> I tried adding it to my config file that #includes XEN3_DOM0; com0
> doesn't show up at probe time.  However -- and for reasons I don't
> understand -- configuring ttys to turn on /dev/console rather
> than /dev/tty00 is working properly, in that it's speaking to the com0
> serial port.  (In a message exchange a few months ago, tjls had
> suggested the opposite -- that doesn't work here.)

I don't have com0 defined in my XEN2 Dom 0. My entire Dom 0 works
through the serial port with just this in the grub config:

default=0
timeout=10
serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
terminal --timeout=10 serial console

title Xen 2.0 / NetBSD (serial)
  root(hd0,0)
  kernel (hd0,a)/xen.gz dom0_mem=73728 com1=115200,8n1
  module (hd0,a)/netbsd-XEN0 ro console=ttyS0

... and of course the following in my ttys file:

console "/usr/libexec/getty std.115200" vt100   on secure