Linux 6.13 KVM Eliminates an "Awful Idea", Many x86_64 Improvements

Linux 6.13 has introduced significant enhancements to the Kernel-based Virtual Machine (KVM), particularly addressing previous security issues related to page reference counting. The major change involves eliminating the problematic practice of KVM guessing which page frame numbers (pfns) are refcounted, which had led to vulnerabilities and mapping failures, especially affecting virtio-gpu resources. This update necessitated a comprehensive adjustment of the architecture-specific code to ensure proper handling of struct pages. Additionally, the KVM updates for ARM include support for hibernation and improved nested virtualization capabilities, while RISC-V hardware now benefits from accelerated KVM operations. The x86_64 improvements focus on reducing virtual CPU jitter, optimizing dirty page logging, and enhancing memory management, including the removal of outdated PowerPC references. These changes collectively streamline KVM functionality and improve performance across various architectures, with detailed documentation available in the recent pull request for Linux 6.13.

- Linux 6.13 KVM updates eliminate previous security vulnerabilities related to page reference counting.

- Enhancements include support for hibernation and improved nested virtualization for ARM.

- RISC-V hardware now allows for accelerated KVM operations.

- x86_64 improvements focus on reducing vCPU jitter and optimizing memory management.

- The update streamlines KVM functionality across multiple architectures.