This evening there was a new issue after which the mouse pointer was distorted in the Windows VM (nothing else). After a VM shutdown and restart everything was fine again.

The host had following messages while the issue occurred:

Nov 12 21:01:15 floor13 kernel: DMAR: DRHD: handling fault status reg 2
Nov 12 21:01:15 floor13 kernel: DMAR: [DMA Write] Request device [00:02.0] PASID ffffffff fault addr ffff800409263000 [fault reason 07] Next page table ptr is invalid
Nov 12 21:01:21 floor13 kernel: i915 0000:00:02.0: Resetting rcs0 for preemption time out
Nov 12 21:04:24 floor13 kernel: DMAR: DRHD: handling fault status reg 3
Nov 12 21:04:24 floor13 kernel: DMAR: [DMA Write] Request device [00:02.0] PASID ffffffff fault addr fffffffff0008000 [fault reason 07] Next page table ptr is invalid
Nov 12 21:04:27 floor13 kernel: i915 0000:00:02.0: Resetting rcs0 for preemption time out

crash dump file is empty