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_ */ 214