Re: Make QEmu HPET disabled by default for KVM?

Gleb Natapov
2010-03-11T08:32:00Z

On Thu, Mar 11, 2010 at 10:28:12AM +0200, Avi Kivity wrote:
> On 03/11/2010 10:23 AM, Sheng Yang wrote:
> >>>I have kept --no-hpet in my setup for
> >>>months...
> >>Any details about the problems? HPET is important to some guests.
> >>
> >Seems like HPET reaction is too slow to satisfy some guests(for it would
> >replace PIT).
> >
> >Here is the thread last time.
> >
> >http://thread.gmane.org/gmane.comp.emulators.kvm.devel/44899
> >
>
> Thanks. We can address this in three ways: first, adjust the guest
> not to do timing related tests when virtualized (since no matter
> what we do, the tests may fail). Second, I think we should
> implement userspace ack notifiers (similar to tpr access notifiers
> already present). Third, we can implement a kernel hpet, which,
> after we solve the zillion bug it introduces, will also give a nice
> performance improvement for hpet intensive workloads.
>
Second will not solve the problem. Presence of ack notifiers will not
make HPET interrupt arrive faster.

--
Gleb.