AMD Virtual NMI Support For KVM Virtualization Merged Into Linux 6.4

Going back to mid-2022 AMD engineers have been working on Virtual NMI support with SVM for the Kernel-based Virtual Machine (KVM) as an efficiency optimization. With the in-development Linux 6.4 kernel the AMD VNMI support has been merged.

Intel CPUs have long supported Non-Maskable Interrupt (NMI) virtualization while with Zen 4 CPUs is initial Virtual NMI support. VNMI amounts to an efficiency optimization as with AMD virtualized guests KVM will not need to track the guest's NMI state and worry about intercepting the IRET for the NMI completion handling.

AMD engineers revised the patches several times to get them into shape over the past year for mainlining. AMD SVM Virtual NMI support was merged to mainline as part of the Linux 6.4 KVM updates.

All the technical details on the AMD Virtual NMI implementation can be found via the AMD programmer's manual.

The KVM pull for Linux 6.4 also includes several ARM64 fixes, various KVM x86/x86_64 optimizations, TDP MMU handling improvements, Intel AMX self-test improvements, and various other changes.