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

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Message-ID: <fb72e067-3f5f-1bac-dc9b-3abd9d7739a2@redhat.com>
Date:   Wed, 11 Jan 2023 17:58:04 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     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>,
        Aaron Plattner <aplattner@...dia.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

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>

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat