Comment 4 for bug 1618431

When I set -rtc clock=vm the mig problem is solved, but what does this flag exactly?

In the docu there is only

" If you want to isolate the guest time from the host, you can set clock to "rt" instead.
  To even prevent it from progressing during suspension, you can set it to "vm"."

what does this means?

Will the VM never be synced with the HW clock and so it will run slower on cpu load on normal running?