pci: add tests for PCIe root bus

Add an integration test that checks that `lspci` correctly locates the
PCIe root complex if PCI is enabled for the microVM. Also, add a
negative test that checks that PCIe root complex doesn't exist when PCI
is not enabled.

Also, extend coverage of, at least some of, the tests to ensure that
they run with and without PCI configuration enabled. Do that by
extending the `uvm_any*` fixtures to yield both variants.

Signed-off-by: Babis Chalios <[email protected]>

Author: bchalios

tests/conftest.py

@@ -526,23 +526,27 @@ def mem_size_mib():
     """Return memory size. Use indirect parametrization to override."""
     return 256
 
+@pytest.fixture(params=[True, False])
+def pci_enabled(request):
+    yield request.param
+
 
 def uvm_booted(
-    microvm_factory, guest_kernel, rootfs, cpu_template, vcpu_count=2, mem_size_mib=256
+    microvm_factory, guest_kernel, rootfs, cpu_template, pci_enabled, vcpu_count=2, mem_size_mib=256 
 ):
     """Return a booted uvm"""
     uvm = microvm_factory.build(guest_kernel, rootfs)
-    uvm.spawn()
+    uvm.spawn(pci=pci_enabled)
     uvm.basic_config(vcpu_count=vcpu_count, mem_size_mib=mem_size_mib)
     uvm.set_cpu_template(cpu_template)
     uvm.add_net_iface()
     uvm.start()
     return uvm
 
 
-def uvm_restored(microvm_factory, guest_kernel, rootfs, cpu_template, **kwargs):
+def uvm_restored(microvm_factory, guest_kernel, rootfs, cpu_template, pci_enabled, **kwargs):
     """Return a restored uvm"""
-    uvm = uvm_booted(microvm_factory, guest_kernel, rootfs, cpu_template, **kwargs)
+    uvm = uvm_booted(microvm_factory, guest_kernel, rootfs, cpu_template, pci_enabled, **kwargs)
     snapshot = uvm.snapshot_full()
     uvm.kill()
     uvm2 = microvm_factory.build_from_snapshot(snapshot)
@@ -563,6 +567,7 @@ def uvm_any(
     guest_kernel,
     rootfs,
     cpu_template_any,
+    pci_enabled,
     vcpu_count,
     mem_size_mib,
 ):
@@ -572,21 +577,65 @@ def uvm_any(
         guest_kernel,
         rootfs,
         cpu_template_any,
+        pci_enabled,
         vcpu_count=vcpu_count,
         mem_size_mib=mem_size_mib,
     )
 
 
 @pytest.fixture
 def uvm_any_booted(
-    microvm_factory, guest_kernel, rootfs, cpu_template_any, vcpu_count, mem_size_mib
+    microvm_factory, guest_kernel, rootfs, cpu_template_any, pci_enabled, vcpu_count, mem_size_mib
 ):
     """Return booted uvms"""
     return uvm_booted(
         microvm_factory,
         guest_kernel,
         rootfs,
         cpu_template_any,
+        pci_enabled,
+        vcpu_count=vcpu_count,
+        mem_size_mib=mem_size_mib,
+    )
+
+
+@pytest.fixture
+def uvm_any_with_pci(
+    uvm_ctor,
+    microvm_factory,
+    guest_kernel_acpi,
+    rootfs,
+    cpu_template_any,
+    vcpu_count,
+    mem_size_mib,
+):
+    return uvm_ctor(
+        microvm_factory,
+        guest_kernel_acpi,
+        rootfs,
+        cpu_template_any,
+        True,
+        vcpu_count=vcpu_count,
+        mem_size_mib=mem_size_mib,
+    )
+
+
+@pytest.fixture
+def uvm_any_without_pci(
+    uvm_ctor,
+    microvm_factory,
+    guest_kernel_acpi,
+    rootfs,
+    cpu_template_any,
+    vcpu_count,
+    mem_size_mib,
+):
+    return uvm_ctor(
+        microvm_factory,
+        guest_kernel_acpi,
+        rootfs,
+        cpu_template_any,
+        False,
         vcpu_count=vcpu_count,
         mem_size_mib=mem_size_mib,
     )

tests/framework/microvm.py

@@ -597,6 +597,7 @@ def spawn(
         log_show_origin=False,
         metrics_path="fc.ndjson",
         emit_metrics: bool = False,
+        pci: bool = False,
     ):
         """Start a microVM as a daemon or in a screen session."""
         # pylint: disable=subprocess-run-check
@@ -637,6 +638,9 @@ def spawn(
             # Checking the timings requires DEBUG level log messages
             self.time_api_requests = False
 
