tests: Add migration dirty-limit capability test

Add migration dirty-limit capability test if kernel support
dirty ring.

Migration dirty-limit capability introduce dirty limit
capability, two parameters: x-vcpu-dirty-limit-period and
vcpu-dirty-limit are introduced to implement the live
migration with dirty limit.

The test case does the following things:
1. start src, dst vm and enable dirty-limit capability
2. start migrate and set cancel it to check if dirty limit
   stop working.
3. restart dst vm
4. start migrate and enable dirty-limit capability
5. check if migration satisfy the convergence condition
   during pre-switchover phase.

Note that this test case involves many passes, so it runs
in slow mode only.

Signed-off-by: Hyman Huang <yong.huang@smartx.com>
Acked-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <e55a302df9da7dbc00ad825f47f57c1a756d303e.1698847223.git.yong.huang@smartx.com>

tests/qtest/migration-test.c

@@ -3091,6 +3091,166 @@ static void test_vcpu_dirty_limit(void)
     dirtylimit_stop_vm(vm);
 }
 
+static void migrate_dirty_limit_wait_showup(QTestState *from,
+                                            const int64_t period,
+                                            const int64_t value)
+{
+    /* Enable dirty limit capability */
+    migrate_set_capability(from, "dirty-limit", true);
+
+    /* Set dirty limit parameters */
+    migrate_set_parameter_int(from, "x-vcpu-dirty-limit-period", period);
+    migrate_set_parameter_int(from, "vcpu-dirty-limit", value);
+
+    /* Make sure migrate can't converge */
+    migrate_ensure_non_converge(from);
+
+    /* To check limit rate after precopy */
+    migrate_set_capability(from, "pause-before-switchover", true);
+
+    /* Wait for the serial output from the source */
+    wait_for_serial("src_serial");
+}
+
+/*
+ * This test does:
+ *  source                          destination
+ *  start vm
+ *                                  start incoming vm
+ *  migrate
+ *  wait dirty limit to begin
+ *  cancel migrate
+ *  cancellation check
+ *                                  restart incoming vm
+ *  migrate
+ *  wait dirty limit to begin
+ *  wait pre-switchover event
+ *  convergence condition check
+ *
+ * And see if dirty limit migration works correctly.
+ * This test case involves many passes, so it runs in slow mode only.
+ */
+static void test_migrate_dirty_limit(void)
+{
+    g_autofree char *uri = g_strdup_printf("unix:%s/migsocket", tmpfs);
+    QTestState *from, *to;
+    int64_t remaining;
+    uint64_t throttle_us_per_full;
+    /*
+     * We want the test to be stable and as fast as possible.
+     * E.g., with 1Gb/s bandwith migration may pass without dirty limit,
+     * so we need to decrease a bandwidth.
+     */
+    const int64_t dirtylimit_period = 1000, dirtylimit_value = 50;
+    const int64_t max_bandwidth = 400000000; /* ~400Mb/s */
+    const int64_t downtime_limit = 250; /* 250ms */
+    /*
+     * We migrate through unix-socket (> 500Mb/s).
+     * Thus, expected migration speed ~= bandwidth limit (< 500Mb/s).
+     * So, we can predict expected_threshold
+     */
+    const int64_t expected_threshold = max_bandwidth * downtime_limit / 1000;
+    int max_try_count = 10;
+    MigrateCommon args = {
+        .start = {
+            .hide_stderr = true,
+            .use_dirty_ring = true,
+        },
+        .listen_uri = uri,
+        .connect_uri = uri,
+    };
+
+    /* Start src, dst vm */
+    if (test_migrate_start(&from, &to, args.listen_uri, &args.start)) {
+        return;
+    }
+
+    /* Prepare for dirty limit migration and wait src vm show up */
+    migrate_dirty_limit_wait_showup(from, dirtylimit_period, dirtylimit_value);
+
+    /* Start migrate */
+    migrate_qmp(from, uri, "{}");
+
+    /* Wait for dirty limit throttle begin */
+    throttle_us_per_full = 0;
+    while (throttle_us_per_full == 0) {
+        throttle_us_per_full =
+        read_migrate_property_int(from, "dirty-limit-throttle-time-per-round");
+        usleep(100);
+        g_assert_false(got_src_stop);
+    }
+
+    /* Now cancel migrate and wait for dirty limit throttle switch off */
+    migrate_cancel(from);
+    wait_for_migration_status(from, "cancelled", NULL);
+
+    /* Check if dirty limit throttle switched off, set timeout 1ms */
+    do {
+        throttle_us_per_full =
+        read_migrate_property_int(from, "dirty-limit-throttle-time-per-round");
+        usleep(100);
+        g_assert_false(got_src_stop);
+    } while (throttle_us_per_full != 0 && --max_try_count);
+
+    /* Assert dirty limit is not in service */
+    g_assert_cmpint(throttle_us_per_full, ==, 0);
+
+    args = (MigrateCommon) {
+        .start = {
+            .only_target = true,
+            .use_dirty_ring = true,
+        },
+        .listen_uri = uri,
+        .connect_uri = uri,
+    };
+
+    /* Restart dst vm, src vm already show up so we needn't wait anymore */
+    if (test_migrate_start(&from, &to, args.listen_uri, &args.start)) {
+        return;
+    }
+
+    /* Start migrate */
+    migrate_qmp(from, uri, "{}");
+
+    /* Wait for dirty limit throttle begin */
+    throttle_us_per_full = 0;
+    while (throttle_us_per_full == 0) {
+        throttle_us_per_full =
+        read_migrate_property_int(from, "dirty-limit-throttle-time-per-round");
+        usleep(100);
+        g_assert_false(got_src_stop);
+    }
+
+    /*
+     * The dirty limit rate should equals the return value of
+     * query-vcpu-dirty-limit if dirty limit cap set
+     */
+    g_assert_cmpint(dirtylimit_value, ==, get_limit_rate(from));
+
+    /* Now, we have tested if dirty limit works, let it converge */
+    migrate_set_parameter_int(from, "downtime-limit", downtime_limit);
+    migrate_set_parameter_int(from, "max-bandwidth", max_bandwidth);
+
+    /*
+     * Wait for pre-switchover status to check if migration
+     * satisfy the convergence condition
+     */
+    wait_for_migration_status(from, "pre-switchover", NULL);
+
+    remaining = read_ram_property_int(from, "remaining");
+    g_assert_cmpint(remaining, <,
+                    (expected_threshold + expected_threshold / 100));
+
+    migrate_continue(from, "pre-switchover");
+
+    qtest_qmp_eventwait(to, "RESUME");
+
+    wait_for_serial("dest_serial");
+    wait_for_migration_complete(from);
+
+    test_migrate_end(from, to, true);
+}
+
 static bool kvm_dirty_ring_supported(void)
 {
 #if defined(__linux__) && defined(HOST_X86_64)
@@ -3301,6 +3461,10 @@ int main(int argc, char **argv)
      */
     if (g_test_slow()) {
         qtest_add_func("/migration/auto_converge", test_migrate_auto_converge);
+        if (g_str_equal(arch, "x86_64") &&
+            has_kvm && kvm_dirty_ring_supported()) {
+            qtest_add_func("/migration/dirty_limit", test_migrate_dirty_limit);
+        }
     }
     qtest_add_func("/migration/multifd/tcp/plain/none",
                    test_multifd_tcp_none);