Re: [Qemu-devel] [PATCH] qdev: Make "hotplugged" property read-only

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 29 Dec 2016 20:38:15 -0200
Eduardo Habkost <ehabkost@redhat.com> wrote:

> The "hotplugged" property is user visible, but it was never meant
> to be set by the user. There are probably multiple ways to break
> or crash device code by overriding the property. One example:
> 
>   $ qemu-system-x86_64 -cpu qemu64,hotplugged=true
>   Segmentation fault (core dumped)
> 
> The DeviceState::hotplugged struct field is set directly by
> device_initfn(), there's no need to provide a setter for the
> property.
this property is meant to be used for individual devices on target side
of migration.
Doing above is a rather big hammer with behavioral change of migrated
instance.

So I'd  fix crash caused by assumption that hotplugged CPU
guarantied to have rtc&fw_cfg available.
I'll post a patch with the fix.

> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
>  hw/core/qdev.c | 9 +--------
>  1 file changed, 1 insertion(+), 8 deletions(-)
> 
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 57834423b9..f5989c41cb 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -1013,13 +1013,6 @@ static bool device_get_hotplugged(Object *obj, Error **err)
>      return dev->hotplugged;
>  }
>  
> -static void device_set_hotplugged(Object *obj, bool value, Error **err)
> -{
> -    DeviceState *dev = DEVICE(obj);
> -
> -    dev->hotplugged = value;
> -}
> -
>  static void device_initfn(Object *obj)
>  {
>      DeviceState *dev = DEVICE(obj);
> @@ -1039,7 +1032,7 @@ static void device_initfn(Object *obj)
>      object_property_add_bool(obj, "hotpluggable",
>                               device_get_hotpluggable, NULL, NULL);
>      object_property_add_bool(obj, "hotplugged",
> -                             device_get_hotplugged, device_set_hotplugged,
> +                             device_get_hotplugged, NULL,
>                               &error_abort);
>  
>      class = object_get_class(OBJECT(dev));