In this case it's not actually the mouse operations themselves causing the
stuttering but the framebuffer change. This is a known limitation with the
async plane updates API in DRM and not something we can really fix in DC until
there's a better API for async updates.

The page-flip IOCTL advertises itself as non-blocking but in reality it's not -
if there's any commit work touching the plane it's going to be blocked until
that finishes and that'll be any non asynchronous cursor update, gamma update,
property update, or anything else that occurs. This is what the stuttering
comes from.

So while it's a valid use of the cursor UAPI to double buffer cursors it's not
something I'd really recommend doing for an atomic driver with how DRM is
currently setup. Maybe this can be a configurable option in the meantime? I'm
not sure how much work that would be to add and maintain, though.