Following in the footsteps of what whas done for vhost-user-i2c
and virtiofsd, introduce a random number generator (RNG) backend
that communicates with a vhost-user server to retrieve entropy.
That way another VMM could be using the same vhost-user daemon and
avoid having to write yet another RNG driver.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 hw/virtio/Kconfig                  |   5 +
 hw/virtio/meson.build              |   1 +
 hw/virtio/vhost-user-rng.c         | 294 +++++++++++++++++++++++++++++
 include/hw/virtio/vhost-user-rng.h |  33 ++++
 4 files changed, 333 insertions(+)
 create mode 100644 hw/virtio/vhost-user-rng.c
 create mode 100644 include/hw/virtio/vhost-user-rng.h

diff --git a/hw/virtio/Kconfig b/hw/virtio/Kconfig
index 0eda25c4e1bf..69066ab14e6d 100644
--- a/hw/virtio/Kconfig
+++ b/hw/virtio/Kconfig
@@ -58,3 +58,8 @@ config VIRTIO_MEM
     depends on LINUX
     depends on VIRTIO_MEM_SUPPORTED
     select MEM_DEVICE
+
+config VHOST_USER_RNG
+    bool
+    default y
+    depends on VIRTIO && VHOST_USER
diff --git a/hw/virtio/meson.build b/hw/virtio/meson.build
index fbff9bc9d4de..e386791f2a05 100644
--- a/hw/virtio/meson.build
+++ b/hw/virtio/meson.build
@@ -25,6 +25,7 @@ virtio_ss.add(when: 'CONFIG_VHOST_USER_VSOCK', if_true: files('vhost-user-vsock.
 virtio_ss.add(when: 'CONFIG_VIRTIO_RNG', if_true: files('virtio-rng.c'))
 virtio_ss.add(when: 'CONFIG_VIRTIO_IOMMU', if_true: files('virtio-iommu.c'))
 virtio_ss.add(when: 'CONFIG_VIRTIO_MEM', if_true: files('virtio-mem.c'))
+virtio_ss.add(when: 'CONFIG_VHOST_USER_RNG', if_true: files('vhost-user-rng.c'))
 
