Date: Tue, 9 Jun 2009 12:25:04 +0200
From: Nick Piggin <npiggin@suse.de>
To: Andi Kleen <andi@firstfloor.org>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
       linux-mm@kvack.org, fengguang.wu@intel.com
Subject: Re: [PATCH] [6/16] HWPOISON: Add various poison checks in mm/memory.c
Message-ID: <20090609102504.GH14820@wotan.suse.de>
References: <20090603846.816684333@firstfloor.org> <20090603184639.1933B1D028F@basil.firstfloor.org>
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On Wed, Jun 03, 2009 at 08:46:38PM +0200, Andi Kleen wrote:
> 
> Bail out early when hardware poisoned pages are found in page fault handling.
> Since they are poisoned they should not be mapped freshly into processes,
> because that would cause another (potentially deadly) machine check
> 
> This is generally handled in the same way as OOM, just a different
> error code is returned to the architecture code.
> 
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> 
> ---
>  mm/memory.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> Index: linux/mm/memory.c
> ===================================================================
> --- linux.orig/mm/memory.c	2009-06-03 19:36:23.000000000 +0200
> +++ linux/mm/memory.c	2009-06-03 19:36:23.000000000 +0200
> @@ -2797,6 +2797,9 @@
>  	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
>  		return ret;
>  
> +	if (unlikely(PageHWPoison(vmf.page)))
> +		return VM_FAULT_HWPOISON;

Again, it would be nice if you just worry about this in your MCE
handler and don't sprinkle things like this in fastpaths.

> +
>  	/*
>  	 * For consistency in subsequent calls, make the faulted page always
>  	 * locked.
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