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/*
* Copyright 2016 Red Hat Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* Authors: Jérôme Glisse <jglisse@redhat.com>
*/
/*
* Generic page table structure with adjustable depth. This is unlike regular
* CPU page table use on many architecture. It is more like radix tree but it
* uses full pages and offers more bits for flags per entry.
*
* Note that resizing it (increase its depth) is something relatively easy to
* add in case someone cares.
*
* Note that we use the private field of root struct page to store the number
* of levels as well as the pfn_shift values. Moreover we use _mapcount field
* to count number of valid entry inside each directory.
*/
#ifndef _LINUX_GPT_H
#define _LINUX_GPT_H
#include <linux/mm_types.h>
#include <linux/spinlock.h>
#include <linux/gfp.h>
#ifdef CONFIG_HIGHMEM64G
#define gte_t uint64_t
#else /* CONFIG_HIGHMEM64G */
#define gte_t unsigned long
#endif /* CONFIG_HIGHMEM64G */
/* 6 level on 64 bits arch with PAGE_SHIFT=12 means 66bits of address space */
#define GPT_MAX_LEVEL 6
struct gpt {
unsigned long start;
unsigned long end;
unsigned long *gdp;
atomic_t refcount;
spinlock_t lock;
uint8_t nlevels;
uint8_t shift;
uint8_t valid_bit;
};
struct gpt *gpt_alloc(unsigned long start,
unsigned long end,
uint8_t shift,
uint8_t valid_bit);
void gpt_free(struct gpt *gpt);
struct gpt_walk {
struct gpt *gpt;
unsigned long start;
unsigned long end;
struct page *gtd[GPT_MAX_LEVEL];
gte_t *gte[GPT_MAX_LEVEL];
};
void gpt_walk_init(struct gpt_walk *walk, struct gpt *gpt);
void gpt_walk_fini(struct gpt_walk *walk);
gte_t *gpt_walk_gtep_from_addr(struct gpt_walk *walk, unsigned long addr);
gte_t *gpt_walk_populate(struct gpt_walk *walk, unsigned long addr);
void gpt_walk_prune(struct gpt_walk *walk,
unsigned long start,
unsigned long end);
typedef int (*gpt_walk_cb_t)(struct gpt_walk *walk,
unsigned long addr,
unsigned long end,
spinlock_t *gtl,
gte_t *gtep,
void *private);
int gpt_walk_range(struct gpt_walk *walk,
unsigned long start,
unsigned long end,
gpt_walk_cb_t cb,
void *private);
/* gpt_walk_gtd_refcount - pointer to atomic use to count valid directory entry
* @walk: walk structure from which to extract directory level
* @level: level for the refcount (0 is the lowest level)
* Returns: pointer to refcount atomic or NULL if directory level is empty
*
* To know when we can prune (free) a directory we count number of valid entry
* and this for all directory levels.
*/
static inline atomic_t *gpt_walk_gtd_refcount(struct gpt_walk *walk,
unsigned level)
{
BUG_ON(level > walk->gpt->nlevels);
if (walk->gpt->nlevels && (level < walk->gpt->nlevels)) {
if (walk->gtd[level])
return &walk->gtd[level]->_mapcount;
return NULL;
}
return &walk->gpt->refcount;
}
/* gpt_walk_gtd_lock_ptr - spinlock pointer for given directory level
* @walk: walk structure with current directory hierarchy
* @level: level to lock (0 is the lowest level and gpt->nlevels the highest)
* Returns: spinlock pointer for given level, NULL if directory level is empty
*
* To provide fine granularity locking to generic page table we use the struct
* page spinlock. This helper just provide a pointer to the appropriate lock
* for a given directory level.
*/
static inline spinlock_t *gpt_walk_gtd_lock_ptr(struct gpt_walk *walk,
unsigned level)
{
BUG_ON(level > walk->gpt->nlevels);
if (walk->gpt->nlevels && (level < walk->gpt->nlevels)) {
if (walk->gtd[level])
return ptlock_ptr(walk->gtd[level]);
return NULL;
}
return &walk->gpt->lock;
}
#endif /* _LINUX_GPT_H */
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