# Linux 7.4 KVM merges ARM64-on-s390, Intel TDX security, AMD Zen 6 PML

> **Key takeaway:** Linux 7.4's KVM subsystem adds initial ARM64 virtualization on IBM Z hardware, Intel Instruction Timeout for TDX VM security, and AMD EPYC Zen 6 Page Modification Logging for hardware-assisted dirty page tracking.

**Published:** 2026-10-27T12:00:00+00:00 
**Source:** Phoronix Benchmarks & Drivers 
**Category:** kernel-os 
**Canonical URL:** https://fosswire.org/news/linux-74-kvm-merges-arm64-on-s390-intel-tdx-security-amd-zen.html 

## Summary
The Kernel-based Virtual Machine (KVM) changes for Linux 7.4 have been merged, bringing architecture-specific enhancements across ARM64, IBM s390, Intel, and AMD server platforms. The most notable addition is initial support for running ARM64 guests on IBM s390/Z mainframes, a capability stemming from IBM and Arm's dual-architecture hardware collaboration announced earlier this year. On Intel, KVM gains Instruction Timeout support (previously Notify VM-Exit) to protect TDX confidential computing VMs from denial-of-service attacks by malicious guests, plus Bus Lock VM Exit support to prevent performance degradation from guest bus lock instructions.

For AMD, Linux 7.4 KVM introduces Page Modification Logging (PML) for EPYC Zen 6 processors, enabling hardware-assisted dirty logging to track guest-modified memory pages without software overhead. This feature activates by default on capable Zen 6 hardware. Additional changes include pKVM state isolation and confidential compute improvements for ARM, plus Bus Lock Detect virtualization on AMD SVM. These updates will reach users through Linux 7.4 when distributions adopt the kernel, expected in release cycles over the coming months.

## KVM architecture changes in Linux 7.4
- **ARM64 on s390:** Initial support for ARM64 guest virtualization on IBM Z servers lands in mainline, following the IBM-Arm dual-architecture hardware announcement; further refinements are expected in future kernel cycles.
- **Intel TDX security:** Instruction Timeout (formerly Notify VM-Exit) mitigates DoS attacks against TDX-protected VMs by preventing malicious guests from blocking interrupt handling or starving host CPU resources.
- **Intel Bus Lock VM Exit:** Forces VM exits to userspace when guest CPUs execute bus lock instructions, addressing both security and performance concerns from misbehaving or malicious virtual machines.
- **AMD Zen 6 PML:** Page Modification Logging provides hardware-assisted dirty page tracking for guest memory, enabled by default on EPYC Zen 6 processors to reduce overhead in live migration and memory management.
- **AMD SVM Bus Lock Detect:** Virtualization support for Bus Lock Detect extends similar protections to AMD platforms, while ARM pKVM gains state isolation and confidential compute enhancements.

## Why it matters
These KVM changes strengthen Linux's position as the dominant hypervisor for enterprise and cloud infrastructure, with security hardening for confidential computing workloads on Intel TDX and performance optimizations for AMD's newest server silicon. Distribution maintainers and cloud providers preparing Zen 6 deployments will benefit from reduced overhead in memory tracking, while the ARM64-on-s390 support opens long-term possibilities for hybrid mainframe workloads.