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

[Cornelia Huck]

On Mon, 15 Jul 2019 13:04:28 +0200
Philippe Mathieu-Daudé <address@hidden> wrote:

> On 7/15/19 12:56 PM, Cornelia Huck wrote:
> > On Mon, 15 Jul 2019 12:48:55 +0200
> > Thomas Huth <address@hidden> wrote:
> >   
> >> 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.  
> > 
> > s/MSI/MSI-X/, IIRC. Not sure how far 'legacy' would stretch.  
> 
> Maybe we can have something like PCI_LEGACY_DEVICES and PCI_MSI_DEVICES?
> 
> So if s390x only selects PCI_LEGACY (not PCI_MSI) bus, then it only get
> legacy devices?

Wrong way around? We need MSI-X for s390x, not plain MSI or
'legacy' (whatever that is).

> 
> Other MSI compliant should select PCI_MSI instead. PCI alone seems to
> give troubles.
> 
> > cc:ing Collin in case there's something else.
> >