Monthly Archives: September 2012

FreeBSD-XEN support: a quick status update

Xen has always supported a wide variety of operating systems as guests while the host-side has always been less bright. Infact, at the moment, most of the host choice is basically around Linux or NetBSD. Seemingly, a renewed interest into improving the FreeBSD support for XEN may drastically change the landscape by adding a further options for hosts. In the last few months, infact, a collaborative effort has been started in order to bring FreeBSD support for XEN to the state of the art and possibly to the same performance as Linux.

FreeBSD-CURRENT XEN support is pretty much the same since the last three years. More precisely, it is defined by the following set of cases (please note: for the reminder of the post, as FreeBSD nomenclature demands, i386 is 32-bit version of x86 architecture while amd64 is the 64-bit version):

  • No Dom0 support.
  • PV support, for i386: kernel support to run FreeBSD as a paravirtualized guest, including PV frontend drivers for blk and net. Specific only to i386 archiecture.
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XenSummit Report and Personal Highlights

Last week, has been a great week for our community. We had the Xen Developer Meeting, XenSummit and a presence at Linux Plumbers Conference, LinuxCon and CloudOpen. It has been a very busy week, and I apologize for not reporting back to you earlier. We have uploaded most XenSummit presentations to (the only ones missing are those the presenters have not sent me yet) and I started converting and uploading the first videos on It will take some time to edit and upload the videos, so please bear with us. Later, I will embed the presentations and videos into the agenda.

First I wanted to thank all speakers and attendees who helped make XenSummit a success. So far, we have had only had great feedback. The sessions were well attended and generally very interactive. The main criticism I have received was that there was too much good content and that some attendees could not see everything. That is a nice problem to have. Also I was approached by many attendees, that we should consider to hold next year’s summit in Europe. message received: I am looking at options at the moment.

As I have not been able to see all presentations, so I will cover some of my personal highlights. Before I go there though, I did want to point out the Xen 4.3 Roadmap presentation, the Xen and BSD Roadmap presentation, the PVOPS presentation and the XCP Update presentation. Generally I was very excited to see the level of innovation that is happening on Xen today: we have not seen so much innovation for some time.

Xen Paravirtualisation in HVM Containers

One of the innovations in Xen that has huge potential for Xen is the new PVH virtualization mode. Xen traditionally supports two virtualization modes: Paravirtualisation and Hardware Assisted Virtualization or HVM in Xen terminology. Both techniques have different trade-offs in terms of code complexity, maintainability and performance. HVM tends to have high performance overheads for I/O due to high CPU overheads when emulating I/O devices: these have been addressed in Xen through the PV-on-HVM mode (or PVHVM) and use of virtio drivers in KVM.

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Xen 4.2 Release

Just a quick update on the Xen 4.2 release. 4.2.0-rc3 was released on 23 August and we intend to release rc4 around the end of the week. Barring any last minute critical bug reports our intention is that rc4 will be the final release candidate.

  • 19 March — TODO list locked down
  • 2 April — Feature Freeze
  • 30 July — Xen 4.2.0-rc1
  • 8 August — Xen 4.2.0-rc2
  • 23 August — Xen 4.2.0-rc3
  • 6/7 September — Xen 4.2.0-rc4 PLANNED

Looking forward to 4.3 George Dunlap has announced that he intends to help coordinate the release. If you intend to work on a feature for the 4.3 release please let George know.