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

[Christian Borntraeger]

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 <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.

I agree, the message is actually not that bad for an error message. With
an wiki entry we should be fine.