DottedT

Hello All, I wanted to document this because I spent a lot of time trying to get an RTX 3060 passed through from Unraid to an Ubuntu VM, and most of the obvious troubleshooting led nowhere. MY SETUP • Unraid 7.2.3 • Ubuntu 24.04.4 LTS VM • NVIDIA GeForce RTX 3060 12 GB, GA106 • NVIDIA driver 580.173.02 • GPU and NVIDIA audio device passed through to the VM • No VBIOS ROM required I did install KDE/Plasma during troubleshooting and was running SDDM/Plasma X11 when I finally diagnosed the problem. However, Kubuntu/KDE was not the fix. The actual problem was in the NVIDIA driver, and the same fix should apply to a normal Ubuntu/GNOME installation exhibiting the same NVIDIA errors. THE PROBLEM The symptom was a black screen on the physical monitor when booting the VM with the RTX 3060 passed through. The monitor would initially display the VM/OVMF boot sequence. Once Linux and the NVIDIA driver took over, the HDMI signal would drop and reinitialize several times and eventually leave me with a black screen. I enabled SSH in the Ubuntu VM and connected to it remotely while the physical display was black. Interestingly, nvidia-smi worked perfectly. It detected the RTX 3060, reported the full 12 GB VRAM, and showed NVIDIA driver 580.173.02. This established that the RTX 3060 was actually being passed through successfully and that the NVIDIA driver could communicate with it. The display manager, however, couldn't start the graphical display. In my case SDDM reported: Failed to read display number from pipe Attempt starting the Display server on vt 2 failed Could not start Display server on vt 2 Looking at /var/log/Xorg.0.log was much more revealing. Xorg successfully: • Loaded the NVIDIA driver • Detected the passed-through RTX 3060 • Detected the connected Samsung monitor on DFP-0 • Read the display information • Validated a display mode Then initialization failed with errors including: Failed to initialize DMA Failed to allocate push buffer AddScreen/ScreenInit failed for driver 0 That was the important clue. This was not a failure to pass through the GPU. It wasn't a missing monitor or EDID problem, and changing from Ubuntu/GNOME to Kubuntu/KDE wasn't what solved it. The failure was occurring in the NVIDIA driver's low-level initialization of the GPU for the graphical display. THE FIX The NVIDIA 580 driver supports NVIDIA's newer GSP firmware architecture. On this passed-through GA106 RTX 3060, the GSP path was apparently failing during DMA/push-buffer initialization. I disabled GSP firmware in the Ubuntu guest. I added: options nvidia NVreg_EnableGpuFirmware=0 to: /etc/modprobe.d/nvidia-graphics-drivers-kms.conf Then rebuilt the initramfs and rebooted the VM. After rebooting, the RTX 3060 produced a working physical display and the graphical desktop started normally. NVreg_EnableGpuFirmware=0 tells the NVIDIA kernel driver not to use its GSP firmware path and instead use the traditional RM driver path. This is not specific to the RTX 3060. NVIDIA documents NVreg_EnableGpuFirmware=0 as the mechanism for disabling GSP firmware, and other NVIDIA GPU users have reported resolving GSP-related Linux problems by disabling it. My specific confirmed configuration is an RTX 3060 with NVIDIA driver 580.173.02 under an Unraid VM, so I can't say that every NVIDIA passthrough black-screen problem has the same cause. However, if another NVIDIA GPU shows the same symptoms, especially the same DMA/push-buffer errors, GSP is worth checking. NVIDIA documentation on GSP firmware and disabling it: NVIDIA vGPU Documentation The particularly misleading part of this problem is that nvidia-smi can work even though the physical display does not. In my case: • The GPU was passed through correctly • The NVIDIA driver was loaded • nvidia-smi worked • The monitor was detected • The display mode was detected • But Xorg still couldn't initialize the actual display The failure occurred later when Xorg attempted DMA/push-buffer initialization. VBIOS WAS NOT REQUIRED The VM is currently working with the VBIOS ROM field left blank. SUMMARY If you're passing an NVIDIA GPU through to an Ubuntu/Linux VM on Unraid and encounter this combination: • VM boots • GPU appears to pass through correctly • nvidia-smi works • Physical monitor goes black when Linux takes over • Monitor/EDID is detected by Xorg • Display manager/Xorg fails to start • Xorg reports DMA or push-buffer initialization errors Try disabling NVIDIA GSP firmware: options nvidia NVreg_EnableGpuFirmware=0 For my RTX 3060 with NVIDIA 580, that was the fix. This workaround is not necessarily limited to the RTX 3060. The important indicators are the NVIDIA driver successfully detecting the passed-through GPU while the graphical display fails during initialization, particularly when the Xorg log contains DMA or push-buffer errors. The move from Ubuntu/GNOME to Kubuntu/KDE during troubleshooting appears to have been unrelated. Based on the eventual diagnosis, I would try the GSP workaround on the original Ubuntu installation before changing desktop environments.