Google Summer of Code 2016 wrap-up: QEMU

Monday, January 23, 2017

This post is part of a series of guest posts from students, mentors and organization administrators reflecting on Google Summer of Code (GSoC) 2016.

QEMU is a machine emulator and virtualizer. It can run operating systems and programs made for one machine (e.g. an ARM board) on a different machine (e.g. your own PC).  It is also used by hypervisors like KVM and Xen to virtualize x86, ARM, POWER and other architectures so virtual machines can run at near-native performance.

This year was QEMU's sixth time participating in Google Summer of Code and we had 6 students from around the world. Here are highlights from GSoC 2016:

Pranith Kumar worked on Multi-threaded TCG, a larger effort to make QEMU's just-in-time compiler multi-core friendly. He studied the memory ordering CPU instructions for many architectures supported by QEMU and devised a TCG opcode that can represent the memory ordering semantics. His patches allow TCG to correctly translate memory ordering instructions (previously they were ignored!). This is one piece of the puzzle to support multi-threaded translation and will help emulation scale to many cores. Pranith also contributed to testing and debugging multi-threaded TCG issues that he encountered while contributing to this cutting-edge part of QEMU.

Gerard Garcia worked on packet capture support for AF_VSOCK in Linux, tcpdump and Wireshark. QEMU recently gained support for the virtio-vsock device that allows socket communication between guest and host. The AF_VSOCK address family didn't support packet capture yet, making it hard to debug and observe communication between applications. Gerard’s patches implement the kernel interfaces and tcpdump/Wireshark functionality needed to monitor traffic over AF_VSOCK. This project was challenging because it required getting code merged in multiple open source projects. Gerard pulled it off with great skill!

Every year QEMU applies to participate in GSoC and we’re delighted for the opportunity to mentor students interested in systems programming, emulation, compilers and low-level code like firmware. You are welcome to get in touch on IRC or our mailing lists any time of the year to find out about contributing to QEMU. We also have a wiki page with small tasks you can get started on as your first step in QEMU programming.

By Stefan Hajnoczi, Organization Administrator for QEMU