KVM: fix the handling of dirty bitmaps to avoid overflows

(Cherry-picked from commit 87bf6e7de1134f48681fd2ce4b7c1ec45458cb6d)

Int is not long enough to store the size of a dirty bitmap.

This patch fixes this problem with the introduction of a wrapper
function to calculate the sizes of dirty bitmaps.

Note: in mark_page_dirty(), we have to consider the fact that
  __set_bit() takes the offset as int, not long.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index bd5a616d9373..ddb7d5840de8 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -116,6 +116,11 @@ struct kvm_memory_slot {
         int user_alloc;
 };
 
+static inline unsigned long kvm_dirty_bitmap_bytes(struct kvm_memory_slot *memslot)
+{
+        return ALIGN(memslot->npages, BITS_PER_LONG) / 8;
+}
+
 struct kvm_kernel_irq_routing_entry {
         u32 gsi;
         u32 type;