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

[Bronek Kozicki]

Have you tried DPC latency checker from https://www.thesycon.de/eng/latency_check.shtml ? It might be some "rogue" driver causing issues, on my computer I had to tweak nVidia a little bit to stop polling power all the time. Perhaps AMD is doing something similar?


B.

-- 
  Bronek Kozicki
  brok at incorrekt.com

On Tue, 25 Dec 2018, at 4:52 PM, Paige Thompson wrote:
> 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. 
> 
> I've sifted through everything I can possibly for KVM/QEMU to make this 
> work. In the process I even figured out how to get Q35 to work with my 
> AMD r9 390 card by virtue of wanting to see if it would solve my problem 
> however it did not. If I had some other USB audio devices to try I would 
> but I don't. It'd be nice to find out what others have done to get one 
> to work as well as it does on bare metal. I think I'm close but I'm not 
> sure. 
> 
> Here is my work log, with a description of what I've tried starting from 
> the top and towards the end in comments things I have tried changing 
> along the way: https://gitlab.com/snippets/1789874
> 
> Most recently I tried reinstalling Windows and using virtio-scsi as the 
> issue seemed to be related to disk I/O on the host. It was working 
> really well without any problems at all until windows installed more 
> updates. In previous attempts I addeed things like isolcpus, hugepages, 
> increasing the global, emulator, and iothread periods, forcing the timer 
> to tsc native, etc. I think all of these things in combination has 
> helped but I'm trying to elliminate the problem completely. Today I 
> tested it under OpenSuse on linux and that didn't suck at all; works 
> perfectly on a linux guest. 
> 
> 
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