As shown in the attached photo, the larger of the two monitors displays a clone of the smaller monitor, with artefacts around the edge.
This an r7xx using KMS DRM from drm-next.
Created attachment 29394 [details]
Photo of console display on larger monitor (artefacts on right)
Please attach full dmesg of a session with kms one
Seems to be fixed with the latest git tree (adea4796cfb9b74d340f9e32ba523fb61305d0b7)