Audio input doesn't work with Intel HDA controller on Debian 12

[Mikhail Kovalev]

The problem occurs with Windows Direct Sound host audio driver, Intel HDA audio controller and a Debian 12 guest. We didn't test other Linux guests, but the same issue might occur with any guest using pulseaudio. With AC97 audio controller the problem does not occur and audio input works fine.

To reproduce the issue, one just needs to configure Intel HDA audio controller, enable audio input and start the VM. For testing the audio input we used

arecord -vv /dev/null

in a terminal and an online mic test in the browser (Chromium/Firefox). An interesting fact is that the microphone starts working as soon as we mute and unmute it in pulseaudio control panel: either via UI or by executing

pacmd set-source-mute 1 1;pacmd set-source-mute 1 0

in another terminal. This "trick" helps only for the running arecord instance or for the running browser instance (with the microphone capture enabled). As soon as we e.g. restart the browser and restart the microphone test, it is not working again.

It looks like the problem is specific to pulseaudio + intel hda driver. When starting arecord directly on the ALSA backend, the microphone works fine.

We observe this problem on VirtualBox 7.1.6 and 7.0.24. On 7.0.14 the problem does not occur. I am attaching the logs from one of the 7.1.7 test builds and from 7.0.14.