From mboxrd@z Thu Jan  1 00:00:00 1970
From: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Subject: Re: [PATCH 5/8] KVM: don't touch vcpu stat after async pf is complete
Date: Thu, 28 Oct 2010 15:35:13 +0800
Message-ID: <4CC927B1.2020807@cn.fujitsu.com>
References: <4CC7EA7D.5020901@cn.fujitsu.com> <4CC7EB75.9030709@cn.fujitsu.com> <20101027104412.GO26191@redhat.com>
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Cc: Avi Kivity <avi@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
To: Gleb Natapov <gleb@redhat.com>
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In-Reply-To: <20101027104412.GO26191@redhat.com>
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On 10/27/2010 06:44 PM, Gleb Natapov wrote:
> On Wed, Oct 27, 2010 at 05:05:57PM +0800, Xiao Guangrong wrote:
>> Don't make a KVM_REQ_UNHALT request after async pf is completed since it
>> can break guest's 'halt' instruction.
>>
> Why is it a problem? CPU may be unhalted by different events so OS
> shouldn't depend on it.
> 

We don't know how guest OS handles it after HLT instruction is completed,
according to X86's spec, only NMI/INTR/RESET/INIT/SMI can break halt state,
it violations the hardware behavior if we allow other event break this
state. Your opinion? :-)