Re: [PATCH v2] Add -build-info and -build-info-json CLI arguments

["Alex Bennée" <alex.bennee@linaro.org>]

Manos Pitsidianakis <manos.pitsidianakis@linaro.org> writes:

> Hello Daniel,
>
> On Tue, 24 Sept 2024 at 11:45, Daniel P. Berrangé <berrange@redhat.com> wrote:
>>
>> On Mon, Sep 23, 2024 at 10:09:32PM +0300, Manos Pitsidianakis wrote:
>> > Hello Daniel,
>> >
>> > On Mon, 23 Sep 2024 19:45, "Daniel P. Berrangé" <berrange@redhat.com> wrote:
>> > > On Mon, Sep 23, 2024 at 09:05:24AM +0300, Manos Pitsidianakis wrote:
<snip>
>> > > ie, look a query-audiodevs to discover what audio baxckends are
>> > > built-in, don't look for CONFIG_XXX settings related to audio.
>> > > If there are gaps in information we can query from QMP, we should
>> > > aim to close those gaps.
>> > >
>> > > IOW, I don't think we should expose this build info info in either
>> > > human readable or machine readable format.
>> >
>> > QAPI/QMP is not the perspective of this patch, this is for people who use
>> > custom-built (i.e. not from a distro) binaries and want to be able to
>> > identify how it was built. Launching a binary to query stuff is
>> > unnecessarily complex for this task, and the info is not generally
>> > interesting to the API consumers as you said.
>>
>> Launching QEMU to talk QMP is our defined public API for querying
>> anything about the capabilities of QEMU. We're worked hard to get
>> away from providing ad-hoc ways to query QEMU from the command
>> line and going back to that is not desirable. It may be slightly
>> more complicated, but not by very much.
>
> Again, this is not a "capabilities discovery" API. It lists the
> build-time configuration of the binary. Perhaps we can expose it in a
> different way so that people don't end up confused?

I think the problem is however much we might say it's not a capabilities
discovery API it's very existence encourages users to use it as one.

What about a script:

  qemu-get-build-info </path/to/qemu>

which would launch the binary and query it over QMP? Would that work?

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro