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[OpenStack Infra <1741230@xxxxxxxxxxxxxxxxxx>]

Reviewed:  https://review.openstack.org/530965
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=8bc7b950b7c0a3c80cdd120fe4df97c14848c344
Submitter: Zuul
Branch:    master

commit 8bc7b950b7c0a3c80cdd120fe4df97c14848c344
Author: Marcin Juszkiewicz <marcin.juszkiewicz@xxxxxxxxxx>
Date:   Wed Jan 3 17:44:27 2018 +0100

    libvirt: use 'host-passthrough' as default on AArch64
    
    Nova is assuming 'host-model' for KVM/QEMU setup.
    
    On AArch64 it results in "libvirtError: unsupported configuration: CPU
    mode 'host-model' for aarch64 kvm domain on aarch64 host is not
    supported by hypervisor" message.
    
    AArch64 lacks 'host-model' support because neither libvirt nor QEMU
    are able to tell what the host CPU model exactly is. And there is no
    CPU description code for ARM(64) at this point.
    
    So instead we fallback to 'host-passthrough' to get VM instances
    running. This will completely break live migration, *unless* all the
    Compute nodes (running libvirtd) have *identical* CPUs.
    
    Small summary: https://marcin.juszkiewicz.com.pl/2018/01/04/today-i-was-fighting-with-nova-no-idea-who-won/
    
    Closes-bug: #1741230
    
    Co-authored-by: Kevin Zhao <Kevin.Zhao@xxxxxxx>
    Co-authored-by: Marcin Juszkiewicz <marcin.juszkiewicz@xxxxxxxxxx>
    
    Change-Id: Iafb5f1790d68489db73b9f0549333108c6426a00


** Changed in: nova
       Status: In Progress => Fix Released

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https://bugs.launchpad.net/bugs/1741230

Title:
  libvirt: use 'host-passthrough' as default on AArch64

Status in OpenStack Compute (nova):
  Fix Released

Bug description:
  At Linaro we have several instances of OpenStack running. Some are
  public, some private. Some at Newton, some at Pike and now some on
  Queens.

  And always we have to set cpu_mode = 'host-passthrough' in [libvirt]
  section of nova.conf file.

  As we use Kolla to build and deploy Queens I added workaround there
  which sets cpu_mode in proper way for AArch64. But this is
  workaround...

  So I looked at code of Nova and created some quick hack:
  https://review.openstack.org/#/c/530965/

  It works for us but may not be proper way of doing it.

  We use Debian 'stretch' as host system with libvirt 3.10.0 backported
  from 'testing'.

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