On Fri, Jul 15, 2022 at 12:32 AM Eugenio Pérez <epere...@redhat.com> wrote:
>
> It allows the Shadow Control VirtQueue to wait for the device to use the
> available buffers.
>
> Signed-off-by: Eugenio Pérez <epere...@redhat.com>
> ---
> hw/virtio/vhost-shadow-virtqueue.h | 1 +
> hw/virtio/vhost-shadow-virtqueue.c | 22 ++++++++++++++++++++++
> 2 files changed, 23 insertions(+)
>
> diff --git a/hw/virtio/vhost-shadow-virtqueue.h
> b/hw/virtio/vhost-shadow-virtqueue.h
> index 1692541cbb..b5c6e3b3b4 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.h
> +++ b/hw/virtio/vhost-shadow-virtqueue.h
> @@ -89,6 +89,7 @@ void vhost_svq_push_elem(VhostShadowVirtqueue *svq, const
> SVQElement *elem,
> int vhost_svq_add(VhostShadowVirtqueue *svq, const struct iovec *out_sg,
> size_t out_num, const struct iovec *in_sg, size_t in_num,
> SVQElement *elem);
> +size_t vhost_svq_poll(VhostShadowVirtqueue *svq);
>
> void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue *svq, int svq_kick_fd);
> void vhost_svq_set_svq_call_fd(VhostShadowVirtqueue *svq, int call_fd);
> diff --git a/hw/virtio/vhost-shadow-virtqueue.c
> b/hw/virtio/vhost-shadow-virtqueue.c
> index 5244896358..31a267f721 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.c
> +++ b/hw/virtio/vhost-shadow-virtqueue.c
> @@ -486,6 +486,28 @@ static void vhost_svq_flush(VhostShadowVirtqueue *svq,
> } while (!vhost_svq_enable_notification(svq));
> }
>
> +/**
> + * Poll the SVQ for one device used buffer.
> + *
> + * This function race with main event loop SVQ polling, so extra
> + * synchronization is needed.
> + *
> + * Return the length written by the device.
> + */
> +size_t vhost_svq_poll(VhostShadowVirtqueue *svq)
> +{
> + do {
> + uint32_t len;
> + SVQElement *elem = vhost_svq_get_buf(svq, &len);
> + if (elem) {
> + return len;
> + }
> +
> + /* Make sure we read new used_idx */
> + smp_rmb();
There's already one smp_rmb(0 in vhost_svq_get_buf(). So this seems useless?
Thanks
> + } while (true);
> +}
> +
> /**
> * Forward used buffers.
> *
> --
> 2.31.1
>
