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Release 4.16 include/linux/memremap.h

Directory: include/linux
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_MEMREMAP_H_

#define _LINUX_MEMREMAP_H_
#include <linux/mm.h>
#include <linux/ioport.h>
#include <linux/percpu-refcount.h>

#include <asm/pgtable.h>

struct resource;
struct device;

/**
 * struct vmem_altmap - pre-allocated storage for vmemmap_populate
 * @base_pfn: base of the entire dev_pagemap mapping
 * @reserve: pages mapped, but reserved for driver use (relative to @base)
 * @free: free pages set aside in the mapping for memmap storage
 * @align: pages reserved to meet allocation alignments
 * @alloc: track pages consumed, private to vmemmap_populate()
 */

struct vmem_altmap {
	
const unsigned long base_pfn;
	
const unsigned long reserve;
	
unsigned long free;
	
unsigned long align;
	
unsigned long alloc;
};

/*
 * 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;
	
bool altmap_valid;
	
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 dev_pagemap *pgmap);
struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
		struct dev_pagemap *pgmap);

unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);

static inline bool is_zone_device_page(const struct page *page);
#else

static inline void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap) { /* * Fail attempts to call devm_memremap_pages() without * ZONE_DEVICE support enabled, this requires callers to fall * back to plain devm_memremap() based on config */ WARN_ON_ONCE(1); return ERR_PTR(-ENXIO); }

Contributors

PersonTokensPropCommitsCommitProp
Dan J Williams2993.55%266.67%
Christoph Hellwig26.45%133.33%
Total31100.00%3100.00%


static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn, struct dev_pagemap *pgmap) { return NULL; }

Contributors

PersonTokensPropCommitsCommitProp
Dan J Williams1257.14%150.00%
Christoph Hellwig942.86%150.00%
Total21100.00%2100.00%


static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap) { return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig16100.00%1100.00%
Total16100.00%1100.00%


static inline void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns) { }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig15100.00%1100.00%
Total15100.00%1100.00%

#endif /* CONFIG_ZONE_DEVICE */ #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; }

Contributors

PersonTokensPropCommitsCommitProp
Jérôme Glisse27100.00%2100.00%
Total27100.00%2100.00%


static inline bool is_device_public_page(const struct page *page) { return is_zone_device_page(page) && page->pgmap->type == MEMORY_DEVICE_PUBLIC; }

Contributors

PersonTokensPropCommitsCommitProp
Jérôme Glisse27100.00%2100.00%
Total27100.00%2100.00%

#endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
static inline void put_dev_pagemap(struct dev_pagemap *pgmap) { if (pgmap) percpu_ref_put(pgmap->ref); }

Contributors

PersonTokensPropCommitsCommitProp
Dan J Williams23100.00%1100.00%
Total23100.00%1100.00%

#endif /* _LINUX_MEMREMAP_H_ */

Overall Contributors

PersonTokensPropCommitsCommitProp
Dan J Williams16540.64%325.00%
Jérôme Glisse16039.41%433.33%
Christoph Hellwig7718.97%325.00%
Logan Gunthorpe30.74%18.33%
Greg Kroah-Hartman10.25%18.33%
Total406100.00%12100.00%
Directory: include/linux
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