Differences in behaviour for nvidia drivers between chaotic-nyx packaged cachyos-kernel and this packaged version

[FKouhai]

System Info:

NixOS Version: NixOS 26.05 (Yarara)
Kernel Version: 6.18.0-cachyos
Nvidia Drivers Version: 590.44.01

When im using the chaotic nyx packaged kernel there is no collision between drivers, as I only have these defined
package = config.boot.kernelPackages.nvidiaPackages.beta;.

So im not particularly sure what the conflicting nvidia driver is acquiring this "lock".

While using this kernel for one of my machines, I see the following output on journalctl,

Dec 17 22:28:11 kraken kernel: Command line: initrd=\EFI\nixos\0ydm66l122ayhw1ypjmpv8f0jv88lghh-initrd-linux-cachyos-latest-6.18-initrd.efi init=/nix/store/nmw6p6aqgyijfpidfl5d7r5chqfyhav5-nixos-system-kraken-26.05.20251208.addf7cf/init pci=nomsi clearcpuid=514 nvidia_drm.fbdev=1 splash loglevel=4 lsm=landlock,yama,bpf nvidia-drm.modeset=1 nvidia-drm.fbdev=1 nvidia.NVreg_OpenRmEnableUnsupportedGpus=1
Dec 17 22:28:11 kraken kernel: Kernel command line: initrd=\EFI\nixos\0ydm66l122ayhw1ypjmpv8f0jv88lghh-initrd-linux-cachyos-latest-6.18-initrd.efi init=/nix/store/nmw6p6aqgyijfpidfl5d7r5chqfyhav5-nixos-system-kraken-26.05.20251208.addf7cf/init pci=nomsi clearcpuid=514 nvidia_drm.fbdev=1 splash loglevel=4 lsm=landlock,yama,bpf nvidia-drm.modeset=1 nvidia-drm.fbdev=1 nvidia.NVreg_OpenRmEnableUnsupportedGpus=1
Dec 17 22:28:11 kraken kernel: NovaCore 0000:01:00.0: NVIDIA (Chipset: GA106, Architecture: Ampere, Revision: a.1)
Dec 17 22:28:11 kraken kernel: input: HDA NVidia HDMI/DP,pcm=3 as /devices/pci0000:00/0000:00:01.1/0000:01:00.1/sound/card0/input17
Dec 17 22:28:11 kraken kernel: input: HDA NVidia HDMI/DP,pcm=7 as /devices/pci0000:00/0000:00:01.1/0000:01:00.1/sound/card0/input18
Dec 17 22:28:11 kraken kernel: input: HDA NVidia HDMI/DP,pcm=8 as /devices/pci0000:00/0000:00:01.1/0000:01:00.1/sound/card0/input19
Dec 17 22:28:11 kraken kernel: input: HDA NVidia HDMI/DP,pcm=9 as /devices/pci0000:00/0000:00:01.1/0000:01:00.1/sound/card0/input20
Dec 17 22:28:11 kraken kernel: nvidia: loading out-of-tree module taints kernel.
Dec 17 22:28:11 kraken kernel: nvidia-nvlink: Nvlink Core is being initialized, major device number 234
Dec 17 22:28:11 kraken kernel: NVRM: The NVIDIA probe routine was not called for 1 device(s).
Dec 17 22:28:11 kraken kernel: NVRM: This can occur when another driver was loaded and 
                               NVRM: obtained ownership of the NVIDIA device(s).

Part of the snippet for my config

# in flake.nix
inputs = {
  nix-cachyos-kernel.url = "github:xddxdd/nix-cachyos-kernel";
}
outputs = {
-- snip--
nix-cachyos-kernel,
}@inputs:
let
  system = "x86_64-linux";
   username = "franky";
  pkgs = import nixpkgs {
  inherit system;
  config = {
   allowUnfree = true;
   };
  overlays = [
   nix-cachyos-kernel.overlay
  ];
};
-- snip --

