If it is installed use ethtool first on each of the interfaces to see which one has an active link and then configure that interface with the ip configuration in /etc/network/interfaces, so something like this.
Then check if it says yes where it says "Link Detected"
Once you find the one that has link create an ip configuration for it, that would something like you had before.
No quite the same error, now it's telling some firmware it's missing. How did you create the VM? virt-install? qemu? Can you show the VM's settings? I wonder if there's something missing from the settings you used when creating the VM.