OK. Sounds like there is a device (/dev/* file) that you're not getting
correct access to. And you can only get around that limitation by
running as root (which is not recommended, for security).
In this case we may find it's an nvidia driver (or installation) bug.
Although your original observation that it's a gdm problem might
actually explain this too. I don't know if it's gdm, systemd or
something else that handles the required privilege escalation to access
/dev/GRAPHICS_THINGS so am reopening the gdm task in the hope that
somebody else knows...
** Changed in: gdm3 (Ubuntu)
Status: Invalid => New
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https://bugs.launchpad.net/bugs/1769857
Title:
Vulkan not working if nvidia-drm.modeset=1 is set and gdm3 is used
(Optimus)
Status in gdm3 package in Ubuntu:
New
Status in nvidia-graphics-drivers-390 package in Ubuntu:
New
Bug description:
Lenovo ideapad 510-15IKB
OS: Ubuntu 18.04 bionic
Kernel: x86_64 Linux 4.15.0-20-generic
DE: GNOME
CPU: Intel Core i5-7200U @ 4x 3.1GHz
GPU: Intel HD 620 + NVIDIA GeForce 940MX (Optimus)
UEFI boot, Secure Boot disabled.
I installed the proprietary graphics driver with Software Properties and
Vulkan applications (e.g. vulkan-smoketest, Unreal Editor, SDK examples,
Dolphin) were working fine.
To get rid of tearing I added nvidia-drm.modeset=1 to
GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub, then ran update-grub &&
update-initramfs -u and rebooted.
After doing that, Vulkan applications stopped working because they couldn't
initialize the Vulkan swap chain until I reverted the changes to GRUB.
Everything works as expected if lightdm is used instead of gdm3.
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