Re: [Qemu-devel] [PATCH] qdev: Fix bus dependency of DeviceState::hotpluggable getter

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, Mar 09, 2014 at 05:48:57PM +0100, Andreas Färber wrote:
> Am 09.03.2014 17:40, schrieb Michael S. Tsirkin:
> > On Fri, Mar 07, 2014 at 07:13:18PM +0100, Andreas Färber wrote:
> >> Commit 1a37eca107cece3ed454bae29eef0bd1fac4a244 (qdev: add
> >> "hotpluggable" property to Device) added a property "hotpluggable" to
> >> each device, with its getter accessing parent_bus->allow_hotplug.
> >>
> >> Add a NULL check.
> >>
> >> Cc: Igor Mammedov <imammedo@redhat.com>
> >> Signed-off-by: Andreas Färber <afaerber@suse.de>
> > 
> > Fair enough but I'm guessing we should
> > assume devices without a parent are not
> > hotpluggable, should we not?
> > 
> > Without a bus what handles hotplug?
> 
> The device has to, in its realize function.
> >> ---
> >>  hw/core/qdev.c | 3 ++-
> >>  1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> >> index 749c83a..cb07863 100644
> >> --- a/hw/core/qdev.c
> >> +++ b/hw/core/qdev.c
> >> @@ -735,7 +735,8 @@ static bool device_get_hotpluggable(Object *obj, Error **err)
> >>      DeviceClass *dc = DEVICE_GET_CLASS(obj);
> >>      DeviceState *dev = DEVICE(obj);
> >>  
> >> -    return dc->hotpluggable && dev->parent_bus->allow_hotplug;
> >> +    return dc->hotpluggable && (dev->parent_bus == NULL ||
> >> +                                dev->parent_bus->allow_hotplug);
> > 
> > So maybe this should be:
> >>     return dc->hotpluggable && dev->parent_bus &&
> >>                                dev->parent_bus->allow_hotplug;
> > 
> > ?
> 
> Hmm... that would render non-x86 CPUs non-hotpluggable. I guess we need
> to check dc->bus_type for a NULL value and if non-NULL use your variant
> and otherwise mine.
> I'll give it some more thought.
> 
> Thanks,
> Andreas

Or clear dc->hotpluggable if there's no parent bus
and we don't want to allow hotplug.

I'm beginning to think your patch is the right one
after all...

> 
> > 
> >>  }
> >>  
> >>  static void device_initfn(Object *obj)
> >> -- 
> >> 1.8.4.5
> 
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