How to tell if your guest VM is vulnerable to Venom

When I first heard about the virtual floppy bug called Venom I wondered if all Xen guests were affected. I quickly discovered that paravirtualized X86 guests are NOT affected. I was pretty sure the Linux guests running on our Exalogic were paravirtualized so I didn’t worry about it. Over the weekend I noticed more publicity about Venom and I decided I should make sure. I don’t have access to Dom0 so I needed to see the virtualization mode from within the guest OS. After a little research I found that if you are using the PVHVM drivers (xen-blkfront for disk, and xen-netfront for network)  you are paravirtualized on Xen. I checked lsmod and verified my initial assumption was correct.

> lsmod | grep -i xen
xen_netfront 16420 0
xen_blkfront 13602 7