Google Summer of Code 2019

From QEMU

Introduction

QEMU is applying to Google Summer of Code 2019. This page contains our ideas list and information for students and mentors. Google Summer of Code is an open source internship program for university students offering 12-week, full-time, paid remote work from May to August!

Applicants: You are welcome to think about project ideas and familiarize yourself with QEMU, but please don't invest too much time at this early stage. Google will announce participating organizations on February 26.

Application Process

After contacting the mentor to discuss the project idea you should fill out the application form at [1]. The form asks for a problem description and outline of how you intend to implement a solution. You will need to do some background research (looking at source code, browsing relevant specifications, etc) in order to form an idea of how to tackle the project. The form asks for an initial 12-week project schedule which you should create by breaking down the project into tasks and estimating how long they will take. The schedule can be adjusted during the summer so don't worry about getting everything right ahead of time.

Candidates may be invited to an IRC interview with the mentor. The interview consists of a 30 minute C coding exercise, followed by technical discussion and a chance to ask questions you have about the project idea, QEMU, and GSoC. The coding exercise is designed to show fluency in C programming.

Here is a C coding exercise we have used in previous years when interviewing students: 2014 coding exercise

Try it and see if you are comfortable enough writing C. We cannot answer questions about the previous coding exercise but hopefully it should be self-explanatory.

If you find the exercise challenging, think about applying to other organizations where you have a stronger technical background and will be more competitive compared with other candidates.

Find Us

  • IRC (GSoC specific): #qemu-gsoc on irc.oftc.net
  • IRC (development):
    • QEMU: #qemu on irc.oftc.net
    • KVM: #kvm on chat.freenode.net

Please contact the mentor for the project idea you are interested in. IRC is usually the quickest way to get an answer.

For general questions about QEMU in GSoC, please contact the following people:

Project Ideas

This is the listing of suggested project ideas. Students are free to suggest their own projects, see #How to propose a custom project idea below.

I2C Passthrough

Summary: Implement I2C device passthrough on Linux hosts so that a single board computer like a Raspberry Pi can be used to develop applications for microcontrollers like the micro:bit.

QEMU emulates I2C devices in software but currently cannot pass through real I2C devices from the host to the guest. It would be useful to access real I2C devices from inside the guest, for example for developers writing and testing software under QEMU on their computer. This would be used like -device i2c-passthrough,device=/dev/i2c-N,hostaddr=0x48,address=0x49 (another possibility is to implement Linux I2C device support as a character device, like -chardev linux-i2c,address=0x48,device=/dev/i2c-N,id=i2c-chardev -device i2c-passthrough,chardev=i2c-chardev,address=0x49.

A very basic implementation of I2C passthrough can be very simple (150-200 lines of code perhaps) using the read/write interface to /dev/i2c-N. However, read/write is very limited and cannot drive all I2C devices because it does not support repeated start conditions. The current I2C API in QEMU is also very limited. Therefore there are many possible extensions:

  • implementing I2C passthrough as an SMBusDevice instead of I2CSlave. SMBusDevice provides a higher-level interface than I2CSlave, with support for repeated start conditions and block transfers. (Question: how would the SMBusDevice API translate to /dev/i2c-N ioctls)?
  • improving SMBusDevice support in QEMU: currently the SMBusDevice->I2CSlave adaptor in hw/i2c/smbus_slave.c only implements a subset of SMBus, in particular it can only read a single byte at a time from the device. Your task could be to improve the QEMU I2CBus API so that, at least for some I2C bus implementations, more functionality of SMBusDevice is accessible via I2CBus.
  • Currently I2C is entirely synchronous. It would be nice to support asynchronous communication between the I2C master and the chardev, where the i2c-passthrough can hold down the I2C clock until linux-i2c has data ready. On the emulation side, this would require clock stretching support in i2c-passthrough.

If you are interested in device emulation especially, you could also implement an I2C adapter from scratch (e.g. the micro:bit TWI controller emulation on the nRF51 system-on-chip) if there's time.

This project will allow you to learn about the I2C bus and how to write device emulation code in QEMU. You will enjoy it if you like working with physical hardware.

