KVM: x86/mmu: Separate TDP MMU shadow page allocation and initialization

Separate the allocation of shadow pages from their initialization.  This
is in preparation for splitting huge pages outside of the vCPU fault
context, which requires a different allocation mechanism.

No functional changed intended.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220119230739.2234394-15-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/tdp_mmu.c

@@ -171,13 +171,19 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
 		if (kvm_mmu_page_as_id(_root) != _as_id) {		\
 		} else
 
-static struct kvm_mmu_page *tdp_mmu_alloc_sp(struct kvm_vcpu *vcpu, gfn_t gfn,
-					     union kvm_mmu_page_role role)
+static struct kvm_mmu_page *tdp_mmu_alloc_sp(struct kvm_vcpu *vcpu)
 {
 	struct kvm_mmu_page *sp;
 
 	sp = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache);
 	sp->spt = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache);
+
+	return sp;
+}
+
+static void tdp_mmu_init_sp(struct kvm_mmu_page *sp, gfn_t gfn,
+			      union kvm_mmu_page_role role)
+{
 	set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
 
 	sp->role = role;
@@ -185,11 +191,9 @@ static struct kvm_mmu_page *tdp_mmu_alloc_sp(struct kvm_vcpu *vcpu, gfn_t gfn,
 	sp->tdp_mmu_page = true;
 
 	trace_kvm_mmu_get_page(sp, true);
-
-	return sp;
 }
 
-static struct kvm_mmu_page *tdp_mmu_alloc_child_sp(struct kvm_vcpu *vcpu,
+static void tdp_mmu_init_child_sp(struct kvm_mmu_page *child_sp,
 				  struct tdp_iter *iter)
 {
 	struct kvm_mmu_page *parent_sp;
@@ -200,7 +204,7 @@ static struct kvm_mmu_page *tdp_mmu_alloc_child_sp(struct kvm_vcpu *vcpu,
 	role = parent_sp->role;
 	role.level--;
 
-	return tdp_mmu_alloc_sp(vcpu, iter->gfn, role);
+	tdp_mmu_init_sp(child_sp, iter->gfn, role);
 }
 
 hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
@@ -221,7 +225,9 @@ hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
 			goto out;
 	}
 
-	root = tdp_mmu_alloc_sp(vcpu, 0, role);
+	root = tdp_mmu_alloc_sp(vcpu);
+	tdp_mmu_init_sp(root, 0, role);
+
 	refcount_set(&root->tdp_mmu_root_count, 1);
 
 	spin_lock(&kvm->arch.tdp_mmu_pages_lock);
@@ -1042,7 +1048,9 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 			if (is_removed_spte(iter.old_spte))
 				break;
 
-			sp = tdp_mmu_alloc_child_sp(vcpu, &iter);
+			sp = tdp_mmu_alloc_sp(vcpu);
+			tdp_mmu_init_child_sp(sp, &iter);
+
 			if (tdp_mmu_link_sp_atomic(vcpu->kvm, &iter, sp, account_nx)) {
 				tdp_mmu_free_sp(sp);
 				break;