1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _LINUX_MEMREMAP_H_ 3 #define _LINUX_MEMREMAP_H_ 4 #include <linux/mm.h> 5 #include <linux/ioport.h> 6 #include <linux/percpu-refcount.h> 7 8 #include <asm/pgtable.h> 9 10 struct resource; 11 struct device; 12 13 /** 14 * struct vmem_altmap - pre-allocated storage for vmemmap_populate 15 * @base_pfn: base of the entire dev_pagemap mapping 16 * @reserve: pages mapped, but reserved for driver use (relative to @base) 17 * @free: free pages set aside in the mapping for memmap storage 18 * @align: pages reserved to meet allocation alignments 19 * @alloc: track pages consumed, private to vmemmap_populate() 20 */ 21 struct vmem_altmap { 22 const unsigned long base_pfn; 23 const unsigned long reserve; 24 unsigned long free; 25 unsigned long align; 26 unsigned long alloc; 27 }; 28 29 unsigned long vmem_altmap_offset(struct vmem_altmap *altmap); 30 void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns); 31 32 #ifdef CONFIG_ZONE_DEVICE 33 struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start); 34 #else 35 static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start) 36 { 37 return NULL; 38 } 39 #endif 40 41 /* 42 * Specialize ZONE_DEVICE memory into multiple types each having differents 43 * usage. 44 * 45 * MEMORY_DEVICE_HOST: 46 * Persistent device memory (pmem): struct page might be allocated in different 47 * memory and architecture might want to perform special actions. It is similar 48 * to regular memory, in that the CPU can access it transparently. However, 49 * it is likely to have different bandwidth and latency than regular memory. 50 * See Documentation/nvdimm/nvdimm.txt for more information. 51 * 52 * MEMORY_DEVICE_PRIVATE: 53 * Device memory that is not directly addressable by the CPU: CPU can neither 54 * read nor write private memory. In this case, we do still have struct pages 55 * backing the device memory. Doing so simplifies the implementation, but it is 56 * important to remember that there are certain points at which the struct page 57 * must be treated as an opaque object, rather than a "normal" struct page. 58 * 59 * A more complete discussion of unaddressable memory may be found in 60 * include/linux/hmm.h and Documentation/vm/hmm.txt. 61 * 62 * MEMORY_DEVICE_PUBLIC: 63 * Device memory that is cache coherent from device and CPU point of view. This 64 * is use on platform that have an advance system bus (like CAPI or CCIX). A 65 * driver can hotplug the device memory using ZONE_DEVICE and with that memory 66 * type. Any page of a process can be migrated to such memory. However no one 67 * should be allow to pin such memory so that it can always be evicted. 68 */ 69 enum memory_type { 70 MEMORY_DEVICE_HOST = 0, 71 MEMORY_DEVICE_PRIVATE, 72 MEMORY_DEVICE_PUBLIC, 73 }; 74 75 /* 76 * For MEMORY_DEVICE_PRIVATE we use ZONE_DEVICE and extend it with two 77 * callbacks: 78 * page_fault() 79 * page_free() 80 * 81 * Additional notes about MEMORY_DEVICE_PRIVATE may be found in 82 * include/linux/hmm.h and Documentation/vm/hmm.txt. There is also a brief 83 * explanation in include/linux/memory_hotplug.h. 84 * 85 * The page_fault() callback must migrate page back, from device memory to 86 * system memory, so that the CPU can access it. This might fail for various 87 * reasons (device issues, device have been unplugged, ...). When such error 88 * conditions happen, the page_fault() callback must return VM_FAULT_SIGBUS and 89 * set the CPU page table entry to "poisoned". 90 * 91 * Note that because memory cgroup charges are transferred to the device memory, 92 * this should never fail due to memory restrictions. However, allocation 93 * of a regular system page might still fail because we are out of memory. If 94 * that happens, the page_fault() callback must return VM_FAULT_OOM. 95 * 96 * The page_fault() callback can also try to migrate back multiple pages in one 97 * chunk, as an optimization. It must, however, prioritize the faulting address 98 * over all the others. 