max_hostmem does not work with virtio-vga-gl
Description of problem:
With property `max_hostmem=1000`, I hope the virgl VGA device can have 1GB video memory. But, after the VM starts, the command `glxinfo -B` returns "Video memory: 0MB", which I think means the virgl VGA does not obtain any video memory, or `max_hostmem=1000` does not work with `virtio-vga-gl`. Is it a bug or virgl has other property parameter to specify video memory?
Steps to reproduce:
1. Build qemu using the following `./configure` options:
```
--prefix=$HOME/.bin --target-list=x86_64-softmmu --enable-kvm --enable-vnc --enable-gtk --enable-vte --enable-xkbcommon --enable-sdl --enable-spice --enable-spice-protocol --enable-virglrenderer --enable-opengl --enable-guest-agent --enable-avx2 --enable-avx512f --enable-hax --enable-system --enable-linux-user --enable-libssh --enable-linux-aio --enable-linux-io-uring --enable-modules --enable-gio --enable-fuse --enable-fuse-lseek
```
2. Install Red Hat Enterprise Linux 8.5 in qemu
3. Run qemu using the above command line.
4. Type `glxinfo -B` in VM terminal
Additional information:
![image](/uploads/c0bfb7a336493387ee90ffe7e6209dfe/image.png)