Intel Arc SR-IOV Hardware Transcoding with Plex on Proxmox VE

My homelab has three new additions: ASUS NUC 15 Pro units, each with an Intel Core Ultra 7 255H. They are surprisingly capable machines, and getting proper hardware transcoding working in Plex using the built-in Intel Arc iGPU was high on the list.

It took longer than expected to get it all sorted, but the end result is solid.

All three NUCs run Proxmox VE 9.x in a cluster. The Intel Core Ultra 7 255H has an Intel Arc iGPU based on the Arrow Lake-P architecture, with PCI device ID 8086:7d51. This is an integrated GPU sharing the same die as the CPU, which matters for how passthrough works.

What is SR-IOV and Why Use It?

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The obvious approach for GPU passthrough is to assign the entire GPU to a single VM. That works, but it creates a strict 1:1 relationship. One GPU, one VM, host loses access entirely. No display output from the NUC, no GPU for other VMs or containers, a permanent commitment of the hardware to one workload.

SR-IOV (Single Root I/O Virtualization) solves both problems. A single physical GPU presents itself as multiple independent virtual devices simultaneously. The host keeps the physical function, so display output works normally. Up to 7 additional virtual functions can be assigned to different VMs or containers at the same time, giving a total of 8 GPU devices: one for the host and seven for guests.

Each virtual function gets access to the full GPU execution engines, but time on those engines is scheduled dynamically based on demand. When only one VM is transcoding, it gets full GPU bandwidth. When multiple VMs are active, the GPU scheduler divides time between them automatically. No hard per-VF resource guarantees, closer to CPU time-sharing than static partitioning. In practice for a Plex server in a homelab this works well, since transcoding workloads are bursty rather than constant.

SR-IOV on Intel integrated GPUs is not enabled in the stock Linux driver. It requires a patched version of i915, which is what the i915-sriov-dkms project provides.

Host Setup

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The first hurdle was the BIOS. On the NUC 15 Pro, the virtualisation settings are not where you would expect on a desktop board. VT-d is under Security rather than Advanced, and the Virtual Display Emulation setting (which keeps the iGPU active with no monitor connected) is under Advanced > Video. Both are required.

On the Proxmox side, three things need to be in place:

1. i915-sriov-dkms patches the i915 kernel driver to enable SR-IOV virtual functions. Version 2026.05.06 supports Proxmox kernel 6.17 through 7.0. Always check the releases page for the latest version and supported kernel range before upgrading the host kernel.

2. Kernel parameters tell i915 to claim the Arrow Lake GPU and prevent the newer xe driver from taking it first. The force_probe=7d51 flag targets the exact device ID, module_blacklist=xe keeps xe out, and i915.max_vfs=7 sets the number of virtual functions.

3. A systemd service loads i915 and creates the virtual functions at boot. Sysfsutils turned out to be unreliable here since i915 needs to be fully loaded before the VF count can be set, and the ordering is not guaranteed without an explicit dependency chain. The systemd service handles this cleanly.

After a reboot: eight VGA devices in lspci, one physical function on the host, seven virtual functions ready to assign.

Proxmox Host Setup Commands

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dmesg | grep -e "IOMMU enabled" -e "Directed I/O"

DMAR: IOMMU enabled
DMAR: Intel(R) Virtualization Technology for Directed I/O

apt update && apt install -y dkms build-essential
apt install -y pve-headers-$(uname -r)

wget -O /tmp/i915-sriov-dkms.deb \
  "https://github.com/strongtz/i915-sriov-dkms/releases/download/2026.05.06/i915-sriov-dkms_2026.05.06_amd64.deb"

dpkg -i /tmp/i915-sriov-dkms.deb
dkms install i915-sriov-dkms/2026.05.06 -k $(uname -r) --force
dkms status

