linux-kernel - Re: [PATCH v5 6/9] KVM: MMU: introduce pte_prefetch_topup_memory

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Message-ID: <4C3C036B.5060108@cn.fujitsu.com>
Date:	Tue, 13 Jul 2010 14:10:51 +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 v5 6/9] KVM: MMU: introduce pte_prefetch_topup_memory_cache()



Avi Kivity wrote:
> On 07/13/2010 08:48 AM, Xiao Guangrong wrote:
>>
>>> Right.  We should fix those too.
>>>
>>> Prefetch is much more worrying though, especially with ept.  If a guest
>>> is using just 1/8 of the pages, it can look to migration as if it's
>>> using 100% of the pages.  The impact can be pretty large.
>>>      
>> We disabled prefetch if ept is enabled since it can break access bit
>> tracking.
>>    
> 
> Oh yes.
> 
>> I'll fix the dirty bit tracking before post the new version of this
>> patchset.
>>    
> 
> Should be simple - disable prefetch for slots that have dirty tracking
> enabled.

Agree.

> 
> What about the Linux accessed and dirty bits?  Need to instantiate the
> speculative sptes with accessed and dirty bits clear (and later examine
> them when we release the page).
> 

I see, will do :-)
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