From the email sent to the freebsd-virtualization list, subject "High vCPU Counts in bhyve"
The cause and fix was described in a follow-on post:
This PR will track the fix.
Return to the mailing list.
I will take it.
For reference, this ticket is being discussed on this review: https://reviews.freebsd.org/D18755
(In reply to Marcelo Araujo from comment #3)
A proposed fix is now available in https://reviews.freebsd.org/D18815