KVM: Fix kvm_clear_dirty_log_protect off-by-(minus-)one

Just imaging the case where num_pages < BITS_PER_LONG, then the loop
will be skipped while it shouldn't.

Signed-off-by: Peter Xu <peterx@redhat.com>
Fixes: 2a31b9db153530df4aa02dac8c32837bf5f47019
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index ad39c57..7883e0a 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1264,8 +1264,8 @@ int kvm_clear_dirty_log_protect(struct kvm *kvm,
                return -EFAULT;
 
        spin_lock(&kvm->mmu_lock);
-       for (offset = log->first_page,
-            i = offset / BITS_PER_LONG, n = log->num_pages / BITS_PER_LONG; n--;
+       for (offset = log->first_page, i = offset / BITS_PER_LONG,
+                n = DIV_ROUND_UP(log->num_pages, BITS_PER_LONG); n--;
             i++, offset += BITS_PER_LONG) {
                unsigned long mask = *dirty_bitmap_buffer++;
                atomic_long_t *p = (atomic_long_t *) &dirty_bitmap[i];