On Fri, Mar 14, 2014 at 10:57:58AM -0600, David Ahern wrote:
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
Hi,
cc-ing the virtualization mailing list for more detail on the kvm
default for ignore_msrs (it defaults off).
1) Just returning 0 for unsupported MSRs is not workable -- 0 may be a
meaningful value for an MSR. RDMSR/WRMSR already have a mechanism
for out-of-band errors, #GP.
2) #GP has been KVM's default behavior for quite some time. Even if we
believe changing KVM's default is appropriate, Linux w/ the RAPL PMU
code enabled will fail to boot on existing KVM versions. W/ this
change, Linux will boot on prior KVM versions.
Thanks,
-- vs;
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