Merge branch 'kvm-x86-mmu-6.6' into HEAD

KVM x86 MMU changes for 6.6:

 - Rip out the ancient MMU_DEBUG crud and replace the useful bits with
   CONFIG_KVM_PROVE_MMU

 - Overhaul KVM's page-track APIs, and KVMGT's usage, to reduce the API surface
   that is needed by external users (currently only KVMGT), and fix a variety
   of issues in the process

 - Fix KVM's handling of !visible guest roots to avoid premature triple fault
   injection by loading a dummy root backed by the zero page