+/* shared for the benefit of the derived pci class */
+#define TYPE_VHOST_USER_DEVICE "vhost-user-device"
+
+#endif /* QEMU_VHOST_USER_DEVICE_H */
diff --git a/hw/virtio/vhost-user-device.c b/hw/virtio/vhost-user-device.c
new file mode 100644
index 0000000000..b0239fa033
--- /dev/null
+++ b/hw/virtio/vhost-user-device.c
@@ -0,0 +1,324 @@
+/*
+ * Generic vhost-user stub. This can be used to connect to any
+ * vhost-user backend. All configuration details must be handled by
+ * the vhost-user daemon itself
+ *
+ * Copyright (c) 2023 Linaro Ltd
+ * Author: Alex Bennée <alex.bennee@linaro.org>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "hw/qdev-properties.h"
+#include "hw/virtio/virtio-bus.h"
+#include "hw/virtio/vhost-user-device.h"
+#include "qemu/error-report.h"
+
+static void vub_start(VirtIODevice *vdev)
+{
+ BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
+ VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+ VHostUserBase *vub = VHOST_USER_BASE(vdev);
+ int ret, i;
+
+ if (!k->set_guest_notifiers) {
+ error_report("binding does not support guest notifiers");
+ return;
+ }
+
+ ret = vhost_dev_enable_notifiers(&vub->vhost_dev, vdev);
+ if (ret < 0) {
+ error_report("Error enabling host notifiers: %d", -ret);
+ return;
+ }
+
+ ret = k->set_guest_notifiers(qbus->parent, vub->vhost_dev.nvqs, true);
+ if (ret < 0) {
+ error_report("Error binding guest notifier: %d", -ret);
+ goto err_host_notifiers;
+ }
+
+ vub->vhost_dev.acked_features = vdev->guest_features;
+
+ ret = vhost_dev_start(&vub->vhost_dev, vdev, true);
+ if (ret < 0) {
+ error_report("Error starting vhost-user-device: %d", -ret);
+ goto err_guest_notifiers;
+ }
+
+ /*
+ * guest_notifier_mask/pending not used yet, so just unmask
+ * everything here. virtio-pci will do the right thing by
+ * enabling/disabling irqfd.
+ */
+ for (i = 0; i < vub->vhost_dev.nvqs; i++) {
+ vhost_virtqueue_mask(&vub->vhost_dev, vdev, i, false);
+ }
+
+ return;
+
+err_guest_notifiers:
+ k->set_guest_notifiers(qbus->parent, vub->vhost_dev.nvqs, false);
+err_host_notifiers:
+ vhost_dev_disable_notifiers(&vub->vhost_dev, vdev);
+}
+
+static void vub_stop(VirtIODevice *vdev)
+{
+ VHostUserBase *vub = VHOST_USER_BASE(vdev);
+ BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
+ VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+ int ret;
+
+ if (!k->set_guest_notifiers) {
+ return;
+ }
+
+ vhost_dev_stop(&vub->vhost_dev, vdev, true);
+
+ ret = k->set_guest_notifiers(qbus->parent, vub->vhost_dev.nvqs, false);
+ if (ret < 0) {
+ error_report("vhost guest notifier cleanup failed: %d", ret);
+ return;
+ }
+
+ vhost_dev_disable_notifiers(&vub->vhost_dev, vdev);
+}
+
+static void vub_set_status(VirtIODevice *vdev, uint8_t status)
+{
+ VHostUserBase *vub = VHOST_USER_BASE(vdev);
+ bool should_start = virtio_device_should_start(vdev, status);
+
+ if (vhost_dev_is_started(&vub->vhost_dev) == should_start) {
+ return;
+ }
+
+ if (should_start) {
+ vub_start(vdev);
+ } else {
+ vub_stop(vdev);
+ }
+}
+
+/*
+ * For an implementation where everything is delegated to the backend
+ * we don't do anything other than return the full feature set offered
+ * by the daemon (module the reserved feature bit).
+ */
+static uint64_t vub_get_features(VirtIODevice *vdev,
+ uint64_t requested_features, Error **errp)
+{
+ VHostUserBase *vub = VHOST_USER_BASE(vdev);
+ /* This should be set when the vhost connection initialises */
+ g_assert(vub->vhost_dev.features);
+ return vub->vhost_dev.features & ~(1ULL << VHOST_USER_F_PROTOCOL_FEATURES);
+}
+
+static void vub_handle_output(VirtIODevice *vdev, VirtQueue *vq)
+{
+ /*
+ * Not normally called; it's the daemon that handles the queue;
+ * however virtio's cleanup path can call this.
