Messages in this thread | | | Date | Sun, 14 Jan 2007 09:39:54 +0100 | From | Ingo Molnar <> | Subject | Re: kvm & dyntick |
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* Avi Kivity <avi@qumranet.com> wrote:
> >( for this to work on my system i have added a 'hyper' clocksource > > hypercall API for KVM guests to use - this is needed instead of the > > running-to-slowly TSC. ) > > > > What's the problem with the TSC? The only issue I'm aware of is that > the tsc might go backwards if the vcpu is migrated to another host cpu > (easily fixed).
this is not a problem of KVM - this is a problem of this laptop: its TSC stops when going idle. So the TSC is fundamentally unusable for reliable timekeeping - and qemu doesnt offer pmtimer emulation to fall back to, so the dyntick kernel refused to go high-res under KVM. Once i added the hyper clocksource to fall back to, it could utilize the PIT and the lapic for clock-events.
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