[RESEND][SRU][A][PATCH 0/1] Fix for LP#1738334 - hibmc regression

[Daniel Axtens]

Just realised I replied to Seth directly - oops! Here's what I said:

======
Hi Seth,

I was thinking we might want to pull in the full patch set that
upstream settled upon for Bionic
(https://lists.freedesktop.org/archives/dri-devel/2017-December/161184.html)
It's a more general purpose solution that will prevent this from
recurring on other sorts of cards. It has been picked up for 4.16.

I can submit that separately - I haven't had time to do a backport and
test yet. Would you want this now, or later once we've moved to a 4.15
kernel? (just thinking of minimising your rebase effort...)
======

I've since had a look at what ended up landing in drm-next, and it
seems the series has been only partially merged, and we can just
cherry-pick the first patch - c67fa6edc8b11. It applies cleanly to
4.15-rc7 and is a trivial backport on to 4.14. (It is still a more
aggressive fix than the patch I submitted for Artful, and I can't
provide test coverage beyond the HiSilicon device, hence why I didn't
propose it for Artful.)

As I mentioned above, I can test and submit it now or later - Huawei's
concern is getting the Artful fix merged in time for inclusion in the
16.04.4 HWE edge kernel, so their users get Xorg support when they
boot the install media. So whatever will make that more likely I will
happily do :)

Regards,
Daniel

On Mon, Jan 8, 2018 at 7:57 AM, Daniel Axtens
<daniel.axtens at canonical.com> wrote:
>
> Hi Seth,
>
> I was thinking we might want to pull in the full patch set that
> upstream settled upon for Bionic
> (https://lists.freedesktop.org/archives/dri-devel/2017-December/161184.html)
> It's a more general purpose solution that will prevent this from
> recurring on other sorts of cards. It has been picked up for 4.16.
>
> I can submit that separately - I haven't had time to do a backport and
> test yet. Would you want this now, or later once we've moved to a 4.15
> kernel? (just thinking of minimising your rebase effort...)
>
> Regards,
> Daniel
>
> On Sat, Jan 6, 2018 at 2:55 AM, Seth Forshee <seth.forshee at canonical.com> wrote:
> > On Thu, Jan 04, 2018 at 10:23:55AM +1100, Daniel Axtens wrote:
> >> [SRU Justification]
> >>
> >> [Impact]
> >> On Artful kernels, X fails to start and a kernel splat is printed.
> >>
> >> This is because 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
> >>
> >> That was deemed too ad-hoc and the community went with a larger fix
> >> instead:
> >> https://lists.freedesktop.org/archives/dri-devel/2017-December/161184.html
> >> However, this comes with an uncomfortably large regression potential,
> >> so I have stuck with the smaller fix for Artful - we can bring the
> >> larger fix in for Bionic.
> >>
> >> [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 and X does not start, 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.
> >
> > I assume this will be wante for bionic also?