[PATCH v2 0/1] Allow injection of virtio-gpu EDID name

[PATCH v2 0/1] Allow injection of virtio-gpu EDID name

[Andrew Keesler]

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",
              },
            ]}'

Andrew Keesler (1):
  hw/display: Allow injection of virtio-gpu EDID name

 hw/core/qdev-properties-system.c    | 44 +++++++++++++++++++++++++++++
 hw/display/virtio-gpu-base.c        | 20 +++++++++++++
 include/hw/qdev-properties-system.h |  5 ++++
 include/hw/virtio/virtio-gpu.h      |  3 ++
 qapi/virtio.json                    | 18 ++++++++++--
 5 files changed, 88 insertions(+), 2 deletions(-)

-- 
2.50.0.727.gbf7dc18ff4-goog

[PATCH v2 1/1] hw/display: Allow injection of virtio-gpu EDID name

[Andrew Keesler]

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 <ankeesler@google.com>
---
 hw/core/qdev-properties-system.c    | 44 +++++++++++++++++++++++++++++
 hw/display/virtio-gpu-base.c        | 20 +++++++++++++
 include/hw/qdev-properties-system.h |  5 ++++
 include/hw/virtio/virtio-gpu.h      |  3 ++
 qapi/virtio.json                    | 18 ++++++++++--
 5 files changed, 88 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..6324e6330c 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 +67,13 @@ 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 = g->conf.outputs->value->name;
+        }
+    }
+
     edid->size = cpu_to_le32(sizeof(edid->edid));
     qemu_edid_generate(edid->edid, sizeof(edid->edid), &info);
 }
@@ -172,6 +182,8 @@ 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;
@@ -188,6 +200,14 @@ virtio_gpu_base_device_realize(DeviceState *qdev,
         }
     }
 
+    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;
+        }
+    }
+
     g->virtio_config.num_scanouts = cpu_to_le32(g->conf.max_outputs);
     virtio_init(VIRTIO_DEVICE(g), VIRTIO_ID_GPU,
                 sizeof(struct virtio_gpu_config));
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..eb6a907c40 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: 9.0
+##
+
+{ '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

Re: [PATCH v2 1/1] hw/display: Allow injection of virtio-gpu EDID name

[Daniel P. Berrangé]

On Mon, Jun 30, 2025 at 03:17:57PM +0000, Andrew Keesler 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?).

IMHO, we should report  an error at realize time if the user specified
a name that is too long to be honoured.

> 
> 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 <ankeesler@google.com>
> ---
>  hw/core/qdev-properties-system.c    | 44 +++++++++++++++++++++++++++++
>  hw/display/virtio-gpu-base.c        | 20 +++++++++++++
>  include/hw/qdev-properties-system.h |  5 ++++
>  include/hw/virtio/virtio-gpu.h      |  3 ++
>  qapi/virtio.json                    | 18 ++++++++++--
>  5 files changed, 88 insertions(+), 2 deletions(-)

With regards,
Daniel
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