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, 6 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a3b25a524c9b..220c83b0fbda 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3466,10 +3466,9 @@ static int kvm_vm_ioctl_reinject(struct kvm *kvm,
 int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
                                       struct kvm_dirty_log *log)
 {
-        int r, i;
+        int r;
         struct kvm_memory_slot *memslot;
         unsigned long n;
-        unsigned long is_dirty = 0;
 
         mutex_lock(&kvm->slots_lock);
 
@@ -3484,11 +3483,8 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 
         n = kvm_dirty_bitmap_bytes(memslot);
 
-        for (i = 0; !is_dirty && i < n/sizeof(long); i++)
-                is_dirty = memslot->dirty_bitmap[i];
-
         /* If nothing is dirty, don't bother messing with page tables. */
-        if (is_dirty) {
+        if (memslot->nr_dirty_pages) {
                 struct kvm_memslots *slots, *old_slots;
                 unsigned long *dirty_bitmap;
 
@@ -3503,6 +3499,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
                         goto out;
                 memcpy(slots, kvm->memslots, sizeof(struct kvm_memslots));
                 slots->memslots[log->slot].dirty_bitmap = dirty_bitmap;
+                slots->memslots[log->slot].nr_dirty_pages = 0;
                 slots->generation++;
 
                 old_slots = kvm->memslots;