From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932069AbXCZGgN (ORCPT ); Mon, 26 Mar 2007 02:36:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932081AbXCZGgN (ORCPT ); Mon, 26 Mar 2007 02:36:13 -0400 Received: from smtp-out.google.com ([216.239.45.13]:11871 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932069AbXCZGgM (ORCPT ); Mon, 26 Mar 2007 02:36:12 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=received:date:from:x-x-sender:to:cc:subject:in-reply-to: message-id:references:mime-version:content-type; b=PSR0hHcQZwje/js2Ew4dDyeUehq46ECdEVG7LXrUFVS0Dfs7wimCI/J0t4Y6qv9Yf 7WwI9iKFZ/6Y2PtkUye8Q== Date: Sun, 25 Mar 2007 23:35:53 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Zachary Amsden 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} In-Reply-To: <4607713F.6010900@vmware.com> Message-ID: References: <4607713F.6010900@vmware.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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?