[Bug]: Stalls at 'Booting from Hard Disk...' when using `windows_legacy` boot mode

Operating system

Arch Linux

Description

When using the windows_legacy boot mode, it stalls forever.

Docker compose

name: "microslop"

services:
  windows:
    network_mode: bridge
    image: custom:windows
    container_name: microslop
    environment:
      VERSION: 10l
      REMOVE: N
      AUTOLOGIN: Y
      USERNAME: USER
      PASSWORD: PASSWORD

      CPU_MODEL: host
      CPU_CORES: 8
      KVM: Y

      RAM_SIZE: 16G
      RAM_CHECK: Y

      DISK_SIZE: 64G
      DISK_FMT: raw
      DISK_TYPE: nvme
      DISK_CACHE: none
      ALLOCATE: Y
      STORAGE: /storage

      DISPLAY: web
      VGA: virtio
      WIDTH: 2880
      HEIGHT: 1920
      GPU: N

      WEB: Y
      WEB_PORT: 8006
      AUDIO: N

      SAMBA: N

      MACHINE: q35
      ARGUMENTS: >-
        -smbios type=0,vendor=INSYDE,date=01/08/2026,version=03.18,release=3.18
        -smbios type=1,manufacturer=Framework,product=13,version=A5,serial=SERIAL,uuid=UUID,sku=SKU,family=laptop
        -smbios type=2,manufacturer=Framework,product=FRANMDCP05,version=A5,serial=SERIAL,asset=*
        -smbios type=3,manufacturer=Framework,version=A5,serial=SERIAL,asset=ASSET
        -smbios type=4,manufacturer=AMD,version=Ryzen
      # BIOS: /storage/bios.bin
      BOOT_MODE: windows_legacy

      BALLOONING: Y

      CONNECTIONS: 10

      TIMEOUT: 10

    ports:
      - "127.0.0.1:8006:8006"
      - "127.0.0.1:3389:3389/tcp"
      - "127.0.0.1:3389:3389/udp"
    cap_add:
      - NET_ADMIN
    stop_grace_period: 10s
    restart: on-failure
    volumes:
      - ./data:/storage
      - ./windows-10-iot-ltsc.iso:/custom.iso
    devices:
      - /dev/kvm
      - /dev/net/tun

Docker log

Attaching to microslop
microslop  | ❯ Starting Windows for Docker v0.00...
microslop  | ❯ For support visit https://github.com/dockur/windows
microslop  | ❯ CPU: AMD Ryzen 5 7640U | RAM: 46/55 GB | DISK: 136 GB (btrfs) | KERNEL: 7.1.5-hardened1-3-hardened
microslop  |
microslop  | ❯ Warning: you are using the BTRFS filesystem for /storage, this might introduce issues with Windows Setup!
microslop  | ❯ Detecting version from ISO image...
microslop  | ❯ Detected: Windows 10 IoT Enterprise LTSC
microslop  | ❯ Creating overlay image...
microslop  | ❯ Adding drivers to image...
microslop  | ❯ Adding win10x64-iot.xml for automatic installation...
microslop  | ❯ Writing overlay image...
microslop  | ❯ Creating a 64 GB preallocated disk image in raw format...
microslop  |
microslop  | ❯ Host: 172.17.0.2/16 (532b147f59ef)  |  DNS: 192.168.50.1
microslop  | ❯ Guest: 172.30.0.2 (Windows)  |  Mode: NAT  |  MAC: 02:35:E7:34:47:B4
microslop  |
microslop  | ❯ Booting Windows (legacy) using QEMU v10.0.11...
microslop  |
microslop  | SeaBIOS (version 1.17.0-debian-1.17.0-1)
microslop  | Machine UUID 0e85624b-e19a-f011-be91-243940600797
microslop  | Booting from Hard Disk...
microslop  |
microslop  | ❯ Windows started successfully, visit http://127.0.0.1:8006/ to view the screen...

Screenshots (optional)