linux-kernel - Re: nouveau 0000:01:00.0: drm_WARN_ON(!found

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Message-ID: <f10791773520f85857749c080af999821dd41a0d.camel@redhat.com>
Date:   Wed, 13 Dec 2023 18:48:22 -0500
From:   Lyude Paul <lyude@...hat.com>
To:     Borislav Petkov <bp@...en8.de>, Paul Dufresne <dufresnep@...o.com>,
        Danilo Krummrich <me@...r.org>
Cc:     nouveau <nouveau@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Ben Skeggs <bskeggs@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: nouveau 0000:01:00.0: drm_WARN_ON(!found_head)

Hopefully you're still on at this point - if you are, could you try starting
the machine up with the following kernel module arguments passed to nouveau?

debug=disp=trace

Then see if you can find any lines that mention INHERIT? I have a feeling I'm
just going to have to add a workaround for the time being, but I'd really love
to know how we're managing to get that far on a hardware generation we never
implemented that nvkm ioctl for…

On Wed, 2023-12-13 at 18:37 -0500, Lyude Paul wrote:
> agh - thank you for repeatedly poking on this, I've been busy enough with GSP
> work I totally missed this. Yes - I'm quite surprised that this is blowing up,
> but considering that looks to be a GT218 I guess display state readback must
> just work a bit differently there since that's really early on into the NV50
> days.
> 
> The reason that was a drm_WARN_ON() was because it indicates that we're not
> reading back OR -> head assignments properly. But, I'm confused how we're even
> getting that far on a non-GSP platform. I'm going to dig into this now, but if
> I don't figure out a good fix by the end of the day I'll just send a patch to
> silent the warning.
> 
> Thanks again for bugging me about this!
> 
> On Wed, 2023-12-13 at 13:49 +0100, Borislav Petkov wrote:
> > On Wed, Dec 13, 2023 at 12:39:36PM +0100, Borislav Petkov wrote:
> > > We're getting close to releasing so I guess we either debug this or shut
> > > up the WARN.
> > 
> > Not only that - panic_on_warn turns this into an explosion so you don't
> > want that in a released kernel.
> > 
> 

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat