runtime-rs: add Qmp object to encapsulate QMP functionality

The constructor handles QMP connection initialisation, too, so there can
be non-functional Qmp instance.

Signed-off-by: Pavel Mores <pmores@redhat.com>

src/runtime-rs/Cargo.lock

@@ -1644,6 +1644,9 @@ dependencies = [
  "nix 0.24.3",
  "path-clean",
  "persist",
+ "qapi",
+ "qapi-qmp",
+ "qapi-spec",
  "rand 0.8.5",
  "rust-ini",
  "safe-path 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2959,6 +2962,65 @@ dependencies = [
  "ttrpc-codegen",
 ]
 
+[[package]]
+name = "qapi"
+version = "0.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c6412bdd014ebee03ddbbe79ac03a0b622cce4d80ba45254f6357c847f06fa38"
+dependencies = [
+ "bytes",
+ "futures 0.3.28",
+ "log",
+ "memchr",
+ "qapi-qmp",
+ "qapi-spec",
+ "serde",
+ "serde_json",
+ "tokio",
+ "tokio-util",
+]
+
+[[package]]
+name = "qapi-codegen"
+version = "0.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ba4de731473de4c8bd508ddb38a9049e999b8a7429f3c052ba8735a178ff68c"
+dependencies = [
+ "qapi-parser",
+]
+
+[[package]]
+name = "qapi-parser"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "80044db145aa2953ef5803d0376dcbca50f2763242547e856b7f37507adca677"
+dependencies = [
+ "serde",
+ "serde_json",
+]
+
+[[package]]
+name = "qapi-qmp"
+version = "0.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e8b944db7e544d2fa97595e9a000a6ba5c62c426fa185e7e00aabe4b5640b538"
+dependencies = [
+ "qapi-codegen",
+ "qapi-spec",
+ "serde",
+]
+
+[[package]]
+name = "qapi-spec"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b360919a24ea5fc02fa762cb01bd8f43b643fee51c585f763257773b4dc5a9e8"
+dependencies = [
+ "base64 0.13.1",
+ "serde",
+ "serde_json",
+]
+
 [[package]]
 name = "quote"
 version = "1.0.35"

src/runtime-rs/crates/hypervisor/Cargo.toml

@@ -43,6 +43,10 @@ safe-path = "0.1.0"
 crossbeam-channel = "0.5.6"
 tempdir = "0.3.7"
 
+qapi = { version = "0.14", features = [ "qmp", "async-tokio-all" ] }
+qapi-spec = "0.3.1"
+qapi-qmp = "0.14.0"
+
 [target.'cfg(not(target_arch = "s390x"))'.dependencies]
 dragonball = { path = "../../../dragonball", features = ["atomic-guest-memory", "virtio-vsock", "hotplug", "virtio-blk", "virtio-net", "virtio-fs", "vhost-net", "dbs-upcall", "virtio-mem", "virtio-balloon", "vhost-user-net", "host-device"] }
 

src/runtime-rs/crates/hypervisor/src/qemu/qmp.rs

@@ -0,0 +1,40 @@
+// Copyright (c) 2024 Red Hat
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+use anyhow::Result;
+use std::io::BufReader;
+use std::os::unix::net::UnixStream;
+use std::time::Duration;
+
+pub struct Qmp {
+    qmp: qapi::Qmp<qapi::Stream<BufReader<UnixStream>, UnixStream>>,
+}
+
+impl Qmp {
+    pub fn new(qmp_sock_path: &str) -> Result<Self> {
+        let stream = UnixStream::connect(qmp_sock_path)?;
+
+        // Set the read timeout to protect runtime-rs from blocking forever
+        // trying to set up QMP connection if qemu fails to launch.  The exact
+        // value is a matter of judegement.  Setting it too long would risk
+        // being ineffective since container runtime would timeout first anyway
+        // (containerd's task creation timeout is 2 s by default).  OTOH
+        // setting it too short would risk interfering with a normal launch,
+        // perhaps just seeing some delay due to a heavily loaded host.
+        stream.set_read_timeout(Some(Duration::from_millis(250)))?;
+
+        let mut qmp = Qmp {
+            qmp: qapi::Qmp::new(qapi::Stream::new(
+                BufReader::new(stream.try_clone()?),
+                stream,
+            )),
+        };
+
+        let info = qmp.qmp.handshake()?;
+        info!(sl!(), "QMP initialized: {:#?}", info);
+
+        Ok(qmp)
+    }
+}