On Fri, Feb 22, 2019 at 04:13:50PM +0800, Jiayu Hu wrote:
> The VIRTIO_RING_F_EVENT_IDX feature of split ring might
> be broken, as the value of signalled_used is unpredictable
> after live migration or start up. This patch fixes it by
> using signalled_used_valid.
Seems you also need to invalidate the signalled_used in e.g.
set_vring_base, as signalled_used may not match last_used_idx
anymore e.g. when guest driver is reloaded.
>
> In addition, this patch makes the VIRTIO_RING_F_EVENT_IDX
> implementation of split ring match kernel backend to suppress
> more interrupts.
>
> Fixes: e37ff954405a ("vhost: support virtqueue interrupt/notification
> suppression")
> Cc: sta...@dpdk.org
>
> Signed-off-by: Jiayu Hu <jiayu...@intel.com>
> ---
> lib/librte_vhost/vhost.h | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> index fc31796..c4e5e34 100644
> --- a/lib/librte_vhost/vhost.h
> +++ b/lib/librte_vhost/vhost.h
> @@ -633,16 +633,20 @@ vhost_vring_call_split(struct virtio_net *dev, struct
> vhost_virtqueue *vq)
> if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX)) {
> uint16_t old = vq->signalled_used;
> uint16_t new = vq->last_used_idx;
> + bool signalled_used_valid = vq->signalled_used_valid;
> +
> + vq->signalled_used = new;
> + vq->signalled_used_valid = true;
>
> VHOST_LOG_DEBUG(VHOST_DATA, "%s: used_event_idx=%d, old=%d,
> new=%d\n",
> __func__,
> vhost_used_event(vq),
> old, new);
> - if (vhost_need_event(vhost_used_event(vq), new, old)
> - && (vq->callfd >= 0)) {
> - vq->signalled_used = vq->last_used_idx;
> +
> + if ((vhost_need_event(vhost_used_event(vq), new, old) &&
> + (vq->callfd >= 0)) ||
> + unlikely(!signalled_used_valid))
> eventfd_write(vq->callfd, (eventfd_t) 1);
> - }
> } else {
> /* Kick the guest if necessary. */
> if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
> --
> 2.7.4
>
