linux-kernel - Re: [PATCH] perf/x86/intel: Use rdmsrl

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Message-ID: <CABPqkBTSKeza=Ax0yGEfMTq5B8NSQHyvfFBe8qVa-h0dE=UCYg@mail.gmail.com>
Date:	Wed, 23 Apr 2014 17:14:33 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Venkatesh Srinivas <venkateshs@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	"Yan, Zheng" <zheng.z.yan@...el.com>
Subject: Re: [PATCH] perf/x86/intel: Use rdmsrl_safe when initializing RAPL PMU.

On Wed, Apr 23, 2014 at 5:09 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Wed, Apr 23, 2014 at 04:49:55PM +0200, Stephane Eranian wrote:
>> On your machine, booted with 3.15-rc2, do you have /sys/devices/power?
>> If not, and you have at least an SNB, you should have RAPL and that
>> RAPL_UNIT MSR.
>>
>> Proof is that if you read that MSR using /dev/cpu/msr it works just fine:
>> # modprobe msr
>> # rdmsr 0x606
>> a1003
>>
>> So something is broken somewhere.
>
> I've not got SNB+ class hardware (for testing). But I believe you that
> there's something funny, I just do not understanding how *msr_safe()
> could cause this.

Or the logic of the test in rapl_cpu_prepare() is wrong, maybe?
Wouldn't rdmsrl_safe() return 0 on success?
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