Pro audio card with VFIO

I’m having some problems getting a Lynx Aes16e-50 sound card to work using it’s native asio drivers in a Win10 guest.
The only way i can get it to work is by using wasapi push style, this works mostly ok sometimes there is a click, pop or skip. When i switch to event style this get much worse and music is unplayable, when using asio the vm freezes hard and i have to restart the host for the Lynx to reset.
i5 7500, 16Gb ram, Msi B250 Pcmate, 500gb Nvme, 80Gb ssd, intel gbit nic, Lynx Aes16e-50(pci-e) and a bunch of other hdds running Fedora 29.
The vm is configured as follows:
2 cores, 8Gb, 89Gb ssd, intel nic and Lynx. I passed both cards through with vfio.

Output of lspci -nnk:

02:00.0 Multimedia audio controller [0401]: Lynx Studio Technology, Inc. Lynx AES16e [1621:0028]
Subsystem: Lynx Studio Technology, Inc. Lynx AES16e [1621:0028]
Kernel driver in use: vfio-pci

04:00.0 Ethernet controller [0200]: Intel Corporation 82574L Gigabit Network Connection [8086:10d3]
Subsystem: Intel Corporation Gigabit CT Desktop Adapter [8086:a01f]
Kernel driver in use: vfio-pci
Kernel modules: e1000e

Here is the config file:

<domain type='kvm' id='1'>
    <libosinfo:libosinfo xmlns:libosinfo="">
      <libosinfo:os id=""/>
  <memory unit='KiB'>8388608</memory>
  <currentMemory unit='KiB'>8388608</currentMemory>
  <vcpu placement='static'>2</vcpu>
    <vcpupin vcpu='0' cpuset='2'/>
    <vcpupin vcpu='1' cpuset='3'/>
    <emulatorpin cpuset='2-3'/>
    <type arch='x86_64' machine='pc-q35-3.0'>hvm</type>
    <loader readonly='yes' type='pflash'>/usr/share/edk2/ovmf/OVMF_CODE.fd</loader>
    <boot dev='hd'/>
      <relaxed state='on'/>
      <vapic state='on'/>
      <spinlocks state='on' retries='8191'/>
      <vpindex state='on'/>
      <synic state='on'/>
      <stimer state='on'/>
      <reset state='on'/>
      <vendor_id state='off'/>
      <frequencies state='on'/>
    <vmport state='off'/>
  <cpu mode='custom' match='exact' check='full'>
    <model fallback='forbid'>Skylake-Client-IBRS</model>
    <topology sockets='1' cores='2' threads='1'/>
    <cache level='3' mode='emulate'/>
    <feature policy='require' name='ss'/>
    <feature policy='require' name='vmx'/>
    <feature policy='require' name='hypervisor'/>
    <feature policy='require' name='tsc_adjust'/>
    <feature policy='require' name='clflushopt'/>
    <feature policy='require' name='ssbd'/>
    <feature policy='require' name='xsaves'/>
    <feature policy='require' name='pdpe1gb'/>
  <clock offset='localtime'>
    <timer name='rtc' tickpolicy='catchup'/>
    <timer name='pit' tickpolicy='delay'/>
    <timer name='hpet' present='yes'/>
    <timer name='hypervclock' present='yes'/>
    <timer name='tsc' present='yes' mode='native'/>
    <suspend-to-mem enabled='no'/>
    <suspend-to-disk enabled='no'/>
    <disk type='block' device='disk'>
      <driver name='qemu' type='raw' cache='none' io='native'/>
      <source dev='/dev/sda'/>
      <target dev='vda' bus='virtio'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x02' slot='0x00' function='0x0'/>
    <controller type='usb' index='0' model='qemu-xhci' ports='15'>
      <alias name='usb'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
    <controller type='sata' index='0'>
