Best Quality and Quantity of Contributions in the New Xen Project 4.6 Release

I’m pleased to announce the release of Xen Project Hypervisor 4.6. This release focused on improving code quality, security hardening, enablement of security appliances, and release cycle predictability — this is the most punctual release we have ever had. We had a significant amount of contributions from cloud providers, software vendors, hardware vendors, academic researchers and individuals to help with this release. We continue to strive to make Xen Project Hypervisor the most secure open source hypervisor to match the security challenges in cloud computing, and for embedded and IoT use-cases. We are also continuing to improve upon the performance and scalability for our users, and aim to continuously bring many new features to our users in a timely manor.

Despite an increase of new features compared to previous releases, the Xen Project Hypervisor codebase has only increased by 6KLOC compared to Xen 4.5. In addition, we were able to increase the number of changesets that we integrated into Xen from 178/month (1812 in total) for Xen 4.5 to 259/month (2247 in total). In addition, the quality of Xen 4.6 was higher than in the past, enabling the CentOS 7 Virtualization SIG and XenServer to include Xen into their upcoming releases.

To make it easier to understand the major changes during this release cycle I have grouped the major updates into several categories:

  • Hypervisor
  • Toolstack
  • Xen Project Test Lab
  • Linux, FreeBSD and other OSes that utilise the new features
  • Greater Ecosystem

General Hypervisor Updates

  • The memory event subsystem has been reworked and extended to a new VM event subsystem. The new VM event subsystems supports both the ARM and x86 architectures. It can be used to intercept all sorts of VM events, such as memory access, register access and more. This enables security applications such as zero-footprint guest introspection, host-wide monitoring and many others. Have a look at Tamas’s presentations and Steve’s presentations on this topic to get more insights.
  • The Xen Security Modules (XSM) now have a default policy that is regularly tested in the Xen Project Test Lab to make sure it is not broken by mistake. This will enable us to switch on XSM by default in the future.
  • vTPM 2.0 support has been contributed by Intel and BitDefender [ 1 ]. To learn more about how to use vTPM and how it can make your host more secure, go to our wiki.
  • Grant table scalability has been improvement significantly by using finer-grained locks in grant tables. In some scenarios aggregate intrahost network throughput has been shown to improve by 100%. Other I/O drivers in Xen should potentially show significant performance improvements as well.
  • We introduced ticket lock to improve fairness, which provides better support of massive workloads from up to hundreds or thousands of VMs on a single host.
  • The unused SEDF scheduler has been removed from the hypervisor and toolstack. The Xen Project is committed to actively remove unused code to keep the code base small and to minimize security risks.
  • We removed Mini-OS from the Xen code base into its own tree. Mini-OS started as a demonstration OS, but received significant contributions in recent years (e.g. it is used by many Unikernels). We decide to treat it as a separately maintained independent project with it’s own mailing list and code tree to make it easier to consume. We hope this will help unikernel communities to more easily consume and contribute to Mini-OS, while reducing the Xen Project Hypervisor footprint.

x86-specific Hypervisor Updates

  • The Intel alternate P2M framework is a new capability for VM Introspection, Security and Privacy in Xen that gives Xen the ability to host up to 10 alternate guest to physical memory domains mappings for a specific guest-domain. It is one of the key technologies to enable zero-footprint VM introspection. It can also help Xen to implement faster NFV applications.
  • Intel Page Modification Logging Technology offloads the page dirty logging duty to hardware. Microbenchmark shows about 7% improvement in SPECJbb and should be particularly beneficial for Live Migration.
  • Intel Cache Allocation Technology allows system administrators to assign more L3 cache capacity to individual VMs, resulting in lower latency and higher performance for high-priority workloads such as NFV, real-time and video-on-demand applications.
  • Intel Memory Bandwidth Monitoring allows system administrators to identify memory bandwidth saturation on a Xen host that may be caused by several memory-intensive VMs running on the same host. Taking corrective actions, such as migrating VMs to a different Xen host, increases scalability and performance in the data center.
  • Intel Reserve Memory Region reporting provides a mechanism to report and reserve memory regions for legacy devices to allow for safe device passthrough.
  • Virtual Performance Monitoring Unit support makes it possible to profile the Xen Project Hypervisor with the Linux perf tool. Note that some work still needs to be completed within Linux to make perf fully functional.
  • Virtual NUMA for HVM guest is a continuation of the NUMA work performed in Xen 4.5 and previous releases. In this release, we exposed the functionality through the XL toolstack and added firmware changes to make the feature fully functional.

