From mboxrd@z Thu Jan  1 00:00:00 1970
From: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Subject: Re: [PATCH] KVM: x86: Avoid zapping mmio sptes twice for generation
 wraparound
Date: Wed, 03 Jul 2013 16:50:10 +0800
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References: <20130703171804.89d6cc2c.yoshikawa_takuya_b1@lab.ntt.co.jp> <51D3E093.3020408@redhat.com>	<51D3E33D.1090704@linux.vnet.ibm.com> <20130703175005.8e02a5d4.yoshikawa_takuya_b1@lab.ntt.co.jp>
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Cc: Paolo Bonzini <pbonzini@redhat.com>, gleb@redhat.com,
	kvm@vger.kernel.org
To: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
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On 07/03/2013 04:50 PM, Takuya Yoshikawa wrote:
> On Wed, 03 Jul 2013 16:39:25 +0800
> Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> wrote:
> 
>> Please wait a while. I can not understand it very clearly.
>>
>> This conditional check will cause caching a overflow value into mmio spte.
>> The simple case is that kvm adds new slots for many times, the mmio-gen is easily
>> more than MMIO_MAX_GEN.
> 
> Unconditional checking in commit_memory_region() is still there
> to treat such cases.

WHY?