[Qemu-devel] qemu 2.7.0 incompatible with host kernel < 3.19

[Brian Rak]

I have some KVM hosts that I just upgraded to qemu 2.7.0.  When the host 
is running a kernel newer then 3.19, everything works fine.

If the host is running on something lower then 3.19, some guests fail to 
start.  I noticed this on a Ubuntu 16.04 guest, it fails to find the 
virtio NIC, and this is printed to dmesg:

virtio_net virtio0: virtio: device uses modern interface but does not 
have VIRTIO_F_VERSION_1

Looking around, I found 
https://lists.gnu.org/archive/html/qemu-devel/2015-12/msg00373.html , 
but this does not appear to fully resolve the issue.  Any suggestions 
here?  I'm currently just rolling back the upgrade until we can get the 
kernel upgraded on the rest of the hosts.