linux-kernel - Re: [PATCH 1/2] KVM: MMU: don't make direct sp read-only if !map

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Message-ID: <4D06CE19.9000908@cn.fujitsu.com>
Date:	Tue, 14 Dec 2010 09:53:29 +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 <kvm@...r.kernel.org>
Subject: Re: [PATCH 1/2] KVM: MMU: don't make direct sp read-only if !map_writable

On 12/13/2010 06:32 PM, Avi Kivity wrote:
> On 12/13/2010 12:31 PM, Xiao Guangrong wrote:
>> Currently, if the page is not allowed to write, then it can drop
>> ACC_WRITE_MASK in pte_access, and the direct sp's access is:
>>     gw->pt_access&  gw->pte_access
>> so, it also removes the write access in the direct sp.
>>
>> There is a problem: if the access of those pages which map thought the
>> same
>> mapping in guest is different in host, it causes host switch direct sp
>> very
>> frequently.
> 
> I just sent a patch to fix this in a different way, please review it.
> 

Your patch is good for me, please ignore this one :-)

Umm, do we need move "access &= ~ACC_WRITE_MASK" into set_spte() then
can remove the same code in the caller?
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