[PATCH v6 5/7] arm64: mm: Implement 4 levels of translation tables
Jungseok Lee
jays.lee at samsung.com
Mon May 12 02:40:51 PDT 2014
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
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Steve Capper <steve.capper at linaro.org>
Signed-off-by: Jungseok Lee <jays.lee at samsung.com>
Reviewed-by: Sungjinn Chung <sungjinn.chung at samsung.com>
Acked-by: Kukjin Kim <kgene.kim at samsung.com>
Reviewed-by: Christoffer Dall <christoffer.dall at linaro.org>
Reviewed-by: Steve Capper <steve.capper at linaro.org>
---
arch/arm64/Kconfig | 8 +++++
arch/arm64/include/asm/memblock.h | 6 ++++
arch/arm64/include/asm/page.h | 4 ++-
arch/arm64/include/asm/pgalloc.h | 20 ++++++++++++
arch/arm64/include/asm/pgtable-hwdef.h | 6 ++--
arch/arm64/include/asm/pgtable.h | 45 ++++++++++++++++++++++++++
arch/arm64/include/asm/tlb.h | 9 ++++++
arch/arm64/kernel/head.S | 54 +++++++++++++++++++++++++-------
arch/arm64/kernel/traps.c | 5 +++
arch/arm64/mm/fault.c | 1 +
arch/arm64/mm/mmu.c | 16 +++++++---
11 files changed, 156 insertions(+), 18 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 9a28cbe..adbb8ea 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -182,12 +182,17 @@ config ARM64_VA_BITS_42
bool "42-bit"
depends on ARM64_64K_PAGES
+config ARM64_VA_BITS_48
+ bool "48-bit"
+ depends on ARM64_4K_PAGES
+
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
@@ -195,6 +200,9 @@ 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/memblock.h b/arch/arm64/include/asm/memblock.h
index 6afeed2..e4ac8bf 100644
--- a/arch/arm64/include/asm/memblock.h
+++ b/arch/arm64/include/asm/memblock.h
@@ -16,6 +16,12 @@
#ifndef __ASM_MEMBLOCK_H
#define __ASM_MEMBLOCK_H
+#ifndef CONFIG_ARM64_4_LEVELS
+#define MEMBLOCK_INITIAL_LIMIT PGDIR_SIZE
+#else
+#define MEMBLOCK_INITIAL_LIMIT PUD_SIZE
+#endif
+
extern void arm64_memblock_init(void);
#endif
diff --git a/arch/arm64/include/asm/page.h b/arch/arm64/include/asm/page.h
index 268e53d..83b5289 100644
--- a/arch/arm64/include/asm/page.h
+++ b/arch/arm64/include/asm/page.h
@@ -35,8 +35,10 @@
#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 --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h
index 4829837..8d745fa 100644
--- a/arch/arm64/include/asm/pgalloc.h
+++ b/arch/arm64/include/asm/pgalloc.h
@@ -26,6 +26,26 @@
#define check_pgt_cache() do { } while (0)
+#ifdef CONFIG_ARM64_4_LEVELS
+
+static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr)
+{
+ return (pud_t *)get_zeroed_page(GFP_KERNEL | __GFP_REPEAT);
+}
+
+static inline void pud_free(struct mm_struct *mm, pud_t *pud)
+{
+ BUG_ON((unsigned long)pud & (PAGE_SIZE-1));
+ free_page((unsigned long)pud);
+}
+
+static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, pud_t *pud)
+{
+ set_pgd(pgd, __pgd(__pa(pud) | PUD_TYPE_TABLE));
+}
+
+#endif /* CONFIG_ARM64_4_LEVELS */
+
#ifndef CONFIG_ARM64_2_LEVELS
static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long addr)
diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index c7c603b..fddcc3e 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -18,8 +18,10 @@
#ifdef CONFIG_ARM64_2_LEVELS
#include <asm/pgtable-2level-hwdef.h>
-#else
+#elif defined(CONFIG_ARM64_3_LEVELS)
#include <asm/pgtable-3level-hwdef.h>
+#else
+#include <asm/pgtable-4level-hwdef.h>
#endif
/*
@@ -27,7 +29,7 @@
*
* Level 1 descriptor (PUD).
