Subject: [PATCH v7 07/11] arm64: mm: Implement 4 levels of translation tables

From: [email-masked] (Joel Schopp)
Date: Mon, 28 Jul 2014 10:40:07 -0500

On 07/16/2014 02:09 PM, Catalin Marinas wrote:
> From: Jungseok Lee <[email-masked]>
>
> 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 <[email-masked]>
> Reviewed-by: Sungjinn Chung <[email-masked]>
> Acked-by: Kukjin Kim <[email-masked]>
> Reviewed-by: Christoffer Dall <[email-masked]>
> Reviewed-by: Steve Capper <[email-masked]>
> [catalin.marinas at arm.com: MEMBLOCK_INITIAL_LIMIT removed, same as PUD_SIZE]
> [catalin.marinas at arm.com: early_ioremap_init() updated for 4 levels]
> [catalin.marinas at arm.com: 4 page tables levels only if !KVM]
> Signed-off-by: Catalin Marinas <[email-masked]>
> ---
>  arch/arm64/Kconfig                     |  9 ++++++++
>  arch/arm64/include/asm/page.h          | 13 ++++++++---
>  arch/arm64/include/asm/pgalloc.h       | 20 ++++++++++++++++
>  arch/arm64/include/asm/pgtable-hwdef.h |  6 +++--
>  arch/arm64/include/asm/pgtable.h       | 40 ++++++++++++++++++++++++++++++++
>  arch/arm64/include/asm/tlb.h           |  9 ++++++++
>  arch/arm64/kernel/head.S               | 42 +++++++++++++++++++++++++++-------
>  arch/arm64/kernel/traps.c              |  5 ++++
>  arch/arm64/mm/fault.c                  |  1 +
>  arch/arm64/mm/ioremap.c                |  6 ++++-
>  arch/arm64/mm/mmu.c                    | 14 +++++++++---
>  11 files changed, 148 insertions(+), 17 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 4daf11f5b403..24cbe72c0da9 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -196,12 +196,18 @@ config ARM64_VA_BITS_42
>  	bool "42-bit"
>  	depends on ARM64_64K_PAGES
>  
> +config ARM64_VA_BITS_48
> +	bool "48-bit"
> +	depends on !KVM
> +	depends on ARM64_4K_PAGES
> +
>  endchoice
Shouldn't we be able to support 48 bit VA with 3 level 64K pages?  If so
why the dependency on ARM64_4K_PAGES?

More generally it seems like a problem to tie the equate the VA_BITS the
page table could address with the VA_BITS the hardware could address. 
Even with 4 level 4K page tables that can address 48 bits the hardware
may only support say 42 bit address space. 

>  
>  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
> @@ -209,6 +215,9 @@ 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
> +
It seems like we should also do ARM64_4K_PAGES and ARM64_VA_BITS_42 as a
valid combination for ARM64_4_LEVELS.  At least if we are assuming the
VA_BITS correspond to hardware.

>  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 6bf139188792..cf9afa0366b6 100644
> --- 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 maaps 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 --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h
> index 48298376e46a..8d745fae4c2d 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 c7c603b489b8..fddcc3efa569 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 6d5854972a77..d9b23efdaded 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)
Here's a good example of where we run into trouble equating page table
addressable bits with hardware addressable bits.  If VA_BITS is 48 due
to 4K 4 level page tables but is running on a 42 bit system this will
end up being out of range.

> +#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
> @@ -347,6 +355,30 @@ 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))
>  
> @@ -355,6 +387,14 @@ 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))
> diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
> index bc19101edaeb..49dc8f03362f 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 fa3b7fb8a77a..847b99daad79 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -476,16 +476,42 @@ 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, tbl, virt
> - * Corrupts:	tmp1, tmp2
> + * Preserves:	pgd, virt
> + * Corrupts:	tbl, tmp1, tmp2
> + * Returns:	pud
>   */
> -	.macro	create_pgd_entry, pgd, tbl, virt, tmp1, tmp2
> +	.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, 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, 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
>  
> @@ -550,7 +576,7 @@ __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)
> @@ -561,7 +587,7 @@ __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
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index 506f7814e305..02cd3f023e9a 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 bcc965e2cce1..41cb6d3d6075 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/ioremap.c b/arch/arm64/mm/ioremap.c
> index 69000efa015e..fa324bd5a5c4 100644
> --- a/arch/arm64/mm/ioremap.c
> +++ b/arch/arm64/mm/ioremap.c
> @@ -104,9 +104,12 @@ void __iomem *ioremap_cache(phys_addr_t phys_addr, size_t size)
>  EXPORT_SYMBOL(ioremap_cache);
>  
>  static pte_t bm_pte[PTRS_PER_PTE] __page_aligned_bss;
> -#ifndef CONFIG_ARM64_64K_PAGES
> +#if CONFIG_ARM64_PGTABLE_LEVELS > 2
>  static pte_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss;
>  #endif
> +#if CONFIG_ARM64_PGTABLE_LEVELS > 3
> +static pte_t bm_pud[PTRS_PER_PUD] __page_aligned_bss;
> +#endif
>  
>  static inline pud_t * __init early_ioremap_pud(unsigned long addr)
>  {
> @@ -144,6 +147,7 @@ void __init early_ioremap_init(void)
>  	unsigned long addr = fix_to_virt(FIX_BTMAP_BEGIN);
>  
>  	pgd = pgd_offset_k(addr);
> +	pgd_populate(&init_mm, pgd, bm_pud);
>  	pud = pud_offset(pgd, addr);
>  	pud_populate(&init_mm, pud, bm_pmd);
>  	pmd = pmd_offset(pud, addr);
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index c43f1dd19489..c55567283cde 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"
> @@ -204,9 +205,16 @@ static void __init alloc_init_pud(pgd_t *pgd, unsigned long addr,
>  				  unsigned long end, unsigned long phys,
>  				  int map_io)
>  {
> -	pud_t *pud = pud_offset(pgd, addr);
> +	pud_t *pud;
>  	unsigned long next;
>  
> +	if (pgd_none(*pgd)) {
> +		pud = early_alloc(PTRS_PER_PUD * sizeof(pud_t));
> +		pgd_populate(&init_mm, pgd, pud);
> +	}
> +	BUG_ON(pgd_bad(*pgd));
> +
> +	pud = pud_offset(pgd, addr);
>  	do {
>  		next = pud_addr_end(addr, end);
>  
> @@ -290,10 +298,10 @@ 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
> +	 * gives us PUD_SIZE 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 + PUD_SIZE;
>  	memblock_set_current_limit(limit);
>  
>  	/* map all the memory banks */
>
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