ARM-specific Hypervisor Updates

  • The supported number of VCPUs has been increased from 8 to 128 VCPUs on ARM64 platforms.
  • Passthrough for non-PCI devices allows users to passthrough devices via partial device trees. Full support for PCI device passthrough is currently being worked on.
  • ARM GICv2 on GICv3 support.
  • 32 bit userspace in 64 bit guest support.
  • OVMF for ARM contributed by Linaro.
  • 64K page ARM guest support.
  • Support for the following new Hardware Platforms has been added: Renesas R-Car Gen2, Thunder X, Huawei hip04-d04 and Xilinx ZynqMP SoC.

Toolstack Updates

  • Live Migration support in libxc / libxl and has been replaced with a completely new implementation (Migration v2). The new version respects different layers in the Xen Software stack and has been designed to be more robust and extensible to better support next-generation infrastructures and work planned in subsequent hypervisor releases.
  • Remus – our High Availability solution – has been reworked and is now based on Migration v2.
  • Libxl asynchronous operations can now be cancelled. This allows libxl users to cancel long-running asynchronous operations and benefits tool stacks such as libvirt and is beneficial for integration with cloud orchestration stacks.
  • Improved SPICE/QXL support.
  • AHCI disk controller support.
  • A new host I/O topology query interface gives upper layer in the software stack the ability to identify the I/O topology of underlying hardware platform.
  • Addition of Xenalyze, which is a tool for analyzing Hypervisor trace buffers and can be used for debugging and optimization, has been added to the Xen Project codebase as a maintained feature.

Xen Project Test Lab Updates

During the Xen 4.6 release cycle, the Xen Project created an Advisory Board funded Continuous Integration Test Lab. It currently has 24 hosts and is going to expanded in the future. This has led to significant improvements in Xen code quality and has allowed the project to expand automated test coverage. The number of test cases doubled during the 4.6 cycle. Some interesting new test cases that have been added are:

  • XSM
  • Stub Domain
  • VM migration using libvirt between two hosts is now tested.
  • Live Migration between hosts of different Xen versions is now tested and will help identify any breakage in our migration code or specification.
  • Test with different disk formats such as QCOW2, VHD and raw format.

More test cases are in the pipeline, including test case for OpenStack’s devstack, performance and scalability tests, FreeBSD Dom0 etc.

Linux, FreeBSD and other OSes

During the Xen 4.6 release cycle, we made significant improvements to major operating systems we rely on to improve interoperability. Some highlights on Linux kernel development spanning from Linux 3.18 to 4.3 were:

  • Xen blkfront multiqueue and multipage ring support.
  • Xen SCSI frontend and backend support.
  • VPMU kernel support.
  • Performance improvement in mmap call.
  • P2M in PV guest can address 512GB or more.

For FreeBSD there were these improvements:

  • Experimental PVH Dom0/DomU support.
  • Removal of classic i386 PV port by FreeBSD developer John Baldwin.
  • Blkfront indirect descriptor support by FreeBSD developer Colin Percival.
  • Removal of broken FreeBSD specific blkfront/back extensions.
  • ARM32 and ARM64 guest support are underway.

Greater Ecosystem

Summary

With dozens of major improvements, many more bug fixes and small improvements, efforts in other projects as well as a greater ecosystem, Xen 4.6 reflects a thriving community around the Xen Project Hypervisor. We are extremely proud of achieving the highest quality of the release while increasing development velocity. In particular, our latest security related features enable Xen to compete in the security appliance market and help answer some of the difficult questions regarding security in the cloud era.

