Re: [Qemu-devel] [RFC 00/15] qmp: Report supported device types on 'query-machines'

[Marcel Apfelbaum <marcel@redhat.com>]

On 11/24/2016 05:41 PM, Markus Armbruster wrote:
> Marcel Apfelbaum <marcel@redhat.com> writes:
>
>> On 11/24/2016 03:34 PM, Markus Armbruster wrote:
>>> Eduardo Habkost <ehabkost@redhat.com> writes:
>>>
>>>> On Wed, Nov 23, 2016 at 06:43:16PM +0200, Marcel Apfelbaum wrote:
>>>>> On 11/22/2016 03:11 AM, Eduardo Habkost wrote:
>>>>>> The Problem
>>>>
>>
>> [...]
>>
>>> Our decision to have hybrid PCI/PCIe devices and buses breeds
>>> considerable complexity.  I wish we had avoided them, but I believe it's
>>> too late to change now.
>>>
>>>>> This still does not solve the problem that some devices makes
>>>>> sense only on a specific arch.
>>>
>>
>> Hi Markus,
>>
>>> Examples?
>>>
>>
>> One quick example would be that we don't want to see
>> Intel's IOH 3420 PCIe Root Port in an ARM machine,
>> or a pxb on a Q35 machine (in this case we want pxb-pcie)
>
> Such a device would be weird.  But would it be wrong?

Define wrong :)

  Wrong enough for
> QEMU to reject it?

QEMU accepts them and they even function correctly as far as I know.

   Unless QEMU rejects it, there's no reason not to
> list it as pluggable.
>

This is the gray area I can't argue. I do think that Eduardo's
work may present an opportunity to change QEMU's mantra:
"everything goes as long as it works" to "here is what this configuration supports".



Thanks,
Marcel

>> I do believe there are other examples, I'll try to think of more.
>>
>> Thanks,
>> Marcel
>>
>> [...]