Re: [Qemu-devel] CPU models and feature probing (was Re: [PATCH qom-cpu 00/16 v10] target-i386: convert CPU) features into properties

[Paolo Bonzini]

Il 07/02/2014 11:16, Eduardo Habkost ha scritto:
> You are not alone. I remember we spent lots of time trying to convince
> Anthony to allow global properties and compat_props affect dynamic
> properties not just static properties, and static properties were a big
> deal due to reasons I didn't understand completely. Now I am hearing the
> opposite message, and I don't understand the reasons for the change of
> plans. I am confused.

Picture me confused as well, but at the same I think I understand the 
reasons for the change of plans.

At some point you have to acknowledge that the grand vision of QEMU as a 
small core and management only poking at QOM objects with properties has 
never materialized, and probably never will.

After seeing no progress whatsoever on 
http://wiki.qemu.org/Features/QOM#TODO after 2 years, we should perhaps 
try to get fresh ideas into QOM based on how we've been using it and 
what we'd like to do with it.  "Design by committee" (more accurately: 
"design by prophet") will not lead us anywhere.

QOM definitely needs dynamic properties for child<>, and for tricks such 
as simulation of array properties.  However, assume Igor or Eduardo or 
Marcel can come up with a new QAPI-friendly static properties design, 
that combines the best feature of QOM dynamic properties and qdev static 
properties, why should it be rejected?

Code should not be frozen against some abstract design, it must evolve 
to solve concrete problems until it can solve all of them easily.  Or do 
we want to become a project where good code is not anymore the best way 
to have other developers change their mind?

Paolo