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 asserts that all virtio queue components have
been placed into swiotlb, by parsing firecracker log messages.

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 +1,66 @@
+# Copyright 2025 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0
+"""Test swiotlb related functionality."""
+import re
+
+import pytest
+
+from framework.properties import global_props
+
+pytestmark = pytest.mark.skipif(
+    global_props.cpu_architecture != "aarch64", reason="swiotlb only supported on ARM"
+)
+
+
+@pytest.mark.parametrize("swiotlb_size", [1, 64])
+def test_swiotlb_boot(microvm_factory, guest_kernel_linux_6_1, rootfs, swiotlb_size):
+    """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": swiotlb_size})
+    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
+    )
+
+    match = re.search(r"Placed swiotlb region at \[(\d+), (\d+)\)", vm.log_data)
+
+    assert match is not None, "Firecracker did not print swiotlb region placement"
+
+    swiotlb_start, swiotlb_end = match.group(1, 2)
+
+    found_any = False
+
+    for match in re.finditer(
+        r"Placed virt queue ([a-zA-Z ]+) at \[(\d+), (\d+)\)", vm.log_data
+    ):
+        found_any = True
+        component, start, end = match.group(1, 2, 3)
+
+        assert (
+            start >= swiotlb_start and end <= swiotlb_end
+        ), f"Guest placed virtio queue component {component} outside of swiotlb region!"
+
+    assert found_any, "Did not find any virtio devices in Firecracker logs"
+
+
+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")