Re: Virtio-GPU Xres and Yres seettings

[Pratik Parvati]

> EDID is optional, so you can try disable the EDID feature bit and see
> what happens.

Thanks Gerd, after disabling the EDID, I was able to get the required resolution (basically width and height) from the driver.

Another strange observation - When the device receives the command VIRTIO_GPU_CMD_RESOURCE_ATTACH_BACKING with the number of entries having a pixel data in scatter gather format, the device is trying to store these bytes in contiguous memory. When I read those sg memory, the device receives all zeros from the driver (for a 1024x768 display, the device receives 3MB of data from the driver). Is this an expected behaviour? - If not, what is the driver trying to display on the screen?

This is happening during linux boot on the guest machine.

Thanks & Regards,

Pratik

On Mon, 20 Dec 2021 at 17:48, Gerd Hoffmann <kraxel@redhat.com> wrote:

  Hi,

> Is it possible that EDID bytes are sent wrong to the driver (as a response
> to VIRTIO_GPU_CMD_GET_EDID command)?? - I am configuring these bytes the
> same way Qemu does.

EDID is optional, so you can try disable the EDID feature bit and see
what happens.

You can also check /sys/class/drm/card0-${output}/edid inside the
guest.

take care,
  Gerd