VM uses clock timer that are not mentioned in VM configuration

The default configuration for the Slackware VM does include the following <clock> definition:

<clock offset='utc'>
    <timer name='rtc' tickpolicy='catchup'/>
    <timer name='pit' tickpolicy='delay'/>
    <timer name='hpet' present='no'/>
  </clock>

Running a slackware (Unraid) VM I see the "tsc" and "acpi_pm" timers running instead. As I'm always experiencing timer problems with "tsc" how can I work around that? Should I add "tsc" to the <clock> element?

Here's the error I see in a Unraid VM. Whenever this happens, performance of the VM degrades by 3/4:

May  4 02:10:40 TowerVM01 kernel: clocksource: timekeeping watchdog on CPU2: Marking clocksource 'tsc' as unstable because the skew is too large:
May  4 02:10:40 TowerVM01 kernel: clocksource: 'acpi_pm' wd_now: 70aa1c wd_last: 51d1b1 mask: ffffff
May  4 02:10:40 TowerVM01 kernel: clocksource: 'tsc' cs_now: 5b65e65f2fb54 cs_last: 5b65e12de6c58 mask: ffffffffffffffff
May  4 02:10:40 TowerVM01 kernel: tsc: Marking TSC unstable due to clocksource watchdog
May  4 02:10:40 TowerVM01 kernel: clocksource: Switched to clocksource acpi_pm

Question #1: Why is a timer running in my VMs that is not declared in the VM configuration?

Question #2: Would it possibly help to add an additional "tsc" timer to the <clock>?

<timer name='tsc' tickpolicy='catchup' mode='auto'/>

Thanks in advance.

Edited May 17, 20215 yr by hawihoney