Re: [Qemu-devel] [RFC][PATCH 14/16] kvm: x86: Add user space part for in-kernel i8259

[Avi Kivity]

On 12/05/2011 03:29 PM, Jan Kiszka wrote:
> On 2011-12-05 14:14, Avi Kivity wrote:
> > On 12/05/2011 02:47 PM, Jan Kiszka wrote:
> >>>
> >>> (the memory API added unstable names, hopefully the QOM can take over
> >>> the stable ones and we'll have a good way to denote the unstable ones).
> >>>
> >>
> >> OK, maybe - or likely - we should make those device models have the same
> >> names in QOM once instantiated. But I'm still convinced they should
> >> remain separated models in contrast to a single model with a property.
> > 
> > What do you mean by separate models?  You share all the code you can,
> > and don't share the code you can't.  To me, single model == single name.
>
> But different configuration.

Right, just like IDE with different backends.

> > 
> >> The kvm ioapic, e.g., requires an additional property (gsi_base) that is
> >> meaningless for user space devices. And its interrupts have to be
> >> wired&configured differently at board model level. So, from the QEMU
> >> POV, it is a very different device. Just the guest does not notice.
> > 
> > It's like qcow2 and raw/native IO are wire differently, or virtio-net
> > and vhost-net.  But it's the same IDE device or virtio NIC.
>
> That would mean introducing a backend/frontend concept for irqchips.

We could do it, have one ioapic model with ioapic_ops->eoi_broadcast(). 
Most of the interfaces already dispatch dynamically (qdev gpio/irq) so
there wouldn't be much more there.

To me, how it's actually implemented is not important.  What is
important is that save/restore, the monitor, and the guest don't notice
any changes.

-- 
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