Unless the host requires that requested pages won't be used until
he us notified (VIRTIO_BALLOON_F_MUST_TELL_HOST), only notify after
deflating the balloon.
This will avoid having to take an exit before actually using the pages.
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <levinsasha928@xxxxxxxxx>
---
drivers/virtio/virtio_balloon.c | 16 ++++++++++------
1 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index e058ace..055f95d 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -148,14 +148,18 @@ static void leak_balloon(struct virtio_balloon *vb, size_t num)
vb->num_pages--;
}
-
/*
- * Note that if
- * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
- * is true, we *have* to do it in this order
+ * If the host doesn't require us to notify him before using
+ * pages which belong to the balloon, update him only after
+ * freeing those pages for guest use.
*/
- tell_host(vb, vb->deflate_vq);
- release_pages_by_pfn(vb->pfns, vb->num_pfns);
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST)) {
+ tell_host(vb, vb->deflate_vq);
+ release_pages_by_pfn(vb->pfns, vb->num_pfns);
+ } else {
+ release_pages_by_pfn(vb->pfns, vb->num_pfns);
+ tell_host(vb, vb->deflate_vq);
+ }
}
static inline void update_stat(struct virtio_balloon *vb, int idx,
--
1.7.6
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