The NVMe ZNS command set has the zone descriptor extension feature for
associating the data to a zone. Devices that supports ZAC/ZBC have zero
zone descriptor extension size.

Signed-off-by: Sam Li <faithilikerun@gmail.com>
---
 docs/interop/qcow2.txt | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt
index a8dd4c3b15..106477d9ad 100644
--- a/docs/interop/qcow2.txt
+++ b/docs/interop/qcow2.txt
@@ -436,6 +436,15 @@ The fields of the zoned extension are:
                    The offset of zoned metadata structure in the contained
                    image, in bytes.
 
+         44 - 51:  zd_extension_size
+                   The size of zone descriptor extension data in bytes.
+                   The value must be a multiple of 64.
+
+                   The zone descriptor extension feature is associating data
+                   to a zone which is only available in the NVMe ZNS command
+                   set. A value of zero indicates the feature is not
+                   available.
+
 == Full disk encryption header pointer ==
 
 The full disk encryption header must be present if, and only if, the
-- 
2.40.1