Eight Features Not In Linux 5.8 From The DirectX Kernel Driver To FSGSBASE & DAMON
Written by Michael Larabel in Linux Kernel on 16 June 2020 at 09:07 AM EDT. 10 Comments
LINUX KERNEL --
Linux 5.8 is shaping up to be one of the biggest kernel releases ever and while there are many new Linux 5.8 features, here is a look at some prominent and recently discussed material that didn't make the cut this cycle.

Some items not in mainline Linux 5.8 include:

DirectX Kernel Driver - Following Microsoft's announcement of bringing Direct3D 12 to WSL2 as part of bringing GPU acceleration and GUI apps to the environment, Microsoft published an open-source DirectX Kernel Driver for interfacing with the Windows host via Hyper-V. As suspected back when it was published given the initial upstream developer feedback and tied to proprietary user-space components, seeing this driver upstreamed will be quite a challenge. There has been no revisions to the patches yet and at this stage seeing upstream acceptance is quite unlikely unless there are some major changes.

FSGSBASE - The long-standing FSGSBASE patches that can offer some performance advantages for some workloads were recently revised as recently as v13 at the end of May. But it didn't land for Linux 5.8 sadly but perhaps in 5.9 we'll finally see this ability come to mainline for this instruction set extension around since Intel Ivy Bridge days.

AMD Radeon "Navi 2" / Sienna Cichlid - Since the start of June AMD has been publishing "Sienna Cichlid" GPU enablement patches that appear to definitely be for Navi 2 graphics cards launching later this year. The patches were sadly a few weeks too late for being reviewed and queued in DRM-Next for Linux 5.8. In turn this work will come in Linux 5.9. Unfortunately though this means the patches won't be in a stable mainline kernel until October rather than with 5.8's debut in August. We'll see when Navi 2 graphics cards end up launching but there is good chances we could see Navi 2 debut before October and thus no mainline stable kernel release with that support. If the patches came earlier for 5.8, it would also allow for out-of-the-box support in the likes of Ubuntu 20.10.

Intel DG1 Support - While there have been Gen12 / Xe Intel patches happening for Linux going back many months, recently the DG1 patches were sent out for lighting up this first Intel discrete graphics card. Those patches along with Rocket Lake should be in Linux 5.9 but at least with DG1 principally focused on developers, not finding it in 5.8 isn't too bad.

AMD Sensor Fusion Hub Driver - Nothing new to report since our last article on the matter from last month, unfortunate for AMD Ryzen laptop owners looking to make use of the SFH functionality.

Intel SGX - The SGX Enclaves support has seen more than 30 rounds of patches but not crossing the finish line. But then again given all the security issues affecting SGX, it seems not many open-source users are eager to make use of this functionality.

DAMON - Earlier this year an Amazon engineer introduced DAMON for monitoring data accesses on Linux. That work is still being discussed but not yet mainlined.

Futex Optimization / Fsync / Futex2 - Valve's Linux gaming optimizations needing kernel changes are still progressing albeit not in 5.8. Just last week was the route of introducing the new futex2() system call that perhaps we'll see in an upcoming kernel version.

Beyond those eight changes there still is other work we are eager to eventually see like in-kernel IPC from the likes of BUS1, Bcachefs, maybe Reiser5 one day, Nouveau re-clocking, and other new hardware enablement.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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