genfb console on hybrid graphics

[<dhop%nwlink.com@localhost>]

Hi all,

I have a Coffee Lake laptop that runs fine with genfb-- even at 4K-- when
the BIOS is configured for discrete graphics.  Now, I don't expect either
i915 or Nouveau to be working yet on this system (Intel UHD 630 and Nvidia
Quadro RTX4000), but when I configure the BIOS for hybrid graphics to test
genfb out on the Intel part, I get a 'no console' panic on NetBSD 8, 9.0_RC1
or -current.  I've tried all the 'gop' modes but I get no console in this
configuration.

In the hybrid boot case both genfb0 (Nvidia) and genfb1 (Intel) are probed:

genfb0 at pci1 dev 0 funciton 0: NVIDIA product 1eb6 (rev. 0xa1)
[...]
genfb1 at pci0 dev 2 function 0: Intel UHD Graphics 630 (rev. 0x82)

...but the console fails to attach-- I assume because it's trying to use the
first possible framebuffer which is pointing the secondary device.  What are
the settings I should be tweaking to test out performance of the Intel
genfb-- if that's possible?

I'm happy to post boot messages but I'm struggling to find a way forward for
serial booting this USB-only laptop.

Thanks,
David