From: Albert Esteve <[email protected]>
Add the QEMU side of the vhost-user-media device, which connects to a
virtio-media vhost-user backend daemon implementing the V4L2 API over
the virtio-media protocol.
The virtio-media device is specified in the VirtIO specification v1.4,
section 5.22:
https://docs.oasis-open.org/virtio/virtio/v1.4/cs01/virtio-v1.4-cs01.html
Tested with the rust-vmm vhost-device-media backend [1]:
cargo run -- -s /path/to/media.sock -d /dev/video0 --backend v4l2-proxy
Example invocation:
qemu-system-x86_64 \
-chardev socket,path=/path/to/media.sock,id=media \
-device vhost-user-media-pci,chardev=media,id=media
[1] https://github.com/rust-vmm/vhost-device/tree/main/vhost-device-media
Tested-by: Dorinda Bassey <[email protected]>
Signed-off-by: Albert Esteve <[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
Message-ID: <[email protected]>
---
MAINTAINERS | 6 +
include/hw/virtio/vhost-user-media.h | 46 ++++
hw/display/vhost-user-media-pci.c | 80 ++++++
hw/display/vhost-user-media.c | 348 +++++++++++++++++++++++++++
hw/virtio/virtio.c | 3 +-
hw/display/Kconfig | 5 +
hw/display/meson.build | 3 +
7 files changed, 490 insertions(+), 1 deletion(-)
create mode 100644 include/hw/virtio/vhost-user-media.h
create mode 100644 hw/display/vhost-user-media-pci.c
create mode 100644 hw/display/vhost-user-media.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 7183babd6a..ec313c3259 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2690,6 +2690,12 @@ S: Supported
F: include/hw/virtio/vhost-user-rtc.h
F: hw/virtio/vhost-user-rtc*
+vhost-user-media
+M: Albert Esteve <[email protected]>
+S: Supported
+F: hw/display/vhost-user-media*
+F: include/hw/virtio/vhost-user-media.h
+
virtio-crypto
M: Gonglei <[email protected]>
S: Supported
diff --git a/include/hw/virtio/vhost-user-media.h
b/include/hw/virtio/vhost-user-media.h
new file mode 100644
index 0000000000..d040c70f63
--- /dev/null
+++ b/include/hw/virtio/vhost-user-media.h
@@ -0,0 +1,46 @@
+/*
+ * vhost-user-media virtio device
+ *
+ * Copyright Red Hat, Inc. 2026
+ *
+ * Authors:
+ * Albert Esteve <[email protected]>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef QEMU_VHOST_USER_MEDIA_H
+#define QEMU_VHOST_USER_MEDIA_H
+
+#include "hw/virtio/virtio.h"
+#include "hw/virtio/vhost.h"
+#include "hw/virtio/vhost-user.h"
+#include "qom/object.h"
+
+#define TYPE_VHOST_USER_MEDIA "vhost-user-media-device"
+OBJECT_DECLARE_SIMPLE_TYPE(VHostUserMEDIA, VHOST_USER_MEDIA)
+
+/* virtio-media config layout, spec 5.22.4 */
+struct virtio_media_config {
+ uint32_t device_caps;
+ uint32_t device_type;
+ uint8_t card[32];
+} QEMU_PACKED;
+
+typedef struct {
+ CharFrontend chardev;
+} VHostUserMEDIAConf;
+
+struct VHostUserMEDIA {
+ /*< private >*/
+ VirtIODevice parent;
+ VHostUserMEDIAConf conf;
+ struct vhost_dev vhost_dev;
+ VhostUserState vhost_user;
+ VirtQueue *command_vq;
+ VirtQueue *event_vq;
+ bool connected;
+ /*< public >*/
+};
