Re: [RFC PATCH] KVM: introduce kvm_check_device

[Scott Wood <scottwood@freescale.com>]

On Wed, 2015-01-07 at 10:55 +0000, Andre Przywara wrote:
> Hi Scott,
> 
> thanks for looking at the patch.
> 
> On 06/01/15 20:52, Scott Wood wrote:
> > Out of curiosity, why do you need to test it from inside the kernel but
> > outside kvm_main.c?
> 
> I need it from arch/arm/kvm/arm.c or alternatively virt/kvm/arm/vgic.c.
> The problem is that while KVM_CREATE_DEVICE works fine with checking the
> availability of the requested device, KVM_CREATE_IRQCHIP does not - and
> the latter is handled in the arch specific parts of the code. At the
> moment the GIC_V2 is the only IRQ chip, so it's all or nothing right
> now. But very soon there will be a GIC_V3, with GIC_V2 compatibility not
> always being available, so KVM_CREATE_IRQCHIP may fail although there is
> an in-kernel IRQ chip available.
> Instead of hacking something up I thought it would be cleaner to use the
> existing framework and just map KVM_CREATE_IRQCHIP to
> KVM_CREATE_DEVICE(KVM_DEV_TYPE_ARM_VGIC_V2).

In that case you'd need the full create_device functionality from
arch/arm/kvm, not just testing whether a device type is present, right?

-Scott