I'm also affected by this bug on Fedora 29.

I hopped on the kernel mainline and started poking around and noticed that I
see this bug on 4.19 but not on 4.20.  So I bisected to find the commit in the
4.20 series that fixes the bug.  The fix appears to be:

commit 970a5ee41c72df46e3b0f307528c7d8ef7734a2e
Author: Ben Skeggs <bskeggs@redhat.com>
Date:   Wed Dec 12 16:51:17 2018 +1000

    drm/nouveau/kms/nv50-: also flush fb writes when rewinding push buffer

    Should hopefully fix a regression some people have been seeing since EVO
    push buffers were moved to VRAM by default on Pascal GPUs.

    Fixes: d00ddd9da ("drm/nouveau/kms/nv50-: allocate push buffers in vidmem
on pascal")
    Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
    Cc: <stable@vger.kernel.org> # 4.19+

I can cherry pick just this commit on top of 4.19 and I get a stable system.