Specialized boot path for speeding up resume from sleep state

摘要

A specialized boot path for speeding up resume from a sleep state is discussed. In a UEFI-compliant system, a specially constructed alternate firmware volume is created which contains only the code modules used during resumption from an S3 sleep state. This alternate firmware volume is copied into Random Access Memory (RAM) during a normal boot. When the system subsequently enters the S3 sleep state and then begins the resume boot process, code in the boot sequence detects it is a resume from an S3 sleep state, restores a RAM configuration and jumps execution to a Pre-EFI Initialization (PEI) core entry point in the alternate firmware volume in RAM instead of to a firmware volume in ROM. This alternate firmware volume performs specified S3 resume tasks and then returns control to the operating system.