Is it safe to encrypt twice with AES, with any mode? Are any combinations of AES, e.g. AES with XTS and AES with CBC, or twice with AES and XTS, more unsafe than just having it encrypted once?
I know CBC isn't very safe in many applications, but the question is if the security somehow becomes degraded if combined in any manner.
In more realistic settings this could apply to having an encrypted root partition, and then running an encrypted virtual machine inside of that encrypted file system.
As a specific example, LUKS for Linux, standard settings. You encrypt it twice, once for your root file system, and once for your guest VM, another Linux system with LUKS.
Is the VM then less safe than it otherwise would have been if it was only encrypted once, i.e. with the host system not being encrypted?