KVM: x86/mmu: fix counting of rmap entries in pte_list_add

Fix an off-by-one style bug in pte_list_add() where it failed to
account the last full set of SPTEs, i.e. when desc->sptes is full
and desc->more is NULL.

Merge the two "PTE_LIST_EXT-1" checks as part of the fix to avoid
an extra comparison.

Signed-off-by: Li RongQing <lirongqing@baidu.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <1601196297-24104-1-git-send-email-lirongqing@baidu.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 1f96adf..5bb1939 100644 (file)
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -856,12 +856,14 @@ static int pte_list_add(struct kvm_vcpu *vcpu, u64 *spte,
        } else {
                rmap_printk("pte_list_add: %p %llx many->many\n", spte, *spte);
                desc = (struct pte_list_desc *)(rmap_head->val & ~1ul);
-               while (desc->sptes[PTE_LIST_EXT-1] && desc->more) {
-                       desc = desc->more;
+               while (desc->sptes[PTE_LIST_EXT-1]) {
                        count += PTE_LIST_EXT;
-               }
-               if (desc->sptes[PTE_LIST_EXT-1]) {
-                       desc->more = mmu_alloc_pte_list_desc(vcpu);
+
+                       if (!desc->more) {
+                               desc->more = mmu_alloc_pte_list_desc(vcpu);
+                               desc = desc->more;
+                               break;
+                       }
                        desc = desc->more;
                }
                for (i = 0; desc->sptes[i]; ++i)