Comment 4 for bug 1615550

Checking the code I'd expect that this kind of access is from:

static void qemu_thread_set_name(QemuThread *thread, const char *name)
{
#ifdef CONFIG_PTHREAD_SETNAME_NP
    pthread_setname_np(thread->thread, name);
#endif
}

This is non fatal, just fails to set the thread name (note that the return value is intentionally ignored).

The code itself if rather old (since qemu 2.0) but not enabled by default.
You could be enabled by:
  -name debug-threads=on

Since this change it is enabled by default by libvirt if supported:
https://www.redhat.com/archives/libvir-list/2016-March/msg00428.html

So with Yakkety you get e.g.
-name guest=testvm1,debug-threads=on
While on Xenial you got:
-name guest=testvm1

That feature enabled is what triggers the apparmor issues now.