Re: [PATCH 1/2] perf, x86: Disallow setting undefined bits for PEBS events

[Peter Zijlstra]

On Thu, Mar 13, 2014 at 02:22:12PM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> 
> The SDM forbids setting various event qualifiers with PEBS
> events. The magic cycles:pp event uses it, but it has caused
> problems in the past. We continue allowing it for cycles:pp,
> but forbid it for all other events to follow the SDM.

Last time this came up I asked for what kind of problems it caused.

No answer then I think, and certainly no answer now.

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