[Bug 1859656] Re: [2.6] Unable to reboot s390x KVM machine after initial deploy

[Andrew Cloke]

After discussing, I realise I had a misunderstanding in comment #30 that
I'd like to correct.

I had incorrectly assumed that feeding the PXEBooting KVM guest a zero
length pxelinux.cfg file *instructed* it to boot from the local disk.

I now realise that is incorrect. Feeding the PXEBooting KVM guest a zero
length pxelinux.cfg file only tells the guest to *fail* it's netboot
attempt.

It's at this stage that the architecture specific behaviour kicks in.

On amd64, the netboot failure will force the KVM guest to move down to
it's second specified boot option, namely the local disk.

However, s390x will NEVER move to it's second specified boot option. If
the first boot option (netbooting) fails, it abandons the attempt and
powers the guest off.

IBM has been informed of this difference in behaviour, but it is
unlikely to be able to address it soon.

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https://bugs.launchpad.net/bugs/1859656

Title:
  [2.6] Unable to reboot s390x KVM machine after initial deploy

Status in MAAS:
  Triaged
Status in QEMU:
  Incomplete
Status in Ubuntu on IBM z Systems:
  Triaged

Bug description:
  MAAS version: 2.6.1 (7832-g17912cdc9-0ubuntu1~18.04.1)
  Arch: S390x

  Appears that MAAS can not find the s390x bootloader to boot from the
  disk, not sure how maas determines this.  However this was working in
  the past. I had originally thought that if the maas machine was
  deployed then it defaulted to boot from disk.

  If I force the VM to book from disk, the VM starts up as expected.

  Reproduce:

  - Deploy Disco on S390x KVM instance
  - Reboot it

  on the KVM console...

  Connected to domain s2lp6g001
  Escape character is ^]
  done
    Using IPv4 address: 10.246.75.160
    Using TFTP server: 10.246.72.3
    Bootfile name: 'boots390x.bin'
    Receiving data:  0 KBytes
    TFTP error: file not found: boots390x.bin
  Trying pxelinux.cfg files...
    Receiving data:  0 KBytes
    Receiving data:  0 KBytes
  Failed to load OS from network

  ==> /var/log/maas/rackd.log <==
  2020-01-14 18:21:24 provisioningserver.rackdservices.tftp: [info] 
boots390x.bin requested by 10.246.75.160
  2020-01-14 18:21:24 provisioningserver.rackdservices.tftp: [info] 
s390x/65a9ca43-9541-49be-b315-e2ca85936ea2 requested by 10.246.75.160
  2020-01-14 18:21:24 provisioningserver.rackdservices.tftp: [info] 
s390x/01-52-54-00-e5-d7-bb requested by 10.246.75.160
  2020-01-14 18:21:24 provisioningserver.rackdservices.tftp: [info] 
s390x/0AF64BA0 requested by 10.246.75.160
  2020-01-14 18:21:24 provisioningserver.rackdservices.tftp: [info] 
s390x/0AF64BA requested by 10.246.75.160
  2020-01-14 18:21:24 provisioningserver.rackdservices.tftp: [info] 
s390x/0AF64B requested by 10.246.75.160
  2020-01-14 18:21:24 provisioningserver.rackdservices.tftp: [info] s390x/0AF64 
requested by 10.246.75.160
  2020-01-14 18:21:24 provisioningserver.rackdservices.tftp: [info] s390x/0AF6 
requested by 10.246.75.160
  2020-01-14 18:21:24 provisioningserver.rackdservices.tftp: [info] s390x/0AF 
requested by 10.246.75.160
  2020-01-14 18:21:24 provisioningserver.rackdservices.tftp: [info] s390x/0A 
requested by 10.246.75.160
  2020-01-14 18:21:24 provisioningserver.rackdservices.tftp: [info] s390x/0 
requested by 10.246.75.160
  2020-01-14 18:21:24 provisioningserver.rackdservices.tftp: [info] 
s390x/default requested by 10.246.75.160

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