Messages in this thread | | | Date | Fri, 14 Mar 2014 08:21:07 -0700 | Subject | Re: [PATCH] perf/x86/intel: Use rdmsrl_safe when initializing RAPL PMU. | From | Venkatesh Srinivas <> |
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On Fri, Mar 14, 2014 at 6:56 AM, Andi Kleen <ak@linux.intel.com> wrote: > 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.
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.
Thanks, -- vs;
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