cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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balloon_compaction.h (6203B)

      1/* SPDX-License-Identifier: GPL-2.0 */
      2/*
      3 * include/linux/balloon_compaction.h
      4 *
      5 * Common interface definitions for making balloon pages movable by compaction.
      6 *
      7 * Balloon page migration makes use of the general non-lru movable page
      8 * feature.
      9 *
     10 * page->private is used to reference the responsible balloon device.
     11 * page->mapping is used in context of non-lru page migration to reference
     12 * the address space operations for page isolation/migration/compaction.
     13 *
     14 * As the page isolation scanning step a compaction thread does is a lockless
     15 * procedure (from a page standpoint), it might bring some racy situations while
     16 * performing balloon page compaction. In order to sort out these racy scenarios
     17 * and safely perform balloon's page compaction and migration we must, always,
     18 * ensure following these simple rules:
     19 *
     20 *   i. when updating a balloon's page ->mapping element, strictly do it under
     21 *      the following lock order, independently of the far superior
     22 *      locking scheme (lru_lock, balloon_lock):
     23 *	    +-page_lock(page);
     24 *	      +--spin_lock_irq(&b_dev_info->pages_lock);
     25 *	            ... page->mapping updates here ...
     26 *
     27 *  ii. isolation or dequeueing procedure must remove the page from balloon
     28 *      device page list under b_dev_info->pages_lock.
     29 *
     30 * The functions provided by this interface are placed to help on coping with
     31 * the aforementioned balloon page corner case, as well as to ensure the simple
     32 * set of exposed rules are satisfied while we are dealing with balloon pages
     33 * compaction / migration.
     34 *
     35 * Copyright (C) 2012, Red Hat, Inc.  Rafael Aquini <aquini@redhat.com>
     36 */
     37#ifndef _LINUX_BALLOON_COMPACTION_H
     38#define _LINUX_BALLOON_COMPACTION_H
     39#include <linux/pagemap.h>
     40#include <linux/page-flags.h>
     41#include <linux/migrate.h>
     42#include <linux/gfp.h>
     43#include <linux/err.h>
     44#include <linux/fs.h>
     45#include <linux/list.h>
     46
     47/*
     48 * Balloon device information descriptor.
     49 * This struct is used to allow the common balloon compaction interface
     50 * procedures to find the proper balloon device holding memory pages they'll
     51 * have to cope for page compaction / migration, as well as it serves the
     52 * balloon driver as a page book-keeper for its registered balloon devices.
     53 */
     54struct balloon_dev_info {
     55	unsigned long isolated_pages;	/* # of isolated pages for migration */
     56	spinlock_t pages_lock;		/* Protection to pages list */
     57	struct list_head pages;		/* Pages enqueued & handled to Host */
     58	int (*migratepage)(struct balloon_dev_info *, struct page *newpage,
     59			struct page *page, enum migrate_mode mode);
     60	struct inode *inode;
     61};
     62
     63extern struct page *balloon_page_alloc(void);
     64extern void balloon_page_enqueue(struct balloon_dev_info *b_dev_info,
     65				 struct page *page);
     66extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info);
     67extern size_t balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info,
     68				      struct list_head *pages);
     69extern size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info,
     70				     struct list_head *pages, size_t n_req_pages);
     71
     72static inline void balloon_devinfo_init(struct balloon_dev_info *balloon)
     73{
     74	balloon->isolated_pages = 0;
     75	spin_lock_init(&balloon->pages_lock);
     76	INIT_LIST_HEAD(&balloon->pages);
     77	balloon->migratepage = NULL;
     78	balloon->inode = NULL;
     79}
     80
     81#ifdef CONFIG_BALLOON_COMPACTION
     82extern const struct address_space_operations balloon_aops;
     83
     84/*
     85 * balloon_page_insert - insert a page into the balloon's page list and make
     86 *			 the page->private assignment accordingly.
     87 * @balloon : pointer to balloon device
     88 * @page    : page to be assigned as a 'balloon page'
     89 *
     90 * Caller must ensure the page is locked and the spin_lock protecting balloon
     91 * pages list is held before inserting a page into the balloon device.
     92 */
     93static inline void balloon_page_insert(struct balloon_dev_info *balloon,
     94				       struct page *page)
     95{
     96	__SetPageOffline(page);
     97	__SetPageMovable(page, balloon->inode->i_mapping);
     98	set_page_private(page, (unsigned long)balloon);
     99	list_add(&page->lru, &balloon->pages);
    100}
    101
    102/*
    103 * balloon_page_delete - delete a page from balloon's page list and clear
    104 *			 the page->private assignement accordingly.
    105 * @page    : page to be released from balloon's page list
    106 *
    107 * Caller must ensure the page is locked and the spin_lock protecting balloon
    108 * pages list is held before deleting a page from the balloon device.
    109 */
    110static inline void balloon_page_delete(struct page *page)
    111{
    112	__ClearPageOffline(page);
    113	__ClearPageMovable(page);
    114	set_page_private(page, 0);
    115	/*
    116	 * No touch page.lru field once @page has been isolated
    117	 * because VM is using the field.
    118	 */
    119	if (!PageIsolated(page))
    120		list_del(&page->lru);
    121}
    122
    123/*
    124 * balloon_page_device - get the b_dev_info descriptor for the balloon device
    125 *			 that enqueues the given page.
    126 */
    127static inline struct balloon_dev_info *balloon_page_device(struct page *page)
    128{
    129	return (struct balloon_dev_info *)page_private(page);
    130}
    131
    132static inline gfp_t balloon_mapping_gfp_mask(void)
    133{
    134	return GFP_HIGHUSER_MOVABLE;
    135}
    136
    137#else /* !CONFIG_BALLOON_COMPACTION */
    138
    139static inline void balloon_page_insert(struct balloon_dev_info *balloon,
    140				       struct page *page)
    141{
    142	__SetPageOffline(page);
    143	list_add(&page->lru, &balloon->pages);
    144}
    145
    146static inline void balloon_page_delete(struct page *page)
    147{
    148	__ClearPageOffline(page);
    149	list_del(&page->lru);
    150}
    151
    152static inline gfp_t balloon_mapping_gfp_mask(void)
    153{
    154	return GFP_HIGHUSER;
    155}
    156
    157#endif /* CONFIG_BALLOON_COMPACTION */
    158
    159/*
    160 * balloon_page_push - insert a page into a page list.
    161 * @head : pointer to list
    162 * @page : page to be added
    163 *
    164 * Caller must ensure the page is private and protect the list.
    165 */
    166static inline void balloon_page_push(struct list_head *pages, struct page *page)
    167{
    168	list_add(&page->lru, pages);
    169}
    170
    171/*
    172 * balloon_page_pop - remove a page from a page list.
    173 * @head : pointer to list
    174 * @page : page to be added
    175 *
    176 * Caller must ensure the page is private and protect the list.
    177 */
    178static inline struct page *balloon_page_pop(struct list_head *pages)
    179{
    180	struct page *page = list_first_entry_or_null(pages, struct page, lru);
    181
    182	if (!page)
    183		return NULL;
    184
    185	list_del(&page->lru);
    186	return page;
    187}
    188#endif /* _LINUX_BALLOON_COMPACTION_H */