maintainer-feedback requested: [Bug 248777] graphics/drm-devel-kmod: Panic when transcoding a video

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Bugzilla Automation <bugzilla at FreeBSD.org> has asked freebsd-x11 (Nobody)
<x11 at FreeBSD.org> for maintainer-feedback:
Bug 248777: graphics/drm-devel-kmod: Panic when transcoding a video
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=248777



--- Description ---
Hi,

I'm running 13.0-CURRENT r364031 with latest drm-devel-kmod installed as I
needed support for the graphics chipset of my Celeron G5900.

The kernel reliably panics when transcoding a certain video with Plex which
leverages libva (hence the graphics chipset).

I have an ongoing discussion about it :
https://lists.freebsd.org/pipermail/freebsd-current/2020-August/076728.html

The interesting part is that the panic never happen when I plug a screen on
HDMI port and happens all the time when no screen plugged. The frame #17 from
the backtrace refers to intel_plane_can_remap() so there might be hint in
there.

I dumped the content of structures from several backtrace frames that you can
see in the discussion linked above.

Thanks.