Direct memory access in a bridge for a multi-processor system

Abstract

A bridge for a multi-processor system includes bus interfaces for connection to an I/O bus of a first processing set, an I/O bus of a second processing set, and a device bus. A bridge control mechanism is configured to provide geographic addressing for devices on the device bus and to be responsive to a request from a device on the device bus for direct access to a resource of a processing set to verify that an address supplied by the device falls within a correct geographic range. A different geographic address range can allocated to each of a plurality of device slots on the device bus. A different geographic address range can also be allocated to the processor set resources (e.g., processor set memory). An address decoding mechanism maintain geographic address mappings, and verifies geographic addresses for direct memory access. The geographic address mappings can be configured in random access memory of the bridge. A slot response register is associated with each slot on the device bus. The slot response register records ownership of a device by the processing sets. The bridge control mechanism responds to a direct memory access request from a device on the device bus to access the slot response register for the slot for the requesting device for identifying the owning processor set, for enabling access to the memory of the owning processor set. The slot response registers can be configured in random access memory in the bridge.