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

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Message-ID: <4C29B93C.9010101@redhat.com>
Date:	Tue, 29 Jun 2010 12:13:32 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.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

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).


>> 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.

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

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