linux-kernel - Re: [PATCH 3/4] KVM: MMU: notrap it if gpte's reserved is set

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Message-ID: <4CE3339F.4020200@cn.fujitsu.com>
Date:	Wed, 17 Nov 2010 09:45:03 +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 3/4] KVM: MMU: notrap it if gpte's reserved is set

On 11/15/2010 05:17 PM, Avi Kivity wrote:
> On 11/15/2010 07:41 AM, Xiao Guangrong wrote:
>> On 11/14/2010 06:56 PM, Avi Kivity wrote:
>> >  On 11/12/2010 12:34 PM, Xiao Guangrong wrote:
>> >>  We can past the page fault to guest directly if gpte's reserved
>> >>  is set
>> >>
>> >
>> >  How can that work? shadow_notrap_nonpresent_pte causes a fault with
>> >  PFEC.P=PFEC.RSVD=0, while we need PFEC.P=PFEC.RSVD=1.
>> >
>>
>> Ah, i missed it for a long time, thanks for you point it out.
>>
>> The same mistake is in 'prefetch' path, i'll fix it in the v2 version.
> 
> Doesn't access.flat catch this?

Unfortunately, it can't catch this.

> 
> Ideally we'd have a test case to catch this, but it may be hard to write.
> 

Um. i'll do it later.

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