Re: Discuss Bug 289320 - graphics/drm-66-kmod: Page fault on 16-CURRENT

On Sat, Sep 6, 2025 at 7:21 AM Cy Schubert <Cy.Schubert@cschubert.com> wrote:
>
> Hi,
>
> I'd like to open up discussion about a weird bug I stumbled across on
> Thursday. You can get the gory details, including backtrace in PR/289320.
>
> Long story short, after the FreeBSD version bump from 15 to 16 amdgpu
> panics on a kernel page fault. For fun I reverted, locally, the commit that
> updated the version strings in FreeBSD-CURRENT from 15 to 16, reverting
> 8b4e4c2737305df8807abc6cd054a32586085c93 on that particular machine, a
> Framework 13 laptop. The panic was solved.
>
> My other machines don't use amdgpu, they either don't use X or in the case
> of my HP 840, it uses the i915 driver (also part of drm-66-kmod), which
> works after the 15 to 16 version bump. But the 15 to 16 version bump causes
> amdgpu also from drm-66-kmod to reference a NULL pointer.
>
> What in drm-66-kmod would be sensitive to a FreeBSD version bump?
Blame it on quantum entanglement..

One a slightly more serious note, I'd grep for uses of MODULE_KERNEL_MAXVER
in the sources as a starting point.

rick

>
>
> --
> Cheers,
> Cy Schubert <Cy.Schubert@cschubert.com>
> FreeBSD UNIX:  <cy@FreeBSD.org>   Web:  https://FreeBSD.org
> NTP:           <cy@nwtime.org>    Web:  https://nwtime.org
>
>                         e**(i*pi)+1=0
>
>
>