Re: [Qemu-devel] [PATCH v5] monitor: introduce query-command-line-options

[Eric Blake]

On 04/25/2013 09:48 AM, Osier Yang wrote:

>> First, some options like -drive, -net, -netdev and -device have an empty
>> QemuOptsList, meaning that option validation is not done upfront.
> 
> Not sure if there is work of libvirt which is blocked by -net, -netdev, and
> -device, but I have one which needs to probe the properties of -drive.
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=821045

That BZ is not public; but the gist of it talked about whether a future
RHEL should support Paolo's work on providing thin-provisioning options
as a parameter to -drive, and as far as I can see, that didn't land in
upstream 1.5.

I'm fairly certain that since we plan adding even more -drive
capabilities than just Paolo's provisioning options in the 1.6 timeframe
(such as a QMP setting of backing file parameters, including fd passing
of a backing file during hotplug/snapshot/drive-mirror...), that we are
safe in suspecting that distros will either rebase to 1.6, or take on
the burden of backporting the parts of 1.6 that make sense for the
features they want to support on whatever earlier qemu version they
branch from.  That means distros will be smart about backporting enough
to give libvirt enough to go on for using those features as part of the
distro's value-added premise.  (ie. if your BZ is about a feature that
doesn't land in 1.5, then you can assume that even if RHEL decides to
base on 1.5 instead of 1.6, there will be enough of 1.6 backported to
make use of your feature easy to probe for.  Of course, all bets are off
when guessing on a public list what Red Hat will actually use as their
baseline for a future RHEL release, or whether the BZ will even be
accepted - but then again, that's a problem for downstream to worry
about, and shouldn't affect what we put into 1.5 upstream).

And I just realized: this patch is queued to go into 1.5, and if I read
it correctly, then once applied, -drive will no longer be empty in
query-command-line-options output:
https://lists.gnu.org/archive/html/qemu-devel/2013-04/msg04810.html

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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