On my tablet/phone do not run X11 applications with the default Ubuntu Touch Saucy configuration (all my favourite desktop applications like okular, kate, x11vnc, etc...). As I found [here][How to load Xmir on Ubuntu 13.10 the XMir is required. Unfortunately Ubuntu Touch on phone/tablet do behaves differently and the reply above do not solve this issue.
I am testing the Xmir on Nexus 7 tablet. There is intalled/running unity8 + lightdm + mir and unity-system-compositor + Xorg.
I am still getting message above after system reboot in the /var/log/Xorg.0.log :
[ 81.542] (II) "glx" will be loaded by default. [ 81.542] (WW) "xmir" is not to be loaded by default. Skipping. [ 81.542] (II) LoadModule: "dri2"