Author Archives: Lars Kurth

About Lars Kurth

Lars Kurth is a highly effective, passionate community manager with strong experience of working with open source communities (Symbian, Symbian DevCo, Eclipse, GNU) and currently is community manager for Lars has 9 years of experience building and leading engineering teams and a track record of executing several change programs impacting 1000 users. Lars has 16 years of industry experience in the tools and mobile sector working at ARM, Symbian Ltd, Symbian Foundation and Nokia. Lars has strong analytical, communication, influencing and presentation skills, good knowledge of marketing and product management and extensive background in C/C , Java and software development practices which he learned working as community manager, product manager, chief architect, engineering manager and software developer. If you want to know more, check out Personally, Lars has a wide range of interests such as literature, theatre, cinema, cooking and gardening. He is particularly fascinated by orchids and carnivorous plants and has built a rather large collection of plants from all over the world. His love for plants extends into a passion for travel, in particular to see plants grow in their native habitats.

Please Welcome new Members of the Xen Project Hypervisor Leadership Team

Evolution of Hypervisor Git Commits within the project. Note that in in the same time period, the number of individuals and organisations contributing to the project has nearly doubled.

Evolution of Hypervisor Git Commits within the project. Note that in parallel the number of individuals and organisations contributing to the project has nearly doubled.

The Xen Project has experienced incredible growth in our community (see diagram on the right) and simultaneously the Xen Project advisory board has funded a lot of great projects that help support the larger Xen Project ecosystem, for example MirageOS, a library operating system that constructs unikernels for secure, high-performance network applications across a variety of cloud computing and mobile platforms. These projects are extremely important to the expansion and betterment of virtualization and cloud computing infrastructure, but also demand more work to be done by committers and maintainers.

We understood that there was plenty of leadership among the community, but didn’t know the best way to promote contributors to maintainers and committer roles for leadership to the Hypervisor and its interface with Linux.

We decided to introduced a new convention, by which we actively reminded community members to nominate or self-nominate themselves for leadership roles. Often times, active developers simply worked on the project, but did not consider to nominate newcomers (or themselves) for these leadership roles within the project.

We also felt that running the entire nomination process in public, which may include public feedback on a nominee, could discourage people from recommending themselves or recommending others. So we decided to follow the approach that Debian uses for Technical Committee seats, where candidates are nominated in private. A group of the senior leadership for the Xen Project would then review the submissions and provide feedback and acceptance, making the overall process less intimidating.

As for committers and maintainers, we promoted several key Xen Project contributors to these distinguished roles based on previous experience and similar work they had already been performing, but didn’t have the authorship to own. This very important as it will ensure the group of maintainers that we currently have will have the support they need to accommodate for the Xen Project hypervisor.

Through taking the approach of consistent promotion and private forums, we have found some incredible new members to the Xen Project Hypervisor Leadership team that we want to introduce to you.

The following people have been elected to be new Committers to the project, they will be joining long-time committers Ian Campbell, Ian Jackson, Jan Beulich and Konrad Rzeszutek Wilk:

Andrew Cooper has been working on the Hypervisor since 2011 and has added a number of major new features such as Migration v2, significant change to trap handling, improvements to cpuid handling for guests and many more.

George Dunlap has been working on the Hypervisor since 2005 and was heavily involved in making the tracing system useable for performance analysis, optimising the shadow code, wrote the credit2 scheduler and developed many other significant features and improvements in the hypervisor. In addition, he was our first Release Manager and is leading the CentOS Virtualisation SIG within CentOS.

Stefano Stabellini has been working on the Hypervisor and the Linux Kernel since 2007 and was instrumental in bringing ARM support to the Xen Hypervisor. He has also been leading many other activities within the project, such as the creation of libxenlight, adding support upstream QEMU to Xen, Xen OpenStack integration and Raisin.

Wei Liu started to work on the Xen Project as a GSoC student in 2011 (working in virtio support). He has been working on libxl support, event channel scalability, MiniOS and many other major Xen features. In addition, he has been the Xen Project Release Manager since Xen Project 4.6 release.

Andrew and Wei celebrated their appointment at the Xen Project hackathon last month by submitting and ACKing a piece of code while on a punt on the river Cam in Cambridge, UK.