We set out at the beginning of this release cycle to foster greater collaboration among vendors, individual developers, upstream maintainers, other projects and distributions. During this release cycle we continued to see an increasing influx of patches and newcomers. As the release manager, I would like to thank everyone for their contributions (either in the form of patches, bug reports or packaging efforts) to Xen. This release wouldn’t have happened without contributions from so many people around the world. Please check out our 4.6 contributor acknowledgement page.

The source can be located in the xen.git tree (tag RELEASE-4.6.0) or can be downloaded tarball from our website. More information can be found at


[ 1 ] Note that when this article was published, the contribution was mistakenly attributed to the US National Security Agency, instead of BitDefender.

Xen now available in CentOS 7 for ARM64 servers

A little more than a week ago at Linaro Connect SFO15 in Burlingame Jim Perrin of the CentOS project publicly announced the availability of the Xen hypervisor in CentOS 7 for ARM64 (also known as aarch64). Jim and I have been working closely with George Dunlap, maintainer of Xen in CentOS for the x86 architecture, to produce high quality Xen binaries for 64-bit ARM servers. As a result you can setup an ARM64 virtualization host with just a couple of yum commands.

CentOS 7 aarch64 is available here. Installation is trivial: download the live image, try it out, and write it to disk if you like it. You can easily extend the root partition and filesystem to match the size of your disk.

Once you have CentOS 7 up and running on your ARM64 server, you can install Xen and Libvirt with the following commands:

yum install centos-release-xen
yum update
yum install xen libvirt

If you are using AppliedMicro X-Gene, you need to add a Xen command line option to specify which serial to use. This is due to the firmware missing one piece of information. We are working with AppliedMicro to fix the issue as soon as possible. In the meantime you can edit /etc/default/grub and add the following to GRUB_CMDLINE_XEN_DEFAULT:

dtuart=/soc/serial@1c020000

recreate the grub config file:

grub2-mkconfig -o /boot/efi/EFI/centos/grub.cfg

Reboot and you’ll have Xen and Libvirt ready to use! Simple, right? :-)

If you want to try running a CentOS guest, just download the CentOS 7 live image, unpack it, and write a basic VM config file, using the Dom0 kernel and initramfs. For example:

kernel="/boot/vmlinuz-4.2.0-0.1.centos.el7.aarch64"
ramdisk="/boot/initramfs-4.2.0-0.1.centos.el7.aarch64.img"
memory=512
root="/dev/xvda4"
disk=[ "file:/path/to/CentOS-7-aarch64-rolling.img,xvda,w" ]
name = "centos7"
vcpus = 1
extra="console=hvc0"

Use xl to create the guest and connect to its console:

xl create -c config

Rinse and repeat as many times as you like, and you’ll have many little CentOS virtual machines keeping you company.

Xen 4.6 will be released shortly and you can count on us updating the Xen rpm in CentOS 7 shortly after. You’ll be able to install the latest and greatest Xen hypervisor release for ARM64 with a simple yum install.

At Linaro Connect I went further by showing ready to use OpenStack packages for CentOS 7 aarch64. Thanks to Anthony Perard, who produced those rpms, setting up Nova with Xen on ARM64 is just a matter of installing the packages and starting Nova services. Jim promised to have the OpenStack rpms online at centos.org in a couple of weeks. Stay tuned!

Xen Project Participates in Round 11 of Outreachy

This is a quick reminder that the Xen Project is again participating in Outreachy (Round 11). Please check the round 11 page for more information about the December 2015 to March 2015 round of interships.

Outreach Program for Women has been helping women (cis and trans), trans men, and genderqueer people get involved in free and open source software worldwide. Note that the program has been extended and now also targets people from more groups underrepresented in FOSS: specifically the program is open to residents and nationals of the United States of any gender who are Black/African American, Hispanic/Latin, American Indian, Alaska Native, Native Hawaiian, or Pacific Islander.

