ntpd fails on recent -current/arm64

Somewhere between c283016-g607bc91d90a3 and c283077-g7f658f99f7ed,
some change in the kernel has made ntpd stop working on my arm64 test
box.  (My amd64 test box is a couple of days behind so I'm not sure if
it's arm-specific).

What I've identified so far:
* The problem is in the kernel, not userland.
* The impact seems to be limited to ntpd (in particular, ntpdate works).
* ntpd appears to be correctly exchanging NTP packets with peers.
* ntpd is not responding to "ntpq -p" queries
* ntp_gettime and ntp_adjtime both return TIME_ERROR to ntptime

I've looked through the commits and, beyond much of netinet being
roto-tilled, I can't see anything obvious.

Is anyone else seeing anything similar?  Can anyone suggest where
to look next?

-- 
Peter Jeremy