linux-kernel - Re: [v2 PATCH 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE

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Date:	Wed, 17 Dec 2014 20:22:43 -0600
From:	Scott Wood <scottwood@...escale.com>
To:	Christophe Leroy <christophe.leroy@....fr>
CC:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	<linux-kernel@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>,
	"Joakim Tjernlund" <joakim.tjernlund@...nsmode.se>
Subject: Re: [v2 PATCH 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW

On Wed, 2014-12-17 at 10:14 +0100, Christophe Leroy wrote:
> On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only pages
> and is set to 0 for RW pages. So we should use _PAGE_RO instead of _PAGE_RW
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> 
> ---
> v2 is a complete rework compared to v1
> 
>  arch/powerpc/include/asm/pte-8xx.h | 7 +++----
>  arch/powerpc/kernel/head_8xx.S     | 3 ---
>  2 files changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/pte-8xx.h b/arch/powerpc/include/asm/pte-8xx.h
> index daa4616..4f5583e 100644
> --- a/arch/powerpc/include/asm/pte-8xx.h
> +++ b/arch/powerpc/include/asm/pte-8xx.h
> @@ -46,7 +46,7 @@
>   * require a TLB exception handler change.  It is assumed unused bits
>   * are always zero.
>   */
> -#define _PAGE_RW	0x0400	/* lsb PP bits, inverted in HW */
> +#define _PAGE_RO	0x0400	/* lsb PP bits */

It looks like pte_update() needs to be updated to match.

>  #define _PAGE_USER	0x0800	/* msb PP bits */
>  /* set when neither _PAGE_USER nor _PAGE_RW are set */

Also update this comment.

>  #define _PAGE_KNLRO	0x0200
> @@ -62,9 +62,8 @@
>  #define PTE_ATOMIC_UPDATES	1
>  
>  /* We need to add _PAGE_SHARED to kernel pages */
> -#define _PAGE_KERNEL_RO	(_PAGE_SHARED | _PAGE_KNLRO)
> -#define _PAGE_KERNEL_ROX	(_PAGE_EXEC | _PAGE_KNLRO)
> -#define _PAGE_KERNEL_RW	(_PAGE_DIRTY | _PAGE_RW | _PAGE_HWWRITE)
> +#define _PAGE_KERNEL_RO	(_PAGE_SHARED | _PAGE_RO | _PAGE_KNLRO)
> +#define _PAGE_KERNEL_ROX	(_PAGE_EXEC | _PAGE_RO | _PAGE_KNLRO)
>  
>  #endif /* __KERNEL__ */
>  #endif /*  _ASM_POWERPC_PTE_8xx_H */

Where did _PAGE_KERNEL_RW go?

-Scott


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