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

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Message-ID: <2102a618-2d5e-c286-311f-30e4baa4f85b@suse.de>
Date:   Wed, 11 Jan 2023 17:20:00 +0100
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Daniel Vetter <daniel.vetter@...ll.ch>,
        DRI Development <dri-devel@...ts.freedesktop.org>
Cc:     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 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.

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

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