Re: [Qemu-devel] [PATCH v2 1/4] qom: provide root container for internal objs

[Stefan Hajnoczi <stefanha@gmail.com>]

On Mon, Sep 25, 2017 at 11:34:58AM +0300, Manos Pitsidianakis wrote:
> On Mon, Sep 25, 2017 at 04:14:26PM +0800, Peter Xu wrote:
> > On Mon, Sep 25, 2017 at 09:14:21AM +0200, Andreas Färber wrote:
> > > Am 25.09.2017 um 08:37 schrieb Peter Xu:
> > > > We have object_get_objects_root() to keep user created objects, however
> > > > no place for objects that will be used internally.  Create such a
> > > > container for internal objects.
> > > >
> > > > CC: Andreas Färber <afaerber@suse.de>
> > > > CC: Markus Armbruster <armbru@redhat.com>
> > > > CC: Paolo Bonzini <pbonzini@redhat.com>
> > > > Suggested-by: Daniel P. Berrange <berrange@redhat.com>
> > > > Signed-off-by: Peter Xu <peterx@redhat.com>
> > > > ---
> > > >  include/qom/object.h | 10 ++++++++++
> > > >  qom/object.c         |  5 +++++
> > > >  2 files changed, 15 insertions(+)
> > > >
> > > > diff --git a/include/qom/object.h b/include/qom/object.h
> > > > index f3e5cff..f567052 100644
> > > > --- a/include/qom/object.h
> > > > +++ b/include/qom/object.h
> > > > @@ -1214,6 +1214,16 @@ Object *object_get_root(void);
> > > >  Object *object_get_objects_root(void);
> > > >
> > > >  /**
> > > > + * object_get_internal_root:
> > > > + *
> > > > + * Get the container object that holds internally used object
> > > > + * instances. This is the object at path "/internal-objects"
> > > > + *
> > > > + * Returns: the internal object container
> > > > + */
> > > > +Object *object_get_internal_root(void);
> > > > +
> > > > +/**
> > > >   * object_get_canonical_path_component:
> > > >   *
> > > >   * Returns: The final component in the object's canonical path.  The canonical
> > > > diff --git a/qom/object.c b/qom/object.c
> > > > index 3e18537..857cee7 100644
> > > > --- a/qom/object.c
> > > > +++ b/qom/object.c
> > > > @@ -1370,6 +1370,11 @@ Object *object_get_objects_root(void)
> > > >      return container_get(object_get_root(), "/objects");
> > > >  }
> > > >
> > > > +Object *object_get_internal_root(void)
> > > > +{
> > > > +    return container_get(object_get_root(), "/internal-objects");
> > > 
> > > Whatever you expose in the QOM tree is no longer internal. Other name?
> > 
> > Hi, Andreas,
> > 
> > If you mean "info qom-tree" here, can we still treat it as internal?
> > Since after all it's not exposed in QMP (while IMHO QMP is the
> > official protocol for QEMU clients).  And IIUC some HMP commands do
> > dump some internal structs for debugging purpose (like: "info
> > ramblock").
> > 
> > Or, do you have any suggestion?
> > 
> > (I did think about something like "hidden-objects", but I believe they
> > are not hidden as well if we think they are not internal...)
> > 
> > Thanks,
> > 
> > > 
> > > Regards,
> > > Andreas
> 
> If there's no need for internal IOThreads to be together with user created
> ones, a simple queue will be enough (include/qemu/queue.h).

Two solutions:

1. Manos' suggestion is Object->parent == NULL.  Simply don't add the
   Object to a parent.

2. Create an internal root that isn't accessible via QMP.
   Object *internal_root = object_new("container).

Stefan