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the old explanation of AP startup might have been correct, but

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I understand this one.
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rtm 2008-08-28 00:52:05 +00:00
parent 02cc595f28
commit 56082468ea
1 changed files with 10 additions and 9 deletions
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19
bootother.S
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@ -1,15 +1,16 @@
#include "asm.h"
# Start an Application Processor. This must be placed on a 4KB boundary
# somewhere in the 1st MB of conventional memory (APBOOTSTRAP). However,
# due to some shortcuts below it's restricted further to within the 1st
# 64KB. The AP starts in real-mode, with
# CS selector set to the startup memory address/16;
# CS base set to startup memory address;
# CS limit set to 64KB;
# CPL and IP set to 0.
# Each non-boot CPU ("AP") is started up in response to a STARTUP
# IPI from the boot CPU. Section B.4.2 of the Multi-Processor
# Specification says that the AP will start in real mode with CS:IP
# set to XY00:0000, where XY is an 8-bit value sent with the
# STARTUP. Thus this code must start at a 4096-byte boundary.
#
# Bootothers (in main.c) starts each non-boot CPU in turn.
# Because this code sets DS to zero, it must sit
# at an address in the low 2^16 bytes.
#
# Bootothers (in main.c) sends the STARTUPs, one at a time.
# It puts this code (start) at 0x7000.
# It puts the correct %esp in start-4,
# and the place to jump to in start-8.
#