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Date: Tue, 16 Jun 2009 19:38:16 +0100
From: Jamie Lokier <jamie@shareable.org>
Subject: Re: Configuration vs. compat hints [was Re: [Qemu-devel] [PATCHv3
	03/13] qemu: add routines to manage PCI capabilities]
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To: Mark McLoughlin <markmc@redhat.com>
Cc: Carsten Otte <cotte@de.ibm.com>, kvm@vger.kernel.org, "Michael S. Tsirkin" <mst@redhat.com>, Glauber Costa <glommer@redhat.com>, Rusty Russell <rusty@rustcorp.com.au>, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, Blue Swirl <blauwirbel@gmail.com>, Christian Borntraeger <borntraeger@de.ibm.com>, Paul Brook <paul@codesourcery.com>, Avi Kivity <avi@redhat.com>

Mark McLoughlin wrote:
> > After libvirt has done -drive file=foo... it should dump the machine 
> > config and use that from then on.
> 
> Right - libvirt then wouldn't be able to avoid the complexity of merging
> any future changes into the dumped machine config.

As long as qemu can accept a machine config _and_ -drive file=foo (and
monitor commands to add/remove devices), libvirt could merge by simply
calling qemu with whatever additional command line options or monitor
commands modify the config, then dump the new config.

That way, virtio would not have to deal with that complexity.  It
would be written in one place: qemu.

Or better, a utility: qemu-machine-config.

-- Jamie