Merge pull request #42846 from ambrop72/optimus-prime-config-master

nixos/xserver: Implement configuration of NVIDIA Optimus via PRIME

nixos/modules/hardware/video/nvidia.nix

@@ -26,9 +26,73 @@ let
   nvidia_libs32 = (nvidiaForKernel pkgs_i686.linuxPackages).override { libsOnly = true; kernel = null; };
 
   enabled = nvidia_x11 != null;
+
+  cfg = config.hardware.nvidia;
+  optimusCfg = cfg.optimus_prime;
 in
 
 {
+  options = {
+    hardware.nvidia.modesetting.enable = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      description = ''
+        Enable kernel modesetting when using the NVIDIA proprietary driver.
+
+        Enabling this fixes screen tearing when using Optimus via PRIME (see
+        <option>hardware.nvidia.optimus_prime.enable</option>. This is not enabled
+        by default because it is not officially supported by NVIDIA and would not
+        work with SLI.
+      '';
+    };
+
+    hardware.nvidia.optimus_prime.enable = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      description = ''
+        Enable NVIDIA Optimus support using the NVIDIA proprietary driver via PRIME.
+        If enabled, the NVIDIA GPU will be always on and used for all rendering,
+        while enabling output to displays attached only to the integrated Intel GPU
+        without a multiplexer.
+
+        Note that this option only has any effect if the "nvidia" driver is specified
+        in <option>services.xserver.videoDrivers</option>, and it should preferably
+        be the only driver there.
+
+        If this is enabled, then the bus IDs of the NVIDIA and Intel GPUs have to be
+        specified (<option>hardware.nvidia.optimus_prime.nvidiaBusId</option> and
+        <option>hardware.nvidia.optimus_prime.intelBusId</option>).
+
+        If you enable this, you may want to also enable kernel modesetting for the
+        NVIDIA driver (<option>hardware.nvidia.modesetting.enable</option>) in order
+        to prevent tearing.
+
+        Note that this configuration will only be successful when a display manager
+        for which the <option>services.xserver.displayManager.setupCommands</option>
+        option is supported is used; notably, SLiM is not supported.
+      '';
+    };
+
+    hardware.nvidia.optimus_prime.nvidiaBusId = lib.mkOption {
+      type = lib.types.string;
+      default = "";
+      example = "PCI:1:0:0";
+      description = ''
+        Bus ID of the NVIDIA GPU. You can find it using lspci; for example if lspci
+        shows the NVIDIA GPU at "01:00.0", set this option to "PCI:1:0:0".
+      '';
+    };
+
+    hardware.nvidia.optimus_prime.intelBusId = lib.mkOption {
+      type = lib.types.string;
+      default = "";
+      example = "PCI:0:2:0";
+      description = ''
+        Bus ID of the Intel GPU. You can find it using lspci; for example if lspci
+        shows the Intel GPU at "00:02.0", set this option to "PCI:0:2:0".
+      '';
+    };
+  };
 
   config = mkIf enabled {
     assertions = [
@@ -36,15 +100,61 @@ in
         assertion = config.services.xserver.displayManager.gdm.wayland;
         message = "NVidia drivers don't support wayland";
       }
+      {
+        assertion = !optimusCfg.enable ||
+          (optimusCfg.nvidiaBusId != "" && optimusCfg.intelBusId != "");
+        message = ''
+          When NVIDIA Optimus via PRIME is enabled, the GPU bus IDs must configured.
+        '';
+      }
     ];
 
-    services.xserver.drivers = singleton
-      { name = "nvidia"; modules = [ nvidia_x11.bin ]; libPath = [ nvidia_x11 ]; };
+    # If Optimus/PRIME is enabled, we:
+    # - Specify the configured NVIDIA GPU bus ID in the Device section for the
+    #   "nvidia" driver.
+    # - Add the AllowEmptyInitialConfiguration option to the Screen section for the
+    #   "nvidia" driver, in order to allow the X server to start without any outputs.
+    # - Add a separate Device section for the Intel GPU, using the "modesetting"
+    #   driver and with the configured BusID.
+    # - Reference that Device section from the ServerLayout section as an inactive
+    #   device.
+    # - Configure the display manager to run specific `xrandr` commands which will
+    #   configure/enable displays connected to the Intel GPU.
 
-    services.xserver.screenSection =
+    services.xserver.drivers = singleton {
+      name = "nvidia";
+      modules = [ nvidia_x11.bin ];
+      libPath = [ nvidia_x11 ];
+      deviceSection = optionalString optimusCfg.enable
+        ''
+          BusID "${optimusCfg.nvidiaBusId}"
+        '';
+      screenSection =
+        ''
+          Option "RandRRotation" "on"
+          ${optionalString optimusCfg.enable "Option \"AllowEmptyInitialConfiguration\""}
+        '';
+    };
+
+    services.xserver.extraConfig = optionalString optimusCfg.enable
       ''
-        Option "RandRRotation" "on"
+        Section "Device"
+          Identifier "nvidia-optimus-intel"
+          Driver "modesetting"
+          BusID  "${optimusCfg.intelBusId}"
+          Option "AccelMethod" "none"
+        EndSection
       '';
+    services.xserver.serverLayoutSection = optionalString optimusCfg.enable
+      ''
+        Inactive "nvidia-optimus-intel"
+      '';
+
+    services.xserver.displayManager.setupCommands = optionalString optimusCfg.enable ''
+      # Added by nvidia configuration module for Optimus/PRIME.
+      ${pkgs.xorg.xrandr}/bin/xrandr --setprovideroutputsource modesetting NVIDIA-0
+      ${pkgs.xorg.xrandr}/bin/xrandr --auto
+    '';
 
     environment.etc."nvidia/nvidia-application-profiles-rc" = mkIf nvidia_x11.useProfiles {
       source = "${nvidia_x11.bin}/share/nvidia/nvidia-application-profiles-rc";
@@ -62,6 +172,8 @@ in
     boot.kernelModules = [ "nvidia-uvm" ] ++
       lib.optionals config.services.xserver.enable [ "nvidia" "nvidia_modeset" "nvidia_drm" ];
 
+    # If requested enable modesetting via kernel parameter.
+    boot.kernelParams = optional cfg.modesetting.enable "nvidia-drm.modeset=1";
 
     # Create /dev/nvidia-uvm when the nvidia-uvm module is loaded.
     services.udev.extraRules =