nvidia_drm remains in use for no apparent reason after Xorg shutdown.

Graphics / Linux Linux
1

Hi, i’m trying to Nvidia “Reverse Prime” with a gtx750 + intel hd4000
Displays are attached to the intel connectors.
What i’ve done so far:
My xorg.conf:

Section "Module"
	Load "modesetting"
EndSection

Section "Device"
	Identifier "nvidia"
	Driver "nvidia"
	#BusID ""
	Option "AllowEmptyConfiguration"
EndSection

.xinitrc:

export DISPLAY=:0.0 
xrandr --setprovideroutputsource modesetting NVIDIA-0
xrandr --auto
openbox --replace &
setxkbmap it
xset mouse 1.4 4
exec sudo -u koko lxterminal &
p1=$!
wait $p1

System starts with intel as the primary adapter, nvidia modules are NOT autoloaded.
So i do:
modprobe nvidia-drm
modprobe nvidia_modeset
modprobe nvidia
Prime synchronization is working fine:

# cat /sys/module/nvidia_drm/parameters/modeset 
Y

All is good whitin the X server, and works as expected, but what seems wrong to me is that as i exit the Xorg session, nvidia_drm remains in use.

lsmod | grep nvidia
nvidia_drm             45056  1
nvidia_modeset        798720  1 nvidia_drm
nvidia              11476992  1 nvidia_modeset
drm_kms_helper        126976  2 i915,nvidia_drm
drm                   299008  7 i915,ttm,nvidia_drm,drm_kms_helper

It took me a while to understand, but there was an open handle to /dev/dri/card1 (nvidia):

# lsof -n | grep "/dev/dri/card/1"
systemd      1           root   19u      CHR              226,1      0t0            21785 /dev/dri/card1

It prevents me from unloading nvidia_drm and i need to do that to pass the gpu to a libvirt domain.

Manually attach to systemd and closing the handle makes it work, but i cannot do that ugly hacks all of the times.
Note that the open handles i am speaking about increases by on on every xorg restart.

Who is to blame? nvidia driver? Modesetting driver?

nvidia-bug-report.log.gz (181 KB)

2

Systemd itself, no?

I don’t even understand why it needs to open the DRI interface in the first place.

3

I don’t know, i’ve the feeling, not knowledge, that systemd and xorg are tightly connected each other.

4

I’ve seen this too recently and the culprit seemed to be systemd-logind. I’m not sure what logind needs with the DRM node but “systemctl stop systemd-logind” fixed it for me.

5

Oh, thank you so much!
May i ask you how did you manage to find the culprit?

6