Security Team
In addition, Andrew Cooper and George Dunlap are now also members of the Xen Project Security Team, alongside Ian Jackson, Jan Beulich, Konrad Rzeszutek Wilk and Tim Deegan.

The following people were also recently added as MAINTAINERS of the project: Doug Goldstein (KConfig, Travis CI), Julien Grall (ARM support, device tree, …), Meng Xu (RTDS Scheduler) and Paul Durrant (x86 I/O emulation, x86 viridian enlightenments, …). In addition, we clarified some ambiguities around the maintainer role.

Linux Kernel Maintainers
Jürgen Gross who has been a Linux kernel and Xen developer since 2004, but has significantly increased his engagement within the community in the last two years, is now Linux Kernel maintainer for the Xen Hypervisor Interface alongside Boris Ostrovsky and David Vrabel. Other maintainers of Xen specific components in the Linux Kernel are Stefano Stabellini, Wei Lui, and Konrad Rzeszutek Wilk.

A couple of months ago two of our committers, Keir Fraser and Tim Deegan, formally stepped down in their roles as committers from the Hypervisor team. We want to thank Keir and Tim for the vast contributions to the project. We look forward to seeing what they work on next and, again, thank them for the success that they brought to the open source Xen hypervisor.

Xen Project Hackathon 16 : Event Report

We just wrapped another successful Xen Project Hackathon, which is an annual event, hosted by Xen Project member companies, typically at their corporate offices. This year’s event was hosted by ARM at their Cambridge HQ. 42 delegates descended on Cambridge from Aporeto, ARM, Assured Information Security, Automotive Electrical Systems, BAE Systems, Bromium, Citrix, GlobalLogic, OnApp, Onets, Oracle, StarLab, SUSE and Vates to attend. A big thank you (!) to ARM and in particular to Thomas Molgaard for organising the event and the social activities afterwards.

Here are a few images that helped capture the event:

Taking a breather and photo opp outside of ARM headquarters in Cambridge

Taking a breather and photo opp outside of ARM headquarters in Cambridge

Working on solving the mysteries of the world.

Working on solving the mysteries of the world

Continuing to work hard on solving the mysteries of the world

Continuing to work hard on solving the mysteries of the world

Xen Project Hackathons have evolved in format into a series of structured problem solving sessions that scale up to 50 people. We combine this with a more traditional hackathon approach where programmers (and others involved in software development) collaborate intensively on software projects.

This year’s event was particularly productive because all our core developers and the project’s leadership were present. We focused on a lot of topics, but two of our main themes this year evolved around security and community development. We’ll cover these topics in more detail and how they fit within our next release 4.7 and development going forward, but below is a little taste of some of the other themes of this year’s Hackathon sessions:

  • Security improvements: A trimmed down QEMU to reduce attack surface, de-privileging QEMU and the x86 emulator to reduce the impact of security vulnerabilities in those components, XSplice, KConfig support which allows to remove parts of Xen at compile time, run-time disablement of Xen features to reduce the attack surface, vulnerabilities, disaggregation and enabling XSM (Xen’s equivalent of the Linux Security Modules which are also known as SELinux) by default.
  • Security features: We had two sessions on the future of XSplice (first version to be released in Xen 4.7), which allows users of Xen to apply security fixes on a running Xen instance (aka no need to reboot).
  • Robustness: A session on restartable Dom0 and driver domains, which again will significantly reduce the overhead of applying security patches.
  • Community and code review: A couple of sessions on optimising our working practices: most notably some clarifications to the maintainer role and how we can make code reviews more efficient.
  • Virtualization Modes: The next stage of PVH, which combines the best of HVM and PV. We also had discussions around some functionality that is currently developed in Linux on which PVH has dependencies.
  • Making Development more Scalable: A number of sessions to improve the toolstack and libxl. We covered topics such as making storage support pluggable via a plug-in architecture, making it easier to develop new PV drivers to support automotive and embedded vendors, and improvements to our build system, testing, stub domains and xenstored.
  • ARM support: There were a number of planning sessions for Xen ARM support. We covered the future roadmap, how to implement PCI passthrough, and how we can improve testing for the increasing range of ARM HW with support for virtualization, also applicable outside the server space.

