My problem comes from the Polkitd error below on the host. It is also related to this post. I will try the Vlastimil_Holer solution.
dec 19 01:43:29 x10 kernel: traps: polkitd[22331] general protection ip:7f8439aa27f2 sp:7fff04b9cb10 error:0 in libmozjs-17.0.so[7f8439966000+3af000]
dec 19 01:43:29 x10 libvirtd[1747]: error from service: CheckAuthorization: Message did not receive a reply (timeout by message bus)
dec 19 01:43:29 x10 libvirtd[1747]: End of file while reading data: Erreur d’entrée/sortie