Multiseat X with two cards: used to work, now segfaulting

[Artefact2]

Greetings to the GNU/Linux community,

I have a problem. I have a triple monitor setup with two cards. What I do is I use twinview for the middle and the right monitor on one X server (1st card), and another X server for the left monitor (2nd card). I then use synergy to make seamless keyboard/mouse transition between both, and it works very well.

I am not using Xinerama across all the screens, because 3D performance is very poor.

Anyway, this setup used to work, but now I had to make a reinstall after a HDD failure, and I can't get it to work. I'm not sure if I'm missing something, or a kernel/driver/xorg update broke something.

Here are the two configuration files I use for the monitors:

http://paste.artefact2.com/p/e0b0dfc <- for the first X server (middle and right screen)
http://paste.artefact2.com/p/269cbd8 <- for the second X server (left screen)

To start my servers, I use:

startx -- -quiet :0 vt07 -config rscr.conf -nolisten tcp -sharevts
startx -- -quiet :1 vt08 -config lscr.conf -nolisten tcp -sharevts

The first server runs fine, but the second one segfaults. Here are the logs produced by Xorg:

http://paste.artefact2.com/p/273009f <- first server
http://paste.artefact2.com/p/4bd6857 <- second server

The error seems to come from "Failed to allocate EVO core DMA push buffer", but I'm not so sure since I can't check if it happened before.

I am using ArchLinux x86_64, with linux 3.4.4, xorg-server 1.12.2 and nvidia driver 302.17.

Thanks for your help!

(Edit: added report log as attachment)

[AaronP]

Multiseat configurations are not supported, I'm afraid. Sorry.

[Artefact2]

Originally Posted by AaronP

Multiseat configurations are not supported, I'm afraid. Sorry.

I'm a bit disappointed to be honest, it used to work perfectly.

What's the point of having two cards then? Is there a way to have a triple head setup with decent 3D performance?

[AaronP]

Yes, you can configure a single X server to have multiple X screens on different GPUs and they will all have OpenGL support.

[Artefact2]

Originally Posted by AaronP

Yes, you can configure a single X server to have multiple X screens on different GPUs and they will all have OpenGL support.

Thanks for the tip!

I had to change my window manager, because xmonad doesn't support non-Xinerama, multiple-screen Xorg setups. I use awesomewm which I configured to behave like xmonad, and it runs pretty good!

This comes at a cost though. I cannot move windows between different monitors, and I cannot have windows span across more than one monitor. I'll have to deal with it, but so far so good.

[AaronP]

Originally Posted by Artefact2

This comes at a cost though. I cannot move windows between different monitors, and I cannot have windows span across more than one monitor. I'll have to deal with it, but so far so good.

That shouldn't have worked with a multiseat configuration either.

If you want to combine the physical X screens into one logical X screen, you can use Xinerama or the BaseMosaic option.

[Artefact2]

Originally Posted by AaronP

That shouldn't have worked with a multiseat configuration either.

If you want to combine the physical X screens into one logical X screen, you can use Xinerama or the BaseMosaic option.

Actually, since I used to use twinview for the first Xorg server, I was able to swap windows between the middle and the right monitors.

Also, as I said in my main post, Xinerama works but has completely horrible 3D performance (I assume that's because all the screen merging is done in software).

BaseMosaic I have never even heard about before (and I did a lot of searching, hehe), but it seems promising. I'll give it a try, thanks!

Edit: I tried BaseMosaic option, and it seems to be SLI-only… Maybe I am doing it wrong?

[ 42299.984] (**) NVIDIA(0): Option "BaseMosaic" "True"
[ 42299.984] (**) NVIDIA(0): Option "MetaModes" "GPU-0.DFP-0: nvidia-auto-select +1920+0, GPU-0.DFP-2: nvidia-auto-select +3840+0, GPU-1.DFP-0: nvidia-auto-select +0+0"
[ 42299.984] (**) NVIDIA(0): Enabling 2D acceleration
[ 42300.979] (EE) NVIDIA(0): Failed to find a valid Base Mosaic configuration.
[ 42300.979] (EE) NVIDIA(0): Invalid Base Mosaic configuration 1 of 1:
[ 42300.979] (EE) NVIDIA(0): GPUs:
[ 42300.979] (EE) NVIDIA(0):     1) NVIDIA GPU at PCI:1:0:0
[ 42300.979] (EE) NVIDIA(0):     2) NVIDIA GPU at PCI:2:0:0
[ 42300.979] (EE) NVIDIA(0): Errors:
[ 42300.979] (EE) NVIDIA(0):     - The video link was not detected
[ 42300.979] (EE) NVIDIA(0):     - Chipset not approved for SLI

Which is confusing because the README says "This is like SLI Mosaic mode except that it does not require a video bridge connected to the graphics cards."

[AaronP]

Which driver version are you using?

[Artefact2]

Originally Posted by AaronP

Which driver version are you using?

I use the 302.17 driver on Archlinux x86_64 (3.4.4 kernel).

[AaronP]

I asked around, and part of the error is correct: you don't need a video bridge for BaseMosaic, but you do need an SLI-capable chipset.

[Artefact2]

Originally Posted by AaronP

I asked around, and part of the error is correct: you don't need a video bridge for BaseMosaic, but you do need an SLI-capable chipset.

Thanks for the reply! I'll try to get my hands on a SLI-capable motherboard on occasion.

(Edit: new motherboard arrived today, and the BaseMosaic option works perfectly! http://uppix.net/2/2/e/420052c0b4a85...ad2403fdec.png )