Re: [PATCH v2 07/11] video/aperture: Disable and unregister sysfb devices via aperture helpers

From: "Samuel Čavoj" <samuel@cavoj.net>
To: Javier Martinez Canillas <javierm@redhat.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>,
	deller@gmx.de, daniel@ffwll.ch, sam@ravnborg.org,
	maxime@cerno.tech, linux-fbdev@vger.kernel.org,
	linux-staging@lists.linux.dev, dri-devel@lists.freedesktop.org,
	Zack Rusin <zackr@vmware.com>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	Alex Deucher <alexander.deucher@amd.com>,
	Zhen Lei <thunder.leizhen@huawei.com>,
	Changcheng Deng <deng.changcheng@zte.com.cn>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>
Subject: Re: [PATCH v2 07/11] video/aperture: Disable and unregister sysfb devices via aperture helpers
Date: Tue, 28 Mar 2023 17:19:19 +0200	[thread overview]
Message-ID: <e556191a3cc9730f3d83c7aaea7d3b3e@cavoj.net> (raw)
In-Reply-To: <87v8ivoc3r.fsf@minerva.mail-host-address-is-not-set>

On 2023-03-20 13:12, Javier Martinez Canillas wrote:
> Samuel Čavoj <samuel@cavoj.net> writes:
> 
> [...]
> 
>>>>> This call to sysfb_disable() has been causing trouble with regard 
>>>>> to
>>>>> VFIO. VFIO has been calling aperture_remove_conflicting_pci_devices
>>>>> to
>>>>> get rid of any console drivers (d173780620792c) using the device in
>>>>> question, but now even unrelated drivers are getting killed. 
>>>>> Example
>>>>> situation:
>>>> 
>>>> Which drivers do you use?
>> 
>> This happens with either no drivers loaded or the proprietary nvidia
>> driver. Nouveau is fine as it doesn't rely on efifb but brings its 
>> own.
>> 
> 
> Which is what all DRM drivers should do. If they want to make sure that 
> a
> fbdev will be present after the DRM driver probes, then should register 
> an
> emulated fbdev.

I don't see how this is specific to Nvidia or DRM drivers.

The efifb is killed if vfio-pci (or another driver which uses the
aperture system to remove conflicting drivers) is bound to ANY pci
device, regardless of whether it's nvidia's fault for not implementing
a framebuffer. Fair enough, I agree that they should, but
I for one expect my efifb to not die at a random time
when a random unrelated driver does a random thing with another
unrelated GPU.

Or is the efifb considered a stop-gap solution the only purpose of
which is early boot--before another GPU driver is loaded?

> 
> There was an attempt to workaround that in [0], in particular patch [1]
> but that effort was not continued since the only DRM driver that would 
> be
> affected is the Nvidia proprietary driver that relies on 
> efifb/simpledrm
> to have a VT.
> 
> [0]: 
> https://patchwork.kernel.org/project/dri-devel/list/?series=711019&archive=both
> [1]: 
> https://patchwork.kernel.org/project/dri-devel/patch/20230111154112.90575-11-daniel.vetter@ffwll.ch/