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