See this thread: https://lists.fedoraproject.org/pipermail/virt/2014-March/003971.html Basically, if the cache value is unset in the guest XML, virt-manager will report it as 'default'. We should report it as 'hypervisor default' to be more clear. We do this in a few other places so this will make things more consistent as well.
Fixed upstream: commit 55c8453d156e31f236d369c0df2f862d79e7e199 Author: Cole Robinson <crobinso> Date: Tue Apr 7 18:08:29 2015 -0400 details: Use 'Hypervisor default' description in more places (bz #1073521)