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System BIOS Programming Guidelines
Version 1.4 A-3
;-----------------------------------------------------------------------;
; InitLocalAPIC( ) ;
;-----------------------------------------------------------------------;
; ;
; Initialize the local APIC to virtual wire mode. ;
; ;
;-----------------------------------------------------------------------;
SVR equ 0FEE000F0H
LVT1 equ 0FEE00350H
LVT2 equ 0FEE00360H
APIC_ENABLED equ 000000100H
public InitLocalAPIC
InitLocalAPIC proc near
push ds ; save regs used for APIC init
push es
push esi
mov al,080h ; ensure NMI disabled
out 070h,al
in al,021h ; read primary imr
push ax ; save settings
mov al,0ffh ; mask all off
out 021h,al
in al,0a1h ; read secondary imr
push ax ; save settings
mov al,0ffh ; mask all off
out 0a1h,al
extrn pmode_on : near
call pmode_on ; switch into real big mode
;
; The APIC spurious interrupt must point to a vector whose lower
; nibble is 0F, that is 0xF, where x is 0 - F. Here we use Int 00FH,
; which handles spurious interrupts and supplies the necessary IRET.
; This vector is assumed to have already been initialized in memory.
;
; Enable the APIC via SVR and set the spurious interrupt to use Int 00F
;
mov esi,SVR
mov eax,[esi] ; read SVR
and eax,0FFFFFF0FH ; clear spurious vector (use vector
00FH)
or eax,APIC_ENABLED ; bit 8 = 1
mov [esi],eax ; write SVR
;
; Program LVT1 as ExtInt, which delivers the signal to the INTR signal of all
; processors' cores listed in the destination as an interrupt that originated
; in an externally-connected interrupt controller.
;
Example A-1. Programming Local APIC for Virtual Wire Mode