> -- Why does this thing hide the fact that my CPU does have PAT from
>    me (even though it might elect to not trust it)?

Attach a trivial (untested) patch that should let know that PAT was 
disabled by kernel.

Matthieu

PS : if you want more tester you should print in this message a link of 
what should be tested to know if PAT is broken in this machine and where 
to report it.