dual monitor linux guest in virtualbox

Question

I read that the newer VirtualBox supports Linux guests with dual monitors. I'm able to get two monitors to start when I start my Arch VM, but I cannot get Xorg to span to the 2nd monitor. They constantly display in clone mode. Has anyone successfully done this? If so, could you share your xorg.conf?

Edit: my xorg.conf (I tried incremental BusID as a test, but had them the same before).

Section "ServerLayout"
        Identifier     "X.org Configured"
        Screen      0  "Screen0" 0 0
        Screen      1  "Screen1" RightOf "Screen0"
        InputDevice    "Mouse0" "CorePointer"
        InputDevice    "Keyboard0" "CoreKeyboard"
EndSection

Section "Files"
        ModulePath   "/usr/lib/xorg/modules"
        FontPath     "/usr/share/fonts/misc/"
        FontPath     "/usr/share/fonts/TTF/"
        FontPath     "/usr/share/fonts/OTF/"
        FontPath     "/usr/share/fonts/Type1/"
        FontPath     "/usr/share/fonts/100dpi/"
        FontPath     "/usr/share/fonts/75dpi/"
EndSection

Section "Module"
        Load  "record"
        Load  "dbe"
        Load  "dri2"
        Load  "glx"
        Load  "extmod"
        Load  "dri"
EndSection

Section "InputDevice"
        Identifier  "Keyboard0"
        Driver      "kbd"
EndSection

Section "InputDevice"
        Identifier  "Mouse0"
        Driver      "mouse"
        Option      "Protocol" "auto"
        Option      "Device" "/dev/input/mice"
        Option      "ZAxisMapping" "4 5 6 7"
EndSection

Section "Monitor"
        Identifier   "Monitor0"
        VendorName   "Monitor Vendor"
        ModelName    "Monitor Model"
EndSection

Section "Monitor"
        Identifier   "Monitor1"
        VendorName   "Monitor Vendor"
        ModelName    "Monitor Model"
EndSection

Section "Device"
        Identifier  "Card0"
        Screen      0
        Driver      "vboxvideo"
        BusID       "PCI:0:2:0"
EndSection

Section "Device"
        Identifier  "Card1"
        Screen      1
        Driver      "vboxvideo"
        BusID       "PCI:0:2:1"
EndSection

Section "Screen"
        Identifier "Screen0"
        Device     "Card0"
        Monitor    "Monitor0"
        SubSection "Display"
                Viewport   0 0
                Depth     24
        EndSubSection
EndSection

Section "Screen"
        Identifier "Screen1"
        Device     "Card1"
        Monitor    "Monitor1"
        SubSection "Display"
                Viewport   0 0
                Depth     24
        EndSubSection
EndSection

Answer 1

Whats in your conf file? If you haven't explicitly told it that you have multiple monitors it will just clone the output. If you're uncertain how to modify the conf to do this there are several good tutorials around such as the one at the xorg archwiki.