Re: [Qemu-riscv] [qemu-s390x] [RFC PATCH 1/3] hw/Kconfig: PCI bus implies PCI_DEVICES

[Cornelia Huck <cohuck@redhat.com>]

On Mon, 15 Jul 2019 12:48:55 +0200
Thomas Huth <thuth@redhat.com> wrote:

> On 15/07/2019 12.19, Peter Maydell wrote:
> > On Mon, 15 Jul 2019 at 11:15, Thomas Huth <thuth@redhat.com> 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 <philmd@redhat.com>
> >>> ---  
> >   
> >>> 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.

s/MSI/MSI-X/, IIRC. Not sure how far 'legacy' would stretch.

cc:ing Collin in case there's something else.