Index: docs/AMDGPUUsage.rst
===================================================================
--- docs/AMDGPUUsage.rst
+++ docs/AMDGPUUsage.rst
@@ -503,6 +503,11 @@
                                                   target feature is
                                                   enabled for all code
                                                   contained in the code object.
+                                                  If the processor
+                                                  does not support the
+                                                  ``xnack`` target
+                                                  feature then must
+                                                  be 0.
                                                   See
                                                   :ref:`amdgpu-target-features`.
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