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Re: [Qemu-devel] [PATCH v2 2/6] virtio-balloon: make stats virtqueue len
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH v2 2/6] virtio-balloon: make stats virtqueue length 1 |
Date: |
Mon, 22 Aug 2016 04:57:19 +0300 |
On Fri, Aug 19, 2016 at 04:39:21PM +0300, Roman Kagan wrote:
> The protocol for virtio-balloon stats virtqueue doesn't allow more than
> one element in the virtqueue.
>
> So, instead of trying to compensate for guest misbehavior if it sends
> new data before the slot has been released by the host, just define the
> stats virtqueue length to 1 initially and rely on the generic virtio
> code to handle overflows.
>
> Signed-off-by: Roman Kagan <address@hidden>
> Cc: "Michael S. Tsirkin" <address@hidden>
> Cc: Ladi Prosek <address@hidden>
> Cc: Stefan Hajnoczi <address@hidden>
This would need a bunch of compat handlers to
avoid changes for old machine types.
> ---
> v1 > v2:
> - added assert in virtio_balloon_receive_stats
>
> hw/virtio/virtio-balloon.c | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> index 5af429a..fb8784e 100644
> --- a/hw/virtio/virtio-balloon.c
> +++ b/hw/virtio/virtio-balloon.c
> @@ -262,12 +262,8 @@ static void virtio_balloon_receive_stats(VirtIODevice
> *vdev, VirtQueue *vq)
> goto out;
> }
>
> - if (s->stats_vq_elem != NULL) {
> - /* This should never happen if the driver follows the spec. */
> - virtqueue_push(vq, s->stats_vq_elem, 0);
> - virtio_notify(vdev, vq);
> - g_free(s->stats_vq_elem);
> - }
> + /* enforced by stats virtqueue depth being 1 */
> + assert(!s->stats_vq_elem);
>
> s->stats_vq_elem = elem;
>
> @@ -443,7 +439,7 @@ static void virtio_balloon_device_realize(DeviceState
> *dev, Error **errp)
>
> s->ivq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
> s->dvq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
> - s->svq = virtio_add_queue(vdev, 128, virtio_balloon_receive_stats);
> + s->svq = virtio_add_queue(vdev, 1, virtio_balloon_receive_stats);
>
> reset_stats(s);
> }
> --
> 2.7.4
- [Qemu-devel] [PATCH v2 0/6] virtio-balloon: assorted fixes, Roman Kagan, 2016/08/19
- [Qemu-devel] [PATCH v2 2/6] virtio-balloon: make stats virtqueue length 1, Roman Kagan, 2016/08/19
- Re: [Qemu-devel] [PATCH v2 2/6] virtio-balloon: make stats virtqueue length 1,
Michael S. Tsirkin <=
- [Qemu-devel] [PATCH v2 4/6] virtio-balloon: keep collecting stats on save/restore, Roman Kagan, 2016/08/19
- Re: [Qemu-devel] [PATCH v2 0/6] virtio-balloon: assorted fixes, Roman Kagan, 2016/08/19
- [Qemu-devel] [PATCH v2 5/6] virtio-balloon: drop ->stats_vq_offset, Roman Kagan, 2016/08/19
- [Qemu-devel] [PATCH v2 6/6] virtio-balloon: drop reset handler, Roman Kagan, 2016/08/19
- [Qemu-devel] [PATCH v2 6/6] virtio-ballon: drop reset handler, Roman Kagan, 2016/08/19
- [Qemu-devel] [PATCH v2 3/6] virtio-balloon: don't restart stats timer in callback, Roman Kagan, 2016/08/19
- [Qemu-devel] [PATCH v2 1/6] virtio: assert on ->inuse underflow, Roman Kagan, 2016/08/19