Re: [Qemu-devel] [PATCH 61/61] pc_q35: apic mode for pci interrupt routing.

[Avi Kivity]

On 09/30/2009 12:18 PM, Isaku Yamahata wrote:
> apic mode for pci interrupt routing.
>
> +static void ich9_lpc_ioapic_update_fn(void *opaque, int reset)
> +{
> +    struct ICH9_LPCIrqState *irq_state = opaque;
> +    struct ICH9_LPCState *ich9_lpc = irq_state->lpc;
> +
> +    /* this can be called via gmch_init() where ich9_lpc isn't
> +       allocated yet */
> +    if (ich9_lpc == NULL)
> +        return;
> +
> +    if (reset)
> +        ich9_lpc->apic_mode = 0;
> +    else
> +        ich9_lpc->apic_mode = 1;
> +}
> +
>    


My understanding was that the OS calls ACPI to set APIC mode.  The ACPI 
routine (_PIC) can then access a register to re-program the interrupt 
router.

Does this reflect how Q35 works, or is this a shortcut?

On my desktop, I have:

    Name (\GPIC, Zero)
    Method (\_PIC, 1, NotSerialized)
    {
        Store (Arg0, \GPIC)
    }

With GPIC later referenced by the various interrupt management routines 
like _PRT; if GPIC is set they return interrupts in the range 16-19, 
otherwise LNKA-LNKD.


--
Do not meddle in the internals of kernels, for they are subtle and quick to 
panic.