TSC time went backwards

[Brook Milligan <brook%biology.nmsu.edu@localhost>]

I have switched a QEMU VM from 1 CPU to 2 with "-smp cpus=2".  Immediately I am getting lots of warnings like the following:

	WARNING: TSC time went backwards by 2452936570 - change sysctl(7) kern.timecounter?

The kern.timecounter variables are:

	kern.timecounter.choice = TSC(q=3000, f=2999970000 Hz) clockinterrupt(q=0, f=100 Hz) lapic(q=-100, f=1000004000 Hz) piixpm0(q=1000, f=3579545 Hz) hpet0(q=2000, f=100000000 Hz) ACP
	kern.timecounter.hardware = TSC
	kern.timecounter.timestepwarnings = 0

Both the host and guest OS are:

	NetBSD 10.1 (GENERIC) #0: Mon Dec 16 13:08:11 UTC 2024  mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64

According to 

	https://oliveryang.net/2015/09/pitfalls-of-TSC-usage/

TSC timekeeping is tricky, but I am not sure how to use that information to solve the problem.

Is this a known issue?  Any help is greatly appreciated.

Thanks a lot.

Cheers,
Brook