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PiSmmCpuDxeSmm consumes SmmAttributesTable and setup page table: 1) Code region is marked as read-only and Data region is non-executable, if the PE image is 4K aligned. 2) Important data structure is set to RO, such as GDT/IDT. 3) SmmSaveState is set to non-executable, and SmmEntrypoint is set to read-only. 4) If static page is supported, page table is read-only. We use page table to protect other components, and itself. If we use dynamic paging, we can still provide *partial* protection. And hope page table is not modified by other components. The XD enabling code is moved to SmiEntry to let NX take effect. Cc: Jeff Fan <jeff.fan@intel.com> Cc: Feng Tian <feng.tian@intel.com> Cc: Star Zeng <star.zeng@intel.com> Cc: Michael D Kinney <michael.d.kinney@intel.com> Cc: Laszlo Ersek <lersek@redhat.com> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Jiewen Yao <jiewen.yao@intel.com> Tested-by: Laszlo Ersek <lersek@redhat.com> Reviewed-by: Jeff Fan <jeff.fan@intel.com> Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>