On Wed, Jul 9, 2025 at 4:11 PM Andrew Keesler <ankees...@google.com> wrote:
>
> Thanks to 72d277a7, 1ed2cb32, and others, EDID (Extended Display
> Identification Data) is propagated by QEMU such that a virtual display
> presents legitimate metadata (e.g., name, serial number, preferred
> resolutions, etc.) to its connected guest.
>
> This change adds the ability to specify the EDID name for a particular
> virtio-vga display. Previously, every virtual display would have the same
> name: "QEMU Monitor". Now, we can inject names of displays in order to test
> guest behavior that is specific to display names. We provide the ability to
> inject the display name from the frontend since this is guest visible
> data. Furthermore, this makes it clear where N potential display outputs
> would get their name from (which will be added in a future change).
>
> Note that we have elected to use a struct here for output data for
> extensibility - we intend to add per-output fields like resolution in a
> future change.
>
> It should be noted that EDID names longer than 12 bytes will be truncated
> per spec (I think?).
>
> Testing: verified that when I specified 2 outputs for a virtio-gpu with
> edid_name set, the names matched those that I configured with my vnc
> display.
>
> -display vnc=localhost:0,id=aaa,display=vga,head=0 \
> -display vnc=localhost:1,id=bbb,display=vga,head=1 \
> -device '{"driver":"virtio-vga",
> "max_outputs":2,
> "id":"vga",
> "outputs":[
> {
> "name":"AAA"
> },
> {
> "name":"BBB"
> }
> ]}'
>
> Signed-off-by: Andrew Keesler <ankees...@google.com>
Reviewed-by: Marc-André Lureau <marcandre.lur...@redhat.com>
> ---
> hw/core/qdev-properties-system.c | 44 +++++++++++++++++++++++++++++
> hw/display/virtio-gpu-base.c | 27 ++++++++++++++++++
> include/hw/display/edid.h | 2 ++
> include/hw/qdev-properties-system.h | 5 ++++
> include/hw/virtio/virtio-gpu.h | 3 ++
> qapi/virtio.json | 18 ++++++++++--
> 6 files changed, 97 insertions(+), 2 deletions(-)
>
> diff --git a/hw/core/qdev-properties-system.c
> b/hw/core/qdev-properties-system.c
> index 24e145d870..1f810b7ddf 100644
> --- a/hw/core/qdev-properties-system.c
> +++ b/hw/core/qdev-properties-system.c
> @@ -1299,3 +1299,47 @@ const PropertyInfo
> qdev_prop_vmapple_virtio_blk_variant = {
> .set = qdev_propinfo_set_enum,
> .set_default_value = qdev_propinfo_set_default_value_enum,
> };
> +
> +/* --- VirtIOGPUOutputList --- */
> +
> +static void get_virtio_gpu_output_list(Object *obj, Visitor *v,
> + const char *name, void *opaque, Error **errp)
> +{
> + VirtIOGPUOutputList **prop_ptr =
> + object_field_prop_ptr(obj, opaque);
> +
> + visit_type_VirtIOGPUOutputList(v, name, prop_ptr, errp);
> +}
> +
> +static void set_virtio_gpu_output_list(Object *obj, Visitor *v,
> + const char *name, void *opaque, Error **errp)
> +{
> + VirtIOGPUOutputList **prop_ptr =
> + object_field_prop_ptr(obj, opaque);
> + VirtIOGPUOutputList *list;
> +
> + if (!visit_type_VirtIOGPUOutputList(v, name, &list, errp)) {
> + return;
> + }
> +
> + qapi_free_VirtIOGPUOutputList(*prop_ptr);
> + *prop_ptr = list;
> +}
