High Precision Event Timer (HPET)

This is implemented in hpet.

See Intel's High Precision Event Timer (HPET) Specification for more details.

The HPET is a hardware timer that is used to provide a high-precision time base for the system.

The other clocks such as TSC is calibrated using the HPET, then TSC is used to provide the time for the system as it is faster than the HPET.

Currently, we only use 1 timer for the clock, and we don't use the interrupts. But we could use it in the future to provide a more accurate time based events.

If HPET is not available or the user has allow_hpet=false in the cmdline (see [Command Line]), HPET will be disabled, and we are going to use PIT.