test(vmgenid): integration test for VMGenID kernel notification

Add an integration test that launches a microVM, snapshots it repeatedly
and checks for the existence of the message that the kernel emits every
time it receives the VMGenID notification.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

tests/integration_tests/functional/test_snapshot_basic.py

@@ -13,6 +13,7 @@
 
 import host_tools.drive as drive_tools
 from framework.microvm import SnapshotType
+from framework.properties import global_props
 from framework.utils import check_filesystem, run_cmd, wait_process_termination
 from framework.utils_vsock import (
     ECHO_SERVER_PORT,
@@ -25,6 +26,20 @@
     start_guest_echo_server,
 )
 
+# Kernel emits this message when it resumes from a snapshot with VMGenID device
+# present
+DMESG_VMGENID_RESUME = "random: crng reseeded due to virtual machine fork"
+
+
+def check_vmgenid_update_count(vm, resume_count):
+    """
+    Kernel will emit the DMESG_VMGENID_RESUME every time we resume
+    from a snapshot
+    """
+    rc, stdout, stderr = vm.ssh.run("dmesg")
+    assert rc == 0, stderr
+    assert resume_count == stdout.count(DMESG_VMGENID_RESUME)
+
 
 def _get_guest_drive_size(ssh_connection, guest_dev_name="/dev/vdb"):
     # `lsblk` command outputs 2 lines to STDOUT:
@@ -118,6 +133,7 @@ def test_5_snapshots(
         microvm = microvm_factory.build()
         microvm.spawn()
         microvm.restore_from_snapshot(snapshot, resume=True)
+
         # TODO: SIGCONT here and SIGSTOP later before creating snapshot
         # is a temporary fix to avoid vsock timeout in
         # _vsock_connect_to_guest(). This will be removed once we
@@ -187,6 +203,7 @@ def test_patch_drive_snapshot(uvm_nano, microvm_factory):
     vm = microvm_factory.build()
     vm.spawn()
     vm.restore_from_snapshot(snapshot, resume=True)
+
     # Attempt to connect to resumed microvm and verify the new microVM has the
     # right scratch drive.
     guest_drive_size = _get_guest_drive_size(vm.ssh)
@@ -495,3 +512,50 @@ def test_snapshot_overwrite_self(guest_kernel, rootfs, microvm_factory):
     # restored, with a new snapshot of this vm, does not break the VM
     rc, _, stderr = vm.ssh.run("true")
     assert rc == 0, stderr
+
+
+@pytest.mark.parametrize("snapshot_type", [SnapshotType.DIFF, SnapshotType.FULL])
+def test_vmgenid(guest_kernel_linux_6_1, rootfs, microvm_factory, snapshot_type):
+    """
+    Test VMGenID device upon snapshot resume
+    """
+    if global_props.cpu_architecture != "x86_64":
+        pytest.skip("At the moment we only support VMGenID on x86_64")
+
+    base_vm = microvm_factory.build(guest_kernel_linux_6_1, rootfs)
+    base_vm.spawn()
+    base_vm.basic_config(track_dirty_pages=True)
+    base_vm.add_net_iface()
+    base_vm.start()
+
+    # Wait for microVM to be booted
+    rc, _, stderr = base_vm.ssh.run("true")
+    assert rc == 0, stderr
+
+    snapshot = base_vm.make_snapshot(snapshot_type)
+    base_snapshot = snapshot
+    base_vm.kill()
+
+    for i in range(5):
+        vm = microvm_factory.build()
+        vm.spawn()
+        vm.restore_from_snapshot(snapshot, resume=True)
+
+        # Make sure the microVM is up
+        rc, _, stderr = vm.ssh.run("true")
+        assert rc == 0, stderr
+
+        # We should have as DMESG_VMGENID_RESUME messages as
+        # snapshots we have resumed
+        check_vmgenid_update_count(vm, i + 1)
+
+        snapshot = vm.make_snapshot(snapshot_type)
+        vm.kill()
+
+        # If we are testing incremental snapshots we ust merge the base with
+        # current layer.
+        if snapshot.is_diff:
+            snapshot = snapshot.rebase_snapshot(base_snapshot)
+
+        # Update the base for next iteration
+        base_snapshot = snapshot