[vfio-users] USB ASIO DAC buffer underruns on Windows guest

[Jan Wiele]

Am 25.12.2018 um 17:52 schrieb Paige Thompson:
> Hi,
> 
> I have a very long standing problem that I've recently been trying to root 
cause and document. As near as I can tell the problem is rooted somewhere in 
Windows itself and/or the virtio drivers for Windows. I believe it must be one 
of the windows virtio drivers because:
> 
> - Both of my DACs work perfectly fine connected to a Windows laptop running 
Windows on metal
> - A Linux guest with the same VM configuration doesn't have this problem 
when using either of my DACs to play back audio
> - I've been able to eliminate the problem intermittently on Windows (It was 
working fine yesterday until a large batch of Windows Updates were installed.)
> 
> Even so, I want to know who out there has tried getting a USB audio DAC to 
work with a Windows Guest on KVM/QEMU? I'm using a USB3.0 pcie card that is 
passed through to the guest, I haven't been able to get it to work any other 
way really.


Hey,
I'm using a SMSL Q5 Pro DAC in my setup without problems, along with USB 
headsets (Plantronics DSP500/Sennheiser PXC550). However, I 
haven't done anything special to get them working right. :/

For USB3 passthrough I'm using a Sonnet Allegro Pro USB PCIe card (on a 
Asrock OC Formula X299 with an Intel i9-7980XE at 4.5GHz with the performance 
governor active). I've attached my domain's xml.

I've read the first entry in your gitlab post. Perhaps we don't share the same 
workloads/setup which causes the problem. Running the heavy IO load dd command 
doesn't cause stuttering in my VM (but reading from urandom is also a very CPU 
intensive task. I get ~200MB/s disk write activity when reading from /dev/
urandom vs. 560MB/s when reading from /dev/zero). 

Regards,
Jan
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