Nouveau crashes at login with Kernel 4.15.0-29 on MacBook Air, so no login screen in a normal sequence

[Anquietas]

I have a MacBook Air laptop which is running Linux (Kubuntu 16.04.5 LTS) with NVidia Graphics Card, KDE, Xorg, SDDM, and so on... Clean and natural install, no funky custom kernel or drivers or anything...

Everything worked fine (with the 4.13.* kernel) until I've upgraded all my packages (which included the "wonderful" 4.15.0-29 kernel, which broke my system).

Now, everytime I try to boot normally, it asks me for my disk password (I have an encrypted LVM) and after that, guess what ?: blank screen. The login screen does not appear.
I can switch the Terminals with Ctrl+Alt+Fx, however.

However, the same kernel, if I boot it in recovery mode and then I select "Resume", the login screen appears, but it lags a little bit...

Needless to say, if I boot the older kernel (4.13), everything works perfectly.

I dug up some logs and found something like "sddm-greeter" segmentation fault in nouveau_dri.so or something like this.

So, it looks like the new kernel doesn't quite seem to look eye-to-eye with nouveau drivers...

And no, I don't want the NVidia proprietary drivers because I get along just perfectly with Nouveau on other machines, and I don't want to reinstall nvidia drivers everytime I'm upgrading the kernel.

And yes, I already have "haveged" installed, to provide sufficient entropy (I saw that the possible lack of entropy might be a problem in some cases)...

If I boot in recovery mode and then select "resume", everything works.

So, what is going on ?

Any help would be appreciated...

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: xorg 1:7.7+13ubuntu3
ProcVersionSignature: Ubuntu 4.15.0-29.31~16.04.1-generic 4.15.18
Uname: Linux 4.15.0-29-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
CurrentDesktop: KDE
Date: Fri Jul 27 10:40:31 2018
InstallationDate: Installed on 2018-07-04 (22 days ago)
InstallationMedia: Kubuntu 16.04.4 LTS "Xenial Xerus" - Release amd64 (20180228)
SourcePackage: xorg
UpgradeStatus: No upgrade log present (probably fresh install)

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1797837

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Joseph Salisbury (jsalisbury)]

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v4.19 kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.19-rc8

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]