 virtio_pci_ss = ss.source_set()
 virtio_pci_ss.add(when: 'CONFIG_VHOST_VSOCK', if_true: files('vhost-vsock-pci.c'))
diff --git a/hw/virtio/vhost-user-rng.c b/hw/virtio/vhost-user-rng.c
new file mode 100644
index 000000000000..3825266bdf46
--- /dev/null
+++ b/hw/virtio/vhost-user-rng.c
@@ -0,0 +1,294 @@
+/*
+ * Vhost-user RNG virtio device
+ *
+ * Copyright (c) 2021 Mathieu Poirier <mathieu.poirier@linaro.org>
+ *
+ * Implementation seriously tailored on vhost-user-i2c.c
+ *
+ * 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-rng.h"
+#include "qemu/error-report.h"
+#include "standard-headers/linux/virtio_ids.h"
+
+static void vu_rng_start(VirtIODevice *vdev)
+{
+    VHostUserRNG *rng = VHOST_USER_RNG(vdev);
+    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
+    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+    int ret;
+    int i;
+
+    if (!k->set_guest_notifiers) {
+        error_report("binding does not support guest notifiers");
+        return;
+    }
+
+    ret = vhost_dev_enable_notifiers(&rng->vhost_dev, vdev);
+    if (ret < 0) {
+        error_report("Error enabling host notifiers: %d", -ret);
+        return;
+    }
+
+    ret = k->set_guest_notifiers(qbus->parent, rng->vhost_dev.nvqs, true);
+    if (ret < 0) {
+        error_report("Error binding guest notifier: %d", -ret);
+        goto err_host_notifiers;
+    }
+
+    rng->vhost_dev.acked_features = vdev->guest_features;
+    ret = vhost_dev_start(&rng->vhost_dev, vdev);
+    if (ret < 0) {
+        error_report("Error starting vhost-user-rng: %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 < rng->vhost_dev.nvqs; i++) {
+        vhost_virtqueue_mask(&rng->vhost_dev, vdev, i, false);
+    }
+
+    return;
+
+err_guest_notifiers:
+    k->set_guest_notifiers(qbus->parent, rng->vhost_dev.nvqs, false);
+err_host_notifiers:
+    vhost_dev_disable_notifiers(&rng->vhost_dev, vdev);
+}
+
+static void vu_rng_stop(VirtIODevice *vdev)
+{
+    VHostUserRNG *rng = VHOST_USER_RNG(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(&rng->vhost_dev, vdev);
+
+    ret = k->set_guest_notifiers(qbus->parent, rng->vhost_dev.nvqs, false);
+    if (ret < 0) {
+        error_report("vhost guest notifier cleanup failed: %d", ret);
+        return;
+    }
+
+    vhost_dev_disable_notifiers(&rng->vhost_dev, vdev);
+}
+
+static void vu_rng_set_status(VirtIODevice *vdev, uint8_t status)
+{
+    VHostUserRNG *rng = VHOST_USER_RNG(vdev);
+    bool should_start = status & VIRTIO_CONFIG_S_DRIVER_OK;
+
+    if (!vdev->vm_running) {
+        should_start = false;
+    }
+
+    if (rng->vhost_dev.started == should_start) {
+        return;
+    }
+
+    if (should_start) {
+        vu_rng_start(vdev);
+    } else {
+        vu_rng_stop(vdev);
+    }
+}
+
+static uint64_t vu_rng_get_features(VirtIODevice *vdev,
+                                    uint64_t requested_features, Error **errp)
+{
+    /* No feature bits used yet */
+    return requested_features;
+}
+
+static void vu_rng_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 vu_rng_guest_notifier_mask(VirtIODevice *vdev, int idx, bool mask)
+{
+    VHostUserRNG *rng = VHOST_USER_RNG(vdev);
+
+    vhost_virtqueue_mask(&rng->vhost_dev, vdev, idx, mask);
+}
+
+static bool vu_rng_guest_notifier_pending(VirtIODevice *vdev, int idx)
+{
+    VHostUserRNG *rng = VHOST_USER_RNG(vdev);
+
+    return vhost_virtqueue_pending(&rng->vhost_dev, idx);
+}
+
+static void vu_rng_connect(DeviceState *dev)
+{
+    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+    VHostUserRNG *rng = VHOST_USER_RNG(vdev);
+
+    if (rng->connected) {
+        return;
+    }
+
+    rng->connected = true;
+
+    /* restore vhost state */
+    if (virtio_device_started(vdev, vdev->status)) {
+        vu_rng_start(vdev);
+    }
+}
+
+static void vu_rng_disconnect(DeviceState *dev)
+{
+    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+    VHostUserRNG *rng = VHOST_USER_RNG(vdev);
+
+    if (!rng->connected) {
+        return;
+    }
+
+    rng->connected = false;
+
+    if (rng->vhost_dev.started) {
+        vu_rng_stop(vdev);
+    }
+}
+
+static void vu_rng_event(void *opaque, QEMUChrEvent event)
+{
+    DeviceState *dev = opaque;
+
+    switch (event) {
