[vfio-users] Nvidia GTX 970 sound is choppy

[Garland Key]

Hi all,

I've successfully passed through my GTX 970 and its audio device (see
below).

    02:00.0 VGA compatible controller: NVIDIA Corporation GM204 [GeForce
GTX 970] (rev a1) (prog-if 00 [VGA controller])
       Kernel driver in use: vfio-pci

02:00.1 Audio device: NVIDIA Corporation GM204 High Definition Audio
Controller (rev a1)
       Kernel driver in use: vfio-pci

Unfortunately, there's a *severe audio stutter* that takes place.  I'm not
sure what could be the cause.  Has anyone else experienced this?  I'm using
kernel *4.5.1-1-ARCH*

*Here's my VM setup:*

<domain type='kvm'>
 <name>win10</name>
 <uuid>f8ba8223-023d-4ba7-a7a5-81c36b3aeb3e</uuid>
 <memory unit='KiB'>8388608</memory>
 <currentMemory unit='KiB'>8388608</currentMemory>
 <vcpu placement='static'>6</vcpu>
 <cputune>
   <vcpupin vcpu='0' cpuset='3'/>
   <vcpupin vcpu='1' cpuset='4'/>
   <vcpupin vcpu='2' cpuset='5'/>
   <vcpupin vcpu='3' cpuset='9'/>
   <vcpupin vcpu='4' cpuset='10'/>
   <vcpupin vcpu='5' cpuset='11'/>
 </cputune>
 <os>
   <type arch='x86_64' machine='pc-i440fx-2.5'>hvm</type>
   <loader readonly='yes'
type='pflash'>/usr/share/edk2.git/ovmf-x64/OVMF_CODE-pure-efi.fd</loader>
   <nvram>/var/lib/libvirt/qemu/nvram/win10_VARS.fd</nvram>
   <boot dev='hd'/>
 </os>
 <features>
   <acpi/>
   <apic/>
   <kvm>
     <hidden state='on'/>
   </kvm>
   <vmport state='off'/>
 </features>
 <cpu mode='host-passthrough'>
   <topology sockets='1' cores='3' threads='2'/>
 </cpu>
 <clock offset='localtime'>
   <timer name='rtc' tickpolicy='catchup'/>
   <timer name='pit' tickpolicy='delay'/>
   <timer name='hpet' present='no'/>
 </clock>
 <on_poweroff>destroy</on_poweroff>
 <on_reboot>restart</on_reboot>
 <on_crash>restart</on_crash>
 <pm>
   <suspend-to-mem enabled='no'/>
   <suspend-to-disk enabled='no'/>
 </pm>  <devices>
   <emulator>/usr/sbin/qemu-system-x86_64</emulator>
   <disk type='file' device='disk'>
     <driver name='qemu' type='raw'/>
     <source file='/home/kindred/.virtualmachines/win10/win10.img'/>
     <target dev='vda' bus='virtio'/>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x03'
function='0x0'/>
   </disk>
   <controller type='usb' index='0' model='ich9-ehci1'>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x04'
function='0x7'/>
   </controller>
   <controller type='usb' index='0' model='ich9-uhci1'>
     <master startport='0'/>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x04'
function='0x0' multifunction='on'/>
   </controller>
   <controller type='usb' index='0' model='ich9-uhci2'>
     <master startport='2'/>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x04'
function='0x1'/>
   </controller>
   <controller type='usb' index='0' model='ich9-uhci3'>
     <master startport='4'/>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x04'
function='0x2'/>
   </controller>
   <controller type='pci' index='0' model='pci-root'/>
   <interface type='bridge'>
     <mac address='52:54:00:7a:ec:24'/>
     <source bridge='br0'/>
     <model type='virtio'/>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x02'
function='0x0'/>
   </interface>
   <input type='mouse' bus='ps2'/>
   <input type='keyboard' bus='ps2'/>
   <hostdev mode='subsystem' type='pci' managed='yes'>
     <source>
       <address domain='0x0000' bus='0x02' slot='0x00' function='0x0'/>
     </source>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x05'
function='0x0'/>
   </hostdev>
   <hostdev mode='subsystem' type='pci' managed='yes'>
     <source>
       <address domain='0x0000' bus='0x02' slot='0x00' function='0x1'/>
     </source>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x06'
function='0x0'/>
   </hostdev>
   <hostdev mode='subsystem' type='pci' managed='yes'>
     <source>
       <address domain='0x0000' bus='0x06' slot='0x00' function='0x0'/>
     </source>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x08'
function='0x0'/>
    </hostdev>
   <hostdev mode='subsystem' type='usb' managed='yes'>
     <source>
       <vendor id='0x04d8'/>
       <product id='0x00df'/>
     </source>
   </hostdev>
   <hostdev mode='subsystem' type='usb' managed='yes'>
     <source>
       <vendor id='0x1b1c'/>
       <product id='0x0c07'/>
     </source>
   </hostdev>
   <memballoon model='virtio'>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x07'
function='0x0'/>
   </memballoon>
 </devices>
</domain>
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