linux-kernel - Re: [PATCH 5/6] KVM: MMU: prefetch ptes when intercepted guest #PF

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Message-ID: <4C19EADE.6090408@cn.fujitsu.com>
Date:	Thu, 17 Jun 2010 17:29:02 +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 5/6] KVM: MMU: prefetch ptes when intercepted guest #PF



Avi Kivity wrote:
> On 06/17/2010 12:04 PM, Xiao Guangrong wrote:
>>
>>
>>> So we can change the fault path to always fault 16 ptes, aligned on 16
>>> pte boundary, with the needed pte called with specualtive=false.
>>>      
>> Avi, i not understand it clearly, Could you please explain it? :-(
>>    
> 
> Right now if the fault is in spte i, you prefetch ptes
> (i+1)..(i+MAX_PREFETCH-1).  I'd like to prefetch ptes (i &
> ~(MAX_PREFETCH-1))..(i | (MAX_PREFETCH - 1)).  Read all those gptes, and
> map them one by one with speculative = false only for spte i.
> 

Thanks for your explanation, i see.
 
> Perhaps we need to integrate it into walk_addr, there's  no reason to
> read the gptes twice.
> 

OK, will do it.
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