linux-kernel - Re: [PATCH -tip] perf_counter/x86: Fix incorrect default branch

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Message-ID: <20090610051521.GB30923@ywang-moblin2.bj.intel.com>
Date:	Wed, 10 Jun 2009 13:15:21 +0800
From:	Yong Wang <yong.y.wang@...ux.intel.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -tip] perf_counter/x86: Fix incorrect default branch

On Tue, Jun 09, 2009 at 04:25:06PM +0200, Ingo Molnar wrote:
> 
> They dont have X86_FEATURE_ARCH_PERFMON set, right?
> 
> I made the switch statement under the assumption that it covers all 
> existing arch-perfmon CPU models. If not, the 'default:' placement 
> would indeed be buggy.
> 

OK, you are right. X86_FEATURE_ARCH_PERFMON eliminates all the old CPUs.
However, the logic still seems not correct. Both the Core2 CPUs I'm
using are recognized as Nehalem/Corei7. /proc/cpuinfo and cpuid outputs
are given below.

The first one:
vendor_id       : GenuineIntel
cpu family      : 6
model           : 23
model name      : Intel(R) Core(TM)2 Duo CPU     P8400  @ 2.26GHz
stepping        : 6

CPUID.0x00000001: eax=0x00010676

The second one:
vendor_id       : GenuineIntel
cpu family      : 6
model           : 15
model name      : Intel(R) Core(TM)2 CPU          6600  @ 2.40GHz
stepping        : 6

CPUID.0x00000001: eax=0x000006f6

Looks like it's not enough to just look at boot_cpu_data.x86_model.

-Yong
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