When CET shadow stack feature is enabled, it needs to use IST for the
exceptions, and uses interrupt shadow stack for the stack switch.
Shadow stack should be 32 bytes aligned.
Check IST field, when clear shadow stack token busy bit when using retf.
REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3728
Signed-off-by: Sheng Wei <w.sheng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
455b0347a7