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config(apple): give Linux guests a sound device for each stream - #8128
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Since the microphone and the speaker of an Apple Virtualization VM were put on one sound device (4784026), a Linux guest has had no sound output: the device's first stream is the input, the Linux sound server (PipeWire, PulseAudio) only uses the first stream of a sound device, so the guest gets a microphone and a "Dummy Output". That change was made for macOS guests, where two devices made coreaudiod busy keeping two clocks in sync. Keep one device there, and give other guests one device for each stream, as before that change. Resolves utmapp#8105 Assisted-by: Claude:claude-fable-5-2
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A Linux guest on the Apple Virtualization backend has had no sound output since 5.0.3: GNOME shows a "Dummy Output" and nothing is played, while the microphone works.
#7692 put the microphone and the speaker on one sound device, input first, to stop
coreaudiodfrom syncing two clocks with macOS guests. In a Linux guest that one device is one sound card with two PCM devices (0 = capture, 1 = playback), and the sound server (PipeWire, PulseAudio) only uses the first one. So it finds a microphone and no output.macOS guests keep the single device. Other guests get one device for each stream again, as before #7692: two sound cards, each with one PCM device, which the sound server uses both.
Resolves #8105
Testing
Tested by an AI agent on a MacBook Pro M2 Max, macOS 27.2 (26B123), with a Debug build of the macOS scheme.
Guest: Ubuntu 26.04 server (arm64 cloud image, kernel 7.0.0-38) on the Apple Virtualization backend, with PipeWire 1.4, WirePlumber and
alsa-utilsinstalled, driven over SSH. The VM was made by scripting, which cannot turn sound on, so for these runs a temporary change (not in this PR) read the sound device layout from an environment variable./proc/asound/pcmwpctl status00-00capture,00-01playback00-00playback,00-01capture00-00capture,01-00playbackauto_null, as in the issue.alsa_output.pci-0000_00_09.0.stereo-fallback. Whilespeaker-testplays a tone in the guest, the Mac'spmset -g assertionsshowscoreaudiodholdingaudio-out BuiltInSpeakerDevice, and it showed none before the tone.pw-recordrecords from the default source.The new
UTMAppleConfigurationAudioTestschecks the devices the configuration creates: a device for each stream for a Linux guest, one device with both streams for a macOS guest, and only the enabled streams for both.testLinuxGuestGetsADeviceForEachStreamfails without the fix ([["input", "output"]]is not equal to[["input"], ["output"]]) and passes with it. The static checks pass.Not tested: listening to the output, a macOS guest (its device layout is unchanged, which the unit test checks), and Debian (the issue also names it; it uses the same sound server).