Re: [Qemu-devel] machines and versions - why so many?

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 06/24/2014 06:17 PM, Markus Armbruster wrote:
> Alexey Kardashevskiy <aik@ozlabs.ru> writes:
> 
>> On 06/24/2014 03:15 PM, Paolo Bonzini wrote:
>>> Il 23/06/2014 23:35, Alexey Kardashevskiy ha scritto:
>>>> nec-usb-xhci is off for PC_COMPAT_1_3 because of what? PIIX emulation was
>>>> broken in 1.3? Or nec-usb-xhci?
>>>
>>> nec-usb-xhci is not "off".
>>
>> Yes, my bad, I understood (but explained this wrong) that XHCI is enabled
>> but without MSI.
>>
>>
>>>
>>>             .driver   = "nec-usb-xhci",\
>>>             .property = "msi",\
>>>             .value    = "off",\
>>>
>>> What's off is MSI (and MSI-X), because it wasn't implemented.
>>>
>>>> If it is the latter, why is the tweak limited by PC?
>>>
>>> Because at the time nobody cared about migration compatibility (even now
>>> only pSeries is starting to care).
>>
>>
>> "only pSeries"? There are plenty of x86 machines already and if it is not
>> for migration support, then what are they all for? :)
> 
> At the time, nobody *else* cared.  Only PC did.

Ah. Misinterpret. My bad. Ok.

> 
> Back then gerd created a way to do the compatibility stuff without
> getting into the other target's hair: compat_props.  They've served us
> well enough, but now that more targets get interested in migration,
> their shortcomings start to hurt.  Having to duplicate device
> compatibility gunk in multiple places, all far away from the device, is
> decidedly suboptimal.  Better ideas welcome.


I would suggest moving PC_COMPAT_X_Y things to platform-independent place
but "[RFC v2 00/39] Convert PC machine-types to QOM classes" is already
huge and complicated, and also "pseries" does not really need stuff below
1.6, may be it is not worth it...



-- 
Alexey