Re: question: HPET for multiple VMs

Avi Kivity
2008-03-22T21:56:50Z

Ryota OZAKI wrote:
> Hi all,
>
> Current kvm allows only one VM to use HPET. Is
> there a plan to implement a functionality to
> allow multiple VMs to use HPET? If so, how
> about the status of that?
>
>

If you use the dyntick clock option (the default, IIRC), and a newer
host kernel, then the kernel provides high-resolution timers, very
likely using HPET internally or some other high resolution clock and
event source.

> And I would like to ask right and wrong to
> implement the functionality in terms of need
> and efficiency (scalability and time accuracy).

I think that for newer kernels we already have the desired accuracy.
We're not always good at exploiting that accuracy; hence the recent
movement of the PIT implementation from userspace to the kernel. But
recent discussion leads me to believe it could have been implemented
with the userspace PIT as well.

--
Any sufficiently difficult bug is indistinguishable from a feature.