test: enable serial console in integration tests

If SSH to guest is failing, we don't really get much useful in terms of
logs in our ci artifacts. Enable serial console so that we get guest
dmesg always.

Disable it for the tests that interact with the serial console via
stdin/stdout (here we are not daemonizing, so we are capturing serial
output anyway).

Disable pylint's "too-many-statements" lint, because it started firing
in microvm.spawn()

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

Author: roypat

tests/framework/microvm.py

@@ -259,6 +259,7 @@ def __init__(
 
         self.api = None
         self.log_file = None
+        self.serial_log_file = None
         self.metrics_file = None
         self._spawned = False
         self._killed = False
@@ -624,6 +625,7 @@ def add_pre_cmd(self, pre_cmd):
     def spawn(
         self,
         log_file="fc.log",
+        serial_log_file="serial.log",
         log_level="Debug",
         log_show_level=False,
         log_show_origin=False,
@@ -654,6 +656,12 @@ def spawn(
             if log_show_origin:
                 self.jailer.extra_args["show-log-origin"] = None
 
+        if serial_log_file is not None:
+            self.serial_log_file = Path(self.path) / serial_log_file
+            self.serial_log_file.touch()
+            self.create_jailed_resource(self.serial_log_file)
+            self.jailer.extra_args.update({"serial-out-path": serial_log_file})
+
         if metrics_path is not None:
             self.metrics_file = Path(self.path) / metrics_path
             self.metrics_file.touch()
@@ -795,12 +803,9 @@ def basic_config(
         The function checks the response status code and asserts that
         the response is within the interval [200, 300).
 
-        If boot_args is None, the default boot_args in Firecracker is
-            reboot=k panic=1 nomodule 8250.nr_uarts=0 i8042.noaux i8042.nomux
-            i8042.nopnp i8042.dumbkbd swiotlb=noforce
-
-        if PCI is disabled, Firecracker also passes to the guest pci=off
-
+        If boot_args is None, the default boot_args used in tests is
+            reboot=k panic=1 nomodule swiotlb=noforce console=ttyS0 [pci=off]
+        which differs from Firecracker's default only in the enabling of the serial console.
         Reference: file:../../src/vmm/src/vmm_config/boot_source.rs::DEFAULT_KERNEL_CMDLINE
         """
         self.api.machine_config.put(
@@ -824,6 +829,10 @@ def basic_config(
 
         if boot_args is not None:
             self.boot_args = boot_args
+        else:
+            self.boot_args = "reboot=k panic=1 nomodule swiotlb=noforce console=ttyS0"
+            if not self.pci_enabled:
+                self.boot_args += " pci=off"
         boot_source_args = {
             "kernel_image_path": self.create_jailed_resource(self.kernel_file),
             "boot_args": self.boot_args,
@@ -1309,13 +1318,13 @@ def open(self):
             return
 
         attempt = 0
-        while not Path(self._vm.screen_log).exists() and attempt < 5:
+        while not Path(self._vm.serial_log_file).exists() and attempt < 5:
             time.sleep(0.2)
             attempt += 1
 
-        screen_log_fd = os.open(self._vm.screen_log, os.O_RDONLY)
+        serial_log_fd = os.open(self._vm.serial_log_file, os.O_RDONLY)
         self._poller = select.poll()
-        self._poller.register(screen_log_fd, select.POLLIN | select.POLLHUP)
+        self._poller.register(serial_log_fd, select.POLLIN | select.POLLHUP)
 
     def tx(self, input_string, end="\n"):
         # pylint: disable=invalid-name

tests/integration_tests/functional/test_api.py

@@ -1136,8 +1136,10 @@ def test_get_full_config_after_restoring_snapshot(microvm_factory, uvm_nano):
     expected_cfg["boot-source"] = {
         "kernel_image_path": uvm_nano.get_jailed_resource(uvm_nano.kernel_file),
         "initrd_path": None,
-        "boot_args": None,
+        "boot_args": "reboot=k panic=1 nomodule swiotlb=noforce console=ttyS0",
     }
+    if not uvm_nano.pci_enabled:
+        expected_cfg["boot-source"]["boot_args"] += " pci=off"
 
     # no ipv4_address or imds_compat specified during PUT /mmds/config so we expect the default
     expected_cfg["mmds-config"] = {

tests/integration_tests/functional/test_cmd_line_parameters.py

@@ -29,7 +29,7 @@ def test_describe_snapshot_all_versions(
         jailer_binary_path=firecracker_release.jailer,
     )
     # FIXME: Once only FC versions >= 1.12 are supported, drop log_level="warn"
-    vm.spawn(log_level="warn")
+    vm.spawn(log_level="warn", serial_log_file=None)
     vm.basic_config(track_dirty_pages=True)
     vm.start()
     snapshot = vm.snapshot_diff()

tests/integration_tests/functional/test_max_devices.py

@@ -18,9 +18,9 @@ def max_devices(uvm):
     match platform.machine():
         case "aarch64":
             # On aarch64, IRQs are available from 32 to 127. We always use one IRQ each for
-            # the VMGenID and RTC devices, so the maximum number of devices supported
-            # at the same time is 94.
-            return 94
+            # the VMGenID, RTC and serial devices, so the maximum number of devices supported
+            # at the same time is 93.
+            return 93
         case "x86_64":
             # IRQs are available from 5 to 23. We always use one IRQ for VMGenID device, so
             # the maximum number of devices supported at the same time is 18.

tests/integration_tests/functional/test_serial_io.py

@@ -51,11 +51,10 @@ def test_serial_after_snapshot(uvm_plain, microvm_factory):
     """
     microvm = uvm_plain
     microvm.help.enable_console()
-    microvm.spawn()
+    microvm.spawn(serial_log_file=None)
     microvm.basic_config(
         vcpu_count=2,
         mem_size_mib=256,
-        boot_args="console=ttyS0 reboot=k panic=1 swiotlb=noforce",
     )
     serial = Serial(microvm)
     serial.open()
@@ -92,7 +91,7 @@ def test_serial_console_login(uvm_plain_any):
     """
     microvm = uvm_plain_any
     microvm.help.enable_console()
-    microvm.spawn()
+    microvm.spawn(serial_log_file=None)
 
     # We don't need to monitor the memory for this test because we are
     # just rebooting and the process dies before pmap gets the RSS.
@@ -174,13 +173,12 @@ def test_serial_block(uvm_plain_any):
     """
     test_microvm = uvm_plain_any
     test_microvm.help.enable_console()
-    test_microvm.spawn()
+    test_microvm.spawn(serial_log_file=None)
     # Set up the microVM with 1 vCPU so we make sure the vCPU thread
     # responsible for the SSH connection will also run the serial.
     test_microvm.basic_config(
         vcpu_count=1,
         mem_size_mib=512,
-        boot_args="console=ttyS0 reboot=k panic=1 swiotlb=noforce",
     )
     test_microvm.add_net_iface()
     test_microvm.start()

tests/integration_tests/performance/test_initrd.py

@@ -29,7 +29,7 @@ def test_microvm_initrd_with_serial(uvm_with_initrd, huge_pages):
     """
     vm = uvm_with_initrd
     vm.help.enable_console()
-    vm.spawn()
+    vm.spawn(serial_log_file=None)
     vm.memory_monitor = None
 
     vm.basic_config(

tests/pyproject.toml

@@ -56,4 +56,5 @@ disable = [
     "too-many-positional-arguments",
     "too-few-public-methods",
     "too-many-branches",
+    "too-many-statements",
 ]