Re: [Qemu-devel] q35 chipset support

[Markus Armbruster]

Anthony Liguori <address@hidden> writes:

> On 06/15/2012 12:57 PM, Jason Baron wrote:
>> On Thu, Jun 14, 2012 at 03:16:03PM -0500, Anthony Liguori wrote:
>>> On 06/14/2012 02:54 PM, Jason Baron wrote:
>>>> Hi,
>>>>
>>>> I recently updated Isaku Yamahata's q35 patches to work on the latest qemu 
>>>> and
>>>> seabios trees. On the qemu side, most of the changes revolved around 
>>>> updating
>>>> to use QOM and updates to the memory API. I was also able to drop quite a 
>>>> few
>>>> patches that had already been resolved by the current qemu tree.
>>>>
>>>> The trees seem pretty stable and can be found here:
>>>>
>>>> git://github.com/jibaron/q35-qemu.git
>>>> git://github.com/jibaron/q35-seabios.git
>>>
>>> I'm got the beginnings of a feature page started:
>>>
>>> http://wiki.qemu.org/Features/Q35
>>>
>>> The approach above will not work in a QOM world unfortunately.  We
>>> need to do quite a bit of ground work before adding another chipset.
>>> The biggest task is converting devices to not require an ISA bus
>>> since ICH9 simply doesn't have an ISA bus.
>>>
>>
>> Right, there is no h/w isa bus, but the LPC interface chip is modeled as an 
>> isa
>> bridge. So having an isa bus hanging off of it doesn't seem unreasonable. 
>> Unless
>> there is some more fundamental reason not do it this way?
>>
>> It hows up in lspci as:
>>
>> 00:1f.0 ISA bridge: Intel Corporation 82801IB (ICH9) LPC Interface
>> Controller (rev 02)
>
> It's not a question of ISA vs. LPC, it's which devices are actually on
> that bus. See my respond to Markus's note.

Maybe I'm naive, but platform devices handing off an ISA bus provided by
that ICH9 ISA bridge looks like a fair approximation to me.  Yes, the
actual wiring is LPC, but that's a hardware detail invisible to device
models and guest, isn't it?

Of course, you can't connect anything but the platform devices to that
bus.  To connect other ISA devices, you'd have to add a second ISA
bridge.  I suspect that's what you meant by "You can still have a
PCI-ISA bridge but the SuperI/O chip is not part of it" elsewhere in
this thread.

No idea whether such beasts exist in the physical world, and how they
work.