From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932184AbXCZTWV (ORCPT ); Mon, 26 Mar 2007 15:22:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932244AbXCZTWV (ORCPT ); Mon, 26 Mar 2007 15:22:21 -0400 Received: from smtp-outbound-1.vmware.com ([65.113.40.141]:46632 "EHLO smtp-outbound-1.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932184AbXCZTWV (ORCPT ); Mon, 26 Mar 2007 15:22:21 -0400 Message-ID: <46082B6B.8010707@vmware.com> Date: Mon, 26 Mar 2007 12:22:03 -0800 From: Zachary Amsden User-Agent: Thunderbird 1.5.0.10 (X11/20070221) MIME-Version: 1.0 To: David Rientjes CC: Hugh Dickins , Andrew Morton , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [patch -mm 1/2] i386: add ptep_test_and_clear_{dirty,young} References: <4607713F.6010900@vmware.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org David Rientjes wrote: > On Sun, 25 Mar 2007, Zachary Amsden wrote: > > >> If you actually clear the bit, you need to: >> >> + pte_update_defer(vma->vm_mm, addr, ptep); >> >> The reason is, when updating PTEs, the hypervisor must be notified. Using >> atomic operations to do this is fine for all hypervisors I am aware of. >> However, for hypervisors which shadow page tables, if these PTE modifications >> are not trapped, you need a post-modification call to fulfill the update of >> the shadow page table. >> >> > > Then why was ptep_test_and_clear_{dirty,young} ever removed in the first > place?? To gain the optimization of one fewer branch and introduce a hack > to advertise it's existance so the generic header file doesn't include its > own version? > Yes, pretty much. Zach