[libvirt] [PATCHv3 1/6] conf: add <irqchip mode> to <features>

[Paolo Bonzini]

On 27/04/2017 16:07, Ján Tomko wrote:
> And if apic:qemu,ioapic:qemu is only for debugging, the <apic> element
> can be dropped too.
> 
> 'ioapic' is also more specific (so if kernel-irqchip starts to be useful
> on other archs, libvirt might need a new element?).

Yeah, using architecture-specific element names brings multiplication of
nodes, but on the other hand it makes little sense to do it otherwise.
And ARM already has <gic>

KVM adopted the "irqchip" moniker, but I don't really like it because
there are many irqchips in a modern computer (usually two layers, with
one irqchip per CPU and one distributing IRQs to the CPUs): x86 has APIC
and IOAPIC (even without considering legacy), PPC has XICS and XICP, ARM
has the GIC and the distributor, and so on.

For what it's worth, KVM on Raspberry Pi (when it happens) will need
"-machine kernel_irqchip=off", so <gic version='...' driver='qemu'/>.

> I'm considering sticking the attribute to the already-existing apic
> element:
> <apic mode='kernel|split'/>

Not really, because with "<apic mode='split'>" the APIC would be in the
kernel. :)

Paolo

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