KVM: x86/mmu: Add lockdep when setting a TDP MMU SPTE

Add lockdep to __tdp_mmu_set_spte to ensure that SPTEs are only modified
under the MMU lock.

No functional change intended.
Reviewed-by: NPeter Feiner <pfeiner@google.com>
Reviewed-by: NSean Christopherson <seanjc@google.com>
Acked-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NBen Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-4-bgardon@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/tdp_mmu.c

@@ -381,6 +381,8 @@ static inline void __tdp_mmu_set_spte(struct kvm *kvm, struct tdp_iter *iter,
 	struct kvm_mmu_page *root = sptep_to_sp(root_pt);
 	int as_id = kvm_mmu_page_as_id(root);
 
+	lockdep_assert_held(&kvm->mmu_lock);
+
 	WRITE_ONCE(*iter->sptep, new_spte);
 
 	__handle_changed_spte(kvm, as_id, iter->gfn, iter->old_spte, new_spte,