> +
> +static void release_virtio_gpu_output_list(Object *obj,
> + const char *name, void *opaque)
> +{
> + VirtIOGPUOutputList **prop_ptr =
> + object_field_prop_ptr(obj, opaque);
> +
> + qapi_free_VirtIOGPUOutputList(*prop_ptr);
> + *prop_ptr = NULL;
> +}
> +
> +const PropertyInfo qdev_prop_virtio_gpu_output_list = {
> + .type = "VirtIOGPUOutputList",
> + .description = "VirtIO GPU output list [{\"name\":\"<name>\"},...]",
> + .get = get_virtio_gpu_output_list,
> + .set = set_virtio_gpu_output_list,
> + .release = release_virtio_gpu_output_list,
> +};
> diff --git a/hw/display/virtio-gpu-base.c b/hw/display/virtio-gpu-base.c
> index 9eb806b71f..7269477a1c 100644
> --- a/hw/display/virtio-gpu-base.c
> +++ b/hw/display/virtio-gpu-base.c
> @@ -19,6 +19,7 @@
> #include "qemu/error-report.h"
> #include "hw/display/edid.h"
> #include "trace.h"
> +#include "qapi/qapi-types-virtio.h"
>
> void
> virtio_gpu_base_reset(VirtIOGPUBase *g)
> @@ -56,6 +57,8 @@ void
> virtio_gpu_base_generate_edid(VirtIOGPUBase *g, int scanout,
> struct virtio_gpu_resp_edid *edid)
> {
> + size_t output_idx;
> + VirtIOGPUOutputList *node;
> qemu_edid_info info = {
> .width_mm = g->req_state[scanout].width_mm,
> .height_mm = g->req_state[scanout].height_mm,
> @@ -64,6 +67,14 @@ virtio_gpu_base_generate_edid(VirtIOGPUBase *g, int
> scanout,
> .refresh_rate = g->req_state[scanout].refresh_rate,
> };
>
> + for (output_idx = 0, node = g->conf.outputs;
> + output_idx <= scanout && node; output_idx++, node = node->next) {
> + if (output_idx == scanout && node->value && node->value->name) {
> + info.name = node->value->name;
> + break;
> + }
> + }
> +
> edid->size = cpu_to_le32(sizeof(edid->edid));
> qemu_edid_generate(edid->edid, sizeof(edid->edid), &info);
> }
> @@ -172,6 +183,8 @@ virtio_gpu_base_device_realize(DeviceState *qdev,
> VirtIOHandleOutput cursor_cb,
> Error **errp)
> {
> + size_t output_idx;
> + VirtIOGPUOutputList *node;
> VirtIODevice *vdev = VIRTIO_DEVICE(qdev);
> VirtIOGPUBase *g = VIRTIO_GPU_BASE(qdev);
> int i;
> @@ -181,6 +194,20 @@ virtio_gpu_base_device_realize(DeviceState *qdev,
> return false;
> }
>
> + for (output_idx = 0, node = g->conf.outputs;
> + node; output_idx++, node = node->next) {
> + if (output_idx == g->conf.max_outputs) {
> + error_setg(errp, "invalid outputs > %d", g->conf.max_outputs);
> + return false;
> + }
> + if (node->value && node->value->name &&
> + strlen(node->value->name) > EDID_NAME_MAX_LENGTH) {
> + error_setg(errp, "invalid output name '%s' > %d",
> + node->value->name, EDID_NAME_MAX_LENGTH);
> + return false;
> + }
> + }
> +
> if (virtio_gpu_virgl_enabled(g->conf)) {
> error_setg(&g->migration_blocker, "virgl is not yet migratable");
> if (migrate_add_blocker(&g->migration_blocker, errp) < 0) {
> diff --git a/include/hw/display/edid.h b/include/hw/display/edid.h
> index 520f8ec202..91c0a428af 100644
> --- a/include/hw/display/edid.h
> +++ b/include/hw/display/edid.h
> @@ -1,6 +1,8 @@
> #ifndef EDID_H
> #define EDID_H
>
> +#define EDID_NAME_MAX_LENGTH 12
> +
> typedef struct qemu_edid_info {
> const char *vendor; /* http://www.uefi.org/pnp_id_list */
