[PATCH] perf, amd: Fix rdpmc index calculation for AMD family 15h

[Robert Richter]

On 06.06.12 09:17:02, tip-bot for Vince Weaver wrote:
> Commit-ID:  c48b60538c3ba05a7a2713c4791b25405525431b
> Gitweb:     http://git.kernel.org/tip/c48b60538c3ba05a7a2713c4791b25405525431b
> Author:     Vince Weaver <vweaver1@xxxxxxxxxxxx>
> AuthorDate: Thu, 1 Mar 2012 17:28:14 -0500
> Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
> CommitDate: Wed, 6 Jun 2012 17:23:35 +0200
> 
> perf/x86: Use rdpmc() rather than rdmsr() when possible in the kernel
> 
> The rdpmc instruction is faster than the equivelant rdmsr call,
> so use it when possible in the kernel.
> 
> The perfctr kernel patches did this, after extensive testing showed
> rdpmc to always be faster (One can look in etc/costs in the perfctr-2.6
> package to see a historical list of the overhead).
> 
> I have done some tests on a 3.2 kernel, the kernel module I used
> was included in the first posting of this patch:
> 
>                    rdmsr           rdpmc
>  Core2 T9900:      203.9 cycles     30.9 cycles
>  AMD fam0fh:        56.2 cycles      9.8 cycles
>  Atom 6/28/2:      129.7 cycles     50.6 cycles
> 
> The speedup of using rdpmc is large.
> 
> [ It's probably possible (and desirable) to do this without
>   requiring a new field in the hw_perf_event structure, but
>   the fixed events make this tricky. ]
> 
> Signed-off-by: Vince Weaver <vweaver1@xxxxxxxxxxxx>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> Link: http://lkml.kernel.org/r/alpine.DEB.2.00.1203011724030.26934@xxxxxxxxxxxxxxxxxx
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> ---
>  arch/x86/kernel/cpu/perf_event.c |    4 +++-
>  include/linux/perf_event.h       |    1 +
>  2 files changed, 4 insertions(+), 1 deletions(-)

This crashs on AMD family 15h. Fix below.

-Robert