Re: KVM's PIT and PIC programming question

[Avi Kivity <avi@redhat.com>]

On 08/20/2009 08:36 PM, Saksena, Abhishek wrote:
> Thnaks,
>
> So just programming of PIC (8259) should do the trick. Do I have to care about IOAPIC or LAPIC programming? You mentioned lapic is disabled by default, what about IOAPIC.
>
>    

The ioapic will not have any vectors programmed so it will do nothing.


> I see in x86.c
>
> case KVM_CREATE_IRQCHIP:
> 		r = -ENOMEM;
> 		kvm->arch.vpic = kvm_create_pic(kvm);
> 		if (kvm->arch.vpic) {
> 			r = kvm_ioapic_init(kvm);
> 			if (r) {
> 				kfree(kvm->arch.vpic);
> 				kvm->arch.vpic = NULL;
> 				goto out;
> 			}
> 		} else
> 			goto out;
> 		break;
>
>
> so ioapic is created.
>
>
>
> I have enabled all the interrupts in 8259s correctly
>
>
> PIC Programming of master and slave 8259s
> ;; PIC
>      mov  al, #0x00
>      out  0x21, AL ;master pic: all IRQs unmasked
>      out  0xA1, AL ;slave  pic: all IRQs unmasked
>
>
>   PIT Programming
>
>   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
>
> But still not see PIT interrupts or Timer ISR being called!
>
>    

I suggest adding printk()s (or trace_printk()s) in stragtegic places to 
see what's going on.  It can be either a guest programming error or host 
bug.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.