DragonFlyBSD Gets Fix To Be Able To Boot AMD Zen 2 Processors
DragonFlyBSD lead developer Matthew Dillon who has been mesmerized by the AMD Threadripper performance for the past year now has his hands on new Zen 2 hardware. But it turns out the current DragonFlyBSD releases can't boot with these processors due to a separate problem from what we've seen on the Linux side.
He explained when landing the fix, "Issue load_fs() in the AP bootstrap. It appears that Zen 2 handles %fs in a weird way when the selector isn't loaded, causing the first wrmsr(MSR_FSBASE) to quietly fail, and possibly others too. For good measure, also issue load_ds() and load_es()."
The three-line patch is now present in DragonFlyBSD Git and thus allowing their latest daily images to hopefully boot fine on all new AMD Zen 2 systems. I'll have some Zen 2 + BSD benchmarks in due course.