Dear Maintainer,
to reproduce install a jessie/sid qemu VM with Cirrus video card.
On VM:
# apt-get install xdm
# echo /usr/bin/xdm >/etc/X11/default-display-manager
# /etc/init.d/xdm restart
Username one types in will not be displayed and once pressed enter
greeting and prompt fonts will not be displayed as well.
# apt-get install devscripts
# debsnap -v -d. --binary -a amd64 xserver-xorg-video-cirrus 1:1.4.0-2
# dpkg -i --force-depends xserver-xorg-video-cirrus_1.4.0-2_amd64.deb
# /etc/init.d/xdm restart
Downgrading to 1.4.0-2, fonts are displayed well.
Another workaround is switching to standard VGA card.