Comment 164 for bug 760131

SRU Justification:

Impact: Since 2.6.36 (23016bf0d25), Linux prints the existence of "epb" in /proc/cpuinfo,
    Since 2.6.38 (d5532ee7b40), the x86_energy_perf_policy(8) utility has
    been available in-tree to update MSR_IA32_ENERGY_PERF_BIAS.

    However, the typical BIOS fails to initialize the MSR, presumably
    because this is handled by high-volume shrink-wrap operating systems...

    Linux distros, on the other hand, do not yet invoke x86_energy_perf_policy(8).
    As a result, WSM-EP, SNB, and later hardware from Intel will run in its
    default hardware power-on state (performance), which assumes that users
    care for performance at all costs and not for energy efficiency.
    While that is fine for performance benchmarks, the hardware's intended default
    operating point is "normal" mode...

    Initialize the MSR to the "normal" by default during kernel boot.

    x86_energy_perf_policy(8) is available to change the default after boot,
    should the user have a different preference.

Patch: commit abe48b108247e9b90b4c6739662a2e5c765ed114 upstream