Re: comments on Performance Counters for Linux (PCL)

[Andi Kleen]

> You're talking about VT stuff, right? 

Yes.

> Does that virtualize the PMU too?

A hypervisor can in software, but another common case is a global profiler on 
the host to be able to profile all guests too. e.g. xenoprofile is able to do 
that.

If you want a full system picture with virtualization that's pretty much 
required.

For that you need a concept of more priviledge levels (host user, host sys,
guest user, guest sys)

> Happen to have more details? If they really run in user context their
> priv level would be the same right, otherwise they run in something
> weird, not quite user not quite kernel. Now that might be the case, but
> I'm utterly ignorant on itanic.

See Documentation/ia64/fsys.txt

-Andi
-- 
ak@xxxxxxxxxxxxxxx -- Speaking for myself only.
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