From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757888Ab0E0KKe (ORCPT ); Thu, 27 May 2010 06:10:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58908 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751978Ab0E0KKd (ORCPT ); Thu, 27 May 2010 06:10:33 -0400 Message-ID: <4BFE4513.8090606@redhat.com> Date: Thu, 27 May 2010 13:10:27 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100330 Fedora/3.0.4-1.fc12 Thunderbird/3.0.4 MIME-Version: 1.0 To: Xiao Guangrong CC: Marcelo Tosatti , LKML , KVM list Subject: Re: [PATCH 2/2] KVM: MMU: fix relaxing permission References: <4BFC8B0D.2060106@cn.fujitsu.com> <4BFC8B8C.7010402@cn.fujitsu.com> In-Reply-To: <4BFC8B8C.7010402@cn.fujitsu.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/26/2010 05:46 AM, Xiao Guangrong wrote: > There is a relaxing permission operation in set_spte(): > > if guest's CR0.WP is not set and R/W #PF occurs in supervisor-level, > the mapping path might set to writable, then user can allow to write. > > @@ -1859,8 +1859,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, > > spte |= (u64)pfn<< PAGE_SHIFT; > > - if ((pte_access& ACC_WRITE_MASK) > - || (write_fault&& !is_write_protection(vcpu)&& !user_fault)) { > + if (pte_access& ACC_WRITE_MASK) { > > The host always sets cr0.wp (in shadow mode) so we can write protect page tables. So when the guest clears cr0.wp, we emulate a gpte with gpte.w=0 and gpte.u=1 in two ways: - spte.w=1, spte.u=0: this will allow the guest kernel to write but trap on guest user access - spte.w=0, spte.u=1: allows guest user access but traps on guest kernel writes If the guest attempts an access that is currently disallowed, we switch to the other spte encoding. -- error compiling committee.c: too many arguments to function