tests: enable cargo test --workspace + #[cfg(devcli_testenv)]

TL;DR: Massive quality of life improvement for devs

Cloud Hypervisor uses the Cargo test framework for multiple tests:

- normal unit tests
- unit tests requiring special environment (the Tap device tests)
- integration tests requiring a special environment

This prevented the execution of `cargo test --workspace`, which results
in a very poor developer experience. Although
`./scripts/run_unit_tests.sh` exists, there are valid reasons why devs
cannot or even don't want to use it.

By adding a new `chv_testenv` rustc config, we can conditionally only
activate tests when the `./scripts/` magic runs them. This improves
the general developer experience by a lot.

Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>
On-behalf-of: SAP philipp.schuster@sap.com

Cargo.toml

@@ -162,3 +162,7 @@ zerocopy = { version = "0.8.27", default-features = false }
 # https://rust-lang.github.io/rust-clippy/master/index.html
 assertions_on_result_states = "deny"
 undocumented_unsafe_blocks = "deny"
+
+[workspace.lints.rust]
+# `level = warn` is irrelevant here but mandatory for rustc/cargo
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(devcli_testenv)'] }

net_util/src/tap.rs

@@ -549,6 +549,7 @@ impl AsRawFd for Tap {
 }
 
 #[cfg(test)]
+#[cfg(devcli_testenv)] // we need special permissions in the ENV to create Tap devices
 mod tests {
     use std::net::Ipv4Addr;
     use std::sync::{LazyLock, Mutex, mpsc};

scripts/dev_cli.sh

@@ -47,6 +47,9 @@ CARGO_GIT_REGISTRY_DIR="${CLH_BUILD_DIR}/cargo_git_registry"
 # Full path to the cargo target dir on the host.
 CARGO_TARGET_DIR="${CLH_BUILD_DIR}/cargo_target"
 
+# Let tests know that the special environment is set up.
+RUSTFLAGS="${RUSTFLAGS} --cfg devcli_testenv"
+
 # Send a decorated message to stdout, followed by a new line
 #
 say() {

scripts/run_integration_tests_aarch64.sh

@@ -191,7 +191,9 @@ if [ $RES -ne 0 ]; then
     exit 1
 fi
 
+# Common configuration for every test run
 export RUST_BACKTRACE=1
+export RUSTFLAGS="$RUSTFLAGS"
 
 cargo build --features mshv --all --release --target "$BUILD_TARGET"
 

scripts/run_integration_tests_live_migration.sh

@@ -83,7 +83,10 @@ PAGE_NUM=$((12288 * 1024 / HUGEPAGESIZE))
 echo "$PAGE_NUM" | sudo tee /proc/sys/vm/nr_hugepages
 sudo chmod a+rwX /dev/hugepages
 
+# Common configuration for every test run
 export RUST_BACKTRACE=1
+export RUSTFLAGS="$RUSTFLAGS"
+
 time cargo nextest run $test_features --retries 3 --no-fail-fast --test-threads=$(($(nproc) / 4)) "live_migration_parallel::$test_filter" -- ${test_binary_args[*]}
 
 RES=$?

scripts/run_integration_tests_rate_limiter.sh

@@ -55,7 +55,10 @@ fi
 
 cargo build --features mshv --all --release --target "$BUILD_TARGET"
 
+# Common configuration for every test run
 export RUST_BACKTRACE=1
+export RUSTFLAGS="$RUSTFLAGS"
+
 time cargo nextest run $test_features --test-threads=1 "rate_limiter::$test_filter" -- ${test_binary_args[*]}
 RES=$?
 

scripts/run_integration_tests_vfio.sh

@@ -26,7 +26,10 @@ fi
 
 cargo build --features mshv --all --release --target "$BUILD_TARGET"
 
+# Common configuration for every test run
 export RUST_BACKTRACE=1
+export RUSTFLAGS="$RUSTFLAGS"
+
 time cargo nextest run --test-threads=1 "vfio::test_nvidia" -- ${test_binary_args[*]}
 RES=$?
 

scripts/run_integration_tests_windows_aarch64.sh

@@ -36,7 +36,9 @@ dmsetup mknodes
 dmsetup create windows-snapshot-base --table "0 $img_blk_size snapshot-origin /dev/mapper/windows-base"
 dmsetup mknodes
 
+# Common configuration for every test run
 export RUST_BACKTRACE=1
+export RUSTFLAGS="$RUSTFLAGS"
 
 cargo build --all --release --target "$BUILD_TARGET"
 

scripts/run_integration_tests_windows_x86_64.sh

@@ -41,7 +41,9 @@ dmsetup mknodes
 
 cargo build --features mshv --all --release --target "$BUILD_TARGET"
 
+# Common configuration for every test run
 export RUST_BACKTRACE=1
+export RUSTFLAGS="$RUSTFLAGS"
 
 # Only run with 1 thread to avoid tests interfering with one another because
 # Windows has a static IP configured

scripts/run_integration_tests_x86_64.sh

@@ -177,14 +177,16 @@ ulimit -l unlimited
 # Set number of open descriptors high enough for VFIO tests to run
 ulimit -n 4096
 
+# Common configuration for every test run
 export RUST_BACKTRACE=1
+export RUSTFLAGS="$RUSTFLAGS"
+
 time cargo nextest run $test_features --retries 3 --no-fail-fast --test-threads=$(($(nproc) / 4)) "common_parallel::$test_filter" -- ${test_binary_args[*]}
 RES=$?
 
 # Run some tests in sequence since the result could be affected by other tests
 # running in parallel.
 if [ $RES -eq 0 ]; then
-    export RUST_BACKTRACE=1
     cargo nextest run $test_features --retries 3 --no-fail-fast --test-threads=1 "common_sequential::$test_filter" -- ${test_binary_args[*]}
     RES=$?
 fi
@@ -192,7 +194,6 @@ fi
 # Run tests on dbus_api
 if [ $RES -eq 0 ]; then
     cargo build --features "mshv,dbus_api" --all --release --target "$BUILD_TARGET"
-    export RUST_BACKTRACE=1
     # integration tests now do not reply on build feature "dbus_api"
     time cargo nextest run $test_features --retries 3 --no-fail-fast --test-threads=$(($(nproc) / 4)) "dbus_api::$test_filter" -- ${test_binary_args[*]}
     RES=$?
@@ -201,14 +202,12 @@ fi
 # Run tests on fw_cfg
 if [ $RES -eq 0 ]; then
     cargo build --features "mshv,fw_cfg" --all --release --target "$BUILD_TARGET"
-    export RUST_BACKTRACE=1
     time cargo nextest run $test_features --no-tests=warn --retries 3 --no-fail-fast --test-threads=$(($(nproc) / 4)) "fw_cfg::$test_filter" -- ${test_binary_args[*]}
     RES=$?
 fi
 
 if [ $RES -eq 0 ]; then
     cargo build --features "mshv,ivshmem" --all --release --target "$BUILD_TARGET"
-    export RUST_BACKTRACE=1
     time cargo nextest run $test_features --retries 3 --no-fail-fast --test-threads=$(($(nproc) / 4)) "ivshmem::$test_filter" -- ${test_binary_args[*]}
     RES=$?
 fi

tests/integration.rs

@@ -2,6 +2,7 @@
 //
 // SPDX-License-Identifier: Apache-2.0
 //
+#![cfg(devcli_testenv)]
 #![allow(clippy::undocumented_unsafe_blocks)]
 // When enabling the `mshv` feature, we skip quite some tests and
 // hence have known dead-code. This annotation silences dead-code