linux-kernel - Re: [PATCH 3/6] KVM: MMU: introduce gfn_to_page_atomic() and gfn_to_pfn

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Message-ID: <4C1885DF.80903@redhat.com>
Date:	Wed, 16 Jun 2010 11:05:51 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>,
	Huang Ying <ying.huang@...el.com>
Subject: Re: [PATCH 3/6] KVM: MMU: introduce gfn_to_page_atomic() and	gfn_to_pfn_atomic()

On 06/16/2010 10:59 AM, Andi Kleen wrote:
> On Tue, Jun 15, 2010 at 02:22:06PM +0300, Avi Kivity wrote:
>    
>> Too much duplication.  How about putting the tail end of the function in a
>> common helper (with an inatomic flag)?
>>
>> btw, is_hwpoison_address() is racy.  While it looks up the address, some
>> other task can unmap the page tables under us.
>>      
> Where is is_hwpoison_address() coming from? I can't find it anywhere.
>
>    

kvm.git master mm/memory-failure.c (19564281fe).

> Anyways hwpoison will not remove the page as long as there
> is a reference to it, so as long as you get the reference
> race free against another task you're ok. Of course there might
> be always an error in between and the hardware may poison
> the data, but we don't try to handle all kernel errors.
>    

The page is fine, the page tables are not.  Another task can munmap() 
the thing while is_hwpoison_address() is running.

-- 
error compiling committee.c: too many arguments to function

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