From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] Refactor hypercall infrastructure Date: Sat, 15 Sep 2007 11:08:44 +0300 Message-ID: <46EB930C.2000909@qumranet.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, Jeremy Fitzhardinge , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Zachary Amsden Return-path: In-Reply-To: <1189827476.5982.143.camel-cxY/u30q8FloTgUnLF1by8fTvwmfpRNyZeezCHUQhQ4@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org 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. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/