According to one or more embodiments of the present invention, a computer implemented method includes receiving a query for an amount of storage in memory of a computer system to be donated to a secure interface control of the computer system. The secure interface control can determine the amount of storage to be donated based on a plurality of secure entities supported by the secure interface control as a plurality of predetermined values. The secure interface control can return a response to the query indicative of the amount of storage as a response to the query. A donation of storage to secure for use by the secure interface control can be received based on the response to the query.