Port virtio media simple device as a vhost user media device. #1895

Databean · 2026-01-29T20:39:07Z

Can this go in a vhost_user_media.MODULE.bazel file in the vhost_user_media directory?

ser-io · 2026-01-24T00:23:44Z

I'll remove this once rust-vmm/vhost/pull/339 is merged in.

Databean · 2026-01-29T20:31:48Z

I'm confused by resume_unwind here, which is documented as

This is designed to be used in conjunction with catch_unwind to, for example, carry a panic across a layer of C code.

I don't see a catch_unwind in this PR, does it come out of one of the libraries?

thread::spawn's NOTES mentions catch_unwind but doesn't explicitly say the two should be used together.

-Original file line number
+Diff line change
@@ Expand Up / @@ -146,6 +146,17 @@ vhost_user_input_crates.from_cargo( @@
     )
     use_repo(vhost_user_input_crates, "vhost_user_input_crates")
+    vhost_user_media_workspace_crates = use_extension("@rules_rust//crate_universe:extensions.bzl", "crate")
+    vhost_user_media_workspace_crates.from_cargo(
+        name = "vhost_user_media_workspace_crates",
+        cargo_config = "@//build_external/crosvm:crosvm.config.toml",
+        manifests = [
+            "//cuttlefish/host/commands/vhost_user_media:Cargo.toml",
+        ],
+        host_tools = "@rust_host_tools_nightly",
+    )
+    use_repo(vhost_user_media_workspace_crates, "vhost_user_media_workspace_crates")
     git_repository = use_repo_rule("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")
     git_repository(
@@ Expand Down @@

-Original file line number
+Diff line change
@@ -0,0 +1,26 @@
+    [workspace]
+    members = [
+        "simple_device",
+        "vhu_media",
+    ]
+    [workspace.dependencies]
+    clap = { version = "4.5",  features = ["derive"] }
+    env_logger = "0.11"
+    libc = "0.2"
+    log = "0.4"
+    thiserror = "2.0"
+    vhost = { version = "0.15", features = ["vhost-user-backend"] }
+    vhost-user-backend = "0.21"
+    vhu_media = { path = "vhu_media" }
+    virtio-bindings = "0.2.6"
+    virtio-media = "0.0.7"
+    virtio-queue = "0.16.0"
+    vm-allocator = "0.1.3"
+    vm-memory = "0.16.2"
+    vmm-sys-util = "0.15.0"
+    [patch.crates-io]
+    vhost = { path = "/usr/local/google/home/sorama/code/github.com/forks/vhost/vhost" }
+    vhost-user-backend = { path = "/usr/local/google/home/sorama/code/github.com/forks/vhost/vhost-user-backend" }

-Original file line number
+Diff line change
@@ -0,0 +1,21 @@
+    load("@rules_rust//rust:defs.bzl", "rust_binary")
+    load("@vhost_user_media_workspace_crates//:defs.bzl", "crate_deps")
+    package(default_visibility = ["//:android_cuttlefish"])
+    rust_binary(
+        name = "simple_device",
+        srcs = ["src/main.rs"],
+        edition = "2024",
+        deps = crate_deps([
+            "clap",
+            "env_logger",
+            "log",
+            "thiserror",
+            "vhost-user-backend",
+            "virtio-media",
+            "vm-memory",
+        ]) + [
+            "//cuttlefish/host/commands/vhost_user_media/vhu_media",
+        ],
+    )

-Original file line number
+Diff line change
@@ -0,0 +1,14 @@
+    [package]
+    name = "simple_device"
+    version = "0.1.0"
+    edition = "2024"
+    [dependencies]
+    clap = { workspace = true }
+    env_logger = { workspace = true }
+    log = { workspace = true }
+    thiserror = { workspace = true }
+    vhost-user-backend = { workspace = true }
+    vhu_media = { workspace = true }
+    virtio-media = { workspace = true }
+    vm-memory = { workspace = true }

