The messaging system connects eight agents together in a mesh configuration.
The message passing between agents can be done exclusively between the sources and
destinations by programming the 128 permission apertures in the LPD_XPPU that
correspond to the 0xFF30_0000 to 0xFF30_01FF
memory range.
The IPI does not control the content of the message buffers. It is up to the source and destination processor agent software to define the back-and-forth interrupt signaling and the content put into the request and response message buffers. The content of the message buffers does not affect the hardware; it is only written and interpreted by the processors. The use of the message buffers is optional.