KVM: convert slots_lock to a mutex

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index bb8873d..492dcc1 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -857,7 +857,7 @@
 	int is_dirty = 0;
 	int r, n;
 
-	down_write(&kvm->slots_lock);
+	mutex_lock(&kvm->slots_lock);
 
 	r = kvm_get_dirty_log(kvm, log, &is_dirty);
 	if (r)
@@ -879,7 +879,7 @@
 
 	r = 0;
 out:
-	up_write(&kvm->slots_lock);
+	mutex_unlock(&kvm->slots_lock);
 	return r;
 }