[PATCH] virtio_balloon: Notify guest only after deflating the balloon
From: Sasha Levin <hidden>
Date: 2011-07-02 03:06:56
Subsystem:
the rest, virtio balloon, virtio core · Maintainers:
Linus Torvalds, "Michael S. Tsirkin", David Hildenbrand, Jason Wang
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 <redacted> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: virtualization@lists.linux-foundation.org Cc: kvm@vger.kernel.org Signed-off-by: Sasha Levin <redacted> --- 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