IOMMU / PCIE passtrough not working

General
1

Like the Subject already states, I seem to be unable or making some error in enabling IOMMU on my HL15 or in the Proxmox install. My Goal is to run Proxmox and pass on a HBA to a VM running TrueNas scale.
I am using a:

  • System: 45 Drives HomeLab 15 (HL15 fully prebuild)

  • Motherboard: Supermicro X11SPH-NCTPF

  • CPU: Intel Xeon Bronze 3204 CPU

  • OS: Proxmox Virtual Environment 9.0.11

So far I have checked these Settings in Bios

1
11222×862 179 KB

2
21193×840 144 KB

And modified the Grub Config:

3
31044×998 75.5 KB

You see “intel_iommu=on” is in there as well as 2 Lines commented out with “iommu=pt” and “intel_pstate=disable”.
Whatever Line I select non of those 3 seem to get it working after “update-grub” and a reboot.

" dmesg | grep -e DMAR -e iommu " does not list anything.
" dmesg | grep ‘remapping’ " does not list anything.

I seem to bee running out of ideas what might cause this. Does someone of you have any sugestions to troubleshoot this?

2

Can you confirm you’re booting legacy BIOS and not UEFI? If you are using UEFI to boot the system then you need to put the kernel parameters into /etc/kernel/cmdline instead of the grub file.

2 Likes
3

Yup, if you’re booting UEFI, you are using systemd-boot, not GRUB.

Here are my notes for enabling IOMMU on my RomeD8-2T, though I’m on AMD. Not sure if your BIOS also needs to enable IOMMU separately from VT-x/SVM, as mine does, or if it’s part of enabling VT-x.

BIOS:

Advanced > CPU Configuration required for AMD virtualization in Proxmox/KVM. For Intel CPUs, the equivalent setting is called Intel VT-x

  • SVM Mode → Enabled

Advanced > AMD CBS > NBIO Common Options

  • IOMMU → Enabled

  • ACS Enable → Enabled Ensures clean isolation of devices into separate IOMMU groups.

  • PCIe ARI Support → Enabled Allows multiple functions (like SR-IOV VFs) on a single PCIe slot.

  • Enable AER Cap > Enabled Advanced Error Reporting - detect, log, and optionally recover from PCIe errors (both correctable and uncorrectable), and record in system’s error log

Proxmox:

for UEFI, you need to edit the Proxmox kernel config file at /etc/kernel/cmdline

for AMD, add amd_iommu=on iommu=pt

for Intel, add intel_iommu=on iommu=pt

then update: proxmox-boot-tool refresh

2 Likes
4

By Now I seem to have got it Figured out. Idefinitly was using Grub like i tought an am e step further.

for d in /sys/kernel/iommu_groups/*/devices/*; do n=${d#*/iommu_groups/*}; n=${n%%/*}; printf 'IOMMU group %s ' "$n"; lspci -nns "${d##*/}"; done

Results in a Listing of IOMMU group numbers and the Devices.

Comment Image|240xauto

Thanks to everyone for Help, tips Suggestions and fresh Coffee :slight_smile: