From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH v2 02/12] KVM: x86: tag the instructions which are used to write page table Date: Wed, 03 Aug 2011 14:02:31 +0800 Message-ID: <4E38E477.2000208@cn.fujitsu.com> References: <4E37DA49.1040000@cn.fujitsu.com> <4E37DA73.7010908@cn.fujitsu.com> <4E37EB8E.6080207@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , KVM To: Avi Kivity Return-path: Received: from cn.fujitsu.com ([222.73.24.84]:62721 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1754436Ab1HCGAo (ORCPT ); Wed, 3 Aug 2011 02:00:44 -0400 In-Reply-To: <4E37EB8E.6080207@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 08/02/2011 08:20 PM, Avi Kivity wrote: > On 08/02/2011 02:07 PM, Xiao Guangrong wrote: >> The idea is from Avi: >> | tag instructions that are typically used to modify the page tables, and drop >> | shadow if any other instruction is used >> | The list would include, I'd guess, and, or, bts, btc, mov, xchg, cmpxchg, and >> | cmpxchg8b >> >> This patch is used to tag the instructions and in the later path, shadow page >> is dropped if it is written by other instructions > > We already have a mechanism for this, the decode tables. Why not add a new flag, PageTable, and set it on all relevant instructions? > OK, will do it in the next version. > Note we don't need to actually emulate, just decode, since page_fault can tell us whether a write failed due to page tables or mmio. > This is a interesting feature. If it happens, i will just drop the shadow pages and retry these instructions directly.