First, download Solaris 11 Express from Oracle.
Install Solaris 11 Express HVM domU with virt-install:
virt-install -n sx11 -r 2048 --vcpus=4 --os-type=solaris --os-variant=opensolaris \ -v -c /path/to/sol-11-exp-201011-text-x86.iso --disk path=sx11.img,size=20 \ -b br1 --vnc --noautoconsole
Of course, adjust domU memory (-r), vcpus, path to Solaris 11 Express DVD, disk path, network bridge (-b).
After installation has started, you can connect to the VNC display. First, determine which port:
virsh vncdisplay sx11 :8
Finish the installation as usual. After reboot, you can start the Solaris 11 Express domU:
virsh start sx11
or have the domain autostarted at dom0 boot:
virsh autostart sx11
Or disable autostarting
virsh autostart --disable sx11
Enjoy!