Genkernel with virtio drivers

A colleague asked me to help analyze problems migrating a Gentoo guest VM from a Xen Server based host to a Proxmox (KVM based) host. The Gentoo VM would not boot beyond the initramfs - it just died saying that the root device could not be found.

Since the VM itself boots, Grub is fine. So I figured it must be a problem with the contents of the initramfs. I made sure that the virtio drivers were properly configured into the kernel - as modules.

After a lot of poking around I found a reddit that mentions genkernel. I was not aware that genkernel is picky about the modules that are included into the initramfs.

In the end I did not try the approach that is suggested in the reddit. I rather compiled all virtio drivers directly into the kernel. Easier to maintain, less fiddling with genkernel. Life’s good again.