linux-kernel - Re: [PATCH v1 1/3] arm: mm: reordering memory type table

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Date:   Fri, 21 Sep 2018 10:43:32 +0900
From:   Minchan Kim <minchan.kernel@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>, linux@...linux.org.uk
Cc:     steve.capper@...aro.org, will.deacon@....com,
        catalin.marinas@....com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kernel-team@...roid.com,
        miles.chen@...iatek.com, jian-min.lui@...iatek.com,
        juju.sung@...iatek.com, Simon Horman <horms@...ge.net.au>
Subject: Re: [PATCH v1 1/3] arm: mm: reordering memory type table

Hi Guys,

Could you have a chance to review this patchset?

Thanks!

On Mon, Sep 17, 2018 at 09:44:49AM +0900, Minchan Kim wrote:
> To use bit 5 in page table as L_PTE_SPECIAL, we need a room for that.
> It seems we don't need 4 bits for the memory type with ARMv6+.
> If it's true, let's reorder bits to make bit 5 free.
> 
> We will use the bit for L_PTE_SPECIAL in next patch.
> 
> A note from Catalin
> "
> > Anyway, on ARMv7 or ARMv6+LPAE, the non-shared device gets mapped to
> > shared device in hardware. Looking through the arm32 code, it seems that
> > MT_DEVICE_NONSHARED is used by arch/arm/mach-shmobile/setup-r8a7779.c
> > and IIUC that's a v7 platform (R-Car H1, Cortex-A9). I think the above
> > should be defined to L_PTE_MT_DEV_SHARED, unless I miss any place where
> > DEV_NONSHARED is relevant on ARMv6 (adding Simon to confirm on shmbile).
> "
> 
> Cc: Russell King <linux@...linux.org.uk>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Steve Capper <steve.capper@...aro.org>
> Cc: Simon Horman <horms@...ge.net.au>
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
>  arch/arm/include/asm/pgtable-2level.h | 19 +++++++++++++++----
>  arch/arm/mm/proc-macros.S             |  4 ++--
>  2 files changed, 17 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm/include/asm/pgtable-2level.h b/arch/arm/include/asm/pgtable-2level.h
> index 92fd2c8a9af0..514b13c27b43 100644
> --- a/arch/arm/include/asm/pgtable-2level.h
> +++ b/arch/arm/include/asm/pgtable-2level.h
> @@ -164,14 +164,25 @@
>  #define L_PTE_MT_BUFFERABLE	(_AT(pteval_t, 0x01) << 2)	/* 0001 */
>  #define L_PTE_MT_WRITETHROUGH	(_AT(pteval_t, 0x02) << 2)	/* 0010 */
>  #define L_PTE_MT_WRITEBACK	(_AT(pteval_t, 0x03) << 2)	/* 0011 */
> +#define L_PTE_MT_DEV_SHARED	(_AT(pteval_t, 0x04) << 2)	/* 0100 */
> +#define L_PTE_MT_VECTORS	(_AT(pteval_t, 0x05) << 2)	/* 0101 */
>  #define L_PTE_MT_MINICACHE	(_AT(pteval_t, 0x06) << 2)	/* 0110 (sa1100, xscale) */
>  #define L_PTE_MT_WRITEALLOC	(_AT(pteval_t, 0x07) << 2)	/* 0111 */
> -#define L_PTE_MT_DEV_SHARED	(_AT(pteval_t, 0x04) << 2)	/* 0100 */
> -#define L_PTE_MT_DEV_NONSHARED	(_AT(pteval_t, 0x0c) << 2)	/* 1100 */
> +#if defined(CONFIG_CPU_V7) || defined (CONFIG_CPU_V6) || defined(CONFIG_CPU_V6K)
> +/*
> + * On ARMv7 or ARMv6+LPAE, the non-shared device gets mapped to
> + * shared device in hardware.
> + */
> +#define L_PTE_MT_DEV_NONSHARED	L_PTE_MT_DEV_SHARED
> +#define L_PTE_MT_DEV_WC		L_PTE_MT_BUFFERABLE
> +#define L_PTE_MT_DEV_CACHED	L_PTE_MT_WRITEBACK
> +#define L_PTE_MT_MASK		(_AT(pteval_t, 0x07) << 2)
> +#else
>  #define L_PTE_MT_DEV_WC		(_AT(pteval_t, 0x09) << 2)	/* 1001 */
>  #define L_PTE_MT_DEV_CACHED	(_AT(pteval_t, 0x0b) << 2)	/* 1011 */
> -#define L_PTE_MT_VECTORS	(_AT(pteval_t, 0x0f) << 2)	/* 1111 */
> -#define L_PTE_MT_MASK		(_AT(pteval_t, 0x0f) << 2)
> +#define L_PTE_MT_DEV_NONSHARED	(_AT(pteval_t, 0x0c) << 2)	/* 1100 */
> +#define L_PTE_MT_MASK           (_AT(pteval_t, 0x0f) << 2)
> +#endif
>  
>  #ifndef __ASSEMBLY__
>  
> diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
> index 81d0efb055c6..367a89d5aeca 100644
> --- a/arch/arm/mm/proc-macros.S
> +++ b/arch/arm/mm/proc-macros.S
> @@ -138,7 +138,7 @@
>  	.long	PTE_CACHEABLE					@ L_PTE_MT_WRITETHROUGH
>  	.long	PTE_CACHEABLE | PTE_BUFFERABLE			@ L_PTE_MT_WRITEBACK
>  	.long	PTE_BUFFERABLE					@ L_PTE_MT_DEV_SHARED
> -	.long	0x00						@ unused
> +	.long	PTE_CACHEABLE | PTE_BUFFERABLE | PTE_EXT_APX	@ L_PTE_MT_VECTORS
>  	.long	0x00						@ L_PTE_MT_MINICACHE (not present)
>  	.long	PTE_EXT_TEX(1) | PTE_CACHEABLE | PTE_BUFFERABLE	@ L_PTE_MT_WRITEALLOC
>  	.long	0x00						@ unused
> @@ -148,7 +148,7 @@
>  	.long	PTE_EXT_TEX(2)					@ L_PTE_MT_DEV_NONSHARED
>  	.long	0x00						@ unused
>  	.long	0x00						@ unused
> -	.long	PTE_CACHEABLE | PTE_BUFFERABLE | PTE_EXT_APX	@ L_PTE_MT_VECTORS
> +	.long	0x00						@ unused
>  	.endm
>  
>  	.macro	armv6_set_pte_ext pfx
> -- 
> 2.19.0.397.gdd90340f6a-goog
>