## Host environment - Operating system: OpenBSD -curent - OS/kernel version: `Build date: 1780513512 - Wed Jun 3 19:05:12 UTC 2026` - Architecture: x86 - QEMU flavor: qemu-system-i386 - QEMU version: 11.0.1 - QEMU command line: ``` qemu-system-i386 -nographic -no-reboot \ -drive file=/tmp/fnstsw-boot-fails.img,format=raw,if=floppy \ -device isa-debug-exit,iobase=0xf4,iosize=0x04 ``` ## Emulated/Virtualized environment - Operating system: self made boot - OS/kernel version: irrelevant - Architecture: x86 ## Description of problem Upgrade of QEMU from 10.2.1 to 11.0.1 leads to not working perl and who know else on OpenBSD/i386. The issue was minimized to this reproducer: ``` .code16 .globl _start _start: movw $0x07c0, %ax movw %ax, %ds fninit fnclex xorw %ax, %ax orw $1, %ax fldl 0x40 fld1 fucompp fnstsw %ax sahf seta %al movw $0xf4, %dx outb %al, %dx 1: hlt jmp 1b .org 0x40 .double 2.0 .org 510 .word 0xaa55 ``` ## Steps to reproduce 1. `cc -c /tmp/fnstsw-boot-fails.S -o /tmp/fnstsw-boot-fails.o` 2. `objcopy -O binary /tmp/fnstsw-boot-fails.o /tmp/fnstsw-boot-fails.img` 3. `qemu-system-i386 -nographic -no-reboot -drive file=/tmp/fnstsw-boot-fails.img,format=raw,if=floppy -device isa-debug-exit,iobase=0xf4,iosize=0x04` on 10.2.1 it exits with `1` which is expected, on 11.0.1 with `3` ## Additional information Relevant mail list thread: https://marc.info/?t=178082576900001&r=1&w=2 And replacing `fnstsw` to `fstsw` in reproducer allows to overstep bug.