crosvm: add --vsock command-line option and config-file parameter.

Add a `--vsock` command-line option that is designed to replace the
`--cid`, `--vhost-vsock-device` and `--vhost-vsock-fd` parameters into a
single one. This parameter can be used on Windows as well as Linux, and
on the latter users can also specify the vhost-vsock device to use.

This parameter is the preferred way to add vsock devices, and thus is
also enabled for configuration files. Also update the book's
instructions in lockstep.

BUG=b:255223604
TEST=run crosvm with `--vsock cid=42` option and ensure the guest device
is working using socat to communicate with the host.

Change-Id: I9515922415e5a55289a9e21d5f2f247a30fadc74
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/4253292
Commit-Queue: Alexandre Courbot <acourbot@chromium.org>
Reviewed-by: Keiichi Watanabe <keiichiw@chromium.org>

devices/src/virtio/vsock/sys/unix.rs

@@ -7,6 +7,7 @@ use std::path::PathBuf;
 
 use serde::Deserialize;
 use serde::Serialize;
+use serde_keyvalue::FromKeyValues;
 
 static VHOST_VSOCK_DEFAULT_PATH: &str = "/dev/vhost-vsock";
 
@@ -14,7 +15,7 @@ fn default_vsock_path() -> PathBuf {
     PathBuf::from(VHOST_VSOCK_DEFAULT_PATH)
 }
 
-#[derive(Debug, Deserialize, Serialize, PartialEq, Eq)]
+#[derive(Debug, Deserialize, Serialize, PartialEq, Eq, FromKeyValues)]
 #[serde(deny_unknown_fields)]
 
 /// Configuration for a Vsock device.

devices/src/virtio/vsock/sys/windows.rs

@@ -11,8 +11,9 @@ pub use vsock::VsockError;
 
 use serde::Deserialize;
 use serde::Serialize;
+use serde_keyvalue::FromKeyValues;
 
-#[derive(Debug, Deserialize, Serialize, PartialEq, Eq)]
+#[derive(Debug, Deserialize, Serialize, PartialEq, Eq, FromKeyValues)]
 #[serde(deny_unknown_fields)]
 // Configuration for a Vsock device.
 pub struct VsockConfig {

docs/book/src/devices/vsock.md

@@ -2,13 +2,13 @@
 
 crosvm supports [virtio-vsock] device for communication between the host and a guest VM.
 
-Assign a context id to a guest VM by passing it with `--cid` flag.
+Assign a context id to a guest VM by passing it with the `--vsock` flag.
 
 ```sh
 GUEST_CID=3
 
 crosvm run \
-  --cid "${GUEST_CID}" \
+  --vsock "${GUEST_CID}" \
   <usual crosvm arguments>
   /path/to/bzImage
 ```

src/crosvm/cmdline.rs

@@ -885,7 +885,7 @@ pub struct RunCommand {
     cfg: Option<Box<Self>>,
 
     #[argh(option, arg_name = "CID")]
-    #[serde(skip)] // TODO(b/255223604)
+    #[serde(skip)] // Deprecated - use `vsock` instead.
     #[merge(strategy = overwrite_option)]
     /// context ID for virtual sockets.
     pub cid: Option<u64>,
@@ -2098,14 +2098,14 @@ pub struct RunCommand {
 
     #[cfg(unix)]
     #[argh(option, arg_name = "SOCKET_PATH")]
-    #[serde(skip)] // TODO(b/255223604)
+    #[serde(skip)] // Deprecated - use `vsock` instead.
     #[merge(strategy = overwrite_option)]
     /// path to the vhost-vsock device. (default /dev/vhost-vsock)
     pub vhost_vsock_device: Option<PathBuf>,
 
     #[cfg(unix)]
     #[argh(option, arg_name = "FD")]
-    #[serde(skip)] // TODO(b/255223604)
+    #[serde(skip)] // Deprecated - use `vsock` instead.
     #[merge(strategy = overwrite_option)]
     /// open FD to the vhost-vsock device, mutually exclusive with vhost-vsock-device
     pub vhost_vsock_fd: Option<RawDescriptor>,
@@ -2158,6 +2158,16 @@ pub struct RunCommand {
     ///         per device.
     pub virtio_snd: Vec<SndParameters>,
 
+    #[argh(option, arg_name = "cid=CID[,device=VHOST_DEVICE]")]
+    #[serde(default)]
+    #[merge(strategy = overwrite_option)]
+    /// add a vsock device. Since a guest can only have one CID,
+    /// this option can only be specified once.
+    ///     cid=CID - CID to use for the device.
+    ///     device=VHOST_DEVICE - path to the vhost-vsock device to
+    ///         use (Linux only). Defaults to /dev/vhost-vsock.
+    pub vsock: Option<VsockConfig>,
+
     #[cfg(all(feature = "vtpm", target_arch = "x86_64"))]
     #[argh(switch)]
     #[serde(skip)] // TODO(b/255223604)
@@ -2535,7 +2545,16 @@ impl TryFrom<RunCommand> for super::config::Config {
 
         cfg.balloon_control = cmd.balloon_control;
 
+        cfg.vsock = cmd.vsock;
+
+        // Legacy vsock options.
         if let Some(cid) = cmd.cid {
+            if cfg.vsock.is_some() {
+                return Err(
+                    "`cid` and `vsock` cannot be specified together. Use `vsock` only.".to_string(),
+                );
+            }
+
             let legacy_vsock_config = VsockConfig::new(
                 cid,
                 #[cfg(unix)]