Highlights of Linux 6.15 include Rust support for hrtimer and ARMv7, a new setcpuid= boot parameter for x86 CPUs, support for sched_ext to count and report internal events, x86 Intel and AMD PMU enhancements, nested virtualization support for VGICv3 on ARM, and support for emulating FEAT_PMUv3 on Apple Silicon.

Also new in Linux kernel 6.15 is a new API to receive information about mount and unmount events of filesystems, support for hardware-wrapped encryption keys in the block layer, support for 48-bit block addressing in the EROFS file system, and a new security hook for the io_uring subsystem giving security modules more control over what’s allowed.

The FUSE file system can now handle file names longer than 1,024 characters, the perf subsystem can now perform latency profiling using scheduler information, the BPF subsystem gained improved verification of programs with loops, and the OverlayFS file system received a new override_creds mount option that changes the credentials used for accessing the lower layers.

On top of that, Linux kernel 6.15 also brings support for new extensions for the RISC-V architecture, including the BFloat16 floating-point extension, the Zaamo and Zalrsc extensions, and the ZBKB extension, support for zoned devices for the XFS file system, and support for zero-copy reception of network data for the io_uring subsystem.

Some new networking features are available as well in Linux 6.15, including a new TCP socket option (TCP_RTO_MAX_MS) that can be used to set the maximum time between retransmit attempts on IPv4 and a new set of BPF callbacks to fetch timestamps from various places in the networking stack.

Hardware support has been enhanced as expected through new and updated drivers, which bring support for Apple Touch Bar, Google Pixel Pro 6 smartphone, MYIR Remi Pi development board, Huawei Matebook E Go embedded controller, Milk-V Jupiter RISC-V board, and HP laptops using CS35L41 HDA audio chips.

Linux 6.15 also updates the ACPI fan driver to handle fans with fine-grained state checking supported, but without fine-grained control, as well as the ACPI button driver to subscribe to system event notifications in addition to device notifications, which on some systems is required for waking up the system from sleep.

Among other noteworthy changes, Linux 6.15 removes support for 32-bit (x86) systems with more than eight CPUs and/or more than 4GB of RAM, and the Landlock security module received a new auditing mechanism designed to make it easier to understand access denials.

There’s also a new fwctl subsystem that allows user space to securely construct and execute RPCs inside device firmware, and the kernel gained a new hardening feature that allows it to seal several memory mappings against changes, but it’s disabled by default as it may break some applications.

You can download Linux kernel 6.15 right now from Linus Torvalds’ git tree or the kernel.org website if you fancy compiling it on your GNU/Linux distribution. However, I recommend waiting for the new Linux release to arrive in your distro’s stable software repositories before updating your kernel.

Now that Linux kernel 6.15 is out the door, the merge window opens for the next major kernel branch, Linux 6.16, which is expected at the end of July or early August 2025. Until then, a first Release Candidate (RC) development version will be available for public testing in two weeks, on June 8th.