FreeBSD as VBox guest: vboxvideo allows only resolution of 800x600

[O. Hartmann]

Hello.

First, please CC me, I do not subscribe this list.

I run VirtualBox (lastes 5.1.X as of ports) on FreeBSD CURRENT and within this
host, I try to run a FreeBSD/NanoBSD appliance. So far, so good. The guest
works well so far, it has port emulators/virtualbox-ose-additions installed and
has 

vboxguest_enable="YES"
vboxservice_enable="YES"

enabled in rc.conf.local.

X11 is also up and running and its SCREEN definition is as follows:

Section "Screen"
        Identifier "Screen0"
        Device     "Card-vboxvideo"
        Monitor    "Monitor0"

        SubSection "Display"
                Viewport        0 0
                #Depth          24
                Depth           16
                #Modes          "1024x768 1366x768 1440x900 1600x900 1920x1200" 
		Modes           "1440x900"
        EndSubSection

EndSection

The Guest OS has always a screensize size of 800x600 pixel. The UEFI initial
console shows efifb with 1024x768 pixel, but whenever the graphics starts, it
is reduced to 800x600.

The driver is configured as

 Section "Device"
        Identifier  "Card-vboxvideo"
        Driver      "vboxvideo"
EndSection

In the lower menu bar, I could, theoretically, switch resolution with menu item
"Virtual screen 1" to a bunch of settings - but only 800x600 is checked and is
selected - nothing else works. I can't select any other resolution!

What is missing here? Something within the driver definition?

I have other guests in the very same VBox, like Windows 7 and I can change
their resolution up to 1920x1080 (I have a screen that is cabapble of
1920x1200).

Thank you very much in advance,

Oliver