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

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Message-ID: <53233516.10005@gmail.com>
Date:	Fri, 14 Mar 2014 10:57:58 -0600
From:	David Ahern <dsahern@...il.com>
To:	Andi Kleen <ak@...ux.intel.com>,
	Venkatesh Srinivas <venkateshs@...gle.com>
CC:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org,
	Stephane Eranian <eranian@...gle.com>, mingo@...e.hu,
	zheng.z.yan@...el.com
Subject: Re: [PATCH] perf/x86/intel: Use rdmsrl_safe when initializing RAPL
 PMU.

On 3/14/14, 10:17 AM, Andi Kleen wrote:
>> The Intel ISR section for RDMSR seems to say: "Specifying a reserved
>> or unimplemented
>> MSR address in ECX will also cause a general protection exception".
>>
>>  From a guest's perspective, MSR_RAPL_POWER_UNIT is unimplemented; kvm matches
>> this behavior.
>
> MSRs are model specific and defined per model number. If you report a model
> number you're expected to implement the MSRs defined for that model number.
>
> AFAIK Xen just reports 0 for unknown MSRs (and I'm surprised KVM doesn't too)
>
> I would suggest to fix KVM.

I believe ignore_msrs parameter to kvm handles that.

David

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