Executive brief
A vulnerability in the Linux kernel's virtualization component (KVM) affects systems running on Hygon Family 18h processors. Due to a hardware flaw, the system may fail to properly wake up virtual machines that are waiting for signals, leading to frozen or unresponsive virtual servers. This can cause significant delays in guest execution and impact the availability of services running in virtualized environments.
Technical details
A hardware erratum (#1235) in Hygon Family 18h CPUs (derived from AMD Zen1) causes the processor to read a stale 'IsRunning=1' bit during Interrupt Command Register (ICR) write emulation. This results in a failure to generate the 'AVIC_IPI_FAILURE_TARGET_NOT_RUNNING' VM-Exit on the sending vCPU. Consequently, KVM misses the necessary wakeup for blocking target vCPUs, causing them to hang. The fix involves extending the existing AMD Family 17h workaround to Hygon Family 18h by disabling AVIC IPI virtualization, ensuring every non-self IPI generates a VM-Exit for correct emulation.
Affected products
- Linux Linux Kernel 6.17 to 6.18.34, 7.0.11
Timeline
- 2026-07-19: disclosed
- 2026-07-19: advisory