libvirt users - Feb 2016 - Configure QCow2 L2 Cache through virt domain XML

Hello, i was wondering if it is possible to configure the l2 cache of a
qcow2 image through the domain xml.
I cannot find any documentation about it... the only thing i've found is
that i can pass custom options to qemu command line through the
<qemu:commandline> tag, but, to my understanding, that would mean entirely
remove the <disk> tag for the image and rewrite it as a list of args for
the command line.
Isn't there an easier way?

An example of what i'm speaking about
is: file=hd.qcow2,l2-cache-size=4194304,refcount-cache-size=262144