test: ensure swiotlb works

Add an integration test on ARM that configures an in-guest swiotlb
region to which all virtio devices should be bound. Asserts the guest
sees the swiotlb region, and also that block and net I/O work
(indirectly through loading of rootfs during boot and by running
commands via SSH).

Also add a test for snapshotting VMs with swiotlb regions, which just
checks the network device after restoration to sanity check that the
swiotlb region was correctly restored.

Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

tests/integration_tests/functional/test_swiotlb.py

@@ -0,0 +1,44 @@
+# Copyright 2025 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0
+"""Test swiotlb related functionality."""
+
+import pytest
+
+from framework.properties import global_props
+
+pytestmark = pytest.mark.skipif(
+    global_props.cpu_architecture != "aarch64", reason="swiotlb only supported on ARM"
+)
+
+
+def test_swiotlb_boot(microvm_factory, guest_kernel_linux_6_1, rootfs):
+    """Tests that a VM can boot if all virtio devices are bound to a swiotlb region, and
+    that this swiotlb region is actually discovered by the guest."""
+    vm = microvm_factory.build(guest_kernel_linux_6_1, rootfs)
+    vm.spawn()
+    vm.basic_config(memory_config={"initial_swiotlb_size": 64})
+    vm.add_net_iface()
+    vm.start()
+
+    _, dmesg, _ = vm.ssh.check_output("dmesg")
+
+    assert (
+        "OF: reserved mem: initialized node bouncy_boi, compatible id restricted-dma-pool"
+        in dmesg
+    )
+
+
+def test_swiotlb_snapshot(microvm_factory, guest_kernel_linux_6_1, rootfs):
+    """Tests that a VM with swiotlb regions attached can be snapshotted and restored
+    again, and that the restored VM can still do I/O."""
+    vm = microvm_factory.build(guest_kernel_linux_6_1, rootfs)
+    vm.spawn()
+    vm.basic_config(memory_config={"initial_swiotlb_size": 64})
+    vm.add_net_iface()
+    vm.start()
+    snapshot = vm.snapshot_full()
+    vm.kill()
+
+    vm = microvm_factory.build_from_snapshot(snapshot)
+
+    vm.ssh.check_output("true")