# File lib/vagrant-libvirt/config.rb, line 369
      def memorybacking(option, config = {})
        case option
        when :source
          raise 'Source type must be specified' if config[:type].nil?
        when :access
          raise 'Access mode must be specified' if config[:mode].nil?
        when :allocation
          raise 'Allocation mode must be specified' if config[:mode].nil?
        end

        @memory_backing = [] if @memory_backing == UNSET_VALUE
        @memory_backing.push(name: option,
                             config: config)
      end