I had the same crash (for the first time) - also on KabyLake, ArchLinux, Kernel
4.14.15-1-ARCH. I'll attach my crash dump.

[drm] GPU HANG: ecode 9:0:0x85dffffb, in Xorg [636], reason: Hang on rcs0,
action: reset
[drm] GPU hangs can indicate a bug anywhere in the entire gfx stack, including
userspace.
[drm] Please file a _new_ bug report on bugs.freedesktop.org against DRI ->
DRM/Intel
[drm] drm/i915 developers can then reassign to the right component if it's not
a kernel issue.
[drm] The gpu crash dump is required to analyze gpu hangs, so please always
attach it.
[drm] GPU crash dump saved to /sys/class/drm/card0/error
i915 0000:00:02.0: Resetting rcs0 after gpu hang
i915 0000:00:02.0: Resetting rcs0 after gpu hang
asynchronous wait on fence i915:kwin_x11[820]/1:23321 timed out
i915 0000:00:02.0: Resetting rcs0 after gpu hang
i915 0000:00:02.0: Resetting rcs0 after gpu hang
i915 0000:00:02.0: Resetting rcs0 after gpu hang