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Date: Thu, 12 Jul 2018 15:04:20 -0300
From: Eduardo Habkost <ehabkost@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] hw/arm/bcm283x: Fix crash with device_add
 bcm2837 on unsupported machines
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, Thomas Huth <thuth@redhat.com>, qemu-arm@nongnu.org, qemu-devel@nongnu.org, Markus Armbruster <armbru@redhat.com>

On Thu, Jul 12, 2018 at 10:05:46AM +0200, Paolo Bonzini wrote:
> On 11/07/2018 22:23, Eduardo Habkost wrote:
> > On Wed, Jul 11, 2018 at 10:16:42PM +0200, Paolo Bonzini wrote:
> >> On 11/07/2018 20:30, Eduardo Habkost wrote:
> >>>> The theoretical behavior should be:
> >>> It's not clear below where you expect
> >>>   qdev_set_parent_bus(..., sysbus_get_default())
> >>> to be called (if it should be called at all).
> >>>
> >>> I don't know where it should be called, but I'm absolutely sure
> >>> instance_init is not the right place.
> >>
> >> I think instance_init is fine to call qdev_set_parent_bus on contained
> >> devices.  Why do you say it's not?
> > 
> > Because object_unref(object_new(...)) is not supposed to affect
> > QEMU global state at all.
> 
> It should not affect it.  Any changes to the global state done by
> instance_init are immediately undone when object_unref destroys the
> child properties of the object.

I would prefer if it didn't, but not a big deal as long as all
QOM code is protected by the BQL (it is, right?).

If we get rid of object_new() in qmp_device_list_properties(),
then most of the restrictions on instance_init can go away,
anyway.

-- 
Eduardo