KVM: Don't accept obviously wrong gsi values via KVM_IRQFD

We cannot add routes for gsi values >= KVM_MAX_IRQ_ROUTES -- see
kvm_set_irq_routing(). Hence, there is no sense in accepting them
via KVM_IRQFD. Prevent them from entering the system in the first
place.

Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
{
	if (args->flags & KVM_IOEVENTFD_FLAG_DEASSIGN)
		return kvm_deassign_ioeventfd(kvm, args);

	return kvm_assign_ioeventfd(kvm, args);
}

kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
{
	if (args->flags & KVM_IOEVENTFD_FLAG_DEASSIGN)
		return kvm_deassign_ioeventfd(kvm, args);

	return kvm_assign_ioeventfd(kvm, args);
}
