> The code waits for all cores to enter SMM, or for up to 1 second, whichever occurs first.

See, this is why the mantra that all blocking operations should have a timeout is stupid and short-sighted no matter how many times junior devs and AIs bleat it in code review. Continuing after arbitrary timeouts usually violates invariants, and failing after arbitrary timeouts introduces hard-to-debug failures under load.

Better for the system to hang so you can debug it --- and maybe reboot as a whole via a watchdog --- than for the code to say "Oh, this operation is supposed to be done after one second, but isn't. Situation normal, everything fine. We continue."

No. That situation is very much not fine.