Dmesg is spewing blkio errors

Find out which device: e.g dm-4, then:
```
sudo virsh list --all --name | while read dom; do sudo virsh dumpxml $dom | grep dm-4 && echo $dom; done
```
To find which domain
After which:
```
sudo virsh dumpxml $domain
```
to find the hostname 

reboot it hard.