Il 03/02/2014 15:06, Michael S. Tsirkin ha scritto:
Linux seems to be trying to read IA32_PERF_CAPABILITIES without checking the
PDCM flag (CPUID[1].ECX[15]).

I can't see why this wasn't crashing before, though. That code seems to be old.

         * v2 and above have a perf capabilities MSR
         */
        if (version > 1) {
                u64 capabilities;

                rdmsrl(MSR_IA32_PERF_CAPABILITIES, capabilities);
                x86_pmu.intel_cap.capabilities = capabilities;
        }

Where does the "v2 and above have a perf capabilities MSR" claim in the code
come from?


But why doesn't it crash on baremetal?
Probably baremetal simply returns 0 or something.
Let me try ..

Because KVM doesn't implement the MSR, but your baremetal likely does.

Paolo

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