diff options
Diffstat (limited to 'include/linux/memremap.h')
| -rw-r--r-- | include/linux/memremap.h | 99 |
1 files changed, 99 insertions, 0 deletions
diff --git a/include/linux/memremap.h b/include/linux/memremap.h index 93416196ba64..79f8ba7c3894 100644 --- a/include/linux/memremap.h +++ b/include/linux/memremap.h @@ -4,6 +4,8 @@ #include <linux/ioport.h> #include <linux/percpu-refcount.h> +#include <asm/pgtable.h> + struct resource; struct device; @@ -35,24 +37,107 @@ static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start) } #endif +/* + * Specialize ZONE_DEVICE memory into multiple types each having differents + * usage. + * + * MEMORY_DEVICE_HOST: + * Persistent device memory (pmem): struct page might be allocated in different + * memory and architecture might want to perform special actions. It is similar + * to regular memory, in that the CPU can access it transparently. However, + * it is likely to have different bandwidth and latency than regular memory. + * See Documentation/nvdimm/nvdimm.txt for more information. + * + * MEMORY_DEVICE_PRIVATE: + * Device memory that is not directly addressable by the CPU: CPU can neither + * read nor write private memory. In this case, we do still have struct pages + * backing the device memory. Doing so simplifies the implementation, but it is + * important to remember that there are certain points at which the struct page + * must be treated as an opaque object, rather than a "normal" struct page. + * + * A more complete discussion of unaddressable memory may be found in + * include/linux/hmm.h and Documentation/vm/hmm.txt. + * + * MEMORY_DEVICE_PUBLIC: + * Device memory that is cache coherent from device and CPU point of view. This + * is use on platform that have an advance system bus (like CAPI or CCIX). A + * driver can hotplug the device memory using ZONE_DEVICE and with that memory + * type. Any page of a process can be migrated to such memory. However no one + * should be allow to pin such memory so that it can always be evicted. + */ +enum memory_type { + MEMORY_DEVICE_HOST = 0, + MEMORY_DEVICE_PRIVATE, + MEMORY_DEVICE_PUBLIC, +}; + +/* + * For MEMORY_DEVICE_PRIVATE we use ZONE_DEVICE and extend it with two + * callbacks: + * page_fault() + * page_free() + * + * Additional notes about MEMORY_DEVICE_PRIVATE may be found in + * include/linux/hmm.h and Documentation/vm/hmm.txt. There is also a brief + * explanation in include/linux/memory_hotplug.h. + * + * The page_fault() callback must migrate page back, from device memory to + * system memory, so that the CPU can access it. This might fail for various + * reasons (device issues, device have been unplugged, ...). When such error + * conditions happen, the page_fault() callback must return VM_FAULT_SIGBUS and + * set the CPU page table entry to "poisoned". + * + * Note that because memory cgroup charges are transferred to the device memory, + * this should never fail due to memory restrictions. However, allocation + * of a regular system page might still fail because we are out of memory. If + * that happens, the page_fault() callback must return VM_FAULT_OOM. + * + * The page_fault() callback can also try to migrate back multiple pages in one + * chunk, as an optimization. It must, however, prioritize the faulting address + * over all the others. + * + * + * The page_free() callback is called once the page refcount reaches 1 + * (ZONE_DEVICE pages never reach 0 refcount unless there is a refcount bug. + * This allows the device driver to implement its own memory management.) + * + * For MEMORY_DEVICE_PUBLIC only the page_free() callback matter. + */ +typedef int (*dev_page_fault_t)(struct vm_area_struct *vma, + unsigned long addr, + const struct page *page, + unsigned int flags, + pmd_t *pmdp); +typedef void (*dev_page_free_t)(struct page *page, void *data); + /** * struct dev_pagemap - metadata for ZONE_DEVICE mappings + * @page_fault: callback when CPU fault on an unaddressable device page + * @page_free: free page callback when page refcount reaches 1 * @altmap: pre-allocated/reserved memory for vmemmap allocations * @res: physical address range covered by @ref * @ref: reference count that pins the devm_memremap_pages() mapping * @dev: host device of the mapping for debug + * @data: private data pointer for page_free() + * @type: memory type: see MEMORY_* in memory_hotplug.h */ struct dev_pagemap { + dev_page_fault_t page_fault; + dev_page_free_t page_free; struct vmem_altmap *altmap; const struct resource *res; struct percpu_ref *ref; struct device *dev; + void *data; + enum memory_type type; }; #ifdef CONFIG_ZONE_DEVICE void *devm_memremap_pages(struct device *dev, struct resource *res, struct percpu_ref *ref, struct vmem_altmap *altmap); struct dev_pagemap *find_dev_pagemap(resource_size_t phys); + +static inline bool is_zone_device_page(const struct page *page); #else static inline void *devm_memremap_pages(struct device *dev, struct resource *res, struct percpu_ref *ref, @@ -73,6 +158,20 @@ static inline struct dev_pagemap *find_dev_pagemap(resource_size_t phys) } #endif +#if defined(CONFIG_DEVICE_PRIVATE) || defined(CONFIG_DEVICE_PUBLIC) +static inline bool is_device_private_page(const struct page *page) +{ + return is_zone_device_page(page) && + page->pgmap->type == MEMORY_DEVICE_PRIVATE; +} + +static inline bool is_device_public_page(const struct page *page) +{ + return is_zone_device_page(page) && + page->pgmap->type == MEMORY_DEVICE_PUBLIC; +} +#endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */ + /** * get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn * @pfn: page frame number to lookup page_map |