Re: Configuration vs. compat hints [was Re: [Qemu-devel] [PATCHv3 03/13] qemu: add routines to manage PCI capabilities]

Anthony Liguori
2009-06-15T12:48:26Z

Avi Kivity wrote:
> On 06/15/2009 12:09 PM, Mark McLoughlin wrote:
>>>>> I think the point is that you don't need version numbers if you
>>>>> have a
>>>>> proper device tree.
>>>>>
>>>>>
>>>> How do you add a new attribute to the device tree and, when a supplied
>>>> device tree lacking said attribute, distinguish between a device tree
>>>> from an old version of qemu (i.e. use the old default) and a partial
>>>> device tree from the VM manager (i.e. use the new default) ?
>>>>
>>>>
>>> -baseline 0.10
>>>
>>
>> That's a version number :-)
>>
>> (I was responding to Anthony's "you don't need a version number")
>>
>
> If you want to prevent incompatibilities, you need to make everything
> new (potentially including bugfixes) non-default. Eventually the
> default configuration becomes increasingly unusable and you need a new
> baseline. You must still be able to fall back to the old baseline for
> older guests. I don't think games with configuration files can hide
> that.

-M pc1
-M pc2

etc.

This is pretty easy to maintain with config files.

Regards,

Anthony Liguori