diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst
index 716f6aa315..da862201ba 100644
--- a/docs/system/deprecated.rst
+++ b/docs/system/deprecated.rst
@@ -646,6 +646,19 @@ as ignored. Currently, users are responsible for making sure the backing storage
 specified with ``-mem-path`` can actually provide the guest RAM configured with
 ``-m`` and QEMU fails to start up if RAM allocation is unsuccessful.
 
+``-smp`` (invalid topologies) (removed 5.2)
+'''''''''''''''''''''''''''''''''''''''''''
+
+CPU topology properties should describe whole machine topology including
+possible CPUs.
+
+However, historically it was possible to start QEMU with an incorrect topology
+where *n* <= *sockets* * *cores* * *threads* < *maxcpus*,
+which could lead to an incorrect topology enumeration by the guest.
+Support for invalid topologies is removed, the user must ensure
+topologies described with -smp include all possible cpus, i.e.
+*sockets* * *cores* * *threads* = *maxcpus*.
+
 Block devices
 -------------