HVM with emulated audio sometimes fails to start

[marmarek]

Observation

openQA test in scenario qubesos-4.3-pull-requests-x86_64-system_tests_audio@64bit fails in
TC_20_AudioVM_Pulse_debian-12-xfce

stubdomain log:

[2024-10-25 14:51:46] pulseaudio: pa_context_connect() failed
[2024-10-25 14:51:46] pulseaudio: Reason: Connection refused
[2024-10-25 14:51:46] pulseaudio: Failed to initialize PA contextqemu: could not connect to PulseAudio server
[2024-10-25 14:51:46] W: [pulseaudio] authkey.c: �[1mFailed to open cookie file '/tmp/pulse/cookie': No such file or directory�[0m
[2024-10-25 14:51:46] W: [pulseaudio] authkey.c: �[1mFailed to load authentication key '/tmp/pulse/cookie': No such file or directory�[0m
[2024-10-25 14:51:46] W: [pulseaudio] authkey.c: �[1mFailed to open cookie file '//.pulse-cookie': No such file or directory�[0m
[2024-10-25 14:51:46] W: [pulseaudio] authkey.c: �[1mFailed to load authentication key '//.pulse-cookie': No such file or directory�[0m
[2024-10-25 14:51:46] E: [pulseaudio] module-vchan-sink.c: �[1;31mvchan module loading�[0m
[2024-10-25 14:51:46] E: [pulseaudio] module-vchan-sink.c: �[1;31musing domid: 0�[0m
[2024-10-25 14:51:46] E: [pulseaudio] module-vchan-sink.c: �[1;31mplay libvchan_fd_for_select=14, ctrl=0x55ad4e484cd0�[0m
[2024-10-25 14:51:46] E: [pulseaudio] module-vchan-sink.c: �[1;31mrec libvchan_fd_for_select=22, ctrl=0x55ad4e485700�[0m
[2024-10-25 14:51:46] E: [vchan-sink] module-vchan-sink.c: �[1;31msink cork req state =1, now state=-2�[0m
[2024-10-25 14:51:46] E: [vchan-sink] module-vchan-sink.c: �[1;31msource cork req state =1, now state=-2�[0m

Test suite description

Audio tests

Reproducible

Fails since (at least) Build 2024102501-4.3

Expected result

Last good: 2024102420-4.3 (or more recent)

Further details

Always latest result in this scenario: latest

[marmarek]

Looks like QEMU and Pulseaudio in stubdomain are started in parallel, and the latter sometimes starts slowly enough that it isn't ready yet when QEMU tries to connect to it.