The CPU giant AMD is enhancing its current CPUs for better virtualization support with new drivers on Linux. The changes on the CPUs are focusing on its x2APIC virtualization capabilities for kernel-based virtual machines, KVMs.
From 255 cores to 511 cores
The new code enables using all of the cores in a dual EPYC system
The company has sent new codes for Linux regarding the x2APIC virtualization support. The old code was supporting up to 255 virtual CPUs, 1 is reserved for the host operations. In AMD’s current EPYC CPU lineup, some products can fill up those virtual CPUs alone with its 128 cores and 256 threads inside.
The upcoming Zen 4 EPYC family currently have a maximum of 128 core member, Bergamo. It might seem to be enough to have 255 virtual CPU support. However, in the data center industry, double-socket motherboards are widely used. Double 128 core CPUs mean a total of 256 cores and 512 threads, which makes the KVM support / maximum virtual CPU number insufficient.
With the new code that AMD engineers sent for Linux, KVMs can get up to 511 virtual CPUs, 1 core is reserved for the host operations again. In addition, the code should enable better efficiency as well.