KVM: arm/arm64: Introduce an allocator for in-kernel irq lines

Having multiple devices being able to signal the same interrupt line is
very confusing and almost certainly guarantees a configuration error.

Therefore, introduce a very simple allocator which allows a device to
claim an interrupt line from the vgic for a given VM.

Signed-off-by: Christoffer Dall <cdall@linaro.org>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>

include/kvm/arm_vgic.h

@@ -121,6 +121,9 @@ struct vgic_irq {
 	u8 source;			/* GICv2 SGIs only */
 	u8 priority;
 	enum vgic_irq_config config;	/* Level or edge */
+
+	void *owner;			/* Opaque pointer to reserve an interrupt
+					   for in-kernel devices. */
 };
 
 struct vgic_register_region;
@@ -340,4 +343,6 @@ int kvm_send_userspace_msi(struct kvm *kvm, struct kvm_msi *msi);
  */
 int kvm_vgic_setup_default_irq_routing(struct kvm *kvm);
 
+int kvm_vgic_set_owner(struct kvm_vcpu *vcpu, unsigned int intid, void *owner);
+
 #endif /* __KVM_ARM_VGIC_H */