sparc64: GRUB causes Unhandled Exception in firmware

[crass]

QEMU: QEMU emulator version 5.2.0 (Debian 1:5.2+dfsg-11+deb11u2)
OpenBIOS: Sparc64 debug build of latest v1.1 release in releases
GRUB ISO: grub.iso.gz

Here's the initial output from OpenBIOS:

OpenBIOS for Sparc64
Configuration device id QEMU version 1 machine id 0
kernel cmdline 
CPUs: 1 x SUNW,UltraSPARC-IIi
UUID: 00000000-0000-0000-0000-000000000000
Welcome to OpenBIOS v1.1 built on Jan 31 2023 22:09
  Type 'help' for detailed information
Trying cdrom:f...
Trying cdrom...
Not a bootable ELF image
Loading a.out image...
Loaded 7680 bytes
entry point is 0x4000
GRUB call-method color!: exception -21 
call-method color! failed with error ffffffffffffffdf
call-method color!: exception -21 

Here is the last many lines when running the GRUB iso in qemu:

kern/ieee1275/openfw.c:57:devalias: device path=/virtual-memory
kern/ieee1275/openfw.c:90:devalias: iterating children of /virtual-memory
kern/ieee1275/openfw.c:57:devalias: device path=/pci@1fe,0
kern/ieee1275/openfw.c:90:devalias: iterating children of /pci@1fe,0
kern/ieee1275/openfw.c:57:devalias: device path=/pci@1fe,0/pci@1,1
kern/ieee1275/openfw.c:90:devalias: iterating children of /pci@1fe,0/pci@1,1
kern/ieee1275/openfw.c:57:devalias: device path=/pci@1fe,0/pci@1,1/ebus@1
kern/ieee1275/openfw.c:90:devalias: iterating children of /pci@1fe,0/pci@1,1/ebus@1
kern/ieee1275/openfw.c:57:devalias: device path=/pci@1fe,0/pci@1,1/ebus@1/eeprom@0
kern/ieee1275/openfw.c:90:devalias: iterating children of /pci@1fe,0/pci@1,1/ebus@1/eeprom@0
kern/ieee1275/openfw.c:57:devalias: device path=/pci@1fe,0/pci@1,1/ebus@1/power@0
kern/ieee1275/openfw.c:90:devalias: iterating children of /pci@1fe,0/pci@1,1/ebus@1/power@0
kern/ieee1275/openfw.c:57:devalias: device path=/pci@1fe,0/pci@1,1/ebus@1/fdthree@0
Unhandled Exception 0x0000000000000030
PC = 0x00000000ffd164c8 NPC = 0x00000000ffd164cc
Stopping execution

Command to reproduce the issue:
qemu-system-sparc64 -no-reboot -nographic -monitor file:/dev/null -serial file:/dev/stdout -cdrom grub.iso -boot d -bios ./openbios-multiarch-latest.zip.d/debug/obj-sparc64/openbios-builtin.elf

The exception happens on an open call into the firmware with path /pci@1fe,0/pci@1,1/ebus@1/fdthree@0. I've followed execution into the forth interpreter and then gave up. It looks like its an issue opening the floppy device, but I've not told QEMU to have anything in the floppy.

Here's a log file of a build from master with some debugging options enabled: grub-openbios-crash.log.gz