Modular Kernel Packaging for Cloud

[Sandro "red" Mathys]

Heads-up: I've taken ownership over the Cloud SIG's planned
"Cloud-Friendly Kernel Packaging" (aka "Modular Kernel Packaging for
Cloud") Change [0].

(Sorry for cross-posting this on the kernel and cloud lists, but both
the kernel team and the cloud SIG need to be involved in this
discussion).

Obviously, we wish for modular kernel packaging and Josh Boyer already
reached out to the cloud SIG in this regard a while ago when we didn't
really know what we want yet [1]. We do now know that somewhat better
[2] but details could still require additional discussion. Our
motivation is to save space, time and bandwidth (the latter two
referring to required updates) as in the cloud, all three equal to
costs. And yes, we also target things other than the kernel to save
space.

So, in our case hardware drivers are rather unnecessary and the kernel
experts might know other ways to shrink the footprint for our limited
use cases. The kernel we require supports all primary architectures
(i686 and x86_64 right now, ARM likely later) and is able to run on a
hypervisor (primarily KVM and Xen but support for ESXi and Hyper-V are
becoming crucial in private clouds). Only. No bare-metal. We also
require support for Linux Containers (LXC) to enable the use of
Docker.

Now, I heard some people screaming when I said HW drivers are
unnecessary. Some people will want to make use of PCI passthrough and
while I think we don't want to ship the necessary modules by default,
they should be easily installable through a separate package. If some
more granularity is acceptable (and makes sense), I think one package
for SRIOV NICs, one for graphic cards (to enable mathematical
computation stuff) and one for everything else PCI passthrough (plus
one for all other HW drivers for the non-cloud products) would be
totally nice.

What does everybody think about this? Can it be done? How is it best
done? What's the timeframe (we'd really like to see this implemented
in F21 Beta but obviously the earlier modular kernels can be tested,
the better)? Do you require additional input?

Please try to keep the discussion as simple as possible (in terms of
us non-kernel hackers should be able to follow it). Just like Josh
requested when reaching out to us: "Explain it to me like I'm a
child."

Thanks,
Sandro

[0] https://fedoraproject.org/wiki/Cloud_Changelist#Change:_Cloud-Friendly_Kernel_Packaging
[1] https://lists.fedoraproject.org/pipermail/cloud/2013-October/002862.html
[2] https://fedoraproject.org/wiki/Cloud_PRD