On 18/02/2021 10:35, Nicolin Chen wrote:

Hi Guillaume,

Thank you for the test results! And sorry for my belated reply.

No worries :)

On Thu, Feb 11, 2021 at 03:50:05PM +0000, Guillaume Tucker wrote:

quoted

quoted

On Sat, Feb 06, 2021 at 01:40:13PM +0000, Guillaume Tucker wrote:

quoted

quoted

It'd be nicer if I can get both logs of the vanilla kernel (failing)
and the commit-reverted version (passing), each applying this patch.

Sure, I've run 3 jobs:

* v5.11-rc6 as a reference, to see the original issue:
  https://lava.collabora.co.uk/scheduler/job/3187848

* + your debug patch:
  https://lava.collabora.co.uk/scheduler/job/3187849

* + the "breaking" commit reverted, passing the tests:
  https://lava.collabora.co.uk/scheduler/job/3187851

Thanks for the help!

I am able to figure out what's probably wrong, yet not so sure
about the best solution at this point.

Would it be possible for you to run one more time with another
debugging patch? I'd like to see the same logs as previous:
1. Vanilla kernel + debug patch
2. Vanilla kernel + Reverted + debug patch

As it turns out, next-20210210 is passing all the tests again so
it looks like this got fixed in the meantime:

  https://lava.collabora.co.uk/scheduler/job/3210192

I checked this passing log, however, found that the regression is
still there though test passed, as the prints below aren't normal:
  tegra-mc 70019000.memory-controller: display0a: read @0xfe056b40:
	 EMEM address decode error (SMMU translation error [--S])
  tegra-mc 70019000.memory-controller: display0a: read @0xfe056b40:
	 Page fault (SMMU translation error [--S])

Ah yes sorry, there are other KernelCI checks for kernel errors
but that wasn't enabled in the bisection so I didn't notice them.

I was trying to think of a simpler solution than a revert. However,
given the fact that the callback sequence could change -- guessing
likely a recent change in iommu core, I feel it safer to revert my
previous change, not necessarily being a complete revert though.

I attached my partial reverting change in this email. Would it be
possible for you to run one more test for me to confirm it? It'd
keep the tests passing while eliminating all error prints above.

If the fix works, I'll re-send it to mail list by adding a commit
message.

Sure, here's next-20210218 as a reference:

  https://lava.collabora.co.uk/scheduler/job/3241236

and here with your patch applied on top of it:

  https://lava.collabora.co.uk/scheduler/job/3241246

The git branch I've used where your patch is applied:

  https://gitlab.collabora.com/gtucker/linux/-/commits/next-20210218-nyan-big-drm-read/

The errors seem to have disappeared but I'll let you double check
that things are all back to a working state.

BTW: This thread is a good example of how having an "on-demand"
KernelCI service to let developers re-run tests with extra
patches would allow them to fix issues independently.  We'll keep
that in mind for the future.

Best wishes,
Guillaume