IDE config drive CDROM doesn't work with q35 machine type

[Artom Lifshitz]

Description
===========

Setting [libvirt]/hw_machine_type=x86_64=q35 in nova-cpu.conf results in any instances booted with a config drive to fail to spawn.

Steps to reproduce
==================

1. Set [libvirt]/hw_machine_type=x86_64=q35 in nova-cpu.conf
2. Boot an instance with a config drive

Expected result
===============

Instance boots correctly.

Actual result
=============

Instance fails to spawn with following error in the compute log:

libvirt.libvirtError: unsupported configuration: IDE controllers are unsupported for this QEMU binary or machine type

Environment
===========

This was reported on OSP15 CI [1] and has been reproduced upstream [2].

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1716358
[2] https://review.opendev.org/#/c/662887/

[Kashyap Chamarthy (kashyapc)]

That is expected, because Q35 machine type does not support IDE at all; only SATA or SCSI.

When using Q35, we should change the default bus to SATA for CD-ROM. (I've double-checked it with the QEMU folks, too. Q35 has on-board SATA.)

One way to set it is via the image metadata property: `hw_disk_bus=sata`

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/663011

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/stein
Review: https://review.opendev.org/663677

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/663011
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=527c452a6fc05a316eb8121796f761af97522772
Submitter: Zuul
Branch: master

commit 527c452a6fc05a316eb8121796f761af97522772
Author: Lee Yarwood <email address hidden>
Date: Tue Jun 4 11:57:18 2019 +0100

    libvirt: Use SATA bus for cdrom devices when using Q35 machine type

    The Q35 machine type no longer provides an IDE bus and will need to use
    a SATA bus to attach legacy devices such as cdroms. More details can be
    found in the following related bug:

    Don't assume the guest machine type to be of 'pc'
    https://bugs.launchpad.net/nova/+bug/1780138

    This change now ensures the blockinfo.get_disk_bus_for_device_type
    method will now return "sata" as the bus type when the Q35 machine type
    is used for cdrom devices on QEMU or KVM hosts that are not PPC, S390 or
    AArch64 based.

    To enable this the _get_machine_type method has been extracted from the
    Libvirt driver into the Libvirt utils module. This method has also been
    simplified through the removal of the caps parameter, replaced with
    calls to the get_arch utility method and additional extraction of
    architecture specific defaults into the existing
    get_default_machine_type utility method.

    Related-bug: 1780138
    Closes-bug: 1831538
    Change-Id: Id97f4baddcf2caff91599773d9b5de5181b7fdf6

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/663677
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=db40cc44cbad32353510819c0aee1d0a3c9e4357
Submitter: Zuul
Branch: stable/stein

commit db40cc44cbad32353510819c0aee1d0a3c9e4357
Author: Lee Yarwood <email address hidden>
Date: Tue Jun 4 11:57:18 2019 +0100

    libvirt: Use SATA bus for cdrom devices when using Q35 machine type

    The Q35 machine type no longer provides an IDE bus and will need to use
    a SATA bus to attach legacy devices such as cdroms. More details can be
    found in the following related bug:

    Don't assume the guest machine type to be of 'pc'
    https://bugs.launchpad.net/nova/+bug/1780138

    This change now ensures the blockinfo.get_disk_bus_for_device_type
    method will now return "sata" as the bus type when the Q35 machine type
    is used for cdrom devices on QEMU or KVM hosts that are not PPC, S390 or
    AArch64 based.

    To enable this the _get_machine_type method has been extracted from the
    Libvirt driver into the Libvirt utils module. This method has also been
    simplified through the removal of the caps parameter, replaced with
    calls to the get_arch utility method and additional extraction of
    architecture specific defaults into the existing
    get_default_machine_type utility method.

    Related-bug: 1780138
    Closes-bug: 1831538
    Change-Id: Id97f4baddcf2caff91599773d9b5de5181b7fdf6
    (cherry picked from commit 527c452a6fc05a316eb8121796f761af97522772)

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 19.0.2 release.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Artom Lifshitz (<email address hidden>) on branch: master
Review: https://review.opendev.org/662887

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 20.0.0.0rc1 release candidate.