An obvious flaw doesn't become less obvious if it has been found. So it might be that some blackhat knew about it before, but there a lot of smart sufficiently-

An obvious flaw doesn't become less obvious if it has been found. So it might be that some blackhat knew about it before, but there a lot of smart sufficiently-pale-shade-of-gray people out in the world for obvious problems to be found in less than decades. So I don't think it's an obvious problem. It seems that at least some ARM might be affected by both Spectre and Meltdown. So far, I have only seen negative meltdown tests for older AMD cores. Is there anything known for Ryzen except for the PR by AMD (and the kernel patch, which might be based on the google project zero information about older AMD cores)? While meltdown is "easy" to fix by not reading memory if unprivileged to do so, spectre is a lot harder. Even if the caches are made safe, for example by having "speculative" cache lines which will be renamed into the "true" cache when the speculative thread is actually accepted and retired: It's not the only place where there is hidden state. For example, the branch prediction might be affected, and might give a timing signal.