[PATCH 3/3] virtio_balloon: Set pr_dev.order to new default

[Yuvraj Sakshith]

Drivers registering with page reporting used zero
as a way to signal page_reporting_order to be set
as a default value (either passed as a param or
MAX_PAGE_ORDER).

Since page_reporting_order can now have zero as
valid order, default fallback value send by drivers
to page reporting is now -1.

Signed-off-by: Yuvraj Sakshith <yuvraj.sakshith@xxxxxxxxxxxxxxxx>
---
 drivers/virtio/virtio_balloon.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 74fe59f5a..3cc3dc28a 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -1044,6 +1044,20 @@ static int virtballoon_probe(struct virtio_device *vdev)
 			goto out_unregister_oom;
 		}
 
+		/*
+		 * page_reporting_register() takes the order either
+		 * from the driver or the commandline. If neither
+		 * are provided, it falls back to MAX_PAGE_ORDER.
+		 *
+		 * Order given by the driver is required to be in the
+		 * range [0, MAX_PAGE_ORDER].
+		 *
+		 * One way for the driver to not provide any order
+		 * is by setting it to -1.
+		 */
+
+		vb->pr_dev_info.order = -1;
+
 		/*
 		 * The default page reporting order is @pageblock_order, which
 		 * corresponds to 512MB in size on ARM64 when 64KB base page
-- 
2.34.1