testiso: Do not add disk as primary disk for s390x pXE test

[Prashanth684]

For s390x in pXE mode, the network device has the bootindex 1. Add a disk
without specifying it as a primary disk with bootindex.

Had to open this anew because #1336 couldn't be reopened because i rebased it .

[cgwalters]

Hmm...like this is something hardcoded into qemu or the firmware or something?

I am trying to get my head around how this works; is it basically that the s390x firmware has builtin logic around "use the disk first if it's bootable, otherwise network" and our adjusting the bootorder breaks it?

[Prashanth684]

i am sure it is something like that..i try without the bootindex and it looks for a bootable disk. I have been tried to get a hold of someone from the s390x world to confirm but no one seems to know.

[Prashanth684]

yup..found sparse doc here: https://wiki.qemu.org/Features/S390xNetworkBoot

[cgwalters]

/test sanity
/lgtm

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[jlebon]

AddPrimaryDisk doesn't just affect the bootindex though. There's a lot of different paths that this is now missing out on, i.e. Ignition config injection and setting the disk serial.

[cgwalters]

There's a lot of different paths that this is now missing out on, i.e. Ignition config injection and setting the disk serial.

First, let's keep in mind this is only changing s390x, and only for tests, and we have plans for a better fix.

That said...I don't understand your comment. We are injecting ignition still with coreos-installer right? And what do you mean here by "disk serial"?

[jlebon]

Yeah, this came up first in my backlog, so it didn't connect that it'd get revamped by #1348. :)

That said...I don't understand your comment. We are injecting ignition still with coreos-installer right? And what do you mean here by "disk serial"?

Just overall, I think having the concept of a primary disk also makes sense for the installer case; it's the disk we're installing to (e.g. if we later add multiple disks to test separate /var or a moved /sysroot or something we'd have to discern between them). The primary disk gets serial=primary-disk, which we could use to find it instead of hardcoding vda (which would break on e.g. NVMe or SCSI). You're right though the Ignition injection bits aren't needed here.

Anyway, I think using QMP as in #1348 is definitely the right path, but just wanted to flag that it's not just about the bootindex.

[cgwalters]

Oh yes...we should probably use the same wwn approach here.