I/O hub-supported atomic I/O operations

摘要

Atomic operations within an I/O device are supported by processor architectures that are not required to include specific atomic instructions, by issuing the atomic operations from an I/O hub. A descriptor that specifies the atomic operation and a target address is retrieved by, or sent to, the hub. A trigger event, which may be a programmed I/O write to the hub with an address of the descriptor, or the contents of the descriptor itself, causes the I/O hub to issue the atomic operation. When the atomic operation is complete on the I/O device interconnect, the result is returned to the hub and a host is notified. The host then retrieves the results of the atomic operation from the hub. The host notification can be performed by interrupt or by polling the hub until a status change is detected.

主权项

1. A method for issuing atomic operations to devices coupled to a processing system by an I/O device interconnect, wherein the method comprises:
triggering by a host processor of the processing system, in an originating device coupled to the I/O device interconnect, the issuance of a particular atomic instruction specifying an atomic I/O operation to be performed atomically over the I/O device interconnect between the originating device and a target device; responsive to the triggering, retrieving a descriptor specifying the target device and the particular atomic instruction; responsive to the retrieving, issuing the particular atomic instruction from the originating device to the target device on the I/O device interconnect; performing the atomic I/O operation by the target device, wherein the I/O device interconnect is operated in an exclusive manner while the atomic I/O operation is being performed to preserve the atomicity of the atomic I/O operation; receiving, at the originating device, an indication that the atomic I/O operation on the I/O device interconnect is complete; and notifying the host processor that the originating device has received the indication that the atomic I/O operation on the I/O device interconnect is complete.