[PATCH v2] tests/qtest/migration: Add mapped-ram/postcopy validation test

[Takeru Hayasaka <hayatake396@gmail.com>]

The migration capability checks reject enabling postcopy-ram together
with mapped-ram, but there is no qtest covering this incompatibility.

Add a validation test that verifies QMP rejects the combination in
both capability ordering cases and returns the expected error.

This keeps the existing capability boundary covered without changing
migration behavior.

Signed-off-by: Takeru Hayasaka <hayatake396@gmail.com>
---
Built with:
  ./configure --target-list=x86_64-softmmu --disable-werror
  ninja -C build tests/qtest/migration-test qemu-system-x86_64

Tested with:
  QTEST_QEMU_BINARY=./build/qemu-system-x86_64 \
  ./build/tests/qtest/migration-test --full \
  -p /x86_64/migration/validate_caps/mapped_ram_postcopy

 v2:
   - Rename do_test_validate_capability_pair to validate_caps_pair
   - Move migrate_start/migrate_end to caller for VM reuse
   - Set only_source to skip target VM
   - Generalize test using migration_test_add_suffix pattern
---
 tests/qtest/migration/misc-tests.c | 50 ++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/tests/qtest/migration/misc-tests.c b/tests/qtest/migration/misc-tests.c
index 196f1ca84287..4131e7b0614d 100644
--- a/tests/qtest/migration/misc-tests.c
+++ b/tests/qtest/migration/misc-tests.c
@@ -215,6 +215,53 @@ static void do_test_validate_uri_channel(MigrateCommon *args)
     migrate_end(from, to, false);
 }
 
+static void validate_caps_pair(QTestState *from,
+                               const char *first_capability,
+                               const char *second_capability,
+                               const char *expected_error)
+{
+    QDict *rsp;
+    const char *error_desc;
+
+    migrate_set_capability(from, first_capability, true);
+
+    rsp = qtest_qmp_assert_failure_ref(
+        from,
+        "{ 'execute': 'migrate-set-capabilities',"
+        "  'arguments': { 'capabilities': [ { "
+        "      'capability': %s, 'state': true } ] } }",
+        second_capability);
+
+    error_desc = qdict_get_str(rsp, "desc");
+    g_assert_cmpstr(error_desc, ==, expected_error);
+    qobject_unref(rsp);
+
+    migrate_set_capability(from, first_capability, false);
+}
+
+static void test_validate_caps_pair(char *test_path, MigrateCommon *args)
+{
+    g_autofree char *cap_pair = g_path_get_basename(test_path);
+    QTestState *from, *to;
+
+    args->start.hide_stderr = true;
+    args->start.only_source = true;
+
+    if (migrate_start(&from, &to, "defer", &args->start)) {
+        return;
+    }
+
+    if (g_str_equal(cap_pair, "mapped_ram_postcopy")) {
+        const char *error =
+            "Mapped-ram migration is incompatible with postcopy";
+
+        validate_caps_pair(from, "mapped-ram", "postcopy-ram", error);
+        validate_caps_pair(from, "postcopy-ram", "mapped-ram", error);
+    }
+
+    qtest_quit(from);
+}
+
 static void test_validate_uri_channels_both_set(char *name, MigrateCommon *args)
 {
     args->listen_uri = "defer",
@@ -276,4 +323,7 @@ void migration_test_add_misc(MigrationTestEnv *env)
                        test_validate_uri_channels_both_set);
     migration_test_add("/migration/validate_uri/channels/none_set",
                        test_validate_uri_channels_none_set);
+    migration_test_add_suffix("/migration/validate_caps/",
+                              "mapped_ram_postcopy",
+                              test_validate_caps_pair);
 }
-- 
2.43.0