** Description changed:
- ea642c3216cb ("drm/ttm: add io_mem_pfn callback") is incomplete: the
- hisilicon hibmc driver does not contain the callback and so X does not
- start.
+ [SRU Justification]
- Discussion and potential fix at https://lists.freedesktop.org/archives
- /dri-devel/2017-November/159002.html
+ [Impact]
+ On Artful kernels, X fails to start and a kernel splat is printed.
- This affects Artful, upstream has not landed on a solution yet as far as
- I can tell, so lets backport the first proposed small fix.
+ This is cbecause ea642c3216cb ("drm/ttm: add io_mem_pfn callback") is
+ incomplete: the hisilicon hibmc driver does not contain the callback and
+ so the kernel tries to execute code at NULL.
+
+ [Fix]
+ There is a discussion and potential fix at
https://lists.freedesktop.org/archives/dri-devel/2017-November/159002.html The
fix hasn't landed yet and it looks like they're going to re-engineer the entire
section instead.
+
+ Rather than wait for that and deal with the massive regression
+ potential, the fix I have picked to submit is very very minimal and
+ touches only hibmc.
+
+ [Regression Potential]
+ Minimal - fix only touches hibmc driver. Tested on D05 board.
+
+ [Testcase]
+ Install patched kernel, try to start X. If it succeeds, the fix works. If
there's a kernel splat, the fix does not work.
+
+ [Notes]
+ HiSilicon would really like this fix in Artful in such time so that when the
next 16.04 point release ships in February, the HWE kernel will work with Xorg.
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https://bugs.launchpad.net/bugs/1738334
Title:
hisilicon hibmc regression due to ea642c3216cb ("drm/ttm: add
io_mem_pfn callback")
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