I solved the problem by following this post from the bugs launchpad. In summary:
Run the following command and look for the vermagic
line:
modinfo nvidia-384 -k 4.4.0-116-generic
It will probably say: vermagic: 4.4.0-116-generic SMP mod_unload modversions
. Here the retpoline string is missing.
You can fix this by removing and re-building the module with DKMS
sudo dkms remove nvidia-384/384.111 -k 4.4.0-116-generic
sudo dkms install nvidia-384/384.111 -k 4.4.0-116-generic
After that the modinfo command will show vermagic: 4.4.0-116-generic SMP mod_unload modversions retpoline
If you are using custom version of gcc this post is also relevant:
If you are using a Ubuntu version of gcc, then gcc probably updated when you got the newer kernel. The changes to gcc necessary to support retpoline should have been backported to most active versions of gcc. However if you have installed a custom version of gcc then your kernel module probably will not build correctly.
So if the above procedure does not work you may have to check which gcc version you are using.
You don't mention which version of Ubuntu you're using. If you're using 18.04, there are a couple of things you can try.
The first thing to do is to make sure the resolution of 1920 x 1080 is supported in grub. To do that reboot your computer and hit Esc repeatedly until you get the purple screen with the recovery and grub options. Hit "c" to get a grub prompt. At the grub prompt, type:
videoinfo
and hit Enter.
Look at the list of "supported" resolutions, and make sure 1920 x 1080 is there. If so, type:
exit
to exit grub and boot.
The boot screen resolution is changed by changing your default grub settings. Open a terminal and enter:
sudo nano /etc/default/grub
Use the down arrow or Page Down until you see the line that looks like this:
#GRUB_GFXMODE=640x480
Below that line, enter the following, substituting the 1920x1080 for a supported resolution:
GRUB_GFXMODE=1920x1080
GRUB_GFXPAYLOAD_LINUX=keep
To save your changes, hit Ctrl+o, with "o" as in Ohio, not zero. To exit nano, hit Ctrl+x. Now, update grub:
sudo update-grub
That should solve the problem in grub, and won't be overwritten by an update. For the login screen, you may be able to fix it with the 4K settings in Ubuntu 18.04. Go Settings -> Devices -> Displays and set "Scale" to 200%. I'm not sure if that will affect the desktop manager or not, but it's the first thing I'd try.
Best Answer
Assuming GDM is still installed:
will let you select what your default display manager is. If it's not installed...well, install it.
It'll go into effect on reboot.