tests/avocado: probe for multi-process support before running test

A recent attempt to let avocado run more tests on the CentOS stream
build failed because there was no gating on the multiprocess feature.
Like missing accelerators avocado should gracefully skip when the
feature is not enabled.

In this case we use the existence of the proxy device as a proxy for
multi-process support.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Cc: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Cc: Jagannathan Raman <jag.raman@oracle.com>
Cc: John G Johnson <john.g.johnson@oracle.com>
Message-Id: <20230321111752.2681128-1-alex.bennee@linaro.org>

tests/avocado/avocado_qemu/__init__.py

@@ -309,6 +309,16 @@ class QemuSystemTest(QemuBaseTest):
         if netdevhelp.find('\n' + netdevname + '\n') < 0:
             self.cancel('no support for user networking')
 
+    def require_multiprocess(self):
+        """
+        Test for the presence of the x-pci-proxy-dev which is required
+        to support multiprocess.
+        """
+        devhelp = run_cmd([self.qemu_bin,
+                           '-M', 'none', '-device', 'help'])[0];
+        if devhelp.find('x-pci-proxy-dev') < 0:
+            self.cancel('no support for multiprocess device emulation')
+
     def _new_vm(self, name, *args):
         self._sd = tempfile.TemporaryDirectory(prefix="qemu_")
         vm = QEMUMachine(self.qemu_bin, base_temp_dir=self.workdir,

tests/avocado/multiprocess.py

@@ -22,6 +22,7 @@ class Multiprocess(QemuSystemTest):
                 machine_type):
         """Main test method"""
         self.require_accelerator('kvm')
+        self.require_multiprocess()
 
         # Create socketpair to connect proxy and remote processes
         proxy_sock, remote_sock = socket.socketpair(socket.AF_UNIX,