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[Xen-devel] Xen 4.2 Release Plan / TODO

  • To: xen-devel <xen-devel@xxxxxxxxxxxxx>
  • From: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
  • Date: Mon, 19 Mar 2012 10:57:25 +0000
  • Delivery-date: Mon, 19 Mar 2012 10:57:55 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>

So as discussed last week we now have a plan for a 4.2 release:

The time line is as follows:

19 March        -- TODO list locked down        << WE ARE HERE
2 April         -- Feature Freeze
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.

Things look pretty good on the hypervisor side of things.

The tools list is quite long but most stuff is known to be in progress
and in many cases preliminary patches are available. I think there is a
name next to everything.

I have gather various items under a top level "xl compatibility with xm"
heading under both blocker and nice-to-have. I expect this is the area
where most bugs will be reported once we hit -rc and users start testing
this stuff in anger.


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
              * agree & document compatibility guarantees + associated
                technical measures (Ian C)
      * xl compatibility with xm:
              * feature parity wrt driver domain support (George Dunlap)
              * xl support for "rtc_timeoffset" and "localtime" (Lin
                Ming, Patches posted)
      * 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)
      * 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
              * 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.
              * Other ideas?
      * Improved Hotplug script support (Roger Pau MonnÃ, patches
      * Block script support -- follows on from hotplug script (Roger
        Pau MonnÃ)

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)
      * Upstream qemu feature patches:
              * Upstream qemu PCI passthrough support (Anthony Perard,
                patches sent)
              * Upstream qemu save restore (Anthony Perard, Stefano
                Stabellini, patches sent, waiting for upstream ack)
      * 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 posted, blocked behind qemu save restore
      * xl compatibility with xm:
              * xl support for autospawning vncviewer (vncviewer=1 or
                otherwise) (Goncalo Gomes)
              * support for vif "rate" parameter (Mathieu GagnÃ)

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

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