KVM: Count the number of dirty pages for dirty logging

Needed for the next patch which uses this number to decide how to write
protect a slot.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 4c5b9a23967..af5c988cafc 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -625,6 +625,7 @@ static int kvm_create_dirty_bitmap(struct kvm_memory_slot *memslot)
                 return -ENOMEM;
 
         memslot->dirty_bitmap_head = memslot->dirty_bitmap;
+        memslot->nr_dirty_pages = 0;
         return 0;
 }
 #endif /* !CONFIG_S390 */
@@ -1491,7 +1492,8 @@ void mark_page_dirty_in_slot(struct kvm *kvm, struct kvm_memory_slot *memslot,
         if (memslot && memslot->dirty_bitmap) {
                 unsigned long rel_gfn = gfn - memslot->base_gfn;
 
-                __set_bit_le(rel_gfn, memslot->dirty_bitmap);
+                if (!__test_and_set_bit_le(rel_gfn, memslot->dirty_bitmap))
+                        memslot->nr_dirty_pages++;
         }
 }