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

[Jiri Novak]

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.


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