From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762868AbXGLIbZ (ORCPT ); Thu, 12 Jul 2007 04:31:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756341AbXGLIa6 (ORCPT ); Thu, 12 Jul 2007 04:30:58 -0400 Received: from ozlabs.org ([203.10.76.45]:59329 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756054AbXGLIa5 (ORCPT ); Thu, 12 Jul 2007 04:30:57 -0400 Subject: Re: [PATCH] lguest: disable SYSENTER for guests From: Rusty Russell To: Avi Kivity Cc: lkml - Kernel Mailing List , Andrew Morton , virtualization In-Reply-To: <4695DCAD.70507@qumranet.com> References: <1184224595.6005.772.camel@localhost.localdomain> <4695DCAD.70507@qumranet.com> Content-Type: text/plain Date: Thu, 12 Jul 2007 18:30:34 +1000 Message-Id: <1184229034.6005.780.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.10.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2007-07-12 at 10:47 +0300, Avi Kivity wrote: > Rusty Russell wrote: > But what kind of daredevil coder would propose such a thing?) > > Ah, so this is why you want ->next in preempt hooks. Well, my plan for > this sort of thing (for kvm has the same issues with the *STAR family of > msrs) is to add a new hook on switching from kernel to userspace, and > swap those msrs there. This allows not only the guest1->guest2 case to > be optimized, but also guest->kthread->guest, which is a common pattern > with I/O (and very common with -rt, which runs interrupts in threads). Adding instructions to the syscall path is not going to make you popular. But if you do it, I'll use it 8) Thanks, Rusty.