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Description Can't revert running guest without RNG device to running snapshot with RNG device and vice versa. Version: libvirt-1.1.1-13.el7.x86_64 How reproducible: 100% Steps to Reproduce: 1.Create a snapshot of the running guest with RNG device. # virsh snapshot-info rng random_run Name: random_run Domain: rng Current: no State: running Location: internal Parent: - Children: 0 Descendants: 0 Metadata: yes # virsh snapshot-dumpxml rng random_run <domainsnapshot> ... <rng model='virtio'> <backend model='random'>/dev/random</backend> </rng> </devices> <seclabel type='dynamic' model='selinux' relabel='yes'/> </domain> </domainsnapshot> 3. Remove the rng device and reboot the guest without RNG device. Then Revert | the guest to the running snapshot with RNG device. # virsh snapshot-revert rng random_run Actual results： Step3： # virsh snapshot-revert rng random_run error: revert requires force: Target domain RNG device count '0' does not match source count '1' Revert running guest with RNG device to running snapshot without RNG device, get the similar error: # virsh snapshot-revert rng run_norng error: revert requires force: Target domain RNG device count '1' does not match source count '0' Expected results: Revert proceeds smoothly without any error. Additional info:
If you are running a VM with a different hardware configuration as the one saved in a snapshot you need to specify the --force argument for snapshot revert as qemu needs to be restarted to accomodate a change in hardware topology. This is also indicated by the error message stated above. This is a desired behavior. Closing as NOTABUG.