1. Save/restore ICR high 32bit value and check Delivery Status before sending IPI. It could be fix the interrupted issue between ICR high/low writes by SMI handler.
2. Save/restore CPU Interrupt state around sending IPI. It could avoid sending IPI be interrupted by CPU interrupt handler.
3. Add note for SetApicMode() API that must not be called from an interrupt handler or SMI handler.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Kinney, Michael <michael.d.kinney@intel.com>
Reviewed-by: Mudusuru, Giri <giri.p.mudusuru@intel.com>


git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15652 6f19259b-4bc3-4df7-8a09-765794883524