+
+#endif /* QEMU_VHOST_USER_MEDIA_H */
diff --git a/hw/display/vhost-user-media-pci.c
b/hw/display/vhost-user-media-pci.c
new file mode 100644
index 0000000000..3e09fcfdd0
--- /dev/null
+++ b/hw/display/vhost-user-media-pci.c
@@ -0,0 +1,80 @@
+/*
+ * Vhost-user MEDIA virtio device PCI glue
+ *
+ * Copyright Red Hat, Inc. 2026
+ * Authors: Albert Esteve <[email protected]>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "hw/core/qdev-properties.h"
+#include "hw/virtio/vhost-user-media.h"
+#include "hw/virtio/virtio-pci.h"
+
+#define TYPE_VHOST_USER_MEDIA_PCI "vhost-user-media-pci-base"
+OBJECT_DECLARE_SIMPLE_TYPE(VHostUserMEDIAPCI, VHOST_USER_MEDIA_PCI)
+
+struct VHostUserMEDIAPCI {
+ VirtIOPCIProxy parent_obj;
+ VHostUserMEDIA vdev;
+};
+
+static const Property vumedia_pci_properties[] = {
+ DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags,
+ VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
+ DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors,
+ DEV_NVECTORS_UNSPECIFIED),
+};
+
+static void vumedia_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
+{
+ VHostUserMEDIAPCI *dev = VHOST_USER_MEDIA_PCI(vpci_dev);
+ DeviceState *dev_state = DEVICE(&dev->vdev);
+
+ if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
+ vpci_dev->nvectors = 1;
+ }
+
+ if (!qdev_realize(dev_state, BUS(&vpci_dev->bus), errp)) {
+ return;
+ }
+}
+
+static void vumedia_pci_class_init(ObjectClass *klass, const void *data)
+{
+ DeviceClass *dc = DEVICE_CLASS(klass);
+ VirtioPCIClass *k = VIRTIO_PCI_CLASS(klass);
+ PCIDeviceClass *pcidev_k = PCI_DEVICE_CLASS(klass);
+ k->realize = vumedia_pci_realize;
+ set_bit(DEVICE_CATEGORY_MISC, dc->categories);
+ device_class_set_props(dc, vumedia_pci_properties);
+ pcidev_k->vendor_id = PCI_VENDOR_ID_REDHAT_QUMRANET;
+ pcidev_k->device_id = 0; /* Set by virtio-pci based on virtio id */
+ pcidev_k->revision = 0x00;
+ pcidev_k->class_id = PCI_CLASS_MULTIMEDIA_VIDEO;
+}
+
+static void vumedia_pci_instance_init(Object *obj)
+{
+ VHostUserMEDIAPCI *dev = VHOST_USER_MEDIA_PCI(obj);
+
+ virtio_instance_init_common(obj, &dev->vdev, sizeof(dev->vdev),
+ TYPE_VHOST_USER_MEDIA);
+}
+
+static const VirtioPCIDeviceTypeInfo vumedia_pci_info = {
+ .base_name = TYPE_VHOST_USER_MEDIA_PCI,
+ .non_transitional_name = "vhost-user-media-pci",
+ .instance_size = sizeof(VHostUserMEDIAPCI),
+ .instance_init = vumedia_pci_instance_init,
+ .class_init = vumedia_pci_class_init,
+};
+
+static void vumedia_pci_register(void)
+{
+ virtio_pci_types_register(&vumedia_pci_info);
+}
+
+type_init(vumedia_pci_register);
diff --git a/hw/display/vhost-user-media.c b/hw/display/vhost-user-media.c
new file mode 100644
index 0000000000..14edc7c668
--- /dev/null
+++ b/hw/display/vhost-user-media.c
@@ -0,0 +1,348 @@
+/*
+ * Vhost-user Media device
+ *
+ * Copyright Red Hat, Inc. 2026
+ *
+ * This is the boilerplate for instantiating a vhost-user device
+ * implementing a virtio-media device.
