s390x (IBM Z) support to pass ignition file to CoreOS guest about mantle

[bgilbert]

@lucab The QEMU developers don't want fw_cfg used in this way and aren't excited about adding a generic userdata mechanism. They've suggested alternatives, several of which won't work because they require waiting indefinitely for udev. coreos/ignition#666 and coreos/ignition#825 have some of the context. One suggestion was that we pass userdata via a virtual PCI device, which might work but we haven't pursued it yet.

Our official guidance for passing userdata on s390x shouldn't be to use guestfish, so we'll still need a proper metadata mechanism. It might be okay for kola to use guestfs in the short term, to unblock testing, but we shouldn't expect that to be the long-term approach.

[lucab]

Thanks for the report!

fw_cfg parameter is not supported for s390x (IBM Z) and ppc64le (Power)

I don't think there is any technical limitation for not having fw_cfg support for those architectures (but I may be wrong, as I'm not an expert in that area). IIRC we already have x86_64 and aarch64 covered.
Do we have tickets to track adding support for those two? What's the current status? Perhaps we can increase the priority of those a bit, if we indeed plan to have consumers?

EDIT: see comments below.

[lucab]

Sorry, I was not aware of the additional discussion on fw_cfg. The backchannel discussion for s390x.qemu is already tracked at coreos/ignition#825 then.

[barthy1]

@lucab So would it be ok for you to use guestfish in the short term to unblock testing activities?

[barthy1]

#1050