I have built a qemu with some modifications, and it can run correctly with cmd like ./qemu-system-x86-64 ....
, but I failed to integrate it into virt-manger, even if I added it to PATH
ahead of default system lib.
There is an option in XML file, you can edit it to enable your own qemu.
<devices>
<emulator>/path/to/your/qemu-system-x86_64</emulator>
<disk type='file' device='disk'>
.........