I’m encountering major issues getting PCIe GPU passthrough working on my homely setup:

Host hardware & firmware
• Dell PowerEdge R740 (dual Xeon Gold 6230R)
• Single NVIDIA RTX A4000 GPU
• BIOS settings confirmed: Virtualization enabled, IOMMU enabled, “Above 4G Decode” enabled
• XCP-ng host (dom0) is not using the GPU; both functions (graphics + audio) are assigned to the VM

VM Guest details
• Guest OS: Arch Linux (also tested Windows)
• VM config: Both PCI devices (GPU + HDMI/Audio) attached via passthrough
• On Arch: kernel cmdline includes pcie_aspm=off nvidia.NVreg_EnableGpuFirmware=0
• On host VM platform flags set: pci-msitranslate=true, pci-power_mgmt=false, device-model=qemu-upstream-compat, UEFI/OVMF enabled

Symptoms
• On Arch: repeated log entries such as:

NVRM: gpuHandleSanityCheckRegReadError_GM107: Possible bad register read …
NVRM: GSP failed to halt with GFW_BOOT …
RmInitAdapter: Cannot initialize GSP firmware RM

•	On Windows: Device Manager shows “Error 43” for the GPU.

What I’ve done so far
• Verified IOMMU groups; both functions isolated and passed through correctly
• Checked FLR support for the GPU: GPU core supports FLR, audio function does not
• Tried disabling ASPM/power management in host & guest
• Tried older NVIDIA driver versions (including 510.xx branch)
• Verified large BARs are present in guest lspci -vvv output
• Uploaded full dmesg logs + BIOS dump from Redfish for review

Attachments
• dmesg_errors.log
• BIOS dump from Redfish[link text]

Request for help
If you have successfully passed through an RTX A4000 on XCP-ng (to Linux or Windows guest), can you share:
• XCP-ng version, guest OS, driver version
• VM platform flags (especially any non-default settings)
• Any custom vBIOS or device reboot/reset tweaks you used
• Any additional steps you found necessary for stability

I’m pretty much out of ideas at this point and would appreciate any working configurations or suggestions.
dmesg_errors.txt
BIOS_Current_Settings.txt