multiseat howto (with some multihead coverage)
==============================================

host side
---------

First you must compile qemu with a user interface supporting
multihead/multiseat and input event routing.  Right now this list is
pretty short: sdl2.

  ./configure --enable-sdl --with-sdlabi=2.0


Next put together the qemu command line:

qemu	-enable-kvm -usb $memory $disk $whatever \
	-display sdl \
	-vga std \
	-device usb-tablet

That is it for the first head, which will use the standard vga, the
standard ps/2 keyboard (implicitly there) and the usb-tablet.  Now the
additional switches for the second head:

	-device pci-bridge,addr=12.0,chassis_nr=2,id=head.2 \
	-device secondary-vga,bus=head.2,addr=02.0,id=video.2 \
	-device nec-usb-xhci,bus=head.2,addr=0f.0,id=usb.2 \
	-device usb-kbd,bus=usb.2.0,port=1,display=video.2 \
	-device usb-tablet,bus=usb.2.0,port=2,display=video.2

This places a pci bridge in slot 12, connects a display adapter and
xhci (usb) controller to the bridge.  Then it adds a usb keyboard and
usb mouse, both connected to the xhci and linked to the display.

The "display=video2" sets up the input routing.  Any input coming from
the window which belongs to the video.2 display adapter will be routed
to these input devices.


guest side
----------

You need a pretty recent linux guest.  systemd with loginctl.  kernel
3.14+ with CONFIG_DRM_BOCHS enabled.  Fedora 20 will do.  Must be
fully updated for the new kernel though, i.e. the live iso doesn't cut
it.

Now we'll have to configure the guest.  Boot and login.  By default
all devices belong to seat0.  You can use "loginctl seat-status seat0"
to list them all (and to get the sysfs paths for cut+paste).  Now
we'll go assign all pci devices connected the pci bridge in slot 12 to
a new head:

loginctl attach seat-qemu \
	 /sys/devices/pci0000:00/0000:00:12.0/0000:01:02.0/drm/card1
loginctl attach seat-qemu \
	 /sys/devices/pci0000:00/0000:00:12.0/0000:01:02.0/graphics/fb1
loginctl attach seat-qemu \
	 /sys/devices/pci0000:00/0000:00:12.0/0000:01:0f.0/usb2

Use "loginctl seat-status seat-qemu" to check the result.  It isn't
needed to assign the usb devices to the head individually, assigning a
usb (root) hub will automatically assign all usb devices connected to
it too.

BTW: loginctl writes udev rules to /etc/udev/rules.d to make these
device assignments permanent, so you need to do this only once.

Now simply restart gdm (rebooting will do too), and a login screen
should show up on the second head.

Enjoy!

--
Gerd Hoffmann <kraxel@redhat.com>