func validateLoadBalancerClassField(oldService, service *core.Service) field.ErrorList {
	allErrs := make(field.ErrorList, 0)
	if oldService != nil {
		// validate update op
		if isTypeLoadBalancer(oldService) && isTypeLoadBalancer(service) {
			// old and new are both LoadBalancer
			if !sameLoadBalancerClass(oldService, service) {
				// can't change loadBalancerClass