-At the moment we basically don't support cross-architecture or
-32-on-64. This limits what is possible for some guests. Filesystem
-operations and FTP export will work fine, but running commands in
-guests may not be possible.
+Previous versions of libguestfs required something called "vmchannel".
+Vmchannel is a special device given to virtual machines which allows
+them to communicate in some way with the host, often (but not always)
+without using a traditional network device. In reality, there is no
+one thing called "vmchannel". This idea has been reimplemented
+several times under the name vmchannel, and other hypervisors have
+their own incompatible implementation(s) too.
+
+In libguestfs <= 1.0.71, we required a specific vmchannel which is
+properly known as "guestfwd" and has been upstream in qemu since here: