[Fedora-xen] Goodbye Xen on RH/Fedora?

[Daniel P. Berrange]

On Wed, Jan 21, 2009 at 08:15:00AM +0000, Evan Lavelle wrote:
> It seems I've been a bit thick. It's been pretty obvious recently that 
> Xen isn't flavour of the month around here, but I assumed there were 
> good reasons for that. Now, rather belatedly, I've found
> 
> http://www.redhat.com/about/news/prarchive/2008/qumranet.html
> 
> In short, RedHat paid $107 million for Qumranet in September 2008. The 
> acquisition includes KVM.
> 
> I've got 2 years invested in Xen, on FC8, and I can't help feeling that 
> I've been shafted. Am I alone?

The acqusition of Qumranet has had absolutely *zero* impact on the 
availability Xen kernels in Fedora. The sole reason for not having Xen
support in Fedora 9/10 is that the Dom0 kernel is not yet merged upstream,
and this problem existed long long before Qumranet joined Red Hat.

When we first shipped Xen in Fedora Core 5 (or was it 4?) none of the Xen
code was merged into the mainline Linux kernel tree. For several releases
we spent a great deal of time forward porting Xen to newer kernels. When
we got to Fedora 9 the guest side was merged into the main kernel, but
the host side was not. Unfortunately the Xen host kernel was still on
2.6.18 while Fedora was on 2.6.24 and the kernel was just too old to work
with the userspace tools. We did not want to drop Xen Dom0 host from 
Fedora 9, but we had no viable options to continue with it in the short
term.

Since that time though, Jeremy Fitzhardinge has done alot of work on 
getting Dom0 patches in shape for merging in upstream Linux. It it still
hard to say just when these will be accepted upstream, but there is a
semi-reasonable we'll be able to turn Xen Dom0 back on in Fedora 11
kernels. 

While we (Red Hat) think KVM is a very compelling technology, as long as
Xen is open source, actively maintained upstream & in mainline Linux 
kernels, there's no reason why it shouldn't be available in Fedora. So 
once the Dom0 kernel is merged, Fedora users will be able to have a choice
between Xen and KVM for many future releases. We have also put effort into 
developing Xenner which  allows paravirt Xen guests to be run under KVM
without having to re-configure the guest kernel, giving people a potential
migration strategy if they need one. 

As for RHEL-5, that continues to support Xen, and will do for the entire
of its 7 year lifetime. If you don't want official Red Hat support, there
is also the option of using CentOS 5 as a Xen host which again will have
Xen support it in for whole of its 7 year lifetime. 

So while it is definitely unfortunate that we don't have a Xen Dom0 kernel
in Fedora 9/10, we are *not* trying to shaft anyone & will re-introduce
Xen Dom0 kernels to Fedora when they become available.

Regards,
Daniel
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