linux-kernel - Re: [PATCH]x86: flush tlb if PGD entry is changed in i386 PAE mode

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Date:	Wed, 16 Mar 2011 09:03:16 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Shaohua Li <shaohua.li@...el.com>
CC:	lkml <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	y-goto@...fujitsu.com,
	"Mallick, Asit K" <asit.k.mallick@...el.com>,
	stable <stable@...nel.org>
Subject: Re: [PATCH]x86: flush tlb if PGD entry is changed in i386 PAE mode

On 03/15/2011 11:37 PM, Shaohua Li wrote:
> According to intel CPU manual, every time PGD entry is changed in i386 PAE mode,
> we need do a full TLB flush. Current code follows this and there is comment
> for this too in the code. But current code misses the multi-threaded case. A
> changed page table might be used by several CPUs, every such CPU should flush
> TLB.
> Usually this isn't a problem, because we prepopulate all PGD entries at process
> fork. But when the process does munmap and follows new mmap, this issue will be
> triggered. When it happens, some CPUs will keep doing page fault.
>
> See: http://marc.info/?l=linux-kernel&m=129915020508238&w=2
>
> Reported-by: Yasunori Goto<y-goto@...fujitsu.com>
> Signed-off-by: Shaohua Li<shaohua.li@...el.com>
> Tested-by: Yasunori Goto<y-goto@...fujitsu.com>

Reviewed-by: Rik van Riel <riel@...hat.com>

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