Re: KVM PMU virtualization

Avi Kivity
2010-02-26T11:49:18Z

On 02/26/2010 01:26 PM, Ingo Molnar wrote:
>>
>>> By far the biggest instrumentation issue is:
>>>
>>> - availability
>>> - usability
>>> - flexibility
>>>
>>> Exposing the raw hw is a step backwards in many regards.
>>>
>> In a way, virtualization as a whole is a step backwards. We take the nice
>> firesystem/timer/network/scheduler APIs, and expose them as raw hardware.
>> The pmu isn't any different.
>>
> Uhm, it's obviously very different. A fake NE2000 will work on both Intel and
> AMD CPUs. Same for a fake PIT. PMU drivers are fundamentally per CPU vendor
> though.
>
> So there's no "generic hardware" to emulate.
>

That's true, and it reduces the usability of the feature (you have to
restrict your migration pools or not expose the pmu), but the general
points still stand.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.