Arch Linux

xilats

Member

Registered: 2018-07-22

Posts: 4

SOLVED - RTFM - NVIDIA - Cannot use second GPU/black XORG screen

Hello!

I am currently experiencing a VERY strange issue.
I recently decided to take my second GPU off of VIRTIO/VFIO duty and move it just to SLI duty for easier coding with the attached monitor and to test gaming in an SLI configuration .
Since they are of the exact same model and type of card, an EVGA FTW 970, I figured this would be really easy.

After removing VIRTIO/VFIO stubbing, I was greeted with black screens on my three monitors, each displaying 'NO SIGNAL', before going into power save mode.
After trying several steps, such as:
    Following https://wiki.archlinux.org/index.php/NV … X_shutdown
    Uninstalling and reinstalling the NVIDIA drivers.
    Removing the SLI Bridge cable, readding the SLI Bridge cable
    Installing the Linux-LTS and Nvidia-LTS arch packages
    Deleting the xorg.conf file
    Rebooting
    And then disabling every module, adding them one by one.

It turns out, that as long as nvidia_drm was not loaded, I could setup the third monitor, set SLI flags using nvidia-xconfig.
But once I enabled nvidia_drm and started a window manager, boom. Black screens.

I have gleaned the following bits DMESG output via SSH:

https://pastebin.com/nKvCG90z

If there is something I am missing, please let me know.
I feel like the solution is obvious, but that my google fu is failing me.

Thank you so much for your advice!

Last edited by xilats (2018-07-23 13:35:52)

Stencon281

Member

Registered: 2016-09-21

Posts: 40

Re: SOLVED - RTFM - NVIDIA - Cannot use second GPU/black XORG screen

Do you have display compositing enabled? If you do, make sure you don't have it enabled in both nvidia settings and your window manager / desktop environment.

xilats

Member

Registered: 2018-07-22

Posts: 4

Re: SOLVED - RTFM - NVIDIA - Cannot use second GPU/black XORG screen

I don't have any compositing enabled at this point in either KDE or the nvidia settings window.
The problem even occurs when I run plain X!
I've also gone ahead and turned on/off IOMMU to see if I could remedy this.

All I know is that each time I'm getting a weird SLUB allocation error, based on DMESG output.
I'm digging deeper to see if I need to be doing something a little different, or to see what could be causing a SLUB problem.

seth

Member

Registered: 2012-09-03

Posts: 51,314

Re: SOLVED - RTFM - NVIDIA - Cannot use second GPU/black XORG screen

/usr/share/doc/nvidia/README, chapter 33

The NVIDIA DRM KMS implementation is currently incompatible with SLI. The X server will fail to initialize SLI if DRM KMS is enabled.

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xilats

Member

Registered: 2018-07-22

Posts: 4

Re: SOLVED - RTFM - NVIDIA - Cannot use second GPU/black XORG screen

Seth, you are awesome.

I completely forgot to read the nvidia readme.
Let the record show that I still do not know how to RTFM.
I will mark this as resolved.