You can install the microcode driver to have Linux provide the updated microcode, if you'd like. (Depending on your distro, it might already be doing it.)
I'm running Proxmox (Debain underneath really) which has a meltdown-spectre checker package available, I followed a debian guide I believe for implementing the microcode and the results are mostly in the green now.
I haven't looked into it but as far as I know I don't think I need to worry about this for the VMs but I could be wrong.
I haven't looked into it but as far as I know I don't think I need to worry about this for the VMs but I could be wrong.