      <alias name='ide'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1f' function='0x2'/>
    <controller type='pci' index='0' model='pcie-root'>
      <alias name='pcie.0'/>
    <controller type='pci' index='1' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='1' port='0x10'/>
      <alias name='pci.1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0' multifunction='on'/>
    <controller type='pci' index='2' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='2' port='0x11'/>
      <alias name='pci.2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x1'/>
    <controller type='pci' index='3' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='3' port='0x12'/>
      <alias name='pci.3'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x2'/>
    <controller type='pci' index='4' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='4' port='0x13'/>
      <alias name='pci.4'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x3'/>
    <controller type='pci' index='5' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='5' port='0x14'/>
      <alias name='pci.5'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x4'/>
    <controller type='pci' index='6' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='6' port='0x15'/>
      <alias name='pci.6'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x5'/>
    <controller type='pci' index='7' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='7' port='0x16'/>
      <alias name='pci.7'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x6'/>
    <serial type='pty'>
      <source path='/dev/pts/1'/>
      <target type='isa-serial' port='0'>
        <model name='isa-serial'/>
      <alias name='serial0'/>
    <console type='pty' tty='/dev/pts/1'>
      <source path='/dev/pts/1'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
    <input type='tablet' bus='usb'>
      <alias name='input0'/>
      <address type='usb' bus='0' port='1'/>
    <input type='mouse' bus='ps2'>
      <alias name='input1'/>
    <input type='keyboard' bus='ps2'>
      <alias name='input2'/>
    <graphics type='spice' port='5900' autoport='yes' listen=''>
      <listen type='address' address=''/>
      <image compression='off'/>
      <model type='qxl' ram='131072' vram='131072' vgamem='65536' heads='1' primary='yes'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <driver name='vfio'/>
        <address domain='0x0000' bus='0x04' slot='0x00' function='0x0'/>
      <alias name='hostdev0'/>
      <address type='pci' domain='0x0000' bus='0x03' slot='0x00' function='0x0'/>
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <driver name='vfio'/>
        <address domain='0x0000' bus='0x02' slot='0x00' function='0x0'/>
      <alias name='hostdev1'/>
      <address type='pci' domain='0x0000' bus='0x04' slot='0x00' function='0x0'/>
    <redirdev bus='usb' type='spicevmc'>
      <alias name='redir0'/>
      <address type='usb' bus='0' port='2'/>
    <redirdev bus='usb' type='spicevmc'>
      <alias name='redir1'/>
      <address type='usb' bus='0' port='3'/>
    <memballoon model='virtio'>
      <alias name='balloon0'/>
      <address type='pci' domain='0x0000' bus='0x05' slot='0x00' function='0x0'/>
  <seclabel type='dynamic' model='selinux' relabel='yes'>
  <seclabel type='dynamic' model='dac' relabel='yes'>

