qemu/docs/qdev-device-use.txt

110   1.  You can use -nodefaults to suppress the default unit 0, see
111   "Default Devices".
120   notify.  It can be set to on (default) or off.
183   uses "braille".  With -device, this useful default is gone, so you
265 virtqueue notify by setting ioeventfd= to on or off (default).
291                 disables more than just VGA, see "Default Devices"
304                 disables more than just VGA, see "Default Devices"
382 === Default Devices ===
384 QEMU creates a number of devices by default, depending on the machine
387 -device DEVNAME... and global DEVNAME... suppress default devices for
390     default device      suppressing DEVNAMEs
399 The default NIC is connected to a default part created along with it.
401 that a bug).  -net and -netdev suppress the default NIC.
403 -nodefaults suppresses all the default devices mentioned above, plus a
404 few other things such as default SD-Card drive and default monitor.