+    case CHR_EVENT_OPENED:
+        vu_rng_connect(dev);
+        break;
+    case CHR_EVENT_CLOSED:
+        vu_rng_disconnect(dev);
+        break;
+    case CHR_EVENT_BREAK:
+    case CHR_EVENT_MUX_IN:
+    case CHR_EVENT_MUX_OUT:
+        /* Ignore */
+        break;
+    }
+}
+
+static void vu_rng_device_realize(DeviceState *dev, Error **errp)
+{
+    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+    VHostUserRNG *rng = VHOST_USER_RNG(dev);
+    int ret;
+
+    if (!rng->chardev.chr) {
+        error_setg(errp, "missing chardev");
+        return;
+    }
+
+    if (!vhost_user_init(&rng->vhost_user, &rng->chardev, errp)) {
+        return;
+    }
+
+    virtio_init(vdev, "vhost-user-rng", VIRTIO_ID_RNG, 0);
+
+    rng->req_vq = virtio_add_queue(vdev, 4, vu_rng_handle_output);
+    if (!rng->req_vq) {
+        error_setg_errno(errp, -1, "virtio_add_queue() failed");
+        goto virtio_add_queue_failed;
+    }
+
+    rng->vhost_dev.nvqs = 1;
+    rng->vhost_dev.vqs = g_new0(struct vhost_virtqueue, rng->vhost_dev.nvqs);
+    if (!rng->vhost_dev.vqs) {
+        error_setg_errno(errp, -1, "memory allocation failed");
+        goto vhost_dev_init_failed;
+    }
+
+    ret = vhost_dev_init(&rng->vhost_dev, &rng->vhost_user,
+                         VHOST_BACKEND_TYPE_USER, 0, errp);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "vhost_dev_init() failed");
+        goto vhost_dev_init_failed;
+    }
+
+    qemu_chr_fe_set_handlers(&rng->chardev, NULL, NULL, vu_rng_event, NULL,
+                             dev, NULL, true);
+
+    return;
+
+vhost_dev_init_failed:
+    virtio_delete_queue(rng->req_vq);
+virtio_add_queue_failed:
+    virtio_cleanup(vdev);
+    vhost_user_cleanup(&rng->vhost_user);
+}
+
+static void vu_rng_device_unrealize(DeviceState *dev)
+{
+    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+    VHostUserRNG *rng = VHOST_USER_RNG(dev);
+
+    vu_rng_set_status(vdev, 0);
+
+    vhost_dev_cleanup(&rng->vhost_dev);
+    g_free(rng->vhost_dev.vqs);
+    rng->vhost_dev.vqs = NULL;
+    virtio_delete_queue(rng->req_vq);
+    virtio_cleanup(vdev);
+    vhost_user_cleanup(&rng->vhost_user);
+}
+
+static const VMStateDescription vu_rng_vmstate = {
+    .name = "vhost-user-rng",
+    .unmigratable = 1,
+};
+
+static Property vu_rng_properties[] = {
+    DEFINE_PROP_CHR("chardev", VHostUserRNG, chardev),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void vu_rng_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
+
+    device_class_set_props(dc, vu_rng_properties);
+    dc->vmsd = &vu_rng_vmstate;
+    set_bit(DEVICE_CATEGORY_INPUT, dc->categories);
+
+    vdc->realize = vu_rng_device_realize;
+    vdc->unrealize = vu_rng_device_unrealize;
+    vdc->get_features = vu_rng_get_features;
+    vdc->set_status = vu_rng_set_status;
+    vdc->guest_notifier_mask = vu_rng_guest_notifier_mask;
+    vdc->guest_notifier_pending = vu_rng_guest_notifier_pending;
+}
+
+static const TypeInfo vu_rng_info = {
+    .name = TYPE_VHOST_USER_RNG,
+    .parent = TYPE_VIRTIO_DEVICE,
+    .instance_size = sizeof(VHostUserRNG),
+    .class_init = vu_rng_class_init,
+};
+
+static void vu_rng_register_types(void)
+{
+    type_register_static(&vu_rng_info);
+}
+
+type_init(vu_rng_register_types)
diff --git a/include/hw/virtio/vhost-user-rng.h b/include/hw/virtio/vhost-user-rng.h
new file mode 100644
index 000000000000..071539996d1d
--- /dev/null
+++ b/include/hw/virtio/vhost-user-rng.h
@@ -0,0 +1,33 @@
+/*
+ * Vhost-user RNG virtio device
+ *
+ * Copyright (c) 2021 Mathieu Poirier <mathieu.poirier@linaro.org>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef _QEMU_VHOST_USER_RNG_H
+#define _QEMU_VHOST_USER_RNG_H
+
+#include "hw/virtio/virtio.h"
+#include "hw/virtio/vhost.h"
+#include "hw/virtio/vhost-user.h"
+#include "chardev/char-fe.h"
+
+#define TYPE_VHOST_USER_RNG "vhost-user-rng"
+OBJECT_DECLARE_SIMPLE_TYPE(VHostUserRNG, VHOST_USER_RNG)
+
+struct VHostUserRNG {
+    /*< private >*/
+    VirtIODevice parent;
+    CharBackend chardev;
+    struct vhost_virtqueue *vhost_vq;
+    struct vhost_dev vhost_dev;
+    VhostUserState vhost_user;
+    VirtQueue *req_vq;
+    bool connected;
+
+    /*< public >*/
+};
+
+#endif /* _QEMU_VHOST_USER_RNG_H */
-- 
2.25.1

