Merge branch kvm-arm64/pkvm-hyp-sharing into kvmarm-master/next

* kvm-arm64/pkvm-hyp-sharing:
  : .
  : Series from Quentin Perret, implementing HYP page share/unshare:
  :
  : This series implements an unshare hypercall at EL2 in nVHE
  : protected mode, and makes use of it to unmmap guest-specific
  : data-structures from EL2 stage-1 during guest tear-down.
  : Crucially, the implementation of the share and unshare
  : routines use page refcounts in the host kernel to avoid
  : accidentally unmapping data-structures that overlap a common
  : page.
  : [...]
  : .
  KVM: arm64: pkvm: Unshare guest structs during teardown
  KVM: arm64: Expose unshare hypercall to the host
  KVM: arm64: Implement do_unshare() helper for unsharing memory
  KVM: arm64: Implement __pkvm_host_share_hyp() using do_share()
  KVM: arm64: Implement do_share() helper for sharing memory
  KVM: arm64: Introduce wrappers for host and hyp spin lock accessors
  KVM: arm64: Extend pkvm_page_state enumeration to handle absent pages
  KVM: arm64: pkvm: Refcount the pages shared with EL2
  KVM: arm64: Introduce kvm_share_hyp()
  KVM: arm64: Implement kvm_pgtable_hyp_unmap() at EL2
  KVM: arm64: Hook up ->page_count() for hypervisor stage-1 page-table
  KVM: arm64: Fixup hyp stage-1 refcount
  KVM: arm64: Refcount hyp stage-1 pgtable pages
  KVM: arm64: Provide {get,put}_page() stubs for early hyp allocator

Signed-off-by: Marc Zyngier <maz@kernel.org>