Controlling resource transfers in a logically partitioned computer system

An apparatus comprising:

• at least one processor;
• a memory coupled to the at least one processor;
• a plurality of input/output (I/O) slots coupled to the at least one processor;
• a plurality of locks residing in the memory, wherein each of the plurality of I/O slots has a corresponding lock;
• a plurality of logical partitions defined on the apparatus;
• a lock mechanism that controls access to each I/O slot by the plurality of logical partitions by requiring exclusive ownership of the corresponding lock before transferring control of the corresponding I/O slot to one of the plurality of logical partitions and before allowing one of the plurality of logical partitions to access the corresponding I/O slot;
• a mechanism for releasing all memory and virtual address bindings to an adapter in a selected I/O slot when control of the selected I/O slot is removed from one of the plurality of logical partitions;
• a mechanism for one of the plurality of logical partitions to relinquish control of an I/O slot that the one logical partition owns without relinquishing ownership of the I/O slot;
• and
• a mechanism for the one logical partition to regain control of an I/O slot that the logical partition owns but for which the one logical partition previously relinquished control.