[Bug 105811] New: kernel 4.15.x boot fails at kms

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=105811

            Bug ID: 105811
           Summary: kernel 4.15.x boot fails at kms
           Product: xorg
           Version: 7.7 (2012.06)
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Driver/intel
          Assignee: chris at chris-wilson.co.uk
          Reporter: ahabig at umn.edu
        QA Contact: intel-gfx-bugs at lists.freedesktop.org

Created attachment 138431
  --> https://bugs.freedesktop.org/attachment.cgi?id=138431&action=edit
A photo of some of the kernel spew.

On my Fedora 27 Thinkpad T430, I have been unable to boot any of the 4.15.x
kernels (4.14.18 and previous work just fine).  The kernel crashes at the
initial kms only 3s into the boot, before any logging to disk happens, making
this one hard to provide information on.  Adding "nomodeset" to the boot lets
the boot process go further: but as soon as a buffer flush tries to write to
the system disk, it hangs (so again, no syslog info beyond a string of ^@'s). 
kdump doesn't help: that needs to write to disk, and this bug seems to be
taking out that ability as it flails.

Complicating matters further is that the screen's backlight is turned off at
the start of the kms (in a normal boot it comes back on later), rendering
console messages hard to read.  Luckily, I found out that with an external
monitor, it will eventually (a minute or two later) light up, resulting in the
attached screenshot which points to the i915 driver.

The initial bug was posted at Fedora's bugzilla:  

  https://bugzilla.redhat.com/show_bug.cgi?id=1557416

and they redirected me here (delayed by travel, sorry).

I see this Ubuntu bug, which shares a similar backtrace:

  https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1751268

although my crash is not dependent on an external monitor.  

Another similar backtrace is on your site here:

  https://bugs.freedesktop.org/show_bug.cgi?id=104573

but that one doesn't seem fatal.

Ideas?  bios update to the laptop didn't change anything.  xorg update didn't
change anything.

F27 is now on xorg-x11-drv-intel-2.99.917-31-20171025.  All 4.15.x kernels
they've put out do the same thing, the latest being 4.15.12-301

Thanks in advance - this has been bugging me for months, and all my usual
debugging techniques have been stymied!

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