[vfio-users] Creative X-Fi XtremeGamer PCI Sound Card Audio Bugs

[Dan Ziemba]

On Tue, 2016-02-23 at 11:02 +0100, Sebastien Mercier wrote:
> So my sound card now use the vfio-pci driver but when I start the VM,
> it makes bips, cliky and white noise sounds randomly.
> When I move a space on terminator on the host and the VM is running,
> it make white noise. Sounds weird.

I think this is just a side effect of running in a VM - due to
scheduling, data sometimes doesn't get copied to the card quickly
enough.  I see the same problems with my onboard sound passed through,
and used to have it even worse when I was using USB sound.  

I found that it is at its worst when the CPU is very loaded.  Using CPU
pinning seems to help, so all vcpus are pinned to some cores while the
emulator is pinned to others.  If you have hyperthreading, make sure
both threads of each core are either given to the VM or not, don't mix
them. Increasing the priority of the qemu processes seems like it helps
a bit too.