Mathieu Poirier <mathieu.poirier@linaro.org> writes:

> Following in the footsteps of what whas done for vhost-user-i2c
> and virtiofsd, introduce a random number generator (RNG) backend
> that communicates with a vhost-user server to retrieve entropy.
> That way another VMM could be using the same vhost-user daemon and
> avoid having to write yet another RNG driver.
>
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> ---
>  hw/virtio/Kconfig                  |   5 +
>  hw/virtio/meson.build              |   1 +

FWIW there are simple merge failures for the meson and Kconfig parts due
to I2C being merged.

<snip>
> +
> +    rng->vhost_dev.nvqs = 1;
> +    rng->vhost_dev.vqs = g_new0(struct vhost_virtqueue, rng->vhost_dev.nvqs);
> +    if (!rng->vhost_dev.vqs) {
> +        error_setg_errno(errp, -1, "memory allocation failed");
> +        goto vhost_dev_init_failed;
> +    }

g_new0 will abort on memory allocation failure (which is fine for
userspace ;-) so you don't need the check and erro handling exit here.

> +
> +    ret = vhost_dev_init(&rng->vhost_dev, &rng->vhost_user,
> +                         VHOST_BACKEND_TYPE_USER, 0, errp);
> +    if (ret < 0) {
> +        error_setg_errno(errp, -ret, "vhost_dev_init() failed");
> +        goto vhost_dev_init_failed;
> +    }
> +
> +    qemu_chr_fe_set_handlers(&rng->chardev, NULL, NULL, vu_rng_event, NULL,
> +                             dev, NULL, true);
> +
> +    return;
> +
> +vhost_dev_init_failed:
> +    virtio_delete_queue(rng->req_vq);
> +virtio_add_queue_failed:
> +    virtio_cleanup(vdev);
> +    vhost_user_cleanup(&rng->vhost_user);
> +}
> +
> +static void vu_rng_device_unrealize(DeviceState *dev)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> +    VHostUserRNG *rng = VHOST_USER_RNG(dev);
> +
> +    vu_rng_set_status(vdev, 0);
> +
> +    vhost_dev_cleanup(&rng->vhost_dev);
> +    g_free(rng->vhost_dev.vqs);
> +    rng->vhost_dev.vqs = NULL;
> +    virtio_delete_queue(rng->req_vq);
> +    virtio_cleanup(vdev);
> +    vhost_user_cleanup(&rng->vhost_user);
> +}
> +
> +static const VMStateDescription vu_rng_vmstate = {
> +    .name = "vhost-user-rng",
> +    .unmigratable = 1,
> +};
> +
> +static Property vu_rng_properties[] = {
> +    DEFINE_PROP_CHR("chardev", VHostUserRNG, chardev),
> +    DEFINE_PROP_END_OF_LIST(),
> +};
> +
> +static void vu_rng_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
> +
> +    device_class_set_props(dc, vu_rng_properties);
> +    dc->vmsd = &vu_rng_vmstate;
> +    set_bit(DEVICE_CATEGORY_INPUT, dc->categories);
> +
> +    vdc->realize = vu_rng_device_realize;
> +    vdc->unrealize = vu_rng_device_unrealize;
> +    vdc->get_features = vu_rng_get_features;
> +    vdc->set_status = vu_rng_set_status;
> +    vdc->guest_notifier_mask = vu_rng_guest_notifier_mask;
> +    vdc->guest_notifier_pending = vu_rng_guest_notifier_pending;
> +}
> +
> +static const TypeInfo vu_rng_info = {
> +    .name = TYPE_VHOST_USER_RNG,
> +    .parent = TYPE_VIRTIO_DEVICE,
> +    .instance_size = sizeof(VHostUserRNG),
> +    .class_init = vu_rng_class_init,
> +};
> +
> +static void vu_rng_register_types(void)
> +{
> +    type_register_static(&vu_rng_info);
> +}
> +
> +type_init(vu_rng_register_types)
> diff --git a/include/hw/virtio/vhost-user-rng.h b/include/hw/virtio/vhost-user-rng.h
> new file mode 100644
> index 000000000000..071539996d1d
> --- /dev/null
> +++ b/include/hw/virtio/vhost-user-rng.h
> @@ -0,0 +1,33 @@
> +/*
> + * Vhost-user RNG virtio device
> + *
> + * Copyright (c) 2021 Mathieu Poirier <mathieu.poirier@linaro.org>
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#ifndef _QEMU_VHOST_USER_RNG_H
> +#define _QEMU_VHOST_USER_RNG_H
> +
> +#include "hw/virtio/virtio.h"
> +#include "hw/virtio/vhost.h"
> +#include "hw/virtio/vhost-user.h"
> +#include "chardev/char-fe.h"
> +
> +#define TYPE_VHOST_USER_RNG "vhost-user-rng"
> +OBJECT_DECLARE_SIMPLE_TYPE(VHostUserRNG, VHOST_USER_RNG)
> +
> +struct VHostUserRNG {
> +    /*< private >*/
> +    VirtIODevice parent;
> +    CharBackend chardev;
> +    struct vhost_virtqueue *vhost_vq;
> +    struct vhost_dev vhost_dev;
> +    VhostUserState vhost_user;
> +    VirtQueue *req_vq;
> +    bool connected;
> +
> +    /*< public >*/
> +};
> +
> +#endif /* _QEMU_VHOST_USER_RNG_H */

