Re: [PATCH v2 2/2] qapi: deprecate implicit filters

[Peter Krempa <pkrempa@redhat.com>]

On Fri, Nov 08, 2019 at 13:56:03 +0000, Vladimir Sementsov-Ogievskiy wrote:
> 08.11.2019 16:27, Peter Krempa wrote:
> > On Fri, Nov 08, 2019 at 13:16:55 +0300, Vladimir Sementsov-Ogievskiy wrote:

[...]

> > Note that 'block-commit' and 'drive-mirror' commands are used by libvirt
> > in the pre-blockdev era. In those instances we gather statistics of
> > block devices by nesting in the output of query-blockstats and
> > query-block rather than selecting the appropriate info by any other
> > means (e.g. by node name).
> > 
> > This means that the output MUST stay consistend when block jobs are used
> > and the hack this patch is deprcating will break those.
> > 
> > Note that in libvirt we don't plan to invest time to add workarounds for
> > non-blockdev cases since blockdev by itself is complex enough and I'd
> > strongly prefer not having a third code path to care about.
> > 
> > Given that -blockdev can't be used in all cases (e.g. for sd-cards)
> > which also blocks deprecation of -drive I don't think that hiding of
> > implicit filter nodes can be deprecated until -drive is deprecated.
> > 
> 
> 
> OK, so, we can't deprecate anything around it now.
> 
> What is the problem with sd-cards?

So the problem was that it was impossible to instantiate it via -device,
but looking at the qemu code base this doesn't seem to be true any more.

I'll have a look whether we can rework the instantiation of sd card
frontends in libvirt somehow or whether it actually ever worked.
Unfortunately the documentation seems to be rather sparse.