linux-kernel - Re: [PATCH 2/2] MIPS: don't select ARCH_HAS_PTE

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Message-ID: <20190701174351.GB24848@roeck-us.net>
Date:   Mon, 1 Jul 2019 10:43:51 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Christoph Hellwig <hch@....de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>, linux-mips@...r.kernel.org,
        linux-sh@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] MIPS: don't select ARCH_HAS_PTE_SPECIAL

On Mon, Jul 01, 2019 at 05:18:18PM +0200, Christoph Hellwig wrote:
> MIPS doesn't really have a proper pte_special implementation, just
> stubs.  It turns out they were not enough to make get_user_pages_fast
> work, so drop the select.  This means get_user_pages_fast won't
> actually use the fast path for non-hugepage mappings, so someone who
> actually knows about mips page table management should look into
> adding real pte_special support.
> 
> Fixes: eb9488e58bbc ("MIPS: use the generic get_user_pages_fast code")
> Reported-by: Guenter Roeck <linux@...ck-us.net>
> Signed-off-by: Christoph Hellwig <hch@....de>

Tested-by: Guenter Roeck <linux@...ck-us.net>

> ---
>  arch/mips/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index b1e42f0e4ed0..7957d3457156 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -6,7 +6,6 @@ config MIPS
>  	select ARCH_BINFMT_ELF_STATE if MIPS_FP_SUPPORT
>  	select ARCH_CLOCKSOURCE_DATA
>  	select ARCH_HAS_ELF_RANDOMIZE
> -	select ARCH_HAS_PTE_SPECIAL
>  	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>  	select ARCH_HAS_UBSAN_SANITIZE_ALL
>  	select ARCH_SUPPORTS_UPROBES
> -- 
> 2.20.1
>