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

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Message-ID: <Y77lyzPOUt8JAyPX@phenom.ffwll.local>
Date:   Wed, 11 Jan 2023 17:37:31 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Thomas Zimmermann <tzimmermann@...e.de>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        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

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 :-)
-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




-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch