tests/qtest/migration: Allow user to specify a machine type

Accept the QTEST_QEMU_MACHINE_TYPE environment variable to take a
machine type to use in the tests.

The full machine type is recognized (e.g. pc-q35-8.2). Aliases
(e.g. pc) are also allowed and resolve to the latest machine version
for that alias, or, if using two QEMU binaries, to the latest common
machine version between the two.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231018192741.25885-12-farosas@suse.de>

tests/qtest/migration-helpers.c

@@ -11,6 +11,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/ctype.h"
 #include "qapi/qmp/qjson.h"
 
 #include "migration-helpers.h"
@@ -266,3 +267,28 @@ char *find_common_machine_version(const char *mtype, const char *var1,
                    "binaries %s and %s", mtype, getenv(var1), getenv(var2));
     g_assert_not_reached();
 }
+
+char *resolve_machine_version(const char *alias, const char *var1,
+                              const char *var2)
+{
+    const char *mname = g_getenv("QTEST_QEMU_MACHINE_TYPE");
+    g_autofree char *machine_name = NULL;
+
+    if (mname) {
+        const char *dash = strrchr(mname, '-');
+        const char *dot = strrchr(mname, '.');
+
+        machine_name = g_strdup(mname);
+
+        if (dash && dot) {
+            assert(qtest_has_machine(machine_name));
+            return g_steal_pointer(&machine_name);
+        }
+        /* else: probably an alias, let it be resolved below */
+    } else {
+        /* use the hardcoded alias */
+        machine_name = g_strdup(alias);
+    }
+
+    return find_common_machine_version(machine_name, var1, var2);
+}

tests/qtest/migration-helpers.h

@@ -45,4 +45,6 @@ void wait_for_migration_fail(QTestState *from, bool allow_active);
 
 char *find_common_machine_version(const char *mtype, const char *var1,
                                   const char *var2);
+char *resolve_machine_version(const char *alias, const char *var1,
+                              const char *var2);
 #endif /* MIGRATION_HELPERS_H */

tests/qtest/migration-test.c

@@ -825,8 +825,9 @@ static int test_migrate_start(QTestState **from, QTestState **to,
         kvm_opts = ",dirty-ring-size=4096";
     }
 
-    machine = find_common_machine_version(machine_alias, QEMU_ENV_SRC,
-                                          QEMU_ENV_DST);
+    machine = resolve_machine_version(machine_alias, QEMU_ENV_SRC,
+                                      QEMU_ENV_DST);
+
     g_test_message("Using machine type: %s", machine);
 
     cmd_source = g_strdup_printf("-accel kvm%s -accel tcg "