[jmull]

Well, these are workarounds because fixing the problem at the source is hard.

The right fix is to prevent speculatively executed code from leaking information.

Here that perhaps means associating cache lines with a speculative branch somehow so that they aren't accessible until/unless the speculative branch becomes the real branch. (I have no idea exactly how that would be done or what the performance cost might be... I'd really need to know the details of how speculative execution is implemented in a particular CPU to even be able to guess.)