Re: [Xen-devel] Re: [Qemu-devel] [PATCH 12/13] set vnc password from xenstore.

[Jamie Lokier]

Daniel P. Berrange wrote:
> On Thu, Aug 21, 2008 at 11:34:41PM +0200, Gerd Hoffmann wrote:
> >   Hi,
> > 
> > > If there are reasons that Xend doesn't want to interact with the monitor
> > > (for instance, if you want to support monitor redirection), we can
> > > certainly discuss how to enhance the monitor (like having multiple
> > > monitor instances).
> > 
> > Multiple monitor instances would be very useful anyway.
> > 
> > Right now there is no way to use the monitor for libvirt-managed qemu
> > instances because libvirt uses the monitor.  Being able to both use
> > libvirt *and* have a monitor prompt to type commands would be great.
> 
> I disagree - that means you'll no longer be able to trust what libvirt
> tells you about the VM, and libvirt won't have a guarenteed consistent
> view of the VM's state because things will be changed behind its back.

If there were multiple monitor instances, you could filter them _all_
through libvirt, so it would always know the VM state.

That's what I do in my vM manager script. User can connect to the
manager's socket and send a monitor command.  It's forwarded to QEMU,
but some filtering so the script knows what's going on, e.g. when
changing CD-ROM, starting/stopping the CPU etc.

You can't do that nicely now, though, because some commands take a
long time to execute.

Also, there's no nice way to wait for events like "tell me when the
guest reboots the CPU" at the moment.

-- Jamie