Please backport https://github.com/libguestfs/libguestfs/commit/af762e43424382d895d3a10aa6632adc601fdbad and https://github.com/libguestfs/supermin/commit/68332640d5d78317e7914995a2c6883574c864e5 to Fedora 22 and Fedora 21 -m virt works just fine on qemu in f21 note that the tegra and all the other kernel variants were dropped from Fedora 18 so they have not been made or available for nearly 3 years now I do not think you need the check for it either.
supermin-5.1.12-1.fc22 has been submitted as an update for Fedora 22. https://admin.fedoraproject.org/updates/supermin-5.1.12-1.fc22
Package supermin-5.1.12-1.fc22: * should fix your issue, * was pushed to the Fedora 22 testing repository, * should be available at your local mirror within two days. Update it with: # su -c 'yum update --enablerepo=updates-testing supermin-5.1.12-1.fc22' as soon as you are able to. Please go to the following url: https://admin.fedoraproject.org/updates/FEDORA-2015-3387/supermin-5.1.12-1.fc22 then log in and leave karma (feedback).
supermin-5.1.10-3.fc21 has been submitted as an update for Fedora 21. https://admin.fedoraproject.org/updates/supermin-5.1.10-3.fc21
*Should* all be done now ...
libguestfs-1.28.6-2.fc21 has been submitted as an update for Fedora 21. https://admin.fedoraproject.org/updates/libguestfs-1.28.6-2.fc21
supermin-5.1.12-1.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.
supermin-5.1.10-3.fc21 has been pushed to the Fedora 21 stable repository. If problems still persist, please make note of it in this bug report.
libguestfs-1.28.6-2.fc21 has been pushed to the Fedora 21 stable repository. If problems still persist, please make note of it in this bug report.