[Bug 2060268] Re: Phantom "Unknown Display" shown in Settings after installing the Nvidia driver

kernels 6.8.0-50 and 6.8.0-51 have regressed, for the same reasons as
kernel 6.11: the simple-framebuffer device in sysfs is no longer at
/sys/devices/platform/simple-framebuffer.0 (comment #99)

But for some reason, I only get a phantom display in Wayland. Instead,
comment #29 previously mentioned that both X11 and Wayland are affected,
and I remember seeing the same. Odd.

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https://bugs.launchpad.net/bugs/2060268

Title:
Phantom "Unknown Display" shown in Settings after installing the
Nvidia driver

Status in OEM Priority Project:
New
Status in linux package in Ubuntu:
Invalid
Status in nvidia-graphics-drivers-470 package in Ubuntu:
Won't Fix
Status in nvidia-graphics-drivers-535 package in Ubuntu:
Won't Fix
Status in nvidia-graphics-drivers-545 package in Ubuntu:
Won't Fix
Status in nvidia-graphics-drivers-550 package in Ubuntu:
Won't Fix
Status in ubuntu-drivers-common package in Ubuntu:
Fix Released
Status in ubuntu-drivers-common source package in Jammy:
Fix Released
Status in ubuntu-drivers-common source package in Noble:
Fix Released

Bug description:
[ Impact ]

After installing Nvidia driver 545 on a single (27") monitor system,
Settings shows a phantom 46" monitor of the same resolution.

It looks like the phantom monitor is /dev/dri/card0 which is still
controlled by simpledrm, while Nvidia uses /dev/dri/card1.

This also seems to be triggering bug 2062426 and bug 2066126.

[ Temporary Workaround ]

1. sudo rm /dev/dri/card0
2. Log in again.

[ Permanent Workaround ]

Add kernel parameter: initcall_blacklist=simpledrm_platform_driver_init
Beware that this has side-effects: see comment #37

[ Test Plan - Nvidia case ]

1. Set up a DESKTOP where the only GPU enabled is an Nvidia one.
2. Open the 'Additional Drivers' app to install a supported Nvidia driver.
3. Reboot and verify the Nvidia driver is now active (lspci -k should mention 'nvidia' and not 'nouveau').
4. Open Settings and verify the only monitors shown are your real monitors.

[ Regression Test Plan - Intel/AMD graphics ]

1. Set up a machine with integrated graphics only.
2. Reboot.
3. Verify that you are able to log into the Ubuntu Desktop Wayland session.
4. Run `apt install nvidia-driver-535`.
5. Reboot.
6. Verify that you are able to log into the Ubuntu Desktop Wayland session.

[ Regression Test Plan - Virtual machines ]

1. Set up a virtual machine without any graphics acceleration (vmware, virtio...)
2. Reboot.
3. Verify that you are able to log into the Ubuntu Desktop Wayland session.
4. Run `sudo apt install nvidia-driver-535`.
5. Reboot.
6. Verify that you are able to log into the Ubuntu Desktop Wayland session.
7. Optionally go back to point 4, and try with nvidia-driver-550.

[ Regression Test Plan - Nvidia+LUKS ]

1. Set up a desktop machine (not a laptop) with an Nvidia GPU and encrypted disk.
2. Open the 'Additional Drivers' app to install a supported Nvidia driver.
3. Reboot
4. Verify that you see the password prompt for decrypting the disk.

[ Where problems could occur ]

Removing the simpledrm card is only safe when it's not being used. If
somehow a machine wasn't using the installed Nvidia driver then there
could be a risk of deleting the only working display.

One case where this could happen is if the Nvidia driver would allow
being loaded even without any nvidia hardware present: if that is the
case, "Regression Test Plan - Virtual machines" would fail.

[ Other Info ]

ProblemType: Bug
ApportVersion: 2.28.0-0ubuntu1
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/seq: dan 4631 F.... pipewire
 /dev/snd/controlC1: dan 4636 F.... wireplumber
CRDA: N/A
CasperMD5CheckResult: pass
DistroRelease: Ubuntu 24.04
InstallationDate: Installed on 2024-01-04 (92 days ago)
InstallationMedia: Ubuntu 24.04 "Noble Numbat" - Daily amd64 (20231127)
MachineType: Intel(R) Client Systems NUC12DCMi7
NonfreeKernelModules: nvidia_modeset nvidia
Package: linux (not installed)
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 TERM=xterm-256color
 XDG_RUNTIME_DIR=<set>
ProcFB: 0 simpledrmdrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-6.8.0-11-generic root=UUID=8434774e-88f2-4e3f-adb8-2eb07dff3cf9 ro quiet loglevel=3 splash vt.handoff=7
ProcVersionSignature: Ubuntu 6.8.0-11.11-generic 6.8.0-rc4
RelatedPackageVersions:
 linux-restricted-modules-6.8.0-11-generic N/A
 linux-backports-modules-6.8.0-11-generic N/A
 linux-firmware 20240318.git3b128b60-0ubuntu1
Tags: noble
Uname: Linux 6.8.0-11-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sudo users
_MarkForUpload: True
dmi.bios.date: 12/20/2021
dmi.bios.release: 5.24
dmi.bios.vendor: Intel Corp.
dmi.bios.version: EDADL579.0046.2021.1220.2351
dmi.board.name: NUC12EDBi7
dmi.board.vendor: Intel Corporation
dmi.board.version: M27908-302
dmi.chassis.type: 35
dmi.chassis.vendor: Intel Corporation
dmi.chassis.version: 2.0
dmi.ec.firmware.release: 3.7
dmi.modalias: dmi:bvnIntelCorp.:bvrEDADL579.0046.2021.1220.2351:bd12/20/2021:br5.24:efr3.7:svnIntel(R)ClientSystems:pnNUC12DCMi7:pvrM30143-302:rvnIntelCorporation:rnNUC12EDBi7:rvrM27908-302:cvnIntelCorporation:ct35:cvr2.0:skuRNUC12DCMi70000:
dmi.product.family: DC
dmi.product.name: NUC12DCMi7
dmi.product.sku: RNUC12DCMi70000
dmi.product.version: M30143-302
dmi.sys.vendor: Intel(R) Client Systems

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