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By Zayden R., August 30, 2026
Linux 7.3 sees the integration of the KVM Chainsaw cleanup, aimed at refining KVM's data structures and addressing bugs. Notable fixes enhance AMD SEV/SEV-ES operations and Intel's TLB handling, ensuring better virtualization performance.
The latest merge window for Linux 7.3 has introduced significant updates to the Kernel-based Virtual Machine (KVM), focusing on bug fixes and code clean-ups. Engineers will be particularly interested in the 'KVM Chainsaw' changes, which have been implemented to refine KVM's data structures, specifically by splitting up one of the 'god' data structures. This update is poised to enhance the management of modern KVM usage.
While these changes might not bring new user-facing features, they are crucial for maintaining a stable and efficient virtualization environment. The kvm_mmu code cleanup is central to this effort, ensuring that the KVM can handle contemporary workloads more effectively. In addition to this, the x86 code for KVM has undergone a 'spring cleaning', further contributing to system reliability.
On the AMD front, the KVM code now allocates full pages for SEV/SEV-ES ENCRYPT/DECRYPT operations. This change rectifies a previous data corruption issue that arose due to the AMD PSP driver assigning pages to firmware prematurely. The update aligns the Linux kernel with AMD SEV-SNP specifications, providing a more secure virtualization experience. Moreover, population ioctls for AMD SEV-SNP have been fortified against potentially erroneous input, enhancing the robustness of Secure Encrypted Virtualization.
Intel users will also notice improvements. Noteworthy fixes address issues with local TLB flushes during failed nested VM-Enter operations, resolving a condition where KVM might miss a TLB on subsequent successful VM-Enter events with the same L2 VPID. Additionally, a bug related to VPID virtualization, which previously resulted in failed hardware TLB flushes, has been fixed.
For those working with RISC-V, KVM now supports Svadu/Zicfiss/Zicfilp FWFT for guests, alongside optimized HFENCE request handling for SMP guests. The updates for LoongArch and ARM primarily focus on bug fixing, underscoring the broader theme of stability and refinement in this release.
Overall, while Linux 7.3's KVM updates may not revolutionize virtualization, they provide essential fixes and enhancements that sysadmins and engineers have been eagerly anticipating. These changes ensure that the virtualization infrastructure remains robust and aligned with current hardware capabilities.
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