From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] [PATCH] Vmchannel PCI device. Date: Sun, 14 Dec 2008 16:56:49 -0600 Message-ID: <49458F31.8040208@codemonkey.ws> References: <20081214115027.4028.56164.stgit@dhcp-1-237.tlv.redhat.com> <20081214131247.GS5555@redhat.com> <49455B5E.8080504@codemonkey.ws> <20081214221346.GA16902@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , qemu-devel@nongnu.org, kvm@vger.kernel.org To: "Daniel P. Berrange" Return-path: Received: from an-out-0708.google.com ([209.85.132.249]:31411 "EHLO an-out-0708.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750931AbYLNW4z (ORCPT ); Sun, 14 Dec 2008 17:56:55 -0500 Received: by an-out-0708.google.com with SMTP id d40so1006842and.1 for ; Sun, 14 Dec 2008 14:56:54 -0800 (PST) In-Reply-To: <20081214221346.GA16902@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Daniel P. Berrange wrote: > On Sun, Dec 14, 2008 at 01:15:42PM -0600, Anthony Liguori wrote: > > One non-QEMU backend I can see being implemented is a DBus daemon, > providing a simple bus for RPC calls between guests & host. The main problem with "external" backends is that they cannot easily participate in save/restore or live migration. If you want to have an RPC mechanism, I would suggest implementing the backend in QEMU and hooking QEMU up to dbus. Then you can implement proper save/restore. > Or on > a similar theme, perhaps a QPid message broker in the host OS. Yet > another backend is a clustering service providing a virtual fence > device to VMs. Why not use virtual networking for a clustering service (as you would in real machines). > All of these would live outside QEMU, and as such > exposing the backend using the character device infrastructure > is a natural fit. > If you don't have QEMU as a broker, it makes it very hard for QEMU to virtualization all of the resources exposed to the guest. This complicates things like save/restore and complicates security policies since you now have things being done on behalf of a guest originating from another process. It generally breaks the model of guest-as-a-process. What's the argument to do these things external to QEMU? Regards, Anthony Liguori > Daniel >