If someone have console=hvc0 kernel command line, it seems that it needs to be removed or replaced with console=ttyS0 when migrating the VMs to F20. With console=hvc0 and latest Fedora kernels, the VM refuses to boot. Without any console= arg, hvc* consoles, defined by: .../console/target/@type='virtio' in the libvirt xml defs, are remaining usable *after* the boot, i.e.: virsh start vm --console will show the login prompt eventually, just does not dumps the kernel messages during the boot. If you need the boot messages, might use console=ttyS0 (+ .../@type='serial'), like before hvc0 feature instead. This perhaps have something to do with the recent reconfiguration of virtio_console as loadable module: http://pkgs.fedoraproject.org/cgit/kernel.git/commit/?id=d58808f https://bugzilla.redhat.com/show_bug.cgi?id=1019569 Maybe, the virtio_console module could be included again as builtin for the Fedora Cloud product kernel? Kind Regards, Alek PS: Some happy day, we might have semantic databases integrating products changes with our local setups and helping with the faster, reliable resolutions of these incompatibility introductions. Or at least nobody can stop us to dream about :-). PPS: My case: Before .6-302, I was used with: console=hvc0 command line for direct kernel boot (my VMs are the simplest possible, provisioned on plain LVMs/ext4 with just yum+xquery and latter updated with in-house salt+libvirt scripts): [*] virsh dumpxml vm: ... <os> <type arch='x86_64' machine='pc-i440fx-1.6'>hvm</type> <kernel>/var/lib/libvirt/boot/vmlinuz-3.11.6-301.fc20.x86_64</kernel> <initrd>/var/lib/libvirt/boot/initramfs-3.11.6-301.fc20.x86_64.img</initrd> <cmdline>ro root=/dev/vda console=hvc0</cmdline> </os> ... <console type='pty'> <target type='virtio' port='0'/> </console> ... With the latest kernels such configuration hangs, because of hvc0.