Could you please provide the output of dmesg after the segfault, as well as the X logs (/var/log/Xorg.0.log, or wherever it is on your computer)?
If you could bisect the kernel between 4.14.13 and 4.15-rc8, that would be awesome (for example, running `git bisect start --term-good=v4.14 --term-bad=v4.15-rc8 -- drivers/gpu/drm/nouveau`, see ). I’ll try to give 4.15-rc8 a spin on my laptop tonight.

(In reply to Pierre Moreau from comment #1)
> Could you please provide the output of dmesg after the segfault, as well as
> the X logs (/var/log/Xorg.0.log, or wherever it is on your computer)?

Sure, later today (as of now I only have ssh access to the machine). 

> If you could bisect the kernel between 4.14.13 and 4.15-rc8, that would be
> awesome (for example, running `git bisect start --term-good=v4.14
> --term-bad=v4.15-rc8 -- drivers/gpu/drm/nouveau`, see ). I’ll try to give
> 4.15-rc8 a spin on my laptop tonight.

I've never done a git bisection before (and I don't have the toolchain installed, this is - was, now that all hell broke loose with Meltdown and friends - a computer with very limited use), but I wager it's going to be painful to do kernel compiles on an Atom 330… I may try to do so on the weekend, but no promises. :(
Actually, I just reported this now because I was expecting this error to be found by someone else, being so obvious. :P It's happening since 4.15-rc1 (the first release I tested after the merge window).

Created attachment 136805 [details]
Xorg log

So I managed to configure lightdm for logging in automatically. This is what I got on the dmesg:

[   40.419929] compiz[912]: segfault at 1a ip 00007f77455ef1e8 sp 00007ffd41c1fba0 error 4 in nouveau_dri.so[7f77453a9000+a86000]

Xorg log attached.

Created attachment 136815 [details]
Kernel logs with 4.15

4.15 is indeed broken on NVAC on my laptop as well (see the kernel logs attached); I am going to run a bisect.

Turns out I had an additional issue, but I think I now see the same issue as you do, with a segfault in nouveau_dri.so when starting sddm.

Created attachment 136840 [details] [review]
Tentative patch

The following patch from Ben Skeggs fixes it for me, hopefully that should also be the case on your laptop.

(In reply to Pierre Moreau from comment #6)
> Created attachment 136840 [details] [review] [review]
> Tentative patch
> 
> The following patch from Ben Skeggs fixes it for me, hopefully that should
> also be the case on your laptop.

Great, thanks a lot for the quick turnaround! :) It's actually a desktop machine, I'll give it a spin as soon as the patch hits the mainline (hopefully today, I saw it's part of the last DRM fixes pull request).

I can confirm it's also fixed on my side, as expected. (I have Chrome's GPU process crashing, but that's an unrelated issue, since it also happens with Linux 4.14.13.) Thanks a lot! :)

Awesome! I saw the fixes in Linus’ tree, and since 4.15 hasn’t been tagged yet, the fixes will be part of the initial release of 4.15.

Thank you for reporting the bug and trying out the patch! :-)