I'm following this helpful guide for USB controller passthrough.

I have followed the procedure and have developed a block for code for hostdev, as explained in step 11b:

    <hostdev mode='subsystem' type='pci' managed='yes'>

      <driver name='vfio'/>

      <source>

        <address domain='0x0000' bus='0x00' slot='0x1c' function='0x0'/>

      </source>

    </hostdev>

I have found the way to see the XML code by editing the VM, and using the Form View / XML View at the right.

The article does not say where the new hostdev section should be inserted in the overall XML.

This post has someone's complete XML with a hostdev section.

In that particular file, the hostdev code goes in the <devices> section, after <video> but before <memballoon model='virtio'>

Is that always the case, or dependent on other factors?

Are there any details on the XML format requirements that could explain where the <hostdev> section should be inserted?

Edited May 25, 20251 yr by timg11

BTW, this is Unraid 7.0.1 on a Dell T440 server

I thought I'd try inserting the code into the XML, so I inserted it in <devices> next to last. (see below for full XML)

I got this error when attempting to start the VM:

Execution error

internal error: Non-endpoint PCI devices cannot be assigned to guests

Not sure if that is due to the location of the hostdev section or something else.

Background information:

root@T440:~# lspci | grep USB

00:14.0 USB controller: Intel Corporation C620 Series Chipset Family USB 3.0 xHCI Controller (rev 09)

01:00.0 USB controller: ASMedia Technology Inc. ASM2142/ASM3142 USB 3.1 Host Controller

Which PCI is each USB bus on?

root@T440:~# readlink /sys/bus/usb/devices/usb1

../../../devices/pci0000:00/0000:00:14.0/usb1

root@T440:~# readlink /sys/bus/usb/devices/usb2

../../../devices/pci0000:00/0000:00:14.0/usb2

root@T440:~# readlink /sys/bus/usb/devices/usb3

../../../devices/pci0000:00/0000:00:1c.0/0000:01:00.0/usb3

root@T440:~# readlink /sys/bus/usb/devices/usb4

../../../devices/pci0000:00/0000:00:1c.0/0000:01:00.0/usb4

The Inatech PCIe USB card appears as usb3 for USB2.0 device, and usb4 for USB3 devices.

As a sanity check the Unraid boot USB drive is on usb2.

IOMMU

IOMMU group 15:                                [8086:a190] 00:1c.0 PCI bridge: Intel Corporation C620 Series Chipset Family PCI Express Root Port #1 (rev f9)

So the Inatech PCIe USB controller is the only thing on 00:1c.0 . Is that not an endpoint?

Here's the entire XML:

<?xml version='1.0' encoding='UTF-8'?>
<domain type='kvm'>
<name>Windows 11</name>
<uuid>530f19ee-2c76-bb83-fe14-b9b745c7552e</uuid>
<description>192.168.27.2</description>
<metadata>
<vmtemplate xmlns="unraid" name="Windows 11" icon="windows11.png" os="windowstpm" webui="" storage="default"/>
</metadata>
<memory unit='KiB'>33554432</memory>
<currentMemory unit='KiB'>8388608</currentMemory>
<memoryBacking>
<nosharepages/>
</memoryBacking>
<vcpu placement='static'>4</vcpu>
<cputune>
<vcpupin vcpu='0' cpuset='4'/>
<vcpupin vcpu='1' cpuset='5'/>
<vcpupin vcpu='2' cpuset='6'/>
<vcpupin vcpu='3' cpuset='7'/>
</cputune>
<os>
<type arch='x86_64' machine='pc-i440fx-9.1'>hvm</type>
<loader readonly='yes' type='pflash'>/usr/share/qemu/ovmf-x64/OVMF_CODE-pure-efi-tpm.fd</loader>
<nvram>/etc/libvirt/qemu/nvram/530f19ee-2c76-bb83-fe14-b9b745c7552e_VARS-pure-efi-tpm.fd</nvram>
</os>
<features>
<acpi/>
<apic/>
<hyperv mode='custom'>
<relaxed state='on'/>
<vapic state='on'/>
<spinlocks state='on' retries='8191'/>
<vpindex state='on'/>
<synic state='on'/>
<stimer state='on'/>
<vendor_id state='on' value='none'/>
</hyperv>
</features>
<cpu mode='host-passthrough' check='none' migratable='on'>
<topology sockets='1' dies='1' clusters='1' cores='2' threads='2'/>
<cache mode='passthrough'/>
</cpu>
<clock offset='localtime'>
<timer name='hpet' present='no'/>
<timer name='hypervclock' present='yes'/>
</clock>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>restart</on_crash>
<devices>
<emulator>/usr/local/sbin/qemu</emulator>
<disk type='file' device='disk'>
<driver name='qemu' type='raw' cache='writeback' discard='unmap'/>
<source file='/mnt/user/domains/Windows 11/vdisk1.img'/>
<target dev='hdc' bus='sata' rotation_rate='1'/>
<serial>vdisk1</serial>
<boot order='1'/>
<address type='drive' controller='0' bus='0' target='0' unit='2'/>
</disk>
<disk type='file' device='cdrom'>
<driver name='qemu' type='raw'/>
<source file='/mnt/user/isos/Win11_24H2_English_x64.iso'/>
<target dev='hda' bus='ide'/>
<readonly/>
<boot order='2'/>
<address type='drive' controller='0' bus='0' target='0' unit='0'/>
</disk>
<disk type='file' device='cdrom'>
<driver name='qemu' type='raw'/>
<source file='/mnt/user/isos/virtio-win-0.1.271-1.iso'/>
<target dev='hdb' bus='ide'/>
<readonly/>
<address type='drive' controller='0' bus='0' target='0' unit='1'/>
</disk>
<controller type='pci' index='0' model='pci-root'/>
<controller type='ide' index='0'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
</controller>
<controller type='sata' index='0'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
</controller>
<controller type='virtio-serial' index='0'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
</controller>
<controller type='usb' index='0' model='qemu-xhci' ports='15'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
</controller>
<interface type='bridge'>
<mac address='52:54:00:c9:68:53'/>
<source bridge='br0'/>
<model type='virtio-net'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
</interface>
<serial type='pty'>
<target type='isa-serial' port='0'>
<model name='isa-serial'/>
</target>
</serial>
<console type='pty'>
<target type='serial' port='0'/>
</console>
<channel type='unix'>
<target type='virtio' name='org.qemu.guest_agent.0'/>
<address type='virtio-serial' controller='0' bus='0' port='1'/>
</channel>
<channel type='qemu-vdagent'>
<source>
<clipboard copypaste='yes'/>
<mouse mode='client'/>
</source>
<target type='virtio' name='com.redhat.spice.0'/>
<address type='virtio-serial' controller='0' bus='0' port='2'/>
</channel>
<input type='tablet' bus='usb'>
<address type='usb' bus='0' port='1'/>
</input>
<input type='mouse' bus='ps2'/>
<input type='keyboard' bus='ps2'/>
<tpm model='tpm-tis'>
<backend type='emulator' version='2.0' persistent_state='yes'/>
</tpm>
<graphics type='vnc' port='-1' autoport='yes' websocket='-1' listen='0.0.0.0' sharePolicy='ignore'>
<listen type='address' address='0.0.0.0'/>
</graphics>
<audio id='1' type='none'/>
<video>
<model type='qxl' ram='65536' vram='65536' vgamem='16384' heads='1' primary='yes'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x1e' function='0x0'/>
</video>
<hostdev mode='subsystem' type='pci' managed='yes'>
<driver name='vfio'/>
<source>
<address domain='0x0000' bus='0x00' slot='0x1c' function='0x0'/>
</source>
<address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
</hostdev>
<memballoon model='virtio'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
</memballoon>
</devices>
</domain>


