Many Linux x86_64 KVM Changes Ready To Go For Linux 4.21

Paolo Bonzini submitted the Kernel-based Virtual Machine (KVM) changes on Sunday for the now-open Linux 4.21 kernel merge window. The x86/x86_64 KVM changes represent most of the work this cycle but there are also POWER and ARM changes too.

On the Intel/AMD KVM virtualization front for Linux 4.21 is support for Processor Tracing virtualization, STIBP support for cross-HT Spectre V2 mitigation within KVM via Single Thread Indirect Branch Predictors, WBNOINVD support as an Icelake server CPU feature for writing back all modified cache lines from the processor's internal cache back to the main system memory while not invalidating/flushing the internal caches, various Microsoft Hyper-V improvements, and other changes.

On the ARM front there is improved tracing, large PUD support for HugeTLC, and more. POWER meanwhile picks up support for nested VFIO.

More details via this pull request.