port-sparc64/53830: sparc64 install CD selects wrong root device under qemu-current

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         53830
>Category:       port-sparc64
>Synopsis:       sparc64 install CD selects wrong root device under qemu-current
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    port-sparc64-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Jan 03 11:10:00 +0000 2019
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date >= 2017.09.15.13.27.53
>Organization:

>Environment:
System: NetBSD
Architecture: sparc64
Machine: sparc64
>Description:

Booting the sparc64 install ISO of NetBSD-current (2017.09.15.13.27.53
or newer) in a version of qemu recent enough to have commit
09d0c187aa4cce9b349f23724f50587a0014b33b fails with "cannot mount root":

   [   4.2043099] root on wd0a dumps on wd0b
   [   4.2043099] vfs_mountroot: can't open root device
   [   4.2043099] cannot mount root, error = 6
   [   4.2043099] root device (default wd0a): 

When using an older version of NetBSD and/or qemu, the correct root
device is identified and the boot succeeds:

    root on cd0a dumps on cd0b
    root file system type: cd9660

The NetBSD commit required for failure is:

   src/sys/arch/sparc64/sparc64/autoconf.c 1.213
   Fri Sep 15 13:27:53 2017 UTC by martin 

   If the bootloader passes us information about the boot device lun/target/
   and wwn, use those to properly match the boot device.
   If the new bootinfo is not available, fall back to the old heuristic
   trying to match the pathname of the boot device (which is ugly, firmware
   dependend and known to fail in some QEMU configurations).

and the qemu commit required for failure is:

   commit 09d0c187aa4cce9b349f23724f50587a0014b33b
   Author: Mark Cave-Ayland <mark.cave-ayland%ilande.co.uk@localhost>
   Date:   Fri Aug 31 12:19:07 2018 +0100

       Update OpenBIOS images to a1280807 built from submodule.

       Signed-off-by: Mark Cave-Ayland <mark.cave-ayland%ilande.co.uk@localhost>

>How-To-Repeat:

For example, install qemu-3.1.0nb1 from pkgsrc and run:

   ftp http://www.gson.org/bugs/qemu/NetBSD-8.99.30-sparc64.iso
   qemu-img create wd0.img 1G
   qemu-system-sparc64 -nographic -drive file=wd0.img,media=disk -cdrom NetBSD-8.99.30-sparc64.iso -boot d

>Fix: