KVM: set_memory_region: Refactor prepare_memory_region()

This patch drops the parameter old, a copy of the old memory slot, and
adds a new parameter named change to know the change being requested.

This not only cleans up the code but also removes extra copying of the
memory slot structure.

Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 8eaf61f..caa72cf 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -479,8 +479,8 @@
 int kvm_arch_create_memslot(struct kvm_memory_slot *slot, unsigned long npages);
 int kvm_arch_prepare_memory_region(struct kvm *kvm,
 				struct kvm_memory_slot *memslot,
-				struct kvm_memory_slot old,
-				struct kvm_userspace_memory_region *mem);
+				struct kvm_userspace_memory_region *mem,
+				enum kvm_mr_change change);
 void kvm_arch_commit_memory_region(struct kvm *kvm,
 				struct kvm_userspace_memory_region *mem,
 				struct kvm_memory_slot old);