QEMU problem with ALSA on Windows Subsystem for Linux

[daista]

Hi,

First of all, thanks for creating this project!
Just wanted to point out the trouble when trying to run it with Windows Subsystem for Linux (WSL).

The first boot command

qemu-system-arm -M vexpress-a9 -m 32M -no-reboot -nographic -monitor telnet:127.0.0.1:1234,server,nowait

throws an error

ALSA lib confmisc.c:767:(parse_card) cannot find card '0'
ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory
ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings
ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory
ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name
ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory
ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory
ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default
alsa: Could not initialize DAC
alsa: Failed to open `default':
alsa: Reason: No such file or directory
ALSA lib confmisc.c:767:(parse_card) cannot find card '0'
ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory
ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings
ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory
ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name
ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory
ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory
ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default
alsa: Could not initialize DAC
alsa: Failed to open `default':
alsa: Reason: No such file or directory
audio: Failed to create voice `lm4549.out'

From a quick google search I figured that this has something to do with audio drivers (and the lack of for WSL), but it took a while to figure out a quick workaround, so I think it is worth posting it here. Setting this environment variable suppresses the error:

export QEMU_AUDIO_DRV=none

One more thing - that very first boot command does not crash under WSL, just hangs. Not sure why. The second try with first-hang.bin works as intended.

[Lee Harrold]

Thanks, daista! You saved me a bunch of time.
I noticed that the first boot command hangs using Ubuntu 20.04 natively. Is that the distro you used for WSL?