On Wed, Mar 22, 2017 at 04:10:27PM +0100, Ladi Prosek wrote: > 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 initializes all tags with U16_MAX which is guaranteed to > be ignored by the host. > > The alternative fix would be to push an empty buffer in init_vqs but > that's not easily done with the current virtio implementation and > would still not eliminate the invariant that update_balloon_stats > has to update all VIRTIO_BALLOON_S_NR fields. > > Signed-off-by: Ladi Prosek <[email protected]> > --- > drivers/virtio/virtio_balloon.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > index 4e11915..d34f56f 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -423,12 +423,16 @@ static int init_vqs(struct virtio_balloon *vb) > vb->deflate_vq = vqs[1]; > if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { > struct scatterlist sg; > + int idx; > vb->stats_vq = vqs[2]; > > /* > * Prime this virtqueue with one buffer so the hypervisor can > * use it to signal us later (it can't be broken yet!). > */ > + for (idx = 0; idx < VIRTIO_BALLOON_S_NR; idx++) > + update_stat(vb, idx, U16_MAX, 0); > +
Can't we fill in actual values? > sg_init_one(&sg, vb->stats, sizeof vb->stats); > if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL) > < 0) > -- > 2.7.4 _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
