xref: /qemu/migration/page_cache.h (revision 27af7d6ea5015e5ef1f7985eab94a8a218267a2b)

/*
 * Page cache for QEMU
 * The cache is base on a hash of the page address
 *
 * Copyright 2012 Red Hat, Inc. and/or its affiliates
 *
 * Authors:
 *  Orit Wasserman  <owasserm@redhat.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or later.
 * See the COPYING file in the top-level directory.
 *
 */

#ifndef PAGE_CACHE_H
#define PAGE_CACHE_H

/* Page cache for storing guest pages */
typedef struct PageCache PageCache;

/**
 * cache_init: Initialize the page cache
 *
 *
 * Returns new allocated cache or NULL on error
 *
 * @cache pointer to the PageCache struct
 * @num_pages: cache maximal number of cached pages
 * @page_size: cache page size
 */
PageCache *cache_init(int64_t num_pages, unsigned int page_size);

/**
 * cache_fini: free all cache resources
 * @cache pointer to the PageCache struct
 */
void cache_fini(PageCache *cache);

/**
 * cache_is_cached: Checks to see if the page is cached
 *
 * Returns %true if page is cached
 *
 * @cache pointer to the PageCache struct
 * @addr: page addr
 * @current_age: current bitmap generation
 */
bool cache_is_cached(const PageCache *cache, uint64_t addr,
                     uint64_t current_age);

/**
 * get_cached_data: Get the data cached for an addr
 *
 * Returns pointer to the data cached or NULL if not cached
 *
 * @cache pointer to the PageCache struct
 * @addr: page addr
 */
uint8_t *get_cached_data(const PageCache *cache, uint64_t addr);

/**
 * cache_insert: insert the page into the cache. the page cache
 * will dup the data on insert. the previous value will be overwritten
 *
 * Returns -1 when the page isn't inserted into cache
 *
 * @cache pointer to the PageCache struct
 * @addr: page address
 * @pdata: pointer to the page
 * @current_age: current bitmap generation
 */
int cache_insert(PageCache *cache, uint64_t addr, const uint8_t *pdata,
                 uint64_t current_age);

/**
 * cache_resize: resize the page cache. In case of size reduction the extra
 * pages will be freed
 *
 * Returns -1 on error new cache size on success
 *
 * @cache pointer to the PageCache struct
 * @num_pages: new page cache size (in pages)
 */
int64_t cache_resize(PageCache *cache, int64_t num_pages);

#endif