How does one get a working serial console with gptboot?

[Freddie Cash]

I feel like an idiot right now because I can just not figure out how
to make $subject work on a -CURRENT system.  :(

I've read through the Handbook chapter on this.  I've done the process
I've used with 8.x systems.  But once the kernel loads, the serial
console stops working.  I'm obviously missing a step somewhere.

Here's what I've done.  Please point out my error(s):

/boot/loader.conf:
    hint.uart.0.disabled="0"
    hint.uart.0.flags="0x30"
    console="comconsole vidconsole"
    comconsole_speed="115200"
    boot_multicons="yes"

/etc/make.conf:
    BOOT_COMCONSOLE_PORT=0x3F8
    BOOT_COMCONSOLE_SPEED=115200

/etc/ttys:
    ttyu0 "/usr/libexec/getty std.115200" vt100 on secure

Then I rebuilt the boot code via:
  cd /usr/src/sys/boot
  make cleandepend; make depend; make; make install

And I loaded the new boot code into the GPT via:
  gpart bootcode -p /boot/gptboot -i 1 ada0

This motherboard (SuperMicro H8DGi-F) includes an IPMI-enabled
serial-over-LAN setup, including a KVM-over-LAN.  The KVM-over-LAN
uses a virtual onscreen keyboard, though, so it's a pain to use, which
is why I'm trying to get the serial console stuff working.

The BIOS is configured to use COM3 for the remote access setup.  The
kernel detects this as uart0, and dmesg shows it as being detect and
set as "uart0: console (115200,n,8,12).

The serial console works at the boot loader screens and I can drop to
a loader prompt, type away, etc.  As soon as I type "boot" and the
kernel loads ... the serial console dies.

Any suggestions?
-- 
Freddie Cash
fjwcash at gmail.com