tests/virtio-scsi: add a virtio_error() IOThread test

Now that virtio_error() calls should work in an IOThread, add a
virtio-scsi IOThread test cases that triggers virtio_error().

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20250922220149.498967-6-stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

tests/qtest/virtio-scsi-test.c

@@ -311,6 +311,31 @@ fail:
     unlink(tmp_path);
 }
 
+static void test_iothread_virtio_error(void *obj, void *data,
+                                       QGuestAllocator *t_alloc)
+{
+    QVirtioSCSIPCI *scsi_pci = obj;
+    QVirtioSCSI *scsi = &scsi_pci->scsi;
+    QVirtioSCSIQueues *vs;
+    QVirtQueue *vq;
+
+    alloc = t_alloc;
+    vs = qvirtio_scsi_init(scsi->vdev);
+    vq = vs->vq[2];
+
+    /* Move avail.idx out of bounds to trigger virtio_error() */
+    qvirtqueue_set_avail_idx(global_qtest, scsi->vdev, vq, vq->size * 2);
+    scsi->vdev->bus->virtqueue_kick(scsi->vdev, vq);
+
+    /*
+     * Reset the device out of the error state. If QEMU hangs or crashes then
+     * this will fail.
+     */
+    qvirtio_reset(scsi->vdev);
+
+    qvirtio_scsi_pci_free(vs);
+}
+
 static void *virtio_scsi_hotplug_setup(GString *cmd_line, void *arg)
 {
     g_string_append(cmd_line,
@@ -383,6 +408,13 @@ static void register_virtio_scsi_test(void)
     };
     qos_add_test("iothread-attach-node", "virtio-scsi-pci",
                  test_iothread_attach_node, &opts);
+
+    opts.before = virtio_scsi_setup_iothread;
+    opts.edge = (QOSGraphEdgeOptions) {
+        .extra_device_opts = "iothread=thread0",
+    };
+    qos_add_test("iothread-virtio-error", "virtio-scsi-pci",
+                 test_iothread_virtio_error, &opts);
 }
 
 libqos_init(register_virtio_scsi_test);