fix(test): kill uffd handler when microvm gets killed

By not killing the uffd handler, we are leaking the resources associated
with the uffd handler, which can be undesirable and cose gradual
slowdown in in snapshot performance tests that restore snapshots using
uffd in a loop.

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

Author: roypat

tests/framework/microvm.py

@@ -341,6 +341,9 @@ def kill(self):
                 stderr == "" and "firecracker" not in stdout
             ), f"Firecracker reported its pid {self.firecracker_pid}, which was killed, but there still exist processes using the supposedly dead Firecracker's jailer_id: {stdout}"
 
+        if self.uffd_handler and self.uffd_handler.is_running():
+            self.uffd_handler.kill()
+
         # Mark the microVM as not spawned, so we avoid trying to kill twice.
         self._spawned = False
         self._killed = True

tests/framework/utils_uffd.py

@@ -77,10 +77,22 @@ def log_data(self):
             return ""
         return self.log_file.read_text(encoding="utf-8")
 
+    def kill(self):
+        """Kills the uffd handler process"""
+        assert self.is_running()
+
+        self.proc.kill()
+
+    def mark_killed(self):
+        """Marks the uffd handler as already dead"""
+        assert not self.is_running()
+
+        self._proc = None
+
     def __del__(self):
         """Tear down the UFFD handler process."""
-        if self.proc is not None:
-            self.proc.kill()
+        if self.is_running():
+            self.kill()
 
 
 def spawn_pf_handler(vm, handler_path, jailed_snapshot):

tests/integration_tests/functional/test_uffd.py

@@ -128,4 +128,4 @@ def test_malicious_handler(uvm_plain, snapshot):
             )
             assert False, "Firecracker should freeze"
     except (TimeoutError, requests.exceptions.ReadTimeout):
-        pass
+        vm.uffd_handler.mark_killed()