+ */
+}
+
+static void do_vhost_user_cleanup(VirtIODevice *vdev, VHostUserBase *vub)
+{
+ vhost_user_cleanup(&vub->vhost_user);
+
+ for (int i = 0; i < vub->num_vqs; i++) {
+ VirtQueue *vq = g_ptr_array_index(vub->vqs, i);
+ virtio_delete_queue(vq);
+ }
+
+ virtio_cleanup(vdev);
+}
+
+static int vub_connect(DeviceState *dev)
+{
+ VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+ VHostUserBase *vub = VHOST_USER_BASE(vdev);
+
+ if (vub->connected) {
+ return 0;
+ }
+ vub->connected = true;
+
+ /* restore vhost state */
+ if (virtio_device_started(vdev, vdev->status)) {
+ vub_start(vdev);
+ }
+
+ return 0;
+}
+
+static void vub_disconnect(DeviceState *dev)
+{
+ VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+ VHostUserBase *vub = VHOST_USER_BASE(vdev);
+
+ if (!vub->connected) {
+ return;
+ }
+ vub->connected = false;
+
+ if (vhost_dev_is_started(&vub->vhost_dev)) {
+ vub_stop(vdev);
+ }
+}
+
+static void vub_event(void *opaque, QEMUChrEvent event)
+{
+ DeviceState *dev = opaque;
+ VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+ VHostUserBase *vub = VHOST_USER_BASE(vdev);
+
+ switch (event) {
+ case CHR_EVENT_OPENED:
+ if (vub_connect(dev) < 0) {
+ qemu_chr_fe_disconnect(&vub->chardev);
+ return;
+ }
+ break;
+ case CHR_EVENT_CLOSED:
+ vub_disconnect(dev);
+ break;
+ case CHR_EVENT_BREAK:
+ case CHR_EVENT_MUX_IN:
+ case CHR_EVENT_MUX_OUT:
+ /* Ignore */
+ break;
+ }
+}
+
+static void vub_device_realize(DeviceState *dev, Error **errp)
+{
+ VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+ VHostUserBase *vub = VHOST_USER_BASE(dev);
+ int ret;
+
+ if (!vub->chardev.chr) {
+ error_setg(errp, "vhost-user-device: missing chardev");
+ return;
+ }
+
+ if (!vub->virtio_id) {
+ error_setg(errp, "vhost-user-device: need to define device id");
+ return;
+ }
+
+ if (!vub->num_vqs) {
+ vub->num_vqs = 1; /* reasonable default? */
+ }
+
+ if (!vhost_user_init(&vub->vhost_user, &vub->chardev, errp)) {
+ return;
+ }
+
+ virtio_init(vdev, vub->virtio_id, 0);
+
+ /*
+ * Disable guest notifiers, by default all notifications will be via the
+ * asynchronous vhost-user socket.
+ */
+ vdev->use_guest_notifier_mask = false;
+
+ /* Allocate queues */
+ vub->vqs = g_ptr_array_sized_new(vub->num_vqs);
+ for (int i = 0; i < vub->num_vqs; i++) {
+ g_ptr_array_add(vub->vqs,
+ virtio_add_queue(vdev, 4, vub_handle_output));
+ }
+
+ vub->vhost_dev.nvqs = vub->num_vqs;
+ vub->vhost_dev.vqs = g_new0(struct vhost_virtqueue, vub->vhost_dev.nvqs);
+
+ /* connect to backend */
+ ret = vhost_dev_init(&vub->vhost_dev, &vub->vhost_user,
+ VHOST_BACKEND_TYPE_USER, 0, errp);
+
+ if (ret < 0) {
+ do_vhost_user_cleanup(vdev, vub);
+ }
+
+ qemu_chr_fe_set_handlers(&vub->chardev, NULL, NULL, vub_event, NULL,
+ dev, NULL, true);
+}
+
+static void vub_device_unrealize(DeviceState *dev)
+{
+ VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+ VHostUserBase *vub = VHOST_USER_BASE(dev);
+ struct vhost_virtqueue *vhost_vqs = vub->vhost_dev.vqs;
+
+ /* This will stop vhost backend if appropriate. */
+ vub_set_status(vdev, 0);
+ vhost_dev_cleanup(&vub->vhost_dev);
+ g_free(vhost_vqs);
+ do_vhost_user_cleanup(vdev, vub);
+}
+
+static void vub_class_init(ObjectClass *klass, void *data)
+{
+ VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
+
+ vdc->realize = vub_device_realize;
+ vdc->unrealize = vub_device_unrealize;
+ vdc->get_features = vub_get_features;
+ vdc->set_status = vub_set_status;
+}
+
+static const TypeInfo vub_info = {
+ .name = TYPE_VHOST_USER_BASE,
+ .parent = TYPE_VIRTIO_DEVICE,
+ .instance_size = sizeof(VHostUserBase),
+ .class_init = vub_class_init,
+ .class_size = sizeof(VHostUserBaseClass),
+ .abstract = true
+};
+
+
+/*
+ * The following is a concrete implementation of the base class which
+ * allows the user to define the key parameters via the command line.
+ */
+
+static const VMStateDescription vud_vmstate = {
+ .name = "vhost-user-device",
+ .unmigratable = 1,
+};
+
+static Property vud_properties[] = {
+ DEFINE_PROP_CHR("chardev", VHostUserBase, chardev),
+ DEFINE_PROP_UINT16("virtio-id", VHostUserBase, virtio_id, 0),
+ DEFINE_PROP_UINT32("num_vqs", VHostUserBase, num_vqs, 1),
+ DEFINE_PROP_END_OF_LIST(),
+};
+
+static void vud_class_init(ObjectClass *klass, void *data)
+{
+ DeviceClass *dc = DEVICE_CLASS(klass);
+
+ device_class_set_props(dc, vud_properties);
+ dc->vmsd = &vud_vmstate;
+ set_bit(DEVICE_CATEGORY_INPUT, dc->categories);
+}
+
+static const TypeInfo vud_info = {
+ .name = TYPE_VHOST_USER_DEVICE,
+ .parent = TYPE_VHOST_USER_BASE,
+ .instance_size = sizeof(VHostUserBase),
+ .class_init = vud_class_init,
+ .class_size = sizeof(VHostUserBaseClass),
+};