Second kexec_file_load (but not kexec_load) fails on i915 if CONFIG_INTEL_IOMMU_DEFAULT_ON=n

[Askar Safin]

 ---- On Fri, 04 Jul 2025 12:29:01 +0400  Jani Nikula <jani.nikula at linux.intel.com> wrote --- 
 > Thanks for the detailed debug info. I'm afraid all I can say at this
 > point is, please file all of this in a bug report as described in
 > [1]. Please add the drm.debug related options, and attach the dmesgs and
 > configs in the bug instead of pointing at external sites.

Okay, now let me speculate how to fix this bug. :) I think someone with moderate kexec understanding
and with Intel GPU should do this: reproduce the bug and then slowly modify kexec_file_load code until it
becomes kexec_load code. (Or vice versa.) In the middle of this modification the bug stops to reproduce,
and so we will know what exactly causes it.

kexec_file_load and kexec_load should behave the same. If they do not, then we should
understand, why. We should closely review their code.

Also, in case of kexec_load kernel uncompressing and parsing performed by "kexec" userspace
tool, and in case of kexec_file_load by kernel. So we should closely review this two uncompressing/parsing code fragments.
I think that this bug is related to kexec, not to i915. And thus it should be fixed by kexec people, not by i915 people. (But I may be wrong.)

But okay, I reported it to that bug tracker anyway: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14598

Maybe there is separate kexec bug tracker?

Also, your bug tracker is cool. One can attach files in the middle of report. Why not whole kernel uses it? :)

--
Askar Safin
https://types.pl/@safinaskar