From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v2 3/10] KVM: MMU: fix direct sp's access corruptted Date: Mon, 28 Jun 2010 14:13:23 +0300 Message-ID: <4C2883D3.2050606@redhat.com> References: <4C2498EC.2010006@cn.fujitsu.com> <4C249BAD.6000609@cn.fujitsu.com> <4C287081.40300@redhat.com> <4C287332.5080803@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , KVM list To: Xiao Guangrong Return-path: Received: from mx1.redhat.com ([209.132.183.28]:54555 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751182Ab0F1LN1 (ORCPT ); Mon, 28 Jun 2010 07:13:27 -0400 In-Reply-To: <4C287332.5080803@cn.fujitsu.com> Sender: kvm-owner@vger.kernel.org List-ID: On 06/28/2010 01:02 PM, Xiao Guangrong wrote: > > Avi Kivity wrote: > > >> Instead of adding a new bit, can you encode the protection in the direct >> sp's access bits? So we'll have one sp for read-only or >> writeable-but-not-dirty small pages, and another sp for >> writeable-and-dirty small pages. >> >> > It looks like it can't solve all problems, it fix the access corrupted, > but will cause D bit losed: > > mapping A and mapping B both are writable-and-dirty, when mapping A write > #PF occurs, the mapping is writable, then we can't set B's D bit anymore. > If B is writeable-and-dirty, then it's D bit is already set, and we don't need to do anything. If B is writeable-and-clean, then we'll have an spte pointing to a read-only sp, so we'll get a write fault on access and an opportunity to set the D bit. > Anyway, i think we should re-intall the mapping when the state is changed. :-( > When the gpte is changed from read-only to writeable or from clean to dirty, we need to update the spte, yes. But that's true for other sptes as well, not just large gptes. -- error compiling committee.c: too many arguments to function