Re: [Qemu-devel] [PATCH 10/10] machine: Skip global registration for non-existing classes

[Marcel Apfelbaum]

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 <ehabk...@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);