linux/arch/arm64/include/asm/page.h
Jungseok Lee c79b954bf6 arm64: mm: Implement 4 levels of translation tables
This patch implements 4 levels of translation tables since 3 levels
of page tables with 4KB pages cannot support 40-bit physical address
space described in [1] due to the following issue.

It is a restriction that kernel logical memory map with 4KB + 3 levels
(0xffffffc000000000-0xffffffffffffffff) cannot cover RAM region from
544GB to 1024GB in [1]. Specifically, ARM64 kernel fails to create
mapping for this region in map_mem function since __phys_to_virt for
this region reaches to address overflow.

If SoC design follows the document, [1], over 32GB RAM would be placed
from 544GB. Even 64GB system is supposed to use the region from 544GB
to 576GB for only 32GB RAM. Naturally, it would reach to enable 4 levels
of page tables to avoid hacking __virt_to_phys and __phys_to_virt.

However, it is recommended 4 levels of page table should be only enabled
if memory map is too sparse or there is about 512GB RAM.

References
----------
[1]: Principles of ARM Memory Maps, White Paper, Issue C

Signed-off-by: Jungseok Lee <jays.lee@samsung.com>
Reviewed-by: Sungjinn Chung <sungjinn.chung@samsung.com>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Reviewed-by: Steve Capper <steve.capper@linaro.org>
[catalin.marinas@arm.com: MEMBLOCK_INITIAL_LIMIT removed, same as PUD_SIZE]
[catalin.marinas@arm.com: early_ioremap_init() updated for 4 levels]
[catalin.marinas@arm.com: 48-bit VA depends on BROKEN until KVM is fixed]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Jungseok Lee <jungseoklee85@gmail.com>
2014-07-23 15:27:40 +01:00

84 lines
2.4 KiB
C

/*
* Based on arch/arm/include/asm/page.h
*
* Copyright (C) 1995-2003 Russell King
* Copyright (C) 2012 ARM Ltd.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* 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.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef __ASM_PAGE_H
#define __ASM_PAGE_H
/* PAGE_SHIFT determines the page size */
#ifdef CONFIG_ARM64_64K_PAGES
#define PAGE_SHIFT 16
#else
#define PAGE_SHIFT 12
#endif
#define PAGE_SIZE (_AC(1,UL) << PAGE_SHIFT)
#define PAGE_MASK (~(PAGE_SIZE-1))
/* We do define AT_SYSINFO_EHDR but don't use the gate mechanism */
#define __HAVE_ARCH_GATE_AREA 1
/*
* The idmap and swapper page tables need some space reserved in the kernel
* image. Both require pgd, pud (4 levels only) and pmd tables to (section)
* map the kernel. The swapper also maps the FDT (see __create_page_tables for
* more information).
*/
#ifdef CONFIG_ARM64_4_LEVELS
#define SWAPPER_DIR_SIZE (3 * PAGE_SIZE)
#define IDMAP_DIR_SIZE (3 * PAGE_SIZE)
#else
#define SWAPPER_DIR_SIZE (2 * PAGE_SIZE)
#define IDMAP_DIR_SIZE (2 * PAGE_SIZE)
#endif
#ifndef __ASSEMBLY__
#ifdef CONFIG_ARM64_2_LEVELS
#include <asm/pgtable-2level-types.h>
#elif defined(CONFIG_ARM64_3_LEVELS)
#include <asm/pgtable-3level-types.h>
#else
#include <asm/pgtable-4level-types.h>
#endif
extern void __cpu_clear_user_page(void *p, unsigned long user);
extern void __cpu_copy_user_page(void *to, const void *from,
unsigned long user);
extern void copy_page(void *to, const void *from);
extern void clear_page(void *to);
#define clear_user_page(addr,vaddr,pg) __cpu_clear_user_page(addr, vaddr)
#define copy_user_page(to,from,vaddr,pg) __cpu_copy_user_page(to, from, vaddr)
typedef struct page *pgtable_t;
#ifdef CONFIG_HAVE_ARCH_PFN_VALID
extern int pfn_valid(unsigned long);
#endif
#include <asm/memory.h>
#endif /* !__ASSEMBLY__ */
#define VM_DATA_DEFAULT_FLAGS \
(((current->personality & READ_IMPLIES_EXEC) ? VM_EXEC : 0) | \
VM_READ | VM_WRITE | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
#include <asm-generic/getorder.h>
#endif