VFIO cannot be used for the Memory Controller

Question

I am trying to set up a PCI Passthrough of my Audio device in QEMU/KVM. The audio device is in the group 9, together with other three devices:

IOMMU Group 9 00:1f.0 ISA bridge [0601]: Intel Corporation Device [8086:9d4e] (rev 21)
IOMMU Group 9 00:1f.2 Memory controller [0580]: Intel Corporation Sunrise Point-LP PMC [8086:9d21] (rev 21)
IOMMU Group 9 00:1f.3 Audio device [0403]: Intel Corporation Device [8086:9d71] (rev 21)
IOMMU Group 9 00:1f.4 SMBus [0c05]: Intel Corporation Sunrise Point-LP SMBus [8086:9d23] (rev 21)

So, I modified my /etc/modprobe.d/vfio with the devices I want to attach:

00:1f.0 0601: 8086:9d4e (rev 21)
00:1f.2 0580: 8086:9d21 (rev 21)
00:1f.3 0403: 8086:9d71 (rev 21)
00:1f.4 0c05: 8086:9d23 (rev 21)

So the file reads

options vfio-pci ids=8086:9d4e,8086:9d21,8086:9d71,8086:9d23

Also, in order to charge them at boot time, I modified the mkinitcpio so it loads vfio vfio_iommu_type1 vfio_pci vfio_virqfd

And it worked:

$ dmesg | grep vfio
[    0.746712] vfio_pci: add [8086:9d4e[ffff:ffff]] class 0x000000/00000000
[    0.746715] vfio_pci: add [8086:9d21[ffff:ffff]] class 0x000000/00000000
[    0.762942] vfio_pci: add [8086:9d71[ffff:ffff]] class 0x000000/00000000
[    0.762968] vfio_pci: add [8086:9d23[ffff:ffff]] class 0x000000/00000000

However, for some reason, the Memory controller continues using the intel_pmc_core kernel driver instead of vfio-pci, as all the others

$ lspci -k -s 00:1f
00:1f.0 ISA bridge: Intel Corporation Device 9d4e (rev 21)
    Subsystem: Hewlett-Packard Company Device 827e
    Kernel driver in use: vfio-pci
00:1f.2 Memory controller: Intel Corporation Sunrise Point-LP PMC (rev 21)
    Subsystem: Hewlett-Packard Company Device 827e
    Kernel driver in use: intel_pmc_core
00:1f.3 Audio device: Intel Corporation Device 9d71 (rev 21)
    Subsystem: Hewlett-Packard Company Device 827e
    Kernel driver in use: vfio-pci
    Kernel modules: snd_hda_intel, snd_soc_skl
00:1f.4 SMBus: Intel Corporation Sunrise Point-LP SMBus (rev 21)
    Subsystem: Hewlett-Packard Company Device 827e
    Kernel driver in use: vfio-pci
    Kernel modules: i2c_i801

And so, qemu complains that not all the IOMMU group is passed by:

$ qemu-system-x86_64 -hda /home/janus/qemu/win10qemu.img -enable-kvm -device vfio-pci,host=0000:00:1f.0 -device vfio-pci,host=0000:00:1f.2 -device vfio-pci,host=0000:00:1f.3 -device vfio-pci,host=0000:00:1f.4
qemu-system-x86_64: -device vfio-pci,host=0000:00:1f.0: vfio error: 0000:00:1f.0: group 9 is not viable
Please ensure all devices within the iommu_group are bound to their vfio bus driver.

What I am doing wrong?

Answer 1

The answer seems to be: of course I cannot pass the Memory Controller to the VM. And since the Audio Card is in the same IOMMU group as the Memory Controller, I will not be able to pass it to the VM.