qemu-system-sparc SS-20 emulation does not report SMP to proprietary firmware?

Host environment

  • Operating system: Slackware 15.0 i586

  • OS/kernel version: uname -a Linux slax 6.12.26-x64 #1 SMP PREEMPT_DYNAMIC Sun May 4 23:16:06 MSK 2025 x86_64 AMD FX(tm)-4300 Quad-Core Processor AuthenticAMD GNU/Linux

  • Architecture: x86

  • QEMU flavor: qemu-system-sparc

  • QEMU version: QEMU emulator version 9.1.50 (v9.1.0-1687-gf0cfd06786-dirty)

  • QEMU command line:

    qemu-system-sparc -M SS-20 -smp 2 -cpu "TI SuperSparc-40" -nographic -bios ~/Desktop/SunOBP2-19_525-1377-06.ROM

Emulated/Virtualized environment

  • Operating system: PROM
  • OS/kernel version: n/a
  • Architecture: sparc32

Description of problem

Firmware boots fine with -smp 2 or higher, but additional cpu does not show up in its report.

Steps to reproduce

  1. Get SS20 PROM from https://fsck.technology/software/Sun%20Microsystems/Sun%20ROMs/SPARCstation%2020%20OBP/
  2. try to boot them with -smp 2
  3. Observe firmware does not show additional cpus

Additional information