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/* SPDX-License-Identifier: GPL-2.0 */
* highmem.h: virtual kernel memory mappings for high memory
* Used in CONFIG_HIGHMEM systems for memory pages which
* are not addressable by direct kernel virtual addresses.
* Copyright (C) 1999 Gerhard Wichert, Siemens AG
* Redesigned the x86 32-bit VM architecture to deal with
* up to 16 Terabyte physical memory. With current x86 CPUs
* we now support up to 64 Gigabytes physical RAM.
* Copyright (C) 1999 Ingo Molnar <>
#ifndef _ASM_X86_HIGHMEM_H
#define _ASM_X86_HIGHMEM_H
#ifdef __KERNEL__
#include <linux/interrupt.h>
#include <linux/threads.h>
#include <asm/kmap_types.h>
#include <asm/tlbflush.h>
#include <asm/paravirt.h>
#include <asm/fixmap.h>
/* declarations for highmem.c */
extern unsigned long highstart_pfn, highend_pfn;
* Right now we initialize only a single pte table. It can be extended
* easily, subsequent pte tables have to be allocated in one physical
* chunk of RAM.
* Ordering is:
* high memory on: high_memory off:
* fixed addresses fixed addresses
* temp fixed addresses/persistent kmap area VMALLOC_END
* PKMAP_BASE temp fixed addresses/vmalloc area
* vmalloc area high_memory
* high_memory
* The temp fixed area is only used during boot for early_ioremap(), and
* it is unused when the ioremap() is functional. vmalloc/pkmap area become
* available after early boot so the temp fixed area is available for re-use.
#define PKMAP_NR(virt) ((virt-PKMAP_BASE) >> PAGE_SHIFT)
#define PKMAP_ADDR(nr) (PKMAP_BASE + ((nr) << PAGE_SHIFT))
extern void *kmap_high(struct page *page);
extern void kunmap_high(struct page *page);
void *kmap(struct page *page);
void kunmap(struct page *page);
void *kmap_atomic_prot(struct page *page, pgprot_t prot);
void *kmap_atomic(struct page *page);
void __kunmap_atomic(void *kvaddr);
void *kmap_atomic_pfn(unsigned long pfn);
void *kmap_atomic_prot_pfn(unsigned long pfn, pgprot_t prot);
#define flush_cache_kmaps() do { } while (0)
extern void add_highpages_with_active_regions(int nid, unsigned long start_pfn,
unsigned long end_pfn);
#endif /* __KERNEL__ */
#endif /* _ASM_X86_HIGHMEM_H */