Re: [PATCH v10] vfio: ABI for mdev display dma-buf operation

[Kirti Wankhede <kwankhede@nvidia.com>]

On 7/19/2017 11:55 AM, Gerd Hoffmann wrote:
> On Wed, 2017-07-19 at 00:16 +0000, Zhang, Tina wrote:
>>> -----Original Message-----
>>> From: Gerd Hoffmann [mailto:kraxel@redhat.com]
>>> Sent: Monday, July 17, 2017 7:03 PM
>>> To: Kirti Wankhede <kwankhede@nvidia.com>; Zhang, Tina
>>> <tina.zhang@intel.com>; Tian, Kevin <kevin.tian@intel.com>; linux-
>>> kernel@vger.kernel.org; intel-gfx@lists.freedesktop.org;
>>> alex.williamson@redhat.com; zhenyuw@linux.intel.com; chris@chris-
>>> wilson.co.uk; Lv, Zhiyuan <zhiyuan.lv@intel.com>; intel-gvt-
>>> dev@lists.freedesktop.org; Wang, Zhi A <zhi.a.wang@intel.com>
>>> Subject: Re: [PATCH v10] vfio: ABI for mdev display dma-buf
>>> operation
>>>
>>>   Hi,
>>>
>>>> No need of flag here. If vGPU driver is not loaded in the guest,
>>>> there
>>>> is no surface being managed by vGPU, in that case this size will
>>>> be
>>>> zero.
>>>
>>> Ok, we certainly have the same situation with intel.  When the
>>> guest driver is not
>>> loaded (yet) there is no valid surface.
>>>
>>> We should cleanly define what the ioctl should do in that case, so
>>> all drivers
>>> behave the same way.
>>>
>>> I'd suggest that all fields defining the surface (drm_format,
>>> width, height, stride,
>>> size) should be set to zero in that case.
>>
>> Yeah, it's reasonable. How about the return value? Currently, the
>> ioctl also returns "-ENODEV" in that situation.
> 
> I think it should not return an error.  Querying the plane parameters
> worked fine.
> 

Sounds good to me too.

Thanks,
Kirti