[PATCH] tests/functional: use QMP to query available machines

[PATCH] tests/functional: use QMP to query available machines

[Ganesh Harshan]

Replace parsing of "qemu -M help" in set_machine() with
QMP "query-machines".

The previous approach relied on parsing human-readable CLI
output and substring matching, which is fragile and prone to
incorrect matches. It is also sensitive to output format changes.

Use QMP instead to retrieve structured machine information,
ensuring accurate matching and better maintainability.

Cache the result at the class level to avoid repeated QEMU
startup overhead.

Signed-off-by: Ganesh Harshan <ganeshredcobra@gmail.com>
---
 tests/functional/qemu_test/testcase.py | 32 +++++++++++++++++++++-----
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/tests/functional/qemu_test/testcase.py b/tests/functional/qemu_test/testcase.py
index eaec1bea13..5920d6a784 100644
--- a/tests/functional/qemu_test/testcase.py
+++ b/tests/functional/qemu_test/testcase.py
@@ -314,14 +314,34 @@ def setUp(self):
         console_log.addHandler(self._console_log_fh)
 
     def set_machine(self, machinename):
-        # TODO: We should use QMP to get the list of available machines
-        if not self._machinehelp:
-            self._machinehelp = run(
-                [self.qemu_bin, '-M', 'help'],
-                capture_output=True, check=True, encoding='utf8').stdout
-        if self._machinehelp.find(machinename) < 0:
+        cls = type(self)
+
+        if not hasattr(cls, "_machines"):
+            tmp_vm = QEMUMachine(self.qemu_bin)
+            tmp_vm.set_machine('none')
+
+            try:
+                tmp_vm.launch()
+                resp = tmp_vm.qmp('query-machines')
+
+                machines = resp.get('return', [])
+                cls._machines = [
+                    m.get('name') for m in machines if 'name' in m
+                ]
+
+            finally:
+                try:
+                    tmp_vm.shutdown()
+                except Exception:
+                    pass
+
+        self._machines = cls._machines
+
+        if machinename not in self._machines:
             self.skipTest('no support for machine ' + machinename)
+
         self.machine = machinename
+        self.vm.set_machine(machinename)
 
     def require_accelerator(self, accelerator):
         """
-- 
2.47.3

Re: [PATCH] tests/functional: use QMP to query available machines

[Daniel P. Berrangé]

On Thu, Jun 25, 2026 at 12:53:10PM -0400, Ganesh Harshan wrote:
> Replace parsing of "qemu -M help" in set_machine() with
> QMP "query-machines".
> 
> The previous approach relied on parsing human-readable CLI
> output and substring matching, which is fragile and prone to
> incorrect matches. It is also sensitive to output format changes.
> 
> Use QMP instead to retrieve structured machine information,
> ensuring accurate matching and better maintainability.
> 
> Cache the result at the class level to avoid repeated QEMU
> startup overhead.
> 
> Signed-off-by: Ganesh Harshan <ganeshredcobra@gmail.com>
> ---
>  tests/functional/qemu_test/testcase.py | 32 +++++++++++++++++++++-----
>  1 file changed, 26 insertions(+), 6 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
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