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tests/functional: add a QMP backdoor for debugging stalled tests

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Support the QEMU_TEST_QMP_BACKDOOR=backdoor.sock env variable as a
way to get a QMP backdoor for debugging a stalled QEMU test. Most
typically this would be used if running the tests directly:

 $ QEMU_TEST_QMP_BACKDOOR=backdoor.sock \
   QEMU_TEST_QEMU_BINARY=./build/qemu-system-arm \
   PYTHONPATH=./python \
   ./tests/functional/test_arm_tuxrun.py

And then, when the test stalls, in a second shell run:

 $ ./scripts/qmp/qmp-shell backdoor.sock

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20241121154218.1423005-18-berrange@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20241121165806.476008-18-alex.bennee@linaro.org>
This commit is contained in:
Daniel P. Berrangé 2024-11-21 16:57:44 +00:00 committed by Alex Bennée
parent 97d79319f0
commit 1a8755a51e
2 changed files with 17 additions and 0 deletions
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10
docs/devel/testing/functional.rst
View File

@ -176,6 +176,16 @@ primarily depend on the value of the ``qemu_bin`` class attribute.
If it is not explicitly set by the test code, its default value will If it is not explicitly set by the test code, its default value will
be the result the QEMU_TEST_QEMU_BINARY environment variable. be the result the QEMU_TEST_QEMU_BINARY environment variable.
Debugging hung QEMU
^^^^^^^^^^^^^^^^^^^
When test cases go wrong it may be helpful to debug a stalled QEMU
process. While the QEMUMachine class owns the primary QMP monitor
socket, it is possible to request a second QMP monitor be created
by setting the ``QEMU_TEST_QMP_BACKDOOR`` env variable to refer
to a UNIX socket name. The ``qmp-shell`` command can then be
attached to the stalled QEMU to examine its live state.
Attribute reference Attribute reference
------------------- -------------------

7
tests/functional/qemu_test/testcase.py
View File

@ -175,6 +175,13 @@ class QemuSystemTest(QemuBaseTest):
log_dir=self.logdir) log_dir=self.logdir)
self.log.debug('QEMUMachine "%s" created', name) self.log.debug('QEMUMachine "%s" created', name)
self.log.debug('QEMUMachine "%s" temp_dir: %s', name, vm.temp_dir) self.log.debug('QEMUMachine "%s" temp_dir: %s', name, vm.temp_dir)
sockpath = os.environ.get("QEMU_TEST_QMP_BACKDOOR", None)
if sockpath is not None:
vm.add_args("-chardev",
f"socket,id=backdoor,path={sockpath},server=on,wait=off",
"-mon", "chardev=backdoor,mode=control")
if args: if args:
vm.add_args(*args) vm.add_args(*args)
return vm return vm