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>

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 94ba45b..cf07cc7 100644 (file)
--- 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

diff --git a/arch/arm64/include/asm/page.h b/arch/arm64/include/asm/page.h
index 1cbde27..cf9afa0 100644 (file)
--- a/arch/arm64/include/asm/page.h
+++ b/arch/arm64/include/asm/page.h
@@ -33,19 +33,26 @@
 
 /*
  * The idmap and swapper page tables need some space reserved in the kernel
- * image. Both require a pgd and a next level table to (section) map the
- * kernel. The the swapper also maps the FDT (see __create_page_tables for
+ * 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>
-#else
+#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);

diff --cc arch/arm64/include/asm/pgalloc.h
Simple merge

diff --cc arch/arm64/include/asm/pgtable-hwdef.h
Simple merge

diff --cc arch/arm64/include/asm/pgtable.h
Simple merge

diff --cc arch/arm64/include/asm/tlb.h
Simple merge

diff --cc arch/arm64/kernel/head.S
Simple merge

diff --cc arch/arm64/kernel/traps.c
Simple merge

diff --cc arch/arm64/mm/fault.c
Simple merge

diff --cc arch/arm64/mm/ioremap.c
Simple merge

diff --cc arch/arm64/mm/mmu.c
Simple merge