Yeah… folks who think this is just some easy to avoid thing should go look around and find the processor without branch prediction that they want to use.

On the bright side, they will get to enjoy a much better music scene, because they’ll be visiting the 90’s.

IBM Stretch had branch prediction. Pentium in the early 1990s had it. It's a huge win with any pipelining.

> Does Branch Privilege Injection affect non-Intel CPUs?

> No. Our analysis has not found any issues on the evaluated AMD and ARM systems.

That's a vast underestimate. Putting in lfence before every branch is on the order of 10X slowdown.

There is of course a slight chicken-egg-thing here: If there was no (dynamic) branch prediction, we (as in compilers) would emit different code that is faster for non-predicting CPUs (and presumably slower for predicting CPUs). That would mitigate a bit of that 10x.

A bit. I think we've shown time and time again that letting the compiler do what the CPU is doing doesn't work out, most recently with Itanium.

The issue is with indirect branches. Most branches are direct ones.

How much improvement would there still be if we weren't so lazy when it comes to writing software. If we were working to get as much performance out of the machines as possible and avoiding useless bloat instead of just counting on the hardware to be "good enough" to handle the slowness with some grace.

Of course I know that.

But if the fix for this bug (how many security holes have ther been now in Intel CPUs? 10?) brings only a couple % performance loss, like most of the them so far, how can you even justify that at all? Isn't there a fundamental issue in there?