*/
-
+#define PUD_TYPE_TABLE (_AT(pudval_t, 3) << 0)
#define PUD_TABLE_BIT (_AT(pgdval_t, 1) << 1)
#define PUD_TYPE_MASK (_AT(pgdval_t, 3) << 0)
#define PUD_TYPE_SECT (_AT(pgdval_t, 1) << 0)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 4a350af..4dafa5c 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -35,7 +35,11 @@
* VMALLOC and SPARSEMEM_VMEMMAP ranges.
*/
#define VMALLOC_START (UL(0xffffffffffffffff) << VA_BITS)
+#ifndef CONFIG_ARM64_4_LEVELS
#define VMALLOC_END (PAGE_OFFSET - UL(0x400000000) - SZ_64K)
+#else
+#define VMALLOC_END (PAGE_OFFSET - UL(0x40000000000) - SZ_64K)
+#endif
#define vmemmap ((struct page *)(VMALLOC_END + SZ_64K))
@@ -44,12 +48,16 @@
#ifndef __ASSEMBLY__
extern void __pte_error(const char *file, int line, unsigned long val);
extern void __pmd_error(const char *file, int line, unsigned long val);
+extern void __pud_error(const char *file, int line, unsigned long val);
extern void __pgd_error(const char *file, int line, unsigned long val);
#define pte_ERROR(pte) __pte_error(__FILE__, __LINE__, pte_val(pte))
#ifndef CONFIG_ARM64_2_LEVELS
#define pmd_ERROR(pmd) __pmd_error(__FILE__, __LINE__, pmd_val(pmd))
#endif
+#ifdef CONFIG_ARM64_4_LEVELS
+#define pud_ERROR(pud) __pud_error(__FILE__, __LINE__, pud_val(pud))
+#endif
#define pgd_ERROR(pgd) __pgd_error(__FILE__, __LINE__, pgd_val(pgd))
#ifdef CONFIG_SMP
@@ -348,6 +356,30 @@ static inline pmd_t *pud_page_vaddr(pud_t pud)
#endif /* CONFIG_ARM64_2_LEVELS */
+#ifdef CONFIG_ARM64_4_LEVELS
+
+#define pgd_none(pgd) (!pgd_val(pgd))
+#define pgd_bad(pgd) (!(pgd_val(pgd) & 2))
+#define pgd_present(pgd) (pgd_val(pgd))
+
+static inline void set_pgd(pgd_t *pgdp, pgd_t pgd)
+{
+ *pgdp = pgd;
+ dsb(ishst);
+}
+
+static inline void pgd_clear(pgd_t *pgdp)
+{
+ set_pgd(pgdp, __pgd(0));
+}
+
+static inline pud_t *pgd_page_vaddr(pgd_t pgd)
+{
+ return __va(pgd_val(pgd) & PHYS_MASK & (s32)PAGE_MASK);
+}
+
+#endif /* CONFIG_ARM64_4_LEVELS */
+
/* to find an entry in a page-table-directory */
#define pgd_index(addr) (((addr) >> PGDIR_SHIFT) & (PTRS_PER_PGD - 1))
@@ -356,6 +388,14 @@ static inline pmd_t *pud_page_vaddr(pud_t pud)
/* to find an entry in a kernel page-table-directory */
#define pgd_offset_k(addr) pgd_offset(&init_mm, addr)
+#ifdef CONFIG_ARM64_4_LEVELS
+#define pud_index(addr) (((addr) >> PUD_SHIFT) & (PTRS_PER_PUD - 1))
+static inline pud_t *pud_offset(pgd_t *pgd, unsigned long addr)
+{
+ return (pud_t *)pgd_page_vaddr(*pgd) + pud_index(addr);
+}
+#endif
+
/* Find an entry in the second-level page table.. */
#ifndef CONFIG_ARM64_2_LEVELS
#define pmd_index(addr) (((addr) >> PMD_SHIFT) & (PTRS_PER_PMD - 1))
@@ -384,8 +424,13 @@ static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
extern pgd_t idmap_pg_dir[PTRS_PER_PGD];
+#ifdef CONFIG_ARM64_4_LEVELS
+#define SWAPPER_DIR_SIZE (4 * PAGE_SIZE)
+#define IDMAP_DIR_SIZE (3 * PAGE_SIZE)
+#else
#define SWAPPER_DIR_SIZE (3 * PAGE_SIZE)
#define IDMAP_DIR_SIZE (2 * PAGE_SIZE)
+#endif
/*
* Encode and decode a swap entry:
diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
index bc19101..49dc8f0 100644
--- a/arch/arm64/include/asm/tlb.h
+++ b/arch/arm64/include/asm/tlb.h
@@ -100,6 +100,15 @@ static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp,
}
#endif
+#ifdef CONFIG_ARM64_4_LEVELS
+static inline void __pud_free_tlb(struct mmu_gather *tlb, pud_t *pudp,
+ unsigned long addr)
+{
+ tlb_add_flush(tlb, addr);
+ tlb_remove_page(tlb, virt_to_page(pudp));
+}
+#endif
+
static inline void __tlb_remove_pmd_tlb_entry(struct mmu_gather *tlb, pmd_t *pmdp,
unsigned long address)
{
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index b96a732..8464087 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -37,8 +37,9 @@
/*
* swapper_pg_dir is the virtual address of the initial page table. We place
- * the page tables 3 * PAGE_SIZE below KERNEL_RAM_VADDR. The idmap_pg_dir has
- * 2 pages and is placed below swapper_pg_dir.