GRUB_CMDLINE_LINUX_DEFAULT="quiet intel_iommu=on iommu=pt i915.enable_guc=3 i915.max_vfs=7 i915.force_probe=7d51 module_blacklist=xe"

update-grub
update-initramfs -u -k all

cat > /etc/systemd/system/i915-sriov.service << 'EOF'
[Unit]
Description=Intel i915 SR-IOV VF Setup
After=systemd-modules-load.service
After=local-fs.target

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/sbin/modprobe i915
ExecStartPost=/bin/sh -c 'sleep 2 && echo 7 > /sys/bus/pci/devices/0000:00:02.0/sriov_numvfs'

[Install]
WantedBy=multi-user.target
EOF

systemctl enable i915-sriov
reboot

lspci | grep VGA | wc -l                              # Expected: 8
cat /sys/bus/pci/devices/0000:00:02.0/sriov_numvfs   # Expected: 7
lspci -nnk -s 00:02.0 | grep "driver in use"         # Expected: i915
systemctl status i915-sriov                          # Expected: active (exited)

VM Setup and the Kernel

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When creating the VM in Proxmox, a few settings are critical:

The PCI device to add is 0000:00:02.1 (or another unassigned device ID 0000:00:02.x ). Never use 00:02.0, that is the physical function which must stay on the host. PCI-Express checked, All Functions and Primary GPU left unchecked.

Two Ubuntu versions have been tested and confirmed working:

• Ubuntu 26.04 LTS with the stock kernel 7.0, no extra steps needed
• Ubuntu 24.04 LTS with mainline kernel 6.17 from kernel.ubuntu.com

Ubuntu 24.04’s default kernel 6.8 predates Arrow Lake SR-IOV VF support entirely, which is why the mainline kernel step is needed. Ubuntu 26.04 ships kernel 7.0 as its default and the DKMS module builds cleanly against it. An in-place upgrade from 24.04 to 26.04 is not yet available as of May 2026, so a fresh install is the only option for 26.04.

The Proxmox hosts running kernel 7.0 does not mean Ubuntu 7.0 behaves identically. The i915-sriov-dkms module targets specific kernel builds, and Ubuntu’s packaging can differ enough to cause build failures. Always verify dkms status shows the module as installed before rebooting into a new kernel.

Verification inside the VM with vainfo confirms the hardware pipeline is working:

vainfo: Driver version: Intel iHD driver for Intel(R) Gen Graphics - 26.1.2
vainfo: Supported profile and entrypoints
      VAProfileH264Main               : VAEntrypointVLD
      VAProfileH264Main               : VAEntrypointEncSlice
      VAProfileHEVCMain               : VAEntrypointVLD
      VAProfileHEVCMain               : VAEntrypointEncSlice
      VAProfileAV1Profile0            : VAEntrypointVLD
      VAProfileAV1Profile0            : VAEntrypointEncSlice
      ...

Both VLD (decode) and EncSlice (encode) entries for H264, HEVC, and AV1 confirm the full hardware pipeline is available.

Plex VM Setup Commands

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sudo apt update && sudo apt upgrade -y
sudo apt install -y dkms build-essential wget gcc-14 linux-headers-$(uname -r)

wget -O /tmp/i915-sriov-dkms.deb \
  "https://github.com/strongtz/i915-sriov-dkms/releases/download/2026.05.06/i915-sriov-dkms_2026.05.06_amd64.deb"
sudo dpkg -i /tmp/i915-sriov-dkms.deb
sudo dkms install i915-sriov-dkms/2026.05.06 -k $(uname -r) --force
dkms status

sudo su -
echo "options i915 force_probe=7d51" > /etc/modprobe.d/i915.conf
echo "blacklist xe" >> /etc/modprobe.d/i915.conf
update-initramfs -u
exit
sudo reboot

uname -r
lspci -nnk | grep -A3 "01:00.0"
sudo dmesg | grep -i "sriov\|guc\|huc" | head -5
sudo vainfo --display drm --device /dev/dri/renderD128

i915 0000:01:00.0: Running in SR-IOV VF mode
i915 0000:01:00.0: GuC firmware PRELOADED
i915 0000:01:00.0: HuC firmware PRELOADED

