vsync in VM?

[Kamil Paral]

Hello,

I wonder whether it's expected that vsync doesn't work in VMs. I've tested
Fedora 28/29/30 Workstation and Fedora 30 KDE guests on Fedora 30 host,
with virtio GPU (3D acceleration on and off) or QXL GPU, and in all cases,
I'm seeing hundreds or thousands of FPS in glxgears, implying that vsync is
not working.

Is that an expected state? Is there a simple way to force vsync on inside a
VM? (using virt-manager + libvirt)

Thanks a lot.
Kamil