Linux Kernel 6.5 Enters Testing Stage with RC1: Discover What’s New

4 min

Linus Torvalds releases Linux Kernel 6.5 RC1 for everyone to test, which brings regular updates, and more support for modern protocols.

The merge window for Linux Kernel 6.5 is now closed, followed by the two weeks of merge window since Kernel 6.4 release. While announcing, Linus mentioned that it is a normal cycle with some minor issues; however, the testing phase may drag on a little more due to vacation seasons in Europe.

Right on schedule two weeks after the 6.4 release, here we are and the merge window is closed.

Nothing hugely unusual stands out – we had some VM annoyance, but the fixes for that don’t even show in the diffstat, which is (as usual) dominated by drivers, with tooling and architecture updates a distant second and third.

Let’s calm this party down. I have this slight suspicion that this may be one of those releases that may drag out, not because there are any particular issues I expect problems with, but simply due to lot of Europe going on vacation for the month of August. But who knows… We’ll see how things develop.


Let’s take a look at briefly what’s new in this Kernel release.

Linux Kernel 6.5 (RC1) – What’s New


Exciting news for users of high-core count Intel Xeon, AMD EPYC, and higher-core HEDT processors. This release is bringing parallel CPU boot support aimed at significantly reducing kernel boot times. This feature will greatly benefit large core count servers, enabling faster boot times, particularly when employing Kexec for seamless kernel version updates.

AMD engineers have been diligently addressing system suspend/resume issues, particularly concerning Ryzen laptops, to enhance reliability. By rectifying a missing check in the USB XHCI driver, a mere one-liner adjustment, they managed to shave off an additional 120ms during system resume time. Though seemingly small, this optimization holds significance within the broader context of AMD’s ongoing efforts to optimize the Linux experience on their Ryzen platform. So, if you are using Ryzen laptops, you might see faster resume time with this Kernel version via various Linux distributions.

With recent additions to the amd64_edac Linux kernel driver, Ryzen 7000 series desktop processors will now receive similar treatment to the EPYC 9004 series in terms of EDAC reporting. This includes ECC error reporting for supported RAM/motherboard configurations.

AMD’s open-source Linux graphics driver team has recently introduced a noteworthy set of patches for their display code, specifically the “DC” codebase within the AMDGPU kernel graphics driver. With the upcoming release of the Linux 6.5 kernel, these patches will bring another attempt at enabling FreeSync Video as the default setting. Previously, there were concerns regarding hang and corruption problems on eDP panels. However, with the latest patches, these issues have been successfully resolved, providing confidence in enabling this feature by default out-of-the-box.

The ASUS ROG CROSSHAIR X670E Hero motherboard sensor monitoring is now available in Linux Kernel 6.5. This is marketed as the high-end motherboard for AMD Ryzen 7000 series / AM5 processors.

More updates and work is complete for the Intel Hybrid CPUs with hyperthreading.

Intel Continues Prepping Meteor Lake Graphics On Linux, Adds VRR eDP Support

Intel continues to push the numerous support for the Meteor Lake graphics, and this release includes variable refresh rate eDP support and HuC loading support.


The NTFS3 file-system driver, which was upstreamed in 2021 for Linux 5.15, brought significant improvements over the previous NTFS kernel driver and NTFS-3G FUSE driver. Since its initial release, the driver has undergone continuous enhancements to further enhance its capabilities.

With the upcoming Linux 6.5 release, the NTFS3 driver now includes support for volinfo and label attributes, making them accessible under sysfs for NTFS volumes. Additionally, an alternative boot mode has been added to handle corrupted primary boots, along with several optimizations implemented throughout the kernel driver codebase.

The Flash-Friendly File-System (F2FS) has received a few enhancements and new features for this release. One of the key focuses in this development cycle has been the investigation of zoned block device support. Various patches have been introduced to address issues such as rectifying write pointers between f2fs and storage, implementing an asynchronous zone reset flow, and managing the number of open zones. Additionally, F2FS introduces a new mount option, “errors=x,” which allows users to specify how to handle unexpected behaviours detected during runtime. This feature provides flexibility in managing and responding to unforeseen issues encountered while using F2FS. Overall, these improvements contribute to the ongoing optimization and reliability of the Flash-Friendly File-System for Linux users.

In Linux Kernel 6.5, EXT4 will experience significantly improved performance in parallel direct I/O (DIO) overwrites. Brian Foster from Red Hat has contributed to this optimization, enabling concurrent unaligned DIO overwrites and yielding remarkable performance gains. With this patch, his test case using FIO demonstrated a substantial increase from 8724 KiB/s to 1565 MiB/s.

Ports and drivers

MIDI 2.0, a significant update to the widely-used MIDI protocol for musical devices, brings notable enhancements such as higher resolution, improved articulation, and the Universal MIDI Packet (UMP) for streamlined transmission of multiple MIDI messages. Linux Kernel 6.5 brings complete MIDI 2.0 support with better driver coverage and compatibility.

The upcoming Linux Kernel 6.5 is set to include improvements to the Broadcom VC4 DRM driver, particularly in relation to HDMI controllers. These enhancements, which were previously only available in the downstream Raspberry Pi kernel, are now being upstreamed to the mainline tree. Notable features include the introduction of a Broadcast RGB property, allowing users to override the HDMI pixel range if the monitor’s data is inaccurate. Additionally, the support for BT.601 and BT.2020 colorspaces, with the latter being significant for Ultra HD TVs with standard dynamic range, is being added.

Virtualization and networking

UEFI Unaccepted Memory support has been successfully merged into Linux 6.5, providing crucial backing for industry standards such as Intel Trusted Domain Extensions (TDX) and AMD Secure Encrypted Virtualization Secure Nested Page (SEV-SNP) backed virtual machines.

Among the various RISC-V KVM improvements for Linux 6.5, the standout feature is the successful implementation of guest snapshot support for KVM guests. This enhancement allows RISC-V KVM guests to benefit from functional live snapshot support for virtual machines, enabling efficient management and operation of VM snapshots.

The networking subsystem changes in the Linux 6.5 kernel encompass several advancements related to the evolving WiFi 7 wireless standard, as well as the inclusion of support for various newer network adapters.

So, that’s about the key changes. As always, the entire changelog is huge for the release, and you should get a release diff after the final release.

Download Linux Kernel 6.5 RC1 source

You can download the RC source tree from the following page.

mainline:6.5-rc12023-07-09[tarball][patch][view diff][browse]

If you are running benchmarks, testing new hardware and finding issues, report to the Kernel mailing list.

Finally, the Linux Kernel 6.5 is expected to be released around August/September 2023 timelines. The Q4 2023 Linux distribution releases – Fedora 39 and Ubuntu 23.10 may get this version.

Please test and report issues if you find any.


Creator and author of Connect with me via Telegram, 𝕏 (Twitter), or send us an email.
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Inline Feedbacks
View all comments