UefiCpuPkg/PiSmmCpuDxeSmm: Enable/Restore XD in SMM
If XD is supported, then SMM enables it. The non-SMM execution
environment can choose to enable or disable XD, so the state of
XD must be detected in each SMI and be enabled/restored.
Cc: Jeff Fan <jeff.fan@intel.com> Cc: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Michael Kinney <michael.d.kinney@intel.com> Reviewed-by: Jeff Fan <jeff.fan@intel.com> Regression-tested-by: Laszlo Ersek <lersek@redhat.com>