[SPICE] How to make SPICE work with GVT-g + DMA-BUF + egl-headless ?
Description of problem:
I try to use GVT-g + DMA-BUF in PVE , vGPU display output can be displayed normally on noVNC, 

but when I try use SPICE, VM would not boot, come up with error: kvm: **The console requires display DMABUF support**.
Steps to reproduce:
1. Create a windows virtual machine
2. Manually add args to the conf file, add the mdev device of GVT-g.
3. Starting the Virtual Machine

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