[PATCH 7/8] arm64: mm: Implement 4 levels of translation tables

Jungseok Lee
2014-04-14T07:43:36Z

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]: Principle 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>
---
arch/arm64/Kconfig | 7 +++++
arch/arm64/include/asm/page.h | 4 ++-
arch/arm64/include/asm/pgalloc.h | 20 ++++++++++++++
arch/arm64/include/asm/pgtable-hwdef.h | 8 ++++--
arch/arm64/include/asm/pgtable.h | 44 +++++++++++++++++++++++++++++--
arch/arm64/include/asm/tlb.h | 8 ++++++
arch/arm64/kernel/head.S | 45 ++++++++++++++++++++++++++++++--
arch/arm64/kernel/traps.c | 5 ++++
arch/arm64/mm/fault.c | 1 +
arch/arm64/mm/mmu.c | 14 +++++++++-
10 files changed, 148 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 431acbc..7f5270b 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -184,12 +184,19 @@ config ARM64_3_LEVELS
help
This feature enables 3 levels of translation tables.

+config ARM64_4_LEVELS
+ bool "4 level"
+ depends on ARM64_4K_PAGES
+ help
+ This feature enables 4 levels of translation tables.
+
endchoice

config ARM64_VA_BITS
int "Virtual address space size"
range 39 39 if ARM64_4K_PAGES && ARM64_3_LEVELS
range 42 42 if ARM64_64K_PAGES && ARM64_2_LEVELS
+ range 48 48 if ARM64_4K_PAGES && ARM64_4_LEVELS
help
This feature is determined by a combination of page size and
level of translation tables.
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 9cd86c6..03ad81b 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 +29,9 @@
*
* Level 1 descriptor (PUD).
*/
-
+#ifdef CONFIG_ARM64_4_LEVELS
+#define PUD_TYPE_TABLE (_AT(pudval_t, 3) << 0)
+#endif
#define PUD_TABLE_BIT (_AT(pgdval_t, 1) << 1)

/*
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index a64ce5e..713811d 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))

/*
@@ -344,6 +352,30 @@ 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(pud_t *pgdp, pud_t pgd)
+{
+ *pgdp = pgd;
+ dsb();
+}
+
+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))

@@ -352,6 +384,14 @@ 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))
@@ -380,8 +420,8 @@ 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];

-#define SWAPPER_DIR_SIZE (3 * PAGE_SIZE)
-#define IDMAP_DIR_SIZE (2 * PAGE_SIZE)
+#define SWAPPER_DIR_SIZE (4 * PAGE_SIZE)
+#define IDMAP_DIR_SIZE (3 * PAGE_SIZE)

/*
* Encode and decode a swap entry:
diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
index df378b2..dedfb04 100644
--- a/arch/arm64/include/asm/tlb.h
+++ b/arch/arm64/include/asm/tlb.h
@@ -99,5 +99,13 @@ 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, pmd_t *pudp,
+ unsigned long addr)
+{
+ tlb_add_flush(tlb, addr);
+ tlb_remove_page(tlb, virt_to_page(pudp));
+}
+#endif

#endif
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 0fd5650..0b0b16a 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -46,8 +46,8 @@
#error KERNEL_RAM_VADDR must start at 0xXXX80000
#endif

-#define SWAPPER_DIR_SIZE (3 * PAGE_SIZE)
-#define IDMAP_DIR_SIZE (2 * PAGE_SIZE)
+#define SWAPPER_DIR_SIZE (4 * PAGE_SIZE)
+#define IDMAP_DIR_SIZE (3 * PAGE_SIZE)

.globl swapper_pg_dir
.equ swapper_pg_dir, KERNEL_RAM_VADDR - SWAPPER_DIR_SIZE
@@ -384,6 +384,20 @@ ENDPROC(__calc_phys_offset)
.endm

