linux-kernel - Re: [PATCH v2 4/7] perf, x86: Save/resotre LBR stack during context switch

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Message-ID: <51D55ED4.5030405@intel.com>
Date:	Thu, 04 Jul 2013 19:39:00 +0800
From:	"Yan, Zheng" <zheng.z.yan@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	linux-kernel@...r.kernel.org, mingo@...nel.org, eranian@...gle.com,
	andi@...stfloor.org
Subject: Re: [PATCH v2 4/7] perf, x86: Save/resotre LBR stack during context
 switch

On 07/04/2013 05:57 PM, Peter Zijlstra wrote:
> On Mon, Jul 01, 2013 at 03:23:04PM +0800, Yan, Zheng wrote:
>> +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
>> @@ -185,6 +185,13 @@ void intel_pmu_lbr_reset(void)
>>  		intel_pmu_lbr_reset_32();
>>  	else
>>  		intel_pmu_lbr_reset_64();
>> +
>> +	wrmsrl(x86_pmu.lbr_tos, 0);
>> +}
> 
> I double checked; my SDM Jun 2013, Vol 3C 35-93 very explicitly states that
> MSR_LASTBRANCH_TOS is a read-only MSR. And afaicr all previous times I checked
> this it did say this too.
> 

thank you for point out this. I will update the patch

Yan, Zheng
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