nova/releasenotes/notes/aarch64-set-proper-cpu-mode-8455bad7d69dc6fd.yaml
Marcin Juszkiewicz 8bc7b950b7 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@arm.com>
Co-authored-by: Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>

Change-Id: Iafb5f1790d68489db73b9f0549333108c6426a00
2018-01-09 09:49:34 +00:00

14 lines
497 B
YAML

---
upgrade:
- |
On AArch64 architecture ``cpu_mode`` for libvirt is set to ``host-passthrough``
by default.
AArch64 currently 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.
.. warning:: ``host-passthrough`` mode will completely break live
migration, *unless* all the Compute nodes (running libvirtd) have
*identical* CPUs.