When SourceLevelDebug is enabled, AP randomly executes the DXECORE timer handler logic. The root cause is the interrupts are not masked in AP wake up procedure. Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com> Reviewed-by: Jeff Fan <vanjeff_919@hotmail.com>