wget -qO - https://repositories.intel.com/gpu/intel-graphics.key | \
  sudo gpg --dearmor -o /usr/share/keyrings/intel-graphics.gpg
echo "deb [arch=amd64 signed-by=/usr/share/keyrings/intel-graphics.gpg] \
  https://repositories.intel.com/gpu/ubuntu noble unified" | \
  sudo tee /etc/apt/sources.list.d/intel-graphics.list
sudo apt update
sudo apt install -y vainfo intel-gpu-tools libva-drm2 libva-x11-2 \
  libva-wayland2 va-driver-all intel-media-va-driver-non-free libigdgmm12 libva2

sudo dpkg -i plexmediaserver_1.43.2.10687-563d026ea_amd64.deb
sudo usermod -aG video plex
sudo usermod -aG render plex
sudo systemctl enable --now plexmediaserver

sudo systemctl stop plexmediaserver
sudo sed -i 's/HardwareDevicePath=""/HardwareDevicePath="\/dev\/dri\/renderD128"/' \
  "/var/lib/plexmediaserver/Library/Application Support/Plex Media Server/Preferences.xml"
sudo systemctl start plexmediaserver

Plex and Hardware Transcoding

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Getting Plex to actually use the GPU was not as straightforward as expected. The VF was working, VAAPI was reporting full codec support, the plex user had access to the render device, hardware acceleration was enabled in settings. And yet Plex kept using software transcoding.

The short version: the current public release of Plex Media Server does not support Intel Arc hardware transcoding on Linux. This caught me completely off guard, since the hardware side was working perfectly and everything pointed to a configuration problem rather than a Plex limitation.

The fix is in Plex Media Server 1.43.2.10687, released on May 4, 2026 as a Plex Pass beta release. Installing this version gets hardware transcoding working immediately. The Plex dashboard shows (hw) next to the active transcode, indicating that hardware transcoding is being used.

To confirm hardware transcoding is actually running, check the transcoder statistics log while a stream is active:

sudo grep "transcodeHw" \
  "/var/lib/plexmediaserver/Library/Application Support/Plex Media Server/Logs/Plex Transcoder Statistics.log" | tail -3

A working setup shows transcodeHwFullPipeline="1" with both transcodeHwDecoding="vaapi" and transcodeHwEncoding="vaapi", confirming both encode and decode are running on the Intel Arc GPU through VAAPI.

This is currently a beta release requiring an active Plex Pass subscription. It is expected to reach the public release channel in a subsequent update.

Upgrading

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The DKMS module and the Proxmox kernel are coupled. Before upgrading the Proxmox kernel, check whether the current DKMS version supports it. Install headers for the new kernel and verify the module builds successfully before rebooting. The dkms status output should confirm the module is installed for the new kernel version before committing to the reboot.

The VM kernel is a separate concern. Do not upgrade the Ubuntu guest kernel through distribution channels expecting the same result as the host. Always verify dkms status after any kernel change and check the i915-sriov-dkms releases page for supported kernel ranges.

After any Plex upgrade, verify the bundled iHD driver is still present:

find /var/lib/plexmediaserver/ -name "iHD_drv_video.so" 2>/dev/null

If hardware transcoding stops working after a Plex update, that is the first place to check.

The Result

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Three NUC hosts running Proxmox VE 9.x with kernel 7.0, i915-sriov-dkms 2026.05.06, and seven SR-IOV virtual functions each. Display output from the HDMI port works normally. Plex VMs confirmed working on both Ubuntu 24.04 with mainline kernel 6.17 and Ubuntu 26.04 with stock kernel 7.0, both running Plex Media Server 1.43.2.10687. Hardware transcoding confirmed working with a full VAAPI pipeline on all three hosts.

VMs can be migrated between hosts with Proxmox offline migration using the force flag, live migration does not work when there is a PCI device assigned to the VM. Hardware transcoding works immediately on the destination host without any reconfiguration, since all three NUCs have identical hardware.