Steps for VM replacement:

(1) Study Sprite VM interface.

(2) Determine mapping of (1) onto Mach VM interface (including mapping
of return values).

(3) Determine which pagers are needed, or at least understand how the
different pagers are used.

(4) Write stubs for lock, spl calls.

(5) Write stubs for task/thread management.

(6) put 3.0 pager back into kernel (merge server/vm/inode_pager and
kernel/boot_ufs code, I guess).

(7) Teach default pager about Sprite FS interface.

(8) Study default exception handler, decide whether to keep or whether
to write a stub for thread_doexception that uses signals.

(9) Merge Sprite and Mach trap handlers.

(10) Write memory management stubs, using Sprite malloc/free

(11) Build with VM; migration turned off.

(12) Add encapsulation/decapsulation routines for process migration.
Re-enable migration.

(13) Write queue package stubs?

(13) Rewrite pageout code to cooperate with file system.  Is there a
limit on the file cache size?  Does the inode pager support sticky
segments?