[Bug 1921870] Re: [UBUNTU 21.04] tools/kvm_stat: Add restart delay

Thx Stefan for the verification.
(I don't know why there is a verification-needed-focal tag on top, since this bug is not marked as affecting focal at all ?! To avoid any blockers, I'm changing it to done, too.)

** Tags removed: verification-needed-focal
** Tags added: verification-done-focal

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https://bugs.launchpad.net/bugs/1921870

Title:
[UBUNTU 21.04] tools/kvm_stat: Add restart delay

Status in Ubuntu on IBM z Systems:
Fix Committed
Status in linux package in Ubuntu:
Fix Committed
Status in linux source package in Hirsute:
Fix Committed
Status in linux source package in Impish:
Fix Committed

Bug description:
SRU Justification:

[Impact]

* Nice to have feature requested by IBM - a systemd service monitoring
KVM guests.
* Adds a new systemd service, not enabled by default.

[Fix]

* Install the systemd .service file when installing linux-tools-host

[Test Plan]

* dpkg -c linux-tools-host_5.11.0-18.19_all.deb
./lib/systemd/system/kvm_stat.service
* Install the package and reboot
* Check if kvm_stat is present and not active after reboot:
ls -l /lib/systemd/system/kvm_stat.service
systemctl -a | grep kvm_stat

[Where problems could occur]

* Service can be enabled and started by mistake or by any further future
Makefile change (enabling all services installed by linux-tools-host).

* The service logs into /var/log/kvm_stat.csv (not journal!) and package does
not provide logrotate by default, thus the logging could eat entire
disk space.

-- Original Description --

Description: tools/kvm_stat: Add restart delay
Symptom: If the kvm service is enabled and the system rebooted,
               Systemd's initial attempt to start the kvm unit file may
               fail in case the kvm module is not loaded. However, once the
               kvm module is loaded, the service is _not_ started.
Problem: Since the unit file does not specify a delay for the retries,
               Systemd restarts with a minimum delay a number of times
               before giving up and disabling the service. Which means a
               subsequent kvm module load will have kvm running without
               monitoring.
Solution: Add an appropriate delay in the unit file.
Reproduction: (1) Enable the kvm service via systemctl
               (2) Reboot
               (3) Verify that the kvm module is not loaded & kvm service
                   not running
               (4) Load the kvm module via 'modprobe kvm'
               (5) Verify that the kvm service came up within the next
                   minute.
Preventive: yes

Just use the attached patch and you're good!

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