There were many more sessions covering performance, scalability and other topics. The session’s host(s) post meeting notes on xen-devel@ (search for Hackathon in the subject line), if you want to explore any topic in more detail. To make it easier for people who do not follow our development lists, we also posted links to Hackathon related xen-devel@ discussions on our wiki.

Besides providing an opportunity to meet face-to-face, build bridges and solve problems, we always make sure that we have social events. After all Hackathons should be fun and bring people together. This year we had a dinner in Cambridge and of course the obligatory punting trip, which is part of every Cambridge trip.

Embarking on the punting journey

Embarking on the punting journey

Continued exploration of discovering the mysteries of the universe, while on a boat

Continued exploration of discovering the mysteries of the universe, while on a boat

Again, a big thanks to ARM for hosting the event! Also, a reminder that we’ll be hosting our Xen Project Developer Summit next August in Toronto, Canada. This event will happen directly after LinuxCon North America and is a great opportunity to learn more about Xen Project development and what’s happening within the Linux Foundation ecosystem at large. CFPs are still open until May 6th!

Call For Participation for the Xen Project Developer Summit in Toronto


Now Accepting Submissions Through May 6

We’re excited to announce the call for speaking proposals for Xen Project Developer Summit 2016, which will be held in Toronto, Canada, August 25-26, 2016. The Xen Project Developer Summit brings together the Xen Project’s community of developers and power users for their annual developer conference. The summit will be co-located with a number of other events, including LinuxCon, ContainerCon, KVM Forum and Linux Security Summit.

To get a sense of past accepted submissions, check out last years presentations. Accepted speakers will be notified by May 27th. The schedule will be announced on June 3rd.

Birds of a Feather Sessions & Discussion Groups

This year, we will again have space for Birds of a Feather Sessions & Discussion Groups, which are in-depth interactive discussions that allow for collaboration between Xen Project developers and community members. We will publish how you can request a BoF closer to the event. In the meantime, here are the ground rules BoFs:

  • Each BoF host will get 3-5 minutes (depending on the number of BoFs on the day) to pitch your BoF to the entire audience. Slides are not allowed.
  • After we publish the Xen Project Developer schedule, community members that have registered for the summit can submit a request to host a BoF (specifying a couple of slots in preference order)
  • BoFs are small discussion groups, not presentations. You are expected to take notes (or nominate an attendee to do so) and post discussion notes on one of our mailing lists after the summit.

Developer Meeting

I am also pleased to announce that we will also be hosting a 1/2 day Xen Project Developer Meeting the day before the Xen Project Developer Summit (space is limited). The event is open to all members of the Developer Community. More details will follow soon.

Where to stay at the summit

Discounted hotels are listed at the event website at the price of CAD $209.00 per night. Reservations have to be made by July 29th. We are sharing a room block with other Linux Foundation events, so please book early.

Xen Project 4.4.4 Maintenance Release is Available

I am pleased to announce the release of Xen 4.4.4. Xen Project Maintenance releases are released in line with our Maintenance Release Policy. We recommend that all users of the 4.4 stable series update to this point release.

Xen 4.4.4 is available immediately from its git repository:;a=shortlog;h=refs/heads/stable-4.4
    (tag RELEASE-4.4.4)

or from the Xen Project download page at

This release contains many bug fixes and improvements. For a complete list of changes in this release, please check lists of changes on the download page.

Note that this is the last Xen Project coordinated release of the 4.4 stable series. The tree will be switched to security only maintenance mode after this release.

ARM hosts Xen Project Hackathon, April 18-19 in Cambridge, UK

I am pleased to announce the next Xen Project Hackathon. The Hackathon will be hosted by ARM in their Cambridge Headquarters from April 18 and 19. I wanted to thank Philippe Robin and Thomas Molgaard from ARM for hosting the Hackathon.

ARMARM designs technology that is at the heart of advanced digital products and has built a broad partner community that increasingly embraces an open source and collaborative development model to keep pace with transitions in the industry. Enabling developer collaboration on open source projects, like Xen, is key to help optimize support for system virtualization. ARM is pleased to host and support this event.

What to expect at a Xen Project Hackathon?

