[PATCH v3 2/7] KVM: X86: Introduce pte_list_count() helper

[Peter Xu <peterx@redhat.com>]

This helper is used to count the number of rmap entries in the rmap list
pointed by the kvm_rmap_head.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 arch/x86/kvm/mmu/mmu.c          | 21 +++++++++++++++++++++
 arch/x86/kvm/mmu/mmu_internal.h |  1 +
 2 files changed, 22 insertions(+)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 5429c20cf2cf..16c99f771c9e 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -998,6 +998,27 @@ static void pte_list_remove(struct kvm_rmap_head *rmap_head, u64 *sptep)
 	__pte_list_remove(sptep, rmap_head);
 }
 
+unsigned int pte_list_count(struct kvm_rmap_head *rmap_head)
+{
+	struct pte_list_desc *desc;
+	unsigned int i, count = 0;
+
+	if (!rmap_head->val)
+		return 0;
+	else if (!(rmap_head->val & 1))
+		return 1;
+
+	desc = (struct pte_list_desc *)(rmap_head->val & ~1ul);
+
+	while (desc) {
+		for (i = 0; (i < PTE_LIST_EXT) && desc->sptes[i]; i++)
+			count++;
+		desc = desc->more;
+	}
+
+	return count;
+}
+
 static struct kvm_rmap_head *__gfn_to_rmap(gfn_t gfn, int level,
 					   const struct kvm_memory_slot *slot)
 {
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index ca7b7595bbfc..62bb8f758b3f 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -131,6 +131,7 @@ bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm,
 				    int min_level);
 void kvm_flush_remote_tlbs_with_address(struct kvm *kvm,
 					u64 start_gfn, u64 pages);
+unsigned int pte_list_count(struct kvm_rmap_head *rmap_head);
 
 /*
  * Return values of handle_mmio_page_fault, mmu.page_fault, and fast_page_fault().
-- 
2.31.1