The Launch of Linux Kernel 6.18: Key Features and Changes
Linus Torvalds recently announced the release of Linux Kernel version 6.18. This update marks a significant milestone, featuring substantial architectural changes, enhancements for hardware support, and various adjustments to existing features. One noteworthy aspect of this release is the shift in how certain subsystems will be managed moving forward.
What’s New: Major Subsystem Changes and Bcachefs Removal
Among the most critical changes in version 6.18 is the complete removal of Bcachefs file system support from the mainline kernel. From now on, Bcachefs will only be accessible as a DKMS module. This decision reflects a significant departure, as this is the first instance where a kernel release has fully disengaged this file system from its core structure.
In addition to the removal of Bcachefs, several notable features are introduced in this release. The Rust Binder driver is now included, alongside a new dm-pcache device-mapper target, allowing persistent memory to act as a caching layer for slower block devices. For x86 platform administrators, a new command-line option, microcode=, provides improved control over microcode loading.
Enhancements to file system components are also notable. The kernel now supports file handles within kernel namespaces and initiates block-size-greater-than-page-size handling for Btrfs. Additionally, LoongArch KVM has added PTW feature detection for newer hardware, and the kernel can now run as a guest under FreeBSD’s Bhyve hypervisor.
Networking, Virtualization, and Performance Improvements
Linux 6.18 also introduces a variety of networking and virtualization enhancements. Features such as PSP encryption support for TCP connections, mixed CQE size support within shared ring buffers, and increased compatibility for Alder Lake-S SoC have been added. AMD’s Secure AVIC guest support and BPF arenas specific to the PowerPC architecture are among the other improvements.
From a performance angle, Linux 6.18 enhances swap behavior and optimizes scaling for NFS servers, while also boosting UDP receive performance. A new feature named “sheaves” is designed to optimize memory allocation within the kernel, and User-mode Linux has added support for sparse interrupts.
File systems such as EXT4 now accommodate 32-bit reserved user and group IDs and feature a new ioctl() interface to manage superblock parameters. Additionally, the TCP stack has begun to implement early support for Accurate Explicit Congestion Notification (AccECN), and OverlayFS now allows for case-folding functionality.
On the virtualization front, KVM has been enhanced to support control-flow enforcement technology (CET) for both Intel and AMD processors. Other enhancements include SEV-SNP CipherText Hiding for x86 hosts and the preservation of vmalloc allocations through Kexec HandOver (KHO). A series of security updates have also been rolled out, addressing multi-LSM support in the audit subsystem and the capability to sign BPF programs. Notably, the TPM feature TPM2_TCG_HMAC is now disabled by default, enhancing security protocols.
Hardware Enablement and Future Developments
Version 6.18 broadens its hardware support with the introduction of new and updated drivers. Among these additions is an EDAC driver for AMD VersalNET memory controllers that reports hardware issues from several IP blocks using IPC-style transport. Another EDAC driver has been incorporated for ADM Cortex-A72 cores to identify L1 and L2 cache errors. Other device improvements include a virtio SPI driver, which allows SPI devices to function within virtual machines, along with support for audio jacks on DualSense controllers and expanded HID handling for haptic touchpads. Notably, Apple’s M2 Pro, M2 Max, and M2 Ultra SoCs are now also supported.
As we look ahead with the completion of Linux 6.18, attention is turning to the upcoming Linux 6.19. The first release candidate is scheduled for December 14, with a full release anticipated in early February 2026. Given that 6.18 is the last kernel release of this year, it is being considered as a strong candidate for the next Long-Term Support (LTS) Kernel Series, pending confirmation from Greg Kroah-Hartman, the long-term maintainer.
