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Date: Fri, 4 Sep 2015 11:43:49 -0500
From: Scott Wood <scottwood@freescale.com>
To: Christophe Leroy <christophe.leroy@c-s.fr>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>, Paul Mackerras
 <paulus@samba.org>, Michael Ellerman <mpe@ellerman.id.au>,
 <linux-kernel@vger.kernel.org>, <linuxppc-dev@lists.ozlabs.org>, Joakim
 Tjernlund <joakim.tjernlund@transmode.se>
Subject: Re: [PATCH] powerpc/book3s32: Only select PPC_HAVE_PMU on e600
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On Thu, Sep 03, 2015 at 11:27:03AM +0200, Christophe Leroy wrote:
> On PPC832x, perf record/report reports martian addresses
> 
>      2.62%  perf_reseau4  libpthread-2.18.so  [.] __libc_send
>      2.56%  perf_reseau4  [kernel.kallsyms]   [k] __ip_make_skb
>      1.62%  perf_reseau4  [kernel.kallsyms]   [k] __ip_append_data.isra.39
>      1.55%  perf_reseau4  [kernel.kallsyms]   [k] ip_finish_output
>      1.33%  perf_reseau4  [unknown]           [k] 0x7ffffd94
>      1.33%  perf_reseau4  [unknown]           [k] 0x7ffffd95
>      1.28%  perf_reseau4  [unknown]           [k] 0x7ffffd97
>      1.26%  perf_reseau4  [unknown]           [k] 0x7ffffda3
>      1.24%  perf_reseau4  [unknown]           [k] 0x7ffffd98
>      1.22%  perf_reseau4  [unknown]           [k] 0x7ffffd92
>      1.22%  perf_reseau4  [unknown]           [k] 0x7ffffd9b
>      [.....]
> 
> This is due to function perf_instruction_pointer() reading SPR SIAR
> which doesn't exist on e300 core. The perf_instruction_pointer() is
> redefined in arch/powerpc/perf/core-book3s.c when CONFIG_PPC_PERF_CTRS
> is selected.
> 
> This patch moves the selection of CONFIG_PPC_HAVE_PMU in 86xx section
> so that CONFIG_PPC_PERF_CTRS won't be selected for other 6xx powerpc
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

So, what happens when a kernel is built that supports both 83xx and 86xx? 
Plus, it's e300, not e600, that is the exception among 6xx-style cores.

-Scott