This patch contains the communication module (XPC) for cross partition
communication on a partitioned SGI Altix.
                                                                                
XPC creates kthreads to manage the channel activity between partitions.
There is an EFI version of XPC (called XPBOOT) that polls rather than uses
multiple kthreads. It's purpose is to provide a diskless boot capability.
It is the reason for the '#if[n]def SN_PROM' code and xpc_stubs.h file.
XPBOOT is included in the PROM/SAL code and can not be released due to
Intel copyright.