Re: State of current pv_ops backend for KVM?

Anthony Liguori
2007-05-29T13:49:41Z

Avi Kivity wrote:
> Anthony Liguori wrote:
>> Howdy,
>>
>> Does anyone know what the state of a pv_ops backend for KVM is? I
>> know Ingo has an implementation that implements CR3 caching but I
>> don't see any branches in Avi's git tree.
>>
>> Perhaps we should try for a simple pv_ops backend for 2.6.23 seeing
>> as how the host infrastructure is there? I'd be willing to do some
>> leg work here...
>
> I think we should aim for a full direct paging implementation, where
> the cr3 cache is just the cherry on top that makes context switches
> proceed at native speed. Jun has a paper on it for OLS and I hope
> patches too.

That's a bit more ambitious than I was thinking. I would be very happy
with a pv timer, interrupt controller, and some basic CPU
optimizations. I'm still not convinced the perf benefits of direct
paging justify the annoyances that come with it (guests being aware of
pfns). This is especially true with NPT/EPT right around the corner.

Regards,

Anthony Liguori

> A minor drawback with direct paging is that you are more or less
> forced to use pae on the guest, but I think that's acceptable.