3 ms·
I think the specter paper stated that the CPU doesn't run both branches at the same time. Instead it picks one based on speculation and runs that branch. If it
by rocqua 9y ago
I think the specter paper stated that the CPU doesn't run both branches at the same time. Instead it picks one based on speculation and runs that branch. If it picked wrong it rolls back and only then does it start running the other branch.
The article states different.
If I'm right that would also require some specter-like attack to make sure the desired branch is actually executed speculatively.
Alternatively, maybe you can catch the exception and use that to indicate the desired branch was run.
- scott_s 9y agoYou're correct that's how speculative execution works: it picks one branch, it does not pick both branches. But that's the Spectre vulnerability, while this article is trying to explain Meltdown, and Meltdown does not involve speculative execution. (See my other comment in this thread for a full explanation.)
- rocqua 9y agoThanks, you comment was really clear :)