Xen 4.2 TODO / Release Plan

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Xen 4.2 TODO / Release Plan

Ian Campbell-10
Plan for a 4.2 release:

The time line is as follows:

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

A lot of new DONE and one of the bigger items (IanJ's async
bootloader/create/fork series) is now in. The remaining big items are
the hotplug script series and asynchronisation of migration.

We have made a freeze exception for George's "pciback autobind" patch to
xl, since it is self contained. Likewise Bastian's suggestion to rename
xs.h -> xenstore.h (since the old name is too short and now conflicts
with another project) has been accepted (with compat symlinks) for 4.2
in order to get the transition under way ASAP.

Other than that I think we should consider the freeze to be in full
effect and the bar to entry to 4.2 to be very high.

hypervisor, blockers:
      * Performance regression due to contention on p2m lock. Patches
        posted, reviewed, updated, to go in shortly (Tim, Andres)
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, I think this was actually DONE a while back and
                I missed it)
              * libxl_wait_for_free_memory/libxl_wait_for_memory_target.
                Interface needs an overhaul, related to
                locking/serialization over domain create (deferred to
                4.3). IanJ to add note about this interface being
                substandard but otherwise defer to 4.3.
              * libxl_*_path. Majority made internal, only configdir and
                lockdir remain public (used by xl). Good enough?
              * Interfaces which may need to be async:
                      * libxl_domain_suspend. Probably need to move
                        xc_domain_save into a separate process, as per
                        <[hidden email]>. Likely need to do the same for xc_domain_restore too. (IanJ).
                      * libxl_domain_create_{new,restore} -- IanJ has
                        patches as part of event series, (DONE).
                      * libxl_domain_core_dump. Can take a dummy ao_how
                        and remain synchronous internally. (IanC, DONE)
                      * libxl_device_{disk,nic,vkb,add,pci}_add (and
                        remove?). Roger Pau Monné fixes disk as part of
                        hotplug script series and adds infrastructure
                        which should make the others trivial. (Roger,
                      * libxl_cdrom_insert. Should be easy once
                        disk_{add,remove} done, IanJ to look at (or
                        doing so?).
                      * libxl_device_disk_local_{attach,detach}. Become
                        internal as part of Stefano's domain 0 disk
                        attach series (patches posted, another round
                      * libxl_fork -- IanJ's event series will remove
                        all users of this. (DONE)
      * [BUG] Manually ballooning dom0.  xl mem-set 0 [foo] fails with
        "libxl: error: libxl.c:2569:libxl_set_memory_target: cannot get
        memory info from /local/domain/0/memory/static-max: No such file
        or directory". This might be suitable for an enthusiastic
        on-looker. (Seems to have been fixed, DONE)
      * xl compatibility with xm:
              * [BUG] cannot create an empty CD-ROM driver on HVM guest,
                reported by Fabio Fantoni in
                <[hidden email]>
              * [BUG] Spurious CPU params error message when starting a
                domain, e.g. "Cpu weight out of range, valid values are
                within range from 1 to 65535". ("George will do it if no
                one else steps up")
              * does not automatically try to select a (set of) node(s)
                on which to create a VM and pin its vcpus there. (Dario
                Faggioli, 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.
      * xl to refuse to run if xend is running, Roger Pau Monné (patch
        posted, needs rebase)
      * Domain 0 block attach & general hotplug when using qdisk backend
        (need to start qemu as necessary etc) (Stefano S, patches
        posted, needs updates)
      * Improved Hotplug script support (Roger Pau Monné, patches
      * Block script support -- follows on from hotplug script (Roger
        Pau Monné)
      * xs.h -> xenstore.h. Should do this for 4.2 rather than have
        distros carry their own patches. (Ian C, patch posted)

hypervisor, nice to have:
      * PoD performance improvements (George Dunlap)

tools, nice to have:
      * Upstream qemu feature patches:
              * Upstream qemu PCI passthrough support (Anthony Perard,
                awaiting qemy upstream review)
                      * Upstream qemu is frozen for their next release.
                        Unlikely that these will be accepted in the next
                        few weeks. Given that upstream qemu is not yet
                        the default I think it is acceptable to defer
                        PCI passthrough support to 4.3.
              * Upstream qemu save restore (Anthony Perard, Stefano
                Stabellini, qemu patches applied, libxl patches applied.
      * Initial xl support for Remus (memory checkpoint, blackholing)
        (Shriram, was waiting on libxl side of qemu upstream
        save/restore, now unblocked)
      * xl compatibility with xm:
              * xl support for autospawning vncviewer (vncviewer=1 or
                otherwise) (Goncalo Gomes, new version of patch posted
      * Directory usage in libxl (Bastian, as part of Debian packaging,
        likely to defer to 4.3 unless there is some big problem with
        packaging deviating from upstream)
              * dumps in /var/xen: wtf?
                      * Bastian: "The FHS defines /var/crash for system
                        crash dumps, but it is not used everywhere. So I
                        would use /var/lib/xen/dump or so."
              * user data files in /var/lib/xen:
                      * What are the guarantees given for this files?
                      * Bastian: "I don't think rebooting the control
                        domain without rebooting Xen will work right
                        now. So /var/run is the correct location."
              * /var/run/libxl for temporary files
                      * "$TMPDIR or the fallback /tmp is the correct
      * xl commands to help rebind pci devices to pciback.

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

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Re: Xen 4.2 TODO / Release Plan

Jan Beulich-2
>>> On 14.05.12 at 12:26, Ian Campbell <[hidden email]> wrote:
> tools, blockers:

Adjustments needed for qdisk backend to work on non-pvops Linux.

> hypervisor, nice to have:

IRQ problem for which debugging code got added by c/s
24707:96987c324a4f. I have a tentative adjustment to this which I
would hope to at least eliminate the bad consequences of crashing
the hypervisor (converting the unsolicited PIC-originated IRQ into
a spurious one). I'll submit as soon as I got to test this a little,
particularly also on an old box without APIC.


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Re: Xen 4.2 TODO / Release Plan

Dario Faggioli
In reply to this post by Ian Campbell-10
On Mon, 2012-05-14 at 11:26 +0100, Ian Campbell wrote:
>       * xl compatibility with xm:
 * `cpus=[2,3]` to select specific mapping vcpu0-->pcpu2, vcpu1-->pcpu3
    as xm does. (Dario Faggioli, patches posted and reviewed, will


<<This happens because I choose it to happen!>> (Raistlin Majere)
Dario Faggioli, Ph.D, http://retis.sssup.it/people/faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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