Re: [libvirt] TSC frequency configuration & invtsc migration (was Re: [PATCH 4/4] kvm: Allow migration with invtsc)
On 05/01/2017 14:00, Daniel P. Berrange wrote:
> If you do this unconditionally, you have another problem: if
> tsc-frequency is set explicitly, migration is only possible if
> TSC frequency of the destination matches[1], or if TSC scaling is
> supported by the destination. It's a good idea to set a TSC
> frequency only if invtsc is enabled explicitly in the config.
If we don't set tsc-frequency and the TSC frequency doesn't
match, does that mean the guest migration succeed, but suddenly
sees different TSC frequency ?
That's the reason why kvmclock exists (or more precisely, the reason why
kvmclock is still useful even when hosts have invtsc).
Paolo
I guess we we allowed that historically we can't break that
now, so setting it only if invtsc is set seems reasonable.