Intel has been publicly working on their Haswell Linux support enablement for the past year when it comes to their graphics driver, compiler support for AVX2 and other new CPU additions, supporting the new chipsets to be timed for Haswell, and other features. With all of the latest Linux code, everything looks to be in shape for the Haswell product launch coming up soon. Meanwhile, Intel has just begin working on Linux support for "Avoton" Atom SoCs.
However, there's still some areas being worked out and further optimized for the next-generation Intel processors on Linux. Some examples in recent days include:
Basic perf PMU support for Haswell v1 - The basic Haswell PMU and PEBS support, late unmasking of the PMI, support for wide-counters, new TSX counter flags, support for check-pointed counters, and new LBR flags for the perf support within the Linux kernel.
Unclaimed registers and power well V2 - The Intel DRM driver should now be "good enough to start disabling the power well when possible."
HDMI/DP - ELD info refresh support for Haswell - There's some minor Haswell-related DRM graphics driver patches still outstanding.
At least the remaining Haswell support as far as the Linux kernel is concerned should be ready for the Linux 3.9 kernel. However, the Linux 3.9 kernel is out of reach for Ubuntu 13.04 and other distributions making it out around early Q2. At least as far as key functionality is concerned, the Linux stack should be in good shape for when Haswell CPUs begin to ship.