* Joerg Roedel <j...@8bytes.org> wrote:

> I personally don't like a self-defined event-set as the only solution 
> because that would probably only work with linux and perf. [...]

The 'soft-PMU' i suggested is transparent on the guest side - if you want to 
enable non-Linux and legacy-Linux.

It's basically a PMU interface provided to the guest by catching the right MSR 
accesses, implemented via perf_event_create_kernel_counter()/etc. on the host 
side.

Note that the 'soft PMU' still sucks from a design POV as there's no generic 
hw interface to the PMU. So there would have to be a 'soft AMD' and a 'soft 
Intel' PMU driver at minimum.

Far cleaner would be to expose it via hypercalls to guest OSs that are 
interested in instrumentation. That way it could also transparently integrate 
with tracing, probes, etc. It would also be wiser to first concentrate on 
improving Linux<->Linux guest/host combos before gutting the design just to 
fit Windows into the picture ...

        Ingo
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