[Bug 103800] New: CNL unable to handle kernel paging request at 00000000fffffffc

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=103800

            Bug ID: 103800
           Summary: CNL unable to handle kernel paging request at
                    00000000fffffffc
           Product: DRI
           Version: XOrg git
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: rafael.antognolli at intel.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 135561
  --> https://bugs.freedesktop.org/attachment.cgi?id=135561&action=edit
Dmesg output showing the error.

I can run into this issue by executing piglit on CNL with the following branch:

https://cgit.freedesktop.org/~rantogno/mesa/log/?h=wip/cnl_disable_pc

The kernel emits a backtrace and the machine becomes unusable shortly after
(it's not a simple GPU hang). Even ssh eventually stops working.

It takes a couple tries to happen. I had it happen with other branches too, and
I believe master also has the same issue.

I was using drm-tip from today, commit hash:
74ae8acff97c1739330154fa34bf5a64e28d608f

I also artificially disabled preemption by setting .has_logical_ring_preemption
= 0 on GEN9_FEATURES. I'll re-enable it and confirm that the bug still happens
(just wanted to start the discussion early).

Steps to reproduce:

 - Disable gdm so that no X or gnome-wayland or anything like that is running
 - with the above kernel, the mentioned mesa branch, and piglit installed, run
something like:

$ EGL_PLATFORM=gbm PIGLIT_PLATFORM=gbm ./piglit run gpu ~/piglit_output/

Make sure you have mesa, waffle and piglit built with gbm support. I believe
the bug would also happen in other platforms too, like X or wayland.

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