Communications between partitioned host processors and management processor

A method for communicating between a management processor and any partition-identifiable host processor in a multi-host multiprocessor computer system comprising:

• establishing a mailbox pair as memory locations in a shared main memory shared by said multi-host multiprocessor computer system, for handling message traffic between said management processor and one of said host processors, a first box of said pair for receiving messages only from said management processor and for being read by said one of said host processors, and a second box of said pair for receiving messages from said one to said host processors and for being read by said management processor,
• before writing a request message into either said first or second box, checking to see if the box is available,
• writing by a request message into the box checked in the previous action, if said box is available, or checking again until it is available or until a timeout,
• reading, responsive to a self-directed polling process, from the mailbox by said processor HOST or MIP that did not write said request message into the box,
• acting on information in said request message by the processor that read said request message and
• replying by the processor that read said request message by writing a response message into the other of said boxes.

A messaging protocol for communications between a host processor and a management processor in a computer system wherein:

• all host processors in said system share a common main memory, said protocol relying on individual communications channels between each host processor and said management processor, wherein each said channel comprises a pair of mailboxes, a first box of said pair being for one of the host processor's outbound communications messages to said management processor, and a second box of said pair being for outbound communications messages from said management processor to said one of the host processors, and wherein mailbox pair for said one of the host processors is located in a partition controlled by said one of the host processors, the messages in said protocol comprising paired messages, wherein outbound messages from a host processor are not equivalent to the outbound messages from the management processor, but wherein there are at least four forms of message pairs, each pair having a request message and a reply message, a first form being a request message having no pointer to a buffer paired with a reply message with a pointer to a buffer, a second form being a request message having a pointer to a buffer paired with a reply message having a pointer to a buffer, a third message pair being a request message having no pointer to a buffer being paired with a reply message having no pointer to a buffer, and a fourth form having a request message with a pointer to a buffer being paired with a reply message having no pointer to a buffer.