[Qemu-discuss] virt-manager: audio without virtualized display ?

[Toerless Eckert]

I am somewhat puzzled, setting up a qemu VM via virt-manager. Debian host,
win10 VM. Graphic is passthrough (works fine). Audio is meant to use the host 
audio.

But it seems i get audio only when i also have host video. Even when i
keep host video with video qxl and display spice, and just disable the
graphics device in windows, Sound will from the windows VM stops. 

I couldn't find a good explanation, documentation seems to be lacking:

man qemu-system-x86_64 ==
https://qemu.weilnetz.de/doc/qemu-doc.html (from 
https://www.qemu.org/documentation/)

only explains "-soundhw" option.

The VMs created from virt-manager do not even use "-soundhw". When i change
in virt-manager the "Sound Device", it impacts only the following qemu 
parameter:

 -device intel-hda,id=sound0,bus=pci.2,addr=0x2
 -device ich9-intel-hda,id=sound0,bus=pcie.0,addr=0x1b 

So... whats the difference between these devices and -soundhw ? And where are
these devices documented (outside of virt-manager source code...) ?

More importantly, how are these virtual devices mapped to anything on the host ?

"qemu --audio-help" gives some hints that seems to be documented nowhere
else, but quite incomplete. For example it lists some drivers like pa, oss,
but does not even mention that you need to set some environment variable 
QEMU_AUDIO_DRV
to make these work. Thats only to be found on some third party like archlinux
web pages.

And then thee are bugs like 
https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/1246929 seemingly 
indicating as if virt-manager doesn't seem to bother to support
any way of passing those environment variables to qemu when it starts it. And
comments like "use alsa, not pulseaudio". Whereas on my latest debian,
"qemu --audio-help" does not even show alsa.

And even if i would figure this all out with some hack like preepending a qemu
shim to setting environment variables to the qemu binary... it still doesn't
explain to me how qemu is mapping from e.g.: multiple specified virtual devices
(e.g.: one ich6, one ich9) to whatever driver is used...

Is this even the right list to ask for virt-manager, or do i first split up
the questioning about qemu binary vs. virt-manager to two mailing lists... ?

Thanks
    Toerless