/*
+ * Macro to populate the PUD for the corresponding block entry in the next
+ * level (tbl) for the given virtual address.
+ *
+ * Preserves: pud, tbl, virt
+ * Corrupts: tmp1, tmp2
+ */
+ .macro create_pud_entry, pud, tbl, virt, tmp1, tmp2
+ 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]
+ .endm
+
+/*
* Macro to populate block entries in the page table for the start..end
* virtual range (inclusive).
*
@@ -445,10 +459,18 @@ __create_page_tables:
ldr x3, =KERNEL_START
add x3, x3, x28 // __pa(KERNEL_START)
create_pgd_entry x25, x0, x3, x5, x6
+#ifdef CONFIG_ARM64_4_LEVELS
+ add x1, x0, #PAGE_SIZE
+ create_pud_entry x0, x1, x3, x5, x6
+#endif
ldr x6, =KERNEL_END
mov x5, x3 // __pa(KERNEL_START)
add x6, x6, x28 // __pa(KERNEL_END)
+#ifndef CONFIG_ARM64_4_LEVELS
create_block_map x0, x7, x3, x5, x6
+#else
+ create_block_map x1, x7, x3, x5, x6
+#endif

/*
* Map the kernel image (starting with PHYS_OFFSET).
@@ -456,9 +478,17 @@ __create_page_tables:
add x0, x26, #PAGE_SIZE // section table address
mov x5, #PAGE_OFFSET
create_pgd_entry x26, x0, x5, x3, x6
+#ifdef CONFIG_ARM64_4_LEVELS
+ add x1, x0, #PAGE_SIZE
+ create_pud_entry x0, x1, x3, x5, x6
+#endif
ldr x6, =KERNEL_END
mov x3, x24 // phys offset
+#ifndef CONFIG_ARM64_4_LEVELS
create_block_map x0, x7, x3, x5, x6
+#else
+ create_block_map x1, x7, x3, x5, x6
+#endif

/*
* Map the FDT blob (maximum 2MB; must be within 512MB of
@@ -474,14 +504,25 @@ __create_page_tables:
add x5, x5, x6 // __va(FDT blob)
add x6, x5, #1 << 21 // 2MB for the FDT blob
sub x6, x6, #1 // inclusive range
+#ifndef CONFIG_ARM64_4_LEVELS
create_block_map x0, x7, x3, x5, x6
+#else
+ create_block_map x1, x7, x3, x5, x6
+#endif
1:
/*
* Create the pgd entry for the fixed mappings.
*/
ldr x5, =FIXADDR_TOP // Fixed mapping virtual address
+#ifndef CONFIG_ARM64_4_LEVELS
add x0, x26, #2 * PAGE_SIZE // section table address
create_pgd_entry x26, x0, x5, x6, x7
+#else
+ add x0, x26, #PAGE_SIZE
+ create_pgd_entry x26, x0, x5, x6, x7
+ add x1, x0, #2 * PAGE_SIZE
+ create_pud_entry x0, x1, x5, x6, x7
+#endif

/*
* 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 0484e81..16d5ee5 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -336,6 +336,11 @@ 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 c23751b..ed4a343 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -61,6 +61,7 @@ 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 6b7e895..321f569 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -222,9 +222,17 @@ 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;

+#ifdef CONFIG_ARM64_4_LEVELS
+ if (pgd_none(*pgd) || pgd_bad(*pgd)) {
+ pud = early_alloc(PTRS_PER_PUD * sizeof(pud_t));
+ pgd_populate(&init_mm, pgd, pud);
+ }
+#endif
+
+ pud = pud_offset(pgd, addr);
do {
next = pud_addr_end(addr, end);
alloc_init_pmd(pud, addr, next, phys);
@@ -274,7 +282,11 @@ static void __init map_mem(void)
* gives us PGDIR_SIZE memory starting from PHYS_OFFSET (which must be
* aligned to 2MB as per Documentation/arm64/booting.txt).
*/
+#ifndef CONFIG_ARM64_4_LEVELS
limit = PHYS_OFFSET + PGDIR_SIZE;
+#else
+ limit = PHYS_OFFSET + PUD_SIZE;
+#endif
memblock_set_current_limit(limit);

/* map all the memory banks */
--
1.7.10.4