Re: KVM's PIT and PIC programming question

[Avi Kivity <avi@redhat.com>]

On 08/20/2009 12:26 AM, Saksena, Abhishek wrote:
> Hi Guys,
> I am writing very simple bios for KVM (not using Qemu but creating a simple io device models around KVM). I am having trouble in receiving regular Timer interrupts after programming PIT.
>
> I think I have enabled PIC and PIT correctly using following code:-
>
> PIC Programming
> ;; PIC
>    mov  al, #0x00
>    out  0x21, AL ;master pic: all IRQs unmasked
>    out  0xA1, AL ;slave  pic: all IRQs unmasked
>
>
> PIT Programming
>
> and also enable PIT to genrate regular timer interruput
>
> SET_INT_VECTOR(0x08, #0xF000, #int08_handler)
>    mov al, #0x34 ; timer0: binary count, 16bit count, mode 2
>    out 0x43, al
>    mov al, #0x00 ; maximum count of 0000H = 18.2Hz
>    out 0x40, al
>    out 0x40, al
>
>
> PIT Timer ISR code
>
> Timer ISR code
>
> ;---------
> ;- INT08 -
> ;---------
> .org 0xfea5 ; INT 08h System Timer ISR Entry Point
> int08_handler:
>    sti
>    push ax
>    push ds
>    mov ax, #0x0040
>    mov ds, ax
>    mov ax, 0x006c ; increment lower word
>    inc ax
>    mov 0x006c, ax
>    jnz inc_done
>    mov ax, 0x006e ; increment upper word
>    inc ax
>    mov 0x006e, ax
>
>
>
> For some reason I never see int08_handler ever been called. Any clues what may be wrong? I am creating only one VCPU
>
>
>    

Things to check:

- have you initialized the kernel PIC and PIT?
- are interrupts enabled?

-- 
error compiling committee.c: too many arguments to function