From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753564Ab1HCJZ4 (ORCPT ); Wed, 3 Aug 2011 05:25:56 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46510 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753502Ab1HCJZu (ORCPT ); Wed, 3 Aug 2011 05:25:50 -0400 Message-ID: <4E391417.6050503@redhat.com> Date: Wed, 03 Aug 2011 12:25:43 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.18) Gecko/20110621 Fedora/3.1.11-1.fc15 Thunderbird/3.1.11 MIME-Version: 1.0 To: Xiao Guangrong CC: Marcelo Tosatti , LKML , KVM Subject: Re: [PATCH v2 02/12] KVM: x86: tag the instructions which are used to write page table References: <4E37DA49.1040000@cn.fujitsu.com> <4E37DA73.7010908@cn.fujitsu.com> <4E37EB8E.6080207@redhat.com> <4E38E477.2000208@cn.fujitsu.com> <4E39021F.8070508@redhat.com> <4E3913CC.7010907@cn.fujitsu.com> In-Reply-To: <4E3913CC.7010907@cn.fujitsu.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/03/2011 12:24 PM, Xiao Guangrong wrote: > > Maybe it's better to emulate if we can't find a fix for that. > > > > One way would be to emulate every 20 instructions; this breaks us out of the loop but reduces costly emulations to 5%. > > > > After much thought about this, may be this optimization is not good since: > - it is little complex > - this optimization is only applied to the instruction emulation caused by #PF > - it does not improve too much: > if we emulate the instruction, we need to do: > - decode instruction > - emulate it > - zap shadow pages > And do this, it can return to the guest, the guest can run the next instruction > > if we retry the instruction, we need to do: > - decode instruction > - zap shadow pages > then return to the guest and retry the instruction, however, we will get page fault > again(since the mapping is still read-only), so we will get another VM-exit and need > to do: > # trigger page fault > - handle the page fault and change the mapping to writable > - retry the instruction > until now, the guest can run the next instruction > > So, i do not think the new way is better, your opinion？ We can change to writeable and zap in the same exit, no? Basically call page_fault() again after zapping. -- error compiling committee.c: too many arguments to function