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Date: Tue, 12 Jan 2010 10:19:13 -0200
From: Luiz Capitulino <lcapitulino@redhat.com>
Subject: Re: [Qemu-devel] QMP forward compatibility support
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To: Markus Armbruster <armbru@redhat.com>
Cc: aliguori@us.ibm.com, dlaor@redhat.com, qemu-devel@nongnu.org, avi@redhat.com

On Tue, 12 Jan 2010 09:16:43 +0100
Markus Armbruster <armbru@redhat.com> wrote:

> >>   Now, if everything is disabled by default and qemu might be running
> >> already, do we really need to have a handshake?
> >>    
> >
> > I think it's valuable to have a discrete period of time when no
> > commands have been executed where features can be enabled.  It
> > simplifies some nasty edge conditions regarding enabling features
> > while there are outstanding commands in flight.
> 
> That's exactly why I lobbied for feature negotiation in the initial
> handshake, i.e. client connects, server sends greeting with features,
> client sends features it wants enabled, and only then we enter the
> normal command loop.  Protocol that don't have that tend to get it
> retrofitted when they evolve.
> 
> Let's do it now, before backward compatibility concerns force us to do
> it in an ugly way.

 Yes, it was good to bring out the issue after all.

 Please, review the design I'm proposing in my reply to Anthony.