linux-kernel - Re: [PATCH 1/4] MIPS: Flush dcache for flush_kernel_dcache

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Date:	Fri, 4 Mar 2016 15:09:00 +0000
From:	Lars Persson <lars.persson@...s.com>
To:	Paul Burton <paul.burton@...tec.com>
CC:	"linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>,
	Ralf Baechle <ralf@...ux-mips.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] MIPS: Flush dcache for flush_kernel_dcache_page



> 1 mars 2016 kl. 03:38 Paul Burton <paul.burton@...tec.com>:
> 
> The flush_kernel_dcache_page function was previously essentially a nop.
> This is incorrect for MIPS, where if a page has been modified & either
> it aliases or it's executable & the icache doesn't fill from dcache then
> the content needs to be written back from dcache to the next level of
> the cache hierarchy (which is shared with the icache).
> 
> Implement this by simply calling flush_dcache_page, treating this
> kmapped cache flush function (flush_kernel_dcache_page) exactly the same
> as its non-kmapped counterpart (flush_dcache_page).
> 
> Signed-off-by: Paul Burton <paul.burton@...tec.com>
> ---
> 
> arch/mips/include/asm/cacheflush.h | 1 +
> 1 file changed, 1 insertion(+)
> 
> diff --git a/arch/mips/include/asm/cacheflush.h b/arch/mips/include/asm/cacheflush.h
> index 723229f..7e9f468 100644
> --- a/arch/mips/include/asm/cacheflush.h
> +++ b/arch/mips/include/asm/cacheflush.h
> @@ -132,6 +132,7 @@ static inline void kunmap_noncoherent(void)
> static inline void flush_kernel_dcache_page(struct page *page)
> {
>    BUG_ON(cpu_has_dc_aliases && PageHighMem(page));
> +    flush_dcache_page(page);

Should we use instead __flush_dcache_page() that flushes immediately for mapped pages ? Steven J Hill's old patch set for highmem had done it like this.

> }
> 
> /*
> -- 
> 2.7.1
>