vhost-device-sound: Add GStreamer audio backend support

[nicholasdezai]

Summary of the PR

This change adds GStreamer audio backend support.

Since the Rust bindings for GStreamer rely on the underlying C libraries, this change introduces additional build dependencies. On Debian/Ubuntu systems, at least libgstreamer1.0-dev and libgstreamer-plugins-base1.0-dev are required.

Requirements

Before submitting your PR, please make sure you addressed the following
requirements:

• All commits in this PR have Signed-Off-By trailers (with
  git commit -s), and the commit message has max 60 characters for the
  summary and max 75 characters for each description line.
• All added/changed functionality has a corresponding unit/integration
  test.
• All added/changed public-facing functionality has entries in the "Upcoming
  Release" section of CHANGELOG.md (if no such section exists, please create one).
• Any newly added unsafe code is properly documented.

[dorindabassey]

the build is failing because gstreamer-base-1.0 is missing from the build environment, looks like we need to update the rust-vmm container with gstreamer.

  pkg-config exited with status code 1
  > PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=1 pkg-config --libs --cflags gstreamer-base-1.0 'gstreamer-base-1.0 >= 1.20'
  The system library `gstreamer-base-1.0` required by crate `gstreamer-base-sys` was not found.
  The file `gstreamer-base-1.0.pc` needs to be installed and the PKG_CONFIG_PATH environment variable must contain its parent directory.
  The PKG_CONFIG_PATH environment variable is not set.

[MatiasVara]

the build is failing because gstreamer-base-1.0 is missing from the build environment, looks like we need to update the rust-vmm container with gstreamer.

  pkg-config exited with status code 1
  > PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=1 pkg-config --libs --cflags gstreamer-base-1.0 'gstreamer-base-1.0 >= 1.20'
  The system library `gstreamer-base-1.0` required by crate `gstreamer-base-sys` was not found.
  The file `gstreamer-base-1.0.pc` needs to be installed and the PKG_CONFIG_PATH environment variable must contain its parent directory.
  The PKG_CONFIG_PATH environment variable is not set.

right, I just did it at rust-vmm/rust-vmm-ci#190

[stefano-garzarella]

@nicholasdezai we just merged #881 that should bring @MatiasVara changes to add GStreamer deps to our CI container, please rebase this PR.

[nicholasdezai]

I submitted a PR to rust-vmm-container to add the missing GStreamer dependencies
(gstreamer1.0-plugins-base and gstreamer1.0-plugins-good) required for running
the GStreamer backend tests in CI.

[stefano-garzarella]

Please rebase this PR on main and keep dep updates (e.g. rust-vmm-ci submodule) in separate commits.

[stefano-garzarella]

Great, thanks for working on this and preparing the container for the CI!

I left some comments, in general I'd avoid unwrap()/expect(). I mean t's fine for the lock or something that should not happen, but for example you have in some places .ok_or(Error::StreamWithIdNotFound(stream_id))? and in others .expect("Can not find stream in stream_in.");. Why? (I didn't look the entire code, so maybe there is a reason).

[nicholasdezai]

I have improved the error handling in the new commit. I hope the error handling makes more sense now

[MatiasVara]

I have tried both playback and recording. Both operations seem working.

[stefano-garzarella]

@dorindabassey @epilys PTAL

[dorindabassey]

@dorindabassey @epilys PTAL

PR LGTM last time I checked, but I’ll do a more thorough review later(tomorrow).

[MatiasVara]

LGTM!

[stefano-garzarella]

@nicholasdezai please in the meantime rebase this on main, I guess you can remove the rust-vmm-ci commit since dependabot recently update it IIRC.

[dorindabassey]

Thank you @nicholasdezai for the work on this PR, I added just a few comments.

[dorindabassey]

Hi @nicholasdezai , I tested this on Fedora42 with kernel-6.14.0 I don't get any audio using the gstreamer backend, and running a simple aplay /usr/share/sounds/alsa/Front_Left.wav is stuck. attaching the logs incase it looks familiar.
RUST LOG debug vhost device.txt
btw, what image are you using to test?

[dorindabassey]

you also need to update the readme with the new backend

     --backend <BACKEND>
            audio backend to be used [possible values: null, pipewire, alsa]

[nicholasdezai]

I’m testing with Debian 13 (trixie), kernel 6.15.5.

[MatiasVara]

I just tried with qemu from master(29b77c1a2db2), Linux v6.16-rc1, and GStreamer 1.24.0, and it seems working.

[dorindabassey]

I used QEMU from master(517e9b4862cc), gstreamer 1.24.0, kernel 6.16.9, f42, also tried debian-13-nocloud-amd64.qcow2 image with gstreamer 1.24.0 i got no audio, but after updating to 1.24.13 it works with the debian image, so probably not an issue with the backend.

[dorindabassey]

PR LGTM, great work! @nicholasdezai