[vfio-users] crackling sound on i440fx-3.1+ and conversion attempts to q35

[mail at peterge.de]

Hi,

this might not be the answer you are looking for, but i set up audio from my windows vm using scream (https://github.com/duncanthrax/scream) via a ivshmem device. This is technical comparable to what looking glass is using (https://looking-glass.hostfission.com/).

It works much better than my previous HDA ICH6 sound device, no crackeling and much lower latency and might copletely circumvent your problem :)

Guide:
https://looking-glass.hostfission.com/wiki/Using_Scream

Mar 21, 2020, 12:10 by jiri.novak at ghorland.net:

> Hello,
>
> after some time, iv;e decided to try again gpu passthrough. i tried to
> resue my old vm, which was done on i440fx-2.1, but had issue with
> crackling audio, apart from that, it works fine. as upgrade to 3.0 break
> windows license, i;ve decided to do it anew on q35, but more on that
> later. i;ve went back to some experineting with the i440fx and with
> recent qemu, 4.2, kernel 5.4 (debian bullseye), i have clear audio on
> i440fx-3.0, but it breaks again on 3.1. same on 4.2 any ideas?
>
> the audio line is         -audiodev pa,id=pa1,server=/run/pulse/native
> -device intel-hda,id=sound4,bus=pci.2,addr=0x3 -device
> hda-duplex,id=sound4-codec0,bus=sound4.0,cad=0,audiodev=pa1 \
>
>
>
> regarding that upgrade to q35, i wanted to go to as new version as
> possible, so ideally q35-4.2 to be future proof for some time with the
> windows license again as i have to relicense it. i tried to setup the
> pcie structure explicitly manually and failed hard. i'm using qemu+kvm,
> no libvirt. 
>
> if i attach all devices (both passed through and directly to pcie.0,
> they will work, aparyh fro GPU with error 43, as it's not initialised
> properly.
>
> if i put them behind pcie-root-port device, they fail with code 10 (both
> gpu and virtio devices. gpu works in vga mode, virtio devices don't work
> at all, both net and storage, no disks show up)
>
> if i understood the docs right, i should be putting pci devices behind
> pcie-to-pci + pci-pci bridge, but that makes them completely undetected
> and don't show up at all (same for virtio devices if i put them there)
>
> so i think 'im missing something completely essential, even after full
> day of googling example configuration on net (most of them are at best
> around q-35-3.0 machine types though)... does anyone have this working
> on q35-4.2 machine?
>
>
> thanks,
>
> Gh.
>