Comment # 2 on bug 1158111 from James Fehlig

Under the covers virt-manager uses libvirt. You can view the qemu command line
libvirt generated in /var/log/libvirt/qemu/<vm-name>.log. Given the illegal
instruction and segmentation violation errors you are encountering, I'd compare
the '-M' and '-cpu' options generated by libvirt with your own.