panic: sbuf_trim makes no sense on sbuf 0xffffff82434d8898 with drain

Hi!
I consistently get this panic while trying to boot a kernel build from 
r243530.  It happens when the entropy harvesting rc.d script starts. 
r243380 worked fine, I haven't tested any revisions in between. 
Attached is the backtrace from the kernel, as gotten by kgdb.  The 
machine uses zfs as a root pool, and there have been churn in this area. 
  To my untrained eyes, however, the issue seem related to hdaa.c. 
Please let me know if I can provide any more information.
Regards!
-- 
Niclas