Comment # 136 on bug 81644 from Alex Deucher

(In reply to comment #131)
> I have just played a youtube video (coincidentally the youtube message from
> AMD's John Byrne regarding Catalyst!) and I have just checked that the
> following messages show up in the dmesg log:
> 
> [ 2053.298531] radeon 0000:05:00.0: Packet0 not allowed!
> [ 2058.548486] radeon 0000:05:00.0: Packet0 not allowed!
> [ 2166.793537] radeon 0000:05:00.0: Packet0 not allowed!

These indicate that userspace is sending a broken command stream (e.g., a bad
count for a packet most likely).  The kernel will reject the command stream if
a bad one is encountered.  There still could be a bug in the command stream
setup in userspace that is just masked in other cases due to the layout of the
commands.