From: Ladi Prosek Date: Thu, 23 Mar 2017 07:04:18 +0000 (+0100) Subject: virtio_balloon: init 1st buffer in stats vq X-Git-Tag: v4.14-rc1~1222^2~2 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=fc8653228c8588a120f6b5dad6983b7b61ff669e;p=platform%2Fkernel%2Flinux-rpi3.git 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 Signed-off-by: Michael S. Tsirkin --- diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 4e11915..fcd06e1 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)