[patch 07/10] KVM: MMU: mmu_parent_walk

[Marcelo Tosatti <mtosatti@redhat.com>]

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Introduce a function to walk all parents of a given page, invoking a handler.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>


Index: kvm/arch/x86/kvm/mmu.c
===================================================================
--- kvm.orig/arch/x86/kvm/mmu.c
+++ kvm/arch/x86/kvm/mmu.c
@@ -147,6 +147,8 @@ struct kvm_shadow_walk {
 		     u64 addr, u64 *spte, int level);
 };
 
+typedef int (*mmu_parent_walk_fn) (struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp);
+
 static struct kmem_cache *pte_chain_cache;
 static struct kmem_cache *rmap_desc_cache;
 static struct kmem_cache *mmu_page_header_cache;
@@ -862,6 +864,65 @@ static void mmu_page_remove_parent_pte(s
 	BUG();
 }
 
+struct mmu_parent_walk {
+	struct hlist_node *node;
+	int i;
+};
+
+static struct kvm_mmu_page *mmu_parent_next(struct kvm_mmu_page *sp,
+					    struct mmu_parent_walk *walk)
+{
+	struct kvm_pte_chain *pte_chain;
+	struct hlist_head *h;
+
+	if (!walk->node) {
+		if (!sp || !sp->parent_pte)
+			return NULL;
+		if (!sp->multimapped)
+			return page_header(__pa(sp->parent_pte));
+		h = &sp->parent_ptes;
+		walk->node = h->first;
+		walk->i = 0;
+	}
+
+	while (walk->node) {
+		pte_chain = hlist_entry(walk->node, struct kvm_pte_chain, link);
+		while (walk->i < NR_PTE_CHAIN_ENTRIES) {
+			int i = walk->i++;
+			if (!pte_chain->parent_ptes[i])
+				break;
+			return page_header(__pa(pte_chain->parent_ptes[i]));
+		}
+		walk->node = walk->node->next;
+		walk->i = 0;
+	}
+
+	return NULL;
+}
+
+static void mmu_parent_walk(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
+			    mmu_parent_walk_fn fn)
+{
+	int level, start_level;
+	struct mmu_parent_walk walk[PT64_ROOT_LEVEL];
+
+	memset(&walk, 0, sizeof(walk));
+	level = start_level = sp->role.level;
+
+	do {
+		sp = mmu_parent_next(sp, &walk[level-1]);
+		if (sp) {
+			if (sp->role.level > start_level)
+				fn(vcpu, sp);
+			if (level != sp->role.level)
+				++level;
+			WARN_ON (level > PT64_ROOT_LEVEL);
+			continue;
+		}
+		--level;
+	} while (level > start_level-1);
+}
+
 static void nonpaging_prefetch_page(struct kvm_vcpu *vcpu,
 				    struct kvm_mmu_page *sp)
 {

--