virtio-scsi-test: Test attaching new overlay with iothreads

This tests that blockdev-add can correctly add a qcow2 overlay to an
image used by a virtio-scsi disk in an iothread. The interesting point
here is whether the newly added node gets correctly moved into the
iothread AioContext.

If it isn't, we get an assertion failure in virtio-scsi while processing
the next request:

    virtio_scsi_ctx_check: Assertion `blk_get_aio_context(d->conf.blk) == s->ctx' failed.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

tests/libqtest.c

@@ -1038,6 +1038,25 @@ QDict *qmp(const char *fmt, ...)
     return response;
 }
 
+void qmp_assert_success(const char *fmt, ...)
+{
+    va_list ap;
+    QDict *response;
+
+    va_start(ap, fmt);
+    response = qtest_vqmp(global_qtest, fmt, ap);
+    va_end(ap);
+
+    g_assert(response);
+    if (!qdict_haskey(response, "return")) {
+        QString *s = qobject_to_json_pretty(QOBJECT(response));
+        g_test_message("%s", qstring_get_str(s));
+        qobject_unref(s);
+    }
+    g_assert(qdict_haskey(response, "return"));
+    qobject_unref(response);
+}
+
 char *hmp(const char *fmt, ...)
 {
     va_list ap;

tests/libqtest.h

@@ -619,6 +619,17 @@ static inline void qtest_end(void)
 QDict *qmp(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
 
 /**
+ * qmp_assert_success:
+ * @fmt...: QMP message to send to qemu, formatted like
+ * qobject_from_jsonf_nofail().  See parse_escape() for what's
+ * supported after '%'.
+ *
+ * Sends a QMP message to QEMU and asserts that a 'return' key is present in
+ * the response.
+ */
+void qmp_assert_success(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
+
+/*
  * qmp_eventwait:
  * @s: #event event to wait for.
  *

tests/virtio-scsi-test.c

@@ -188,6 +188,53 @@ static void test_unaligned_write_same(void *obj, void *data,
     qvirtio_scsi_pci_free(vs);
 }
 
+static void test_iothread_attach_node(void *obj, void *data,
+                                      QGuestAllocator *t_alloc)
+{
+    QVirtioSCSIPCI *scsi_pci = obj;
+    QVirtioSCSI *scsi = &scsi_pci->scsi;
+    QVirtioSCSIQueues *vs;
+    char tmp_path[] = "/tmp/qtest.XXXXXX";
+    int fd;
+    int ret;
+
+    uint8_t buf[512] = { 0 };
+    const uint8_t write_cdb[VIRTIO_SCSI_CDB_SIZE] = {
+        /* WRITE(10) to LBA 0, transfer length 1 */
+        0x2a, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00
+    };
+
+    alloc = t_alloc;
+    vs = qvirtio_scsi_init(scsi->vdev);
+
+    /* Create a temporary qcow2 overlay*/
+    fd = mkstemp(tmp_path);
+    g_assert(fd >= 0);
+    close(fd);
+
+    if (!have_qemu_img()) {
+        g_test_message("QTEST_QEMU_IMG not set or qemu-img missing; "
+                       "skipping snapshot test");
+        goto fail;
+    }
+
+    mkqcow2(tmp_path, 64);
+
+    /* Attach the overlay to the null0 node */
+    qmp_assert_success("{'execute': 'blockdev-add', 'arguments': {"
+                       "   'driver': 'qcow2', 'node-name': 'overlay',"
+                       "   'backing': 'null0', 'file': {"
+                       "     'driver': 'file', 'filename': %s}}}", tmp_path);
+
+    /* Send a request to see if the AioContext is still right */
+    ret = virtio_scsi_do_command(vs, write_cdb, NULL, 0, buf, 512, NULL);
+    g_assert_cmphex(ret, ==, 0);
+
+fail:
+    qvirtio_scsi_pci_free(vs);
+    unlink(tmp_path);
+}
+
 static void *virtio_scsi_hotplug_setup(GString *cmd_line, void *arg)
 {
     g_string_append(cmd_line,
@@ -204,6 +251,15 @@ static void *virtio_scsi_setup(GString *cmd_line, void *arg)
     return arg;
 }
 
+static void *virtio_scsi_setup_iothread(GString *cmd_line, void *arg)
+{
+    g_string_append(cmd_line,
+                    " -object iothread,id=thread0"
+                    " -blockdev driver=null-co,node-name=null0"
+                    " -device scsi-hd,drive=null0");
+    return arg;
+}
+
 static void register_virtio_scsi_test(void)
 {
     QOSGraphTestOptions opts = { };
@@ -214,6 +270,13 @@ static void register_virtio_scsi_test(void)
     opts.before = virtio_scsi_setup;
     qos_add_test("unaligned-write-same", "virtio-scsi",
                  test_unaligned_write_same, &opts);
+
+    opts.before = virtio_scsi_setup_iothread;
+    opts.edge = (QOSGraphEdgeOptions) {
+        .extra_device_opts = "iothread=thread0",
+    };
+    qos_add_test("iothread-attach-node", "virtio-scsi-pci",
+                 test_iothread_attach_node, &opts);
 }
 
 libqos_init(register_virtio_scsi_test);