[$] Kernel support for processor undervolting

Overclocking the processor - running it above its specified maximumfrequency to increase performance - is a familiar operation for many readers. Sometimes, however, it is necessary to go the other direction and decrease a processor's operating power point by lowering its voltageto avoid overheating. Recently, Jason Donenfeld submitted a shortpatch removing a warning emitted by the kernel when user space accessesspecial processor registers that allow this "undervolting" on x86processors. It caused a long discussion that might result in a kernelinterface to allow users to safely control their processor's voltage.