CVE-2026-64172KVM: SVM: Disable AVIC IPI virtualization on Hygon Family 18h (erratum #1235)

Official description

In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Disable AVIC IPI virtualization on Hygon Family 18h (erratum #1235) Hygon Family 18h CPUs are derived from AMD Family 17h (Zen1) silicon and share the same erratum #1235: hardware may read a stale IsRunning=1 bit during ICR write emulation and silently fail to generate an AVIC_IPI_FAILURE_TARGET_NOT_RUNNING VM-Exit on the sending vCPU. The absence of the VM-Exit causes KVM to miss the required wakeup of blocking target vCPUs, leading to hung vCPUs and unbounded delays in guest execution. Extend the existing AMD Family 17h erratum #1235 workaround to also cover Hygon Family 18h. With IPI virtualization disabled, KVM never sets IsRunning=1 in the Physical ID table, so every non-self IPI generates a VM-Exit and is correctly emulated.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/94ade38f317ea086a181db0e6b69c574b3b70a5e
• https://git.kernel.org/stable/c/9560e6fee887a9594a89fa265b5b9c79b1591803
• https://git.kernel.org/stable/c/9a12fa5213cfc391e0eed63902d3be98f0913765