virtio-devices: Use a common method for spawning virtio threads

Introduce a common solution for spawning the virtio threads which will
make it easier to add the panic handling.

During this effort I discovered that there were no seccomp filters
registered for the vhost-user-net thread nor the vhost-user-block
thread. This change also incorporates basic seccomp filters for those as
part of the refactoring.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

virtio-devices/src/thread_helper.rs

@@ -0,0 +1,43 @@
+// Copyright © 2021 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+use crate::{
+    seccomp_filters::{get_seccomp_filter, Thread},
+    ActivateError,
+};
+use seccompiler::{apply_filter, SeccompAction};
+use std::thread::{self, JoinHandle};
+
+pub(crate) fn spawn_virtio_thread<F>(
+    name: &str,
+    seccomp_action: &SeccompAction,
+    thread_type: Thread,
+    epoll_threads: &mut Vec<JoinHandle<()>>,
+    f: F,
+) -> Result<(), ActivateError>
+where
+    F: FnOnce(),
+    F: Send + 'static,
+{
+    let seccomp_filter = get_seccomp_filter(seccomp_action, thread_type)
+        .map_err(ActivateError::CreateSeccompFilter)?;
+
+    thread::Builder::new()
+        .name(name.to_string())
+        .spawn(move || {
+            if !seccomp_filter.is_empty() {
+                if let Err(e) = apply_filter(&seccomp_filter) {
+                    error!("Error applying seccomp filter: {:?}", e);
+                    return;
+                }
+            }
+            f()
+        })
+        .map(|thread| epoll_threads.push(thread))
+        .map_err(|e| {
+            error!("Failed to spawn thread for {}: {}", name, e);
+            ActivateError::BadActivate
+        })
+}