how to increase vram in windows guest?

Hello: I'm using kvm to host a windows 7 guest vm, I've install the latest spice guest tools from https://spice-space.org/download/windows/spice-guest-tools/spice-guest-to..., and I've set video section like this: <video> <model type="qxl" ram="262144" vram="262144" vram64="262144" vgamem="131072" heads="1" primary="yes"/> <alias name="video0"/> <address type="pci" domain="0x0000" bus="0x00" slot="0x01" function="0x0"/> </video> but the graphics in windows guest is laggy, I' found that the guest have only use 16MB as vram: How can I increase the real usage of vram in the windows guest vm?