Reset dirty log on full snapshot path

src/vmm/src/persist.rs

@@ -249,7 +249,10 @@ fn snapshot_memory_to_file(
                 .dump_dirty(&mut file, &dirty_bitmap)
                 .map_err(Memory)
         }
-        SnapshotType::Full => vmm.guest_memory().dump(&mut file).map_err(Memory),
+        SnapshotType::Full => {
+            let _ = vmm.get_dirty_bitmap().map_err(DirtyBitmap)?;
+            vmm.guest_memory().dump(&mut file).map_err(Memory)
+        }
     }?;
     file.flush()
         .map_err(|err| MemoryBackingFile("flush", err))?;

tests/integration_tests/functional/test_dirty_pages_in_full_snapshot.py

@@ -0,0 +1,30 @@
+# Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0
+"""Test scenario for reseting dirty pages after making a full snapshot."""
+
+
+def test_dirty_pages_after_full_snapshot(uvm_plain):
+    """
+    Test if dirty pages are erased after making a full snapshot of a VM
+    """
+
+    vm_mem_size = 128
+    uvm = uvm_plain
+    uvm.spawn()
+    uvm.basic_config(mem_size_mib=vm_mem_size, track_dirty_pages=True)
+    uvm.add_net_iface()
+    uvm.start()
+    uvm.ssh.run("true")
+
+    snap_full = uvm.snapshot_full(vmstate_path="vmstate_full", mem_path="mem_full")
+    snap_diff = uvm.snapshot_diff(vmstate_path="vmstate_diff", mem_path="mem_diff")
+    snap_diff2 = uvm.snapshot_diff(vmstate_path="vmstate_diff2", mem_path="mem_diff2")
+
+    # file size is the same, but the `diff` snapshot is actually a sparse file
+    assert snap_full.mem.stat().st_size == snap_diff.mem.stat().st_size
+
+    # diff -> diff there should be no differences
+    assert snap_diff2.mem.stat().st_blocks == 0
+
+    # full -> diff there should be no differences
+    assert snap_diff.mem.stat().st_blocks == 0