After a hot migration, there are messages seen on the virtual machine similar to:
Clocksource tsc unstable (delta = 125001663 ns). Enable clocksource failover by adding clocksource_failover kernel parameter.
Hot migration of a virtual machine
This is not a critical issue, but in most cases it is caused by having different CPUs in the hypervisors involved in the migration. This can happen on the same CPUs, but it is very rare.
To decrease the chances of this happening, it is recommended to use the same CPU across all hypervisors, keep the hypervisors' operating system and kernel updated and use the latest stable templates available.