Re: [PATCH] testdev: adjust for ISA irq changes

Avi Kivity
2011-05-29T15:26:28Z

On 05/29/2011 06:21 PM, Jan Kiszka wrote:
> > Suppose our motherboard wired
> > the PCI links to GSI16-19 (or GSI16-23, as we once wanted before we had
> > MSI-X)? We'd need an API to access non-ISA interrupt lines.
> >
> > So what's the clean fix here? gsi_get_irq()?
>
> Maybe. Depends on the requirements of the testdev. If you also want to
> address PIC and IOAPIC separately or simulate injection from a specific
> device, we need more logic.

It's impossible to address them separately, the input lines are tied
together (esp. with kvm irq routing). I think using GSIs is the right
thing here.

> We also need a better interface to discover and track legacy IRQ routes
> for device assignment. Markus is currently collecting requirements for
> qdev enhancements, and I think generic IRQ manipulation and discovery
> belongs there.

Possibly. But note that attempting to shoehorn everything into
bus/device model may not work. Motherboard devices, especially, often
bypass the bus/device relationship, just because everything is available
to them on the motherboard, and because hardware designers didn't go to
software engineering schools but instead do what's necessary to get
things working. We have to be prepared for exceptions.

--
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