KVM series, console conversion, and security fixes

Kernel development on this day centered on large KVM patch series for nested virtualization performance and clock correctness, plus security fixes in uprobes and pidfd. Debates continued over hot-page promotion infrastructure and powerpc preemption costs.

KVM nSVM TLB flush optimizations

A 28-patch series for KVM proposes optimizing nSVM TLB flushes through separate per-vCPU L2 ASIDs and static allocation. The changes target 8-15% gains on recent AMD CPUs. Virtualization developers should watch this for nested SVM workload improvements.

8250 serial driver NBCON conversion

Version 11 of the patches converting the 8250 driver to NBCON console support has been posted. Greg KH has queued the series after a prior revert. Console and serial subsystem maintainers will want to review the revised approach.

KVM clock cleanup series

David Woodhouse posted version 7 of a 36-patch KVM series that addresses clock imprecision, discontinuities, and migration issues. It removes pvclock_gtod_data and adds TSC and guest clock APIs. This matters for anyone dealing with reliable timekeeping under KVM, especially across migrations.

Uprobes NULL dereference fix

A patch fixes a NULL pointer dereference oops in uprobes that occurs during fork of a task with a pending uretprobe. The issue was found in production. Kernel users relying on uprobes should note the stability correction.

Pidfd namespace ioctl locking

A patch adds the missing exec_update_lock around pidfd namespace ioctls to match an earlier procfs fix for CVE-2026-64371. The change closes a locking gap in the pidfd path. Security-conscious developers tracking namespace and process file descriptor interfaces will care about the consistency.

Hot page tracking and promotion debate

Version 8 of the mm hot-page tracking and promotion infrastructure (pghot) for CXL tiering drew maintainer debate against DAMON and existing NUMA balancing. The discussion remains heated over whether the new subsystem is the right approach. Memory management developers interested in tiered memory should follow the arguments.

Powerpc dynamic preemption regression

Discussion continues around a performance regression on ppc64le after the dynamic preemption enablement patch. Participants including McKenney debated the cost of RISC preempt_count handling. Powerpc and preemption subsystem contributors need to weigh the trade-offs.

S390 KVM arm64 guest support

Version 5 of a 31-patch s390 KVM series introduces arm64 guest support via shared code extraction, build-time header and include copying, and a new SAE instruction. The work expands cross-architecture guest capabilities inside s390 KVM. Developers working on multi-arch virtualization will find the shared-code approach relevant.