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authorLadi Prosek <lprosek@redhat.com>2017-03-23 08:04:18 +0100
committerMichael S. Tsirkin <mst@redhat.com>2017-03-28 20:41:27 +0300
commitfc8653228c8588a120f6b5dad6983b7b61ff669e (patch)
tree93023e1808febcc42d14c19f9529e5b650fa21c1 /drivers/virtio
parentde85ec8b07f82c8c84de7687f769e74bf4c26a1e (diff)
downloadlinux-fc8653228c8588a120f6b5dad6983b7b61ff669e.tar.bz2
virtio_balloon: init 1st buffer in stats vq
When init_vqs runs, virtio_balloon.stats is either uninitialized or contains stale values. The host updates its state with garbage data because it has no way of knowing that this is just a marker buffer used for signaling. This patch updates the stats before pushing the initial buffer. Alternative fixes: * Push an empty buffer in init_vqs. Not easily done with the current virtio implementation and violates the spec "Driver MUST supply the same subset of statistics in all buffers submitted to the statsq". * Push a buffer with invalid tags in init_vqs. Violates the same spec clause, plus "invalid tag" is not really defined. Note: the spec says: When using the legacy interface, the device SHOULD ignore all values in the first buffer in the statsq supplied by the driver after device initialization. Note: Historically, drivers supplied an uninitialized buffer in the first buffer. Unfortunately QEMU does not seem to implement the recommendation even for the legacy interface. Cc: stable@vger.kernel.org Signed-off-by: Ladi Prosek <lprosek@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'drivers/virtio')
-rw-r--r--drivers/virtio/virtio_balloon.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 4e1191508228..fcd06e16a1a2 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -429,6 +429,8 @@ static int init_vqs(struct virtio_balloon *vb)
* Prime this virtqueue with one buffer so the hypervisor can
* use it to signal us later (it can't be broken yet!).
*/
+ update_balloon_stats(vb);
+
sg_init_one(&sg, vb->stats, sizeof vb->stats);
if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
< 0)