Wrap it in triple backticks. (```)

Like this, for example:

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

1 Like


I have to add, the card works perfectly under asio when booting windows native.
My iommu groups look fine as well:

IOMMU Group 0 00:00.0 Host bridge [0600]: Intel Corporation Xeon E3-1200 v6/7th Gen Core Processor Host Bridge/DRAM Registers [8086:591f] (rev 05)
IOMMU Group 10 00:1f.0 ISA bridge [0601]: Intel Corporation 200 Series PCH LPC Controller (B250) [8086:a2c8]
IOMMU Group 10 00:1f.2 Memory controller [0580]: Intel Corporation 200 Series/Z370 Chipset Family Power Management Controller [8086:a2a1]
IOMMU Group 10 00:1f.4 SMBus [0c05]: Intel Corporation 200 Series/Z370 Chipset Family SMBus Controller [8086:a2a3]
IOMMU Group 11 00:1f.6 Ethernet controller [0200]: Intel Corporation Ethernet Connection (2) I219-V [8086:15b8]
IOMMU Group 12 02:00.0 Multimedia audio controller [0401]: Lynx Studio Technology, Inc. Lynx AES16e [1621:0028]
IOMMU Group 13 03:00.0 USB controller [0c03]: ASMedia Technology Inc. ASM2142 USB 3.1 Host Controller [1b21:2142]
IOMMU Group 14 04:00.0 Ethernet controller [0200]: Intel Corporation 82574L Gigabit Network Connection [8086:10d3]
IOMMU Group 15 05:00.0 Non-Volatile memory controller [0108]: Samsung Electronics Co Ltd NVMe SSD Controller SM981/PM981 [144d:a808]
IOMMU Group 1 00:01.0 PCI bridge [0604]: Intel Corporation Xeon E3-1200 v5/E3-1500 v5/6th Gen Core Processor PCIe Controller (x16) [8086:1901] (rev 05)
IOMMU Group 1 01:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Baffin [Radeon RX 460/560D / Pro 450/455/460/555/555X/560/560X] [1002:67ef] (rev cf)
IOMMU Group 1 01:00.1 Audio device [0403]: Advanced Micro Devices, Inc. [AMD/ATI] Baffin HDMI/DP Audio [Radeon RX 550 640SP / RX 560/560X] [1002:aae0]
IOMMU Group 2 00:08.0 System peripheral [0880]: Intel Corporation Xeon E3-1200 v5/v6 / E3-1500 v5 / 6th/7th Gen Core Processor Gaussian Mixture Model [8086:1911]
IOMMU Group 3 00:14.0 USB controller [0c03]: Intel Corporation 200 Series/Z370 Chipset Family USB 3.0 xHCI Controller [8086:a2af]
IOMMU Group 3 00:14.2 Signal processing controller [1180]: Intel Corporation 200 Series PCH Thermal Subsystem [8086:a2b1]
IOMMU Group 4 00:16.0 Communication controller [0780]: Intel Corporation 200 Series PCH CSME HECI #1 [8086:a2ba]
IOMMU Group 5 00:17.0 SATA controller [0106]: Intel Corporation 200 Series PCH SATA controller [AHCI mode] [8086:a282]
IOMMU Group 6 00:1b.0 PCI bridge [0604]: Intel Corporation 200 Series PCH PCI Express Root Port #21 [8086:a2eb] (rev f0)
IOMMU Group 7 00:1c.0 PCI bridge [0604]: Intel Corporation 200 Series PCH PCI Express Root Port #5 [8086:a294] (rev f0)
IOMMU Group 8 00:1c.6 PCI bridge [0604]: Intel Corporation 200 Series PCH PCI Express Root Port #7 [8086:a296] (rev f0)
IOMMU Group 9 00:1d.0 PCI bridge [0604]: Intel Corporation 200 Series PCH PCI Express Root Port #9 [8086:a298] (rev f0)

Have you tried in your modprobe.d:

options vfio_iommu_type1 allow_unsafe_interrupts=1

So the problem with passthrough is that it introduces latency. This isn’t problematic in itself, but with an audio device like what you’re using, it can be since it’s very sensitive to latency.

Are you getting any error or warning messages in dmesg or in your libvirt logs?

Your XML looks good to me.

I personally use a Zoom H5 and a USB 3.0 passthrough controller with Message Signaled Interrupts enabled for the controller. If you use a 2.0 port without Message Signaled Interrupts, you’ll get audio dropouts.

@SgtAwesomesauce I added those options but they make no difference unfotunately.
There are no errors in dmesg or the libvirtd logs, all looks fine.
@FurryJackman I have enabled Message Signaled interrupts for the Lynx but that has no effect.

I was reading the thread about optimizing vga passthrough performance with changing roothubs, i did try it but i couldn’t get it to work. Maybe that is an idea though?

It could be an FPGA. FPGAs require initialization and passthrough doesn’t passthrough the FPGA initialization call. USB does not suffer this issue cause with a Zoom Recorder or Behringer 204HD, USB passes along ASIO configuration calls to the device, but I think on PCI-E this is not possible if the device uses an FPGA. I deal with Blackmagic capture cards using FPGAs, and they don’t work in passthrough. I have to use UVC USB 3.0 to use a capture device in a passthrough VM.

That is interesting and certainly a possibility, i’ll have a look at the pcb see if i can find something but i’m afraid you might be right. I think Digigram works under linux, maybe that’s an option so i can skip the vm all together.

Edit: Yep quick google confirmed it…

Digigram and Audioscience pci-e cards can work natively on Linux

I saw mention of Lynx22 card using oss driver on old Ardour forum post, but nothing that would suggest it is likely

Is OSS still a thing? Anyway i found a used Digigram VX222e for less than what i can sell the Lynx for.

Thanks for the help guys much appreciated!

never used OSS. Heard mention of it once before as possible solution for lack of hardware ALSA support, but that user changed hardware too

I tried it once maybe 8years ago for the same reason. It was some old usb dac that was acting up. Seemed to work better in some ways but also more finicky.