OpenBSD 7.9 lands with SpacemiT K1 RISC-V support and heterogeneous CPU scheduling

OpenBSD 7.9 brings broad platform work alongside meaningful kernel changes. RISC-V gets first-class support for the SpacemiT K1 SoC, including a new clock/reset driver, Zicbom and Svpbmt extensions, and a fix for spurious SIGSEGVs on X60 cores. On amd64, MAXCPUs jumps to 255, DM PTE/PDE pages are zeroed to fix systems above 512GB RAM, and floating-point state leakage on Zen 1 is mitigated. OpenBSD also now runs on Apple Virtualization.

The scheduler gains a hw.blockcpu sysctl that lets operators classify cores as SMT, performance, efficient, or lethargic and exclude slow ones — a pragmatic answer to heterogeneous CPUs on amd64 and arm64. Kernel mutexes swap their CAS spinlock for a parking lock, parallel fault handling is enabled on amd64 and arm64, and a delayed hibernation feature wakes suspended machines to hibernate before the battery dies. The DRM stack tracks Linux 6.18.22.

Virtualization sees considerable polish: vmd(8) gains vmboot to enable sysupgrade inside VMs, AMD SEV confidential-computing paths for virtio devices, 32-bit direct kernel launch, and fixes for several termination, pause, and networking races. Userland touch-ups include XDG_RUNTIME_DIR support via login_cap, a USB4 controller driver (nhi), and a long list of small reliability fixes across sndiod, mg, ksh, and xargs.