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From: Marcel Apfelbaum <marcel@redhat.com>
Message-ID: <5766CAB9.9000608@redhat.com>
Date: Sun, 19 Jun 2016 19:39:21 +0300
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Subject: Re: [Qemu-devel] [PATCH 10/10] machine: Skip global registration
 for non-existing classes
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To: Eduardo Habkost <ehabkost@redhat.com>, qemu-devel@nongnu.org, Markus Armbruster <armbru@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, Igor Mammedov <imammedo@redhat.com>

On 06/15/2016 11:32 PM, Eduardo Habkost wrote:
> MachineClass::compat_props may point to class names that are not
> compiled into the QEMU binary. Skip registering those as global
> properties. This will allow the qdev global property code to
> implement stricter checks on the global property values in the
> future.
>
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
>   hw/core/machine.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index d6f6be4..51697cb 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -583,6 +583,7 @@ static void machine_class_finalize(ObjectClass *klass, void *data)
>   void machine_register_compat_props(MachineState *machine)
>   {
>       MachineClass *mc = MACHINE_GET_CLASS(machine);
> +    ObjectClass *oc;
>       int i;
>       GlobalProperty *p;
>
> @@ -592,6 +593,14 @@ void machine_register_compat_props(MachineState *machine)
>
>       for (i = 0; i < mc->compat_props->len; i++) {
>           p = g_array_index(mc->compat_props, GlobalProperty *, i);

Hi Eduardo,

> +
> +        /* Skip registering globals for non-existing device classes */
> +        oc = object_class_by_name(p->driver);

This I understand. It ensure a corresponding class is in QEMU binary.
But even so, if such property is not available should we silently continue?
Maybe the user things the property is set...


> +        oc = object_class_dynamic_cast(oc, TYPE_DEVICE);

This I don't understand. Do we check here?

Thanks,
Marcel

> +        if (!oc) {
> +            continue;
> +        }
> +
>           /* Machine compat_props must never cause errors: */
>           p->errp = &error_abort;
>           qdev_prop_register_global(p);
>