Tag Archives: hypervisor

Call for Proposals Open for the Xen Project Developer and Design Summit Happening in June!

Registration and the call for proposals are open for the Xen Project Developer and Design Summit 2018, which will be held in Nanjing Jiangning, China from June 20 – 22, 2018. The Xen Project Developer and Design Summit combines the formats of Xen Project Developer Summits with Xen Project Hackathons, and brings together the Xen Project’s community of developers and power users.

Submit a Talk

Do you have an interesting use case around Xen Project technology or best practices around the community? There’s a wide variety of topics we are looking for, including cloud, server virtualization, unikernels, automotive, security, embedded environments, network function virtualization (NFV), and more. You can find all the suggested topics for presentations and panels here (make sure you select the Topics tab).

Several formats are being accepted for speaking proposals, including:

  • Presentations and panels
  • Interactive design and problem solving sessions. These sessions can be submitted as part of the CFP, but we will reserve a number of design sessions to be allocated during the event.
    • Proposers of design sessions are expected to host and moderate design sessions following the format we have used at Xen Project Hackathons. If you have not participated in these in the past, check out past event reports from 2016, 2015 and 2013.

Never talked at a conference before? Don’t worry! We encourage new speakers to submit for our events!

Here are some dates to remember for submissions and in general:

  • CFP Close: April 13, 2018
  • CFP Notifications: April 30 – May 2, 2018
  • Schedule Announced: May 3, 2018
  • Event: June 20 – 22, 2018


Come join us for this event, and if you register by May 2, you’ll get an early bird discount of $125/ 800 Yuan Travel stipends are available for students or individuals that are not associated with a company. If you have any questions, please send a note to community.manager@xenproject.org.

Curious about last year’s event? Check out a few of our presentations last year here!

PV Calls: a new paravirtualized protocol for POSIX syscalls

Let’s take a step back and look at the current state of virtualization in the software industry. X86 hypervisors were built to run a few different operating systems on the same machine. Nowadays they are mostly used to execute several instances of the same OS (Linux), each running a single server application in isolation. Containers are a better fit for this use case, but they expose a very large attack surface. It is possible to reduce the attack surface, however it is a very difficult task, one that requires minute knowledge of the app running inside. At any scale it becomes a formidable challenge. The 15-year-old hypervisor technologies, principally designed for RHEL 5 and Windows XP, are more a workaround than a solution for this use case. We need to bring them to the present and take them into the future by modernizing their design.

The typical workload we need to support is a Linux server application which is packaged to be self contained, complying to the OCI Image Format or Docker Image Specification. The app comes with all required userspace dependencies, including its own libc. It makes syscalls to the Linux kernel to access resources and functionalities. This is the only interface we must support.

Many of these syscalls closely correspond to function calls which are part of the POSIX family of standards. They have well known parameters and return values. POSIX stands for “Portable Operating System Interface”: it defines an API available on all major Unixes today, including Linux. POSIX is large to begin with and Linux adds its own set of non-standard calls on top of it. As a result a Linux system has a very high number of exposed calls and, inescapably, also a high number of vulnerabilities. It is wise to restrict syscalls by default. Linux containers struggle with it, but hypervisors are very accomplished in this respect. After all hypervisors don’t need to have full POSIX compatibility. By paravirtualizing hardware interfaces, Xen provides powerful functionalities with a small attack surface. But PV devices are the wrong abstraction layer for Docker apps. They cause duplication of functionalities between the guest and the host. For example, the network stack is traversed twice, first in DomU then in Dom0. This is unnecessary. It is better to raise hypervisor abstractions by paravirtualizing a small set of syscalls directly.

PV Calls

It is far easier and more efficient to write paravirtualized drivers for syscalls than to emulate hardware because syscalls are at a higher level and made for software. I wrote a protocol specification called PV Calls to forward POSIX calls from DomU to Dom0. I also wrote a couple of prototype Linux drivers for it that work at the syscall level. The initial set of calls covers socket, connect, accept, listen, recvmsg, sendmsg and poll. The frontend driver forwards syscalls requests over a ring. The backend implements the syscalls, then returns success or failure to the caller. The protocol creates a new ring for each active socket. The ring size is configurable on a per socket basis. Receiving data is copied to the ring by the backend, while sending data is copied to the ring by the frontend. An event channel per ring is used to notify the other end of any activity. This tiny set of PV Calls is enough to provide networking capabilities to guests.

We are still running virtual machines, but mainly to restrict the vast majority of applications syscalls to a safe and isolated environment. The guest operating system kernel, which is provided by the infrastructure (it doesn’t come with the app), implements syscalls for the benefit of the server application. Xen gives us the means to exploit hardware virtualization extensions to create strong security boundaries around the application. Xen PV VMs enable this approach to work even when virtualization extensions are not available, such as on top of Amazon EC2 or Google Compute Engine instances.

