From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH v2 3/10] KVM: MMU: fix direct sp's access corruptted Date: Tue, 29 Jun 2010 17:08:44 +0800 Message-ID: <4C29B81C.3040605@cn.fujitsu.com> References: <4C2498EC.2010006@cn.fujitsu.com> <4C249BAD.6000609@cn.fujitsu.com> <4C287081.40300@redhat.com> <4C287332.5080803@cn.fujitsu.com> <4C2883D3.2050606@redhat.com> <4C2949A5.1070303@cn.fujitsu.com> <4C299B7E.5020303@redhat.com> <4C29A30A.8020107@redhat.com> <4C29A49C.8040804@cn.fujitsu.com> <4C29B3FD.8040802@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , KVM list To: Avi Kivity Return-path: In-Reply-To: <4C29B3FD.8040802@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org Avi Kivity wrote: > On 06/29/2010 10:45 AM, Xiao Guangrong wrote: >> >>> - there was once talk that instead of folding pt_access and pte_access >>> together into the leaf sp->role.access, each sp level would have its own >>> access permissions. In this case we don't even have to get a new direct >>> sp, only change the PT_DIRECTORY_LEVEL spte to add write permissions >>> (all direct sp's would be writeable and permissions would be controlled >>> at their parent_pte level). Of course that's a much bigger change than >>> this bug fix. >>> >>> >> Yeah, i have considered this way, but it will change the shadow page's >> mapping >> way: it control the access at the upper level, but in the current >> code, we allow >> the upper level have the ALL_ACCESS and control the access right at >> the last level. >> It will break many things, such as write-protected... >> > > spte's access bits have dual purpose, both to map guest protection and > for host protection (like for shadowed pages, or ksm pages). So the > last level sptes still need to consider host write protection. > Yeah, i see your mean, thanks, :-)