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

[Thomas Huth]

On 19.07.2017 15:03, Cornelia Huck wrote:
> On Tue, 18 Jul 2017 16:24:46 +0200
> Cornelia Huck <address@hidden> 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.

 Thomas