Merge branch 'kvm-coco-pagefault-prep' into HEAD

A combination of prep work for TDX and SNP, and a clean up of the
page fault path to (hopefully) make it easier to follow the rules for
private memory, noslot faults, writes to read-only slots, etc.

diff --cc arch/x86/include/asm/kvm_host.h
Simple merge

diff --cc arch/x86/kvm/mmu/mmu.c
Simple merge