+ *
+ * Authors:
+ * Albert Esteve <[email protected]>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "qemu/error-report.h"
+#include "hw/core/qdev-properties-system.h"
+#include "standard-headers/linux/virtio_ids.h"
+#include "hw/virtio/virtio-bus.h"
+#include "hw/virtio/vhost-user-media.h"
+
+static const int feature_bits[] = {
+ VIRTIO_F_VERSION_1,
+ VIRTIO_F_NOTIFY_ON_EMPTY,
+ VIRTIO_RING_F_INDIRECT_DESC,
+ VIRTIO_RING_F_EVENT_IDX,
+ VIRTIO_F_RING_RESET,
+ VHOST_INVALID_FEATURE_BIT
+};
+
+static void
+vu_media_get_config(VirtIODevice *vdev, uint8_t *config_data)
+{
+ VHostUserMEDIA *media = VHOST_USER_MEDIA(vdev);
+ Error *local_err = NULL;
+ int ret;
+
+ memset(config_data, 0, sizeof(struct virtio_media_config));
+
+ ret = vhost_dev_get_config(&media->vhost_dev,
+ config_data, sizeof(struct virtio_media_config),
+ &local_err);
+ if (ret) {
+ error_report_err(local_err);
+ return;
+ }
+}
+
+static void vu_media_start(VirtIODevice *vdev)
+{
+ VHostUserMEDIA *media = VHOST_USER_MEDIA(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(&media->vhost_dev, vdev);
+ if (ret < 0) {
+ error_report("Error enabling host notifiers: %d", -ret);
+ return;
+ }
+
+ ret = k->set_guest_notifiers(qbus->parent, media->vhost_dev.nvqs, true);
+ if (ret < 0) {
+ error_report("Error binding guest notifier: %d", -ret);
+ goto err_host_notifiers;
+ }
+
+ media->vhost_dev.acked_features = vdev->guest_features;
+
+ media->vhost_dev.vq_index_end = media->vhost_dev.nvqs;
+ ret = vhost_dev_start(&media->vhost_dev, vdev, true);
+ if (ret < 0) {
+ error_report("Error starting vhost-user-media: %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 < media->vhost_dev.nvqs; i++) {
+ vhost_virtqueue_mask(&media->vhost_dev, vdev, i, false);
+ }
+
+ return;
+
+err_guest_notifiers:
+ k->set_guest_notifiers(qbus->parent, media->vhost_dev.nvqs, false);
+err_host_notifiers:
+ vhost_dev_disable_notifiers(&media->vhost_dev, vdev);
+}
+
+static void vu_media_stop(VirtIODevice *vdev)
+{
+ VHostUserMEDIA *media = VHOST_USER_MEDIA(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(&media->vhost_dev, vdev, true);
+
+ ret = k->set_guest_notifiers(qbus->parent, media->vhost_dev.nvqs, false);
+ if (ret < 0) {
+ error_report("vhost guest notifier cleanup failed: %d", ret);
+ return;
+ }
+
+ vhost_dev_disable_notifiers(&media->vhost_dev, vdev);
+}
+
+static int vu_media_set_status(VirtIODevice *vdev, uint8_t status)
+{
+ VHostUserMEDIA *media = VHOST_USER_MEDIA(vdev);
+ bool should_start = virtio_device_should_start(vdev, status);
+
+ if (vhost_dev_is_started(&media->vhost_dev) == should_start) {
+ return 0;
+ }
+
+ if (should_start) {
+ vu_media_start(vdev);
+ } else {
+ vu_media_stop(vdev);
+ }
+ return 0;
+}
+
+static uint64_t vu_media_get_features(VirtIODevice *vdev,
+ uint64_t requested_features,
+ Error **errp)
+{
+ VHostUserMEDIA *media = VHOST_USER_MEDIA(vdev);
+
+ return vhost_get_features(&media->vhost_dev, feature_bits,
+ requested_features);
+}
+
+static void vu_media_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_media_guest_notifier_mask(VirtIODevice *vdev, int idx,
+ bool mask)
+{
+ VHostUserMEDIA *media = VHOST_USER_MEDIA(vdev);
+
+ if (idx == VIRTIO_CONFIG_IRQ_IDX) {
