Re-tested on drm-next, at:

commit ef64cf9d06049e4e9df661f3be60b217e476bee1
Merge: 279b9e0cc300 f3980dc50c51
Author: Dave Airlie <airlied@redhat.com>
Date:   Thu Jan 30 10:46:06 2014 +1000

    Merge branch 'drm-nouveau-next' of
git://anongit.freedesktop.org/git/nouveau/linux-2.6 into drm-next

Still reproducible:

  nouveau E[Xorg[1140]] failed to idle channel 0xcccc0000 [Xorg[1140]]
  nouveau E[     PFB][0000:01:00.0] trapped read at 0x002001e020 on channel
0x0001fb14 [unknown] SEMAPHORE_BG/PFIFO_READ/00 reason: PAGE_NOT_PRESENT