From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: [PATCH 3/6] KVM: MMU: introduce gfn_to_page_atomic() and	gfn_to_pfn_atomic()
Date: Wed, 16 Jun 2010 12:40:48 +0300
Message-ID: <4C189C20.2070804@redhat.com>
References: <4C16E6ED.7020009@cn.fujitsu.com> <4C16E75F.6020003@cn.fujitsu.com> <4C16E7AD.1060101@cn.fujitsu.com> <4C16E999.6050004@cn.fujitsu.com> <4C17625E.3020308@redhat.com> <20100616075918.GA17599@basil.fritz.box> <4C1885DF.80903@redhat.com> <20100616084900.GB17599@basil.fritz.box>
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Cc: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>,
	KVM list <kvm@vger.kernel.org>,
	Huang Ying <ying.huang@intel.com>
To: Andi Kleen <andi@firstfloor.org>
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In-Reply-To: <20100616084900.GB17599@basil.fritz.box>
Sender: linux-kernel-owner@vger.kernel.org
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On 06/16/2010 11:49 AM, Andi Kleen wrote:
>> The page is fine, the page tables are not.  Another task can munmap() the
>> thing while is_hwpoison_address() is running.
>>      
> Ok  that boils down to me not seeing that source.
>
> If it accesses the page tables yes then it's racy. But whoever
> looked up the page tables in the first place should have
> returned an -EFAULT. There's no useful address attached
> to poison.
>    

We need to distinguish between genuine -EFAULT and poisoned address.

That's why I suggested get_user_pages_ptes_fast.  You can return page = 
NULL (-EFAULT) and the pte in the same go.  No race, and useful for 
other cases.

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