GUI configuration

Video RAM adjustment for high-resolution displays

When a qube starts, a fixed amount of RAM is allocated to the graphics buffer called video RAM. This buffer needs to be at least as big as the whole desktop, accounting for all displays that are or will be connected to the machine. By default, it is as much as needed for the current display and an additional full HD (FHD) display (1920×1080 8 bit/channel RGBA). This logic fails when the machine has primary display in FHD resolution and, after starting some qubes, a 4K display is connected. If the buffer is too small, and internal desktop resize fails.

To increase the minimum size of the video RAM buffer:

qvm-features dom0 gui-videoram-min $(($WIDTH * $HEIGHT * 4 / 1024))
qvm-features dom0 gui-videoram-overhead 0

Where $WIDTH×$HEIGHT is the maximum desktop size that you anticipate needing. For example, if you expect to use a 1080p display and a 4k display side-by-side, that is (1920 + 3840) × 2160 × 4 / 1024 = 48600, or slightly more than 48 MiB per qube. After making these adjustments, the qubes need to be restarted.

In the case of multiple display with different orientations or if you plug/unplug displays, the following code will set correct memory size using xrandr.

qvm-features dom0 gui-videoram-min $(xrandr --verbose | grep "Screen 0" | sed -e 's/.*current //' -e 's/\,.*//' | awk '{print $1*$3*4/1024}')

The amount of memory allocated per qube is the maximum of:

  • gui-videoram-min
  • current display + gui-videoram-overhead

Default overhead is about 8 MiB, which is enough for a 1080p display (see above). So, the gui-videoram-overhead zeroing is not strictly necessary; it only avoids allocating memory that will not be used.

You might face issues when playing video, if the video is choppy instead of smooth display this could be because the X server doesn’t work. You can use the Linux terminal (Ctrl-Alt-F2) after starting the virtual machine, login. You can look at the Xorg logs file. As an option you can have the below config as well present in /etc/X11/xorg.conf.d/90-intel.conf, depends on HD graphics though -

Section "Device"
        Identifier "Intel Graphics"
        Driver "intel"
        Option "TearFree" "true"

GUI Troubleshooting

See GUI Troubleshooting for issues relating to the Qubes graphical user interface and how to fix them.