> main takeaway should be "speculative execution creates exploitable side-channels, and you should assume your hardware is exploitable until proven otherwise."
Speculative execution does not create side-channels in and of itself, side effects of speculative execution does that. In this case the side effect of cache state. Just don't change the cache during speculative execution and there's no problem.
And roll them back? It can, but it doesn't for performance reasons. What the performance impact would be is unknown but this requires a silicon change so unless you work at Intel you'll probably never know.
