2 files changed, 33 insertions, 1 deletions

diff --git a/Documentation/admin-guide/sysctl/index.rst b/Documentation/admin-guide/sysctl/index.rst
index e153c96119df..50f00514f0ff 100644
--- a/Documentation/admin-guide/sysctl/index.rst
+++ b/Documentation/admin-guide/sysctl/index.rst
@@ -84,7 +84,7 @@ sunrpc/		SUN Remote Procedure Call (NFS)
 user/		Per user namespace limits
 vm/		memory management tuning
 		buffer and cache management
-xen/		<undocumented>
+xen/		Xen hypervisor controls
 =============== ===============================================================
 
 These are the subdirs I have on my system or have been discovered by
@@ -104,3 +104,4 @@ it :-)
    sunrpc
    user
    vm
+   xen
diff --git a/Documentation/admin-guide/sysctl/xen.rst b/Documentation/admin-guide/sysctl/xen.rst
new file mode 100644
index 000000000000..6c5edc3e5e4c
--- /dev/null
+++ b/Documentation/admin-guide/sysctl/xen.rst
@@ -0,0 +1,31 @@
+===============
+/proc/sys/xen/
+===============
+
+Copyright (c) 2026, Shubham Chakraborty <chakrabortyshubham66@gmail.com>
+
+For general info and legal blurb, please look in
+Documentation/admin-guide/sysctl/index.rst.
+
+------------------------------------------------------------------------------
+
+These files show up in ``/proc/sys/xen/``, depending on the
+kernel configuration:
+
+.. contents:: :local:
+
+balloon/hotplug_unpopulated
+===========================
+
+This flag controls whether unpopulated memory ranges are automatically
+hotplugged as system RAM.
+
+- ``0``: Unpopulated ranges are not hotplugged (default).
+- ``1``: Unpopulated ranges are automatically hotplugged.
+
+When enabled, the Xen balloon driver will add memory regions that are
+marked as unpopulated in the Xen memory map to the system as usable RAM.
+This allows for dynamic memory expansion in Xen guest domains.
+
+This option is only available when the kernel is built with
+``CONFIG_XEN_BALLOON_MEMORY_HOTPLUG`` enabled.