+        if pci:
+            self.jailer.extra_args["enable-pci"] = None
+
         cmd = [
             *self._pre_cmd,
             str(self.jailer_binary_path),

tests/integration_tests/functional/test_net.py

@@ -89,9 +89,9 @@ def test_multi_queue_unsupported(uvm_plain):
 
 
 @pytest.fixture
-def uvm_any(microvm_factory, uvm_ctor, guest_kernel, rootfs):
+def uvm_any(microvm_factory, uvm_ctor, guest_kernel, rootfs, pci_enabled):
     """Return booted and restored uvm with no CPU templates"""
-    return uvm_ctor(microvm_factory, guest_kernel, rootfs, None)
+    return uvm_ctor(microvm_factory, guest_kernel, rootfs, None, pci_enabled)
 
 
 def test_tap_offload(uvm_any):

tests/integration_tests/functional/test_pci.py

@@ -0,0 +1,24 @@
+# Copyright 2025 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0
+"""Tests for the PCI devices"""
+
+def test_pci_root_present(uvm_any_with_pci):
+    """
+    Test that a guest with PCI enabled has a PCI root device.
+    """
+
+    vm = uvm_any_with_pci
+    devices = vm.ssh.run("lspci").stdout.strip().split('\n')
+    print(devices)
+    assert devices[0].startswith(
+        "00:00.0 Host bridge: Intel Corporation Device"
+    ), "PCI root not found in guest"
+
+def test_pci_disabled(uvm_any_without_pci):
+    """
+    Test that a guest with PCI disabled does not have a PCI root device but still works.
+    """
+
+    vm = uvm_any_without_pci
+    _, stdout, _ = vm.ssh.run("lspci")
+    assert "00:00.0 Host bridge: Intel Corporation Device" not in stdout, "PCI root not found in guest"

tests/integration_tests/functional/test_rng.py

@@ -8,10 +8,10 @@
 from host_tools.network import SSHConnection
 
 
-def uvm_with_rng_booted(microvm_factory, guest_kernel, rootfs, rate_limiter):
+def uvm_with_rng_booted(microvm_factory, guest_kernel, rootfs, rate_limiter, pci_enabled):
     """Return a booted microvm with virtio-rng configured"""
     uvm = microvm_factory.build(guest_kernel, rootfs)
-    uvm.spawn(log_level="INFO")
+    uvm.spawn(log_level="INFO", pci=pci_enabled)
     uvm.basic_config(vcpu_count=2, mem_size_mib=256)
     uvm.add_net_iface()
     uvm.api.entropy.put(rate_limiter=rate_limiter)
@@ -21,9 +21,9 @@ def uvm_with_rng_booted(microvm_factory, guest_kernel, rootfs, rate_limiter):
     return uvm
 
 
-def uvm_with_rng_restored(microvm_factory, guest_kernel, rootfs, rate_limiter):
+def uvm_with_rng_restored(microvm_factory, guest_kernel, rootfs, rate_limiter, pci_enabled):
     """Return a restored uvm with virtio-rng configured"""
-    uvm = uvm_with_rng_booted(microvm_factory, guest_kernel, rootfs, rate_limiter)
+    uvm = uvm_with_rng_booted(microvm_factory, guest_kernel, rootfs, rate_limiter, pci_enabled)
     snapshot = uvm.snapshot_full()
     uvm.kill()
     uvm2 = microvm_factory.build_from_snapshot(snapshot)
@@ -44,9 +44,9 @@ def rate_limiter(request):
 
 
 @pytest.fixture
-def uvm_any(microvm_factory, uvm_ctor, guest_kernel, rootfs, rate_limiter):
+def uvm_any(microvm_factory, uvm_ctor, guest_kernel, rootfs, rate_limiter, pci_enabled):
     """Return booted and restored uvms"""
-    return uvm_ctor(microvm_factory, guest_kernel, rootfs, rate_limiter)
+    return uvm_ctor(microvm_factory, guest_kernel, rootfs, rate_limiter, pci_enabled)
 
 
 def list_rng_available(ssh_connection: SSHConnection) -> list[str]: