1. 根目录:
2. arch
3. arm64
4. include
5. asm
6. pgtable-2level-hwdef.h

/*
 * 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_PGTABLE_2LEVEL_HWDEF_H
#define __ASM_PGTABLE_2LEVEL_HWDEF_H

/*
 * With LPAE and 64KB pages, there are 2 levels of page tables. Each level has
 * 8192 entries of 8 bytes each, occupying a 64KB page. Levels 0 and 1 are not
 * used. The 2nd level table (PGD for Linux) can cover a range of 4TB, each
 * entry representing 512MB. The user and kernel address spaces are limited to
 * 512GB and therefore we only use 1024 entries in the PGD.
 */
#define PTRS_PER_PTE		8192
#define PTRS_PER_PGD		1024

/*
 * PGDIR_SHIFT determines the size a top-level page table entry can map.
 */
#define PGDIR_SHIFT		29
#define PGDIR_SIZE		(_AC(1, UL) << PGDIR_SHIFT)
#define PGDIR_MASK		(~(PGDIR_SIZE-1))

/*
 * section address mask and size definitions.
 */
#define SECTION_SHIFT		29
#define SECTION_SIZE		(_AC(1, UL) << SECTION_SHIFT)
#define SECTION_MASK		(~(SECTION_SIZE-1))

#endif