[alacombe]

Trying to foresee the future...

Could we expect Intel to fix the design flaw^Wfeature so that future server appliance (but also desktop) can run without KPTI while still not being affected by Meltdown ? If so, what timeline could we expect ? Say a year for new CPU designs, plus a year to roll-out new machines in datacenter ?

[MBCook]

What I’ve seen is it takes five years to design a CPU from scratch.

I imagine they’ll try and rush this to get it out there as fast as possible (obviously a lot of people would like to buy CPUs they don’t have this issue for security/performance reasons) but it’s going to take a while. I think years is definitely the minimum.

Meltdown is easy enough (relatively) but Spectre is kind of a disaster. What do you do? Does the branch predictor have to start tagging every branch guess with some sort of process ID to prevent one process from messing with another’s predictions? Tag the cache lines instead so even though the data is in cache you can’t see it because YOUR process didn’t pull it in yet? What a mess.

[voidlogic]

>Does the branch predictor have to start tagging every branch guess with some sort of process ID to prevent one process from messing with another’s predictions?

Its worth pointing out that for their newest designs AMD (and Samsung Exynos) uses the full memory address for branch predictions; no doubt Intel's next design will be doing this.

[MBCook]

Ah, that makes since. Sounds like a much less complicated fix than my idea.

[dboreham]

Just isolate code on different cores.