+ return;
+ }
+
+ vhost_virtqueue_mask(&media->vhost_dev, vdev, idx, mask);
+}
+
+static bool vu_media_guest_notifier_pending(VirtIODevice *vdev, int idx)
+{
+ VHostUserMEDIA *media = VHOST_USER_MEDIA(vdev);
+
+ if (idx == VIRTIO_CONFIG_IRQ_IDX) {
+ return false;
+ }
+
+ return vhost_virtqueue_pending(&media->vhost_dev, idx);
+}
+
+static int vu_media_handle_config_change(struct vhost_dev *dev)
+{
+ virtio_notify_config(dev->vdev);
+ return 0;
+}
+
+static const VhostDevConfigOps media_ops = {
+ .vhost_dev_config_notifier = vu_media_handle_config_change,
+};
+
+static int vu_media_connect(DeviceState *dev)
+{
+ VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+ VHostUserMEDIA *media = VHOST_USER_MEDIA(vdev);
+
+ if (media->connected) {
+ return 0;
+ }
+ media->connected = true;
+
+ /* restore vhost state */
+ if (virtio_device_started(vdev, vdev->status)) {
+ vu_media_start(vdev);
+ }
+
+ return 0;
+}
+
+static void vu_media_disconnect(DeviceState *dev)
+{
+ VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+ VHostUserMEDIA *media = VHOST_USER_MEDIA(vdev);
+
+ if (!media->connected) {
+ return;
+ }
+ media->connected = false;
+
+ if (vhost_dev_is_started(&media->vhost_dev)) {
+ vu_media_stop(vdev);
+ }
+}
+
+static void vu_media_event(void *opaque, QEMUChrEvent event)
+{
+ DeviceState *dev = opaque;
+ VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+ VHostUserMEDIA *media = VHOST_USER_MEDIA(vdev);
+
+ switch (event) {
+ case CHR_EVENT_OPENED:
+ if (vu_media_connect(dev) < 0) {
+ qemu_chr_fe_disconnect(&media->conf.chardev);
+ return;
+ }
+ break;
+ case CHR_EVENT_CLOSED:
+ vu_media_disconnect(dev);
+ break;
+ case CHR_EVENT_BREAK:
+ case CHR_EVENT_MUX_IN:
+ case CHR_EVENT_MUX_OUT:
+ /* Ignore */
+ break;
+ }
+}
+
+static void do_vhost_user_cleanup(VirtIODevice *vdev, VHostUserMEDIA *media,
+ struct vhost_virtqueue *vhost_vqs)
+{
+ virtio_delete_queue(media->command_vq);
+ virtio_delete_queue(media->event_vq);
+ g_free(vhost_vqs);
+ virtio_cleanup(vdev);
+ vhost_user_cleanup(&media->vhost_user);
+}
+
+static void vu_media_device_realize(DeviceState *dev, Error **errp)
+{
+ VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+ VHostUserMEDIA *media = VHOST_USER_MEDIA(dev);
+ struct vhost_virtqueue *vhost_vqs;
+ int ret;
+
+ if (!media->conf.chardev.chr) {
+ error_setg(errp, "vhost-user-media: chardev is mandatory");
+ return;
+ }
+
+ if (!vhost_user_init(&media->vhost_user, &media->conf.chardev, errp)) {
+ return;
+ }
+
+ virtio_init(vdev, VIRTIO_ID_MEDIA, sizeof(struct virtio_media_config));
+
+ media->command_vq = virtio_add_queue(vdev, 128, vu_media_handle_output);
+ media->event_vq = virtio_add_queue(vdev, 128, vu_media_handle_output);
+ media->vhost_dev.nvqs = 2;
+ media->vhost_dev.vqs = g_new0(struct vhost_virtqueue,
+ media->vhost_dev.nvqs);
+ vhost_vqs = media->vhost_dev.vqs;
+
+ vhost_dev_set_config_notifier(&media->vhost_dev, &media_ops);
+ media->vhost_user.supports_config = true;
+
+ ret = vhost_dev_init(&media->vhost_dev, &media->vhost_user,
+ VHOST_BACKEND_TYPE_USER, 0, errp);
+ if (ret < 0) {
+ do_vhost_user_cleanup(vdev, media, vhost_vqs);
+ return;
+ }
+
+ qemu_chr_fe_set_handlers(&media->conf.chardev, NULL,
