Mouse pointer jumps around with guest_hwcursor=false
Mouse pointer jumps when changing shape (such as entering or leaving a terminal window) if guest_hwcursor=false (which is the default currently). Seen with Slax 7.x live CD with R128 X driver, x86_64 guest and host. (To get X starting one may need to manually load aty128fb kernel module and edit xorg.conf to add R128 driver and Option "UseFBDev" "1".)
To debug this one has to check how HW CUR_* registers are poked (enable ATI_DEBUG_HW_CURSOR in qemu/hw/display/ati.c and prepare to analyse huge amount of logs or find a better way to identify what's going on).