Round 11 of Outreachy

outreachy-poster-2015-December-March
The application deadline for interns is November 2, 2015. For a list of projects for interns and more information on how to apply, check our Xen Project Outreachy portal.

We have many different projects in many different areas! Check out the following table, which lists projects covering

  • Hypervisor Development (requiring Linux/BSD, C, scripting skills – there is also a Windows related project)
  • Mirage OS Development (requiring Linux/BSD, OCaml or Functional programming skills)
  • A Xen Code Review Dashboard project (requiring SQL, Javascript, HTML5 skills)

Learn about the Experience of past Applicants

At the 2014 Xen Project Developer Summit, we ran a panel discussion that included OPW interns, GSoC students as well as mentors.


You may also want to read Women interns rocking open source at Xen Project.

Looking forward to hear from you!

Xen Project Test Day for 4.6 RC4 Scheduled for October 1

Our Fourth (and Possibly Final) 4.6 Release Candidate to be Tested This Thursday

TestDayOur Xen Project Test Days help insure that upcoming releases are ready for production, beyond what our automated testing through our Test Lab can accomplish. It is particularly important that our users test out the upcoming release in their own environment. We rely on your functional testing of features, stress-testing, edge case testing, and performance testing to prove that the code is ready for consumption. And this is your opportunity to verify that the new code will continue to work well in your particular situation.

Xen Project 4.6 Release Candidate 4 Testing

Continuing our current release cycle, the Test Day for Xen Project 4.6 RC4 has been set for Thursday, October 1, 2015.

This may be the final RC before release, so the time to test the software is now!

Test Day Information

Additrional information about Test Days can be found here:

Join us on Tuesday in #xentest on Freenode IRC!
Test a Release Candidate! Help others, get help! And have fun!

Our Next Test Day is September 15: Xen Project 4.6 RC3

The Third 4.6 Release Candidate to be Tested on Tuesday

TestDayOur Xen Project Test Days help insure that upcoming releases are ready for production, beyond what our automated testing through our Test Lab can accomplish. It is particularly important that our users test out the upcoming release in their own environment. We rely on your functional testing of features, stress-testing, edge case testing, and performance testing to prove that the code is ready for consumption. And this is your opportunity to verify that the new code will continue to work well in your particular situation.

Xen Project 4.6 Release Candidate 3 Testing

Continuing our current release cycle, the Test Day for Xen Project 4.6 RC3 has been set for Tuesday, September 15, 2015.

Additional Test Days are expected to be scheduled roughly ever other week until Xen Project 4.6 is ready for release.

Test Day Information

Additrional information about Test Days can be found here:

Join us on Tuesday in #xentest on Freenode IRC!
Test a Release Candidate! Help others, get help! And have fun!
If you can’t make Tuesday, remember that Test and Issue Reports are welcome any time.

Xen Project 4.6 RC2 Test Day is September 1, 2015

Join 4.6 Release Candidate Testing on September 1, 2015

39833137_mAlthough the Xen Project performs automated testing through the project’s Test Lab, we also depend on manual testing of release candidates by our users. Our Test Days help insure that upcoming releases are ready for production. It is particularly important that our users test out the upcoming release in their own environment. In addition, functional testing of features (in particular those which can’t be automated), stress-testing, edge case testing and performance testing are important for a new release.

Xen 4.6 Release Candidate Testing

A few weeks ago, Xen 4.6 went into code freeze and Xen 4.6 RC2 is now ready for testing. With this in mind the Test Day for Xen 4.6 RC2 has been set for next Tuesday, September 1, 2015.

Subsequent Test Days are expected to be scheduled roughly ever other week until Xen 4.6 is ready for release.

Test Day Information

General Information about Test Days can be found here:

Join us on Tuesday in #xentest on Freenode IRC!
Test a Release Candidate! Help others, get help! And have fun!
If you can’t make Tuesday, remember that Test and Issue Reports are welcome any time.