Since this parameter is not part of the LDAP-schema, please set the vram attribute in
<video>
<model type="qxl" vram="9216" heads="1"/>
</video>
to 64MB (65536) instead of the default 9M.
For a discussion why, see:
http://spice-space.org/page/FAQ
https://bugs.freedesktop.org/show_bug.cgi?id=36186
According to the action of Christian to set the bug "open-fixed"