[Qemu-devel] New kvm-related qemu patch queue

[Avi Kivity <avi@redhat.com>]

In order to improve qemu.git kvm integration quality wrt performance, 
features, and reliability Marcelo and I will begin to maintain a patch 
queue based on qemu.git containing kvm-related patches.  We will review 
and apply patches to this queue, test them using the same test suite 
that is used for qemu-kvm.git, and regularly submit them for inclusion 
in qemu.git, mimicking the relationship between kvm.git and Linus' 
linux-2.6.git.

One of the problems of qemu.git kvm support is that it is a clean 
reimplementation, and thus some of the nuances that were carefully 
ironed out in qemu-kvm.git are lost.  To that end, we would like to 
change the process of adding features as follows:

  - first, the feature in qemu-kvm.git master is morphed to a form 
suitable for merging into qemu.git
  - when that has been accomplished, the feature is broken into patches 
and merged into the patch queue

This process ensures that important details are not lost: the morphing 
step attempts to preserve all the nuances, and it is much easier to spot 
a behaviour change in a review than to spot a missing behaviour in a new 
feature.  This was successfully used to merge i386 and x86_64 arch 
support in Linux.

Some qemu-kvm.git features (primarily support for very old kernels) can 
be dropped, simplifying the convergence process.

Over time, qemu-kvm.git master will converge with qemu.git master and 
all that will remain is the patch queue.

Features in qemu-kvm.git not present in qemu.git include:
- smp support
- in-kernel irqchip
- in-kernel pit
- tpr patching
- device assignment
- kvm paravirtualization
- boot=on (extboot, or a real option rom)
- test suite
- ia64
- signalfd support

Many others are implemented differently in the two trees.

The patch queue will appear as a branch 'uq/master' (for 'upstream 
queue); if necessary branches for the stable series will also be created.

In order to get a kvm feature into qemu.git, please observe the 
following process:

- post a patch series against qemu-kvm.git/master that implements the 
feature, or changes an existing feature to use qemu.git infrastructure
- once that's merged, post a patch series against qemu-kvm.git/uq/master 
that brings the same code into qemu.git.

The new branch will be subject to the same automatic testing that 
qemu-kvm.git is.

Please post patches to both qemu-devel and kvm mailing lists.

This won't work for all features, so we'll have to feel our way and make 
decisions on a case by case basis.


-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.