Re: [Qemu-riscv] [RFC PATCH 1/3] hw/Kconfig: PCI bus implies PCI_DEVICES

[Thomas Huth]

On 15/07/2019 12.19, Peter Maydell wrote:
> On Mon, 15 Jul 2019 at 11:15, Thomas Huth <address@hidden> wrote:
>>
>> On 15/07/2019 11.55, Philippe Mathieu-Daudé wrote:
>>> If a controller device provides a PCI bus, we can plug any PCI
>>> daughter card on it.
>>>
>>> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
>>> ---
> 
>>> diff --git a/hw/pci/Kconfig b/hw/pci/Kconfig
>>> index 77f8b005ff..0f7267db35 100644
>>> --- a/hw/pci/Kconfig
>>> +++ b/hw/pci/Kconfig
>>> @@ -1,5 +1,6 @@
>>>  config PCI
>>>      bool
>>> +    imply PCI_DEVICES
>>
>> No, please don't change this. This was done on purpose, since almost all
>> PCI_DEVICES do not work on s390x (so s390x does *not* imply PCI_DEVICES).
> 
> But that means that every board that provides PCI has to have an
> "imply PCI_DEVICES" line, which is pretty clunky just to work
> around an s390x limitation.
> 
> Is there some way in the Kconfig syntax for s390x to say
> "no PCI_DEVICES" so we can have the corner-case be handled
> by the s390x Kconfig in one place rather than in 20 places
> affecting everywhere except s390x?

IIRC the problem on s390x are the legacy IRQs. s390x has only MSIs. So I
guess the correct way to fix this would be to introduce some
PCI_LEGACY_IRQ switch and let all old devices that do not work with MSI
depend on it.

 Thomas