[Bug 91127] New: Graphics problems with intel_iommu=on on Linux >= 3.7

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=91127

            Bug ID: 91127
           Summary: Graphics problems with intel_iommu=on on Linux >= 3.7
           Product: DRI
           Version: unspecified
          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: lantw44 at gmail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 116752
  --> https://bugs.freedesktop.org/attachment.cgi?id=116752&action=edit
Serial console log of Linux 4.1

I found Intel-IOMMU.txt in Linux documentation says I should file a bug if
intel_iommu=igfx_off fixes anything.


When using Linux 3.7 or later versions, characters on the screen become broken
after the graphics driver is loaded. Here is the screenshot. It is the same as
bug 90037, so I don't attach the screenshot again:

https://bugs.freedesktop.org/attachment.cgi?id=115079

After the display server (Xorg or Wayland) is started, it shows more errors and
crashes the system, so I cannot access the system to run dmesg or other
commands. I will attach a serial console log instead.

git bisect says the bad commit is
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=398b7a1

If I use intel_iommu=igfx_off, there is no graphics problem.


I found some behavior differences between Linux 3.6 and Linux 3.7.
https://bugs.freedesktop.org/show_bug.cgi?id=90037#c8


(CPU and GPU)
Intel Core i5 CPU 650 @ 3.20GHz
Intel Ironlake Desktop

(Motherboard)
ASUSTeK Computer INC. P7H55D-M EVO

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