Loongson 3 CPUs Beginning To Work With Linux KVM Virtualization

Recently there has been an uptick in Linux upstream support activity around Loongson CPUs, the Chinese-made MIPS64 CPUs. With Linux 5.8, the newest Loongson 3 CPU models can even begin supporting KVM-based virtualization.

Merged already were the main KVM changes for Linux 5.8 while coming in as a secondary Kernel-based Virtual Machine (KVM) pull request were some additional changes, just before this weekend's code freeze and 5.8-rc1 release.

Most notable to this second round of KVM updates is Loongson-3 now being supported. Or in particular, the Loongson-3A R4 (Loongson 3A4000) models and beyond with the 3A2000/3A3000 models having incomplete support. Loongson 3A4000 came out last year as the latest update to the Loongson 3 family and features four cores with clock speeds up to 2.0GHz and making use of the MIPS64 Release 5 instruction set.

This KVM virtualization support was spearheaded by Loongson vendor Lemote. Though don't expect much out of the virtualization performance or capabilities of the Loongson 3A4000 as the specs still leave a lot to be desired. As well, this work is the host side changes for Linux 5.8 while further guest-side work is still coming as well as the necessary alterations to QEMU.

This pull request lists all of the KVM round two changes for Linux 5.8 but the Loongson-3 support is most notable while the remainder of the changes are principally focused on fixes.