Links:

Details:

  • Skill level: advanced (the project is not very difficult, but it is larger than usual)
  • Language: C
  • Mentor: Paolo Bonzini <pbonzini@redhat.com> ("bonzini" on IRC), Stefan Hajnoczi <stefanha@redhat.com> ("stefanha" on IRC)
  • Special requirements: you should already own already a relatively powerful single board computer (for example a Raspberry Pi 3 or a Le Potato) and one or more I2C devices (for example real-time clocks, temperature sensors, Wii Nunchuks) and basic tools for connecting them such as a soldering iron and 0.1" jumper cables and header pins. It is important that you have these before the coding period begins; if you don't, take into account shipping and customs time, and/or talk to the mentors.

virtio-net oss-fuzz support

Status: Alexander Oleinik is working on this project for GSoC.

Summary: Integrate oss-fuzz into QEMU so that the virtio-blk device can be fuzz tested.

oss-fuzz offers a fuzz testing service to open source projects. This means random inputs are continuously tested against the program in order to find crashes and other bugs. Fuzz testing complements hand-written test suites by exploring the input space of a program and therefore the code paths that may be taken.

The goal of this project is to experiment with integrating oss-fuzz into the virtio-net device that Qemu emulates for guest networking. virtio-net-pci is a PCI device connected to the virtual machine's PCI bus and has a configuration space that can be programmed by the guest. The device itself is specified by the VIRTIO specification which describes the functionality of the device. Bugs could potentially exist at both the PCI and VIRTIO levels, so it's important to fuzz both of them. Care should be taken to pick a design that could be generalized for all virtio devices, eg. virtio-blk.

Fuzzing emulated devices involves accessing their hardware registers randomly to make the device respond. QEMU has a device testing interface called "qtest" that accepts read/write and other commands over a socket and is ideal for writing device-level tests. You may find that oss-fuzz works better integrated directly into the QEMU program instead of as a separate qtest program, so you can consider adding a new command-line option to QEMU for running in oss-fuzz mode.

This project involves learning about VIRTIO and PCI devices, as well as figuring out how to integrate oss-fuzz into QEMU so that it can effective explore the code paths in virtio-net device emulation code. You will enjoy this project if you want to learn how device emulation works and are interested in fuzzers.

The project will primarily be in three phases. The first phase involves understanding the ecosytsem - Qemu, qtest, oss-fuzz and llvm etc. The second phase involves utilizing the qtest framework or utilizing the functionality to integrate in Qemu to fuzz the virtio-net device registers. THe third phase will involve running our fuzzing framework, analyzing results and identifying bugs.

Links:

Details:

  • Skill level: intermediate
  • Language: C
  • Mentor: Bandan Das <bsd@redhat.com> ("bsd" on #qemu IRC), Paolo Bonzini <pbonzini@redhat.com> ("bonzini" on #qemu IRC), Stefan Hajnoczi <stefanha@redhat.com> ("stefanha" on #qemu IRC)

Project idea template

=== TITLE ===
 
 '''Summary:''' Short description of the project
 
 Detailed description of the project.
 
 '''Links:'''
 * Wiki links to relevant material
 * External links to mailing lists or web sites
 
 '''Details:'''
 * Skill level: beginner or intermediate or advanced
 * Language: C
 * Mentor: Email address and IRC nick
 * Suggested by: Person who suggested the idea

How to propose a custom project idea

Applicants are welcome to propose their own project ideas. The process is as follows:

  1. Email your project idea to qemu-devel@nongnu.org. CC Stefan Hajnoczi <stefanha@gmail.com> and regular QEMU contributors who you think might be interested in mentoring.
  2. If a mentor is willing to take on the project idea, work with them to fill out the "Project idea template" above and email Stefan Hajnoczi <stefanha@gmail.com>.
  3. Stefan will add the project idea to the wiki.

Note that other candidates can apply for newly added project ideas. This ensures that custom project ideas are fair and open.

How to get familiar with our software

See what people are developing and talking about on the mailing lists:

Grab the source code or browse it:

Build QEMU and run it: QEMU on Linux Hosts

Important links

Information for mentors

Mentors are responsible for keeping in touch with their student and assessing the student's progress. GSoC has a mid-term evaluation and a final evaluation where both the mentor and student assess each other.

The mentor typically gives advice, reviews the student's code, and has regular communication with the student to ensure progress is being made.

Being a mentor is a significant time commitment, plan for 5 hours per week. Make sure you can make this commitment because backing out during the summer will affect the student's experience.

The mentor chooses their student by reviewing student application forms and conducting IRC interviews with candidates. Depending on the number of candidates, this can be time-consuming in itself. Choosing the right student is critical so that both the mentor and the student can have a successful experience.

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