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

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Date:	Wed, 23 Apr 2014 17:44:30 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	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 5:35 PM, Borislav Petkov <bp@...en8.de> wrote:
> On Wed, Apr 23, 2014 at 05:18:29PM +0200, Stephane Eranian wrote:
>> On Wed, Apr 23, 2014 at 5:16 PM, Borislav Petkov <bp@...en8.de> wrote:
>> > On Wed, Apr 23, 2014 at 05:14:33PM +0200, Stephane Eranian wrote:
>> >> Wouldn't rdmsrl_safe() return 0 on success?
>> >
>> > Yes.
>> >
>> then the if() test is wrong:
>> if (!rdmsrl_safe())
>>    return -1;
>>
>> Should be:
>> if (rdmsrl_safe())
>>   return -1;
>>
>> Or am I missing something?
>
> Yeah, that is wrong:
>
>         if (!rdmsrl_safe(MSR_RAPL_POWER_UNIT, &msr_rapl_power_unit_bits))
>                 return -1;
>
> On error we return -EIO, on success 0. Just remove the "!".
>
Yeah, will post a patch ASAP. A comment describing return values
where rdmsrl_safe() is defined would maybe help avoid problems in the future.
Thanks.

>
> --
> Regards/Gruss,
>     Boris.
>
> Sent from a fat crate under my desk. Formatting is fine.
> --
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