linux-kernel - Re: [PATCH 11/11] video/aperture: Only remove sysfb on the default vga pci device

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Message-ID: <ad725823-f4ef-904f-c04c-90a6aad43323@nvidia.com>
Date:   Wed, 11 Jan 2023 11:21:18 -0800
From:   Aaron Plattner <aplattner@...dia.com>
To:     Javier Martinez Canillas <javierm@...hat.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        DRI Development <dri-devel@...ts.freedesktop.org>
Cc:     Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Helge Deller <deller@....de>, Sam Ravnborg <sam@...nborg.org>,
        Alex Deucher <alexander.deucher@....com>,
        stable@...r.kernel.org
Subject: Re: [PATCH 11/11] video/aperture: Only remove sysfb on the default
 vga pci device

On 1/11/23 8:58 AM, Javier Martinez Canillas wrote:
> Hello Daniel,
> 
> On 1/11/23 16:41, Daniel Vetter wrote:
>> This fixes a regression introduced by ee7a69aa38d8 ("fbdev: Disable
>> sysfb device registration when removing conflicting FBs"), where we
>> remove the sysfb when loading a driver for an unrelated pci device,
>> resulting in the user loosing their efifb console or similar.
>>
>> Note that in practice this only is a problem with the nvidia blob,
>> because that's the only gpu driver people might install which does not
>> come with an fbdev driver of it's own. For everyone else the real gpu
>> driver will restor a working console.
> 
> restore
> 
>>
>> Also note that in the referenced bug there's confusion that this same
>> bug also happens on amdgpu. But that was just another amdgpu specific
>> regression, which just happened to happen at roughly the same time and
>> with the same user-observable symptons. That bug is fixed now, see
> 
> symptoms
> 
>> https://bugzilla.kernel.org/show_bug.cgi?id=216331#c15
>>
>> For the above reasons the cc: stable is just notionally, this patch
>> will need a backport and that's up to nvidia if they care enough.
>>
> 
> Maybe adding a Fixes: ee7a69aa38d8 tag here too ?
> 
>> References: https://bugzilla.kernel.org/show_bug.cgi?id=216303#c28
>> Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
>> Cc: Aaron Plattner <aplattner@...dia.com>
>> Cc: Javier Martinez Canillas <javierm@...hat.com>
>> Cc: Thomas Zimmermann <tzimmermann@...e.de>
>> Cc: Helge Deller <deller@....de>
>> Cc: Sam Ravnborg <sam@...nborg.org>
>> Cc: Alex Deucher <alexander.deucher@....com>
>> Cc: <stable@...r.kernel.org> # v5.19+ (if someone else does the backport)
>> ---
>>   drivers/video/aperture.c | 7 ++++---
>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/video/aperture.c b/drivers/video/aperture.c
>> index ba565515480d..a1821d369bb1 100644
>> --- a/drivers/video/aperture.c
>> +++ b/drivers/video/aperture.c
>> @@ -321,15 +321,16 @@ int aperture_remove_conflicting_pci_devices(struct pci_dev *pdev, const char *na
>>   
>>   	primary = pdev == vga_default_device();
>>   
>> +	if (primary)
>> +		sysfb_disable();
>> +
>>   	for (bar = 0; bar < PCI_STD_NUM_BARS; ++bar) {
>>   		if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
>>   			continue;
>>   
>>   		base = pci_resource_start(pdev, bar);
>>   		size = pci_resource_len(pdev, bar);
>> -		ret = aperture_remove_conflicting_devices(base, size, name);
>> -		if (ret)
>> -			return ret;
>> +		aperture_detach_devices(base, size);
> 
> Maybe mention in the commit message that you are doing this change, something like:
> 
> "Instead of calling aperture_remove_conflicting_devices() to remove the conflicting
> devices, just call to aperture_detach_devices() to detach the device that matches
> the same PCI BAR / aperture range. Since the former is just a wrapper of the latter
> plus a sysfb_disable() call, and now that's done in this function but only for the
> primary devices"
> 
> Patch looks good to me:
> 
> Reviewed-by: Javier Martinez Canillas <javierm@...hat.com>

Thanks Daniel and Javier!

I wasn't able to reproduce the original problem on my hybrid laptop 
since it refuses to boot with the console on an external display, but I 
was able to reproduce it by switching the configuration around: booting 
with i915.modeset=0 and with an experimental version of nvidia-drm that 
registers a framebuffer console. I verified that loading nvidia-drm 
breaks the efi-firmware framebuffer on Intel on Arch's 
linux-6.1.4-arch1-1 kernel and that applying this patch series fixes it. So

Tested-by: Aaron Plattner <aplattner@...dia.com>

FWIW, the bug ought to be reproducible with i915.modeset=0 + any other 
drm driver that registers a framebuffer.

-- Aaron