[Feature request] Multiple X servers on one graphics card?

Prof. Dr. Klaus Kusche klaus.kusche at computerix.info
Tue Aug 2 04:54:24 PDT 2011

On 2011-08-02 12:26, Alan Cox wrote:
>> Hence, that's no argument against multiple DRM devices on a single card,
>> because the other solutions suffer from the same problem.
> Displaylink USB devices don't have this problem - they have others. Ditto
> mulitple graphics cards doesn't.

Multiple single-seat graphics cards won't allow me to connect 15-25
users to one PC / server, and the main goal is to have a whole
classroom on a *single* machine: No network and file sharing
to configure, no remote software distribution and updates to manage,
no remote authentication, no boot from net, ...

And chances are that the machine has to be dual boot with Microsoft
Multipoint Server.

15-25 USB graphics devices might work technically, but they will be
much slower than the unaccelerated solution with multi-output
graphics cards and Xephyr's, perhaps even slower than thin clients
(given that they are all USB 2 and the total USB 2 bandwidth is
quite limited).

>> In the long term, it needs to be fixed,
>> but in a classroom environment, that's not my primary concern
>> (and I believe 90 % of all multiseat installations
>> will be classroom or home environments).
> Certainly with such security limits it won't catch on in many places, and
> I suspect it wouldn't be much use in many classroom environments students
> being what they are!

Such configurations will be rare and will have different hardware and
software. I doubt that someone will publish a ready-to-run exploit
which works out of the box on all of them. Hence, exploiting this
will require some technical intelligence. I don't believe that
pupils and students in the basic courses have that
(and we're not talking about graduate courses).

And what would they get? Their neighbour's screen contents.
They could just as easily look at their neighbour's screen directly.
And as long as I do not run individual VM's with strict firewalling
on the host OS, they will find other ways to exchange information
(or sabotage each other) anyway, by IPC or whatever...

I've been told that it is almost impossible to completely block
information exchange between pupils on Microsoft Multipoint Server
even on naive levels, too, and nevertheless that product is selling

So the security aspect is something to keep in mind,
but not something which excludes a shared-graphics-card solution
a priori.


Prof. Dr. Klaus Kusche
Private address: Rainstraße 9/1, 88316 Isny, Germany
+49 7562 6211377 Klaus.Kusche at computerix.info http://www.computerix.info
Office address: NTA Isny gGmbH, Seidenstraße 12-35, 88316 Isny, Germany
+49 7562 9707 36 kusche at nta-isny.de http://www.nta-isny.de

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