linux-kernel - Re: [PATCH v2 2/3] arm64/mm: Unitify CONT_PTE

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Date:   Fri, 11 Sep 2020 12:30:31 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Gavin Shan <gshan@...hat.com>, linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, catalin.marinas@....com,
        will@...nel.org, shan.gavin@...il.com
Subject: Re: [PATCH v2 2/3] arm64/mm: Unitify CONT_PTE_SHIFT


On 09/10/2020 03:29 PM, Gavin Shan wrote:
> CONT_PTE_SHIFT actually depends on CONFIG_ARM64_CONT_SHIFT. It's
> reasonable to reflect the dependency:

Also always better to avoid direct numerical such as 5, 7, 4. A config
option with a right name (even with constant values), gives them some
meaning.

> 
>    * This renames CONFIG_ARM64_CONT_SHIFT to CONFIG_ARM64_CONT_PTE_SHIFT,
>      so that we can introduce CONFIG_ARM64_CONT_PMD_SHIFT later.

Agreed.

> 
>    * CONT_{SHIFT, SIZE, MASK}, defined in page-def.h are removed as they
>      are not used by anyone.

Makes sense.

> 
>    * CONT_PTE_SHIFT is determined by CONFIG_ARM64_CONT_PTE_SHIFT.
> 
> Signed-off-by: Gavin Shan <gshan@...hat.com>
> ---
>  arch/arm64/Kconfig                     | 2 +-
>  arch/arm64/include/asm/page-def.h      | 5 -----
>  arch/arm64/include/asm/pgtable-hwdef.h | 4 +---
>  3 files changed, 2 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 6d232837cbee..7ec30dd56300 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -211,7 +211,7 @@ config ARM64_PAGE_SHIFT
>  	default 14 if ARM64_16K_PAGES
>  	default 12
>  
> -config ARM64_CONT_SHIFT
> +config ARM64_CONT_PTE_SHIFT
>  	int
>  	default 5 if ARM64_64K_PAGES
>  	default 7 if ARM64_16K_PAGES
> diff --git a/arch/arm64/include/asm/page-def.h b/arch/arm64/include/asm/page-def.h
> index f99d48ecbeef..2403f7b4cdbf 100644
> --- a/arch/arm64/include/asm/page-def.h
> +++ b/arch/arm64/include/asm/page-def.h
> @@ -11,13 +11,8 @@
>  #include <linux/const.h>
>  
>  /* PAGE_SHIFT determines the page size */
> -/* CONT_SHIFT determines the number of pages which can be tracked together  */

This does not get added back in <pgtable-hwdef.h>, would you please
add one comment, for both CONT_PTE_SHIFT and CONT_PMD_SHIFT in their
respective patches.

>  #define PAGE_SHIFT		CONFIG_ARM64_PAGE_SHIFT
> -#define CONT_SHIFT		CONFIG_ARM64_CONT_SHIFT
>  #define PAGE_SIZE		(_AC(1, UL) << PAGE_SHIFT)
>  #define PAGE_MASK		(~(PAGE_SIZE-1))
>  
> -#define CONT_SIZE		(_AC(1, UL) << (CONT_SHIFT + PAGE_SHIFT))
> -#define CONT_MASK		(~(CONT_SIZE-1))
> -
>  #endif /* __ASM_PAGE_DEF_H */
> diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
> index 8a399e666837..6c9c67f62551 100644
> --- a/arch/arm64/include/asm/pgtable-hwdef.h
> +++ b/arch/arm64/include/asm/pgtable-hwdef.h
> @@ -81,14 +81,12 @@
>  /*
>   * Contiguous page definitions.
>   */
> +#define CONT_PTE_SHIFT		(CONFIG_ARM64_CONT_PTE_SHIFT + PAGE_SHIFT)
>  #ifdef CONFIG_ARM64_64K_PAGES
> -#define CONT_PTE_SHIFT		(5 + PAGE_SHIFT)
>  #define CONT_PMD_SHIFT		(5 + PMD_SHIFT)
>  #elif defined(CONFIG_ARM64_16K_PAGES)
> -#define CONT_PTE_SHIFT		(7 + PAGE_SHIFT)
>  #define CONT_PMD_SHIFT		(5 + PMD_SHIFT)
>  #else
> -#define CONT_PTE_SHIFT		(4 + PAGE_SHIFT)
>  #define CONT_PMD_SHIFT		(4 + PMD_SHIFT)
>  #endif
>  
> 

Looks good to me and there are no obvious regressions as well.

Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>