tests: Add iommufd integration tests

Add an `iommufd` flag to existing VFIO integration tests. When false,
tests use the legacy vfio container/group backend (existing behavior).
When true, tests use vfio cdev with iommufd and vfio_p2p_dma=off.

vfio_p2p_dma=off is required because the VFIO test runner uses a stock
Ubuntu 24.04 kernel (v6.8) which does not support mapping device MMIO
pages (VM_PFNMAP) through iommufd, causing IOMMU_IOAS_MAP to fail with
-EFAULT on MMIO BAR regions.

Signed-off-by: Bo Chen <bchen@crusoe.ai>

scripts/run_integration_tests_vfio.sh

@@ -30,7 +30,14 @@ cargo build --features mshv --all --release --target "$BUILD_TARGET"
 export RUST_BACKTRACE=1
 export RUSTFLAGS="$RUSTFLAGS"
 
+# Run VFIO tests using legacy vfio interface with container/group
 time cargo nextest run --no-tests=pass --test-threads=1 "vfio::test_nvidia" -- ${test_binary_args[*]}
 RES=$?
 
+# Run VFIO tests using vfio cdev interface backed by iommufd
+if [ $RES -eq 0 ]; then
+    time cargo nextest run --no-tests=pass --test-threads=1 "vfio::test_iommufd" -- ${test_binary_args[*]}
+    RES=$?
+fi
+
 exit $RES