Re: [Qemu-devel] [PATCH 0/2] Pointer properties and device_add

["Andreas Färber" <afaerber@suse.de>]

Am 01.12.2013 14:13, schrieb Marcel Apfelbaum:
> On Fri, 2013-11-29 at 10:43 +0100, armbru@redhat.com wrote:
>> From: Markus Armbruster <armbru@redhat.com>
>>
>> Pointer properties can be set only by code, not by device_add.  A
>> device with a pointer property can't work with device_add only unless
>> the property may remain null.  cannot_instantiate_with_device_add_yet
>> needs to be set then.  PATCH 1/2 sets it when needed and else
>> documents why not.  PATCH 2/2 documents this for future users of
>> pointer properties.
>>
>> This applies on top of my "[PATCH v4 00/10] Clean up and fix no_user"
>> series.
> 
> Even that I am not familiar with this code, I've checked all the changes
> and I agree with them.
> 
> Reviewed-by: Marcel Apfelbaum <marcel.a@redhat.com>
> 
> Anyway, I do have a question:
> Why not asserting on qdev_device_add if we have a pointer property?

When we do device_add / device-add, the guest is usually running and we
shouldn't kill a running guest just because the user is trying something
stupid that we can easily prevent. ;)

The alternative BTW is dropping all those pointer properties and
replacing them with link<> properties. Paolo tried that for the OMAP
timers once but I fear that series was never picked up...?

> Instead of checking only cannot_instantiate_with_device_add_yet,
> we can go over properties and if we have a pointer property, assert or
> return...

Raising an error for certain property types may be an option. Although
theoretically the existence of an incompatible property would not
necessarily indicate incompatibility to instantiate the device, in
practice I believe we don't have such excess properties.

Regards,
Andreas

> 
> Thanks,
> Marcel
> 
>>
>> Markus Armbruster (2):
>>   hw: cannot_instantiate_with_device_add_yet due to pointer props
>>   qdev: Document that pointer properties kill device_add
>>
>>  hw/audio/marvell_88w8618.c   |  2 ++
>>  hw/dma/sparc32_dma.c         |  2 ++
>>  hw/gpio/omap_gpio.c          |  4 ++++
>>  hw/i2c/omap_i2c.c            |  2 ++
>>  hw/i2c/smbus_eeprom.c        |  2 ++
>>  hw/intc/etraxfs_pic.c        |  4 ++++
>>  hw/intc/grlib_irqmp.c        |  2 ++
>>  hw/intc/omap_intc.c          |  4 ++++
>>  hw/net/etraxfs_eth.c         |  2 ++
>>  hw/net/lance.c               |  2 ++
>>  include/hw/qdev-properties.h | 17 +++++++++++++++++
>>  11 files changed, 43 insertions(+)
>>
> 
> 
> 


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