arm64: MMU definitions

The virtual memory layout is described in
Documentation/arm64/memory.txt. This patch adds the MMU definitions for
the 4KB and 64KB translation table configurations. The SECTION_SIZE is
2MB with 4KB page and 512MB with 64KB page configuration.

PHYS_OFFSET is calculated at run-time and stored in a variable (no
run-time code patching at this stage).

On the current implementation, both user and kernel address spaces are
512G (39-bit) each with a maximum of 256G for the RAM linear mapping.
Linux uses 3 levels of translation tables with the 4K page configuration
and 2 levels with the 64K configuration. Extending the memory space
beyond 39-bit with the 4K pages or 42-bit with 64K pages requires an
additional level of translation tables.

The SPARSEMEM configuration is global to all AArch64 platforms and
allows for 1GB sections with SPARSEMEM_VMEMMAP enabled by default.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 43 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/pgtable-2level-hwdef.h b/arch/arm64/include/asm/pgtable-2level-hwdef.h
new file mode 100644
index 000000000000..0a8ed3f94e93
--- /dev/null
+++ b/arch/arm64/include/asm/pgtable-2level-hwdef.h
@@ -0,0 +1,43 @@
+/*
+ * 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