MSR_PERF_CTL
msr = rdmsr(MSR_PERF_CTL);
wrmsr(MSR_PERF_CTL, msr);
case MSR_PERF_CTL: return "perf control";
case MSR_PERF_CTL: vmm_decode_perf_ctl_value(val); break;
msr = rdmsr(MSR_PERF_CTL);
wrmsr(MSR_PERF_CTL, msr);