Re: [PATCH 0/1] qom: fix setting of qdev array properties

["Daniel P. Berrangé" <berrange@redhat.com>]

On Fri, Sep 08, 2023 at 11:25:54AM +0200, Kevin Wolf wrote:
> Am 07.09.2023 um 11:35 hat Peter Maydell geschrieben:
> > On Thu, 7 Sept 2023 at 10:33, Markus Armbruster <armbru@redhat.com> wrote:
> > >
> > > Kevin Wolf <kwolf@redhat.com> writes:
> > >
> > > > Am 04.09.2023 um 18:25 hat Daniel P. Berrangé geschrieben:
> > > >> By the time of the 8.2.0 release, it will have been 2 years and 6
> > > >> releases since we accidentally broke setting of array properties
> > > >> for user creatable devices:
> > > >>
> > > >>   https://gitlab.com/qemu-project/qemu/-/issues/1090
> > > >
> > > > Oh, nice!
> > >
> > > Nice?  *Awesome*!
> > >
> > > > Well, maybe that sounds a bit wrong, but the syntax that was broken was
> > > > problematic and more of a hack,
> > >
> > > A monstrosity, in my opinion.  I tried to strangle it in the crib, but
> > > its guardians wouldn't let me.  Can dig up references for the morbidly
> > > curious.
> > 
> > I don't care about the syntax on the command line much (AFAIK that's
> > just the rocker device). But the actual feature is used more widely
> > within QEMU itself for devices created in C code, which is what it
> > was intended for. If you want to get rid of it you need to provide
> > an adequate replacement.
> 
> I have a patch to use QList (i.e. JSON lists) that seems to work for the
> rocker case. Now I need to find and update all of those internal
> callers. Should grepping for '"len-' find all instances that need to be
> changed or are you aware of other ways to access the feature?

IMHO we can just leave the internal only code callers unchanged. I was
about to send this patch to prevent usage leaking into user creatable
devices:

diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
index 357b8761b5..2d295411ef 100644
--- a/hw/core/qdev-properties.c
+++ b/hw/core/qdev-properties.c
@@ -584,6 +584,12 @@ static void set_prop_arraylen(Object *obj, Visitor *v, const char *name,
     void *eltptr;
     const char *arrayname;
     int i;
+    DeviceClass *devc = DEVICE_CLASS(object_get_class(obj));
+
+    if (devc->user_creatable) {
+        error_setg(errp, "array property not permitted for user creatable devices");
+        return;
+    }
 
     if (*alenptr) {
         error_setg(errp, "array size property %s may not be set more than once",



With regards,
Daniel
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