linux-kernel - Re: [PATCH v2 3/10] KVM: MMU: fix direct sp's access corruptted

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Date:	Tue, 29 Jun 2010 17:13:44 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 3/10] KVM: MMU: fix direct sp's access corruptted



Avi Kivity wrote:
> On 06/29/2010 12:04 PM, Xiao Guangrong wrote:
>>
>>> Simply replace (*spte&  SPTE_NO_DIRTY) with a condition that checks
>>> whether sp->access is consistent with gw->pt(e)_access.
>>>
>>>      
>> If the guest mapping is writable and it !dirty, we mark SPTE_NO_DIRTY
>> flag in
>> the spte, when the next #PF occurs, we just need check this flag and
>> see whether
>> gpte's D bit is set, if it's true, we zap this spte and map to the
>> correct sp.
>>    
> 
> My point is, SPTE_NO_DIRTY is equivalent to an sp->role.access check
> (the access check is a bit slower, but that shouldn't matter).
> 

I see.

> 
>>> Can you write a test case for qemu-kvm.git/kvm/test that demonstrates
>>> the problem and the fix?  It will help ensure we don't regress in this
>>> area.
>>>
>>>      
>> OK, but allow me do it later :-)
>>
>>    
> 
> Sure, but please do it soon.

Sure, i will do it as soon as possible.
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