Guide on how to setup ASMedia 1166 Passthrough in Proxmox

asmedia_1166_proxmox_passthrough.md

Guide: Setting Up ASMedia 1166 on Proxmox

To flash the controller with the correct firmware, you must have access to a Windows machine.

⚠️ Do NOT use version 241224-0000-00!

With this version, starting the VM in Proxmox will hang indefinitely. The VM start command never completes, and you're forced to hard reset the Proxmox host. This is also the version reporting 32 SATA Devices instead of 6.

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Firmware

Download and flash this firmware version: 211108-0000-00 (archived version). Other might work as well, but this is the one I'm using.

My System:

• AMD Ryzen Pro 5655G
• GIGABYTE B550I AORUS PRO AX

Kernel Parameters

If Proxmox is installed using ZFS:

Edit /etc/kernel/cmdline and append the following parameter:

iommu=pt

If installed using LVM/ext4:

Edit /etc/default/grub and add it inside the GRUB_CMDLINE_LINUX line:

GRUB_CMDLINE_LINUX="... iommu=pt"

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Check IOMMU Groups

Run the following to list your IOMMU groups:

shopt -s nullglob
for g in $(find /sys/kernel/iommu_groups/* -maxdepth 0 -type d | sort -V); do
  echo "IOMMU Group ${g##*/}:"
  for d in $g/devices/*; do
    echo -e "\t$(lspci -nns ${d##*/})"
  done
done

If your ASMedia 1166 controller shares an IOMMU group with other devices, add this parameter as well:

pcie_acs_override=downstream,multifunction

Add it to /etc/kernel/cmdline or /etc/default/grub, depending on your setup.

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Load Required Modules

Edit /etc/modules and add the following lines:

vfio
vfio_iommu_type1
vfio_pci

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Blacklist AHCI for ASM1166

Create /etc/modprobe.d/ahci-blacklist.conf with the following content:

options vfio-pci ids=1b21:1166
softdep ahci pre: vfio-pci

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Rebuild Initramfs

Run:

update-initramfs -u -k all

Then reboot your system.

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Verify the config

After reboot, run:

lspci -nnk | grep -A 3 ASM1166

You should see something like:

03:00.0 SATA controller [0106]: ASMedia Technology Inc. ASM1166 Serial ATA Controller [1b21:1166] (rev 02)
    Subsystem: ZyDAS Technology Corp. ASM1166 Serial ATA Controller [2116:2116]
    Kernel driver in use: vfio-pci
    Kernel modules: ahci

The line Kernel driver in use: vfio-pci confirms that the controller is bound correctly.

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Add Device to VM

Now, you can add the ASM1166 controller to your VM under Hardware -> Add -> PCI Device in the Proxmox UI.

asmedia_sata_firmware(station-drivers.com).zip

I've been debugging the vm/host hanging issue too before I've found this gist, and by booting the VM with a debug build of OVMF I've realised that the issue is due to rombar.

This happened with stock firmware that came preinstalled, and also happened with some random firmware I've found online.

Last lines printed before OVMF hangs:

PciBus: HostBridge->NotifyPhase(AllocateResources) - Success
Process Option ROM: BAR Base/Length = 81000000/80000

so I tried disabling rombar on this device (rombar=0 in qemu terms) and that fixed the issue: everything seems to work correctly.

I'll leave a comment if I have any issues, but so far it seems to be working with firmware 241224000000:

sudo xxd -p -s 240 -l 6 "/sys/bus/pci/devices/$(lspci -mD -d 1b21:1166 | cut -d' ' -f1)/config"
241224000000

TL;DR: instead of refreshing the ASM1166 to an older firmware you can disable rombar for this pci passthrough device.
another workaround is booting the vm in legacy mode with SeaBIOS instead of UEFI+OVMF.