On Tue, Jul 22, 2025 at 07:08:24PM +0000, Andrew Keesler wrote:
> In 454f4b0f, we started down the path of supporting separate
> configurations per display head (e.g., you have 2 heads - one with
> EDID name "AAA" and the other with EDID name "BBB").
>
> In this change, we add resolution to this configuration surface (e.g.,
> you have 2 heads - one with resolution 111x222 and the other with
> resolution 333x444).
>
> -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",
> "xres":111,
> "yres":222
> },
> {
> "name":"BBB",
> "xres":333,
> "yres":444
> }
> ]}'
>
> If no virtio_gpu_base_conf.outputs are provided, then
> virtio_gpu_base_conf.xres/virtio_gpu_base_conf.yres will still be
> respected, preserving backwards compatibility.
IIUC from the current code, xres/yres are only set against the
first head. The 2nd and later heads are left undefined by the
virtio-gpu-base code at least - I'm unclear if something else
in QEMU will fill in defaults later, or if they set to 0x0.
> Otherwise, if any virtio_gpu_base_conf.outputs are provided, then
> virtio_gpu_base_conf.outputs.xres/virtio_gpu_base_conf.outputs.yres
> will take precedence. In this case,
> virtio_gpu_base_conf.outputs.xres/virtio_gpu_base_conf.outputs.yres
> must be non-zero.
Makes sense.
> Signed-off-by: Andrew Keesler <[email protected]>
> ---
> hw/display/virtio-gpu-base.c | 12 ++++++++++++
> qapi/virtio.json | 6 +++++-
> 2 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/hw/display/virtio-gpu-base.c b/hw/display/virtio-gpu-base.c
> index 7269477a1c..1fc879cc93 100644
> --- a/hw/display/virtio-gpu-base.c
> +++ b/hw/display/virtio-gpu-base.c
> @@ -206,6 +206,10 @@ virtio_gpu_base_device_realize(DeviceState *qdev,
> node->value->name, EDID_NAME_MAX_LENGTH);
> return false;
> }
> + if (node->value && !(node->value->xres && node->value->yres)) {
> + error_setg(errp, "invalid resolution == 0");
> + return false;
> + }
> }
>
> if (virtio_gpu_virgl_enabled(g->conf)) {
> @@ -233,6 +237,14 @@ virtio_gpu_base_device_realize(DeviceState *qdev,
> g->req_state[0].width = g->conf.xres;
> g->req_state[0].height = g->conf.yres;
>
> + for (output_idx = 0, node = g->conf.outputs;
> + node && output_idx < g->conf.max_outputs;
> + output_idx++, node = node->next) {
> + g->enabled_output_bitmask |= (1 << output_idx);
This change means that all heads are enabled by default if the 'outputs'
property array is set, which is a semantic difference from the previous
behaviour before xres/yres are added as properties.
Is it relevant to set xres/yres on outputs, even when they are
not (yet) enabled ? Perhaps we should have an explicit 'enabled: bool'
property in the 'outputs' struct ?
> + g->req_state[output_idx].width = node->value->xres;
> + g->req_state[output_idx].height = node->value->yres;
> + }
For head 0, this is overwriting the defaults set a few lines
earlier.
I think we should probably report an error if xres / yres
are set at the global level and also set against any individual
output, so the two approaches are mutually exclusive.
> g->hw_ops = &virtio_gpu_ops;
> for (i = 0; i < g->conf.max_outputs; i++) {
> g->scanout[i].con =
> diff --git a/qapi/virtio.json b/qapi/virtio.json
> index 9d652fe4a8..36581690c7 100644
> --- a/qapi/virtio.json
> +++ b/qapi/virtio.json
> @@ -970,11 +970,15 @@
> #
> # @name: the name of the output
> #
> +# @xres: horizontal resolution of the output in pixels
> +#
> +# @yres: vertical resolution of the output in pixels
> +#
Sorry, we missed the boat for 10.1, so these two new properties
will require an explicit "Since 10.2" tag against them, separate
from the overall struct versrion below.
> # Since: 10.1
> ##
>
> { 'struct': 'VirtIOGPUOutput',
> - 'data': { 'name': 'str' } }
> + 'data': { 'name': 'str', 'xres': 'uint16', 'yres': 'uint16' } }
This is a backcompat problem, because xres/yres are mandatory if
'outputs' is present.
$ ./qemu-system-x86_64 -device
'{"driver":"virtio-vga","outputs":[{"name":"AAA"},{"name":"BBB"}],"max_outputs":2,"id":"v0"}'
qemu-system-x86_64: -device
{"driver":"virtio-vga","outputs":[{"name":"AAA"},{"name":"BBB"}],"max_outputs":2,"id":"v0"}:
Parameter 'outputs[0].xres' is missing
These need to be marked optional, to be compatible with existing use
of 'outputs' from the 10.1.0 release.
With regards,
Daniel
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