There's been work on Nouveau GK110 driver support since last year and with the Linux 3.10 kernel came NVF0 mode-setting support.
With the Linux 3.11 kernel there weren't any exciting GK110/NVF0 changes, but just now there's been a rare xf86-video-nouveau commit.
The Nouveau DDX X.Org driver commit is nearly 700 lines of new code provides for EXA and X-Video acceleration on NVF0. The principal author of this work is Red Hat's Ben Skeggs.
Aside from being found in the NVIDIA GeForce GTX TITAN and GTX 780, this GPU core was first found in NVIDIA's Tesla K20 and K20X graphics cards.
Update: A few minutes after the xf86-video-nouveau commit, Ben Skeggs has pushed more GK110/NVF0 code into the Nouveau DRM repository and mainline Mesa. The DRM driver code deals with making microcode for NVF0 and other changes.
The new Nouveau Gallium3D code meanwhile provides very initial 3D support for the GK110, built on the Nouveau NVC0 Gallium3D driver. When used in conjunction with the updated DDX and Nouveau DRM (which likely will not be mainlined until now the Linux 3.12 kernel), there is basic OpenGL support. Ben says about the NVF0/GK110 OpenGL support status, "Shaders need a lot of work still. Basic stuff generally works, so this is basically just fine for gnome-shell, OA etc at this point."