Otherwise:

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée

Hi Alex,

On Wed, Jul 21, 2021 at 09:52:50AM +0100, Alex Bennée wrote:
> 
> Mathieu Poirier <mathieu.poirier@linaro.org> writes:
> 
> > Following in the footsteps of what whas done for vhost-user-i2c
> > and virtiofsd, introduce a random number generator (RNG) backend
> > that communicates with a vhost-user server to retrieve entropy.
> > That way another VMM could be using the same vhost-user daemon and
> > avoid having to write yet another RNG driver.
> >
> > Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> > ---
> >  hw/virtio/Kconfig                  |   5 +
> >  hw/virtio/meson.build              |   1 +
> 
> FWIW there are simple merge failures for the meson and Kconfig parts due
> to I2C being merged.
> 

Right, merging I2C before this set will definitely break things.

> <snip>
> > +
> > +    rng->vhost_dev.nvqs = 1;
> > +    rng->vhost_dev.vqs = g_new0(struct vhost_virtqueue, rng->vhost_dev.nvqs);
> > +    if (!rng->vhost_dev.vqs) {
> > +        error_setg_errno(errp, -1, "memory allocation failed");
> > +        goto vhost_dev_init_failed;
> > +    }
> 
> g_new0 will abort on memory allocation failure (which is fine for
> userspace ;-) so you don't need the check and erro handling exit here.
> 

Ok, I'll fix this.

