diff --git a/performance-metrics/src/util.rs b/performance-metrics/src/util.rs
index 09d6ad7e6..3ba9a9eee 100644
--- a/performance-metrics/src/util.rs
+++ b/performance-metrics/src/util.rs
@@ -5,11 +5,12 @@
 //! Shared benchmark helpers.
 
 use std::io::{ErrorKind, Seek, SeekFrom, Write};
+use std::os::unix::fs::FileExt;
 use std::thread;
 use std::time::Duration;
 
 use block::async_io::AsyncIo;
-use block::qcow::{QcowFile, RawFile};
+use block::qcow::{BackingFileConfig, ImageType, QcowFile, RawFile};
 use block::qcow_async::QcowDiskAsync;
 use block::qcow_sync::QcowDiskSync;
 use vmm_sys_util::eventfd::EventFd;
@@ -143,6 +144,44 @@ pub fn empty_qcow_tempfile(num_clusters: usize) -> (TempFile, QcowDiskSync) {
     (tmp, disk)
 }
 
+/// Create a QCOW2 overlay backed by a raw file with `num_clusters`
+/// pre-populated clusters.  Returns (backing_tempfile, overlay_tempfile).
+fn create_overlay_tempfiles(num_clusters: usize) -> (TempFile, TempFile) {
+    let virtual_size = QCOW_CLUSTER_SIZE * num_clusters as u64;
+
+    let backing = TempFile::new().expect("failed to create backing tempfile");
+    {
+        let f = backing.as_file();
+        f.set_len(virtual_size).expect("set_len failed");
+        let buf = vec![0xA5u8; QCOW_CLUSTER_SIZE as usize];
+        for i in 0..num_clusters {
+            f.write_at(&buf, i as u64 * QCOW_CLUSTER_SIZE)
+                .expect("write_at failed");
+        }
+    }
+
+    let overlay = TempFile::new().expect("failed to create overlay tempfile");
+    {
+        let raw = RawFile::new(overlay.as_file().try_clone().unwrap(), false);
+        let backing_config = BackingFileConfig {
+            path: backing.as_path().to_str().unwrap().to_string(),
+            format: Some(ImageType::Raw),
+        };
+        QcowFile::new_from_backing(raw, 3, virtual_size, &backing_config, true)
+            .expect("failed to create overlay qcow2");
+    }
+
+    (backing, overlay)
+}
+
+/// QCOW2 overlay with raw backing opened via QcowDiskSync.
+pub fn qcow_overlay_tempfile(num_clusters: usize) -> (TempFile, TempFile, QcowDiskSync) {
+    let (backing, overlay) = create_overlay_tempfiles(num_clusters);
+    let disk = QcowDiskSync::new(overlay.as_file().try_clone().unwrap(), false, true, true)
+        .expect("failed to open overlay qcow2 via QcowDiskSync");
+    (backing, overlay, disk)
+}
+
 /// Spin and wait until the given eventfd becomes readable.
 pub fn wait_for_eventfd(notifier: &EventFd) {
     loop {