+ NULL, vu_media_event,
+ NULL, (void *)dev, NULL, true);
+}
+
+static void vu_media_device_unrealize(DeviceState *dev)
+{
+ VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+ VHostUserMEDIA *media = VHOST_USER_MEDIA(dev);
+ struct vhost_virtqueue *vhost_vqs = media->vhost_dev.vqs;
+
+ /* This will stop vhost backend if appropriate. */
+ vu_media_set_status(vdev, 0);
+ vhost_dev_cleanup(&media->vhost_dev);
+ do_vhost_user_cleanup(vdev, media, vhost_vqs);
+}
+
+static const VMStateDescription vu_media_vmstate = {
+ .name = "vhost-user-media",
+ .unmigratable = 1,
+};
+
+static const Property vu_media_properties[] = {
+ DEFINE_PROP_CHR("chardev", VHostUserMEDIA, conf.chardev),
+};
+
+static void vu_media_class_init(ObjectClass *klass, const void *data)
+{
+ DeviceClass *dc = DEVICE_CLASS(klass);
+ VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
+
+ device_class_set_props(dc, vu_media_properties);
+ dc->vmsd = &vu_media_vmstate;
+ set_bit(DEVICE_CATEGORY_MISC, dc->categories);
+ vdc->realize = vu_media_device_realize;
+ vdc->unrealize = vu_media_device_unrealize;
+ vdc->get_features = vu_media_get_features;
+ vdc->get_config = vu_media_get_config;
+ vdc->set_status = vu_media_set_status;
+ vdc->guest_notifier_mask = vu_media_guest_notifier_mask;
+ vdc->guest_notifier_pending = vu_media_guest_notifier_pending;
+}
+
+static const TypeInfo vu_media_info = {
+ .name = TYPE_VHOST_USER_MEDIA,
+ .parent = TYPE_VIRTIO_DEVICE,
+ .instance_size = sizeof(VHostUserMEDIA),
+ .class_init = vu_media_class_init,
+};
+
+static void vu_media_register_types(void)
+{
+ type_register_static(&vu_media_info);
+}
+
+type_init(vu_media_register_types)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 848fe8539e..0b2fbbed3f 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -198,7 +198,8 @@ const char *virtio_device_names[] = {
[VIRTIO_ID_AUDIO_POLICY] = "virtio-audio-pol",
[VIRTIO_ID_BT] = "virtio-bluetooth",
[VIRTIO_ID_GPIO] = "virtio-gpio",
- [VIRTIO_ID_SPI] = "virtio-spi"
+ [VIRTIO_ID_SPI] = "virtio-spi",
+ [VIRTIO_ID_MEDIA] = "virtio-media",
};
static const char *virtio_id_to_name(uint16_t device_id)
diff --git a/hw/display/Kconfig b/hw/display/Kconfig
index b3593fe981..060274b1e6 100644
--- a/hw/display/Kconfig
+++ b/hw/display/Kconfig
@@ -120,6 +120,11 @@ config VHOST_USER_VGA
default y
depends on VIRTIO_VGA && VHOST_USER_GPU
+config VHOST_USER_MEDIA
+ bool
+ default y
+ depends on VIRTIO && VHOST_USER
+
config DPCD
bool
select AUX
diff --git a/hw/display/meson.build b/hw/display/meson.build
index ffecedbf70..d8b4e121fe 100644
--- a/hw/display/meson.build
+++ b/hw/display/meson.build
@@ -37,6 +37,9 @@ system_ss.add(when: 'CONFIG_NEXTCUBE', if_true:
files('next-fb.c'))
system_ss.add(when: 'CONFIG_VGA', if_true: files('vga.c'))
system_ss.add(when: 'CONFIG_VIRTIO', if_true: files('virtio-dmabuf.c'))
system_ss.add(when: 'CONFIG_DM163', if_true: files('dm163.c'))
+system_ss.add(when: 'CONFIG_VHOST_USER_MEDIA', if_true:
files('vhost-user-media.c'))
+system_ss.add(when: ['CONFIG_VHOST_USER_MEDIA', 'CONFIG_VIRTIO_PCI'],
+ if_true: files('vhost-user-media-pci.c'))
stub_ss.add([files('acpi-vga-stub.c'), pixman])
if (config_all_devices.has_key('CONFIG_VGA_CIRRUS') or
--
MST
