docs/multiseat.txt

   1
   2 multiseat howto (with some multihead coverage)
   3 ==============================================
   4
   5 host side
   6 ---------
   7
   8 First you must compile qemu with a user interface supporting
   9 multihead/multiseat and input event routing.  Right now this
  10 list includes sdl2 and gtk (both 2+3):
  11
  12   ./configure --enable-sdl --with-sdlabi=2.0
  13
  14 or
  15
  16   ./configure --enable-gtk
  17
  18
  19 Next put together the qemu command line:
  20
  21 qemu    -enable-kvm -usb $memory $disk $whatever \
  22         -display [ sdl | gtk ] \
  23         -vga std \
  24         -device usb-tablet
  25
  26 That is it for the first head, which will use the standard vga, the
  27 standard ps/2 keyboard (implicitly there) and the usb-tablet.  Now the
  28 additional switches for the second head:
  29
  30         -device pci-bridge,addr=12.0,chassis_nr=2,id=head.2 \
  31         -device secondary-vga,bus=head.2,addr=02.0,id=video.2 \
  32         -device nec-usb-xhci,bus=head.2,addr=0f.0,id=usb.2 \
  33         -device usb-kbd,bus=usb.2.0,port=1,display=video.2 \
  34         -device usb-tablet,bus=usb.2.0,port=2,display=video.2
  35
  36 This places a pci bridge in slot 12, connects a display adapter and
  37 xhci (usb) controller to the bridge.  Then it adds a usb keyboard and
  38 usb mouse, both connected to the xhci and linked to the display.
  39
  40 The "display=video2" sets up the input routing.  Any input coming from
  41 the window which belongs to the video.2 display adapter will be routed
  42 to these input devices.
  43
  44 The sdl2 ui will start up with two windows, one for each display
  45 device.  The gtk ui will start with a single window and each display
  46 in a separate tab.  You can either simply switch tabs to switch heads,
  47 or use the "View / Detach tab" menu item to move one of the displays
  48 to its own window so you can see both display devices side-by-side.
  49
  50 Note on spice: Spice handles multihead just fine.  But it can't do
  51 multiseat.  For tablet events the event source is sent to the spice
  52 agent.  But qemu can't figure it, so it can't do input routing.
  53 Fixing this needs a new or extended input interface between
  54 libspice-server and qemu.  For keyboard events it is even worse:  The
  55 event source isn't included in the spice protocol, so the wire
  56 protocol must be extended to support this.
  57
  58
  59 guest side
  60 ----------
  61
  62 You need a pretty recent linux guest.  systemd with loginctl.  kernel
  63 3.14+ with CONFIG_DRM_BOCHS enabled.  Fedora 20 will do.  Must be
  64 fully updated for the new kernel though, i.e. the live iso doesn't cut
  65 it.
  66
  67 Now we'll have to configure the guest.  Boot and login.  "lspci -vt"
  68 should list the pci bridge with the display adapter and usb controller:
  69
  70     [root@fedora ~]# lspci -vt
  71     -[0000:00]-+-00.0  Intel Corporation 440FX - 82441FX PMC [Natoma]
  72                [ ... ]
  73                \-12.0-[01]--+-02.0  Device 1234:1111
  74                             \-0f.0  NEC Corporation USB 3.0 Host Controller
  75
  76 Good.  Now lets tell the system that the pci bridge and all devices
  77 below it belong to a separate seat by dropping a file into
  78 /etc/udev/rules.d:
  79
  80     [root@fedora ~]# cat /etc/udev/rules.d/70-qemu-autoseat.rules
  81     SUBSYSTEMS=="pci", DEVPATH=="*/0000:00:12.0", TAG+="seat", ENV{ID_AUTOSEAT}="1"
  82
  83 Reboot.  System should come up with two seats.  With loginctl you can
  84 check the configuration:
  85
  86     [root@fedora ~]# loginctl list-seats
  87     SEAT
  88     seat0
  89     seat-pci-pci-0000_00_12_0
  90
  91     2 seats listed.
  92
  93 You can use "loginctl seat-status seat-pci-pci-0000_00_12_0" to list
  94 the devices attached to the seat.
  95
  96 Background info is here:
  97   http://www.freedesktop.org/wiki/Software/systemd/multiseat/
  98
  99 Enjoy!
 100
 101 --
 102 Gerd Hoffmann <kraxel@redhat.com>