# in configuration.nix
-- snip --
boot.kernelPackages = pkgs.cachyosKernels.linuxPackages-cachyos-latest;

[FKouhai]

this is the output I get after switching back to the chaotic nyx packaged kernel

Dec 17 22:55:24 kraken kernel: Command line: initrd=\EFI\nixos\p7g5p050c7b8sjk00nq33jylmvl9mc4f-initrd-linux-6.18.0-initrd.efi init=/nix/store/cdy8s7hsgrj7q5lfc8sn8yj8yf0549vx-nixos-system-kraken-26.05.20251208.addf7cf/init pci=nomsi clearcpuid=514 nvidia_drm.fbdev=1 splash loglevel=4 lsm=landlock,yama,bpf nvidia-drm.modeset=1 nvidia-drm.fbdev=1 nvidia.NVreg_OpenRmEnableUnsupportedGpus=1
Dec 17 22:55:24 kraken kernel: Kernel command line: initrd=\EFI\nixos\p7g5p050c7b8sjk00nq33jylmvl9mc4f-initrd-linux-6.18.0-initrd.efi init=/nix/store/cdy8s7hsgrj7q5lfc8sn8yj8yf0549vx-nixos-system-kraken-26.05.20251208.addf7cf/init pci=nomsi clearcpuid=514 nvidia_drm.fbdev=1 splash loglevel=4 lsm=landlock,yama,bpf nvidia-drm.modeset=1 nvidia-drm.fbdev=1 nvidia.NVreg_OpenRmEnableUnsupportedGpus=1
Dec 17 22:55:25 kraken kernel: nvidia: loading out-of-tree module taints kernel.
Dec 17 22:55:25 kraken kernel: nvidia: module verification failed: signature and/or required key missing - tainting kernel
Dec 17 22:55:25 kraken kernel: nvidia-nvlink: Nvlink Core is being initialized, major device number 237
Dec 17 22:55:25 kraken kernel: nvidia 0000:01:00.0: vgaarb: VGA decodes changed: olddecodes=io+mem,decodes=none:owns=none
Dec 17 22:55:25 kraken kernel: NVRM: loading NVIDIA UNIX Open Kernel Module for x86_64  590.44.01  Release Build  (nixbld@)  
Dec 17 22:55:25 kraken kernel: nvidia-modeset: Loading NVIDIA UNIX Open Kernel Mode Setting Driver for x86_64  590.44.01  Release Build  (nixbld@)  
Dec 17 22:55:25 kraken kernel: [drm] [nvidia-drm] [GPU ID 0x00000100] Loading driver
Dec 17 22:55:25 kraken kernel: input: HDA NVidia HDMI/DP,pcm=3 as /devices/pci0000:00/0000:00:01.1/0000:01:00.1/sound/card1/input20
Dec 17 22:55:25 kraken kernel: input: HDA NVidia HDMI/DP,pcm=7 as /devices/pci0000:00/0000:00:01.1/0000:01:00.1/sound/card1/input21
Dec 17 22:55:25 kraken kernel: input: HDA NVidia HDMI/DP,pcm=8 as /devices/pci0000:00/0000:00:01.1/0000:01:00.1/sound/card1/input22
Dec 17 22:55:25 kraken kernel: input: HDA NVidia HDMI/DP,pcm=9 as /devices/pci0000:00/0000:00:01.1/0000:01:00.1/sound/card1/input23
Dec 17 22:55:27 kraken kernel: [drm] Initialized nvidia-drm 0.0.0 for 0000:01:00.0 on minor 1
Dec 17 22:55:27 kraken kernel: nvidia 0000:01:00.0: vgaarb: deactivate vga console
Dec 17 22:55:27 kraken kernel: fbcon: nvidia-drmdrmfb (fb0) is primary device
Dec 17 22:55:27 kraken kernel: nvidia 0000:01:00.0: [drm] fb0: nvidia-drmdrmfb frame buffer device

the main difference I see is this NovaCore mentioned in the kernel packaged in this repo.
Also the latest chaotic nyx kernel is 6.18.0-cachyos

[xddxdd]

This issue is caused by the nova_core kernel module, which is a new driver for NVIDIA GPUs that isn't enabled by nixpkgs by default. You can blacklist the module for now.

When paired with CachyOS's kernel config, nixpkgs's buildLinux function enables a lot of additional modules, including nova_core. I will see if I can get the kernel config to be as close to CachyOS upstream as possible.

[xddxdd]

I reverted the change because disabling autoModules causes boot issues on my machine. Instead I'm disabling nova_core module by default. Those who want nova_core can override the kernel and enable it for themselves.