-Original file line number
+Diff line change
@@ -0,0 +1,108 @@
+    // Copyright 2025, The Android Open Source Project
+    //
+    // Licensed under the Apache License, Version 2.0 (the "License");
+    // you may not use this file except in compliance with the License.
+    // You may obtain a copy of the License at
+    //
+    //     http://www.apache.org/licenses/LICENSE-2.0
+    //
+    // Unless required by applicable law or agreed to in writing, software
+    // distributed under the License is distributed on an "AS IS" BASIS,
+    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+    // See the License for the specific language governing permissions and
+    // limitations under the License.
+    //! simple_device
+    use std::{
+        path::PathBuf,
+        process::exit,
+        sync::{Arc, RwLock},
+        thread::{JoinHandle, spawn},
+    };
+    use clap::Parser;
+    use log::error;
+    use thiserror::Error;
+    use vhost_user_backend::VhostUserDaemon;
+    use vhu_media::VhuMediaBackend;
+    use virtio_media::devices::simple_device;
+    use virtio_media::protocol::VirtioMediaDeviceConfig;
+    use vm_memory::{GuestMemoryAtomic, GuestMemoryMmap};
+    #[derive(Debug, Error)]
+    pub(crate) enum Error {
+        #[error("Could not create daemon: {0}")]
+        CouldNotCreateDaemon(vhost_user_backend::Error),
+        #[error("Fatal error: {0}")]
+        ServeFailed(vhost_user_backend::Error),
+    }
+    type Result<T> = std::result::Result<T, Error>;
+    #[derive(Parser, Debug)]
+    #[clap(author, version, about, long_about = None)]
+    struct CmdLineArgs {
+        /// Location of vhost-user Unix domain socket.
+        #[clap(short, long, value_name = "SOCKET")]
+        socket_path: PathBuf,
+    }
+    #[derive(PartialEq, Debug)]
+    struct Config {
+        socket_path: PathBuf,
+    }
+    impl TryFrom<CmdLineArgs> for Config {
+        type Error = Error;
+        fn try_from(args: CmdLineArgs) -> Result<Self> {
+            Ok(Config {
+                socket_path: args.socket_path,
+            })
+        }
+    }
+    fn start_backend(args: CmdLineArgs) -> Result<()> {
+        let config = Config::try_from(args)?;
+        let socket_path = config.socket_path.clone();
+        let handle: JoinHandle<Result<()>> = spawn(move || {
+            loop {
+                let mut card = [0u8; 32];
+                let card_name = "simple_device";
+                card[0..card_name.len()].copy_from_slice(card_name.as_bytes());
+                use virtio_media::v4l2r::ioctl::Capabilities;
+                let config = VirtioMediaDeviceConfig {
+                    // device_caps: (Capabilities::VIDEO_CAPTURE_MPLANE | Capabilities::STREAMING).bits(),
+                    device_caps: (Capabilities::VIDEO_CAPTURE | Capabilities::STREAMING).bits(),
+                    // VFL_TYPE_VIDEO
+                    device_type: 0,
+                    card,
+                };
+                let backend = Arc::new(RwLock::new(VhuMediaBackend::new(
+                    config,
+                    |event_queue, host_mapper| {
+                        simple_device::SimpleCaptureDevice::new(event_queue, host_mapper)
+                    },
+                )));
+                let mut daemon = VhostUserDaemon::new(
+                    String::from("vhost-user-media-backend"),
+                    backend,
+                    GuestMemoryAtomic::new(GuestMemoryMmap::new()),
+                )
+                .map_err(Error::CouldNotCreateDaemon)?;
+                daemon.serve(&socket_path).map_err(Error::ServeFailed)?;
+            }
+        });
+        handle.join().map_err(std::panic::resume_unwind).unwrap()
+    }
+    fn main() {
+        env_logger::init();
+        if let Err(e) = start_backend(CmdLineArgs::parse()) {
+            error!("{e}");
+            exit(1);
+        }
+    }

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Port virtio media simple device as a vhost user media device. #1895

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Databean Jan 29, 2026

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ser-io Jan 24, 2026

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Databean Jan 29, 2026

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-Original file line number
+Diff line change
@@ -0,0 +1,23 @@
+    load("@rules_rust//rust:defs.bzl", "rust_library")
+    load("@vhost_user_media_workspace_crates//:defs.bzl", "crate_deps")
+    package(default_visibility = ["//visibility:public"])
+    rust_library(
+        name = "vhu_media",
+        srcs = ["src/lib.rs"],
+        edition = "2024",
+        deps = crate_deps([
+            "libc",
+            "log",
+            "thiserror",
+            "vhost",
+            "vhost-user-backend",
+            "virtio-bindings",
+            "virtio-media",
+            "virtio-queue",
+            "vm-allocator",
+            "vm-memory",
+            "vmm-sys-util",
+        ]),
+    )

Port virtio media simple device as a vhost user media device. #1895

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