nvidia-container-toolkit: set cdi mode for nvidia-container-runtime (#485584)

nixos/modules/services/hardware/nvidia-container-toolkit/default.nix

@@ -151,6 +151,17 @@
     };
 
   config = lib.mkMerge [
+    (lib.mkIf (config.virtualisation.docker.enableNvidia || config.virtualisation.podman.enableNvidia) {
+      hardware.nvidia-container-toolkit.enable = lib.mkDefault true;
+
+      warnings = lib.mkIf (!config.hardware.nvidia-container-toolkit.enable) [
+        ''
+          `virtualisation.docker.enableNvidia` or `virtualisation.podman.enableNvidia` is enabled,
+          but `hardware.nvidia-container-toolkit.enable` is disabled. The nvidia-container-toolkit
+          module is required for GPU support in containers.
+        ''
+      ];
+    })
     (lib.mkIf config.virtualisation.docker.enableNvidia {
       environment.etc."nvidia-container-runtime/config.toml".text = ''
         disable-require = true
@@ -162,7 +173,7 @@
         no-cgroups = false
         path = "${lib.getExe' pkgs.libnvidia-container "nvidia-container-cli"}"
         [nvidia-container-runtime]
-        mode = "auto"
+        mode = "cdi"
         runtimes = ["docker-runc", "runc", "crun"]
         [nvidia-container-runtime-hook]
         path = "${lib.getOutput "tools" config.hardware.nvidia-container-toolkit.package}/bin/nvidia-container-runtime-hook"