[fedora-virt] [Fedora-xen] Dom0 xen support in Fedora 15?

W. Michael Petullo mike at flyn.org
Mon Nov 8 03:25:39 UTC 2010

> I am trying to work out whether it is practical to propose Dom0 xen 
> support as a feature for Fedora 15.
> The kernel situation is that Domain 0 has been accepted upstream for 
> 2.6.37. Assuming a 3 month kernel release cycle, F15 will most likely ship 
> with a 2.6.37.x kernel, with 2.6.38 coming out either after the F15 
> release or just before but too late to be included. If the plan to get key 
> xen drivers into 2.6.38 succeeds, then F15 may be become usable as a 
> Domain 0 system at some point during its lifetime as the kernel package in 
> a Fedora version typically has one major update.
> If the kernel team accept backported patches then it might just be 
> possible to ship F15 with usable Domain 0 support but the timescale for 
> that would be very tight.
> The other thing we would need to consider is what needs to be done to make 
> xen friendly enough to be usable by an ordinary user. The page 
> https://fedoraproject.org/wiki/Features/XenPvopsDom0 contains plans from 
> when dom0 xen support was expected to make a quick return to Fedora, but 
> they are a couple of years old now so probably need updating.
> I think as a minimum we would need a way to add a dom0 enabled grub entry 
> for a kernel, rather than requiring the user to hand edit the grub file. 
> We should also make sure that xen works with the other Fedora 
> virtualisation tools.
> What do others think about this? For example is it achievable as a 
> feature, is it too early and better to wait for F16, and what else should 
> we aim to do to make xen usable in Fedora?

My personal opinion is that we should make an aggressive attempt to get
Domain 0 in Fedora 15. As Michael Young points out, there is presently
some uncertainty as to when the Xen drivers will be upstream. They may
make the 2.6.37 series and therefore Fedora 15 or they may
not. Regardless, we will have to touch a lot of subsystems (e.g. grubby,
Red Hat Bugzilla #640486), so it makes sense to start early.

If the Xen drivers don't make Fedora 15, then little is lost. We can
continue to test the Domain 0 kernel (without Domain U) and work on the
supporting infrastructure. It would be useful for our effort to have a
working Domain 0, grubby, etc in Fedora 15 even if other features do
not make it. In the worst case, we may delay the announcement of the
Domain 0 feature to Fedora 16, but can include all progress completed
in Fedora 15. There is no shame in a delayed feature -- this happened
to systemd during the preparation for Fedora 14.



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