> const char *name;
> diff --git a/include/hw/qdev-properties-system.h
> b/include/hw/qdev-properties-system.h
> index b921392c52..9601a11a09 100644
> --- a/include/hw/qdev-properties-system.h
> +++ b/include/hw/qdev-properties-system.h
> @@ -32,6 +32,7 @@ extern const PropertyInfo qdev_prop_cpus390entitlement;
> extern const PropertyInfo qdev_prop_iothread_vq_mapping_list;
> extern const PropertyInfo qdev_prop_endian_mode;
> extern const PropertyInfo qdev_prop_vmapple_virtio_blk_variant;
> +extern const PropertyInfo qdev_prop_virtio_gpu_output_list;
>
> #define DEFINE_PROP_PCI_DEVFN(_n, _s, _f, _d) \
> DEFINE_PROP_SIGNED(_n, _s, _f, _d, qdev_prop_pci_devfn, int32_t)
> @@ -110,4 +111,8 @@ extern const PropertyInfo
> qdev_prop_vmapple_virtio_blk_variant;
> qdev_prop_vmapple_virtio_blk_variant, \
> VMAppleVirtioBlkVariant)
>
> +#define DEFINE_PROP_VIRTIO_GPU_OUTPUT_LIST(_name, _state, _field) \
> + DEFINE_PROP(_name, _state, _field, qdev_prop_virtio_gpu_output_list, \
> + VirtIOGPUOutputList *)
> +
> #endif
> diff --git a/include/hw/virtio/virtio-gpu.h b/include/hw/virtio/virtio-gpu.h
> index a42957c4e2..9f16f89a36 100644
> --- a/include/hw/virtio/virtio-gpu.h
> +++ b/include/hw/virtio/virtio-gpu.h
> @@ -20,6 +20,7 @@
> #include "hw/virtio/virtio.h"
> #include "qemu/log.h"
> #include "system/vhost-user-backend.h"
> +#include "qapi/qapi-types-virtio.h"
>
> #include "standard-headers/linux/virtio_gpu.h"
> #include "standard-headers/linux/virtio_ids.h"
> @@ -128,6 +129,7 @@ struct virtio_gpu_base_conf {
> uint32_t xres;
> uint32_t yres;
> uint64_t hostmem;
> + VirtIOGPUOutputList *outputs;
> };
>
> struct virtio_gpu_ctrl_command {
> @@ -167,6 +169,7 @@ struct VirtIOGPUBaseClass {
>
> #define VIRTIO_GPU_BASE_PROPERTIES(_state, _conf) \
> DEFINE_PROP_UINT32("max_outputs", _state, _conf.max_outputs, 1), \
> + DEFINE_PROP_VIRTIO_GPU_OUTPUT_LIST("outputs", _state, _conf.outputs), \
> DEFINE_PROP_BIT("edid", _state, _conf.flags, \
> VIRTIO_GPU_FLAG_EDID_ENABLED, true), \
> DEFINE_PROP_UINT32("xres", _state, _conf.xres, 1280), \
> diff --git a/qapi/virtio.json b/qapi/virtio.json
> index 73df718a26..5e658a7033 100644
> --- a/qapi/virtio.json
> +++ b/qapi/virtio.json
> @@ -963,17 +963,31 @@
> { 'struct': 'IOThreadVirtQueueMapping',
> 'data': { 'iothread': 'str', '*vqs': ['uint16'] } }
>
> +##
> +# @VirtIOGPUOutput:
> +#
> +# Describes configuration of a VirtIO GPU output.
> +#
> +# @name: the name of the output
> +#
> +# Since: 10.1
> +##
> +
> +{ 'struct': 'VirtIOGPUOutput',
> + 'data': { 'name': 'str' } }
> +
> ##
> # @DummyVirtioForceArrays:
> #
> # Not used by QMP; hack to let us use IOThreadVirtQueueMappingList
> -# internally
> +# and VirtIOGPUOutputList internally
> #
> # Since: 9.0
> ##
>
> { 'struct': 'DummyVirtioForceArrays',
> - 'data': { 'unused-iothread-vq-mapping': ['IOThreadVirtQueueMapping'] } }
> + 'data': { 'unused-iothread-vq-mapping': ['IOThreadVirtQueueMapping'],
> + 'unused-virtio-gpu-output': ['VirtIOGPUOutput'] } }
>
> ##
> # @GranuleMode:
> --
> 2.50.0.727.gbf7dc18ff4-goog
>
--
Marc-André Lureau
