Coherent attached processor proxy supporting coherence state update in presence of dispatched master

摘要

A coherent attached processor proxy (CAPP) of a primary coherent system receives a memory access request specifying a target address in the primary coherent system from an attached processor (AP) external to the primary coherent system. The CAPP includes a CAPP directory of contents of a cache memory in the AP that holds copies of memory blocks belonging to a coherent address space of the primary coherent system. In response to the memory access request, the CAPP performs a first determination of a coherence state for the target address and allocates a master machine to service the memory access request in accordance with the first determination. Thereafter, during allocation of the master machine, the CAPP updates the coherence state and performs a second determination of the coherence state. The master machine services the memory access request in accordance with the second determination.

主权项

1. A coherent attached processor proxy (CAPP), comprising:
transport logic having a first interface configured to support communication with a system fabric of a primary coherent system and a second interface configured to support communication with an attached processor (AP) that is external to the primary coherent system and that includes a cache memory that holds copies of memory blocks belonging to a coherent address space of the primary coherent system; operation handling logic including:
a CAPP directory of contents of the cache memory in the AP;one or more master machines that initiate memory access requests on the system fabric of the primary coherent system on behalf of the AP;one or more snoop machines that service requests snooped on the system fabric; wherein the operation handling logic, responsive to receiving a memory access request from the attached processor (AP), performs a first determination of a coherence state for the target address with respect to the CAPP and allocates a master machine among the one or more master machines to service the memory access request in accordance with the first determination; and wherein during allocation of the master machine to service the memory access request, a snoop machine among the one or more snoop machines causes an update to the coherence state for the target address with respect to the CAPP, the operation handling logic performs a second determination of the coherence state for the target address with respect to the CAPP, and the master machine services the memory access request in accordance with the second determination.