Re: Two accelerated xservers on a single G550

[Helge H. <hel...@ai...>]

Aivils Stoss wrote:
 
> Congratulations! You open new "matrox psyho circus" thread.

Does this imply there were an earlier matrox psycho
circus thread?  If so, is there a searchable archive somewhere?

> IMHO with right config You solutions works. Of course any
> cyberpunk may use neighbour display, but that by-product only.
> 
Well, the NAT box on my home network only lets ssh through,
so I don't worry too much about X security. 
But why would there be a problem?  The two X servers are independent
and each can enforce security on its own connections.  The only
security breach I can imagine is that one logged-in user
may read the other logged-in user's window contents because he
has access to the same framebuffer memory.  "Any cyberpunk" on the
net (or even logged-in but not running X) shouldn't be more
of a problem than with a ordinary setup?

Right now those xserves are insecure because they are dri-trunk servers
wich happens to have no security compiled in. But I don't need
that for the dual setup, it is only to get DRI.  

> Please test config, whrere both xf86 use _two_ screens without
> xinerama. If You use both screens of matrox device, then You
> can determine "who is who".
>      1st xf86 "matrox device screen=0" as _fisrt_ xf86 Screen
> in ServerLayout, but "matrox device screen=1" as second
>      2nd xf86 swap order of "matrox device" in ServerLayout.
> "matrox device screen=1" is _first_ for this server.
> 
Great idea!
Both users can stick to his/her "first" screen and simply not
use the second one (which only would stomp on the other users
display)

I guess only one user really need a setup with two displays, 
using the  first one as a "placeholder".  The user with the
first display can simply keep using that.

> Both servers setup both screens, which one may work according
> Your reports above. Because matrox device order is swaped, then
> sys admin can determine where runs programs under each xf86.
> 
> "xterm -display :0.0" runs on owner display
> "xterm -display :0.1" runs on neighbour display
> 
> But DISPLAY=":0.0" always.

I believe the first user will see his display as :0.0 and
the other user's display as :0.1?

And the other user will see his display as :1.0 and the
first user's display as :1.1?

One xserver start as :0 and the other as :1 with the
current single-screen setup.

> 
> You might add in .xinirc line
> xsetroot -display :0.1 -color most-compatible-colour
> 
> This solution cannot be called "technical correct".
The "correct" way would be to tell an xserver to use the 
second G550 display only.  I don't know if that is
possible to do though.

> You can try patch program Xnest to use independ mouse
> and keyboard.

I don't understand this.  Ruby already provides
independent keyboards.  And the two X servers have no
problem using independent mice.

From my /etc/X11/xdm/Xservers file:
:0 local /usr/X11R6/bin/X :0 vt17  -deferglyphs 16 -nolisten tcp
:1 local /usr/X11R6/bin/X :1 vt7 -deferglyphs 16 -nolisten tcp -xf86config xf86config-4

The vt7/vt17 decides the keyboard, :0/:1 sets display numbers. The first server uses
standard XF86Config-4 and the other uses the alternative xf86config-4.
The XF86Config-4 is unchanged from ordinary single-user setup,
using accelerated mga on the first display.
Contents of xf86config-4 varies depending on what I want to do.
It is usually set up for fbdev X on the second framebuffer device,
I also tried  letting it use the mga driver and got two servers
using the same screen.  Using the two-screen setup you mentioned will
be an interesting experiment.

Helge Hafting