msi-gpu-switcher

Minimal GPU MUX switcher for MSI laptops on Linux.

⚠️ Use at your own risk. This tool writes directly to UEFI variables and Embedded Controller registers. I take no responsibility for any damage or loss caused by its use.

Tested Hardware

Laptop	EC Firmware
MSI Alpha 17 C7VG	17KKIMS1.114

Other MSI models may work if they share the same UEFI variable and EC layout. Open an issue with your model and firmware version if it works or fails.

Requirements

• Linux with efivarfs mounted at /sys/firmware/efi/efivars
• ec_sys kernel module loaded with write_support=1
• debugfs mounted at /sys/kernel/debug
• Root privileges

Installation

NixOS

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    msi-gpu-switcher = {
      url = "github:elxreno/msi-gpu-switcher";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = { nixpkgs, msi-gpu-switcher, ... }:
    {
      nixosConfigurations."hostname" = nixpkgs.lib.nixosSystem {
        ...
        modules = [
          ({ pkgs, ... }: {
            environment.systemPackages = [
              msi-gpu-switcher.packages.${pkgs.stdenv.hostPlatform.system}.default
            ];

            # Required for EC writes
            boot.kernelModules = [ "ec_sys" ];
            boot.extraModprobeConfig = "options ec_sys write_support=1";
          })
        ];
      };
    };
}

Manual build

go build -o msi-gpu-switcher .

Usage

  msi-gpu-switcher [command]

Available Commands:
  completion  Generate the autocompletion script for the specified shell
  dgpu        Switch to dGPU (discrete)
  help        Help about any command
  igpu        Switch to iGPU (hybrid)
  status      Show current GPU/MUX/UEFI status

Flags:
      --debug   enable debug logging
  -h, --help    help for msi-gpu-switcher

A reboot is required after switching.

Troubleshooting

UEFI variable is immutable:

chattr -i /sys/firmware/efi/efivars/MsiDCVarData-DD96BAAF-145E-4F56-B1CF-193256298E99

The tool attempts this automatically via FS_IOC_SETFLAGS; run manually if it fails.

EC writes fail — reload ec_sys with write support:

modprobe -r ec_sys && modprobe ec_sys write_support=1

ec0 not found — mount debugfs:

mount -t debugfs none /sys/kernel/debug

How it works

Low-level details

Switches the primary GPU output by:

• Writing the UEFI variable MsiDCVarData (GUID DD96BAAF-145E-4F56-B1CF-193256298E99)
• Triggering the EC switch (0xD1)
• Toggling the EC MUX bit (0x2E, mask 0x40)

Notes

• Written with the help of AI.