146 lines
5 KiB
Text
146 lines
5 KiB
Text
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multiseat howto (with some multihead coverage)
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==============================================
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host devices
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------------
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First you must compile qemu with a user interface supporting
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multihead/multiseat and input event routing. Right now this
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list includes sdl2, gtk (both 2+3) and vnc:
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./configure --enable-sdl
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or
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./configure --enable-gtk
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Next put together the qemu command line (sdk/gtk):
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qemu -accel kvm -usb $memory $disk $whatever \
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-display [ sdl | gtk ] \
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-vga std \
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-device usb-tablet
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That is it for the first seat, which will use the standard vga, the
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standard ps/2 keyboard (implicitly there) and the usb-tablet. Now the
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additional switches for the second seat:
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-device pci-bridge,addr=12.0,chassis_nr=2,id=head.2 \
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-device secondary-vga,bus=head.2,addr=02.0,id=video.2 \
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-device nec-usb-xhci,bus=head.2,addr=0f.0,id=usb.2 \
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-device usb-kbd,bus=usb.2.0,port=1,display=video.2 \
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-device usb-tablet,bus=usb.2.0,port=2,display=video.2
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This places a pci bridge in slot 12, connects a display adapter and
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xhci (usb) controller to the bridge. Then it adds a usb keyboard and
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usb mouse, both connected to the xhci and linked to the display.
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The "display=video2" sets up the input routing. Any input coming from
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the window which belongs to the video.2 display adapter will be routed
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to these input devices.
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Starting with qemu 2.4 and linux kernel 4.1 you can also use virtio
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for the input devices, using this ...
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-device pci-bridge,addr=12.0,chassis_nr=2,id=head.2 \
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-device secondary-vga,bus=head.2,addr=02.0,id=video.2 \
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-device virtio-keyboard-pci,bus=head.2,addr=03.0,display=video.2 \
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-device virtio-tablet-pci,bus=head.2,addr=03.0,display=video.2
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... instead of xhci and usb hid devices.
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host ui
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-------
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The sdl2 ui will start up with two windows, one for each display
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device. The gtk ui will start with a single window and each display
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in a separate tab. You can either simply switch tabs to switch heads,
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or use the "View / Detach tab" menu item to move one of the displays
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to its own window so you can see both display devices side-by-side.
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For vnc some additional configuration on the command line is needed.
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We'll create two vnc server instances, and bind the second one to the
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second seat, similar to input devices:
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-display vnc=:1,id=primary \
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-display vnc=:2,id=secondary,display=video.2
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Connecting to vnc display :1 gives you access to the first seat, and
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likewise connecting to vnc display :2 shows the second seat.
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Note on spice: Spice handles multihead just fine. But it can't do
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multiseat. For tablet events the event source is sent to the spice
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agent. But qemu can't figure it, so it can't do input routing.
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Fixing this needs a new or extended input interface between
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libspice-server and qemu. For keyboard events it is even worse: The
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event source isn't included in the spice protocol, so the wire
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protocol must be extended to support this.
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guest side
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----------
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You need a pretty recent linux guest. systemd with loginctl. kernel
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3.14+ with CONFIG_DRM_BOCHS enabled. Fedora 20 will do. Must be
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fully updated for the new kernel though, i.e. the live iso doesn't cut
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it.
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Now we'll have to configure the guest. Boot and login. "lspci -vt"
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should list the pci bridge with the display adapter and usb controller:
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[root@fedora ~]# lspci -vt
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-[0000:00]-+-00.0 Intel Corporation 440FX - 82441FX PMC [Natoma]
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[ ... ]
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\-12.0-[01]--+-02.0 Device 1234:1111
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\-0f.0 NEC Corporation USB 3.0 Host Controller
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Good. Now lets tell the system that the pci bridge and all devices
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below it belong to a separate seat by dropping a file into
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/etc/udev/rules.d:
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[root@fedora ~]# cat /etc/udev/rules.d/70-qemu-autoseat.rules
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SUBSYSTEMS=="pci", DEVPATH=="*/0000:00:12.0", TAG+="seat", ENV{ID_AUTOSEAT}="1"
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Reboot. System should come up with two seats. With loginctl you can
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check the configuration:
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[root@fedora ~]# loginctl list-seats
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SEAT
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seat0
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seat-pci-pci-0000_00_12_0
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2 seats listed.
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You can use "loginctl seat-status seat-pci-pci-0000_00_12_0" to list
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the devices attached to the seat.
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Background info is here:
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http://www.freedesktop.org/wiki/Software/systemd/multiseat/
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guest side with pci-bridge-seat
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-------------------------------
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Qemu version 2.4 and newer has a new pci-bridge-seat device which
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can be used instead of pci-bridge. Just swap the device name in the
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qemu command line above. The only difference between the two devices
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is the pci id. We can match the pci id instead of the device path
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with a nice generic rule now, which simplifies the guest
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configuration:
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[root@fedora ~]# cat /etc/udev/rules.d/70-qemu-pci-bridge-seat.rules
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SUBSYSTEM=="pci", ATTR{vendor}=="0x1b36", ATTR{device}=="0x000a", \
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TAG+="seat", ENV{ID_AUTOSEAT}="1"
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Patch with this rule has been submitted to upstream udev/systemd, was
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accepted and should be included in the next systemd release (222).
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So, if your guest has this or a newer version, multiseat will work just
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fine without any manual guest configuration.
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Enjoy!
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--
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Gerd Hoffmann <kraxel@redhat.com>
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