cardwire

A GPU manager for Linux using eBPF LSM hooks to block GPUs

Creator and Main maintainer: @luytan

Disclaimer

• This project is in early development. Expect bugs and incomplete functionality

Note

Regarding the use of AI in this project: AI was used early on to prototype and fix some errors. The code has since been mostly rewritten by hand. The only AI-generated code left is in pci_devices.rs, specifically the load_pci_name_db function, which will be rewritten soon

Getting Started

Head to the docs to see how to install Cardwire on your system

Usage

The cardwire CLI lets you manage GPU states and system modes

Modes

• Integrated: Blocks the discrete GPU
• Hybrid: Unblocks the discrete GPU
• Manual: Default mode for safety, allows individual GPU blocking/unblocking

Note: Integrated/Hybrid modes only work on host with two GPUs

Note 2: Manual mode is not implemented

# Set system mode
cardwire set integrated / hybrid / manual

# Get current mode status
cardwire get

# List all detected GPUs and their status
cardwire list

# Manually block/unblock a specific GPU by ID
cardwire gpu 1 --block
cardwire gpu 1 --unblock

Configuration

The daemon reads its configuration from /etc/cardwire/cardwire.toml.

# /etc/cardwire/cardwire.toml
auto_apply_gpu_state = true
block_nvidia_vulkan = false
battery_auto_switch = false

block_nvidia_vulkan is an experimental feature that blocks the nvidia's vulkan icd, must be used with caution

Building and Development

Using Nix

# Enter development shell
nix develop

# Build the project
nix build

# Run formatting checks
nix build .#checks.x86_64-linux.pre-commit-check

# Run integration tests in VM
nix build .#checks.x86_64-linux.vm-test

# Build the vm and enter
nix run .#nixosConfigurations.x86_64-linux.config.system.build.vm

Manual Compilation

If you don't use Nix, ensure you have clang, libbpf (devel), hwdata and cargo installed (needed for eBPF compilation during the Rust build)

# Build the project
make

# Install binaries, systemd service, and D-Bus config (requires sudo)
sudo make install

How it works

Cardwire uses eBPF with LSM hooks to intercept file operations on GPU device nodes, such as /dev/dri/renderDX, /dev/dri/cardX, sysfs config and nvidiaX

When a GPU is "blocked," the eBPF program returns -ENOENT for any syscall targeting that device. This provides several key benefits:

• Instant App Startup: Prevents applications (like Electron apps or GTK apps) from attempting to initialize the GPU, this eliminates the 3–4 second "hang" typically caused by waiting for a sleeping GPU to power up
• Power Efficiency: By blocking access at the syscall level, the GPU is never woken from its lowest power state (D3cold), extending battery life on laptops
• Non-Invasive: Unlike traditional methods that might require driver unloading, risky unbind or complex X11/Wayland setups, this approach is transparent to the rest of the system and easy to toggle
• Also works with games

Project Structure

• crates/cardwire-cli: User CLI to interact with the daemon
• crates/cardwire-core: Low-level GPU manager and IOMMU discovery
• crates/cardwire-daemon: System daemon managing state and D-Bus communication
• crates/cardwire-ebpf: BPF program and LSM hooks

Notes

• I'm still learning Rust, if some parts of the code are bad or unoptimized, feel free to open a PR

Credits

• Asus-linux Discord for helping me find the ebpf method
• Caelestia shell for the flake.nix, i used it as a reference

License

This project is licensed under the GNU General Public License v3.0 - see the LICENSE file for details.