On Mon, Mar 24, 2025 at 7:01 AM Jason Wang <jasow...@redhat.com> wrote:
>
> Factor out the core logic for updating last_used_idx to be reused by
> the packed in order implementation.
>
Acked-by: Eugenio Pérez <epere...@redhat.com>
> Signed-off-by: Jason Wang <jasow...@redhat.com>
> ---
> drivers/virtio/virtio_ring.c | 43 +++++++++++++++++++++---------------
> 1 file changed, 25 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index fe3e6f3d0f96..bd4faf04862c 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1749,6 +1749,30 @@ static bool more_used_packed(const struct
> vring_virtqueue *vq)
> return virtqueue_poll_packed(vq, READ_ONCE(vq->last_used_idx));
> }
>
> +static void update_last_used_idx_packed(struct vring_virtqueue *vq,
> + u16 id, u16 last_used,
> + u16 used_wrap_counter)
> +{
> + last_used += vq->packed.desc_state[id].num;
> + if (unlikely(last_used >= vq->packed.vring.num)) {
> + last_used -= vq->packed.vring.num;
> + used_wrap_counter ^= 1;
> + }
> +
> + last_used = (last_used | (used_wrap_counter <<
> VRING_PACKED_EVENT_F_WRAP_CTR));
> + WRITE_ONCE(vq->last_used_idx, last_used);
> +
> + /*
> + * 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->packed.event_flags_shadow == VRING_PACKED_EVENT_FLAG_DESC)
> + virtio_store_mb(vq->weak_barriers,
> + &vq->packed.vring.driver->off_wrap,
> + cpu_to_le16(vq->last_used_idx));
> +}
> +
> static void *virtqueue_get_buf_ctx_packed(struct vring_virtqueue *vq,
> unsigned int *len,
> void **ctx)
> @@ -1792,24 +1816,7 @@ static void *virtqueue_get_buf_ctx_packed(struct
> vring_virtqueue *vq,
> ret = vq->packed.desc_state[id].data;
> detach_buf_packed(vq, id, ctx);
>
> - last_used += vq->packed.desc_state[id].num;
> - if (unlikely(last_used >= vq->packed.vring.num)) {
> - last_used -= vq->packed.vring.num;
> - used_wrap_counter ^= 1;
> - }
> -
> - last_used = (last_used | (used_wrap_counter <<
> VRING_PACKED_EVENT_F_WRAP_CTR));
> - WRITE_ONCE(vq->last_used_idx, last_used);
> -
> - /*
> - * 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->packed.event_flags_shadow == VRING_PACKED_EVENT_FLAG_DESC)
> - virtio_store_mb(vq->weak_barriers,
> - &vq->packed.vring.driver->off_wrap,
> - cpu_to_le16(vq->last_used_idx));
> + update_last_used_idx_packed(vq, id, last_used, used_wrap_counter);
>
> LAST_ADD_TIME_INVALID(vq);
>
> --
> 2.42.0
>
