[Spice-devel] [Qemu-devel] [PATCH] [RFC] LZ4 compression option for SPICE

[Markus Armbruster]

Fabio Fantoni <fantonifabio at tiscali.it> writes:

> Il 27/01/2015 09:26, Markus Armbruster ha scritto:
>> Eric Blake <eblake at redhat.com> writes:
>>
>>> On 01/26/2015 01:48 AM, Javier Celaya wrote:
>>>> Sorry, I forgot to patch the command-line help. Hope it helps.
>>>>
>>>>>> Recently, SPICE included the lz4 compression algorithm. This patch adds
>>>>>> a command line option to select it.
>>>>> How is libvirt going to introspect whether the command line supports
>>>>> this option?  Is there some QMP command that lists the set of valid
>>>>> compression formats understood by a given qemu binary?
>>> No, patching the command line --help does NOT help libvirt.  It needs to
>>> be discoverable via QMP to be introspectible, as scraping --help output
>>> is not machine-friendly.  (That said, you DO want to expose it in --help
>>> output; I'm just complaining that --help output alone is not enough).
>> We should really, really, really provide access to (the relevant subset
>> of) the QAPI schema over QMP!  Until we get that, useful progress is
>> delayed by problems like this one, and we keep growing special-purpose
>> solutions to problems like this one.
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>>
>>
>>
>
> Hi, any news about spice lz4 support still missed in qemu upstream?
>
> Thanks for any reply.

I'm committed to delivering QMP introspection in the next development
cycle.  That'll answer "does this version support X in QMP" questions,
which may in turn be a usable indicator for "does it support X' on the
command line", at least for some X.

If the SPICE LZ4 feature is such an X, the patch can then go in without
further work.