feat: add host-backed entropy device support and update kernel configuration

tests/test_firecracker_config.py

@@ -3,9 +3,11 @@ from __future__ import annotations
 import unittest
 from ipaddress import IPv4Address, IPv4Network
 from pathlib import Path
+from unittest.mock import patch
 
 from uvm.config import Settings
 from uvm.domain import VmRecord
+from uvm.errors import FirecrackerError
 from uvm.firecracker.api import FirecrackerClient
 from uvm.firecracker.config import build_config, vcpu_count
 
@@ -45,6 +47,10 @@ class FirecrackerConfigTests(unittest.TestCase):
                 self.assertEqual("keep_bootcon" in arguments, architecture != "x86_64")
                 self.assertIn("console=ttyS0", arguments)
                 self.assertIn("ip=10.42.0.2::10.42.0.1:255.255.255.0::eth0:off", arguments)
+                client = RecordingFirecrackerClient()
+                client.configure_and_start(config)
+                self.assertEqual(client.calls[-2], ("PUT", "/entropy", {}))
+                self.assertEqual(client.calls[-1], ("PUT", "/actions", {"action_type": "InstanceStart"}))
 
     def test_builds_a_writable_vm_disk_configuration(self) -> None:
         vm = VmRecord(
@@ -101,6 +107,7 @@ class FirecrackerConfigTests(unittest.TestCase):
                 "/boot-source",
                 "/drives/rootfs",
                 "/network-interfaces/eth0",
+                "/entropy",
                 "/actions",
             ],
         )
@@ -110,6 +117,36 @@ class FirecrackerConfigTests(unittest.TestCase):
         )
         self.assertEqual(client.calls[-1][2], {"action_type": "InstanceStart"})
 
+    def test_entropy_failure_prevents_guest_boot(self) -> None:
+        config = {
+            "machine-config": {"vcpu_count": 1, "mem_size_mib": 512},
+            "boot-source": {},
+            "drives": [{}],
+            "network-interfaces": [{}],
+            "entropy": {},
+        }
+        client = RecordingFirecrackerClient()
+
+        def request(method: str, path: str, body: object) -> None:
+            client.calls.append((method, path, body))
+            if path == "/entropy":
+                raise FirecrackerError("entropy device unavailable")
+
+        with patch.object(client, "_request", side_effect=request):
+            with self.assertRaisesRegex(FirecrackerError, "entropy device unavailable"):
+                client.configure_and_start(config)
+
+        self.assertEqual(client.calls[-1], ("PUT", "/entropy", {}))
+        self.assertNotIn("/actions", [path for _method, path, _body in client.calls])
+
+        for entropy in (None, [], False):
+            with self.subTest(entropy=entropy):
+                client.calls.clear()
+                config["entropy"] = entropy
+                with self.assertRaisesRegex(FirecrackerError, "no valid entropy device"):
+                    client.configure_and_start(config)
+                self.assertEqual(client.calls, [])
+
     def test_uses_the_configured_network_netmask_in_guest_boot_arguments(self) -> None:
         settings = Settings(
             network=IPv4Network("10.50.0.0/16"),