The aim of the Hackathon is to give developers the opportunity to meet face to face, to discuss development, coordinate, write code, and collaborate with other developers. And, of course, the event will allow everyone to meet in person and build relationships. To facilitate this, we will have a social event on the evening of the 18th. We will cover many hot topics such as the latest Xen Project Hypervisor 4.7 features, planning for the next Xen Project Hypervisor release, Cloud Integration, Cloud Operating Systems, Mirage OS as well as Xen Project in emerging segments such as embedded, mobile, automotive and NFV. But, at the end of the day, the community will chose the topics that are covered — more on our process here below.

To ensure that the event runs efficiently, we adhere to the following process: Each day is divided into several segments. We will have a number of work areas that are labelled with numbers (or other unique identifiers). Each morning starts with a plenary and scheduling session. Every attendee who cares about a topic can announce a topic, which we will map against a work area and time-slot. This makes it easy for other attendees to participate in projects and discussions they care about. We also encourage attendees to highlight projects they plan to share before the event by adding them to our wiki.

We will wrap up each day with another short plenary session: the aim of this session is to summarize what was done, show brief demos and make improvements to the process.

To give you a sense of the venue, we attached a few pictures of the venue:

ARM Cambridge Arm Cambridge Panorama ARM Cambridge Atrium

How to Register?

As spaces at the Xen Project Hackathon are limited, we are asking attendees to request an invitation. You will need to cover your own travel, accommodation and other costs such as evening meals, etc. We do have a very limited number of travel stipends available for individuals who cannot afford to travel. Please contact community dot manager at xenproject dot org if you need to make use of it.

Reports from Previous Hackathons

More Information

Xen Project Contributor Training v2

Two weeks ago, I embarked onto a road trip to China with the aim to meet Xen Project users as well as contributors. I visited a number of vendors in Hangzhou and Beijing on this trip. Part of the objective was to give training to new contributors and developers, and to strengthen existing relationships.

Hypervisor contributions from Chinese developers

Hypervisor contributions from Chinese developers

A year ago I travelled to China and pioneered our developer training, because many of our Chinese developers had some challenges working with the community. The good news is that the training activities have helped, which can be seen in contribution statistics. This leads us to the “bad news”: a new group of developers joined the community, who could benefit from training. In addition, a lot of process and operational changes are currently discussed or have recently taken place within our community.

What is remarkable, is that many of the latest contributors to the project have only recently graduated from University (in 2014 or 2015). Working with the Xen Project and Linux was often their first experience with open source. Working with open source projects is not always easy, in particular when doing so in a non-native language and with a manager behind you, who expects that you get a feature into an open source project by a certain time. In addition, as a community we need to balance the needs of different stake-holders (enterprise, cloud, embedded, security companies) and make informed decisions on the relative importance of new features vs. quality vs. security vs. … which has led to increasingly strict criteria and more and more scrutiny, when reviewing code contributions. This means, that contributing to the project for the first time can sometimes feel like a real challenge. Part of the reason why I regularly travel to China, is to explain what is happening in the community, to explain that all members of the community can influence and shape how the project is run and to understand local community issues and address them as they occur.

Contributor Training v2

Since the creation of the training material last autumn, there have been a few changes in how the project operates. Most notably in the Security Vulnerability Management Process and Release Management. Many other areas of how the project operates are also being reviewed and discussed. The goals behind these discussions and proposed changes intend …

  • to make the communities’ development processes more efficient and scalable.
  • to make conscious decisions about trade-offs, such ease of feature contribution vs. quality and security.
  • to make it easier for newcomers to join the project.
  • to encourage more contributors to review other people’s code, test our software, write test code and make other non-code contributions to the project.

Thus, I updated our training material to reflect these changes and added new material. It is divided into 4 separate modules, each of which takes approximately 2.5 hours to deliver. The training decks are designed as reference material for self-study. Each training module has many examples and embedded links in it. The material is available from our Developer Intro Portal as slides or as PDFs. I embedded the updated and new training modules into this blog for your convenience:

If you have any questions, feel free to ask by contacting me via community dot manager at xenproject dot org and I will improve the material based on feedback. My plan is to keep the training material up-to-date and to modify it as new questions and new challenges arise.