This solution is as secure as Xen VMs but efficiently tailored for containers workloads. Early measurements show excellent performance. It also provides a couple of less obvious advantages. In Docker’s default networking model, containers’ communications appear to be made from the host IP address and containers’ listening ports are explicitly bound to the host. PV Calls are a perfect match for it: outgoing communications are made from the host IP address directly and listening ports are automatically bound to it. No additional configurations are required.

Another benefit is ease of monitoring. One of the key aspects of hardening Linux containers is keeping applications under constant observation with logging and monitoring. We should not ignore it even though Xen provides a safer environment by default. PV Calls forward networking calls made by the application to Dom0. In Dom0 we can trivially log them and detect misbehavior. More powerful (and expensive) monitoring techniques like memory introspection offer further opportunities for malware detection.

PV Calls are unobtrusive. No changes to Xen are required as the existing interfaces are enough. Changes to Linux are very limited as the drivers are self-contained. Moreover, PV Calls perform extremely well! Let’s take a look at a couple of iperf graphs (higher is better):

iperf client

iperf server

The first graph shows network bandwidth measured by running an iperf server in Dom0 and an iperf client inside the VM (or container in the case of Docker). PV Calls reach 75 gbit/sec with 4 threads, far better than netfront/netback.

The second graph shows network bandwidth measured by running an iperf server in the guest (or container in the case of Docker) and an iperf client in Dom0. In this scenario PV Calls reach 55 gbit/sec and outperform not just netfront/netback but even Docker.

The benchmarks have been run on an Intel Xeon D-1540 machine, with 8 cores (16 threads) and 32 GB of ram. Xen is 4.7.0-rc3 and Linux is 4.6-rc2. Dom0 and DomU have 4 vcpus each, pinned. DomU has 4 GB of ram.

For more information on PV Calls, read the full protocol specification on xen-devel. You are welcome to join us and participate in the review discussions. Contributions to the project are very appreciated!

Virtualization Mini Summit, July 22, 2008 at linuxsymposium 2008


linuxsymposium 2008, Ottawa, Canada, July 23 – July 26, 2008 http://www.linuxsymposium.org

The intent of the Virtualization MiniSummit is to provide a forum for attendees to explore all aspects of Linux virtualization. Whether that be the underlying technology, application of the technology in their environment or new tools for managing and doing interesting and new things with virtualized servers.

Attendees can range from those developing virtualization technologies, using virtualization, managing virtualized environments to wanting to learn more about virtualization.

A potential list of topics:

* Review and/or provide deep insight into the fundamentals of specific virtualization technologies
* Exploration of project development opportunities
* Discussion of ideas to improve virtualization technologies
* How virtualized environments can be made manageable
* What’s worked and what has not worked
* New and emerging ideas for virtualizing Linux systems


Presentation time slots will be on the order of 50 minutes and should include time for questions (10-15 minutes).

The proposal submission process requires that you submit a proposal and a personal biography that will be displayed on the Virtualization Mini Summit web site at: http://virtminisummit.linux.hp.com. Proposal submissions will be accepted until June 20, 2008. Early submitters will be given preferential consideration.

The proposal is your opportunity to show that your topic has merit and that you have the background to provide an excellent presentation at the virtualization Mini Summit.


# Maximum of 200 words
# Two paragraphs: The first should describe the topic you will be presenting in concise detail; The second should explain why your topic will be of interest to the attendees of the Virtualization Mini Summit.

# Maximum of 100 words
# Written in 3rd person
# One paragraph describing your professional work experience, and related projects you are currently or have been involved in.

Submission of a paper is not required, but would be greatly appreciated be the Virtualization Mini Summit attendees. Papers and/or Presentations must be submitted by July 16, 2008 so that they can be posted to the Virtualization Mini Summit in time for the event.

Accepted presenters will be provided instructions on submission of presentation, and paper upon notification.

Presentation Submissions

Please login to http://virtminiconf.linux.hp.com and submit to the Virtualization Mini Summit. Please create a login account via the “new user?” link located in the login box on the main page. Login and navigate to the “Call for Presentations” -> “Submit Here” folder. In the upper right drop-down menu “add to folder” your “file” or new “page” with your submittal (see the example template). In the same upper right menu bar, ensure that the content is the state of “private”, only the admin will have access to review the proposal. Please include the following information in your proposal:

Email Address (will be obscured in posting):
Title of Proposal:
Short Presentation Abstract: (200 words)
Short Biography: (100 words max.)

Submission Timeline:

  • Abstract submission deadline: Friday, June 20, 2008
  • Presentation acceptance notification before: Wednesday, June 27, 2008
  • Program schedule and abstracts posted: Wednesday, July 2, 2008
  • Paper/Presentation submission: Wednesday, July 16, 2008

Virtualization mini summit: Tuesday, July 22, 2008