Re: [Qemu-devel] [RFC PATCH] qemu spapr-pci: added IRQ list to PCIBus

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 17/05/12 13:00, Benjamin Herrenschmidt wrote:
> On Thu, 2012-05-17 at 12:16 +1000, Alexey Kardashevskiy wrote:
> 
>>> It actually can change dynamically on x86 due to acpi interrupt links
>>> which allow the guest a generic way to select from a set of possible
>>> interrupt routing schemes.  And of course a chipset driver could twiddle
>>> bits if it wanted as well.  So, we really do need the update notifiers
>>> from my tree that this patch drops.
>>
>>
>> You mean notifiers like these: ioapic_add_gsi_eoi_notifier?
>> I did not drop them, we need them so I implemented them for XICS interrupt controller.
> 
> So I haven't completely understood the problem, however:
> 
>  .../...
> 
>> So it stores global IRQs in the config space but it really unclear who writes these _global_ numbers
>> there. Is it the guest who allocates IRQs and writes the numbers into the config space so QEMU knows
>> what pin is what IRQ? If so, I am wrong, you are right :)
> 
> So you can certainly not write our global irq numbers in the config
> space, since the config space IRQ_LINE register is only 8 bits long
> which means it's not long enough.

[had a char]
No, it is all about piix3 extended capability.



-- 
Alexey