From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754695AbZCHWML (ORCPT ); Sun, 8 Mar 2009 18:12:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753648AbZCHWL5 (ORCPT ); Sun, 8 Mar 2009 18:11:57 -0400 Received: from terminus.zytor.com ([198.137.202.10]:56554 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753521AbZCHWL5 (ORCPT ); Sun, 8 Mar 2009 18:11:57 -0400 Message-ID: <49B441D9.4010004@zytor.com> Date: Sun, 08 Mar 2009 15:08:25 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Ingo Molnar CC: Jeremy Fitzhardinge , Andrew Morton , the arch/x86 maintainers , Linux Kernel Mailing List , Xen-devel Subject: Re: [PATCH] xen: core dom0 support References: <1235786365-17744-1-git-send-email-jeremy@goop.org> <20090227212812.26d02f34.akpm@linux-foundation.org> <20090228084254.GA29342@elte.hu> <49A907DD.6010408@goop.org> <20090302120859.GB29015@elte.hu> <49B23907.8030103@goop.org> <20090308110150.GA19151@elte.hu> <49B43F1D.2000400@zytor.com> <20090308220609.GA23447@elte.hu> In-Reply-To: <20090308220609.GA23447@elte.hu> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ingo Molnar wrote: > > Since it's the same kernel image i think the only truly reliable > method would be to reboot between _different_ kernel images: > same instructions but randomly re-align variables both in terms > of absolute address and in terms of relative position to each > other. Plus randomize bootmem allocs and never-gets-freed-really > boot-time allocations. > > Really hard to do i think ... > Ouch, yeah. On the other hand, the numbers made sense to me, so I don't see why there is any reason to distrust them. They show a 5% overhead with pv_ops enabled, reduced to a 2% overhead with the changed. That is more or less what would match my intuition from seeing the code. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.