Re: [Qemu-devel] [PATCH 2/2] Add file-posix-dynamic-auto-read-only feature

[Kevin Wolf]

Am 28.03.2019 um 19:45 hat Eric Blake geschrieben:
> On 3/28/19 1:28 PM, Kevin Wolf wrote:
> > auto-read-only=on changed its behaviour in file-posix for the 4.0
> > release. This change cannot be detected through the usual mechanisms
> > like schema introspection. Add a new feature to query-qemu-features to
> > allow libvirt to detect the presence of the new behaviour.
> 
> Oddly enough, introspecting the schema is sufficient to learn about this
> particular feature (that is, until we actually have a runtime feature
> that requires us to run the command, merely seeing what features the
> command supports is useful on its own). But that doesn't change the fact
> that we should keep things as a command.

Yes, I thought the same. But without the command, the type would
disapear from query-qmp-schema, so it has to be there either way.

I think, however, that libvirt should actually run the command, not only
test for its presence. Maybe we end up with some case where a new
version can't provide the feature unconditionally for some reason, and
then we want to be able to turn a static feature into a runtime one.

Kevin

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