multiseat.txt (5147B)
1 2 multiseat howto (with some multihead coverage) 3 ============================================== 4 5 host devices 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, gtk (both 2+3) and vnc: 11 12 ./configure --enable-sdl 13 14 or 15 16 ./configure --enable-gtk 17 18 19 Next put together the qemu command line (sdk/gtk): 20 21 qemu -accel kvm -usb $memory $disk $whatever \ 22 -display [ sdl | gtk ] \ 23 -vga std \ 24 -device usb-tablet 25 26 That is it for the first seat, 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 seat: 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 Starting with qemu 2.4 and linux kernel 4.1 you can also use virtio 45 for the input devices, using this ... 46 47 -device pci-bridge,addr=12.0,chassis_nr=2,id=head.2 \ 48 -device secondary-vga,bus=head.2,addr=02.0,id=video.2 \ 49 -device virtio-keyboard-pci,bus=head.2,addr=03.0,display=video.2 \ 50 -device virtio-tablet-pci,bus=head.2,addr=03.0,display=video.2 51 52 ... instead of xhci and usb hid devices. 53 54 host ui 55 ------- 56 57 The sdl2 ui will start up with two windows, one for each display 58 device. The gtk ui will start with a single window and each display 59 in a separate tab. You can either simply switch tabs to switch heads, 60 or use the "View / Detach tab" menu item to move one of the displays 61 to its own window so you can see both display devices side-by-side. 62 63 For vnc some additional configuration on the command line is needed. 64 We'll create two vnc server instances, and bind the second one to the 65 second seat, similar to input devices: 66 67 -display vnc=:1,id=primary \ 68 -display vnc=:2,id=secondary,display=video.2 69 70 Connecting to vnc display :1 gives you access to the first seat, and 71 likewise connecting to vnc display :2 shows the second seat. 72 73 Note on spice: Spice handles multihead just fine. But it can't do 74 multiseat. For tablet events the event source is sent to the spice 75 agent. But qemu can't figure it, so it can't do input routing. 76 Fixing this needs a new or extended input interface between 77 libspice-server and qemu. For keyboard events it is even worse: The 78 event source isn't included in the spice protocol, so the wire 79 protocol must be extended to support this. 80 81 82 guest side 83 ---------- 84 85 You need a pretty recent linux guest. systemd with loginctl. kernel 86 3.14+ with CONFIG_DRM_BOCHS enabled. Fedora 20 will do. Must be 87 fully updated for the new kernel though, i.e. the live iso doesn't cut 88 it. 89 90 Now we'll have to configure the guest. Boot and login. "lspci -vt" 91 should list the pci bridge with the display adapter and usb controller: 92 93 [root@fedora ~]# lspci -vt 94 -[0000:00]-+-00.0 Intel Corporation 440FX - 82441FX PMC [Natoma] 95 [ ... ] 96 \-12.0-[01]--+-02.0 Device 1234:1111 97 \-0f.0 NEC Corporation USB 3.0 Host Controller 98 99 Good. Now lets tell the system that the pci bridge and all devices 100 below it belong to a separate seat by dropping a file into 101 /etc/udev/rules.d: 102 103 [root@fedora ~]# cat /etc/udev/rules.d/70-qemu-autoseat.rules 104 SUBSYSTEMS=="pci", DEVPATH=="*/0000:00:12.0", TAG+="seat", ENV{ID_AUTOSEAT}="1" 105 106 Reboot. System should come up with two seats. With loginctl you can 107 check the configuration: 108 109 [root@fedora ~]# loginctl list-seats 110 SEAT 111 seat0 112 seat-pci-pci-0000_00_12_0 113 114 2 seats listed. 115 116 You can use "loginctl seat-status seat-pci-pci-0000_00_12_0" to list 117 the devices attached to the seat. 118 119 Background info is here: 120 http://www.freedesktop.org/wiki/Software/systemd/multiseat/ 121 122 123 guest side with pci-bridge-seat 124 ------------------------------- 125 126 QEMU version 2.4 and newer has a new pci-bridge-seat device which 127 can be used instead of pci-bridge. Just swap the device name in the 128 qemu command line above. The only difference between the two devices 129 is the pci id. We can match the pci id instead of the device path 130 with a nice generic rule now, which simplifies the guest 131 configuration: 132 133 [root@fedora ~]# cat /etc/udev/rules.d/70-qemu-pci-bridge-seat.rules 134 SUBSYSTEM=="pci", ATTR{vendor}=="0x1b36", ATTR{device}=="0x000a", \ 135 TAG+="seat", ENV{ID_AUTOSEAT}="1" 136 137 Patch with this rule has been submitted to upstream udev/systemd, was 138 accepted and should be included in the next systemd release (222). 139 So, if your guest has this or a newer version, multiseat will work just 140 fine without any manual guest configuration. 141 142 Enjoy! 143 144 -- 145 Gerd Hoffmann <kraxel@redhat.com>