Mar
22
2009

Fedora 11 will likely not include Xen Dom0 (virtualization) support

xen logo

I (like many of you) have been patiently waiting since Fedora 8 for Dom0(Domain 0) Xen support in Fedora.  Why hasn’t Red Hat or the Fedora Project made an announcement? Haven’t we been good? I mean libvirtd is great and all, but Xen PV(paravirtualized) VM’s destroy. I did some googling to get to the bottom of this. I found a fedora project page with a January 2009 status update.

Here is a snipit:

“Currently, the Fedora kernel-xen package is based on forward-porting of the XenSource patches from 2.6.18 to more recent kernel versions. This has many problems, including:

  • XenSource code has no chance of being merged upstream, in the near future, making the forward-porting work needed for all new kernel versions.
  • Lots of porting work for each new kernel version
  • Because of the above, kernel-xen has been some releases behind the non-xen kernel package, and the lag between kernel and kernel-xen has been increasing constantly”

And also:

“As of November 2007, the kernel-xen forward-porting was being finished for 2.6.22, and Linux 2.6.24 was about to be released. The effort needed for 2.6.23, 2.6.24 and later would have been even bigger with the introduction of paravirt_ops and the i386-x86_64 merge upstream. Thus, the decision was made to abandon the forward-porting effort and focus on upstream paravirt_ops.”

So where does this leave us?  Unmodified guest are old news.  Even Microsoft can do that.  Well not really, as I understand it, Microsoft’s HyperV platform contains Xensource licensed code.  But a customer of the company I work for likes HyperV a lot(incidently).  On the Xen Wiki it says that Paravirt_ops will be ported to the 2.6.30 kernel.  My prediction, Xen Dom0 support will be available toward the end of Fedora 11’s cycle or Fedora 12.

Why does Dom0 matter?  Dom0 is the specially modifed Xen-linux kernel that sits on top of the hypervisor. From Dom0 you can run fully virtualized guest and partially virtualized guest (paravirtualization).  Paravirtualized guest enjoy a method for allowing the use of a set of generic virtual device drivers provided by Dom0.  PV guest are known to have outstanding perfomance compared to their fully virtualized counterpart.  Paravirt_ops refers to Dom0 integration with the Linux kernel.





2 Comments »

  • Hi,

    you might care or you might not, but I’ve seen the same situation for some time and over the last year have come to wonder if I shouldn’t switch all my Xen Hosts from CentOS to SUSE SLES, and even buy a full support contract to go.

    Personally I have always been annoyed by SUSE Linux’ odd automatisms, but there is some fact: If I want a current kernel, a current Xen Version, vendor driver support for 10ge nics or server hardware, a current OCFS2 version, Veritas VxVM and a dozen other stuffs I just end up there. SUSE is offering the features that I, as an end user *want*!

    Whereas RHEL/Fedora – which as RHCE and admin of a better 100 of RHEL systems feel home at, hasn’t brought me much more than:
    – libvirt (which basically does nothing more than *not* expose any Xen feature that doesn’t exist in KVM, so noone notices)
    – over 3 months fix time for bugs in pci delegation
    – the most dated Xen version you can find (ok, that part isn’t fedora-related, but quite invalidates the talk about porting lag)

    Comment | October 11, 2009
  • mattb

    Thank you for reading savelono.com. Novell is certainly trying hard on many fronts, but I myself prefer Fedora/RedHat. More because I’m used to it then on technical merits. Also, the last time I used YAST I was terribly unimpressed.

    You raise some very good points about libvirtd and virt-manager. Lack of USB 2.0 support really bothers me. It would be nice to have my Itunes and Iphone working on my Windows VM. However I’m not sure where the fault lies. Fedora uses the latest kernels and software. Kernels that the Xen team have been unable to get Dom0 running on. I hear that Dom0 support should be available in Fedora 12 – 2.6.30 kernel. Here’s to hoping.

    One other thing to note(off the subject), KVM Windows VM will not properly play Microsoft Silverlight DRM Netflix content. I have no idea why but virtual box does… although I found it helpful to turn off the Intel VMX processor extension.

    Comment | October 12, 2009

RSS feed for comments on this post. TrackBack URL

Leave a comment