>machdep.nkpde ... you need to recompile sysctl for it to grok the name.
>(*sigh*, for a better sysctl interface...)

Looks like I'd done a userland make locally, before supping the update,
but after the sup times changed.   The relevant user code didn't
get rebuilt.  Sigh.  Sorry for bothering you about sysctl(8) here.