multiprocessor support:
- Implement MP-safe halt.
- Make the FPU saving code more like Bill's on the i386 MP branch.
XXX This code will no doubt be revisited again.
- Pass the cpu_info and trapframe to IPI handlers, saving some work
in the handlers themselves, and also making it possible for the
"pause" handler to reference register state for DDB.
- Add "machine cpu" to DDB, making it possible to reference other
CPUs registers (and thus get e.g. a traceback) from whichever
CPU is actually running the debugger.
- Garbage-collect "machine halt" and "machine reboot" DDB commands.
They don't have a prayer of working properly in multiprocessor
kernels, and didn't really work all that well in uniprocessor kernels.
additional processors are spun up on multiprocessor Alpha systems.
Now, each processor gets its own idle thread (the primary processor
uses proc0). This idle thread is used in switch_exit(), rather than
explicitly referencing proc0.
Also, make `curproc', `fpcurproc', and `curpcb' per-cpu values. This
required some data structure rearrangement; cpu info is now statically
allocated in the BSS, rather than via malloc(), and cpu_softc is gone.
(Modeled somewhat after NetBSD/sparc's multiprocessor info structures.)
exported to the MI kernel. Almost everything here was formerly in cpu.h.
Optionally, this module could in the future be used to #include anything
that is always needed by arch/alpha modules.
thorpej