Chapter 12 – Boot Flows

Two roads diverged in a wood….

—Robert Frost, “The Road Less Taken”

The restart of a system admits to many possibilities, or paths of execution. The restart of a CPU execution for a given CPU can have many causes and different environment states that impinge upon it. These can include requests to the firmware for an update of the flash store, resumption of a power management event, initial startup of the system, and other possible restarts. This chapter describes some of these possible flows and how the UEFI PI handles the events.

To begin, the normal code flow in the UEFI PI passes through a succession of phases, in the following order:

  1. SEC
  2. PEI
  3. DXE
  4. BDS
  5. Runtime
  6. Afterlife

This chapter describes alternatives to ...

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