Original problem description by Greg Kurz:
> Since commit "9a4c0e220d8a hw/virtio-pci: fix virtio
> behaviour", passing -device virtio-blk-pci.disable-modern=off
> has no effect on 2.6 machine types because the internal
> virtio-pci.disable-modern=on compat property always prevail.
The same bug also affects other abstract type names mentioned on
compat_props by machine-types: apic-common, i386-cpu, pci-device,
powerpc64-cpu, s390-skeys, spapr-pci-host-bridge, usb-device,
virtio-pci, x86_64-cpu.
The right fix for this problem is to make sure compat_props and
-global options are always applied in the order they are
registered, instead of reordering them based on the type
hierarchy. But changing the ordering rules of -global is risky
and might break existing configurations, so we shouldn't do that
on a stable branch.
This is a temporary hack that will work around the bug when
registering compat_props properties: if we find an abstract class
on compat_props, register properties for all its non-abstract
subtypes instead. This will make sure -global won't be overridden
by compat_props, while keeping the existing ordering rules on
-global options.
Note that there's one case that won't be fixed by this hack:
"-global spapr-pci-vfio-host-bridge.<option>=<value>" won't be
able to override compat_props, because spapr-pci-host-bridge is
not an abstract class.
Signed-off-by: Eduardo Habkost <ehabk...@redhat.com>
---
Changes v1 (RFC) -> v2:
* New commit message
* Clarified comments
Suggested-by: Halil Pasic <pa...@linux.vnet.ibm.com>
* Moved variable declaration outside of loop
Suggested-by: Cornelia Huck <cornelia.h...@de.ibm.com>
---
hw/core/machine.c | 39 ++++++++++++++++++++++++++++++++++++---
1 file changed, 36 insertions(+), 3 deletions(-)
diff --git a/hw/core/machine.c b/hw/core/machine.c
index b0fd91f..213e8e0 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -554,11 +554,31 @@ static void machine_class_finalize(ObjectClass *klass,
void *data)
g_free(mc->name);
}
+static void register_compat_prop(const char *driver,
+ const char *property,
+ const char *value)
+{
+ GlobalProperty *p = g_new0(GlobalProperty, 1);
+ /* Machine compat_props must never cause errors: */
+ p->errp = &error_abort;
+ p->driver = driver;
+ p->property = property;
+ p->value = value;
+ qdev_prop_register_global(p);
+}
+
+static void machine_register_compat_for_subclass(ObjectClass *oc, void *opaque)
+{
+ GlobalProperty *p = opaque;
+ register_compat_prop(object_class_get_name(oc), p->property, p->value);
+}
+
void machine_register_compat_props(MachineState *machine)
{
MachineClass *mc = MACHINE_GET_CLASS(machine);
int i;
GlobalProperty *p;
+ ObjectClass *oc;
if (!mc->compat_props) {
return;
@@ -566,9 +586,22 @@ 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);
- /* Machine compat_props must never cause errors: */
- p->errp = &error_abort;
- qdev_prop_register_global(p);
+ oc = object_class_by_name(p->driver);
+ if (oc && object_class_is_abstract(oc)) {
+ /* temporary hack to make sure we do not override
+ * globals set explicitly on -global: if an abstract class
+ * is on compat_props, register globals for all its
+ * non-abstract subtypes instead.
+ *
+ * This doesn't solve the problem for cases where
+ * a non-abstract typename mentioned on compat_props
+ * has subclasses, like spapr-pci-host-bridge.
+ */
+ object_class_foreach(machine_register_compat_for_subclass,
+ p->driver, false, p);
+ } else {
+ register_compat_prop(p->driver, p->property, p->value);
+ }
}
}
--
2.7.4
