Re: [RFC 5/5] x86,perf: Only allow rdpmc if a perf_event is mapped

[Martin Schwidefsky]

On Mon, 20 Oct 2014 10:48:13 +0200
Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> >  - cpumsf_pmu_event_idx is the same as power_pmu_event_idx.
> 
> Oh cute, lets ask the s390 people, do you guys have a userspace
> instruction to read the actual counter value?

The "extract cpu counter" ECCTR instruction can be authorized to
be used in user-space with a bit in CR0. With the current code
this bit is not set, the cpu measurement facility is not usable
in user space without a patch to the kernel.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

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