Re: [PATCH-for-5.0 1/2] hw/acpi/piix4: Add 'system-hotplug-support' property

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Hi Igor, Paolo.

On 3/23/20 12:04 PM, Marcelo Tosatti wrote:
> On Mon, Mar 23, 2020 at 09:05:06AM +0100, Paolo Bonzini wrote:
>> On 22/03/20 17:27, Philippe Mathieu-Daudé wrote:
>>>>>
>>>> That 'ugly' is typically used within QEMU to deal with such things
>>>> probably due to its low complexity.
>>>
>>> OK. Can you point me to the documentation for this feature? I can find
>>> reference of GPE in the ICH9, but I can't find where this IO address on
>>> the PIIX4 comes from:
>>>
>>> #define GPE_BASE 0xafe0
>>
>> It's made up.  The implementation is placed in PIIX4_PM because it is
>> referenced by the ACPI tables.  Real hardware would probably place this
>> in the ACPI embedded controller or in the BMC.
>>
>> Paolo
> 
> Yes, there was nothing at 0xafe0 at the time ACPI support was written.
> 

Igor earlier said:
"it's already pretty twisted code and adding one more knob
to workaround other compat knobs makes it worse."

Is that OK to rename this file "hw/acpi/piix4_twisted.c" and
copy/paste the same content to "hw/acpi/piix4.c" but remove the
non-PIIX4 code (GPE from ICH9)?

This seems counterproductive from a maintenance PoV, but the PIIX4 bug
(https://bugs.launchpad.net/qemu/+bug/1835865) is more than 1 year old
now...

If someone has a clever idea, I'm open to listen and implement it, but
keeping ignoring this issue is not good.

Note there is a similar issue with the LPC bus not existing on the
PIIX, so maybe renaming this to something like "piix_virt.c" and having
someone writing the specs (or differences with the physical datasheet)
is not a such bad idea.

Thanks,

Phil.