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

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Date:	Fri, 14 Mar 2014 06:56:52 -0700
From:	Andi Kleen <ak@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Venkatesh Srinivas <venkateshs@...gle.com>,
	linux-kernel@...r.kernel.org, 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 Fri, Mar 14, 2014 at 09:44:29AM +0100, Peter Zijlstra wrote:
> On Thu, Mar 13, 2014 at 12:36:26PM -0700, Venkatesh Srinivas wrote:
> > CPUs which should support the RAPL counters according to
> > Family/Model/Stepping may still issue #GP when attempting to access
> > the RAPL MSRs. This may happen when Linux is running under KVM and
> > we are passing-through host F/M/S data, for example. Use rdmsrl_safe
> > to first access the RAPL_POWER_UNIT MSR; if this fails, do not
> > attempt to use this PMU.
> 
> This kvm thing is getting tedious :-(

It sounds bogus to me too, VMs are supposed to return 0 
on reading unknown MSRs, no #GP.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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