[PATCH v2 5/9] tests/qtest: Introduce qtest_resolve_machine_alias

[Fabiano Rosas <farosas@suse.de>]

The migration tests are being enhanced to test migration between
different QEMU versions. A requirement of migration is that the
machine type between source and destination matches, including the
version.

We cannot hardcode machine types in the tests because those change
with each release. QEMU provides a machine type alias that has a fixed
name, but points to the latest machine type at each release.

Add a helper to resolve the alias into the exact machine
type. E.g. "-machine pc" resolves to "pc-i440fx-8.2"

Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
 tests/qtest/libqtest.c | 16 ++++++++++++++++
 tests/qtest/libqtest.h | 10 ++++++++++
 2 files changed, 26 insertions(+)

diff --git a/tests/qtest/libqtest.c b/tests/qtest/libqtest.c
index c0e4f05979..f2f1756de1 100644
--- a/tests/qtest/libqtest.c
+++ b/tests/qtest/libqtest.c
@@ -1522,6 +1522,22 @@ void qtest_cb_for_every_machine(void (*cb)(const char *machine),
     }
 }
 
+char *qtest_resolve_machine_alias(const char *var, const char *alias)
+{
+    struct MachInfo *machines;
+    int i;
+
+    machines = qtest_get_machines(var);
+
+    for (i = 0; machines[i].name != NULL; i++) {
+        if (machines[i].alias && g_str_equal(alias, machines[i].alias)) {
+            return g_strdup(machines[i].name);
+        }
+    }
+
+    return NULL;
+}
+
 bool qtest_has_machine_with_env(const char *var, const char *machine)
 {
     struct MachInfo *machines;
diff --git a/tests/qtest/libqtest.h b/tests/qtest/libqtest.h
index 083b2a6520..75f9310bb0 100644
--- a/tests/qtest/libqtest.h
+++ b/tests/qtest/libqtest.h
@@ -894,6 +894,16 @@ void qtest_qmp_fds_assert_success(QTestState *qts, int *fds, size_t nfds,
 void qtest_cb_for_every_machine(void (*cb)(const char *machine),
                                 bool skip_old_versioned);
 
+/**
+ * qtest_resolve_machine_alias:
+ * @var: Environment variable from where to take the QEMU binary
+ * @alias: The alias to resolve
+ *
+ * Returns: the machine type corresponding to the alias if any,
+ * otherwise NULL.
+ */
+char *qtest_resolve_machine_alias(const char *var, const char *alias);
+
 /**
  * qtest_has_machine:
  * @machine: The machine to look for
-- 
2.35.3