i915 error state capture is not working
Current drm-tip error state capture during GPU hangs doesn't seem to work anymore, at least both on ICL and TGL.
These are two error states captured in ICL, one with drm-tip (broken) and one with kernel 5.5.2-arch1-1 from archlinux (working).
error-icl-working error-icl-broken
The bad error state is corrupt, and contains a lot of invalid instructions or NO-OPs that are useless for debugging.
An easy way to reproduce the issue is to apply the following patch to IGT:
It removes the last instruction from the fragment shader (SEND with EOT), and causes it to hang. Then run the test:
sudo ./gem_render_copy --run-subtest y-tiled