KVM: introduce a table to map slot id to index in memslots array

The operation of getting dirty log is frequent when framebuffer-based
displays are used(for example, Xwindow), so, we introduce a mapping table
to speed up id_to_memslot()

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6e8eb15dd30b..e289486edc6d 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -446,7 +446,7 @@ static void kvm_init_memslots_id(struct kvm *kvm)
         struct kvm_memslots *slots = kvm->memslots;
 
         for (i = 0; i < KVM_MEM_SLOTS_NUM; i++)
-                slots->memslots[i].id = i;
+                slots->id_to_index[i] = slots->memslots[i].id = i;
 }
 
 static struct kvm *kvm_create_vm(void)
@@ -674,8 +674,13 @@ static int cmp_memslot(const void *slot1, const void *slot2)
  */
 static void sort_memslots(struct kvm_memslots *slots)
 {
+        int i;
+
         sort(slots->memslots, KVM_MEM_SLOTS_NUM,
               sizeof(struct kvm_memory_slot), cmp_memslot, NULL);
+
+        for (i = 0; i < KVM_MEM_SLOTS_NUM; i++)
+                slots->id_to_index[slots->memslots[i].id] = i;
 }
 
 void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new)