Kernel build speedups, RISC-V IOMMU, Apple USB4

Kernel traffic on 2026-09-09 focused on large kbuild parallelization work claiming major compile time gains, plus hardware enablement for RISC-V IOMMU and Apple Silicon USB4. Several security-oriented fixes also landed for DRM scheduling, TCP, and a staging wireless driver.

kbuild series targets major build speedups

A 23-patch proposal updates kbuild, modpost, objtool, and Rust build paths to improve parallelization. The series claims 20 to 36 percent faster allmodconfig builds and up to 90 percent speedups on noop rebuilds. Kernel developers working with large configurations would see shorter compile cycles if the changes land.

RISC-V IOMMU adds MSI remapping and VFIO

Version 5 of a 17-patch iommu/riscv series enables MSI remapping so IOMMU_DMA can be turned on by default and VFIO device assignment works. Three participants discussed the set on linux-kernel. The work advances DMA isolation and virtualization support on RISC-V platforms.

Initial USB4 support for Apple M1 M2 M3

A second-revision 22-patch series adds first-cut USB4 and Thunderbolt support, including ACIO, NHI, DART, and device tree nodes for Apple M1, M2, and M3 SoCs. Four participants exchanged 35 messages on the proposal. Mainline Linux moves closer to usable high-speed interconnects on those systems.

drm/sched fence timeline use-after-free fix

A fourth-revision three-patch series corrects a use-after-free on the fence timeline name inside drm/sched, a path shared by multiple drivers and previously tied to CVEs. Seven participants debated the fix across 35 messages. Closing the hole improves memory safety in the DRM scheduler.

fwnode PCS API for networking

Version 15 of a 12-patch net-next series introduces a fwnode PCS provider and consumer API, phylink integration, documentation, and an Airoha driver. Two participants handled the review. The change modernizes PCS binding for firmware-node and device-tree platforms.

TCP IPv6 syn-recv race backport

A stable patch for 6.12.y fixes a potential race in tcp_v6_syn_recv_sock() before ehash insertion, originally found by syzbot. The single-message submission went to netdev. It closes a concurrency window during IPv6 TCP connection setup.

rtl8723bs protected frame validation

A second-revision staging patch adds length checks in the rtl8723bs RX decrypt path so short protected frames cannot trigger underflow or out-of-bounds access. Two participants reviewed the change. Staging users of the driver gain a defense against malformed frame attacks.

Rust SPDM requester library

Version 3 of a 21-patch series posts a Rust SPDM requester library intended for kernel device authentication and attestation over PCIe and similar buses. Three participants discussed the set. The library supplies modern attestation primitives written in Rust.