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

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Message-ID: <f1a33f9001bc642fd71280559ec0f612936db2a8.camel@redhat.com>
Date:   Wed, 13 Dec 2023 19:29:40 -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)

Nevermind - I don't think I'll need the logs, I stared at the code for long
enough and I think I realized what's happening.

I will have a patch for you to test in just a moment, just waiting for it to
compile so I can verify nothing else breaks

On Wed, 2023-12-13 at 18:48 -0500, Lyude Paul wrote:
> 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