I really wonder why so many are so concerned if they think of the issue.
IF two threads hit one core in a hyperthreaded CPU at the same time
IF one is a hacked thread
IF no context switches happen
IF the hacked thread can dump the L1 cache data
IF that date contains useful data and is transfered
IF it's accessed and makes it through all other security measures and firewalls
IF it's decoded
IF it's useful
THEN it's a problem
Lot's of IF's and random happenings
So ESXi has can stop scheduling for hyperthreads
It's doesn't schedule for hyperthreading (in the best/worst case situation that's maybe a 30% decrease in performance)
My guess is they'll code for selective hyperthreading, IF a VM is multicored then it'll let it hypertheard and let the OS deal, But not let cross VM hyperthreading unless Intel fixes the microcode.
Older CPUs that Intel has no intention of addressing microcodes, do they take any performance hit on patched VIBs?
Can late builds of ESXi have its patches "disabled"?
I'd rather let backups protect everything, and leave ESXi running without bandaids.