+ * the page tables 3 * PAGE_SIZE (2 or 3 levels) or 4 * PAGE_SIZE (4 levels)
+ * below KERNEL_RAM_VADDR. The idmap_pg_dir has 2 pages (2 or 3 levels) or
+ * 3 pages (4 levels) and is placed below swapper_pg_dir.
*/
#define KERNEL_RAM_VADDR (PAGE_OFFSET + TEXT_OFFSET)
@@ -46,8 +47,13 @@
#error KERNEL_RAM_VADDR must start at 0xXXX80000
#endif
+#ifdef CONFIG_ARM64_4_LEVELS
+#define SWAPPER_DIR_SIZE (4 * PAGE_SIZE)
+#define IDMAP_DIR_SIZE (3 * PAGE_SIZE)
+#else
#define SWAPPER_DIR_SIZE (3 * PAGE_SIZE)
#define IDMAP_DIR_SIZE (2 * PAGE_SIZE)
+#endif
.globl swapper_pg_dir
.equ swapper_pg_dir, KERNEL_RAM_VADDR - SWAPPER_DIR_SIZE
@@ -368,16 +374,42 @@ ENDPROC(__calc_phys_offset)
.quad PAGE_OFFSET
/*
- * Macro to populate the PGD for the corresponding block entry in the next
- * level (tbl) for the given virtual address.
+ * Macro to populate the PUD for the corresponding block entry in the next
+ * level (tbl) for the given virtual address in case of 4 levels.
+ *
+ * Preserves: pgd, virt
+ * Corrupts: tbl, tmp1, tmp2
+ * Returns: pud
+ */
+ .macro create_pud_entry, pgd, tbl, virt, pud, tmp1, tmp2
+#ifdef CONFIG_ARM64_4_LEVELS
+ add \tbl, \tbl, #PAGE_SIZE // bump tbl 1 page up.
+ // to make room for pud
+ add \pud, \pgd, #PAGE_SIZE // pgd points to pud which
+ // follows pgd
+ lsr \tmp1, \virt, #PUD_SHIFT
+ and \tmp1, \tmp1, #PTRS_PER_PUD - 1 // PUD index
+ orr \tmp2, \tbl, #3 // PUD entry table type
+ str \tmp2, [\pud, \tmp1, lsl #3]
+#else
+ mov \pud, \tbl
+#endif
+ .endm
+
+/*
+ * Macro to populate the PGD (and possibily PUD) for the corresponding
+ * block entry in the next level (tbl) for the given virtual address.
