KVM: s390: a utility function for migration

Introduce a utility function that will be used later on for storage
attributes migration, and use it in kvm_main.c to replace existing code
that does the same thing.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.vnet.ibm.com>
Message-Id: <1525106005-13931-2-git-send-email-imbrenda@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

include/linux/kvm_host.h

@@ -309,6 +309,13 @@ static inline unsigned long kvm_dirty_bitmap_bytes(struct kvm_memory_slot *memsl
 	return ALIGN(memslot->npages, BITS_PER_LONG) / 8;
 }
 
+static inline unsigned long *kvm_second_dirty_bitmap(struct kvm_memory_slot *memslot)
+{
+	unsigned long len = kvm_dirty_bitmap_bytes(memslot);
+
+	return memslot->dirty_bitmap + len / sizeof(*memslot->dirty_bitmap);
+}
+
 struct kvm_s390_adapter_int {
 	u64 ind_addr;
 	u64 summary_addr;

virt/kvm/kvm_main.c

@@ -1169,7 +1169,7 @@ int kvm_get_dirty_log_protect(struct kvm *kvm,
 
 	n = kvm_dirty_bitmap_bytes(memslot);
 
-	dirty_bitmap_buffer = dirty_bitmap + n / sizeof(long);
+	dirty_bitmap_buffer = kvm_second_dirty_bitmap(memslot);
 	memset(dirty_bitmap_buffer, 0, n);
 
 	spin_lock(&kvm->mmu_lock);