Since Linux 6.16 the [1]Intel APX support has been ready for the kernel infrastructure and goes along with the compiler toolchain support for [2]Advanced Performance Extensions with the likes of GCC and LLVM/Clang. The latest element being worked on for [3]APX enablement in the open-source/Linux world is for allowing KVM guest virtual machines (VMs) to make use of APX.

Intel engineers on Sunday sent out their first post-RFC (request for comments) patches for enabling APX support for KVM guests, which is important for VMs and for future Intel Xeon Diamond Rapids cloud instances.

Similar to Intel AMX and the like needing special handling for guest VMs, so does the Advanced Performance Extensions. There is a refactoring of the general purpose register (GPR) accessor code, VMX support for the extended register index with APX, emulation support for REX2, and other changes needed for properly enabling APX use within KVM guest VMs.

As a reminder, Advanced Performance Extensions are debuting with Intel Nova Lake and Diamond Rapids processors.

[4]This patch series is what's working on enabling APX for KVM guests. We'll see if this work gets buttoned up in time for the Linux v6.20~7.0 kernel, which will have added importance as being the default kernel version of Ubuntu 26.04 LTS that is sure to see lots of virtualized/cloud use.



[1] https://www.phoronix.com/news/Linux-6.16-Released

[2] https://www.phoronix.com/search/Advanced+Performance+Extensions

[3] https://www.phoronix.com/search/APX

[4] https://lore.kernel.org/lkml/20251221040742.29749-1-chang.seok.bae@intel.com/