Messages in this thread | | | From | "Allister, Jack" <> | Subject | Re: [PATCH 2/2] KVM: selftests: Add KVM/PV clock selftest to prove timer drift correction | Date | Wed, 10 Apr 2024 10:15:29 +0000 |
| |
> AFAIR, I copied check_clocksource() from existing code during that > time.
> The commit e440c5f2e ("KVM: selftests: Generalize check_clocksource() > from kvm_clock_test") has introduced sys_clocksource_is_tsc(). Later > it is renamed to sys_clocksource_is_based_on_tsc(). > Any chance to re-use sys_clocksource_is_based_on_tsc()?
Yes I'm more than happy to change it to that. I was using your original mail as a reference and did not realise there was a utility present for this.
> Is configure_scaled_tsc() anecessary? Or how about to make it an > option/arg? > Then I will be able to test it on a VM/server without TSC scaling.
So if TSC scaling from 3GHz (host) -> 1.5GHz (guest) I do see a skew of ~3500ns after the update. Where as without scaling a delta can be seen but is roughly ~180ns.
In V2 I've adjusted the test so that now by default scaling won't take place, however if someone wants to test with it enabled they can pass "-s/--scale-tsc" to induce the greater delta.
Thanks you for the feedback, Jack Allister
| |