Re: [Qemu-devel] [PATCH RFC v2 0/9] s390x: zPCI detangling

[Cornelia Huck <cohuck@redhat.com>]

On Mon, 24 Jul 2017 12:44:43 +0200
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> On 07/19/2017 03:31 PM, Thomas Huth wrote:
> > On 19.07.2017 15:03, Cornelia Huck wrote:  
> >> On Tue, 18 Jul 2017 16:24:46 +0200
> >> Cornelia Huck <cohuck@redhat.com> wrote:
> >>  
> >>> Next try of the zPCI detangling, taking cpu models into account.
> >>>
> >>> The goal of this is twofold:
> >>> - Being able to disable PCI support in a build completely, as for v1.
> >>> - Properly fencing off PCI if the relevant facility bit is not provided.
> >>>
> >>> The second one leads to an interesting usability problem: -device help
> >>> still shows the various pci devices, but you cannot add them if the
> >>> cpu model does not include zpci, due to the phb not being instantiated.
> >>> The user is presented with
> >>>
> >>> qemu-system-s390x: -device virtio-rng-pci: No 'PCI' bus found for device 'virtio-rng-pci'
> >>>
> >>> ...which is not very helpful, as it does not point to the root cause (no
> >>> zpci in the cpu model, and therefore no pci at all). Not sure how one can
> >>> communicate this root cause, ideas welcome.  
> >>
> >> An idea on how to improve this would still be welcome :)  
> > 
> > IMHO it's ok to keep that error message ... but we should add a section
> > to http://wiki.qemu.org/Documentation/Platforms/S390X about PCI devices,
> > including a sample error message as above and a note what has to be done
> > to get a machine with PCI support, so that people can find that page via
> > Google in case they run into this problem.  
> 
> I agree, the message is actually not that bad for an error message. With
> an wiki entry we should be fine.
> 

Updated https://wiki.qemu.org/index.php/Documentation/Platforms/S390X
with some info... review (or editing :) welcome.