Why host device disappear in libvirt doman xml?

<https://stackoverflow.com/posts/73854544/timeline> I'm using Kubevirt to manage my virtual machine instances. When I using Kubevirt to create a vm(with two GPUs), kubevirt will generate a libvirt guest domain xml for this vm which includes two GPUs, the domain xml as follow : <hostdev mode='subsystem' type='pci' managed='no'> <driver name='vfio'/> <source> <address domain='0x0000' bus='0x83' slot='0x00' function='0x0'/> </source> <alias name='ua-gpu-gpu0'/> <address type='pci' domain='0x0000' bus='0x06' slot='0x00' function='0x0'/> </hostdev> <hostdev mode='subsystem' type='pci' managed='no'> <driver name='vfio'/> <source> <address domain='0x0000' bus='0x84' slot='0x00' function='0x0'/> </source> <alias name='ua-gpu-gpu1'/> <address type='pci' domain='0x0000' bus='0x07' slot='0x00' function='0x0'/> </hostdev> No one ever edit this domain xml, but these two hostdev element disappeared in the domain xml. During this time, I've run the gpu_burn command to do a stress test for these two GPUs. My question is : - when will libvirtd change the guest domain xml ? - why libvirtd delete these two hostdev from domain xml ?