System and method for selectively restricting access to memory for bus attached unit IDs

A method for bus attachment of one or more adapter units to a protected shared memory comprising the steps of:

• storing in a program accessable store, a predetermined address range for restricting the range of said shared memory accessable by one or more adapters and storing predetermined associated identities of said one or more adapters that are enabled to access said range of said shared memory;
• receiving a first adapter unit address and first adapter unit identity from a first adapter unit by way of a first bus;
• comparing said first adapter unit address and first adapter unit identity with a said predetermined address range and associated predetermined identities to determine if said first adapter unit address is authorized;
• and
• signaling an exception if said first adapter unit is not authorized to access said first adapter unit address.

A method for bus attachment of one or more adapter units to a shared memory comprising the steps of:

• storing in a program accessable store, a predetermined address range for restricting the range of said shared memory accessable by one or more adapters and storing predetermined associated identities of said one or more adapters that are enabled to access said range of said shared memory;
• receiving a first adapter unit address and a first adapter unit identity from a first adapter unit by way of a first bus;
• incrementing said first adapter unit address for subsequent first adapter unit accesses to said shared memory;
• comparing said incremented first adapter unit address and said first adapter unit identity with said predetermined address range and said predetermined associated identity to determine if said incremented first adapter unit address is authorized;
• signaling an exception if said first adapter unit is not authorized to access said first adapter unit address;
• and
• communicating by way of a second bus when said first bus is not available.

A method for bus attachment of one or more adapter units to a protected shared memory comprising the steps of:

• storing in a program accessable store, a predetermined address range for restricting the range of said shared memory accessable by one or more adapters and storing predetermined associated identities of said one or more adapters that are enabled to access said range of said shared memory;
• granting to a first adapter unit, control of a first bus;
• receiving a bus transaction from a first adapter unit by way of said first bus;
• creating a first adapter unit address and a unique first adapter unit identity for said first adapter unit based on information received from said bus transaction;
• and
• associating said unique first adapter unit identity with all bus accesses to shared memory while said first adapter unit maintains control of said first bus;
• comparing said first adapter unit address and first adapter unit identity with said predetermined address range and said predetermined associated identities to determine if said first adapter unit address is authorized;
• and
• retaining status in said program accessable store and signaling an exception if said first adapter unit is not authorized to access said memory range.