Message-ID: <4C31A13F.9030408@cn.fujitsu.com>
Date: Mon, 05 Jul 2010 17:09:19 +0800
From: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
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To: Avi Kivity <avi@redhat.com>
CC: Marcelo Tosatti <mtosatti@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
       KVM list <kvm@vger.kernel.org>
Subject: Re: [PATCH v4 5/6] KVM: MMU: combine guest pte read between walk
 and pte prefetch
References: <4C2C9DC0.8050607@cn.fujitsu.com> <4C2C9E6C.2040803@cn.fujitsu.com> <20100702170303.GC25969@amt.cnet> <4C2F117C.2000006@cn.fujitsu.com> <4C2F2835.5060508@redhat.com> <4C2F2A0C.90704@cn.fujitsu.com> <4C2F2C5B.9020503@redhat.com> <4C2F2DBB.50904@cn.fujitsu.com> <4C2F30BD.7050702@redhat.com> <4C2F31D9.5010104@redhat.com> <4C2F3527.3020307@cn.fujitsu.com> <4C309B23.9060808@redhat.com> <4C3148FF.3030209@cn.fujitsu.com> <4C319699.9000104@redhat.com> <4C319BBB.5020408@cn.fujitsu.com> <4C31A069.6090806@redhat.com>
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Avi Kivity wrote:

> 
> I'm not convinced we can bypass the checks.  Consider:
> 
> 
> VCPU0                 VCPU1
> 
> #PF
> walk_addr
> -> gpml4e0,gpdpe0,gpde0,gpte0
> 
>                       replace gpdpe0 with gpdpe1
>                       #PF
>                       walk_addr
> -> gpml4e0,gpdpe1,gpde1,gpte1
>                       fetch
>                       -> establish hpml4e0,hpdpte1,hpde0,hpte1
> fetch
> read hpdpe1
> if (present(hpdpe1))
>     continue;
> ...
> write hpte0 using shadow hieratchy for hpte1
> 

Ah, i missed this case, thanks for you point it out, i'll fix it in
the next version.
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