linux-kernel - Re: [RFC] KVM MMU: thinking of shadow page cache

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Message-ID: <4BB46365.7020400@redhat.com>
Date:	Thu, 01 Apr 2010 12:12:05 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC:	Ingo Molnar <mingo@...e.hu>, Marcelo Tosatti <mtosatti@...hat.com>,
	Sheng Yang <sheng@...ux.intel.com>,
	KVM list <kvm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] KVM MMU: thinking of shadow page cache

On 04/01/2010 12:05 PM, Xiao Guangrong wrote:
>
>> We've considered this in the past, it makes sense.  The big question is
>> whether any guests actually map the same page table through PDEs with
>> different permissions (mapping the same page table through multiple PDEs
>> is very common, but always with the same permissions).  Do you know of
>> any such guest?
>>      
> I also don't know whether have such guest.
> Maybe my idea is no good for current OS, thanks for your comments.
>    

In fact there are plans to make kvm such a guest (when running in nested 
mode) - when we perform live migration we write-protect all guest pages, 
and it's reasonable to use the top-level shadow page to write protect 
all memory at once instead of iterating over all mmu pages.  When that 
goes in, we should also implement your idea.

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

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