Intel MultiProcessor manual Operating System Programming Guidelines, Operating System Boot-up

B

Operating System

Programming Guidelines

The goal of the MP specification is to transfer enough information about the hardware environment to the operating system that a single, shrink-wrapped, operating-system binary can boot-up and fully utilize a wide variety of multiprocessor systems. The following sections explain how the operating system can take advantage of this specification to handle these operations:

1.Operating-system boot-up.

2.Self configuration.

3.Interrupt mode initialization.

4.Application processor startup.

5.Application processor shutdown.

6.Dynamic interrupt masking.

7.Support for unequal processors.

B.1 Operating System Boot-up

While all processors in an MP-compliant system are functionally identical, one of the processors will be designated as the boot processor (BSP) at system initialization by the system hardware or by the system hardware in conjunction with the BIOS. The rest of the processors are designated as the application processors (APs). The BSP is responsible for booting the operating system. Once the MP operating system is up and running, the BSP functions as an AP.

Usually a processor is designated as the BSP because it is capable of controlling all system hardware, including AP startup and shutdown. The operating system must determine and remember the APIC ID of the designated BSP, so it can keep the BSP operating as the last running processor during system shutdown. The BSP is not necessarily the first processor, especially in fault-tolerant MP systems in which any available processor can be designated as the BSP.

At the time that the first instruction of the operating system is executed, the APs are in the following state:

∙The APs have been restrained (either by the BIOS or by the hardware) from executing operating system code.

∙The APs are in a halted condition with interrupts disabled. This means that the AP’s local APICs are passively monitoring the APIC bus and will react only to INIT or STARTUP interprocessor interrupts (IPIs).

Version 1.4 B-1