linux-kernel - Re: [PATCH 2/2] MIPS: Flush highmem pages from dcache in __flush_icache

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Date:	Wed, 24 Feb 2016 09:02:46 +0100
From:	Lars Persson <lars.persson@...s.com>
To:	Paul Burton <paul.burton@...tec.com>, <linux-mips@...ux-mips.org>,
	Ralf Baechle <ralf@...ux-mips.org>
CC:	Lars Persson <larper@...s.com>, <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH 2/2] MIPS: Flush highmem pages from dcache in __flush_icache_page


On 02/22/2016 07:09 PM, Paul Burton wrote:
> When a page is to be mapped executable for userspace, we can presume
> that the icache doesn't contain anything valid for its address range but
> we cannot be sure that its content has been written back from the dcache
> to L2 or memory further out. If the icache fills from those memories,
> ie. does not fill from the dcache, then we need to ensure that content
> has been flushed from the dcache. This was being done for lowmem pages
> but not for highmem pages. Fix this by mapping the page & flushing its
> content from the dcache in __flush_icache_page, before the page is
> provided to userland.
>

Reviewed-by: Lars Persson <larper@...s.com>

> Signed-off-by: Paul Burton <paul.burton@...tec.com>
>
> ---
>
>   arch/mips/mm/cache.c | 9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
> index 3f159ca..734cb2f 100644
> --- a/arch/mips/mm/cache.c
> +++ b/arch/mips/mm/cache.c
> @@ -16,6 +16,7 @@
>   #include <linux/mm.h>
>
>   #include <asm/cacheflush.h>
> +#include <asm/highmem.h>
>   #include <asm/processor.h>
>   #include <asm/cpu.h>
>   #include <asm/cpu-features.h>
> @@ -124,10 +125,14 @@ void __flush_icache_page(struct vm_area_struct *vma, struct page *page)
>   	unsigned long addr;
>
>   	if (PageHighMem(page))
> -		return;
> +		addr = (unsigned long)kmap_atomic(page);
> +	else
> +		addr = (unsigned long)page_address(page);
>
> -	addr = (unsigned long) page_address(page);
>   	flush_data_cache_page(addr);
> +
> +	if (PageHighMem(page))
> +		__kunmap_atomic((void *)addr);
>   }
>   EXPORT_SYMBOL_GPL(__flush_icache_page);
>
>