linux-kernel - Re: [PATCH v2 5/5] KVM: MMU: retry #PF for softmmu

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Date:	Mon, 15 Nov 2010 17:55:25 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	Gleb Natapov <gleb@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 5/5] KVM: MMU: retry #PF for softmmu

On 11/15/2010 05:30 PM, Avi Kivity wrote:

>> Yeah, this 'retry' is unnecessary if the process is killed, but this
>> case is infrequent, the most case is the process keeps running and try
>> to access the fault address later.
> 
> The problem is that if we retry in this case, we install an incorrect spte?
> 

......

>> can avoid if the page mapping have been fixed.
> 
> The guest may have changed page directories or other levels.
> 

......

>> >  Or another thread may have mmap()ed something else over the
>> >  same address.
>>
>> The mmap virtual address is also visible for other threads since the
>> threads
>> have the same page table, so i think this case is the same as above?
> 
> Again, don't we install the wrong spte in this case?
> 

I think it doesn't corrupts spte since we will walk guest page table again
and map it to shadow pages when we retry #PF.
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