Doesn't that make it even harder to do any sort of specific attack on anything? From what I understand, these side-channel attacks depend on being able to predict the addresses you'll read from and an idea of what you're after as well as a stable environment in which enough timing information can be collected, and any small changes in the environment will mean you can start reading something completely different without even knowing; a CPU that could be running literally who-knows-what at any time seems like it wouldn't let you collect much in the way of coherent data, and of course the VM you're doing it from could itself be moving uncontrollably across CPUs.