[vfio-users] Choppy sound after updating QEMU/KVM

[Patrick O'Callaghan]

I've updated my host system to Fedora 29 (from F28). As part of the
update I now have the following qemu-* packages:

$ rpm -qa qemu\*
qemu-audio-pa-3.0.0-1.fc29.x86_64
qemu-block-curl-3.0.0-1.fc29.x86_64
qemu-audio-alsa-3.0.0-1.fc29.x86_64
qemu-block-dmg-3.0.0-1.fc29.x86_64
qemu-block-nfs-3.0.0-1.fc29.x86_64
qemu-ui-sdl-3.0.0-1.fc29.x86_64
qemu-img-3.0.0-1.fc29.x86_64
qemu-audio-oss-3.0.0-1.fc29.x86_64
qemu-ui-curses-3.0.0-1.fc29.x86_64
qemu-block-gluster-3.0.0-1.fc29.x86_64
qemu-block-rbd-3.0.0-1.fc29.x86_64
qemu-system-x86-3.0.0-1.fc29.x86_64
qemu-guest-agent-3.0.0-1.fc29.x86_64
qemu-system-x86-core-3.0.0-1.fc29.x86_64
qemu-common-3.0.0-1.fc29.x86_64
qemu-ui-gtk-3.0.0-1.fc29.x86_64
qemu-kvm-3.0.0-1.fc29.x86_64
qemu-block-iscsi-3.0.0-1.fc29.x86_64
qemu-block-ssh-3.0.0-1.fc29.x86_64
qemu-audio-sdl-3.0.0-1.fc29.x86_64

I now find that sound in my Win10 guest, which previously had no
issues, is now quite choppy. Windows is configured to use the basic HDA
device, i.e. not the guest GPU (an Nvidia GTX-1080). This wasn't a
problem before the update. Sound on the host using the same device is
fine.

The relevant section of the guest spec (unchanged from before) is:

   <sound model='ich6'>
      <alias name='sound0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
    </sound>

Any suggestions? 

poc