KVM: x86/mmu: Move kvm_mmu_(get|put)_root to TDP MMU

The TDP MMU is almost the only user of kvm_mmu_get_root and
kvm_mmu_put_root. There is only one use of put_root in mmu.c for the
legacy / shadow MMU. Open code that one use and move the get / put
functions to the TDP MMU so they can be extended in future commits.

No functional change intended.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-3-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -3120,12 +3120,10 @@ static void mmu_free_root_page(struct kvm *kvm, hpa_t *root_hpa,
 
 	sp = to_shadow_page(*root_hpa & PT64_BASE_ADDR_MASK);
 
-	if (kvm_mmu_put_root(kvm, sp)) {
-		if (is_tdp_mmu_page(sp))
-			kvm_tdp_mmu_free_root(kvm, sp);
-		else if (sp->role.invalid)
-			kvm_mmu_prepare_zap_page(kvm, sp, invalid_list);
-	}
+	if (is_tdp_mmu_page(sp) && kvm_tdp_mmu_put_root(kvm, sp))
+		kvm_tdp_mmu_free_root(kvm, sp);
+	else if (!--sp->root_count && sp->role.invalid)
+		kvm_mmu_prepare_zap_page(kvm, sp, invalid_list);
 
 	*root_hpa = INVALID_PAGE;
 }

arch/x86/kvm/mmu/mmu_internal.h

@@ -123,22 +123,6 @@ bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm,
 void kvm_flush_remote_tlbs_with_address(struct kvm *kvm,
 					u64 start_gfn, u64 pages);
 
-static inline void kvm_mmu_get_root(struct kvm *kvm, struct kvm_mmu_page *sp)
-{
-	BUG_ON(!sp->root_count);
-	lockdep_assert_held(&kvm->mmu_lock);
-
-	++sp->root_count;
-}
-
-static inline bool kvm_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *sp)
-{
-	lockdep_assert_held(&kvm->mmu_lock);
-	--sp->root_count;
-
-	return !sp->root_count;
-}
-
 /*
  * Return values of handle_mmio_page_fault, mmu.page_fault, and fast_page_fault().
  *

arch/x86/kvm/mmu/tdp_mmu.c

@@ -43,7 +43,7 @@ void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm)
 
 static void tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root)
 {
-	if (kvm_mmu_put_root(kvm, root))
+	if (kvm_tdp_mmu_put_root(kvm, root))
 		kvm_tdp_mmu_free_root(kvm, root);
 }
 
@@ -55,7 +55,7 @@ static inline bool tdp_mmu_next_root_valid(struct kvm *kvm,
 	if (list_entry_is_head(root, &kvm->arch.tdp_mmu_roots, link))
 		return false;
 
-	kvm_mmu_get_root(kvm, root);
+	kvm_tdp_mmu_get_root(kvm, root);
 	return true;
 
 }
@@ -154,7 +154,7 @@ hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
 	/* Check for an existing root before allocating a new one. */
 	for_each_tdp_mmu_root(kvm, root, kvm_mmu_role_as_id(role)) {
 		if (root->role.word == role.word) {
-			kvm_mmu_get_root(kvm, root);
+			kvm_tdp_mmu_get_root(kvm, root);
 			goto out;
 		}
 	}

arch/x86/kvm/mmu/tdp_mmu.h

@@ -8,6 +8,24 @@
 hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu);
 void kvm_tdp_mmu_free_root(struct kvm *kvm, struct kvm_mmu_page *root);
 
+static inline void kvm_tdp_mmu_get_root(struct kvm *kvm,
+					struct kvm_mmu_page *root)
+{
+	BUG_ON(!root->root_count);
+	lockdep_assert_held(&kvm->mmu_lock);
+
+	++root->root_count;
+}
+
+static inline bool kvm_tdp_mmu_put_root(struct kvm *kvm,
+					struct kvm_mmu_page *root)
+{
+	lockdep_assert_held(&kvm->mmu_lock);
+	--root->root_count;
+
+	return !root->root_count;
+}
+
 bool __kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, int as_id, gfn_t start,
 				 gfn_t end, bool can_yield, bool flush);
 static inline bool kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, int as_id,