 187         resource_size_t phys = PFN_PHYS(pfn);
 188
 189         /*
 190          * In the cached case we're already holding a live reference so
 191          * we can simply do a blind increment
 192          */
 193         if (res && phys >= res->start && phys <= res->end) {
 194                 percpu_ref_get(pgmap->ref);
 195                 return pgmap;
 196         }
 197
 198         /* fall back to slow path lookup */
 199         rcu_read_lock();
 200         pgmap = find_dev_pagemap(phys);
 201         if (pgmap && !percpu_ref_tryget_live(pgmap->ref))
 202                 pgmap = NULL;
 203         rcu_read_unlock();
 204
 205         return pgmap;
 206 }
 207
 208 static inline void put_dev_pagemap(struct dev_pagemap *pgmap)
 209 {
 210         if (pgmap)
 211                 percpu_ref_put(pgmap->ref);
 212 }
 213 #endif /* _LINUX_MEMREMAP_H_ */