From c79b954bf6c006f2d3dd9d01f231abeead13a410 Mon Sep 17 00:00:00 2001 From: Jungseok Lee Date: Mon, 12 May 2014 18:40:51 +0900 Subject: 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 Reviewed-by: Sungjinn Chung Acked-by: Kukjin Kim Reviewed-by: Christoffer Dall Reviewed-by: Steve Capper [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 Tested-by: Jungseok Lee --- arch/arm64/Kconfig | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'arch/arm64/Kconfig') diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 94ba45b198f..cf07cc7295b 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -195,12 +195,17 @@ config ARM64_VA_BITS_42 bool "42-bit" depends on ARM64_64K_PAGES +config ARM64_VA_BITS_48 + bool "48-bit" + depends on BROKEN + endchoice config ARM64_VA_BITS int default 39 if ARM64_VA_BITS_39 default 42 if ARM64_VA_BITS_42 + default 48 if ARM64_VA_BITS_48 config ARM64_2_LEVELS def_bool y if ARM64_64K_PAGES && ARM64_VA_BITS_42 @@ -208,6 +213,9 @@ config ARM64_2_LEVELS config ARM64_3_LEVELS def_bool y if ARM64_4K_PAGES && ARM64_VA_BITS_39 +config ARM64_4_LEVELS + def_bool y if ARM64_4K_PAGES && ARM64_VA_BITS_48 + config CPU_BIG_ENDIAN bool "Build big-endian kernel" help -- cgit v1.2.3-70-g09d2