Technologies are provided for function-targeted virtual machine switching. In some examples, function usage times on a virtual machine (VM) may be profiled by a virtual machine manager (VMM) and used to manage VM switching in order to preferentially switch VMs during specific targeted functions. The targeted functions and/or VM switching preferences may be adjusted over time in order to provide switching unpredictability, for example to frustrate side-channel attackers by forcing the attackers to gather data for much longer periods of time (e.g., weeks or months) if they want to detect or attack.