From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753059Ab3A2Xiz (ORCPT ); Tue, 29 Jan 2013 18:38:55 -0500 Received: from mx1.redhat.com ([209.132.183.28]:18216 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751657Ab3A2Xiu (ORCPT ); Tue, 29 Jan 2013 18:38:50 -0500 Date: Tue, 29 Jan 2013 19:53:45 -0200 From: Marcelo Tosatti To: Xiao Guangrong Cc: Avi Kivity , Gleb Natapov , LKML , KVM Subject: Re: [PATCH v2 03/12] KVM: MMU: simplify mmu_set_spte Message-ID: <20130129215345.GA27735@amt.cnet> References: <50FFB5A1.5090708@linux.vnet.ibm.com> <50FFB5E9.2010500@linux.vnet.ibm.com> <20130129002151.GB10814@amt.cnet> <51073A1C.1050600@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51073A1C.1050600@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 29, 2013 at 10:55:24AM +0800, Xiao Guangrong wrote: > On 01/29/2013 08:21 AM, Marcelo Tosatti wrote: > > On Wed, Jan 23, 2013 at 06:05:29PM +0800, Xiao Guangrong wrote: > >> In order to detecting spte remapping, we can simply check whether the > >> spte has already been pointing to the pfn even if the spte is not the > >> last spte, for middle spte is pointing to the kernel pfn which can not > >> be mapped to userspace > > > > This check is detecting spte overwrite, when a large spte is replaced by > > pointer to spte table. > > > > Can't see why check for different pfn is safe: only 'int level' can > > differ, and pfn be equivalent, for example. > > The 'u64 *sptep' must on the "int level" we want to set, that means: > page_header(__pa(sptep)).role.level == "int level". Right, then stick a comment there noting which cases that condition handles. Keep the current comment and add more. > We discussed this before :), the discussion can be found at: > http://marc.info/?l=kvm&m=135345057329427&w=2. Note http://marc.info/?l=kvm&m=135345059929436&w=2, please take into account in the future.