10 minutes ago, timg11 said:

So the Inatech PCIe USB controller is the only thing on 00:1c.0 . Is that not an endpoint?

That is the PCI root bridge the card is 01:00.0 You can bind to vfio in system devices and it will show in PCI other in the VM template. Or use bus 01, slot 00 function 0 in your xml

@SimonF thanks for the reply.

I don't understand "bind to vfio in system devices". I searched on that phrase with the term unraid, and found only one article that didn't explain it. On the Unraid VM Edit page, I don't find "system devices" in the form view, or in the XML.

I think I understand your second suggestion, though.

You're saying because the IOMMU of 00:1c.0 is the PCI bridge, I should go down one level to the USB controller which is 01:00.0

root@T440:~# readlink /sys/bus/usb/devices/usb3

../../../devices/pci0000:00/0000:00:1c.0/0000:01:00.0/usb3

root@T440:~# readlink /sys/bus/usb/devices/usb4

../../../devices/pci0000:00/0000:00:1c.0/0000:01:00.0/usb4

That would make my hostdev section like this:

    <hostdev mode='subsystem' type='pci' managed='yes'>

      <driver name='vfio'/>

      <source>

        <address domain='0x0000' bus='0x01' slot='0x0' function='0x0'/>

      </source>

    </hostdev>

For my original question about the location of the hostdev section, I'm guessing the way I inserted it in the XML above is correct?

With the changes in bus/slot/function it should work now?

Success!

The XML with   <address domain='0x0000' bus='0x01' slot='0x0' function='0x0'/> as shown above works.

Inserting the XML between </video> and <memballoon model='virtio'> works.

5 hours ago, timg11 said:

@SimonF thanks for the reply.

I don't understand "bind to vfio in system devices". I searched on that phrase with the term unraid, and found only one article that didn't explain it. On the Unraid VM Edit page, I don't find "system devices" in the form view, or in the XML.

I think I understand your second suggestion, though.

You're saying because the IOMMU of 00:1c.0 is the PCI bridge, I should go down one level to the USB controller which is 01:00.0

root@T440:~# readlink /sys/bus/usb/devices/usb3

../../../devices/pci0000:00/0000:00:1c.0/0000:01:00.0/usb3

root@T440:~# readlink /sys/bus/usb/devices/usb4

../../../devices/pci0000:00/0000:00:1c.0/0000:01:00.0/usb4

That would make my hostdev section like this:

    <hostdev mode='subsystem' type='pci' managed='yes'>

      <driver name='vfio'/>

      <source>

        <address domain='0x0000' bus='0x01' slot='0x0' function='0x0'/>

      </source>

    </hostdev>

For my original question about the location of the hostdev section, I'm guessing the way I inserted it in the XML above is correct?

With the changes in bus/slot/function it should work now?

Glad you got it working.

Tools->system devices, check box allows to be bound to vfio

Then a PCI card should show in this section - Other PCI

Thank you for showing me how the system devices are done.

As I noted in my other thread, I'm also having trouble with passthrough of an embedded VGA controller.

Now that I know how and where to bind to vfio in system devices, I'll remove the hostdev XML code and try the bind checkmark on the VGA controller.