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

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Message-ID: <2117daa3-f26e-12c9-865c-42bd9c5b43ad@suse.de>
Date:   Thu, 12 Jan 2023 08:48:52 +0100
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     DRI Development <dri-devel@...ts.freedesktop.org>,
        Aaron Plattner <aplattner@...dia.com>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>, stable@...r.kernel.org,
        Javier Martinez Canillas <javierm@...hat.com>,
        Alex Deucher <alexander.deucher@....com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Sam Ravnborg <sam@...nborg.org>, Helge Deller <deller@....de>
Subject: Re: [PATCH 11/11] video/aperture: Only remove sysfb on the default
 vga pci device

Hi

Am 11.01.23 um 17:37 schrieb Daniel Vetter:
> On Wed, Jan 11, 2023 at 05:20:00PM +0100, Thomas Zimmermann wrote:
>> Hi
>>
>> Am 11.01.23 um 16:41 schrieb Daniel Vetter:
>>> 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.
>>>
>>> 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
>>> 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.
>>>
>>> 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();
>>> +
>>
>> There's another sysfb_disable() in aperture_remove_conflicting_devices()
>> without the branch but with a long comment.  I find this slightly confusing.
>>
>> I'd rather add a branched sysfb_disable() plus the comment  to
>> aperture_detach_devices(). And then add a 'primary' parameter to
>> aperture_detach_devices(). In aperture_remove_conflicting_devices() the
>> parameter would be unconditionally true.
> 
> Yeah I was on the fence, but should be easy to redo with all the prep work
> out of the way. It does mean we call sysfb_disable once for every bar, but
> that shouldn't matter in any reasonable case :-)

Or leave it as is. It's not so important. The idea of the current design 
was that aperture_remove_conflicting_device() would be the general 
implementation and aperture_remove_conflicting_pci_device() would be a 
helper that only detects the correct PCI BAR. That never really worked 
in practice.

Best regards
Thomas

> -Daniel
> 
>>
>> Best regards
>> Thomas
>>
>>>    	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);
>>>    	}
>>>    	if (!primary)
>>
>> -- 
>> Thomas Zimmermann
>> Graphics Driver Developer
>> SUSE Software Solutions Germany GmbH
>> Maxfeldstr. 5, 90409 Nürnberg, Germany
>> (HRB 36809, AG Nürnberg)
>> Geschäftsführer: Ivo Totev
> 
> 
> 
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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