linux-kernel - Re: [PATCH v2 03/12] KVM: MMU: simplify mmu_set

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Message-ID: <51089210.2080705@linux.vnet.ibm.com>
Date:	Wed, 30 Jan 2013 11:22:56 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Marcelo Tosatti <mtosatti@...hat.com>
CC:	Avi Kivity <avi.kivity@...il.com>, Gleb Natapov <gleb@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 03/12] KVM: MMU: simplify mmu_set_spte

On 01/30/2013 05:53 AM, Marcelo Tosatti wrote:
> On Tue, Jan 29, 2013 at 10:55:24AM +0800, Xiao Guangrong wrote:
>> On 01/29/2013 08:21 AM, Marcelo Tosatti wrote:
>>> On Wed, Jan 23, 2013 at 06:05:29PM +0800, Xiao Guangrong wrote:
>>>> In order to detecting spte remapping, we can simply check whether the
>>>> spte has already been pointing to the pfn even if the spte is not the
>>>> last spte, for middle spte is pointing to the kernel pfn which can not
>>>> be mapped to userspace
>>>
>>> This check is detecting spte overwrite, when a large spte is replaced by 
>>> pointer to spte table.
>>>
>>> Can't see why check for different pfn is safe: only 'int level' can
>>> differ, and pfn be equivalent, for example.
>>
>> The 'u64 *sptep' must on the "int level" we want to set, that means:
>>  page_header(__pa(sptep)).role.level == "int level".
> 
> Right, then stick a comment there noting which cases that condition handles.
> Keep the current comment and add more.
> 

Okay.

>> We discussed this before :), the discussion can be found at:
>> http://marc.info/?l=kvm&m=135345057329427&w=2.
> 
> Note http://marc.info/?l=kvm&m=135345059929436&w=2, please take into
> account in the future.

Okay, i will make that patch more simpler in the next version.


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