> I have this issue too, disabling page flipping fixes it for me on my vega10. It started with 4.16rc1 IIRC

Negative. I checked back as far as the DC/DAL was integrated (4.15) and it's
been there from the start. 

It's in the kernel somewhere, in the DC DRM layer above the device specific
stuff. I looked in and couldn't see anything that's grossly problematic. I
suspect Michel's suggestion for async cursor updates might be the fix, but I
can't help wondering why the legacy DRM code is unaffected.