Intel SPR erratum SPR4 says that if you trip into a vmexit while
doing FPU save/restore, your AMX register state might misbehave...
and by misbehave, I mean save all zeroes incorrectly, leading to
explosions if you restore it.
Since we're not using AMX for anything, the simple way to avoid
this is to just not save/restore those when we do anything, since
we're killing preemption of any sort across our save/restores.
If we ever decide to use AMX, it's not clear that we have any
way to mitigate this, on Linux...but I am not an expert.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rich Ercolani <rincebrain@gmail.com>
Closes#14989Closes#15168
277f2e587b