From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753132Ab3A3DXJ (ORCPT ); Tue, 29 Jan 2013 22:23:09 -0500 Received: from e28smtp06.in.ibm.com ([122.248.162.6]:41692 "EHLO e28smtp06.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752424Ab3A3DXH (ORCPT ); Tue, 29 Jan 2013 22:23:07 -0500 Message-ID: <51089210.2080705@linux.vnet.ibm.com> Date: Wed, 30 Jan 2013 11:22:56 +0800 From: Xiao Guangrong User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Marcelo Tosatti CC: Avi Kivity , Gleb Natapov , LKML , KVM Subject: Re: [PATCH v2 03/12] KVM: MMU: simplify mmu_set_spte References: <50FFB5A1.5090708@linux.vnet.ibm.com> <50FFB5E9.2010500@linux.vnet.ibm.com> <20130129002151.GB10814@amt.cnet> <51073A1C.1050600@linux.vnet.ibm.com> <20130129215345.GA27735@amt.cnet> In-Reply-To: <20130129215345.GA27735@amt.cnet> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13013003-9574-0000-0000-00000664EE8F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/30/2013 05:53 AM, Marcelo Tosatti wrote: > 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. > Okay. >> 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. Okay, i will make that patch more simpler in the next version.