> > +
> > +    ret = vhost_dev_init(&rng->vhost_dev, &rng->vhost_user,
> > +                         VHOST_BACKEND_TYPE_USER, 0, errp);
> > +    if (ret < 0) {
> > +        error_setg_errno(errp, -ret, "vhost_dev_init() failed");
> > +        goto vhost_dev_init_failed;
> > +    }
> > +
> > +    qemu_chr_fe_set_handlers(&rng->chardev, NULL, NULL, vu_rng_event, NULL,
> > +                             dev, NULL, true);
> > +
> > +    return;
> > +
> > +vhost_dev_init_failed:
> > +    virtio_delete_queue(rng->req_vq);
> > +virtio_add_queue_failed:
> > +    virtio_cleanup(vdev);
> > +    vhost_user_cleanup(&rng->vhost_user);
> > +}
> > +
> > +static void vu_rng_device_unrealize(DeviceState *dev)
> > +{
> > +    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> > +    VHostUserRNG *rng = VHOST_USER_RNG(dev);
> > +
> > +    vu_rng_set_status(vdev, 0);
> > +
> > +    vhost_dev_cleanup(&rng->vhost_dev);
> > +    g_free(rng->vhost_dev.vqs);
> > +    rng->vhost_dev.vqs = NULL;
> > +    virtio_delete_queue(rng->req_vq);
> > +    virtio_cleanup(vdev);
> > +    vhost_user_cleanup(&rng->vhost_user);
> > +}
> > +
> > +static const VMStateDescription vu_rng_vmstate = {
> > +    .name = "vhost-user-rng",
> > +    .unmigratable = 1,
> > +};
> > +
> > +static Property vu_rng_properties[] = {
> > +    DEFINE_PROP_CHR("chardev", VHostUserRNG, chardev),
> > +    DEFINE_PROP_END_OF_LIST(),
> > +};
> > +
> > +static void vu_rng_class_init(ObjectClass *klass, void *data)
> > +{
> > +    DeviceClass *dc = DEVICE_CLASS(klass);
> > +    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
> > +
> > +    device_class_set_props(dc, vu_rng_properties);
> > +    dc->vmsd = &vu_rng_vmstate;
> > +    set_bit(DEVICE_CATEGORY_INPUT, dc->categories);
> > +
> > +    vdc->realize = vu_rng_device_realize;
> > +    vdc->unrealize = vu_rng_device_unrealize;
> > +    vdc->get_features = vu_rng_get_features;
> > +    vdc->set_status = vu_rng_set_status;
> > +    vdc->guest_notifier_mask = vu_rng_guest_notifier_mask;
> > +    vdc->guest_notifier_pending = vu_rng_guest_notifier_pending;
> > +}
> > +
> > +static const TypeInfo vu_rng_info = {
> > +    .name = TYPE_VHOST_USER_RNG,
> > +    .parent = TYPE_VIRTIO_DEVICE,
> > +    .instance_size = sizeof(VHostUserRNG),
> > +    .class_init = vu_rng_class_init,
> > +};
> > +
> > +static void vu_rng_register_types(void)
> > +{
> > +    type_register_static(&vu_rng_info);
> > +}
> > +
> > +type_init(vu_rng_register_types)
> > diff --git a/include/hw/virtio/vhost-user-rng.h b/include/hw/virtio/vhost-user-rng.h
> > new file mode 100644
> > index 000000000000..071539996d1d
> > --- /dev/null
> > +++ b/include/hw/virtio/vhost-user-rng.h
> > @@ -0,0 +1,33 @@
> > +/*
> > + * Vhost-user RNG virtio device
> > + *
> > + * Copyright (c) 2021 Mathieu Poirier <mathieu.poirier@linaro.org>
> > + *
> > + * SPDX-License-Identifier: GPL-2.0-or-later
> > + */
> > +
> > +#ifndef _QEMU_VHOST_USER_RNG_H
> > +#define _QEMU_VHOST_USER_RNG_H
> > +
> > +#include "hw/virtio/virtio.h"
> > +#include "hw/virtio/vhost.h"
> > +#include "hw/virtio/vhost-user.h"
> > +#include "chardev/char-fe.h"
> > +
> > +#define TYPE_VHOST_USER_RNG "vhost-user-rng"
> > +OBJECT_DECLARE_SIMPLE_TYPE(VHostUserRNG, VHOST_USER_RNG)
> > +
> > +struct VHostUserRNG {
> > +    /*< private >*/
> > +    VirtIODevice parent;
> > +    CharBackend chardev;
> > +    struct vhost_virtqueue *vhost_vq;
> > +    struct vhost_dev vhost_dev;
> > +    VhostUserState vhost_user;
> > +    VirtQueue *req_vq;
> > +    bool connected;
> > +
> > +    /*< public >*/
> > +};
> > +
> > +#endif /* _QEMU_VHOST_USER_RNG_H */
> 
> Otherwise:
> 
> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

Thanks for taking the time to review this set.

> 
> -- 
> Alex Bennée