[Xen-devel] Xen 4.2 Release Plan / TODO

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

Plan for a 4.2 release:
http://lists.xen.org/archives/html/xen-devel/2012-03/msg00793.html

The time line is as follows:

19 March        -- TODO list locked down
2 April         -- Feature Freeze
                                                       << WE ARE HERE
Mid/Late April  -- First release candidate
Weekly          -- RCN+1 until it is ready

The updated TODO list follows. Per the release plan a strong case will
now have to be made as to why new items should be added to the list,
especially as a blocker, rather than deferred to 4.3.

We have now entered Feature Freeze. Patches which have been posted
before or which address something on the list below are still acceptable
(for now, we will gradually be getting stricter about this), everything
else will be deferred until 4.3 by default.

Lots more DONE this week, still a few big ticket items or items with no
progress (that I've noticed) please let me know if the status of
anything has changed.

>From next week I think I will start also tracking bugs on these lists.
Please let me know if you have something which you feel should be listed
here, as well as your justification for it being a blocker rather than
"nice to fix".

hypervisor, blockers:
      * NONE?
 
tools, blockers:
      * libxl stable API -- we would like 4.2 to define a stable API
        which downstream's can start to rely on not changing. Aspects of
        this are:
              * Safe fork vs. fd handling hooks. Involves API changes
                (Ian J, patches posted)
              * locking/serialization, e.g., for domain creation. As of
                now,  nothing is provided for this purpose, and
                downstream toolstacks have to put their own mechanisms
                in place. E.g., xl uses a fcntl() lock around the whole
                process of domain creation. It should OTOH be libxl job
                to offer a proper set of hooks --placed at the proper
                spots during the domain creation process-- for the
                downstreams to fill with the proper callbacks. (Dario
                Faggioli)
                      * Thinking to defer this until 4.3?
              * agree & document compatibility guarantees + associated
                technical measures (Ian C, DONE)
      * xl compatibility with xm:
              * feature parity wrt driver domain support (George Dunlap,
                DONE)
              * xl support for "rtc_timeoffset" and "localtime" (Lin
                Ming, DONE)
      * More formally deprecate xm/xend. Manpage patches already in
        tree. Needs release noting and communication around -rc1 to
        remind people to test xl.
      * Domain 0 block attach & general hotplug when using qdisk backend
        (need to start qemu as necessary etc) (Stefano S, patches
        posted)
      * file:// backend performance. qemu-xen-tradition's qdisk is quite
        slow & blktap2 not available in upstream kernels. Need to
        consider our options:
              * qemu-xen's qdisk is thought to be well performing but
                qemu-xen is not yet the default. Complexity arising from
                splitting qemu-for-qdisk out from qemu-for-dm and
                running N qemu's.
              * potentially fully userspace blktap could be ready for
                4.2 (unlikely to be available in 4.2)
              * use /dev/loop+blkback. This requires loop driver AIO and
                O_DIRECT patches which are not (AFAIK) yet upstream.
              * Leverage XCP's blktap2 DKMS work. (Useful fallback for
                some usecases
        Stefano has done a lot of work here and has proposed some
        performance improvements for qdisk in both qemu-xen and
        qemu-xen-traditional which make them a plausible alternative for
        Xen 4.2. This is likely the route we will now take. Need to
        mention in release notes?
      * Improved Hotplug script support (Roger Pau Monné, patches
        posted)
      * Block script support -- follows on from hotplug script (Roger
        Pau Monné)

hypervisor, nice to have:
      * solid implementation of sharing/paging/mem-events (using work
        queues) (Tim Deegan, Olaf Herring et al -- patches posted)
              * "The last patch to use a waitqueue in
                __get_gfn_type_access() from Tim works.  However, there
                are a few users who call __get_gfn_type_access with the
                domain_lock held. This part needs to be addressed in
                some way."
      * Sharing support for AMD (Tim, Andres).
      * PoD performance improvements (George Dunlap)

tools, nice to have:
      * Configure/control paging via xl/libxl (Olaf Herring, lots of
        discussion around interface, general consensus reached on what
        it should look like. Olaf has let me know that he is probably
        not going to have time to do this for 4.2, will likely slip to
        4.3 unless someone else want to pick up that work)
      * Upstream qemu feature patches:
              * Upstream qemu PCI passthrough support (Anthony Perard,
                patches sent)
              * Upstream qemu save restore (Anthony Perard, Stefano
                Stabellini, qemu patches applied, waiting for libxl etc
                side which has been recently reposted)
      * Nested-virtualisation. Currently "experimental". Likely to
        release that way.
              * Nested SVM. Tested in a variety of configurations but
                still some issues with the most important use case (w7
                XP mode) [0]  (Christoph Egger)
              * Nested VMX. Needs nested EPT to be genuinely useful.
                Need more data on testedness etc (Intel)
      * Initial xl support for Remus (memory checkpoint, blackholing)
        (Shriram, patches reposted recently, was blocked behind qemu
        save restore patches which are now in)
      * xl compatibility with xm:
              * xl support for autospawning vncviewer (vncviewer=1 or
                otherwise) (Goncalo Gomes, patches posted)
              * support for vif "rate" parameter (Mathieu Gagné, patches
                posted)
              * expose PCI back "permissive" parameter (George Dunlap)

[0] http://lists.xen.org/archives/html/xen-devel/2012-03/msg00883.html


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