I added WITNESS to a kernel I've been running and during boot I got 
this result:
vm exit[0]
         reason          VMX
         rip             0xffffffff8078c1a7
         inst_length     7
         status          0
         exit_reason     2
         qualification   0x0000000000000000
         inst_type               0
         inst_error              0
Abort trap (core dumped)
anyone have a decoder ring?
julian