can not migrate serve on aarch64

[Eric Xie]

Description
===========
We setup OpenStack env on aarch64 KylinOS.
Failed to live migrate instance cause of 'This operating system kernel does not support vITS migration'.

Steps to reproduce
==================
1. Setup OpenStack on aarch64 servers with openstack-helm
2. Live migrate instance from compute02 to compute03

Expected result
===============
Success, instance locate on compute03

Actual result
=============
Failed, instnace locate on compute02

Environment
===========
1. Exact version of OpenStack you are running. See the following
stable/rocky
# apt list --installed |egrep "libvirt|qemu"
ipxe-qemu/now 1.0.0+git-20180124.fbe8c52d-0ubuntu2.2~cloud0 all [installed,local]
ipxe-qemu-256k-compat-efi-roms/now 1.0.0+git-20150424.a25a16d-0ubuntu2~cloud0 all [installed,local]
libvirt-bin/now 4.0.0-1ubuntu8.11~cloud0 arm64 [installed,local]
libvirt-clients/now 4.0.0-1ubuntu8.11~cloud0 arm64 [installed,local]
libvirt-daemon/now 4.0.0-1ubuntu8.11~cloud0 arm64 [installed,local]
libvirt-daemon-system/now 4.0.0-1ubuntu8.11~cloud0 arm64 [installed,local]
libvirt0/now 4.0.0-1ubuntu8.11~cloud0 arm64 [installed,local]
qemu/now 1:2.11+dfsg-1ubuntu7.15~cloud1 arm64 [installed,local]

# uname -a
Linux compute03 4.4.131-20190726.kylin.server-generic #kylin SMP Tue Jul 30 16:44:09 CST 2019 aarch64 aarch64 aarch64 GNU/Linux

2. Which hypervisor did you use?
libvirt+kvm

Logs & Configs
==============
nova-compute:
File "/var/lib/openstack/local/lib/python2.7/site-packages/libvirt.py", line 1745, in migrateToURI3
    if ret == -1: raise libvirtError ('virDomainMigrateToURI3() failed', dom=self)
libvirtError: internal error: unable to execute QEMU command 'migrate': This operating system kernel does not support vITS migration

libvirt:
2019-12-07 05:34:34.820+0000: 57546: error : qemuMonitorJSONCheckError:392 : internal error: unable to execute QEMU command 'migrate': This operating system kernel does not support vITS migration
2019-12-07 05:34:35.226+0000: 57546: error : virNetClientProgramDispatchError:177 : internal error: qemu unexpectedly closed the monitor: 2019-12-07T05:34:29.355638Z qemu-system-aarch64: Not a migration stream
2019-12-07T05:34:29.355781Z qemu-system-aarch64: load of migration failed: Invalid argument

[Eric Xie (eric-xie)]

As we found, the failed reason is that libvirt create 'gic version='3'' in instance's domain.
  <features>
    <acpi/>
    <apic/>
    <gic version='3'/>
  </features>

gicv3 should be supported after kernel version 4.13, so we changed to gicv2. Then live migration worked.

I think should add feature 'gic version' for aarch64.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/698905

[OpenStack Infra (hudson-openstack)]

Change abandoned by Eric Xie ([e-mail]) on branch: master
Review: https://review.opendev.org/698905