KVM: leverage change to adjust slots->used_slots in update_memslots()

update_memslots() is only called by __kvm_set_memory_region(), in which
"change" is calculated and indicates how to adjust slots->used_slots

  * increase by one if it is KVM_MR_CREATE
  * decrease by one if it is KVM_MR_DELETE
  * not change for others

This patch adjusts slots->used_slots in update_memslots() based on "change"
value instead of re-calculate those states again.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 587e1a0..acc951c 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -805,20 +805,25 @@ static int kvm_create_dirty_bitmap(struct kvm_memory_slot *memslot)
  * sorted array and known changed memslot position.
  */
 static void update_memslots(struct kvm_memslots *slots,
-                           struct kvm_memory_slot *new)
+                           struct kvm_memory_slot *new,
+                           enum kvm_mr_change change)
 {
        int id = new->id;
        int i = slots->id_to_index[id];
        struct kvm_memory_slot *mslots = slots->memslots;
 
        WARN_ON(mslots[i].id != id);
-       if (!new->npages) {
-               WARN_ON(!mslots[i].npages);
-               if (mslots[i].npages)
-                       slots->used_slots--;
-       } else {
-               if (!mslots[i].npages)
-                       slots->used_slots++;
+       switch (change) {
+       case KVM_MR_CREATE:
+               slots->used_slots++;
+               WARN_ON(mslots[i].npages || !new->npages);
+               break;
+       case KVM_MR_DELETE:
+               slots->used_slots--;
+               WARN_ON(new->npages || !mslots[i].npages);
+               break;
+       default:
+               break;
        }
 
        while (i < KVM_MEM_SLOTS_NUM - 1 &&
@@ -1054,7 +1059,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
                memset(&new.arch, 0, sizeof(new.arch));
        }
 
-       update_memslots(slots, &new);
+       update_memslots(slots, &new, change);
        old_memslots = install_new_memslots(kvm, as_id, slots);
 
        kvm_arch_commit_memory_region(kvm, mem, &old, &new, change);