On Wed, 4 May 2011 23:51:38 +0300, "Michael S. Tsirkin" <m...@redhat.com> wrote:
> Add support for the used_event idx feature: when enabling
> interrupts, publish the current avail index value to
> the host so that we get interrupts on the next update.
>
> Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
> ---
> drivers/virtio/virtio_ring.c | 14 ++++++++++++++
> 1 files changed, 14 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 507d6eb..3a3ed75 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -320,6 +320,14 @@ void *virtqueue_get_buf(struct virtqueue *_vq, unsigned
> int *len)
> ret = vq->data[i];
> detach_buf(vq, i);
> vq->last_used_idx++;
> + /* If we expect an interrupt for the next entry, tell host
> + * by writing event index and flush out the write before
> + * the read in the next get_buf call. */
> + if (!(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)) {
> + vring_used_event(&vq->vring) = vq->last_used_idx;
> + virtio_mb();
> + }
> +
Hmm, so you're still using the avail->flags; it's just if thresholding
is enabled the host will ignore it?
It's a little subtle, but it keeps this patch small. Perhaps we'll want
to make it more explicit later.
Thanks,
Rusty.
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