*
- * Preserves: pgd, tbl, virt
- * Corrupts: tmp1, tmp2
+ * Preserves: pgd, virt
+ * Corrupts: tmp1, tmp2, tmp3
+ * Returns: tbl -> page where block mappings can be placed
+ * (changed to make room for pud with 4 levels, preserved otherwise)
*/
- .macro create_pgd_entry, pgd, tbl, virt, tmp1, tmp2
+ .macro create_pgd_entry, pgd, tbl, virt, tmp1, tmp2, tmp3
+ create_pud_entry \pgd, \tbl, \virt, \tmp3, \tmp1, \tmp2
lsr \tmp1, \virt, #PGDIR_SHIFT
and \tmp1, \tmp1, #PTRS_PER_PGD - 1 // PGD index
- orr \tmp2, \tbl, #3 // PGD entry table type
+ orr \tmp2, \tmp3, #3 // PGD entry table type
str \tmp2, [\pgd, \tmp1, lsl #3]
.endm
@@ -442,7 +474,7 @@ __create_page_tables:
add x0, x25, #PAGE_SIZE // section table address
ldr x3, =KERNEL_START
add x3, x3, x28 // __pa(KERNEL_START)
- create_pgd_entry x25, x0, x3, x5, x6
+ create_pgd_entry x25, x0, x3, x1, x5, x6
ldr x6, =KERNEL_END
mov x5, x3 // __pa(KERNEL_START)
add x6, x6, x28 // __pa(KERNEL_END)
@@ -453,7 +485,7 @@ __create_page_tables:
*/
add x0, x26, #PAGE_SIZE // section table address
mov x5, #PAGE_OFFSET
- create_pgd_entry x26, x0, x5, x3, x6
+ create_pgd_entry x26, x0, x5, x1, x3, x6
ldr x6, =KERNEL_END
mov x3, x24 // phys offset
create_block_map x0, x7, x3, x5, x6
@@ -479,7 +511,7 @@ __create_page_tables:
*/
ldr x5, =FIXADDR_TOP // Fixed mapping virtual address
add x0, x26, #2 * PAGE_SIZE // section table address
- create_pgd_entry x26, x0, x5, x6, x7
+ create_pgd_entry x26, x0, x5, x1, x6, x7
/*
* Since the page tables have been populated with non-cacheable
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 506f781..02cd3f0 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -339,6 +339,11 @@ void __pmd_error(const char *file, int line, unsigned long val)
pr_crit("%s:%d: bad pmd %016lx.\n", file, line, val);
}
+void __pud_error(const char *file, int line, unsigned long val)
+{
+ pr_crit("%s:%d: bad pud %016lx.\n", file, line, val);
+}
+
void __pgd_error(const char *file, int line, unsigned long val)
{
pr_crit("%s:%d: bad pgd %016lx.\n", file, line, val);
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 89c6763..663397b 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -62,6 +62,7 @@ void show_pte(struct mm_struct *mm, unsigned long addr)
break;
pud = pud_offset(pgd, addr);
+ printk(", *pud=%016llx", pud_val(*pud));
if (pud_none(*pud) || pud_bad(*pud))
break;
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 3a729de..ce09ed3 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -32,6 +32,7 @@
#include <asm/setup.h>
#include <asm/sizes.h>
#include <asm/tlb.h>
+#include <asm/memblock.h>
#include <asm/mmu_context.h>
#include "mm.h"
@@ -190,9 +191,15 @@ static void __init alloc_init_pmd(pud_t *pud, unsigned long addr,
static void __init alloc_init_pud(pgd_t *pgd, unsigned long addr,
unsigned long end, unsigned long phys)
{
- pud_t *pud = pud_offset(pgd, addr);
+ pud_t *pud;
unsigned long next;
+ if (pgd_none(*pgd) || pgd_bad(*pgd)) {
+ pud = early_alloc(PTRS_PER_PUD * sizeof(pud_t));
+ pgd_populate(&init_mm, pgd, pud);
+ }
+
+ pud = pud_offset(pgd, addr);
do {
next = pud_addr_end(addr, end);
@@ -262,10 +269,11 @@ static void __init map_mem(void)
* memory addressable from the initial direct kernel mapping.
*
* The initial direct kernel mapping, located at swapper_pg_dir,
- * gives us PGDIR_SIZE memory starting from PHYS_OFFSET (which must be
- * aligned to 2MB as per Documentation/arm64/booting.txt).
+ * gives us PGDIR_SIZE (2 and 3 levels) or PUD_SIZE (4 levels) memory
+ * starting from PHYS_OFFSET (which must be aligned to 2MB as per
+ * Documentation/arm64/booting.txt).
*/
- limit = PHYS_OFFSET + PGDIR_SIZE;
+ limit = PHYS_OFFSET + MEMBLOCK_INITIAL_LIMIT;
memblock_set_current_limit(limit);
/* map all the memory banks */
--
1.7.10.4
More information about the linux-arm-kernel
mailing list