Re: [Qemu-trivial] [Qemu-devel] [PATCH] RFC kvm irqfd: add directly mapped MSI IRQ support

[Anthony Liguori <anthony@codemonkey.ws>]

"Michael S. Tsirkin" <mst@redhat.com> writes:

> On Mon, Jun 24, 2013 at 08:34:52AM -0500, Anthony Liguori wrote:
>> Gleb Natapov <gleb@redhat.com> writes:
>> 
>> Isn't this more or less what Avi's previous proposal was around changing
>> the APIC interfaces to userspace?
>> 
>> Regards,
>> 
>> Anthony Liguori
>
> While that's not very elegant, I think we can use the existing
> interface for this: just encode things in a fake
> "msi message" in the format that kernel expects.

This is, in fact, exactly what we do today.  The MSI interfaces aren't
for MSI.  They are for sending messages to the APIC bus.  What we should
do is:

#define KVM_SIGNAL_LAPIC	KVM_SIGNAL_MSI
#define KVM_IRQ_ROUTING_LAPIC	KVM_IRQ_ROUTING_MSI

And switch to using the new #defines in QEMU.  That would make it more
obvious where we need to refactor things.  We currently hard code
routing via a local APIC with MSI.  We need to change this into a bus
specific function that can choose the right interface.

I think Power is fine with just doing all routing through the irqchip
interface.  We may need other routing interfaces for other architectures
though.

Regards,

Anthony Liguori

>
>> >
>> >> It seems like the only sane way to actually support (2) and (3).
>> >> 
>> >> Regards,
>> >> 
>> >> Anthony Liguori
>> >
>> > --
>> > 			Gleb.