Linux Kernel Hygon Family 18h CPUs KVM AVIC IPI Virtualization Vulnerability

A vulnerability in the Linux kernel's KVM (Kernel-based Virtual Machine) module for Hygon Family 18h CPUs has been addressed. These CPUs, derived from AMD Family 17h (Zen1), share a specific erratum (#1235) that can disrupt virtual interrupt handling. During emulation of interrupt control writes, the hardware may incorrectly read a stale 'IsRunning' bit, failing to signal when a virtual CPU is not active. This oversight prevents KVM from waking up blocked target virtual CPUs, causing them to hang and delaying guest execution. The issue has been resolved by extending the existing workaround for AMD Family 17h to also include Hygon Family 18h, ensuring proper virtualization of interrupt processing and preventing execution delays.

Impact

The vulnerability could lead to virtual CPUs hanging and causing unbounded delays in guest execution.

Remediation

Users can upgrade to the latest version of the Linux kernel where this vulnerability has been addressed. Instructions for downloading the patched version are available in the Linux kernel documentation.