99 * 100 * 101 * The page_free() callback is called once the page refcount reaches 1 102 * (ZONE_DEVICE pages never reach 0 refcount unless there is a refcount bug. 103 * This allows the device driver to implement its own memory management.) 104 * 105 * For MEMORY_DEVICE_PUBLIC only the page_free() callback matter. 106 */ 107 typedef int (*dev_page_fault_t)(struct vm_area_struct *vma, 108 unsigned long addr, 109 const struct page *page, 110 unsigned int flags, 111 pmd_t *pmdp); 112 typedef void (*dev_page_free_t)(struct page *page, void *data); 113 114 /** 115 * struct dev_pagemap - metadata for ZONE_DEVICE mappings 116 * @page_fault: callback when CPU fault on an unaddressable device page 117 * @page_free: free page callback when page refcount reaches 1 118 * @altmap: pre-allocated/reserved memory for vmemmap allocations 119 * @res: physical address range covered by @ref 120 * @ref: reference count that pins the devm_memremap_pages() mapping 121 * @dev: host device of the mapping for debug 122 * @data: private data pointer for page_free() 123 * @type: memory type: see MEMORY_* in memory_hotplug.h 124 */ 125 struct dev_pagemap { 126 dev_page_fault_t page_fault; 127 dev_page_free_t page_free; 128 struct vmem_altmap *altmap; 129 const struct resource *res; 130 struct percpu_ref *ref; 131 struct device *dev; 132 void *data; 133 enum memory_type type; 134 }; 135 136 #ifdef CONFIG_ZONE_DEVICE 137 void *devm_memremap_pages(struct device *dev, struct resource *res, 138 struct percpu_ref *ref, struct vmem_altmap *altmap); 139 struct dev_pagemap *find_dev_pagemap(resource_size_t phys); 140 141 static inline bool is_zone_device_page(const struct page *page); 142 #else 143 static inline void *devm_memremap_pages(struct device *dev, 144 struct resource *res, struct percpu_ref *ref, 145 struct vmem_altmap *altmap) 146 { 147 /* 148 * Fail attempts to call devm_memremap_pages() without 149 * ZONE_DEVICE support enabled, this requires callers to fall 150 * back to plain devm_memremap() based on config 151 */ 152 WARN_ON_ONCE(1); 153 return ERR_PTR(-ENXIO); 154 } 155 156 static inline struct dev_pagemap *find_dev_pagemap(resource_size_t phys) 157 { 158 return NULL; 159 } 160 #endif 161 162 #if defined(CONFIG_DEVICE_PRIVATE) || defined(CONFIG_DEVICE_PUBLIC) 163 static inline bool is_device_private_page(const struct page *page) 164 { 165 return is_zone_device_page(page) && 166 page->pgmap->type == MEMORY_DEVICE_PRIVATE; 167 } 168 169 static inline bool is_device_public_page(const struct page *page) 170 { 171 return is_zone_device_page(page) && 172 page->pgmap->type == MEMORY_DEVICE_PUBLIC; 173 } 174 #endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */ 175 176 /** 177 * get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn 178 * @pfn: page frame number to lookup page_map 179 * @pgmap: optional known pgmap that already has a reference 180 * 181 * @pgmap allows the overhead of a lookup to be bypassed when @pfn lands in the 182 * same mapping. 183 */ 184 static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn, 185 struct dev_pagemap *pgmap) 186 { 187 const struct resource *res = pgmap ? pgmap->res : NULL; 188 resource_size_t phys = PFN_PHYS(pfn); 189 190 /* 191 * In the cached case we're already holding a live reference so 192 * we can simply do a blind increment 193 */ 194 if (res && phys >= res->start && phys <= res->end) { 195 percpu_ref_get(pgmap->ref); 196 return pgmap; 197 } 198 199 /* fall back to slow path lookup */ 200 rcu_read_lock(); 201 pgmap = find_dev_pagemap(phys); 202 if (pgmap && !percpu_ref_tryget_live(pgmap->ref)) 203 pgmap = NULL; 204 rcu_read_unlock(); 205 206 return pgmap; 207 } 208 209 static inline void put_dev_pagemap(struct dev_pagemap *pgmap) 210 { 211 if (pgmap) 212 percpu_ref_put(pgmap->ref); 213 } 214 #endif /* _LINUX_MEMREMAP_H_ */ 215