qemu-i2c-integration

Integration project for the work on the QEMU i2c chardev device. Motivated by work for OpenPRoT.

Overview

In the scope of the OpenPRoT project we needed a QEMU with an I2C device that can support an external application and also allow MCTP over I2C communication.

While the implementation in QEMU should be generic enough. The integration focuses on testing/developing this with MCTP via I2C in mind.

Usage

The project uses Task for build automation. Available tasks can be viewed with task --list.

Running a Test Cycle

To test the MCTP over I2C communication:

1. Start the echo server (host side):

   task test-echo

   This starts the host MCTP I2C echo server that listens on a Unix socket (vi2c_bus.sock).

2. Run QEMU (in another terminal):

   task run-qemu

   This starts QEMU with the AST2600 EVB configuration and connects to the echo server via the chardev.

3. Connect to the serial console (in another terminal):

   task run-serial

   This connects to the QEMU serial console.

4. Run the MCTP echo test inside QEMU:

   • Login as root (no password required)
   • Run the MCTP echo application:

     mctp-echo

Other Useful Tasks

• Connect to QEMU monitor:

  task run-monitor

• Run QEMU with debug tracing (chardev_i2c traces):

  task run-qemu-debug

• Rebuild custom packages (mctp-echo, mctp-init):

  task rebuild-packages

Submodules

This project uses the following submodules:

• QEMU: git@github.com:9elements/qemu.git (branch: groenke/wip/i2c_chardev)
• Buildroot: git@github.com:mynetz/buildroot.git (branch: feat/ast2600-nvme-mi)
• Host MCTP I2C Tools: Rust-based tools for testing MCTP over I2C (see host-mctp-i2c-tools/)

Contents

This repository contains these components:

• QEMU i2c chardev device implementation (via qemu submodule)
• A buildroot environment to run inside QEMU (target) for tests and development (via buildroot submodule)
• Tests and programs for the i2c chardev device for the host and target side
  • See br2-external for the buildroot external tree with custom packages
  • Host tools in host-mctp-i2c-tools/ (echo and initiator)
• Documentation and examples for using the i2c chardev device

Building

Prerequisites

• Task - Build automation tool
• Rust toolchain (for host MCTP I2C tools)
• Standard build tools (gcc, make, etc.)
• QEMU build dependencies

Build Steps

1. Initialize submodules:

   task init-submodules

2. Build QEMU:

   task build-qemu

   Builds qemu-system-arm with the I2C chardev device support.

3. Build Host MCTP I2C Tools:

   task build-host-mctp-i2c-tools

   Builds the echo and initiator binaries in host-mctp-i2c-tools/target/release/.

4. Build Buildroot:

   task build-buildroot

   Builds the Linux kernel, rootfs, and device tree for the AST2600 EVB target.

Note: Building QEMU and Buildroot can take 10-20 minutes on a fast machine. The buildroot build includes building a complete toolchain as the prebuild toolchain from Bootlin lacks the kernel headers required for MCTP tooling.

Clean Targets

• task clean-qemu - Clean QEMU build artifacts
• task clean-buildroot - Clean Buildroot build artifacts
• task clean - Clean all build artifacts

BR2_EXTERNAL Structure

The br2-external directory contains a Buildroot external tree with custom packages and configurations:

Packages

• mctp-echo: A simple test application that currently prints a hello world message. Will be
• extended to support MCTP over I2C testing.

Notes

• The dependency on the custom buildroot can probably be droppen, if the custom changes are moved to the external tree in this repository. Right now we re-use some previuosly done work for another project.
• The buildroot project does not check the hashes for the downloaded archives right now. something in the u-boot build triggered a wrong hash check and broke the build.
• The available mctp devices should look like this

  mctp l
  dev lo index 1 address 00:00:00:00:00:00 net 1 mtu 65536 up
  dev mctpi2c1 index 6 address 0x10 net 1 mtu 254 down
  dev mctpi2c2 index 7 address 0x20 net 1 mtu 254 down