In POST:
http://post-office.corp.redhat.com/archives/rhvirt-patches/2012-April/msg00662.html

Verified PASS with libvirt-0.9.10-14.el6.

virsh will reject the following xml:
<memory>1G</memory>
<currentMemory>1G</currentMemory>

# virsh edit xp
error: XML error: could not parse memory element ./currentMemory[1]

# virsh define /tmp/xp.xml 
error: Failed to define domain from /tmp/xp.xml
error: XML error: could not parse memory element ./currentMemory[1]

# virsh create /tmp/xp.xml 
error: Failed to create domain from /tmp/xp.xml
error: XML error: could not parse memory element ./currentMemory[1]

Reproduced this bug with libvirt-0.9.10-12.el6.
libvirt silently use <memory unit='KiB'>1</memory> instead of 1G.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2012-0748.html