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Date:	Mon, 20 Oct 2014 11:24:13 +0200
From:	Martin Schwidefsky <>
To:	Peter Zijlstra <>
Cc:	Andy Lutomirski <>,
	Valdis Kletnieks <>,
	"" <>,
	Paul Mackerras <>,
	Arnaldo Carvalho de Melo <>,
	Ingo Molnar <>,
	Kees Cook <>,
	Andrea Arcangeli <>,
	Erik Bosman <>,,,
Subject: Re: [RFC 5/5] x86,perf: Only allow rdpmc if a perf_event is mapped

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

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

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