Processing multicast messages in a data processing system

An apparatus for processing multicast messages in a data processing system, the data processing system comprising a plurality of compute nodes, each compute node comprising a communications controller, the communications controllers operatively coupled for data communications amongst the compute nodes of the data processing system, each compute node in the data processing system executing at least one logical partition, the data processing system further comprising a hypervisor adapting communications controllers of the compute nodes to logical partitions for multicast communications, the apparatus comprising a computer processor, a computer memory operatively coupled to the computer processor, the computer memory having disposed within it computer program instructions that, when executed by the computer processor, cause the apparatus to carry out the steps of:

• receiving, by more than one of the communications controllers, a multicast message;
• responsive to receipt of the multicast message, signaling, by one of the communications controllers, an interrupt in the hypervisor without signaling an interrupt by any other communications controller;
• determining, by the hypervisor, that the message received by the interrupt signaling communications controller is a multicast message;
• and providing, by the hypervisor, the multicast message to at least one logical partition configured to receive multicast messages;
• wherein:
• the multicast message further comprises a group identifier, the group identifier specifying a subset of the data processing system's logical partitions intended to receive the multicast message;
• providing the multicast message to at least one logical partition configured to receive multicast messages further comprises providing the multicast message to all logical partitions configured to receive multicast messages;
• and the apparatus further comprises computer program instructions that, when executed, cause the apparatus to carry out the step of determining, by each logical partition receiving the multicast message, whether the receiving logical partition is specified by the group identifier.

A computer program product for processing multicast messages in a data processing system, the data processing system comprising a plurality of compute nodes, each compute node comprising a communications controller, the communications controllers operatively coupled for data communications amongst the compute nodes of the data processing system, each compute node in the data processing system executing at least one logical partition, the data processing system further comprising a hypervisor adapting communications controllers of the compute nodes to logical partitions for multicast communications, the computer program product disposed upon a computer readable medium, wherein the computer readable medium in not a signal, the computer program product comprising computer program instructions that, when executed, cause a computer to carry out the steps of:

• receiving, by more than one of the communications controllers, a multicast message;
• responsive to receipt of the multicast message, signaling, by one of the communications controllers, an interrupt in the hypervisor without signaling an interrupt by any other communications controller;
• determining, by the hypervisor, that the message received by the interrupt signaling communications controller is a multicast message;
• and providing, by the hypervisor, the multicast message to at least one logical partition configured to receive multicast messages;
• wherein:
• the multicast message further comprises a group identifier, the group identifier specifying a subset of the data processing system's logical partitions intended to receive the multicast message;
• providing the multicast message to at least one logical partition configured to receive multicast messages further comprises providing the multicast message to all logical partitions configured to receive multicast messages;
• and the computer program product further comprises computer program instructions that, when executed, cause the computer to carry out the step of determining, by each logical partition receiving the multicast message, whether the receiving logical partition is specified by the group identifier.