agent: Use cfg-if for s390x CCW

Uses fewer lines in upcoming VFIO-AP support.

Signed-off-by: Jakob Naucke <jakob.naucke@ibm.com>

src/agent/Cargo.lock

@@ -801,6 +801,7 @@ dependencies = [
  "async-recursion",
  "async-trait",
  "capctl",
+ "cfg-if 1.0.0",
  "cgroups-rs",
  "clap",
  "futures",

src/agent/Cargo.toml

@@ -48,6 +48,7 @@ slog-scope = "4.1.2"
 slog-stdlog = "4.0.0"
 log = "0.4.11"
 
+cfg-if = "1.0.0"
 prometheus = { version = "0.13.0", features = ["process"] }
 procfs = "0.12.0"
 anyhow = "1.0.32"

src/agent/src/device.rs

@@ -16,13 +16,12 @@ use std::str::FromStr;
 use std::sync::Arc;
 use tokio::sync::Mutex;
 
-#[cfg(target_arch = "s390x")]
-use crate::ccw;
 use crate::linux_abi::*;
 use crate::pci;
 use crate::sandbox::Sandbox;
 use crate::uevent::{wait_for_uevent, Uevent, UeventMatcher};
 use anyhow::{anyhow, Context, Result};
+use cfg_if::cfg_if;
 use oci::{LinuxDeviceCgroup, LinuxResources, Spec};
 use protocols::agent::Device;
 use tracing::instrument;
@@ -54,6 +53,12 @@ pub const DRIVER_VFIO_TYPE: &str = "vfio";
 pub const DRIVER_OVERLAYFS_TYPE: &str = "overlayfs";
 pub const FS_TYPE_HUGETLB: &str = "hugetlbfs";
 
+cfg_if! {
+    if #[cfg(target_arch = "s390x")] {
+        use crate::ccw;
+    }
+}
+
 #[instrument]
 pub fn online_device(path: &str) -> Result<()> {
     fs::write(path, "1")?;

src/agent/src/linux_abi.rs

@@ -3,6 +3,8 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 
+use cfg_if::cfg_if;
+
 /// Linux ABI related constants.
 
 #[cfg(target_arch = "aarch64")]
@@ -64,8 +66,11 @@ pub fn create_pci_root_bus_path() -> String {
     ret
 }
 
-#[cfg(target_arch = "s390x")]
+cfg_if! {
+    if #[cfg(target_arch = "s390x")] {
         pub const CCW_ROOT_BUS_PATH: &str = "/devices/css0";
+    }
+}
 
 // From https://www.kernel.org/doc/Documentation/acpi/namespace.txt
 // The Linux kernel's core ACPI subsystem creates struct acpi_device

src/agent/src/main.rs

@@ -20,6 +20,7 @@ extern crate scopeguard;
 extern crate slog;
 
 use anyhow::{anyhow, Context, Result};
+use cfg_if::cfg_if;
 use clap::{AppSettings, Parser};
 use nix::fcntl::OFlag;
 use nix::sys::socket::{self, AddressFamily, SockFlag, SockType, VsockAddr};
@@ -34,8 +35,6 @@ use std::process::exit;
 use std::sync::Arc;
 use tracing::{instrument, span};
 
-#[cfg(target_arch = "s390x")]
-mod ccw;
 mod config;
 mod console;
 mod device;
@@ -74,6 +73,12 @@ use tokio::{
 mod rpc;
 mod tracer;
 
+cfg_if! {
+    if #[cfg(target_arch = "s390x")] {
+        mod ccw;
+    }
+}
+
 const NAME: &str = "kata-agent";
 
 lazy_static! {