These kernel configs are the default kernels for the Tilaa Gentoo images. Tilaa is a hosting provider that uses KVM for virtualization. For more info about them, please visit http://tilaa.nl. The kernel configs are very stripped and will only work on KVM virtualization (since these are the only drivers shipped). There's nothing specific in the config that ties them to Tilaa, so feel free to use them for your own setups. Furthermore, there isn't something that forces you to only use these for Gentoo as well, but I won't give you a guarantee that Ubuntu or some other flavor assumes other config choices. They come in i686 and amd64 flavors.