On ppc64 el host, SMT is not set at off upon reboot

[Benjamin Allot]

Following a hardware issue on a ppc64el host, the server was restarted.

However, upon reboot, smt was not set as off, given that no juju changed had occurred, the hooks were not run.

As a result, qemu was not happy:
"""
2019-05-13T12:38:12.824598Z qemu-system-ppc64: -chardev pty,id=charserial0,logfile=/dev/fdset/2,logappend=on: char device redirected to /dev/pts/7 (label charserial0)
error: kvm run failed Device or resource busy
This is probably because your SMT is enabled.
VCPU can only run on primary threads with all secondary threads offline.
"""

I created this little systemd unit to do the trick upon reboot:

"""
[Unit]
Description=Set SMT to off
After=network.target
Before=libvirtd.service

[Service]
Type=oneshot
ExecStart=/usr/sbin/ppc64_cpu --smt=off
ExecStop=
RemainAfterExit=true
StandardOutput=journal

[Install]
WantedBy=multi-user.target libvirtd.service
"""

But it would be better to have a way to turn it on or off at boot time, not only during hooks, based on option and/or architecture
At least on ppc64el, it should be turned off permanently.

Regards,

[James Page (james-page)]

This is a bit of a fallout from the change in behaviour in Juju which means config-changed only runs after something actually changes - a reboot no longer triggers this hook.

[Haw Loeung (hloeung)]

The charm should probably just ship out the systemd file above on ppc64el hosts.