linux-kernel - Re: [PATCH v4 9/9] drm/vkms: convert to use faux

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Message-ID: <fa5f9e9c-09f6-4f92-8f6d-4e057f9fc5a9@suse.de>
Date: Fri, 13 Jun 2025 10:15:05 +0200
From: Thomas Zimmermann <tzimmermann@...e.de>
To: José Expósito <jose.exposito89@...il.com>,
 Simona Vetter <simona.vetter@...ll.ch>
Cc: Greg KH <gregkh@...uxfoundation.org>, Jonathan.Cameron@...wei.com,
 airlied@...il.com, aleksander.lobakin@...el.com,
 andriy.shevchenko@...ux.intel.com, bhelgaas@...gle.com, broonie@...nel.org,
 dakr@...nel.org, dri-devel@...ts.freedesktop.org, hamohammed.sa@...il.com,
 lgirdwood@...il.com, linux-kernel@...r.kernel.org,
 linux-usb@...r.kernel.org, louis.chauvet@...tlin.com, lukas@...ner.de,
 lyude@...hat.com, maarten.lankhorst@...ux.intel.com, mairacanal@...eup.net,
 melissa.srw@...il.com, mripard@...nel.org, quic_zijuhu@...cinc.com,
 rafael@...nel.org, robin.murphy@....com, rust-for-linux@...r.kernel.org,
 simona@...ll.ch
Subject: Re: [PATCH v4 9/9] drm/vkms: convert to use faux_device

Hi

Am 13.03.25 um 18:20 schrieb José Expósito:
> On Thu, Mar 13, 2025 at 03:22:21PM +0100, Simona Vetter wrote:
>> On Wed, Mar 12, 2025 at 07:22:07AM +0100, Greg KH wrote:
>>> On Tue, Mar 11, 2025 at 06:20:53PM +0100, José Expósito wrote:
>>>> Hi everyone,
>>>>
>>>>> On Tue, Feb 25, 2025 at 02:51:40PM +0100, Louis Chauvet wrote:
>>>>>>
>>>>>> Le 25/02/2025 à 12:41, Thomas Zimmermann a écrit :
>>>>>>> Hi
>>>>>>>
>>>>>>> Am 10.02.25 um 15:37 schrieb Louis Chauvet:
>>>>>>>> On 10/02/25 - 13:30, Greg Kroah-Hartman wrote:
>>>>>>>>> The vkms driver does not need to create a platform device, as there is
>>>>>>>>> no real platform resources associated it,  it only did so because it was
>>>>>>>>> simple to do that in order to get a device to use for resource
>>>>>>>>> management of drm resources.  Change the driver to use the faux device
>>>>>>>>> instead as this is NOT a real platform device.
>>>>>>>>>
>>>>>>>>> Cc: Louis Chauvet <louis.chauvet@...tlin.com>
>>>>>>>>> Cc: Haneen Mohammed <hamohammed.sa@...il.com>
>>>>>>>>> Cc: Simona Vetter <simona@...ll.ch>
>>>>>>>>> Cc: Melissa Wen <melissa.srw@...il.com>
>>>>>>>>> Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
>>>>>>>>> Cc: Maxime Ripard <mripard@...nel.org>
>>>>>>>>> Cc: Thomas Zimmermann <tzimmermann@...e.de>
>>>>>>>>> Cc: David Airlie <airlied@...il.com>
>>>>>>>>> Cc: dri-devel@...ts.freedesktop.org
>>>>>>>>> Reviewed-by: Lyude Paul <lyude@...hat.com>
>>>>>>>>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>>>>>>> Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>
>>>>>>>
>>>>>>>> Tested-by: Louis Chauvet <louis.chauvet@...tlin.com>
>>>>>>>> Reviewed-by: Louis Chauvet <louis.chauvet@...tlin.com>
>>>>>>>>
>>>>>>>> Thanks for the modification, it seems to work.
>>>>>>> Should this patch be merged through DRM trees? drm-misc-next is at
>>>>>>> v6.14-rc4 and has struct faux_device.
>>>>>> Hi,
>>>>>>
>>>>>> I was not aware the faux-device was merged, as it is a new feature, I
>>>>>> expected it to reach drm-misc-next on 6.15-rc1.
>>>>> I added it to Linus's tree just so that DRM could get these changes into
>>>>> their tree now :)
>>>>>
>>>>>> I plan to merge [1] today/tomorrow (well tested with platform_device), and
>>>>>> then I will submit an updated version of this patch (only trivial conflicts,
>>>>>> but never tested with multiple VKMS devices).
>>>>>>
>>>>>> [1]:https://lore.kernel.org/all/20250218101214.5790-1-jose.exposito89@gmail.com/
>>>>> Great, thanks!
>>>>>
>>>>> greg k-h
>>>> Testing this patch again as part of some IGT tests I'm working on,
>>>> I noticed that, applying this patch on top of the latest drm-misc-next
>>>> triggers a warning at drivers/gpu/drm/drm_gem.c:571, in
>>>> drm_gem_get_pages():
>>>>
>>>>      if (WARN_ON(!obj->filp))
>>>>              return ERR_PTR(-EINVAL);
>>> I don't see how the faux bus change would have anything to do with a
>>> filp as that's not related as far as I can tell.  But I don't know the
>>> drm layer at all, where does that filp come from?
>> Yeah that filp is the shmem file that backs gem bo. That's very far away
>> from anything device/driver related datastrctures. If this is a new
>> failure due to the aux bux conversion then it would be really surprising.
> Agreed, I find it surprising, but reverting the patch removes the warning.
>
> It's most likely an issue on my side, but I decided to double check just
> in case someone else is also seeing this warning.

Any news on this issue?

Best regards
Thomas

>
> Jose
>
>> -Sima
>>
>> -- 
>> Simona Vetter
>> Software Engineer, Intel Corporation
>> http://blog.ffwll.ch

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)