Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756690AbXIOIJD (ORCPT ); Sat, 15 Sep 2007 04:09:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753041AbXIOIIr (ORCPT ); Sat, 15 Sep 2007 04:08:47 -0400 Received: from il.qumranet.com ([82.166.9.18]:37439 "EHLO il.qumranet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752431AbXIOIIq (ORCPT ); Sat, 15 Sep 2007 04:08:46 -0400 Message-ID: <46EB930C.2000909@qumranet.com> Date: Sat, 15 Sep 2007 11:08:44 +0300 From: Avi Kivity User-Agent: Thunderbird 2.0.0.5 (X11/20070719) MIME-Version: 1.0 To: Zachary Amsden CC: Anthony Liguori , kvm-devel@lists.sourceforge.net, Jeremy Fitzhardinge , linux-kernel@vger.kernel.org Subject: Re: [kvm-devel] [PATCH] Refactor hypercall infrastructure References: <11897991353793-git-send-email-aliguori@us.ibm.com> <46EAF4C6.8090903@goop.org> <46EAF6FC.80207@codemonkey.ws> <1189804847.5982.137.camel@bodhitayantram.eng.vmware.com> <46EB00D8.3090903@codemonkey.ws> <1189827476.5982.143.camel@bodhitayantram.eng.vmware.com> In-Reply-To: <1189827476.5982.143.camel@bodhitayantram.eng.vmware.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-3.0 (firebolt.argo.co.il [0.0.0.0]); Sat, 15 Sep 2007 11:08:44 +0300 (IDT) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1695 Lines: 39 Zachary Amsden wrote: > On Fri, 2007-09-14 at 16:44 -0500, Anthony Liguori wrote: > > >> So then each module creates a hypercall page using this magic MSR and >> the hypervisor has to keep track of it so that it can appropriately >> change the page on migration. The page can only contain a single >> instruction or else it cannot be easily changed (or you have to be able >> to prevent the guest from being migrated while in the hypercall page). >> >> We're really talking about identical models. Instead of an MSR, the #GP >> is what tells the hypervisor to update the instruction. The nice thing >> about this is that you don't have to keep track of all the current >> hypercall page locations in the hypervisor. >> > > I agree, multiple hypercall pages is insane. I was thinking more of a > single hypercall page, fixed in place by the hypervisor, not the kernel. > > Then each module can read an MSR saying what VA the hypercall page is > at, and the hypervisor can simply flip one page to switch architectures. > VA as in "Virtual Address"? the ppc people don't have hypervisor-visible virtual addresses, and the hypervisor (on x86) can't safely select a virtual address, and ... That means you need a physical address, so you need a central initialization routine, and drivers for unmodified OSes can no longer be self contained. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/